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I have designed a group of medieval towns located on a valley, all of them connected by a navigable river wich ends on a big waterfall. There are some elevators at the side of the waterfall that connect two ports, one on the top and one on the bottom.
The port on the bottom is the only one who could be access by ships from out of the valley while the one on the top recives ships from the valley.
I want to freeze the waterfall and part of the coast during the winter. I understand this is very possible. So my doubts are:
* How cold does it have to be to freeze the waterfall?
* If the waterfall is frozen, must the river been frozen too?
* If everything is frozen, were are they going get water?
* If everything is frozen, is it possible to use the river like a highway for sleds
I was thinking on a 25-40 meters river widht and a waterfall of 50 meters high
I have some ideas about it, and I am researching for examples on real world, but I would like to know what you think about it.
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Obviously, below freezing. The colder it is, the faster the water will freeze. Depending on the size of the river and the brightness of daytime sunshine, it might have to be a *long* way below freezing.
[This waterfall](https://wearederbyshire.co.uk/derbyshire-ice-climbers-scaled-a-frozen-kinder-downfall-after-one-of-the-coldest-nights-of-the-year/) (Kinder downfall) froze during a period of slightly-below-freezing weather, after a slightly-more-freezing night (only about -6° Celsius or so) but it doesn't deliver a huge volume of water and it melted in the sunlight later that day. Conversely, a more substantial waterfall like [Niagara Falls](https://metro.co.uk/2019/01/23/incredible-pictures-frozen-niagara-falls-temperatures-hit-20c-8377750/) remained partially liquid even at -17° Celsius.
Have a read up about [ice climbing](https://en.wikipedia.org/wiki/Ice_climbing), which often involves frozen waterfalls.
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> If the waterfall is frozen, must the river been frozen too?
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Quite possibly, but remember that liquid water flowing over the icefall can then itself freeze. This is how icicles form... they don't just spontaneously materialise as huge spikes of ice, but form as liquid water runs down small icy areas and freezes itself.
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In big rivers and lakes, you'll get water under the ice. Bash a hole, scoop it out. It may also be possible to get food from lakes and rivers too, via [ice fishing](https://en.wikipedia.org/wiki/Ice_fishing).
Wells will still work too, as the freezing line won't penetrate too far into the ground unless you're actually in the arctic permafrost.
You can always melt ice and snow over a fire.
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> If everything is frozen, is it possible to use the river like a highway for sleds
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If it is big enough and frozen enough, sure. At river-freezing temperatures you may find that the snowpack is sufficient for sledging over pretty much anywhere, though rivers do have the advantage of being nice and flat and so make for good roads.
Note that it is possible for rivers and lakes to freeze without being traversable, though you'd hope that people who lived near such places and used them as means of transport would understand these things. A frozen surface on a plunge pool under a non- or partially-frozen waterfall is probably *not* a good place to walk over, for example.
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**How far below zero it needs to be is not the most important factor here**
The real important factors are the dimensions of your river, how slowly it freezes, how fast the water is moving, and how far your drop is.
Waterfalls do not just suddenly freeze in place, instead the surface of the river freezes creating a surface for the liquid water underneath to cling to as it flows under it and itself subsequently freezes. A wider, faster moving waterfall is harder to freeze because you must first freeze the entire top edge of the waterfall in a fashion that creates an ice bridge to build on. This makes narrower waterfalls more ideal. If you have a wider river, you will want many rocky outcroppings at the waterfall's edge so that you have several shorter ice bridges instead of one longer one. Otherwise your river will have more time to freeze depriving you of the needed flow before you can start building your actual icy waterfall.
Once you have a solid icebridge over flowing water, you get icicles that slowly form. The slower your water freezes the better because once the river freezes through you will eventually stop having flowing water to continue to build the ice up. A slower starting water flow is also better because if the water is flowing too quickly with too much volume, then it will melt the ice faster than the cold air can build it up.
As the icicles grow they will also become heavier increasing their odds of breaking and falling off under their own weight, ideally the temperature will continue to slowly drop as the icicles form strengthening the ice at the top so it does not snap will allowing enough water to keep flowing to continue to build the ice up. The longest icicles in recorded history were ~27 feet long; so, that is probably about the limit of how high an ice waterfall can be... however, if you have a multi-stepped waterfall, you may get a much larger ice-face from ice bridges forming at multiple points in your decent.
**Is Your Waterfall Doable?**
In short, yes but it is much harder if your waterfall is not shaped right or if it is moving too fast. In the examples below, the first waterfall has a lot more shelves and narrow areas to bridge making it easier to freeze. The second one would probably not freeze except under extraordinary conditions.
[](https://i.stack.imgur.com/KNHZl.png)
Speaking of extraordinary conditions, Starfish Prime's Niagara falls example demonstrates, several really good points about this process that I think deserves a little bit of extra attention. If you look at section (A) below you will see where an ice bridge formed and the waterfall is just stepped enough to get the multiple layers of icicles. Section (B) shows another mechanic by which larger faster flowing waterfalls can freeze where by the water at the bottom freezes and builds up. It is more structurally sound than hanging ice but typically requires lower temperatures because you need to contend with the depth of the water at the waterfall's base. It also tends to look more like piled up clumps of snow and ice and less like a "frozen waterfall"; so, it probably does not answer your question as well, but I suppose it can help compensate for a bigger more overhanging waterfall if it builds up high enough.
[](https://i.stack.imgur.com/oSXFM.png)
**As for your related questions:**
The main river does not need to be completely frozen for this to happen, but there will at the very least be patches of ice, probably along the shores and shallows. The middle, deeper parts of the river will take longer to freeze, but if you want the icefall to be around for awhile, it will need to stay cold enough that the river will eventually fully freeze.
In the event of a long term, full freeze, they can just melt ice and snow for water. Should not be a big deal.
If the ice is thick enough, yes you could use sledges to traverse it, but it has to get and stay pretty cold for a long time for the ice to get thick enough for this to be a good idea. The icefall would probably need to form at the beginning of a freeze, and they would need to wait days or weeks for the river to harden enough to support traffic.
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It is possible, indeed. The temperatures have to fall below around -6ºC for the flowing water to start [supercooling](https://en.wikipedia.org/wiki/Supercooling). After that, small shards of ice will start forming in the top of the waterfall (where the water starts falling), building and growing over time, until its height makes the waterfall seem to be frozen.
A waterfall can start freezing without the river being completely frozen, but if enough time passes, the entire waterfall will be solid frozen, and the river as well.
About the water issue, as @LiJun stated, they can melt the ice by using fire, or they can break the ice in the river to get the water below (remember that only the superficial layer of rivers will freeze).
And yeah, they could use the frozen rivers as highways for sleds, but it might be dangerous if the ice isn't thick enough (but if the waterfall froze, it is probably thick enough).
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**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
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This question does not appear to be about **worldbuilding**, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help).
Closed 6 years ago.
[Improve this question](/posts/87916/edit)
Question inspired by Made in Abyss.
So for whatever reason, our world has a large crater/hole tens of kilometers in diameter and maybe 100 km deep (maybe our world's crust is a little thicker, maybe the hole goes past the crust). This hole is home to lost technologies and an exotic ecology, which tempts explorers and divers of all kinds.
Humans get altitude sickness climbing mountains, and diver's disease from underwater pressure and rapid ascension. **In what ways can we get sick from going down into the hole? What are the factors that causes these sicknesses?**
For the sake of the question, assume the ecology isn't the cause of any of these sicknesses. We're interested in the change in environment and altitude. Bonus cookies if you can provide ways to avoid such ailments.
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There are many issues that arise. The body is not designed for high pressures.
As an example, as you go lower, you have to breathe air which has a smaller and smaller concentrations of oxygen. This is because if the partial pressure of oxygen rises too high (1.4-1.6atm), it becomes [toxic](https://en.wikipedia.org/wiki/Oxygen_toxicity) and kills you.
There's [nitrogen narcosis](https://en.wikipedia.org/wiki/Nitrogen_narcosis). Nitrogen has a narcotic like effect on people at depth (20-30m, depending on the individual), and deep see diving is not a healthy place to suffer narcotic effects.
Going below 150m with helium in your breathing mixture comes with the risk of [High Pressure Nervous Syndrome](https://en.wikipedia.org/wiki/High-pressure_nervous_syndrome), which can cause all sorts of problems. In fact, many commercial divers will breathe trimix, a mixture of oxygen, helium, and nitrogen. They introduce the nitrogen, and the risks of nitrogen narcosis, to decrease the partial pressures of the helium to offset HPNS. These mixes are often adjusted on the fly, depending on your particular depth at that time.
Around 2-4km deep, we *believe* we will run into issues with [helium narcosis](https://www.quora.com/What-is-the-maximum-depth-a-human-body-can-go-to-under-water-beyond-which-the-pressure-would-be-intolerable). Helium is considered to be the least narcotic gas known, and models suggest it becomes fatal at those depths. At this time, nobody knows if there's a way past that boundary or not.
The human body was not designed to survive the pressures 100km down. It's chemical engines are simply being run outside of their specifications at that point.
Edit: All of this was based on the idea that the hole was in water. If the hole was in air, obviously the pressures accumulate much slower. [This calculator](https://www.mide.com/pages/air-pressure-at-altitude-calculator) suggests that at 100km, we would experience an air pressure of 500atm. That's roughly equivalent to 5km depths of water. So if that calculator is correct, the bottom of the hole will still be just outside of the limits of the human body's susceptibility to helium narcosis.
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This sickness is very common for divers. If we stay in the air (rather than water), pressure increasing much less, so we need to go much deeper to experience the same problems.
1. [Decompression sickness](https://en.wikipedia.org/wiki/Decompression_sickness) is common when humans return from high to low pressure too quickly. Gases that were dissolved in blood at high pressure start to boil, and this may cause serious health damage.
2. [Oxygen toxicity](https://en.wikipedia.org/wiki/Oxygen_toxicity). While decompression sickness can easily be avoided, high air pressure is not. Under higher pressure, amount of oxygen in each breath is higher, and here lies the problem. Actually, just 50% increase in pressure may cause the oxygen to become toxic.
3. [Nitrogen narcosis](https://en.wikipedia.org/wiki/Nitrogen_narcosis) also occurs at high pressure. Nitrogen, while mostly inert with respect to human body, at high pressure (typically 5+ bar starting at about 2 bar) affects our brains, causing a number of possible effects, including death.
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**Anything that's a concern for the mining industry should also be yours.**
Long term exposure to [radon](https://en.wikipedia.org/wiki/Radon#Health_risks) that has accumulated in the hole will give you lung cancer.
Elevated levels of Carbon Dioxide, Carbon Monoxide, Hydrogen, Hydrogen Sulfide, Oxygen, Methane, Nitrogen, Nitrogen Dioxide, and Sulfur Dioxide are also hazardous, and are the main concerns of miners. This link contains spread sheets for their effects at given concentrations. ([miningquiz.com/download/minegases.htm](http://miningquiz.com/download/minegases.htm))
I'm unsure exactly which of those increases solely with depth (other than radon). Any that are heavier than air will accumulate in higher concentrations the further down you go.
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I'm not 100% on the numbers, but the temperature increases by as much as 30K per km of depth. This means that as you descended, by 5km (probably not a huge pressure difference, only half as deep as Everest is high) the temp would be that of an oven. I think that your explorers would be cooked before they had to worry hugely about pressure differences. So the ailment might well be good old heat stroke.
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A lot of the answers have assumed that the deeper you go, the heavier the air pressure. This is [not always that case](https://what-if.xkcd.com/153/), because going down means closer to the earth's core, means higher temperature, means lighter air. So, you probably have to choose the sweet spot between pressure related issues and temperature related issues.
Lower down, you probably have water running into the hole, so at the bottom there may be a lake. Or if it's boiling hot, maybe the water vaporizes.
We can go pretty far underwater, and every 33ft (34ft in fresh water) leads to another atmosphere of pressure (water doesn't compress like a gas would, so is far more stable). So we can extrapolate a lot of [deep sea diving](https://en.wikipedia.org/wiki/Deep_sea_diving) problems and solutions, most especially about breathing under pressure.
A rigid ship or suit might be the easiest thing to deal with. It hides a lot of the issues specifically, and still gives you a "dangerous" feel. Alternatively, you probably want heat reflective clothing and a helium-oxygen blend to breathe; and to have plenty of time for acclimating as you go down/up.
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One thing that also might affect somebody travelling down that deep is the change in gravity. As you get closer to the bottom, depending on how large your world is, there's a good chance that you'll experience a noticeable change in gravity. At depths (in caves for example) or heights (on mountains for example) of just a few kilometers max on Earth this change is negligible, but based on your world at say 100km depth, this change could definitely be felt.
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The bends/ decompression sickness might count. In this case gas forms bubbles that will mess you up. <https://en.m.wikipedia.org/wiki/Decompression_sickness>
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I want to build a planet (or satellite) that:
* **is smaller than Earth,**
* **has a thicker atmosphere than Earth** but breathable,
* has neither intense volcanism, nor any extreme condition of that sort that would increase atmosphere density,
* revolves around a binary star similar to [BY Draconis](http://en.wikipedia.org/wiki/BY_Draconis)
A higher gravity makes for a higher atmosphere density. If feels like this is the best option in order to keep the planet a peaceful place, hence my question.
**Question:**
How is that possible? Is it coherent in such a system with at least two (small young) stars?
Bonus questions: What would the stellar system be like? Would the other telluric planets in the system necessarily look the same? Would there still be gas giants?
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I think the others have done a good job of answering the main question of what it would be composed of (I'd have said iron, too, or something similar), so I'll address some of the other stuff.
The [BY Draconis](http://en.wikipedia.org/wiki/BY_Draconis) system is *young*. Really, really, young. Components A and B certainly aren't well developed, because they haven't yet exited the protostar phase of their lives. As far as I know, there is no protoplanetary disk in the system. A good rule of thumb is this: No protoplanetary disk $\implies$ No planets. This would seem to rule out this entire scenario - at least at this point in time. I'm also doubtful that the system could capture any rogue planets. They just aren't old enough for the probability of that to happen.
Any planet orbiting component A or B would not be conducive to life. These two stars constitute a [BY Draconis variable](http://en.wikipedia.org/wiki/BY_Draconis_variable). This means that there can be drastic changes in luminosity due to surface activity, such as star spots (the extrasolar equivalent of sunspots). Variable stars in general aren't great for life, because of their variability. Some are periodic, though, which does make them regular, but BY Draconis variables are not periodic.
This doesn't rule out component C, though. It appears to be a red dwarf, far out from the two others. (The whole system reminds me of a younger version of the Alpha Centauri/Proxima Centauri system) The danger here is that if the red dwarf is a flare star, it, too, may not be friendly to life. Also, I'm unsure of how easy it would be for a planet to get out here, given that much of the system's mass is at the center of the binary pair, meaning that they would be more likely to scoop up any possible planet-forming material.
So I highly doubt that *any* planets could form in the system, and if they did, they most likely would (certainly at the moment) not be habitable. I think this also rules out the "other planets" part of your question, although Wikipedia does say this:
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So that gives us some hope.
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It is unlikely for a natural planet to have a density significantly higher than iron. Barring some outside force elements lighter than iron will be more common than elements heavier than iron. A collision of two planets might work. The collision could separate a part of a core from the rest of the mass, probably into a moon. The core fragment could, I suppose, have density higher than iron. You'd then need a second "just right" collision to strip the moon of lighter materials ejected at the same time. I don't think it is flat out impossible, but it is very unlikely.
Incidentally, gravity and atmospheric density are not directly related, but atmospheric composition and gravity are. So you'd actually want only near 1G gravity, not something significantly higher, which should help. Also "breathable" puts a limit on the atmosphere. It might be better not to go exotic here,and just have a smaller, denser Earth.
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Surface gravity is a function of both the mass of the planet and its radius. By [Newton's law of gravitation](https://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation), the force experienced by a mass at the surface of a planet with mass $M$ and radius $r$ is proportional to $M/r^2\!$. If the planet's density is $\rho$, then its mass is proportional to $\rho r^3\!$, so the gravity at the surface is proportional to $\rho r$. Therefore, if you want a smaller planet than Earth to have higher surface gravity, you're going to need it to have higher density.
One way to achieve that might be to have a proportionally larger core than the Earth's, or denser crust. But I've no idea how feasible that would be.
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How could a smaller planet than Earth have a higher gravity?
The easiest way is to make the core mostly Gold. Now is this likely? No, Is it possible? Yes. It would certainly be fun to have a 'gold' planet in a sci-fi world.
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It is possible. You would need either:
1. A larger core relative to the mantle.
2. A denser core, perhaps gold, lead or uranium.
3. An accretion around some ancient alien tech, perhaps a gravity drive.
4. Some other source of mass. Perhaps the planet is an extrusion into our universe of a 4 dimensional hypersphere. Perhaps it is locked with a larger object shifted sideways out of our dimension.
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I'm not an expert in this, but it seems to me that **if the planet has a heavier core than Earth's, it would also have higher gravity.**
Earth has an iron-nickel alloy [core](http://www.wikipedia.org/wiki/Inner_core). A look at a periodic table shows several elements heavier than iron, some of which might be suitable as a planet's core.
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To have a gravity equal to or greater than earth, the planet would have to have a mass equal to or greater than earth.
Given the gravitational effects at play with that kind of mass and binary stars, you will have volcanic activity.
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# Make it a Failed Alien Experiment
As other answers have put it, it's pretty unlikely an object similar to your description will naturally occur. So my suggestion to you is to make it into a failed alien experiment. This will add mystery to your story, and as a bonus makes great grounds for prequels and sequels.
Some long extinct alien race have accumulated a large amount of very dense material in an orbit around the system. About a million years have passed now, in which time comets and the remnants of the proto-stars have created a very thin (~50-100 meter) crust on the object. Atmosphere was also created by the aliens, who seem to have breathed Oxygen, just like humans.
Densest material known to humans is the quark-gluon plasma, but that might be too exotic, and needs special containers, which are unlikely to survive million years. The densest known element is Osmium, and Iridium follows closely. If we use an Osmium-Iridium alloy, the density will be slightly more than 2.2 kgm-3. If we account for the thin crust and settle for a mean density of 2.2 kgm-3, for a planetoid with 0.25 Earth radii you will get a gravitational acceleration of very nearly 1 g (9.78 ms-2). For a Moon-sized planetoid, gravity will be 10.68 ms-2, and will give you the slightly dense atmosphere you wanted.
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Suppose there is a planet where intelligent life (with intelligence approximately same as that of a being of the human species, say) exists. However, due to certain conditions (such as, for example, a sun which gives out light mostly in the IR spectrum), these beings have eyes that see "heat" (in the form of rays of infrared radiation), but not colour (i.e., they can't "see" visible light, ironic as that may sound).
How would the fundamental design of everything be changed?
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For example, a door handle may have to be warmed slightly, so as to be able to distinguish it from the surrounding door, assuming the surrounding door is at the same temperature.
Update: Let's ignore this example I provided. Unfortunately, the fact that it somehow did not strike me that IR rays could be reflected seems to have become the focal point of the question at present. In all fairness, putting in an example of a glowing handle was not, well, the brightest of ideas. Apologies.
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# A lot of people have covered sight, but one factor people have missed is the *size* of the eye.
Insects see ultraviolet wavelengths because UV-light has a much shorter wavelength. **For a cell to detect a vibration in the electromagnetic spectrum, it would needs be be at least as large as the vibration**. Hence why smaller animals see smaller wavelengths. Therefore, to have an eye that detects much larger wavelengths, the cells would need to be larger, which would mean the eyes would probably be bigger too.
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Addendum on eye size.
Sadly, I can't find a specific reference and I'm not a biologist, but I did read the [wikipedia article of photoreceptors](http://en.wikipedia.org/wiki/Photoreceptor_cell) and I found a [good article on the evolution of vision](https://whyevolutionistrue.wordpress.com/2013/03/08/why-dont-any-organisms-detect-radio-waves-or-whats-so-special-about-the-visible-spectrum/). As I understand it light detection in cells requires the cell to be excited by a photon of the appropriate wavelength. This excitation is based on the energy of the photon and the number of photons reaching the eye - the more photons, the more stimulus. To maximise the stimulus, you want to catch as many photons as possible, which means the cell needs to be at least as large as the photon wavelength (otherwise the photon travels around you). For example, some radio waves have a wavelength of several meters, so the chance of a radio wave hitting you in the eye (let alone a specific cell is quite low).
If we assume cell size has to increase to catch the right wavelengths of light, if a creature wanted to have similar visual resolution to humans, the number of cells would remain constant, thus the eye would need to increase.
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Civilization may be very similar to ours or very different. The exact wavelenghts seen by people of that species are not so decisive.
What we call visible light is only a small amount of wavelenghts, which we can detect with four different receptors in our eyes (three for daylight colour vision and another one for intensity-only nighttime gray vision). We call these three wavelenghts red, green and blue, and a certain mixture of them white light (precisely a good approximation of our Sun's light that can reach us through our atmosphere).
If there were a different set of wavelenghts that our cells could detect, those would be the "real" colours, and what we now call "visible light" would be in the infra-something or in the ultra-something ranges. If these three colours were "foo", "bar" and "baz" in the infrared, our visible light would be part of the "ultrabaz", invisible light, while most of our infrared would be "infrafoo".
It happens that the range of temperatures on which water is liquid (0C-100C, 273K-373K) are those which we consider suitable for life (particularly those in which proteins are stable, thus reducing the set to about 0C-35C (273K-308K). At these temperatures, all bodies radiate[1](https://i.stack.imgur.com/fJhh0.jpg) with peaks between 10.6µm and 9.4µm (what we call the near side of far infrared).
If the species has their cells tuned to near infrared or medium infrared, there would be no difference with our vision: objects still would not glow. It just happens that the temperature at which they start glowing (red hot metal) is lower than it is for us.
On the other hand, if the species has their cells tuned to the far infrared, objects will naturally glow. Artificial light is not necessary (unless going to very cold places), but fire still would be need for cooking, ore processing, etc. Since fire and wheel are the same, and most technology would develop from that two main inventions, they could be very similar to us.
(This paragraph added after kaine's comment) Another important issue is that of transparency. The set of transparent materials is quite different from what we think is transparent for "visible light". Air will continue being transparent, as well as glass, but water is not. Heatened gases will not only disturb vision due to blur, but since they glow as well, they'll be like having colour smoke in front of you. On the other hand, lightweight clothes would be far more exposing than they are for us.
Wildlife does not necessary be different from ours, but it can be. Please note that most animals do not actually see the same wavelenghts as we do. Dogs do not detect red light, bees use ultraviolet, and some bats see infrared. It is up to you to question if wildlife for that species share their vision or is as wide as ours.
Sociologically, there are wider implications. Sexual arousal and lies would be more difficult to hide, since they cause an increase of body's temperature, which would be quite visible for this species.
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Seeing 'heat' is really just viewing a different section of the electromagnetic spectrum. Similar to how many insects (especially bees) tend to see well into the ultra-violet side of things.
Different items absorb and release heat differently, while it is unlikely that a infrared vision would have the detail of 'visible' light you would still get stuff. Look up images of infrared. you can see gradients and intensities, (granted they are usually painted with colors in our visible spectrum but it still gives an idea.
Heat will not be absorbed or released evenly on any object or room, though a room where everything is exactly the same temperature would be very limiting, kind of like putting us in a dark room or say a bright white one where everything is the same color as the ambient light, very difficult to move around in.
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Assuming the hypothetical being (HB) had 2+ eyes or reasonable spatial visualization, the HB would see as if the entire world were monochromatic (black/grey/white) but could still discern three-dimensional objects just as you can watch a black and white television show and realize that part of a wall is, in fact, a door.
Additionally, there is a significant enough chunk of spectrum in the IR band that the HB could possibly see "colors" in a completely different (but adjacent) spectrum than what humans consider "visible light". Think of what was shown as the predator's vision from the movie of the same name.
In either of these cases, warming the door handle would be equivalent to making the door handle glow and cast its own light, reflections, and shadows.
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User @bowlturner makes the fundamental point.
There is additionally the issue of colour.
Our eyes have evolved to "see" that narrow range of electromagnetic radiation we call optical light. Within this range, we differentiate between (essentially) three different sub-ranges that we call *red*, *green*, and *blue*. These colours help our brains to fill in the details when we look at our environment. However, these colours only exist in our mind, they do not exist in reality.
We see an object as red if that object reflects the red spectrum but absorbs the green and blue spectrum. Mixed colours like brown come from a mixture of red and blue (?). Etc...
If our eyes had evolved to detect different wavelengths, then we would most likely have evolved colour sense in a similar fashion.
Finally, "heat" covers the widest of spectra. The sun produces highly energetic (short wavelength) radiation in the form of heat, while the friction between my fingers and my keyboard produces only a low energy (long wavelength) heat.
**EDIT** Elaborating a bit on my final point. To see heat across the full spectrum of electromagnetic radiation would mean seeing **everything** : Gamma rays, X-rays, ultra-violet, optical, infra-red, microwave, and radio waves. I may have missed some.
**EDIT 2** What I should have said in the first place is that all electromagnetic radiation has a property which we call *heat*. In this sense, what we see with our eyes is *heat*, namely that heat which is present in a narrow range of wavelengths from the electromagnetic spectrum.
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It is very likely that their body language would incorporate temperature patterns and signals. For example a warm smile could be literally a warm smile. An agressive action might be accentuated with a flash of heat. You will see things of this nature in squid, octopi, and cuttlefish where visual information on the skin accentuate posture in conveying information.
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"Infrared is heat" is a simplification. At a given temperature a particular spectrum of light which excludes any frequencies above a particular limit, quickly ramps up to a peak, and then trails off through the long frequencies.
The visible frequencies are the peak at temperatures in the thousands of Kelvins.
We can think of humans as having a "visible" range of temperatures as well. Those temperatures where we might have some sort of meaningful direct experience of them. Those temperatures are in the rough vicinity of 300 Kelvins.
So we have a mismatch. By the time we start seeing any visible light, we are well into the range of ridiculously hot things that will cause immediate, significant damage to us if we touch them, starting with things like the red of stove heating elements and going up from there.
Infrared is a wide swath of the spectrum. Much wider than the visible spectrum. Temperature wise, it starts down below the range we're comfortable with, all the way up to where your stove starts to glow red.
Since the lowest frequency infrared overlaps our range of "normal temperatures" we call it thermal infrared. Higher frequencies are far infrared, then mid infrared, and finally the highest frequencies are near infrared.
So we already see heat in the same way thermal imaging does. We just see much hotter light. Light from the sun. Of course we can see light that doesn't come from heat as well like fluorescent light bulbs, and thermal IR can be produced by other means than incandescence as well.
Now it's important to note that if you are are about the same temperature as the things whose thermal infrared you want to see, you are going to be generating a great deal of light. Any focusing optics that are part of your body will be emitting light you can see. Even the very photoreceptors would be emitting light that would trigger themselves. This is why early Thermal Imaging systems, had to be cooled to below the temperature range of the heat they need to see. Now, as long as we know the amount of interference, we can filter it out electronically, but cooled sensors are still better.
So, sensing heat in your own body heat range is a highly improbably evolutionary development. There's no benefit without a filter, and no reason to develop the filter without the capability. There may be some especially odd path where some other capability was re-purposed like an ability to actively cool the surface, although I can't think of any use for that either.
Life built around a solvent with a lower freezing temperature than water like ammonia or methane might well end up seeing in what *we* consider thermal infrared. They would probably regard us the way we would regard aliens that live in molten metal and would not think of their own vision as being 'heat vision' To them, "normal hot things" would emit even lower infrared, or high frequency microwaves.
If things with a significantly higher temperature than you are important, you can get some level of radiant heat sensor. Pit Vipers for instance have this ability for detecting birds and mammals, although the capability is at best "something warm is in front of me" rather than vision.
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[Question]
[
Humans wear gloves to protect our hands from dangerous or just unpleasant substances, in exchange for some decrease in sensitivity (and sometimes also dexterity, depending on how thick the gloves are).
Now, consider an elephant. It manipulates things with the tip of its trunk... which it also uses to breathe, and suck up liquids, and blow on things. Its range of functions is considerably greater than that of a human hand, so covering it with a simple mitten would seem to be a much worse trade off--and putting nostril holes in the mitten would fail to protect sensitive nasal passages in many situations.
So, what does a useful glove look like for a more-intelligent elephant that needs protection for, e.g., working in a foundry, or a chemistry lab, etc.?
[Answer]
Don't put the horse before the cart - ask first what kind of glove can an elephant MAKE?
Intelligent elephants (intelephants?) are going to have a very different relationship with fabrics to humans. For one thing, they aren't likely to have as many options - Leather, vellum and other heavy duty materials are by-products of being omnivores who eat other animals and thus end up with skins and furs to use for other purposes. There are some alternatives - Burlap, which I originally assumed was a kind of leather is in fact plant based, and of course cotton can be be treated to take on extra heft, but the point is they will approach the whole idea of fabric from a different angle. I can stretch my imagination to allow Elephants to domesticize other animals, giving them access to wool or silk, but systemized slaughter and skinning just doesn't seem to fit.
Furthermore, the fabrics they do use will be used differently. Knitting, sewing and weaving as we know them have all been optimized for two hands with thumbs. Elephants will come up with their own methodology to fit what comes naturally to their trunks. I feel like their textiles will end up being circular rather than rectangular, and there may be other distinctions as well.
Meanwhile, there are also going to be options available to them that aren't as realistic for us. Elephants are already going to be used to getting mud all over their trunks, so coating the lengths of their trunks in a resistant material won't feel icky or weird. Early civilizations will probably use unbaked clay or maybe processed tree sap or resin, but as they develop chemistry, more resistant substances can be developed. What I'm imagining now is that they'd temporarily plug their trunk, dip it in what is essentially a resistant coat of paint, let that set, and then get to work. This just seems all-around more convenient and natural than imagining how an elephant might design, make, put on and take off some kind of clothing for its trunk.
[Answer]
**NosePods‚Ñ¢**
They have tubes inside the gloves that fits their nostrils like earpods for nostrils. They can put the other end behind their ears so that way they don't have to breath through their mouth to risk toxic chemicals getting in their lungs. Also you can filter the other end and use NosePods‚Ñ¢ in other dangerous environments that doesn't actually require gloves but still toxic or with contaminated air.
[Answer]
Elephants can breathe through their mouths, they do it all the time when their trunks hold water, for drinking or spraying. (They can drink with their mouth as well, in fact baby elephants only drink by mouth; they put their head half under the water, and breath through their trunk to drink.)
In the winter I can breath through several layers of closely knitted yarn that protect my face; a ski mask and a double-wrapped scarf. If you just want a glove on the trunk to keep it warm, or to act like a pot holder.
You wouldn't need that for something like an armored glove the elephant used in battle; those are also typically porous and breathable.
If you really want a fully closed glove on the trunk for some reason, the elephant would naturally and instinctively breathe through it's mouth. If you really wanted to, you could provide ventilation by running some air-tubes up the inside of the glove (attached to the glove), tip to cuff, to allow breathing in and out.
But elephants can just breathe through their mouth, they do it every time they take a drink with their trunk!
[Answer]
**Flanges**
[](https://i.stack.imgur.com/kx4yk.jpg)
Elephants can make a pinching motion with the tip of their trunk, like how a human hand can pinch with the four fingers held together pinching with the thumb. [See the pinching motion in action.](https://vp.nyt.com/video/2021/06/01/93980_1_01TB-TRUNKvid3_wg_1080p.mp4)
The most sophisticated type of glove has:
1. Tubes running into the nostrils and back up the length of the trunk to allow breathing.
2. Padding on the body of the trunk and also the sensitive tip.
3. Hardened plates (flanges) to still allow the *pinching* motion of the trunk to work. Imagine you had fireproof fake nails:
[](https://i.stack.imgur.com/hpY7k.png)
Yuck. Anyway you could use these nails to handle small hot things without touching them with your fingertips. For example you could pull out a wire rack from the hot oven.
Now imagine you have asbestos gloves with slits cut out to let your fake nails protrude. Then you are fireproof with more dexterity than just the gloves. The elephant glove is similar except it only has two heatproof flanges rather than five.
[Answer]
>
> So, what does a useful glove look like for a more-intelligent elephant that needs protection for, e.g.,
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No different from humans, gloves would be specific to the tasks. People ride motorcycles with mittens. Work in the garden with gloves to protect them from thorns, others to protect from heat, dive, go into space etc. There is no one glove solution.
When you stop for lunch at a factory, you remove the safety gloves before eating or anything else. You only wear them for the task.
Elephants were in wars with armour, if you could teach them to sword fight, they would have attached swords to the trunks.
[Answer]
# Condoms
It is best to check in real life what kind of options we already have. Condoms might try to protect for different reasons, disease and pregnancy, but their goal is to separate two 'objects' from each other, including any liquids or other stuff containing disease.
We can try to apply this to an elephant. It can roll down a condom, which I'll further refer to as a plastic glove, over the trunk on the outside. The inside can be tricky. The glove has 2 long plastic flexible tubes attached, good for each nose. These can be sucked in by the elephant, creating a sort of laminated inside, protected like a condom would do.
If the glove has sealed ends it has to be sucked in together with whatever needs to be handled. The elephant knows the limit, as when it reaches the full extent of the glove the resistance to further sucking spikes. As it can breathe through the mouth it should have no problem moving it to a different location. It can then blow the contents when needed. The glove can get folds and be difficult to suck in when doing this. That increases the chance of breakage, but depending on the safety thickness we can make very safe options. I understand (similar to) condoms are used in survival kits on open seas, as they can expend to many times the size with little chance of breaking. This way they can hold sea water that'll be treated to be drinkable (never had the chance to fact check this though).
An alternative for less dangerous stuff is an open end. This way the elephant can smell it and inhale at least some of the contents. On the end can be a filter or even just tiny holes for extra safety. I assume an elephant feels until where it sucked the contents and can stop before it reaches the hole. That way it is easier to suck stuff in and blow it out, as the glove can stay fixed in the trunk.
Gloves and condoms can give plenty of fine touch sensation if high quality. Though cheaper gloves like some heavy duty ones I have for cleaning can still function great when handling stuff. Even though it's very clunky.
Though with much more dangerous materials we can also go the smart way. In many hazardous materials labs we use machines, mechanical arms or even something as simple as a trolley or a drum to move these materials. A smart elephant wouldn't come close to these materials.
[Answer]
**Long tube with air-filter**
This could be a long tube made of
* rubber
* leather
* flexible plastic
(depending on the place of use) with air-filter at the end as shown
[](https://i.stack.imgur.com/W4kuR.png)
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[Question]
[
With current (early-21st century) technology and science level, suppose that a new fruit is discovered on some island. This fruit is imported and marketed around the world.
Unknown to anyone, this fruit extends the life span of those who consume it. The more regularly you eat this fruit, the longer your life will be. I'm not a biologist, so I can't really define the method by which this is done, but something along the lines of slowing the aging process, e.g. by allowing more cell replications than the usual limit. So the earlier in life you start consuming this fruit, the longer your life will be - in some cases even double your life span.
My question is - will this property of the fruit be discovered at all? If so - how will it be done and how long will it take?
Longer life spans can easily be attributed to advances in medicine and science, so I'm not sure how easily this will be traced back to consuming this fruit.
It might depend on how common this fruit is going to be, so please specify in the answer if the identification method requires common/rare consumption.
[Answer]
Without some significant immediate effect, such as erasing some of the obvious signs of aging (wrinkles, liver spots, etc) within a short period of time, the life extension properties won't be noticed at all for several decades, if at all.
After 10 years, a few people will have lived ~5 years longer than they otherwise would have. That's well within the normal variation and will go completely unnoticed.
20 years after the fruit is introduced a larger group of people will have lived an extra 10 years. Since they were already in the 'very old' group at the start, and many of their peers have succumbed to illness, pre-existing conditions and so on. While the age numbers are starting to reach a statistical threshold, the numbers are still quite small. People might start to notice that a lot more people are living past 100 years, but the average age of death has been increasing for centuries so it's not really big enough to be *interesting.*
30 years, and now we're getting to interesting territory. The record for the oldest person in the world has been broken a few times. The average age of the top 100 oldest people in the world goes from ~115 years (I know, right?) to > 120 years. This is a major statistical anomaly, but one that might not be noticed by anyone not actively studying the statistics of age.
40 years on and the odds are fairly high that a person will reach 130 years of age for the first time. People start to take note. Studies are begun to identify the causes, but with 40 years of medical advances and so on it's going to take a while before someone even realizes that the numbers started 4 decades back. Rigorous statistical analysis will identify the time-frame of the cause, then a bunch of studies will be done to identify what changed around that time. With thousands of factors to consider it's going to take a while. They'll probably find it eventually, but it might be 50 years after introduction before it becomes clear that the fruit is the source of the increased lifespan.
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There are a few ways this can go horribly wrong.
## GMO Hell
Meanwhile, the fruit has become so valuable as a desirable food crop that the agricultural industries have already made a number of changes to the genetics of the plant. They've made the fruit larger, grow faster and so on. In the process of breeding the plant for these desirable traits they destroyed the genetic sequence that produced the specific enzyme that increases the lifespan. While the original genome still exists in a small number of plants, the commercially modified version is by far the most common. Only a handful of small fruit farms - specializing in the purest of organic, natural foods - still produce the original fruits, and only their customers are getting the benefits. Suddenly that anomaly in the age statistics flattens out and drops back to historical norms, with only a tiny increase over historic trends.
Having failed to identify the cause, most of the researchers will eventually be moved to more profitable work.
If this happens then it's going to be a long, long time before anyone discovers that the original fruit, now only available from a handful of organic hobby farms around the world, is anything special. Probably by accident.
### Exclusivity
Maybe in the first few years someone starts using the fruit as feed for lab animals and notices that mice who eat the fruit as part of their diet tend to have fewer degenerative diseases and live longer on average. They start a study, feeding various parts and amounts of the fruit to different groups of rats and figure out the most effective numbers. They end up with a 6 year old mouse, twice the average maximum age of a mouse in lab conditions.
Of course humans being what they are the next thing that happens is that someone publishes a detailed - and entirely false - paper claiming that the plant is actually toxic to some fraction of the population and is in fact to blame for the increase in some obscure health condition. Governments move to restrict the sale of the fruit, eventually banning it altogether as a foodstuff. Federal troops start burning crops again, and nobody really complains because it's just some odd fruit that is nice and all, but if it's actually toxic then better to get rid of it.
A few pharmaceutical companies spend billions of dollars trying to isolate the compound, while a small number of powerful, wealthy people are the only ones left in the world who have access to the raw fruit. Within a decade the only plants left are the ones on special production farms where the fruit is grown for 'medical research' purposes. The largest pharmaceutical companies begin to sell age extension products at a price that only the top 0.5 percent of the population - and the CEO of the pharmaceutical company - can even consider. It's the most expensive fruit juice the world has ever known.
### Free Access
Letting the effects stack up until they become statistically noticeable is going to take a long time - at least 20 years before it becomes significant enough to pique someone's interest. To get it noticed earlier you're going to need to see the effects either on a population of short-lived animals (like the lab mice) or in an existing population of humans that have been eating the fruit for a long time. Let's say there are native tribes who live in the area the fruit was found, but don't have much interaction outside of their tribal groups. They actually live for well over 150 years on average, but nobody has ever been able to figure that out. Eventually an anthropologist studying one of the tribes figures out that some of the village elders are way over 100 after they start talking to him about some major event they witnessed and he figures out how long ago it was.
This leads to studies being conducted and the world finds out about the small tribe in Papua New Guinea or the Amazon Basin that lives to be 150 years old. Researchers spend years trying to work out why it is happening, and eventually figure out that the ones who live the longest are the ones who regularly eat the fruit. The ones who don't like the taste or don't have access to the fruit due to geography have normal life spans for other tribal groups in the region.
By the time the cause is discovered it is too late for the world powers to cover it up. The fruit is already out there, exported to various parts of the world as a new foodstuff. It grows well in a variety of environments, appeals to the majority of people and becomes a favorite food for many. Juice from the fruit starts to out-sell orange juice, and orange-producing locations in various parts of the world transition to producing the new fruit. Before anybody knows about the medical properties of the fruit - and the juice as well - it has become far too common to be suppressed.
Within 50 years the average age of death from age-related causes has risen significantly. People are staying fit and healthy for much longer, average retirement age has gone up 20 years and the world's population has risen by 80% over even the most generous estimates, and it's getting worse. World poverty levels rise out of control, infrastructure designed for the prior predictions proves insufficient and systems fail. Food production can't keep pace with the population growth. Disease and famine claim millions of people a day, violence accounts for millions more, and still the population climbs. Some few people try to save the world from itself, but end up just causing more problems.
Pretty soon the world starts looking like *Mad Max* had a hate child with *Idiocracy.* *Brave New World* was the midwife.
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I'm sure there are some good ways this could go, but I'm really not feeling positive about it. Perhaps a borderline misanthrope is not the best source of ideas here. ;D
[Answer]
The property will probably be discovered, as the large use base will dramatically increase the chances someone stumbles on the effect.
It's very likely that somebody will notice it starting from a pet, i.e. giving this fruit to a rodent, like a hamster or a guineapig or some cage bird. Since these animals are way shorter lived than us, an increase in their life span will be easily noticed, until somebody will start to look into the rumor to see if it has any scientific foundation. For some really clever observer it might simply take the observation that fruit flies born from this fruit live way longer than their relatives born from other fruit.
It's sort of a similar path with respect to how dangerous substances are identified.
[Answer]
**While I find @Corey's answer more or less plausible, it depends on the specifics**
So I will present a counterpoint how this fruits property will be discovered. First of all your part about "will be marketed around the world": no, not really. Unless it tastes good, is grown very cheaply and does well with ripening-in-containers etc. it won't see any widespread distribution. It'll be available in some niche exotic-fruits-shops, but nobody but people into that will buy it.
Which changes when some contact with the local tribe on the island is made (this time the ethno-protectionists lost), and it is discovered that they all live for 150 years regularly, despite the primitive level of medicinal care. A wild research hunt begins on the island, and the fruit will eventually be singled out (especially if the benefits are somewhat tangible, because then some exotic fruit connoisseurs will notice the subtle changes / boost in health etc., and work it backwards from there. Any "superfood" eventually gets some formal research when the hype becomes big enough, and imagine the shock if all the clickbait is scientifically proven!
[Answer]
**Rare fruits for elite class only.**
If the fruit is found on a distant island and is native to the place, then it's rare. And do you know what happens to the rare things in our world? They are strictly limited to the rich and elite. These rich and elite have all the resources and usually make sure to stay fit and get their body check-up on a thorough and regular basis, by highly trained doctors.
So, It happened one day that an old man was getting his checkup done and the doctor notices unusual healthy cells, same as he notices in his grandson. Then he start making inquires about eating habits and soon will reach to the conclusion that a new fruit is added to the diet.
A few more studies, experiments and voila, research papers, and noble prizes. :)
**Note:** Even if the fruit can essentially be grown anywhere on the planet, the rich (and the merchents too) will make sure to keep the fruit rare and limited to the island.
[Answer]
# Already happened
Malnutrition has been a major cause of death ever since the dawn of humanity. It still kills a lot of people prematurely today. Notice that this is different from hunger; A middle age, "well fed" citizen from any developed nation nowadays that dies of hamburger-clogged arteries is not hungry, but malnourished.
One form of malnutrition is poor vitamin intake. The "vita" in "vitamin" actually stands for "vital". One condition related to poor intake is called scurvy, a well known disease that killed every other sailor during the Age of Sail. It is caused by a vitamin C deficit. Minor forms of scurvy would also affect people who never sailed in their life, as long as they would have a poor intake of vitamin C.
If so happens that all citric fruits are a rich source of that vitamin, so as long as you consume **oranges, lemons, tangerines or grapefruit** regularly, you are mostly protected from scurvy (and many other conditions). Vitamin C also regulates a lot of bodily functions, including collagen production to immunity, so having a proper intake will also increase your lifespan and chances to live to have offspring in other subtle ways.
In many places during old times, having access to such fruits was a luxury - you either had access to an orchard or you had to find your supply of vitamin C somewhere else - for example: raw liver, if you are into that (though that has its own problems). Once electricity became commonplace and refrigeration became a thing, you could keep fruits fresh for long spans. Industrialization also made them cheap and widespread.
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Sorry for all my rumbling above. As for the question proper:
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> will this property of the fruit be discovered at all?
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[From Wikipedia:](https://en.wikipedia.org/wiki/Scurvy)
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> In 406 CE, the Chinese monk Faxian wrote that ginger was carried on Chinese ships to prevent scurvy.
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> The knowledge that consuming foods containing vitamin C is a cure for scurvy has been repeatedly forgotten and rediscovered into the early 20th century.
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[Answer]
You make the statement that advances in science and medicine could be easily identified as a contributing factor to increased lifespan. There's a few things I could say about this, but the first would be to ask how? I would not necessarily associate longer lifespans with advances in medical technology per se. I think there are an "extremely high" number of factors that, both nuanced and opaque, contribute to longer life. 2020 saw a decline in the average lifespan for example. Was this because technology and medicine regressed? The [probably] obvious answer is no; it had more to do with statistical deviation due to a six sigma event. Discarding that data point however still doesn't explain how someone born in 1809 lived to be 95 years old at a time when the average was much lower than 95.
And then of course there's the question about whether or not eating this fruit would be considered an advance in medicine and how that would be measured within the larger data set.
Since the original question is about how this strand of spaghetti would be separated from the whole, the traditional answer would be that it could only be done statistically in a controlled experiment with a large data set and a control (those who didn't eat the fruit). That would provide the essential data needed to answer the question as to whether or not this singular lifestyle adaptation produced the results that were expected (increased longevity).
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[Question]
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A sentient species of water-dwelling aliens achieve space-flight.
Their living quarters contain water [no free gases].
They have evolved over millions of years to regulate their buoyancy at will.
**Question**
Will they be able to withstand much higher acceleration than an air-dweller.
**Reason for question**
If they maintain neutral buoyancy they won't sink to the bottom and they won't float to the top. Will they merely experience an increase in water-pressure? They are used to dealing with extreme changes in pressure when they dive deep and return to near the surface of their ocean. Therefore surely high acceleration won't inconvenience them.
**Notes**
If preferred you are at liberty to discuss the difference between turbulent takeoff through an atmosphere or smoother acceleration in a vacuum. I originally intended that the acceleration would only be along the axis of travel.
[Answer]
The answer is no; they'll not even be able to withstand normal human acceleration limits. Not because of the pressure (induced by *constant* acceleration), but because of the momentum change in their environmental medium (caused by the sudden changes in acceleration, especially at the beginning of the launch).
A simple experiment that explains this (don't try this at home *edit - for ethics reasons, not because I'm worried about the results*); take a small fishbowl, and put a lizard in it, seal the top and shake it. Afterwards, the lizard will be sore and more than a little pissed off at you, but it will be alive. Take a fishbowl full of water and a goldfish, seal the top and shake it. Your fish will be dead, almost instantly.
*Further Edit - Another analogy that you might consider here is the shockwaves caused by [Blast Fishing](https://en.wikipedia.org/wiki/Blast_fishing#Description), which also causes large changes in momentum over a short time.*
Why? Because water is a non-compressible medium (and it's very dense). In any collision, the most deformable object is the one that also absorbs as much of the kinetic energy of the impact as it can. This is why modern cars are so 'flimsy' by comparison to older cars, and consequently so much safer. In an accident, the car breaks so that it absorbs as much of the kinetic energy as it can before transferring the balance to you. Older, more rigid cars don't do that and as a result many people found out what being the most deformable object in a collision actually meant right before they died.
Air is very compressible (read as deformable in this answer) meaning that it can absorb a lot of energy by comparison to its mass. Unfortunately, that doesn't mean much because its density is very low, so the two tend to balance each other out. Still, our lizard only has to worry about being the deformable object every time he hits a wall on the fishbowl. Strap him in, and he's going to fair a lot better (hence seatbelts).
Your fish on the other hand is in a medium that is not only non-compressible, but very dense. This means that it's going to take a LOT more energy to launch all that water because of the mass, and more importantly, the sudden acceleration change is going to throw all that non-compressible mass your way as soon as you start your acceleration, likely crushing you. This also means that any form of maneuvering in space or engine issues that cause significant vibrations or shaking are of concern because of rapid and large momentum changes other than the constant acceleration along your line of axis.
The problem with the reasoning in your question is that buoyancy is not the same thing as pressure. Buoyancy is *relative* density, whereas pressure is the force of a mass being applied against you (this is a simplification but functionally correct). Sure, the pressure deep in the ocean depths can be extreme, but it can also be introduced to your creatures slowly - they don't instantly go from 10m depth to 1000m depth, and it would kill them to do so. But, in a rocket, that's exactly what you're asking them to endure.
They'd be far better in some form of gel, that allows them to breathe but is lighter weight and can absorb most of the impact for them. Water is not the best medium to find oneself in when face with sudden acceleration.
[Answer]
Assuming that the spaceship is totally filled with water (i.e. no air gaps) then there will be two effects experienced by the aliens.
Firstly, the effect of the acceleration on the water mass in the spaceship. For any significant acceleration there will a gradient in the water pressure along the axis of acceleration. Assume a 200 m long spaceship, at 10 g acceleration. At the 'front' of the ship, the water-pressure will be negligible, at the back end it would be equivalent to that found on Earth at a depth of about 2 km (around 200 Atmospheres). If the spaceship then decelerated at the same rate there would be an almost instantaneous reversal; of the pressure gradient (now negligible at the rear of the craft and 200 Atmospheres at the front). These pressures would scale up in a longer vessel or with higher accelerations - 500 m long and 20 g would give you an almost instantaneous 1000 atmospheres. Equivalent to almost instantaneously diving to the bottom of the Marianas trench! So if the creature relied on swim-bladders for buoyancy moderation they would be in big trouble (deep-sea fish don't to well when they are dredged up to the surface quickly). Internal baffling in the spaceship could solve this problem but then it would be very difficult to open/close doors and move around during acceleration.
Secondly, there would be the effect of acceleration within the body of the creature itself. Land-based creatures often experience significant local acceleration and jarring as a result of jumping, falling etc, so have evolved so internal organs of varying density are constrained in position against these forces. A sea creature, depending on its normal mode of transport within water *may* not be subjected to these acceleration/jarring effects in its normal life (consider a jelly-fish for example). So if they are used to being cushioned in water their internals may be more sensitive to acceleration than ours.
So the answer would depend on the specifics of the creature. Muscular, deep-diving porpoise - maybe. Floppy, floating jelly-fish - probably not.
[Answer]
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> Will they merely experience an increase in water-pressure? They are used to dealing with extreme changes in pressure when they dive deep and return to near the surface of their ocean. Therefore surely high acceleration won't inconvenience them.
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The biggest problems will arise wherever there are density differences within their body. Think of putting a steel cube inside a mold of jello. As you subject them to higher pressure, nothing bad happens (there are no air pockets to be compressed).
But as you accelerate it, you are changing the forces at the boundary where the density changes. The denser steel cube wants to be at the "bottom" of the pan. As you increase the local gravitational field, the greater the stresses required to maintain out-of-order densities.
Do the creatures have bones? Sensitive, but light organs? Complex organs with multiple tissues of different densities? The greater the acceleration, the greater the forces that appear within them.
In human studies, the greatest damage at the limits reached wasn't with lungs or other aspects of empty spaces, but with the retina. That takes place entirely within an enclosed liquid container, but is still subject to damage at high accelerations.
[Answer]
Yes, they will be able to handle higher accelerations. This has been answered by Steve and AlexP in the comments (possibly others as well)
First, it's useful to turn the question around, why do air breathing creatures suffer from acceleration more than aquatic creatures? Imagine standing under 10g of acceleration in air. Also let's just say your blood is water to simplify things. The pressure increase at your feet:
$$ \begin{align} \Delta P&= \rho g \Delta h \\
& \approx(1000)(10\times 10)(2) \\
& =200kPa\\
& =2bar
\end{align}$$
Whereas the external air pressure increase at your feet:
$$ \begin{align} \Delta P&= \rho g \Delta h \\
& \approx(1)(10\times 10)(2) \\
& =200Pa\\
& =2mbar
\end{align}$$
There is nearly 2 bar of pressure difference between the blood in your feet and the air outside them.
Lots of blood pools in your feet and legs, your heart won't be able to pump it up to your head, you lose consciousness.
If instead of air, you are surrounded by water, the pressure difference between the blood in your feet and the surrounding medium is zero, no blood pools. You stay conscious.
But there is still nearly 2 bar of pressure between your head and your feet, you might worry that your heart has to work hard to pump against that pressure gradient. It doesn't really, provided everything is incompressible. Let's simplify your circulatory system to be a simple loop. It now looks like this:
$${\Huge 0}$$
With your heart as an infinitely thin pump on one side. As your heart pumps water up one side, it is replaced by water moving down the other side. The replacing water arrives at the pump at very very nearly the same pressure as the water moving up - as it's all a sealed closed loop with an incompressible fluid - so it doesn't have to overcome a high pressure difference, as it is effectively being feed water at a high pressure to begin with. This is basically how pressure suits in fighter aircraft work.
Lastly some answers suggest that the pressure changes in a deep column of fluid will kill them, this is true if they are bad engineers. If they build their space ship as a 100m continuous water column, they will have a bad time at high accelerations. If instead they break that 100m into 100 1m high sealed rooms, with no water column to the floors above, then they experience much lower pressure rises. At some point 10cm of water column above them will kill, but it'll take a lot of acceleration.
Provided they use a fluid with similar density to their blood, correctly design their spaceship for high accelerations they will be able to tolerate higher accelerations than land animals. It'll also help if they don't regulate buoyancy with an air bladder like arrangement.
[Answer]
Another factor that hasn't been mentioned yet--water creatures are generally going to be a lot weaker than similar land creatures. A water creature doesn't have to support it's own mass, let alone it's own mass taking a fall.
[Answer]
Yes, so long as they can withstand high pressures they will be able to withstand much higher accelerations than a human could (in air.)
Acceleration is equivalent to gravity, and your intuition may work better thinking of it that way (I know mine does.) Increasing gravity on a canister of water is going to increase water pressure linearly. So for example, if you can withstand 10x the pressure at 1g, you can withstand 10gs of acceleration.
[Answer]
if you want an advanced aquatic like species, just make the homeworld have an insanely dense atmosphere.
the way buoyancy works are (tldr) you need to be less dense than what you are floating in (that's ignoring displacement and stuff)
the density of water is 997kg/m³ while humans are about 985 kg/m³.
now, I know what you are thinking. "if the gas will be as dense as water anyway, why don't I just limit the pressure, and just go aquatic anyway?"
the reason is a running joke in the forums of a game called 'thrive'.
ITS IMPOSSIBLE FOR A OCEANIC SPECIES TO DEVELOP TECHNOLOGY.
combustion is impossible in water. they cant craft metal tools. just.... go to thrive and they will explain it better.
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I'm wondering if Earth would try to keep any colonies we put on other celestial bodies in this solar system to be economically dependent on the mother planet.
Greater distances make 'ruling' more difficult and makes it easier for the ruled to feel the distant government is out of touch with their reality.
So in order to head off revolts or just declarations of independence on colonies on the moon or Mars or else where, would Earth try to keep them dependent for something(s) in order to control them and keep them as 'profitable' colonies however that works out? Bonus, what is the most likely thing to keep the (im)balance of power?
"I owe my soul to the company store..."
EDIT: I know that mining raw materials on Mars and shipping them back to Earth is not likely viable situation that would cause Earth to make/want colonies. However, Mars has a much lower gravity and two tiny moons that you can almost jump into orbit on. It also happens to be significantly closer to the asteroid belt.
So getting the raw materials to make parts for space ships and space stations (or even building the whole thing) could be dramatically cheaper. This could be a huge incentive to not let Mars be independent.
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**We absolutely would.**
Look what happened with America and Great Britain. While independence may be one of America's proudest moments, there is no way we'd let the same thing happen again, not when we're on the other side. No, I'm not saying the US *is Earth* (though some might, 'merica), but there is a good chance that the US will be involved in the colonizing efforts for other planets (assuming the US can increase STEM education and become a leader in science and engineering again).
We'd probably achieve this by first enacting laws similar to union laws requiring the use of Earth sevices. And also by suppressing technologies that would lead to complete independence, like terraforming.
This is actually well explored in "[The Moon is a Harsh Mistress](https://en.wikipedia.org/wiki/The_Moon_Is_a_Harsh_Mistress)" by Heinlein. The Earth government has tried to set up the Moon colonies as being very dependent on Earth.
But in that story (spoiler):
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> There is a rebellion, but it only works because the supercomputer Mike becomes an ASI, and it is able to coordinate the entire rebellion.
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Something unlikely to occur in any real world situation. At least, it's not a miracle that can be planned for.
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> I'm wondering if Earth would try to keep any colonies we put on other celestial bodies in this solar system to be economically dependent on the mother planet.
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**Earth won't feel any need to try**
Given our current level of technology, it is quite plausible that we could send a manned mission to any of the planets in our solar system. The problem is that it would be a one-way mission — it would take significantly larger rockets with a lot more fuel in them (or multiple trips putting fuel into orbit) in order to get to space with enough left over to get to another planet and back. Still, if there was another habitable planet in our solar system, it would be reasonably easy for us to get people there.
However, as you should be aware, there aren't any other habitable planets in our solar system. Both Mercury and Venus are too hot, and everything from Mars on out is too cold. Any colonies on the other planets in our solar system will require high-tech solutions in order to simply survive.
Because of this, any extraterrestrial colonies will be heavily dependent on the Earth for quite a while. What will it take for them to not be dependent? They'll need to be capable of manufacturing everything they need for their survival and for growth.
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Let's use Mars as a concrete example, as it is probably the least hostile. It's atmosphere is not breathable — way too thin, and way too much CO2 in it — but it could be compressed and added to the air in a greenhouse in moderate amounts. This would increase the total air supply available to the colony. The soil is reasonably close to what plants need to grow, and it wouldn't be too hard to either bio-engineer plants that can handle Martian soil and/or treat the soil.
The biggest obstacles will be getting enough electricity in order to process enough raw materials to be able to enlarge existing structures and build new ones. Iron is quite common, but smelting pure iron from ore takes quite a bit of energy. At first this will happen using solar energy, but when they can get nuclear energy going things will go much faster (now that I think of it, it would make sense for them to design a combined nuclear reactor and smelter). There's uranium on Mars, so it doesn't have to be imported from Earth, but without being able to just pump regular atmosphere down into mines, mining will be harder than it is on Earth.
All hydrocarbons (oil, plastic, rubber) will need to be made the hard way — taking organic material and processing it.
It's likely that colonies will expand primarily underground where you can build without needing to use significant amounts of airtight materials.
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Now that I've shown some of the reasons why it will be hard for an extraterrestrial colony to be self-sufficient, how can the Earth "profit" from owning such a colony?
*It can't.*
It's going to take a significant amount of time and/or imported materials in order to get enough infrastructure set up for the colonies to be self sufficient, making for huge upfront costs. Even then, what economic or political advantages could a colony provide? Anything that could be produced on Mars could be produced on Earth, and even if Mars' lower gravity made it easier to produce the shipping cost would easily overwhelm that advantage.
Also, suppose that the colonists on Mars figure out how to make something new that we don't have on Earth yet? As I've said, it will be quite expensive for them to expand their available area. Even with a head start of a decade, it would not take Earth long at all to reverse engineer whatever it is, figure out how to manufacture it, and build up even larger factories to produce it at a much faster rate.
One thing that could tip the balance in Mars' favor is if the planet has been terraformed. However, that will be an absolutely massive undertaking - with its atmosphere currently at 1% the density of Earth's, an enormous amount of gas will need to be produced. That undertaking will take millennia - easily long enough for any ownership issues to be worked out.
A colony doesn't provide any political power, either — suppose China had a colony on Mars right now, and the US and China got into a war (whether military, trade, or whatever). What's the colony going to do? Shake their fists at us?
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There *are* useful things that Mars can provide, but none of them are really dependent on a colony belonging to Earth. If humanity continues to grow, we'll eventually start running out of room on Earth. Living space on Earth could become so expensive that moving to Mars is actually reasonable. This would work best if there is already a colony on Mars, but it doesn't really matter if that colony belongs to a particular Earth country or corporation or not.
Another possibility is inventions. I've already mentioned some of the difficulties I can foresee a Martian colony needing to overcome. In particular with hydrocarbons, there will be quite a bit of interest in developing new strategies to process waste biomatter into useful hydrocarbons. These new techniques could prove quite useful on Earth as well.
However, none of these things require being *on* Mars, just *going* there. The US space program has resulted in quite a few useful inventions (such as velcro), but they have been a result of solving the problems of going to space rather than some product of being there. Similarly, I believe that going to Mars or other planets will result in a number of very useful inventions, but none of them will actually require anything from the other planets.
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I'd vote "**no**".
As others have noted the colonies would start almost entirely dependent on Earth. Not such for their economy, but for their survival. As such it would be redundant to deliberately try enforce dependency and the priority would be to create robust self-sustaining economies that do not collapse with all the investment so far lost, if the sponsoring nation needs to make budget cuts.
In general it is better for the colony to have enough autonomy both politically and economically to be separated from issues back home unless they actually do concern the colonists. The cheapest way to avoid costly wars of independence is to give the colonists a fair deal. And to simply give them independence if they want it.
It is vital to remember that colonies are not established solely for the prestige of owning more land. It has happened, but mainly the purpose is to give the sponsor access to valuable resource and to deny it to the competition. In other words trade with the colony. Actually controlling the colony is generally just an unavoidable expense. More of the work you can push to the locals, better off you are.
More hypothetically, if the current belief in reasonably free trade being most efficient remains in effect, **all** colonies will be accessible for trade regardless of who controls them. This means the main benefits of controlling colonies would not exist. Losing the colony to competitor would be embarrassing so steps would be taken to avoid it. Having the colony declare independence would probably save money and would be encouraged. This is very different from the era of European colonialism when the dominant economic model was either [mercantilism](https://en.wikipedia.org/wiki/Mercantilism) or [protectionism](https://en.wikipedia.org/wiki/Protectionism).
Under either of those models it would make sense to control the colony and its economic activity. But while arguments for limited forms of protectionism remain viable, the kinds of restrictive models where economic control of the colony would make sense are generally seen as discredited.
Basically, such heavy restriction on trade and economic activity is too counter-productive and the main loser would be the sponsor who made the initial investment in the colony. It would actually make more sense to encourage economic independence and diversity since that would encourage economic growth in the colony and maximize return of investment for the sponsor.
Of course, politics and rationality do not necessarily mix. Politicians often take great pride on acting on values which is just an euphemism for: "Too lazy to think and do not really care about consequences, so let us decide based on my gut feeling."
[Answer]
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> So in order to head off revolts or just declarations of independence on colonies on the moon or Mars or else where, would Earth try to keep them dependent for something(s) in order to control them and keep them as 'profitable' colonies however that works out?
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I don't think so. The first problem is that colonies can't be profitable so long as they are dependent on Earth. The cost of delivering supplies is too high. They need to be self-sufficient in order to be anything other than a huge cost sink.
This is essentially the same problem that comes up in [questions that ask what Mars would trade to Earth](https://worldbuilding.stackexchange.com/q/1064/2113). The general answer is not much. If Mars has nothing that it can profitably send to Earth, then why would the Earth try to keep the colony dependent on it?
The Earth would be much better off putting the resources it could use maintaining dependence to use on the Earth. The return will be much better.
The Moon might be a slightly better option for a dependent colony. It's closer and could send products to the Earth more cheaply. But the truth is that the most effective place to put a dependent colony is on a space station.
The space station can send products to the Earth the most cheaply and doesn't require pulling anything out of a gravity well. It can get raw materials from the asteroid belt. The only thing that the Moon could do better would be in turnaround time. Mars doesn't even have that. Is the occasional rush order enough to justify the expense of maintaining dependence for a colony?
All that said, the Earth or a government on Earth may not do the economically sensible thing. Maybe they will want to keep the colony dependent for whatever reason. But history suggests that they won't succeed.
The colony won't like being dependent and will want self-sufficiency. Radicals will attempt to create the dependence causing good or goods. Or source from somewhere other than the Earth. They'll point out that the system is economically stupid and unfair. Because so many Earth countries have formerly been dependent, there will be sentiment in favor of them.
Perhaps the Earth will go so far as launching a war to maintain the system in the face of rebellion. Again, economically stupid. If the Earth wins the first round, then the next round will be terrorism. No one wins that, but it makes an already economically stupid system even dumber. Eventually the Earth will either destroy the colony entirely or give up on maintaining dependence.
Personally, I think it would be better to just allow the colony independence when it wants it. Whether that view will win out or not, I don't know. There's plenty of historical basis for understanding the problem. But maybe they'll hope that this time will be different.
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It entirely depends on the answer to one question. **How cheap is travel to the colony site?**
On the hard SF end of things, with currently known or near future technologies, there's absolutely no possible economic incentive to try. There's nothing the colony will have to trade that's even remotely worth the shipping costs. Space is expensive, $20K per Kg to low earth orbit or more.
If travel is cheap, this may end up much more like the colonial era, where some form of phelbotinium unavailable on earth is traded. I feel this is unlikely however, for reasons well expressed in other answers. Particularly @Ville Niemi
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The main issue that might incentives Earth to control the colonies is the fact that orbital and interplanetary velocities are so great that even a small spacecraft, cargo pod or even space rock could strike Earth with a devastating multi kiloton or megaton impact. For example, consider the body which disintegrated over Russia recently:
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> The Chelyabinsk meteor was a superbolide caused by a near-Earth asteroid that entered Earth's atmosphere over Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC), with a speed of 19.16 ± 0.15 kilometres per second (60,000[5]–69,000 km/h or 40,000[5]–42,900 mph).[6][7] It quickly became a brilliant superbolide meteor over the southern Ural region. The light from the meteor was brighter than the Sun, up to 100 km away. It was observed over a wide area of the region and in neighbouring republics. Some eyewitnesses also felt intense heat from the fireball.
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> On account of its high velocity and shallow angle of atmospheric
> entry, the object exploded in an air burst over Chelyabinsk Oblast, at
> a height of around 29.7 km (18.4 miles, 97,400 feet).[7][8] The
> explosion generated a bright flash, producing a hot cloud of dust and
> gas that penetrated to 26.2 km, and many surviving small fragmentary
> meteorites, as well as a large shock wave. The bulk of the object's
> energy was absorbed by the atmosphere, with a total kinetic energy
> before atmospheric impact equivalent to approximately 500 kilotons of
> TNT (about 1.8 PJ), 20–30 times more energy than was released from the
> atomic bomb detonated at Hiroshima.
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Now the governments of Earth are not going to take an implied threat like this very lightly, and will probably have very strict control over any spacecraft in the solar system, even to the point of having the ability of the Space Patrol to override computers or initiate self destruct sequences over spacecraft considered to be "rogue" or even wildly off course.
The other means to control the colonies is the fact that all life depends on phosphorus, and there seems to be a very limited supply of that element easily accessible outside of Earth. Potential rebels can be brought to heel by simply choking off the supply of phosphorus and watching the life support systems stagnate. There is very little that can be done about this, and since Earth also controls the movement of spacecraft, you can't just go prospecting on handy asteroids trying to find a replacement source of phosphorus.
Would be rebels will have a very difficult time of things, although Earth will be very generous in allowing colonies to develop economically so Earth won't be stuck paying for them. The simmering rebellion on Mars trope probably won't play very well in the future.
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I don't think they'd have to try too hard.
Most other planets or moons in the Solar System are naturally inhospitable to human life; too hot, too cold, no water, ambient atmospheric pressure too high or low, etc etc. Establishing a colony on such a planet requires a lot of supplies and technology, which is only going to come from one place in the Solar System.
For instance, a colony on Mars, even knowing liquid water still flows there, would require many hundreds of tons of starting material to allow for plant life even using the local water. Martian soil is rich in iron, sodium, potassium and several other plant nutrients, but is poor in nitrogen and carbon relative to what Earth plants would require to survive. This means, in addition to requiring shelter from the Martian day's extreme heat and an atmospheric pressure that won't cause the plants to freeze-dry, practically all the organic and nitrate compounds required for plant metabolism would have to be imported, likely in a combination of natural and artificial fertilizers (compost, ammonium nitrate etc). There is carbon dioxide present as dry ice near the poles (where the temperature is stable enough and the pressure low enough that the CO2 solidifies), which we might be able to tap and which would provide additional building blocks for Earth plants to grow and reproduce (as well as allowing us to create oxygen gardens to avoid having to constantly import it from Earth's atmosphere). The soil is also fairly alkaline and chlorinated; nitric acid would be an important compound to balance pH and add additional nitrates using the soil's natural alkali metal content.
All this material would represent an enormous expense on the part of whatever organization was sending it to Mars. Not just the material itself, but the rockets and fuel needed to get it out of Earth's gravity well and then to Mars, which is going to represent over 99% of the mass placed on a launchpad at the Cape or other suitable location. The resulting colony would, according to most current law regarding space, be the property of the organization that put it there.
The Mars colony, in turn, really has only one export partner; Earth (by way of the corporation funding the colonization venture). Once Mars becomes largely self-sufficient, as well as economically important enough to produce goods and other economic property that is of interest to Earth (perhaps we find an economically viable way to mine Mars' iron and aluminum content, which coupled with the weaker gravity well means Mars could become a shipbuilding hub), there's really only one customer (your home corporation), and if you piss that customer off by, say, declaring your sovereign independence, economics shows that trade isolation will bring your economy to a standstill, to say nothing of what your former corporate masters might do to reassert control (it wouldn't take much to destroy a relatively fragile self-sufficient state on Mars; orbital dynamics alone would make a simple metal sphere a fearsome weapon). Eventually, in a timespan of hundreds more years, we might have additional outposts on moons like Ganymede, Titan and Europa around Jupiter and Triton orbiting Neptune, for which Mars might be an important waystation and (for at least part of each planet's solar year) the closest available avenue for communications and emergency aid. Mars's development to that point could make it politically important enough to be autonomous, but fully independent? Likely not, at least not before such terms as sovereignty cease to have meaning for any number of reasons (the most desirable of which is that humanity puts aside such childish things as weapons to kill each other and focuses instead on infrastructure to support an eventual steady-state population of 9 billion humans).
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There are many variables at play here. First is that, to the best of our knowledge, the only rock we can live on in this solar system is the one we currently occupy. All of the others would require effort to become habitable and someone has to pay for that.
Unfortunately, it's unlikely that anyone would pony up simply to have done it, so there needs to be a compelling reason and THAT reason will determine who owns the colony-at least at first.
Some examples:
Early exploration of Titan reveals large deposits of a substance remarkably similar to crude oil-Exxon sets up a permanent drilling site on the surface and staffs it with employees and their families. Exxon owns the colony initially.
The population of Earth grows out of control and the governments begin to terraform the Moon and Mars just for the extra room. The colonies are owned by the participating nations so long as they need supplies from Earth.
At some point, the oil workers might decide they'd rather own the oil and sell it to Exxon or anyone who can outbid them. The Lunar and Martian colonists might decide they no longer identify with the homeworld any longer and want to be their own nation.
Would they be granted independence? Should they be? I don't know. How much time has passed? How much have their homeworld benefactors invested in them? Are they willing to pay that back (terraforming can't be cheap-neither can getting drilling equipment in orbit of Saturn)? What ongoing support, if any, would they need from Earth?
My personal take on it is that within a single star system, it's difficult for colonies to split away from one another. It would be easier if we were talking about interstellar colonies because then the colonies wouldn't have to depend on the homeworld and vice versa to share the resources of the star system.
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Few of more big questions. What do you mean by "earth" and how tough is it ship to and from the colonies and what are you shipping?
If the state of world affairs is like it is now and it is as expensive as it is now and there isn't a lot of value out there, no one would bother. A colony won't succeed as anything other than an experiment.
A big game changer would be cheap shipping. With world affairs as they are now you couldn't control the colony. I don't have to buy my soil from the US, I could buy it from Brazil or China.
With cheap shipping and if there were something really valuable out there then it would be the wild wild west. Probably crazy impossible to control.
A world government on earth would change things again. It would be hard to do anything other than some little smuggling if all tech is controlled by the man.
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I don't think they would be let independent. I imagine the colonization would go something like that, e.g. Mars. A scientific crew goes to Mars and starts building a research station. In that state there will be not even a thinking on being independent or even having political issues, as the crew will be to small, maybe +-10 people also they might be from every nation, see ISS. Then they also will be dependent on earth for basically all supplies. While the station is growing also the political situation on earth will dramatically change, as we are not speaking of a process of weeks, but more of decades. From a point of now, the first non-science people there might be politicians or very rich people on vacation. Then we this happens regularly people might open a hotel there and also start opening businesses to support those people. Still talking about decades at least. At this point I think we can speak of a colony, if it will be independent from earth mainly will depend if it can sustain itself, which depends on the possibility on getting energy up there and other resources.
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Assuming that a vampire expends as much energy as a human of similar size how much blood would they need to consume a day?
My naive estimate is 2500 calories a day, there are (apparently) about 9 calories per ounce of blood, thus they need about 7 litres a day, but I don't know enough about biology and nutrition to know if there are other issues at play (like vampires needing more or less energy then humans?, is it easier to digest blood? etc).
The operational definition of vampire for this question is a creature that used to be a human, but subsists entirely on blood. As such the internal structure is more or less similar to humans but it can be assumed that whatever changed them into a vampire optimized the digestive system for blood consumption (and muscles for strength and speed in case that's relevant).
So in general what I'm curious about is:
* How much blood would a vampire need a day to have enough energy to move around?
* What effect would it have on the victim (is possible/practical to withdraw non-lethal amounts from several people, or would they need to kill several times a day to stay mobile)?
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This the nutritional information of lamb's blood. I will use it as an approximation for real blood. They would lack vitamin A (bad sight... live in the dark... that makes sense), potassium, and they would often develop scurvy due to vitamin C deficiency unless they could find other ways of supplementing these nutrients. The serving size of one human would be 9525 grams of blood (unless they go after children...). They would have a lot of fat, a lot of sodium, and a lot of protein (this might be where vampire super strength comes from). The average human would get extremely fat. Perhaps vampires don't die due to a fast metabolism and a very active lifestyle. The high iron count supports this idea. The average human would die by drinking a serving size of blood due to iron overload. Vampires however, might survive by producing many red blood cells, using the iron inefficiently so that the vampire doesn't die of iron overload (this increased red blood cell count might be where vampire stamina comes from). Vampires would need to drink water.
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Depends what you think a vampire is. If its a dead body walking around by "magic", then the energy requirements are solely that needed to keep the magic working (whatever that might be). If vampires are supernatural entities (that don't really exist, hence you cannot see them in mirrors etc) then the blood might not even be required for energy expenditure but to give them some "magical" link to the physical world we live in.
Some vampire traditions require human blood - cow's blood doesn't work (or they could just live without the conflict we expect from vampires). That suggests its something special from the blood that is more supernatural in itself (ie human blood contains some magical energy that makes us sentient or 'alive', and the vampire needs this to exist rather than the physical material that makes the blood cells)
I think from all mythological concepts of traditional vampires, they do not need to feed on blood like we need calorific energy from food. So the answer is all down to what kind of mechanism it is that allows a vampire to exist.
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Apparently a vampire bat needs to drink half its weight in blood every two nights at least. The average 80kg adult has about 5L of blood. Blood weighs about 525g to 500mL apparently so basically 1:1 let's just round it. So an average 80kg vampire, assuming they are exactly the same as the vampire bat would need to drink 20L of blood every day. A person will die if they lose 40% or more of the blood they have and severe symptoms occur around 20% + I think, so if the vampire wanted to never kill they would have to drink 1L from 20 people for every 24hrs. That's a damn freaking lot. It's only 4-5 average adults though if the vamp sucked them dry, but they'd have a very hard time getting that consistently. I'm not sure if vampire bats also consume certain fruits to acquire additional nutrients, who knows. I'm also assuming that the vampire is restricted to human blood, I know nothing about other animal blood however vampire bats seem to live quite comfortably on cattle blood and other large mammal's blood. The transformation of the digestive system would be rather extensive though I think so perhaps this isn't what you're looking for. More likely would be the need for a magical lifeforce or perhaps they don't need nutrition but are incapable of replenishing blood supplies. If this is the case then they would only need to feed a few times a year assuming their blood cells die at the same rate as human blood cells. I hope I helped ^^.
[Answer]
It depends on other things, like metabolism and digestion.
If you convert the blood into proteins and sugars like we do, then it isn't very efficient, however you could use blood from other sources like cattle.
But classic vampires don't feed off anything but humans.
So maybe it's not just the blood.
Sympathetic magic has always been a big thing; get a couple hairs, a toenail, some blood... If you get into that kind of power then you could be getting life/energy from the victim through the sympathetic link, instead of just digesting the blood. Otherwise there are a lot of other fluids that would be more energy dense than blood.
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Or, just to place as an alternative, we can limit the amount of blood the vampire drinks by simply using blood as an addiction or habit rather than a form of primary nourishment, like what heroin is to an addict. Our vampire must drink blood because without it, he or she will suffer severe and potentially lethal withdrawal effects, and he or she gets a high when drinking blood.
In this way, we can have relatively plausible vampires that can live without drinking liters of blood. You will need to excrete that much liquid intake, and urinating all over the streets would *not* be a good method of staying undercover as a vampire.
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First off, I want to say, I think it's cool to consider this scientifically. If a vampire is driven by hunger for human blood, it makes sense to ask the question, "how much is enough."
Using a vampire bat as a guide isn't good I don't think because due to the volume of the bat relative to the skin's surface area, the bat loses a lot of energy and therefore must eat more relative to its body weight than other creatures. The shrew for instance is so small, it loses so much energy it eats almost constantly. Vampires are much bigger and being dead, don't lose energy at all when still.
I think you can justify any amount you chose, but if I were to approach this scientifically, I think I would vary the amount used. The cool thing is, when at rest, no energy used. Humans use, I think, about 400 calories while they sleep just to stay alive. Vampires on the other hand classically have the ability to climb walls, change form, move with ethereal quickness and charm people.
I haven't done the calculation, but since it's imaginary (except my next door neighbor) you could just do a quick and dirty calorie calculation for everything the vampire does assigning them values and then use the values given from these answers about calories in blood and reconcile the two. Example: the CDC says a 150 pound person uses 110 calories to do moderate exercise and twice that do vigorous exercise. So our vampire sits in a chair monologuing to his would-be hunter: 0 calories burned.
Hunter makes a move toward his knife. Vampire moves at lightning speed to come up behind the hunter to prove his superiority. That's superhuman speed. I'm thinking 1000 calories, right there. Then the hunter plasters a cross on his forehead, burning him, weakening him. Maybe he has to make that up in blood. That cost him a couple hundred calories worth of energy. Now he has to fight. If he fought like a human, 220 calories for 30 minutes. If he uses superhuman strength, 900 calories. After he dispatches the human, he sucks down 5 liters of blood for 1785 calories. Sounds like he's still hungry and might want to go trolling for more victims.
But on a light night, he might just stroll down the dark streets at pedestrian speeds using very little energy and snack on a hooker for a nice positive energy total. Also, maybe vampires can go for a little while at a deficit, like humans can. I'd say in a normal night for a vampire he'd need to drain about 1 human. If he's been battling a group of five vampire hunters, depending on the ferocity of the battle, I'd say maybe 1 human for every 5 minutes of melee. On a light night, maybe he would just down a pint or two from someone he has chained in the dungeon. No need to kill him, just keep him weak, which incidentally is exactly what Dracula did. He didn't kill them all.
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Ok I may be totally off mark here, but one concept to blood is that it helps the muscles right? in terms of biology, our muscles is filled with water and blood to help them expand and contract. Being that they are dead, their body is more than likely not creating new blood cells. So as they use their super human strength (also due to the fact they would lack the ability to feel cramps from having dead nerves) and high endurance due to their bodies being "dead", they need to feast on blood to replace the dead and old blood that has been used up.
Since Vampires are typically believed to be human, it would be natural that they feed off of a human to regenerate/replace blood as it would directly match their body needs. Other animals may closely match humans, but it still isn't human blood filled with nutrients that the human body uses.
They know when they need to feast again because typically it is before this feasting that vampires feel their weakest. Referring back to my first paragraph about how the blood helps the muscles, this can be related to the weakness since blood needs to help the body move. This triggers the "urge" to feed and once they feel their body is replenished again they stop.
This is a really simplistic idea and probably lacks the scientific exact volume you may be looking for, but logically it makes sense as a plausible start and stop reasoning to me anyways.
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Looking for a ballpark estimate of the wattage of a pulse laser that would do a similar amount of damage as a .22 LR round. Something farmers would use for pest control. This is for flavor in a far-future story, so doesn’t have to be super accurate.
(Edited)
E.g. The raccoon was back again. The farmer grabbed his 400-Joule pulse laser carbine. “This is the last time you go after my chickens,” he sneered.
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I am going to go on a limb here, and say that if there is a farmer that uses a laser rifle as varmint repellent, then the tech level of that world is off the charts (why then there still is varmints to be repelled is another question, maybe the technology has peaked and has become apocryphal, like in StarWars or Dune?).
So let's get with it. As the other answers have already shown in quite some detail, it is not advisable to use a laser where a .22 would suffice. IF, that is, you want to go the path of Boom-Splat.
But what if you where to *utilize the laser in a different way?*
## **Five Punch Laser Exploding Heart Technique**
(maybe go for the acronymically more pleasing Six Punch Laser Aorta Tearing Technique)
Aim, press trigger. A plethora of different-wavelength lasers scans the target - UV to millimeter-wave. A microsecond later, the target is identified, probability-vectors of movement for the next millisecond (1cm at varmint-speed) are locked in, reflectivity and absorption of different wavelengths by different tissues in the target mapped.
The gun still feels as if you are in control, but in reality the phased array emitters will keep a lock on the target irrespective of your jitter. The tactile feedback from the triggerpress has not even reached back to your brain, and the rifle now knows exactly how to end the critter.
A barrage of high-wattage ultrashort laser pulses goes down on the target, vaporizing miniscule amounts of matter in a preplanned rythm, scattering impacts all over the body, while building to a destructive, well actually constructive, crescendo when the soundwaves associated with the microimpacts interfere to burst the aorta of the victim.
A sound like a dull pop filters back, right as you experience fully depressing the trigger, and the critter rolls, twitching and slightly smoking. Dead.
You congratulate yourself on the ...paralegal upgrade for your rocksplitter tool, set the dial back to the crystal-plane cutter and continue the carving you had underway.
See [this paper](https://www.sciencedirect.com/science/article/pii/S1000936114001010) for a guesstimate of Lasers to push Space debris by ablation at several 100kms
* Rough estimate on the wattage / energy of the above laser rifle at .22-range : 100kW, 10 Joule per Varmint
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# It's not so much the wattage, it's how you focus it
Square cube laws answer is ballpark correct; the figure I got was 2g impacting at 200m/s has 0.5 \* 0.002 \* 200^2 joules of kinetic energy. That's works out to about 400 joules. And Mike's comment is correct, a kw laser for 100ms it's only going to slightly warm the skin on impact.
A bullets impact doesn't go into heating the skin, it goes into ripping it. A laser is a poor choice of weapon for this, but if we have to use it:
Focus the energy into a smaller region than a typical bullet impact. Those laser guns have adaptive optics that auto focus all that energy into a pinprick a few square microns across.
A 10 square micron surface exposed to 2kw of power is going to be damaged much more severely than a normal laser impact. What happens depends exactly on the surface its hitting, but fires, nasty skin burns and surfaces liquifying and wrupting are all likely to happen. Sweat turns to steam and flash boils, as your only heating a miniscle mass of skin, but your heating that miniscle amount of skin to extreme levels. Possibly plasma.
A direct hit on a rat by a farmer with a 2kw laser rifle will likely take a chunk out of the rat from moisture flash boiling alone. Itll be a tiny hole and it might die a painful slow death, but if you wanted to kill it faster, use projectiles.
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> that would do a similar amount of damage as a .22 LR round
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This criteria makes the question a non-starter. It is impossible for an pulsed energy beam weapon to do a similar amount of damage to a projectile weapon.
The damage done by a projectile weapon is almost totally due to impact energy. It is a kinetic energy weapon. F=ma. The force applied is from the acceleration and deceleration of mass. It smashes bones, gashes flesh, renders skin to create huge gaping holes, penetrates deep into the body tearing blood vessels asunder. The destruction goes far deeper than just surface damage, and it is widespread.
The damage done by a pulsed energy beam is due almost exclusively to localized heating. The conversion of one form of energy to another, particularly heat. A pulsed energy beam has almost no impact (kinetic) energy. It can not break bones, or rupture blood vessels. It can burn a hole in a bone or blood vessel, but it can not smash it and tear it apart. And the burn is entirely localized. Unless the beam is continuous, it can not 'cut'.
I am afraid that, sci-fi writing aside, a pulsed beam weapon makes a horrible device for killing rodents. Kinetic energy weapons will always win over pulsed beam weapons. The energy ratio between the two in order to achieve a 'kill' shot are so extreme as to be absurd. For a pulsed energy beam to do the damage of a kinetic energy weapon, the localized heating would have to be so extreme and so sudden as to cause the immediate vaporization of liquids, and the sudden expansion of the steam explosion would have to be so extreme as to allow the shock wave to propagate through the flexible and elastic flesh and muscle layer sufficiently to cause physical structural damage. That is a very big demand.
Now, if you were to propose a kinetic energy weapon that was projected by a light beam, say the photons could somehow be converted to REAL mass, or real mass could be driven by light, you might have something. But then you would have the perfect reaction mass - light propulsion spaceship drive.
I mean, really, I can stand directly in front of the world's most powerful spotlight and not be propelled back at all. Zero impact damage. Maybe blinded, and perhaps badly sunburned, but zero impact damage.
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"It depends"
I'm of the opinion that until someone can make a decent pulse laser, then lasers just aren't very useful weapons (and a quick glance at EDL and Ash's answers will confirm this). A pulse laser needs to deliver enough energy to vapourise a chunk of the target, and deliver enough of those pulses in a short enough time to carve a hole through the target. Your question presupposes the existence of consumer-grade, effective laser weapons, so that's what I'll run with.
A low powered laser might deliver, say, twenty pulses of 20 joules each in under a millisecond. Focussed down to a spot less than half a centimetre across, a short enough pulse duration will in fact drill a hole through meat. Not a big hole, or a wide one, but it should do the job. A longer pulse train would be preferable for drilling bigger holes, as would better focus.
Peak power will be enormous... 10-20MW, probably. Pulse lasers *need* that kind of massive power because they need to turn room-temperature matter into hot gas or plasma. You might not want to refer to the weapons as a "20MW pulse whatever" though... 400J would do a better job of informing people about the weapon's capabilities. Maybe "20x20" would be better, including both pulse energy and the number of pulses in a shot.
If you wanted to be more pedantic, it probably wouldn't be a "rifle" either. Rifling on lenses isn't useful! It'd probably look more like a little video camera than 22LR rifle. Here's a vintage super-8 that seems like a reasonable proxy:
[](https://i.stack.imgur.com/i6iTz.png)
(a laser weapon would probably have a trigger guard, mind you)
Not shown: cooling vents. There might be a little fan to provide forced-air cooling to the heatsink that stops the laser frazzling itself as well as whatever it is pointed at.
The eyepiece for the reflex gunsign is at the back; you can't see it from here. The front element of the lens is ~40mm across. A civilian weapon might sensibly produce a wavelength of 1000nm... near IR, invisible to human eyes. It blinds by burning the cornea rather than the retina, making eye damage potentially repairable by surgery. At this wavelength, the diffraction limited range for a 5mm diameter spot (about the largest you'd want for zapping pest species) would be ~160m, but real-world range would be probably more like 100m and maybe less. This seems roughly comparable to a 22LR, though the (probably) shorter effective *killing* range of the laser is more than made up for by the fact that it has negligible flight time, no bullet drop or windage, and as it uses a reflex gunsight (eg, you look down the barrel at the target, using the same set of optics) you'll hit exactly where you're pointing.
At very close range, say 20m or less, you'd have no problem blasting a hole clean through an unarmoured human, or fatally wounding big game. At maximum range, the wound *could* be fatal for humans, but I wouldn't rely on it. bad news for raccoons, though.
(note that at longer ranges, the laser is still dangerous, it can blind and burn and seriously wound, though it is unlikely to deliver an immediately fatal wound even to small game)
You could probably have a folding stock on the back if you wanted, but for this sort of weapon and purpose you probably wouldn't need one. If battery technology hasn't marched on enough (and current advances suggest it probably will) a stock might be a good place to put the battery.
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A .22LR bullet has 41 Joules of kinetic energy at leaving the muzzle.
$J\_{vaporize\ water} = 2260 kJ/kg$
A Watt is $Joules \over seconds$, so how dangerous your Laser Rifle is depends on the pulse width.
1 ms pulse width = 0.3 Joules
1 second pulse width = 300 Joules if and only if you can keep the rifle trained on the critter. And as was mentioned before collimation is important. If your beam is tiny enough and burns through the critters fur, and hits the skin, you'll start vaporizing its flesh -- assuming its effectively water -- at rate of $$ Vaporize\_{critter} {kg \over sec} = {{W\_{laser} \times Pulse\ Width} \over J\_{vaporize\ water}} $$
Your 300 W laser with a pulse width of 1 second will vaporization 1 milligram of Racoon per second.
So not very lethal. Might hurt. Only dangerous maybe to the eyes -- as has been observed in previous answers.
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The ammo type you mention delivers [in the range of 178 to 259 joules](https://en.wikipedia.org/wiki/.22_Long_Rifle) per shot. Just divide this value by the pulse duration to find the wattage. I.e.: if the pulse lasts 100 ms, then the wattage would be in the range of 1,780 to 2,590 W.
If one shot is composed of multiple pulses, use the total pulse duration.
This is for short to medium range. For really long shots atmospheric attenuation might have a larger role, so you'd have to increase the output to get the same energy delivered to the target.
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As long as the pulse is short enough, the width of the pulse hardly matters to the racoon at all, so quoting wattage doesn't tell you anything about the killing power of the pulse rifle.
Better to quote the rifle's pulse energy in Joules.
A 300 Joule rifle puts out pulses with energy similar to bullets, but you have to worry about how well it's absorbed.
Obviously you'd want a Kill-o-Joule rifle instead.
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As the majority of the answers indicate, radiation weapons are a joke versus projectiles for damage. But maybe we can exploit their properties to use them smarter.
You can easily realign your EM beam with mirrors (auto-aim). With (very) high tech, it is possible that a weapon with an enemy anatomy database could direct a high-power penetrating (xray/gamma) beam to fry/massively mutate a point in the brain that will cause almost instant death due to cessation of some important function, like heart beating.
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We are in the future in northern North America (U.S or Canada). The land has "risen" (or more accurately, filled in) with several hundred feet of earth and sand and silt so that a modern city will show only the tops of skyscrapers emerging from the otherwise-even land. The question is what might have caused this?
Additional thoughts: The cause of the cataclysm need not be a single event (nuclear war, asteroid) but rather a cascade of socio-political events starting with a catalyst (e.g. climate change leads to sea levels rising, which exacerbates tensions in the Koreas, which prompts the North Koreans to … etc.) I'll worry about the story. But the larger is issue is how and why land would rise.
ANCHORS (Set parameters for answers)
1. We are in the future approximately 300 years, and the events that change the world happen 100 years from now (i.e. 2117 for simplicity's sake).
2. The world is sparsely populated as a consequences of events. Enough to form sustainable communities, but the existing geo-political world of nation-states is long gone.
3. The skies have changed and the aurora are more visible much farther south (and often) than today.
ENGINES (what drives creativity within those parameters)
A. The timeline can be adjusted but not radically.
B. A single, unlikely coincidence (but not two!) is acceptable (asteroid strikes while X is taking place, leading to …)
C. We can play with technological advances during the next 100 years to create new conditions, possibilities or circumstances.
D. [Later addition after several answers posted]. The effects need not be global. It is OK for this to be a regional phenomenon whereas other effects (but the same cause) are felt elsewhere (e.g. the tide goes up in one place as it goes down in another …)
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Multiple, worldwide volcanic eruptions depositing ash at a rate faster than humans can remove it. This would be on an epic/global scale, but in real life, it would appear like this:
[](https://i.stack.imgur.com/S5k9t.jpg)
Edit: Mind you, this kind of ash-deposit would be a disaster that could easily qualify as a (human) extinction-level event. All soil for crops would be buried under hundreds of feet of sterile ash - presumably globally.
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Instead of the land rising, why doesn't the city fall?
There are many examples of sinkholes and sinking buildings.
The most famous is the tower of [Pisa](https://en.wikipedia.org/wiki/Leaning_Tower_of_Pisa). But there is also a modern version in the [Millennium Tower](https://www.theguardian.com/us-news/2016/oct/06/san-francisco-leaning-millennium-tower-investigation).
The tower of Pisa is cited as behaving in the following way:
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> The tower began to sink after construction had progressed to the second floor in 1178. This was due to a mere three-metre foundation, set in weak, unstable subsoil, a design that was flawed from the beginning
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So, it could be that due to changing circumstances, melting of the poles, rising tides, hotter temperature, heavier buildings, runoff sewage, bad city planning, tectonic movements, earthquakes, or even all of the above have caused a city, or some cities to start sinking. And slowly, slowly, only the tops of the tallest towers remain.
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## Massive Deforestation
Northern Africa, where the Sahara desert now is, [used to be lush grasslands and forests](http://www.messagetoeagle.com/changed-green-sahara-desert/):
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> Most scientists believe the Sahara dried up due to a change in the Earth’s orbit, which affects solar insolation, or the amount of electromagnetic energy the Earth receives from the Sun. Or to use simpler words, insolation refers to the amount of sunlight shining down on a particular area at a certain time. It depends on factors such as the geographic location, time of day, season, landscape and local weather.
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> In 1999, a group of German scientists used computer simulation to create a model of the Earth’s climate thousands of years ago. They concluded that the climatic transition of the Sahara took place abruptly, within a possible span of about 300 years.
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In addition, man-made deforestation can also cause desertification. [North Africa used to be called the "land of continuous shade", but deforestation has left it a wasteland of sand.](https://www.jstor.org/stable/4314180?seq=1#page_scan_tab_contents)
So, a significant change in the temperature of the environment can change lush grasslands and forests into wastelands of sand.
The Sahara desert's sand is [about 150 meters on average, with a max of 320 meters.](https://www.google.com/search?q=how%20deep%20is%20the%20sand%20in%20the%20sahara%20desert&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari) Since [skyscrapers are at least 100 meters tall, maxing out at 600 meters,](https://en.wikipedia.org/wiki/Skyscraper) a desertification complete with sand dunes could create the scenario you describe.
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# Abandonment, then desertification
No, you cannot have several hundred feet of soil / sand magically appear evenly all over the continents. That concept you need to abandon more or less immediately.
However...
Buried cities exist in real life. Especially in tropical areas we have discovered several such locations, such as [these in Cambodia](https://www.theguardian.com/world/2016/jun/11/lost-city-medieval-discovered-hidden-beneath-cambodian-jungle). And looking even closer in time, there are many fascinating abandoned places, such as Pripyat, the town that housed the workers for the Chernobyl nuclear power plant.
[](https://i.stack.imgur.com/7ndNQ.jpg)
*Nature is reclaiming Pripyat after all the humans left ([Image source](http://www.ibtimes.co.uk/chernobyl-disaster-inside-exclusion-zone-abandoned-ghost-town-pripyat-photos-1523628))*
So the first step to start covering cities is simply to remove people. Invent any disaster you like; super-plagues, war, alien attack...
But if you then want these towns to be covered in soil or sand, then you need to destroy all of this plant matter. [Desertification](https://en.wikipedia.org/wiki/Desertification) will do that for you. Dramatic climate changes kills the plant-life and eventually it will decay.
Do note that wind will carry some of the dead plant matter away. This means that the coverage will not been even. On great plains, the dust clouds will just keep blowing, compare [the 1930's Dust Bowl](https://en.wikipedia.org/wiki/Dust_Bowl). So to have this phenomena, you need cities that are in places that will capture the blowing soil. Depressions, mountains and other geological features can serve as soil traps.
In summary:
First the calamity killed the people. Abandoned cities started growing over and eventually were half-buried in plant matter. After that the great desertification happened. Some cities remained relatively unburied, but some trapped much of the migrating dust clouds and were buried.
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This is my first post, and I'm therefore a bit uncertain when to post an answer. But it's been about a month, discussion is winding down, and I am pressed on with the writing. So I thought I might share my answer:
Before providing it allow me to first say, thank you. This has been a very interesting experience and quite engaging. I'm happy to say that the following ideas would not have been possible without this discussion.
It strikes me that the moment to stop answering the question isn't when we've built a fully valid proposition, but rather when the needs of the story have been satisfied. In this case, my story is set a few hundred years into the future, and the disruptive event (the Rise) look place about 100 years from now. It seems quite reasonable as well as dramatically interesting for the characters **themselves** to wonder whether or not the earth rose around the buildings or whether the buildings fell into the earth (as per Inbar Rose's reflections above). If two cultures develop legends and lore around those alternative readings of the physical world, it becomes a dramatic rich point for story development. In my case, I think this works quite well.
That does not relieve the burden, however, for me to create a plausible set of conditions for the world to be in such a state (i.e. my original question). It does, however, relieve me from having to articulate it in the body of the story itself (which is not an evasion but a deference to the storytelling).
So here's what I'm thinking which will result in the world I am building but need not be mentioned in the story:
Massive solar activity disrupts communications at a politically sensitive time, thereby undermining international cooperation because conspiracy and suspicion about "what happened" overshadows scientific evidence; There is agreement on the solar flares, but beliefs hold that some countries or actors took advantage of that for gain. Global warming massively increases as cooperation ends and regional wars begin using weapons that I fear will be more in use 100 years from now (if multilateral cooperation cannot halt the proliferation) including biological and chemical weapons coupled with cyber attacks on infrastructure. Man-made pandemics with cascading consequences become very plausible. That takes care of most of the humans and many of the animals.
Deforestation does indeed take place with global warming and the solar activity and the (previous) man-made contributions results in "global weirding" (a term now used to explained the intensification of locally strange weather as a function of globally warmer weather). At that point, I feel I can reasonably stop because I can imagine (with your help above) a set of plausible conditions where a city (not all cities) face the dramatic "rise" I mentioned.
As it happens, I do think the earth will have risen (not the buildings having fallen), but the debate is of greater value to my story than the immediate answer.
A few final thoughts on details for those of you kind enough to share your ideas:
* I think earthquake protection and higher building standards are more likely as buildings go up from now (2017) to the time of the event in at-risk areas (LA, Tokyo, Rome, Tehran, etc.). So it seems that the most modern of buildings by that time will be those most likely to survive. Consequently, most of the older buildings will indeed have fallen. So the Old World poking through might mean six or seven buildings, not 50 or 60.
+ Deforestation, desertification, changing of the quality of top soil, the movement of earth (i.e. soil) from nearby mountains down into the city's valley — all these matters could conjoin to create a plausible (local) scenario.
+ I agree that changes to ocean currents, desalination and other matters can be viewed as primary causes in the wider model.
Thank you all very much! This is connected to what I hope will be my fourth novel and I will announce its title if/when it sees the light of day.
Respectfully yours.
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**Trash**
If current trends hold true, we are producing more trash than ever before. If it blows around, it would likely get caught in trees and among buildings. The ensuing health crisis kills off most everybody. Remaining scientists utilize cloud seeding or repurpose chemical warfare arsenals to disperse a rubbish eating micro-organism that renders the primary components to soil.
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Best and most likely scenario is Yellowstone going up.
However one eruption would not create that amount of ash build up so maybe have multiple eruptions over a 100 year period and that could account for a larger layer.
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Nanobot "[Grey goo](https://en.wikipedia.org/wiki/Grey_goo)" apocalypse — almost. The standard scenario is self-replicating bots go out of control and consume all matter on Earth. You just need a more limited version — they just replicate out of control, but don't consume everything. You're asking for a lot of sheer mass and volume, and you would need somewhere for that to come from — possibly automated asteroid mining. Or if you don't need it over the whole Earth, just *regular* mining, leaving deep pits elsewhere.
Bonus: If the material is iron from asteroids, perhaps that could alter the Earth's magnetic field enough to sound like an explanation for your aurora change idea.
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TLDR: CO2 rise `->` Sea Level rise `->` coastal city mostly flooded `->` Humans engineered marine life that sucks CO2 out of the air super fast and stores it in shells which sink to the sea floor `->` Sea floor builds up around city (made of shells e.t.c.) `->` CO2 falls `->` Sea level falls.
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May need to up timeline by a century or two, but with sufficient acceleration of climate swings through human intervention or artistic license could be squeezed into 300 years. (No need to wait till 2117 years before the events start happening as they are happening now!)
Even if you don't believe in man-made global warming, you could for the purposes of the story or invent another cause for it...
Full Timeline:
* Global warming, ice caps melt at ever accelerating rate, Humans, in the effort to prevent global warming, genetically engineer a [phytoplankton](https://en.wikipedia.org/wiki/Phytoplankton) that grows much faster than normal and sheds lots of calcium containing shells [(see Coccolithophores and chalk formation)](https://en.wikipedia.org/wiki/Coccolithophore). (Causing Coccolithophore blooms has already been suggested as a way to prevent CO2 rise, minus the genetic engineering bit).
* Sea level rises massively anyway, swamping a coastal city ([perhaps over 50m rise if all ice on earth melted](http://ngm.nationalgeographic.com/2013/09/rising-seas/if-ice-melted-map)). (Climate always lags behind CO2 anyway so dropping CO2 now may still not prevent further short term warming, so very plausible).
* A small river that used to flow through the city is now bigger due to a shift in local weather patterns (very plausible given world climate shift) and water erosion of previously arid lands containing lots of loose soil leads to the river [dumping tonnes of silt into the sea over the city](https://en.wikipedia.org/wiki/River_delta#Formation).
* The water around the city will be super nutrient rich from all the silt, this would feed the genetically engineered algae's growth massively, shells are dropped around the city with the silt, speeding up its burrial.
* The action of the algae worldwide does lead to CO2 depletion, eventually the temperature catches up with the CO2 levels (even lower than before the human caused spike) enough for icecaps to begin forming again.
* In the far future, this cooling could lead to a [snowball earth](https://en.wikipedia.org/wiki/Snowball_Earth) (if the algae removed enough CO2) but for your setting there could be similar weather conditions to the ones we have now (perhaps even slightly cooler).
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I already have an answer listed, but thought of another that combines with Inbar Rose's. Inbar said the buildings sink. I started to think of what could cause the ground to be unstable or at lease less supportive of the weight of buildings. I've heard of this being used.
**Vibration**
Due to directed sonic attack or prolonged aftermath, the building structures moved in a harmonic resonance that worked the building deeper into the ground as if it were in quicksand. Depending on the depth to bedrock, some buildings would sink lower than others.
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Alternative/additional scenario to the [deforestation/desertification one](https://worldbuilding.stackexchange.com/a/66919/26061) above: a significant (say 100m?) drop in the ocean level (e.g. the caverns in the "Journey to the center of the Earth" filled through a crack? Or just [nuclear fracking](https://en.wikipedia.org/wiki/Project_Chariot) in [some place](http://www.forbes.com/sites/timdaiss/2016/05/22/why-the-south-china-sea-has-more-oil-than-you-think/#6363f49b3a3f) gone terribly wrong?) lets lots of silt/sand to be carried by wind in the form of massive coastal dunes.
Info on [the total amount of water](https://water.usgs.gov/edu/gallery/global-water-volume.html) - water is about 0.001% of Earth by volume; insignificant percentage, reasons for water going underground may be easy to imagine/justify.
See an [example of a town](http://www.nullarborroadhouse.com.au/remnants-of-a-lost-town-the-eucla-telegraph-station/) swallowed [by coastal dunes](https://commons.wikimedia.org/wiki/File:Eucla_Telegraph_Station_DSC04567.JPG) and [the story](http://members.iinet.net.au/~oseagram/eucla.html) featuring rabbits and cats; feel free to add other potential causes for accelerated desertification.
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continuous sandstorms and windstorms after a global water reduction. There could be numerous reasons for such but massive shifts of earth blown around in a multitude of storms over time. The earth and sand moved would then compact and sedentarily set over more time to form a more hardened surface.
Just a thought.
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This could be caused by an Expanding Earth. Originally this was hypothesized as the explanation for the phenomena that would be later identified as due to continental drift.
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> The expanding Earth or growing Earth hypothesis asserts that the position and relative movement of continents is at least partially due to the volume of Earth increasing.
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Source: [Expanding Earth](https://en.wikipedia.org/wiki/Expanding_Earth)
If instead of this being a discredited geological hypothesis, what if this expanding Earth turned out to be real. Then the land rise would be a natural result of the expanding Earth in the post-apocalyptic future.
The Expanding Earth theory isn't a joke, this was a genuine scientific hypothesis. The author of this answer had the strange experience of sitting in a lecture given one of the major proponents of this theory, S. Warren Carey, the Professor of Geology at the University of Tasmania. Since this is Worldbuilding, there's no reason why the concept can't be used here.
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> 1. Earth's mass has remained constant, and thus the gravitational pull at the surface has decreased over time.
> 2. Earth's mass has grown with the volume in such a way that the surface gravity has remained constant.
> 3. Earth's gravity at its surface has increased over time, in line with its hypothesized growing mass and volume.
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In the real world, the Expanding Earth theory was discredited.
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> The hypothesis had never developed a plausible and verifiable mechanism of action.[10] During the 1960s, the theory of plate tectonics—initially based on the assumption that Earth's size remains constant, and relating the subduction zones to burying of lithosphere at a scale comparable to seafloor spreading[10]—became the accepted explanation in the Earth Sciences.
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> The scientific community finds that significant evidence contradicts
> the Expanding Earth theory, and that evidence used in support of it is
> better explained by plate tectonics:
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Source: ibid.
If the Earth was expanding, then three hundred years in the future land both locally and globally could have risen.
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To have a city barely peaking out from the top of sand or soil you would have to move a lot of earth and anything that moves that much earth/ash/sand unfortunately would be devastating to all life on the planet. Our earth is over due for its next ice age. All it take is global warming to continue to cause catastrophic scenarios.
Delicate systems and currents around the world would be destroyed. Too much fresh water in the oceans not only causes the water levels to rise, but it also devastates the natural jet streams that keeps the currents moving. When this system is disrupted it also effects the wind currents and weather. More water means more rain, and a tendency for things to cool down.
Now that all of this water has risen say, 50-80(your choice) feet you now have New York City underwater. We undergo the ice age and New York is now a frozen block of ice. Snow piles up and eventually it becomes a frozen wasteland. The Poles creep down the planet and soon enough the only reasonably habitable places are closer to the equator, Florida would have weather closer to what New York or Canada has now. Florida would also be immensely smaller. It would snow in places it has never snowed before. This would be your best option and most likely scenario that could occur.
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If you're looking at coastal real estate then there are a couple of solutions 1. consider that if we manage to melt the West Antarctic and the Greenland ice sheets then the sea will rise about 80 feet which would then lead to large-scale deposition of sediment across what are today coastal cities, if we then managed to reverse the temperature build up the ocean recedes and those buried cities are back on the coast. 2. cataclysmic cooling like the movie *The Day After Tomorrow* would result in large-scale sand dunes blowing inland from the exposed continental shelf which could easily bury cities in a number of areas.
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an asteroid impact triggers numerous sub tectonic activities. Landmasses rise high above the other.
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Every culture has its myths and myths always fit in with the culture they belong to. From the Native Americans and their stories of respecting nature to the blood and brutal of the Aztecs. If I had the myths of Chinese mythology in the Norse world it would feel off.
Needless to say the myths a culture has are important to keep the feel of the world. How can I make sure that the beliefs and myths of the culture fit in with the culture itself?
[All Culturally Correct Questions](https://worldbuilding.meta.stackexchange.com/questions/3960/culturally-correct-series/3961#3961)
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Myths and other similar details, give a setting depth. They are in essence the nitty gritty of culture, the grain of sand level detail that really makes a world come alive.
That necessitates a few pre-requisites before you can come up with myths that make sense and feel organic. Ask yourself the following and myths, history, religion and culture will start creating themselves so to speak.
**Questions:**
* What is the planet like. Is it earth-like? How many planets are in the solar system? Is plant life green, the sun yellow and the sky blue? What flora and fauna are important to the people? Weather matters as well, many of Earth's early deities were tied into aspects of weather.
* Cosmology, the actual cosmology is less important than what people believe to be true. How was the world created and why. Who created the world and people? Is there one god or many, perhaps none? How does the divine interact in the world? What does the deity require of worshipers?
* Sentient beings. Are we talking humans or something else? How we see the world depends on who we are. If you have a race that is blind, for example, color won't play into myth (as it so often does).
* Culture/Society/Civilization. You seem to have this pretty well locked down at this point with your migratory blimp people. What natural phenomenon will be important to them based on their lives? What are the challenges they face? What is the worst situation a group or individual could end up in, i.e. what are their fears and conversely hopes. What makes a 'good death' and 'good life'.
* Resources. What resources are important to them, how do they get said resources? What are the challenges and why is the resource (or resources) important to them. If they use gas in their blimps for example the gas could be the *"breath of [insert deity name here]"*
* Heroes and villains. What historical figures have impacted their society and how did they do it? What is the acutal story versus the myth?
* Tribal differences, how do people diverge (if you have more than one group). How do their myths differ and why?
Once you have all these things locked down you can develop a myth for the culture. In many ways you can make a myth what you want it to be but you should keep the setting in mind and ensure that it doesn't contradict how a person in the situation defined would think.
**Examples:** Here is an example. (your world...)
The people are constantly on the move. Things that impair or facilitate that movement are of primary concern. Several myths can develop from this. The obvious myth is a heroic myth. The hero that came up with their floating civilization, or the hero that saved a floating city from destruction. Pick your poison here, it could be a villain myth attached or maybe a natural disaster.
Cosmology would likely revolve around a sun deity, the obvious path here is that you must constantly follow him to stay alive, which is quite literally true in this case. The religion just kinda creates itself now doesn't it?! The antithesis of course would be darkness and some deification of the chasing darkness, the idea is ripe for a cult...sacrifice to @bowlturner...err the dark lord.
**Notes:**
How myths show themselves in your world is important. There can be storytellers and priests that share lore and law. Sayings that don't make sense to outsiders or that most don't know the origin for.
**Resources:**
My personal favorite resources is *[The Hero with a Thousand Faces](https://en.wikipedia.org/wiki/The_Hero_with_a_Thousand_Faces)*. Joseph Campbell is a great read for world builders and I highly recommend it even if, academically speaking, some of his theories are arguable.
* <https://en.wikipedia.org/wiki/Joseph_Campbell>
* <https://en.wikipedia.org/wiki/Monomyth>
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A good myth is going to focus around a common question that your culture will ask, or will have difficulty with. It will provide guidance and explanation in the form of symbolism and important characters. In your culture, it will deeply resonate with your individuals and, the myths that survive best will be the best stories, the ones the kids want to hear again and again.
1. Find a question that your society is always going to ask. "*Where did we come from?*" "*Why are we different from those other people?*" "*What is special about [common cultural thing]?*"
2. Use your culture's famous symbols, people, or events in a story, which explains the answer to the question and shows what is important to your people.
3. Make sure the story correlates to your culture - If the evil bad guy was a generic bull, bulls are likely unpopular animals to this culture. It wouldn't make sense to worship them.
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I think this is a chicken and the egg type thing. Myths, go hand in hand with the culture that spawns them, and in turn help mold that same culture.
So the more you know about the culture you want to create myths for the easier the myths will be to create, and the better your myths for a culture are the better you can refine the culture from the stories.
So if you know how a typical person from a culture should react to a given situation (being culturally driven) then there are likely stories in that culture praising/rewarding that same behavior. That is a good place to start. Or on the flip side, there might be punishments/ostracizing should someone NOT perform a certain way. Some cultures will have more negative lessons others will have more positive lessons.
Also the more you know about the history of the culture, taking some of the known 'heroes' and 'villains' and stretching their exploits and making them larger than life is another great place to go. Most myths have some kernel of truth in them, even if it's just an ideal to be passed on.
Oh and villains, tend to represent what the culture considers to be bad traits the heroes ideals to aspire to. So a hero in one culture can be a villain in the next.
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My advice for creating a system of myths would look something like this:
1. What religions, beliefs, etc. have you already laid out? This might determine the theme of the myths. For an abstract example, in a religion with good and evil, moralistic fables might be common, or mythical creatures might be fearful demons or, conversely, benefactors.
2. What is familiar to people, and assumed to be a given? The people might assume the characters in their myths are like them, or they may be set apart by the fact they don't do something.
3. What is scary/mysterious/unknown/unlucky in this culture? Some myths might stem from that. Also, many, many myths serve to explain what science can't. If the people don't know about something, they'll assume whatever fits for them.
4. Think of cultural traditions and manners. Might myths factor in to this? In Ancient Greece, the gods could disguise themselves as humans, so people were hospitable to strangers because you could never tell if they were a deity in disguise.
5. What creatures are there in your world? Are they a danger? Do they provide people with something they need? What do they mean to the people? Predators are often seen as fierce, and can be either wicked or noble. Animals the people need to survive often represent fertility. How your world views animals can affect legends and myths.
6. What are the morals of these people? Ultimately, this decides how the stories are told. What qualities are praised? What is taboo? How rigid is the society's power structure? The last one is important in that a rigid society might have stories with the connotation of "know your place," while a society with more opportunities might have a few "rags to riches" myths.
7. What aesthetic do you want your myths to have? Myths can be biased. They can praise, instruct, or simply entertain. Myths can be full of imagery and detail, or stripped down to the bare bones of its intention. What time period was this myth made? How did it come to be? How did it evolve over time? Was the meaning changed to suit society? Where parts taken out because of taboo, or something else? Another part of this is figuring out how symbolic you want the myths to be. They can be legends of everyday heroes, or they can be seeped in the culture, assumptions, and associations of the people so much that a foreigner would scratch their head at the meaning.
Hope this helps!
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Creating believable myths goes hand in hand with creating a believable culture and a believable history.
The first thing to consider is the functions myths fulfil:
* They explain why the world is as it is
* They explain why you should behave in a certain way
* They pass on and explain history and give an identity to the people
* They are entertainment
A good myth will fulfil as many of these functions at the same time as possible.
So where do those myths come from?
The first thing to look at is the physical conditions those people live under. From their point of view, there is no such thing as a year, there's only one period, the solar day; however perception of the day will be more like the year for us.
Since those people migrate with the light, they will not know the night, nor the stars. For them, the sky is where the sun shines, and darkness means death. They will fear the darkness, since they know that out of darkness, only death comes. They won't see the living creatures adapted to darkness, because those never see the light; however they will see deceased creatures of darkness, and they will see creatures of light that went into darkness and died. They will also know that where the world comes out of darkness, it is cold; indeed, it's probably dangerous for them to even come close to that region, due to the coldness there. Since from the dead bodies they know there are creatures on the dark side which undoubtedly look gross to them, they probably will see the dark side as a world of evil and death, and the bright side as the side of the good and of light.
The main question of their life would then be, why is there a dark and a bright side, and why are they moving around the planet (since they migrate with the sun, they will be aware that going round the planet, you get back to where you started; thus probably they recognize the spherical form of the planet).
There will be myths about why the world is like that; for example, they could assume that originally, all the planet was in light, but then a god turned evil and created the creatures of the dark, which ate away the light on half of the planet. They are constantly eating, but as they are eating the light on one side of the planet, behind their back the sun brings back the light on the other side.
There will probably also be myths about people who accidentally got into the dark side, and fought some of the mythical evil creatures living there, either successfully (for example with help of magic, or with help of the sun god) or unsuccessfully (the latter would serve as a warning to people never to enter the dark side).
Moreover, since the people are constantly migrating, there will likely be conflicts when two groups migrate to the same place. Such conflicts are likely driving history, and when they are sufficiently long ago, larger conflicts also will pass into myths, the stories of battles will get enriched with concrete ways the gods or mythical creatures intervened into the battles and cause one side to win (the side who tells the story is, of course, always the good side; this is true for both sides).
Note also that myths evolve; as they are told from generation to generation, they get enriched, put into relation to each other, get adapted to fit newer experiences, elements from one myth may enter another one, some myths may be merged, others may split into several different myths.
From the set of myths will eventually emerge a religion, and the religion will in turn again reshape the myths to fit. A religion always is also justifying the power structures in the groups following that religion. Therefore there will also be myths that relate to the power structures, that explain why those in power are in power, and why they have to be in power.
Over time, there will also be a large body of knowledge about which plants are edible and which are poisonous, which animals can be hunted, etc. Also this knowledge will likely be connected with myths. There might for example a plant that is extraordinarily poisonous. Then there may be a myth that explains how that plant became so poisonous.
In short, the key to believable myths is that they are born out of the experiences of the people, are made to appeal them, and in turn again shape their behaviour, therefore they cannot be invented in isolation, but only by considering how the people experience the world, what they fear, what they hope, and what they want to understand.
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Often, myths are created by people in order to explain things that they don't know or understand in terms of things that they *do* know or understand. In most cultures, this involves ascribing some form of personality and intelligence to observed natural phenomena, and then trying to relate that back to their everyday existence.
Thus, "the river" becomes "the river that makes our crops grow", which becomes "Mother River, who feeds us from her breast". The question "if she loves us, why does Mother River flood and destroy our village every year?" leads to "why do other women in our lives become mean from time to time?" leads to "oh, she must be on her period".
From here, there's usually added a thousand years of people sitting around the campfire being bored, and trying to outdo each other with their stories. Anecdotes, gossip, bragging, propaganda, and outright slander from these people's lives get run through the filter of the existing mythic framework, and they come out as a soap opera about the lives of gods and heroes.
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I would start with Jung's archetypes of human myths. From wikpedia:
*"Jung described archetypal events: birth, death, separation from parents, initiation, marriage, the union of opposites; archetypal figures: great mother, father, child, devil, god, wise old man, wise old woman, the trickster, the hero; and archetypal motifs: the apocalypse, the deluge, the creation.
Although the number of archetypes is limitless, there are a few particularly notable, recurring archetypal images, "the chief among them being" (according to Jung) "the shadow, the wise old man, the child, the mother ... and her counterpart, the maiden, and lastly the anima in man and the animus in woman".[9]
Alternatively he would speak of "the emergence of certain definite archetypes ... the shadow, the animal, the wise old man, the anima, the animus, the mother, the child"."*
And:
*""These images must be thought of as lacking in solid content, hence as unconscious. They only acquire solidity, influence, and eventual consciousness in the encounter with empirical facts."[5]"*
You don't have to actually subscribe to this analysis to find it useful as a framework for idea generation for your myths. If you consider the collective subconscious of the blimp people, and factors like - how does their theory of mind differ from ours - you might be able to come up with a revised list of archetypes for the blimp people and then use them to construct myths.
In Watership Down for example, which is a seminal example of Xenofiction, the primary archetypal motif for the rabbit protagonists is the **trickster** (embodied by the invented myths of el-ahrahrah, prince of the rabbits), whereas in human mythology the trickster is less important. This simple difference serves to create an endearing and effective rabbit mythos that feels quite alien.
The other advantageous aspect of adopting Jungs archetypes as a guide is that the literature that uses Jungs framework to deconstruct human myths is very rich.
By way of example, since the world is mostly land and rain is revered, the human 'deluge' archetype would need to be replaced by its polar opposite. Another suggestion is to try and specify the anima and animus - the archetypes of ideal male and female form.
Lastly I would also say that if the blimp people are not the only sapient race then the existence of other minds (now the people need two theories of mind one for themselves and one for the bats), is going to have to represent a huge difference between human and blimp-person myths, along with alterations to archetypes due to the long day/night cycle.
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What I want to add is a little different to what other have contributed thus far.
Think of the story you are telling in your world, and tease out themes. Once you've decided which are the ones you want to emphasize, write a story (using some of the excellent references here) about that theme.
Once you've got the general plot (myths and legends are usually all plot with flat characters), imagine how that plot would have changed over time. I'm looking at a book on my shelf right now from 1893 called "Cinderella: 345 Variants". Different cultures in your world would interpret and re-tell the same story. The older your world is, the less the variations on the myth would retain similarities to each other.
The important thing is (for your story at least, not the real world), the THEME of the myth should stay the same. Or at least similar but interpreted differently.
My favorite example is "The Tale of the Three Brothers" from Harry Potter and the Deathly Hallows. The theme of the Harry Potter books is death. JK Rowling wrote other fairy tales, but this one, where the titular three brothers literally meet death, is the one she included in the book and integrated into the plot.
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One of the most important aspects I see in myth development is that, from time to time, an individual is going to act on the assumption that myth is true. If the result is undesirable, statistically speaking, the myth is not going to prosper. As a result, I have found most useful myths provide enough useful value for driving a culture forward to make up for the occasional time where it proves to be a falsehood.
An excellent example is the myth of Icarus. Icarus flew too close to the sun on his makeshift wings, melted the wax, and fell. Every now and then someone might actually take this seriously, and fear getting too close to the sun. On its own, that myth would do nothing but pin people on the ground. However, it also tells an important tale of reaching too far towards glory, and paying the price. The value of this tale more than offsets the cost of people taking it literally. Good myths should all do this.
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### Context
In the arms race of survival many animals have developed ways of evading predators, but the animal I am interested in for this question would be the tiger moth. So basically these guys jam bat echolocation through their wing flapping patterns, this causes the bat to get mixed signals and be confused so the moth can get away. It just so happens another predatory animal uses echolocation to hunt, the sperm whale, and what they hunt are giant/colossal squids...
### Question
What sort of biological or technological adaptation of an already existing giant/colossal squid part could be used to manipulate sperm whale sonar to lead them into traps and cancel out the sonar to avoid being stunned by it?
[Answer]
**A cloud of smaller host creatures scatters the sonar.**
The squid is followed by a cloud of small creatures that scavenge the scraps of the squid's food. In return they serve to scatter the sonar waves of a sperm whale.
In order to scatter the sonar properly, the space between the creatures should be on the same scale as the wavelength of the sonar. We can calculate that.
The wavelength of the sonar is $ S \ /\ F$ for $S$ the speed of sound in water (metres per second) and $F$ the frequency (hertz). Since we're in the deep ocean let's say the water temperature is $2 C$ and we're 2km down. Then there are $200$ atmospheres of pressure and [Wolfram Alpha](http://%20Let's%20look%20at%20some%20numbers:%20The%20wavelength%20of%20the%20sonar%20is%20$%20S%20%5C%20/%5C%20%20F$%20for%20$S$%20the%20speed%20of%20sound%20in%20water%20(metres%20per%20second)%20and%20$F$%20the%20frequency%20(hertz).%20Since%20we're%20in%20the%20deep%20ocean%20let's%20say%20the%20water%20temperature%20is%20$2%20C$%20and%20we're%202km%20down.%20Then%20there%20are%20$200$%20atmospheres%20of%20pressure%20and%20Wolfram%20Alpha%20says%20$S%20=%201445$) says $S = 1445$. [This BBC article](http://www.bbc.com/earth/story/20160331-the-worlds-loudest-animal-might-surprise-you) claims a Sperm whale clicks at about $10 \text{ kHz}$ so we get $F = 10,000$. Dividing gives the wavelength of $14.45\text{cm}$.
So I suggest a cloud of small creatures a few metres across with about $15\text{cm}$ distance between each member. Perhaps these creatures can anchor themselves to the squid like remoras and only detach when they hear the first click.
A hunting whale is still able to detect the presence of a squid but with less precision depending on how effective the scattering is. They know the squid is is *over there* but that might be 30km away and they have to guess exactly where to aim. By the time they get there the squid has moved somewhere else. After a while the whale evolves to ignore these *blurred* signals and specialises hunting non-jamming squids.
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I've a few thoughts:
1. Similar to the use of specific geometry and materials in stealth aircraft and watercraft to foozle radar, one could envision a very *bright* colossal squid draping itself with carefully-orchestrated kelp stalks and fronds to disguise its form, and to both absorb and randomly scatter the acoustic energy of a sonar ping...
2. Or possibly there's another simpler answer - if the squid's tissues were in fact close to water's density (and acoustic properties), *and* the surface tissues were carunculated enough (convoluted like the brain) to scatter sonar to hide the transitionary edge condition from glancing angle pings...
3. We could also consider *aggressive* countermeasures: what if the squid had incredibly sensitive hearing in the frequency range most commonly used by its typical predators (5 to 50 kHz.), and what if that hearing was across the whole body surface (with cephalopods, this is quite possible) and upon detecting sonar pings the squid could rapidly triangulate and get the approach vector of the predator in two to three pings, and then *fired a **massive** sonic response on that same frequency with very tightly **focussed** sound* (see second reference below) along *exactly* the same vector, hoping to overwhelm the predator's auditory receptors? Given the auditory sensitivity of the most common predators (30 and 50 dB re 1 μPa) this might not only act as a locational countermeasure, but could possibly induce pain or damage, protecting more than just the individual squid.
References:
<https://en.wikipedia.org/wiki/Underwater_acoustics>
<https://www.sciencedaily.com/releases/2010/04/100421172602.htm>
<https://qz.com/1176982/a-new-superpower-is-discovered-in-the-wondrous-cuttlefish/>
<http://news.bbc.co.uk/earth/hi/earth_news/newsid_8095000/8095977.stm>
[Answer]
**Bubble decoy**
Bubbles are very bright acoustically. Bubble containing solutions are used as contrast for echocardiograms.
<https://www.londoncardiovascularclinic.co.uk/cardiology-info/investigation/bubble-contrast-echocardiography>
This principle was used as an early antisonar measure: a bubble generating decoy.
<https://en.wikipedia.org/wiki/Bold_(decoy)>
So too the squids. Along with ink, they can eject a cloud of bubbles which serve as a decoy while the squid quietly slips away.
Squids generate these bubbles internally by including copious quantities of sea vegetables in their diet.
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[Tiger moths can do this](http://science.sciencemag.org/content/325/5938/325.full)! The mechanism seems similar to GerardFalla's third answer, though they can also [create ghost images](http://phenomena.nationalgeographic.com/2009/07/17/tiger-moths-jam-the-sonar-of-bats/).
@Joe Bloggs: I don't see any reason the squid couldn't do this at a range of frequencies. I haven't done the research, but I wouldn't imagine the frequencies for whale and ship sonar are terribly different
[Answer]
[Noise cancellation](https://en.wikipedia.org/wiki/Active_noise_control). Just send a sound back at the source that is identical to the sonar but exactly out of phase with it. This will result in no noise being returned to the sonar's source.
So what part of a squid could evolve to generate this sort of noise? I'd suggest a modification of their mantle cavity. Squids can suck water into their mantle cavity and squeeze it out to propel themselves. They are string to propel themselves out of the water for short distances [[wikipedia]](https://en.wikipedia.org/wiki/Squid#Description). This organ could conceivably be modified to produce sound by vibrating the cavity.
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**Imagine**: A Kardashev Type I civilization mainly resides on a planet analogous to Earth, with one moon, analogous to Earth's moon. Eventually, the society grows so complex that machines filling space becomes a serious problem: the world's growing population needs food more than it needs machinery, but it still wants to balance both with the space it has.
Their solution: Building a Death Star like object, roughly the size of their existing moon, in orbit. Its function will be doing all computations required for the civilization, and then some; it will handle all storage of data, and other things that the planet can access wirelessly, to preserve space for farmland and residential areas at home.
**Let's ignore unless necessary:**
* How such an object will be constructed. Let's just assume at this point in the civilization's life, building this is plausible.
* Where the resources to build it will come from. Assume that all necessary materials can be procured and transported from the inner asteroid belt with relative ease. Somehow.
* Why it needs to be so large. Assume this civilization plans to rely on this object for centuries or millennium to come, so they are building it with far more processing power than they currently need.
**But let's not ignore the following:**
**In this scenario**
how would such an object realistically receive power?
*Note that this method should be on or inside the satellite, that it should power the entire volume of the sphere, and that if it produces heat, there should be a way to reduce its effect on the machinery.*
[Answer]
I like your [original](https://worldbuilding.stackexchange.com/revisions/58737/1) formulation more, as it shows some of your thoughts about such construction.
# a) Prevent Collisions
1. You can build this structure on the moon itself.
2. If you build it in lower or higher orbit it will take ages for a collision, to happen if any. There is a lot of space between planet and moon where such construction will be perfectly fine.
3. Build it in the same orbit as the moon, but on opposite side of the Earth. It will need some positional corrections, but as far as materials go, it should be not a problem. (Do it same way as you would haul materials to the moon-station.)
# b) Power
Solar power is not a bad choice actually, since you are primarily concerned about interior temperature. Solar power will provide the same order of magnitude of power as the waste heat you can radiate away from your station.
Solar is reliable; it will work for long time, will not blow up your station, and is a constant steady flow of energy.
You are wrong saying that the station - *will be at an angle too acute or too obtuse to use effectively with stationary solar panels*. The station should rotate with angular velocity 2$\pi$ rad per year so it faces the Sun with one side (there will be small perturbations, parallax, not perfectly circular earth orbit, and construction should avoid earth's shadow by choosing orbit->orbital period).
For most orbits(for orbits with inclination more then few grad) there will be 2 times per year when shadow of earth covers small section of that orbit, and station should not be there for that time. So we just should avoid Sun eclipses, but that is actually rare situation and no very long lasting one as we may see on moon examples, and it is possible to avoid it, in case when we choose orbit and phase angle of our station on that orbit and have some means to correct orbit a little.
If you have thermonuclear power - great, but to exceed amount of power you get from solar you need to have big radiator, almost the same size as you would need solar collectors for same power production. Thermonuclear may be more efficient allowing radiators to work at higher temperatures (because hot end of thermonuclear reactor is millions of Kelvin).
* hot end temperature of thermonuclear reactor is millions of Kelvin, temperature of plasma where reaction is happening, so if cold end will be 10000K, so potentially efficiency may be 99.99%, and 10000K of radiator (plasma ball contained by magnetic field) will radiate away 10000 more energy then 1000K radiator. Efficiency of TR will not be 99.99%, mostly because we are not capable to convert all sorts of energy released in the process - neutrons, gamma, muon's, at that temperature(million's of kelvin), as we can do it with plasma. And energy released in the ways which we can't efficiently to utilize may be significant portion of total energy, it differs for different reactions but it counts by 10's of percent of it.
# c) Temperature and Power
* *Generator*: The temperatures of the hot and cold reservoirs of your power generation system define Carnot efficiency: $\small\text{Efficiency}=\frac{T\_{hot}-T\_{cold}}{T\_{hot}}$
* *Radiator*: The heat radiator works using black body radiation. Power emission from a black body follows the Stefan-Boltzmann law, $Q=\sigma T^4$, where $σ = 5.67×10^{−8} W m^{−2} K^{−4}$, where $T$ is radiator temperature.
* Assume desired internal temperature of 300K
For solar power generation $T\_{hot}$ is about 6000K as maximum; If the cold reservoir is 1000K, then maximum efficiency is about 83 percent.If 1000K is the temperature of radiator, then it will emit 56700W from each square meter of surface. For each 1MW produced electricity you should have about 3.62 $\text{m}^2$ of radiator, and about 245 $\text{m}^2$ of collector.
A second set of radiators is used to dissipate heat and cool down the internal structures of the system, where we use this 1MW of electricity (which eventually generates 1MW of heat) to do some computation work. Assume coolant temperature is about 300K (same as internal temperature) on the input of radiator and 250K coolant on the output end from radiator back in to internal system, then average energy flow from radiator will be: $j^\*=\frac{\sigma}{5}\frac{300^5-250^5}{300-250}\approx 330W/m^2$
* 1/5 comes from integration $\frac {\int \sigma T^4}{\Delta T}$, it is kinda average flux from radiator over surface of that radiator, because of temperature changes from 300K to 250K on radiator surface. We pump heat carrier in to radiator at 300K, and return it at 250K. Radiator will have hotter zones and cooler zones. And if we have radiator divided in 50 zones(for each 1K) with equal surface for each zone, average emitted energy will be that integral divided on temperature difference between heat carrier we pump in and pump out.
* Result is just approximation and do not includes other effects which maybe good to consider there - like [Heat capacity](https://en.wikipedia.org/wiki/Heat_capacity) is not strictly a constant, and if heat carrier changes phase gas-liquid-solid. Heat carrier can be solid object, which you just physically move as solid object. Those details depend on particular implementation and construction of that radiator and heat carrier(s) used.
* also I use 1 side of radiator here and in other calculations below, but for flat radiator it is possible to use both sides(both sides emit energy, it is kinda my error, because I'm used to spherical emitting surfaces), so for flat radiators 1/2 surface of my calculations is possible.
* kindly added by [kingledion](https://worldbuilding.stackexchange.com/users/23519/kingledion) upper limit for thickness of radiator shell made of aluminum.
To support this heat transfer, you need sufficient heat flux in your radiator. Assuming an aluminum heat sink (thermal conductivity $k = 205 \frac{\text{W}}{\text{m}\cdot\text{K}}$), then using 1-d Fourier's law $330 \frac{\text{W}}{\text{m}^2} = 205 \frac{\text{W}}{\text{m}\cdot\text{K}} \cdot \frac{dT}{dx}$, $\frac{dT}{dx} = 1.6 \frac{\text{K}}{\text{m}} = \frac{50 \text{K}}{x}$, so radiator can be no more than 31 meters thick or heat flux will be too low. Heat flux is no problem.
For each 1MW of electricity used inside the station you will need about 3030 additional square meters of radiator. You can use active cooling and have higher radiator temperature and thus less surface area. 600K will get you 16 times reduction of radiator surface, but overall energy efficiency of the system will drop.
The heat radiation efficiency of this system is already a problem. With 1000K of radiator temperature, the surface of a station the size of the moon can dump 56700 $\small W/m^2$. And for each square meter of surface there is 580000 cubic meters of volume in a 'death star'-like sphere where this 1MW of energy can be used. 56700W used there is literary nothing as one 1x1x2 meters box of servers can consume 10kW easy. So to use that volume efficiently -- lets say 1kW per cubic meter of volume -- the surface of your radiator should be about 10000 times more then whole surface of your moon station.
This volume efficiency is the reason why building on the moon itself isn't a bad idea, because you would barely need all the volume a spherical station would have. You could utilize a 50-100 meter thick layer with hot radiator (1000K), and something like 1 meter thick layer with 300K radiator - covering moon.
You could still solve that problem, and pack 1kW per cubic meter of volume, but the radiator size will be huge. In case, if it is another sphere, then it should have a 173000km radius (which would stretch halfway from the moon to the earth; or 2.5 the size of Jupiter). If it is a disk then the radius must be 2 times bigger: 346000km. And that is when the radiator temperature is 1000K, when it is 300K it will be 13 times bigger, for both the sphere and the disk.
# d) Self Repair
The station would be repaired with the same technology you built it with. If we consider the radiator to be moon size, it will be 37.6 million square kilometers of 1-100 meter thick structure. So you probably should use some replacement for human labor there, probably 100% of it have to be replaced with sort of automatic building producing system. Because even if you use automatic construction machinery for 99% of work(including teleoperation), and there is still 1% of work you can't do remotely, it is kinda similar to situation when people have to build 376000 km$^2$ by them self and it is kinda equivalent to build 300 cities size of 5 million people each, it needs lot of work force(labor) hundreds of million people, they will need life supporting and all kinda stuff humans need, so they have to live there by hundreds of millions. And this situation will be incompatible with reason of freeing space on earth, as obviously shows that humans can live with that technology level in space.
Just use blocks, produce them, and replace them when they are broken and recycle broken ones. Using human there will ruin all your idea of doing that thing in first place.
There are other options possible, but you will still have to have some program for maintenance and repair (aka software and hardware solutions): it will not repair itself, if developer did not developed this process to be part of the system. The designer must choose which technologies to use to repair. Nanomachines, micromachines, macrofabrics and robots could all be used, but these would be the same technology you used to build the station.
Simplest algorithm to repair, just demolition of old block and build in new one on that place.
# e) Own gravity
I will recommend [Isaac Arthur](https://www.youtube.com/channel/UCZFipeZtQM5CKUjx6grh54g) youtube channel, [Megastructures](https://www.youtube.com/playlist?list=PLIIOUpOge0LtW77TNvgrWWu5OC3EOwqxQ) playlist, first 6 videos(as they numbered in titles) or 5th one [Shell Worlds](https://www.youtube.com/watch?v=TfMr_XkWcEs&list=PLIIOUpOge0LtW77TNvgrWWu5OC3EOwqxQ&index=6) if I recall correctly.
Pay attention to active supporting structures, what are their capabilities. So gravity of the body is not a big problem there (body as moon).
* In short, one can build layered structure, supported by active supporting structures(they work same way as [Launch loop](https://en.wikipedia.org/wiki/Launch_loop) can be suspended above the atmosphere of Earth). So any stress which comes from gravity of body itself, can be compensated by those means.
* These active structures may be used to transfer energy in the station, and transfer heat from the station.
* technology used in [this](https://worldbuilding.stackexchange.com/a/45273/20315) answer may be used to solve problems with your station (as it capable to implement an active supporting structure and actually it is used in answer).
Problem with that solution is that by using it, you do not need to build your station explicitly, for the reasons you mention: as for future use and to free space on earth. But such station may exists for other reasons, as example - we just need a big computer. (*Ed note: unclear, please clarify* - overpowered solutions for op's needs/reasons: same way it is possible to move everything from earth in to space(manufactures, people, animals), build new earth each year using Jupiter matter, etc. Problem will not exists, or will have completely different solution. But having Raw computing power is always good reason, where to use is not a problem, problem is to have enough)
Motivation is a big problem in your question, but I consider that also as a thing to ignore, along with problems like where to get materials, where to get energy, which technologies used for building etc.
Regarding gravity and system effects - if earth has 2 moons of the same mass it will have no effect on solar system, and not big effects on earth(there will be some, tides will be reduced significantly, how behave atmosphere(wind maps may change)).
However, if you move the station to L1, and solve L1 instability problem (as example by releasing and contracting counterweights that may be part of the station itself like cores and radiators), then gravity forces from that body will be 4% compared to moon forces, with will significantly reduce any effects this body may have on earth, including tidal problems.
But considering the radiator problems, if the size of the structure is limited by the size of the radiators being equal to the moon's surface area, then the mass of the whole construction will be an insignificant, 0.00X% of the moon's mass - and it will have no effects on earth.
## Critique
In short, if you have the problems stated in the original post, it is very hard to both stay on earth and be able to build this station. It will need considerable amounts of energy generated in space, materials moved, etc. If you can already do that, it might be easier just to build space habitats which will free from lot of constrains, including those you have mention.
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Let's focus on the "how does it recieve power" question, as you wish :)
I suggest using a [Dyson Sphere](https://en.wikipedia.org/wiki/Dyson_sphere). It's the one single most reliable and powerful source of energy you can obtain in our solar system. If that's not what you are looking for, why not put a few fusion powerplants into your death star? If that tech is not available, nuclear power plants will also do. And if they are also not what you require, nuclear batteries can produce low levels of energy for a loooooong time (iirc there are radioactive materials that can provide energy for 17.000 years+). you will need a lot of those, though.
Whatever you do, no source of power comes without maintenance, and given things like [Moores Law](https://en.wikipedia.org/wiki/Moore%27s_law), your computer will require upgrades all the time, anyway. Also, radiation in space is not friendly to computer parts, requiring extensive shielding and exchanging broken parts. So i am pretty sure your moon will be full of people maintaining and working on the computer.
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The entire paradigm of massive scale, dealing with enormous amounts of power and dissipating heat really leads to the conclusion that you don't *want* a moon sized object at all. Rather, you need to take the volume of the computing devices you intend to build and distribute it over a large volume in space.
This has a multitude of benefits:
First off, it scales nicely. Each day your launch system can deliver an arbitrary amount of computing devices into orbit or into deep space (more on that later). Your system is available from day one, and continues to scale much like adding racks to the server farms of cloud computing companies, or massive datacenters like Amazon.com or Google.
Second, every element can be exposed to sunlight for energy. You don't have to worry about huge fusion reactors, geothermal taps, cable bundles and RF interference from the electrical system, each chip is attached to a small solar cell which provides energy.
Third, since each element is exposed to space, the Carnot efficiency (which MolbOrg talked about in his answer) is going to be extremely high. The hot end is the solar cell exposed to the Sun, while the "cold end" is pointed at deep space, and radiating to the background temperature of the Universe. In the outer solar system, you would realistically be radiating to an infinite heatsink with a temperature of 3K. In the inner solar system, the background temperature is a bit higher. (Incidentally, this is one of the reasons solar cells here on Earth have difficulties, the temperature differentials between the hot and cold sides of the cells is very limited).
Finally, the actual volume of materials will be far less than a moon or planet sized supercomputer, since there is no need for supporting structures, cabling, cooling circuits, lunchrooms for the technical staff (or charging closets for the robots), access tunnels etc. Put another way, you can subtract the volume of the supporting structure and have as much computing power on a smaller budget, or use the entire budget for computing elements and have a much greater amount of computing power.
"Wow!", you say, "where can I get such a system?"
Amazingly enough, this is based on the work of Keith Lofstrom (Inventor of the [Lofstrom Loop](http://launchloop.com)), and he calls this idea "[Server Sky](http://server-sky.com)". Early versions can be in orbit around the planet itself, for proof of concept and low latency (since the elements are close together and close to uplink points on Earth). Later on, these elements can be moved (or new ones launched) to the L4 and L5 points, so you can have massive clouds of elements in free space with much more computing power. The "Server Sky" in Low Earth Orbit can be maintained as the cache so users on the ground still get high speeds.
[](https://i.stack.imgur.com/zsdcB.png)
*Conceptual design of a single Server Sky element*
[](https://i.stack.imgur.com/1rQPz.png)
*Server Sky 1.1 in GEO, hovering over a point on Earth 24/7*
Lofstrom once wrote a small article about Server Sky (which I haven't been able to retrieve, unfortunately) which talked about the ultimate evolution of the system, with a Dyson swarm of trillions of elements sharing the orbit of Uranus around the Sun, utilizing the cold background of space to maintain high levels of efficiency in the computing and energy generation system. You can imagine subsidiary Server Sky clouds scattered throughout the Solar System at various Lagrange points or an artificial "asteroid belt" acting as storage and caches for the massive Server Sky cloud in the far reaches of the Solar System.
So this is a relatively simple, massively scalable, modular system to achieve the goals of massive computing infrastructure for a K1 level civilization. In its fully developed form with clouds of elements in the deep solar system, it is an analogue of Dyson Swarms to create a [Matrioshka Brain](https://www.youtube.com/watch?v=Ef-mxjYkllw), which should provide all the computing power a single solar system could need.
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My gut feeling is that you apply a paradigm from the 1960s, the mainframe, to the far future. Projecting current trends, I imagine that data processing will look much different in the future. It will be hard to pinpoint, actually, because *everything will be a computer*. All human artifacts will be intelligent and networked. It's possible that self-organizing computers will extend into the earth's crust using self-replicating nano or micro technology. Low-power will be a paradigm, and everything will just use heat differentials (including geological ones) or light as energy source and thus not contribute to global warming. Computing power will be where you need it (what good is an answer from the fastest computer if it takes the eternity of 2 seconds to arrive?).
But then, I may just be applying a paradigm of the 2010s to the far future.
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The problem is not how it could receive the power (could use the internal nuclear power source like a star, seems plenty of energy for everything) but how would it dissipate the heat, much bigger problem in the modern human made machines.
Unless some advanced technology allows the computer to operate at stellar temperatures, making it a "thinking star".
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I read somewhere that there are really gigantic electric currents circling around in our magnetosphere. For a machine the size you are thinking of, can there be a solution involving having a liquid iron core, a big magnetic field and capturing solar wind charge as energy? Someone with better physics than me might be able to expand on this idea.
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Let's focus in the main question. The moon where the supercomputer would be built should have a hot core, as Earth has but not our moon, in order to exploit its [geothermal energy](https://en.wikipedia.org/wiki/Geothermal_energy).
If the civilization is advanced enough to be able to build a planet-sized supercomputer, it should be able to take efficiently the energy from the depth of the moon, as a first step in the design of this colossal system.
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[Question]
[
The consensus ([1](https://en.wikipedia.org/wiki/Megafauna#Timing_and_possible_causes), [2](https://en.wikipedia.org/wiki/Quaternary_extinction_event#Overkill_hypothesis)) is that the reason most continents have relatively few large animals compared to Africa is that humans, even stone age humans, were able to drive them to extinction. African animals survived to some extent because they had time to adapt to us before he had decent weapons.
What could prevent an expanding human civilization from driving to extinction the megafauna in a newly-settled area?
For the scenario I have in mind, humans have early-Renaissance technology: iron and steel, some gunpowder arms, sophisticated governments with the ability to finance exploration and conquest in remote areas. Magic also exists, but I'd prefer not to handwave with "[a wizard did it](http://tvtropes.org/pmwiki/pmwiki.php/Main/AWizardDidIt)."
One simple answer is that these humans simply value large animals more than... any people historical ever have. Yet even if there's some interest in and understanding of ecology, it's hard to see how that could prevent hunters from knocking out the largest (and presumably slowest-breeding) animals like [Elasmotherium](https://en.wikipedia.org/wiki/Elasmotherium).
Note that a few large animals did survive humans' arrival - bison, kangaroos, llamas. I'm looking for reasons why an area may plausibly retain a substantial quantity of large animals despite, say, a hundred years of very low density settlement (trappers, prospectors, a few trading towns) and another century or so of low density farming and hunting.
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Make them tastes bad. Make them mildly poisonous.
So that people don't eat them all.
Make them non hostile.
So that people don't hunt them to protect their communities.
**Make them produce economically useful materials in a way that doesn't require their death.**
Perhaps their dung is the ultimate fertilizer, perhaps their hair/fleece makes the finest garments or their urine is a source of a useful drug or material.
So that people want them alive near them on a continuous basis.
Make their hides/skins/organs/tissues that require their death to extract awful to work with or only useful for low quality work.
So they don't get killed for their skin, teeth, bones etc
Make them breed reasonably fast. So they don't go the way of the panda.
Have them eat things which humans and their livestock don't normally eat.
So they're not in competition with humans.
Make them trainable and friendly so that humans are likely to use them as work animals like giant dogs.
Give the humans a religious reverence for large animals.
To make it socially taboo to harm them.
[Answer]
* Make them useful and easily domesticated. If the draft mammoth is more efficient than the draft horse, people will keep it around.
* Make them useful in the wild and let people realize that. Perhaps the wild mammoth is the only thing to keep tyrannosaurs in check, yet harmless to people. To prevent mammoth-slaying by selfish hunters give them religious significance.
[Answer]
Dragons!
Humans thrive in any area where they are the uncontested apex predator.
If a team of properly equipped humans can take down an area's biggest predator, then that predator and all of its prey, are on the short list for extinction.
Second only to ice-ages and meteor strikes, we are the greatest extinction machines that our poor world has ever known.
So the answer to your question is, dragons! ...as in Reign of Fire Dragons.
Add an apex predator that is so fast, so well armored, and so vicious, that no number of renaissance-level humans can win against even a single one.
The presence of a greater threat will unify the humans and all the other potential dragon prey, into an internally non-combative group; focused on their collective mutual survival.
Then after a few generations of cooperative peace between the animals and the humans, have the dragons fly away, to hunt in other lands.
[Answer]
The megafauna would need to not be worth making extinct. It really is that simple.
Have them not directly compete for resources (perhaps they live in inhospitable areas). Have them not worth hunting. No valuable tusks, not much meat or very bad tasting meat, even make them poisonous.
Imagine something like a poisonous tusk-less woolly mammoth (or just have a culture where tusks have no value). You can't eat it. It's dangerous to hunt. It spends a lot of time living in areas where humans don't want to.
To be honest just making them poisonous or really bad tasting herbivores would most likely be enough. (And poison that isn't easy to get rid of by just cooking them). Herbivores mean they aren't hunting humans. Poisonous means humans aren't hunting them.
[Answer]
## World-wide spread Islam (or Judaism or any food annoying religion).
Hallal and Kasher rules do not really forbid hunting. But it makes it so unpractical that it almost doesn't occur (at least in Indonesia, where I am living).
If other religion still exist, believers could hunt for money (hence the elephant or rhino hunting occurring in Muslim countries). But if worldwide it would stop food-driven hunting.
## Super-efficient vultures
If not in a fully controlled environment (a slaughter house) as soon as you kill an animal, swarms of scavengers (rodents, birds, flies... you choose) arrive and steal your kill. Making hunting impossible
## Low human population
Because of wars, epidemic, world size (ringworld)
## No overlapping
Obviously, megafauna survive in ocean because human dwells on land. In a highly different world, you can imagine human living underworld or in elevated cities (Ewok style or balloons)
## Milking
Not literally as I can't imagine milking a wild T-Rex. But sperm whale poop is used to make perfume.
You can imagine a similar useful resource to be found in large mammal dung.
Not too far fetched: it's the only fertilizer they know
This would means people wandering the countryside towing a cart and waiting for some diplodocus to have a shit :-)
## protection
In this world, human have deadly predator (giant eagle?). But this predator dare not approach something as big as a mammoth.
## Animal heat
Extreme seismology make house building unpractical. The best way to survive a cold night is to curl next to a sleeping mammoth (who accepts you as you protect him from predator ... meaning you don't want those predators to get extinct)
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One very simple way is, nonlethal weaponry. Actually it is easier to develop a reputation as something to be avoided if the ones who have to avoid you survive. Think of skunks. Does anybody bother them? No. Humans could develop powerful repellents that would drive the predatory, belligerent megafauna away without killing them.
The simplest way to prevent humans from driving megafauna to extinction is geography. Put some kind of big, fat wall\* between the humans and the giant beasts, and have humans just not really that crazy to go there. Suppose that on the American continent, there was a tree that killed off humans by poison. All the Megafauna became immune. Humans have not as yet felt the need to conquer America. Since the explorers never got back, maybe they don't even know it exists.
\*Obviously, this would not be a literal wall, but a natural barrier, unless there was a super civilization that wanted to preserve the megafauna. In that case, it's still all about the barrier, but not really. Then we need to know why the megafauna is desired.
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I like to go with the simplest answer. Perhaps it's just a question of conscientiousness. We need other species in the world - we're not the kings of the planet. If we keep destroying everything everywhere, we'll end exiled, without other species, and we will basically plunge into self-extinction.
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The only way I see mega fauna surviving in human settled lands is if they were inedible and either useful or innocuous.
1. If they can be farmed and are a more efficient form of meat than
other animals (like the grass is too tough and to invasive for cows
but megas can eat it) then their populations will increase as we
assure their survival. If they are more useful for transportation
they will be kept and bred.
2. If the mega fauna isn't useful, and we can't eat it, then it's only
hope is to not be a problem. If it doesn't eat humans or their
crops and, for some reason, they don't trample our crops, people
won't take the time to wipe them out. That doesn't mean that we
won't wipe them out, just that there's a chance that we won't.
[Answer]
Large animals mostly survived in Africa. Because humanity evolved there for hundreds of thousands of years and those animals evolved accordingly. When humans migrated to other continents, big animals there simply didn't have time to change(biological evolution is slow).
So if there is one big continent that is reasonable easy to travel around, then humans would spread easily and most megafauna would adapt and survive.
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[Question]
[
I am toying with a scenario in a RPG where *the catastrophe* has
happen (financial desaster, meteorite hit whatever) which has wiped
out large parts of humanity and caused a complete breakdown of civilisation.
In the course people who have been overspecialized must now learn
to improvise and learn general techniques again. No "I cannot do *that*"
or "I haven't learned *this*", there is nobody else available. Poor
metallurgy expert for plane turbines, you are learning making knives
again, hehe.
One of the characters will be a housepet vetenarian who is now
responsible for the health of the group. This raises the question:
**How much knowledge has a vetenarian which (s)he can apply to hairless
great apes?**
At least I think (s)he should be able to healing wounds, giving shots and setting bones. While I have background knowledge for the other characters, I am quite clueless what veterinarians could do. Given that vets forced to
heal humans comes up in other media, it is also a general question about the abilities of vets and how to realistically portray them.
The group has all relevant knowledge (anatomy maps, pharmaceutical
products) available (rugged laptop with solar power cells).
[Answer]
Depends on the veterinarian--same with doctors. Like a Podiatrist or Oncologist might not have SURGICAL SKILL at all. They might leave that to someone else. It's not like TV.
A veterinary doctor is far more likely to have more flexible skills, actually, unless they specialize in something like reptiles or birds.
**Stitching and cleaning a wound**: Both vets and human doctors can do this. Both know how to. Both know about antibiotics.
**Basics of Setting a Bone**: Both vets and docs can do this, but again, it depends on the individual.
What we're talking about is emergency medicine, which EMTs are trained to do. A vet actually does have to perform emergency medical stuff in a dang field in the middle of nowhere more often than a regular doctor.
Anything beyond this, like major surgery will be... different. Though not as different as you might think. Research on dogs and cutting edge treatments not yet available to people sometimes appear in the vet world.
The best vet or doctor will be one who doesn't specialize and has lots of work.
I lived in a rural area, with lots of farms, I know vets, and I have seen them work. In some cases, they will actually be more equipped to deal with a medical emergency and calmer than a conventional doctor. In a single day I watched vet look at a sonogram in the middle of an open field, stitch up an eye wound, and clear up a case of colic. A typical doctor will likely be ear nose and throat -- or a gynaecologist, or a gastro doc. But a vet has to deal with all these on a day to day basis, mainly with mammals.
[Answer]
First, I upvoted Erin's answer; Vets should be great at just about everything.
I keep dogs as pets; one of my dogs had bladder stones and my local vet did the surgery of opening him up; cutting open the bladder, feeling around and getting all the sand and stones out; and putting him all back together. She didn't screw it up, my dog recovered fine. My dog wasn't her first; she had done dozens before him.
Vets can do full hip replacement surgery on animals with arthritis, they can amputate hopelessly damaged or diseased limbs and fit animals with prosthetics; in my neighborhood there is a dog with an artificial front right foot (I don't know the owner; another neighbor says the dog's original foot was run over by a car. Must have been a traumatic time for all).
The extremes may be a problem, things that vets often do **not** deal with, because at some point we just euthanize animals; such as those struck by cars or bitten by snakes.
Also the vet may not have had any experience with many cases of human health care like transplants, or chronic illnesses like tuberculosis or spreading cancer.
Human doctors have hundreds of ways of keeping a person alive for years, spending hundreds of thousands of dollars, long after an animal owner would have given up. Vets may be ***aware*** of such measures but have never been personally involved --- just because euthanasia is very seldom a choice (or may even be illegal) for human doctors, patients, and guardians of patients. Especially euthanasia to **save money** on further (or continuous) treatment or medicine.
I am noting this because in game play, these extremes may present useful obstacles. On average your vet would be able to treat things like gunshot wounds, knife stabs, broken legs, etc. In such cases consider the vet exactly like an E.R. doctor, with full surgical ability and complete medicinal knowledge.
But if you need plot points where players must make choices, your vet might not have any experience with more extreme health care choices.
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Building on Erin's answer (which I upvoted): Vets will have tendency to rely on what they see instead of what the patient tells them, which may be an asset in an emergency.
Anatomy and physiology of mammals is similar enough that much of what applies to animals can also be applied to humans.
As Amadeus points out (I did not upvote him because I think conclusions he draws are not pertinent) Vets are much more used to consider their patients "expendable", so some finer (and decidedly all "cosmetic") aspects would be lacking.
Another point favoring Vets in respect to "real" M.D. (and to keep in mind in the plot) is a lower degree of specialization; essentially farm animals and pets (there's more than that, but majority is there), while human medicine has become fractionated in such a high number of sub-sub-sectors it's very likely a modern doc would be almost useless for at least two reasons: his knowledge is restricted and thus probably case at hand lies outside it (with possible exception of First-Aid M.D.s) and he is too spoiled, relying heavily on Lab tests and other exotic specialistic exams which might not be available.
A thing a Vet is better to learn fast is humans are much less resistant than animals (even house pets) so they must be treated with more precision (drug dosage, suture points, ...) or they'll break.
## Disclaimer
Everything I wrote above and all I will write below is from my personal knowledge and experience and is thus limited, in particular it's geographically and culturally localized to Europe, in general, and Italy, in particular, which is where I live and work. I strongly suspect things may be very different elsewhere.
I don't know if this is the recommended way to answering to other posts (see below); please redirect me as needed.
## Clarification
As there has been an exchange of comments with @Amadeus I feel like I need to clarify my position.
I am specifically speaking about M.D.s as we averagely find in Europe, I'm pretty sure nothing of this would apply (as an example) to someone operating in a small hospital in some sub-Saharian village.
Medicine, in the Western countries, has progressed impressively in the last 50 years (that's the period I witnessed, being slightly over 60), as many other things, including computers and transportation.
The latter is particularly important because it opened the road (pun intended) to the switch, in Italy it happened in 1974, to the abolition of the so called "Medico Condotto" who was responsible for sanity in a neighborhood assigning this responsibility to nearby hospitals, rationale behind this was road system was good enough to allow fast intervention even from a reasonably longer distance.
For Medicine this was an epochal change because it shifted responsibility from a single individual (however supported) to a "structure" where many individuals cooperated, but none was alone.
All this lead to a better services (up till current crisis where financing has perilously dropped, but that's not relevant here), but also to fragmentation of knowledge, to the point that, since 2001, it is possible to become M.D. without *any* knowledge in First Aid.
Similar path was followed by pharmacists; I remember very well, when I was a kid) staring for hours to the village chemist (a friend of my father's) weighing and mixing and diluting and compressing and ... whatever. Nowadays perhaps a Pharmacy in ten (at most!) will accept to do Galenic preparation (and most of them sub-contract others to do the real job) and pharmacists, after years of studying chemistry and the like are reduced to the status of "high level sales clerk" who never used their knowledge to do anything more "practical" than discerning two boxes contain the same thing under different names.
Vets, OTOH, are following the same route, but they are very late and thus, if it is true we see some "vet clinics" (mainly for pets) which are structured like hospitals (with comparable set-up and *prices*), it is also true most of them operate alone, often with very low-tech equipment, a much restricted array of instrumentation and drugs and less (if any) lab tests.
Speaking about blood (or whatever) test labs: they followed the same path, with the "real work" done by machines, so that analysts are more or less tending and calibrating machines they would hardly be in position to replace personally.
While I'm *not* trying to belittle the gigantic steps done by medicine in the last 100 years, I see that it has become increasingly dependent on a wide organization and in a post-apocalyptic scenario the very first thing breaking down is exactly organization; this means:
* Machines would break down and it would be increasingly difficult to get replacements.
* Supplies will be in short availability and would have to be substituted with "equivalents" (if and when available).
* The doctor would be alone, possibly with whomever he managed to train.
* The pharmacist would have to actually prepare the drugs, possibly resuscitating whatever knowledge about medical plants.
* Herbalists would become in great demand (not the ones we see selling herbs coming pre-packaged from exotic places, but people able to harvest herbs in the woods and/or to grow them in the backyard).
* Lab analysts would restrict a lot their capabilities and would be forced to do things personally, including gathering supplies.
In this condition, for the sole reason of being already nearer to these (bad!) conditions, I believe a Vet would be immediately much more effective than a generic M.D. and *infinitely* more effective of an old specialist (who had the time to forget anything about general medicine he learned so much time ago).
In a reasonable amount of time (few years) I believe a young generic M.D. could adapt and learn to be what's needed in the mutated conditions, possibly surpassing Vet abilities.
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In terms of emergency medicine, vet is good (I upvoted Erin's answer too).
On the other hand, a **human doctor will know much, much more human illnesses than vet**.
For example, someone has raised temperature and rash. It could indicate to hundreds of diseases. Experienced therapist
* Knows what is more probable for *this* patient in *this* case
* Could recognize different types of what we call *raised temperature*
* Knows what to look at to detect the disease
* Knows what pills could help and how different pills interact with each other
* etc
The veterinar could read some books, but the real reason could be described in the last page, modern drug is absent and outdated one is present but described in another foliant. So it maybe too late.
Also with surgery: without practice the veterinar could find something in patient's belly from third try.
---
My own hierarchy of useful doctors:
1. Human doc with experience both in three areas: rescue service, surgery and general therapy
2. Human doc with experience in any two areas from three
3. Human doc with experience in only one area. It's what most people mean when say **doctor without narrow specialization**
4. Veterinar with experience in large animals from farm.
5. Human doc with pratical specialisation like therapist
6. **Just man** with experience in rescue service
7. Veterinar with experience in cats/dogs surgery
8. Human doc with experience in non-practical specialisation like *gastro doc*. They also learned general human-oriented medicine theory so they know at least name and symptoms of many diseases.
9. Human doc with only theory in three areas from **1.** option
10. Similarly to the 1-5 but without practical experience and with theory only
[Answer]
To add to previous answers: worth considering that a vet with recent experience of farm animals may encounter issues more familiar to post apocalyptic humans; mineral deficiencies, infections, parasites, etc. Other answers and comments have discussed surgery quite a lot, but in rural places often it's being able to identify micronutrient deficiencies and the like, which is definitely going to be a problem with humans rummaging about the ruins too. People in the developed world sometimes suffer mineral deficiencies, never mind when the food supply has collapsed. Sheep wandering the hillside suddenly appear akin to human survivors.
Vets might find an animal like a goat which had been living in the countryside, but the owner complains it has lost all energy and can barely stand up. They take a look at it, there's nothing obviously wrong. So they give it a [salt lick](https://en.wikipedia.org/wiki/Mineral_lick), and all of a sudden it gets up and seems back to normal. Maybe a mineral lick is most undervalued item in a post-apocalyptic scenario?
However, best possible medical professional would likely be an army surgeon recently from a conflict like the Korean War. In that war they ran out of medical supplies after two weeks and had to improvise.
Field doctors often told soldiers to put it in a bucket of hot water. Which worked wonders for minor ailments given the magical power of the placebo effect. Another common concern was parasites. Sometimes soldiers weren't grooming themselves enough, complained of feeling exhausted, only to take off their shirt and reveal they were crawling with blood sucking lice. Or complain they had worms. How did they know? One crawled out of their nose. Okay, well take two tablespoons of engine oil. Why? It'll make you sick, but it'll make the worm sicker.
Those sorts of problems will be far more familiar to a large animal vet than many specialist doctors. And undoubtedly far more likely in a post-apocalyptic scenario.
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Vets are likely to be quite effective as doctors, generally, although they may lack some more specific knowledge and some areas, like for example psychological trauma, are probably beyond their area of expertise.
However, there are distinct differences in the way in which vets and doctors interact with their patients, and this is likely to make a difference in how they are perceived by, and interact with, a human patient. They are more likely to be 'hands on' in diagnosis, less likely to take into account patient's descriptions of symptoms (or necessarily to understand them) and, although they may well have normal interpersonal social skills, would not have the interpersonal skills which an experienced doctor would have acquired and may appear off-hand and detached when dealing with a patient of their own species. They may also feel awkward when making intimate physical examinations of friends and colleagues, even though as a vet such physical examinations would be essential to their modus operandi.
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**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
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You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49).
Closed 6 years ago.
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In my story, there is a character who can go back in time, and has done so already, for the purpose of getting rich. He is not the main antagonist, neither is he the main character. He is mostly just a guy who saw a chance to get a ton of money and took it, and will obviously be important to the plot.
His "get rich" technique went like this. Bring with you, either in paper or virtual format, many interesting stories, books, movie scripts, etc. I haven't decided yet exactly how far he went in the past, but let's assume he has no trouble reading his stuff, so no more than a few decades.
Then, back in time, he "writes" himself big hits like Harry Potter, to get all the money and fame instead of J.K Rowling. He does that for several big media. He copies them word for word, and releases them early enough so that the "real" author can't go to court with their own manuscript, because they have no such thing, and even if they do, everyone thinks they copied our guy's book, and not the other way around.
It works pretty well, and he earns a reputation for mastering several different writing styles and settings.
My main character is aware of the existence of time travel, but has not used it himself yet. He lives in the "past" that our con man travelled to. Time travel is **not** widely known, and both those guys encountered the information by complete chance.
I'm looking for a way to figure out the con's scheme from the past, when all you have is a vague suspicion someone is up to something through time travel, because they need specified tech for another purpose.
The setting is not final, but it goes like this: in 2010, mr X steals time travel technology from evil corp, and uses it to get rich in 1990. Evil corp has no way to reproduce the technology, but has already sent one more guy a bit earlier for their evil plan. Main character in 1995 is aware of evil plan, and tries to stop it, and his only chance is by borrowing/stealing time travel device from mr. X in 1995 and use it. Main character would not be thrilled by mr. X's scheme, but also has more important priorities so wouldn't mind allying himself with him if required. Mr X didn't plan on using the machine again, but is doing all in his power to hide its existence while still making millions.
I am looking for a way to see through the scheme enough to at least make contact with mr. X, even without understanding the whole thing. What mistakes are either unavoidable or very likely to be overlooked when using that plan? What signs are noticeable to someone who is aware the tech exists, but not where it is or if even anyone has used it?
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The first thing that will stand out about this con man is that he will likely be self published. If he's working with a publisher he'll be working with an editor and when the editor says "can you change this" massive red flags will be raised when the change comes back with a wildly different writing style.
This gives him two options. He needs a patsy editor to rubber stamp the books(although I'm not sure how many publishers will accept an outside editor), or more likely no matter how big he gets he will be self published.
Of course unless your protagonist is in the publishing industry they're not likely to be privy to this sort of information. So the more likely red flag is the different writing styles.
Every writer has his own style, little choices that when put together are like a fingerprint. To take an extremely simple example i would use colour over color as I come from a Commonwealth background rather than an American one, so one book with Commonwealth spelling and one with American would be a massive red flag. Of course spelling is simple to change with a word editor but choice of words, and construction of sentences and paragraphs is more fundamental and difficult to change.
So a good way of getting your protagonist to discover this is have them be a massive fan of Mr X and have them realise that it feels like there are different authors writing these books, yet there's the same guy's photo in the back of the book. With his suspicions aroused the protagonist could start investigating.
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It is not uncommon for an author to have notes, ideas, fleshed out scenes and the like done years ahead of the work in which they finally appear. MC could be the brother of one of these starving artist types - a truly gifted guy who has been trying to get his stuff published for years but whose eccentricities and disorganization works against him.
When the artist recognizes his exact text in the best seller he has a cow of course. But Mr X is famous, gets lots of attention from groupies, fans, enemies etc and unfortunately the artist has had some mental health issues in the past. No-one believes him except his brother MC who actually had read the stuff some years before.
The eccentric artist brother is a fine side character for something like this. I envision Luna Lovegood played by Steve Buscemi. MC has to be methodical and organized which gets boring.
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The days directly following Mr. X arrival in the past, are when he will be most vulnerable and detectable. At that point, he has no time-appropriate credentials, no personal contacts and is pitifully out of sync with the culture and current events of his destination date. This is also the point when Mr. X will be addressing his greatest and therefore most revealing challenge... making sure that time travel does not get created in the future from which he comes. Only by changing the events which lead to the discovery of time travel, can Mr. X make himself safe from Evil Corp's retaliation. So during the first few days of his time in the past, Mr. X has the least resources and the most outlandish goals. This is the time when your hero can uncover his evil plan.
But even during these vulnerable moments, your hero needs three things...
* She must be in the right place and time to encounter Mr. X
* She must witness Mr. X behaving in a manner which defies other explanation
* and she must believe in the possibility of time travel, because without such belief, she will just write Mr. X off as that rare multi-genre talent (like James Patterson) who can produce best sellers in a diverse spectrum of genre. (I personally don't believe in real-world time travel, but Mr. Patterson and his co-authors are beginning challenge that disbelief.)
The easiest solution to these three requirements is to make your hero a graduating physics student in the process of applying for work at Evil Corp. Have Mr. X know that she is the maverick genius who will someday create the time machine. Have him know that her immediate future history involves her joining a high security research project at Evil Corp, during which time she will be completely isolated from human contact. Mr. X's arrival date is also the date of her final interview. His last chance to stop her from eventually creating time travel is to stop her from getting to that interview.
During Mr. X's under-prepared-for, bungling attempt to intercept her, he drops one of his books (perhaps Harry Potter and the Prisoner of Azkaban as it involves time travel). As she escapes Mr. X's clutches, with incriminating book in hand, she has met all three of the requirements above and she is well on her way to uncovering his evil plan.
-- on a brief aside --
I believe that Mr. X's plan would probably not work. Any successful book is much more than simply great writing. Best seller's come from those rare moment's when everything clicks! Just the right story reaches just the right initial audience which wins it the support of just the right spokespersons to put it in front of the world at a moment when the world is hungering for just that story. With all due respect to J.K. Rowling's beautiful prose, I doubt that Harry would have become a household name, if his adventures had started even one year earlier or been published and marketed by anyone other than the people and firms who pulled off that real world magic.
In your story, Mr. X is most likely destined to see only moderate success with his purloined creations and will very quickly wish that he had pursued the more standard sci-fi trope of historic stock investing.
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There are a few ways that Mr. X could slip up in a noticeable way.
A lot of authors' longer works are based on ideas, settings, characters, and plots that they previously explored in other media, such as short stories.
For example, Doc Smith's [Lensman](https://en.wikipedia.org/wiki/Lensman_series) series of books were mostly published in the 1950s, but they were based on short stories Smith had written (and published) in 1930s and 40s. The same pattern (of writing successful novels based on short stories previously published in pulp magazines) holds true for much of golden age science fiction, from Heinlein and Asimov to Bradbury and Clarke, but the pattern extends to modern authors as well, such as Stephen King (whose 1982 *The Dark Tower* was a collection of stories published from 77 to 82).
Another consideration is that copies of manuscripts can exist several years prior to a work being published. For example, JK Rowling's Harry Potter manuscript was written in 1995 and rejected by 12 publishing houses before being published in 1997. If Mr. X doesn't pay careful attention to the history of each manuscript, he may run the risk of introducing it after it's already been written in some form; he may even submit it to a publishing house where it's already been rejected.
As an aside, a slightly different take on this underlying premise has been partially explored to great comedic effect in the short story "[Who's Cribbing?](http://www.unz.org/Pub/StartlingStories-1953jan-00083)" by Jack Lewis (Startling Stories, 1953). I won't spoil it for you, but it's worth the read.
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Here is a story snippet for this case.
When he is a little kid, the main character develops an encryption technique to hide messages in text, and never tells anyone about this. He doesn't necessarily suspect anything at this point. He is just an eccentric guy who likes to do unique things.
As a habit, he uses this technique on every text he reads and writes. Someday he notices several books that generates interesting messages when this technique is applied and he begins to suspect the existence of this time traveler. These books are all written with the same style and he suspects that he is the author.
To clear his suspicions, he begins to write a book, which he planned since he was little so he will surely recognize if it was his book. He hides a secret message with his encryption technique, as he always planned to do with his books.
To discover the identity of Mr. X, he should add a little twist to this encryption technique, or include a message only X will understand. He could talk to X using his books. He could exploit a habit of X. This part is tricky but there are many possibilities, and this is what that will make your story unique.
Long story short, he cannot discover the identity of X being a third person. He should be the one whose books are stolen. He will also need cooperation from X. If X really wants to stay anonymous, MC would never be able to find him.
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I'm assuming that the time traveler will publish before the original author is even born, let alone starting to write.
Works of fiction have lots and lots of cultural references. Ask yourself without google, since when are suspects being read their rights in the US? When did the UK start to award O-Levels to students (cf O.W.L.s in Harry Potter)?
Works of science fiction have lots and lots of fictional cultural references. A well-known example is Heinleins [dilating door](http://tvtropes.org/pmwiki/pmwiki.php/Main/DilatingDoor).
An astute reader might wonder about cultural references to events/developments which came after the delivery of the manuscript, and which the author got *exactly* right. Say a "Miranda" warning in a 1965 crime story, when that case was still in state courts and going against Miranda.
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If the time traveler brought back books, the suspicious person could locate the stash of books and just check the copyright date. It's no proof, but it's certainly evidence.
If the suspicious person destroyed the books and the time traveler ceased writing, that would foil the get-rich-quick scheme as well as providing more evidence of foul play.
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For a third person, it is virtually impossible to detect "Mr. X", unless he has some major slip up.
An original author would suspect that something is not right, but unless the manuscript was prepared years in advance (and there was a proof for it), the author would most likely be quiet. So everybody else would not suspect anything.
So, what mistakes can Mr. X make?
Obviously, he may be caught in the act of time traveling, or accidentally bring some artifacts from the future. Or his books may contain references to real world events that have not happen yet in 1990, but would happen few years later. Or (since Mr. X is from near future) there is a younger version of Mr. X in 1990, and if those two versions are not closely and carefully cooperating, some people would notice. Or Mr. X may have one too many drinks with your protagonist at the bar.
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The day on Earth begins as normal. People go to school, go to work, eat ice cream; nothing is amiss. Then, without warning, the sky seems to break open in a cacophony and flashing lights, and one-million unrelated people from around the globe find themselves falling upwards and into it. When they are able to orient themselves, the multitudes make two important discoveries:
1. They are currently treading water in the ocean about one hundred meters off-shore .
2. A ton of trash, loose objects, and furniture that could serve as aids to flotation seem to have accompanied them in the transition.
Unbeknownst to them, they have been instantaneously transported to another planet, perfectly earth-like (same/extremely similar flora/fauna, same size/gravity, same sun type, same moon type). There is absolutely zero chance of making contact with Earth, or returning (the planet is on the other side of the Milky Way, or in another galaxy altogether).
**So here's the question: How long does it take them to get out of this dire strait, onto dry land, and to develop a new social order/civilization?** I'm looking for estimates with good reasoning behind them, taking into account the number of people, their 21st century knowledge, whether whatever items they happened to have in their pockets could play a significant role, as well as whatever you think may be important. The climate that they've appeared in is Mediterranean.
The preferable unit for an answer would be generations, but feel free to give one in an actual time-unit as well if you think you can make a good case for it.
**This has been getting some great answers! Here's an edit to clarify some points:**
1. Detail on the population
* Anyone in the world could be part of this group, therefore things like language and cultural barriers are as problematic as you'd expect.
2. More on the circumstances of departure
* Everyone leaves at the same time. This means that some people are at a disadvantage, because it is night when they are taken.
* However, assume that the transition is disruptive enough that if you are asleep, you WILL be rudely awakened, and have enough time to come to your senses before you're dumped into the water.
3. More on the circumstances of arrival
* The area area of arrival is around 35 degrees north of the equator.
* It is early summer on the planet.
* The people arrive in the early morning (~ 30 minutes after dawn).
* The people are distributed up and down the coast widely enough that on average each person has a bubble of personal space 10 feet in radius.
* There is enough flotsam that people who cannot swim/poor swimmers have a reasonable chance to survive until rescue or until they are washed ashore.
4. The ocean
* No strong swells or currents; there is a light breeze.
5. The land
* Sandy beach gives way to sparse woodland/plains around 50 meters from the shore. It becomes mountainous around 20 miles inland.
* There are ample sources of fresh water: streams, creeks, one or two major rivers. People won't have trouble finding water (though contamination may become a problem quickly?).
* Otherwise, you can assume that the land is as accommodating to survival as any that naturally occurs on Earth.
6. The sky
* Stars, planets are completely different from Earth's.
* Moon is same size and brightness, but its surface has not been changed to resemble our own.
7. **What I mean by "civilization"**
* I'm actually surprised that no one has called me out on this one yet. By civilization, I mean a centralized society that encompasses a large percentage of the descendants and has developed a unique language, culture, and identity.
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First things first:
## G - The Gathering
You say that
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If this is true, then those people are gathered at different times - or they arrive at different times, or there is some way that they are gathered at different times but arrive at the same time.
If people are gathered at the same time, their state in Earth previous to G will be different: if Americans are caught at work, the Chinese will be caught at sleep, and conversely. This may significantly affect the prospects of survival. If you are caught at work, or transportation, while fully awake, it may be a lot confusing to find yourself in the water of a foreign world, but you are at least awake. Being transported while sleeping will add a lot more confusion and disorientation, and might give those people a lesser chance of surviving.
If they are gathered at the same moment of the day - ie, at 8 AM in the US and 8 AM in China, and so at different times - they would arrive at different times to the new world; if the Americans arrived in the morning, the Chinese would arrive at night. And this would again massively affect their survival prospectives, those who arrived during the day having way better chances to get to the shore than those that arrived at night.
And these differences in survival opportunities between the Chinese and the Americans would probably reflect in the cultural/linguistic environment of the surviving newcomers. Randomly, about 250,000 of them should be Chinese, but if the Chinese are caught at night or arrive at night, their numbers could be severely harmed, resulting in a less heterogeneous - and less representative - sample of newcomers-who-get out from the ocean.
So the logic solution is that everybody gets caught in the morning, not too early - say, about 9:00 AM - but by some magic/fluke of reality all of them arrive simultaneously. That is, G is spread along full 24 hours, but A - The Arrival - is within a single moment.
This unfortunately does not solve a similar problem regarding the year time. If Russians or Canadians are gathered in December, they will probably be too much dressed to swim properly, and will be at a disadvantage regarding people from the Southern Hemisphere or the Tropics. So perhaps everybody needs to be disrobed for the "trip", in order to preserve the proportion between Swahili speakers and Slavic languages speakers. Or G would have to happen all across the year, with people magically arriving at the same time.
After (I suppose; with this kinds of things one should not be too assured that the arrow of time doesn't misbehave, or that causality doesn't get messed) being caught, then people will be ready for
## A - The Arrival
The time of arrival won't mess with the proportions of people of different cultures/languages/nationalities as much as G - but it will affect the prospects of everybody. Few people will get to the beach if A is at night, and if people arrive late in the afternoon, even if there is still light enough for everyone to see where the shore is, they won't be able to get a decent dinner before sleep, nor a breakfast the following dawn. Their chances would be maximised, in contrast, if A was relatively early in the morning, allowing them time to collect some fruit, hunt some birds, or fish something for lunch.
Similarly, I would say pretty much everybody would die if they arrive in Winter, or late Autumn, and perhaps even early Spring, and the place of arrival is too far from the Equator. So time and place of A should be taylored for this circumstance; either something like late May at 30 degrees North, or October at 30 degrees South, or under 20 degrees from the Equator either side.
Weather will be important, too - it is different to arrive at a whole new world in a sunny day with a mild breeze, or under heavy rain and strong winds. And these waters where they are arriving - are they free from sharks and other predators? Is it the high tide? Are there strong currents?
But all of this is easy. Big problem is, we are talking about one freaking million people, and people occupy space. They won't be able to swim, or do much besides drowning in their respective places, if they do not have a considerable space to move. In a **very** conservative estimate, at the very least some six square meters per person, a three meter long and two meter wide rectangle, so that they can move their arms and legs without hitting and kicking each others (and I fear this is still way too crowded for a happy outcome). This means the very bare area of six million square meters, which my school teacher told me equals six square kilometers! That is, if everybody is in between 100 and 200 meters from the shore - a tenth of kilometer wide band - they need to be spread through sixty kilometers, parallel to the coast. And better the coast ahead of them be relatively plane shores, not cliffs or rocky formations. So the place for A should be sixty kilometers long of calm waters, in front of nice beaches.
So, they come to the shore. That's
## L - The Landing
Now everything went well, and the best part of a million people are at the beaches of an unknown continent - or is it an island? - of an unknown world. There is again a problem of space. They will again need some 100 meters between the sea line and mountains or jungle or other rough terrain, so that they can seat down, make some protective arrangement to avoid sunburns, and be able to even think about sleeping next night.
So L needs to be situated in relatively wide coastal plains, with not too dense jungle too close to the shore, but also not completely barren, for people will need shadows to protect themselves - palm trees, perhaps, with long and wide enough leaves that one can rest under them. And people will need fresh water - rivers, brooks, lakes - unless this new world has oceans of dessalinised water. Which will quickly change the geometry of the aglomeration of people - instead of a narrow band along the seacoast, narrow bands along the riversides. Which in turn demands more depth for the plains and lightly vegetated area towards the interior.
So the placement of L is quite complicated if you want to avoid high mortality on the first day.
Now that we have a million people landed into a new, unknown world, without the pressing need of disposing with too many thousands of dead co-catastrophers, the simple phase is over. It is time for complicated things, such as
## B - The Breakfast
People will soon get hungry. And besides perhaps a few candy bars or cookies they might have in their pockets, or find among the debris, they have nothing to eat. So they will look for fruit. And here is the problem; you say that this is
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> another planet, perfectly earth-like (same/extremely similar
> flora/fauna, same size/gravity, same sun type, same moon type
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And I am quite willing to believe you about gravity, sun, and moon (and atmosphere, and relief, and wheather, and whatnot), but fauna and (especially) flora will be different, barring some magical intervention from the gods who organised this event, because Earth's flora and fauna have been deeply modified by human activity. It would nice to find some bananas there, but they will probably be much smaller and less sweet than Earth's bananas, artificially selected and hybridated, during millenia, for size and flavour. And if they meet wolves or mooses, those won't be Earthan wolves or mooses, who know humans, and how much dangerous we are.
At this point, objets randomly transported from Earth may be important. Who wouldn't like to have a gun, or a steel knife, or a packet of matches (but those would be wet, and as such useless, unless they can dry them, perhaps?) in such a situation? Those things will be the more precious as they will not be renewable in the foreseeable future; once the matches have been used, fire will be only possible through more primitive methods. Luckily someone will have a magnifier, and be willing to use it to light bonfires for everyone. All hail our leader, the magnifier owner.
But let's admit that people find enough fruit - or edible mollusks and insects (though probable it will take some days starving for them to overcome their prejudices against those, and with some luck they will find ways to capture some rodents and fish, or perhaps even a deer or some other bigger prey), so B is solved. What humans do when their bellies are full? Exactly, here comes
## T -The Thinking
Something extraordinary has just happened. Up to now, people had to swim, get shelter, and some food, so they were too busy to think about the extraordinariness of this event (and those who tried probably failed at the more urgent tasks). So what happened? Is this a different location on Earth? Are we going to be rescued? Why don't the cellphones work? Is it Heavens (where are my 72 virgins?!) Or is it Hell? The sun and sky seem the same as Earth's sun and sky, so why would anyoune think this is another planet? Maybe when night comes people will realise that the stars and constellations are different; if it is a night of full moon, they will noticed that it doesn't display exactly the same pattern of craters and maria we are acquainted it (how many of those million people would be able to notice that?). Or is the similarity so great that the moon is not only the same size and brightness, but has the same selenography? Is there a place in the Milky Way from where we would see essentially the same sky as in Earth?
Anyway, unless some totally unusual thing shows them that this is definitely not Earth, people will spend what part of the morning they aren't searching for food wondering about rescue, and probably wasting time at trying to bring it upon themselves. Ligthing a huge bonfire, struggling against those mute cellphones, trying to google what to do, writing on the sand, whatever. If other things, such as fauna easily recognisable as un-Terran, or differences in sky (a green sun, two moons, where is Ursa Major or the Southern Cross?) don't help their insights, they will take days, perhaps even generations, to realise that this is another planet.
This is going to affect their strategies. If you realise you are never going to see your homeland again, it is a whole other situation; you are no longer trying to get back to where you come from, and your actions need to be different. But this will be not only thought; it is going to be talked about. Now languages come into issue. You can help a person to get out of water, you can point to a fruit or for something that give some shelter, and language won't be a real problem. But you cannot discuss what this event really is unless you share a language. People who speak relatively uncommon languages will be at a disadvantage now, and only a few languages - Chinese, English, Spanish, Russian, Portuguese, Hindi, Arabic, Japanese - will have really significant amounts of speakers, in the tenths of thousands.
But with talking, comes
## C - The Conflict
Now people have material for one of their preferred activities: infight. Doubtlessly, religions explanations will be immediately popular. It is the end of the world, it's the second coming of Christ, God is punishing us, we are the chosen ones (one has to wonder why how many infidels among the chosen, but who wants to get across God and his misterious ways?), on the contrary, we are the damned, repent, rejoice, prepare to die, mend your ways, pray, ask for forgiveness - there is plenty of material for big and small cults, sects, religions.
Such conflicts will have practical consequences, of much more concern than theological ones. Should we move or stay here? Should we explore the hinterland or remain close to the shoreline? Should we try to make boats and explore the sea (are there visible islands that might spark their imagination?), should we go up the river(s)?
From C, evidently, comes
## D - The Dispersion
And about time, because we wouldn't like them to suffer overpopulation in an underpopulated world. They will move around, some along the shore, to the North or to the South (or East and West if it is the case), some will go up the river, some will try life in the forest or the mountains, some will get boats and try to reach other islands, some will stay close to the landing point. And this will criss-cross with the languages they speak and with the interpretations they make of the meaning of the Event. We'd rather talk in English about how God is punishing us than listen to the Japanese bragging about being the chosen ones.
Then the size of the new world lands comes into question. If it is a small island, far from the continent and from other islands, they may be condemned to an overpopulation crisis very soon. Else they will disperse and lose contact with each others; in three generations, the Event starts to become legend, the existence of other human groups may become dubious, the idea that they "came" from a different world will become more and more unlikely.
And so they prosper, multiply, and conquer the new world.
Until the next Event. Also known as Volume 8 of the Trilogy of five...
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From the comments below,
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> However, the one thing that it's missing is technically answering the question - from here, how many generations do you believe it will take before a centralized civilization(s) forms?
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Their situation somewhat reminds me of Trotsky's theory of uneven development of capitalism. These people have gadgets produced with ultimate 21st Century technology, but they do not have either the knowledge nor the material or social means to reproduce them. And, worse than that, they miss older technologies too. It is true that a lot of those people will be agricultural workers if the sample is representative of our world. But a modern agricultural worker deals with seeds that have been amply modified by a hundred centuries of continuous agriculture, and it is dubious that they can identify the wild varieties of wheat, oranges, or spinach that gave origin to the modern plants, or that they will have the knowledge of how to grow them - not to talk about how to avoid insects, fungi, and other plagues that may attack their plantations. Or how to grow any plant without additives for the soil.
They will have to try, but that experience will take months, during which people will have to resort to collection, fishing, and hunting. If they succeed, it is then possible that they will have restablished the Neolithic within a year; but that demands that people can feed themselves without agriculture for that period - without agriculture, without many modern tools and without any medieval or ancient tools (a few guns perhaps, but no bow and arrows, for instance), and without palaeolithical knowledge that has long been lost (how to make tools of silex, how to identify the signs of nearby venisom, how to fish with a spear, how to identify poisonous berries and shrooms, etc). So this is going to be a very critical and stressful first year; if they landed too far from the Equator, a failure in that first year will quite likely mean mass starvation, resulting in possible extinction or at least in greately reduced numbers. A tropical setting would be more promising because they would probably be able to survive on collected fruit and roots even during the cooler season.
If they manage to successfully grow plants in their first year, then they will have the basis for sedentary life, and some of them will be settled in villages in a relatively short span of time. It is unlikely that all that population would agree to wait for the success of the agricultural experience without dispersing into the hinterland. Once the coastal groups have amassed some grain, it is quite probable that they would be faced by those who opted for nomadism coming back and demanding some of it, which could spark a first war among them. In such scenario, the nomads, who would have been perfecting weapons for hunt, would probably be in a better position to fight. That could destroy the fledgling new civilisation, and remand all of the new world mankind into pre-agricultural modes of existence.
Of course, recognising useful knowledge and skills will be essential for survival. The problem is that knowledge and skills that are useful nowadays probably won't make any difference in such setting. What good is a IT wizard, or an engineer for people who have to learn how to hunt and how to plant? Even an artisanal smith or weaver, supposing there were some among them, what could they do without iron mines, without lambs for wool, without furnaces and looms? It is possible that people would be better served by an archaeologist who knows how to chip silex.
Worse than that, remains of modern knowledge and technology can be actually harmful. A gun and a few round of ammonition may give people some meat for some time, while delaying serious efforts to develop new weapons - and possibly allowing those who own those guns and know how to use them lopsided positions of power, from which they can actively disencourage research for technologies that would reduce their authority.
So there is going to be a huge crisis in transmission of knowledge to the next generation. Whatever those people know, they will try to pass ahead; but their ability to discern what, from their Earth experience, is useful in the new conditions will be dubious - and those born in the new world may come to reject such experience as useless and fantasist. A great problem will be writing; without proper material support for the activity - and they won't have paper, not to even talk about electronics - and without an immediately visible utility, it may be lost, or reduced to a few individuals that may make of it the basis for a caste distinction, subjugating others to the "magic" of mysterious symbols.
With those caveats, I would say that, with luck, they can be able to retain the technological level of neolithic settlements, and so start from a position corresponding to about 10 thousand years in Earthan past. They will certainly have some objects to remind them of more advanced technology, but if those things cannot be put into use and reproduced - and most of them won't - they will probably acquire the status of magic objects within three or four generations, ie, as soon as there is no longer anyone to remind them that those things were practical gadgets for their ancestors. Development from this early neolithic stage would probably be easier and faster for them than it was for us, but I wouldn't expect them to re-develop metallurgy, much less iron and steel, before several generations; they may have metallic models to inspire them, but the art of extracting metal from ore will be lost and will have to be relearnt from scratch.
Much will have to do with impredictable events - floods, droughts, rigorous winters, epidemics, that could set them back for long times and destroy accumulated knowledge. Nate Silver makes the point, in his The Signal and The Noise, that previous to the printing press, mankind could not even think of knowledge as a long term cumulative process, rather thinking defensively of knowledge as something to be preserved against the attacks of time. If so, the idea of progress, so dear to us, would be lost in the new world, because the printing press certainly would be among those things forgotten in the firts three generations.
In such a scenario, it would be difficult to predict how fast they would move ahead. Anything besides agriculture, perhaps pottery and the wheel, will quite certainly need to be reinvented, because they won't be able to rebuild it in three generations, and from the fourth generation on, the direct connection with the old world will be lost.
From the early neolithic into civilisation, we spent about 5,000 years, or 250 generations, in Earth. If they have a huge enough continent with decent rivers, or an archipel with sufficiently close and numerous islands to move from one another, if they can retain agriculture in the first years, and if they are not decimated by war or natural disaster in the first two or three generations, they should not take longer than that, and would probably be able to do it in a quite shorter time, perhaps "only" a millenium or two. But it won't be a revival of Earth's civilisations; it will be a whole new civilisation (or rather, a whole set of brand new civilisations) built from scratch.
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## It's gonna be a few centuries
Economy is a function of organization and population size. Losing 60 to 70% of the first million is going to make it hard to recover quickly to 2010-level technology.
In the first five minutes, you'll lose about 44% of your people since the Red Cross estimates that only about [56% of people can actually swim competently](http://www.redcross.org/news/press-release/Red-Cross-Launches-Campaign-to-Cut-Drowning-in-Half-in-50-Cities). So there's your first evolutionary bottleneck. *If you can't swim, you died in the first 10 minutes.*
## 1st Hour
Anyone who's going to make it ashore has done so. One hundred meters offshore isn't too far to swim but fighting with so many people to get ashore will further increase the casualties. Let's assume that another 10% of the original million drown from exhaustion. Combine this with all the random junk that people can get caught up in; this landing is going to make D-Day look like a cake walk.
## 1st Day
The stench of 600,000 bodies is starting to kick in encouraging the survivors to move away from the landing zone. Water is going to be a huge and immediate concern. Tribes will start forming as soon as people hit the beach. Unification based on language, skin color, dress, whatever, will start quickly. Communication and coordination will play a huge role in who lives and who dies.
## 1st Week
The dispersal is fully underway. Without agriculture, there just isn't enough food to support hundreds of thousands of people. Food acquisition will be a huge concern. Tribes will spread out looking for food, shelter and safety. Some of the more forward thinking start looking for potential iron and copper sites to start mining for tool production. They'll probably find them.
Survivalists are in their prime.
## 1st Month
Doctors, engineers and scientists will be in high demand. Doctors to keep everyone alive (as much as they can); engineers to design the new tools that everyone will need; scientists to figure stuff out. As anyone who has a played a survival video game will tell you, keeping yourself alive is hard. Many of the tropes in post-apocalyptic movies will show up. Roaming gangs, murder over bread, war lords, sickness, extreme tribalism. Hopefully, with the lush Mediterranean climate, much of this ugliness won't need to happen.
All of the old trades, blacksmith, weaver, potter, smith, that people did because they were fun as a hobby, find themselves in demand. Blacksmiths rocket to the top of the popularity charts as the people who can make anything.
## 1st Year
Welcome to the Stone Age! Without any iron/steel/copper tools, everyone is going to have to make do with stick and stones. Geologists will be in high demand to find and exploit iron and copper deposits. Metallurgists and smelter operators can command any price they like because they're the only people who know how to take iron ore into something remotely useful.
## 1st Decade
A new language has emerged that pulls influences from all the languages of the suvivors. Primitive economies have formed. Trade routes are underway. There's probably been the first plague by this point. Assuming that humanity hasn't sunk into the classic post-apocalyptic downward spiral, I would be making a huge effort to preserve as much knowledge from Earth as possible before the people who know it die off. Gaining that knowledge took centuries on Earth, so the more info/knowledge that can be preserved, the farther ahead these reluctant colonists will be.
With the kickstart of Earth knowledge, it's possible that iron work has improved to low quality steels. Using these crude materials, it's probably possible to make lathes, drill presses and other metalworking machines. Even without specific knowledge of how a machine is supposed to work, an operator will know the behavior of their machines on earth and will work to duplicate those capabilities. Metric measurements will have finally won. Since there isn't any incumbent manufacturing to prevent migration from imperial measurements to metric, there's nothing to stop everyone from finally standarizing on metric. Finally!
Cities and towns have grown up using local materials, styles and preferences. Agriculture has been worked out or there won't be enough people to form a civilization.
## 1st Century
Population is stable and growing. Adaptations to the local climate and food supplies have finished. Animal domestication is in full swing. Everyone who first came from Earth is dead. Hopefully, they wrote down the things they knew before they passed. With good enough tools, they might be able to get primitive vacuum tube computers. Going beyond vacuum tubes could be tricky since the economy may not be big enough yet to support the kind of capital investments required to allow transistor development.
## 1st Millenium
Assuming a 1.2% growth rate, the population at the end of 1000 years will be about [60 million](http://www.metamorphosisalpha.com/ias/population.php) or somewhere between [3000 and 1000 BCE](https://en.wikipedia.org/wiki/World_population_estimates#Before_1950) (depending on who you ask). Welcome to steampunk Ancient Egypt!
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### Civilization is People and Processes, not Gadgets
What they have in their pockets and what they carry ashore from the debris is **completely** meaningless. Civilization stands and falls with having a society.
* They will have to start with subsistence farming. Not enough of the people will be farmers. The realistic answer would be mass starvation and die-offs.
* A random group of people will have some criminals. In a modern society, most citizens have delegated dealing with them to trained professionals. Another random group of people will be cops, judges, prosecutors, but they won't be *organized* enough to keep the law.
* Who pays the cops, and the teachers, and the sanitation workers? Will the survivors accept the tax collectors when they come around?
* For that matter, there won't be consensus on what the law is and should be.
* Medical professionals will know much more than a tribal shaman, but they expect pills to come out of a bottle.
User SRM mentioned *Lost* in his comment. *Lost* were [few enough people](https://en.wikipedia.org/wiki/Dunbar%27s_number) to form a community. A million is too much without governmental structures.
### My Prediction for X plus 10 Years
* There will be fortified villages or city states with outlying villages.
* Roving gangs of bandits in the forests.
* Wooden huts, perhaps even stone buildings.
* Most tools are wood or stone. There will be some surviving tools and a trickle of new production iron (no steel yet).
* They will attempt to produce paper and preserve a written culture, but it will be touch and go. Do they have materials to make paper?
But it won't be entirely neolithic. People accept the concept of democratic government and fair trials, at least in principle. They understand the germ theory of disease, the principle of crop rotation, etc.
### My Prediction for X plus 10 Generations
The villages will unite into states. Bits of preserved knowledge will have been implemented (water mills, perhaps steel, perhaps even electricity). They might retain things like algebra and even general relativity, but there are few practical applications for that.
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Sorry, but there is high chance all of the people will die or at least enough that any form of civilization is not possible.
Let's go through it in order
* Dropping shocked, clothed, people directly into water with sea currents is recipe for genocide. I would guess at least third of people would die right there.
* Those that will survive this will have hard time following that. Nearby area they landed on will be stripped of any food within hours. And they most probably won't spread fast enough to get into areas with plenty of food. So I would guess next third of people will die within few days from starvation or being killed by other people.
* Their 21 century knowledge is actually working against them. Most people from developed countries don't know how to farm, what food can be foraged from wilderness, how to make even basic tools from wood, stone and plants. Etc.. So even if people will not drown and move into area with plenty of resources, they will be on the level of neolithic.
If you don't want to just kill them all, you should instead grab them calmly from their sleep, place them gently on the ground in area without many natural dangers and spread out enough that people don't compete for resources. Maybe even give them few books on food that can be foraged and prepared without farming.
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"*Rome wasn't built in a day*", goes the popular saying, and it hasn't ever been truer.
Civilisations are formed from the co-operation of thousands upon tens-of-thousands of individuals, each possessing relevant skills and knowledge enough to survive and prosper by converging together - generally under the leadership of a select capable sect - in the name of life.
The people of the largest or strongest civilisations, in almost all cases, originated form the same planetary origins - regions, countries or pre-existing colonies that expanded their numbers by conforming the populous of surrounding locations to their way of life. Their pre-existing social cohesion acts as a foundation for further empirical growth, which without would see any hope of a greater civilisation fall to pieces (there being no trust or structure or purpose among it's members).
Simply dropping a million persons, from all regions of the world, with very little in common in the way of cultural likeness, language and beliefs, is a recipe for civil destruction rather than growth. By simply looking at humanities judgments toward each other, to those ethnicities other than oneself or social minorities today, it becomes apparent that this will be no leisurely journey...
[Dunbars Number](http://www.bloomberg.com/news/articles/2013-01-10/the-dunbar-number-from-the-guru-of-social-networks) refers to the theoretical limit to how many relationships a person can maintain at any given time, derived from the regular brains capacity for storing information; every single relationship made will count on this planet. These million people (or those who survive the initial splash down) will form instant connections with those they relate to on a more personal/cultural level, immediately dividing the future-civilisation, for despite them all being in the same survival situation, pre-existing bias/barriers still exist; this will need to be over-come if there is to be any chance at colonial development.
The skill range of these people will also need to be taken into account; by law of distribution, almost no-body in the million will possess the skills relevant to survival (accounting or quantum-physics not exactly the most helpful...), potentially thousands having no knowledge on life at all (being children or un-educated) and those who do will be limited in who they associate with to begin with...
This civilisations best hope comes in the emergence of a clear governing body, a caucus of people who share the essential knowledge of survival - hunting, farming, construction, human resource management, health care- who will be most qualified to lead the masses; but as explained, this will be no easy task and could potential prove to divide the emerging culture more.
## So.
This established, how long will it take?
In a word entirely devoid of usable power, functioning technology, advanced tools and appliances, basic shelters, readily attainable food sources... Civilisation is going to take a while to take off.
If a leadership group emerges, it will most likely only get a small fraction of the million to co-operate, humans being largely self obsessive, the rest resisting to form their won splinter "alliances" with those people who most resemble one another in ethnicity, language, culture or belief system.
This isn't such a bad thing though, provided violence remains frowned upon and any who commit "felonies" are dealt with according to judgement of the majority (hence the beginning of a justice system).
The groups would live in relative proximity to one another, forming ever more intricate housing over time, as people learn from their leaders or from experiencing failure (the gathering and distribution of essential knowledge); any non-vital information will be forgotten over time (as those who held it die/ find it irrelevant).
As groups form alliances with their closer neighbours, they may merge, this process continuing over the course of generations until there remains only one sole community of which internal social sects (the original groups) provide a different skill set or value to the civilisation as a whole - just as modern day people live and work.
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I'm a bit more of an optimist. If you were lucky and had a few people who stepped up and were experienced and talented leaders with an immediate vision (e.g. someone experienced leading large military units to organize aid following major natural disasters), it might be possible to get a critical mass of people into a series of large organized chiefdom polities with perhaps several hundred to a thousand people each quite quickly. And, the bigger the short term initial groups are, the less time it takes for them to consolidate with each other into something resembling proper nations.
Normally, it is hard to get people to coalesce around a leader, but in a total vacuum of leadership or society organization, it is amazing how many people one leader can get to follow their lead spontaneously.
For example, I have run large (several hundred attendee) political caucuses in Presidential election years on several occasions. And, most people have no clue what to do. But, if you shout clearly and loud enough to be heard by everyone in earshot and act like you know what you are doing, and quickly draft a few people who aren't totally dazed to be your lieutenants, you can bring a gathering that large to order remarkably quickly because in the situation, nobody resists your authority that you establish in mere seconds.
I've either heard described, or seen with my own eyes, similar feats of mass crowd control at political rallies, rock concerts, boy scout jamborees, military exercises, religious gatherings, sporting events, a beach full of people where someone has figured out that a tsunami is imminently en route, and in cities facing imminent air raids or attacks in wartime.
A loud voice and communication of a clear vision from someone who sounds like they know what their doing can go a long way, as long as the vision holds out.
The trick is, however, that for this to work, the would be leader has to seize authority over a large group while everyone in that large group is atomized and hasn't had time to form localized alliances and factions with their neighbors. If this happens enough times in the first couple of hours, the cause of civilization will be advanced by decades. If it doesn't, it will be a long slow haul.
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I'd also recommend reading "Why the West Rules (For Now)" and any other work which tries to put history in a broad context. It talks about the major developments required for civilisation to start up and move to the next step.
I'm not going to talk about any of what happens regarding immediate arrival, since people have come up with some amazing answers regarding that, but rather, talk a bit about some of the major milestones that affected Civilisation that are worth thinking about.
So, @LuisHenrique pointed out that the biosphere has been heavily modified by human interaction. This is true. One of the really interesting things about the development of early agriculture, when we went from hunter-gatherers to the first settled societies (with the largest urban dwellings being villages) was that it involved (at least in the Western parts) a mutation involving grain that wasn't useful for it but very good for us. Similar mutations in rice kicked off the Eastern civilisation a bit later and similar things happened with squash, potatoes etc elsewhere.
Also domestication of the first animals and the selective breeding to ensure they become more useful caused animal agriculture to become useful.
Have these happened? What is the available biosphere? Depending on your choices, it's possible there's nothing anyone can do to achieve a standard of living better than hunter-gathering. Additionally, I don't think the earliest crops or domestic animals were very wide-spread. Depending on the exact nature of the biome make-up and the spread of crops, gathering the necessary stuff could be easy or impossible hard. Whether the society ever gets beyond hunter-gatherer would strongly depend on that.
I notice you say 35 degrees north and that's interesting, because if you're feeling kind, the easiest start you can give them is the Turkey/Syria Hilly Flanks region. Off the top of my head, that small region is 11 of our world's staple food crops and animals, which, while the best of all the places agriculture started independently on Earth, isn't a wide variety of food and animal labour. Next best is China, I think, and it took Roman times until the crops from one centre of civilisation crossed to the other.
Still, assuming you do give people a good chance in terms of available species, I'd imagine the jump to farming would happen very quickly because people would know to go looking for these things (if they exist) and would probably pass them on quite quickly, which was the limiting factor in their earlier spread. It's also worth noting that wild animal populations will not be low like they are now, so traveling will be dangerous.
The next stage detailed in the book involves large major irrigation projects on large rivers. So, it assumes you have large river systems to do irrigation on and the technology to organise society (writing, social methods of cohesion not just involving force), which might get retained if the population can get through the previous stage quickly enough to preserve knowledge.
One of the super-useful things speeding up civilisation will be the lack of disease as a civilisation ending thing. One of the very damaging things that happened was when various independent centres of civilisation started exchanging their diseases with each other. While everyone knows about the colonisation of the Americas, the same things happened between Western and Eastern cores earlier (with just as much death) and at least one reason America was so screwed was that it got both sets of diseases, not just the Western ones. In this case, you probably wouldn't get that, even if people separated for a hundred years or so. Yes disease would be present and increase as medicine collapsed, but you wouldn't get the damaging plagues of mass death. This would rapidly speed things up.
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Hard to give a definite time frame but I will try to give it my best guess.
First week many people die because there don't have the skills to survive in the wilderness.
Second and third week. People begin forming into small groups to share skills and resources in order to survive.
First month the groups become hunter gather tribes.
Second year people began experiment with growing plants.
Fourth year people have built successfully farmes and are forming villages.
One hundred years. The villages have grown to form small city states.
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Ever throw a banana to a group of monkeys? The monkey who catches the banana doesn't have a friend in the world. It's every monkey for himself. It's rather hilarious entertainment.
At the end of the first week, the people who make it to the shore will be in the same condition. After the first time they are robbed of their catch and left with nothing, the survivalists make sure to eat their fill before bringing anything back.
Then when they bring back less than the last time, the self-appointed leaders of the community will accuse them of hoarding. This will lead to quarrels and manslaughter.
The survivalists who aren't killed in this will say, "forget this noise," and leave, taking with them the most attractive member of their preferred sex who agrees to go with them.
Everyone else either learns what the survivalists already knew, or they starve.
Your million people will be around a thousand by the end of the second month.
] |
[Question]
[
In Pokemon, each individual Pokemon “evolves” into a new stage of its evolution. A lot people claim that this can be explained using mere metamorphosis, but there are no mammals that go through such complex metamorphosis.
Using Earth-like biology how can I explain how so many animal kinds (from canines and felines to giant snakes and land sharks) can undergo massive and limb growing metamorphosis? Why would evolution favor a creature changing its form so radically?
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**Biological Baggage** (*emphasis on the logical*)
Some Pokemon, even the mammalian seeming ones, shoot beams of intense cold out of their mouths (Dewgong), lightning out of their cheeks (Pikachu), and have actual burning flames as a part of their bodies (Ponyta). Others appear to be composed of non biological matter (Muk, Porygon).
Given all the laws of biology and physics they seem to break, a little thing like changing form, which real animals already do, hardly seems worth quibbling about.
But let's assume the evolving creatures in your world do not have these unusual abilities, they are just normal animals that undergo vast physical changes.
**Metamorphosis**
As Fayth85 mentioned, insects undergo fairly advanced changes as they go from larva to pupa to adult.
She /he also mentioned birds. [Look at this picture of the Canada Goose.](http://swh.schoolworkhelper.netdna-cdn.com/wp-content/uploads/2011/06/Canada-Goose-2.jpg) It is not just a size difference. The chicks have a much shorter proportional neck and different color and texture of feathers.
Not mentioned however are [frogs](http://cdn-1.frog-life-cycle.com/images/Tadpoles.jpg). The change from a purely aquatic tadpole, to a legged, amphibious animal is fair drastic.
But none of those are mammals. However Humans are. During gestation, before certain hormones take effect, [all fetuses appear physically female](http://www.menshealth.com/health/3-signs-you-started-as-a-girl). They are not, technically the still forming reproductive organs are neither. But in terms of body shape they are, and males undergo a moderate change. Then again, when Humans enter puberty, they go another set of physical changes; growing additional hair, change in voice for male, breasts for females. Which bring us to topic two.
**Sexual Dimorphism**
Even within a given species, the male and the female can have dramatic differences. Male lions are larger, and have a prominent mane that female lack. The male platypus is also generally larger, and also has poisonous spurs on the feet that females lack. Peacocks have huge tail feathers females lack.
There are dozens of other examples one can easily find, but the point here is that difference between individuals in a species need not be limited to age.
**The Answer**
You want a biological way for your creatures to undergo a sudden metamorphosis. Like an egg hatching or a butterfly leaving the cocoon. In which case I point you towards reptiles.
When a reptile outgrows its skin, the outer layer is shed, revealing a new layer, which is generally much more vibrant, and in some species even a different color (some change colors as they age or based on environment or diet).
Your not-Pokemon could do a similar thing, especially if the change was not dramatic (Pikachu to Raichu rather than Teddiursa to Ursaring). The creature changes on the inside at a slower rate, but once it is ready, casts off its outer layer of skin/fur to reveal the new, 'evolved' form.
Or you could just not go with the 'instant' change, and then you wouldn't even need an additional explanation.
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They are artificial creations. Like our current tech, they are designed using modular components, and they accept updates in the field. My Blu-Ray player or dishwasher downloads new firmware; Industrial enginines by [IH](https://en.wikipedia.org/wiki/International_Harvester) can have features like total horsepower *unlocked* or configured by software [while in-place](https://en.wikipedia.org/wiki/JTAG).
So consider the “upgrade” to be designed as something like an in-app purchase from the original maker.
With the loss of original maker and the (actual) evolution of the forms as they became feral, the code is a bit mixed up, like with the [*Dragon’s Teeth* of Mirabile](https://www.goodreads.com/book/show/1141442.Mirabile) by master world builder Janet Kagen. Rather than buy an unlock code, the needed triggers are found by side-effects or evolved access to useful survival traits by the feral form. You might read Kagen's stories to bet a feel for what I have in mind about the DNA.
Being modular, distinct traits like limbs can be recessive or switched off or damaged in a feral remixed offspring. Many features are simple configuration options using common code. Although inspired by legacy bioforms that were unrelated and incompatible, the engineered lifeforms used inter-compatible standardized traits and developmental configuration programming.
Now in ourselves such a change like extra toes would only be effective in the germ line, as development occurs once. But these animals were designed for having upgrades applied. Re-development — metamorphosis — was **designed in** so changes could be *applied* to existing phenotypes.
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Well, the only real-life comparisons I can offer are in insects. But this is similar to a post:
<https://www.reddit.com/r/askscience/comments/1wa9lo/what_is_the_evolutionary_advantage_to/?st=iqqzg3f8&sh=49d88c3b>
If you want to go purely with evolution (no "magic did it"), you might want to consider things like longer lifespans, or simply larger beings that go through phases during their growth. There aren't any non-insect examples I can think of, but a halfway example are birds.
<http://www.pigeoncontrolresourcecentre.org/html/about-pigeons.html>
Because they live 3-5 years on average, it isn't too weird that their metamorphosis goes relatively quickly, but if you take a much larger animal that needs a similar metamorphosis? It could be argued that said changes would take considerably longer.
As for multi staged changes (as in the two higher 'evolutionary' stages of certain Pokemon)? Well, I would argue that because it takes so long, they need to hunt to survive, and therefore evolution favoured a 'multi-stage metamorphosis', to raise survivability of the species.
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As I stated in my answer about cancer, DNA is a form of code. This means that certain conditions could trigger some "code".
For instance, when you go from one page to two page mode in Microsoft word is that a "sudden evolution"? Probably not but the analogy holds.
Simply put, the DNA has sections of code that are essentially massive while loops in sequential order. When the conditions for the loop are no longer held, it continues to the next set of code. The cells change what they do in a drastic metamorphic manner. This could be instantaneous or whatever.
As for how they came to be?
Humans made them. I said in this my poke ball explanation. Granted, these humans do it in secret, and therefore, said pokemon are thought to be a product of evolution.
Also, as charizard came to mind I would like to point out a flaw in my concept:
Birds (and therefore probably dragons) get 60% of their lung capacity from within theor wings. This means that when charizards cells begin to migrate during the sudden cellular behavioral change, even 10% of those cells failing to relocate properly could cause the dragon to be deformed, and possible die. It is incredibly likely that pokemon in this universe jave a high likelihood of death and are therefore an "evolutionary abberation" to most experts.
So, a charizard can exist, and it can potentially grow and evolve properly, but 75% of them will likely die. Perhaps this is the in-universe explanation as to why wild charizards do not exist in the games?
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## Dominant individuals evolve to defend the herd
Pokemon evolution is not quite analogous to insect metamorphosis. The main advantage of insect metamorphosis is that the children and the adults have a separate food source, preventing competition between generations. However, most Pokemon are similar in shape to their evolved forms and would appear to eat the same foods. Furthermore, evolution is not an essential part of their life cycle; most Pokemon are capable of reproduction without evolving, and evolution is not triggered by age, but by winning fights.
I would therefore guess that Pokemon evolution evolved through kin or group selection; it exists to benefit the species or group more than the individual. Most Pokemon are social (which would explain why they are so easily trained) and their forms reflect their social status; the individuals that are best at fighting evolve and become the leaders and protectors of the group. Evolved Pokemon are larger and need more food, so it benefits the group to have only a small number of "alphas", reducing intra-group competition.
There are some real-life animals that do similar things: Dominant male mandrills have that distinctive blue and red coloration on their face and backsides, dominant female hyenas are larger and develop masculine characteristics, and dominant male clownfish and groupers turn into females. All of these species are highly aggressive and their transformations are thought to be linked to their win/loss ratios in fights.
Evolution as it is depicted in the games and show, where a Pokemon suddenly increases in size and mass, is impossible due to conservation of mass. My guess is that this is an exaggeration of the process; evolution is a change of form accompanied by a rapid growth spurt, but it isn't THAT fast.
[Answer]
I remember in middle school, my biology teacher said that evolution can never happen in one generation, but instead happens over many generations. If I remember correctly it is part of the definition of the word "evolution". However, I have read an novel that I think answers your question as believable as possible.
In the novel, the author plays on the concept that we humans only use 10% of our brain/potential (this concept has already been proven wrong, but still simple enough to have a similar concept to play around with). Similar to TheGreatDuck's answer, the author uses DNA code to layout the human potential of being 5 stages, with most humans living in the first stage their whole life. The story gives an example of a news story of an old lady's lifting up a car in order to save her grandson in the spur of the moment (example he made up in the novel), but the old lady dies shortly after. The rule here is that when humans face near death experience, or in the old lady's case, to protect loved ones, we temporarily unlock our next genetic stage, but will have to endure immense pain shortly after. If one cannot withstand the pain and give in, they die. But if they sustain the pain, they retain their next stage forever.
So there's the author's version of "evolution", where humans "evolve" when facing near death experiences. If that's what you were looking for.
I am unable to provide the novel because it is an online Chinese novel, and is not translated.
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[Question]
[
A small creature I have in mind is highly toxic and constantly glows as a distinctly visible warning to everything else at night. It would use other warning methods but they're not really visible in the dark and is only active at night due to its nocturnal nature.
It is an insectivore scale-less reptile that has a similar body build to a gecko and has the ability to glide if it needs to.
The constant glowing skin is from the luciferase pumping through its veins and is produced by an organ specifically dedicated to do so. While I know organisms can produce luciferase, I don't know how metabolically expensive it is and if its constant production is feasible.
**Is it feasible for an animal to constantly produce luciferase for bioluminescence purposes or would it be at risk of going into a metabolic or nutritional deficit because of it?**
[Answer]
Wikipedia states regarding [bacterial luciferases](https://en.wikipedia.org/wiki/Luciferase#Mechanism_of_reaction):
>
> The efficiency of many examples of bioluminescence in nature is
> astounding; with more than 90% of energy input turned into light. By
> contrast, figures quoted for a 150lm/W LED suggest that around 20% of
> the total energy used is converted to visible light
>
>
>
**Compare to a mouse:**
A mouse [base metabolism of 0.35 W](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596737/), if an additional equivalent amount were expended on light production (needing just twice the food for rest metabolism), then it could produce the equivalent of the light output of a 1.5 Watt LED, that's pretty bright (I should add that my favourite keyring-torch is less than a tenth of that power).
**Conclusion.**
Lizard's rest metabolism is much lower, so the cost in food for that is reduced leaving more spare for lighting effects: no problem.
[Answer]
Here in New Zealand we have the NZ glowworm which glows from luciferase all the time, and lives in cold, dark, low food environment (caves) in huge numbers. They're tourist attractions, some huge caves are positively covered in them. And many very deep sea fish are bioluminescent as well, so the signs are good.
Most bioluminsecent molecules are actually not consumed by glowing, they expend ATP to produce an excited state in the bioluminescent molecule itself to do so. Luciferase works this way, it's just a means of using ATP to make light.
I'm an inorganic chemist and couldn't comment on luciferase itself but the luminescent molecules I synthesised in undergrad were not spectacularly complex or energetically unfavourable, no more than e.g. common flavoured and coloured molecules.
You'll have to wait for an exact answer from a biochemist but I bet luciferase is a mundane protein with an interesting but not-fantastically-expensive active site, and in any event, it's the ATP fuel you need to make continuously, not the luciferase itself. It ought to be possible.
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[Question]
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In my world, dragons are big, and require lots of energy just to support their massive bodies and huge brains - and of course, to fly, using enormous oversized wings. Rather than causing mass extinctions when they have breakfast, I want my dragons to gain part or all of their energy needs by other means.
I would like to keep these dragons as classic as possible, so I had the idea that they should make lairs inside of volcanoes, and have the ability to hibernate in these lairs. They would sustain their organism on the geothermal heat that's plentiful in their environment. Efficiency is not a huge concern, as the dragons can have a fairly arbitrary amount of heat in the lair, and equally arbitrary energy needs when hibernating.
But how do they turn heat into energy that their organism can use? As far as I can tell, even bacteria near hydrothermal vents don't use the heat for energy, but rather "eat" sulfur compounds ejected by the vent. I do not particularly care if these dragons are warm-blooded, cold-blooded, reptilian, mammalian, whatever, so long as they are organic beings and don't require magic or particularly intense hand-waving.
[Answer]
## Try [thermosynthesis](https://en.wikipedia.org/wiki/Thermosynthesis).
Thermosynthesis is a hypothetical mechanism, usually applied to the [RNA world](https://en.wikipedia.org/wiki/RNA_world) theory for the rise of life on Earth. In a nutshell, it states that an organism could function as a [heat engine](https://en.wikipedia.org/wiki/Heat_engine), where thermal energy is gained from a heat reservoir - in this case, a volcano.
Thermosynthesis allows you to synthesize molecules via [anabolic pathways](https://en.wikipedia.org/wiki/Anabolism); it's not too far a conceptual leap to imagine that this organism could store chemical energy through thermosynthesis in the form of sugars, and from there, use a mechanism similar to respiration to unlock the energy from those sugars. More specific details can be found in [an answer by Dubukay](https://worldbuilding.stackexchange.com/a/96542/627).
Would it be evolutionary feasible? Well, that's another question entirely. From an evolutionary perspective, it would be unlikely that thermosynthesis would be selected as an animal's method of energy generation, because a primarily thermosynthetic organism would need to stay close to the source of heat. Thus, it doesn't make sense for the creature to be mobile. So you'd probably see something less complicated - like, say, a fungus - evolve first.
Perhaps an animal of sorts would arise to use thermosynthesis, but only on a world where most other forms of energy generation are impractical or impossible. [It has been suggested](https://worldbuilding.stackexchange.com/q/35201/627) that thermosynthesis could be handy on a world that's cold, where the creature would take advantage of the temperature difference between the atmosphere and frozen ground. This is sort of the reverse scenario; the ground is hot and the air is comparatively cold.
I think thermosynthesis is the closest you can get to what you're looking for. The odds are against such a creature, but it's not impossible at all.
[Answer]
You cannot actually gather usable energy from heat directly (that's a law of thermodynamics). You need a heat differential. The movement of heat from a hot reservoir to a cold reservoir is required in order to actually gain energy.
There are many ways to build a heat-engine to transfer heat from hot to cold in this way, but I would recommend two processes.
The first is for use in the lair. While in the lair, you have limited access to cold objects to transfer heat to. However, the lair itself is going to have some heat differential from top to bottom. We can leverage that. In fact, the dragon may intentionally make the top of their lair cooler (by adding things like metals to conduct heat to the surface... and Gold just happens to be a very good heat conductor). This won't generate much energy, because the temperature differential is minimal within the lair. However, it could generate enough energy to keep the dragon alive and functioning if they have to stay in their lair for long periods.
The second approach is neater. Some reactions favor one direction or another at different temperatures. For example, CaO(s)+H2O(l)⇌Ca(OH)2(s)+heat, the conversion of quicklime to slaked-lime, is tremendously exothermic. It's a great energy source. However, at high temperatures, the reaction reverses, taking slaked-lime and converting it to quicklime and water. You can use this to form a heat engine within your dragon. While it is in its lair, it stores slaked-lime in its body, which gets converted naturally into quicklime. Later, when the dragon emerges to fly, needing substantial energy to stay in the air, it can decrease the temperatures of these quicklime stores (using the outside air to cool them), and convert them back to slaked-lime using an enzyme which captures the energy of this conversion rather than just wasting it as heat.
This energy is now in a "usable" form, so can be used immediately or stored in compounds which can be used for metabolism both inside the lair and outside, and can be used on a moment's notice (if your dragon doesn't have time to air-cool a bunch of quicklime)
I'm not sure if the slaking of lime will be an acceptable reaction for you (it's hard to tell if dragon metabolism can balance that equation correctly for volcanic temperatures), but it's an example of the kind of reaction which lets you draw energy from the volcano.
[Answer]
The big issue with your concept is that life, the universe, and everything does not run on energy. Instead, we run on the flow of energy. The universe has been going for billions of years, but the total energy content in the universe is the same now as it was at the very beginning - this is known as "conservation of energy". However, the energy is not equally distributed. There are places (in atomic bonds, for example) where the energy density is high and other places where it is lower. As it has opportunity, the energy flows to disperse itself. It is this flow of energy that is the actual driver of processes, including life.
Heat itself is a form a energy, so the literal answer to your question of how to convert heat into energy is "it already is". What you really want is "how do you make use of that heat to live". And there is the problem. Your dragon is surrounded in a high concentration of heat energy. But that energy has to flow before it can used, and in environs where everything is the same temperature, there is no where for it to flow. There is no way for your dragon to survive simply off of living in a hot environment. Even with magic, it is magic that the dragon would be using to survive, not the heat.
There are two possible solutions. The sessile solution is for the dragon to physically bridge the gap between the hot environment near the volcano to cooler surroundings. Then it can make use of the flow of temperature from the hot environment to the cooler.
The other solution is to make use of the mobility of the dragon. The dragon has both heat-reservoir and heat-sink organs. The reservoirs are exposed while in its volcanic lair, allowing the external heat to flow freely into them, while the sinks are kept insulated, allowed to heat up slowly from the internal processes keeping the dragon alive. When the sink gets too warm, the dragon must leave the lair and move to someplace colder, where the sink is exposed and the reservoir is insulated. The sink sheds its heat quickly while the dragon uses the flow of heat out of the reservoir to live.
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[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
Note - I have tagged this as [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") because, apart from feasibility, I'm hoping for some actual numbers that will tell me the capabilities of such vehicles.
---
**Background**
On a planet far away there are constant thunderstorms over the plains of Groth.
Until the advent of science and technology, the locals kept well away from the area, despite what would have provided excellent trading routes. This was because the chances of you and your pack-animals surviving were minimal.
Now however planet-wide electrical technology has reached the level of early 20th century Earth. Gasoline-powered vehicles have not been invented.
Someone has the idea that the Grothlanders would be the ideal people to test out the newly invented electrical motors because they live all around the perimeter of the Plains. There is a continual although not exactly continuous supply of electricity from lightning.
**How the vehicles work**
They are 4-wheeler carts steered from the front and powered by an electric motor driving the rear axle.
They have an aerial sticking out of the top to catch the frequent lightning strikes. The driver and passengers are protected by a Faraday-type cage to avoid being killed. They have padded helmets to muffle the constant deafening noise.
**Question**
Given a lightning strike every few minutes, would such a vehicle be feasible? It has to travel up to 100 miles across the Plains of Groth on any particular journey.
In particular, is it feasible to catch, store and use lightning in this way and would the weight of all the necessary equipment to make this work be excessive?
**Assuming that the idea is feasible at all: Given the energy of a typical Earth lightning bolt, how often on average would a minimal-sized vehicle have to be struck in order to keep going pretty much continuously at, say, 30mph (approx 50kph)**?
---
**Assumptions**
**Please ask for further necessary details before answering.**
* **A minimal-sized vehicle** has condensers to store the electricity, an electric motor, is capable of driving hundreds of miles whilst being struck by lightning, carries a human-sized driver and one passenger, and a Faraday cage to protect them. The plains are more-or-less flat with firm but wet going. Some suspension is necessary but there is no rough terrain. Ball-bearings are available.
* There are future plans for some kind of railway network. But but this is still years away. For now, all they have are self-contained 4-wheeler motor carts. Most of these are home-built apart from the electrical motors that they have to purchase.
* The lightning storms are equivalent to those on Earth but go on day and night through some climate anomaly not disclosed here. If you venture onto the Plains you can expect to be struck pretty regularly. Exactly how often is part of my question.
[Answer]
**So the maths works**
A lightning bolt contains ~5 gigajoules of energy, or as [Wikipedia helpfully tells us](https://en.wikipedia.org/wiki/Harvesting_lightning_energy) 38 gallons of gasoline. So if you could get a lightning bolt to hit you, and could store all the energy at 100% efficiency, that's enough to drive a [2019 Acura](https://www.fueleconomy.gov/feg/noframes/39950.shtml) 1000 miles. (Exactly 1000 - it's rated as 3.8 gal / 100 miles).
Even if you lose 90% of the energy, that's still 100 miles per strike. Even if your go-cart things guzzle fuel at 7.6 gal / 100 miles, that's still miles per strike.
**But the lightning doesn't**
The trouble is getting the lightning to strike you. Because of this, the exact design wont work.
Lightning travels in steps of about 60m - looking for the path of least resistance greedily like water flowing down hill. (This is why lightning can strike a tree a few hundred meters away from a tall building.)
[](https://i.stack.imgur.com/CWthb.png)
[](https://i.stack.imgur.com/aC2f0.png)
You attract all lightning to you over distance d based on [this equation](https://what-if.xkcd.com/16/) (from XKCD's "what if").
$$
d = \sqrt{ - h ( h - 120)}
$$
If your car has a 3m rod sticking up - it will cast a lightning shadow 18.7m wide - so anything going to hit the surrounding 19m will come for your lightning rod.
10m? 33m radius. Once you hit 60m, the shadow is at its peak. A lightweight 4-wheeler cart with a 60m tower is going to fall over over on the slightest slope.
**So what will?**
However; Some 60m towers, spaced about 100m apart with lightning rods powering a nearby electric train network. That's starting to become possible.
4 towers holding the corners of a large 100x100m mesh of thick wire will capture all lightning coming for the region under the mesh.
Also possible is lightning mixed with some technology to convert the power to liquid or gas fuel. Eg electrolysis to create a hydrogen fuel, and pumps to compress it. You lose a bit of power in the conversions but JBHs hypothetical maths can be a reality with a big factory cranking out compressed hydrogen.
[Answer]
**I don't think it would work in practice...**
While lightning has more than enough energy, you'd have problems [harnessing it](https://en.wikipedia.org/wiki/Harvesting_lightning_energy). Problem is enormous power (high voltage and current), ie. lots of energy which is delivered in very very short period of time.
And to transmit/store that high power, you need big conductors (to carry high current), with extremely low resistance (think ideally: superconductors). Otherwise, you'd have big power losses in small space, which amounts to extreme heating, which amounts to metal becoming vapor in very small fraction of a seconds, ie. explosion (not chunky enough conductors would be blowing like overloaded [fuses](https://en.wikipedia.org/wiki/Fuse_(electrical)#High_voltage_fuses))
What might work for mobile units is using lightning indirectly, by being isolated enough so lightning never strikes vehicle, and using other effects to harness its energy, perhaps like:
* [induction](https://en.wikipedia.org/wiki/Electromagnetic_induction) which is usually responsible for frying your electronics when lightning strikes. eg. any moving current (like lightning) creates changing EM field, and any voltage is induced in any conductor in changing EM field. Longer the conductor, higher the voltage. That's how modern wireless phone charging works (although phone wireless charging uses much lower voltages and MUCH more rapid changing)
* making use of [step voltages](https://en.wikipedia.org/wiki/Earth_potential_rise) - ground potential is NOT the same on different radiuses from center point of lightning strike. Bigger the distance (and more perpendicular to the point of origin of lightning strike), higher the voltage difference.
Those two indirect methods generate **MUCH less power** than direct lightning strike, so they bring needed electrical devices into realm of possibility for car-like vehicle. However, unless the ground close to you gets hit by lightning VERY often, energy harvested would probably be too low to use such car (unless you park it for days in such stormy area to charge before using it).
[Answer]
**It won't work, but it's cool to think about**
The good news: Oh, yeah, you could operate a car on lightning strikes. [Lightning can deliver 10 GW of electricity](https://www.energy-cast.com/41-lightning.html). Now, that article downplays the power of lightning by telling you that when you extrapolate the power to KWh, it isn't much (and, in terms of running a whole city, it ain't). But that's still 10 GW to work with (you don't divide the power into the length of the lightning strike or the claim would be 50 MW).
So, 10 GW. That's a honking lot of power. From [this source](http://www.kerrywong.com/2006/05/26/how-much-energy-do-we-use-driving/) we learn that to drive 400 miles an "average" car (and that's one wild guess. Cars are all over the map, so you should treat this as a ball park figure) will burn 560 KWh. And... 10 GW / 60 / 60 kinda = 2,775 KWh or almost 5X the energy needed to run the car for 400 miles. So, you can easily run for 800 miles (10 hours of driving at 80 MPH) with the A/C on, every light you can hook up, and your stereo running loud enough to be heard in Iceland.
>
> EDIT: Curiously, no matter how poorly I did the math, it appears I was basically right, anyway. From [this source](https://en.wikipedia.org/wiki/Harvesting_lightning_energy) we learn that "A single bolt of lightning carries a relatively large amount of energy (approximately 5 gigajoules or about the energy stored in 38 gallons of gasoline)." Average passenger car gets 30 mpg so one bolt is worth 1,140 miles - well beyond a single day's supply.
>
>
>
**But that's not the problem**
The problem is how to attract the lightning. Electricity follows the path of least resistance to the lowest electrical potential — which will *almost never* be the car (and it's not just the high-insulation vulcanized rubber tires). Even if you paved the roads with silver (great conductor) and used gold instead of rubber for the tires (great conductor), the best you're going to get is an average electrical potential equal to the ground within about a 3 meter radius of you. If you're cresting a hill, you have a great chance of being struck. If you're at the lowest point around you... not so much.
**But hope is not lost for good science fiction!**
Because what you could do is operate your car on *negative voltage* compared to "ground." And in a car, that's "chassis ground" or the voltage of the chassis metal. (Said another way, to keep passengers safe, the chassis of the car is used as the 0V reference.) Normally a car operates at +6VDC, +12VDC, or +24VDC (depending on what kind of vehicle it is).
Yours operates at -480VDC. And that honker can *haul the mail!* The benefit? You can put the -480VDC charging terminal on the top of the vehicle where it will (science fiction) draw all the lightning bolts you can handle!
And when your car is charged, a +24VDC plate covers the connector so that the lightning is pushed away from it. *And we'll ignore what happens when two plates with a potential difference of 504VDC do. It's called a capacitor. Just ignore it. Science fiction. :-)*
**But is it safe?**
It's your world. Declare it to be safe. Those folks grew up on it so lightning management would be a fundamental technology. The operator's cabin would be electrically isolated (very well insulated) from the rest of the car. There'd be some way of discharging electrical "overburden" (me, I want an arc lamp that rivals [The Luxor Hotel](https://media-cdn.tripadvisor.com/media/photo-s/01/1f/40/80/las-vegas.jpg)).
And keep in mind, you'd need to only be struck *once a day at the most* to keep this car rolling. You can't run a city on lightning — but a car? Not hard at all.
Big ol' trucks might need to be hit multiple times a day.
A motorcycle might need to be hit once in your lifetime. Your lifetime, not the motorcycle's. Your people probably abandoned motorcycles a long time ago. The 2 Km search radius for the rider was too much work for the Search & Rescue team.
[Answer]
**Yes**, it is possible to make such a machine. A lightning strike would bring about one billion ([1,000,000,000](https://www.realclearscience.com/blog/2012/05/could-we-harness-lightning-as-an-energy-source.html#:%7E:text=An%20average%20bolt%20of%20lightning,door%20refrigerator%20for%20a%20day.)) joules of energy. Aviation fuel contains [43 million](https://theconversation.com/electric-aircraft-the-future-of-aviation-or-just-wishful-thinking-45817) joules per kilogram. Hence we have the equivalent of 23 kg of fuel from the single strike, 6 gallons. [BMW i3 Giga](https://www.consumerreports.org/fuel-economy-efficiency/best-worst-fuel-economy/) can drive 846 miles, 1361 km on that! Even a small aircraft like Cessna 172 only requires about 10 gallons for a whole hour. So under any bearable efficiency of the lightning collector, a vehicle getting a strike per minute could not only ride, but even fly, even if heavy and inefficient. Or, probably, a strike per half an hour should be enough.
Some sources estimate the energy of the single strike to be about 20 times less (and there are different types of lightnings). This would still work even for the mentioned Cessna aircraft if we count on a strike per minute.
It is however technically challenging to extract all power from the lightning. Some kind of advanced supercapacitor is required that could take lots of energy very quickly and be charged to a very high voltage. Then no less advanced voltage converter needs to convert the energy into something that a normal electric engine could use. So probably not with the steampunk technology and not with 100 % efficiency. But if really a strike per minute, it seems that there is a huge efficiency margin for building something that just moves over ground.
[Answer]
This is likely to be far more 'practical' if the lightning strike were to generate steam, and not be stored as a pile of electrons.
[Answer]
Let's approach it from the [other direction](https://www.youtube.com/watch?v=TYFMU7XfyzE).
## Let's audit the tech available at the time.
Electric cars were abundant, readily available, and *just worked*. They were the vehicle of choice for society ladies who wished personal mobility. Gasoline engines required a "driver" who was as much a mechanic to keep the fidgety engines working - on *Downton Abbey* this was [Tom Branson](https://downtonabbey.fandom.com/wiki/Tom_Branson)'s original job.
Without any application for engine starting, lead-acid batteries become a poor choice, done only on the cheapest vehicles. **So other tech, notably Edison's nickel-iron batteries**, are a huge winner. (Nickel-iron batteries are long-lived and almost indestructible, but have high internal resistance, so do poorly with "engine cranking". Not an issue for electric cars, but it may be an issue here.)
However, I'm burying the lede.
The 600 pound gorilla of the early 20th century was **electric railroads**. This technology had exploded onto the scene, with streetcars replacing horse cars, but much more importantly, **interurban electric railroads**.
These are high-speed (for the time) trains that ran at 70-100 miles per hour. They ran as small as single cars (a bit longer than a streetcar), or fairly long trains. The electric power ran normally at 600 volts, but as high as 4000 volts DC or 12,000 volts AC.
This is dragging us to a conclusion: The right way to do this is ferry the automobiles on flatcars on the interurban railway.
## Catching the lightning
**The trolley wire will be a magnet for lightning strikes**. You build this system with a huge amount of capacitance at megavolt levels - so you make the rail network as vast as possible, without circuit breaks.
Now, here is where we need to know the polarity of the lightning. If your lightning is consistently the same polarity, that will play nicely with a DC system. Otherwise some of your strikes will work against you, and those tend to be the more powerful strikes. Remember, we don't get diodes in this half of the century.
It won't work to have one track positive and the other track negative polarity. The lightning either wouldn't care or would be drawn to the more opposite.
AC is right out. First, half your strikes will be the wrong polarity (because of timing), and the net energy would be nil. Second, a vast system with a lot of capacitance will have a lot of problems both due to the capacitance and phase drift due to the vast distance.
Substations, in as many places as possible, will have some sort of unknown ultra-capacitor technology of some kind, including possibly a very tall stack of those lovely, indestructible Edison batteries.
Another option is to have a transmission line well above (vertically) the trolley wire. The transmission line would catch the lightning. This transmission would be the highest voltage DC that can be mustered given the tech of the age. It would have DC-DC conversions at substations. This was not easy in 1915, but not impossible.
[Answer]
I would say no. Safety is probably the core issue.
Air around lightning is heated to [50,000 degrees F](https://www.weather.gov/safety/lightning-temperature). Air is a terrible conductor but unless the devices used to store AND ground the lightning are superconductors, there's bound to be tremendous heat around it. Since it's possible to expect one every few minutes, catching two in a row within seconds might be too hazardous.
Shock waves from the thunder are enough to cause [property damage and bruises](https://en.wikipedia.org/wiki/Thunder). It's similar to that of an explosion or supersonic aircraft 'boom'.
Let's assume the heat and shock waves don't kill you. We're looking at [10 GW of electricity](https://en.wikipedia.org/wiki/Harvesting_lightning_energy). Living within [50m of a 765 kV power line carries risk of cancer](https://emfacademy.com/power-lines-dangers/). Lightning is over 1000 times stronger than that, and at a much closer proximity. You'll likely get a lot of near fatal radiation over one drive.
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[Question]
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While trying to figure out a way that individuals could own spacecraft in my sci-fi setting without having access to things that could double as weapons of mass destruction, I settled on the widespread adoption of civilian solar sails, or more specifically, photon-particle sails.
It has quite a few advantages, like being mechanically simple and cheap to produce with bulk graphene production, along with having an omnipresent power source. The only problem is this omnipresent power source is unidirectional.
Even worse, there is a limit to how many lasers can be fired from X, Y, and Z bodies, to redirect these hundreds of thousands of crafts, along with the economic costs of firing all that energy and possible lack of infrastructure depending on where you're going.
How can a craft powered by solar wind and rays return to their place in the inner solar system?
[Answer]
There are a number of ways to use solar sails to make round trips. For relatively short distances like going from the Earth to Mars, the sail can be sent on an elliptical orbit which "grazes" Mars. At that point the payload is released and aerobrakes into the Martian atmosphere, either to settle into a circular orbit around Mars or land on the Martian surface. The sail continues in a long, elliptical orbit and eventually returns to Earth about two and a half years later. (Unfortunately, I seem to have misplaced the orbital calculations where this was explained, so perhaps someone can find a link or post the actual calculations).
In a more general sense, sails can actually "tack" with the solar wind. This is more usable when dealing with trip to the outer planets, since a flypast orbit like the Martian example will be going so fast that the aerobraking will likely be unsuccessful, and the sail itself will be heading out to deep space, not returning for centuries. The genera idea for taking a solar sail is that if the sail is set so the thrust is aligned against the gravitational field of the sun, the sail will spiral outwards, while if the thrust is in line with the Sun's gravitational field, it will spiral inwards.
[](https://i.stack.imgur.com/ru8HT.gif)
*Tacking with a solar sail*
By careful use of sunlight and a suitably lightweight sail, you can achieve very fine control of the sail and move throughout the Solar System with ease.
[Answer]
You can use the sail to deflect sideways the light and thus increase or decrease your orbital speed.
If you stop your orbital speed then all you have to do is to close the sail to plummet straight down (toward sun).
In practice Sun has *two* force sources:
* gravity: pulling
* solar wind: pushing
While the first is always pulling in a well defined direction you can use sail to maneuver, to a point.
In particular you can use it to increase or decrease your orbital speed amd let gravity do the rest.
[Answer]
The other posters have covered the main question of orbital adjustment by angling the solar sail. I can't improve on those answers. However...
>
> ...without having access to things that could double as weapons of mass destruction...
>
>
>
Given that a solar sail is a giant mirror, and not a completely rigid one at that, it should be reasonably simple to add a small amount of curve to the mirror to effectively focus the incoming light onto a target smaller than the sail area. Assuming that your sail hasn't been specifically designed for such a thing you probably won't get a great focus, but you can make up for that by sheer size. Ants under a magnifying glass would be a reasonable comparison.
If you specifically design the sail to be adjusted to any curve you specify (using sail spin and a tensioning system perhaps) then you could get several thousand square kilometers of reflector focusing to a point a few hundred meters across. It's going to drift as the sail accelerates away, but if you adjust focus as you move then you could probably get enough energy into the target zone to vaporise it and the rock beneath.
It would be interesting to see what happens to a society that suddenly discovers that the safe, cheap and slow method of allowing citizens to cruise around their solar system suddenly becomes a method of destruction greater - if much slower -
than nuclear weapons. How would Earth react if all of the space-faring citizens ganged up to carve a great big molten X across the face of the moon before demanding that Earth stop ordering them around?
The moral of the story is: don't assume that just because it's big and slow that it's not going to eat you.
[Answer]
Solar sails must be paired with traditional gravity maneuvers to achieve practical mobility. The exception is things like permanent habitats where station-keeping is the real purpose of the sail.
This makes the course planning of such a vehicle extremely important and limits the useful tracks available within a planetary system, though it places few limitations on tracks among stars (as the target star can be used to gravity assist a return path on a grazing approach, which implies that the craft would have to be equipped to withstand a close approach).
**From the storytelling angle...**
If your problem is that you want civilians to have access to advanced technologies that cannot be used as weapons of mass destruction then your task is hopeless in the face of any serious investigation. I would recommend as a writer or world designer that you commit to solar sails *not* because other propulsion systems may be related to nuclear technology, but because you want to place a mechanical constraint on the actors in the system *that can be usefully employed to drive the plot or game system*. For example, because solar sails require gravity maneuvers the useful tracks within a planetary system are constrained. This also would have the effect of concentrating human habitation along the useful tracks -- which already gives a population and therefore political focus to your world (assuming you need such a thing).
It is much easier to justify the technology of solar sails by cost than "safety". In the somewhat near future it is very likely that nano manufacturing techniques will give rise to things profoundly more devastating than mere nuclear weaponry, and such things will probably be impossible to keep out of the hands of civilians. And that's not even sci-fi. (Incidentally, I smell another interesting hard sci-fi premise here...)
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Gravity assisted maneuvers are an important part of stellar travel. Not only can you use a gravity well to change directions, but they can provide huge boosts in speed. This diagram shows that using a planet to reverse your direction adds your own initial velocity to twice the partial velocity of the planet in the direction you are heading. That can get things moving pretty quickly.
[](https://i.stack.imgur.com/z6Cup.png)
Assuming your solar sailors can steer their ships, not just directly away from the suns rays, but perhaps tangential to them, they can sail out to planets (or other objects orders of magnitude more massive than their ship) and use them to turn into the sun. From there, they lower their sails and coast into port.
Just make sure you don't sail past the furthest gravity turn-around. The Solar Coast Guard would have to rescue you with their expensive rockets.
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The late Dr. Bob Forward wrote numerous papers on this, most famous among them is <http://www.lunarsail.com/LightSail/rit-1.pdf>
He also popularized the concept of laser-boosted concentric-ring sails in his Rocheworld series of SF books. By dropping the outermost ring and reversing the ship, the remaining mirror can be used to slow/stop/reverse the ship.
There are heaps of caveats to this approach, most notably the law of diminishing returns, as each concentric sail has less area with which to collect light.
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As others have explained, solar sails can be used to apply gradual delta-V to an orbit in either direction, to go in or out.
However... that means you can apply delta-V to any object, such as a large rock. It only takes a small amount of it to change a "near miss" into a "planet-destroying hit". We get a few decent near misses every year - see <https://en.wikipedia.org/wiki/List_of_asteroid_close_approaches_to_Earth>
You don't even need to use the sails to move them. You can deflect them in any number of ways, so long as you can get close to them at matched velocity, early enough - which a solar sail would let you do, if you knew the object's expected path.
So all planets and stations having a defense against such asteroids would be necessary to fulfull your "no weapons of mass destruction". Since... well, a near-earth-shatteringly large mass that's been weaponized is very literally a weapon of mass destruction.
---
In 2013, NASA estimated it had identified 95% of the potential "planet-killers" of 1km or more (about the same as the dinosaur-killer), and only 10% of those smaller than 300 meters.
Tracking rocks *appears* easy, but there are many rocks that are visible to earth only by obscuring other things, or on close approaches to the sun. Even among those that have been detected, they aren't constantly tracked; their orbital paths are calculated once they're detected, then they are filed away and forgotten about until that orbit is due to become interesting again.
That changes if there are things which might push them out of those predictable orbits.
Even if 100% of dangerous objects were identified and were continuously tracked... solar sails are essentially mirrors, which makes them black to anything outside a very narrow angle, so they are undetectable other than in their effect on the rock. If the solar sail obscures the rock, or if the rock has been covered in carbon-black, then the rock will not be visible to telescopes either.
So the whole system of falling-rock-detection currently on earth would need to be improved several thousandfold, to detect and track rocks far more constantly and aggressively than our current snapshot-based system. We could no longer rely on objects moving in predictable orbits, and no longer rely on passive image detection; a networked array of telescopes detecting stars being obscured, and using some form of active detection (very long distance radar?) for concealed rocks.
Deflecting a rapidly-moving rock requires a whole lot more force than aiming; dropping a thing on a planet is a lot harder than it oughtta be, because it is likely to just get caught in an orbit instead of spiralling inwards, but still, the person aiming has the significant advantage of lead time. The closer it gets, the more force must be applied to deflect it, and I think the increase scales with 1/distance^2.
There's also the shotgun problem: no matter how many rock-deflecting missiles you have in your armory, your foe only needs to send one more planet-destroying rock than that, in order to destroy your planet. Only one needs to get through.
Have one large visible rock followed by a stream of smaller blackened ones hidden behind it.
Have what appears to be one rock spread apart into many once the planet deploys deflection measures.
Scatter larger high-albedo and smaller low-albedo rocks together in the same "shotgun blast", so that the glare from the shiny ones masks the stealthy ones until it's too late to deflect them.
...and so on.
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In sailing, you can tack, or zig zag, to head back upwind. You do this by aiming about 15-45 degrees away from the wind, or in this case, the sun. By pulling in your sail, it allow wind to move past the sail, but still exerts pressure on the sail. Using this, you could tack back towards a star. Given, wind doesn't act exactly like photons, but heading on a bearing and degrees farther out from the star. Also, depending on the shape of the sail, you could pull it in closer to the body of the ship, and use mirrors to reflect light, and therefore photons back into the sail, giving a powered descent down into the gravity well if you were in a hurry.
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The year is 3030 and the robots (who have replaced humanity as the dominant intelligent beings on Earth) have decided to build a Dyson sphere around the sun. They're planning on disassembling Venus for materials and building a sphere with a radius a bit less than the orbital radius of the planet they're consuming.
The sphere is opaque to all solar radiation, barring a few high-energy gamma rays that manage to punch through, and also blocks the solar wind. It's thin, so it will reach thermal equilibrium fairly quickly and radiate energy as a blackbody based on its equilibrium temperature.
Earth, prior to the construction of the sphere, has a climate similar to that of modern day Earth. Neither nuclear war nor pollution has catastrophically damaged the biosphere. The Earth of 3030 is about 3°C warmer than it is today and is home to a stable population of 11 billion humans.
How uninhabitable will the construction of the Dyson sphere render the Earth? It will block out all sunlight, but should ultimately radiate the same amount of energy it's absorbing, effectively replacing the Sun with a much larger, cooler star. What life on Earth would we expect to survive in the post-sphere era?
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Life on Earth will suffer severely. Instead of the energy coming mostly in visible spectrum, now it will be coming in the far infrared part of spectrum. Skies will be dark - no Sun, no Moon, no planets, except for the stars. Because Earth's atmosphere is much more opaque to far infrared radiation, temperatures will plunge. The vast majority of living organisms will perish. Some might adapt to sustain on far infrared light, but this would be less concentrated energy than, for example, that which a hot geyser produces. I think the only remaining organisms will survive on geothermal energy and chemicals.
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Frank Cedano's answer means that the robots building the Dyson sphere can use a tiny proportion of the energy it collects to power a giant space sun lamp to illuminate the Earth (if they want to).
If the 11 billion humans on planet Earth also have advanced technology in the year 3030 they can build giant space fusion power generators with a total power output equal to that which Earth receives from the Sun and use the power in an orbital space lamp to illuminate the Earth. Presumably they already use fusion power plants on Earth to power their civilization anyway.
Or the humans can use infrared sensitive Sun orbiting solar panels (orbiting outside the Dyson sphere) to collect some of the waste infrared emitted by the Dyson sphere which the robots have no use for. The solar panels will convert the infrared to maser or laser frequencies and beam them to Sun orbiting power receivers (orbiting outside the Dyson sphere) that will beam the power to a giant orbiting sun lamp orbiting Earth.
If the Dyson sphere or shell stops the solar wind the humans may also have to build some sort of defense against cosmic rays that will now penetrate the inner solar system in greater numbers.
Presumably both the robots and the Humans will have highly advanced technology in 3030. So if the robots start a vast and long project that might have a negative impact on Earth the humans will have a long time to persuade the robots to modify the project to keep Earth habitable, or fight a space war with the robots, or make their preparations to keep Earth habitable, or build and move to space habitats using fusion power for energy.
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Have your robot's build a dyson yo-yo instead.
Imagine two Venus orbit wide hemispheres encapsulating the sun but leaving a wide swath of open space between them. Span the open space with rigid cables to hold each hemisphere in proper relation to each other and their captured sun.
Now align the open space with the orbital plane of Earth and adjust it as needed with hemisphere mounted rockets.
Your robots get a tonne of new real-estate while Earth gets to keep its place in the sunshine.
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Not an answer, but I'd like to correct:
>
> effectively replacing the Sun with a much larger, cooler star
>
>
>
The amount of solar-derived radiation reaching the Earth should be unchanged. Consider the surface of the Dyson structure occluding the Sun: call it the Dyson-Sun. It will absorb the same amount of radiation as the Earth currently does, and then re-emit it in the Earth's general direction.
What about thermal conduction? Every other part of the Dyson structure will be absorbing solar radiation at the same rate per surface area, so the temperature should be relatively uniform.
What about scattering? Some of the re-emitted radiation from the Dyson-Sun may not be directed towards the Earth; the remaining surface area of the Dyson structure will also be re-emitting scattered radiation, some in the direction of the Earth.
Some radiation would be scattered back towards the Sun, but as the Dyson structure has turned it into a closed system, eventually it will be absorbed and re-emitted out away from the Sun.
I would expect that the future inhabitants, comparing the old Sun to the Dyson-Sun, would perceive the latter to be hotter (since more EM radiation would be shifted to infra-red), darker, slightly bigger (because of the scattering), and blurrier.
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As long as there is a radiator orbiting the earth that puts out the same energy the sun deposited on earth then nothing would change. This radiator would have to be big enough to radiate energy on the same surface area as well as put out the same electromagnetic frequencies. Since the earth consumes only a small part of the energy of the sun now, you can certainly release that much energy easily from the dyson sphere.
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If we assume continued industrial growth and not an energy stall, the limiting factor of planet-based civilizations energy consumption in the near future is radiating waste heat away.
A Dyson Sphere surrounding the sun would shut off visible light and replace it with infrared. This would, as others have noted, significantly reduce the surface temperature of Earth, probably to ice-ball levels, and wipe out the non-geological based biosphere.
However, if the level of technology required to disassemble a planet and build such a sphere is a K type 2 civilization. Managing the entire energy budget of Earth is a trivial task to a K type 2 civilization; it is literally 0.00000001% (give or take a 0, I may have lost count) of their energy budget.
If Earth is anywhere near at that technology level, they will require significant cooling efforts to deal with the pre-solar-shutdown; possibly the reduced radiation from the sun would be a boon and allow more technological development and energy use on Earth.
At this level, the biosphere will have to be heavily managed regardless of the sun being shut off.
As an aside, note that the "right" way to capture entropy (well, enthalpy maybe) from the sun is to not only have 1 layer; you want to harness the heat emitted by the first layer and use it for more work before radiating it again. So stopping at one layer isn't long term.
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For some reasons, Stack Exchange became its own country and decides to use its reputation system as the official currency.
What would be the advantages and the disadvantages of such a system in comparison with current monetary systems?
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Your question is similar to [this real-world one](https://bitcoin.stackexchange.com/questions/331/is-there-a-way-to-set-up-proof-of-work-systems-so-they-would-be-even-more-useful), which asks how we could take a system like Bitcoin, but issue new currency when people do something more useful than bitcoin-mining. Someone else already mentioned Cory Doctorow’s fictional *Whuffie*.
The new currency would have a lot of the same problems as Bitcoin, one of which is that nobody is managing the money supply, and having the right quantity of money, avoiding massive inflation or deflation, turns out to be important. StackExchange the country might work around this with some Modern Monetary Theory: instead of controlling the source of money, it could control the money *sink*: that is, tax everyone’s reputations not in order to fund public expenditures, but in order to prevent inflation. If there’s a risk of harmful deflation, it might temporarily grant a bunch of bonuses just to get more currency out there. This mechanism might also be a way to achieve what some real-world scrips have tried to: encourage people to spend it quickly instead of hoarding it by having it expire. Or just increase or reduce the point values of upvotes arbitrarily, although this would create resentment.
Most other details of economic policy depend on StackExchange the country and its balance of trade. If there’s a central bank that collects reputation, purchases foreign-exchange reserves, and uses them to maintain a peg against the dollar (for example), then reputation becomes dollars by another name, except that the benefits of seigniorage go not to the government, but to users who ask and answer questions. They effectively have jobs working for the government. That seems as if it would be vulnerable to cliques, but it makes more sense than giving it to people who own gold or silver mines. Only, dollars wouldn’t have the same unpredictable, unavoidable taxation needed to make the system work, so everyone would want to convert their reputation into dollars immediately, and the system would not be stable.
One wrinkle is that there isn’t one kind of reputation: there’s World-Building reputation, TeX reputation, StackOverflow reputation, and so on. It would probably be impossible to maintain a single exchange rate between these; some would have more rarity and utility than others.
If the exchange rates are allowed to float, reputation would not be a good store of value. (Bitcoins are mainly useful, compared to other currencies, as a way to get around Chinese currency controls.) Someone would need to want to buy it for its value not to collapse, and StackExchange right now would need to import just about everything. So the idea is only viable if people need to buy about as much reputation as people want to sell: this could happen if StackExchange sells as many services to the outside world as its citizens import, and the people buying answers need to buy rep using dollars or euros to pay for them. Then, those dollars and euros could be used to buy imports without the whole shebang becoming dangerously unbalanced.
Along the way, “reputation” would completely lose all connection to your actual reputation on StackExchange and just become a measure of net worth.
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One disadvantage is that it would tie monetary gain to hive mind thinking.
Say you live in an area where the majority of people see women as second class citizens.
If you get up and say "You know, I think women should be treated as equals, and get to drive cars and own property" you'd get down voted all over the place and there goes your life savings.
This could be an advantage if the current popular opinion is one you agree with, but even then it could discourage people from thinking new things that they believe might be controversial at first.
It also gives trolls to much power over you.
Also, people who are charismatic and good at communicating will do better than those that aren't as strong in that area.
Something similar to this is the reputation system in the book Down And Out In The Magic Kingdom by Cory Doctorow, where they are essentially post scarcity, except in service related areas, so they are able to make it work.
The more you help others, the higher your reputation, and the higher your reputation score the more likely people are going to want to help you. If you start freeloading then your reputation will suffer, and you'll have to work harder to get it back.
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Pro's: it would be costless to mint new currency. Also, people would be paid for their knowledge and skill, just like in the real world.
Cons: Rampant inflation. In just a few hours, someone can earn hundreds of reputation from a smart question.
*Interesting wrinkle in this problem: What about hive-voters? Say an organization of, say, 10,000 people form up and upvote all of each others questions and answers, they will be insanely rich in a matter of minutes.*
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It's pretty bad.
It cannot be exchanged between users except for a complex system of bounties. It can't be exchanged against other currencies, complicating imports and exports. And loses its value by the minute. The central bank can't control the hyperinflation. Etc.
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Currencies only have value as long as people trust they have value. You wouldn't accept a dollar if you don't believe you won't be able to buy anything for it.
So, the risk? People will stop believing that somebody would accept it as a currency. It is kind of self-fulfilling prophecy.
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There would be several difficulties with that system. For one, every citizen in the country would need to have access to Stack Exchange to gain money and survive. Also, I would imagine this could lead to massive inflation because high-rep users with 20k rep and more. In a way, your idea doesn't make sense because when you award a correct answer with 10 reputation, where does the rep come from? Not from your rep account, and not from their rep account, so from the government? Or maybe some higher being? If it was the government, soon, citizens would be far richer and thus more powerful than the government, so no matter which way you look at it, this potentially catastrophic idea would lead to civil war and tremendous loss of life.
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It's far too easy to hack.
You only need a valid e-mail address to create Stack Exchange account.
If gaining points was valuable, you could create 21 accounts, have them ask and answer questions and upvote each other's answers and questions. If each fake provides 5 answers and the fakes upvote them, they all jump to 1000 rep overnight, even without any real humans liking them.
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For the sake of the question, assume conditions are Earth-like in all manners other than those which would be required to spur the development of such a plant. I want the plant to gestate in the digestive tract and slowly kill the 'infected' by sucking the nutrients from them (like a tape worm). When said person dies the plant uses his/her body as compost to support growth and development.
* How would such a plant evolve (is there any precedent)?
* How would it work (besides the basics I laid out for you)
* Is this realistic for a story?
[Answer]
The biggest problem is that you want the plant to thrive in two very different environments (relatively speaking):
```
Body Ground
Temperature Hot Cold
Moisture Wet Dry
Respiration Liquid Air
Nutrients Bloodborne Soil/compost
Energy Glucose Photosynthesis
```
Therefore, for this to work, you really need to have a two stage lifespan. Similar to a caterpillar that meta-morphs into a butterfly, your plant will likely have to transition from thriving in one environment to another.
The seed, therefore must be inhaled, consumed, or embedded somehow. Natural processes suggest inhalation or ingestion as the most successful route. While I'd prefer inhalation (close to bloodstream and air, not as harsh as digestive), it appears you've already selected digestive.
So the seed has to not only survive the digestive tract, but the plant has to provide some enticement to being eaten. If it were inhalation, it wouldn't have to entice - it would merely send out spores or microscopic airborne seeds when jostled. The plant, therefore, provides significant satisfying nutrition, so as to get hosts to eat it.
Once consumed, the seed has to pass through the upper digestive tract, but get stuck in the lower digestive tract (lower acidity). This seems difficult, but perhaps it has a germination time of 1-2 hours once the outer acid protective surface is cleaned off. It then starts rooting in several directions, preventing it from moving further down the digestive tract. Small barbed roots that can absorb nutrients from the partially digested food would be best.
At this time it just absorbs energy that will be used during its transition, and builds into a tumor, with longer and longer roots. Eventually it will completely obstruct the digestive tract or the roots will pierce too many blood vessels or veins, and the host will die. If it's necessary that the host doesn't feel pain until near death, then it either synthesizes anesthetic which it emits through its roots, or it doesn't send out roots and instead merely becomes a digestive obstruction.
When the host dies, the process of decomposition sends chemical signals to the seedling and within a few hours it is expending energy sending a tendril upward (any way could be up at this point, but gravity leads the way) seeking light. Once light is obtained, the plant sends out leaves, roots itself more firmly to the host and ground below, and, eventually, flowers and fruits to catch another host for its offspring.
Pulling off the metamorphosis is the tricky part, but since we have animal analogs that do this, it shouldn't be too difficult to explain to the audience.
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Well there are currently some plants that need their seeds to travel through the digestive track of animals before they can germinate. I was looking but couldn't find them right now. I think they got their coating so they could pass through a digestive system and be carried away.
So step that up a bit, and let it 'catch' in the digestive system, then start to sprout. Though making it more a symbiotic relationship (with at least one or two species) would make it more likely, maybe it helps process some other foods. And when the host dies, it will sprout out and use the body as a food source.
If it always killed it's host every time it is eaten most would learn to avoid it quickly.
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**Plant Growing in the Lungs**
This is a story ripped from the headlines. It is a [plant growing in a living person's lung.](http://www.medicalnewstoday.com/articles/197623.php)
>
> Ron Sveden, a retired teacher from Brewster, Massachusetts in the US
> was astonished to discover that what he thought was a tumor growing in
> his lung was actually a plant that had sprouted from an inhaled pea.
>
>
> 75-year old Sveden said he was told the pea seed had split and
> sprouted in his lung. It was about half an inch long (about 1.25 cm),
> which "is a pretty big thing", he said according to a news report from
> NBC.
>
>
>
Pea growing in lungs - example of plant growing in a living animal.
Not the digestive tract but pretty close.
**Fungus Growing in the Body**
Another close match is [fungal pneumonia](http://jim2b.blogspot.com/2014/12/december-chest-ct-fungal-pneumonia.html) (which I have). It is an example of fungus growing in a living animal's lungs. You inhale the spores and they take up residence, germinate, and begin growing.
My fungal pneumonia - example of fungus growing in living animals
After the fungus reaches a certain amount of growth, the fungal growth releases fungal cells into your blood system and spreads to other parts of the body. This enables the fungus to spread to any part of your body (intestines, brain, heart, liver, you name it) and begin a new fungus colony (this is the stage they caught mine at).
It is fatal if not treated.
**Other Thoughts**
The lungs are probably a more benign environment than the intestines.
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My thought would be that a plant couldn't do it. At least not by itself. Mostly because a plant needs to carry out photosynthesis in order to live.
**HOWEVER** there is an analog of a [parasitic fungus](http://en.wikipedia.org/wiki/Cordyceps) that will kill its insect host then "bloom" out of the body as it continues to gather nutrients from its now deceased host.
**ALSO** there is an analog for a symbiotic relationship between fungi and plants. These are the [lichens](http://en.wikipedia.org/wiki/Lichen). Now these organisms still use photosynthesis, but, unlike a plant, which is defined by use of photosynthesis, nothing says that lichens necessarily require photosynthesis.
**BY EXTENSION** A particularly virulent strain of cordyceps mutates that can infect mammals. However, there is a bit of an issue. As diets change and mammals evolve stronger stomach acid, it is harder for the fungus to survive past the digestive tract. So it evolves a way of attaching itself to a plant ovum and hitching a ride into the digestive tract. The stomach acid erodes the tough outer shell of the seed and the cortyceps is released into the intestines and blooms with the added benefit of pushing the seed out of the mammal to so it can sprout, utilizing the decaying body for nutrients while getting that sweet sweet sunlight fix. Further evolution happens involving little hooks on the seed to adhere to the intestinal wall and cortyceps producing higher level of nitrogen locking the cortyceps and plant into a codependent symbiosis. Then the plant starts producing tasty fruit, humans start eating said tasty fruit, cortyceps-tree evolves to utilize humans, a new plague upon all of humanity is unleashed, and millions of grotesque mafia deaths happen in movies. All because you couldn't be bothered to core an apple.
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There is a virus or something that infects an ant and makes it climb a tree before sprouting or creating spores inside it's dying/dead body. Can't remember the ant or the plant/virus that does this but have heard this from a few sources,
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>
> Is this realistic for a story?
>
>
>
In a modern society - no. We bury our dead in boxes (and those that we don't bury we *burn*), and don't grow anything near them.
The life-cycle of this plant makes sense for animals, but not for people. It would make sense for ancient, pre-historic cavemen, but not for any civilisation in the past few thousand years.
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If you inserted the seed into the rectum, it could sprout in the composting faeces. The sprout could move upwards and puncture the lung, receiving the carbon dioxide plants need. The human would absorb it oxygen, and so could survive symbiotically under water. Excess moisture in the lung would be absorbed by aerial roots. If the tree could send chlorophyll through the blood vessels to the skin, the skin would turn green and photosynthesise, providing energy to both.
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Parasitoid wasps are kind of a nightmarish bug: they lay eggs in their target, usually a caterpillar; the eggs hatch and the larvae grow inside the body of the target, feeding on non essential tissue so not to kill it, then they get out of the body of the caterpillar and make a cocoon in which they mutate into wasps, while the target caterpillar, still alive, has been hacked into protecting the cocoons from any aggressor, renouncing to feeding until the wasps come out and the caterpillar dies of starvation.
The fictional parasitoid wasp I am designing follows the same route, however
* it is the size of a hornet and target primates, humans included.
* The eggs are laid in 2-3 rounds, 20-30 eggs per round about 5 days apart form each other, in the same target.
* An egg hatches in about 5 days and the resulting larva eats and grows for 3 weeks before emerging and building the cocoon, which will then be protected by the target until the adults come out after 2 more weeks.
From the moment the first egg is inoculated, the target starts feeling attracted by water until, when the first egg hatches, it does nothing more than settling around a water source (to prevent dying from dehydration).
The problem I am having is finding a suitable target tissue: I though about adipose deposits, but those are the first to be consumed when food intake stops.
Which tissue in a primate/human body can be consumed by the larvae without affecting the capability of the target in defending the cocoons? Survival of the target at the end of the whole process is not expected.
[Answer]
Humans, as with all primates, are remarkably adept at scratching, self-and-social grooming. Any parasite that can be attacked from the surface, will be.
A parasite needs to either dig deep enough so that normal scratching and grooming cannot dislodge it, or present such a small irritation factor (and be not obviously visible) so as to ensure the parasite's survival.
Typical successful parasites on humans:
* Fleas: small enough to not be obvious, mobile enough to evade removal, and low enough irritant value to not instigate massive retaliation. Not a god match for your flesh-devouring Wasp larvae.
* Tapeworm: fully internal thus not reachable by any manipulation. Additionally, it does very little damage to the host, ensuring host survival thus longterm parasite survival. Again, not a very good match for flesheating worms.
Your parasite *has* to enter via the a skin puncture, as it is deposited by a wasp.
Make the egg and larvae secrete a local anesthetic which nullifies the pain and irritation factor. Maybe some anti-inflammatory and antibiotic secretions too, to massively reduce its visible effect on the host. No pain, no swelling, no itching.
Make the larvae burrow deep into muscle tissue, latch on to an artery, and sip the sweet nectar from their host's bloodstream. This should cause minimal irritation, only very minor muscle damage and not *excessively* weaken the host, while providing ample nutrition (and waste removal) for the larvae. It also provides a handy pathway to fiddling with the host's internal chemistry, providing all sorts of psycho-control opportunities if your larvae is "smart" enough for that.
And please tell me what planet you are releasing this terror upon,. so I can move to a galaxy far,far away. It is at the very minimum a horrid incurable wasting disease, and could very easily be the root of a classic Zombie Apocalypse.
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First things first: half of what you want already exists. There is a condition called [myiasis](https://en.wikipedia.org/wiki/Myiasis) which is caused by some kinds of flies laying eggs in the human skin. From there the larvae hatch in as little time as eight hours and then burrow deeper into subcutaneous issue. The flies that cause this will usually target the buttocks of livestock, but when it comes tohumams they are not picky about specific body parts. They will exploit any sores they can find though. I have personally seen surgery done to remove larvae from a woman's scalp.
Worst thing is, since the flies are able to lay their eggs on an open wound, people may get myiasis without noticing it if they have an untreated wound and are distracted. If your wasp can facultatively do this, it will be that more dangerous.
If the wasp must pierce through, then soft areas will be preferred. Ask any nurse about the best places to innoculate someone with a vaccine, and you may learn that after the arm another common target is the bum. The belly is also a possibility - it used to be that people in risk of rabies would get their shots there. Consider also the armpits, the space between ribs, and a little spot right above the colllarbone.
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That said, the preference for damp places is a matter of also injecting some venom along with the eggs. Many kinds of substances will cause a person to feel thirst. If the wasp also injects THC, the active drug in cannabis, the victim may get the munchies which is favourable to keeping them distracted and fed, thus leading to a higher ratio of larvae making it to adulthood. Maybe the wasp feeds on cannabis or other poisonous plants or fungi and hyperconcentrates the dosage in their [ovipositor](https://en.wikipedia.org/wiki/Ovipositor).
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# The Brain:
[And the worms ate into his brain.](https://genius.com/Pink-floyd-hey-you-lyrics)
Wasps that enslave other insects are able to perform a simple form of [brain surgery on cockroaches](https://www.scientificamerican.com/article/how-a-wasp-turns-cockroaches-into-zombies1/) to assure they are compliant. If you want to control a mammal's behavior, there's no better target than the central nervous system. While A wasp can't pierce the skull, there's no reason that eggs injected into the blood stream of a primate can't [migrate to the brain](https://www.merckmanuals.com/home/brain,-spinal-cord,-and-nerve-disorders/brain-infections/parasitic-brain-infections) and do the work directly there.
Anyone who's had a brain tumor can (hopefully) tell you they can take up a large part of the skull and still have a semi-functional person. A primate driven by larvae to perform instinct-like behavior doesn't need to last forever, just long enough to release its hornets.
But as was pointed out, the larvae can subsist perfectly well on blood, so they don't need to eat the entire brain, just make a big enough compartment (similar to a tumor) for the larvae to grow. If the primate survives the initial infection process, they could continue growing larvae as long as their body could survive.
My suggestion is that the hornet crawls into the ear, then injects the primate with eggs. The eggs either migrate through the blood (like encysting tapeworms) or hatch in the ear and burrow into the brain and make a space for larvae to live (ideal, since most insects would need a hole to obtain oxygen for respiration). Larvae in the brain can potentially control any behavior you want - Rabies is known to make people repelled by water, and [attraction to water](https://www.nytimes.com/2019/11/22/science/parasites-insects-drown.html) is known for earwigs. Diseases can make animals engage in risky behavior so as to increase the odds of predation (and thus allowing the next step in a life cycle) so the infected might seek out areas where the hornets are prevalent to allow repeated infection. The larvae may even stimulate the pleasure centers, so the primates are deliriously happy about being infected and don't seek treatment or help. The larvae could suppress hunger (allowing the person to support more larvae till the starve) or cause ravenous hunger (so the host does anything to keep eating, allowing them to continue growing larvae). Then they could either seek out other primates to increase the odds of cross-infection, OR avoid other primates to reduce the odds of getting help. These behaviors could be controlled by paranoia or aggression.
The larvae hatch and crawl out of the ear a new hornet.
[Answer]
**Sinuses.**
[](https://i.stack.imgur.com/Xhea0.jpg)
[](https://i.stack.imgur.com/mYQEV.jpg)
sinuses
<https://www.agric.wa.gov.au/livestock-parasites/nasal-bots-sheep>
<https://teachmeanatomy.info/head/organs/the-nose/>
Depicted: nasal botfly maggot in sheep sinus, human sinuses.
The thing about insects: they are not worms. They cannot oxygenate in a liquid environment like helminths. They have to breathe air. That limits where they can live as parasites. The deep tissues do not have free air and larvae will suffocate.
The sinuses work fine. They are aerated. They are vascular and the larvae would have loads of blood and protein rich secretions to eat. This is how sheep botflies do it. Humans can be infected with sinus botflies too.
The sinuses also have access to the CNS via the cribriform plate.
<https://en.wikipedia.org/wiki/Cribriform_plate>
[](https://i.stack.imgur.com/DAWLA.png)
The larvae in the sinuses give off chemicals which diffuse into the brain and reduce motivation and causes these people to sleep by the river.
I think I like about this scenario is that it might not be fatal. The infected would sit and sleep along the river banks with faces swollen and their noses dripping purulent stuff. Some might lose an eye, or both. But they have family and the family knows what is up. People take shifts watching over the infected at night. They bring them food. They keep them warm. They fend off predators.
The larvae hatch in about a month and fly off, then the people wake up. If you survive this infection you are resistant to a second infection both immunologically and because your sinuses are so scarred. Survivors can resume a normal life. More or less normal - it is not hard to tell who they are, because they do not look the same afterwards.
---
I envision the healer with her jar of these larvae, each with a thread tied around it. She puts some in the nose of the sick person and over the next few days he settles down and becomes somnolent and uncaring. Then she can do the surgery he needs. Once she is done, she pulls the larvae out by the threads and saves them for the next patient.
[Answer]
## Leg Muscles
A healthy human has a lot of muscle on their lower body.
A human laying next to a water source while being consumed from the inside does not need legs.
Therefore, this (horrifying) parasite targets leg muscles, possibly extending to core and back muscles near the end.
## Predator Defense
Primates are pretty good at hitting things with sticks and rocks. A primate without legs is significantly less maneuverable, but is still dangerous to provoke.
If the parasitic wasp remains near its victim, it could aid in its defense, since it is a highly mobile attacker.
Even if the primate is killed, predators tend to prioritize high value parts like organs, and are likely to save the already necrotic leg muscles for a time of great need. There's a good chance that some of the larva will survive to their horrifying adult phase.
[Answer]
**## The back of the mouth or throat**
Some advantages of this location are:
* Soft, easily penetrable tissue
* Plenty of moisture
* Steady supply of oxygen
* Whatever the host eats and drinks can supplement the larvae's diet
* Depending on where they embed, larvae may be difficult to see and difficult to reach with fingers and tools
* Larvae may retaliate against removal attempts by triggering a violent gag reflex and vomiting
* Easy access to nasal cavity, which is apparently a [great place](https://link.springer.com/article/10.1007/s13346-020-00891-5) to deliver brain-altering drugs
* Exhaled carbon dioxide could help adult parasites track hosts and locate ports of entry (this is one of the ways that [mosquitos find us](https://www.sciencedaily.com/releases/2013/12/131205141852.htm)).
Some disadvantages are:
* Tissues are easily irritated and will likely require injection of anesthetic and anti-inflammatory agents
* Lots of mucus-and-saliva-filled crevices that small insects could get trapped in
* Egg implantation attempts will only go unnoticed if target is asleep
* Oral entry/exit limits target availability to those who sleep with mouth open
* Nasal entry/exit limits allowable size of adult parasite
While I'm not aware of any real-life macroscopic parasites that specifically target the human throat, there are several species of worm that may [take up](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4345721/) [residence](https://www.livescience.com/parasitic-worm-tonsil-sashimi.html) there after being ingested by the host (e.g. [*Clinostomum complanatum*](https://en.wikipedia.org/wiki/Clinostomum) and [*Pseudoterranova azarasi*](https://en.wikipedia.org/wiki/Pseudoterranova)).
However, the main inspiration for this answer was the [tongue-eating louse](https://youtu.be/PXpLkRh_NQ4) ([*Cymothoa exigua*](https://en.wikipedia.org/wiki/Cymothoa_exigua)), a horrifying parasitic isopod that clamps onto the tongue of a fish and eventually replaces it, becoming the fish's new tongue. Obviously, this approach wouldn't work on animals that can dig things out of their mouths with fingers and tools, so some reimagining will be required. But the "ewww" factor might make it worthwhile. How creepy would it be if someone yawned in your direction, and you thought you spotted the glint of beady little bug-eyes looking back at you from dark cavity of their mouth?
[](https://i.stack.imgur.com/RZBex.png)[](https://i.stack.imgur.com/3TBEm.png)[](https://i.stack.imgur.com/bssJO.png)
Another inspiration was the mythology about [creepy crawlies entering people's mouths](https://www.scientificamerican.com/article/fact-or-fiction-people-swallow-8-spiders-a-year-while-they-sleep1/) while they sleep. Typically presented in the form of a statistic to give it that "factual" quality (e.g. "on average, you swallow 8 spiders in your sleep each year"), some variation has probably been heard by just about everyone. Even though I know it's a myth, the thought of it does occasionally drive me to roll onto my side at night. I suspect that's the sort of feeling the OP is aiming for.
] |
[Question]
[
If an average human is 5'10" (1.8m), when scaled to be roughly 50 ft (15 m) how much food would it need to remain healthy?
Let's also assume there are three types of this giant; carnivorous, herbivorous and omnivorous. What would be the dietary requirements of each?
[Answer]
The giant is 8.6 times taller than the human. This means that your giant is roughly 630 times heavier than a human. The square cube law is your biggest problem here. Your giant is simply too big to hold his own weight up. Good news for you, your giant is magical and doesn't care about that particular piece of physics.
Fortunately, 630 times greater mass does not mean 630 times greater food. If this relationship were true, large animals would never be able to find enough food, and mice would eat a kernel of corn per week. The real relationship is less than linear.
[Kleiber's Law](https://en.wikipedia.org/wiki/Kleiber%27s_law) states that the metabolism of a creature is proportional to its body weight to the 0.75 power. **GM = C\*GW0.75** In this GM and GW are giant metabolism and weight, and C is a constant number depending on the type of animal.
If we say that the average man weighs 80 kilograms and, requires 2000 calories per day we can write this as:
$ 2000 \frac{calories}{day} = C\*80 Kg$
We can also say that the giant weighs about 50400 Kg. We can solve both equations for C and equate them, and substitute in GW=50400.
$\frac{GM}{50400^{0.75}}=\frac{2000}{70^{0.75}}$
Solving for giant metabolism gives us 280000 calories per day, **138 times as much as is needed for an average human.**
A pound of beef has roughly 1100 calories. It would take 250 pounds of beef per day to feed this giant. If the giant doesn't eat entrails and bones, that comes out to a whole cow every other day. A pound of grain comes out to roughly 1400 calories. It would eat 200 pounds of grain per day.
*Note: I made edits to calories in grain. My original figures were incorrect.*
Note that these are rough estimates and do not take into account SOOO many other factors. [Wikipedia](https://en.wikipedia.org/wiki/Kleiber%27s_law#/media/File:Kleiber1947.jpg) has a link to Kleiber's original chart. Kleiber didn't see any animals who have 10 times higher metabolism than his law predicted, but he did examine a few who were half or double his predictions.
**In conclusion: An omnivorous giant would eat a quarter cow and 100 pounds of grain per day or twice that, or half that.**
[Answer]
So, basing these calculations on the dietary guidelines released by the US department of health for 2015-2020, and the x630 mass factor given by @Nex Terren in their comment, these are the recommended daily allowances for a giant:
```
Calories: 1260000 - 1890000
Protein: 28980 - 32760 g
Carb: 81900 g
Fiber: 17640 - 19404 g
Linoleic acid: 7560 - 10080 g
Linolenic acid: 693 - 1008 g
Calcium: 630000 - 819000 mg
Iron : 6930 - 11340 mg
Magnesium: 195300 - 258300 mg
Phosphorus: 441000 - 787500 mg
Potassium: 2961000 mg
Sodium: 1449000 mg (This is an upper limit - not a recommended allowance)
Zinc: 5040 - 6930 mg
Copper: 560700 - 567000 mcg
Manganese : 1134 - 1386 mg
Selenium: 34650 mcg
Vitamin A: 441000 - 567000 mg
Vitamin E: 9450 mg
Vitamin C: 47250 mg
Thiamin: 693 - 756 mg
Riboflavin: 693 - 819 mg
Niacin: 8820 - 10080 mg
B6: 819 mg
B12: 1512 mcg
Choline: 267750 - 346500 g
Vitamin K: 47250 - 56700 mcg
Folate: 252000 mcg
```
So our giant will be eating a whole lot, to say the least. For reference, an entire cow, properly butchered, yields approximately 513,713 calories. That would be a suitable entrée for our giant, with a side salad of an entire lettuce patch.
[Answer]
A 5'10" man should weight 129-174 lb, and would require 2,433-2,854.5 calories per day. A 50 ft tall giant would weigh 81,236-109,574 lb and require 305,852.4-358,839.1 calories per day.
[There are a few different animals that could provide enough calories.](https://qz.com/951238/a-scientist-calculated-the-nutritional-value-of-a-human-being/)
hare - 3,852
roe deer - 13,200
ibex - 45,780
beaver - 48,000
reindeer - 60,000
humans - 81,500
deer - 119,040
musk-ox - 140,400
red deer - 163,680
horse - 200,100
boar - 324,000
cow - 367,200
bear - 600,000
A man for breakfast, a deer for lunch and a deer for dinner every day should do just fine.
For the herbivorous giant, it would have to eat a ridiculous amount of food to stay alive.
apples - 520 per kg
bananas - 890 per kg
sweet potatoes - 1010 per kg
brown rice - 1230 per kg
avocado - 1600 per kg
chickpeas - 1640 per kg
bagels - 2500 per kg
macadamia nuts -7180 per kg
So unless your giant is eating 500 pounds of avocados a day, it's going to have to be a carnivore, or at least an omnivore.
[Answer]
Let's use formulas that apply to normal humans and scale them up, this won't necessarily be 100% accurate, but neither are actual giants so let's go!
A fifty foot human would need to weigh between 9500 and 12750 lbs to be in a healthy range of BMI (18.5-24.9). That said, other ranges are certainly possible. To answer this question we will use multiple metabolic equations such as the harris-benedict equation and use activity multipliers that we use for real humans to come up with how many calories these giants need to sustain themselves each day.
[](https://i.stack.imgur.com/sztcu.png)
So what do these numbers mean and what are the implications? These numbers represent your giant's total daily energy expenditure (or TDEE for short), this is how many calories your giants expend on a daily basis. Ranges were provided to suggest how individual differences are a thing, so a light male who is sedentary and burns 70k per day will likely continue to burn 70k per day. Being younger means energy expenditure is higher and being older means that energy expenditure is lower (values were calculated for 30 years of age). If a giant consumes less than his or her TDEE, that giant will lose weight. If a giant consumes more than his or her TDEE, that giant will gain weight.
This leads me to the implications. Your giants are likely going to be sedentary and light individuals unless food is simply incredibly abundant. Additionally, your giants are likely going to live in VERY small groups and be pretty territorial about land since getting sufficient food will likely be difficult. Your giants will likely be carnivores since vegetables tend to be light on calories. A grown cow weighing about 1000 lbs might provide about 650 lbs of meat which would give your giants somewhere in the range of 0.5-0.75 million calories. Enough to feed about 10 or so sedentary giants. Would they only want to eat meat though? Hard to say, it might not sustain them nutritionally and giants may die young due to nutritional deficiencies. Additionally because of the high energy costs of activity, giants would not go out of their way to be active.
Herbivorous giants are out of the question, but carnivorous and omnivorous giants are more plausible. Perhaps they operate as herders. Skyrim's concepts of giants keeping mammoths as company seems entirely logical from this perspective. I do not believe that they would do so well without a constant reliable food source however which circles back to them being territorial, not active unless the need arises, and not particularly large (more thin giants than anything else).
] |
[Question]
[
# Question
The alien want to make some new virus (or editing the gene of existing virus) to increase human death rate, and they don't want human to know the virus has been edited. I have read some similar conspiracy theory, such as the [SARS conspiracy](https://en.wikipedia.org/wiki/SARS_conspiracy_theory). Some scientists said SARS is man-made while some said it is not man-made. How can scientists know whether the virus is man-made? What kind of changes in genetic structure is impossible to happen in the natural environment?
If you want to know more about the background:
# Background/Premises
Aliens from another universe came to the earth. Some functions in the human brain are useful to them. (The details are not related to the question.) People whose brain is to be used by the aliens will be dead. The aliens don't want people to know of their existence, so they don't want to use living people directly. Should the alien do so, then there would be many strange deaths occurring and human may discover the truth. So the aliens want to use ["clinically dead"](https://en.wikipedia.org/wiki/Clinical_death) people. There is a [10 minute](http://infolific.com/health-and-fitness/first-aid/clinical-death-biological-death/) window of for the aliens to make use of the brain before brain damage occur. (The alien don't need to go to the scene and take out the brain from the human body.)
Quote from the second link:
>
> Once someone has stopped breathing they have about 4-6 minutes until
> some brain damage begins to occur. At around 6-10 minutes some brain
> damage is likely. And, generally speaking, after 10 minutes,
> irreversible brain damage is almost certain. However, as mentioned
> earlier, there's no way to know with certainty so don't assume and
> stop rescue efforts.
>
>
>
To sum up, the aliens want more people to die, however, they want "sustainable development", the alien only want to increase the death rate instead of eliminating all humans.
[Answer]
There are a few ways one might try to identify an unnatural viruses. Human scientists would look for:
## Remnants of genetic tools
Man-made recombinant viruses usually contain **artificial elements**, such as:
* Selective markers, genes conferring resistance to weak lab antibiotics. These are used not by the virus itself, but while the virus is being put together in lab bacteria. However it's not rare to find natural bacteria that already have these, so their presence would not really be a giveaway.
* Restriction enzyme recognition sites. These are usually six to eight base pairs. They occur often enough in natural viruses that detecting a few would not immediately suggest genetic manipulation by humans.
* Multi-cloning sites. These are long clusters of recognition sites for several different restriction enzymes. One of these appearing in a virus would immediately give away that it is man-made.
All of these remnants could **easily be masked** by other tools (such as CRISPRs) that alter DNA without leaving a trace. So, aliens with genetic technology similar to our own could already hide the remains of the genetic tools used to make a virus.
## Cat's tongue and Eye of Newt
DNA-sequencing. Results are in! Alright...huh? Potato starch-breaking enzyme? Deep-sea shrimp phosphatase? Tasmanian-Devil face-cancer cell protein? What are these doing in a "natural" virus? This kind of thing would be a clear giveaway of an artificial virus, man-made or otherwise. The man-made viruses we currently have today tend to contain elements from very **distantly-related species**. However, again, this is not strictly a giveaway. Natural viruses often species hop during their evolution, and incorporate (actually are made from) bits of diverse host DNA. So aliens could **mimic the naturally-occuring diversity** of these bits and pieces to get their virus under the radar.
## Homology to known virus types
This is the big one. On finding any potentially "new" virus from a human population, the first thing researchers will do is **compare its sequence** with known families of virus. Nowadays this takes about two seconds. An alien-made and controlled super-virus is likely to be **very different** to any naturally occuring virus family. What will happen:
* virologists are surprised,
* publish in Nature,
* become famous
Depending on how much advanced improvements/controls the aliens have built into their virus, its discovery could hit the field of virology from so far out in left field that the discoverers get accused of faking it, cheating etc. All the attention would only encourage us to look further into where this virus came from.
So, to play it very safe, aliens should restrict themselves to **using an already-existing virus family** such as SARS, and applying only a few point mutations.
Would that be enough to dramatically increase the human death rate? We don't know. But remember, in a farm or a forest somewhere, Mother Nature herself is putting those same mutations into SARS right now...
[Answer]
Nothing is *impossible*. Science will never definitively prove anything (nor does it have to). However, it can bring up some very solid evidence to support or refute the hypothesis that it is a man made virus.
There is a big difference between how man-made products work and how evolved products work. The man made product has a purpose, and it is tailored to that purpose. Any purposeful construction quickly reveals that it had a purpose.
Evolved products are typically spaghetti code, taking advantage of whatever could be found at the time. A gene for the eyeball is good for the liver? Great! Upregulate it and start churning out liver enzymes! However, this makes the product of such evolution *notoriously* difficult to predict. It's hard to look at a genome and say "this make a Monkey" or "this causes hemorrhagic fever." If a product is man-made, that unpredictability gets in the way of achieving the man-made purpose. We typically design structures which can be analyzed to prove that they work.
A great example is Stuxnet, the virus that hit the Iranian nuclear refinement centrifuges. After we analyzed the code for Stuxnet, it was *very* clear that it had exactly one target. A particular model of controller by a particular company was targeted, and the damage done was extremely targeted to the devices being controlled. Nobody who saw the disassembled code for Stuxnet could disagree on what its purpose was.
Let's contrast this with an evolved example: sickle cell anemia (SCA). SCA is a debilitating disease buried in our genetic code. You'd think we'd have evolved away from such a useless bit of code, but we haven't. It's not obvious why until you look at the entire ecosystem and find malaria. Malaria is a major killer in many parts of the world, and it turns out that if you have just one set of SCA genes, rather than the 2 required to get the disease, you gain resistance against malaria.
Both of these are examples of a very focused goal, but the results differ greatly. When you disassemble Stuxnet, it's very clear what it was intended to do. When you disassemble the genes for SCA, there's no obvious way to tell that it's a solution to malaria. The body simply found some genes that did the job, and ran with them. Without malaria, it's just a message without a context. **With man-made things, the context is always visible.**
You might be able to cover your tracks a bit by "evolving" a virus artificially in a computer. However, you would still likely do it fast enough that there would be telltale signs of order, signs of trying to accomplish an objective.
[Answer]
>
> The alien only want to increase the death rate instead of eliminating
> all humans.
>
>
>
They cannot do it with a disease. With any disease the death rate (the number of deaths for given number of births) will rise for a short time but will quickly stabilize at the same rate as with healthy population: every human can die only once. So to have more deaths they should increase births rather than spread disease.
[Answer]
Assuming no attempt at obfuscation, an intelligently designed tool will not have aspects unrelated and unuseful for its function. Your new cordless drill will not have 3 power cords, two of which end in bristle brushes and cannot transmit power. It will not have pointless redundancy. It will be made economically. Also, if you are familiar with the tech, you will recognize aspects of the tech from earlier iterations of the same or similar objects; if not the components itself, the tech used to produce them. An engineered bacterium can be recognized because there is are standard toolkits used to insert or delete genes and these kits leave their signatures in the end product. Sort of like moldmarks on a plastic item or codes on a capacitor.
If I were these aliens I would not make a killer from the ground up, like Stuxnet. For one it is laborious and for two it will require cumbersome field trials before you can determine it will not work. I would modify some organism which was already a capable killer and augment it. This is more efficient and starting with something that has a track record means it is likely to work - at least no worse than the starting material.
If you are unfamiliar with the toolkit used by the aliens it would be trickier to determine something had been artificially augmented. If the augmentation was minor modification of existing structures / dna or addition of dna from a related organism it would be more difficult still.
Augmenting lethality is not trivial. Aliens might or might not have an understanding of what limits the lethality of a given lethal organism - for example, why did the 1918 flu not kill everyone? What limits the spread of cholera or ebola? These things are not obvious even to smart people who live on earth and try to figure them out.
An interesting spin on this would be the patience of the aliens. How fast do they need their brains? If they can take the long view a good strategy would be a farm approach: something which cut life expectancy at 45 but did not affect fertility or birth rate, and in fact increased both.
] |
[Question]
[
I've spent time hand-drawing, and then scanning, and colorizing a world map using Paint.Net. The map uses a rectangular projection (something like an Equirectangular, Plate Caree, or Behrmann Projection). I'd like to take this map and project it onto a globe like Google Earth: I'd like to be able to rotate the globe and zoom in to see additional detail.
How do I take my rectangular map and put it onto a globe like Google Earth?
Presumably, this is going to require specific software:
* What software can I use to allow me to do this?
* If the software requires me to split my rectangular map into tiles to handle different zoom levels (this is my understanding of how Google Earth works), does it help with this process? Is there different software that will help with this process? Do I have to do it by hand?
+ If I have to provide tiles for the most-zoomed-in-level, it would be preferable if the software automatically built the less-zoomed-in-tiles based on them.
[Answer]
If your map is equirectangular, you can use **Google Earth**. Here are the steps you should take.
1. **Check the size of your image:** (If you have Google Earth Pro you can skip this step, the Pro version automatically creates image tiles from your image) In Google Earth, go to `Help > About Google Earth` and look for the field labeled `Max Texture Size`. This is the largest size image you can use. On my computer it's 16384x16384, but your result will vary depending on your computer hardware.
2. **Create an Image Overlay:** Right-click `My Places` and select `Add > Image Overlay`. Give the overlay a name, and then either put the URL of the image in the `Link` box or click the `Browse...` button to use a file from your computer.
3. **Position the Image:** On the `Location` tab change the borders of the image so it covers the whole globe, i.e. `North: 90N, South: 90S, East: 180E, West: 180W`.
Remember to turn off any layers that will interfere with your map, such as roads, borders, labels, terrain, etc. If the borders don't line up with yours, you probably have a map projection other than equirectangular. As long as the distortion is not too bad, just turn off the borders and ignore the mismatch.
[Answer]
This does not answer the entire question, but [GProjector](http://www.giss.nasa.gov/tools/gprojector/) can get you part of the way there.
As described on their site:
>
> GProjector is a cross-platform application which can transform an equirectangular map image into one of over 100 global and regional map projections. Longitude-latitude grid-lines and continental outlines may be drawn on the map, and the resulting image may be saved to disk in GIF, JPEG, PDF, PNG, PS or TIFF form.
>
>
>
In order to make a globe-like projection, change the projection type to "Sinusoidal" and then change "Format" to "Interrupted: 30deg Gores". I've used this to print out a map and glue it together into something that resembles a globe. It's not digital and you can't zoom in, but it's awesome seeing a physical representation of your world.
[Answer]
A few other utilities not already mentioned that allow you to upload maps and stick them onto globes;
Kevin Gill's [PlanetMaker](http://planetmaker.wthr.us), or Redditor /u/notcaffeinefree's [MapToGlobe](http://maptoglobe.bitbucket.org) and [Drawable MapToGlobe](http://maptoglobe.bitbucket.org/draw/).
If you have minimal web-programming experience, you might try the jQuery [Planetarium](http://www.onextrapixel.com/2014/04/01/construct-interactive-planets-and-build-the-universe-on-your-website), or this [WebGL globe tutorial](http://www.html5rocks.com/en/tutorials/webgl/globe/), or this [Three.js globe tutorial](http://learningthreejs.com/blog/2013/09/16/how-to-make-the-earth-in-webgl).
Also worth looking into are GIMP's [MapToSphere](https://www.youtube.com/watch?v=ZUYbj4x4OxY), the third-party extension [Flexify](http://www.flamingpear.com/flexify.html) for Photoshop, and AfterEffects' native [CCSphere](https://www.youtube.com/watch?v=t3Xx2TXu37w) (not available in the demo).
For low-tech methods, you could always try Shrinkwrap, Light projection, or good old-fashioned Paste. ;)
[Answer]
I have used the freeware (but not open-source) Windows application [Wilbur](http://www.fracterra.com/wilbur.html) to do this. It supports a number of map projection modes.
It is also a handy tool for playing with height data such as DEM files that you can download from various US government sites (including NSAS's DEMs for Mars). It is not always the easiest piece of software to use, but it is a way to try out some things for free.
[Answer]
Here they are some online tools, standalone software, images repositories and scripts for building globes:
* [GlobeMaker](http://turnipsoft.com/jim/palaeogeography/globemaker.htm)
* [Ready-made gores for Earth](https://www.loc.gov/item/76694920/)
* [PERL script for Gimp](http://www.vendian.org/mncharity/dir3/planet_globes/TemporaryURL/make_globe_gore_map)
* [Standalone PERL script](http://www.vendian.org/mncharity/dir3/planet_globes/TemporaryURL/make_gores_pl.txt)
* [Tool online per creare i petali](http://www.winski.net/?page_id=12)
* [USGS Daisy-Petal creator (requires.NET 2.0) (for "flower petals"
projection](http://www.winski.net/?page_id=7)
* [GMT - Generic Mapping Tools for Windows](http://gmt.soest.hawaii.edu/gmt4/gmt/gmt_windows_SOEST.html)
] |
[Question]
[
One day, you suddenly get superpowers! Whoo-hoo, you can speed up or slow down the flow of time for yourself. This means you can run faster than a jet, right? So you decide to test it out. You go out to some deserted spot and start speeding up. You start running, and as you go faster, you start to notice a problem. It's getting really hard to breathe, and harder and harder to run. It's like you're running through water or something. Then you realize that since you're speeding up, the rest of the world seems to be slowing down. And since force is measured in $kg \cdot m/s^2$ (also known as Newtons), and you're decreasing the length of a second for everything else, you're increasing the force required to draw air into your lungs and move around by the square of whatever time-distortion factor you are at. So the question is, assuming that the time-field extends a few inches out from your body and gradually ramps up to the full effect right at your skin/the entrance to your mouth/nose, **how much can you speed up time without suffocating?** And is there any training you can do to improve this speed?
[Answer]
**You're dead fairly quickly in this scenario**
And it's cool that you've brought this to our attention.
The force required to move air in and out of your lungs isn't the problem. The air in the pocket immediately surrounding your body is in the same time frame as your lungs. Therefore, breathing is quite normal.
The real problem is the exchange of atmosphere through the time differential. How much differential can there be, before the buildup of CO2 inside your time bubble kills you?
*And the worst thing about that is while your superhero can train him/her/itself for high-percentage CO2 breathing, such as hiking at high altitudes a lot... your superhero can't do a thing about how slowly the molecules move between the time frames.*
**Which depends completely on how you define that transition in your story**
I've enjoyed fiction that suggests things can move between time streams (e.g., the movie *interstellar* where time was affected by the gravity of a black hole) and where they can't (e.g. Star Trek NG ["Time's Arrow"](https://en.wikipedia.org/wiki/Time%27s_Arrow_(Star_Trek:_The_Next_Generation))).
Unfortunately, that means asking us how quickly those molecules can move through the differential is Too Story-Based. If the nature of your superpower permits no movement through the differential, even with training (and due to how little air is kept within inches of the body), your superperson has minutes at any time differential before suffering [cerebral hypoxia](https://en.wikipedia.org/wiki/Cerebral_hypoxia)... and only a few minutes after that before dying. If you do permit movement through the differential, then you need to tell us what the equation is defining the movement.
**However, there is a bit of comical coolness here**
Did I say he'd die? Heh... not really. What'd he'd do is black out, and I assume his superpower would shut off along with his consciousness. Until learning his limits, he'd seem to speed up and then collapse and skid across the pavement, suffering substantial road rash.
[Answer]
JBH has an excellent answer. I thought I'd add a different issue: freezing to death.
You exist in thermal equilibrium with your environment: the amount of heat you export through radiation/convection/conduction is equal to the amount you absorb, and the net allows you to maintain your body temperature. Since you are generating heat internally, your body temperature is greater than your surroundings (most of the time).
Let's assume that you are operating at twice "normal" rate. Ignore conduction. What happens? Your surroundings are radiatively cold, since from your point of view they are radiating with half the power they normally do. Generally speaking, objects radiate at a rate proportional to the fourth power of their temperature (where temperature is in degrees Kelvin). Room temperature is about 300 degrees Kelvin. So your surroundings are effectively at 252 degrees K, or about -54 degrees F. Furthermore, convection will not supply much heat for the same reason it doesn't supply much oxygen - especially if you are not moving.
From the point of view of the rest of the world, you have become extremely hot, and will continue to be so while you freeze solid.
[Answer]
# Short answer: suffocation won't be an issue
Even without breathing, your hero can do a lot. Freediving, where people don't breathe at all, have records involving considerable physical activity of around 20+ minutes (current record for simply holding one's breath in a pool is over 24 mins). Everyone can learn to handle longer breath-holding, to some degree, and your hero has a *really good motive*.
Hypoxia and CO2 toxicity would only arise somewhat gradually and probably not be too harmful (accidents and bad luck aside) because any moderate-to-severe effect would, as a side effect, presumably remove the problem.
They also have many ways to mitigate the issue of suffocation. It would be quite simple to make some kind of slim body-shaped CO2 scrubber/rebreather unit, and/or also an oxygen supply/oxygen concentrator unit if needed, that fits in the effect space, which would provide long term breathing help.
But the maths of durability under "ordinary" breathing is fun. So let's have a go...
# Using Maths!
Focussing just on suffocation (not heat, cold, momentum, etc):
Unbreathed air comprises ~79% nitrogen, 21% oxygen, 0.03% CO2. Exhaled air has the same nitrogen but closer to 16% oxygen/5% CO2. An adult at rest breathes around 10000 - 15000 L of air per hour ([1](https://iqpowertools.com/air-how-much-do-i-breathe) [2](https://www.quora.com/How-much-volume-do-we-inhale-and-exhale-in-a-day)). CO2 becomes uncomfortable, then disabling, then toxic, at lowish concentrations however, and that's regardless of the oxygen level in the air. [This page](http://kimberlymoynahan.com/2012/04/friday-fiction-facts-trapped-in-an-airtight-room/) suggests that
* 0.1% CO2 = headache
* 1% CO2 = hot clammy fatigue concentration + "jelly legs"
* 2% CO2 = 50% faster breathing (roughly one breath every 2 secs not 3 secs, at rest), headache after some hours, tired.
* 3% CO2 = breathing doubles (panting), severe headache, dizzy, visual and hearing disturbances (sparks, low night vision), blood pressure up. "Extremely sluggish but not usually fatal"
* 4-5% CO2 = "immediately dangerous", in addition to above, 4x normal breathing, choking/"unable to breathe" feeling, unconscious <30 mins, extended exposure = possible permanent effects and risk of death.
* 5%+ CO2 = additionally: tinnitus, confusion, panting, impaired vision
* 10% CO2 - unconsciousness/death in minutes.
Your superhero will probably respond to these in a self limiting way - the less functional they are, the more likely it is they would drop superpower engagement due to distress or at worst, unconsciousness).
Oxygen deficient air (hypoxia) is also dangerous. [This page](https://www.airproducts.com/~/media/Files/PDF/company/safetygram-17.pdf) suggests that:
* 15-19% affects thinking, coordination and judgement
* 12-15% causes poor coordination/judgement, fatigue on exertion, and emotional upset
* 10-12% causes "very poor" coordination/judgement, nausea/vomiting, possibly unconsciousness within minutes, impaired respiration, possible cardiac damage.
* <10% almost immediate unconsciousness, physical torpor, convulsions, death.
We can assume that suffocation involves 2 issues - whichever hits sooner, out of hypoxia (lack of oxygen) and CO2 toxicity.
We also need an idea of the volume of air and diffusion rate. Those are very handwavey, but let's suppose the effect extends about 6-8 inches (15-20cm).
* Humans have ~ 1.5 - 2 sq.m. of skin ([Wikipedia](https://en.m.wikipedia.org/wiki/Human_skin)) so the person has an air volume of ~ 225-400 L carried by the effect. Suppose that fading if the effect with distance means that they only get effective use of 60% of this volume, they effectively have an air space of 135-240 L of usable air. We'll also ignore diffusion around the body shape, and assume the air close to them can mix nicely.
* Breathing produces an equal volume but with 5% CO2 instead of negligible, so they produce about 5% x (10k - 15k) litres of CO2 in an hour, or about 500 - 750 L/hr, or 8.3 - 12.5 L/min. They use up oxygen at about 2.1k - 4.1k L/hr (10-15k breathed x 21% O2), or about 35At those rates, CO2 is likely to be by far the more serious problem.
* The CO2 leaches out and O2 leach in, at some rate - I'm not going to do the differential equations for partial gas pressures in a handwaved physics scenario, instead I'll ignore this for now, and see what time scale we get initially, without diffusion (worst case).
* I'm also going to assume they are relaxed and conserve energy (they know to do a bit, breathing slowly, and repeat once they catch breath, is better than doing a lot at once). So they use oxygen at near-resting rates.
* I'm also assuming they don't forcibly project exhaled air away, in order to obtain greater rates of fresh air.
On those assumptions, and simplifying a lot, it should be easy to graph how their oxygen and CO2 go, and roughly when it becomes difficult/dangerous because of either of these.
# Problem..
But it's not that easy, I'm going to have to go think hard, first, about how to reconcile 2 wildly different figures:
* several sites say a person breathes 10k-15k air per hour
* but we also have about 20 breathes a minute at rest = 1200 breathes per hour, with a tidal volume of ~ 1/3 L, suggesting a tidal intake of 400L/hour. (In addition to 2.5-3 L residual volume).
Once I figure out what that's about, I'll try to finish this. But for now, this should still be useful enough to add anyhow.
# Mitigation/breathing aids
The kicker is, they could mitigate both suffocation issues pretty easily. The effect extends a few inches, and that's plenty of space to fit a custom-made slim oxygen supply, oxygen concentrator unit, or CO2 rebreather/scrubber unit, if they needed to. Those things can be quite small, and can be designed flat, to fit against the skin within the effect's "few inches".
So after the first couple of unpleasant incidents, which are survivable bad luck/accidents aside), your hero learns they need this, and develops it or has it custom made, tests it, refines it, and then laughs happily next time.
[Answer]
The following is a very long answer but it'll be worth it, if only because it comes to the opposite conclusion compared to the question and all answers so far.
To get a better idea of what's going to happen we are going to go throught the process of the trial-run.
To start off, you've realized that your time-field is basically the reverse of time-dilation that happens near black-holes or when you are moving at tremendous speed but without the negative gravity or kinetic energy required to get that time acceleration for yourself. A time dilation field would simulate something similar to what you are experiencing: The time outside the dilation field is accelerated compared to the time inside the dilation field and we know that matter is free to move inbetween those time barriers without problem. So you know the air will still diffuse into your field.
Now you've moved to the desert and want to start slow by just standing still while you activate your field, you never know what's going to happen right? So you activate your time acceleration field, accelerate yourself to twice the time and wait.
The first thing you notice is that you are getting warmer. While you receive less radiative heat from your surroundings and still generating the same radiative heat per time unit, you are also producing more heat and are somewhat insulated from the outside world. Radiative heat is one of the least efficient ways to lose heat (which is why space is such a good insulater despite it's cold, as you can mostly lose heat through radiation), so the netto gain of being insulated from the outside world makes you warmer for quite some time, but it's going to get colder if you wait long enough.
Compared to you the air particles at your skin don't accelerate at all, but compared to the outside world they'll be going twice as fast. They act as though they have twice the heat energy but without the actual kinetic energy! To get this into equilibrium, the air particles next to your skin will need to slow down to the speed of the particles outside of your field.
<https://en.wikipedia.org/wiki/Kinetic_energy>
The kinetic energy of the air particles next to your skin will drop. E=0,5\*m\*V^2. Regardless of the mass, any 50% loss of speed means a 25% of energy loss, so the air around you is about to get a lot colder! What's worse is that this is just a 2x time acceleration, at any multiple acceleration higher this difference will exponentially grow! But it's not going to be instant. If the air around you was actually twice as hot as the surroundings, it would simply diffuse away slowly. So it takes a while before you start feeling colder, especially since you are now generating more heat and losing less. The way your field acts also protects you: The air particles that bump into eachother will have barely any time difference even at the edges of your time-field. While the air particle that is faster in time is going to lose more energy to the other particle in the reaction, it won't be a lot more than it would normally as that difference is going to be so small when they touch.
But as you stand there in your slowly colder and colder environment you notice something worse: The air pressure is dropping around you. The time barrier makes it harder for your air particles to escape as they push against the "slowed" air particles that take a lot more energy to budge. Still, since your particles move faster compared to the rest you'll have more air particles "escape" your time accelerated zone and less return to it. As the pressure drops at higher time accelerations it'll keep dropping untill you might suffer from hypoxia. For a moment you panic and move your head... And sweet fresh normal-pressure air rushes in as you move the time-acceleration field over them. Something the other answers seem to be missing is that as long as you move you'll "push" normal pressure and normal temperature air into your time-field. And that air can easily be breathed in and out. Any CO2 and low-pressure cold air will be left behind your body, so suffocation won't be imminent! Yet.
To prevent hypoxia, you start to move at a leisurely pace while playing with the acceleration. What you immediately notice is that the gravity is still the same, but every movement you make has a lot more force behind it. Previously you might put 10 newton per second into moving a particular limb, but due to the time acceleration it looks to the outside world like you put in 20 newtons per second! Fortunately you won't be jumping a mile and dying on impact when walking as anything within your field acts normally, so you'll be able to walk normally (gravity doesn't change either). Any interaction with the outside world where a portion of the object is outside of your field (say a person you punch) will experience the full effect of your time-accelerated extra newtons per second (besides that the time-acceleration field's boundries will likely wreak havoc on their blood supply and chemical balance).
As you start going faster you notice an air-pressure buildup in front of you, slowing your down. The time-field prevents the air in front of you from getting away easily into the non-accelerated air around it. It does try to flow around you but the normal flow is choked by the boundries of the time-field. This kind of pressure makes you think off a space-ship re-entering atmosphere and heating up and makes you afraid for a moment, but you'll never reach anywhere near enough speed to heat up (<https://what-if.xkcd.com/28/> ;) ). In fact, you'll be cooling down as the air that previously insulated you is now flowing against you at accelerated speed. How fast you cool down depends on the temperature of the air, but it's there.
As the air in front of you builds up and pushes against you, you start feeling a "pull" behind you. Normally when you move the air around you fills up the area you left. Unfortunately most of the air is slowed down, and it'll be up to the high-pressure area in front of you to try and fill it. This accellerates the air around your body even more, causing potential choked flow (<https://en.wikipedia.org/wiki/Choked_flow>). Not pleasant in any way, you are going to get cold!
As you accelerate the air will cool you down and the higher pressure air will start to choke you (<https://biology.stackexchange.com/questions/41639/breathing-becomes-harder-in-certain-wind-conditions>). As you run faster you risk dying of hyPERoxia (<https://en.wikipedia.org/wiki/Hyperoxia>), rather than hyPOxia.
The cold is likely going to be the first problem, but it also has a laughably simple solution: Wear a coat. The worst problems happen at your skin due to the time difference, but a coat would cover and insulate the air at the point where the worst time difference is. You could simply wear a backpack with a few coats (and a raincoat, they work wonders against wind), and each time you want to accelerate time faster you stop for a moment, put on a thicker coat and then start running again. This should work wonders for protecting you against the cold and the choked flow.
You'll still die of hyperoxia if you go too fast though. Only with airtanks close to your body would this be solvable, just be sure that all the air will be within the maximum air acceleration zone or the pressure difference in the tank might cause problems for your breathing.
I don't know at what point the cold or the pressure will be a problem. But this is just a start to figure out at what speed you could go at the maximum. Considering some people have survived multi-MACH velocity aircraft breakups and survived (linked in the What-if, they survived through their pressure suits and immediately slowing down so only go this fast for a fraction of a second) you could probably be going pretty damn fast with the right preparation, just not for long.
[Answer]
You look hot!
Consider: Your normal body temp is 300K has a peak wavelength of 9.7 micron. If you run at 3 times speed, your radiation's wavelength just shrank by a factor of 3, corresponding to 900K, a sullen red glow.
Go up to 5 time speed up and to an outsider, and you're going to be bright yellow.
But the other problem occurs too.
Light from outside will be red shifted. Even at a speedup of 2-3 visible light will be red-shifted into infrared -- you'd have to see by what the rest of us mortals call UV. During the day there is enough UV for you to see, although the world will be dim. It will also have seriously distorted colour. For an idea look at infrared colour film.
At night you would be blind at speedups of over 2. You might have to move like a cockroach, who apparently doesn't have enough brain to see and run at the same time. They sprint. Stop. Sprint. Stop.
Or you could carry a flashlight. It's photons would be shifted to UV going out, and converted by to your visible coming back. Note that this flashlight could do serious damage to people around you. Bright UV sources are not good for people's eyes.
[Answer]
Assuming that you don't suffocate or freeze to death...
You would be extremely loud, to the point of causing permanent damage to the hearing of everyone around you, breaking fragile items like glass and computers, and causing structural damage to any building that you enter. Maybe even killing everyone you walk near.
The surface of your time bubble will act as a sort of reversed event horizon for sound, where sound can get out, but it can't get in.
Every breath you take will make quiet noises that spread out at the speed of sound right to the edge of the time bubble, right to its own event horizon.
Every time you brush your clothes. Every footstep. Every heartbeat.
Each sound will add to the amplitude of sound that is already at the edge of your time bubble, just building up, compounding, and, while no time will have passed for our observers outside, from our hero's perspective, that sound is just waiting for us to release control of time, to have a moment of inattention, then BOOM, there's an explosion as the pure pressure, that behaves just like detonating a high explosive, complete with the overpressure damage to everything nearby.
[Answer]
One other issue to consider, as the title asks about issues/limits generally (not just suffocation). Would pressure gradients be stable? Meaning, if your air has different physics (different distribution of velocities, and different power inflow/outflow "as seen from the other side", would you have a problem that air in your bubble is more or less energetic *simply because of being in that part of.spacetime*, and therefore an unstable situation arises in that air tends to constantly leave the space, leading to low pressure/vacuum, or constantly move into it? Could this lead to an equilibrium pressure (or lack of one) that was harmful to your hero?
[Answer]
Let us begin with a time bubble with a given surface $S$, time factor $F$, and opacity $R$.
* $S$ describes the shape of the surface itself (in which will be required to do integrations). Evidently, $S$ is a closed continuous surface (otherwise nothing makes sense).
* The time factor $F$ indicates the factor in which time speeds up inside $S$.
* $R$ is the reflectivity, a dimensionless number between 0 and 1, which indicates the probability of a random molecule hits $S$ and gets reflected back.
---
**Velocity distribution**
We'll start with Maxwell-Boltzmann distribution, and compare it inside and outside of $S$. The probability density function is:
$$
f(\mathbf v) = \left(\frac{m}{2\pi kT}\right)^{3/2}\exp\left(-\frac{m\mathbf v^2}{2kT}\right)
$$
Where $k$ is the Boltzmann constant, $T$ is the temperature of the environment. This gives the probability density of finding a particle with velocity $\mathbf v$. This probability will shift due to the time-field.
For sake of simplicity, let's move to inside the field, and analyse the outside (we could do the opposite, and, we should get the same results). Outside, the time is slowed down by factor $F$.
Meaning, the velocity of everything is slower by a factor $F$. Thus, the probability function outside shifts:
$$
f\_F(\mathbf v) = \left(\frac{mF^2}{2\pi kT}\right)^{3/2}\exp\left(-\frac{m\mathbf v^2 F^2}{2kT}\right)
$$
To see that's the actual probability, one can calculate the speed mean $\langle v\rangle$ and see that it got slowed down by $F$. Other possibility is $v\_{rms}$.
The added $F^2$ inside the exponential near the velocity is explained, but the added $F^2$ near temperature outside the exponential, is solely due to normalization -- we are, after all, talking about a probability density function.
The mean keeps being zero even with $F$, but now the standard deviation of the velocity distribution is different. Notice, it makes no sense the temperature to change, because every single physics phenomenon has slowed down: velocities did so, but also heat transfer, and everything else involving actual movement.
Equilibrium is reached when the number of molecules per unit time leaving the bubble equals the number of molecules per unit time entering the bubble. For $F=1$, this is trivial. For $F\neq 1$, if we're inside the bubble, particles outside will be moving much slower (the shift in the velocity distribution). *Initially*, less will enter the bubble, and more will leave, causing the density of particles in the bubble to decrease, until equilibrium is reached: until flow is equal. So, we expect the air inside the bubble to become much more thin, then in the outside (for $F>1$). In reverse, if $F<1$, atmosphere inside will have greater pressure than outside. Our objective, is to calculate the molecular density ratio (or the pressure ratio) with respect to $R$ and $F$. :).
We need to calculate the exact number of particles/molecules per unit time which are going from outside to inside (crossing the barrier). Call it, $s\_{io}$ That number, is:
$$
s\_{io} = \frac{dN\_{io}}{dt} = \int\_S \int\_{\mathbf v\cdot\mathbf n \le 0} f(\mathbf v)\mathbf v\cdot \mathbf n dS d\mathbf v
$$
Good luck with that integral! You're going to need it.
---
**Atmosphere inside the time bubble**
Actually, we already have plenty of luck: the gas is spreaded isotropically, there's no external potential, and all sorts of nice approximations we can make, because it is true.
Let's simplify. Let $n\_i$ be the density inside the bubble, and let $n\_o$ be the density outside. Same for the pressures $p\_i$ and $p\_o$. We'll assume the time bubble has a 'cubic' form, which will allow considerable simplification of the surface integral. But, due to isotropy, the result remains valid for complicated shapes. Furthermore, let us be inside the bubble. Let $s\_{io}$ the flow from inside to outside (the number of particles per unit time per unit area leaving the bubble). And let $s\_{oi}$ be the flow from outside to inside (the number of particles per unit time per unit area entering the bubble). We'll calculate these quantities for $yz$ plane, but, any other face calculations are analogous.
$$
s\_{io} = \frac{1}{A}\frac{dN\_{io}}{dt} = n\_i (1-R) \int\_{v\_x \ge 0} v\_x f(v\_x, v\_y, v\_z) dv\_x dv\_y dv\_z
$$
Expanding:
$$
s\_{io} =
n\_i (1-R)
\left(\frac{m}{2\pi kT}\right)^{3/2}
\int\_{0}^\infty v\_x \exp\left(\frac{mv\_x^2}{2kT}\right) dv\_x
\int\_{-\infty}^\infty\exp\left(\frac{mv\_y^2}{2kT}\right) dv\_y
\int\_{-\infty}^\infty\exp\left(\frac{mv\_z^2}{2kT}\right) dv\_z
$$
Integrating:
$$
s\_{io} =
n\_i (1-R)
\left(\frac{m}{2\pi kT}\right)^{3/2}
\left[\frac{1}{2}\frac{2 kT}{m}\right]
\left[\frac{2\pi kT}{m}\right]
=
n\_i (1-R)\left(\frac{m}{2\pi kT}\right)^{1/2}\frac{kT}{m}
$$
Thus:
$$
s\_{io} = n\_i (1 - R)\sqrt{\frac{kT}{2\pi m}}
$$
Analogously, we can calculate the other factor the same way:
$$
s\_{oi} = \frac{1}{A}\frac{dN\_{oi}}{dt} = n\_o (1-R) \int\_{v\_x \le 0} v\_x f\_F(v\_x, v\_y, v\_z) dv\_x dv\_y dv\_z
$$
And, we'll arrive at:
$$
s\_{oi} = n\_o (1 - R)\frac{1}{F}\sqrt{\frac{kT}{2\pi m}}
$$
Demanding equilibrium, we finally arrive:
$$
\frac{s\_{io}}{s\_{oi}} = \frac{n\_i}{n\_o} = \frac{1}{F}
$$
Using ideal gas law, $P = nkT$, we also get the pressure ratio between outside and inside:
$$
\frac{p\_i}{p\_o} = \frac{1}{F}
$$
The pressure inside falls as $1/F$. If pressure outside is 1atm, if $F=10$ times faster in the bubble, then, the pressure inside will be 0.1 atm. Not a good pressure to breath while running..... Notice that **the pressure ratio does not depend on the opacity** of the time bubble $R$, as the $R$ cancel out.
---
**Time to reach equilibrium**
Now, because these are equilibrium equations, there's no clue in how much time it will take to reach equilibrium. That's what we are going to investigate here. But, that is not hard to calculate. For that, we define $N\_i$ the amount of molecules inside, and $N\_o$ the amount of molecules outside. Due to conservation of particles, if 1 particle left the barrier, then, there exists one less particle inside. We apply it:
$$
\frac{dN\_i}{dt} = \frac{dN\_{oi}}{dt} - \frac{dN\_{io}}{dt}
$$
Therefore:
$$
\frac{V}{A}\frac{dn\_i}{dt} =
\frac{1}{A}\frac{dN\_{oi}}{dt} - \frac{1}{A}\frac{dN\_{io}}{dt} =
s\_{oi} - s\_{io}
$$
Thus, we are left with the following first order differential equation:
$$
\frac{V}{A}\frac{dn\_i}{dt} =
\frac{n\_o}{F}\alpha
-n\_i\alpha
,\quad\quad
\alpha = (1 - R)\sqrt{\frac{kT}{2\pi m}}
$$
Fortunately, that is easy to solve. The solution is simply:
$$
n\_i(t) = n\_o \left(1 - \frac{1}{F}\right)\exp\left(-\alpha\frac{A}{V} t\right) + \frac{n\_o}{F}
$$
We can put the solution in the form:
$$
n\_i(t) = n\_o \left(1 - \frac{1}{F}\right)\exp\left(-\frac{t}{t\_c}\right) + \frac{n\_0}{F}
$$
Where $t\_c$ is call the time constant. That time gives us a clue, an intuition, of how long the system takes to relax to equilibrium. That time is:
$$
t\_c = \frac{V}{A}\frac{1}{\alpha} = \frac{V}{A}\frac{1}{1-R}\sqrt{\frac{2\pi m}{kT}}
$$
Notice something important: apparently, **the time constant does not depend on the time factor $F$** (hopefully I made no mistakes in the calculations -- feel free to check) (though now that I thought about it, it makes a bit of sense: if two environments were at different pressures, and one opened a wall for equalization, the time constant wouldn't depend on the pressure difference itself, rather, the geometry of everything. In here, equilibrium causes a pressure difference, and, again, time constant only depends on geometry and temperature, not on the pressure difference, and thus, the factor $F$).
The greater the volume of the bubble, the greater the time. The greater the area, the smaller the time it takes. The greater the opacity $R$, the greater the time it takes. The greater the temperature of the environment, the less time it takes. And so on.
---
**A numeric example**
Let's plug some numbers! The volume of the human body is approximately $V\approx 0.07 m^3$. The area of the human body is roughly $A\approx 1.7 m^2$. Assume temperature $T=300K$, with atmosphere composition of nitrogen, $m = 2.3258671 \cdot 10^{-26} Kg$. Boltzmann constant $k = 1.38\cdot 10^{-23} J/K$. Let's put no opacity, $R=0$. This gives us a time constant $t\_c$ of.... [adds suspense]........ $t\_c = 0.00024s$. That is, 0.2 milliseconds. Um... I guess I suggest that your hero never activates the time bubble for too greater $F$, otherwise, in less than a millisecond later, equilibrium will be reached. If $F$ is too high, that could be compared to explosive decompression.
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
In many science fiction stories, crystals where used by ancient alien civilisations to store information that could last millions of years.
For example, in Stargate, "control crystals" that looked like hexagonal-shaped rods could store information and could be interfaced into larger computer systems to perform different functions. In some cases, the crystals where fashioned into flat boards and apparently where more efficient than the crude hexagonal rods.
My question is, could we humans in the near future use crystals like those in Stargate to store electronic data? Could we use Quartz crystal to achieve this? or would we need to use a different type of mineral? And would this technology be better than other conventional data storage methods we use today?
[Answer]
**Yes. Crystals can be used to store data.**
[Holographic data storage](https://en.wikipedia.org/wiki/Holographic_data_storage) uses crystals to store data.
The data density has the possibility to be much higher than common magnetic or existing optical data storage methods. This is because holographic data storage records information in the entire volume of the crystal and is capable of recording multiple images in the same area utilizing light at different angles.
The method may also be faster as it can be used to read the data in parallel more easily than existing methods, [reading over one million bits at once](https://en.wikipedia.org/wiki/Holographic_data_storage#Reading_data). You can think of this like shining a light through a photo slide, all the information comes out at once (further [described here](http://www.ece.drexel.edu/courses/ECE-E642/articles/sci_american.pdf)).
You can use quartz for a read-only data storage, but due to that limitation it's unlikely to gain widespread use. There are a lot of types of crystals. The word crystal is like the word salt, it's the name for a general class of something, but is commonly used to refer to a single poster child in the class. So, while quartz will not likely be used for data storage because it doesn't display a high photorefractive effect, crystals of a different type will be used to achieve read-write data storage. Crystals that do display high [photorefractive effects](https://en.wikipedia.org/wiki/Photorefractive_effect):
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> Photorefractive materials include [barium titanate](https://en.wikipedia.org/wiki/Barium_titanate) (BaTiO3), [lithium niobate](https://en.wikipedia.org/wiki/Lithium_niobate) (LiNbO3), [organic photorefractive materials](https://en.wikipedia.org/wiki/Organic_photorefractive_materials), certain [photopolymers](https://en.wikipedia.org/wiki/Photopolymer), and some [multiple quantum well](https://en.wikipedia.org/wiki/Quantum_well) structures.
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Additionally, it's not likely the form factor will be like that seen in Superman, more likely these crystals will be very small and encased in a protective covering.
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You could use crystals to store data, but you have to create them yourself.
A "perfect" crystal provides a perfectly regular structure that repeats itself (the most famous examples being salt and diamonds).
Since the structure is so regular, you can store data by altering somewhat that structure (putting atoms of different sizes); alterations of the structure could be detected (v.g., through X-rays refraction) and interpreted as the data they represent.
Of course, that also means that (unless very advanced technology/magic is available) you do not use them as you use your HD or USB drive... they are "read-only" data devices; once built you cannot modify them.
Additionally, the need to use a "perfect" crystal as the base and the need to carefully measure the alterations to its structure means that you cannot "mine" it, but grow it in a lab or a similar device.
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Yes, we do it every day. All transistors are crystals. you question intimates can a 3d crystal store information. Yes again. Why don't we use them more? because I can store an incredible amount of info, cheaper and more reliably on a 'flat' chip( which by the way has 3D qualities), than a difficult to fabricate 3d multi-layered chip. The idea of a hologram is interesting, but the technology is un inspired. theoretically we could have a holographic CD reader that has no moving parts. practically .. why I have a 'thumb drive' that can store a terabyte of info on the size of, well my thumb nail... which by the way equals a topo map of the world above and below sea level for $200.
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A 3-D storage media that can be read and written to might be referred to as a *crystal* by virtue of being a 3D grid of unit storage cells, no matter what the underlying technology may be.
It is more likely to be called a *crystal* if it looks like a gemstone: optically translucent. If it is read/written by lasers, that will be the case, in order to access the interior.
The storage cells would not be any kind of natural mineral. I can imagine a cell being a few atoms on each side of a cube, but carefully engineered to provide multiple stable states and mechanism to absorb the laser light and cause a change; something like a Chlorophyll absorbs light and drive an electron transport chain to eventually push the state into a different stable valley. But rather that being able to harness as much light as possible, it would be tuned to require precise frequencies simultaneously, allowing intersecting beams to address it.
(Actually, the intended cell size is too small to uniquely address that way. So a larger clump might have one "receiver" that takes coded data to a local grid of storage bits.)
The "state" can be stored in any number of ways that re-arrange a small number of atoms without adding or removing any: folding, flipping a group to a different permutation, orienting something differently within the surrounding structure, moving atoms to a different position. But state can also be stored as *charge* like in current flash memory or the perminant field in an "electoret" or magnet; or as energy levels within electron orbitals; or the quantum *spin* of electrons.
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Can crystals be used to store data? [It's already been done](http://physicsworld.com/cws/article/news/2013/jul/17/5d-superman-memory-crystal-heralds-unlimited-lifetime-data-storage). As @Samuel mentioned, these are not Superman-esque crystals, however.
So what advantages do crystals have over other storage mediums? You actually mentioned the most important reason you would use crystals in your first line - "to store information that could last millions of year".
[Current storage technologies](http://www.storagecraft.com/blog/data-storage-lifespan/) typically have a lifespan that in the ballpark of 10 years. There are some storage technologies that could theoretically last up to a 1000 years, but that's still not very long in the grand scheme of things. Crystal-based storage technology could last a million years.
So why don't we use them more? Well, when was the last time *you* needed to store something and make sure it would last for a million years? With our current lifespans, we won't need that durability of storage unless we figure out that humanity is going to be wiped out by some sort of apocalyptic event.
Also, there's no easy way to write to them. The increased storage sized in not significant enough to compensate for the fact that they are, for the time being, read-only storage.
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Yes, crystals can be used to store data.
[Quantum dots](https://en.wikipedia.org/wiki/Quantum_dot) are nothing more than nanometer scaled crystals, and when properly designed they can exhibit magnetic properties. Use a lot of them in a properly arranged way, and BANG, you have a way to store information with crystals which resembles good old floppies.
You can also embed the quantum dots into a crystalline matrix for a better handling.
Another option is to use their light emitting properties, by using N different emission lines to encode the information in base N.
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What I mean is most (all?) eusocial species are tiny (ants, social bees, termites, and even mole-rats).
I know that my father (who is a biologist) told me that the reason most massive animals (like orangutans, tigers, bears, great white sharks, basking sharks, and blue whales) are solitary is because when you are big, you need a lot of food, so you do not always want to share it with a pack.
So, is a eusocial species weighing on average 2,000 kilograms (or two metric tons, or 4,400 pounds, if you want) (2,000 kilograms is the mass of a massive adult female great white shark) possible? If so, where could it evolve?
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## As a counterpoint to the splendid answer by Legio, which looks at the background theory, I've taken a different tack:
This is slightly tough as the definitions of eusociality are the subject of hot debate, so I'll take the points one by one.
### Cooperative brood care including offspring from other individuals:
Killer whales live in matrilines, the children remaining with their mothers for life. These matrilines collect together in groups of up to four to make pods, comprising perhaps twenty individuals.
African elephants are similarly matriarchal, they live in groups with up to three family lines, taking care of each-other's children.
### Overlapping generations within a single group:
Killer whales: yes, see above.
Elephants: yes, with the exception of the males who leave the group circa age 15 and are then solitary. (Male bees (drones) are similarly driven out of the hive in harsh winters and they're considered a eusocial species)
### The division of labor into reproductive and non-reproductive groups:
Killer whales: Not as such, but the matriarch continues to fulfill her role even after her reproductive days are over.
Elephants: The matriarch continues in her role as with whales, they have distinct nursing casts for the very-young, and separate "juvenile care" units for the growing children. But to be fair this doesn't stop them reproducing as-such, so it's a case of "nearly, yes".
**Edit:** As it turns out, a [recent study in Zimbabwe](https://www.abc.net.au/science/articles/2013/10/28/3874904.htm#:%7E:text=A%20Zimbabwean%20study%20has%20found,an%20adequate%20supply%20of%20oocytes.&text=While%20egg%20numbers%20then%20decrease,at%20the%20age%20of%2069.) has shown that female African elephants may potentially remain fertile until natural death by old age.
### Individuals from one "caste" lose the ability to perform tasks in other "castes":
It's unclear from my basic researches if this is the case for either elephants or whales, but the indications are it's probably not the case, though some elephants prefer to specialise.
## In conclusion:
Probably, somewhat - in the cases above, but not rigidly fitting *some* of the definitions. To quote Hobbamok's comment: "any world you build can very very reasonably include giant eusocial species with slim to even no deviation from our reality".
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Dinosaurs were huge and plenty of them lived in herds, oh and elephants too.
Eusocieties happen when helping your cousins and brothers is as good of an option as helping yourself, which means when there are many of them.
Sacrificing yourself, your own reproduction to save a stranger is stupid, sacrificing yourself to save 2 brothers is efficient, as efficient as if you reproduced yourself.
Sacrificing yourself to save 4 first degree cousins is efficinet, or 8 second degree cousins or 16...and so on..
Eventually when you have 100'000 sisters like an ant, it's more efficient to die and save 100'000 sisters instead of being selfish and maybe produce a few offsprings, selfish offsprings which wont help you out when they grow up.
There's a reason many animals adopt close relatives whos parents died, theres a reason gays and lesbians did not go extinct and they are found in many species, because even if they don't reproduce,they help their family survive better. There's even evidence of gay animals protecting sisters and cousins from being raped, instead of leaving and building their own family, they stick with the old one and help out.
Big animals are already eusocial, just to a lesser extent...to make them more eusocial make them have more brothers and sisters.
You can even see it in human children, I don't remember which experiment, old memory....they found out that male children will often display self sacrificing acts in oder to defend their brothers if they are many, like stepping in front of the danger and covering the other siblings behind their back, but will cower and hide if they are only two...unless its a female....male kids will almost always self sacrifice for a sister.
Iyou have to think like an animal, animals don't care about evolution, they don't have plans for the next millenia, but selfish animals have selfish genes which produce selfish offsprings...which means that selfsih parents will have to compete with their selfish offpsrings.
Cooperating animals help one another, selfish animals eat their own children to eliminate the competition...literally.
When animals start having hundreds of offsprings at once or live long enough to produce multiple generations, then selfish genes always fail against cooperative ones.
Cause having possibly 2 or 3 generations of offsprings helping you is better than having to kill as many of your offsprings as possible to not be outcompeted.
This is not a choice made by the animal trying to figure out the most efficient way, it just happens that cooperative animals are more successfull and starve selfish animals or at least out reproduce them. And selfish animals are often more successfull in harsh environments like the deep dark sea or the desert or except when they find a good niche which allows them to prosper regardless.
Good rule of thumb is, if you have more 2 siblings then sacrificing yourself for their good will always be more efficient than building your own family, so it will slowly...really slowly develop your genes, passed by your siblings into an eusocial society. To speed up the process, just have more sibblings.
The only problem is, big animals have long pregnancies, so evolving eusocieties is not impossible but it is incredily slow and tedious, our planet is really young and our universe is also young...it might take so much more time to see fully eusocial gigantic fauna.
By the time an elephant has had 1 new generation, a cat produces two generations, cats live less but evolve faster.
Heck...for most of the time earth existed there was only micro fauna or animals as small as a lizard...big animals have just appeared on the universal clock, dinosaurs died half a second ago on the universal clock and life on earth was born yesterday...
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The most common reason for a species becoming eusocial is that the males only have one of each chromosome. That means that all their sperm is identical. If the queen mates for life with one male her female offspring will inherit 100 % of the male's genes and 50 % of the queen's genes. It means that the sisters will share 75 % of their genes.
That's the magic thing. For the females it makes more sense to help their sisters who they share 75 % genes with rather than having their own offspring who they share only 50 % of genes with.
Eusociality has evolved at least 8 times in hymenoptera, order that contains wasps, bees, and ants. The males have one of each chromosome and the females have a pair of each chromosome. Eusociality has evolved only a handful of times in all other orders. It can happen but it's a lot less likely.
If the shark males were haploid, meaning they only have one of each chromosome instead of a pairs of chromosomes like the females and they mated for life, they could evolve eusociality.
<https://en.wikipedia.org/wiki/Evolution_of_eusociality>
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On the one hand, not all eusocial insects contribute much to the colony's central food stores. Deborah Gordon (a computational biologist specializing in red harvester ants at Stanford) recounts an incident in her book *Ant Encounters* where a fellow biologist was trying to find a bullet ant's nest; he set out a dead cricket as bait in a bullet ant's path, hoping that it would lead him back to its nest. Unfortunately for him, the ant simply ate the cricket and kept going. She suggests the possibility that ants that come from small colonies may only feed themselves and the brood (rather than keeping large central food stores).
On the other hand, there is the issue of why an animal that large can't simply get food and reproduce on their own. Most ants (and eusocial insect species in general) have at least some degree of division of labor, with some ants (typically the older ants) being foragers, some queens producing eggs (most ants are sterile females), and some taking care of larva. On the other hand, most large animals are quite capable of reproduction and food-gathering on their own (or in small "packs" like lions and wolves). You don't really see as much division of labor among, for example, Great White Sharks because they simply don't need it - they can do everything they need to themselves or in relatively small groups anyway, so there's less of a value add to a colony-type arrangement.
Also, some other comments and answers have pointed this out, but ants in the same colony can be more than 50% related, which means that they have a strong incentive to be "altruistic" and cooperative towards others in their colony.
Incidentally, this is a little off-topic, but the fact that foragers tend to be older may be in part due to the fact that eusocial insect foragers tend to "smell like" foragers, which may help eusocial insects know what kind of food to forage for; also, there is some evidence that ants in particular [perform a form of social distancing with foragers](https://www.nature.com/articles/srep13393) to prevent the spread of disease. Also, foragers are at higher risk from accidents, disease, and predators, so if older ants are performing more dangerous jobs it would effectively raise the average lifespan of the colony.
In short, in order for something like that to "work," you would need some kind of extensive division of labor, closely related individuals within a group, and a large foraging range.
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Unless you consider it cheating, laying down whatever laws say it is possible on your world, is your privilege.
If at least partial adherence to your father's knowledge and wisdom is required then move back a level and create a food source abundant enough for your eusocials but quite unattractive to other critters.
Throughout, please remember from the point of view of the ant and, the mole-rat isn't "tiny" at all.
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I'm creating an rpg medieval setting, and I want it to feel pretty real. Castles make fun locales, so I'm trying to figure out how many castles I can plausibly cram into a 5,000 mi² region. The region is presided over by a Duke-like figure, who likely has some number of lesser lords underneath them. I assume all lords need at least a keep, but perhaps there are other additional castle needs.
My *general* question relates to the factors that determine how many castles will be in a given Medieval Setting. I can guess at some of the factors (population density, agricultural productivity, military defense needs) **but what I'm looking for here are some real figures.** What was the castle density of Medieval Europe? Where was this density high? Where was it low? Why?
There's a very nice answer [here](https://worldbuilding.stackexchange.com/questions/77600/in-a-medieval-setting-how-far-apart-should-towns-be) about the proximity of medieval towns to one another, but I wasn't able to turn that into an answer specifically relating to castles.
**EDIT:** Thank you for the input so far. The prevailing answer at the moment seems to be "you have as many castles as you have lords". I'm sure there are also as many castles as there are castle-courtyards, but that doesn't really help me very much. If # of castle = # of lords, what determines the number of lords?
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So we have a duchy of some 5,000 square miles, or 14,000 square kilometers, some 120 km by 120 km, which makes it about one third the size of the medieval [Duchy of Bavaria](https://en.wikipedia.org/wiki/Duchy_of_Bavaria) or about one fifth of the modern [Free State of Bavaria](https://en.wikipedia.org/wiki/Bavaria). Wikipedia has a great list of [627 castles in Bavaria](https://en.wikipedia.org/wiki/List_of_castles_in_Bavaria) (by which they mean the modern state); *pro rata* this results in some 100 to 110 castles in the hypothetical duchy in the question.
A "castle" is a very ambiguous thing. There at least three kinds of "castles" in European history:
* The purely utilitarian military constructions, where nobody wanted to live if he was not paid for it. Their purpose was to defend important points, such as a river crossing, a mountain pass, a major crossroads and so on. Those were the most expensive military weapons platforms of the day -- if the dukedom is rich, there will be plenty of those, and if the dukedom is not so rich there will be as many as they could afford. Don't forget to add a small castle to any [toll-collection point](https://en.wikipedia.org/wiki/Toll_castle).
* The combined fortress and residence castles, where the duke and his counts lived. Those are of course fewer, and larger, and more confortable, and had actual inner courts. In the small duchy in question there may well be anything from half a dozen to maybe a dozen and a half of those, depending on the specifics of your duchy; Bavaria, to continue the example, is full of mountains so there were more residential fortresses than usual. The dukes will maintain multiple residences, so that they can divide their time between the various parts of the land, e.g., there was the Duke's Castle ("Herzogskasten") in Ingolstadt, the [Trausnitz Castle](https://en.wikipedia.org/wiki/Trausnitz_Castle) (what the dukes called home), Dachau Palace etc.; then the counts or marquesses which ruled over the counties or marks will each have their own fortress-residence.
* Then there are the purely residential "castles" which were really strongly built large houses. Each noble family will have one of those.
Depending on the particular setup, there could also be a set of royal or imperial castles, not subordinated to the duke.
Then one must not forget the walled cities. This is the Middle Ages, and any city worth its charter will want to build walls. For example, in Bavaria, [Bamberg](https://en.wikipedia.org/wiki/Bamberg),
[Ingolstadt](https://en.wikipedia.org/wiki/Ingolstadt),
[Nuremberg](https://en.wikipedia.org/wiki/Nuremberg),
[Passau](https://en.wikipedia.org/wiki/Passau),
[Rothenburg](https://en.wikipedia.org/wiki/Rothenburg_ob_der_Tauber),
[Würtzburg](https://en.wikipedia.org/wiki/W%C3%BCrzburg), etc. Each will have a fortress, and also a town hall which may well resemble a miniature castle...
As @Kingledion suggested, I should add that during the modern period there was a time, say from about 1700 to 1850, when rich aristocrats built [follies](https://en.wikipedia.org/wiki/Folly) and non-functional castles for pleasure. Compare:
[](https://en.wikipedia.org/wiki/New_Castle_(Ingolstadt)#/media/File:Neues_Schloss_Ingolstadt_Front.JPG) [](https://en.wikipedia.org/wiki/Neuschwanstein_Castle#/media/File:Neuschwanstein_castle.jpg)
*On the left, the New Castle in Ingolstadt; this is a real late-medieval castle. On the right, Neuschwanstein Castle; this is a modern 19th century palace built by [Ludwig II of Bavaria](https://en.wikipedia.org/wiki/Ludwig_II_of_Bavaria) as a sort of overpriced country retreat. Hint: one of them looks similar to the Disney castle, the other doesn't.*
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This is a pretty complex question even if it seems simple. A couple things.
**1. Castles can exist for many reasons**
* Military/defense/control
* Fortress of a city
* Resource protection
* Geographic location
**2. Castles range greatly in size and scope**
* From small wooden keeps to large stone keeps with curtain walls
**3. Castles don't just pop up in geographically even distribution**
* Your map is going to play an important role in placement
* Population density is important as well, it takes a lot of humans to build and maintain a fortress
* The geopolitical climate, a bunch of nations that get along won't really be building castles.
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So, to lead off, castles are expensive. Really expensive. You're not going to invest the resources into one unless absolutely necessary.
Before you can get a count you need to figure out your map. You need to know where rivers and roads (medieval transportation routes) are. Identify mountains and passes. Figure out your political boundaries and the history of the nations involved. Its easy for us to think of castles as all being contemporaries but in reality they were built over the course of millennia. Keep population density in mind as well.
**Step 1: Establish geography, population, geopolitics and history**
Once you complete that step (which is the biggest one) you can begin placing cities and forts. Where things intersect be it political boundaries/transportation routes/geographically important points, or better yet a combination of them, are good candidates for large defensive structures.
**Step 2: Find overlapping/intersecting points of interest**
Now you have sites for major defensive structures. Next step would be keeping in mind resources. Stone is hard to quarry with medieval technology, I also hear its heavy. This makes it expensive. As such, some places may not have stone defenses. Wood, sandstone, regular stone, even dirt can all be used to create fortifications.
**Step 3: Figure out resources available for building**
Once you get your big/major locations sorted out you can work your way down, the less complex and smaller the more common they will be. If you are talking about a small wooden keep you can have pretty much as many as you want.
**So in short...we can't really give you a number. There are a lot of variables to consider.**
Run through the process above and you should get to a decent answer, do what makes sense, don't just try to pick a certain number.
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As Dan Clarke says, your overall density is at least one castle per lord. The wealthier/more economically strategic a lord's holdings are, the more likely it is to be stone; the more powerful, wealthy and influential the lord, the more likely he is to have more than one castle (not necessarily all stone).
According to this Quora post, ***how many lords you have, as a percentage of the population, depends on your exact setting***. For instance, militarized borders will have more lords (with better fortified castles), while some cultures had so many people who could claim some sort of title that most of them didn't have castles.
<https://www.quora.com/In-a-medieval-European-society-what-percentage-of-people-were-farmers-peasants-how-many-were-clergy-and-how-many-were-nobles>
As a general rule of thumb, I'd suggest that cultures where political power has been consolidated by a few, 5% of your population will be lords with castles, up to 10% for militarized areas.
Given your time setting, here's what most of your castles are going to be like. Shad buries the lede, so you can skip to about 3 minutes in if you want. However, he does try to give you a good idea of the ratio of stone-castle-density to not-stone-castle-density.
<https://www.youtube.com/watch?v=Q3uvVV2bEfk>
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1 keep per Lord. These range from simple large stone houses that are defensible to large castles that can house hundreds and withstand an army. Poorer lords may only have thick wooden walls around their home, or may make large wooden forts instead of small stone keeps.
Along the border, especially on roads and rivers, and important harbours you might find a string of small stone or wood forts to keep enemies out, most will be fairly small and basic, acting more as a trip wire and a show of force against raiders. Depending on the financial situation of the kingdom these could be crumbling old forts that are ready to fall apart or well maintained structures that can have thriving trading towns surrounding them and soldiers in nice new shiny armour.
**Edit:**
The number of lords and castles depends on a whole host of issues. Sometimes there will be many castles per lord, sometimes they'll be forced to have a single small keep or a palace. 1 Castle per lord, was used as a fairly reasonable means of keeping things simple, with the limited information we were given.
**What is the population of the country?**
The higher the population generally means more nobles to ensure no one noble gets too much power, and that they are able to maintain their lands. Bureaucracy wasn't as advanced back then, having too many people under one nobles control is simply too hard to handle. Also a king would not want a noble who rivals his power, they can't always prevent it, but eventually it reaches the point where a war occurs and either the noble is broken or the noble becomes the king.
**How much power does the king have?**
In countries where kings were dominate, generally castles were limited. In countries where nobles had more power, there were more castles.
Spain has 2500 castles because it had a very turbulent history. The Muslim invasion of Spain saw hundreds of keeps and castles built by both sides to defend their land. Then during the Reconquista, more castles were built. However after the Reconquista was completed, virtually no castles were built, there wasn't the need. Many castles fell into disrepair as the nobles and the royalty couldn't maintain all of them.
France before the 16th century had an extremely weak king. The nobles ruled and fought amongst each other while the kings generally stayed out of the way. They built lots of keeps and castles during those times to deal with their neighbours. After the rise of the absolute French monarch, new castles were not built by the nobles. Smaller keeps and forts were abandoned or taken over by the King, and some castles were destroyed, others were taken by the King and some were left to the nobles.
In England, after the Second English Civil War, the parliament ordered many of the castles and keeps damaged or destroyed to ensure any future civil war would be easier to put down. Again after this time new castles were not made, only palaces.
Japan in the Edo period, after Japan was united, made a law that only one castle could be built in a lords domain unless given special permission by the Emperor.
Now Bavaria was mentioned in another message, with 620 or so castles. Bavaria was frequently caught up in wars, and there was no strong central government. So the nobles, towns, cities and anyone with money really built keeps and castles to protect themselves.
So what type of government do you have?
**Peaceful or Warlike?**
A country at peace and having known peace for a long period of time will not have a lot of keeps and castles. Older keeps and castles will exist, but most won't be kept up.
If raiders aren't a problem, why would a mine have anything more than a basic stockade? That's money being wasted.
Nobles didn't often have a lot of money, building castles and keeps to show off is a waste that could be better spent on creature comforts, impressing allies with gifts and bribes, etc. A palace is much better for showing off than a castle.
If the border is a desert with very few people living in it, than castles aren't necessary for defence. Instead a few keeps on or near the oases will ensure no army can invade unnoticed, while saving money.
Now if war, either between nobles or outsiders is common, you're going to see lots of castles. Like in Bavaria, every place of some importance is going to have a castle, keep or fort. So is there lots of fighting or not?
**Trade Routes?**
Is the nation landlocked, an island, is it surrounded by equally powerful or more powerful nations right on the border, is it isolated forests, deserts or mountains, or is most of it coastline?
The major ports, rivers that are usable for shipping and major roads near the borders will have a castle or keep. The size of it, as well as the upkeep depends on how peaceful the neighbours are. Again more warlike neighbours will see well built castles, peaceful smaller nations will get keeps.
**Population centers**
Are people spread out all over the country or are they mostly centered in a few key areas?
If this is a desert kingdom with a few cities and towns around oases, ports or rivers, you'll need very few castles. If it's more like England with multiple cities, many large towns, and a whole host of villages, castles will be spread out to cover all the various areas.
That's about it, figure out those details and you can come up with the number of castles.
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I'm trying to build a world that has the setting of medieval or middle-ages fantasy. Stuff like adventurer guild and so on is also implemented alongside the usual mercenary and freelance knight. One of the problems I'm facing is their lodging. I know that there were inns in the medieval era. But I am aiming at maybe a dorm-like type of lodging that the adventurer/mercenary can rent for a few months or so. Is there a type of lodging like that that actually existed in the past? Maybe like a boarding house? But from what I know, the concept of boarding house appeared around the 19th century. Any input, information, or reading material will be greatly appreciated.
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Usual caveats: I assume you mean Western and Central European Middle Ages. I assume that you know the difference between the Middle Ages and the Renaissance. Hint: if your world has courtly love, it's the Middle Ages. If it has middle class or noble women flirting with adventurers, it's the Renaissance.
The Middle Ages were not spectacularly different from the Ultra Modern age in what concerns accomodations. Essentially, from the cheapest to the most expensive, during the High and Late Middle Ages you could rent:
* A place on the floor in the common room strewn with fresh straw (or not). This was usually rented by the night; it was the basic accomodation available at inns for the vast majority of travelers (such as pilgrims, couriers or servants of richer travelers).
* A place in a bed in the common room or in a private room. This was rented by the night; it was the typical accomodation for middle-class travelers, such as not very rich merchants. It was *very* common. Sexes were separated, of course; but since public baths were unisex, this did not matter much.
* A room. This could be rented by the night at an inn (by very rich travelers, or by a group of travelers), or by the month or year in a town or a city (for use by middle-class people, such as merchants, lawyers, clerks, students etc. who had to spend some time away from home).
* A room and board. Rented by the month or year in towns or cities by middle-class eople, such as merchants, lawyers, clerks, students etc. who had to spend some time away from home. Has the advantage of providing basic service and food at a competitive price. Has the disadvantage that the basic service and food were usually nothing to write home about.
* A suite of rooms. This was rented by the month or year by rich people, such as successful merchants, professors, medical doctors, and of course noblemen who had to spend some time away from home. Usually included accomodation for the suitable number of servants (typically, places in beds in common rooms).
* A wing of a palace. Rented by the year by very rich noblemen or noblewomen (say, from duke or duchess onwards) who had to spend considerable time away from home, either in a diplomatic or military mission for their lord (emperor or king or prince...), or in exile. More commonly it was provided free of charge by the local ruler.
Notes:
* In the Early Middle Ages the post-classical population crash was so severe that inns were a rarity, and so was money. No way to rent something, except in exceptionally civilized cities, such as Rome or Paris or London.
* Almost nobody traveled for fun. Travel had almost always a practical or spiritual purpose. It was both expensive and dangerous.
* Such things were quite different in the Eastern Roman Empire, and later in the Arab world and the Ottoman Empire. They had much better travel infrastructure and services were more readily available.
* Upper middle class men (and their betters) always traveled with servants. Middle class women (and better) always traveled with servants. Honorable lower class women never traveled without their husbands. Men seldom traveled with their wives.
* Houses were very rarely available for rent, if at all. A room, a suite of rooms, or a wing in a palace. Not a house.
* Hospitality was thing. In peaceful ares/regions/countries well-off people who stayed some time away from home tended to arrange accomodation through family or professional relationships. In remote places even poor peasants offered overnight hospitality to weary travelers.
[Answer]
From [Canterbury Tales](http://academic.brooklyn.cuny.edu/webcore/murphy/canterbury/2genpro.pdf)
>
> Befell that in that season on a day
>
> In Southwark at The Tabard as I lay
>
> Ready to wenden on my pilgrimage
>
> To Canterbury with full devout couráge,
>
> At night was come into that hostelry
>
> Well nine and twenty in a company
>
> Of sundry folk by áventure y-fall
>
> In fellowship, and pilgrims were they all
>
> That toward Canterbury woulden ride.
>
> The chambers and the stables weren wide
>
> And well we weren easėd at the best.
>
>
>
[](https://i.stack.imgur.com/v7VqF.png)
from Wikipedia
In the prologue above the narrator describes a tavern named the Tabard where he and fellow travelers are stopping on their pilgrimage. Chambers were wide and food was good as can be seen in the picture. This is was about 1300. I am not sure how long a person could stay - probably until his money ran out.
May I encourage your writings to take inspiration from the Millers Tale.
The next I can think of is from the early 1600s. From [The Three Musketeers](https://archive.org/stream/thethreemusketee01257gut/1musk11.txt)
>
> Thus d'Artagnan entered Paris on foot, carrying his little packet
> under his arm, and walked about till he found an apartment to be let
> on terms suited to the scantiness of his means. This chamber was a
> sort of garret, situated in the Rue des Fossoyeurs, near the
> Luxembourg.
>
>
>
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My first thought was "tavern", but that idea has been extensively explored already. Most people didn't travel from their home in Medieval Europe, but an exception were the "Journeymen".
A skilled young person, having completed their apprenticeship, could travel from town to town. Having presented themselves at the town office, or aldermen (to have their identity checked), they would be introduced to the local guild, where they would offer their skills, in exchange for bed and board. If your adventurer were to disguise himself as a "journeyman", he could get free lodging, without raising too many eyebrows. However, the guilds tried to stop this. Journeymen had to wear distinctive clothing, kept passbooks, and used secret handshakes to make it hard for adventurers or others to disguise themselves as workers.
This tradition still exists in parts of Europe, notably in Germany, where there are about 800 people on the *"walz"* at any time.
In France, buildings used for housing journeymen exist and are known as a cayenne. Large ones may house 100 "Compagnons" at a time.
Further ideas from <https://en.wikipedia.org/wiki/Journeyman_years>, <https://en.wikipedia.org/wiki/Compagnons_du_Tour_de_France> and links therein.
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So let's say it's a big planet, like a Jupiter. Not talking about our Solar System. This is hypothetical. But say a Jupiter-esque planet in a solar system suddenly disappears. And by disappears I mean just that. It's there one moment and gone the next. No large chunks spiraling out to hit other planets. No debris of any kind.
Its gravitational pull is therefore gone. And it had a good chunk of the mass of the solar system. Now that 20% or so of total solar system mass is no longer pulling.
What would happen to the other planets in the solar system? If that missing planet had moons, what happens to those moons?
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I know you said this is not a real planet, but I'm going to do some math with our Solar System to give you some idea of what the effects might be. Also, I'm ignoring your statement of 20% of the mass of the solar system. An object that was 20% of our solar system would be 1/4 the mass of the sun, and most definitely undergoing fusion: not a planet.
# Effect of Jupiter on the other planets
Lets calculate the effects of Jupiter's gravity on Mars (the closest planet to it) compared to the effects of the Sun. The distance from the Sun to Mars is around $2.28\times10^{11} \text{ m}$ and the standard gravitational parameter ($GM$) of the Sun is $1.33\times10^{20}\text{ m}^3\text{s}^{-2}$. The acceleration of the Sun on Mars is $$\frac{GM}{r^2} = 0.00256 \text{ m/s}^2.$$
The distance from Jupiter to Mars is around $5.50\times10^{11} \text{ m}$ at nearest approach and the standard gravitational parameter ($GM$) of Jupiter is $1.27\times10^{17}\text{ m}^3\text{s}^{-2}$. The acceleration of Jupiter on Mars is $$\frac{GM}{r^2} = 0.000000420 \text{ m/s}^2.$$ That is about four orders of magnitude smaller than the effects of the Sun, and two orders of magnitude smaller than the effect of the moon on the Earth.
While the presence of lack thereof of Jupiter will certainly change things in the Solar System in the *long run*, its effects at the present time would be negligible. For example, if Jupiter were 10 times bigger and 10 times closer to Mars, its effects would be similar to the effects of the moon on Earth. It is hard to imagine a solar system where a planet's disappearance would affect the other planets on timescales shorter than millions of years.
# Effect of Jupiter on its own moons
This would obviously be significant. According to this [handy-dandy calculator](http://keisan.casio.com/exec/system/1360310353), the escape velocity from Jupiter's orbit to the galaxy is 18.47 km/s. Thus, any satellite lined up so that its speed in the solar frame of reference was 18.47 km/s more than that of Jupiter would end up leaving the Solar System.
The [orbital speed](https://en.wikipedia.org/wiki/Orbital_speed#Mean_orbital_speed) of a a moon relative to the main planet is $$v\approx \frac{2\pi a}{T}$$ for a low eccentricity orbit.
Looking at the [list of the moons of Jupiter](https://en.wikipedia.org/wiki/Moons_of_Jupiter#List), the farthest satellite that could potentially end up ejected from the solar system would be Thebe with an orbital speed of about 23.9 km/s. The other moons, including all four Galilean mooons, are not going fast enough to get ejected, no matter what orientation in orbit they are in.
Now keep in mind that Jupiter itself is moving at about 13 km/s. So if a satellite's orbit has it going the opposite direction from Jupiter's direction of motion, it would begin a retrograde orbit of the sun. For example, if Io at 17.3 km/s were in such a path when Jupiter disappeared, it would suddenly be orbiting the Sun the wrong way at 4.3 km/s; much too slow. This means it would fall into the inner solar system gaining speed until it shot back out to the former orbit of Jupiter.
Of course, Io would have a rough ride trying to follow this orbit for a few million years; inevitably it would interact gravitationally with the much larger Venus, Earth or Mars, and end up being thrown about again. It could even collide with one of the inner planets.
All in all, the moons would get thrown willy-nilly about the solar system. While it is relatively unlikely that any of them will be ejected from the Solar System based on their initial velocity, they could end up being slung out of the Solar System by the outer planets, caught into orbit of a different gas giant, hurled into the Sun, or they could collide with just about anything.
# Conclusion
While the immediate effects of Jupiter's disappearance would not cause any harm, the medium-term effects of its many moons and [Trojans](https://en.wikipedia.org/wiki/Jupiter_trojan) flying around the solar system are potentially cataclysmic. Assuming your disappearing planet had as many co-orbital elements as Jupiter, this would basically be a repeat of the [Late Heavy Bombardment](https://en.wikipedia.org/wiki/Late_Heavy_Bombardment), and I would hate to be in a non-spacefaring civilization in that system during the next few million years.
To be more clear, with the four quite sizable Galilean [former] moons roaming the solar system at will for millennia, there will be significant perturbations of the Asteroid belt, various Trojans and Centaurs and whatever. All these new flying rocks will be the biggest and most proximate problems, added on top of the hundreds of medium sized moons to moonlets that Jupiter will release directly.
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The moons would probably careen off tangentially at the point they were at when the body disappeared. Whether or not those bodies leave the solar system depends on their orbiting velocity and direction. They may leave or settle into new orbits.
Now your planet is quite massive. Does the mass of your solar system include its sun? If so, then your gas giant is absurdly large. Our Jupiter is 1/1000th the mass of the Sun. Your Jupiter is enough to affect not just the other planets to a considerable margin, but the star itself. Your planets were likely experiencing highly irregular orbits caused by 2 massive bodies. Their orbits will likely stabilize if your star has enough mass. Whether this affects the ecology / seasons of your planets is up to you.
The solar system itself will experience a trajectory change as well. The sun was likely wobbling because the orbit of this massive planet. I would wager that the sun will change trajectory through space. The whole system will also lose momentum as it travels through space, but the magnitude of its velocity will remain constant..
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On top of Kingledion's answer, pointing out that effects would be visible on long term, there are few other consideration to be made.
1. Jupiter, together with Saturn, helps keeping the inner solar system safer, by "sweeping" asteroids and comets. With Jupiter gone, one could expect an increased rate of asteroids impact on the inner solar system.
2. Jupiter's gravity is the main reason for having the asteroids belt instead of a planet. The present time is probably too late for having, Jupiter gone, the formation of a new planet, but depending on the evolution phase during which Jupiter was MIA the outcome could have been different.
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# Consider how Neptune was found:
Small "[irregularities](https://en.wikipedia.org/wiki/Discovery_of_Neptune#Irregularities_in_Uranus.27s_orbit)" in the orbit of Uranus got people looking. Neptune is smaller than Jupiter and farther out, but the difficulty in proving Neptune's *existence* should be a sign how small the direct effects will be.
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I have asked multiple questions about [giant caterpillars](https://worldbuilding.stackexchange.com/questions/217348/feasibility-of-giant-caterpillar-archetypes), now it's time to account for their evolutions. Sure, giant flowers could and probably would exist in Alendyias; an [Engorger](https://worldbuilding.stackexchange.com/questions/196989/gaining-the-engorgement-enchantment-for-peasants) dying in a flowery meadow would likely create a whole patch of giant flowers right off the bat, a dying Bloat Blob could definitely make a giant flower (as explained [here](https://worldbuilding.stackexchange.com/questions/214204/uses-for-surplus-plops), and a dying [Wild Anklebiter](https://worldbuilding.stackexchange.com/questions/217510/determining-the-best-wild-anklebiter-predator) would definitely engorge a nearby flower, so it could happen.
However, given that giant caterpillars are either partially or entirely carnivorous, there is another possibility, one that seems a *little* easier to pull off than giant flowers. **Vampire butterflies!** Giant flowers aren't exactly common, and they'd be a big change to my setting, but giant creatures already exist in Alendyias, have since the beginning, and could easily serve as a food source for giant butterflies if they just feed off blood instead of nectar.
However, I must ask; **is it feasible?**
More specifically, **given that giant flowers can and will exist in Alendyias, would predatory giant butterflies develop anyway, or would they be predatory only in their larval stage?**
**Specifications for Best Answer:**
1. The best answer will account for the pros and cons of feeding on either **blood** or **nectar** for giant butterflies, and determine which one is more likely from an evolutionary standpoint. If they are equally likely, that's fine, just explain why.
2. The best answer should also account for the adaptations necessary for either taking nectar from giant flowers or drinking blood from large animals, like buffalo, to determine how difficult or easy, likely or unlikely, that path would be.
**EDIT:** These butterflies are giant because of magic, just like their larval stage.
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# Yes.
[](https://i.stack.imgur.com/ANqa4.jpg)
Meet the [siberian vampire moth](https://www.nationalgeographic.com/animals/article/vampire-moth-discovered-evolution-at-work). This little critter is believed to have evolved from moths which themselves would feed on the sweet contents of fruits, and like some other moth species, it's believed that this diet originated from the process of adaptation in order to feed on tears and other fluids from animals (also yes, there are moth species that pierce the skin of birds to feed on the salty contents of their lacrimal glands).
Essentially, apart from the necessary adaptations in the digestive track necessary to make the most out of a predominantly liquid diet, which many butterflies and moths already seem to do to an extent, all you need to achieve this is to make the tip of their long mouthparts, already adapted for drinking, into a more harpoon-like structure capable of piercing the skin.
So overall the presence of real life examples and a lifestyle already mostly adapted to a similar type of diet makes it pretty likely that your butterflies could feed on blood.
Now, let's talk about the problems associated with a hematophagus diet:
* Nutritional value. Surprisingly enough, blood is actually not all that good as a food source. Human blood for example is 78% water, and out of the actually nutritious parts you'll find it to be composed of about 94% proteins, 1% sugars (carbohydrates) and almost zero vitamins and minerals. Vampire bats have adapted to this diet by having very high diversity of gut bacteria which is shares a symbiotic relationship with, making the most of its blood meals. Something else noteworthy about vampire bats, despite not being arthropods is that their need to feed often still indicates the problems of this diet: a vampire bat will starve if it goes more than 3 days without a decent blood meal. Your giant butterflies, despite not necessarily having a metabolism as high as a similarly sized mammal's, will most likely Also need to feed often in order to survive long enough to find a mate and lay its eggs in a suitable place.
* prey. A very common trait among virtually all creatures which feed on blood is that they're smaller than whatever they're attacking. All blood-eating creatures are, in a way or another, parasites, and one key trait of all parasites is that a dead host is no good for them. The only potential counter example to this would be vampire spiders, which don't feed exclusively on blood but prefer to target female mosquitoes which have fed on human blood. Another advantage of being a parasite much smaller than what the thing whose blood you're sucking is that so long as you don't make a big fuss or cause pain, you might be able to go unnoticed, such as how vampire bats silently creep on the large mammals they feed on, as this ensures they only need to be strong enough to anchor themselves while feeding, rather than having to, say, pin down a mouse during the entire meal. Not only could that potentially kill the rat, it'd demand much more energy.
So in other words, according to what we normally see on earth, your vampire moths/butterflies would likely not act as predators per say, but rather as parasites of much larger creatures.
* Hydration and impurities. As I said before, blood is mostly composed of water, but it's also composed of things such as ammonia and urea, meaning that in addition to the already present methods of easily getting rid of the excess water many butterfly species have due to their natural diet, your butterflies should be able to handle and more specifically get rid of this extra amount of additional toxins. This should be the easiest thing to solve out of all of these topics, and chances are that they could manage this without a problem.
* diseases. Another thing vampire bats need to engage in their blood drinking activities is a strong immune system due to the risks of the blood they feed on carrying blood-borne pathogens that could make them sick and even kill them. Your butterflies too might benefit from a sturdy immune system to prevent itself from accidentally being infected by blood-borne pathogens in your world. Again though, the presence of vampire moths show that this isn't that major.
So essentially, it's very likely that your butterflies could have a blood-based diet without problems, because we have real life confirmation that it's possible. The big wrench in the gears here is that, overall, a mostly blood-based diet is incompatible with a predatory lifestyle, with most of if not all animals that feed exclusively on blood acting as parasites to larger, normally warm-blooded animals.
"but I want them to be predators and have a liquid diet, what do I do?"
Then you need to look at a different strategy: instead of simply adapting to feed on blood, your butterflies would need to adapt to a different type of liquid diet: one more like the [Japanese water bug's](https://www.nationalgeographic.com/animals/article/giant-water-bugs-ducklings-snakes-predators).
[](https://i.stack.imgur.com/XBC49.jpg)
Japanese water bugs are also creatures adapted for a more liquid diet, not because they simply drink the blood or tears from whatever they catch, but because they use their sturdy dagger-like mouthparts to stab their prey, injecting enzymes and anesthetics that break whatever they catch down into a nutritious liquid which they drink through the very same proboscis they used to inject said enzymes. These bugs also rely on powerful raptorial front legs (essentially front legs adapted for grabbing things, a good example is the praying mantis'forelegs) to pin down prey while they let the enzymes they injected do the rest. Their size and potent digestive chemicals allow them to prey on a variety of creatures, including snakes, fish, baby turtles and even ducklings.
In order for your butterflies to have such a diet, they'd need to undergo some changes. I do believe a moth-like body plan would be more suitable as their habit of keeping their wings more well tucked to their bodies would make it less likely that they'd be damaged. As for the other anatomical changes they'd require to be predators: not only would they need to change their long flexible mouthparts for sturdier shorter ones, more in line with what's seen on water bugs, assassin bugs and other insects that engage in such a predatory behavior, they'd need to adapt their legs into raptorial appendages suitable to pinning down prey. My personal guess is that their front legs would resemble those of an [ochteran mantis fly](http://www.realmonstrosities.com/2014/04/ochtheran-mantis-fly.html) in many ways (see below).
[](https://i.stack.imgur.com/J8RXt.jpg)
So summing up: can they feed on blood? Yes, but that'd make them parasites and would likely leave them dependent on the presence of large enough creatures for them to feed on. Could they be predators? Also not impossible, but rather than just blood they'd drink the liquefied remains of whatever they managed to catch, and would most certainly require changes to their mouth parts (particularly involving them becoming shorter and sturdier in addition to the adaptations related to piercing), the ability to produce and secrete special digestive enzymes, their legs to adapt into stronger raptorial limbs more in line with a predatory lifestyle centered around grabbing hold of and pinning prey down while the digestive enzymes to the magic and potentially their wings would need to be capable of folding more tightly against their bodies in order to minimize the risk of damage by the wild flailing of caught prey trying to escape.
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# They exist - as *small* creatures.
First, to be clear, your [vampire butterflies](https://www.discovermagazine.com/planet-earth/how-citizen-scientists-uncovered-the-strange-behavior-of-vampire-butterflies) and [vampire moths](https://entomologytoday.org/2015/10/30/vampire-moths-suck-the-blood-of-vertebrates-including-humans/) have already been done quite nicely. That said, you still have the infamous square-cube law to deal with - this isn't as absolute a barrier as some make it out to be, but you'll need to propose stronger faster muscles and wings and mechanisms to get the energy to them. The [mechanism of flight](http://main.cadit.com.sg/wp-content/uploads/2017/03/Api_015-1.pdf) is not so easy to comprehend, but changing these other parameters is likely to alter the important aerodynamic considerations, driving an overall redesign in wing shape and usage. But butterflies are also infamous for their easily abraded scales - the pretty wing patterns come off in curious fingers. If you have to turn up the air flow to helicopter speeds, you'll need a work-around. The wings, naturally, will have to be thicker (and heavier) to hold up so much weight. The proboscis will need an extensive redesign, because it will be pulling fluid over a distance that interferes with the normal role of [capillary action](https://cecas.clemson.edu/kornevlab/article/57.pdf). So ... by the time you finish reevolving your butterflies, they probably will no longer look or act in a way that seems very butterfly-like. Even an Earthly animal as closely related as the [hawkmoth](https://www.youtube.com/watch?v=_usXevoDNCs) no longer seems very much like most people's mental picture of a lepidopteran.
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"Giant Butterflies as *Predators*" doesn't fit well with "*Vampire* butterflies!"
* If you decide "as Predators", pray make them eat the entire prey, energetically it make sense. Why would one let food on the table if the food is already in a state it cannot put up an opposition?
Even more so that the blood contains just a small percentage of the nutrients in their prey - for example, the maximum concentration of glucose in human blood is [2g/litre](https://www.mayoclinic.org/diseases-conditions/diabetes/diagnosis-treatment/drc-20371451) (after a good meal), which makes the total sugar available in all the blood of a victim (estimated at 10%) to be `10%*0.2% = 0.02%`. The fat (as cholesterol) is in the same range.
Now, were I to be a predator, *I wouldn't even get out of bed in the morning to put a fight with the 100% of my prey for just a 0.04% of reward*. Not even if the prey would be served to me on a golden plate - my metabolical cost of just extracting all the blood and make the nutrients in it pass through my gut lining is higher. It just doesn't makes sense, it's a gross insult to my predator intelligence!!!
* If you decide to "Vampire butterflies!" - you'll push them into the parasites "courtyard". As a parasite, they (individually) have no interest to kill their host and, necessarily, will be smaller than their hosts. So, if your vampire butterflies are huge, their prey will need to be at least 2 orders of magnitude larger.
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The problem with butterflies of any size as predators is maneuvering. Butterflies (and lepidoptera in general) tend to flap their large wings gracefully and slowly as they flutter through the air. So how do they catch their prey?
There are, as the answer by @ProjectApex points out, moths that have evolved a carnivorous lifestyle. However, in doing so they've evolved much smaller wings that what we consider typical of butterflies (and the showier moths). So your carnivorous butterflies won't look like butterflies.
One possible approach is to model your creatures after the hummingbird moths: <https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/hummingbird_moth.shtml> While they also don't look much like the conventional idea of butterflies (they look and behave like hummingbirds - a great example of convergent evolution), it's fairly easy to imagine them evolving a carnivorous lifestyle. Instead of sucking nectar from flowers, they dart at animals, pierce their skin with their sharp proboscis, and feed, in the manner of a giant mosquito.
Another would be to have your giant lepidopterans be stealthy predators. Like the vampire bat, they sneak up on sleeping prey.
If you want giant (ignoring square-cube law problems and such) insect-like flying predators that are also fairly showy, why not consider dragonflies instead? They're fast & highly maneuverable winged predators.
Another problem with butterflies as predators is that some of them don't actually eat. They live off food stores gathered as catepillars. For instance, the Hercules moth, about as close as Earth gets to a giant butterfly: <https://en.wikipedia.org/wiki/Coscinocera_hercules>
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## Liquefying its prey for more efficient consumption.
*Time for another answer that doesn't fit the mould! Guess what we'll be doing today? Making a giant butterfly that melts the insides of its prey... hooray?*
**If you want your butterflies to have gigantism they need to get as much energy from their prey as possible.** Only feeding on blood is very limiting. Consider this: it takes between 600 and 650 kilocalories of energy for your body to replace the contents of a pint of blood. The capacity of your body to store muscle and liver glycogen, however, is limited to approximately 1,800 to 2,000 calories worth of energy, or enough fuel for 90 to 120 minutes of continuous, vigorous activity. All of this energy excluding your fat stores, that's a big meal indeed.
**You'd want to rupture every cell in the preys body to get all of the nutrients in liquid form, the only form a butterfly can consume. So I suggest external digestion similar to how spiders eat (or drink rather).**
1. Puncture prey with a sharp proboscis.
2. Inject it with digestive enzymes.
3. Wait for it to dissolve.
4. Enjoy the meal.
**The problem with this method is the melted prey leaking**, which would waste precious nutrients. Wrapping their prey in a cocoon is an option, IF they maintain this ability into adulthood (seems unlikely). **Wrapping the wings around the prey while eating seems like a cooler concept.** A flying Venus flytrap!
This wouldn't be straightforward to adapt (it's basically puke feeding), but neither are giant caterpillars. Your magic system can help with that.
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[Animated creatures generally have four fingers (including thumbs).](https://news.avclub.com/here-s-why-cartoon-characters-only-have-4-fingers-1798259730) In a real-world context what physical possible consequences would result in having only four (or 8) fingers?
Physiologically, what tasks (if any) would be rendered more difficult by having only three fingers and a thumb? Or is the human fifth finger merely unnecessary and make no significant difference?
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Speaking from a software guy's perspective.
If we (homo sapiens) had evolved without the pinky finger, some tasks would be more difficult, and some would become easier.
Any task that has to do with gripping would become slightly more difficult, as the pinky allows your hand to more fully encompass an object (5 areas of contact for gripping a baseball as an example). The loss of a pinky would have to be replaced with a broadening of the other fingers to increase grip surface, and perhaps even a slight offset of what is now the ring finger (similar to how the thumb is offset, though not so extreme).
On the plus side, evolution with 8 digits instead of 10 would likely introduce counting in base-8 (or [octal](https://en.wikipedia.org/wiki/Octal)) Which would make binary-based tasks (such as low level computing and digital information transfer/storage) much more intuitive, since 8 is a power of 2, and 10 is not.
The sudden loss of the pinky from our current state (as opposed to evolving without it) would be almost entirely detrimental though, as we evolved to utilize it.
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Answers:
* **Little fingers disappears** as evolutionary trait, it means that hand will be smaller, to optimize use of remaining fingers, or index, middle finger and anular will become broader to accomodate this change. But since, again, this would be the result of evolution, the species wouldn't even care, if not on a scientific curiosity. it's not as if we, ourselves, go try being quadruman with feet that no longer serve that function.
* **Anular and middle finger unite** so we have a hand with a larger finger than the other. And again, we'd have adapated to its use. Would it be clumsier or not? The inhabitants of this parallel world wouldn't know, since they wouldn't care about the 'before' of eons ago.
And mathematics wouldn't change radically. Arab didn't introduce the 0 to count to ten. And 0, like 1, in informatics, serve to define a state of an input, not as part of a countdown -speaking of which, yes, that would start with Eight.
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A disadvantage would be much simpler music.
Most musical instruments utilize all our fingers, to produce richer sounds. Our music would be much more simple with 20% less fingers.
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Like earlier answers I would agree that from an evolutionary standpoint, it wouldn't make too much of a difference to the individuals who never knew any different. Imagine if you had a sixth finger, just to flip your perspective. A four fingered hand would likely be slightly different in proportion though. The fingers would almost certainly be larger in order to compensate for the loss of gripping ability. That could take the form of either thicker fingers on an equivalent palm, or longer fingers on a smaller one. Possibly even a combination of the two.
This could have various affects depending on which direction you take, it's really up to you. Maybe longer fingers means you have increased dexterity. This could mean the species has an advantage when manipulating intricate objects, think a spider manipulating prey caught in its web (although 5 fingers also allows us certain advantages in manipulation). Or maybe thicker fingers means they have more muscle and are thus stronger. This could be handy (excuse the pun) if the species does quite a bit of climbing or needs the strength to crush hard food sources like coconuts or shellfish.
Either of those could evolve into any number of differences in technology for a more advanced race. Think of the things that we need tools to help us that wouldn't be necessary for beings with hands like that.
From a mental perspective there really shouldn't be any difference except for the also previously mentioned use of base 8 math. After all, we think in 10s because we have 10 fingers, if we had 8 it only makes sense that we would think in 8s. This could however lead to various technological differences because base 8 math is in many ways more efficient than base 10, and is after all a different type of math. Basic arithmetic should be pretty much the same, but any advanced math would change drastically. And that would even more drastically change the development of almost any advanced technology.
These are just a few of my own thoughts on the subject, but rereading your question I now realize that you were asking for disadvantages, not possible advantages. I suppose if the hand had no change in proportion, and differed only in number of digits, the hand would then have losses in the above alternatives. There would be a decrease in both dexterity and strength. The fifth finger (whichever finger you choose as the fifth) provides both increased points of contact for grip and manipulation, as well as the simple addition of more muscle. A person with 4 fingers on a hand would thus have weaker hands and be less agile when performing complex tasks.
[Answer]
Advantages for having 5 fingers:
* More redundancy just in case you lose a finger or two.
* The odd number of fingers allows the middle finger to act as an anchor/pivot so that your hand doesn't pronate or supinate inadvertantly.
Advantages for having 4 fingers:
* Simpler musculature.
* Probably finer dexterity since you fewer fingers to focus on.
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[Question]
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On the planet of the Aves, birds have evolved to dominate the Earth instead of mammals. Of the thousands of species in this world, both on the [ground](https://worldbuilding.stackexchange.com/questions/51622/planet-of-the-aves-quadrabirds) and in the [water](https://worldbuilding.stackexchange.com/questions/51661/planet-of-the-aves-aquabirds), the only one to develop sapience are a species of flying birds whose ancestors are the New Caledonian Crow.
As I design this species, I have wondered what I could expect their homes to look like, post sapience. After all humans went from basic grass nests to the universal walls and roof as its been coined (By me, just now) So obviously it stands to reason that Crows nests would also become more intricate.
What could I expect a sapient crows post sapience den to look like? What accommodations would a house made by birds for birds have to take into account? Could the Sapient Crow even get past the nest. The Un-human physiology of crows provides a number of constraints in the ways a house can be built and lived in, but does it also allow other new options?
A list of all Planet of the Aves questions can be found [here](https://worldbuilding.meta.stackexchange.com/questions/3939/planet-of-the-aves-series/3940#3940)
[Answer]
I simply love this question. Also, i'm quite hyped for the planet of the aves thing, amazing idea.
Enough fanboying, back to the question.
I think before we can think about how the individual nests would look like, we have to wrap our heads around everyhting else... especially the questions: where is our nest, and what is around it?
## **Why do creatures build homes**
You build a home primarily to protect yourself from the elements. Winds that chill you, rain that wets and chills you, snow and ice, searing sun and freezing winter winds. All of them can be endured or even enjoyed much better when you are inside. So, naturally, your home needs some kind of roof. It keeps away the rain and sun. Snow doesnt get into your sleeping areas. Walls do keep the wind out, and allow for something else: controlling the temperature.
The second reason why you build a home is security. Your home is hidden well or locked, so other predators can't get in to eat you while you sleep. If you do not have locks, you build your home in a way so it can be easily guarded by very few individuals, protecting a whole family or clan from predators. Less guards mean more people to go hunt or work the next morning.
And the last big reason is defensibility (is that even a word?). You can defend your home better against hostile persons. Or at least your settlement. If your species builds settlements...
Minor other reasons for building a home are about comfort and advanced problems of civilization. You have a place to store stuff, which is then safe and secure (protected by locks, guards, neighbours, family etc...). Without a home you can only own what you can carry, or hide your stuff and hope it's not found. Big tools can only be build if you have a home to build it in (anvils, forges etc...). And some tools things can only be build if you live in a community. also called a settlement.
A good home also allows you to settle in areas where you'd normally not be able to live (usually because you die from heat during the day or freeze during night).
So all in all, we have some requirements that a home needs, and some advances it allows. If your civilisation has mastered home-building a while ago, it will also have started to benefit from the "advances". These advances change how you build your homes, though, so let's imagine....
## **What the crows do in their homes**
I imagine that of course, their homes shelter them from the elements somehow. That also means that the way they build will differ from climate to climate. I will focus on a mild european-like climate here.
So the crows will live in their homes, i imagine in some kind of settlement where a whole murder lives. They use their settlements to live, breed, store food, treat wounded (especially warriors that have had their feathers clipped, glued or otherwise lost them in combat, since they cannot fly at the moment and are super vulnerable. Maybe they have guard duty?) and.. make tools. So some larger workshops or something will be around. A nursery, a place to store and look for eggs, some kind of hospital. Storage areas are a given. And then there is going to be personal "nests".
Another problem will be the water supply. You can't dig a well in a tree. And you can't carry up all the water all the way. So how to solve this? Where to create your settlement in the first place? Let's look at...
## **Where to settle the crows**
So before we think of how our settlement looks, let's think about where to build it. We need water, food, shelter, space and an optimum security. Problem: water can only be found on the ground. But on the ground is also where the crows are weakest, where strong predators can reach them, while they are asleep. Where their eggs are vulnerable.
I think protecting your offspring is the strongest urge. So they shall not build on the ground, but in the trees, on cliffsides or on high rocks. Maybe... maybe our prototypical, perfect setting would be on a huge tree near a very small waterfall. Far enough to avoid being sprayed and wet all the time, but let's say 20-30 meters away, so it is possible to build some kind of water ramp to our settlement? maybe other settlements don't have this luxury, they have to gather rain water, or carry the water back to their settlement, but let's assume our newfouned village has a waterfall nearby. And it's located on a huuuge tree. So predators can't get there.
Now, finally, we can imagine how the settlement might look like...
## **How our settlement might look like**
I imagine a flying species to require a LOT of space in their settlement. A crow is relatively small. But expanding their wings takes a lot of space. Flying inside the settlement also does. So either you loosely flock a lot of small nests (like bird nests) together in one tree, and lose defensive advantages and easier guardability (is THAT a word?), or you build freakin huge habitats. But i think that is what the crows will go for. They take one big branch as a basic (taking into consideration the health of the tree, and therefore guarding and caring for the tree, too!), and construct a wooden platform on it. Maybe it's just loose branches and grass webbed together, but they make a giant nest in a way that it's hard to access it from below. Making if more difficult for predators to climb in. maybe the edges are littered with sharp sticks.
Then, the crows construct a dome. made of the big, big leaves of the tree. They bend in branches, and tie or sew the leaves togehter, so their giant nest is protected by a dome. It might not be 100% water proof, and i think there will be a gap between the nest and the dome, but it helps. It will give shadow, protect against light rain and wind, hide the settlement from aerial predators and limits the accessability of the settlement (easier guarding). I imagine the individual nests to be hanging below the dome, so the "ground" is free.
The settlement might have a central hatchery, where all the eggs are kept safe, and that is most difficult to get to (the heart of the settlement). This might even be built from hardened clay (since it rests on the branch, and is not hanging freely), to provide a nice, even temperature inside, and protect from parasites and small ovivores. Also, the settlement will have some water storage or (in our case) a long channel made of bamboo or bone, that delivers a constant stream of fresh water. If you had a water storage, the central dome might be build in a way that leads fresh rain water right and dew into the water storage.
Food must be stored too, and again i am thinking of small clay pots hidden around the hatchery, that keep a constant temperature inside and are used to preserve food. Maybe our settlement keeps some clay pots at the bottom of the waterfall, which uses the cool water to preserve food during summer.
And finally...
## **How the individual homes might look like**
Usually, a birds nest is barely big enough for 1-2 birds to sit in. this does not fulfil the requirements of a civilized avian. You need better shelter, storage space etc. A birds nest can easly manage to fulfil shelter and security. Make it a spherical nest with leather roof. There you go. Waterproof. Windproof. Warm. Only one entrance. Up in the tree. But how do you keep personal belongings there? How to express individuality, arts, where to think about inventions?
I think crows might be more murder-oriented than us humans. So maybe they are really just using their individual nests for basic needs, but find fulfillment in the murder? So, i think the nests will be considerably bigger than our real-world ones. Maybe... they really hang them from branches. Since they can hunt, they can work with leather. And strings. And birds ARE good at weaving. (look at their real life nests). So i imagine a crows nest to be a small platform of woven sticks and branches, maybe even worked wood, that was hung up in the trees with strings or sinews. The "walls" are made of woven sticks, covered with a layer of leather. Personal belongings can be hung from the ceiling, and maybe some nests are big enough to contain two or more "levels". Nests might also be hung up next to each other and have connections to each other, especially good if you fall in love and you just "move" your lovers home next to yours and connect them.
Additional storage space might be made by hanging stuff *under* your nest. Maybe the less valuable stuff, so your neighmours don't get envious.
Activities that require a lot of space like sparring, training, arts, crafting etc.. will be conducted on the basic platform, where the murder also stores the common tools.
At least that would be my vision of this :)
[Answer]
Growing the structure of a house out of a live tree is an awesome idea.
But prepare yourself for meat houses...
<https://www.ted.com/talks/mitchell_joachim_don_t_build_your_home_grow_it?language=en>
Alternatively birds already have several very interesting types of structures that they have developed without high intelligence.
<http://mentalfloss.com/article/55936/10-weird-and-wonderful-bird-nests>
See the article for full explanation
**#1 Grass colony**
[](https://i.stack.imgur.com/DbsYe.jpg)
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**#5 Made from saliva**
[](https://i.stack.imgur.com/zieqI.jpg)
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**#6 Adobe**
[](https://i.stack.imgur.com/0T6iO.jpg)
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**#7 Hammock-like**
[](https://i.stack.imgur.com/xfACk.jpg)
The most interesting of which is the one made of the bird's own saliva, which humans collect and eat, as a delicacy.
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### Edit
With respect to the saliva nest, from the comments below this answer:
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> Some really nice options here, and the Ewoks reference I think is particularly inspired. A natural progression of nests in trees! – Shaun K
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> Indeed, however, the saliva nest bugged me from the moment I recalled having seen it elsewhere and decided to include it here. One can easily see this as a non-sentient, pre-industrial form of 3D printing - from the bird's own mouth. How satisfying it would be to bring an ancient craft/ritual such as this into a modernized Avian culture where the very principle, physics and chemistry were founded on tradition itself. It would perhaps be one of the guilds to Aves evocative of ancestral memory as are cooking with fire, blacksmithing, weaving, pottery, etcetera to humans. – Nolo
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Obviously, however, those structures need a boost into more modern technology and design. The [Ewok village](http://starwars.wikia.com/wiki/Bright_Tree_village) is an interesting example which merges high technology with pre-industrial structures, in a post-modern, presumably sustainable ethos. Compare #1 at the above link to the Ewok village.
[](https://i.stack.imgur.com/6Wkt6.jpg)
Colonies of mud thatch structures like #6 could similarly be juxtaposed with cliff villages like the [Mesa Verde](https://en.wikipedia.org/wiki/Mesa_Verde_National_Park) cliff dwelling for example.
[](https://i.stack.imgur.com/CquyS.jpg)
[Answer]
Nolo's image of cliff structures is nice way to go. A good example are the Xindi Avian race from Star Trek Enterprise.
[](https://i.stack.imgur.com/36g67.jpg)
You'll notice the wide open windows between columns and the open entrance (where the shuttle is entering). Cliffs like this offer good protection, are weather resistant, and provide good take-off and landing platforms. Looking at the other questions for your planet of the Aves this fits in nicely with the weapon and armour designs you were maybe envisioning. It would be easy to launch gliders off of platforms like this.
Designs offering such open plans and a good view of the sky kind of make sense to me when considering what birds might like. The cliffs make sense when considering how the habit evolution may have expanded from living in overhangs on cliff faces. Humans have evolved housing that closely resembles the caves of our early years. So I'm thinking in terms of cave-birds, if that makes sense.
I imagine Star Trek creators modelled this design on birds that tend to form larger flocks (I don't believe New Caledonian Crow's do this but I could be wrong) but I can't see why your species of crow wouldn't.
You can read more about the Xindi Avians [here](http://memory-alpha.wikia.com/wiki/Xindi-Avian).
[Answer]
Fun question...!
I'd like to think that sapient crows would develop some pretty advanced topiary skills. So, you could end up with a tree with a large flat area sprinkled around with raised perches for resting or hopping from one side to the other.
You'd have a domed roof to keep out the elements, and perhaps a curving entrance way (wide enough to fly down, but curved enough to baffle incoming wind/rain). The roof could be covered in the tree's foliage, or larger leaves could be harvested and placed on top as part of on-going maintenance.
For the young ones to be brought up, you'd need a separate room or maybe even a totally separate nesting complex.
In the living quarters, you'd need nice cosy roosting pods, somewhere to stockpile food, and an altar for collected trinkets.
I did think that you could have a normal "spherical" shaped tree, but with various platforms and such within the main canopy, but this seems fairly simplistic. Crows are pretty intelligent creatures, so let them build, I say...
[Answer]
Shelters do 3 things. They protect from the elements, from dangerous animals, and from other intelligent beings.
Settlements need a way to get resources for each person in (water and food). Nomad settlements (herding or hunting) would follow their food around (or guide it), and stop at places that provide resources for both their food and for themselves (that they don't get from their food).
Early human sedentary settlements where at or near fishing grounds. These permitted more capital investment in the settlement. You'd take your boats out to fish for resources, and bring the harvest back to the settlement. As you are an outside context problem for your prey, you could generate huge amounts of resources in a short travel distance and bring them back.
The capital investments this made possible include sturdier shelter, food storage technology like fired clay jars, fortified food processing locations for dried fish, and static defensive walls. Specialization becomes possible, with some people fishing and others producing goods for the fishers (cloth, boats, non-fish food, security, food processing, etc).
Farming of grains permitted this kind of high density settlement away from fishing grounds. Grains can be stored longer, and central storage led to central control. Cities with extreme amounts of specialists (ranging from tax men to weavers) result.
Humans move slowly, and it takes lots of energy to move. So settlements have to be located near clean, fresh water, food must be preserved and delivered.
Birds can, as far as I can tell, move longer distances with less energy, assuming proper wind currents. So a bird settlement is going to want to engineer favorable winds for ease of transport.
How those birds manage the effort:energy ratio of food is going to be key to the location and shape of their settlement, as is how they manage water.
At early iteration, survial against nature is important. In poor weather or bad seasons, having access to water is needed for long-term survival of a settlement. Protecting water access from preditation is important. Reducing the work required to get said water is key.
Carrying food to the storage location has to be low energy. Getting to the food source has to be easy. Birds are not good at carrying heavy things; they are light for a reason. So a low-tech civilization without efficient heavy-load beasts of burden is going to be hard.
Climbing without wings should be tricky for birds, more so than humans. But a concentric wall (no doors) with shelters inside could be viable.
Hostile animals should quickly no longer matter to a civilized race. They'll either wipe out or otherwise deal with dangerous animals near their settlements.
Weather and climate remains dangerous, as do other members of their civilized race. Use of hostile animals as weapons of war remains a concern (like humans used horses as weapons of war), but ground-based defences may matter less to such a race.
A tree or cliff-based civilization runs into the problem that getting building materials *up* is very hard. But once you have done it, the high launch spot is useful. Getting water remains hard: capturing godwater won't reasonably be enough over the area of a settlement. A waterfall off a cliff (either preexisting or engineered) could be used, if vulnerable to hostile action, but that doesn't help the tree dwellers.
Poop falls down, so being directly above your water source isn't safe. Being further from the water is worse than being near it. Being on top of it suddenly makes things horrible.
Trees, while useful, also get in the way. They don't permit ground-based cargo transport, and as noted above you'll need to use beasts of burden on the ground to move around the mass of materials a larger city needs to function.
Replacing trees with stacked houses might be inevidible. Building up is hard; both engineering wise and because it takes energy to lift materials up. On the other hand, the lack of requiement for non-service stairs, and the lower energy budget to go up and down, might make vertical housing more popular. Poop flows down, so lower households will be the worst ones, with the poor living on the ground floor. Some would live on the ground floor, simply because there is space there, and people expand everywhere.
Being above the poor poses a security risk, as it implies some kinds of mingling. In addition, fire and rot risks your building. So I'd expect these towers to have a social gradient, but not a ridiculous one. The richer birds would have their servants at or near the ground floor, or even their service animals down there with the servants living above it.
The box-shaped home we build has nothing to do with how we lived prior to intelligence, and is all to do with the packing problem and simplicity of engineering.
So I'd imagine highly vertically stacked homes with artificial thermals arranged nearby. Each household would have a social gradient within it, with the poorest living at the bottom. Roads would matter less; thermal generators would be as important or more so; roads would merely exist for beasts of burden, ground-based animals that pull cargo around.
[Answer]
How I imagine intelegent bird houses is long poles in the sky with nests on them (like you see bird nests on streetlights)
Maybe even some seagull species that lives in/on floating nests in the ocean!
They might have some problems building advanced buildings since they do not have thumbs though...
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[Question]
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## Some Background
The government is very good at catching people. Even the few who can keep away from them are forced into a life of running. Many years ago, a teleporter named [Dave](https://worldbuilding.stackexchange.com/questions/40907/how-can-we-catch-a-teleporter) was discovered and [successfully captured](https://worldbuilding.stackexchange.com/questions/40922/how-can-we-imprison-a-teleporter) but there is a new enhanced person with an even more difficult to detect ability: shapesphifting. A young woman named Eden, born in Jerusalem and currently living in China, has been discovered to have the ability to change her form into any object; alive or inanimate. This could be the most significant human discovery of all time. Shapeshifting would have major effects on the way human live their everyday life; the technology would be worth billions. Unlike with Dave we realize we must have a plan of action. They have again requested the help of Earth's greatest minds to come up with a solution.
## A Few Details about Eden
* Unlike Dave, Eden is not a criminal; she doesn't have street smart skills and is only being hunted down for her abilities.
* Eden is not against killing, but will choose flight first.
* Eden is able to transform into any solid object: a person, a table, a building—anything goes.
* The only thing that gives her away is that while inanimate she still breathes and while animate her eyes are a bright yellow; other than this, she appears to be what she is.
## The Rules
1. The governments have become desperate and are willing to spend whatever it takes to bring Eden into custody.
2. They do not want to kill Eden, they just want to bring her into custody.
3. The solution cannot result in any casualties.
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Using the above information how can the Chinese Government catch Eden?
[Answer]
I think there are two big points here that lead to a rather simple solution:
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> Unlike Dave, Eden is not a criminal; she ... is only being hunted down for her abilities.
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> They do not want to kill Eden, they just want to bring her into custody.
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The easiest way to get Eden is to get her to come willingly. You mentioned that the governments are willing to spend quite a bit to find her. Rather than spending a lot of money trying to forcibly capture her, simply offer some of it to her directly!
For example, if your budget is one billion dollars, then offer her a million dollars a year (with some guaranteed minimum in case you quickly don't need her, such as if studying a blood sample is good enough) *and a significant degree of freedom*. You could put it in terms of hiring her to be a research subject, and work out the terms with her. She might like doing two hours of research each day, or she might like a full day once a week. She should also be allowed to take vacations, perhaps by doing a week of full-day research to fill her research quota in advance.
Just to make it clear, giving her a lot of freedom is really important to making sure she'll come and that she'll willingly stay. In particular, I'd suggest that she be given easy access to the researchers who will be working with her. Allow her to ask them questions about what they're doing, what they're trying to accomplish, etc. If she's interested, let her help, especially if she has a particular direction that she wants to take the research - if she's *doing* research instead of having research *done* on her, she'll be much more enthusiastic and cooperative.
If this works you get the added bonus of being able to use her as the poster child for cooperating with the government - the next time someone with an unusual ability shows up, they're much more likely to come in on their own! Or, if it's not possible to make it public knowledge, she'd be an excellent negotiator to send in to talk to them.
Give her the VIP treatment, and it's likely that she'll come willingly. If she's still not willing, then you can resort to other ways of bringing her in.
[Answer]
I'm pretty sure the only option is to take her family into custody and tell her they won't be released until she gives herself up, it goes without saying they'll be tortured.
You've said she can turn into anything, there's no situation in which it's not possible to turn herself into something that'll get her out of it. Even if that something is a super-critical mass of weapons grade uranium.
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> As the police dogs run into the city square where Eden was last reported, all the pigeons fly away, Eden among them, perhaps, or is she one of the dogs, actually she's a grain of sand down between the stones.
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So it's a breathing grain of sand, you're never going to find it.
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> Then she was spotted near the financial district, how were you to know that the new tower at the end of the row that's been under construction for months hadn't actually been finished yet.
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Ah well, maybe next time
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> Loading the dogs back into the van at the end of the day you realise that you have one too many and finally she's on the run. The helicopters are up stopping her taking to the air. She's tired, scared, she turns down a blind alley, cornered at last and changes...into a copy of Ayres Rock. A living, breathing, mountain.
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You've caught her, technically, but now what?
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> You turn your back for a moment and there's a spec of dust blowing in the wind, the last you ever see of her.
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The psychological approach is the only way, you'll have to get her through friends and family, the direct approach is a dead loss.
[Answer]
Eden is going to be a handful and you are going to need tools specifically designed to capture this unique person.
Lucky for you *some* of the tools already exist
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So lets start with what gives her away.
1. **The eyes**, when morphed into a creature with ocular parts they will be unnaturally yellow.
2. **She has to respire** in any form...I don't even want to know what it looks like when an end table respires...anyway...
3. You don't mention this but I would suggest that unless your system dictates otherwise this would be the biggest...**Heat.** Unless your shape shifting dictates otherwise, when shifted into any object she is going to give off heat as the energy in her cells doesn't magically disappear.
The major challenge is that she can appear to be anyone or anything...in the end its not that she is hard to catch, its that she is hard to find.
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So, we know what gives her away, now we need to know how to use that to catch her.
1. The eyes. Not the most helpful giveaway necessarily for example she could turn into a cat...well...great but cat's can close their eyes.
This would be one part of tracking her if not necessarily catching her. Video networks and search algorithms would have to be set up to spot this trait.
2. Breathing...If you have a narrowed down location to search this becomes helpful, lock down the building and search via thermal for the exhaust.
3. Heat. Similar to breathing you are going to want thermal imaging equipment on the teams trying to track her down. *Heyyyyyy....that bowling ball is the temperature of a human!"*
In the case of 2/3 the thermal imaging stuff already exists. For number 1 you are going to have to create your standard fantasy "big brother" scenario where the authorities can utilize all cameras everywhere to track people down.
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Extra stuff. Having a DNA sample would be helpful but probably difficult to get. Dogs could potentially be useful if her scent remains when she is shifted (which would make sense).
**In the end a shape shifter is a whole lot easier to catch than a teleporter...**
[Answer]
I'm afraid there's absolutely no way to find her.
She could hide in any village that doesn't have TVs and newspapers and become a changeling. The news only reach those places in form of rumors, and those are highly inaccurate and unreliable. She could try rural China, or rural Siberia, or maybe reservations or Amish communities.
Or, if she prefers to stay in touch with the civilization, she can just pretend to be blind and transform into eyeless version of herself when someone takes her glasses off.
[Answer]
Gas her. Since she has to breathe she can easily be gassed once located in an area. Of course if she can shift into complex mechanical or biological shapes she may be able to defeat the gas, but presumably it will work the first time at least. Does she return to her normal form if rendered unconscious or distressed?
Sonic weapons at low frequencies can also severely incapacitate folks, which she may or may not be able to resist.
The cruel method is to find someone or something important to her and take it hostage in order to force her to turn herself in, or at least come investigate. Assuming she isn't also super-strong/damage resistant like a T-1000 she could be apprehended during a rescue op.
But if she can turn into a BUILDING then she can presumably turn into a tank as well, or a microbe, so her powers may necessitate a tactical strike from orbit, "just to be sure" as she would be impossible to contain.
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[Question]
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Imagine a tidally locked gas giant moon, which is otherwise earth-like. One side of the moon will have a huge planet constantly hovering in the sky (24 hour day/night cycle with a Jupiter-sized primary works out to about 30° angular diameter)
Questions:
1. Will the "Jupiter" be always fully visible during daytime? Will there be phases?
2. How bright will it be during nighttime? Will there even be a proper dark night outside of solar eclipses?
3. Does it depend on the exact location of the observer on the planet-facing side? (I.e. is it significantly brighter when the gas giant is directly overhead compared to low above horizon?)
[Answer]
I decide to simulate the situation in question. After trying Celestia and Kerbal Space Program with mixed results I stumbled upon [Space Engine](http://en.spaceengine.org) which turned to be an awesome tool for this. Below are pictures from a roughly earth-like moon in orbit around a gas giant (which I'll call Jupp)
**Morning. Jupp is faintly visible**
**A crescent appears as the visible side of Jupp becomes lit by the Sun.**
**During the day, Jupp waxes**
**Late evening. Jupp is almost full which signifies the forthcoming night.**
**Early night. The full Jupp provides significant amount of illumination. I'd guess reading by jupplight is possible.**
**As night progresses, Jupp wanes and it becomes significantly darker.**
**The darkest hour is just before the dawn - literally!**
**The Sun rises...**
**...only to hide behind Jupp in a spectacular eclipse! This occurs every day and provides a couple hours of true darkness.**
**The Sun reappears and the cycle begins anew.**
[Answer]
What's daylight/nighttime? Some large fraction of the time, the moon will be on the dark side of the planet. Most of the rest of the time, one side will face towards the planet but away from the sun. There will be a relatively brief period where the planet and the sun are both in the sky. Absent cloud cover, the planet will almost certainly be visible even in sunlight.
There will be phases, as the time when both the planet and sun are visible is when the moon is to the side of the planet. Note that the phases will change based on where on the moon someone is. Looking from the point of the moon that is closest to the planet, the planet will never be full while the sun is in the sky. It will be about half full. From a point where the moon is farthest from the planet, the planet will never be visible and the sun will produce a relatively normal day/night cycle. From a point mid-way between, the planet will be visible low on the horizon and have full phases. There will be a normal day/night cycle from the sun (albeit with short days, as part of the day will be blocked by the planet).
At that distance, the sun will be less bright than it is on the Earth. Note that when the moon is on the far side of the planet, that side of the planet doesn't get light from the sun. So there wouldn't be light coming from the planet to the moon. So the moon will have a real nighttime then. Neither the sun nor the planet will be visible.
This is screaming out for a good image. Hopefully someone will produce one or more.
[Answer]
You've asked a few questions here.
As for the brightness of Jupiter, Jupiter has an albedo of around 0.5, compared to 0.12 for the moon. This means that Jupiter will reflect roughly 4x the light that the moon does. However, Jupiter is significantly larger than the moon. You've indicated a 30 degree angular diameter for your Jupiter, this being 60x the diameter of the moon, will result in 3600x the angular area of the moon. Combined this means the Jupiter will shine roughly 14,400 times as brightly as the moon. Given that the moon shines at 0.05 - 0.3 lux, a "full" jupiter will shine with 720-4320 lux. When half of Jupiter is illuminated, it will shine with half this lux. When a quarter is illuminated, it will shine with a quarter this lux etc... This is very bright.
You've asked how bright Jupiter will be during the night. The brightness of the Jupiter will be the same everywhere on the planet at once, but the time of day everywhere on the planet will be different. Because the Earth is now tidally locked to Jupiter, there will be a certain region where Jupiter is constantly straight up at all times (in reality, the Jupiter will wobble a little bit depending on how circular and angled the Earth is orbiting, but it won't be much). This point will have a fully illuminated Jupiter during its midnight, and a halfway illuminated jupiter at dawn/dusk. The darkest it will ever get in this region will be when the Sun is being eclipsed, which will be often.
Depending on where Jupiter appears to be in the sky, Jupiter's phase will be offset from the day/night cycle by some constant amount depending on the longitude. The lower Jupiter appears in the sky, the less sunlight will be present during Jupiter's "dark" phase, giving a true "night". Also worth noting, will be that half of the Earth will never see this Jupiter, and thus never be illuminated. This part of the Earth will be akin to the Dark Side of the moon.
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To give a bit of background and ground the question in context:
I'm concerned with the technology level from prehistory to Renaissance, or thereabouts. Analogous to Earth history, the 'normal' land-based species have already developed fully-rigged, square-masted ships.
However I also have an amphibious species that thrives equally well on land and in water (sea). They are based on a large archipelago with a lot of natural defences (straits, shallows, reefs, etc.). Their native islands are rich in natural resources in terms of ore, wood, and whatever else would provide the materials for conventional sea-faring tall ships.
My question, therefore, is what kind of ship designs would such an amphibian species develop? For my part, I've considered the following:
* Primarily only serves as a means to carry more cargo, as the species doesn't need shelter / protection from the sea
* Probably has some kind of 'anchor' points for the sailors that operate it to stay attached to it, so when they're sleeping in/under the water they don't drift away from the ship
I've also considered the wild thought of some kind of submarine thing instead of a 'ship' per se, since drowning wouldn't be a concern (although goods would still get damaged). I'm not sure what kind of propulsion system this would employ, however.
If it impacts the answers at all, there is limited magic in the setting, but it's quite expensive (think blood, sacrifice, etc.) and tends more towards adjusting already extant possibilities in the world rather than 'conjuring' completely supernatural effects or events.
I'm also happy to clarify further or add info if this isn't enough.
Thanks in advance for any help, this one really has me stumped, as I'm not at all inclined towards engineering or anything like that.
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Your ship will most likely resemble an ordinary ship of the period.
The drag of the ship limits its sailing speed, and to minimize it, you generally want to minimize surface area. Sleeping quarters, anchor points, underwater openings and such all provide excess surface area, slowing down the ship.
A simple, smooth hull will be faster, and drag also influences how high a sailing ship can point to windwards, with enough drag a ship will soon be unable at all to get to windwards. Square riggers with their poor performance going to windwards are especially susceptible to excess drag.
The second reason is that being in the wake of a ship is dangerous, and highly uncomfortable given that you are effectively in a current. The wake may toss you about, smashing you against the hull, and even if you avoid that, items will be washed away, and you will be constantly pushed aft, while an amphibious species may be able to swim fast enough to keep up, it will be a constant strain.
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**Like our initial transport techniques on land, perhaps they would use similar ones in water.**
Perhaps think of the culture they would have, and the technological developments needed to lead up to their current status.
For instance, I would image being amphibious, just like we are on land but they are underwater, that they would master domestication of animals first prior to any creation of machinery in much the same way we used horses to easily transport us around land prior to advanced ships.
This means perhaps that they would have trained fish / whales / dolphins to do their bidding since if they could 'breathe' underwater for extended periods this would be the easiest.
The examples where then more mechanical ships would be need are where there are deficiencies in using tamed animals as transport, namely:
* Limited cargo capacity, and perhaps too slow for them
* Limited conflict / warfare use
So the creation of machines for these purposes make sense (same as development of our land vehicles). The wind could be used, but I would imagine it would combine with flexible hull materials combined with a flexible mast structure that could be erected or stowed on long voyages, propelled in other instances perhaps using available animals.
As time progresses, if animals were dispensed with completely, then sail ship with hulls full of water seem logical, prior to the invention of steam engines (if this is on the cards at all). For machinery, this would require all the developments we had on land, but in the water (difficult to say the least).
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**Submersible ships.**
Topside these are hulled ships with masts, copied from landgoer tech. These boats can also be propelled via stern sculling.
[](https://i.stack.imgur.com/98qpL.jpg)
<http://www.douglasbrooksboatbuilding.com/ro.html>
<https://en.wikipedia.org/wiki/Stern_sculling>
>
> Stern sculling is the process of propelling a watercraft by moving a
> single, stern-mounted oar from side to side while changing the angle
> of the blade so as to generate forward thrust on both strokes. The
> technique is very old and its origin uncertain, though it is thought
> to have developed independently in different locations and times. It
> is known to have been used in ancient China,[4] and on the Great Lakes
> of North America by pre-Columbian Americans.
>
>
>
Topside sail driven propulsion is the fastest because of lack of water resistance. Topside sculling with the crew working several oars is second fastest.
If there is bad weather or the crew wants to hide they move the boat to depth. The hull cover can be pulled shut and the boat looks somewhat like an almond with smooth upper as well as lower surface. The boat is flooded and submerged. The amount of water allowed into the boat can be adjusted; generally the crew want to boat to be neutrally buoyant at a given depth. When empty the boat carries ballast rocks to adjust buoyancy. The almond shaped boat is hydrodynamic and the sculling oars work just as well submerged. The boat can move along at depth powered by the oars. For use at depth there is a horizontal rudder as well as the vertical rudder\*.
\*although I do not see a rudder on the Japanese scull-oar powered ship. I wonder if these use a different method of steering...
As regards how the crew sleeps I imagine an amphibious species has sorted that out long before they were building boats. Maybe they sleep one half of the brain at a time like cetaceans. That would have interesting ramifications - for example could they still row when half asleep?
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In addition to the other answers, these amphibious creatures would probably build fully submersible swimming enhancers that allow them to swim faster, or drag large cargo.
Simple swimming enhancers would just be hydrodynamic shields that they push in front of them. The hydrodynamic shape of the swimming enhancer reduces drag and allows the creature to swim faster or more easily. More complex swimming enhancers might involve propellers/screws/paddle-wheels/flippers.
Underwater carts would be large hydrodynamic shields that you place in front of large awkwardly shaped cargo to reduce it's drag. You might also hitch an underwater cart to a trained whale or something.
This prototype bicycle submarine (swimming enhancer) allows a human to self propel at 9.2mph underwater. Most humans can swim at about 2mph on the surface and slower, maybe 1-1.5mph underwater. The bicycle submarine increases a humans' top speed by about 4 times <https://road.cc/content/news/15591-pedal-powered-submarine-takes-air>
You might criticise this idea by pointing out that they are amphibious, they're evolved to travel underwater. However the ability to move on land requires compromises for swimming, such as having legs. This means that any amphibious creature is much slower underwater than a fully underwater creature. The hydrodynamic swimming enhancers would reduce the drag caused by having legs, arms and necks.
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The basic construction principles of ships would not change, because the problem the ship is supposed to solve (transporting things from A to B via waterway) does not change.
An amphibious species would indeed have less problems building submarines because they don't need to solve the problem of keeping the crew dry and supplied with breathable air. But submarines are for niche applications. You only need them for stealth or if you want to go someplace that's under water. They are inferior to surface ships when it comes to transport. They require more energy to maintain the same speed (because water has more resistance than air) and they can't use wind energy. So if you want to transport cargo or people in the most efficient manner, you would use a surface ship.
The only difference is that an amphibious species might not be that concerned about drowning, which means safety is less of a concern. A ship built by an amphibious species might have a less secure railing and have less life-saving equipment on board (like lifeboats). But that depends mostly on how their survival chances are if actually lost in the open ocean.
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If it's compatible with the rest of your vision for the amphibian's culture/history you could have them rely on a network of suspiciously convenient and reliable underwater currents, which they can ride with no assistance like an escalator, or use a underwater sail to move more efficiently. This would imply that at some point in the past they did a whole lot of ritual sacrifice to build this network.
Aside from that, it might make sense to have them utilize sailboats that are more advanced than the land-based cultures. The idea being that since seafaring is easier/safer for them by default (not needing a fresh water supply, being able to forage more effectively, etc), they likely started developing ships much earlier. They also could build ships which are less sturdy (hence, lighter, faster, can be build larger with less material, etc) since they can more easily make repairs at sea, and minor leaks and such wouldn't bother them as much.
You could also explore some interesting ideas for domesticated/tamed animals. E.g. cargo barges dragged by whales / large fish. Notably this could also have started much earlier into their cultural development than it's land-based equivalent would have, since they didn't need to invent the wheel or axel first, a bunch of logs lashed together with kelp tied to a tamed whale that filter-feeds as it pulls could give you a really efficient cargo transport with very early technology.
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I really like the point about enhancing the mobility of swimmers with mentioned by @UEFI above, I think that the salt/fresh water issue mentioned above aside, that vessels would be more adapted to having free flooded areas. A vessel would have three main characteristics.
Be able to carry stuff - this could include stuff from land that would be damaged by water, cargo like grains for example. Keeping stuff dry would be a problem. Corrosion of metals would be a problem too... as would barnacles and sea-growth on surfaces.
Be able to move efficiently - getting part of the hull out of the water would reduce drag, being able to use wind would allow faster transport. Being able to control buoyancy would allow a submersible like vehicle to be pulled underwater more easily, but could also have the disadvantage of being pushed by currents very easily. So some choices there about how to keep you craft in position and not have it drift and move with the tide or currents.
Transition from one environment to another - Being able to transition from sea to land. This is more difficult to do efficiently, but there is a lot of room to play with different concepts. Is a wheel an obvious invention for an amphibious species? But there is another constraint which is the depth, and pressure of operation that your craft would be able to operate, both for the amphibians and for the vessel itself. Free flooding reduces the differential pressure, but as soon as you want to have dry chamber, or buoyancy control understanding how pressure would impact the design would be important. In addition to pressure, it gets dark pretty quickly as you dive quicker underwater.
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In the event that both planets of a binary planet system were life supporting, and both ended up developing a sapient, tool using species, at what technological level would they be able to start effectively talking to each other?
Now when I say "effectively communicate" I mean at what point would it be reasonable for meaningful massages to be send to the other world(the ability or the other to respond would be nice, but not needed immediately)? would this be possible prior to both species having developing Radio communications to send and receive with?
Obviously the technological levels of each species would vary due to countless reasons, and one will notice that there is a civilization on the world in the sky before they other(though cultural, religious, and other preconceptions/biases would cloud how they interpret this fact until they have really good observation technology to more closely/accurately look at their neighbors), but beyond doing things that are basically "hey! We exist! look at this giant structure we made to get your attention!" and "we know! here's visually identical one we build to acknowledge it!" which could be easily motivated by and misinterpreted through those previously mentioned biases and preconceptions of the universe, not to mention if it happened before a species had fully explored its own world(or at least the tidally locked side facing the other) then this could lead to an interplanetary game of telephone as civs build structures inspired by alien structures that were inspired by structures from another part of their own world(but that's going into the psychology and cultures of two alien races growing up next to each other, and how it effects each other over the course of their histories, which is a bit beyond what I'm asking here)
EDIT: Since someone asked for details on the worlds themselves here they are; the binary worlds are of course tidally locked to each other at a distance where they'd have an Earth-moon like view of each other, they are of similar "temperate" climates and changing seasons due to their similar position relative to their sun, though obviously the weather would be different due to the atmosphere and landscape of each world having differences(higher or shorter mountains, shallower or deeper oceans, how much surface area those oceans cover, different ratios of nitrogen, oxygen, carbon dioxide, and other gasses, and so on).
And to go into more detail on the species as well, since I have a vague idea of what I'd want them to be like, though I'm not sure if that's that relevant to the question of what tech they'd need to start properly talking to each other; the one living on the world with more oceans is a partially amphibious species, and the other is a "reptilian" species that endures the winters with a form of hibernation that induces a lucid dreaming like state of mind.
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Well, you're on the right track by first considering that their technological and sociological evolution wouldn't parallel our own world's history (even if they somehow were both human races on earth-like planets) nor each other's.
Something to take into account is how close the binary planets are to one another. Are we talking a Rocheworld, where they're so close they even distort each other's shape due to gravity, and even share a tiny bit of connecting atmosphere, or are we talking more along the lines of Earth/moon distance? If the former, it's actually going to be pretty difficult for both planets to support much life, or either to support intelligence due to the numerous destructive forces a Rocheworld would experience.
If the latter, it depends on how you define meaningful communication. Again, you were on the right track by touching on "we can see each other, and build structures to show we're here". If they're close enough that a pre-industrial society with telescopes can see at a decent level of detail, then really, they don't need to be too much more advanced than our renaissance/expansionist periods of the 14th-18th centuries.
Certainly, communication permitted by radio or other high technologies would be far MORE meaningful and dense in information, but mariners in the ancient days had ways of communicating meaningfully across distances sound couldn't travel well. These included semaphores and precursors to Morse code communication by blinking lights.
This sort of system would be really easy to work out in a tidally locked binary planet system, where stations on both worlds where they face one another could be set up, with large reflective mirrors (which needn't be the type of perfect mirrors used for lasers and telescopes) and fire to provide the light.
It would be tricky to establish the initial communication - to develop a mutually intelligible code, but with enough trial and error and a basic grasp of maths, that could be achieved.
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Agriculture-level, plus some rudimentary telescopes, should be enough.
If you create *massive* tulip fields, I mean.
[](https://i.stack.imgur.com/mq06b.jpg)
Tulips can be used to effectively paint the landscape. If your races are dedicated enough and have some big, wide open areas visible to each other, with suitable flowers, they can *paint the surface of their planets* to make drawings to each other.
This will consume time and space, of course, but hey - if you draw something on your super garden, and the other planet nearby does a similar super garden, you wouldn't be amazed by it and invest more time to it?
They will probably need some sort of telescopes to check the gardens of each other, but the sheer cuteness of space aliens talking to each other by gardening already makes me want to write this story!
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The techs they would need:
**Astronomy** (to know that there's another planet that might have people on it).
**Beginning radio** would do it if they throw enough power into it (cubed root drop off).
They might even be able to do this without astronomy if they both have radio and are pumping out enough wattage. That's unlikely however. Why put that much juice into a signal if you don't know there's someone out there to receive it. I just mentioned this because their tech development order does not have to mirror ours completely. It just seem likely that astronomy will occur first.
If they learn enough to make parabolic reflectors, they can aim more of the signal at the target and use less power to make the transmission. the parabolic reflectors also allow them to pick up weaker signals. So only one of the pair needs them. That will make communication easier.
It will become easier still when they figure out masers.
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First I'd like to talk a bit about statistics. Our planet has existed for some 4 billion years-ish, and support human-like life for perhaps half that, if im being generous.
Of those two billion years, humanity has been intelligent enough to looks at the stars in a scholarly fashion for perhaps 3000, again if i'm really generous. Lets say it takes us another 1000 to set up a bus to go to the moon and back.
That's a time frame of 2 000 000 000 years that a planet has stupid life, compared to 4 000 years of intelligent life. Meanwhile, with such a fertile planet that close, humanity would spread across it's surface like mice in a barn. If the moon were fertile and of even remotely suitable atmosphere, you can be pretty sure we'd have a colony there already. Statistically speaking, either intelligent species will colonize the other planet long before a species can evolve there to be about as smart.
To make your story believable, I hope you got something to remedy these statistics.
As for communication, I think radio is the first method available. With a good telescope, you can figure out there's life on the other rock a couple hundred years early, basically as soon as you get higher quality glass working for lenses. However, how would you agree to any communication protocol ? You probably can't. Every communication protocol we use, both sides have an understanding of how it works, we encode and decode the information. This was a consideration for the old voyager drones - part of what was done was engraving pictures of humans in a plate of gold, as well as an attempt to codify a small message in a sort of language we hope is easy to understand, but all our perspectives are human, not alien. Your races would have likewise problems.
It's not like talking to other humans. It's like talking to animals. With a lot of training, we can for example teach sign language to certain types of monkeys. However, establishing any mutual understanding that way requires close contact. Even if you found geeks on either planet who talk by radio and attempt to make sense of what the other one's trying to say, chances they'll reach some understanding in any short amount of time is really slim.
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Once they have radio, communication is clearly possible. You could send a message to another planet with pulsed lasers but that's a more complex technology than radio.
But they could at least theoretically communicate well before that. They might, for example, build giant bonfires that would create enough light to be seen with telescopes from the other world. Once you have something that is detectable, you can vary it in one way or another to create meaningful messages. Like create a string of fires in some pattern that conveys a message.
The big question is, how big a bonfire? I found a formula that says that the maximum resolution of a telescope, in radians, is R=w/D, where w is the wavelength of light and D is the diameter of the telescope. (I have no idea where this formula comes from or how to prove it.) If we assume visible light is about 600 nM and the telescope is 10 m, that gives R=60e-9. The smallest object we could then see would be x=sin(R)\*s, where s is the distance between the planets. Let's say they're as far apart as Earth and Mars, around 60e9 km at closest approach. So sin(60e-9)\*60e9 = 3600 m, or about 3 1/2 kilometers.
You can distinguish light versus darkness much more easily than resolving an object in general, so I think a bonfire much smaller than this would be visible. Anybody know how to calculate that? I guess it's still at least hundreds of meters. So, big project, but doesn't seem impossible.
Of course just sending a signal and actually working out a comprehensible message are two different things. That's another whole dimension. If aliens could send us a letter with printed text, could we figure it out? It's hard enough to decipher ancient languages, which are of course written by fellow humans. What would it take to decipher a message from aliens?
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I think it all boils down to the aliens' sensationary capabilities. Do they both have vision? Maybe they're colorblind? What if only one of them does, and the other has evolved bat-like sonar?
I'd say the question needs some clarification from the OP on that part.
However, as soon as they get technologically developed enough (like 20th century) and they're both on the same techological level, they could use radio-waves for communication. But are they? The OP should also specify that.
In the end, it seems to me extremelly improbable to learn o feach-other's existence, barring space-shuttle visits to each other. Just imagine, humans on one planet and dolphins on the other...
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## Size limit you could see on Earth
Bluring from the atmosphere limited best angular resolution in about 1 arcsec which is 1/3600 of a degree. This mean that 10 kilometers field could be recognized from distance 2,061,100 km and 1km field from 206,105 km. For example, average distance from the Moon is 384,402 km and [L2 point](https://en.wikipedia.org/wiki/Lagrangian_point) is about 1,500,000 km. Thus, 1km objects could NOT be seen from the Moon.
I suppose that paired planets should have distance between them more than distance from the Moon and less than L2 point.
## Astronomy development
In our 17th century people could see mountains on the doubled planet, compute distance from it and estimate how high is this mountains. Although estimations was rough and even wrong, this could lead to early attempts to communicate through flashes and square-of-fields signs. But these attempts should be very naive since people could not estimate how bright flash and how big square should be.
In 19th century people have precise values for distance from the planet and size of its continents/mountains. The clouds restrict ability to observe the same area for a long time. This time correct estimations could lead to success attempts to show signs of squares/circles. Most likely it would be 10km\*10km fields covered by cloth of different color. Then colors should be changed after some weeks. This is very expansive though.
In the late 1890 first radio was invented. The first [radioastronomy](https://en.wikipedia.org/wiki/Radio_astronomy#History) observations was made 40 years later, in early 1930. After that radio is the main factor to find out neighbors.
Gas analysis through it spectrum came in 20th century and after radio invented so this way is not useful.
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I doubt that single mediveal field could span 10 km long. So my estimation they could know about each other in 20th century.
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You could use light semaphore and telescopes, depending on how close they are together, you could have that they are very close at one point in their rotations.
Obviously this would have been after they had been using more primitive methods to communicate.
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Take Charles Stross’s *Laundry* stories as an exemplar for this modern day approach that makes explicit the analogy between computer geeks and fantasy mages. If P = NP then magic is possible. Here’s a passage for bringing the reader up to speed in one of the later *Laundry* novels:
>
> I’m actually a specialist in a field called Applied Computational Demonology: the summoning and binding to service of unspeakable horrors from other dimensions, by means of mathematical tools. **Magic is a branch of applied mathematics: we live in a multiverse, there is a platonic realm of pure numbers, and when we solve** [sic] **certain theorems, listeners in alien universes hear the echoes.** By performing certain derivations and manipulating theorems, we can make extradimensional entities sit up and listen, and sometimes get them to do what we want them to.
>
>
>
There have been variations in other stories, but Stross seems to lead the pack in mashing up supernatural and information technology.
Consider the bold part of the blockquote above. In (for example) Terry Pratchett’s [*Discworld®*](https://en.wikipedia.org/wiki/Discworld) series, supernatural beings *listen* to people and might decide to meddle; speaking or performing rituals gets the specific attention of those paying general attention to human activity.
# ❝ what exactly does *solving a theorem* do? ❞
But what exactly does *solving a theorem* **do**? If all theorems exist in the Platonic realm, in what manner does knowing about it bring on some action? If it's in a book somewhere, does a human mind *going over the steps* tickle something? Or does it require some degree of *understanding* of the complete proof?
How might this trope be made a little more rigorous?
(See also [this story](http://qntm.org/ra) where magic is an API. It was described as being discovered by working on physics and math theorems as above, but upon reviewing I see it’s like a programming language and is spoken. So how did that initial discovery “work”?)
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Going through each question one by one:
**what exactly does solving a theorem do?**
underlying question: what is a theorem? A theorem is a tautology, something that can't be false. 2=2 **IS** a theorem (not an interesting one, I agree but still). With this definition I think you can understand that the word "solving" has little to do with theorems. However you can prove that something is a theorem (which is I assume, what you wanted to say).
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</hard-math> <philosophy>
```
In this case proving that something is a theorem depends on how you see math. Some think that mathematics is a human invention that only exists in our mind and has been created to help us understand the complexity of our world. In this case **math does not exist by itself** and proving a theorem means **creating it**
Other people think that mathematics is part of the physical world, it exists as rules just like physics does, it does not come from our mind but from us observing how the world works. In this case it's obvious that proving a theorem means **discovering it** (since it already exists in nature).
Now concerning your trope: Maybe the first interpretation suits you better: if the platonic realm is created as we prove theorems (because it only exists in our mind), your alien living in this realm does not even exist before it has been proven to exist between two symbols. Then your alien can't do anything until it has been proven to be able to alter his world in some ways, and \* **tadadadam** \* can't alter our world until he has been proven to be able to do so. **That's your initial discovery.**
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**Means of perception: could be anything**
If we go by the model in the *Laundry* books, given that it is said that the those beings who perceive that a human Applied Computational Demonologist has solved a theorem are to be found in alien universe**s** in-the-plural, the means by which they perceive this could vary literally infinitely. (And if you can say that tongue-twister three times quickly, you too can summon a demon.)
For some demons it could be hearing a voice from the skies or inside their minds, for others a searing pain, for others their personal computer sends them an alert.
**Level of human mental involvement that will trigger the spell - could vary along a scale**
Summoning cannot reasonably work by merely reproducing the steps of the mathematical proof without comprehension; otherwise we would be able to completely automate the process and it wouldn't be magic at all - or much of a story. At the other end of the spectrum, a computational magician writing, typing or speaking the spell/series of equations with full understanding and concentration ought to be virtually certain to be able to summon the demon and control it. However most summonings lie between these extremes. A person who never did get to grips with algebra can probably look at the Program of Summoning with no effect. A more mathematically-aware human skim-reading the relevant equations probably does no more than give a demon a slight headache.
**Spell macros: allowed or not?**
Depending on how your magic system works, the rules of magic might or might not allow a human to write or type a spell in advance, perhaps leaving off the final line until the last minute, and then press "send" when activation is required. If this is allowed then the once-common peril of making a mistake in saying the spell and so letting the demon out of the pentacle would be eradicated. However one might argue that magic, even mathematical magic, requires a human act of will to break through the barriers between universes and because of the way the human mind works just pressing "send" wouldn't cut it. On this model, it is psychologically impossible for a magically and mathematically skilled person to mentally go through the steps of the proof but stop before the end, just as I could not write out all but one of the steps of a geometrical proof and then stop myself from *perceiving* the last step whether I wrote it or not.
**What is *solving a theorem* anyway?**
By a rather sinister coincidence given the topic under discussion, Alexandre Thouvenin's mind-bending answer has appeared at the very moment when I was about to embark on a discussion of what exactly is meant by this, and the answer I give now incorporates ideas I got from him.
My mathematical studies are long ago, but I don't remember *solving* theorems. I *solved* simultaneous equations and suchlike (i.e. found values of previously unknown variables for which certain conditions held true) and *proved* theorems. Since I wasn't Euclid, "proving" the theorems meant in practice just remembering the proof someone else had invented and writing it out again. Although it helped me to remember the proof if I understood it, that wasn't necessary. This seems unsatisfactory for magic, somehow. I feel intuitively that mathematical magic must be a process of discovery, like solving simultaneous equations. But there is a problem here. The "process" of discovery only feels like discovery because I lack the intelligence to perceive instantly the solution that is inherent in the equations. When some prehistoric genius first made explicit the statement "two plus two equals four", that this equivalence was possible was a discovery - but to you and me it is a tautology. Several mathematicians have pointed out that in a sense *all* mathematical statements are tautological if we could but perceive it.
This leads me to not exactly an answer to your question of what exactly counts as "solving" a mathematical theorem for it to trigger the summoning, but at least to a revelation about the process: **summoning demons is only possible because humans are stupid.** We can only do it with the help of that surge of satisfaction we get from *finally* perceiving the answer. Demons perceive the answer as obvious as soon as they look at the question, which simply doesn't excite them enough. This is why demons cannot summon humans. Can you imagine how irritating this is to know? It's why they are so angry when we summon them.
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**True Names**
[True names](https://en.wikipedia.org/wiki/True_name) are a powerful tool in lots of works, and give an individual with the knowledge of an entities' true name either power over or power via them. Perhaps in the Magic=Math universe, the beings with power don't have Names, but Equations, and knowledge of the supernatural equations gives power. If these equations live in a realm of pure math, the more complex the equation the greater the potential power. After all, Knowledge is Power.
Additionally, if you go down this route, it's quite easy to have imperfect knowledge be incredibly dangerous. If you don't understand the equation correctly, the equation itself could cause untold damage as the parts not wholly understood seek freedom on behalf of the whole equation.
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**Knowledge is power.** What if this was taken to the extreme?
Let's presume we don't really understand what happens when information is "lost to entropy." This isn't much of a make-believe story to believe in, it's actually pretty accurate. We know the information gets diffused (such as the information contained in a tendril of smoke is diffused into the wind), and the information becomes inaccessible to us, simply because it has been mixed with other information until it is incomprehensible. Entropy seems to work this way in the physical world. Even Stephen Hawking's latest theory involves the topological mixing of information on the event horizon of black holes to avoid all sorts of confusion about information getting destroyed or being preserved.
But what if there was more to it than just the physical realm? What if information or knowledge was actually a metaphysical thing. This also is not such a flight of fancy. Many who believe in a dualist philosophy that there is some mental component to us which is more than just the bare matter that makes us up already believe this. We like to believe we are "something more."
Now let's start to depart from our world. What if our world was in a unique position at the cusp of a multiverse. Knowledge or information in our world which was "consumed by entropy" from our perspective actually influences the other universes, potentially jeopardizing their very survival. The only hope of survival for such universes is to make sure to manipulate our world such that some knowledge just doesn't get out. As long as its never discovered in our world, that knowledge can never heart their world.
In such a world, Aliens would have a vested interest in interfering with our world, and in particular with us. As humans we are either the single most powerful source of information in the universe, or at least one which stands out in the crowd, we would see quite a lot of interference. They may not want certain information to get consumed by entropy in certain ways, and they may be willing to expend a great deal of energy to do so. We may not understand what the particulars of their needs are (in particular, we may have no idea what particular ways entropy could consume information to trigger an effect), but we may understand that certain shapes or equations lead Aliens to action.
Presumably they would want to teach us how to search for new knowledge without causing their universe trouble. They might carefully teach us particular tricks that help them. This could pick up an element of gnosticism. You could have an outer message, in the form of a mathematical proof, which itself is useful, and an inner message which contains the true power to influence that universe. Or they might pick up a Daoist perspective, trying to get us to accept that we are all part of one fabric to be preserved and enjoyed. They might even come in with an Abrahamic approach, with a show of force and the dictation of a set of rules for us to follow.
It would also permit some of the more anarchistic groups to seek symbols and equations which are destructive to all universes.
How did this come to pass? Tying it up in a nice little bow, we entered this path because one day, somebody discovered that information lost to entropy wasn't just getting mixed up like we thought.. it was actually getting lost. Somehow they managed to disseminate this information. Whether they escaped the violent reach of Entropy, or whether Entropy struck a deal with them, we may never know. Regardless, now we know, and knowing is half the battle. We still don't know what Entropy is, mind you, but maybe that's the whole point.
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It's really a form of the same trope as summoning demons by pronouncing certain words/names, or following certain rituals. Or making yourself subject to external influences by reading the *Necronomicon*. How, rigorously, does a demon know whether you've said its name or not? Really good inter-dimensional hearing? Some kind of universal monitoring system that rushes off and tells it whenever someone says its name, like demonic Echelon? How does it detect from another world, what kind of incense you're using and what sigils you've drawn? Similarly, how does it know what mathematics you're doing?
Part of the point of magic is that the mechanism is not rigorous: if it was then it would be physics, or just a political or commercial interaction with the demon.
But as a general theme, the idea seems to be either that certain energies or entities are attracted to certain words/signs/substances/etc (by some form of sympathy), or else that certain states of mind allow the practitioner to perceive or interact with a world they normally cannot.
Converted to mathematical form, it could be that there's some etheric substance that is pushed around by mathematical symbols, and that a proof of a theorem pushes that substance into a mechanism that then is able to do whatever it takes to pierce the veil. So, proving Fermat's Last Theorem is like building the machine in Sagan's *Contact* except that you're not building it out of material substance, you're building it out of some magical hand-wavey stuff that exists locally, and responds to local stimulus, but then is capable of a distant effect. In that case, a written proof might be a permanent magical doohickey provided that the symbols continue to hold the machine in shape. You still have to explain how the energy "knows" that the symbol "2" means the number that comes after the number represented by the symbol "1", but perhaps what matters is the structure of the patterns/relationships among symbols, and this explains why the actual symbols used are irrelevant.
Alternatively, it might be that humans happen to be innately equipped with some faculty that draws the attention of demons, but that we're unable to use that faculty except when guided into a series of very specific mental states/visualisations, corresponding to the steps of a proof. In that case, a written proof in a book is nothing, but when someone reads it and it has its intended effect on them (of understanding the proof that it represents) then the magic happens and they start dreaming of unknown Kadath. The proof itself is no more or less magical than the mental exercises used by a Zen archer to shoot a bow, (and vice-versa the shooting exercises used to achieve mental and spiritual development). It's just that in the case of demon-summoning humans are actually so awful at it without the exercises as to be incapable.
Or in a broader sense of the law of sympathy, perhaps there is some entity that definitionally *is* (or has some direct connection with) the platonic ideal of the number 2. Wherever things appear in pairs, or whenever someone thinks about the mathematical properties of the number 2, there that entity is, just as we might say that Thor exists wherever thunder does, or that silver is connected with the powers/associations of the Moon, or that God is omnipresent. Naturally then demons respond to mathematics: to do mathematics is to touch a part of their multi-dimensional self. It's then up to you whether the demon summoned is the demon of Fermat's Last Theorem specifically, or whether the general fuss and commotion caused in the region of the platonic universe corresponding to the intersection between "elliptic curves" and "modular forms", by proving the Taniyama-Shimura conjecture, is what attracts other demons.
As for the rigorous details of *why* there is a law of sympathy at all, or *what causes* there to be a God of Thunder or a demon of Banach-Tarski dissections, or *how* the force is mediated by which symbols to build etheric machines, or *by what mechanism* humans have an innate capacity to summon demons or shoot bows: those may have to remain as irreducible principles of your in-fiction theory of magic. No doubt you can drill into some of them by introducing further concepts that dictate them.
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I've got a slightly different take on this. Think of quantum physics and the observer effects. Quantum states that only "collapse" once observed.
From the point of view of our universe all the demons are in a quantum state of possibility, a quantum state where they may or may not exist. By solving the right theoretical mathematics and visualizing it in your mind you are actually collapsing the wave-form of that demon and allowing it to come into physical form.
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**A mathematical variation of the True Name trope**
Since the entities are real numbers, what is relevant is not their name, but their formal definition: roughly, a real number is [definable](https://en.wikipedia.org/wiki/Definable_real_number) if it can be uniquely described by a finite mathematical formula. For example, $\sqrt{2}$ is the positive solution of $x^2=2$; $e\simeq 2.71$ is the value at $1$ of the solution of the differential equation $y'=y$ with initial condition $y(0)=1$; etc...
With that idea, you define have a hierarchy of powers among your entities using the complexity, that is the length of the shortest formula describing it. A surprising consequence of Cantor's theory of cardinals is that most real numbers are not definable.
Notes:
* You can adapt this to use the concept of computable numbers. That would be a natural setting if you want your story to speak about Alan Turing
* Why limiting yourself to a "dimension of pure numbers", when you can consider the behemothic universe of mathematical objects?
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My first answer explored how a theorem itself could be valuable. The bounty suggests more interests is needed, so I wanted to put forth a theory that suggests the theorem itself isn't as important as it may appear.
I wanted to focus on two parts of the question
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> "Discworld" series, supernatural beings listen to people and might decide to meddle; speaking or performing rituals gets the specific attention of those paying general attention to human activity.
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> How might this trope be made a little more rigorous?
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I think this trope can be made more rigorous by not looking at the theorem itself, but rather what the act of "solving" it implies. To this end, the theorems the supernatural beings listen for are not all that meaningful at all. However, the fact that a sentient mind "solved" these theorems could be of great interest. If they can solve that theorem, what else might they be able to do?
If there are things which the supernatural do not want us doing, or ideas the supernatural do not want us to think of, they would be encouraged to meddle in our affairs to prevent us from doing or thinking those things. "Solving" a theorem might demonstrate that we are capable of taking the next step and thinking of the forbidden thing, or capable of leveraging that theorem to do some forbidden thing.
What makes this powerful is that the "solving" of a theorem can now be treated as a symbolic gesture, rather than the thing that actually has power. This provides key direction for questions such as:
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> If it's in a book somewhere, does a human mind going over the steps tickle something? Or does it require some degree of understanding of the complete proof?
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The answer is now dependent on how the supernatural being feels, rather than some strict rule set. Perhaps for a given entity, one must truly *understand* the implications of a proof of Fermat's Last Theorem before the entity cares enough to be cajoled into action. It may be that the entity doesn't actually care about his Last Theorem at all, but does care about some other great problem which can be solved using a similar approach. Someone who understands Fermat's Last Theorem is a likely candidate for being able to solve this entity's great problem.
On the other hand, the same entity may treat a proof of P=NP differently. This may be a sufficiently powerful tool in the hands of a mathematician that the entity has to pay attention to anyone who knows the proof, even if they don't fully understand it. It may be that the entity wants to snuff out all memory of this proof, for fear that an uneducated person who memorized the proof might tell it to an educated person who would then understand it and know what to do with it.
Approaching the theorems this way makes the theorems into threats and other gestures targeting the supernatural. This sort of posturing is very rigorous in other disciplines such as hand to hand combat. In addition, it offers many many quirks. Perhaps an entity doesn't really care about P=NP. What they really care about is BQP=NP. An entity might appreciate the fact that mathematicians are constantly getting sucked off into P=NP and aren't paying as much attention to BQP=NP. Perhaps that entity might reward a math-wizard for "solving" theorems in a way that encourages others to waste their time on P=NP. The options are limitless, and yet it would be easy to develop a rigorous structure within which any given supernatural being might choose to operate.
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* Every concept, such as a theorem, is matter in Platonic realm for being able to exist.
Only in math can you 100% prove something. => The concept has to materialize itself in our world, because the theorem is perfect not only in the Platonic realm, but also in our world. This means that it is either a perfect copy of the concept in Platonic realm, or it brings the concept from that realm. => If latter, the concept may still have a tendency to stay in the Platonic realm.
Then, there must be some conditions when a concept materializes itself in our world. It could be that it only materializes itself when somebody is thinking it clearly enough, aka. casting a spell by going the theorem in mind or in word. People think a bit differently when they speak (it even has a difference when sitting or standing). That might explain why the mages speak when casting.
EDIT PS: This would also explain miracles, created by pure or perfect love, belief, friendship etc. Just might make a nice plot element if well implemented, but with high risk of being mawkish.
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You depict the math physically and bring it into the world. Draw the pattern. Build the temple. Play the fugue and variations. Bring the geometry and ratios into the physical world. Humans have been honoring and courting supernatural beings thus for thousands of years.
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Meaning, cause a seemingly normal winter to suddenly take a turn within hours or a day/two into a completely frozen territory? From what I've read, abrupt climate change happens from ocean currents. Would dramatically shifting the weather happen due to maybe a giant glacier melting up north? **I know there's global warming, but I'm looking for a natural "what if" for a story or man-made accident that would speed this up in a way that humans are unprepared for - and how this would affect the world.**
Here's what I was reading:
<http://www.wunderground.com/resources/climate/abruptclimate.asp>
Was reading that the Bering Straight is a 50 mile gap separating Siberia from Alaska, so if that closed, what would happen? It sounds like a more likely idea to use the Meridional overturning circulation (ocean currents) to trigger what's close to an ice age in North America?
Ideas? How can this be explained to me in layman terms? Thanks in advance!
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The simple answer is that if you want a permanent change then it is unlikely to happen overnight. There's a lot of inertia in the environment and it takes time for things like currents and suchlike to work.
However there are three candidates that might give what you want, and all act in roughly the same way:
* A supervolcano
* A meteor strike
* A nuclear war
All three of these would act by sending a huge amount of debris, dust and ash into the upper atmosphere.
That dust then blocks and reflects away the sunlight. This kills off all the plantlife and also drops the temperature of the planet rapidly as the sunlight is reflected away instead of warming the planet.
This would normally last at least a few years before it cleared, and it would then take a long time for ecosystems to recover, but the effects in the long run are temporary.
In a hypothetical worse-case scenario a massive meteor strike at one side of the planet can send shockwaves through it. That then causes massive eruptions both at the impact point and at the opposite side of the planet from the impact (as the shockwaves focus again there). If those eruptions were serious and long lasting enough they could extend the resulting cooling for as long as decades or even centuries.
For example the [Deccan Traps](http://en.wikipedia.org/wiki/Deccan_Traps) and the [Chicxulub](http://en.wikipedia.org/wiki/Chicxulub_crater) impact:
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> The release of volcanic gases, particularly sulfur dioxide, during the formation of the traps contributed to contemporary climate change. Data points to an average drop in temperature of 2 °C in this period.
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> Because of its magnitude, scientists formerly speculated that the gases released during the formation of the Deccan Traps played a role in the Cretaceous–Paleogene extinction event (also known as the K–Pg extinction), which included the extinction of the non-avian dinosaurs. Sudden cooling due to sulfurous volcanic gases released by the formation of the traps and localised gas concentrations may have contributed significantly to mass extinctions. However, the current consensus among the scientific community is that the extinction was triggered by the Chicxulub impact event in Central America (which would have produced a sunlight-blocking dust cloud that killed much of the plant life and reduced global temperature, called an impact winter).
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> The impact would have caused some of the largest megatsunamis in Earth's history. A cloud of super-heated dust, ash and steam would have spread from the crater as the impactor burrowed underground in less than a second. Excavated material along with pieces of the impactor, ejected out of the atmosphere by the blast, would have been heated to incandescence upon re-entry, broiling the Earth's surface and possibly igniting wildfires; meanwhile, colossal shock waves would have triggered global earthquakes and volcanic eruptions. The emission of dust and particles could have covered the entire surface of the Earth for several years, possibly a decade, creating a harsh environment for living things. The shock production of carbon dioxide caused by the destruction of carbonate rocks would have led to a sudden greenhouse effect. Over a longer period, sunlight would have been blocked from reaching the surface of the earth by the dust particles in the atmosphere, cooling the surface dramatically. Photosynthesis by plants would also have been interrupted, affecting the entire food chain.
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Something that can trigger a climate change is a sudden change in the orbital pattern around the star. For example, if a gas giant or other massive body passes near the planet, it can disrupt the orbit and either send it into a closer orbit, a further orbit, a more (or less) elliptical orbit or even into the star or out of the system entirely. this isn't as sudden as other events, but depending on the speed and magnitude of change, it can be dramatically different.
This is also something that doesn't have an immediate devastating effect on the population. Nuclear war, a supervolcano or a meteor strike strong enough to have these effecs will also immediately destroy vast areas of your world. A massive body close enough to exert gravitational pull will cause earthquakes and flooding, and potentially some radiation, but it isn't as devastating as the events suggested by Tim B.
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### General problem
Note that unless you introduce a massive heat sink, there is an inherent time it takes to cool down the earth or a piece of it because of the following:
We have the climate we have, because the following processes are roughly in equilibrium:
* Dissipation of heat to space.
* Absorption of heat from the sun.
* Absorption of geothermal heat from the earth’s core ([this effect is negligible](http://en.wikipedia.org/wiki/File:Earth_heat_flow.jpg)).
* If you are only looking at a particular area: Absorption from or dissipation to neighbouring areas.
To cool down the whole climate, you have to tilt this balance such that more heat goes out than comes in.
The big issue now is that **it’s very difficult to increase the amount of heat that goes out**. This may be very surprising at first, because it’s comparably easy to heat things up – you just need to convert some non-thermal energy to heat. However, to cool something down, you can**not** just convert heat back to some non-thermal energy, but you have to transfer this heat somewhere (which then heats up)¹. Therefore you either need something very cold or a heat pump (which consumes energy – which is why a fridge in sum heats up a room and you cannot cool a room by leaving the fridge door open). Both are arguably not applicable to your scenario, so you have to rely on the existing large-scale heat drains and the only thing you can do is to attenuate the heat sources and wait.
If the above is to abstract, the following analogy might help: Heat behaves like the water in a lake (with high water level corresponding to high temperatures). There are some rivers feeding this lake (heat from the sun, geothermal heat) and certain rivers draining it (dissipation of heat into space). Right now, the amounts of water going in and out are roughly balanced and thus the water level of our lake does not drastically change. What you want corresponds to draining the lake. However, as you cannot build a new canal to drain the water (introduce a heat sink), you have to wait for the lake to drain via the existing outgoing rivers.
### Once more, with numbers
Here are the first two effects in numbers and for illustration:
(from [Wiki Commons](http://en.wikipedia.org/wiki/File:The_green_house_effect.svg))
To take the highest number, we have 343 W/m² incoming heat and 343 W/m² outgoing heat. These numbers being almost equal is the aforementioned equilibrium, which keeps the temperature of earth from drastically changing.
To make a rough and benign calculation, let’s ignore the transfer of heat between areas and assume that you manage to fully switch off the incoming 343 W/m² while keeping the outgoing 343 W/m², i.e., you essentially remove the sun. Further assume, that all you want to do is freeze all the water (i.e., you go from 0°C water to 0°C ice) and that your area is covered by a water column of 1 m on average. We thus have for each square meter:
* 1 m × 1 m² = 1 m³ of water, which corresponds to 1000 kg.
* Water’s [heat of fusion](http://en.wikipedia.org/wiki/Enthalpy_of_fusion) is 334 J/g. So we need to deduce 1000 kg · 334 J/g ≈ 3·10⁸ J of heat.
* Going by our assumptions, we deduce 343 W = 343 J/s.
* Thus, it takes us 3·10⁸ J/343 W ≈ 10⁶ s ≈ 11 d.
**So, even under these extreme conditions, it takes eleven days to fully freeze some water.** While many assumptions went into this, this should at least give you an idea how long such things take. For comparison, also consider the delay of the seasons with respect to the sunlight: The minimum of solar irradiation actually occurs at what is generally considered the *beginning* of winter, not the middle.
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¹ This is a consequence of the second law of thermodynamics. While [there are exceptions](http://en.wikipedia.org/wiki/Phase-change_material) to this, they are not applicable on a geological level.
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AS Wrzlprmft points out...you aren't going to have a rapid globe freeze or warm-up from an 'earth losses or gains energy' all to readily with a couple exceptions. I won't repeat Tim B's list...except to maybe add a massive space event such as a supernova wave coming our way, or even something off our sun (could have fun there as not only would it impact climate, it'd fry all of our monitoring electronics and make us close to blind)...but I'll give you the redistribution possibility.
The Earth is an incredibly efficient redistributor of energy...in a very short amount of time, energy circulates from the equatorial regions and makes it ways to the polar region to cool. I'll describe 2 main points, though there is a lot more to it:
1. North Atlantic. Warm water from the Caribbean makes it's way north on the surface of the ocean and makes it's way up towards Europe. The air currents warm on this and blow towards the UK and Europe, providing them with relatively warm trade winds that keep the northern regions relatively warm and rainy, even in winter months.
2. Pacific. The Pineapple express is a weather pattern (not just a pot reference) where warm air from hawaii and the tropical parts of the Pacific makes its way towards the pacific coast and provides a jet stream of relatively warm and humid air that keeps area's like Seattle and Vancouver very wet, especially in the winter months.
The opposite is true...though I suspect you have some knowledge of that (wunderground is a great site, realclimate is as well) where colder waters descend and make their way back towards tropical regions.
This system is a huge amount of energy in the works...so I'm not entirely sure what it would take to actually halt this system, but in the event it did, I can speculate a few things.
but first:
The storm situation in 'the day after tomorrow' has quite a few flaws in it and the cooling effect wouldn't be so rapid. They explain it as extreme cool air from the upper upper atmosphere being sucked down incredibly quickly by this massive storm...unfortunately that air is also the exact opposite of dense and would warm extremely quickly as it descended. Mountain ranges also have the noted ability to tear apart the air flow in larger systems like this and would prevent the storm systems from forming in their proximity.
second:
air currents move pretty rapidly, however it's not an over night change. It takes around 4 days for particles in forest fires in alaska to blow over canada and end up flowing through canada's tailpipe (the maritimes). Even at it's most extreme, I cannot see this change taking less than a couple weeks, even a couple months.
With that in mind:
Within a week of the system shutting down, water temperatures in northern ocean regions will drop significantly while the regions around the equator would quickly warm up. The UK would probably experience the effect first as the wind changes from Caribbean warmed trade winds to arctic winds coming off a cold ocean. It would happen relatively quickly (within the week time frame) and snow would start to take a permanent grip on the UK landmass. A similar event would start to occur on the west coast of North America as well.
The tropics are a different matter as they would begin to mass heat. There are 2 major factors in hurricane development...ocean surface temperatures and wind sheer. Higher ocean temperatures give hurricanes more energy that result in stronger winds and larger storm surges. I would suggest that hurricanes would be extremely more powerful than we have experienced in the past. That said, I would also expect less of them. Hurricanes are gigantic beasts and stretch from the earths surface to upwards of 60k feet into the air. This creates the scenario where the wind speed in the upper atmosphere can be significantly different than the wind speed at the surface...when this happens, the top of the hurricane that drives the force of the storm is ripped away from the bottom of the storm that has the rotation. So there would be less of an opportunity for hurricanes to form, but when they do watch out.
The end result (2 months?) would be a large icecap over the northern and southern poles and exceedingly warm tropical regions that would hit temperatures outside of what humans consider habitable. The region between the hot and cold would be a massive jetstream of wind that would likely produce sustained windspeeds far greater than what we've seen on Earth so far (I'd go as far as thinking the 'ring clouds' of Jupiter or Saturn could even form).
The only thing that I could consider for a 'abrupt change' is our failing to recognize that this is infact happening (or disagreeing that it is) and we don't realize until the massive hurricane or winter storm strikes. The change would likely be minor at first and not the easiest to detect until the abrupt onset of one of these storms (an arctic storm hitting the UK from the north, or a hurricane of abnormal proportions hitting the Caribbean/US or into the Philippines and china.
Adding in:
Don't neglect an extreme solar event from the list of potentials here. Space weather has a tremendous effect on earth and there is recent research that is linking our weather and storm systems directly to the weather of the sun and the magnetic lashes it sends us. An extreme solar event coming our way could also spawn a series of weather disasters and cripple our electronic ways of monitoring it.
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An extreme low-probability event but possible: two rogue planets collide at the L1 position, the merged mass ends up orbiting at the L1 position. While it won't totally block the sun it would make for a quasi-permanent (it's not exactly stable) partial eclipse.
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For a man-made variant of @TimB's super-volcano, the characters of your story might build a **large** space mirror (for an unobtanium furnace? for a publicity stunt?) at a Lagrange point and *accidentally* point it at the Earth.
Good ol' [xkcd](https://what-if.xkcd.com/141/) describes an extreme case (which, as so often, destroys the earth). But if you scale it down (maybe a moon- or planet-sized parabolic mirror? I don't have the math to work it out) you would rapidly heat a small area of the earth, with extreme effects.
To be honest, I don't know whether this would lead to a super-cold or super-hot scenario, but it would certainly ruin your day.
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After reading the following question about [anti-gravity](https://worldbuilding.stackexchange.com/questions/183939/how-to-realistically-explain-antigravitation), I wondered what the largest hollow structure you can make in space is. None of the questions about hollow earth seem to answer this. To put it clearly into a question:
**What is the largest structure that can be created in space?**
The structure I imagine isn't completely hollow. It is filled with a supporting structure. This can be a honeycomb structure for example. The idea is to make it as large as possible, without it caving in structurally thanks to the gravity it generates. I wonder if it might even be possible to make the hollow structure large enough that you can continue near indefinitely to enlarge the structure, because of the low mass and thus low gravity.
Assumptions:
* The structure itself must be solid enough to have hollow spaces.
* existing or theoretically existing materials are allowed. So no Unobtanium, but if large superstructures of carbon nano-tubes are theoretically possible, they are fair game.
* There are no limitations in amount of material in existence.
* There are no technological limitation on how the structure is created. It is basically as if a god placed the structure there in space in an instant. I'm only interested in the materials used to make a large as possible structure.
* Although all forms of structures are allowed, a sphere is probably the strongest.
* It just needs to be a structure floating in space. No habitats, computers, or even other celestial bodies in the neighbourhood are required, unless you think it somehow adds to the strength of the structure (like electrifying some part of the structure and it becomes stronger due to the electricity).
* The structure doesn't have to be rigid. It just needs to be able to exist and be as large as possible.
* Hollow in this case means that a large part can be filled with oxygen. This is regardless if it'll just immediately be blown away into the vacuum of space.
[Answer]
**TL, DR**
Using a lattice structure and steel we arrive at ~ 2800 km across, a few hundred km smaller than earths moon. only about 2% of the volume are actually filled.
**The problem with thin shells**
You can't make a shell with an arbitrarily thin shell, as thin shells will [buckle](https://en.wikipedia.org/wiki/Buckling), long before the stress reaches the compressive strength. Approximately half of the other answers don't take this into account and are wrong.
I interpret the spirit of the question: Can there be a porous, honeycomb structure with lots of internal volume?
Luckily, lattices (3D-honeycombs) have been investigated and can be [approximated as a bulk material](https://royalsocietypublishing.org/doi/full/10.1098/rsta.2005.1678#d16288025e1). In a built structure - unlike a planet, which is by definition in hydrostatic equilibrium - the upper layers can carry their own weight and need not exert pressure on the lower layers. This is why thin shells are so popular in the answers here.
**Approach 1**
We can approximate a sphere as series of layers, each designed to carry their own weight. Analytically, we treat them as infinitely thin, however as we assume lower layers we need not worry about buckling. It might make sense structurally to transfer some load downward, but then the math gets more hairy. The upside of this approach is that the interior of the structure is less filled with stuff.
What we need to do is take the formula for the stress in a thin shell under it's own weight, and modify for the lower density and strength of the lattice.
The Force $F$ acting on piece of size $A$ of the outermost shell with thickness $t$ depens on the mass of the whole structure and is given with:
$$F = A \rho t G \rho \frac{4}{3} \pi$$
Note how $\rho$ goes into the left part - weight of the shell-element - and right part - total gravity - of the right hand side. If we move $A$ to the left by division we arrive at a sort of pressure acting on the shell. The [hoop stress](https://structx.com/Stress_Strain_006.html) in pressure vessel is given by $\sigma = \frac{Pr}{2t}$, this relationship holds here too, its just compressive stress (not tensile stess). For the stress in our outtermost shell we arrive at:
$$\sigma = \frac{2}{3}G \rho^2 r^2 \pi$$
The paper mentioned above gives the following link between density and yield strength:
[](https://i.stack.imgur.com/8F3XX.png)
We see that by picking a pyramidical lattice and 0.02 denstiy - meaning 2% of the available volume is filled by the material - we get about 1% of the yield strength. Presumably the pyramidical lattice looks something like this:
[](https://i.stack.imgur.com/k48ed.png)
Now it's just entering numbers for your favorite material, with *my* favorite material (concrete), these are a compressive strength of 20-80 Mpa and a denstiy of about 2600 kg/m³. We'll assume 20 Mpa to account for a safety factor and arrive at 727 km radius, and 84 million tons. This is almost twice as large as Ceres, but far lighter.
Now, how about mild steel? Values for compressive strength for steel are hard to find, as metal rods under compression usually fail in shear or buckling. However the strength is higher than the tensile strength. So we assume a high strength alloy with a yield strength of 690 MPa and a density of 7.8 g/cm³. For funs sake, no safety factor is assumed. With these values I arrive 1426 km radius
and 1.8 billion tons. As above, the surface gravity is on order of magnitude of 10^-5 m/s² - not enough to hold an atmosphere. The radius is only 300 km less than earths moon!
Why are these so small? Remember, the outtermost layer has to carry it's own weight. This means that at any circular hoop the weight of one hemisphere presses against the other, causing compressive stress. The weight scales (assuming constant gravity) with the square of the radius, the are only linearily. The same reason pressure vessels and pipe become weaker against internal pressure with larger size and constant wall thickness.
Note that my approach rests on assuming thin shells and in practice the thinnest thinkable shell in a lattice structure is at least as strong as a truss is long, this may introduce major errors - I simply don't know & don't know how to solve without doing a finite element analysis (which I also don't know how to do).
**A view from the inside**
From the image above we see that one cell of our lattice has 24 outer trusses and 12 inner trusses, but half of the outer trusses "belong" to other cubes so for the following we assume a total of 24 trusses. With the length of a truss $l$, the cube has an edge length of $l\_c = \sqrt{2}l$. The *filled* part of this cube is $V\_f=lr^2\pi n$, with $n$ the number of trusses. From all of this we see that:
$$r = l \sqrt{\frac{\sqrt{2}^3 \rho\_{rel}}{24}}$$
$\rho\_{rel}$ is the relative density, our 2% from above. If wes assume trusses 10 km long to allow some flying in out structure, each truss will be about 960m thick (diameter). For a proper analysis we would need to calculate the load on an individual truss and prove that it does not exceed the critical load causing buckling and I won't do that. However, this[critical load on a slender column](https://en.wikipedia.org/wiki/Buckling#:%7E:text=The%20formula%20derived%20by%20Euler%20for%20long%20slender%20columns%20is%20given%20below.&text=The%20elasticity%20of%20the%20material,area%20of%20the%20cross%20section.) scales with $\frac{r^4}{l^2}$. Since, to keep our $\rho\_{rel}$ constant, $r$ scales with $l$ we can just make the column longer and thicker to make it stronger. If you want to fly around in your structure, it surely could be engineered that way!
You could also have hollow trusses for the same total mass, say 1.4 km outer diameter and 960 m inner diameter, with the inside of the trusses filled with an atmosphere.
**Approach 2**
This maybe something another user want to play with: a sequence of thin shells, but each shell is a geodesic structure with minimal support between shells. Don' know enough about geodesics to try it myself, the beauty is that it would give a better visual feel for the finished structure.
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# TLDR: Almost As Large As You Like (but not due to the Shell Theorem)
To really understand this, let's first think about what causes a mega-structure to collapse- *Gravity*.
Since this structure is filling 3-D space, any point on the outer surface of the structure is going to feel a gravitational force due to all the other components. On the surface of your structure, that will result in a gravitational force pointing to the center-of-mass. Wherever that center-of-mass is.
(Yes, this is even true if the structure is a hollow shell. In that case, anything bouncing around inside doesn't feel gravity, but the shell itself does! This can be found considering the gravity acting on something on the surface, or something that is the surface.)
So how can we overcome gravity? Put it to work by *spinning.*
The reason why spinning objects (or curving objects...) can go in a circle is because some force is acting to push the object toward the center of curvature. It could be a rope, friction from a car's wheels, or ... *the gravity of a megastructure*!
So, choose your rotation correctly, choose a nice shape (like a cylinder, series of cylinders approximating a sphere, etc.), and build to your heart's content. A "nice" shape lets you use the force of gravity to keep the structure together, so you'll want something with more-or-less uniform distance from the center of rotation.
# What about Longitudinal Forces?
There is the question of forces which exist along the axis of rotation. This is a question of ingenuity and creativity- there are likely many solutions which let you go up in scale.
An fun solution for this is for the structure to not be rigid, but dynamic. Imagine a series of rings which approximate a sphere. They're spinning at the right speeds so they don't feel any radial stress. Remove half of the rings such that they can flatten down into a disk. Arrange them so the along-the-axis-of-rotation forces make the overall sphere collapse into a disc, then back out into a sphere, and you've just solved this issue. It'll oscillate forever until you do something, like put air in between the rings. There are likely other solutions to this problem, but this doesn't impose any material limitation.
A less fun solution is to just make a thin hollow rod which forms a *really* large ring, and keep increasing R until you've realized that this lets you fill in infinite amount of gas, fulfilling the "hollow" criteria. After a certain point, the difference in gravitational force between the top and equator won't matter anymore, so no bending issues!
# Speed of Light Issues
Okay, so the speed of light is a limit on how fast you can go. If you take [Newton's law of gravity](https://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation) and set it equal to the formula for [centripetal force](https://en.wikipedia.org/wiki/Centripetal_force), you can get a rought theoretical limit for any structure. I happened to do this for a radially symmetric structure, which gives a general equation of
$$\int\_{0}^{2\pi} \frac{m-dm}{r} = \frac{c^{2}}{G} $$
with *c* being the speed of light, m being your total mass (also depends on radius), and *G* being the universal gravitational constant.
Some important items to consider:
* For newton's law, examine a small slice of your structure as your second mass, the first mass being the 'total' mass (that's an approximation there)
* You can express the small slice of mass (dm) in terms of a small angle (a dtheta) times r, the cross-sectional area, and density. Integrate over the whole structure to this down to simple algebra. (This substitution changes for each choice of structure: rings will do differently than cylinders...)
* Once integrated, you solve for r to get your maximum size limit.
I don't know what the ideal shape is for this, though. I do know this gives you the limit. I may come back and solve for some suggestions later...
# The Real Challenge Is Building It
Building that structure is another question entirely. Your ideal balance between speed and structure only works once built. Getting there involves applying a force and having incomplete geometry, which means the structure will need to be load-bearing.
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TLDR: when considering materials and manufacturing methods available to modern humans (bar the scale of course), possibly a few thousand light-years, or the size or a small galaxy.
I'm basing this heavily on an answer to a similar question (How large could a decoy planet made of extruded polystyrene be?): <https://worldbuilding.stackexchange.com/a/138280/29103> The conclusion that answer comes to, for a thin spherical shell, is something like this:
$$R < \frac{P}{\pi T \rho^2 G},$$
where $R$ is the radius of the shell, $T$ its thickness, $\rho$ its density, $P$ its tensile strength, $\pi=\tau/2$ and $G\approx6.6\cdot 10^{-11}\ \mathrm{m^3\ kg^{-1}\ s^{-2}}$ is the gravitational constant.
For EPS and a thickness of 1 m, this comes to $4.71\cdot 10^{11} \ \mathrm{m^2}$, or around 3 AU. It can be easily computed for different materials (e.g. more than 10 times the size for [3D graphene](https://advances.sciencemag.org/content/5/2/eaat6951)); somebody into hi-tech materials could provide the numbers for something extremely strong and lightweight, to give some more numbers.
This formula shows the problem with the "shell theorem" discussion. While you can increase the size by making the shell thinner (e.g. over 0.5 light-year for 1 mm 3D graphene), and in theory you can have as large shell as you want if you keep it infinitely thin, with real materials (made of solid matter) you cannot get under the thickness of 1 molecule. So the particles on the OUTSIDE of the shell WILL be pulled towards the center by the gravity of the rest of the shell. You could "lighten" your shell by making it sparser, or introducing "holes", but the more you do that, the less of a perfect sphere it is, and you'll hit the limits soon.
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The one constraint that is always with you no matter which materials you are using is the gravitational field. Its magnitude is determent by the Gauss' flux theorem for [gravity](https://en.wikipedia.org/wiki/Gauss%27s_law_for_gravity#Relation_to_the_integral_form). Basically it says that the flux through the closed surface is proportional to mass inside this closed surface. Then from this flux considering that the shape of the construction is spherical, one can calculate the gravitational acceleration on the surface(or inside) the construction:
$$\begin{gather}
g(r) = -\frac{GM}{r^2},\ M = \rho V = \rho \frac{4\pi r^3}{3} \\
g(r) = -G\rho \frac{4\pi r}{3}
\end{gather}$$
* $M$: structure's mass
* $\rho$: structure's density
* $V$: structure's volume
* $r$: structure's radius
* $g$: gravitational acceleration.
Knowing the acceleration it is possible to calculate the weight of objects on the surface of the construction. Then it is possible to calculate the pressure of the "upper" structures to "lower" structures:
$$P = \frac{m\_u \cdot g(r\_c)}{S}$$
where
* $P$: pressure from upper structures to lower structures
* $m\_u$: the mass of upper structures
* $r\_c$: the mass center of the upper structure
* $S$: the surface of contact
Then to determent the critical radius of the structure, one should solve the equation with respect to $r$ - structure radius while on the left side is the critical pressure when the weakest construction will collapse. In the spherically symmetric case, the weakest is somewhere low, because it has the most pressure on it.
This approach will provide the upper boundary for the radius depending on the critical pressure of the weakest point of the structure.
For the more precise answer(especially in the form of the number) one needs to find the data for the honeycomb structure and solve the equation.
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Note:
This answer is for more or less habitable hollow structures in space that are at least partially habitable. Uninhabitable structures which are just monuments or artworks floating in space might possibly be larger.
Short Answer:
The place to start researching this question is "Bigger Than Worlds", Larry Niven, *Analog Science Fiction/Science Fact*, March, 1974, which has been reprinted many times.
Long Answer:
One type of hollow structure in space that is often discussed is a hollow cylinder that rotates to simulate gravity in the inner surface.
There are structural limitations to how many miles wide such a structure might be but possibly no structural limitations on how long it could be, or limitations which show up only after it gets very long.
Thus a hollow rotating cylinder in space could be 1 kilometer or mile wide,
or 10 kilometers or miles wide,
or 100 kilometers or miles wide,
or possibly 1,000 kilometers or miles wide.
And that hollow rotating cylinder could be
1 kilometer or mile long,
or 10 kilometers or miles long,
or 100 kilometers or miles long,
or 1,000 kilometers or miles long,
or 10,000 kilometers or miles long,
or 100,000 kilometers or miles long,
or 1,000,000 kilometers or miles long,
or 10,000,000 kilometers or miles long,
or 100,000,000 kilometers or miles long,
or 1,000,000,000 kilometers or miles long,
And so on and so on.
See here:
<https://en.wikipedia.org/wiki/Topopolis> [1](https://en.wikipedia.org/wiki/Topopolis)
And there have been discussions of other types of very large structures in space.
Many far out ideas for vast structures in outer space were discussed by Larry Niven in "Bigger Than Worlds", *Analog Science Fiction/Science Fact*, March, 1974, which has been reprinted many times.
<http://www.isfdb.org/cgi-bin/title.cgi?133302> [2](http://www.isfdb.org/cgi-bin/title.cgi?133302)
<https://en.wikipedia.org/wiki/Bigger_Than_Worlds> [3](https://en.wikipedia.org/wiki/Bigger_Than_Worlds)
And of course that article was published 46 years ago, and there could have been many ideas about mega structures in space and their structural limitations since them.
See also:
<https://tvtropes.org/pmwiki/pmwiki.php/Main/DysonSphere> [4](https://tvtropes.org/pmwiki/pmwiki.php/Main/DysonSphere)
<https://tvtropes.org/pmwiki/pmwiki.php/Literature/Ringworld> [5](https://tvtropes.org/pmwiki/pmwiki.php/Literature/Ringworld)
Note:
This answer is for more or less habitable hollow structures in space that are at least partially habitable. Uninhabitable structures which are just monuments or artworks floating in space might possibly be larger.
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# How many angels can dance on the head of a pin? Answer: As many as wanting.
**Assumption:** The structure is built in intergalactic space.
Now, granted, we don't necessarily know a lot about intergalactic space. For all we know there are swarms of giant space-bees out there. But, insofar as we understand everything right now, the space between galaxies is very empty and the interfering gravitational forces are very small.
Which means we can build a structure out of aluminum beams and tarps from your local hardware store — and it can be at least as large as half the distance to the nearest galaxy.
* The [Shell Theorem](https://en.wikipedia.org/wiki/Shell_theorem) teaches us that gravity is zero inside the shell of an object. That means there's no gravity at all inside a hollow shell. So long as we don't have anything inside like the marble or ball bearing inside a can of spray paint that could bounce around, gain momentum, and eventually rip the thing apart, nothing on the inside can hurt the structure.
* The things on the outside would include moving rocks (asteroids, meteors, rogue planets, streams of intergalactic dust...), gravity (which is intentionally very light and, more or less, statistically balanced in this scenario), and light (which has pressure, but at those distances it ain't very much). I'm banking that none of those have a significant influence.
*It is important to realize that external gravity can cause problems. This structure is obviously humongous and will have considerable gravity — heck, it might have enough gravity to affect all those nearby galaxies. I'm ignoring that because I'm not prepared to calculate the actual mass of the object I'm describing. THAT would be a fair and legitimate limiting factor in the ultimate size of the any such object. (It isn't that outside gravitational influences would be great enough to hurt it, it's that it would draw galaxies into itself, which would be bad.) Let's assume for the sake of argument that the gravitational attraction of our structure must be equal to or less than 1% of the mass of the closest nearby galaxy. That limitation, based on what building materials and techniques are available, would limit the size of the structure and probably (in fact, certainly) force it to be less than the size I've proposed. My thanks to @BThompson for pointing out this deficiency in my answer.*
* I am ruling out alien interference. I'm not being sarcastic, something that big sitting between galaxies is bound to attract attention and there must be *somebody* else out there when we're talking about surrounding galaxies....
I don't have the time to figure out an arbitrary point of intragalactic space and then calculate half the distance to the closest galaxy to provide a precise estimate. I'm not sure it's relevant. The structure could be a whole lot larger than that (if the gravitational forces are small enough), I'm just assuming that at the 50% point that closest galaxy might have enough gravitic influence to start deforming (and eventually destroying) the shell.
But my point is, for all intent and purposes, it's so ginormous that it might as well be considered infinitely large. It's a space that could surround *multiple galaxies* and yet, due to its flimsy nature, would exert so little gravity itself that it wouldn't change (I believe) anything in the universe.
Might be a good place to put the bees, though. :-)
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Assuming you will permit an active structure, as big as you have mass for.
Inside the shell you have spinning bands, they exert an outward force. This balances the inward pressure of the self-gravity of the shell. You can drive the overall force to zero, the only strength required is between supports and if you have enough bands you can drive this as low as you want. Other than the maglev coupling between the bands and the shell you could build it out of tissue paper. (Although it would no doubt be cheaper to use something stronger.)
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Other answers have correctly concluded that rings may be as large as you want in Newtonian gravity. And the speed of light has been mentioned as a limit in relativity. But the true relativistic limit is cosmological: if your ring is bigger than a cluster of galaxies, the expansion of space due to dark energy will stretch it until it breaks. Maybe 10 megaparsecs in size, depending on your local matter density. However, at this scale things happen very slowly: your ring could last billions of years.
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Provided the structure is built as a relatively thin shell it can be arbitrarily large. In a large enough void in space far away from any large gravitational fields, ignoring construction “difficulties” and assuming sufficient mass was available, the structure could be many light years in diameter.
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Imagine a planet that's identical in pretty much every aspect (including Homo Sapiens) to our own current Earth, with only a single exception - the continental crust has, for whatever reason, much less iron in it. What's in the core/mantle is not all that important, as long as it provides the conditions above.
I read that life could develop similarly with very little *mineable* iron ([Can an earth-like world lack mineable iron?](https://worldbuilding.stackexchange.com/questions/102915/can-an-earth-like-world-lack-mineable-iron)) so I'm happy with identical life forms. What I wonder about, is how would human civilisations develop if there were 10 times less iron accessible (with ancient and industrial revolution era technology) than there was in the Earth's actual history.
What would be the major differences? Would iron age happen at all? Would industrial revolution (leaving socio-economic readiness aside) happen at all, or how much later? How would it all change if there was 100 or 1000 times less iron available?
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## You'd barely notice a difference
... mainly because iron is so incomprehensively common.
Iron is about 1000 times as common as copper and 20,000 times as common as tin in the Earth's crust.
SEE: <https://periodictable.com/Properties/A/CrustAbundance.v.html>
So, even with 10-1000 times less of it, iron/steal would still be easy to make in significant amounts. At 10-100 times less common, you would probably not notice much of a difference in our world's history. Steel would be a bit more expensive, but still a pretty universally accessible metal. 1000 times less common, and it would probably extend the period of time where Iron and Bronze were used interchangeably much longer, but not really prevent the use of steel since it is still the better option a lot of the time. Instead of iron replacing broze, you'd just see each used based on when one is better than the other, or when one is more available in your region.
At 10-100 times less common, no industry would be significantly impacted from developing, but some places in the world might be iron scarce. This could affect the balance of power between economies throughout history such that some empires may rise instead of others and from this you could speculate all sorts of butterfly effects, but by in large, there would be enough places to acquire iron in that world that no country would be fully cut off from having it as a readily available resource.
At 1000 times though, you may also start to see the industrial revolution impacted, but not really prevented. There would still be plenty enough steel for mechanized production machines to remain economically viable. So early industrialization like grain mills, textile factories, etc. would still happen. But... things like trains, automobiles, and highrises use a LOT of steel, and this is where you would see the scarcity bottle neck maybe start to affect you. Just like copper started becoming scarce when we decided to wire and pipe up our entire world with the stuff, iron might become scarce if we tried laying down too many railroad tracks, making too many car engines, or making a bunch of steel framed highrises. There would still be enough viable ore to go around to get you started, but you'd often have to go farther to find it which would make it more expensive.
The transportation revolution would seem to be in jeopardy because of this except for a very important discovery that happened in 1888 called the Bayer Process which is where we learned to mass produce aluminium. Aluminium is even more common in the crust than iron; so, the Bayer Process opened up a virtually limitless supply of metal even without abundant steel. By replacing most of our bulk steel with aluminium, the industrial revolution could stay more or less on track. Aluminum, like copper, needs to be alloyed to become comparable to steel in strength, but instead of needing something rare like tin, it normally alloys with trace amounts of magnesium, silicon, and/or zinc which were all easily isolated elements by 1888; so, by the time the automotive and high-rise structure industries really starts to take off enough for steel supplies to be a problem, we'd already have enough enough access to aluminium alloys to pretty much replace steel even at very large scales.
The bottle neck would be cost, new aluminum costs about 3x as much as steel per pound to refine but is twice as strong for its weight. This would make things like sky scrapers much more expensive at first because you would need a similar weight of aluminum as steel to hold up the weight of all that concrete, but things like automobiles would be less affected because you are only engineering to the weight of chase. Either way, the cost of aluminum would cause an initial adoption issue for a few years, but would not stay a lot more expensive for long.
Aluminum is much cheaper to recycle, form, and transport than it is to refine. So, recycled aluminum products are only about 1/2 the cost of steel; so, as your civilization starts to have enough old stock to blend with the new stock, the cost of aluminum will drop to prices that could be comparable to steel today.
All this would really mean for anyone today is that cars would be a bit more expensive maybe making public transportation a bit more common and high rises would also not be as high. But on the surface, society and our history would still be pretty recognizable.
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Ten times less iron would make iron more valuable but overall many things would look similar. Iron is very common. But if we assume iron is made *scarce* by these changes, then the world does begin to look different.
## Brass, Bronze, and various formulations would largely replace iron
While Iron is more generally useful than bronze and copper and so on, there are still smithing and smelting techniques that can improve the qualities of other metals beyond the level it is generally assumed the bronze age sat at (especially considering many issues with various bronzes were caused by lack of tin or proper equipment).
However even so, the relative advantage of these metals is lower - they are rarer, and harder to produce - so wooden or even stone weapons would not be considered quite so primitive. Clubs and maces would potentially be more common, and more warriors might go armourless. Simple tools that rely on size or force might be still used alongside smaller metal tools that rely on hardness.
## Skilled woodcrafting and wood treatment would be used in large-scale constructions and everyday goods for longer
While in many cases iron replaced wood for use in household items and such, the relative higher scarcity of copper would likely mean that things like lanterns or shutters, latches, locks etc would use treated hardwoods more often rather than metal. Likewise, lacquering would probably be more popular, as well as using high-labour cost expensive but tough fabrics.
Supply issues, technological issues, and social issues led some areas of Asia (notably japan but also many pacific islands, korea) to reserve iron for warlike uses and use more of other materials in construction and household goods - those are good references for the kind of workarounds in pottery, stone, cloth, and timber that humans will use when they don't have iron to spare.
## Good steel would be more of a semi-mythical metal than an everyday item
How to make good steel was non-obvious. It took a very long time of constant and widespread use for people to figure out how to create stronger iron. If iron was rarer, there would be less opportunity for that kind of development - however, if it was rare, perhaps more effort would be spent on refining it (iron was largely improved when people figured out safe techniques to *cheaply* improve its quality - there were very labour intensive methods to improve the quality but those were typically only used to produce luxury items aimed at the upper class) resulting in a kind of 'damascus steel' where a labour-intensive (and secret) method is used to make good quality iron or steel. A well-made steel sword would give an immense advantage in a fight over a bronze sword or a club, as would steel armour over (heavier and usually not stronger) bronze, leather or wooden armour.
There would potentially be religious or social rules over the use of iron or steel, which did exist in some areas of the globe, but to a greater extent due to the rarity than existed in our world.
## Industrialization would proceed significantly slower
Methods to produce strong materials that are not based on iron do exist but are often more difficult in terms of mass production. They rely on harder-to-produce raw materials and/or processing methods that take longer or require more complex factories and machinery that were produced later in the industrial revolution than industrial furnaces/smelteries and in many cases were powered by or relied upon iron equipment that would be more expensive to reproduce in bronze, wood, or stone.
## The discovery and utilization of aluminium would be a far bigger deal
Although it is actually quite hard to get a usable metal aluminium out of naturally occurring minerals, in an iron-poor world having a sudden source of an abundant and useful metal would be absolutely game-changing and potentially kick off a harder and faster industrial age than had existed previously.
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Although clearly less available than today, even at one thousandth the quantity we have there might still be substantial ore available because there is so much of it.
This might mean it was available to some nations and not others and it might run low before the iron age took off. But assuming a worse case situation where iron is not available in concentrated form any more It would change the course of history. The Bronze Age would last longer and instead of an iron age there would have been a nickel age or similar.
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Many civilisations have developed with little to no iron. Maoris, for one. You would get a lot of fishing, wooden boats, sails etc but nothing very strong or long-lasting. Everything would need to be created multiple times and constantly repaired.
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[
So I've got this civilization that doesn't have electricity, but *does* have municipal power distribution via compressed air lines.
Now, you can do a lot of useful things with compressed air. Even in the real world, compressed-air tools are fairly common. You can even use it for heating, via vortex tubes (not terribly efficient) or heat pumps (much more efficient), although suggestions for better ways of providing heat via compressed air would be appreciated.
But what I can't figure out is, is there any way practical way to produce *light* directly from compressed air power? Or are these people just going to be stuck using Victorian-style gas lamps, with separate municipal supplies for compressed air and natural gas?
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**Compression heats things up.**
Compressed air gets hot. The compression of air in the cylinder of a Diesel engine is used to heat the fuel to ignition. The King of Random here made a clear acrylic "slam rod" fire starter. When he slams down the piston and compresses the gas, it gets hot enough to cause the piece of char cloth tinder he has in there to glow. It is really excellent.
<https://www.youtube.com/watch?v=SkWJdWGdgaM>
[](https://i.stack.imgur.com/MDmmy.jpg)
Compressed air piped in already got hot wherever the factory is, and so when you let it decompress it will get cold. But if you use it locally to compress room temperature atmospheric pressure air, that air will get hot.
In the screenshot, the glow is because the char cloth tinder in there is superheated by the hot compressed gas. It glows so hot it catches fire (and you will see in the video it is just then a little cinder) But it is cheating to just have light from burning stuff - that is a torch. How to use the heat of compression to make something glow without burning? Can we just keep it glowing like that?
If you heat something up in the absence of oxygen, it will glow but not burn. This is how incandescent light bulbs work: the filament inside is heated by an electrical current passing through it and it glows.
Depicted: [carbon filament incandescent bulb](https://en.wikipedia.org/wiki/Incandescent_light_bulb#Dominance_of_carbon_filament_and_vacuum).
[](https://i.stack.imgur.com/a7xbZ.jpg)
Some incandescent bulbs are full of vacuum. Others are full of inert gas - like noble gases or nitrogen. The reason: without oxygen the filament will not burn up, but will just keep glowing.
What if there were a device like the King's slam rod that was repeatedly and rapidly compressed - basically imagine a clear 4 cylinder Diesel engine. The difference: the compressed gas does not contain oxygen. Nitrogen gets just as hot on compression but will not sustain combustion. A piece of carbon in the cylinder will not burn up. It will heat up and glow, just like when he hit the cylinder.
The lighting apparatus working on this principle will have multiple clear / durable cylinders in a row, driven by a compressed air powered drive shaft. The element on the piston in each is heated to glowing by the repeatedly compressed nitrogen. The gentle glow lights the room.
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[](https://i.stack.imgur.com/uNsef.jpg)
Flint and steel mills introduced by Carlisle Spedding (1696-1755). A steel disk was rotated at high speed by a crank mechanism. Pressing a flint against the disk produced a shower of sparks and dim illumination. These mills were troublesome to use and were often worked by a boy, whose only task was to provide light for a group of miners.
They were used because inventor hoped that flint sparks would not ignite mine gas (he was wrong).
Use a small compressed air powered engine to rotate this and you would get light.
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I do not like the premise that light requires heat. Must it be so?
Consider neon light bulbs.
[](https://i.stack.imgur.com/LNIYe.jpg)
from <http://www.instructables.com/id/Static-discharge-toy/>
A neon bulb contains low pressure neon and is lit by an electrical discharge across it. A static charge caused by persons shuffling their feet across dry carpet will suffice.
Yes, this society lacks electricity. I take this to mean they lack generators, dynamos, motors, electric lights and electrical transmission: current electricity.
[Static electricity](https://en.wikipedia.org/wiki/Static_electricity), however, is a different animal.
Thales of Miletus discovered and described the generation of static charges, which he produced by rubbing amber on fur - this in 585 BC. Here is a stamp celebrating Thales and his discovery.
[](https://i.stack.imgur.com/M0UNE.jpg)
So a light without heat:
This society with experience using pressurized gas should not have trouble making a bulb which can contain low pressure neon (or other handy noble gas). A turning wheel powered by compressed air or at the site of the bulbs generates a static charge ([an electrostatic generator](https://en.wikipedia.org/wiki/Electrostatic_generator)), which is allowed to go to ground through the bulbs.
I see that a static electricity generator (like rubbing the bulb with a sweater) can also be used to light fluorescent bulbs: this too without current electricity and without an excess of heat.
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# Light requires high temperatures
The problem with generating light is that you need really high temperatures to do so. The excited air that is light-emitting in a candle or campfire is around 1000 C. Light bulb filaments are in the range of 2500 C.
The issue with these kinds of temperatures is that they are hard to contain. For a fire there are obviously some precautions that must be taken to keep things that are flammable away form the fire. But neither torch nor candle nor lantern require any complex mechanisms for handling the 'fuel' the way that any sort of mechanism involving compressed air will.
1000 C is pretty hot. For example, stainless steels (except the very expensive types) are [not rated to 1000 C](http://www.ssina.com/composition/temperature.html) for intermittent use. Surely there are materials that can handle such temperatures routinely, but they are expensive and hard to come by; commonplace metals simply can't handle repeated cycling at that temperature.
# Grid distribution of compressed air has a high cost
You simply can't send compressed air that far without losing most of the pressure. When I imagine high pressure air, I am thinking in Navy terms with 3000 psi systems. This is equivalent to 20 MPA or aboout 200 atms. At this rate, with a 1" (25 mm) piping and 10 m$^3$/min of flow, you [will lose](https://www.engineeringtoolbox.com/pressure-drop-compressed-air-pipes-d_852.html) about 0.04 psi to the meter. Run a kilometer of pipe and you lose 40 psi. That will quickly add up; and note that 1 " piping is huge; much larger than anything we see in the Navy.
I strongly doubt that a compressed air generating station would be able to provide compressed air to even a medium sized city. A big city would need dozens of stations to provide satisfactory pressure.
# Conclusion
Using compressed air to run a factory seems legitimate. Residential distribution of compressed air does not seem practical, and using that to generate light has significant materials hurdles. Any civilization able to create the necessary materials should probably already have discovered electricity.
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Well in looking for an answer I found this very applicable Wikipedia page:
<https://en.wikipedia.org/wiki/List_of_light_sources>
Some useful ones:
Biological or chemical reactions, which could be controlled by altering the supply of air into a sealed container. Basically something like a glow stick.
[](https://i.stack.imgur.com/EsPx9.jpg)
Triboluminescence - mechanical action breaking chemical bonds can release light, usually involving breaking crystals. Sugar responds this way, which is what makes [biting winter green life savers in the dark](https://recipes.howstuffworks.com/question505.htm) spark. Similarly quartz crystal will do the same thing, the [Ute Indians](https://en.wikipedia.org/wiki/Triboluminescence#Uncompahgre_Ute_Indians) made leather shakers filled with quarts pieces that when shaken would show sparking visible at night. Most of these reactions are not very bright.
[Argon Flash](https://en.wikipedia.org/wiki/Argon_flash) - Similar to heating causing things to emit light, heated noble gases, like Argon, will release a very intense light. Rapidly compressing it can be used to heat it, normally this is done with a small explosive charge. A well designed compression device could possibly do this repeatedly.
Any of the methods that produce a short intense light source could be made more useful by surrounding it with a material to absorb the light and reemit it over a longer period of time or a different wavelength, something like [Florescence](https://en.wikipedia.org/wiki/Fluorescence) or [Phosphorescence](https://en.wikipedia.org/wiki/Phosphorescence).
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There may be another possibility, albeit very complicated and inefficient: Gas dynamic Lasers. With the right gases, an expanding nozzle, and a resonant cavity and optics you can actually attain population inversion by the expansion of those gases. The efficiency is about 30%, (good for a laser actually), but the light obtained is typically in the infrared range for common gas mixtures like CO2 and nitrogen, so you ought to use that light to heat up a filament or excite some chemical substance or crystal to produce visible light, so there is likely going to be a loss of energy in this step too. Considering incandescent lightbulbs are averagely 5% efficient, maybe there is some way to make this system feasible.
<https://en.wikipedia.org/wiki/Gas_dynamic_laser>
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Here a "compressed-air-powered-bio-light" which may be possible but I don't think that anyone has done it yet.
* The compressed air is used to pump water and make water pressure.
* The water pressure is used on a semipermeable biomembrane.
* The membrance contains ion channels which are powered by the ions following the pressed water through the membrane.
* The ion channel produces some energy container (ATP?)
* The energy container powers bioluminescence and there will be light.
* Water and Ions may be "recycled".
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I like this question and I think I have a smart solution utilising the above mentioned flint mill. Imagine if you will a small glass jar around 6 inches in height and roughly 6 inches across, within it is a small paddle with steel fingers, let’s say there are 4 paddles in a cross pattern and each paddle has 6 fingers but are staggered so the gaps of one paddle are where the fingers are on the next one, alternating on each paddle. 2 strips of flint are in the jar on each side, perhaps glued to the side or mounted on some sort of cushioning to keep tension on the fingers when they are passed over it. The jar could be screwed into a socket on the ceiling which has a small turbine in the housing so as the air is pushed past the fins the steel paddles are spun against the 2 flint rods creating a shower of sparks contained within the glass jar, they could be easily changed by simply unscrewing the jar, they could be dimmed by spinning it slower and would create a neat way for people in your town to make an income by coming and emptying these jars of the blackened flint remnants. Admittedly they wouldn’t last long but they would be cheap to replace or they could be expensive to replace and a house with bright lights could be seen as wealthy across the city.
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The slam rod must contain some combustible material that starts the fire. The air generates heat only upon compression. All heat will dissipate through the pipes once compressed air is generated and transported. A possible way is that a compressor will compress air locally inside a metal pipe. The compression ratio must be high enough to heat the pipe until it glows like an incadescant lamp. There are two drawbacks:
1- The compressor runs on compressed air, so in reality it must compress air into a tube with a thin inner diameter. So, it uses lts source of air to power a lamp by compressing a smaller volume of air.
2- The tube must be sturdy enough to withstand high pressure even when hot, so it must have a thick wall...
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What about a crank flashlight like what preppers keep in their bug out bags , the faster you crank the handle the brighter the light shines. It must have some type of magneto in it. Now instead of cranking it by hand what if you integrated it into your pneumatic system and have the air pressure crank it for you , the more pressure supplied the faster it would crank and the brighter the light would glow.
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[Wind instruments](https://en.wikipedia.org/wiki/Wind_instrument)--such as flutes, [panpipes](https://en.wikipedia.org/wiki/Pan_flute), and even [glass bottles](https://www.youtube.com/watch?v=2o8ZnG19rV4)--are able to create sounds due to air being blown over the top of or into an opening on a given instrument. This is largely possible because humans are able to form the correct [embouchure](https://en.wikipedia.org/wiki/Embouchure) with their cheeks and lips, allowing for a steady stream of air and an overall clearer, fuller sound. A creature with a snout, however, lacks these traits and would not be able to make sounds with our wind instruments, instead opting to create their own.
My question, then, is whether it would be possible for a race with snouts to create wind instruments, and if so, how these would work?
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**Fipples**
Other answers have mentioned fippled flutes, otherwise known as whistles, where an unshaped stream of air is blown over a shaped piece of material (bone, wood, ceramic, metal, etc). The player provides the air, but has very limited ability to shape the tone because it's produced by the fipple. Recorders, native american flutes, organs, and Irish whistles are all examples of fippled wind instruments.
**Would a snout really stop them?**
I'm not convinced that a snout would truly prevent a traditional flute, as long as the creature had sufficient control over the shape of their mouth. A flautist makes a very small hole in the lips to blow a focused stream of air over the flute's chimney. If the whole mouth was open, a human would have nearly as much difficulty as an animal with a snout whose mouth was open. This is true playing both transverse flutes like the westen classical flute or upright flutes like the panpipes. If your creatures communicate verbally, they're likely to have a similar level of control as humans, even with a snout. Whether they can play a wind instrument will depend on their facial musculature more than the shape of their mouth.
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Everyone1 in the UK grew up with the plastic descant recorder and the horrible noises made when these tortured instruments were handed out to a primary school class.
Why the descant recorder though?
For two basic reasons
1. It's cheap
2. Embouchure doesn't matter, it'll make a noise
The total lack of consideration for embouchure by the average child is compensated for by the shape of the mouthpiece. The shrieks emitted from these poor instruments merely a function of how hard said child blew down it.
While this particular instrument may not be ideal for your situation, the basic principle of design would certainly be transferable.
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1 *For a given value of everyone*
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Probably something like how a whistle works, where the air enters a chamber, goes through a windway, and then over the mouth opening:
[](https://i.stack.imgur.com/FmDia.gif)
If the windway was shaped similar to how human lips form the air then you could get a pretty consistent flow and sound.
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They might use their nostrils. I have a friend who can play a regular flute with her nose, there's no reason your snouted creatures would not be able to play an instrument specifically created to be played this way.
Also, if your creatures have such a hard time plying wind instruments, they might simply never invent them or the instruments might never become popular.
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A bagpipe could work. The bag itself is what supplies the air to the chanter (melody pipe) and drones. The mouthpiece is just used to keep the bag filled, and there are pipes that use a bellows instead of needing the player to supply the wind.
A simple bagpipe with a single chanter and no drones could sound very similar to a clarinet, though with a constant tone throughout the performance.
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The answers already given regarding fipple flutes (recorders, whistles, etc) and bagpipes are excellent, but there might be more options.
Most woodwind instruments depend on the position and tension of the lips (the "embouchure") to control the speed and direction of the air column and the vibration of the reed. It might be possible to exert similar control by using hand1 pressure; imagine a rubber tube, say, coming from the player's snout and stretched over the mouthpiece of a clarinet. The player could then wrap their fingers1 around the mouthpiece and apply pressure to control the reed.
You might be able to manage a transverse flute or a brass instrument in a similar way, but I suspect the results would be better with reeds.
1*For sufficient values of "hand" and "finger"*
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They would place a bag over their snout enabling them to blow into their instrument despite the obstacle of their snout
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"Have a snout" is too general to give a good answer. You have to know how well this race can direct/manipulate a stream of air before you can wonder which kinds of wind instruments they could use. The more control it has, the larger the range of instruments it can play.
Wind instruments are instruments where the sound comes from agitating a column of air. This agitation can be done by the vibrating lips of the player (brass instruments -- even if the instrument is made from wood), or because air is blown over or against something (a reed for instance) which makes the air vibrate.
But this can also be done indirectly, or mechanically. A bagpipe player only uses his/her month to pressurize a bag (and to keep it pressurized). The bag is then squeezed causing the chanter and drones to create a sound. Pipe and pump (or reed) organs use pumps to blow air into pipes, no mouth required. Squeezeboxes use bellows to vibrate framed reeds. And then there are the mechanical organs, which are either hand cranked or machine driven, and which use music books, barrels or rolls to direct air flow to pipes.
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In a setting I am presently working on, I have envisioned a world similar to [](https://i.stack.imgur.com/FccjM.jpg) Star Wars' Takodana, in that its water is mainly in the form of large rivers, or smaller seas (I generally picture it being all rivers, unlike this picture; but I'm flexible). See also; [Takodana's surface](http://vignette3.wikia.nocookie.net/starwars/images/a/ae/Takodana_surface_1.png/revision/latest?cb=20160416023739 "Takodana's surface").
**How realistic is this?**
Fleshing out the question-
* Would water erosion processes allow for all of the water to be separated, rather than being in an enormous, consolidated ocean that spans the world?
* Could high geologic activity provide the necessary variance in altitude, or would that be in the benefit of oceans forming?
* Would mesas be a prevalent feature in this landscape, or just hills and plains (as pictured [here](http://vignette3.wikia.nocookie.net/starwars/images/a/ae/Takodana_surface_1.png/revision/latest?cb=20160416023739 "Takodana's surface"))?
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I think the current answers are all thinking of a very Earth like planet, including its orbit around its star.
As others have said, rivers have to flow somewhere, so your world would be more like full of seas or lakes than rivers.
How about we change things a little and have your planet orbit another, much more massive planet, such as a gas giant?
Get the giant in an orbit around a yellow star like our sun, and your planet will have as much sunlight as we do (though the gas giant may make for really interesting eclipses).
I am including the gas giant here because it will have tidal effects on the planet, much like the Moon does to Earth, but on a larger scale. Water will be pulled with extreme force towards the gas giant on the side that faces it, and away from the gas giant on the other side.
Now, if your planet is [tidally locked](https://en.wikipedia.org/wiki/Tidal_locking), that water will be pretty much stuck. If not, your rivers will be pretty interesting, in that they will perpetually be running - but not necessarily towards the sea!
**Huge edit** @shufflepants has called my attention to the fact that the rivers wouldn't reverse their flow twice a day as I expected. So I am striking the previous text for this part of the answer, and including a couple scenarios that more probable, though still quite exciting.
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In one scenario, your rivers could simple go around the world. On your planet, water will try to settle in the lowest places just like here on Earth. But there is no ocean, because there isn't a sea much below the river beds. Instead, the motive force behind the flow of the rivers are the tides. The tides will follow the gas giant, and the rivers will follow the tides. The interesting part is that this means the margins of the rivers will change within the course of a day. Some parts of the river may only be crossable by boat on the high tide, and may be crossable by foot on the lower tide.
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Or, your planet could have oceans much like the earth. If it does, another interesting effect happens. You see, rivers end up in the oceans because usually they are more elevated than the sea. But during high tides, the water level on the sea may be higher, and the sea will go into rivers. When this happens on large rivers on Earth, the effects may be pretty... cinematographic, to say the least. In the Amazon river, the flow of the river is reversed in a five hundred miles strech starting where it meets the sea. Salt water enters the river in the form of waves that can be 12-feet tall at some points. [This is what it looks like](https://youtu.be/s6QLlaswADQ?t=1m30s). You can surf on a single wave for more than half an hour!
This is technically called a tidal bore. There are dozens other places on Earth where this phenomenon happens. So you could just imagine that your world is an extrapolation of this, with these waves happening at least once a day for rivers that are to the east of an ocean (supposing your planet goes around the gas giant in the same way Earth goes around the Sun).
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Both scenarios would give your planet interesting seasons. When the gas giant and the Sun rise together on the sky, or when the Sun and the gas giant are in opposite directions, the water of the high tide will be at its hottest ("tidal summer"?). But when they have a difference of 90°, you get the coldest high tide ("tidal winter"?)
As for geography of landmasses, it's up to you:
* If the soil is very hard this movement of the rivers may act as a saw, digging ever deeper canyons on the land. So in high tides you get crossable rivers, but on the low tides you get deep ridges or fjords according to your worldbuilding taste.
* If the soil is soft and will take the movement of the water, you can either have rolling hills or plains that get flooded in interesting patterns, or you can have places that look like tropical islands at high tide but look like deserts on the low tide.
You can also define how fast the water comes and goes... Depending on the force of the pull of the gas giant, the water may come slowly, or it may come like a tsunami (not very friendly to intelligent, surface dwelling life, though).
Also remember that your planet can have as many varied geographical features as real Earth does! You can mix all of the scenarios described above as you like.
One last thing, since I'm trying to be scientifically accurate here... Planets subjected to such tidal forces suffer from a special kind of geological effect because they are constantly being stretched in the directions towards and away from their "parent" planet. It is believed that [this is what drives volcanism on Io](https://en.wikipedia.org/wiki/Volcanology_of_Io#Heat_source) (the most volcanically active place in the solar system). So your planet may be very active geologically too, if you want it to!
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This is definitely realistic. What's actually interesting about this is that several of the issues you bring up sort of resolve each other. I'll go through them one by one.
In order to have this happen, you would need less water on the planet than Earth does. So right off the bat, even if you had an enormous consolidated ocean it would be smaller than the oceans of Earth. So right off the bat, you're going to be having less of an effect from erosion. Coupled with evidence from Earth, namely the Caspian Sea - which is completely landlocked - it's quite possible to keep the water separated.
There probably wouldn't be too much geologic activity. We currently think that [large amounts of water are necessary for plate tectonics](https://www.quora.com/Why-is-liquid-water-necessary-for-plate-tectonics), that the plates formed by oceans leaving sediment until eventually the weight cracked Earth's crust. Since we don't have large oceans on your world, no plate tectonics, so less geologic activity.
Similarly, since we don't have very much geologic activity, there probably won't be mesas. Mesas [are formed through eroding rocks uplifted by tectonic activity](https://en.wikipedia.org/wiki/Mesa#Formation), so there would be fewer than on Earth, if any at all.
**Speculation:** One way I can see a planet like this developing is experiencing asteroid/meteorite impacts more frequently than Earth did. The way I see it, this would cause the planet to take longer to cool, meaning that the increased number of impacts would ultimately lead to a more pockmarked surface. When the planet does cool enough that liquid water can begin to build up, the craters would then become small seas. (Don't quote me on this part though, as I'm certainly no expert on planetary formation - I'm just extrapolating off what I know.)
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The major issue I see is that rivers are flowing bodies of water. If the world was composed primarily of rivers and river systems, to where would all of that water be flowing? When the water reached its destination, what force would make it continue flowing? Gravity generally only works downhill, so I think to make a river world possible, it would have to extremely flat, effectively turning the rivers into canals.
Now, if a planet were incredibly massive, the gravity of such a planet may act to keep the planet flat (but flat enough, who knows?) For @John Robinson's idea of continued bombardment delaying the cooling to have an effect, the planet would have to have little to no atmosphere, creating an issue for the formation of life as we know it.
But an interesting thought I had is that the planet only has to **be** flat. That doesn't mean that it has to have been formed that way. Arguably, a sufficiently advanced (and motivated) society could flatten a world (realistically speaking, a smaller world than Earth) on purpose. Reasons for such a super-task might be the allocation of water to all parts of the globe/ populations; the facilitation of marine-based travel (the preferred mode of travel other than by foot for most of human-history); or self-preservation reasons like to control [El Niño](https://en.wikipedia.org/wiki/El_Ni%C3%B1o)-type storm effects from a heating and cooling ocean, or to alter the planet's [albedo](https://en.wikipedia.org/wiki/Albedo) for various reasons.
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Water erodes the land. Weather erodes the mountains, in general. Eventually this landform will flatten out. So, you need some geological mechanism to uplift the land with history that allows for the specific form that erodes into lots of rivers separated by harder rock.
It will be temporary, and probably only on part of the planet. Do you want it to be a *common* thing, with new such regions forming after old ones erode away? Or is it a one-time episode?
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You are showing a planet with massive lakes, consider the scale of the water features. Zoom out on google maps and see what water features we have that are on the same scale. Massive inland seas and the great lakes, not rivers.
So what you have is a fairly flat surface with few mountain ranges or evidence of tectonic activity, but still a fair amount of surface water. Perhaps the planet underwent planetary bombardment in the distant past which leveled the surface into a more uniform height (still lots of local elevation changes, but nothing like the deep sea to continental plateau elevations we have on earth). All the water on the planet was vaporized and re-condensed, raining down and being distributed in valleys.
These smaller "seas" can communicate with each other to some degree, circulation is primarily due to evaporation and rainfall. Without giant oceans and high mountain ranges, the surface of the planet is more uniform so weather patterns will be quite different (no sea currents to distribute temperatures, for example, or mountain ranges to stop rainfall). So the planet will have to be in a VERY sweet "goldilocks" zone to not freeze (an ice age will definitely carve up the terrain) or boil, thus it will probably be pretty tropical. Could even have a "tumbling" orbit so there are no polar regions and every part of the surface gets roughly the same amount of solar radiation to add to the uniformity of the entire surface (or perhaps a binary star system?).
Obviously this is not likely to be a "natural" planet, but one that saw intelligent intervention in the past that allowed it to develop life despite the circumstances that cause it to be a "river world" when seen from orbit.
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Today you hear [allot](http://www.thefreedictionary.com/allot) of people talking about loophole abuse and ways to meet the letter of a law without the spirit of it.
In truth as I understand it that isn't always the case, and common law already has a good degree of concepts that are designed to avoid blatant exploiting of loophole or adherence to letter of the law beyond reason or fairness. For instance a contract that was patently unfair to one side,which is signed under duress, or is designed to prevent someone from understanding what they were agreeing to will often be nullified by the courts as clearly not keeping with the spirit of a fair agreement (through various different common law concepts).
However, I'm wondering about a world that took this a step further, where their culture and society puts a heavy emphasis on spirit of agreement and does not approve of loophole abuse in any format; and the legal system is built around this cultural belief. I want to create a legal system that prioritizes the spirit of the law in addition to the explicit letter of the law wherever possible, while still being a viable and fair system.
To give an example, and I'm not necessarily committed to this example...
Imagine a situation where laws had two parts, a spelling out of the actual law and rules as exist now, and a second step describing spirit and intent of the rule, why it was written and what it is desired to do and not do. At a later date in addition to traditional legal augments and appeal process there is a separate way to argue that someone is in violation of the letter of the law, but not the spirit. An appeal may propagate up through the court in much the same way we have now to argue rather the laws spirit is violated by finding someone guilty.
Similarly, someone may have some way to draw the courts attention to loophole abuse where someone is not in violation of the technical law, but in violation of the spirit of the law. This can lead to a court case and prosecution as well. Presumably punishments for violating the spirit of a law would be less severe then the letter of the law, and be based partially off of the severity of the violation of the spirit.
In cases where an entity is not certain rather a decision is violation of spirit of the law will have a way to petition the court for a decision prior to acting in given manner. Those that petition the court and don't get a ruling are generally treated very favorably if their later seen as violating spirit on the presumption that they were acting in good faith.
Any ruling on spirit of a law will become a precedent that affect future laws as with current rulings.
In effect this is not too far away from common law now, particularly common law as it applies to personal individuals interaction (contracts between individuals and the like). However, I'm looking at simply expanding the idea by including more detail on spirit and intent of the law when a law is written. I also want to expand it further into areas where statutory law is more common in modern legal systems.
To give an example, say you have a law that says that sex with a minor is punishable by some penalty; I think we all mostly agree with this. In my system part of the law would explain the intent, the emotional harm of adults forcing children, how children feel the need to listen to adults make them easily susceptible, and how children may not understand sex and sexuality enough to make an informed decision etc etc.
Later two individuals, both minors of approximately the same age, choose to have sex without being compelled and are caught. Both minors have had sex with a minor, which means both have violated the letter of the law. However, the spirit of the law was written in such a way to make it clear that the intent was to protect minors from being compelled by adults, which did not happen. A ruling may find them technically in violation of the law, but not in violation of the spirit since the harm the law was trying to avoid does not apply here. This becomes a precedent which applies to other minors of similar age in the future. Later you may have situations such as a 17 year 11 month old man having sex with a 18 year 0 month old women and find it technically violating the law, since one is under 18, but argue the spirit does not apply. Further ruling on more complex situations will help to cover any similar ambiguities over time.
My question is how could a system like this be developed such that it works. Which is to say that the spirit of law is considered, but we don't bog down society with a million people all claiming their case fits the spirit of the law. Or, the harder to imagine, how to reliable handle situations where someone abides by the letter of the law and later is found guilty of the spirit without creating a situation that is unfair or leaves people afraid of always being found guilty of a spirit violation while acting in good faith.
Can society move much further towards a legal system with spirit of the law as a key tenant that is still consistent and fair, or is the concept of 'spirit' too ambiguous and thus too prone to someone finding out they violated a law without knowing it? Are there legal rules we could set to help address situations where one is found guilty of spirit of a law that will still be fair to them?
In addition if a society very culture was built along spirit of a law how will it handle appeals. Finding someone guilty of a law and later setting them free on appeal due to finding that finding them guilty is not within the spirit of the law seems viable, but that would imply the person being in jail until the appeal goes through; and a culture that had spirit of a law ingrained into it may be offended that someone would have to spend time in jail while we 'proved' they were acting in keeping with the spirit of a law. Can a more responsive system be developed, that considers spirit of the law from the begging, exist without leading to an overwhelmed court where everyone argues they are in keeping with spirit?
While I welcome arguments that this simply can't be done I am looking for ways to make it happen. I'm open to a system that still is close to ours with strict rules, and with only certain avenues for handling spirit of a law ruling, if that is the only approach that seems viable; but I appreciate a best attempt at suggesting how legal system could be developed to consider spirit in any manner while still being viable for large first world country governance.
Edit: to clarify I do not need an all or nothing approach. I'm okay with objective laws without 'spirit' clauses existing in some cases, and suspect they must. My question is how can a realistic society focus more on spirit of the law then current systems; that does not require throwing out all objective rulings or making everything based purely off of legal intent. It may be the only viable system is only a minor tweak from our current system, and that is a sufficient answer.
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This is actually really easy to visualize. **Take a look at the US judicial system: it's the system you are looking at.** The legislature passes laws, and the judicial branch builds up a history of cases forming precedent for how to interpret the laws.
**That's not what you're looking for?** I figured as much, but it seemed like as good of a starting point as any. My suggestion fits the letter of your question, but not your spirit! Lets dig further, shall we?
The single biggest factor preventing US law from becoming what you want is the fanatical obsession with "equality" and "objectivity." Such objective words are an anathema for "spirit of the law" thinking. **If the spirit of the law could be captured in objective terms, then we would have no need for it -- the letter of the law would suffice.** If we want to have more attention drawn to the spirit of the law, we need more power taken out of the law and put... elsewhere. This brings up the key question: who judges according to the spirit of the law. I will assume there is a judge, trained in such matters, but I think there's room for more open solutions like a jury of peers (assuming you can inspire enough conscious thought in the average citizen to make a collection of them worth of being called a good judge of law). **Regardless, there will be an entity (which I will call a Judge), which will need great latitude in its decision making capacity.**
One class of Judges which meet our needs are the Magistrates. Not only do they decide guilty or innocent, but they have power to pass sentence at the same time. Not dividing this power in two gives the Magistrate great power to do brilliant sentencing. From one book I read, *The Diamond Age: or a Young Lady's Primer*, they had a sentencing by a magistrate for "100 lashes, 99 suspended," with some clever requirements placed on the suspended sentence. If a separate entity, such as a jury, had to decide guilt, and a judge proscribed punishment, it would be harder for the jury to *trust* the judge to be fair.
So those are some pieces. How about we dig deep down into what a judicial system *is*, and see if we can pull some more details from that. **The fundamental assumption that can be had with any judicial system, especially one based on the spirit of the law, is that there is a disagreement between two or more parties.** This is important because it points out that judicial systems crop up on the sharpest edge of society. On one side, everyone is behaving in accord. On the other side, there are disagreements which are so irreconcilable that you need a force of law.
I think the application of this is important for your "spirit of the law" approach. The judicial system is literally acting as the power of the nation pressing downward to resolve conflict that requires more force than can be applied in smaller doses. The "feel" of that force is important. If it feels like a sword, you will end up with King Solomon's law, threatening to slice the child in half to resolve a dispute. If it feels like a bunch of cogs whirling, you can expect to find a class of individuals who have practice in aligning those cogs to reach a desired verdict (we call these "lawyers" in our world).
Clearly some tasks have different needs of force than others. A divorce settlement needs more loving care than a murder trial, which calls for more exacting justice. We need a smooth gradient. However, it is often hard to determine what severity to use at the start of a proceedings. If one likes the concept of "innocent until proven guilty" then we need to start all proceedings as "soft" and work our way up to "hard."
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So I think that's enough backstory. I think it's time to start cracking on what such a system will look like. **Fundamental to this system is the assumption that if, at any time, one side's argument feels objective, without any subjective component to it, it may be cordoned off and resolved objectively, according to the letter of the law. Any argument that wishes to be heard for longer than that *must* retain some subjective disagreement for the proceedings to resolve.** Our system certainly has that in many places, but this behavior will be more noticeable here.
To adapt to levels of severity, a pyramidal structure will be stood up, similar in shape to the US system of courts, but with very different behaviors. The pyramid starts very wide, but exponentially gets narrower as it approaches the more severe parts (the actual rate of narrowing would depend on the culture).
Now for the primary difference: **the court never issues objective rulings on any subjective disagreement.** This is very different from our courts, where guilty and innocent are objective terms that are part of the court's duties. When entering the legal system, each side (or all sides, in the case of 3 or more parties) enters an argument, containing subjective content. From this point on, court is in session until the issue is resolved. The courts can do one of four actions
1. If both sides agree upon any objective facts, the courts may act upon them objectively. For example, if there is an argument about a theft, where the items stolen is disagreed upon, the court may assign punishment based on a stolen necklace that both sides agree was stolen while simultaneously continuing to explore the disputed question of whether the $500 stolen at the same time was actually the property of the thief or not.
2. If there is disagreement about objective facts, the court usually may take no action. Sorry, no dice. This courtroom does not arbitrarily declare guilt or innocence based on evidence. It calls for agreement. (Sound impossible in a murder trial? The "harder" courts can make your life miserable *during* the proceedings, to get you to confess. The question of "duress" is only offset by the expectation that these high judges who would do such a thing are some of the most civil and conscious judicial minds on the planet, and are expected to use their power in kind. Also, see the discussion of "scaffolding" later, which can be used to retrain judges which are too trigger happy).
3. If both sides agree upon any subjective statements, they may "go in peace," and such subjective claims are deemed closed.
4. If there is disagreement upon any subjective statements, the courts may seek to mold the wordings and meanings into a form which is easier to decide upon. This is the case where the "softness" of the system is decided. The harder the courts, the more force they apply to massaging the wordings. If a case reaches high enough levels, the court may literally bend the wordings and meanings faster than the legal council can hold onto them, resolving the issue quickly. This is not considered to be a fault in the system -- it's a fault on the lawyer for trying to escalate to a higher court than they were comfortable with, and getting burned for it.
Now for the last detail: courts do not always decide directly on cases. In our world the connection from case to courtroom is very strict. The supreme court hears **a** case with clear lines to a lower courts proceedings. **Instead, courts act upon disagreements.** The higher courts serve to resolve disagreement in the lower court systems. However, there is no requirement that this be a simple connection. Instead, the court system's job is to properly bundle up disagreements to be decided by the highest courts. There may or may not be a clear connection to a set of cases on the bottom. In fact, the cases may have been resolved amicably, but the lower courts generated so much internal disagreement by doing so that the higher courts must step in long after the fact to smooth the courts over -- otherwise they would exhibit strong biases.
This has an interesting effect of allowing some "free" disputes, which are disputes being dealt with in the higher courts but which have no clear connection to an existing case. This sounds wasteful, but its part of the system. It allows the judicial system to keep up with the times, rather than having to lag behind them, waiting for a case to cross their courtroom.
The system, of course, needs to be held down to laws, or else it gets to be a tricky concept in a hurry. The written laws, being the letter of the law and not the spirit, are not directly included in the proceedings. However, at any place in this pyramid, it is valid for a "nearby" judge to call for a disagreement about the handling of an issue. If this occurs, the law is treated as a "scaffolding" from which to better develop agreement. The scaffolding is brought into the disagreement in subjective wordings, and those words are used to resolve the disagreement within the courtrooms, using the same approaches as resolving subjective disagreements between individuals. This is a key feature: there is only one system to train and act, not two separate systems.
A final piece to put in place is the overflow valve. In theory, an issue could polarize the nation so greatly that the judges cannot come to an opinion, even as they directly continue to act
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A note on the ability to act on people *while* decisions are being made, instead of after: In our "objective" court rooms, things like duress confessions are considered illegal. This is because they violate the objectivity of the statement, and subject someone to the letter of the law in an unacceptable form. However, when the issues are subjective, the ability to cause duress substantially changes the flavor of the proceedings, turning them into more of a conversation instead of a query/reply. For instance, take software patent trolls. The court systems would have enough power to "capture" them, affecting their day to day business. Done to a single troll, it would be cruel and abuse of force. However, if the courts were to structure several hundred patent proceedings into one properly sharpened debate in the high courts, the high courts may elect to push on the patent trolls until they can work with the defendants to suggest new resolutions at the lower levels. Perhaps some rules regarding patent law may never actually get written down, but exist as a convention agreed upon by all when the court systems actually flexed their might.
Also, it is worth noting that *nothing* in this system suggests "unbiased" is of high value. In fact, the only part resembling unbiased is how a judge may bring up a disagreement written within the scaffolding of the word of law. There *will* be regions of this system which are more lenient to one group of individuals or another. This is okay, because we are not going for "unbiased," we're going for spirit of the law. It is expected that egregious differences between judges will be smoothed out as part of the system trying to attain its own ideal, but it is never expected that it will be fully "unbiased." This, of course, opens up doors as well. If a section of the court system is busy dealing with gay marriage issues (a hot button issue today), it would make it easier for people's arguments to be heard in that venue. However, it also means those who chose to mob the system are subject to being treated as a mob. If the mob turns out to be unwise, and loses their disagreements, those individuals may be caught in mob justice. To use the existing hot-button issue as a highly contentious landmine of an example, the religious constituents who opposed gay marriage may find that not only did they lose the argument, but they may lose rights as well. As part of arguing their "sanctity of marriage" argument, they may elect to accept a court-sanctioned document making it much harder for them to divorce (as they put their money where their mouth was on the sanctity of marriage argument). Note that this doesn't show up as a "punishment," as much as it was part of the proceedings. If a defendant can be pushed into admissions on the borderline of duress, it's only fair that the prosecution can be convinced to demonstrate their argument with actions rather than words, and be bound to those actions long after the proceedings are over.
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G. K. Chesterton once wrote, "When you break the big laws, you do not get liberty; you do not even get anarchy. You get the small laws."
What he meant was, it would be great if we could have a society where people lived by broad general principles, like "love your neighbor" and "be fair in your business dealings" and "never do anyone harm unjustly". But in real life, we always see that sooner or later someone breaks these laws, and when challenged, he pleads that the law was vague. What does it mean to be "fair"? He didn't think it was unfair to not bring up the fact that that "new" car he sold really has an engine with 100,000 miles on it, and the other person didn't ask. What's does it mean to be "unjust"? Oh, you think it means I can only punch someone if it's in self-defense? But that guy over there said I'm allowed to punch someone if he insults my wife. I thought it meant I can punch someone if I don't like his face. Etc. We could argue endlessly about what is "just" and "fair" and so on. And so for rules to be enforceable in practice, they have to be specific.
That is, people think that by taking advantage of loopholes they are gaining freedom. Others often warn that if people get away with such loopholes, they are not creating freedom, but anarchy. But Chesterton replies that you get neither. What you inevitably get is a mass of very specific rules to plug every loophole that someone can think of.
In theory, you could have a legal system where we went entirely by the spirit of the law rather than the letter. The law could just say, "don't cheat", "don't steal", etc. But then someone would have to decide in every specific case whether the spirit of the law was being met or not. Presumably a judge or a jury or some other group invented for this purpose.
But that instantly creates two problems. The more extreme is, what if the judge (or whomever) is biased or corrupt? What if, say, the judge is a racist and so in any dispute between a white person and a black person he always assumes that the black person is at fault? Etc, I'm sure you can think of many other examples. You could have an appeals process, of course, but ultimately that just means that what matters is the biases of the higher court rather than the lower court.
But even barring that, assuming all judges are fair and honest, you have the problem that no one could ever be quite sure what the law is. Like, the law says that a manufacturer cannot build a car that is "unsafe". But what is "unsafe"? No manufacturer could guarantee that no one will ever be injured in one of their cars no matter what the nature of an accident or failure. So what is "safe enough"? Do we have to have airbags, or are seat belts good enough? Is it good enough if the car can sustain a 20 mph hour collision? Or does it have to be 25 mph, or 30, or 27, or 26 1/2, or what?
If courts respected precedent, than over time case law would build up and people could say, oh, here was this case 5 years ago similar to mine and here's how the court ruled, etc. But ultimately that would mean that you'd have a whole bunch of detailed rules, and you're back where you started from.
Of course all of this happens to a certain extent with our present legal system here in the U.S., and I presume in other countries. Even with specific laws, there are always cases that no one thought of when the law was written, extenuating circumstances, etc.
To an extent, the system DOES apply a spirit-of-the-law test. Prosecutors regularly exercise what is called "prosecutorial discretion", which means that sometimes, even though someone is clearly guilty of breaking the law, they don't bring charges against him or bring lesser charges because his behavior was understandable given the circumstances, or because he has already suffered enough, etc.
In short, I think the answer is, Barring some radical change in human nature, there's no way a system could be either purely spirit of the law or purely letter of the law. It's always going to be some mix, with legislators trying to make laws as specific as they can and judges and prosecutors trying to apply them fairly.
Which reminds me of an article I read years ago by a judge. At the time, Congress had passed a law with "mandatory sentencing guidelines". People had complained that judges had too much discretion, that one judge might impose 20 years in jail for some crime and the same day another judge in another court would impose probation for the same crime. So to make justice more fair and even-handed, Congress passed a law detailing specific penalties for specific crimes. I don't have any of the details off the top of my head, but just to make up an example, if you stole something worth \$500 you might get 1 year in jail while if you stole \$1000 you'd get 3 years, and if you used a gun that would automatically add 2 years, etc. Judges and lawyers protested that while this sounded fair, it took away the judge's discretion to consider the details of the circumstances. Someone who started a fight after months of harassment and abuse and provocation would get the same penalty as someone who started a fight for kicks, etc. So, did the new law make justice more even-handed, regardless of one's view on the fairness? No, this judge said. What really happened was that now the judge and the prosecutor would sit down and discuss what penalty this defendant really deserved. Then they'd take out the charts from this law and figure out exactly what crime or crimes to charge him with to get the "right" penalty. If, say, including the illegal firearms charge would give a penalty that they thought too harsh, then they just wouldn't bring that up in court. If the obvious crime had a penalty that was too small, then they'd think of other crimes they could charge him with. Toss in "criminal trespass" or "menacing" or some other vaguely-defined crime. Etc.
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# The opposite: the totally rules-oriented system.
So, all modern systems are partially both sides: partially rules-oriented, partially interpretative/spirit-oriented. The best insight you're going to get is probably to take the most rules-oriented system you know of and completely reverse it. Let's call them the rules-oriented system (ROS) and the spirit-oriented system (SOS).
In the totally rules-oriented system, justice is meted out by mathematics: with 60% probability you have performed the crime, which is worth 30 years in jail, you will spend f(0.60, 30 years) = 2.6 years in jail (or whatever). If new information becomes available, you may either get added time or credits against future criminal activity. (The ROS would be an interesting premise for a dystopian world; people who "game the system" have to be explicitly legislated against, people who are wrongfully imprisoned are allowed some latitude to steal/murder.)
In the middle, you have our system. What is the difference between our system and the ROS, and how can we push that difference even further into the SOS?
# Community judgment.
I think one of the biggest things about the ROS is that the rules-oriented approach has 0% human personality entering into the justice system. Its opposite would be to have 100% human personality entering into the system. The community as a whole, or maybe some subset, would be presented with what you seemed to have done, your story for why you did it, a list of who was wronged and how, and their consensus would have to judge you.
### Educated subsets, relation to power
An open question which individual worlds will have to ask is: do you concentrate judgment in the hands of an educated few, or do you allow everybody to judge?
This changes the role of lawyers. In modern law, of course, the lawyer's job is to know the entire history of the application of the law, as well as what legal principles should be brought to bear in this particular case. The role of lawyers in the ROS is simply to make sure that all of your appropriate discounts have been applied. In the SOS with some sort of community-judgment we have to think: if there's an educated subset then the lawyer is still somewhat like our lawyers: but if there's not, then a lawyer has a much richer goal as *rhetoricians*, trying to build up a crowd-moving speech that would sway people to thinking that you had maintained the spirit of the community.
The numbers game also applies to the people doing the judgment. There is a trade-off here, a very important trade-off. The more independent-of-society and small-in-number the judgment-facility is, the more efficient society as a whole is (division of labor), but also the more risk that they will absorb authority into themselves and become a political power. An educated minority passing judgments for the sake of the community has definite advantages over the community doing the same, as the society gets larger than about 100 people: but if it has power then it buts heads with the powers-that-be in the society. The Popes were a small powerful moral authority throughout the late Antiquity and Medieval periods of European history; they often had power-clashes with the regional kings and other elite.
Speaking of power, there is *another* sliding-scale between the dictatorial (leaders are exclusive judges) and democratic (everybody is a judge) extremes in the relationship between leadership and judiciary. We can't say whether the SOS would be on one side or the other of this scale: it depends on what world you want to build. (They are not completely independent questions, of course: if political power = judicial power then the number of judges is just the number of political officials, so if it's a democracy then everybody is both a political and judicial authority, or if it's a dictatorship then the dictator is both a leader and a judge.)
So even on the far-SOS side, we have these fundamental questions of "who are the judges, how many of them are there, are they educated or just chosen at random from the population at large, and do they also lead others or not?" that must be addressed -- and they might be addressed in any number of other ways.
# Not what you did, but who you are.
The obsessive focus on what you've done, with no regard to who you are in the larger society, is maybe the second biggest thing which sticks out to me about the ROS. Pushing it to the opposite, we can imagine that everything is interpreted without probabilities as a question of "who are you, what value do you have to society?" that determines whether you go to jail or remain free, whether you are punished or rewarded.
A verdict could then be interestingly "meta-" for example: a judgment that "you are dishonest!" would have severe ripples through the community as everybody treats you like a known liar. Historically, the process of shunning those who were perceived to be guilty of crimes (called *ostracism*) was a powerful punishment meted out by a community who refused to do business with someone. It effectively cuts someone out of productive city-life.
# No pretense of consistency.
The ROS intends to be 100% consistent, the same rules applied to the same people at all times. Our legal systems try to be sort-of-consistent; the legal judgments themselves are supposed to be "interpreted" in each others' light. I think a true SOS system will completely abandon the value of consistency between how they judge X and how they judge Y: these are different people in different circumstances and even if they did the exact same thing, they may not have both violated the spirit of our community, or if they both have, they may have violated it in different ways.
So the SOS is probably "every case is its own isolated judgment, they do not need to establish any sort of precedent with each other, except perhaps for a global feeling about what our shared principles ultimately mean.
# Possible world idea: the free press.
Suppose there is no judiciary *per se* but there is a wild notion of freedom-of-press: the authorities have collectively decided that there is nothing wrong with the written word, whether libelous or truthful. Justice depends on these magazines, and you might pay reporters (who are now effectively the "lawyers") to write good articles about you or slanderous ones about your enemies. The whole of the law is maintained by the authorities in perhaps 100 or so precepts. Everyone learns these precepts at school and is educated that they have an important hand in establishing justice. (I don't think 100 is unreasonable; the UN has attempted to declare human rights, a similarly nebulous concept, in 30 precepts.)
Individual clerks and shops may refuse to deal with you depending on what the news says you've done. Prison and community service are often-voluntary forms of penance that you can inflict on yourself to absolve yourself in the public's eyes. However, you cannot just keep "getting away with" crimes because someone will forcibly kill/restrain you and be lauded in the newspapers as a folk hero. If it's a democratic system, those people might very well be elected officials looking to gain a few extra points.
As such a system grows, its main growing pain will be that not every member of the community can have an explicit "good/bad" status known to every other member of the community! To rectify this, we can imagine that technology saves us, and expect that the news periodicals essentially turn into "eBay reviews" of every person in the society. From the moment that some woman walks into your store, there is some pop-up on your screen saying "she has 4.5 stars among 80 reviews, but only 4.0 stars among the 70 who are not immediate family and friends." Part of this would probably be voluntary microchipping, with people who refuse the chip being regarded widely as dangerously untrustworthy, and politicians routinely campaigning that they'll protect you from unchipped hooligans.
# An all-too brief summary of the Socratic dialogues
Very similar to the above idea was democratic Athens. Athens was a **tychocracy**, a rule by the lucky, as well as a **direct democracy** where every adult man had a say. There were 10 tribes recognized in Athens and each one had 35 days a year during which they ruled via 50 people chosen by lot, who would randomly take turns "presiding" over that council. Furthermore, there were 9 chief judges (the Archons) also appointed by lot, and the "Ecclesia" or "Assembly" was a regular gathering open to all Athenian men to hear, speak about, and vote on decrees which would affect Athens as a whole. [There's a lot of material to cover](http://www.stoa.org/projects/demos/article_democracy_overview?page=6&greekEncoding=) if you want to know more.
Athens had a very important role for "philosophers" as the lawyers/rhetoricians of the Assembly; this was how the **Sophists** are displayed in the Platonic dialogues. These "lawyers" argued in front of the Ecclesia with whatever wordplay they could muster to get their clients out of trouble.One Sophist, Gorgias, is even so bold as to have written *The Encomium of Helen*, a defense of *Helen of Troy*, the "face that launched a thousand ships" (the villainous woman in Homeric poetry whose pivotal immoral act of infidelity led to a massive war, the Trojan War, containing the deaths of countless heroes and kings). The implication, of course, is "if I can get Helen off for starting a war, I can get you off too, whatever your crimes are." In the dialogues the Sophists are drunken fun-seekers who basically think: there is no greater truth, isn't it great how we can play these word games, oh I'm so clever now that I can argue anyone into nonsense, because really there's all sorts of ambiguity in language, ahahaha. One pivotal tactic, for example, is that they often *define terms by example*, exploiting the ambiguity created by the word "good" in "a good knife, a good life, a good wife." Socrates hates this and wants something closer to mathematics: if you want to define a term, I'm going to ask you for something which everything which everything inside that set has, but only those things have: "if" and "only if".
So in Athens there are rules, yes, enforced by the tychocracy and often made by the democracy, in a complicated mess which was easily swayed by inspirational speeches and rhetoric. That rhetoric often dipped down into dirty word-games and surely tarnishing reputations also occurred.
Another thing to learn is that there doesn't seem to be a difference here between criminal and civil judgments, unless I'm horribly mistaken. It seems like the only time the Ecclesia would legislate something is if one man had a beef with another man: they would resolve the dispute. So it'd be interesting to instead write out a system which was sufficiently modern to need things like *speeding tickets* where there must be some group whose job is to say, "no, you are doing the wrong thing for everyone," even though you're not offending anyone in particular.
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A point which is often neglected is that in many cases the legitimacy of an action should depend upon the intent behind it. Without the ability to read minds (and thus determine the true intention behind an action), it's necessary to be able to have standards for how well-intentioned people should behave, and presume that people who behave according to such standards are acting with good intentions, but such a presumption should be just that--a *presumption*, not a *determination*. In many cases, maintaining the "spirit" of the law, rather than just the "letter", would require little more than recognizing that actions undertaken in bad faith are automatically illegitimate on that basis alone, *no matter how well they otherwise fit the standards for how well-intentioned people should behave*.
An example of this principle may be found in one of the rules in the American Contract Bridge League, which specifies that deliberate violation of the rules of the game is cheating, *even if one would be willing to accept normal prescribed penalty for committing the same infraction accidentally*. For example, a klutz who sometimes accidentally drops cards so partner can see them will generally incur minor procedural penalties, but a player who deliberately exposes a card to partner may be disqualified and possibly even ejected from the League. While there may be some room for judgment on whether the Tournament Director should impose the normal penalty or a harsher one, there is no room for judgment regarding whether a player is allowed to show an unplayed card to partner in exchange for accepting a procedural penalty. Such behavior is absolutely, clearly, expressly, and unequivocally forbidden.
Recognizing that a presumption of good faith should, like any presumption, be considered rebuttable would go a long way toward balancing the "letter" of the law with the "spirit". An honorable person shouldn't ask how far he can go beyond the letter of a law whose legitimacy and meaning are not in dispute; that a person would even ask such a question would suggest that minor infractions which might have been forgivable under a presumption of good faith should be presumed deliberate.
It's possible that the only thing that would change as a result of recognizing presumptions as rebuttable would be that discussions of how to get around the law without consequence would be forced underground. On the other hand, having such discussions go underground creates many possibilities for intrigue, especially if respectable people want to avoid any association with such discussions.
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After reading a comment, I decided that there was an alternative to the system I gave in my first answer:
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> You might want to search for Chthonic Law. The short answer is: once people write down authoritative explanations of what the Spirit of the Law really is, those are by definition written laws and people start lawyering them, too. – Lorehead
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Now my argument would be that, if you could write a law down fully, such that the written law was complete, the law would have no spirit. The only exception seemed to be words which are designed to have spirit, like poetry.
So why not?
A system where all laws are written in poetry instead of legaleese, designed to capture the best intents of all humanity. Anyone who tried to read the law in any literal way would be laughed out of court.
It opens up great opportunities for legislation that has never been possible, like properly compensating a jilted lover. It also can be nurturing, to raise the poor uneducated minor out of his ghetto life before the gangs take hold of him.
One could even include concepts into such a legal system which defy wording entirely:
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> "At the temple there is a poem called 'Loss' carved into the stone. It
> has three words, but the poet has scratched them out. You cannot read
> loss, only feel it." ― Arthur Golden, Memoirs of a Geisha
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How's this for an idea. There is a group of people (IMHO they often come off as a bit looney) who really push the idea of Jury Nullification (aka Fully-Informed Jury) who think that a jury should be able to ignore the law and the judges comments and possibly toss out a case they deem to be unjust. Judges (and probably most rational people?) read the law and prefer to put some parameters on what choices the jury can make. For instance, the jury has to base its conclusion on legally obtained evidence, etc.
So, what if we push it to an extreme. You and another person have a legal squabble. You present if front of a jury (it's funnier if you imagine them on drugs). They don't bother looking at the law or precedent at all. They just decide according to who seems more reasonable or convincing. That certainly would get you away from the letter of the law and loopholes really wouldn't be an issue at all...
(Come to think of it, this would get me to actually WANT to get called for jury duty, so there is that benefit.)
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Everybody seems to be discussing courts and lawyers.
As I see it, the question is mostly about *culture*.
Consider a man who has exploited a loophole in a contract or law to gain something.
In most cultures on Earth, he will go around bragging about this, and people will applaud how clever he has been. And this means he will try to do it again.
In some cultures, both on Earth and in fiction, people will think he has been a bad person who should be ashamed of himself. And this means he will NOT try to do it again.
Most cultures are somewhere between these extremes, of course.
The form of the laws and courts are irrelevant. They only reflect the norms of their culture.
[Editted to add:]
You were interested in how courts would work in such a culture.
I think the settlement courts would be more important. In this court, both parts have agreed to meet to settle a disagreement. The focus of the court would be find an agreement both parts can accept. But if negotiations fail, the judge(s) would have the power to decree a settlement. There would be no question of fines and punishment, just recompense.
As for criminal law, community service would be more common. Also recompense to the victims.
Or so I guess.
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In contrast to the answers of Cort Ammon and Jay I think it is entirely possible to build a non-specific-rule "spirit of justice" system. The problem is that it hits so many ingrained subconscious assumptions that such a system is hard to imagine.
* First and foremost thing: **There are no rules, only guidelines and the guidelines must have a priority in case guidelines conflict. These guidelines are culture-specific.** You can have ultra-draconian guidelines like in medieval Japan where even minor offenses are punished by death or you can have very lenient guidelines avoiding harsh penalties. One view on the guidelines and you pretty much know what you have to expect from society. *Allowing to know the guidelines is already a guideline*, cultures are not obliged to inform outsiders about their guidelines (again medieval Japan, entering or leaving Japan was punished by death). *Use precedents to judge a case is already a guideline*, a culture can claim rightfully that each case is individual, but it can also claim that precedents are important. **Priority is important**: If there are two conflicting guidelines the culture must choose from its values what is more important. One guideline is to allow any kind of speech to prevent censorship, another guideline is to disallow hurting or harming people. The USA decided that free speech is more important, Germany decided otherwise.*None of them are contradictory*, both approaches are consistent and the systems must live with the implications.What really hurts law-orientated systems **is that the existence of all-encompassing "natural" laws** will be very likely denied, while many cultures will probably have a common subset they will almost always have a specific exception where a "human right" will be strongly denied (else we would not have so much problems with human-right violations).
* **The deciding instance must have the support of the culture for which the guidelines are specified and it must given the power to uphold verdicts.** Forcing a culture to adopt guidelines of another culture is asking for trouble, it will inevitably lead to parallel and silent justice. That means that the jury/judge won't get evidence, witnesses or even cases, the people will avoid the court like a pest.
* **The guidelines must be applied to a case and this means a Judge or Jury**. This automatically gives the ruling instance tremendous power, so the judge/jury can (and will) issue both outragous and wise judgements. It is culture-dependent if and how revisions and controls will be implemented.
* **There is no barred evidence and there is no need for lawyers in the common sense. The guideline law concentrates on evidence-gatering, not using rules to the advantage of one side, There is no "no punishment without law"**. Rule-based systems are trying to uphold standards of equality, fairness and non-manipulation and do that by applying rules which can be again used as loophole. So both criminals and the society have their appointed agents which will try to game the system for their preferred outcome. So given the problem that you cannot suppress evidence, you need to come up with a stringent explanation for *all* of the possible unearthed evidence.
* **Very interestingly it means that even a fully-accepted guideline court system will be likely seldom used except for felonies.** People like to be on the secure side and if you really go into depth, it often sheds a bad light on both participants. Yes, A *did* screw you, but he was smarter than you after you tried to take advantage of him. Rule-based systems may decide against you, but most of the time you can *trust* that not breaking a law will give you immunity. It also gives you privacy (the judge will not know what you have done before) and more case-specific ruling (your social standing, your problems with society). So a guideline system will likely develop a mediator system to settle problems out of court and both participants will know most of the time how their position is and try to get a gentleman's agreement.
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For this kind of system to exist ( and it is the goal of many legal systems so it's debatable how achievable it might be ) then you probably need to operate at different levels - most legal systems operate on a basis of principle/intent => legislation => case law. In the situation you describe, it seems as though possibly the case law part of the scenario might be given far less weight- rather than comparing the current case with previous similar ones, it could be compared purely with the legislation and it's stated intent. That still ties in to the letter-of-the-law but gets closer to the principle and intent, although of course it is also much less efficient because the same conclusions have to be derived in similar situations rather than being able to compare directly with how they were concluded before.
**Consider the orientation of the law**
An interesting alternative might be to change the orientation of the law, so that the underlying principle is changed from "it is the will of society that you should not do X" to something else. An example of this that I find particularly interesting is "a crime is an action performed by a person of agency which has a victim."
This creates a very different shape of legal system, where the nature of the victimhood and establishing a victim becomes the core of legal process. A 'simple' crime such as assault is fairly clear-cut in this respect, but things get interesting when organisations are victims, when a victim is hypothetical ( dangerous driving my not have a physical victim but the potential for creating them is very high ) or when an action has a slim effect on many victims ( polluting the environment could be an example of this ) and so on. It would result in a complex and comprehensive legal system that could have the same effects as our own, but which comes from a very different place and responds to crimes and their victims in a different way.
We could look at some outcomes of this:
* There are no crimes against oneself alone. If you have agency ( by which I mean effectively you are rational and capable of decision-making in your own right ) then you cannot be both victim and perpetrator. That gets rid of many drug offences straight away.
* If it is legal to consume drugs then supplying them cannot be criminal in cases where there is no victim.
* *However,* if a person's actions whilst under the influence of drugs or the consequences of a person's addiction create a victim ( a neglected child, harm to an unborn foetus, theft to finance the addiction ) then those actions have criminal implications.
* In cases where there is potential for victim, but no definite victim, like ( to continue on this theme ) driving under the influence, the approach may be based on a unit of risk, a little like a [Micromort](https://en.wikipedia.org/wiki/Micromort). So if driving under the influence resulted in damaging property 50% of the time, causing injury in 20% of cases and causing fatality in 5% of cases, then you have effectively 0.75 victims at three different magnitudes of severity. This combination of scale of potential victim and magnitude of severity would be used to decide the seriousness of the crime and the punishment due. Given that the course of law in this case relates to establishing a victim, both prosecution and defence might use statisticians to argue the case that this was a more or less serious event and therefore the defendant should or should not be punished.
In this case the legal system becomes less of a question of rules and more a matter of the effects of individual choices on the people around us, which is an interesting exercise and would probably be reflected in other cultural elements.
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
A key part of the plot in a story I'm working on revolves around the main region being on top of volcano that is set to erupt. The trouble is that the region in question in my setting is roughly the size of Wyoming. It's on an Earth-like planet.
Clearly, the volcano needs to be a [supervolcano](http://en.wikipedia.org/wiki/Supervolcano). However, I'm having my doubts about it being so big. I also think that perhaps a volcano this big isn't necessary, because sizable volcanic activity can be had from much smaller volcanos (for an extreme dramatization, see [*Supervolcano*](http://en.wikipedia.org/wiki/Supervolcano_(film)).
How big can a volcano be?
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Note: The setting doesn't take place on the *sides* of a volcano, but at the very top of it. I originally set it in a caldera, but it turns out that the volcano doesn't have to have erupted yet for the idea to be plausible. I'd also like answers rooted in [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'").
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**Clarifications**
* The planet is Earth-like, but plate tectonics don't have to be Earth-like.
* I care about width, especially at the top, but overall height isn't important.
* It seems like things are as I thought they might be - the idea is unrealistic. I might consider using smaller volcanic features, but they would all have to be tied together. The answers don't have to be edited to cover this; it's just my musings.
* No hand-waving, please! I can change the gravity of the world if necessary (in my story), but the gravity is still as I originally said - like that of Earth.
* The volcano doesn't have to exist on the Earth we live in, though if the biggest volcanic feature(s) on Earth is/are the limit, I'll be happy to hear about them.
All the answers so far are good - don't change them! I'd like some more sources (*a la* the [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") tag) - not that I doubt them, but because I'd like to do a bit of reading afterwards about this topic. A volcanologist I am not.
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[Related question on Skeptics](https://skeptics.stackexchange.com/questions/5848/can-mountains-on-earth-grow-higher-than-49-000-feet-15-000-m), mentioned in [How high/large can a mountain range get?](https://worldbuilding.stackexchange.com/questions/3418/how-high-large-can-a-mountain-range-get).
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## Is this large enough?
If you've ever heard of the Permian–Triassic boundary, about 251 to 250 million years ago, **[the Siberian Traps](http://www.ucmp.berkeley.edu/education/events/cowen2a.html)** are what caused it. Well, the Permian-Triassic boundary is such a bland term for it. A better word for it is **the Great Dying** or the **Great Permian Extinction,** Earth's most severe known extinction event, with up to 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct. At 2.5 million sq. km. (!!!) in area and perhaps 3 million cu. km. in volume, this is the kind of **fun stuff** that could seriously ruin your day.
## Too big? Try the Deccan Traps instead
The Deccan Traps are one of the largest volcanic provinces in the world. It consists of more than 2,000 m of flat-lying basalt lava flows and covers an area of nearly 500,000 square km (roughly the size of the states of Washington and Oregon combined) in west-central India. Estimates of the original area covered by the lava flows are as high as 1.5 million square km.
The volume of basalt is estimated to be 512,000 cubic km (the 1980 eruption of Mount St. Helens produced 1 cubic km of volcanic material). Most of the basalt was erupted between 65 and 60 million years ago. Hmm, does that seem awfully close to another extinction event?
## How does it work?
([Shamelessly ripped from here](http://www.ucmp.berkeley.edu/education/events/cowen2a.html))
In addition to plate tectonics, the Earth also has plume tectonics. Occasionally, an event at the boundary between the Earth's core and mantle sets a giant pulse of heat rising toward the surface as a plume. As it approaches the surface, the plume melts the crust to develop a flat head of basalt magma that can be 1000 km across and 100 km thick. Penetrating the crust, the plume generates enormous volcanic eruptions that **pour hundreds of thousands of cubic kilometers of basalt** ("flood basalts") out over the surface. If a plume erupts through a continent, it blasts material into the atmosphere as well.
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As you've mentioned, you don't need a mountain. Just a volcano...preferably a mega-caldera like Yellowstone. Now we can ignore pesky gravity limitations and focus in on the geological issues
On an Earth-like planet, this is going to be hard. If you want a Caldera the size of Wyoming, you are going to need a similarly large hot spot to fuel it, or are going to need a really freaking weird tectonic layout.
The largest caldera on Mars is on Arsia Mons, and is merely 105km in diameter. Venus is a bit better with a max of around 150km.The largest caldera in the solar system is Tvashtar Paterae on Jupiter's moon Io at a diameter of 290km.
But a circle with the area of Wyoming would have a diameter of 568km. There isn't a caldera in the solar system that is anywhere close.
And, there is a further problem. On Earth, 60% of our volcanic activity is spread around plate tectonic lines. Only 40% is attributed to hot spots. If one hotspot is big enough to heft the entire state of Wyoming...imagine the volcanic activity of the rest of the planet.
So...what you would basically end up needing here is incredibly improbable, and even then, I can't find proof that it would work. Your region would likely need to be subducting multiple plates around itself...AND you would need a hotspot situated in the middle. This might, MAYBE give you enough geothermal activity to produce a sufficiently large volcanic area. And you'd need a lot of other stuff going on to prevent constant, running volcanic eruptions happening all over the place, allowing it to build up as a mega-caldera...such as the bedrock being a massive, impermeable sheet of basalt or granite...so that the lava ends up lifting the landmass, instead of leaking out in regular eruptions.
You would still have a lot of geothermal activity, like hot springs, geysers (think Yellowstone, but on the scale of an entire state). If this ever went off...expect total extinction on the planet.
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Getting a Wyoming sized mountain peak wouldn't be possible on something like an Earth-Like planet.
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> The cosmic mountain-building recipe is simple: the weaker the gravity on the surface of an object, the higher its mountains can reach. Mount Everest is about as tall as a mountain on Earth can grow before the lower rock layers succumb to their own plasticity under the mountain's weight.
> - [Neil deGrasse Tyson](http://www.haydenplanetarium.org/tyson/read/1997/03/01/on-being-round)
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Additionally, the current or impending volcanic activity is going to lower the viscosity of the area further reducing any possible maximum size.
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> But something else is going on that’s often not talked much about which is that mountains eventually tend to fall down, just through their own weight. And the important concept here is something called viscosity which if you like in the runniness of the rock that’s inside the mountains. A useful analogy is something like syrup. So, if you imagined that you created the Himalayas out of syrup, I think it would be easy to see that as soon as you start pushing the mountain up in the air, it also starts to fall down because the syrup will flow out sideways. - [How high can a mountain be?](http://www.thenakedscientists.com/HTML/questions/question/1000143/)
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If we want a large, mountain-like volcano with lots of building space at the 'top' then a Shield Volcano might be the way to go, but that has the downside of not necessarily having 'cataclysmic' eruptions. If you went this route, allowing for slightly less gravity and slightly less active plate tectonics we could possibly look at Olympus Mons as an example. That shield volcano has an area of 290,000 km^2 which is larger then Wyoming but still the [summit is only 50mi or so wide](http://marsprogram.jpl.nasa.gov/gallery/atlas/olympus-mons.html) vs the 300 you're looking for.
So from there I think it's going to be important to prioritize your wants and needs for this system and realize that it won't all work together.
* Size of Settlement: How important is the size and placement of the settlement? Can it be scaled down at all, or possibly it's just the capital that is located on the peek / within the caldera?
* Size & Distinctiveness of Volcano: Does it need to be something noticeable as a volcano? A lot of the larger calderas you wouldn't really think of as a volcano. (And I think in one of the previous links as well, it mentioned that if you were on something the size of Olympus Mons, it's so large in scale you wouldn't even notice the slope of the sides because it would be past the horizon!)
* Power of the Volcano: Does the volcanic activity have to potentially encompass the whole settlement or can you get away with lesser volcanic activity? Like @guildsbounty brought up, it's going to be difficult to get to a volcano of that size with a Pompeii like eruption without it already have happened earlier along the way. Could the volcanic activity consist of smaller flows like those that go on in Hawaii instead of a singular eruption type event?
* Sticking to Hard-Science - Can you get away with some hand-waving? Maybe the planet is more Mars-like, but we're just going to treat is as Earth-like anyway. Perhaps the planet's core has mysteriously moving hot-spots that just so happened to follow with the tectonic movements allowing for the larger volcano.
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For a single mountain/volcano on a Earth sized planet, (actual Earth) Mount Everest is calculated to be at about the maximum height that can exist. When it gets much larger than that gravity takes over and knocks it down, Mars has much smaller gravity and thus is able to support a much larger volcano.
Otherwise, if you are looking at just a 'large area' volcano then the supervolcano under Yellowstone is very large, something the size of Wyoming would pretty much be a planet killer, Yellowstone when it goes will likely be a mass extinction event.
here's a [link](http://www.hk-phy.org/articles/mount_high/mount_high_e.html) that has some calculations for mountain height.
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[**Tamu Massif**](http://en.wikipedia.org/wiki/Tamu_Massif) is the largest known Earth volcano.
It's about half the size of Olympus Mons, but that includes the entire thing, not just the summit. It's also bigger than Wyoming.
Now, that's probably not the largest volcano possible. But if the summit area is 10% of the total, you would need a volcano an order of magnitude larger to get what you're looking for. I think that's pretty iffy - I'll bet you start running into scaling issues - but I wouldn't rule it as entirely impossible either.
But what about a [Ring of Fire](http://en.wikipedia.org/wiki/Ring_of_Fire) type situation instead?
Set your location on a small tectonic plate fragment that's been pushed up. Due to activity in the past, it's surrounded by several supposedly dormant volcanos. An eruption of one could easily trigger eruptions in the other, leading to region-wide devastation.
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I'm not sure that the volcano would have to be a Supervolcano. On Mars, the tallest mountain is [Olympus Mons](http://en.wikipedia.org/wiki/Olympus_Mons), a shield volcano. Mars is, at least to me, the most Earth-like planet in our solar system, so I don't think it would be that far-fetched for a volcano like Olympus Mons to form on Earth. It is about 26km (16mi) at its highest point and overall it is about the size of Arizona, which is a bit bigger than Wyoming, but not by much, so I'm sure it could be scaled down a bit. Also, it doesn't slope very much, so I don't think it would be hard for a people to live there (well, after they were able to climb it). Because it is a shield volcano, it wouldn't have an explosive eruption, but the effect of an eruption would still be devastating.
For a steeper incline, you'll probably want a stratovolcano. The tallest stratovolcano on Earth is [Ojos del Salado](http://en.wikipedia.org/wiki/Ojos_del_Salado). If the volcano has a high eruption rate (or at least did for a long time) then it can be much bigger. If the crust of your planet is more like Mars than Earth, then the volcanoes can also be taller. The volcano will have to be a hot spot volcano though. The moving plates on Earth cause the lava to get spread out over many volcanoes, but on Mars the plates stay stationary, causing a lot of lava to pile up on one volcano. The eruption would probably be explosive too, because it is a stratovolcano.
Also, the gravity on your planet would have to be a lot lower because as bowlturner said in a comment, Mount Everest is about as tall as a mountain can get without being pulled down by gravity.
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Check out this paper: <http://pirlwww.lpl.arizona.edu/~jani/radebaugh-pateraeio-jgr01.pdf> Which talks about Paterae on Io, which are a type of Caldera. The max size given for those are 200 km diameter; with a mean size of 41 km, which is close to the mean diameters for caldera's for Mars (47.7 km) and Venus (68 km). On earth it lists that ash flow calderas are mean sized at 18.7 km.
The largest Caldera on earth is possibly the [first phase Island Park Caldera](http://en.wikipedia.org/wiki/Island_Park_Caldera) associated with the [Yellowstone hotspot](http://en.wikipedia.org/wiki/Yellowstone_Caldera). Note however that the hotspot wasn't associated with that area prior to the first phase Island Park eruption, but was further west and I don't believe that it would have been known that there was a caldera there prior to the initial eruption. Given the initial eruption the hotspot tends to stay in roughly the same place so if they built in something like the Island Park Caldera one of the other eruptions could happen. That is 50 miles by 40 miles, which is massive, but Paterae are bigger. Note though that the Island park ashfall covered from California to the Mississippi and would have had a global climate impact.
The Deccan traps wouldn't seem to work for what you describe as looking for. While such events are the largest examples of volcanism, they aren't [properly volcanoes](http://www.wired.com/2013/04/stop-calling-flood-basalt-provinces-a-single-volcano-or-eruption/) as they happen with multiple fissures and over long time spans.
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Perhaps the largest volcanic eruption in human history was the Toba catastrophe @ 77,000 years ago.
The eruption gouged out a 100km X 30 Km caldera complex and is estimated to have ejected up to 3000 cubic kilometres of rock into the atmosphere, causing a "nuclear winter" at least 6 years long and cooling the climate for perhaps 1000 years.
While not the size of Wyoming, this is thought to have caused a genetic bottleneck in the human population and was possibly close to leading to the extinction of the species.
Even "small" volcanic eruptions like Mount Tambora in 1816 can cause a year without summer, and Krakatoa created tsunamis which killed an estimated 40,000 people.
How much more apocalyptic do you want?
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If you're looking for an instance of a city built on top of a volcano, Naples in Italy is a pretty good example. It's built right next to the caldera of a large volcano, with some of the suburbs inside. <http://en.wikipedia.org/wiki/Phlegraean_Fields>
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One could have a huge volcano-like event occur as a consequence of an exit wound from a meteor impact on the opposite side of the planet. Certainly anything small that hits something big could come right thru and out the other side, or make a shockwave which produces an eruption of interior material out the other side, or both.
It has been posited that this has happened before on Earth.
<http://earthepochs.blogspot.com/2014/10/600-mile-wide-impact-crater-in-pacific.html>
Wyoming is a square roughly 300 miles each side so this is the same order of magnitude.
I could imagine a scenario where inhabitants live on a nonrotating planet, shielded by the planet's mass from meteors which strike the far side regularly. They feel secure until one of these exit wound type meteor strikes empties a sea in proximity to them. They then realize that their own position is not as secure as they thought.
This scenario is also nice because if one identified the incoming asteroid likely to produce such an event you could send Bruce Willis to go sort it out.
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Imagine that we live in a setting where there are [**a trillion humans**](https://worldbuilding.stackexchange.com/questions/10388/how-long-will-it-take-human-population-to-exceed-one-trillion/10394#10394) (see linked question). A bit crowded, I know. Further imagine that at least the entire energy output of the Sun was available to this trillion humans to play with. Perhaps evenly distributed, perhaps with some variation. If evenly distributed, each individual would get at least 10 times current humanity's total power output.
Would it be possible to police such a society? In our world, if someone **goes postal** or runs amok (that is, goes on a homicidal spree), there's only so much damage they can cause. With Terawatts of power at your fingertips, that would not necessarily be true any longer.
So, **can a thousand billion such superempowered beings live in close proximity, or do I have to disperse them like an overheated gas across the galaxy?**
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If you think about it, any society which can harness and manipulate the power of the sun will have tools at their disposal to harness energy. If one unruly person decides to use "their share of the power for destruction," they will have to figure out how to do damage with their portion. Mere terawatts isn't enough.
A society that can harness the power of the sun is going to have some waste energy. Consider: if society uses their energy 99.999% effectively (which is an extraordinary feat, given we're topping out around 25% efficient at our best), **your share of the power is still 10-million fold less than the waste energy coming off of the rest of society.** A society which cannot handle that raw power will simply not progress to the point where you have that much energy available to yourself.
Now what is more interesting is when they want to use that energy with fine-tuned control. **A well controlled fine-tuned weapon tuned to a weakness is far more dangerous than a wideband uncontrolled one.** Think of the strobes used by SWAT teams. The actual energy is piddly. It'd be hard to fry an ant with it. But strobed at the right frequency, it disorients the perpetrator and lets the SWAT team take them down. Rather than using a solar-furnace flash light to melt the opponent, they found a weak direction and struck with high precision.
**Of course, the only limit to this is the ingenuity of a human.** This is an arms race that has been going on for thousands of years (billions, if you believe in Evolution). Nothing changes except the scale. You're still going to see individuals choosing to try to attack weak-points, and individuals trying to shore those weak-points up.
So how did you get to this point of trillions of gods? It's not like you dumped a trillion teenagers on a planet surface and gave them each part of a sun as part of some TV teen drama. Along the way, you're going to have developed an entire sun's worth of safeguards and protection devices. What they look like is up to you.
*I'd say the sky is the limit, but when you have the power of the sun, you have to set your eyes a bit higher than that.*
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I don't know if this future is a whole lot different than what we have now in terms of general human behavior. Lots of humans live in very close proximity to each other without major (ie, population-level) destruction. Most 'postal' types of incidents are usually somewhat targeted and aren't necessarily out to destroy a whole city, for instance.
Granted if any one person could destroy the entirety of civilization would *someone* attempt it? Probably. But we'd have to get to that point first, and I would imagine that we'd see that coming and some form of checks and balances would hopefully detour any such finality.
As to whether these humans could remain human...that seems like an entirely different question and I'm not sure how it'd directly relate to access to energy.
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Backups :)
With that much energy to spare everyone will be backed up at multiple different location. If someone does flip out and take out some people then they die and their backups never get used - whereas everyone they did hurt gets restored from backup.
It's like Stack Exchange, Wikipedia, etc. If everyone can edit how come it isn't vandalized?
The answer is that some people do try, but there are more people fixing the damage than doing it and tools have been provided to mitigate (protecting questions, etc) or repair (roll back, deletion, etc) the damage.
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I can't help but answer politically and or philosophically.
I'm not a conspiracy theory guy, but if I was, the one conspiracy I would throw my tinfoil hat at would be that that 1989 Time magazine reveal of cold fusion wasn't a hoax. No government would allow every citizen to carry near infinite power in their handbag. No government that has the capacity to rally the entire human race to build the infrastructure to put a billion people in play is going to risk giving the ability to deconstruct that to the people themselves. I don't think the idea is feasible logistically.
...without outside help. If our robot/alien overlords are "helping" us stay committed to the task, we could theoretically achieve a billion.
...and they would most assuredly NOT give us access to that kind of power.
The only way I can see it happening is that we are "guided" to the population point, and then loosed to our own ambitions... maybe our overlords finally succumbed to a 1000 year enfluenza virus, or it was all an elaborate setup for a robot casino game...
Then... yeah... I predict really REALLY bad things... maybe after 100 years and 90% of the populations gets killed a truly enlightened exceptional human society rises from the ashes... but there WILL be growing pains, and then retaliation for those growing pains, and then a century of fighting over arbitrary nonsense...
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As Robert Heinlein famously said, "An armed society is a polite society. Manners are good when one may have to back up his acts with his life." If you don't want to take some old writer's word for it, this is pretty much the same concept behind the modern military doctrine of [Mutually Assured Destruction](https://en.wikipedia.org/wiki/Mutual_assured_destruction), which has successfully prevented widespread use of nuclear weapons for decades now.
In other words, if every individual on Earth has access to enough power to destroy a small city, they also have enough power to disintegrate anyone who tries. Of course, the whole strategy of "the best defense is a good offense" doesn't work so well against suicide bombers, so it would be good to have an *actual* defense as well. The details will depend on what you allow within your setting; we could be talking surveillance, power dampening fields, force fields, etc. But whatever form it takes, if a large majority of the population is willing to direct just a few percent of their power into a shared defense, that easily, vastly overpowers any single individual who might be tempted to go on a rampage.
So I would say not only that such superpowered beings *could* live in proximity, but that, just like today, they would almost *have to* for safety from each other.
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No, you probably cannot keep all of humanity lumped together. Simply due to individual preferences, even if the vast majority of humans choose to stay in place, you'd surely have billions (<0.1%) who would choose to go and colonize the rest of the galaxy. Since they can build their own Dyson spheres without needing to share with a trillion others, they (or their descendants) would be fantastically energy-rich by comparison, triggering further imitation immigration waves. Over the millennia, the distribution of humans would come to resemble that of a thin gas spread across the galaxy.
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The higher the threat, the more are people willing to sacrifice.
See our world - imagine Terrorists would have the means to produce nuclear weaponry and use it for bombings to destroy whole cities. Most of us would probably give up most of their rights and deal with increased surveillance and more investments into police force and intelligence agencies until we have banned the threat.
In such a future access to the energy will probably be highly regulated - either by a giant bureaucracy with surveillance and protective means to keep everyone safe from psychos. Or some major mafia-like families or super-rich companies (ala Shadowrun) who control most of the energy/weapons/defenses market and have no interest in someone blowing up half the planet and lower their profits.
Humanity will adapt to a state where everyone can live reasonable safe...
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In a hypothetical futuristic society that blends arcane magic with science, humanity has spread across the galaxy. FTL drives exist, but they are relatively slow and must exit at the outer edge of a gravity well and crawl towards their destination. Interstellar travel is slow, and trade takes place in times measured in months and years.
But there is another option. Several researchers, infamous for their less than savoury practices, have discovered that an extra planar race is capable of transporting a human ship instantly from one place to another. The problem however, is that for all of human history these extra-planar entities have been regarded (with good reason, for the most part) as devils. The ritual to summon one of these entities involves acts of blood sacrifice and dark rituals and the public is overwhelmingly against it, but the promise of instantaneous interstellar travel is alluring to governments and corporations both.
Would people in this universe make common use of this technosorcery? Or would public opinion and the effective cost (a deal with the devil, as it were) restrict it to only the most pragmatic.
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Like anything in human society, there will be people across the board on this. First there will be studies/negotiations to find out how much of what is needed to seal the deal to be transported? Does someONE actually have to die? Can an animal fill the bill? Does the level of the ritual affect how much can be transported?
These kinds of questions would be asked and needed to 'justify' their use. If 'sacrificing' a pint of my blood would work it might be much more likely to become along the main stream. If an actual human death is needed (or just needed for large shipments) then corporations and governments are likely to be the most likely to use them.
Governments would start by using murderers, child molesters and rapists because they would be 'OKish' 'as long as the need was great'. But if there wasn't enough they would expand it quickly to homeless, 'dissidents' and enemies of the state.
Corporations would just hide it well, keeping pens of 'undesirables' at hand.
Of course organized crime would have both hands in the deal. This is also quite likely an avenue Corporations would go, let OC provide the service and keep their hands 'clean'. Governments would use them as an excuse for why they need to have it available, to help combat the criminals.
Of course you will always have the extremists who will even go to the lengths to kill to prevent someone else from doing so or using the offered services. In this case it would be very ironic.
ETA one last idea
Likely someone in big business would claim they designed a 'drive' that is just as fast, and hide what is actually going on in the background. Allowing travelers to feel better about themselves in their travels.
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## Yes, but with devastating consequences
Anyone willing to use the technology clearly has morality issues.
Such a technology would introduce a massive imbalance of power. Even a small rogue fleet would be easily able to outmanoeuvre a large empire, striking any undefended target at will, then melting away.
A pirate warlord would be able to dismantle a 1000 year empire piece by piece with no possibility of retaliation.
A sudden imbalance of technologies like this would likely lead to the weaker side reacting with fear and adopting the technology without public consent, i.e. tyranny.
This would start a war and lead to chaos, insurrection, wholesale destruction, the collapse of empires, and death, basically an apocalypse.
Perhaps this was the intended consequence of the "pact" all along.
So yes, people would make use of it, but with fairly devastating consequences.
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## People are weird
To start with, there is [Church of Satan](http://en.wikipedia.org/wiki/Church_of_Satan) which has no problem in devil worshipping *right now.* Also, there are people who like to eat people and people who consent of being eaten. Just to continue my first horror story, do not forget [BDSM](http://en.wikipedia.org/wiki/BDSM) niche where even blood could be a fetish.
In nutshell, even though it can (and will) be seen as bad practice by majority, there always be (small) minority willing to do it and even enjoying doing it.
## How are you going to stop me?
Imagine, I live in your universe, on Earth. How exactly are you going to stop me? Imagine, I will watch popular sport competition happening here on Earth, then sacrifice someone I rarely know (homeless person) and move in a second to Mars colony. Place a bet here on the winner and win a huge amount of money. (because I will be here before the signal from Earth reaches Mars, so before anyone knows how the competition will end)
How do you want to stop me?
And, how do you want to hunt me, if I can escape really *really* quickly, and, bonus, be rich enough to actually buy a nice piece of land?
## People will do anything for money
Or exchange "money" for a personal gain. There are weird stories about what you can find on [Deep Web](http://en.wikipedia.org/wiki/Deep_Web). For instance the one I heard is, that you can order assassination of someone you hate. And you pay with [Bitcoin](http://en.wikipedia.org/wiki/Bitcoin) - untraceable money.
Imagine how big upper hand am I given if I can travel the whole Universe *in a second.*
Being you, I would think of means of regulation. Otherwise, although you might be against it (who would like to do blood sacrifice nowadays?), using it brings **huge** upper hand worth considering.
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To answer the stated question - Yes, ***someone*** would use the technology no matter the consequences (other than immediate death, even then sometimes).
A couple other comments:
- The only way that this could be restrained is if the punishment for it's use IS immediate death (or something at least as bad.)
- One could use people condemned to death to summon the demons. This would probably lead to a lot of otherwise benign behaviors leading to a death sentence.
- In a non-egalitarian state, the most powerful would somehow use the weakest members as sacrifices.
superluminary's comment about how de-stabilizing this would be is also very important. Maybe you could make it so that it was not quite so obviously overpowering.
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I am reminded of the history of lead in gasoline: everyone with any knowledge of chemistry said, when leaded gas was introduced, "why, this will poison a lot of stuff and people!"
The oil industry replied: "it reduces engine knocking!" and proceeded to poison a lot of stuff and people, for decades, with zero consequences.
You could also look at the interlocked economies of rum, sugar, slaves, and cotton, or the market for crack cocaine, or opium, or the United Fruit Company, or e-waste dumping in Africa, or Foxconn.
Short answer: human sacrifice is utterly routine here and now. The stakes you describe are much higher, and so will overwhelm "public outcry" all the more easily.
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This is your world. It would be perfectly reasonable for just about anything to come about, so long as you rationalize it.
I feel you are asking for potentialities and rationalizations for them. So here are some:
1) No, never. Its heinous and society, whether repressive or progressive, will not allow it anywhere. Only supervillians and the like have access. Dogmatic repressive societies may have inquisitions and such to root out the Devil-magic.
2) Depends on where you are. Some empires oppose it and wage wars and crusades against those who use it. Those who use it are fewer in number (and possibly doomed, depending upon how you plan to play evil and commupances) but have an enormous edge from their instaneous travel.
3) Yes, its common. Perhaps because its quite dystopic, a sort of Feudal galaxy and lords can largley do whatever they want within their domains. Outward demonstrations of piety may mask smuggling empires and dark pacts. Perhaps its a built-up society, and within the dark corners of corporations the incentives, and pressures, and lack of morals, simply get too desperate...
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Here is an idea
Have your government start a campaign that shows how all of the world's problems stem from undesirables (some minority) who are baby eating devil worshipers (or done other slur)
Create camps to protect the rest of humanity from these undesirables and start using then to fuel your vessel.
You can even pick up orphans, hobos, the mentally ill, and political enemies to act as fuel for your starships.
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In my world, the main "evil" race lives in a labyrinth like rock formation. They use a method of magic that gives them a hive mind advantage, so they all know how to move around within it. My question is, are there any notable real world geographical formations that could potentially work for this? If not, I'm open to fictional concepts for this.
I recall that in the movie 'The Croods', there is a scene involving such a geography. Based on how basalt columns form, I don't think it would be out of the realm of possibility to use those either.
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A large area of limestone in a climate where chemical erosion is more important than physical erosion (because chemical reactions speed up as temperature increases) can produce all sorts of cool pinnacles, gorges and caves, sometimes over vast areas of land. Have a look at this page on the [South China karst](http://whc.unesco.org/en/list/1248) (a world heritage site for geology) and click on the picture gallery.
Or here is an aerial shot of limestone pinnacles in Madagascar: [Tsingy de Bemaraha National Park](http://l7.alamy.com/zooms/f3a1f234510c4d359ab6052496ffe077/eroded-limestone-pinnacles-aerial-bemaraha-national-park-madagascar-bfb21j.jpg)
[](https://i.stack.imgur.com/SZfC0.jpg)
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[Puzzle wood](https://en.wikipedia.org/wiki/Puzzlewood) is used a lot for filming, however i'm pretty sure its features are the result of ancient mining, not natural formations:
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> Over a mile of pathways were laid down in the early 19th century to provide access to the woods, and provide picturesque walks. The area contains strange rock formations, secret caves and ancient trees, with a confusing maze of paths. Puzzlewood is said to be one of J. R. R. Tolkien's inspirations[3](https://i.stack.imgur.com/oomgr.jpg) for Middle-earth in The Lord of the Rings.
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> Puzzlewood was used as a filming location for many episodes of BBC TV show Merlin, **"The Labyrinth of Gedref"** and "The Nightmare Begins",[7] and also the 2010 Doctor Who episode "Flesh and Stone" and the 2013 Doctor Who Christmas Special "The Time of the Doctor"[8] as well as, the BBC's 2016 adaptation A Midsummer Night's Dream. Puzzlewood was used as a film location for Star Wars: The Force Awakens.[9][10]
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If you are really taking the route of an evil race living in rock mazes, then volcanism should do the trick for you.
One month ago I went to Iceland and visited [Dimmuborgir](https://en.wikipedia.org/wiki/Dimmuborgir), an old lava field that was really like a bubble of solid lava that collapsed on itself, with erosion (and man's hand) creating the strange structures and pathways as we see it nowadays.
[](https://i.stack.imgur.com/BciOZ.jpg)
The place is really a gigantic labyrinth, and there is no picture on the internet or even in my own pictures that really retranscribes the feel of walking into such a natural maze, as we were surrounded by rocks (sometimes as sharp as glass), with the edges of the collapsed "bubble" as high as great walls, serving the role of natural fortifications because there was no more than one or two entries in the entire lava field.
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Limestone makes some very cool rock formations and interesting caves that would be perfect for your labyrinth given they have Stalactite's
[](https://i.stack.imgur.com/5diU0.jpg)
These lime stone caves become enormous, currently the deepest cave in the world is know as the [Dark Star](https://en.wikipedia.org/wiki/Dark_Star_(cave)), measuring 17km at a depth of 900m. The whole thing is lime stone and not even completely explored. It is known as [the underground Everest](http://www.nationalgeographic.com/magazine/2017/03/dark-star-deepest-cave-climbing-uzbekistan/).
[](https://i.stack.imgur.com/L58PH.jpg)
Having a lime stone cave system with a lot of water draining through it to create Stalactite columns should work perfectly for your labyrinth.
[](https://i.stack.imgur.com/EI7tp.jpg)
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You can have real rock mazes when large rock formations break and open-up corridors in them.
Think [Black Hills rock maze](https://www.youtube.com/watch?v=Cg2fm07_Qr4) on steroids.
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One way could be [Hoodoos](https://en.wikipedia.org/wiki/Hoodoo_(geology)), similar to the basalt columns you described, but with an uncommonly high density of such columns.
Another option could be sort sort of [large, winding cave system](https://en.wikipedia.org/wiki/Cave#Physical_patterns) that has been uncovered by erosion to form a labyrinth.
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**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
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You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49).
Closed 3 years ago.
[Improve this question](/posts/179326/edit)
There was an old SCP I liked called SCP-3008 (The Infinity IKEA) here it is: <http://www.scp-wiki.net/scp-3008>
My question is, if a group of people were trapped within SCP-3008, what would be the optimal way to survive safely?
**For the uninformed, here are the facts:**
* it is an IKEA. The only tools and materials you have access to are those that can be found in an IKEA.
* Every night (from about 10 PM to 8 AM) creatures called the staff attack. You must defend yourself from them.
* The staff are humanoid entities. While superficially resembling humans they possess exaggerated and inconsistent bodily proportions, often described as being too short or too tall. They possess no facial features and in all observed cases wear a yellow shirt and blue trousers consistent with the IKEA employee uniform.
* During the "night" instances of the staff will become violent towards all other lifeforms within SCP-3008. During these bouts of violence they have been heard to vocalize phrases in English that are typically variations of "The store is now closed, please exit the building". Once "day" begins the staff immediately become passive and begin moving throughout SCP-3008 seemingly at random. They are unresponsive to questioning or other verbal cues in this state, though will react violently if attacked.
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Since the staff seems to be reacting only to presence during night, you can safely close yourself into a wardrobe. Even better, you can take two of them, remove the sliding doors and put them face to face. so that you can stay within.
You can even lay one small wardrobe flat on the ground and use it coffin style, if you fancy it.
Additional passive defensive mean can be
* some shattered mirrors all around the wardrobe (mirrors are available in the appropriate section of the store)
* cut metal springs into pointy objects and lay them on the floor
If you want some attack weapon, you can build something resembling a spear using either the metal side of the wardrobe sliding door, aptly sharpened, or a shower rail where you have stuck something spiky (screws, glass shards, cut springs). You will find a tool box with screwdriver and plier.
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Go to the magazine area. There will be tools there, including forklifts to reach the higher shelves. Clear some of these higher shelves during the day, build the furniture you want and bring food from the restaurant. Create ropes made out of bedsheets and the like to be able to climb up and down, and remove the access point when you are up there. Steal all keys from all forklifts in the area to make sure no one else uses them. You can use pieces of IKEA equipment to make railings so you don't fall off and also to ward off employees that try to climb higher.
More materials can be gained from the assembly center where employees combine orders. They have access to rope, large amounts of wrapping plastic, electric tools like drills and basic screwdrivers and such tools available to them.
As time passes, you are likely able to clear neighbouring stacks and push them closer, creating a larger surface area to live in. It's pretty safe, you can build furniture to live there, it can be expanded, throwing large pieces of wood, fire extinguishers and other somewhat heavy objects would deal with any employees that might find you and try to push the stack over, which is going to take a lot of employees.
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Spend the day examining the vicinity (the particular part of the infinite store that you find yourself) to find where the manager of this part of the store spends most of his working time and where the keys are. If this takes a long time take refuge behind some heavy furniture with some knives. When the keys have been located steal them. Use a lift as a safer hideaway. Put a mattress and food in it use the keys to fiddle around to power it down, disable the doors or park it between levels.
Ultimately use the keys to identify some lockable back room offices and use those as a base.
Another potential hideaway would be the warehouse – find a sparsely filled high bay area with an empty stack, find a ladder and build a refuge up there. You should be able find some tools and could assemble a hideaway out of flat-pack furniture tree house style. Pull the ladder up after you and keep a supply of knives and projectiles. falling glass jars, cacti or big heavy tins should deter most staff if they discover you.
(Assuming the infinite store is an endlessly repeating series of more traditional stores and includes back rooms, lifts and warehouse areas as well as the sales floor area displaying the goods).
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Just disguise yourself as the enemy, and they won't bother you! Rafael in [El Crimen Perfecto](https://www.imdb.com/title/tt0395125/) lives in the store (as an employee), so if they think you're one of them, you'll be all right.
You can take an IKEA uniform from the closed areas. (look for a changing room)
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In many fantasy worlds, there is a "common" language spoken by the majority of all races. While there can be some dwarfs who reject to speak common and speak only dwarf, in many worlds these are a minority.
**Setup:** I have generic medieval world, where there are elves, dwarfs, hobbits, trolls and humans. Humans and hobbits speak common language, while all other races speak their own language.
There is a city operated by humans which is used by all races for trade purposes. What language do people speak in this city?
Looking in Earth history, if the ancient cultures did meet and did trade, they did still use their languages. For instance [ancient Thera](https://en.wikipedia.org/wiki/Ancient_Thera) is believed to be a place where people could understand up to 9 languages.
Is it plausible for a fantasy world to use one language as majority? And if no, what would make using just one language (as major one) plausible?
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I'd argue that any realistic world has to have different languages - its simply the way civilisation develops. Take the UK for example. Geordie and Scots are very nearly different languages to English - very strong dialects eventually become different languages.
It's perfectly reasonable to have a [Lingua Franca,](https://en.wikipedia.org/wiki/Lingua_franca) that a lot of the races speak. In the setting you describe, assuming the city you're speaking of is a major (or the major) trading partner, its not unreasonable to expect that the majority of visitors to the city will have a degree of fluency. Equally, its not beyond the realm of possibility to have elvish or dwarven speakers speaking a mix or a strongly accented version of the common language, similar to [Spanglish](https://en.wikipedia.org/wiki/Spanglish) or [Wenglish](https://en.wikipedia.org/wiki/Welsh_English).
In fact, Welsh is an interesting one because its very different to English, and is a good example to look at in terms of minority languages - should you have a similar issue in the world you're creating.
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To have a *worldwide* "common tongue" is unlikely, given the difficulty of transport and communications in a medieval world. The people on one side of the planet don't even know what manner of creatures live on the other side of the world, let alone what language is spoken there. However to have a *regional* common tongue is very likely, in fact almost inevitable.
However the implausibility of a worldwide lingua franca might evaporate if your world has magical means of instantaneous communication or transport. The effects of a telepathy spell on your world would be similar to the effects of telegraph, radio and the internet on our world. The world would be much more culturally unified, and one language would probably become a global lingua franca, as English is becoming on our world. Instantaneous transport by teleportation spell would take this unifying process even further than in our world.
There are previous questions on Worldbuilding Stack Exchange similar to yours [here](https://worldbuilding.stackexchange.com/questions/17880/would-it-be-possible-for-an-earth-sized-world-to-speak-a-single-language?rq=1) and [here](https://worldbuilding.stackexchange.com/questions/25396/creating-a-realistic-world-spreading-languages).
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There are thousands of languages, which can be grouped into few dozens of families, on Earth with just one sapient species and it used to be even more when there were much fewer people living on this planet. That means, you just need a couple of tens or hundreds of thousands of speakers to establish a language and keep it alive, as long as they are living close enough together and don’t get (re-)assimilated by a larger culture.
A fantasy world where all members of one species speak the same native language is unrealistic, especially if they are spread across several large habitats and when there is no means of instantaneous communication and travel.
In a trade city or in any other agglomeration with strong ethnic diversity, there will certainly be a dominant auxiliary language (“lingua franca”) which is spoken and understood to some degree by almost everyone. Usually it will be the one of the majority of inhabitants or the one of the (maybe former) local or regional power.
Most pidgins that develop in such scenarios tend to be relatively short-lived due to their adhoc nature, but some become proper creole languages. Note that there are often also special-purpose languages, e.g. sacral and sign languages, that are used in parallel by some people.
Since different fantasy species may have very different physical properties from one another, their vocal and auditory systems may favor certain phonemes and phonetic patterns that are hard or even impossible to pronounce or hear for members of some other species. On the one hand, this will result in characteristic dialects when speaking the same language, and on the other, it should favor separate languages for separate species. That is even more so if species evolved and lived in separate regions until quite recently. After they have lived together for a couple of hundred years (or more than a handful of generations) they will probably share common languages.
In a book, the major in-world language will usually surprisingly equal the native tongue of the author. There are some authors who actually pretend to have just translated the book from its original fantasy language. Either is okay, but it may be more disturbing in film and other visual art: *seeing* English written in the roman script on signs in Middle Earth (in the LotR movies), for instance, can be off-putting, especially if you watch the film dubbed in another language.
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A common language would be based on the language of either the historically dominant people or the most expansive and trade-oriented people. Depending on the extent of the contact between all peoples involved it might grow into a simple trade language only used for traveling and trading, or a complete one usable in every facet of daily life.
With slow travel and no mass media, the odds of a common language being spoken by every random villager is very low in a medieval type world, as there just isn't that much contact outside one's village. Along trade routes and especially in cities with mixed populations, the common language would be more well-known.
For people to know a second language, the following need to be true:
1. There is a pressing need to learn it or formal education is mandatory
2. There is education / training available (whether at home, in a guild, etc)
3. There is enough exposure to the language to practice and keep it current
Let's take two small villages along the border between elf and troll lands.
In the elf village, there is a school where all children learn the human and troll languages. The parents force them to practice the human language by only conversing with them in human for a month of their lives. They find troll too harsh/distasteful to speak it much. The local leader often meets with his troll counterpart, as do the traders.
In this village, everyone will understand and speak a decent amount of human but despite the proximity will only be able to barely make themselves understood in troll, with only the leader and traders having a need to keep up their troll.
On the other side, the troll children learn from their parents as they accompany them to work every day. The farmers, bakers, millers etc. speak only troll, since they have neither a need nor an opportunity for learning any other language. There are some exceptions:
* The village elder speaks a little human but no elf, since the elf leader and messengers all speak troll.
* The innkeeper on the other hand speaks decent human, elf and some dwarf, since he gets travelers from all those groups. He is also called on by the village merchant and blacksmith to speak with customers.
* The village healer is fluent in elf, since she's had much interest from the elf healer, who has taken it upon himself to teach her and her daughter.
Without universal education, the troll villagers only learn other language on an individual basis, preventing any common language from spreading.
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I think that this is very plausible. Think of how it happens today in the real world (in fact right here and now):
People all over the wold speak different languages, like me, I am a German, others are British, Chinese, etc. and we all have different languages. But as we need to interact witch each other and work together, we need a way to communicate. This is done by agreeing on a *common* language - here on SE and many other places it is English.
In your fantasy world, this is very much the same. You have different species, just like we have nationalities, that need to cooperate:
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I would say probably human, as it is the main local presence - but it could be anything, that the community agrees on really.
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For the people in your city it seems most plausible that the common language will be that of humans.
Since your setup suggests that since the city is run by humans, one can assume that at least in the beginning, humans formed the vast majority of the population. Those humans spoke the same language.
Over time, members of the other races migrated to your city. While it is possible that they kept their own language, it seems fair to assume that they also learned the language of the city people.
So, it seems likely that you will end up with one language that is common to the vast majority of the inhabitants, regardless of their race. But the members of the different races will still speak their native languages, especially with other members of their race, particularly when they would prefer "outsiders" not to understand (so easily).
Take a look at any of the large cities today: you have a common language (almost) everybody speaks to some degree, and the different ethnic groups often still speak their native language (to some degree) within their group.
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It is very unlikely for a "common spoken language"---which is also within general every-day use---to develop in any continent, or world.
Far more likely is that a non-verbal "trade language" would develop, which would see use mainly when different peoples came together to trade goods, on the pattern of the Native American "world." This "trade language" had been developed to be non-verbal, to get past how nuances of pronunciation, one language to another, would render many spoken words very difficult if not impossible to understand, when pronounced by persons of different tribes.
The "Native American sign language" had evidently come about as a trade language, originally, and very early narratives by Caucasian explorers had often remarked how persons from tribes whose "ranges" were separated not only by hundreds of miles, but also in many cases by physical barriers such as the Mississippi river, or areas under control of hostile tribes, had been able to communicate with one another by "signs."
The Caucasian observers had often viewed the use of a sign language as amazing; virtually bordering on "magic," in some cases. Their initial amazement and even misgiving hadn't interfered with their eagerness to adopt the new sign-language, however!
"Indian signs" had no nuances of pronunciation, such as are seen when comparing many, many modern examples---there are vast differences in word-pronunciation when comparing Northern vs. Southern states; those Eastern vs. Western regions; the Left-Atlantic vs. Right-Atlantic countries; and even those Northern-Hemisphere vs. Southern-Hemisphere countries.
Most of these differences in English pronunciations also exist at a time of major trade and human inter-action; when it's common for people to hear, see, and often even befriend, speakers from other areas. With so much inter-regional communication going on, one might assume people would work actively to minimize pronunciation differences. Instead, the opposite seems the case, with people celebrating the "roots," and the "heritage," of their different areas-of-birth.
The same great differences in pronunciation are evident in other languages that have now grown to span oceans. At times, it's extremely difficult for an "Old World" speaker to understand what's being said by a "New World" speaker, and there are no signs that any steps are being taken to make the "dialects" easier to understand.
Modern onlookers must not imagine that "Indian sign language" was in any way inferior to a spoken tongue: Complex thoughts could be communicated; not merely information relating to the various quantities and relative values of goods.
It also showed the ability to very rapidly evolve, as seen by the speed by which signs had been created, and had evolved, to include new-comers, (such as Caucasians) and Christian clergy; and to include new Caucasian technologies, such as firearms and ammunition.
The same general "evolution" of a sign-language to take the place of a spoken dialect to allow foreigners and traders to communicate with far-flung peoples has been seen in South America, along the Amazon.
The development of similar sign-languages had been seen in other places where traders or explorers had sought to communicate with widely-separated tribes of groups of people---Africa is the most obvious example, but similar use of sign-languages had been seen along the various island-chains in the Pacific--
space does not allow detailed investigation.
In the end, vagaries of pronunciation effectively rule out there being the evolution of any SPOKEN "trade-language" on such a world.
It would be extremely unlikely for distantly-related "races" or "species" such as "Humans" and "Dwarves" to share very much of a language-base, as well! At one time, there had been well over a hundred Native American "Tribes" on the Continent, and there had been dozens of "Tongues" that were shared by many (BUT NOT ALL!) tribes, within an "alliance," or "Confederation." This was the case, world-wide.
We have no blueprint for any single wide-spread language existing. Historically, it was the case that community leaders---shamans or chiefs---would be fluent in two to four regional languages: Those languages of their own tribe, plus brother-tribes or sister-tribes, of applicable; plus the languages of the neighboring tribes . . . who were often counted as their foes, unfortunately.
A Shaman or Chief might be fluent in half a dozen languages, but this would probably not "get him very far" so to speak, on the ground.
That is why many, if not most, members of almost every tribe in North America were fluent in "Sign Language."
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As highly unlikely as a common language would be, it would be possible in theory for there to be a language that makes learning it and other languages much easier.
In our real world, we have Esperanto, which was developed specifically so that it would be a common tongue of the world, and make learning other languages easier to do.
Although it didn't succeed, with only an estimated two million speakers worldwide, you are the ultimate arbiter of what goes and doesn't go in your universe, and therefore can declare that there's a successful example in your world. You could say that there's an international auxiliary language that's easy to learn and makes the learning and comprehension of other languages easier. Then, you could declare that to be the closest it gets to a common language.
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The only reason for a common language I could imagine would be some shared history. This could be a common religion, which forces everyone to read their holy scripture in the original language (e.g. like in Islam). Else there would be pidgin languages e.g. for trade, but it is hard to see how a "global" language could develop in this scenario.
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It is possible, but depends upon your world history. If you assume Earth as an analogue, then you had common languages among different cultural groups only after a conquest. So you get Latin in Europe, Arabic through the middle east, Chinese Asia. Absent such a conquest, you have much less commonality, for example, North America pre-European conquest (but post conquest, you have Native Americans speaking French and English, so there you go.
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I will disagree with consensus here for one main reason. Fantasy worlds tend to be **tiny**. A mid-sized real world country will have millions of inhabitants, hundreds of thousands of square kilometers of land, hundreds if not thousands of cities, all (usually) speaking mostly the same language.
If your entire world consists of a few hundred cities or less, it is entirely plausible that all races have homogenized into a single "common" tongue (though they may keep using their hometown amongst each other language as a point of racial pride).
If your world is more comparable to Earth in size, then their certainly will be many different languages, but it is entirely possible (I would even say likely) that a de facto language of trade would eventually develop, similar to the status that English enjoys on Earth.
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Learning a new language is governed by need. If you don't have to learn any language other than your own in order to exist, most people won't bother, barring the occasional eccentric. I think that unless one faction conquered the known world at some point, it's unlikely that a global language would develop other than a possible 'de-facto trading language'. My reasoning below.
One of the most common needs that pop up is trade. If you want to trade with someone, you can manage with gestures and pointing for a while, but you'll quickly start trying to pick up a few words to ease the process. If you want to move on to more complex trade such as agreements or orders, you'll really have to have a common language. Typically, this would be the language of the party that has the most power, either trading power or military power. Unless this trade is important enough that the majority of the people are involved in it, most people still won't have a need to learn this new language: they can trade with the trader, who will then trade with the foreign party.
Another good reason would be conquest. If you're conquered by another nation, they will probably insist that at least part of the populace learn their language, since otherwise governing matters are complicated.
As for a common language spanning an entire world, this would require either one power being so dominant that its reach spans the larger part of that world, or some sort of unobtainium that can only come from one place but is used globally.
For a real-world parallel to the first, look at English. English is spoken throughout the world because for a long time their reach spanned a large part of the globe and they were a dominant force in global trade at the time.
In the second case, it's still unlikely that the entire population of the world will speak the common language, but it is likely that this language will become the dominant language since only the traders really need to speak it. Since trade with the party that has the unobtainium is so important though, one can expect every trader to know the language, which can lead to all trade being conducted in that language as a matter of convenience: learning that one language allows you to trade with any people without having to learn their specific language.
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(First question I've ever asked here, don't be too harsh on me, please!)
Suppose you have a *kitsune* (Ahri from *League of Legends* is a perfect example of what I have in mind), who loves to roam near human cities – more specifically, the story is set in Russia.
She has visible, non-human features: her ears and tail – everything else is anatomically the same. How would she conceal them, in order to approach humans without raising suspicion?
Her aim is mostly to observe, rather than to socialise, and is quite agile. That is, she can easily jump between roofs, climb walls, and quickly escape, if she's caught.
You might object that she doesn't have to conceal herself, if she's so good at running away: I'd say that if she's caught multiple times, people would get wary/curious about her, and she'd lose her prized anonymity, which is necessary to observe people closely.
So, clothing is a necessity for her ends. The tail can be easily tucked under a thick coat. And an *[Ushanka](http://i00.i.aliimg.com/wsphoto/v1/502281672/Holiday-Sale-New-Arrival-Rabbit-font-b-Fur-b-font-font-b-Hat-b-font-Hot.jpg)* could hide her ears. **But, how/where could she obtain these items?**
She's not driven by instinct, and is perfectly conscious, able to speak fluent Russian, in other words behave like anyone else. Eventually, she desires to try and live in the city.
**What jobs could she do?** – it may be useful to point out that she's considered quite attractive. Before you suggest modelling, I'd like to point out that she isn't afraid to be naked, but she's loathed by the idea that people would lust after her.
**How could she go about her daily life?** – she can't bare her head in a public place, and is reluctant to do so even in a private area, with few people. Say, how could she get her hair styled? (She's proud of hear appearance, but not to a narcissistic degree). Would she just wait until the hairdresser's has served the last customer, and is about to close, so that she's alone, and she'd show her ears to less people?
**Would she be able to live like that?** – would she be able to live like this? She'll find a human companion that takes her in, eventually, which makes her life easier; but still, until then: how long do you think she'd be able to go on?
Thanks in advance.
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She could claim that her tail and ears aren't real, but just an unusual form of surgical [body modification](https://en.wikipedia.org/wiki/Body_modification). I think that most people would find that explanation a lot more plausible than her being a mythological creature. Anyone she can convince of that might think of her as a bit strange, but would then interact with her normally.
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She might not be able to get a white-collar job where body modifications are frowned upon. But I think she could easily get a job somehow related to geek culture. A saleswoman in a manga store who looks like a catgirl might attract quite a lot of customers. But that would likely force her into a lot of social interaction and looking at your description I get the impression that she might not enjoy that. Alternatively she could also perform any job where she wears a uniform with a hat which conceals her ears.
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When she is not born to human parents, then I think her main problem would be that she has no documented identity. She has no birth certificate, ID or tax number. Officially she does not exist. That means it is impossible to get a legal job, open a bank account, rent an apartment or do lots of other things which are required to live a normal life in human society (at least that's the case in most western societies - I don't know how much this applies to Russia).
[Answer]
It helps that she's in Russia. Even moreso, if she's in, say, [Yakutsk](http://en.wikipedia.org/wiki/Yakutsk). But, let's keep it in a big city; she could consider the following.
**Wintertime** - Going about business in winter, in Russia, wearing lots of layers and covered head, face & neck was not an odd sight (well, this was ten years ago). She could consider seasonal activity, and mostly outdoors work, like construction or running a shop, like a Baltik at a busy intersection.
**The Internet & Acceptance** - Building a network of well-meaning people (however small) is critical for anyone, not to mention someone with peculiar attributes. The Internet brings a *wide* variety of people together, and I see no reason why a little research won't help find the right ones. Often, this becomes a geographical reality; we have a neighborhood of cat clowns (don't ask me: it's Portland, Oregon), who go about their day, working at the post office, taking out the trash, etc., dressed as cat clowns. So an accepting home and group of friends will have to be sought out.
**The Internet v2** - You can get almost anything online now, for the summer months. Groceries, hardware, etc. are available for delivery in larger cities; even, presumably in Russia's major cities.
**Own it** - Be known by ignorant people as a freak of nature and by intelligent people as someone special. Go on TV shows for a little spending cash.
**Crime** - Your character sounds adept, so if you want to go that way with your story, it should be easy.
Happy writing!
[Answer]
[](https://i.stack.imgur.com/5hCqZ.gif)
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Anything that would allow her to work through the internet. She could work in IT through home office, for example. And if you think she cannot bare her head because ears, she could be a youtuber who uses that as part of her "being in character". There are youtubers who always wear masks and are successful, so she could just say the ears are fake.
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There is a condition called [hikikomori](https://en.wikipedia.org/wiki/Hikikomori) which causes people to stay in reclusion for months, sometimes years at a time. In an age where you can order food and goods, work, pay your bills and pay online, this is becoming practical to the point where it might even cease being a condition.
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## 2020 update
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> **How could she go about her daily life? Would she be able to live like that?**
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The pandemic just showed us how any of us can live like that. Really no long shot and business as usual. Going outside is totally superfluous.
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Kitsune come from the Japanese legends. One origin I've heard is that if a fox survives to be 100 years old, it gains a second tail and the ability to turn into a human. And yes, no fox-ears, though the shadow of the tails and sometimes the tails themselves become visible if they lose concentration.
They are typically mischief-makers rather than evil.
For your version of Kitsune, she might initially steal these items of clothing, and pay victim back once she has money. Pretty much any job is open to her. I like the suggestion of her working at a manga/comic book store which her ears and tail(s) would be seen as an elaborate costume.
A few random Kitsune things:
Tom Smith has a great song, ["Kitsune and the Master of Zen."](https://www.youtube.com/watch?v=wH735AGxr_g) It is a great example of the shaping game along with more innuendo that I could ever put into a song.
When I use them in games (I used to GM a lot, and they can make great player characters) not even the player knows if they are women who can turn into a fox, or a fox that can turn into a woman.
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There are major religions which call upon women to cover their heads and bodies. If she were willing to submit to their requirements, she could easily hide these non-human features.
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**Jobs**
*Kitsune* have often been represented in Japanese folklore as noblewomen and courtesans, although you don't have to follow that trend. The first thing I thought of was that she might be a model for an artist or sculptor, as opposed to a fashion model. Or she could be a gymnast if she's agile - that might do wonders for showing character competency too.
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Kitsune are masters of illusions so one possible solution would be to create an illusion to hide her ears and tails from humans. She would still have them, they would just be hidden.
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For my setting, I wanted my people to have entirely no concept of sexism whatsoever. To facilitate this, I have made it so that the females of my race are broad-shouldered and generally flat-chested, having the same upper body strength as males. The only way to tell they were female would be if they removed all their armor, whereby their slightly more prominent hips and feminine facial features would become appreciable.
However, there still remains one more issue, which is the problem of childbirth. Now, I have no issues with the conventional way of conception, but in my setting, it would be a notable evolutionary advantage for the mother if she were not overtly hampered in combat while she was with child. This is because many of the women do the same crazy, foolhardy tasks as the men, and nature/dragons/golems don't particularly care who they decide to mess up.
So in short, is there any way for the soon-to-be mothers of my setting to not be hampered by childbirth (if you could include a way around breastfeeding, that'd be grand)? I would prefer a non-sci-fi solution (e.g. no artificial birthing chambers).
Notes: Don't worry about how they raise the children afterwards. Different city-states handle children differently.
Some ideas I already thought of, feel free to argue against them or for them:
1. They lay eggs
2. They give birth to tiny little barely-recognizable creatures, ala Kangaroos.
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it's nearly impossible to have traditional mammalian live births without pregnancy and childbirth being major issues. I don't think any small or even moderate level of change can fix that without going into the realm of impractical. I can think of a few far more extreme approaches which would work, most of which involve doing away with mammalian reproduction for some other alternative.
1. The simplest and most in keeping with traditional sexes is to have a uterine replicator. Females were originally evolved to carry children, but now of days the embryo is removed and grows within a replicator that better protects it then the mother can. This frees the mother from all the hardship of childbearing and puts her on effectively equal footing with the male. Of course this only works in a scientifically advanced society
2. Biological uterine replicators. Perhaps the species has evolved to utilize another creature as their replicator. Think of how female kangaroo give 'birth' the the baby within weeks of fertilization, but what is born is not able to survive on it's own without living in the mother's pouch. Now imagine if instead of using the mother's pouch you used another species as the 'pouch mother'. This would do the same thing as uterine replicators, and be allowed in less advanced societies. Now how to justify this is still an issue. there are a few ways
* A) Domestication. Have a creator that evolved along a similar path to your protagonist species, but is not sapient itself. Think the difference between humans and monkeys. However, this species has evolved a pouch and a similar reproductive method. It could be domesticated and it's pouch used to raise the young 'joeys' of your species. If domesticated awhile ago it could be bred to be a better brood mare for your young. I actually really like this idea and think it would be pretty cool to see implemented now that I thought of it.
* B) Symbiosis. The two species evolved a symbiotic relationship long before sapience occurred. This is actually difficult to do in a believable manner, but I could think of a few ways to do it. If you really are interested in this post a follow up question and I could explain some believable ways to have such a symbiosis occur. The key point is that the species has to gain quite a bit from your protagonist species for it to benefit from such a specialized symbiosis. Personally I think the domestication option is far more viable, and offers an interesting bit of world building without require rethinking the evolutionary psychology of the species.
* C) Symbiosis again, but this time symbiosis with a *plant* that is not sapient. I think this sort of symbiosis is actually more believable, though still takes work to implement. The plant may very well depend on the protagonist species to care for and nurture it entirely. Strong symbiosis between plant and animal has existed, to the point that one can't exist without the other, before. Still, this idea works better if your protagonist species is smaller and tends towards having more than one at a time with a few of them dying. R-selective species are more likely to develop a system that is dependent on trusting an outside force then a K-selective species. It makes more sense if the species started out heavily R-selective and then adapted to more of a K-selective approach only *after* it started using plants for child-rearing. This implies many other species would *also* use plants for child-rearing. It also works better if the species still have some elements of R-selective species, such as having twins and triplets more often and possible being prone to one or two young dying at an early age.
3. Have the species able to transfer the young between male and female, the way the seahorses do, and each trade off carrying the young. Maybe both male and female have pouches and regularly transfer the 'joey' between them. Perhaps it's difficult for one creature to carry the 'joey' to term, thus forcing a couple to have a child which could in turn have interesting effects on the concept of nuclear family and what a 'deadbeat dad' means.
4. Have the species lay eggs, and take turns caring for the eggs.
5. Have a species that employs a combination of R and K reproductive strategies, so they invest very little effort into rearing the child during the original vulnerable stage, and can provide equal effort into later rearing of the children that survive (see my edit below)
All of these are extreme changes from the norm, but these are the only ways I can see to keep pregnancy and birth from being a major difference between the sexes. Similar ideas can be come up with, but the key point is you have to move away from our sexual reproduction to a system where the female does not do all the carrying of the child as it develops.
Other approaches that are slightly different and lower, but not remove, the disparity of the mother are:
* Have the children be born very undeveloped and tiny (but not nearly as bad as the kangaroo example where you still effectively need someone to carry the child in a pouch) so the mother doesn't carry the child as long or is as disabled by it, but the parents have to work together to care for such a week and underdeveloped infant. This is hard to justify except with species employing a hybrid R/K reproductive strategy (see below), but there is room to vary how much they lean towards R vs K.
* Remove sexes and go with hermaphrodites that perform each role. This in turn allows the concept of mating leading to both carrying the child, to concious choice as to which will be the 'female', or to sexual conflict where both 'fight' to be the male when mating (look up penis fencing for an example). The latter would still have an interesting level of sexual conflict, the ones currently carrying children may even be seen as 'weaker' for loosing the sexual conflict.
* Make it comparatively easy for one sex to change to the other sex, thus allowing them to pick their preferred sex. many fish and amphibians can do this so it's not impossible. Though again such an adaptation would require rethinking other aspects of culture and evolution that would occur due to it.
EDIT (indirectly inspired by falco comment):
I wanted to add an aside about R vs K reproduction. R reproduction implies having lots and lots of young, K involves having a few young that develop extensively. Generally sapience is something you would expect only from the K reproductive strategy. Our brains are a *huge* cost. They are what make childbirth harder, but more importantly they require a much higher energy cost, requiring us to consume far more nutrients, and take longer to develop. Instead of being born with instincts that let us survive on our own we need to learn everything. The smarter we will become the more helpless we have to start out as.
However, many of the reproductive strategies I listed are ones used by those that use the R strategy, having lots and lots of young that they leave to fend for themselves and expect to die out. The reason mammals carry their young for so long is because they have so few and are investing so much that they want to be able to help the young develop. Things such as relying on symbiosis with trees or other creatures as brood mares are very much R strategies, and even eggs tend a little more toward the R strategy, though plenty of species like penguins still lay eggs despite being a K species.
Simply put if you want a sapient species they almost have to rare a very small number of young with a high childcare cost, R strategies are not viable scientifically.
The easiest way to address this is to imply that the species started out as an R strategy and later evolved into more of a K strategies as sapience developed. However, this should still be evident. If the species uses R strategies they will likely tend to have twins and triplets, perhaps with a larger time span between litters, rather than one child at a time.
Another option is to say the species has a combination of R and K strategies. Maybe the species produces a massive number of young and force them to survive on their own originally, and only later does higher parental involvement occur with the remaining young that survive. Imagine a frog-like species with an intermediate tadpole phase. The mother births a massive number of young the same way frogs do, and they are left to develop as 'tadpole' like creatures on their own, with many dying to predation or even competition with their siblings. The parents then take a small number (no more then 5, more likely 2-3) that survive this phase and begin to invest effort into raising them. Thus there is little effort from either species in original childbirth, and equal rearing expense after they adopt the surviving 'tadpoles'.
I suggest a separate tadpole phase because brains are expensive, and R strategies don't work with highly intelligent sapient species. Thus they would have to have one phase where they are not sapient, animals like tadpoles, where they are simply trying to survive physically, followed by a metamorphosis into a creature the emphasizes intellect and brain power that still requires a high parental commitment to develop that brain power before it's self sufficient.
Many animals in nature employ strategies that have siblings compete against themselves to select the strongest to survive. birds will sacrifice their weakest, the weak pups often die in litters, hyena young will try to kill each other when their mother isn't looking, and there are species of sharks that actually fight and kill each other while *still in the womb* so that only one is born. It's plausible that this could evolve, less likely than traditional mammals, but could be done. It works best if you can explain why the survival as tadpole helps to select creatures that are more likely to have reproductive success as adults. The simplest strategy that comes to mind is imply a world with high mutagens, like radiation, so that the 'tadpole' phase is to filter out all the young that are born with birth defects or mutated to find the few that managed to be born 'normal' and healthy.
An even more interesting concept would be to have a species that doesn't always metamorph. Perhaps sapient adults birth hundreds of young which grow as smaller 'tadpole' like creatures. They pick a few of the strongest and somehow trigger the metamorphosis of those young into their sapient phase, these young will get high parental involvement and rearing into sapient adults. The remaining young are allowed to continue to grow and develop, and are even capable of eventually reproducing; but won't reach sapient. They are left to live in the wild and survive on their own, with little or any parental involvement, but can still become part of the non-sapient species breeding pool. This strategy combines both R and K strategies and offers some extremely interesting world building options. However, creating a world where this would evolve is difficult, and the implications for their psychology must be considered. I may post a world building question about this since I think it could be very interesting if done right. :)
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To keep things somewhat like they currently are (once again, a bit of a dark answer)
Physical change:
* Shortened pregnancy, and birthed humans are significantly less developed
* Increased fertility, increased chance of twins and triplets
Ethics change:
* Women would not be as attached to their offspring and the connection they make with a baby/child would not be as strong as it currently is.
* It's understood that most children/babies will never make it to adulthood
The idea here is to aim more towards the 'litter' mentality...if 9 in 10 children/babies die either while in their mothers womb during combat or as exceedingly undeveloped newborns, then the mother would need to get pregnant 10 times in a year to ensure one child makes it to adulthood while the other 9 most likely perish along the way
There is a bit of an ethics change here as it challenges the sanctity of life value we hold today where we try to give every child some fighting chance of making it to being adults. But it works in a medieval environment where combat and death is more frequent.
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Have them be **hermaphroditic** - each individual having both male and female sex organs. It doesn't negate the downside of childbirth, but it applies it equally to everyone instead of just the females.
You're already making them appear very similar, so it's a small step to make them totally identical (on average).
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I have an idea for negating the effects of childbearing, and in fact, it may even make pregnant women even more martially deadly. We have all heard of the stories of mothers becoming strong enough to lift trees off their children, so why not extend it to their unborn children instead.
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My solution is to make it so that while childbearing, the females generate more hormones, which toughen and bulk them out, which makes them even tougher than before, in order to be able to protect themselves and their child. This makes them better, faster and stronger than before.
This hormone surge would allow your child bearing women to be so strong they are capable of defeating anything they can not run away from. You could also say that their abdomen also toughens, so to protect the baby.
So yeah, child-bearing she-hulks. This means that child-bearing women are no longer martial liabilities, but could also be used as an elite force. One dark spin on this you do, then, is to have a squad of elite warrior women, who go out and fight, while not truly caring about their child. If their child survives her fights, good for her, if not, they can always make more
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Thanks to the recent discovery of [handwavium](http://www.extremetech.com/extreme/190691-new-diamond-nanothreads-could-be-the-key-material-for-building-a-space-elevator) [‡](http://tvtropes.org/pmwiki/pmwiki.php/Main/HandWave) filaments that can in principle be extruded to any length, we will be able to build [space elevators](https://www.youtube.com/watch?v=Zws0V6Kre5I) sooner than most people would expect.
The interesting question is **where to put it**. The first state to deploy a space elevator will likely have a [significant cost advantage](http://www.news.com.au/news/race-to-build-worlds-first-space-elevator/story-fna7dq6e-1111118059040) and could potentially control all space activities.
Now I was initially considering minimizing the distance covered, so putting it on top of a tall mountain at the equator, such as Mount Chimborazo in Ecuador:
On the plus side, it would look damn cool.
But a country like Ecuador probably can't seriously consider doing this on its own, and experience with the Suez and Panama Canals suggests that maintaining control of the facility in a foreign country is not always feasible, despite any initial investment.
Moreover, the need to steer the cable in orbit around the occasional satellite that might get in the way might mean we want to be able to move the ground-socket about quite a bit, in addition to the thrusters and lasers in orbit or along the cable.
So would we rather place it in the open ocean? Perhaps somewhere in the doldrums?
That would have the advantage of being free of national boundaries, and close to sea-traffic so large objects could be shipped by sea to the elevator. But I worry about storms.
**So, what is the best location for a space elevator?**
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Sea based near the area of Curacao seems a good choice.
<http://www.hurricanecity.com/city/abcislands.htm>
Aruba,Bonaire & Curacao Islands history with tropical systems
Longest gap between storms
25 years 1892-1918
How often this area gets affected?
brushed or hit every 6.50 years
Average years between direct hurricane hits.(5)
once every 28.60 years
Average MPH of hurricane hits. (based on advisories sustained winds, not gusts)
103mph
Statistically when this area should be affected next
1 year overdue
Last affected by
2007, Sept 2nd Hurricane Felix passes just north with 105mph winds while moving west,area sustained TS force winds & some flooding .
This areas hurricane past
1877 Sept 23rd 105mph from the ENE
1886 95 mph Aug 26th from the East.
1892 Oct 8th 95mph from the east.
1932 Nov 3rd 95mph from the NE,HURDAT lists this as a Category 2 hurricane at 12.9N, 71.3W at 12 UTC just north of Aruba
1954 Oct 8th Hurricane Hazel passes just north while moving West with 125mph winds
Also
<http://www.budgettravel.com/blog/storm-free-caribbean-islands-during-hurricane-season,12404/>
Also
<http://spaceplace.nasa.gov/hurricanes/en/>
Additional Edit
Near the Galapagos islands which is closer to the equator said to be **not affected by cyclones**
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> !<http://www.noonsite.com/Countries/Galapagos/pacific-planning-advice>
> !the Galapagos and Easter Island can be dismissed at they are not affected by cyclones
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> !<http://www.scubaiguana.com/html/galapagos_information.html>
> !The coldest month is September. There are no storms in Galapagos
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If someone can add another link for Galapagos Islands it will be much appreciated. Looking for data on places that don't experience storms always gives results on vacation websites.
Additional Edit 2
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> <http://www.pbs.org/wgbh/nova/space/edwards-elevator.html>
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> Q: I think the space elevator is a terrific idea, and I understand how it works, but how would you maintain stability above, say, 1,000 feet? Couldn't one severe storm start the apparatus twisting and swaying, bringing the structure down? Jim Suss, Marietta, Georgia
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> Edwards: Due to the dynamics, the elevator is held extremely tight and will be fairly rigid. Storms and winds will blow it around and move it. We will need to deal with twisting and oscillations, but one thing to remember is that the frequency of this system is seven hours, a very slow oscillation. ***The other aspect is that the anchor will be located in the eastern equatorial Pacific Ocean at a place devoid of major storms, wind, or lightning, just north of the doldrums.***
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> Q: Would the space elevators have to be placed exactly on the equatorial line, like a satellite in a geosynchronous orbit, to maximize the centripetal force of the Earth's rotation to stiffen the elevator cable? Or would they work equally well anywhere on the surface of the Earth? What would be the "orbital physics 101" considerations here? Attila Gyuris, Lake Matthews, California
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> Edwards: The elevator can be placed anywhere within 20 degrees of the equator due to the dynamics, but the performance is best at the equator. As you get off the equator, the ribbon goes up at an angle and eventually is lying close to the ground and is unusable.
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Another viewpoint on equatorial and non-equatorial space elevator
<http://gassend.net/spaceelevator/non-equatorial/>
non Equatorial uniform stress space elevator
<http://gassend.net/spaceelevator/3rd-conference-notes/OffEquator-Talk.pdf>
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Have you considered Brazil? It's a large country with solid economic growth, so it could subsidize construction. It has [launch capacity](http://en.wikipedia.org/wiki/Brazilian_space_program) already. The equator runs through it and intersects the coastline, so easy access to freight shipping. Shipping could come straight from the US or Europe, while Japan and other Asian countries could get there via the Panama Canal. A location near [Macapá](http://en.wikipedia.org/wiki/Macap%C3%A1) seems quite feasible.
I'm not convinced that moving the grounded end is necessary. It would probably take a long time for the change to propagate up the cable. I think that satellites might have to steer to miss it rather than it trying to miss satellites. If the cable does have to move, it may be better to attach thrusters at orbiting level rather than try to move the cable from one end or the other.
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Most of the space elevators stories I've read have placed it at Mt. Kilimanjaro. Perfect location.
I believe that the reasons for anchoring a space elevator on a continent are:
1. Storms are **much** weaker than at sea. Continents are where hurricanes, this planet's most powerful storms, go to die.
2. Access to greater transportation infrastructure.
3. Almost 6 km "for free" of elevation. Every little bit of a space elevator costs even when made from handwavium.
4. Easier access to the anchoring substrate.
5. Only 3 degrees from the equator.
6. Still able to take good advantage of sea ports.
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**Important considerations for the location of a space elevator:**
**Political stability** - Elevator must be placed in the territory of a politically stable country. Construction and operation of an elevator will require an enormous financial investment, and likely be funded and operated via multiple countries. Countries will not invest in such a venture unless it is located in a politically stable location. See Panama Canal as a previous example.
**Equatorial or non-equatorial** - An elevator located away from the equator offers better options in regards to politically stable countries and the possibility of milder weather. However, the work done by Blaise Gassend (<http://gassend.net/index.html>) and others has demonstrated that the elevator needs to be relatively close to the equator especially since deploying the elevator initially will be highly difficult away from the equator. Construction of a space elevator may also have multiple phases which will be easier to accomplish closer to the equator.
**Land or sea** - The complexity of a modern offshore drilling rig and the possible risk of loss of an ocean based platform are two reasons why a floating offshore elevator platform would not be optimal. The ease of access and the reduced cost of transportation to any land based facility will also easily outweigh the benefits of any floating platform. Ask any sailor and they will tell you they would rather be on land during bad weather than at sea. Thus, a land based facility offers more benefits with less risk than a floating platform.
**Mountaintop or sea level** - Once technology allows us to produce the 22,000+ miles of carbon nanotubes to build a space elevator, saving a few miles by locating the elevator at a higher land elevation will have minimal savings. Other considerations like access to a transportation, weather, nearby population, and environmental concerns will likely be more significant drivers of the location decision.
**Weather** - The enormous financial investment and the risk of damage to a space elevator requires that it be placed in as mild a climate as possible. Regions frequented by hurricanes/ typhoons or strong electrical storms would need to be avoided. Areas like the Caribbean would be avoided while the relatively calmer western coasts of most continents would be acceptable.
**Transportation access** - The materials to be moved up a space elevator need to first reach the elevator site here on earth. Efficient transportation networks will be required and consist of roads, ports, and airports.
**Population density** - Cape Canaveral, FL, is a good rocket launch site due to the ability to launch rockets over the ocean. When a mishap does occur, impact to residents is normally avoided as debris will fall into the ocean. To reduce risks to people, a space elevator should be located on or next to an ocean and away from any large population centers.
**Environmental Impact** - Any elevator site will need major infrastructure improvements constructed around it and thus could not be placed in an environmentally or ecologically sensitive area. For example the rich diversity of the Galapagos Islands, would rule it out as a possible location due to the expected damage done to its ecosystem.
Given these considerations, several immediately viable locations for a space elevator are realized. The coast of Ecuador and French or U.S. territorial islands in the Pacific. A multinational effort could be established in Ecuador with a long-term lease of a small parcel of land, see Cuba's Guantanamo Bay example (<https://en.wikipedia.org/wiki/Guantanamo_Bay_Naval_Base>). Ecuador meets many of the important considerations and would benefit immensely from the economic activity surrounding the facility. More remote sites with less desirable transportation options and weather would be several of the French or U.S. territorial islands in the Pacific like Tahiti, American Samoa, Howland Island or Baker Island.
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To add to the existing answers for advantages and drawbacks of a sea-based anchor (e.g. storms and easy accessibility) - and citing from [Wikipedia](http://en.wikipedia.org/wiki/Space_elevator#Base_station):
Mobile platforms (large oceangoing vessels) advantages over stationary bases are the possibility to move the base station, therefore outmaneuvering trouble; like high winds, storms, and space debris, yes even space debris as movement of the lower anchor will also move the rest of the ribbon so to avoid impact. This of course requires accurate tracking of space debris - which fortunately is already done by NASA and others.
Another advantage is the fact that the oceanic anchor could be placed in international waters, thus less trouble with a single nation's legislation (maybe).
High mountains and fixed bases however seem to offer a simpler design, less costs in logistics and the benefit of using its natural high.
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I suggest anchoring the elevator on an artificial island off the coast of Singapore. Two reasons for this:
1. Singapore is only one degree north of the equator, making it ideal from an engineering perspective. Its relatively central position in Southeast Asia, as well as its close proximities to China and India, make the location immensely accessible.
2. The Strait of Malacca is already one of the busiest shipping lanes in the world. meaning goods bound for orbit won't need to make a costly detour.
Ideally the artificial island's location means administration of the anchorpoint would fall under the joint jurisdiction of the Singaporean and Indonesian governments. Technically Singapore can do it themselves, and considering two of Singapore's official languages are English and Mandarin - the global lingua fraca and the most commonly spoken language of the local superpower - they would be ideal. But joint control, even if it's just a formality, is necessary to maintain good relations with Jakarta.
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Since ya'll downvote without bothering to cite, why don't you try reading:
<http://en.wikipedia.org/wiki/Skyhook_(structure)#Non-rotating>
In fact, given that we're hand-waving the strength problem away - you'd be dumb to have a space elevator *at all*, since that requires power to climb it. When instead you could go to orbit for **free**. See the rotating options on that wikipedia page.
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Don't tether it to the Earth. Drop it down so it's reachable by planes, then you've got a lot fewer problems if something hits it/severs it; everything above the sever doesn't become a potential kinetic impactor, and if you've put rockets along the length up, you can fire them and take the rest away as well.
If you place it in the ocean, and when it drops you'll take out coasts on both shores.
Added bonus, since its terminal end is not anchored, you can move it around if the country / ocean you're above becomes problematic, or doesn't want to pay you enough / trade demands - you go somewhere else.
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If you have problems anywhere along the length of your elevator, it's going to lose its balance, and become a nice falling object.
As long as the damage happens to the half which is below the equilibrium point, the remainder of the portion above the severance point will fly off into space (ie: not becoming an impactor).
If you've secured one end to the planet, any damage above that point *has* to become an impactor (ie: up to 99.9% of your elevator) unless you have coping mechanisms.
The simplest coping mechanism is to quickly spool up anything that's not severed, or to rapidly put a larger weight further out. You can also joist anything below the equilibrium point up with rockets, assuming you cut the tether at the ground level - otherwise you're merely putting off impact until your rockets run out of fuel.
If you're tethered to the Earth, then you have a pretty hard limit on how much remaining elevator length you have. If you lose it right at the equilibrium point, you will need a rocket which can lift the whole remaining mass up out of the gravity well (expensive), as well as being able to release it from the ground.
If it's not tethered to the ground, you have a lot more options for anything that's not severed from your structure (ie: the only risk is up to half of the elevator below the equilibrium point (which is also shorter since it doesn't reach all the way to the ground). You also have more time to react, since you've got 10K feet (for example) before impact starts to occur.
The simplest way to do this, is to have a landing bay/pad at the lowest end of the non-tethered elevator, and if anything happens, sever that weight (which is lowest, and probably weighs less than your at-risk portion of the elevator). Yes, you drop something from 10K feet, big splash. You don't lose the rest of your elevator. In this example, the tether/ribbon/elevator is longer, or has a counterweight past the equilibrium point to balance the weight of your landing bay.
Or, to be more clear:
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> How does cutting the bottom 5-30 km from a 36000+km ribbon prevent it from becoming a kinetic impactor?
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It prevents 35,940+ km worth of ribbon from being an impactor, which if the top 30km of your tethered ribbon got severed by terrorist, space junk, micrometeorite, etc would (most likely) be the case.
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If we for a moment drop the idea of putting the anchor on the equator, the first place that comes to my mind is the Tibetan Massif. But since that is very hard to reach, and this extra 5 kilometers doesn't mean much, that may seem a silly idea.
The reason it isn't silly, is that the anchor must be placed on solid rock and in teritory where there are no earthquakes. It would be dumb to lose such a project by bad positioning, like they almost did with Hubble. Given that, the Equator and Africa are bad ideas. The sea is a very bad idea, it would be quite complicated unless we combine the ideas of a tower-like elevator, which would be raised from stable ocean bed to the stratosphere and from there an line like elevator would be anchored.
If we position this contraption on the equator and in the lifting air currents area it could work. Mind that any extra forces would be great to overcome our gravity.
It also occured to me that we don't know the nature of gravity, and learning that in the near future might make an elevator project look like the projects for horse dung storage in New York in the beginning of the XXth century. And cheers to that.
But for a kind of cheap prototype - it is just a hunch, I didn't do any math - I would bet on the Tibetan Massif. I know, politics, Russia, China - but unless we calm down and work on this one together in peace we aren't going nowhere, in the first place. Somebody dumb enough might just strike it with bomb or plane and here we go.
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The largest self-powered vehicle in the world is the [NASA crawler-transporter](https://en.wikipedia.org/wiki/Crawler-transporter), a 2700 ton machine designed to transport the Space Shuttle a short distance and in a straight line.
[](https://i.stack.imgur.com/2Ajto.gif)
During WW2, German engineers designed the [P1000 Ratte](https://en.wikipedia.org/wiki/Landkreuzer_P._1000_Ratte), a ridiculously huge thousand-ton supertank. It was never built, and likely would have been a complete waste of resources. It would have been extremely vulnerable to bombing, and would have severe difficulty traversing the landscape of continental Europe.
[](https://i.stack.imgur.com/CFHMw.jpg)
Fictionally, the larger vehicles of Homeworld: Deserts of Kharak appear based on the aesthetic of the crawler-transporter, but scaled up to ludicrous size. Note that the dune buggy-like vehicle in the lower right is large enough to have a multi-person crew, for reference.
[](https://i.stack.imgur.com/b0XZf.png)
In the real-world, megavehicles like these are militarily non-viable. They would be vulnerable to airpower and tactical nuclear strike, incapable of traversing bridges or following roads, and offer no apparent benefit over a convoy of more specialized vehicles.
Deserts of Kharak appears to attempt to address these issues through its worldbuilding- the setting is a massive desert without bridges or roads, airpower is minimal because of sandstorms, and the extreme heat of the desert requires that vehicles be reasonably self-sufficient (ie crews cannot make camp outside their vehicles, and must live onboard 24/7). The technological base is science-fictional, but not dramatically more advanced than the present day in most respects, with the exception that nuclear weapons are not available.
My naive intuition is that if armor is viable as protection, the square-cube law favors larger vehicles as they gain greater protection for an equivalent armor mass fraction. However, by the same token, ground pressure increases at the same rate, and in sandy terrain that becomes a problem. I'm assuming that any realistic take on this concept will at least need much more track surface than the crawler-transporter or Deserts of Kharak vehicles, for the sake of ground pressure.
**Do these conditions actually favor very large land vehicles for military use? If not, what are the minimum changes necessary to the environment or technological base to make such megavehicles practical?**
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A good place to start with this would be to look at the history of naval battle, where this issue has already been addressed.
From the 1700s through to the 1940s, battleships got larger and larger, and carried heavier and heavier armour. To be sure, there were some forays into more agile, lightly armoured battleships (called battlecruisers) but for the most part, battleships were bigger and bigger, more heavily armoured, and carried larger guns.
This last point is the most important. Their size meant that they could carry guns that were more powerful, had longer range and could do far more destructive damage. This culminated in ships like the USS Missouri that could hit targets well over the horizon with shells weighing more than some vehicles.
The problem with such ships was that they needed aerial spotters for their targets, and carried SO MUCH firepower that its use was controlled, even in a battle situation. It was also vulnerable to short range attacks from much smaller boats (like torpedo boats) and of course submarines. This is why we have a concept of battle groups; small fleets of smaller boats that protect the primary offensive weapon, in this case the battleship.
That said, we don't make these ships anymore. Why not? Aircraft carriers.
Aircraft are effectively longer range weapons without recoil effects on your battle platform. A normal modern aircraft carrier can now carry between 50 and 100 planes, meaning that you can strike multiple targets, at any range, and create a far more effective defensive screen for your weapons platform than a conventional battleship. Again, it's about range and size of destructive potential.
So; if you want to build large land based weapons platforms, those platforms *have* to bring some military advantage that cannot be achieved by assigning the same amount of resources (engineers, metal, etc.) to a fleet of smaller vehicles. What I'm guessing is that would have to be ranged attacks of larger destructive power.
The thing is, in a modern world with cruise missiles and other long range guided missiles, this just isn't viable. You can hold a massive ranged destructive potential on an articulated truck these days, that can act as a missile launch platform. Have a couple of tanks and 50-cal jeeps protecting your ranged missile launcher and you have the same configuration as a naval battle group, only cheaper, smaller and faster. Additionally, I don't think you'll get the larger land vehicles through mountain passes and the like.
One potential option is a large land based mobile platform for landing and refuelling (and rearming) VTOL aircraft. Ironically enough, introducing aircraft in an environment with little to no permanent buildings or fixed infrastructure may be the reason for large mobile bases as such.
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**Its going to be a lot bigger than you think in a lot of ways you haven't thought about**
I'm a former Marine Infantryman (anti tank gunner), I don't know much mechanics, but I know tactics. There is a very good reason military vehicles have been trending towards being smaller and more mobile rather than large and "indestructible." Primarily, that nothing is indestructible. The larger a heat signature and the less ability the vehicle has to move out of the way of incoming fire the less likely such a vehicle is to survive. Its better to decrease detection signature and increase mobility than it is to increase size and armor. Anything as big as what you are talking about is going to be a massive target for artillery and air-strikes. Also, there is not real way to transport the vehicle to the combat theater. The only way such a vehicle would be feasible is if it were being deployed well behind the front echelon as a defensive measure or command and control asset. It would need to be heavily screened with air cover and be far enough into the rear echelon that artillery could not reach it. This becomes a long, loooong distance when you factor in the fact that modern artillery rockets such as the HIMAR system in use by the USA can accurately strike targets hundreds of miles away. Additionally it would need air to air defenses the likes of which we could only dream of in Reagan's Star Wars program to prevent waves of cruise missiles being deployed against it from other continents.
So, in summary, for such a super-heavy "Land-Ship" type vehicle to make sense tactically it would need to be far, far away from the action, have massive amounts of resources dedicated to defending it, and posses a nearly impenetrable air defense system. I'm talking at least an entire battalion of infantry, a battalion of armor, an artillery battery or two, a squadron of aircraft, a battalion of engineers and mechanics, a logistics and supply battalion. You're basically going to be dedicating and entire force big enough to invade most small nations just to supply, maintain, and defend the thing. You are going to need efficient enough logistics to supply not only the land-ship as it moves, but also the regimental sized security and logistics detachment you have following it around. This thing would basically be a land based Marine Air Ground Taskforce (MAGTF.) To give you an idea of how big a MAGTF is, the last time I saw an actual MAGTF summoned together we all ended up invading Iraq and controlling a province the size of Massachusetts.
Its not physically impossible, or even tactically impossible enough not to be used in fiction. Its just going to be a way, WAY bigger undertaking than you think if depicted realistically.
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Rather than think 'earth-based' military tactics, one needs to look at the tactics of this particular planet, and of the purpose of the vehicle. Would there be a situation where such a vehicle would be advantageous?
As described, I understand the planet to be a huge barren, flat land mass, perhaps as big as Pangaea, with no particular geological features. No colliding tectonic plates to create mountains, for instance. Populated zones are at the poles, widely separated by this huge land mass. Covering it would take a week of travel, perhaps, with no permanent pit stops except on well-established but limited transportation corridors.
Limiting air travel is not difficult, once it is recognized that aircraft engines require a specific composition of the atmosphere. Limit the oxygen, limit the air travel, for instance. A high concentration of nitrogen in the atmosphere, perhaps. Thus, along with fuel, the aircraft would also have to carry the oxidizer. They would have very limited range, or they would be extremely inefficient payload wise.
In such a case, I would see this vehicle as a 'land-based air craft carrier'. A vehicle that would carry auxiliary vehicles from temporary base to temporary base. Vertical take-off and landing craft. Given the vagarities of the weather patterns on your planet, and the limitations on air cover, such a tactic would be very useful for close support. Move the airfield to where it was needed.
Maintenance bases for ground based troops, days away from any supply depot, would be easy targets. Supply routes would be extremely vulnerable, as they would be limited and very long. Instead of having military bases spread out over the entire land mass, make them portable. Move the base to where it was needed.
On your planet, long-distance sensors and detection would pretty much span the entire land mass, so the 'enemy' could clearly be spotted before any potential engagement. Air-born weapons would have to traverse a great distance before hitting their target. Sufficient intercept time to destroy them. Under such conditions, engagements would be localized. Hit and run. Attrition.
As an aside, it is not hard to imagine a species that was adapted enough to survive in a low-oxygen, high nitrogen atmosphere. Their metabolism would not mimic ours, but earth once had such an atmosphere, and life developed. Think slow-moving creatures, low metabolic rate.
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Ground effect craft.
[](https://i.stack.imgur.com/pkIWa.jpg)
I know this is over water but it may be possible to use ground effect over smooth ground such as deserts.
This is not an air plane it is the Caspian sea monster
<https://en.wikipedia.org/wiki/Caspian_Sea_Monster>
General characteristics
* Length: 92.00 m (301 ft 10 in)
* Wingspan: 37.60 m (123 ft 4 in)
* Tail stabilizer span: 37 m (121 ft 5 in)
* Height: 21.80 m (71 ft 6 in)
* Wing area: 662.50 m2 (7,131.1 sq ft)
* Empty weight: 240,000 kg (529,109 lb)
* Max takeoff weight: 544,000 kg (1,199,315 lb)
* Powerplant: 10 × Dobrynin VD-7 turbojet, 127.53 kN (28,670 lbf) thrust each
Performance
* Maximum speed: 500 km/h (311 mph; 270 kn)
* Cruise speed: 430 km/h (267 mph; 232 kn)
* Range: 1,500 km (932 mi; 810 nmi)
* Ground effect altitude: 4–14 m (13 ft 1 in–45 ft 11 in)
* Maximum sea state: 1.2 m (3 ft 11 in)
hopefully I don't get down voted to badly, but I just love this thing.
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Many of the answers here address the issue of why they aren't practical, and can be summed up as: it's big, slow and hard to defend.
So what would change this?
**Option 1: Add more power**
Add super-advanced engines (and super advanced shock absorbers) that allow you vehicle to reach 100kph. It'll still be vunerable to bombing (so you'll need AA), but should be less vulnerable to ICBM's and other artillery now.
The only option I can think of here are fusion reactors.
**Option 2: Add more armour**
Obviously this has it's own issues (such as weight), so let's run science-fiction and introduce .... shielding. If you can shield from incoming attacks, then your super-huge vehicle can now be used. *Maybe shield generators need a lot of power, or are physically huge, so only large land vehicle can support them.*
**Option 3: Hide it**
Add really powerful ECM to make it hard for long range targets to target it, or cloaking, or some method to hide it. Yes, I am talking about cloaking a massive vehicle. If sci-fi has cloaking devices on spaceships, why not on massive land vehicles? (Uh, sir, the giant tank tracks just, uh, stop in the middle of the desert)
Ok, so now that it's now blown out of the water as soon as it rolls out of your production facilities, what can we use it for?
* Destroying towns by driving over them
* Mobile air-base/fueling depo/resupply unit. No long supply lines.
* Manufacturing vehicles/arms on-demand
* Standing force for enforcing control over a captured area
* Presumably it has lots of guns, so perhaps area denial
* A safe place for the president
* Psychological warfare
And how do we get it places? Well, I guess you either drive it or teleport it.
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> My naive intuition is that if armor is viable as protection, the square-cube law favors larger vehicles as they gain greater protection for an equivalent armor mass fraction.
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Your intuition is not naive, but it is also not completely correct either.
The biggest problem a supergiant tank would face would be power. If you follow the square-cube law, as the vehicle design grows, the armor and other heavy parts will become heavier at too fast a rate for the engines to pick up.
For example, the [M1 Abrams tank](https://en.wikipedia.org/wiki/M1_Abrams) weights around 60-70 tons. The [Honeywell AGT 1500](https://en.wikipedia.org/wiki/Honeywell_AGT1500), its engine and main power plant, [weights 1.134 tons](https://www.forecastinternational.com/archive/disp_pdf.cfm?DACH_RECNO=180). So we can say that the power plant to vehicle weight ratio is around 1:60.
That tank is about 10 meters long. If we scale it to be 100 meters long, the whole thing could weight as much as 216,000 tons. The engine, on the other hand, would weight 1.459 tons. The powerplant to vehicle weight ratio then becomes 0.00000675. Not only the tank would be stuck in place, it would probably be unable to move its turret and other parts.
The immediate way to solve this problem is by making the engine bigger in relation to the rest of the vehicle, but that takes space and mass from other things such as guns and armor, reducing the advantage of large sizes. At some scale the advantages of a large size are negated, and over that scale everything becomes dead weight. This is not efficient.
If you got the materials to build a huge vehicle that would be unnefective, you would make better use of your resources by building smaller vehicles, or a ground base (i.e.: a bunker or a missiles silo) rather than a giant tank.
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Of course, if a leap in power generation technology happens, larger vehicles become more viable. In the 1920's cars were generally bigger and most engines back then were in the 25-30 HP range. Motorcycles nowadays can easily reach 150 or more HP with much less size and weight. If the trend goes on, giant tanks may be possible within this century or the next.
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For the record, the space shuttle transport in the question is far from being the largest self-powered vehicle in existence. Bucket wheel excavators easily reach 14,000 tons, and the Seawise Giant is over 640,000 tons heavy.
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* Ships need hulls to displace water, aircraft need wings to generate lift, tanks need tracks or wheels to carry the weight. Of these, wings and tracks depend on area while ship dispacement is proportional to volume. So air and ground suffer from the square-cube relationship, water does not.
* Ground vehicles **can** easily stop where they are, load ammo from a supply vehicle to a firing vehicle, or take supplies from a supply dump. Underway replenishment for water and air vehicles is more difficult. *Even in the desert, if suited crew cannot step outside for loading, how can any vehicle operate there?*
* Ground vehicle crews could also sleep in camping vans or the like instead of their combat vehicles, because volume behind the thick armor will be at a premium. Volume in a merely climate-controlled shell is cheaper.
So water vehicles can and need to get relatively large, air vehicles might need to get large but cannot, ground vehicles don't need to get all that large. That being said, tanks **have** grown over the years, just not as much as you suggest.
* Once upon a time, 30 or 40 tons was a *medium* tank, 50 or 60 tons was a *heavy* tank.
* Then they dumped the heavy and designated the medium *main battle tank*.
* By today, MBTs have grown to 60 to 70 tons, heavier than a [M103](https://en.wikipedia.org/wiki/M103_(heavy_tank)).
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As military vehicles never, as extraction equipment the military needs to defend sure, mining is already pushing for bigger and bigger machines as they are more cost effective. maybe the vehicles are really mobile refineries and just carry armaments becasue the are targets. Would help explain why they are on such a planet in the first place.
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**Energy Shields**
As other posters have said, with current technology, big vehicle = big target.
If you have to supply power to a heavy, expensive energy shield, You would want to get as much stuff inside the shield as possible.
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The main issue with huge vehicles is that they lack protection against air attack.
Proposed solution: Configure your world so that air based attacks are impractical (strong unpredictable storms? Only heavy energy sources available eg nuclear reactors?)
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As everyone else has said, your tank's biggest enemy would be concentrated artillery/airstrikes.
Your best defense against this would be the specifics of the planet. You've already got dust storms, good!
Add some high, gusty winds to disrupt ballistic artillery, add in some particulate to the storms that can disrupt/scatter radio/IR, that way guided missiles are ineffective. Essentially, make it such a hostile environment for anything in the air and sensors that air support is impossible.
The hostile conditions could include high levels of radiation in certain atmospheric layers, nasty particulate, corrosive gas layers, etc. Make it so the only viable fighting terrain is on the ground.
Once the war is fought on the ground, add some serious point defense, use it as a mobile base, and protect it with scouting parties.
Unfortunately, due to the atmospheric conditions, targeting/visibility would also be severely reduced, so combat is kept within 5 miles, say. No longer a massive artillery platform, but more like a moving bunker/trench system.
It'd have to be one nasty planet, but it should be doable!
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**If driving is all you can, driving is what you'll do.** You don't have to summon the worms of Dune, but you need to have a reason why **staying in one place does not work** (Weird alien proscriptions? Some legal loophole ('No *permanent* structure shall...')? Something geological (the terminator of a very slow-revolving planet makes the local lanscape go boom)? Something celestial (Pityful atmo (perhaps mostly sand in VVLEO?), no magnetic field, and some harsh irradiators in the vicinity that burn everything they face)?). This builds the **economic case to design everything mobile**: quarters, industry, garages, hospitals, refineries, even warehouses.Your already established reasons against flying will prevent airships popping up as solutions, going orbital is discouraged by the necessity to return to ground for replenishing handwavium stores and the associated risk in crossing the atmosphere.
So the only viable path is going mobile, and the only way to conserve energy is going mobile in as few vehicles as possible. the energetic overhead of airconditioning (make the desert cold, not hot, otherwise that relation will be reversed. Poisonous atmosphere is a bonus), radiation-proofing, and generally xyz-ing everything that favours mass over surface will automaticall lead to huge crawlers. Now if you absolutely HAVE to have military conflict on a scale that includes attacks that could endanger whole vehicles structurally (instead of just limited raiding, or boarding-attemps), you'll have to go the way of the carrier group: huge vehicles with rather small scale weaponry and some incredibly costly cargo (be it industry or attack-craft) accompanied by smaller, faster, energetically more costly vehicles with more punch. Everyone will just engage in short range attacks and mine-laying because your aerial interdiction (winds? aliens with plane-allergies?) may be extended to make artillery shelling unreliable (bad aerial reconnaissance-possiblities already go a long way to making artillery short range).
A word on numbers:
Mass goes by the cube of size, while the area (both atmospheric surface and touched surface) goes by the square of size. Ground pressure on a tank can average up to around 100kPa for the heavier ones, which is easy to remember, because that is one atmosphere of pressure. If you want to keep your lawn, you should not exceed 10kPa, if you just want the ground to bear you, everything from 100kPa (loose sand) to 800kPa (dense clay-y gravel) may apply. So in a sandy desert, we should not much exceed the current heavyweight tanks? I'm not convinced - for very large surfaces, the admissible ground-pressure may well be much higher, because the material simply has nowhere to go - The Schwerbelastungskörper was a Nazi test of how much the ground would actually bear: They weighed down 100m² with 12kt of concrete (so 1200kPa)- not much sinking was observed. You might need speial treads to actually achieve full coverage of huge areas, but why not go with pressurized mats or some other area-spreading technique? Clunky steel treads don't fare well with sharp edges of unyielding material.
Also google **Schreitwerk** for a very cool alternative to treads...
Bucket wheel excavators weigh in the 10kt range and have a motor in the 15MW range (Abrams: 0.06kt, 1MW, so talk about scaling...) - they also have extensive booms and overhang, so the actual tread-to-mass-ratio is probably much smaller than in tanks.
Sure, to generate 1MW you need about 100grams of fuel *per second*, but that weird landcrawlers haunting alien deserts would need some kind of handwavium was clear from the get-go, i think.
I say take a good look at bucket excavators, scale up, armor (if you absolutely can't stop yourself) and let 'em rip!
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With today's technologies firing a gun inside a spacecraft could be catastrophic, [although not certain](https://space.stackexchange.com/questions/4617/could-a-gun-fired-inside-the-iss-rupture-it) it's widely agreed that firing weapons inside the space stations is very risky.
Assuming space travel was much more prevalent but technology not significantly far beyond ours I'm interested in the sort of weaponry and tactics police, army and other tactical organisations would use.
For example:
* A hostage situation onboard the ISS
* The armed response team want to save the hostages and the station itself
I assume
* Projectile weapons
* Explosives
* Tasers
Are all out for fear of damaging the station and killing everyone. How would they do it? What weapons would they use?
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Space stations are confined spaces. Assuming that you can get in at all (this will be quite a dangerous struggle), consider gas weapons. Especially if you can find some plumbing on the outside to pump it in. A teargas canister will incapacitate the unprepared and not affect your suit-wearing boarding team.
But what if they *are* prepared in suits? This levels the field somewhat with your boarding team who have to wear suits. Try [expanding foam](http://articles.latimes.com/1995-06-11/news/mn-12061_1_non-lethal-weapons): you can very quickly fill the area around someone. Within a confined space station, even an inflatable object made of tear-resistant material becomes a useful area denial weapon. Nets will also be good weapons, a concept dating from Roman gladiatorial times. You could have memory-wire or heatshrink technologically advanced netting that speeds up the process.
Another possibility is laser weapons for blinding rather than burning. One flash of a suitable laser onto a specular reflective surface and everyone nearby who isn't wearing the right filters is *permanently* blind. These are banned under the Geneva convention for this reason, but if ocular reconstruction technology is cheap and easy you could imagine them becoming un-banned.
However, any kind of "dead man's switch" on a bomb or critical systems would easily make it a Pyrric victory. The station is very easy to destroy if the occupiers want to prevent its capture.
The easiest thing to do is vent their atmosphere, forcing them into suits with limited air supply, and wait. The disadvantage of this is it takes time and will result in deaths of hostages.
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Well, if your space station is a military-type installation, or built anywhere near those standards, I can imagine that they would invest in bulkheads similar to what you'd see on a modern naval ship. Right now, the reason we have relatively fragile things in space is the cost of putting materials into orbit. If space travel has become prominent, then it can be assumed that we overcame that challenge.
So, that being said, if you build a space craft like a modern naval ship...the walls are tough enough to shrug off small arms fire. Low-velocity hollow rounds would probably be the safest...enough punch to go through a squishy human, but a steel wall would stop it cold, with little more than a dent to tell of the impact. It makes sense that a craft built with the potential of being boarded is going to be built in such a way that it can survive the first person to fire a gun onboard. Otherwise, boarders will hop aboard, breach your hull, then just sit back and wait.
Barring the idea that someone would build a space station such that a kid with a .22 wouldn't be able to breach the hull, or considering your specific scenario here are some other options that currently exist.
Sonic weaponry (you can use the right frequencies to reduce humans to nauseous puking messes on the floor), Infrared weaponry (so called 'heat rays' inflict debilitating pain on organics, but do practically nothing to anything non-organic), anything used for riot control (rubber bullets, beanbags, stingball grenades, gas, etc.).
Flashbang + melee is always good too, that is a very common means for close quarters combat, and is probably what would be used in a situation like the ISS. Perhaps not with your standard flashbang grenade, but the idea is sound: blind/disorient opponents, swarm in and take them down without firing a shot. And yes, this works in military applications as well; I have first hand accounts of someone who was onboard a ship when, during a training exercise, it was boarded and taken over without the boarding team firing a single 'shot'.
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There are a variety of weapons that are designed to be non-lethal for riot control.
Rubber and plastic bullets (which need to be fired from special guns) don't penetrate people, so I would tend to think the spacecraft should be okay.
There are specialized versions of rubber and plastic bullets called pepper rounds which are used for home defense. In addition to the non-lethal stopping power, they also leave a trail of pepper dust which can irritate eyes, skin etc... Of course, there are a whole host of agents both lethal and non which can be used in its place.
Sponge grenades and bean bag rounds are larger rounds, but also could be effective.
There are also varieties of lower powered bullets like .22 shorts. These are largely used for target practice and hunting little creatures. They do not penetrate as deeply. Occasionally they are made of compressed metal dust, common at target ranges, which essentially disintegrate on impact.
But the holy grail in this case is probably a bullet like the Glaser Safety Slug which is the ammo of choice for Sky Marshals in the US. The Glaser is a hollow bullet filled with bird shot which disintegrates on impact with any surface that is harder than it. They theoretically cannot pierce an aircraft's hull, they don't ricochet, but they'll still take down those space pirates.
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The power of a single hole to suck things through it has been overstated in a lot of fiction.
Having said that holing of a space station/space craft is something you would generally try to avoid. In Babylon 5 that was actually one of the reasons they gave for the energy weapons they use - they don't do serious damage to ship hulls etc.
Tasers would be safe enough to use - the amount of charge they deliver would be dissipated harmlessly if they struck a wall/floor/ceiling. If they directly struck sensitive electronics they may burn out those electrics but that would just involve replacing a few components or circuit boards to repair. They wouldn't work very well against people in space suits though.
Explosives might actually be a very effective weapon in a military operation not involving hostages or if some or all of the kidnappers are in a separately airtight area of the base. The attackers would be wearing combat-reinforced space suits. If they deliberately blow a large hull breach then everyone inside would be sucked out and/or killed by the explosive decompression then you can clear up, repair the breach and refill the atmosphere. If repairing and refilling are not practical and you want to keep the space station/craft then obviously explosives are not a good idea.
Projectiles as mentioned in the comments would risk some damage so would be best avoided, if they were used then low caliber and low power rounds would probably be preferred. One good option would be riot guns and beanbag rounds. They would be unlikely to damage the station but be very effective at subduing the people inside it.
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Given that AFAIK the ISS gets all its energy from solar power, I guess a good strategy would be to block the sunlight from the solar cells, and then wait until the hostage-takers give up.
That's of course assuming they are not the suicide-terrorist type. But if they are, I doubt much can be done anyway.
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The hard sci-fi RPG *[Diaspora](http://www.vsca.ca/Diaspora/diaspora-srd.html)* mentions the possibility of a boarding party using old-fashioned bladed weapons, like swords and daggers, for this very reason. However, to use swords effectively requires enough open room to swing them, so if space is cramped, that might be an issue.
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If we ever get to the point of having "space marshals", they will probably carry frangible bullets(safety bullets made of polymer packed with bird shot so they fragment on impact rather than pierce) just like air marshals used to. While the little pellets would cause their own problems in zero G, it shouldn't be too hard to believably work around or hand wave away low penetration round with no details on how it works. Perhaps bean bags like some less lethal weapons fire.
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**This question already has answers here**:
[What should architecture of an Imperial capital be like in order to accommodate differing people of differing sizes?](/questions/9507/what-should-architecture-of-an-imperial-capital-be-like-in-order-to-accommodate)
(3 answers)
Closed 6 years ago.
More specifically, given that you have to accommodate creatures that can be anything between 2 and 21 feet tall, and you want all these creatures to have accommodations such as inns or houses, and also be able to trade and mingle with each other (perhaps in bars, stores, or plazas)?
Background:
I am in a Pathfinder game (Tabletop RPG, D&D-like) and our group is setting up what is essentially a federation of allied tribes who have access to mostly stone-age tech and only recently have been exposed to medieval-level tech.
We are planning a city where our allies can trade, mingle, and plan future wars together.
However, when the Storm Giants joined ("Adults are typically 21 feet tall and weigh 12,000 pounds.") we realized we have a logistical problem.
The game master later joked that it'll get worse when we have Pixies ("Most pixies stand just over 2 feet tall and weigh about 30 pounds and can fly"), but I took that as a dire warning.
A regularly constructed city that's normal for humans would be... Sub-optimal to say the least, however I have very few ideas on how to plan a city that could make this work - my best one so far is simply "Tall buildings, big doors with smaller ones built into them".
I could really use some advice on the matter!
Keep in mind that this uses Pathfinder rules for magic (they are easy enough to find online), so any solution or planning that involves magic is acceptable as long as it doesn't require an army of wizards casting powerful spells continuously.
[Answer]
## Have you played Tetris?
From your question, it sounds like the differently-sized groups (mostly) get along with each other, and would be expected to co-mingle. If this weren't the case, a (practical, not socio-political) segregation would allow you to simply construct separate districts for each size group. (The giants district has big buildings, pixies have smaller buildings, perhaps at least with larger lobbies so there's room for a giant or two to come for a meeting.)
However, if they co-mingle and co-habitate, your suggestion:
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> Tall buildings, big doors with smaller ones built into them
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... is already a reasonable approach. Even with magic, building smaller rooms/buildings is easier (and probably cheaper) than building larger ones, and if you have limited real-estate as well, that compounds the problem.
Have you played Tetris?
Let's use the Inn as an example. You obviously need a front door, lobby, and common areas that can accommodate all sizes. That means you build that part giant-sized, of course. From there, however, you can build the individual rooms of varying sizes.
Public buildings like a town hall would need to be giant-sized. Having one small and one large door would indeed make sense. 2ft fairies could probably open a human-sized door without undue effort, so you don't need a different door for *everyone.*
The trick to making it all space-efficient is to only build as many "giant" areas as you need to, to accommodate the number of giants that will need to access any area at once. Giants are the limiting factor; it will be relatively easy to pack in the accommodations for the smaller species once the giants are settled.
Keep in mind also that giants can probably sit or stand on the 1st floor and talk to people on the 2nd floor, so you could have common areas with "open" designs that give the giants some multi-floor headroom while still providing a 2nd floor around the edges of the room for the shorter patrons.
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I won't talk about the small-scale structure of buildings, since the answer by type\_outcast has that well-covered. However, I will mention the feasibility issues in constructing buildings suitable for a variety of creatures. The height of the giants is the limiting factor. The minimum height of a ceiling should be such that if the largest person likely to enter a building raised their hands, they wouldn't touch the ceiling. Otherwise, the construction may well feel cramped. Of course, grander buildings are often significantly taller than this criterion would suggest. Storm giant adults are typically 21 feet tall. If their heights follow a roughly Gaussian distribution, as is the case with humans, and we assume that the standard deviation is simply scaled up with the mean, then storm giants who are 23 feet tall are feasible within a modestly sized population. Regardless, a Huge bipedal creature is assumed to be able to reach 32 feet without jumping.
So we see that a ceiling **must be 32 feet high**, merely to prevent storm giants from brushing the ceiling when they reach up and stretch. The best bet for constructing ceilings this high is stone. However, your technology is barely coming out of the Stone Age! You might have trouble making reliable ceilings 32 feet tall or higher with technology alone.
## You're a wizard, prospective architect
**Fortunately, you have magic**. The best bet is the *Moaning Diamond*. Yes, this is a major artifact, but it is truly powerful. It can reshape 5,000 cubic feet of stone (or earth for that matter) *three times per day*. With a decent knowledge of engineering (or some trial and error), quite high stone ceilings are plausible.
Let's say that you make the walls 9 feet thick (like Notre Dame). Of course, this will only be at the base, and is certainly excessive, but it serves as an upper bound. Then a 555 square foot area can be constructed each day from the underlying stone, which in a mere ten days would allow the construction of a cubic stone building 52 feet on a side. Obviously, the building could be even larger, since the stone would be much thinner at the top, and 9 feet, even at the base, is very thick indeed (Notre Dame is about 100 feet tall under the vault, far larger than the minimum needed by our giants). But the point is, with such powerful magic, an area with a great deal of underlying stone, and the insane intelligence of a high-level wizard or such, the construction of giant-size buildings would be child's play.
There are other techniques, of course. *Stone shape* is a weaker alternative to the *Moaning Diamond*, which at level 20 can reshape 30 cubic feet per use. A cleric with the Earth domain can theoretically cast this spell 35 times per day, which comes to 1050 cubic feet of stone per day. This is about one-fifteenth the strength of the *Moaning Diamond*, but a building of the sort mentioned before could be crafted in about 150 days, which is not all that bad. Keep in mind, though, that this is a single building that a storm giant might find comfortable, and it requires a powerful cleric to lock up all their high-level spell slots for months on end building it. If the cleric wanted to be prepared for their enemies, or minister to the sick, the construction could take a year or more.
One should note storm giants around could vastly simplify any large projects, due to their height and prodigious strength. However, the basic architectural issues would still exist, and would likely better be solved by stone-shaping.
## But wait! There's more....
There is even a construction method perhaps even more potent than the Moaning Diamond: *polymorph any object*. Suppose a 20th-level sorcerer or wizard transmutes a nonliving mineral object of up to 2000 cubic feet into something (a) the same size, (b) also a mineral, and (c) as a mineral, of the same Intelligence (0). This transmutation will then be permanent, allowing a caster to (for example) create iron reinforcements in a wall created with *stone shape*, or glass windows, or indeed metal doors. It is probably wise to require that only contiguous, firmly bound "objects" (which also rules out fluids of any sort) be affected by *polymorph any object*, so as to avoid players turning the ground beneath their enemies' feet to polonium or something. After all, *transmute rock to mud* is one thing--*transmute rock to plasma* is quite another. In this case, of course, the stone will need to be moved away from the portion to be transmuted, and the portion held in place by *telekinesis* or such while it is transmuted, and then the stone sculpted back in. Nonetheless, the potential for extremely sturdy buildings is there.
## Pixie condominiums
Building for pixies is barely harder than building for giants. Pixies may not have the strength to construct houses easily from the inside, and humans (let alone giants) would lack the ability to construct such fine structures. However, a sufficiently powerful wizard-architect could build a scale model. It would have to be less than 40 cubic feet, because of certain spell limitations. This is large enough to construct details like doors and such with *stone shape*, or simply to add them manually, while small enough that quite a lot of artistry (whether magical or mundane) could be applied. Then, boom! *Permanent shrink item*, and stick the pixie apartment into the pixie condominium. Stone shape them together. Rinse and repeat.
So the gist of this is that although Stone Age communities would have trouble building habitations large enough for giants, or small enough for pixies, a **single** powerful spellcaster, or anyone equipped with a powerful artifact, could manage it extremely quickly. Some time would be needed for trial and error, of course, since one does not learn architectural principles in a day--but being able to shape a new building from solid stone every few days would definitely help the learning curve.
## Cat flaps for pixies (and humans)
Well, we know how to construct massive stone buildings for giants. How do we make sure that everyone can enter the building? Clearly the highest priority is to build massive doors for the giants. Now, we could put small doors in for the humans, and smaller doors in for the pixies. But come on! If you are a 20th-level wizard constructing a city with an artifact of the elemental lords, are you really going to bother making three doors when you could make two?
No. You make a *permanent phase door*. *Any* creature of size Medium or smaller can use one, as long as you put the right conditions on it! Bonus: no doorknobs, so even creatures without hands can enter. And, of course, cats.
## Cat flaps are for lesser mortals! I shall make a single door!
It is true. Why make two doors when you can make one? In fact, why not make...no doors at all? Enter the *permanent teleportation circle* (actually, two). Think of it as a doormat that also acts as a door. For someone with the finances of a 20th-level character, plus those of a city, even the high gp cost of this spell will be manageable. The circle will be set to teleport anyone who activates it a mere few feet, into the building itself. This includes creatures of any size, including our Huge storm giants. Of course, there may need to be emergency doors, in case some fiend (literal or otherwise) disjoins your nice teleportation circle. However, barring such catastrophes, this solves the problem of having to create three doors, or force pixies to struggle with human doors, or humans to struggle with giant-sized doors.
[Answer]
Reduce person is a 1st level spell as is enlarge person. Suggests that changing a persons size is dirt cheap magically. Put the city inside an extra-dimensional space accessed thru various gates of differing sizes that conveniently convert everyone entering to medium size until they exit the space.
Would be expensive, but since you want it to be a trade city and connect members of your federation using gates to cut the distances could be justified. Additionally, since something like this would be essentially "plot magic" the DM could make setting it up an entire campaign as you search for the magic that enables it. And defending it from the *whatever* that built the space and gates originally or killed the original inhabitants or whatever would make for another. Sell it as an impregnable fortress for your alliance and then spend the next decade trying to defend it...
JDlugosz asks some good questions in comments, my answers aren't really that good, but people interested in this idea should read the comments.
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For beauty, think fractals: self-similar across a range of scales. That means people will generally know what to expect and can find the smaller units and navigate the larger units, just learning from what he sees on his own scale.
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I'm going to suggest a slightly different analogy... Mezzanine vehicle decks on ships.
If you've been on any ferries which carry cars and lorries you'll see how they pack in as many cars as possible. To achieve this they make use of mezzanine desks so two layers of cars are transported for every one of trucks.
So let's take this a little further. What would a meeting room look like? I'd suggest a sort of amphitheatre with the largest occupants in the middle and ever diminishing races towards the outside. You'd only fit in a few giants but at least they could see everyone!
What about creatures sitting at a bar? How about a very tall serving area with seats of increasing feet from giant sized stools (for the pixies) to tiny seats for the giants. The barman could walk up and down the bar as they wished.
Roads? Instead of subdividing traffic by speed split it by size so the giants don't accidentally injure the smaller races.
How would houses work? I'd envisage the majority of the house being made up by the giant's home. Alongside that would be two human homes, one stacked on top of the other. Fours dwarves would live alongside the husband and six or even right pixies would take the smallest homes.
This gives rise to an interesting economic problem. If a landlord could subdivide their building to accommodate either one giant or sixteen pixies then they're going to want sixteen times the income every time. Any restaurant keener would rather serve fifty dwarves than ten giants. Being big would suddenly become very expensive!
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Since I am tired of actually working;
I have to suggest taking the idea of adapting cathedral architecture seriously. A cathedral with a 100ft ceiling is not unusual. As for build time, while cathedrals were built using public funds and donations and took 100 years to finish, when a king wanted a similar castle or monument, it might be finished in less than 10. The Pantheon in Rome was built in about 8-10 years. Harlech Castle was built in 7. The Hagia Sophia was finished in only 5. Krak des Chevaliers took about 30 years, but would be a small village even to storm giants. If storm giants are actually involved in the building, build time would be seriously cut.
As for traffic and intermingling, I pick the Gothic cathedral to adapt. If you look at a picture of an interior, you will see that most have a second floor gallery that wraps around the whole building. This would be about the perfect height for humans and giants to see eye-to-eye. A little imagination and you could add a second scale gallery for smaller citizens.
For two examples of how this might play out, there is "The Borrowers" as a fun book to read. If you prefer, "Arrietty" was a fairly good adaptation to a movie. A second example would be two or three episodes from "Macross Frontier" that showed what a modern shopping mall would be like for both humans and truly giant beings. The walkways for humans end up looking like a facade on the walls to the Zentradi, but it puts them both at about eye level.
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The easiest answer would be to have different districts, based on size. For a good example of what this would look like, watch Zootopia, because of course Disney would think through this problem.
Elephant District:
<http://vignette3.wikia.nocookie.net/disney/images/5/54/Zootopia_Finnick_and_the_Popsicle.png/revision/latest?cb=20160129144610>
Mouse District:
<http://www.kansascity.com/entertainment/movies-news-reviews/8vynmp/picture63564807/ALTERNATES/LANDSCAPE_1140/zootopia-200.0_064.00_0083>
Yes, that is the same rabbit in both shots. The movie should also provide some insight into the functioning of such a city, as well as some of the problems that might arise.
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As previously noted, magic would most likely be able to be studied by the scientific method. Indeed, science would likely at least try to understand magic, if not incorporate it. My question is, what would prevent scientists from studying magic?
Namely, I imagine that, for one reason or another, scientists refuse to study magic and magicians refuse to study science. Of course there are *some* people who study both, but these are generally on the fringes of both communities. Indeed, scientists try and dismiss magical discoveries, and magicians dismiss scientific discoveries (I haven't determined the specifics of this dismissal (perhaps they claim that the other group is falsifying their claims, only doing tricks to make it look like they discovered something)).
Out of story, science would correspond to phenomenon that occurs in our universe, and magic to phenomenon that don't occur in our universe (think fantasy magic).
Of course, you can argue that true science would encompass both "science" and "magic", but the people of these world haven't realized this (besides the fringe people).
Given the last paragraph, I'm looking for a societal reason. If you can, provide a parallel of two areas of study that basically study the same thing with about the same amount of effectiveness, but completely deny effectiveness of the other (sort of like Keynes v.s. Austrian economics perhaps?).
One major problem is I want both magic and science to be useful (and even more useful together), and it is hard to dismiss useful things. Solving this issue should hopefully make the rest fall into place.
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The easiest reason I can think of is simple: **religion.** Make either magic or science borderline religious and/or funded by a religious organization, and make the opposing side composed of staunch atheists (or simply another religion). Regardless of whether or not the other side has a point, the polarized nature of the system will keep science and magic apart for decades by petty feuds and heated debates - long enough to tell your story, although not forever and not in every area, just locally, where you want to tell your story.
A more complicated reason: **metaphysics.** Perhaps magic is intrinsically mystical as a consequence of the way that God/the gods/happenstance made the universe. Every time you try to apply the scientific method to it, it inevitably, wildly fails, because magic is a wild entity in and of itself that only allows select people to access it... and if it doesn't like someone, it might do something entirely unpredictable or even malicious. Most scientists are not welcome to magic because they don't respect it (and because they aren't welcome, they respect it less, leading to a vicious cycle). For that matter, maybe *science/the laws of physics* is an entity alongside magic, causing people who mix the two to generally have bad luck. Mages who try to interact with science ruin the results of tests by the magic inherently within them. Scientists who try to interact with magic ruin the results of spells by the science and/or lack of magic within them.
There may or may not be religious ramifications if this the case - I'm guessing your culture would have an order vs. chaos dualist dichotomy between science and magic, possibly having names and opposing deities for each of these. Maybe you even want this to be true within the setting - perhaps Magic God and Science God *hate* each other, and it's hard to follow both.
A very complicated reason: **superstition and culture.** Maybe there's a Demon of Forbidden Knowledge or equivalent and it's believed that amassing too much knowledge for the sake of attaining knowledge will be disastrous. This sort of reality would, of course, make both mages studying the arcane and scientists studying the mundane rather hypocritical, as both of them seek knowledge. Only the fringe people would realize "this is ridiculous, there's nothing wrong with wanting knowledge" and study both.
A reason that will require a lot more worldbuilding: **politics** and a cold war. Perhaps magic and science worked together for awhile, but have now diverged because of opposing ideologies. Many would now argue that there are good elements of both communism and capitalism, but during the Cold War, no one would admit that the other side had merit. If you have one group of nations that believe that magic is the True Path, and another group of nations that believe that science is the Only Truth, along with a superpower in each group… it is very well conceivable that one side could suppress magic and the other traditional science.
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In other words, you don't have to try to make a *rational* reason behind scientists and mages hating each other. People aren't always terribly rational creatures. Give them an irrational religious, superstitious, cultural, and/or political reason to hate each other and they probably will (especially if Magic God and Science God also irrationally hate each other).
A **mixture of these** may provide the best results. Religious differences between the magical and scientific community, ancient superstition and general attitude, and hatred between polarized people may lead society to only acknowledge the effectiveness of one or the other. Adding a latent layer of bad luck and metaphysics may serve to enhance this, even if you never really discuss it in depth.
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If Science and Magic emerged simultaneously within a culture, and if their effectiveness in problem solving were approximately the same, then each discipline would attempt to integrate aspects of the other into its own domain. A fireball casting mage who understands the laws of combustion is more effective than one who does not, simply because of the targets that each would choose. A scientist who can magically slow down time will be significantly better at studying chemical reactions than one who cannot. The benefits of merging the two far outweigh almost any cultural, spiritual or philosophical difference which might otherwise divide them.
Unless the absolutely oppose each other at a fundamental level...
Science is built upon a history of experiments, involving measurable materials and energies, which when repeated without variation, lead to identical results.
Magic is driven by the will of the caster and by the influence of unmeasureable forces which naturally vary from casting to casting. Replication of identical results is not even a possibility when using magic.
So whenever magic is around, science falters. Test results cannot be trusted because any result, whether expected or not, might have been caused by a casting. Scientists get pissed when you mess with their science, and they know many nasty tricks like how to make gunpowder and poisons. Don't let the lab coats and nerd glasses fool you... Scientists are dangerous.
Magic users would be well advised to steer clear of their laboratories and universities.
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I can't think of any reason why real science wouldn't investigate "magic", because in this context it isn't actually magic at all. It's like asking why science wouldn't investigate magnetism.
That said, I can imagine a culture with superstitions about one branch of science or another. It's especially plausible if we add in some type of religious viewpoints. Obviously, real science is faith-agnostic. But real scientists have the same human traits as anyone else.
And, let's go a little further. Real science includes things like testing on human slaves. It's our human morality that keeps us from doing it. Not that I think we should do it, but we need to look at the big picture and recognize that even in our enlightened world, we have constraints on science.
So now, imagine a culture who finds fireballs to be inherently immoral. In this culture, scientists would obviously study fireballs, but they would find it wrong to go out of their way to cast those fireballs to study them, so the progress would be limited to accidents and miscreants, and could take a long time.
If your world has gods and such who take an active role in the world, they could have any number of personality quirks, including things like "thou shalt not use fireballs". In this scenario, it would be much more plausible for fireballaphobia to remain part of culture for long periods of time.
If there aren't gods or similar, it would be harder to keep superstitions up, but it's certainly not impossible. Isolation would help tremendously, because opposing viewpoints would be rare and easier to quash.
Then, of course, you could have similar viewpoints for the "magic" group, who might find metal forging and other "science" stuff to be unnatural and unwholesome.
Note that this doesn't really solve the problem of the factions outright denying the effectiveness of the other faction's science. But where there are differences of opinion, there will be propaganda to coincide. A strong enough control over the local media could keep the propaganda in place as the "one true truth", with denouncers being derided, exiled or even executed for something along the lines of heresy.
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What would separate magic and science so much that neither acknowledges the existence of the other? I suggest this hangs on the nature of magic itself. Magic as it appears in most fantasies functions like a form of super-powers. Example: wizard points her wand at cowering victim and a bolt of purple lightning zapped victim into a neat pile of ash. If magic was like that there's no way science could ignore its existence.
Also readily reproducable magic could be studied, eventually the mechanisms for magic would be discovered, then magic could be improved and upgraded. Leading to a civilisation where magic and science would work hand in hand transforming our world for good or evil.
The way magic operates in traditional societies (this means pre-industrial pre-scientific, and pre-modern) was more like this. A tree falls on Fred's house and no-one's hurt. That's an accident. Just nature at work undermining the tree so it fell down. If the tree fell on Fred's house killing him. Now that's sorcery. When unexpected events harm or kill people, then malign intent must be behind them. The sorcery expresses malign intentions, but it may turn up in unexpected and unanticipated ways. Perhaps even the sorcerer cannot predict what will happen. This is quite unlike magic operating like default super-powers.
What a sorcerer might do is perform a ritual and then sometime later harm will come to the intended victim. For example, sorcerer writes Fred's name and the word DIE on a piece of paper and burns it. Two years later Fred dies of a heart attack or it could be his wife who dies instead. Later Fred dies from despair and a broken heart. This isn't the same as Fred dropping dead straight after the ritual.
This model of magic suggests by its very nature magic may be wilful and contrary. So if scientists suspected ritual magic was real and tried to study it, this makes it impossible to get verifiable results. This is apart from the problems in trying to their research approved by the Ethics Committee. Perhaps if the magic they tried to test only was aimed at producing beneficial results. Like poor Fred winning the lottery (his luck had to change eventually).
Anyone who looks at what magic was like historically or how it is perceived by societies studied by anthropologists will soon realise these traditional forms of magic were and are rarely susceptible to scientific study. Magic is often very different from how it is presented in fantasy.
This provides an answer to why scientists would ignore magic. Its influence in the natural world is invisible and not very different from chance outcomes. Also, people who believe in sorcery are obviously deluded because they believe their spells, incantations and rituals can influence the course of events.
Now for the other part of the question: why don't magic users study science, perhaps with the object of improving their magic, or just understanding magic better? I admit this isn't the strongest reason, but here goes. Perhaps there is something about the scientific worldview that undermines the practice of magic. Once a sorcerer studies and thinks of the nature of the world scientifically, this means they can no longer work magic.
Actually this might go the other way too. Any scientist who fully embraced a magical worldview might be unable to do science well. This also means scientists who believed in magic and wanted to study it scientifically would be rubbish at research into magic (as scientists).
This means I've come up with two answers (not what I intended doing, but sometimes the magic works by itself). One, the nature of magic itself may be such that it can't be studied by science. Scientists would ignore magic, because nothing in nature needs magic to explain it. Sorcerers would practice their magic, but even they might not be able to study how it works. Two, magic and science require mutually exclusive worldviews. This is more than sufficient to separate magic users and scientists into distinct and mutually exclusive communities, each effectively invisible to each other.
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What's to say they don't today? I know a lot of people who consider birth to be "magic," even though science studies it. In fact, many of those who consider it magical are indeed the scientists!
This is, of course, merely a definitions question. What is the study of magic? What is the study of science? In a world with "real magic," would the two concepts have separate terms? Maybe they would only have one field, which covers both.
Personally, I find it effective to draw the line between them based on how they define their explanations. Science defines rules which, theoretically, cannot be overturned. Magic, if you look back at the history, generally involves invoking powers which don't always do what you say. There's often a sense of agency to the magic, acting of its own accord. You never see science supporting the agency of the particles it defines (except maybe in QM, where I get away with personifying particles more often than one might think!).
Accordingly, if those definitions suit your fancy, magic and science start from opposite extremes and reach out towards the middle. Science wouldn't study deep magic, not because it can't, but because magic is simply better at it. Likewise, nobody would magic anything which is better suited for science and engineering. To do so would be wasteful. There would, of course, be individual tastes. You might *really* like to summon Zuul to check your email, because, frankly, let's face it: a lord of darkness isn't quite as frightening as digging through spam, Nigerian scams, and women who apparently want to date me but have some all natural supplements to accentuate key parts of my body first.
This also suggests there is a line of things that are hard for both science and magic to explain. I'd argue this exists today. Just look at evolution. Theoretically, science has it licked, and yet we still feel more comfortable personifying evolution in many cases, trying to talk about it as though it has a will of its own. Perhaps there is magic yet.
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One way people would tell that magic was real in a universe in which there would be magic is that we could use our understanding of it to make predictions instead of just using it to figure out what is already known. We would in this case be able to figure out equations that describe how it works.
For instance if telekinesis was real we might predict that it's force would drop off with the square of the distance meaning it would be four times more effective on an object ten meters away than something twenty meters away. Also one could predict that if telekinesis was real it would be harder to use it on massive objects than objects with less mass. Also if telekinesis were real then according to the third law of motion someone using it could only either use it to move two objects in opposite directions or if you used telekinesis the telekinesis would cause you to move in the opposite direction of the object you are moving in your mind. Also if telekinesis were real then there would also be telekinetic potential energy between someone who had the power of telekinesis and any object the person could use it on in the same way that there is electric potential energy between two charges. It might also predict that there would be telekinetic waves that would travel at the speed of light that would be emitted by someone who was either turning telekinesis on or off in the same way that there are electromagnetic waves and gravitational waves in our universe.
Magic would also be very useful in a world where it was real and would likely be used in the same way that we use technology in our world. For instance it might be used to regenerate limbs that had been lost and cure diseases that would otherwise be permanent and it would be more powerful than a placebo in such a world. It would in this case also be possible to write equations that would show how quickly it could be used to cause a limb to spontaneously regenerate and so predict how effective it would be on certain injuries.
In a world with magic it might be used as the primary way to stop crime as someone could use mind control to prevent someone from committing a crime by making it so that the person cannot think about harming others.
If someone could use telepathy it could also be used to make very specific predictions such as what the phone number would be of the next person he/she would ask for the phone number of.
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If magic depends on an inborn talent, those who are not born with magical abilities would be prevented from any deep study of it, and would have to limit themselves to purely physical interests.
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Science is the study of *natural* phenomena and understanding them. The most prominent thing about science is that is methodical and mathematical (as in, you can write equations to explain things).
Magic on the other hand, works by will and force. It is not natural (as in, there is no magic going on in the absence of a spell-caster) and you cannot understand *how* it works. Magical effects cannot be presented in the form of mathematical formulas.
The natural/unnatural and mathematical/non-mathematical differences are so vast that these can never be united under the same branch of knowledge, unless that branch of knowledge includes *everything* in the universe.
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Something I thought of might be based in the scientists' view of magic as being inherently unpredictable and hard to control, even for skilled mages. Maybe enough notable scientists were blown up or teleported into solid matter, or otherwise met a violent end while trying to study magic, that the science community said "enough" and declared it a taboo subject, much the way human dissection was once considered off-limits due to the sanctity of the human body.
Those who manifest magical power, for their part, find that their powers are quite controllable and useful *if* you don't push the boundaries; magic is ultimately a human quality, and the further you push your limits, the more likely you are to unwittingly exceed them, with disastrous consequences. As they see no need to use science to more deeply understand what they do (they just do it), and the scientists forbid each other to work with mages in this understanding, the two sides soldier on in mutual segregation and distrust.
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I am taking this to be a question about paradigms: why do the proponents of one paradigm refuse to validate another? In your case, scientists know magical powers exists and could potentially be modeled and predicted, and mages know that there are good models about the physical world that lead to useful predictions, but neither believes the other is worth a damn. Why would this occur?
My answer is: suffering, and identity. The world is a place where people suffer and die, and people define themselves through the way they deal with these conditions, and how they classify reality.
Ok, **everyone is concerned with the real.** There's a good argument that all art is an attempt to depict "the real." Religion is an attempt to explain the transcendental reality at a higher level of being. Science is an attempt to understand and predict real events. Your paradigm defines your reality, and your reality defines your identity.
**Mages would be interested in the metaphysical.** This presumes mutual exclusivity of magical and physical phenomena, but presumably magical phenomena would necessarily lie behind a metaphysical "curtain" that defined it as magic. There would be an inherent unknowability to it. The existence of something like this could convincingly invalidate the significance of physical phenomena and existence. It could make scientific pursuits seem completely trivial in comparison. Why would someone count beans in this world when there is so much power behind the veil, in the realm of magic?
Take religion as an example. Western christians/agnostics/athiests cannot seem to reconcile themselves with certain followers of Islam like ISIS - they disagree to such an extent they are willing to kill and die over their disagreement. The motivation for this disagreement comes from suffering - western rationalists are largely concerned with physical suffering in this life, whereas radical muslims are primarily concerned with the metaphysical consequences of misbehaving in this life, i.e. suffering in the eternal afterlife. Each side founds its identity on its relation to reality and its definition of "real" suffering, and because of the mechanisms of evolution, we are hardwired to avoid "real" suffering as much as possible, and so both sides refuse to acknowledge the other.
**Scientists would be interested in the physical.** Magic is essentially cheating. Miracles are essentially cheating. You don't see many scientists studying miracles, simply because a miracle by definition is something that defies explanation. As soon as you start investigating, say, [Jesus feeding the masses](https://en.wikipedia.org/wiki/Feeding_the_multitude), it quickly becomes implausible, and reduces to "an act of faith," which is essentially a synonym for "you can never know, you just have to accept it." A scientist in a world of magic would see it as a moot point - why study something inherently unstudyable? What foolishness would compel someone to waste their time at a sisyphean task like that when there are "real" problems to be solved like sepsis, famine, and labor?
**Most people have suffered in their lives**, some more than others. At the very least, everyone is aware that suffering exists and that it is not good. Its plausible that scientists and magicians could be so concerned with ending this suffering that their inability to reconcile the other sides pursuit created a snowball effect that drove a wedge between the two disciplines.
[Answer]
Two possibilities:
1. Magic is like intelligence it is an irreducible emergent property. Science understands the world by breaking it down into small separate pieces that can be studied and proven individually, and then brought together to build more powerful understandings.
Some properties can't be broken down the individual components won't exhibit the ability unless all are present. Neurons don't exhibit intelligence unless there is a huge number arranged in a brain. The study of these fields is slower without provable theorems. Magic could be like psychology: we study it and recognize trends and do valuable work in it, but lack verifiable theorems.
2. The other would be that magic is chaotic and not repeatable. If you perform the same experiment 50 times and get a somewhat different answer every time science can't progress in the normal manner.
[Answer]
Any system that has consistent, observable rules will eventually yield to science. So your magic must behave inconsitently and actively resist observation. My suggestion is to have magic be granted to humans by gods, who can change the rules as they fancy, and take it away when people try to 'learn the rules' too much.
So instead of casting fireball by learning the words and chanting them, you must gain favor with the fire god, and *each time* you want to cast fireball, he has to want it to happen, and the size and power of it is up to him. When you try to cast fireball in a laboratory, he doesn't allow it to work, because he personally objects to his followers using him like that. This inconsistency makes hard science impossible. Science can only test what is testable and predict what is predictable.
Yet magic can still be studied in a limited way. Schools of magic would compile stories of encounters with Gods and try to sort the truths from the legends. They would look over records of how the Gods have behaved in the past to try to learn their personalities and motivations. But building a personality profile of a human being isn't hard science. Hard science can not reliably predict the behavior of an individual human yet. A human's motivations are too complex. So the motivations and choices of a magical, likely invisible and vastly old, vastly powerful being who has relationships and histories you haven't seen, that's just heuristic guesswork. The old wizard can predict the Gods' favor better than the young, and studying the Gods will help you earn their favor and keep it, but no one can make any 100% certain statement about magic, because in the end it's up to the gods.
[Answer]
**Frame Challenge: Everything Useful is Science**
At its most basic level, science is simply making predictions, and applying them. Coming up with a model that makes testable predictions, then testing them, is the scientific method (shorthand). Done badly, with steps missing, these predictions would be often wrong. The scientific method is simply a way to make these predictions more accurate.
Basically, every time you do anything with a hope of a result, you are using science. You swing your arms in a certain way with a ball in your hand, and release at a certain time? You are predicting that you will throw that ball. You are making that prediction based on a model you have about the world. You are using science.
You put weird little pieces of plants in the ground, add water to them everyday, and wait for a few month? You are predicting that things will grow out of the ground and give you things to eat. That's science!
You swing a staff around, chant some magic words, think some good thoughts? You are predicting that what you did slightly increased the chance of something good happening for the next few days! That's science!
So now the question becomes: how come two branches of science don't intersect? Well, we can think of two reasons: **Complexity** and **Cognitohazards**. The first is why quantum string theorists don't dabble in Freudian psychiatry. The latter? Well, just imagine if there is some weird effect in place that learning more about how to launch fireballs make a person unable to think about the atom structure.
[Answer]
## The Tools of the Archaic
I don't think the separation of Magic and Technology needs drastic pressures.
**Example:** Right now guns are amazing, but it you told how effective they would be to a medieval knight, he'd just pull a stupid face wondering how a slow-firing, inaccurate iron pipe would ever surpass him.
**Engineers:** They probably don't know much about magic, the unnatural sciences. They've probably heard stories of horrible accidents. They probable don't know many if any magicians. Plus, they are on the cutting edge of science.
**Magicians** They probably don't know much about engineering and the natural sciences. They've probably heard stories of horrible accidents. They don't even know many if any engineers. Plus, they are on the cutting edge of science.
Both think their work is superior and the other builds archaic relics. They only really know the worst parts of there profession's creations and disaster, what makes the papers... and report normal news to normal people so strange arcana and new patents are left out entirely.
[Answer]
Many years ago, I wrote my favorite Stack Exchange answer to [What is the Smallest Change to Physics Required to Allow Magic](https://worldbuilding.stackexchange.com/questions/40949/whats-the-smallest-change-to-physics-required-to-allow-magic/40992#40992), which I'm proud to say is still the 5th highest voted answer on WB. I highly recommend it as a frame challenge, which argues that magic is everywhere.
That being said, there are some things that science is just frustratingly bad at.
* Things that are centered around a willfull "self." Science needs to be able to dissect a situation to predict its results. If the effects of magic are truly tied to a self-aware "self," a lot of the tools we use simply don't work. Consider the need for double-blind studies. The purpose of that is to lock out any awareness. You don't want a medical study test subject to heal themselves with the power of the human body, rather than with the medicine. Contrast this with Traditional Chinese Medicine (TCM), in which *everything* is centered around the subject as a person. No surprise, TCM remedies feel like magic to us.
* Non-associative things. Science really likes associative logic, which lets us group small pieces, analyze them, and then see how they play a part in the whole. Non-associative systems don't let you do this. You have to start from the "right" point, and work your way out. This is often frustrating for science because the starting point tends to be something rather ill controlled. This may sound like a silly detail, but its prolific. The usual approach to non-associative things is to either focus smaller and smaller until all the annoying bits go away, or to invent an imaginary associative system around it, and then sneak in a constraint after the fact to only work in a small non-associative region.
* Holistic things. Any time where you have to start with the universe and work your way down to the individual, science falters. The mathematics we base science on are built around assumptions that make this terribly hard (in particular, there are no infinite descending sets). Science can't touch anything explained with The Dao in Eastern thought, because that topic basically defies all scientific inquiry.
] |
[Question]
[
I've always found animal intelligence to be fascinating, particularly that of the cephalopods, some of which show some pretty remarkable talents for tool usage, mimicry, and pattern recognition.
[Apparently](https://en.wikipedia.org/wiki/Octopus#Intelligence):
>
> Two-thirds of an octopus's neurons are found in the nerve cords of its
> arms, which have limited functional autonomy. Octopus arms show a
> variety of complex reflex actions that persist even when they have no
> input from the brain.
>
>
>
Perhaps this explains the feeling that while the the octopus is obviously intelligent it remains somewhat challenging to anthropomorphize.
I was thinking about designing a creature that lacked a central brain altogether.
I'm thinking of an octopus-like creature that used 8, or so, separate "brains" in concert. Each "brain" would be capable of maintaining the creatures basic bodily functions (cardiovascular, respiratory, digestive, and so on...), as well as being able to function independently or cooperatively with the other "brains".
Would such a creature design be feasible/believable for an animal level intelligence?
Taking this a step further, if we were to take this creature and anthropomorphize it a bit, would it appear to have some sort of dissociative identity disorder (split personality)? Would each decision would have to be run through committee or would it make more sense to have each brain take control from time to time?
(See also a different approach: [What are the conditions in which a creature would evolve more than one brain?](https://worldbuilding.stackexchange.com/questions/14807/what-are-the-conditions-in-which-a-creature-would-evolve-more-than-one-brain))
[Answer]
From an evolutionary standpoint, the main reason why you'd have separate brains or a decentralized brain as in the case of the octopus is to dedicate "brain" to certain actions without detracting from other processes. In other words, the central brain of an octopus would likely not have to think about how to grapple its prey, only that it wants to grapple its prey, and the nerve cells in its tenticles make the individual detailed decisions regarding how it could grapple its prey.
You could think of it as having a graphics processing core like most modern graphics cards have nowadays. While the CPU could perform the same calculations as the GPU, due to the quantity of calculations that must be performed, it is more efficient to specialize these calculations. And like this metaphor, the GPU doesn't act on its own accord, but rather it is the CPU that tells it to act. In the same way the nerve cells in the tenticles of an octopus specialize in dealing with how the tenticle should move.
It is difficult to imagine, but in a certain sense we do it too. The part of our brain that deals largely with automated actions like breathing and blinking our eyes is closer to our spinal cord and as such, those signals rarely arrive to our waking brain. Does this mean we can't control when we breathe or when we blink our eyes? No, however, to a certain extent, you could think of these functionalities as being specialized in order to not detract from thinking about other things. You may not realize, but the reason *why* you come up with ideas much more readily on the toilet is because your brain is not preoccupied with standing and, more importantly, balance. Thus you have more brain power to think about other things.
>
> I'm thinking of an octopus like creature that used 8, or so, separate
> "brains" in concert. Each "brain" would be capable of maintaining the
> creatures basic bodily functions (cardiovascular, respiratory,
> digestive, and so on...), as well as being able to function
> independently or cooperatively with the other "brains".
>
>
> Would such a creature design be feasible/believable for an animal
> level intelligence?
>
>
>
It wouldn't make much sense to have a separate brain *just* for cardiovascular, respiratory, digestive, etc. Monotonous tasks like breathing and beating of your heart don't require much "brain" to do. Based on what you find in nature, it is far more likely that you would have separate brain to govern movement and actions, which can get quite complex. Also, if one of these separate brains were in a less-protected part of the body and got injured, then if it handles movement of the limb, you could still survive. If it handled cardiovascular activity, you're dead. So perhaps there is also a good reason in terms of survivability that this tends to be what happens in nature.
>
> Taking this a step further, if we were to take this creature and
> anthropomorphize it a bit, would it appear to have some sort of
> dissociative identity disorder (split personality)?
>
>
>
This, you don't see anywhere in nature, so we have no frame of reference. However it is also true that we can't just put them on a psychologist's couch and ask them what they're thinking, so we also can't know for sure. However speculating, we could look at ourselves. While it's true that we don't have truly separate brains, we have two hemispheres that work in synch to solve problems. The left brain tends to dominate in most people, and concerns itself with logic and detail while the right brain tends to deal with aspect and overall appearance (though recent studies suggest that this difference isn't as strong as initially thought).
The reason behind the fact that most people in their adult years still draw stick figures is due to the fact that the left brain, not knowing how to draw a person but thinking it knows anyway, forces control over the right brain which otherwise would have carefully and patiently studied and remembered how a person looks in order to draw effectively. What feels like you drawing a stick figure is actually your left brain saying, "Hey, back off, right brain, I know how to do this.. just make a circle and a stick underneath with a line for the arms and two lines for the legs.. DONE!" In fact the first step to learning how to draw well is dropping preconceptions about how to draw things and just trying to draw what you *see*. You may still have difficulty drawing doing so, but only because your right brain is practicing for the first time.
If our hemispheres were separate, due to the distance to send signals, it may not seem so much like you but more like your left and your right. This is just speculating, but our identity too might get split somewhat. However remember that evolution won't support a creature that can't "work," so despite this conflict in identity, they would have to get along well (no two-headed ogre stuff or nothing would get done).
>
> Would each decision would have to be run through committee or would it
> make more sense to have each brain take control from time to time?
>
>
>
Returning back to the discussion of drawing, in that instance, the left brain just takes over. There is no consensus, and in a certain sense, there shouldn't be any, or you wouldnt' get anything done. Certain pathways tend to allow one hemisphere to have an edge over the other.
However this isn't to say that your hemispheres don't battle certain decisions out. [The Rubber Hand Experiment](https://www.youtube.com/watch?v=sxwn1w7MJvk) is a classic example of such conflict. Your left brain *knows* the hand is fake, but your right brain sees and feels something different. When danger strikes, you're forced to come to terms with which hemisphere is right. Even though you know otherwise, you still get the same response as you would if someone were to try to hammer your real hand, because one of your hemispheres believed it were real. Usually when confronted with such a conflict, the signal that claims danger is the one that dominates (and for good reason). So to answer your question, likely each brain would formulate its own opinion on the matter and the brain with the strongest opinion would probably win over the others. However this is all very much speculative.
[Check here for recommended reading on the subject.](http://www.livescience.com/3261-left-battle-brain-discovered.html) I hope that helps.
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A creature with a decentralized brain could get rid of the standard idea of a nervous system altogether, and simply have brain tissue spread evenly throughout it's body, perhaps similar to the way fat is distributed throughout the human body.
This would mean no split-personality problems, because it is one big brain, and some redundacy - chop off it's head and it will have enough brain left to continue functioning (although, depending on brain structure, there could be some physchological damage, as seen in victims of severe head trauma).
[Answer]
Animals like flies have less centralized nervous systems, and I think an extreme example is the [box jellyfish: 24 eyes and no brain](http://io9.gizmodo.com/5795906/box-jellyfish-have-24-floating-eyes). The six distinct eyes at each corner have different dedicated purposes and together simple logic to combine them is all that's needed for navigation and avoiding the crowded tree roots it forages among.
The signal speed in a nerve is very low, which provides both reasons to keep things together *and* reasons to distribute. Consider the *very* large long-necked dinosaurs. Extending its neck vertically would starve the brain of blood, so the brain is the size of a walnut. Yet, the signal delay means putting reflexes necessary to balance and walk near the limb being controlled. Consider that mammals have reflex handling at the spine; that might be true for other vertebrates, and can develop complexity from there.
Since the walking, balance, tail swishing, etc were already distributed, the main brain could shrink under evolutionary pressure (the long neck and unique food source higher than others could reach) shifting function to other places.
Consider what *might* happen under similar conditions: the neck becomes just another limb, with local processing for the eyes and eating, but new layers of complexity that in vertebrates wrapped around each previous layer would grow in a second brain at the base of the neck.
Consider different biology too, to change the rules. If nerves with high speed information transfer existed, there would be less reason to centralize processing. Or, look at our optic nerve: it's not a simple wire, but an elongated processing pipeline that puts each end where needed but does the needed work along the way. The spacial transport is free since it needed to run through those steps anyway and they can be arranged in a line.
What if you took that to the extreme and had no brain at all in the sense of a big bump; processing occurs in the cables connecting the systems together. When more complexity is needed, instead of layering like us, they grow more 1-dimential filaments in rings attached along the main line.
Back to the colony organism idea: different specialized parts could occur as different phenotypes, like we have different organs with one genome. Different individuals would link up and combine "brains" as well as functions. An intelligence could change its being by swapping parts, as with [Verner Vinge's multi-body beings](https://en.wikipedia.org/wiki/A_Fire_Upon_the_Deep#Intelligent_species).
[Answer]
Larry Niven had a species like this - the [Jotoki](http://en.wikipedia.org/wiki/Jotoki).
The idea is that originally they are several distinct animals. Then as part of their lifecycle, 5 animals join up, creating a collective animal with five semi-independent brains (kind of like a giant starfish).
Per the split personality question: I think one of the reasons the Jotoki had five segments was because that's an odd number, it prevents split decisions. So as soon as at least three brains agree on something, they can act on it. Keep in mind though that a creature that developed like this is probably going to have a different view of individuality than humans. The brains also "grow up" together, and will likely all be friendly simply because it's required for survival.
One other advantage of the multi-brain system that he also brings up is sleep. The Jotoki "sleep" in cycles, leaving at least three brains active at all times while two rest. So the creature in total can be active 100% of the time.
[Answer]
Why limit yourself to eight brains when you can have eight millions? ;)
Take a look at the [Portuguese Man-o-War](https://en.wikipedia.org/wiki/Portuguese_man_o%27_war). It is not a single creature, but a colony of small organisms, theoretically independent but so specialized that they cannot live if separated from the rest of the colony.
Imagine something like that, but created by more advanced organisms, like ants or bees which evolved from their nowadays state of eusociality into a much more integrated form of a superorganism. In fact, even now in some contexts we can talk about an anthill as an organism of its own. For example, ants as a colony may perform tasks much more complex than one ant is able to comprehend, like finding the best way to the food source by leaving pheromone trails which are strengthened when they are more often travelled and expire when they are not: [Ant Colony Optimization Algorithms](https://en.wikipedia.org/wiki/Ant_colony_optimization_algorithms).
Let's take it into another level: an "anthill" of creatures so integrated that they act as cells of a single organism, but each with their own tiny brain communicating with each other via pheromones. As such, they would probably be unable to move far away from each other or the link gets broken, so in the search of food the "anthill" would release lines of these "ants", each one moving just after another and being able to process and pass pheremone signals, so the anthill - acting as the superbrain formed from all the "ants" which stayed behind - may control this weird flimsy tentacle. As it is with several species of ants we know about, the anthill itself might be just a big group of these "ants" holding to each other and could do without any structure made from earth or leaves. This way the whole "anthill" would be even able to move if necessary.
Not exactly what you had in mind probably, but when I started to develop thw idea, I wasn't able to stop myself :)
[Answer]
"Intelligent Design": Such creature could be *constructed*. It's about impossible for it to develop through evolution, simply because brain requires a lot of energy to operate, and that much redundancy in a single organism is much less "survivable" than if all the brains belonged to separate organisms. Octopuses work, because their sub-brains are highly specialized, each operating one tentacle. If all brains were "general purpose" though, duplicating their capabilities, that would be a waste.
It's a design that would work, but wouldn't work well "in the wild", requiring more nutrients than competitors while not possessing any major physical benefits that would help finding these nutrients.
If you go in this direction though, you might want to evaluate the idea of multiple organisms that can live independently, but can clump together and create neural connections between each other; special areas of skin that provide neural connectivity to such areas on the skin of another.
That *could* have developed naturally, say, through a joint in the body that requires neural communication, but not all the time, and at one point the two halves separate entirely. These creatures could "exchange memories", "brainstorm" and stick together until they all agree on a pack tactic or activity, then either proceed as a bulking mass to engulf a large prey, or dissipate into a swarm following pre-loaded instructions and foraging for plankton or insects. It is quite possible over time the big mass form could develop intelligence, and its mental capacity would be proportional to the number of the small creatures.
[Answer]
>
> a creature that lacked a central brain altogether.
>
>
>
That sounds a lot like:
>
> "All these centuries we thought starfish wandered aimlessly, a sort of
> aquatic Roomba. We thought so right up until somebody made time-lapse
> movies, and found that starfish have an active social life, and
> dominance contests, and are such deadly hunters that when one comes
> around the snails all flee as fast as each one's little head/foot can
> carry it. (Bugs hunt, too, but **starfish have no brain**.)"
>
>
>
-- Nathan Myers
<http://advogato.org/article/917.html>
According to the fictional book "Starfish" by Peter Watts,
>
> "A starfish," Acton tells her, "is the ultimate democracy."
> ...
> "So there's nothing to coordinate the tube feet, they
> all move independently. Usually that's not a problem; they all tend to
> go towards food, for example. But it's not unusual for a third of
> these feet to be pulling in some other direction entirely. The whole
> animal's a living tug-o-war. Sometimes, some really stubborn tube feet
> just don't give up, and they literally get torn out at the roots when
> the others move the body someplace they don't want to go. But hey:
> majority rules, right?"
>
>
>
[Answer]
There are many animals and living organisms with no CNS ("brain"). Various alternative control methods are implemented.
[Slime molds](http://phys.org/news/2016-06-slime-mold-insight-intelligence-neuron-less.html) - We actually have no effing clue how this really works, but basically a bunch of cells get together and act like a single organism with a reasonably complex brain that doesn't exist - probably pheremones, electrical potentials, or carefully constructed individual reaction chains leading to complex swarming behavior are to blame.
[Plants](http://www.abc.net.au/science/articles/2010/09/30/3025894.htm) - Basically they get on fine by cutting out silly brains and getting directly to the stimulus detection and response loop. Their brain is their body, and vice versa.
All this brainless talk is to point out that generally, nature takes advantage of the *emergent* properties of her systems whenever possible (because evolution is *lazy* and always wants to make the most of the least genetic change). If an animal has several brains, or a brain that IS it's body - command and control decisions are likely to be the emergent property of each of these systems making its own decisions independently, independently taking in stimuli from the decision results of the other brains, such that in fact the apparent unity of the system is only a happy accident and not a well-defined thing.
Really when you get right down to it, brains in general work this way - ours are all squished together, but figuring out how one part works in concert with another to give rise to our unitary conscious experience is such a profound mystery it has been given its own name: the [Binding Problem](https://en.wikipedia.org/wiki/Binding_problem).
[Answer]
If you consider an ant colony to be one (super)organism, they meet all of your requirements. each ant (even the queen) is capable of maintaining the required functions to keep the colony alive.
Each ant can act independently and cooperatively with the other ants in the colony.
While making decisions, for example to move the colony to a different home, these decisions are being made by one ant at first, who starts acting on it, and in the mean time this ant will try to "convince" other ants in the colony to join in on the decision. kind of like the colony has split personality disorder.
now you might say "all nice, but ants are separate creatures, i want one creature", then i would like to point out that some ant species often combine into one bigger creature when they, for example, form an ant bridge.
[Answer]
### Consider Plants Also
This may be a tad "out there" for your question, but there is growing evidence that certain plants (namely trees and certain types of fungi) appear to have communication abilities. The book [The Secret Life of Trees](https://rads.stackoverflow.com/amzn/click/com/0141012935) examines some of the science around this, and is worth reading if you are into this sort of thing.
For example, trees have behavioral changes in response to their leaves being eaten, which get send through roots and pollen in the air, and surrounding trees respond in ways to limit scents being emitted, and therefore decrease the risk of animal consumption. This is not altogether unlike pheromones in animals in response to certain events.
Another example would be how some inter-connected trees (think Aspens, which have interconnected root systems) will continue "supporting" (send nutrients to) stumps of chopped-down trees which were their own offshoots ("children", so-to-speak), but will not "support" other trees' off-shoots, even if their roots are interconnected.
Although this is hotly debated, and is easily explainable through purely causal factors (ie is not necessarily indicative of any type of "intelligence"), the jury is most certainly still out, and research will be done for many decades to come on this topic.
For the purposes of a fictional story, however, it's not altogether unbelievable that the "communication" of trees (and/or fungi) might actually be a type of decentralized intelligence.
] |
[Question]
[
Earth is destroyed in explosive fashion by an unknown force. How does this affect the rest of the Solar System? Does sudden absence of that mass affect the orbits of the other planets at all? Let's say that the moon is relatively unscathed in that it missed some of the major chunks expelled out in the initial boom. With the earth gone, does its previous orbital momentum launch it towards the Sun or towards the asteroid belt to be pummeled into oblivion by stray rocks? Where would the chunks of planet be flung to? How would all of this affect a halfway terraformed Mars?
* There is a sizeable population on Mars, which as mentioned is halfway terraformed with five major cities and a rail system connecting them.
* The moon has a pretty big population as well, though it's mostly novelty tourist stuff, space cruise terminal, and mining barge construction bays.
* There are science outposts on some of the moons of the outer planets, and one on Pluto, plus mining stations within the asteroid belt.
I tried to simulate this in Universe Sandbox, but before I could even press the boom button, the moons of Jupiter and Saturn decided to fly off into oblivion for some reason.
[Answer]
Mostly likely, immediately after a planet shearing explosion the pieces of the Earth would not fly off into space. I doubt you could add enough energy to all the mass of the Earth to escape the mutual gravitation and somehow also protect the moon from that release.
**If the Moon is still there, then most of the mass of the Earth is also likely still there, think [Praxis](http://en.memory-alpha.org/wiki/Praxis) rather than [Alderaan](http://starwars.wikia.com/wiki/Alderaan).**
In that case, the Moon's Earthly orbit might be highly disturbed. With the pull of Earth severely weakened, the Moon would continue in its orbit around the Earth while spiraling outward at some significant, but not necessarily exciting, velocity. The spiral would only be from the point of view of the Earth. Even the ellipitcal orbit doesn't look like much from the [point of view of the Sun](https://en.wikipedia.org/wiki/Orbit_of_the_Moon#Path_of_Earth_and_Moon_around_Sun).
This spiral (or wobble from the Sun's perspective) would increase its deviation until the pull of the Sun was too strong for the Earth shards to pull it back.
*The gray line is the Moon's orbit around Earth from the point of view of the Sun. Blue is the Earth, naturally.*
At that point, the Moon would be defined as an asteroid by the artificial brain holding the uploaded mind of Neil DeGrasse Tyson. However, some small, but vocal, group of people would hate scientists for this terrible act. They would demand, as if science were a democracy, that the Moon is still a moon.
The orbit of Mars would not be significantly disturbed. It would be altered, but not in any significant or noticeable way.
[Answer]
Where would Moon go is obvious and answered by others - interesting is **how will human colonies deal with the consequences?**
Where would Earth debris fly, **depends of the energy and direction of the death blow.**
* With enough energy, debris would **fly all over the inner solar system** - and Moon, after surviving first impact, will continue near Earth orbit (which will be also path of most of the Earth debris). Such debris are danger for Mars and Moon (and other asteroid mines), but not Pluto.
* With less energy, **debris will fly close to original Earth orbit** and with just little energy, Moon might be able to orbit remnants of the Earth, and debris would be less of a danger for Mars.
Big chunk of the **debris might re-accrete into new Earth** - it will not be habitable for millions of years, but at least other human colonies would be safe from debris. If not, we have new (inner) asteroid belt - some chunks could cool down in few hundred/thousands years to be useful for mining for resources like metals. **Good source of iron, already orbiting - and we will need it.**
Absence of Earth will not have any major impact on the other planets - Sun's gravity sets the rules.
What **would have impact** would be flying debris. Bombardment of human colonies on Mars and especially Moon by Earth remnants would be great danger for centuries. Moon would have likely most of the colonies on the Earth side - and they would be heavily impacted by original explosion.
**What about other human colonies?**
Survival of the other the human colonies would depend on how independent their ecologies are. It will be rather hard, I presume, to grow all the food, but food production would be obviously highest priority. Quality of life would decrease substantially on Mars - but it's better to struggle than to be dead. If Moon is just tourist trap, most or all population would quickly starve.
Pluto is so far that it **has to be independent** (nuclear-powered hydroponics anyone?) - so Pluto most likely will survive, even if Mars could not survive bombardment by Earth debris and damage to its ecology. Any rogue debris from Earth will take long time to get to Pluto, and it's trajectory could be simply changed to less dangerous. So maybe it will be Pluto which will repopulate Solar system.
If Earth debris form another asteroid belt, survivors from Pluto and Mars would have excellent mining base to build interstellar spaceships.
Terraforming Mars is IMHO fools errands, [Mars would lose new atmosphere for exactly same reasons it lost old one](https://worldbuilding.stackexchange.com/questions/6472/if-somehow-mars-suddenly-had-our-exact-atmosphere-could-there-be-lots-of-life-i/6474#6474), especially with the extremely limited resources on Mars. Of course it depends of danger of bombardment by Earth debris, and how close is terraforming from being finished. Maybe if some chunks of frozen Earth water can be safely dropped on Mars, **destruction of the Earth could even speed up terraforming Mars** - not sure what plans has OP, it depends on the storyline.
Possibly, scarce resources on Mars would be better spend to build underground cities on Mars (protection from bombardment of Earth debris), and **developing interstellar travel**.
It will be most important to settle some asteroids and get them moving toward other solar systems: **whatever destroyed Earth, may return and destroy rest of the human colonies.** You definitely want to **get out of there**. This Solar system is doomed, dude.
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According to physics a systems center of mass does not change, unless external force is applied. So if earth blows up on its own accord, then the earth remains would just stay in much same orbit slightly dispersed, gravitationally nothing much would change until debris start to hit other bodies than earth moon system. Mostly it would just collapse back.
If earth was hit by something then earth debris and the hitting body don't change their internal center either, but now it would be different orbit. Again presumably not much gravitational problems, as the collider presumably existed previously but now you have a new orbit to consider. This is a major problem possibly for inner planets.
If earth gets disintigrated by some mystical thing that annihilates matter, then the energy needs to go somewhere, and that is like a supernova going off.
Most likely you'd just end up with a new planet, or asteroid (or shall we say eartheroid) belt.
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I think the biggest problem that could happen is where does the pieces of Earth go? What destroys the planet could affect other things, especially in how much kinetic energy it applies. If it blows up like putting a stick of dynamite in a bowling ball, you are going to have a lot of material expanding away from the center point. The moon is unlikely to be unscathed, it might not be destroyed but it will take a lot of damage in the form of meteors. Over time depending on how much of the earth is left in orbit, it might become the center for a small planet. Just because the earth is destroyed doesn't mean the mass affecting the moon is just 'gone'.
If there is a lot of kinetic energy it might push pieces of earth all the way into the orbits of the nearby planets would could be some very big meteors. Maybe in as little as a matter of 5-10 years, once again depending on the energy used.
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I ran this in Universe Sandbox and the moons did not fly off. The best thing was that nothing happens except to the moon which goes into a more elliptical orbit. Sadly this orbit takes its average temperature down to about -4 degrees Celsius every lunar year (assuming it had an Earth-like atmosphere). Mars is completely not affected and neither are any of the other planets. If Earth "blows up" then the pieces sometimes fly close to the moon, but not enough to affect it.
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[Question]
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The game [Rodina](http://store.steampowered.com/app/314230) features four planets, all with different colored skies. For some reason, the sun is a different color from each planet's surface (use [this guide](http://steamcommunity.com/sharedfiles/filedetails/?id=298884536) for reference).
The four planets, in order:
1. Perun - Purple sky, sun appears green.
2. Veles - Red sky, sun appears rust-colored.
3. Jarilo - Salmon sky, sun appears blue.
4. Morena - Turquoise sky, sun appears red.
Ignoring the fact that this choice is likely just stylistic, how realistic are these scenarios? Is there a correlation between the apparent color of the sky and the color of the Sun? Our planet has a blue sky and the Sun appears yellow, although I've heard of scenarios proposed where the sky could be white and the sun would look blood red (and these conditions have occurred and been documented).
TL;DR: Are the listed combinations of sky color and apparent sun color possible?
[Answer]
**QUITE POSSIBLY**
TL;DR: Atmospheric colors are determinate by a vast amount of variables, combinations are endless.
Here’s a quick hypothetical attempt
1. Perun – similar as Jarilo (*see later*) but trace amount of methane in
the atmosphere turn everything more blue-greenish.
2. Veles – the thick, nitrogen-methane atmosphere filter the light, resulting in a red tinge and in a darker sun.
3. Jarilo – thin atmosphere is filled with 1 micron wide particles so that certain wavelengths are strongly scattered, while others are
only affected about half as strongly: consequently the sun appear
bluish and the sky is opaque salmon (this happens on Earth also,
although rarely, when ashes from fires or volcanic eruptions are
suspended in the atmosphere).
4. Morena - this planet has a pure, particulate free molecular atmosphere of about 10 bars: the sky color is turquoise, and there
are less violet and blue in the sunlight; all colors are shifted to
the longer wavelengths, thus the sun appears red.
***Long answer:***
The color of the sky is affected by a huge number of factors, not all related to just the thickness of the atmosphere or the wavelength of the star’s light. For example scientists didn’t expected Mars pink skies, because they didn’t take into account fine particles of iron oxide suspended in the thin atmosphere.
To put it simple, assuming an earth-like pressure, in a transparent atmosphere like our own the Rayleight effects would cause a blue color because short wavelengths (blue) are more scattered than longer wavelengths (red). If in the atmosphere is also present a small amount of methane the sky will appear significantly more blue-green, since the methane absorbs red light... if the amount becomes excessive however, the methane would turns into dense red fog under sunlight and the opposite becomes true.
Thin atmospheres tend to be darker, while denser atmospheres become more and more saturated with color; as density and pressure rise, the sky (if made of transparent gases) will progressively become yellow, golden, then pink and finally red, exactly as in Earth’s sunsets.
Suspended materials play also an important role in determining the color of the sky. Transparent droplets (like water vapor) will turn the sky paler as they accumulate because such particles are much larger than the wavelength of light and so they scatter all light equally. If the particles are just a little larger than a certain wavelength they can resonate with light and scatter that particular wavelength strongly, while letting other colors pass through. Differently colored suspended material would also tinge the sky accordingly. In a sci-fi scenario you can even theorize airborne algae or bacteria to play a role. Gravity and stellar type also are very important.
If you are interested in these kinds of hard-science topics, I suggest you this great [article](http://www.orionsarm.com/page/321).
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[Rayleigh scattering](https://en.wikipedia.org/wiki/Rayleigh_scattering) is the primary reason that the sky is blue. Particles in the atmosphere "scatter" light in random directions. Blue light (along with violet light) has a shorter wavelength, and is therefore scattered more. For this reason, the sky appears blue, because there is scattered blue light appearing from all directions.
However, the sky can appear to be other colors. We often see magnificent shades of yellow, orange, or red near sunset and sundown. This is because the Sun is lower in the sky, and the light travels further. It is therefore scattered more (across all wavelengths) and the longer wavelengths dominate.
How can we apply this to the present case? Well, simply change the densities of the atmospheres. A greater density should shift the sky color to the redder end of the spectrum; a lower density should shift the sky color to the bluer end of the spectrum. Play around a bit and see what you can do.
The Sun appears yellow because shorter wavelengths - such as orange and yellow - deviate less from their original path. Thus, the redder light that is emitted from the Sun stays closer to its original path than the bluer colors do. Again, play around with the density to see if you can change this. A greater density might simply mean that redder wavelengths dominate even more, in which case you'll see a redder Sun in all cases of higher density atmospheres (retaining the same composition as Earth's).
[This lecture](https://courses.cit.cornell.edu/ece303/Lectures/lecture34.pdf) has an excellent summary diagram of this at the end, if you're interested:
[](https://i.stack.imgur.com/jZagl.png)
[Answer]
>
> Is there a correlation between the apparent color of the sky and the color of the Sun?
>
>
>
The color of the atmosphere is **complementary** to the color the sun appears, with respect to the total set of frequencies reaching the observer's color sensor.
That is, some frequencies of the light from the sun will be scattered by the atmosphere and the atmosphere will appear to be that color. The sun will appear to be a blend of the colors that are not scattered out.
The atmosphere could also have particles acting as a filter, which absorb certain frequencies of light (or, high enough up, reflect them back into space) causing both the atmosphere and the sun to appear more one color and less of another. For example, a certain kind of dust might cause the sky and the sun to appear a lot more reddish than they otherwise would, akin to wearing rose-colored glasses but at a larger scale.
Third, you can play with the frequencies emitted by the source. The above paragraphs assume that the sun emits at a high level across the whole visible spectrum, but this need not always be true of other suns.
Fourth, and interacting with the third, you can change what frequencies of electromagnetic radiation are visible to the inhabitants of your world. Even this Earth looks quite different to non-fictional creatures that can see better in the UV range.
Finally, you could fictionally change the way people perceive colors. I assume that when you say things like "purple" and "green" above you are referring to particular wavelengths of light that you and I have both been taught are associated with those labels, but there's no good way to know (yet) if your experience of "purple" is the same as mine; the mental experience of "purple" for you might be very similar to my experience of "green" and vice versa.
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[Question]
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Yes, magic means I can say 'make it so' and it is. But I see too many options and not sure which ones would make more sense. I'm picking one idea that I've never seen in a book.
So a Magivore is an animal that 'eats' magic to survive. (I'm thinking of things like Chemovore? Thermovores)
In this particular case the Magivore is like a bacteria, it gives a spell caster a 'cold' seriously affecting his/her ability to perform magic lets call it "The Jitters". It can spread like the common cold too, affecting others.
**Now I'm wondering about detection, spread and sterilization of such a critter How?.** It would also make magical warfare more interesting, get a Typhoid Mary or two... It would become more essential to be able to deal with it...
I've been working on this to make it a decent question but not sure if it has made it over the hump. More than willing to improve it
[Answer]
**Detection**
A wizard might wake up one day and feel that his magic is weaker. Spells and incantations that normally come naturally to him seem harder to grasp, and casting them takes a toll on the user.
Depending on the level of technology in your world, this bacteria could be considered a curse, or a divine punishment. Doubtless very few of the common folk - even magic users would take a while to figure out exactly what is going on. This magical blight could not be cured by any magical means, as any attempts to get rid of it would only be devoured by the bacteria. Technically, one could 'verify' that they have the bacteria by injuring themselves and attempting to cure or heal the wound using magic.
**Spread**
If this is a bacteria with magical properties, as you said, it could be spread in a similar fashion to any bacteria. Contact with the infected, or with contaminated items are enough to spread the Magivore to a new host.
As for magical warfare, an infected person - even a non-magic user - could easily infiltrate an enemy kingdom or school of magic and wreak havoc.
**Sterlization/Cure**
Obviously, a simple Cure Disease spell isn't going to work here. However, your world could take a cue from our own Black Death here and adopt basic hygiene methods such as washing regularly, sterilizing foods before eating, and disposing of waste cleanly and efficiently.
Alternatively, there are several plants that produce naturally-growing antibiotics that could help get rid of infection. There's a list [here](http://www.piam.com/mms_garden/plants.html) with a variety of medicinal and antibacterial plants and herbs, if you'd like to take a look. I would imagine alchemists and potion-brewers would be in high demand during and after this outbreak.
[Answer]
So your giving your characters, and the society they live in, the freedom to conjure and create, but only at the risk of attracting a magivore which will take their magical abilities away. Sort of like a "get out of jail free" card that you might only be able to use once. That elevates the choosing of which crime to commit, to a very interesting level. I'm using the word "crime" here with a little artistic license. I don't want to imply that using magic is in any way morally wrong.
Two schools of thought are obvious...
1. There will be some who use their magic immediately, to jump ahead of
the competition, hoping to create the seeds of a prosperous life and
set themselves up before they loose the ability. These people are gambling on their ability survive and thrive after the magic is gone.
2. Others will hold onto their magic to use as a last resort. These
people are gambling on their ability to find prosperity without
magical assistance and pessimistically, they are trying to stay
prepared for the inevitable challenge that only magic can solve.
Both attitudes have merit, but since your magivores spread like a common cold, the second type of people are gambling against their likelihood of catching that cold and loosing the magic without ever getting any benefit from it.
**Detecting it**:
Magic is out in the open, accepted by the society and free from secrecy. Contracting a Magivore infestation would probably be comparable to getting leprosy. Once your magic falters, people wouldn't want to get near you anymore. There would be isolated colonies for contaminated people and social customs would evolve to test for contamination before getting to close to a stranger. *I didn't know either of the approaching men, so I gestured a rune in the air between us. The glowing lines of my magic shone in the air between us, demanding that they respond. They each gestured in kind, and the light they caste was free of flicker or fault. Confident in our mutual safety, we dropped our runes and entered the room together.*
**Spreading it**: You've suggested that magivores are like bacteria, but I would find it more interesting if they were larger, maybe mouse size, invisible and intangible flying creatures. Their invisibility, intangibility and flight capabilities might be the very reason that they need to eat magic, to keep their defenses working.
If they were flying ghost-mice, you could still have your characters and their society thinking that they are a disease. It might just happen that glass, plastic and latex can block their intangibility, so normal anti-bacterial defenses would also work against them. Until somebody caught one in its magic-starved, defenseless state, nobody would know that they were an infestation rather than a infection.
**Sterilizing it**: Personally, I would leave the culture impotent in their attempts to cure the "sickness". Since they fundamentally misunderstand the nature of their enemy, everything they have tried has failed. Magivore infection, like leprosy or a social disease, would be seen as a permanent, non-fatal condition, with a slight chance of remission, but no hope for a cure. This would free you to use your new creation in some very real social commentary. Any fiction you wrote about the world where these creatures live could easily be crafted into a metaphor of our world, with magic representing sex and the magivores playing all the dark roles from VD to Aids. Such metaphors are precious and rare, so you should make use of them when you find them.
[Answer]
**Make magic eatable** - The word *mana* comes into mind as first. But because recently I finished Frank Herbert's *Dune,* I am having *spice* in mind: You eat it and the higher volume in your blood, the more magical abilities you have. Above certain volume of mana in your blood, you have to train your mind in order to manage normal living.
So, in other words, such bacteria would survive on natural resources of mana.
**Infection:** While eating mana can be pretty safe, you actually get infected if some of mana gets in your blood directly - does not go through your digestive system (which could kill the bacteria). Simple small injury in your mouth can get you infected.
**Killing it off:** Such bacteria should not be really deadly. Lying down for one week, not eating mana should get you well (as of common flu. I know that flu is virus, but just for your idea)
**Protection:** Magical rituals. Duh. In magical rituals, you do a loads of *weird looking* stuff involving weird fluids. So why not to wash your hands using some destillate?
**Mindset** Such disease would be considered as "If you play with fire you can get burned" and accepted as common backfire of doing *black magic*. People would die in same way as we die on having flu.
Obviously, the biggest hurdle to overcome for you is, how you actually tell in the story itself, that *It was bacteria all the time*. And sadly, I do not have answer for this
[Answer]
Generally speaking, magical fantasies have this much in common - a lot of uninhabited space and the concept of wizards being 'ascended', in touch with their higher natures or whatever.
The magivore you said eats magic to survive - then the obvious cure would be to supress one's magic by entering a trance; the magivore should simply starve to death. This also requires the wizard to enter a remote place, since on finding no food source the creature will actively seek out other sources.
As for warfare, using the magivore could be a two-edged sword. On one hand it cannot be preserved without nourishment - meaning you'll need someone infected with it close to the battlefield - where they could infect their own. On the other hand it could spawn some sort of outcast guild or brotherhood who specialize in anti-magic warfare - sort of like how poor lepers were outcasts and are still in many countries.
A third method would be to somehow seal it in vacuum spheres or something and have a mage feed magic into the sphere to keep the magivore alive. Firing said sphere into the enemy camp would cause the now-starving magivore to infect viciously.
Detection? It would be awesome if there were a stain on the eye. The wizard himself would not see it (unless mirrors are common) and it can prove to be a good twist for a particularly respected one to suddenly find himself shunned. In fact I'm sure it would prove to be a new era if many wizards went into exile to cure themselves of the magivore.
[Answer]
The Magivore nature must depend on the nature of its food (some kind of resource, "mana", whatever).
1. Is destroying magic only a side-effect? Is "mana" the only kind of food they eat?
2. What is the source of this resource? Is it being generated by humans, or is it being controlled by humans but generated by some kind of nature sources?
3. Is this source (and mana itself) transcendental to the world? Or is it just a part of the world? (some kind of energy or a chemical)
If "mana" is being generated by humans performing magic spells, and magivores eat it completely, they are doomed to starving death. They must become parasites, weak spellcasters, but not ultimately deny spellcasting. However, one could get rid of magivores, temporary suspending their magic practices.
If the source are transcendental, so must be magivores. In this case, you could never find them without using magic. Basically, our modern world could be populated with magivores, and they are the reason we cannot use magic anymore.
[Answer]
Suppose a creature eats mana or magic.
What is mana?
D&D's Planescape has the possible answer that different dimensions or planes that are strongly tied to different concepts and moralities such as heaven or hell. Furthermore, it has the idea that certain creatures such as Angels or Demons are composed of the substance of the plane that they live on.
I like this idea. So in some of my settings, mana is strongly held moralities and concepts in material form, souls are made out of a form of mana and dimensions are made out of a form of mana.
Drawing upon this idea you could have a magivore that is a type of spiritual tapeworm that eats mana and the souls of infected creatures.
**Detection**
Souls are a form of mana and can be seen the same way magic can be seen and detected. Spells such as Detect Magic or Detect Evil could be used to detect the tapeworm infection.
**Spread**
These tapeworms are spread along with the transfer of mana. Mana is just strong concepts and moralities and so the tapeworms are spread through discussions and conversations on ethics. These tapeworms are also spread through the use of magic spells.
**Sterilization**
These tapeworms survive best on unaligned mana. Very good or evil souls are poisonous to these tapeworms. So, holy scripture and religious practices of all sorts would be used to ward off these tapeworms. Very powerful aligned energies such as from holy water, the fires of hell or a large group of zombies could be used to kill the tape worms as well.
[Answer]
Have magic as a power from another realm, one invisible and intangible. Magic users can channel that, and the magivore gets in the way. When magic is used on something or someone, the caster is linked to the target through that realm.
**Detection** The mage's spells don't have as much horsepower as they used to. If some of the spells are used for his own health, this can hurt or kill him.
**Spread** It can spread through contact, *but can also spread over a distance if someone casts a spell on someone already infected*. If another mage is brought in to cast a diagnostic spell, poof, he catches it too. The same for anyone trying healing spells.
**Cure** The victim must refrain from all magic for a few months, and no magic can be used on that victim, either. The thing is, magic is so danged useful that the mage has become really dependent on it. And if the mage has a job important to others, like being a healer or a combat mage, abstaining from magic may actually cost lives.
**Edit:** Maybe also have people handicapped by a complete lack of magical ability. These people, usually considered handicapped to some degree, would be immune to the magivore, and would, ironically, be the only ones who could safely take care of very powerful mages who are ill with this.
[Answer]
If *mana* is a consumable as in Nivin's stories, then any beast whose metabolism depends on magic, such as dragons, could be said to "eat" magic. It is a resource to be exploited by the living cell, like anything else, and a bacteria that figures out how to use (meaning both *make-use-of* and *consume* since once used it is spent) mana to exploit a niche and replicate a lot, will sound like the kind of thing you asked about.
Dragons only live in regions with mana to use as a kind of vitimin, but a primitive Prokaryote may pick up a trick of using mana fairly directly to replicate like mad. These can become organelles and internal symbiotes in Eukaryotes and higher life forms, and may be how dragons are able to harness mana for their limited means.
I can imagine *weeds* that grow near rich mana sources, and may be a way to spot magic areas. A magician concentrates mana in and around his body, so an infection would deplete his powers, mess up his application of power, and as a side effect make him sick through biological means just because they are there.
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[Question]
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I've been collaborating with someone on a new version of a planetary classification system for our sci-fi settings and I had an idea recently. From looking at a phase diagram for nitrogen, it should be possible for a world to exist which could have liquid nitrogen on its surface in equilibrium with a nitrogen atmosphere. I decided to try and make one in Space Engine to put in a star system for my worldbuilding project but found myself wondering something.
Would a nitrogen sea look white from orbit? Liquid nitrogen is described as colorless. Barring any contaminants, would that look white? I found plenty of info online for some other exotic oceans, but not for this.
[](https://i.stack.imgur.com/DX5d4.jpg)
[Answer]
As HDE 226868 noted, it is rather difficult to find data on the transmission / absorption spectrum of LN2.
However, we can make some guesses at what it *should* look like over large depths, based on comparing its structure with that of water.
Water strongly absorbs red and infrared wavelengths because it has lots of degrees of rotational and vibrational freedom, with molecular energy level gaps in the red to infrared range.
Molecular nitrogen, in comparison, has only *one* degree of vibrational freedom, and a much stronger, stiffer bond. Thus, while liquid nitrogen and liquid water are difficult to distinguish in the quantities in which liquid nitrogen is typically produced on Earth, both being colorless, we can expect nitrogen to remain effectively colorless, with minimal visible absorption, at much greater depths. The color of an ocean would thus be approximately the color of whatever is under it, and whatever is reflecting off of it.
There remains one other coloring effect, though: Rayleigh scattering, which is what makes the sky blue. A thick atmosphere of pure nitrogen would be just as blue as our thick atmosphere of mostly-nitrogen-and-some-oxygen, and you could expect the ocean to take on some of that color by reflection. On top of that, Rayleigh scattering also occurs in liquids, so extreme depths of liquid nitrogen would appear blue in transmission--thus, ocean on the limbs of the planet should be tinted lightly blue, and a deep ocean which reflects light back up from the floor will have the color of bright features of the floor shifted towards red, while the bulk of the ocean surface will be slightly blue in compensation.
The most likely color of that floor is white, due to precipitation of nitrogen ice under pressure. So, a world with a shallow nitrogen ocean should look mostly white, with blue tinges from the nitrogen atmosphere on the limbs, while a world with a deeper nitrogen ocean (possible on smaller worlds where pressure increases more slowly with depth) should shift more towards the unsaturated (whitish) blue due to liquid Rayleigh scattering, with orange-red patches where the seafloor is highly reflective.
Of course, if there is anything *dissolved* or suspended in that ocean, the color could change drastically. LN2 isn't a very good solvent, but the ultimate color of a world with an LN2 ocean could be determined by whatever life ends up developing in it, if any, and then it could be pretty much any color you want; such life would have to use some other intracellular biosolvent, but that just means the nitrogen ocean will be to it much like what the nitrogen atmosphere is to us--a medium that it moves through, and uses for temperature regulation, but which is otherwise biologically inert.
[Answer]
In its flyby of Pluto in 2016, the *New Horizons* spacecraft determined that the dwarf planet is at least partially [covered by the frozen remnants of a liquid nitrogen sea](https://www.nasa.gov/feature/pluto-s-mysterious-floating-hills). In its solid form, the ice looks nearly pure white, with impurities due to water ice:
[](https://i.stack.imgur.com/RyTck.jpg)
Image credit: NASA/JHUAPL/SwRI
Liquid nitrogen, on the other hand, is colorless, not white. Therefore, its color will depend on how it absorbs incoming light. For example, [water (which often appears colorless) is blue in oceans because it absorbs redder colors](https://oceanservice.noaa.gov/facts/oceanblue.html#:%7E:text=The%20ocean%20acts%20like%20a%20sunlight%20filter.&text=The%20ocean%20is%20blue%20because,spectrum%20for%20us%20to%20see.&text=Hardly%20any%20light%20penetrates%20deeper,penetrates%20deeper%20than%203%2C280%20feet%20.) and reflects bluer colors. It's not easy to find optical absorption spectra for liquid nitrogen, unfortunately (far-infrared and ultraviolet spectra, though, are plentiful!), so we have to do some guessing.
I would be surprised if the optical properties of liquid nitrogen were drastically different than water, though, particularly given that both are naturally colorless (though it's possible I'm wrong). Plus, unlike water, nitrogen ice is denser than liquid nitrogen, meaning that if any formed, it would sink, rather than float. We would then have a clear/maybe-slightly-blue liquid above a whiteish ice, presumably leading to a whitish-bluish color.
Any planet cold enough to have a liquid nitrogen sea would likely be far from the star, making it favorable for nitrogen ice to form, too - particularly given that liquid nitrogen can only exist in a small range of temperatures.
[Answer]
one possibility is this could be a tidally locked world orbiting a red dwarf or a white dwarf.
the night side could have oceans of nitrogen, and the day side an atmosphere of Nitrogen.
and it would have white colored skies mostly, with the color of the water reflecting white.
good choice of game by the way.
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[Question]
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What would the consequences be of a high number of solar systems being within close proximity to one another? I'm mainly interested in the consequences for life on multiple planets. When I say 'close proximity' I mean the stars all being between 1000-100,000 AU apart from one another, and roughly all being G-category stars?
I'm trying to create a setting where the distances between other exo-planets is not as vast as our own relative position in the galaxy, due to the issues limiting light-speed space travel.
The effects I am taking note of are:
* Gravitational effects (how much the stars will be attracting one another, and how it will affect planetary orbits)
* Stars heating planets
* The amount of light being received by close stars
Would habitable planets be able to survive with such a dense amount of stars nearby? If so, what are other variables to consider that would change the planets features?
[Answer]
Your environment is quite similar to that in a globular cluster. At its densest, a globular cluster may see peak stellar number densities of [$\sim1000$ stars per cubic parsec](http://www.astro.keele.ac.uk/workx/globulars/globulars.html), which implies a mean separation of about 20,000 AU. This leads us to conclude that [many, if not most, planets will be stripped away](http://adsabs.harvard.edu/abs/2009ApJ...697..458S) through encounters with other stars, leading to a large population of free-floating planets.
Your systems will experience the same problems. However, $N$-body simulations have revealed some characteristics of the planetary systems that will survive intact:
* Planets will [likely have orbits close to their parent stars](http://adsabs.harvard.edu/full/1992ApJ...399L..95S). For instance, planets around pulsars would likely have semi-major axes of $\sim0.1\text{-}1.0$ AU.
* Moreover, [systems with large numbers of planets are quite unlikely](https://arxiv.org/abs/1706.03789), given that multi-planet systems are even more susceptible instabilities after experiencing these encounters.
With mean distances of a few tens of thousands of AU, light from other stars will not affect habitability, thanks to the inverse-square law. A star 20,000 AU away should contribute a bit more than one billionth the flux of the Sun, if the Sun was 1 AU away.
[Answer]
I'd say that the central stars would have lifeless small rocks as the planets would lose their original orbits. The inner most stars would get hotter from the output of the ones surrounding them. The central region would be high in radioactivity from all the solar winds streaming in. The perimeter stars would be richer in planets from having captured the wanderers.
Starlight intensity would not vary much given the nearest star is 200 times as distant as Pluto is from the sun.
No comets. They can't survive even a single pass without falling into one star or another.
Life's chances for any peripheral system that's more than a few thousand AU's from nearest neighbor are pretty much the same as on singleton systems.
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[Question]
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I'm currently writing a narrative and hoping to include a world which is home to a sea of some form of 'nasty' substance (doesn't have to be acid).
The varieties of inhabitants of this world have evolved mostly on the lands and eventually built their cities right up to the shorelines of this acidic sea. (In some cases I may even have cities that float and migrate across it).
I'm imagining some kind of scientific or industrial endeavor they perform whereby they've created ships that can withstand the chemicals (at least in short term) by lining their hulls with a type of [ablative shielding](https://en.wikipedia.org/wiki/Ablative_armor).
Also desirable (although not essential) would be for the composition to not be immediately fatal. A carbon life form (or would they likely be silicate?) could fall in and maybe swim for a few minutes and leave with only some semi minor chemical burns. Yet prolonged exposure would most definitely be fatal.
I'm also wondering if the inhabitants could harness this chemical in some imaginative way such as for propulsion or agricultural/industrial means?
My question is, what kind of chemical/cocktail could I use to fit these kinds of parameters?
Disclaimer: also posted to [chemistry](https://chemistry.stackexchange.com/questions/44740/which-acid-to-choose-when-designing-a-world-with-acid-seas).
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Acids are very harsh on minerals so your world will be devoid of metals, bases, and basic rocks.
Additionally acids weaken with use, so you'd have to have them constantly replenished somehow, while also filtering out all the diluted substrate.
I suggest you maybe consider a water based ocean with heavy enzyme activity. The enzymes might be continually released by some microbial ecology while being quite adept at disolving non-native biology or machinery without natural defenses.
sort of a toned down, all natural [grey goo](https://en.wikipedia.org/wiki/Grey_goo).
there is [precedent](https://en.wikipedia.org/wiki/Great_Oxygenation_Event) for this in earths history. When photosynthesis evolved and bacteria started dumping this toxic stuff called oxygen into the atmosphere and wrecked anaerobic lifestyles.
* proteases and peptidases split proteins into small peptides and amino
acids.
* lipases split fat into three fatty acids and a glycerol
molecule.
* amylases split carbohydrates such as starch and sugars
into simple sugars such as glucose.
* nucleases split nucleic acids
into nucleotides
feel free to mix and match, or invent something if you need to digest metals.
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To maintain a toxic level of acidity in your oceans, you will need to have a large amount of acid-forming chemicals in your environment.
One possible example would be CO2 with a partial pressure of about 1 atm. The resulting carbonic acid would be about the strength you need. The acid will precipitate out as carbonates when available calcium ions, etc. are added to the ocean. Over eons, you likely must have a carbon cycle to justify the ongoing high CO2 level.
Of course, this level of atmospheric CO2 is toxic to virtually all animal life on earth, though a different animal biology would perhaps be compatible.
Other acids will also likely require their own equivalent to a carbon cycle. But they also share a common problem in that the corresponding atmospheric partial pressure will also often be toxic. For example sulfuric acid has a vapor pressure of 0.001 mmHg at 20 C. Not much, but enough to damage delicate lung tissues, etc., esp. considering constant exposure. Nitric acid has a much higher vapor pressure and hydrogen chloride is a gas at STP.
I don't know the vapor pressure of all the potential acids off the top of my head, but it is important to consider this for any suggested acid.
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If you don't need to ocean and atmosphere to be in balance because the ocean was recently polluted with large quantities of the acid that have not had the time to pollute the atmosphere significantly, you can ignore the condition needed for a long-term balance.
One realistic choice for recent or long term ocean acidification could be an ocean-based bacteria that produces abundant organic acids salts, perhaps the salt for oxalic acid. This could be a mutation of a common land-based bacteria that aggressively consumes the oxalic acid in the atmosphere -- this combination of bacteria could provide the required imbalance. It is not unrealistic for oxalic acid to be important to biology, in fact, [you have oxalic acid in your blood and it is a bi-product of metabolic processes. Some plants are known to metabolise oxalic acid.](http://dergipark.ulakbim.gov.tr/tbtkzoology/article/download/5000029277/5000029514), Other organic acids have similar chances for production in the ocean and consumption on land that could maintain the imbalance between ocean and atmosphere.
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Also note evolutionary theory would suggest that ocean organisms would tend to develop resistance against oxalic acid though land-based organisms would be far-less likely to develop resistance. This may mean that ocean based food **could** be toxic (mildly or strongly) to land based creatures. It would depend upon whether the ocean adaption is passive -- developing tolerance to oxalic acid, or aggressive -- developing mechanisms that reduce oxalic acid levels within their bodies.
Why did I suggest [oxalic acid](https://en.wikipedia.org/wiki/Oxalic_acid)?
* It is a strong acid, at 0.1 normality, pH is 1.3. For comparison sulfuric acid at 0.1N has pH 0.3
* It is known to be actively used in nature including consumption and waste output. Some bacteria are known to produce the oxalate. It is also a significant component of many common foods.
* It only consists of very common atoms, oxygen, hydrogen and carbon
* Accumulation within humans causes problems at low concentrations. It is also the chief component of kidney stones (calcium oxalate), which is why stones sufferers are advised to avoid sweet potatoes, asparagus, etc. that are rich in oxalates.
* It is colorless in solution, won't interfere with ocean photosynthesis, etc.
* It is cheap, about 600-700 USD per tonne at industrial grade (99.6% pure) from Alibaba today (2016-02-05)
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[There are acidic saline lakes on earth](http://www.scientific.net/AMR.825.28), down to pH 1 in ponds in Chile. That abstract mentions solutions of Cl-SO4-Na and Cl-SO4-Mg: I don't claim to understand the chemistry that determines their pH at a given concentration.
I'm not certain, but I think that's acidic enough to give you a bad day if you stay in there long enough. They do sustain carbon-based life, but extremophile cyanobacteria rather than fish.
As far as I know, these are generally formed by the concentration of whatever minerals are in them, over a geological period of time, by the evaporation of water that's run down from nearby mountains and whatnot and brought the minerals with it. That is to say, dead-end rivers.
Obviously your "sea" needs to be a lot larger than these ponds to be worthy of the name, but the general principle is that if you have a land-locked body of water, far enough away from the ocean that it hasn't been diluted and mixed any time in the last few million years, then it can concentrate pretty much anything water-soluble in the area, including acid salts. You don't need the whole planet or its atmosphere to be acidic, you need an enormous acid salt deposit plus just enough water to float a ship. The water might be seasonal or the result of the current climate in your world being somewhat wetter in this region than it had been during a previous epoc during which large acid salt plains formed.
For scale, [Salar de Uyuni](https://en.wikipedia.org/wiki/Salar_de_Uyuni) in Bolivia covers 4000 square miles and contains 10 billion tonnes of salt. It's not currently wet enough to constitute a sea, and it's not acidic, but combine the scale of this with the chemistry of acidic brines and you're there. You can argue what's "really" a sea and what's "really" a lake: this is a lot bigger than the Dead Sea, but I think the Dead Sea is normally considered a lake not a sea. I've seen the Sea of Marmara claimed as the "world's smallest sea" -- Salar de Uyuni is only a third the size.
One problem, though: I don't think building a ship to resist this level of acidity would be a huge big deal. It probably wouldn't require enormous ablative hull shields, but perhaps you're prepared to take dramatic license and/or increase the amount of sulphuric acid in there. Fundamentally, if you can use ceramics then I guess you can resist any acid not near-instantly fatal to humans.
It's true that acid gets "used up" as it reacts, but if you compare millions of years of deposit against thousands of years of humans operating boats, I don't see why something of this sort couldn't *appear* stable even though technically the salt deposits are being eroded as a result of currently having more water present than the long-term average, and a certain amount of stuff falling in and reacting.
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There could be a lifeform (e.g. an algae or plankton) that filters salts out of the ocean that turns the salt products of an acid-base reaction back into the components. The lifeforms could "capture" the base, incorporating it into their body and protecting it from acid. This releases the acid back into the sea.
Apart from the salt itself, the organism would rely on two main things for this reaction: energy and hydrogen.
Since neutralisation reactions are exothermic (releases energy/heat), the inverse will be endothermic (requires energy). Thus you could expect the organisms to thrive particularly well around geothermal activity, and to live more slowly in smaller numbers on the surface (particularly in warm/sunny areas). Solar-adapted versions may have the ability to build a small "charge" from solar energy over time.
Hydrogen is needed to replace the base from the salt and turn it back into an acid. If they're in a water body, there's hydrogen in water (again, endothermic to split H20). This would release atomic or molecular oxygen into the water, which the organism or other organisms might use for respiration. This isn't a substitute for photosynthesis in the world, though; they're not splitting carbon dioxide.
So if we look at this, we have an organism that dwells on the surface and around geothermal activity, which captures bases from salts and keeps the ocean acidic. This will gradually erode the mineral landscape, but this may be a tectonically active planet. When the organisms die they may sink down and form protective layers (assuming however they hold the base safe from the acid is stable), preventing the acid from eating downwards.
So why are people living in places where these organisms live? Perhaps it's just because they want the same things - geothermal activity can provide uses for people, and often contributes to land fertility. Perhaps there are other dangerous organisms that the acidic seas keep at bay.
**So, which chemicals??**
Firstly, which salt? There'll be a few factors that make it more likely for this kind of organism to survive. The "lattice enthalpy" of a compound relates to the energy required to break the bonds, so different salts are more easily broken than others. I don't know if the organism would survive better with an easily ionised salt (because it takes less energy to break it) or a more strongly ionised one (because the bonds it forms by adding the molecules to its body are more stable). I don't know enough about chemistry to work out which salts have more or less lattice enthalpy!
Which acid? The stronger the acid, the harder it will be for the organism to store the base safely. However, a stronger acid will also react with other things faster (e.g. minerals in the landscape), forming food for the organisms. Because the organisms are limited in their "processing" by their intake energy, they might be more likely to have evolved with a medium-strength acid.
I'm no chemist or biologist, so I don't know which to recommend! Probably pick whichever's more suitable for the setting. Depending on the use of the setting you might not want to specify the acid or salt in question, and just describe the effect.
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I would go with a weak dissolution of acid. Where most of the ocean is water, but has a 'high' concentration of acid. Take something like Hydrochloric acid say in "The Works" toilet bowl cleaner and water it down by 1/3 to 1/4. This might still allow some kind of water cycle to continue working on your planet.
It won't be immediately fatal, but you won't want to spend any more time in it than it takes to get back out, strip and rinse off.
Ships and docks would likely have stashes of ammonia or some other mild base to help quickly neutralize the acid, when people get pulled out.
The bigger problems would be how an ocean was turned to acid and even more what process is KEEPING it acid, since it tends to react with stuff and be neutralized. This can be handwaved away, but some thought might be put into that.
If you notice our oceans are full of salt, which happens when a base and acid are mixed.
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This image might be helpful:
Hope it helps.
However, a list of some acids are: Sulfuric, Hydrochloric, Nitric. More [here](http://www.endmemo.com/chem/acidslist.php).
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If humans were to vanish completely from the Earth rapture-style, other primates would possibly slowly evolve and eventually take our place (in a few million years?), since they have both the basic cognitive architecture and similar manipulators that could evolve to allow finer motor control more easily, compared to a dog's brain and front paws.
I have seen other non-primate animals use tools, such as [ravens using tools to get tools to get food](https://www.youtube.com/watch?v=DDmCxUncIyc). And there are other types of manipulators even here on earth (jaws, beaks, claws, [tentacles](https://www.youtube.com/watch?v=GQwJXvlTWDw), trunks). Heck, Koalas even have two thumbs per hand. To me, however, it seems like there's a catch - literally, in that the human hand might just be the most precise and versatile environmental manipulator (relative to our size) that has ever evolved here on Earth. It allows **multifunctionality, power, precision, and sustained use,** which would be my **criteria** of choice for comparisons.
So here's a question for the more biologically and mechanically inclined among Worldbuilders: **Could other solutions solve the difficult problem of grasping (holding, scooping, throwing, etc.) without the same adaptation? In other words, can claws, jaws, tentacles, beaks or trunks do the job (of building tools, fire and a civilization) as well as a hand or is there something vital that's missing in those manipulators?**
To give two specific examples, would evolved elephants or some land-adapted octopi be able to achieve the kind of motor control we enjoy?
This will be useful in refining the degree of convergent evolution that needs to take place in my alien/abandoned-earth worlds...
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Trunks are unbelievably adaptable, but they require a large amount of time to learn how to use. Elephants could easily do what is needed.
Trunks are as dexterous as a human hand, and in many ways even more dexterous. The price you pay for a trunk is complexity. The human body has about 800 muscles to do everything, from manipulation of objects with our hands, to digestion. An elephant trunk has 150,000 individually addressable muscles! It has more degrees of freedom than just about anything we've ever seen.
In fact, a trunk is so complex and fluid and thriving, that people in contact with an elephant often get the feeling that there are two individuals there: the elephant and its trunk. We often feel like the trunk is alive on its own accord
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Another possibility would be lobster type manipulators. More specifically their mouths. Crustaceans and some insects have multiple layers of manipulators to breakdown their food. They get smaller and more precise the closer they get to the mouth. No one layer is supper dexterous but combined very versatile.  
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[Cephalopods](https://en.wikipedia.org/wiki/Cephalopod) (squids, octupus, and [cuttlefish](https://en.wikipedia.org/wiki/Cuttlefish)) have many dexterous tentacles which can grip and manipulate. Often their whole body gets into the act. They've demonstrated [intelligence and problem solving](https://en.wikipedia.org/wiki/Cephalopod_intelligence) which has been called "alien" given how distant their relationship is with mammals.
Cephalopods, particularly [cuttlefish](https://en.wikipedia.org/wiki/Cuttlefish#Skin), use skin color, body shape, and their tentacles to communicate. One can imagine an sentient octopus performing a task with four tentacles while carrying on a conversation with the other four.
[Cephalopod vision is excellent](https://en.wikipedia.org/wiki/Cephalopod_eye) which is important for fine tool use. Their eye is better designed than the vertebrate eye with no blind spot, and they can see polarization.
* [Octopus escaping a jar](https://www.youtube.com/watch?v=IvvjcQIJnLg).
* [Cuttlefish communication](https://www.youtube.com/watch?v=gnhc1KALHxE).
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In the limit, **how small can a brain get and still host an identifiably human-like consciousness**?
Obviously, they can be smaller than an adult human's, since children (with smaller brain volumes) and patients who lost upwards of half their brain exhibit behavior that we would consider conscious and report experiencing an internal representation of the world through qualia. Furthermore, since human brains are large, noisy and lossy environments, this means that many brain structures have redundant features to get around this noise problem. Smaller organisms could and often do have smaller cells and don't need as much error-correcting duplication.
So are we talking *chimp-brain-size*? *Dog-brain-size*? *Ant-ganglion-size*? To simplify, assume that the biology in question retains opposable thumbs or at least vocal chords to ease communication.
Re: What do I mean by conscious: do other entities we recognize as conscious recognize it in turn as conscious? This might miss on some (or even most) forms of consciousness, but saves me endless definitional hassles.
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I don't think the terms "self-aware" and "conscious" are defined well enough to give you an answer. On one hand, we haven't given the title "self aware" to anything smaller than an Orangutang. However, depending on your definitions, you could make a hard sell that a standing wave such as a quantum waveform has self-aware traits.
My answer, if I had to peg definitions for "self-aware" and "conscious," would be that the answer depends on how hostile the environment is. The more hostile the environment is, the less value there is in understanding yourself (you spend all your energy battling the environment). The friendlier the environment is, the more an understanding of how "you" operate becomes an important trait.
At the smallest scales, Brownian motion is a dominant force. Its randomness is going to keep a small organism evolving to deal with its effects, not its effects on itself. However, if temperatures were chilled, it may evolve to be more aware of itsself on its surroundings.
Pack your local area close enough, however, and your neighbors all work like you. Suddenly its really useful to understand yourself so you can understand your neighbors.
Bacteria exhibit interesting behavior in biofilms. They effectively form a quorum, at which point they all agree that banding together is good for the group. They then react differently, "realizing" the power of their combined force is greater than the sum of their Selves.
What about parts of a body? Currently there is belief that the Anterior cingulate cortex may possibly be the "throne" of the brain's consciousness. Is it? We don't yet know. But this does suggest that there's a smaller part of our brain responsible for this funny thing we call consciousness.
Going all the way to the waveform argument, consider a standing wave in a flute. If any air molecule is perturbed, such as from Brownian motion, it falls back in sync, because it "knows" the relationship between its momentum and its position. Or does it? This quickly becomes a philosophy question. What does it mean "to be aware of one's self?"
Philosophy majors will take it all the way. There is a category of philosophies called idealism which all center around the idea that everything is conscious thought. Every grain that makes up the sandy beach is a conscious aware entity. It's a bit extreme, but it points out just how hard of a question you are asking. In the other direction, there is a physicalilst argument that consciousness is simply an illusion, and nothing is conscious, not even us.
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Edit: in light of your edit, I recommend two Wikipedia articles:
* [Animal consciousnes](http://en.wikipedia.org/wiki/Animal_consciousness)s is not a well defined topic. Some tests, such as the mirror test, admit some primates and pigs, but dogs often fail that test (which is counter intuitive for many dog owners). On the other hand, some tests are with regard to the handling of pain, which many animals, including dogs, pass.
* The actual issue you are going to have to grapple with is the [Problem of Other Minds](http://en.wikipedia.org/wiki/Problem_of_other_minds). It is an extremely difficult topic, which can go so far as to say "all other humans are merely zombies... I am the only conscious one." I recommend looking into this problem, because your edit suggests this direction: you are seeking to make them "similar" enough to humans to ease identification via the ability to vocalize and so forth.
Because of how hard the Problem of Other Minds is, and how much harder it is to convey this issue as an author, consider side-stepping the issue entirely. Use [Sanderson's First Law of Magic](http://brandonsanderson.com/sandersons-first-law/) to make your life simpler:
>
> Sanderson’s First Law of Magics: An author’s ability to solve conflict
> with magic is DIRECTLY PROPORTIONAL to how well the reader understands
> said magic.
>
>
>
Decide to yourself "this creature size is conscious." It doesn't really matter what line you pick, pick a line that suits you and your intuition. Call it magic -- you defined something magical called consciousness. Cool! Now by Sanderson's first law, you are free to call them "conscious" as long as you please, up until the point where you try to resolve conflict with it. At that time, you need to have taught the reader enough about this "micro-consciousness" that the reader understands enough to let you solve the conflict.
Because the understanding of your particular definition of consciousness is narrow at the start of the work, concentrate on showing how *it solves problems that the reader would relate to that sized animal.* For instance, ants don't like water on their nest. It does really bad things when the nests flood, so they have to take action like move the young closer to the entrance. An ant would be interested in keeping the nest area dry. However, they would not invent robotics to cut down a giant banana leaf to cover the nest, but they would develop gorgeous Mandela of small leaves which interlock to make something watertight, but which can be moved by a single ant. Now we have demonstrated problem solving.
Now lets say there's a particular parasite of a larger creature that is considered "good food" by the ants (for any reason you please). Every now and then, an ant might come across one and get to take it back, but its a lot of work. However, the larger creatures are smart -- they can be trained. Consider an ant colony that will rearrange their Mandela to signal nearby creatures with parasites to come be groomed (or they may arrange their Mandela differently to signify that they have enough food, and would prefer to leave their nest less-trampled). This would be along the lines of the small cleaner wrasse who clean the mouths of sharks. Suddenly we have the ant colony communicating with a greater species, and communication is a strong "walks like a duck" moment in any consciousness story.
At some point you should be able to wrap the reader up into questioning "is the ant conscious, or is the ant colony as a whole conscious?" That is the point where you have them wrapped up in your particular definition of consciousness, and you can start saying "let me explain to you why *this* is the sound of a duck quacking," and no reader will disagree.
The key to all of this is that you never use consciousness to solve a conflict that the reader does not already understand: and you start from conflicts that could be reasonably resolved by a creature of similar size and move up.
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What if the said consciousnesses are digitised into a computer?
(Summary: Probably not possible with existing silicon-based computer technology, but very possible with future exotic computing techniques)
With the ever-decreasing size of transistors, it could theoretically be very possible that a future digitial mind will be capable of becoming vanishingly small.
Of course, this requires that artificial intelligences be natively programmed, instead of being emulated (which would be significantly smaller and more efficient, but we cannot tell for sure how much smaller).
To do a back-of-envelope calculation
A [supercomputer cluster](http://en.wikipedia.org/wiki/K_computer) (10 petaflops) [achieved a speed ratio of 1:2400](http://www.extremetech.com/extreme/163051-simulating-1-second-of-human-brain-activity-takes-82944-processors) while emulating a fraction (~2%) of the human brain's neurons. Using naive scaling, it would seem that 1.2 zettaflops $(10^{21}$) would be required to emulate the entire brain.
The said supercomputer uses 45nm node transistors made using single-layer silicon lithography. Assuming Moore's Law is broken at 1nm (atomic-sized) transistors, and that this "future CPU" design stacks 1000 layers of silicon, the proposed "future silicon processor" will be approximately 2 million times faster than the supercomputer, which therefore would be able to simulate the human brain with a 16x speedup, or simulate 16 simultaneous human brains. Since even simulating one brain would still require multiple server racks, this would not represent a shrink.
What about [computronium](http://en.wikipedia.org/wiki/Computronium)? [A Nature paper](http://puhep1.princeton.edu/~mcdonald/examples/QM/lloyd_nature_406_1047_00.pdf) on the ultimate limit of computational miniaturisation seems to suggest that 1kg of computronium would at best be able to carry out $5 \times 10^{50}$ flops (by collapsing it into a black hole). Assuming 1.2 zettaflops are required to simulate a human brain, less than one atomic mass unit ($1.66 \times 10^{-27}$ kilograms) of computronium would be required to simulate the human brain. A native computational intelligence would be significantly smaller.
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As a writing exercise (I never figured out the plot details) I wrote exposition on an ET who has gone unnoticed by Earthlings because he is the size of a mosquito.
Looking upmthe complexity of a human brain and estimates of its processing power, I was able to imagine a plausable technology to just barely fit. This would be an uploaded mind or AI in an advanced engineered computer, not natural biology.
Another idea I played with was sentient life on the scale of our single cells. Lacking physical count of parts, they used quantum mecanical processes and lots of time to think: their perception of time was about a day to our year. Nanomachines are rheir natural scale and (e.g.) motors are grown on dometicated lifestock (flagellium motor bread to be more what they want and less natural). The explaination is handwaving, not real engineering, but OK for a story that really treats it as a given.
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Imagine that a group of [Inuits](https://en.wikipedia.org/wiki/Inuit) from Greenland settled in Antarctica; let's say on the Antarctic peninsula, if there is no better place in Antarctica.
Could they survive there with their traditional lifestyle, i.e. hunting and fishing without access to any modern technology ? If no, what necessary resources they would lack ?
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Yes, they could probably survive.
The most important things to the Inuit's survival would be the local animal species. People often misunderstand the completely different lifestyle lived by the people of the extreme north.
**What do they burn if there is no wood?** They burn seal and whale fats, but mostly they stay well insulated in layered animal hides and eat a high fat diet for energy/warmth.
**What do they build their dwellings out of with no wood?** The igloo is made of ice and other structures are made with stone or animal hides reinforced with bone or wood.
Wood was very important to the people, but it was still not common. They did not harvest trees, none grow in the far North, mostly they obtained wood from the ocean as driftwood, and it was kept and preserved as a structural tool not wasted on a fire.
Most all of the same resources would be available in Antarctica. Along the coasts seals and whales are plentiful providing most needed resources. Some resources would be different, no polar bears or caribou, but I bet they would find some uses for all the penguins.
**Temperatures**
[](https://i.stack.imgur.com/3DlJf.png)
As shown the average winter temperatures on the Antarctic Peninsula are ~ -10 to -20 C. compared to the Arctic winter temperatures around Northern Greenland of -30 C, this is fairly warm.
[](https://i.stack.imgur.com/8nwdF.png)
For a historical comparison, many of the more successful explorations of the *interior* of Antarctica (much colder and inhospitable than the coasts) in the 19th and early 20th century adopted techniques used by the various Eskimo peoples; dog sleds, layered fur clothing, high fat diets, etc.
Life on the edge of habitability requires adaptation or you die. The Inuit knew how to survive, most of their methods would still work with locally available resources, and they would adapt to the changes in available resources.
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There are only 2 species of [flowering plant](https://www.bas.ac.uk/about/antarctica/wildlife/plants/) in the Antarctic. I read somewhere that the traditional Inuit diet contains more insects than plant material, but nevertheless they did use plants. None of the useful ones which produce berries are available in the Antarctic. So that's one vital resource gone...
Insects... there are no flying insects in the Antarctic. In fact the arthropods which are there are tiny [like springtails.](https://www.bas.ac.uk/about/antarctica/wildlife/land-animals/) Another source of food gone.
Plus any animal that eats flying insects or berries (e.g. various birds) is absent.
There are no herbivores in the Antarctic. No hares, caribou, musk ox, lemmings. Your colonists therefore can't eat these.
There are no land-based predators in the Antarctic. (Polar bears are Arctic animals). The seals, penguins and seabirds which live there will be really easy to kill, because they are entirely without defence strategies against a big land-based predator. So your Inuit colonists would annihilate their way through the breeding colonies much like sailors annihilated their way through the dodos on Mauritius! Great to start with, then they starve.
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The answer is yes, they probably could, but it would not be the same lifestyle due to one key part that your question gets wrong. Greenland isn't really home to much for Inuit populations...it's controlled by Denmark and is more like Nordic populations than Inuit. Try Canada and the province of Nunavut.
The Inuit peoples make their living in a very similar fashion as the polar bear does...although the land means a lot, much of their survival is based on the sea ice instead, especially when it comes to food gathering. Seals in particular are significantly easier to hunt while on the ice flows. The arctic still ices over (mostly) during the winter and this connects the land. For what it's worth, it's usually hard to tell if they are on land or on sea ice.
This will be the major difference between arctic and antarctic living...shelter, transport, and warmth will be basically the same as their lives in the far arctic goes...however they will have to adapt heavily to different forms of hunting and gathering as they are now on a land locked continent and not on ice connected islands. I'd imagine they'd live more like far north nordic populations than the Inuit populations do.
Edit:
After a little research, turns out I'm wrong myself...Greenland is host to a population of Inuit. <http://www.inuitartsociety.org/sheila-romalis-greenland-canadian-inuit-culture> a few differences between them...I was unaware Native Greenlanders also use the term Inuit for themselves. In any case, it's the same change to overcome...Antarctic is a continent locked under the ice and as such is a much different hunting environment.
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Food is fish, krill, seals, penguins and their eggs — commercially bred.
Heat would come from burning fish oil
Water is everywhere — Ice.
Then you trade for raw materials for clothing and other basic needs.
Then the last thing is the Antarctic economy would have to circle around the service industry.
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## **TL;DR**
No way for them to survive *totally alone*. If they import their own tools, they will last until they break. Otherwise, they won't be able to even build their houses.
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Well, there are already [a lot of people living there](http://www.coolantarctica.com/Antarctica%20fact%20file/science/can_you_live_in_antarctica.php), even if they do not live an entire year or so. They are mainly there for scientific purposes like [Keri Nelson](http://www.cosmopolitan.com/lifestyle/news/a46171/keri-nelson-year-on-ice-antarctica-interview/), so sustaining there as humans is widely possible.
Considering eskimoes ... I guess they could. Igloos are excellent at [keeping warm air inside](http://www.physlink.com/education/askexperts/ae579.cfm), and fishing should not be a problem, as they already fish in sub-zero conditions. Hunting penguins and predators should also be in their skill range, but I keep asking myself ...
*Where would they find flammable materials ?* Or more importantly ...
*Where would they find wood ?*
I guess this would be the top lacking resource. They could melt ice to get water, sleep in a warm place, wash themselves (rough tho), **but** they would need some beginning materials to do so. Maybe from crashed ships or something, but to start a fire (and heat up), they **need** flammable materials. I don't know a lot about Antarctica, but I think it would not be wood-proficient, considering temperatures, climate and environment.
In the same way, to hunt, build and fish, they would need tools. Tools that you could craft with wood, or iron. To build igloos, you need to cut hard snow into block, and I do not think they could to it bare-handed.
According to [CoolAntacrtica.com](http://www.coolantarctica.com/Antarctica%20fact%20file/antarctica%20environment/whats-it-like-in-Antarctica.php):
>
> Antarctica has no trees or bushes at all, vegetation is limited to about 350 species of mostly lichens, mosses, and algae.
>
>
>
So no, without any help and all alone, they won't be able to live, nor survive a few days. They could take their own tools, but they'll eventually break some day.
---
**NB**: some people have already [discussed the manner](https://answers.yahoo.com/question/index?qid=20080612184044AAWepIE), so you can check how does real eskimoes survive without wood or fire.
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[Question]
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The [black death](http://en.wikipedia.org/wiki/Black_Death) wiped out anywhere between 20% and 50% of the human population, and so without it obviously the world population would be billions more than it is now. What I'm more interested in is how else history would be different without it, some notable related events include:
* Lots of human cadavers were readily available, and autopsies began to be performed in England which was essential to the foundation of modern medicine, therefore medical knowledge would be a few decades (at least) behind current knowledge.
* Some famous literature such as The Canterbury Tales may not have existed
Are there any other events which would make 2014 significantly different without the Black Death than it is now?
[Answer]
Of course we can only guess, but my guess I will provide.
**Summary/TL;DR:** In 2014, the difference wouldn't have been very big.
---
First let's look at the effects the black death had in this history.
* The black death caused the demand for labor to rise, and it caused the downfall of the serf system in most of Europe. Aristocrats didn't have as much control over the serfs and so lost power. Serfs often moved into cities, which boosted industrialization
* The black death helped modern medicine come into being. Because people recognized that traditional, superstitious medicine didn't work they didn't trust it. The black death also caused hospitals to work harder to properly organize themselves.
* The black death actually helped education. Previous higher education (college) has not been doing very well. Few people went, and few people became professors. After the black death, much knowledge was lost, but a lot of people became interested in education. Some colleges were even founded with the express purpose of replacing the knowledge lost in the black death.
* The black death effected the religious landscape of Europe. Many people lost faith in God, though some clung to him tighter. The Catholic Church as an entity was especially hurt, as it could not explain why the black death happened. This may have contributed to the rise of Protestantism.
* The black death wiped out large portions of the population. This lowered genetic diversity at the time, and that change might still be reflected today.
---
Ok, so let's look at one the effect would be if each of these changes *didn't* occur.
* **Serf System:** The black death helped destroy the serf system, so it's possible that a stronger aristocracy would be in place today if the black death hadn't occurred. I think that this wouldn't have made a huge difference, because the aristocracy would not have crossed the ocean to the colonies. This means that the American Revolution would have still happened. Like happened in this history, the U.S. would probably have been an example to other nations and the same revolutions would occur. In 2014, this difference would be minimal. I think the main difference is that the residual aristocracies that we see today (in, say, England) would be stronger.
* **Modern Medicine:** This change is hard to predict. I think it is likely that superstitious medicine would have lasted longer in Europe without the black death. It still would have faded but it would have taken longer. In 2014, I think this would have had little difference; maybe medicine would be weaker because we would have had less time to develop it. But then again, the black death killed many scientists, so maybe the difference wouldn't be nearly none.
* **Education:** This would change in a different way. Serfs couldn't go to college, so if the serf system still existed, colleges would likely be less full, but still there. After the serf system fell, they would start to evolve to what they are today.
* **Religiously:** I don't think there would be a huge difference. The reformers of Catholicism (Luther and others), would likely still have found the problems in the Catholic regime, and pointed them out.
* **Genetic Difference and Population:** Europe wouldn't have had a depression at the time of the black death had the population not dropped. But in the long run, this didn't turn out to be a problem, the same with genetic variety. In England, there is less genetic variety today, but otherwise there isn't much difference.
[Answer]
Others have argued that there wouldn't be much difference. They might be right. Perhaps many of the changes were inevitable. However, I want to argue that there would have been a difference (perhaps just to be contrary). I'm going to assume that there never is a Black Death plague event, not just that it's delayed.
## Serfdom
The Black Death made it easier to be a (surviving) serf. The shortage of labor meant that the aristocracy had to pay more attention to their serfs. Without that, there might never have been an English civil war. The anti-aristocracy movement might never have gotten off the ground because there wouldn't have been a middle class to fuel it.
## Inheritance
Since the deaths were unevenly distributed (some families were wiped out while others were mostly intact), they had the effect of creating concentrations of wealth as some survivors were inheriting the wealth of many non-survivors. This created prosperity for some, allowing someone who had been poor to be at least middle class.
## Colonies
It's been argued that the aristocracy wouldn't have gone to the new world. But in a true feudal society, if the aristocracy didn't go, who would? Colonization was itself a result of the hungry middle class created by the Black Death.
## Science and Engineering
Without a middle class, engineering would have been much weaker. Serfs wouldn't have been able to become engineers and aristocrats would not have wanted to do so. Science would be in a bit better shape, but there wouldn't have been as much science done by middle class engineering families (e.g. Huygens). There also wouldn't have been the same contributions from the judicial system (e.g. Descartes, Fermat, Pascal) as that would have continued to be controlled by the aristocracy.
## The Renaissance
Absent a middle class, we'd have failed to develop the Renaissance. Wealth would have been spread out more. Artists would have lacked the leisure to develop their craft and patrons would have lacked the wealth to sponsor them.
## Religion
Without a middle class, Martin Luther would not have received the education that he did. Without that education, it seems unlikely that he would have become a friar much less the inspiration of the Reformation. As a serf, Martin Luther would likely be unknown to us today.
So given all that, we would be further behind in the sciences, have no serious engineers, a more monolithic religious regime, no colonies, and a system of serfdom. And we'd be stuck there, much as the Egyptians were stuck. Lacking barbarians to overthrow us, we'd stay in a feudal, dark ages system.
To reiterate, my basic argument is that the Black Death created the middle class by concentrating the wealth of certain families and by making labor more valuable. Since it was the middle class that drove many of the positive changes in the arts, science, engineering, religion, and exploration, those changes would not have happened. This would have left Europe in a more stagnant state.
[Answer]
It has been theorized that between 90%-95% of the Native American population died of the plague soon after initial European contact. By the time of active colonization, there were vast tracts of uninhabited land not because it was virgin wilderness, but because the previous civilizations had died off.
Imagine any wars involving the American Indians with a 10x to 20x greater population available to them. Even if the native peoples been successfully subjugated (a large IF!) the population diversity would be entirely different. Rather than being a tiny minority dwelling on reservations, they would either be the majority ethnic group or largest minority (similar to African racial ratios).
[Answer]
**Option 1:** The more things change...
The earth would be...wait for it...the same, or at least roughly equivalent. Disease is a natural inevitable check on humanity. Had the black death not wiped out large portions of Europe, something else would have. Sanitation was terrible, population density was high (for the time) and the world was opening up to a very limited global trade. Think of what happened to Native American populations when Europeans showed up, disease ran rampant. All that combined with limited medical care makes it very likely that some disease would have popped up and done the job.
**Option 2:** The more they stay the same...
I still think it is tough to avoid a disease, but maybe Europe lucked out and it happened significantly later, lets say 200 years later. So according to wikipedia:
>
> The plague repeatedly returned to haunt Europe and the Mediterranean
> throughout the 14th to 17th centuries.[60] According to Biraben, the
> plague was present somewhere in Europe in every year between 1346 and
> 1671
>
>
>
If we move that 200 years into the future...we have 1546 - 1871. So first, what happened between 1346 and 1546 with no plague. Certain aspects would have evolved in a similar fashion, though at a slower rate. Peasant revolts, food shortages, religious and political conflict between nation states. The population would likely have ballooned and grown significantly larger. The landed elite would have gotten much more powerful as increasingly cheap labor stymied development. Standing armies and guards would have grown in number to manage the larger population. Likely a few traditional feudal systems would have been overthrown at least locally. Learning from the middle east and asia would have made their way into Europe much in the same way they did and exploration/colonization would have been much farther along.
Once the plague hit it would have been even more catastrophic than it was in reality as trade is more common on a global scale, population centers are larger and medicine still relies on limited understanding of what disease really is. Where the black death was a mainly Eurasian concept it now spreads to east asia and the america's wiping out settlements and colonies around the globe. This has the potential to break the European system completely and send it reeling backwards. Nations lose control of their colonies and native populations have time to advance and can later hold them off. Things stagnate for decades and religious fervor climbs to new heights making the Inquisition look like an afternoon at the spa. I could go on ...and on.
**Option 3:** No plague at all. This scenario is less interesting...in the case of no mass plague at all, I think things don't change as drastically as one may expect. Democracy still would have developed, international trade would still have created a middle class that had to be listened to by the elite, peasant revolts would have been more common, and in the end I think the world develops, if more slowly at first, much in the same way it did. Most of the social and economic changes that came out of the black death years were already underway when the plague first hit. Now the political implications are impossible to figure out. Maybe the turks don't overthrow the Byzantines and the empire lasts another couple hundred years...who knows.
**Final Note:** The specifics in my answer are less relevant than the overlying options and thought processes. When dealing with alternate history you are completely free to work out how you want things to function. Just keep in mind to get a setting that feels real the alternate reality needs to come about via the complexities that exist in real life. One single event is rarely going to drastically change history by itself.
[Answer]
>
> Are there any other events which would make 2014 significantly different without the Black Death than it is now?
>
>
>
It is generally thought that The Great Fire of London destroyed as much as it did because of conditions brought on by the plague. Without the great fire, London would not look the same as it does today. There would be no St. Paul's Cathedral, or any of the dozens of other beautiful Christopher Wren buildings shaping central London today. In fact, the great fire brought about the complete redesign of the layout of central London. I'm sure similar influences can be found in most of the large (and small) continental cities that suffered the plague. So I think it is fair to say that the black death had a profound influence on the existing architecture and layout of the cities of Europe.
Isaac Newton is a name we associate with shaping our modern world. He graduated with a B.A. in 1665. By all accounts, he was an undistinguished student. Shortly afterwards, the plague forced him to flee Cambridge and return to his home in Lincolnshire.
He spent the next two years at his family home, removed from the academic life of Cambridge. During this time he developed his theory of optics, his law of gravity, and the calculus. Would he have done the same if he was still confined to a ill suited academic environment?
And let's not forget : "Bring out your dead." ( You know how it goes... "I'm feeling much better. I think I'll go for a walk...")
[Answer]
[**The Renaissance**.](http://en.wikipedia.org/wiki/The_Renaissance) -Wiki
>
> **Black Death\Plague**
>
>
> One theory that has been advanced is that the devastation caused by the Black Death in Florence, which hit Europe between 1348 and 1350, resulted in a shift in the world view of people in 14th-century Italy. Italy was particularly badly hit by the plague, and it has been speculated that the resulting **familiarity with death caused thinkers to dwell more on their lives on Earth, rather than on spirituality and the afterlife**.[36] It has also been argued that the Black Death prompted a new wave of piety, manifested in the sponsorship of religious works of art.[37] However, this does not fully explain why the Renaissance occurred specifically in Italy in the 14th century. The Black Death was a pandemic that affected all of Europe in the ways described, not only Italy. The Renaissance's emergence in Italy was most likely the result of the complex interaction of the above factors.
>
>
>
[...]
>
> The survivors of the plague found not only that the prices of food were cheaper but also found that lands were more abundant, and that most of them inherited property from their dead relatives.
>
>
>
'Old wealth' might have been distributed differently, prescribing drastic changes from our current culture and social structures. We also might not know how Venus was born:
[Nascita di Venere](http://en.wikipedia.org/wiki/The_Birth_of_Venus_%28Botticelli%29), Sandro Botticelli, c. 1486
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[Question]
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One science fiction short story I read (I don't remember the title or author, sorry!) featured some small creatures (unnamed) that were formed from metal, with the argument that "just like life developed on Earth with a carbon base, why shouldn't life be able to form elsewhere, with a metal base?"
**Is this realistic?
Is there anything similar to this that already exists on Earth** (ie, life based on something other than carbon)**?**
[Answer]
There is very detailed discussion about this issue in the field of Astrobiology. There is many constrains for "reasonable" life. I will try to go through most of them in short points.
Let me use following approximate definition of life in my answer:
>
> Life is very complicated machinery of proteins (or other sufficiently complicated molecules or structures) that sustain themselves out of thermodynamical equilibrium in proper conditions, are capable of replication and of undergoing darwinian evolution.
>
>
>
To me, this seems quite general, and (I think) it does not trigger obvious counter-examples. For example fire is out of thermodynamical equilibrium, it is capable of replication, but does not undergo darwinian evolution nor consists of sufficiently complicated structures. Mule or other sterile animals are not alive per se according to the definition, but the environment in which they live and which produced them definitely contains life. This is a minor bug of this definition, but I do not know any better.
### Life needs [fermions](http://en.wikipedia.org/wiki/Fermion)
This criterion seems quite obvious. Fermions are elementary particles that follow the Pauli exclusion principle. Without it, everything collapses into one point or passes everything else and it is very difficult to imagine that there would be any reasonable complicated structured process involved. For example life based purely on electromagnetic waves is very implausible, since photons pass each other without noticing and they therefore cannot form structures.
Obvious candidates are electrons, which create atoms and molecules together with nuclei. But for example in the Forward's book [Dragon's Egg](http://en.wikipedia.org/wiki/Dragon's_Egg), there are aliens inhabiting a neutron star and they are composed of neutrons and some protons in very dense degenerate neutron matter. This seems plausible in principle, since neutrons are fermions and could theoretically form structures in this environment.
### Life needs liquids and membranes
If we investigate life based on chemistry, it seems life needs liquids. This is not an absolute criterion, however it seems that life as we know it strongly depends on liquid environments. There are incredibly complicated chemical processes in a cell, that require very precise conditions (pressure, concentrations of chemical compounds, density, etc.) In a gas, like in a nebula in space, density fluctuates heavily and it would be very difficult to do anything so complicated. Moreover, it seems that life needs to separate the relevant complex molecules it synthetized from the outer environment.
Plasma would be problematic too, since:
* It is as volatile as gas
* It is too hot for any complex molecules to be created
Metals and other solids have different problems. Complex molecules created in one part of the solid cannot be easily transported to another place, where they are required. In a cell full of liquid, every molecule floats around in a membrane or inside the cell and can randomly encounter other molecules and trigger chemical reaction. In solids, such mixing does not happen or would happen after very, very long time. (Of course now we are not talking about life looking like intelligent robots, that are assembled in factories. These would be probably plausible - but we are talking about life as a chemical process that could evolve on its own from more basic chemistry.)
### Life needs complex polymers
If we investigate life based on chemistry, it seems it also needs stable polymers with rich chemistry. And here is a point at which carbon seemingly beats [the alternatives](http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry#Non-carbon-based_biochemistries):
* **Carbon:** Very rich biochemistry with many polymers with hydrogen, nitrogen, sulphur, phosphorus, and others. Bonds C-H, C-O, C-C, C-S, C-N have similar energy, which allows for big complexity.
* **Silicon:** Usually considered "the second best choice". Silicon, however, binds to oxygen much more strongly than to other atoms. This leads to a situation where either (on smaller temperatures) are silicon-oxygen bonds locked and cannot change, which makes things very difficult for complex chemistry, or (on higher temperatures) all bonds but the oxygen-silicon are broken and the complex chemistry must happen only between silicon and oxygen. ([Silicones](http://en.wikipedia.org/wiki/Silicone).) In absence of oxygen (which might be a problem, since oxygen is very abundant in the universe), and at very low temperatures, [silane chemistry](http://en.wikipedia.org/wiki/Silane) could be viable alternative for life. [Zeolites](http://en.wikipedia.org/wiki/Zeolite) at high pressures and temperatures seem like potentially viable option.
* **Phosphorus, sulphur, boron, nitrogen:** These elements form polymers, but they are very unstable. Life utilising them would have to work at very low temperautes, where it could be problem to find a viable solvent. (Life needs liquids). Moreover, these elements would much more likely form simple stable molecules than polymers, which would strip such life of a building material.
* **Metal oxides:** According to [Wikipedia](http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry#Non-carbon-based_biochemistries), oxides of metals have very rich chemistry, which could form a basis for life at very high temperatures and pressures (Like in Earth's mantle, for example).
**As a conclusion:** The universe seems to be quite restrictive about where life is plausible and what forms can it take. This list is not complete nor is it by any means certain, but it can give some idea what are the most probable candidates for life from the point of view of science.
Very good source can be found [here](http://thomastapir.deviantart.com/art/Alternative-Biochemistries-WIP-129132049) - it is a short table listing polymer-forming elements and this is paired with typical solvent, that could take role of the liquid solvent in which the life based on given element could form. There is also another, even more extensive source on alternative biochemistries [here](http://www.bibliotecapleyades.net/vida_alien/xenology/08.0.htm).
[Answer]
There are several reasons why carbon based lifeforms thrive:
1. Carbon molecules can form polymers, such as amino acids. This allows for proteins to form.
2. Carbon molecules are stable, meaning that lifeforms won't have to regenerate their chemicals as rapidly as with a different chemical base.
3. Carbon molecules react easily. This means that a lifeform will not need to put too much effort into keeping itself alive.
Silicon based life is often referred to as a possible base for life. [This is inaccurate though](http://www.scientificamerican.com/article/could-silicon-be-the-basi/) as silicon does not have adequate properties for life to be formed from it.
You may have heard about [arsenic based bacteria](http://www.nature.com/news/arsenic-life-bacterium-prefers-phosphorus-after-all-1.11520) found. This has not only been disproved, but also miscommunicated - the arsenic was not replacing the carbon in its DNA, but the phosphorus.
In short, carbon is your best bet if you want to create a lifeform. It's unlikely that another chemical would form complex life.
[Answer]
There is another answer to this, namely Chromium. The reason why we are called 'Carbon Based' life is that carbon has a high valency, or ability to connect other atoms to itself to create large chain like molecules. The next most prolific element that has a valency that is high enough to do this that we ordinarily (not scientifically) consider to be a metal is Chromium.
Is it possible? Yes. Is it realistic or does it exist on Earth? No. The reality is that if elements are fairly evenly distributed across the universe, Chromium is going to exist on planets in far smaller quantities than carbon, meaning that any life that is going to form and be competitive is going to be Carbon based in the vast majority of circumstances. If you want more detail on this, I've already [written an answer](https://worldbuilding.stackexchange.com/questions/136499/iron-based-life/136501#136501) that covers this on a question about iron based life that can give you more detail.
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[Question]
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
The [Karman Line](https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line) is one of the most commonly-used definitions of the "edge of space". As an airplane flies higher in the atmosphere, the air gets thinner and thus the lift decreases. This can be compensated by flying at a faster speed. The Karman line is the altitude at which you would need as much speed as the orbital velocity. You are no longer flying; you are in orbit.
Earth has a gaseous atmosphere, and a Karman line that calculates to about 100 km.
[This Space.SE question](https://space.stackexchange.com/questions/29910) examines the Karman line of a planet without an atmosphere (i.e. a solid surface). The general consensus of the answers is that the solid surface itself is the "edge of space". The moon is such a body.
So we have...
* the edge of space with a **solid** surface (moon).
* the edge of space with a **gaseous** atmosphere (Earth).
What about a planet (or moon) with a **liquid** surface -- namely, *could there be any contrived, theoretical scenario where the Karman line occurs **below** sea level*?
The oceans do not necessarily have to be water (e.g. ammonia, mercury, or hydrocarbons are fine). You may adjust temperature, pressure, and gravity to any plausible values that support liquid oceans. Presumably, to keep the oceans from boiling away, there would need to be a solid crust above the ocean, or some atmosphere inadequate for flight (your choice).
Interestingly, such a possibility would mean that no creature or vehicle could "swim" to the surface of their ocean.
Obviously, Earth itself proves you can have a Karman line *above* a liquid sea level.
[Answer]
# No
As long as you are in a liquid, the density will be high enough that an airfoil shape will be able to give you lift. In that case, you can always get to the surface of the liquid, with a sub-orbital velocity. Therefore, the Karman line can't be below the surface of the liquid.
### Definition of the Karman line
The Karman line's [mathematical definition](https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line#Definition) is
$$\frac{1}{2}\rho v\_0^2SC\_L = mg$$
where $v\_0$ is the orbital velocity; $m$ and $S$ are mass and wing area; and $C\_L$ is coefficient of lift. The [wing loading](https://en.wikipedia.org/wiki/Wing_loading) of an airplane is $m/S$ and is around 600 kg/m$^2$ for a commercial airplane. Via [Aviation.SE](https://aviation.stackexchange.com/questions/9682/where-can-i-find-data-tables-for-lift-and-drag-coefficients-of-airliners) we can get [lift coefficients](https://aeroknowledge77.files.wordpress.com/2011/09/58986488-theory-of-wing-sections-including-a-summary-of-airfoil-data.pdf). Lift varies based on angle of attack, but $C\_L=1$ is a good enough approximation. We can plug this into the equation to get:
$$ \frac{1}{1200}\rho v\_0 = g.$$
So now we have a relationship between orbital velocity, gravity, and fluid density. Given a fluid density of water at 1000 kg/m$^3$, the surface gravity must be 0.83 times the orbital velocity, in units of m/s$^2$ and m/s, respectively, for a the Karman line to be below the liquid level.
### Relationship between escape velocity and surface gravity
Now, escape velocity is not the same as orbital velocity, but it can give us an approximation of what orbital velocity is. LEO on Earth is ~7 km/s while escape velocity is 11.2 km/s. This will be close enough an approximation, as we will see.
Escape velocity can be expressed as a product of surface gravity by
$$v\_0 = \sqrt{2gr}$$. We will use escape velocity as a stand-in for orbital velocity. Combine this equation with $g = 0.83 v\_0$ and we get $v\_0 = 1.7 r$, with units of m/s and m.
If escape velocity is the same as Earth, then the planet needs to be 19,000 km in radius (Earth is 6370) with surface gravity of 9260 $g$. If the planet is to have surface gravity of 9.8 m/s$^2$, then the escape velocity of this 'planet' is 12 m/s and its radius is 20 meters.
### Calculation of required mass
So here you can see the impossibility forming. Escape velocity is
$$ v\_e = \sqrt{\frac{2GM}{r}}.$$ If we plug in 12 m/s and a radius of 20 meters, we get a mass of $2.2\times10^{13}$ kg; this is a density of $4.4\times10^{8}$ kg/m$^3$ which is electron-degenerate matter.
# Conclusion
The only way to make this happen is to put a liquid ocean over a small asteroid's worth of electron degenerate matter. So, no, this cannot happen.
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[Question]
[
I want a world in which animals roam the wilderness on four legs, yet at least some of them are able to do the kind of carrying and fine handling of objects done by humans. The planet is superficially similar to Earth, but it is not Earth, and there are no humans around (at least not yet; who knows what humans might do once they figure out interstellar spaceflight...)
There seem to be basically two ways to go about reaching that goal; either give the ancestor of land life on that planet six legs, allowing for two to evolve into arms and hands in a manner similar to how those of humans evolved; or give the ancestor four legs, and have their forelimbs serve both purposes, not unlike gorillas on Earth.
For the alien feel, as well as the additional options it gives, I'm currently leaning toward six legs, the foremost two of which could evolve (or not, depending on the species) into hand-like extremities.
This is intended to be a realistic world, so the normal issues of evolutionary selection pressure apply.
Suppose that an intelligent designer is faced with the choice of, for an ancestor species, ticking the "four legs" or the "six legs" checkbox on the requisition form. **What, if any, would be good reasons for them to select four legs rather than six?** Or, in other words, **what disadvantages would be confered to the creature by having six legs as opposed to four?**
For simplicity's sake, you may assume a single ancestor species for all relevant land life on the planet, so for example "some other species would be more energy-efficient in not needing to grow an extra two limbs" does not apply. Other species on the planet may have a different number of legs (compare to how there's also spiders and caterpillars on Earth), but can be ignored for the purposes of this question.
This question is basically the opposite of [Why would an animal need six legs?](https://worldbuilding.stackexchange.com/q/48966/29)
[Answer]
There's at least [one paper](https://www.sciencedaily.com/releases/2014/01/140127112729.htm) suggesting the reason for four limbs is because of the way embryos develop.
Basically, an embryo's cells develop early on into three layers: ectoderm, mesoderm, and endoderm. The endoderm becomes the digestive tract, the ectoderm the skin and nervous tissue, and the mesoderm everything else (bone, muscle, other organs). The mesoderm itself splits into two layers, one that lines the inside of the body cavity, the other that lines the gut.
The hypothesis is that the places the mesoderm will form bone and muscle that creates limbs is near the front and rear ends of the gut, because that's where the layers are close enough together to interact with the ectoderm and each other, but not close enough to merge completely, which leads to the formation of the tail and head, and not far enough apart, as they are along the gut, to prevent the tissue that will become limbs from forming.
If that's true, then in order to have six limbs, you need the early gut, for some reason, to be shaped kind of like an hourglass or peanut, some place where you get the right conditions for the proper distances to allow for limb creation between the front and rear ends. If this hypothesis is true, the the choice between four limbs and multiple limbs is set very early on in development, long before a body would have to deal with allocating resources for limb development.
That being the case, there's no particular reason why six limbs wouldn't develop if the early embryonic development wasn't just a slight bit different from ours.
[Answer]
Ultimately, the preference for 4 or 6 legs within a given environment would come down to the environmental pressures themselves. In its simplest form, the problem is one of agility v. strength.
In an environment where your animal has a survival strategy akin to 'tanking', or making themselves as strongly armoured and stable as possible, 6 legs will win because there are more feet on the ground, and that serves the double purpose of providing a more stable platform and more supportive strength for the armour plating you are going build on your animal. Think animals like Stegosaurus, Ankylosaurus, etc. These were heavy, slow creatures whose survival strategy was based on their ability to withstand attack long enough to give them time to damage or scare off their attackers with their spiked or clubbed tails respectively, and of course their scary roar (we assume).
Such animals would have actually *benefited* from 6 legs because they could have grown bigger (more legs supporting their weight) but the tradeoff is that they would have been slower. In other words, you're trading speed for toughness.
The extra legs add mass to your body, meaning that they adversely impact the square cube law. That is to say, as you scale up your animal it finds it more difficult to jump and agilely change direction faster because there is more mass by comparison to the relative size of torso for a creature with fewer limbs.
BUT; that's not the *real* impact of the square cube law for increasing limbs on creatures you want to give speed and agility.
**More legs doesn't equal more speed**
Adding more legs may increase your torque as a creature, meaning that you can climb steeper mountains or go for longer on the straight, but it simply cannot increase your upper speed. It *might* increase your acceleration from a standing start in some cases, but that's it. In point of fact, it can actually *lower* your upper speed because you have to find a gait that combines more feet in an efficient sequence and that's not easy to do.
**Torso size can be smaller with fewer limbs**
Fewer limbs mean that your torso only has to handle a smaller set of appendage points, so not only do the limbs you have get to be more spread out (and therefore not in the way of each other when running), but the torso can be proportionally smaller meaning that you get the real benefit of the square cube law by decreasing body size generally. Also, the shape of the torso can be squatter, allowing you to fit more organs in a more compact space without disrupting gait. All this leads to a leaner, faster creature suited to the open plains.
**Standing**
Ever seen a Praying Mantis holding its food with its front appendages? It's not standing but it's doing the closest thing it can to that. Why? Because when man's first ancestors started standing, they only had to tilt one pair of appendages; their legs. In doing so, the spine goes from horizontal to vertical immediately (oversimplification, but true enough for the purposes of this answer) because the hips served as a pivot point.
If your 6 legged creatures want the advantage of height as a vantage point from which to see their enemies approaching, which is largely what proto-man was doing, then you don't have a pivot point because you have **2** sets of hips to contend with. Unless you have a spine with a hinge in it, you're not going to stand upright. Remember, centaurs would have a very complicated spinal column that doesn't really work in the real world because you're essentially attaching an extra spine where the horse's neck normally goes. This is highly unlikely to develop in concert with using the forelegs as hands, and would be a separate and more complicated journey to uprightness than a simple pivot in the hips.
So; the general rule of thumb is;
**6 legs** - Tankers, slow and cumbersome, but heavily armoured and strong.
**4 legs** - Faster and agile, more likely to stand upright and develop 'hands' at some point.
As such, your 4 legs are more likely to develop on savannahs or in a world of ambush predators, your 6 legs will develop around large predators that prefer a fight before dinner.
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**Interesting question, [Sleipnir approves](https://en.wikipedia.org/wiki/Sleipnir). The short answer is, it sort of depends on your creature's body design.**
From the reading it sounds like you are describing something that would function similarly to a centaur...possibly. It's also possible that the creature would travel on all six legs with the front pair functioning similar to a gorilla where they can be used for both travel and more fine motor skills.
The finer you want the motor skills to be the less likely your creature will use the front pair of limbs for locomotion.
What your creature is specialized for could range pretty widely as well.
I can envision a **prairie/grassland creature** with bison or rhino like characteristics using its size and bulk as a defense...maybe some horns just for fun.
* This creature would be low to the ground with strong legs. It would be very stable.
* The complications of extra legs in the creature's gait could be removed/mitigated by short stout legs and a slightly longer body than traditional prairie creatures
* This body design doesn't work particularly great for giving it precision digits, if you want to do that you probably need something more akin to a centaur body design with an upright portion that doesn't touch the ground.
* It likely wouldn't be all that fast but you can probably make an argument that it could move pretty quick in a strait line.
You could also have a **tree-dwelling, monkey like creature**, I can see an extra set of limbs being great for climbing.
* All six limbs would need to have gripping digits. Like monkeys these don't have to have opposable thumbs, the can simply hook to latch onto tree branches.
* If you are going to have thumbs it makes the most sense to develop them on the middle set of arms. Using the top and bottom set for climbing would be the most stable, then the middle arms could manipulate whatever while climbing.
* I see no inherent difficulty with gait in this setup.
**Aquatic creatures** also make a lot of sense.
* Extra fins could make the creature faster and more agile in the water.
* If you want an aquatic creature with actual hands you probably need the extra set of arms to make them remain decent swimmers.
* I find this creature less likely than the others to develop digits as survival, especially earlier in their evolution is going to depend on speed and agility in the water...not much need to evolve from that.
I struggle to see extra legs being beneficial **in the mountains**...but it could probably work, life finds a way to evolve in bizarre and unexpected ways all the time. Nothing immediately comes to mind on this one...the extra legs would be a hazard for a mountain goat as an example.
**Predators are interesting** with this setup...but complicated. I am immediately reminded of this guy from Avatar super awesome looking, and frankly a bit terrifying. Its actually what I was picturing though probably smaller in my [sonic hunter](https://worldbuilding.stackexchange.com/questions/11610/a-human-hunter-with-sonic-powers) question.
[](https://i.stack.imgur.com/mYv7I.png)
The weird thing about predators...rarely if ever are they the biggest creature.
* In Africa you have lions and cheetahs, they prey on animals much larger than themselves
* In North America you have wolves and cougars/bobcats which are quite a bit smaller than most of their prey
* Bears may be a decent example...but grizzly bears primarily go fishing, they don't really hunt deer or anything, they are not equipped to chase things for long
* In jungles you have a jaguar, they tend to hunt sloths, tapirs and monkeys. So this may be the best example of a predator that goes after smaller prey.
On a creature that is generally on the ground with a small frame, extra legs seem like they could be more a problem than a benefit...
* I suppose if you altered the frame a bit you could make it work. If you give the creature four front legs and two back legs I think you could get a gait that works. Plus the extra front legs would allow the predator to grip better when they latch onto their prey.
* When you specialize your digits to help you grab on and tear open something else it's not super likely you are going to evolve human manual dexterity.
* Predators are high energy creatures which makes size a liability, being bigger requires consuming more food more often, in lean years, be it from overhunting or a drought...that's not great, so a cool as the six-legged battlecat from avatar is...it doesn't seem real practical.
* It'd be strange but I can picture six legs where while hunting the middle legs are basically wrapped around the creature's abdomen but it looks creepy and weird in my head.
* As in avatar I can see six legged creatures working better in a world of larger creatures.
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The only disadvantage that I can see is the extra consumption of resources.
We can see from Earth that six legs are not needed. Therefore the extra resources that are needed to grow and operate those extra legs could be put into other things (other adaptations or a slight increase in overall population).
I don't see this as a huge advantage but it is the only thing that I could think of that would answer this question.
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A creature that walks on 4 legs and carries objects with the other 2 legs would need good support if their torso bends upwards.
Either strong muscles and/or bones arranged in a way to support most of the weight. Think about how easily humans pull out their backs when bending over to pick up something.
Such a creature might be better off carrying objects by bending down and under, holding their cargo against their bellies. This would require less effort, but would only make sense if their back or middle legs where for carrying. Otherwise how would they see where they were going?
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Given the example of the development of the scorpion, it started out as a segmented worm with a pair of legs/swimming paddles per segment. These legs later developed into a variety of appendages, such as pedipalps, mandibles, pincers, and land traversing legs.
Beetles similarly developed palps, maxilla, mandibles, wing case lifting appendages, a set of four wings or wing counter weights, and six legs. If you consider the specialization of legs into structures as mentally nimble as a scorpion's pincers or a grasshopper's wings. I don't see any inhibition for a six legged terrestrial or possibly arboreal animal in development of manipulative appendages.
If the structure of any creature has a survival advantage the species tends to retain the structure. The concept that it is too mentally taxing to control large numbers of limbs is disproved by looking at the large number of multilegged creatures with rudimentary brains. A shrimp has four sets of manipulative maxillapeds, two sets of periopeds (walking legs) and five sets of pleopods (swimming legs) and two sets of uropods (fins) in its tail. With its undeveloped microscopic brain it can coordinate all twenty six of them to work in unison to locomote, maneuver and manipulate things in its environment.
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Evolutionary selection pressure will always favor the solution that has the best cost/performance.
If having 4 legs is good enough to move around, then you will not see any animals with 6 legs.
Having 6 legs has upsides and downsides for animals
Upside:
* more stability, easier movement on hilly/accidented terrain
* can survive loss of a leg or two
Downside:
* movement speed is slower
* higher energy cost
On Earth the downsides were bigger than the upsides so 4 legs became the favored solution
You could see 6 legged animals with different evolutionary pressures. A planet with high gravity (think 2 or 3g) combined with a very accidented terrain with almost no flat land would probably favor 6 legged animals.
In those conditions, having more stability is worth the extra cost and lower movement speed.
On a planet with even higher crushing gravity, you d probably have animals with no legs. Crawling like snakes or worms would be the favored solution to move around.
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There is a very real disadvantage to more appendages.
Controlling more appendages simultaneously takes much more concentration. Ask any fingerpicking guitarist. If you watch them they don't use the little finger on the picking hand. Because it's extremely difficult to control when you're already concentrating on the rest. Going from using 3 to four is relatively easy. 4 to five isn't.
So coordination of extra limbs would be a big factor in fine control scenarios.
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If you use all your limbs for locomotion, then 4 makes sense because you can lift one while maintaining balance on the other three. If you only had 3 legs, you would have to maintain balance on two of them whenever you moved, and if you can do that easily then you don't need more than two legs for locomotion. If you had more than 4 legs, then you don't gain anything with the extras.
That said, it benefits bugs to have more legs because of their other functions, such as climbing/hanging/landing on ceilings, quickly navigating/braiding complex webs, or being able to lose segments without dying.
So, for a large creature to justify having more than 4 limbs, it would need to have some needful task or danger which merits the extra limbs. Some example ideas:
* The planet has creatures who are adept at attacking from behind (for some reason), and so the other creatures evolved an array of sensitive hairs and an extra set of limbs on their backside to detect and deflect such attacks
* The planet is covered in pools of fluid with high surface tension, so having more legs disperses the creature's weight enough to let them run across those pools with relative ease.
* The creatures fly and need to be able to land on very complex/porous/webbed terrain.
* The creatures primary source of food tends to hang off the edges of cliffs, so they need to be able to support themselves by gripping the cliff edge and food stalk, without putting too much pressure on the stalk itself.
I'm sure there are endless good reasons for having more than 4 legs, but given the ecosystem and environment on planet earth, most of our creatures have exactly the number of legs that they need; more would be wasteful and fewer would make survival difficult.
Hope this helps!
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So from my understanding of the situation, the early dominant species to walk on land in this world were six legged and they went on to evolve into many other animals, some of those descendants went on to evolve into four legged animals with two arm like appendages.
Why would animals have evolved this way though? Most obvious answer would be speed. You don't need six legs to gallop.
Hopping would be an alternative (just think of fleas or other insects of that ilk), but that becomes problematic as the animals get bigger and probably not great in certain terrains (un-even ground or densely wooded areas).
I envisage that at some point a common ancestor of your six limbed (four legged, two armed) animals developed running on four legs and picked its fore limbs up off the ground to do this. Natural selection kicks in and the two pairs of back legs get further apart and the front legs become smaller. Animals which survive by pure strength/stability may stay on six legs.
Some animals may lose the use of the fore arms altogether if they find no evolutionary need for them.
But other animals could find different uses for those fore limbs like pulling plants up to get at the roots, latching onto prey, pick fruits from trees, mating rituals/displays or building things (nests, burrows, dams, etc.). These are the sort of activities that may spur evolution in the direction of fingers/thumbs and fine manipulation.
Of the animals that did find a use for their fore limbs, they could end up like your desired state animal of being four legged, with the ability to carry and manipulate things in a way similar to humans.
Only thing I would say, is that I can't see an obvious evolutionary path to have animals with an upright front half (centaur like). More likely that the animals limb joints (shoulders, hips, mid-hips?) would line up as opposed to forming an angle. As mentioned in another answer, a centaur would have great difficulty in picking something up off the floor. Although it's head would need to be above the shoulders so the arm like limbs don't interfere with peripheral vision.
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There is no real disadvantage other than the material cost you get with any limb, but keep in mind tissue needs a use to be kept over prolonged evolutionary time so make sure your "missing link" species also has a use for them. The main reason modern tetrapods only have four is they evolved from fish that also had four limbs.
there is one notable exception for an animal with an upright posture, 4 limbs has a distinct advantage because six limbs start to get in each others way during the stride, so either you need a much longer (and thus more massive) creature or you need to be slow moving.
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Your question reminded me of the 'hexapoda' (six-legged) dominant life forms on pandora, from Avatar (The movie, not cartoon). Some examples are the six legged horse, the 'dire horse' and the feline-like animal called a 'viper wolf'.
However to answer your question, four is the preferable number of limbs.(A good example of course being primates).Adding more limbs would just require more brain-power to control them, and would require a major change in configuration that would mean that it would have to have some benefit.
* While we don't have dire horses or 'viper wolves' on earth, we do know one species that have six limbs- insects. When a creature runs on two or four legs, only one or two feet remain in contact with the ground at any point in time. When an insect runs on a surface, three limbs usually remain in contact with the ground at all times. For insects like a fly, for example, this is an advantage because it means it has greater stability when clinging to a vertical surface or upside-down. That's not an advantage that other animals need walking upright on a flat surface.
* In many ways, six legs would hinder normal creatures. Insects on
Earth that have six legs have them splayed out from the body so they
don't get in each other's way. If your life form is anything like
Avatar's, then all the creatures would have their six legs in line
with their bodies, which would cause them to bump into or get tangled
up together easily.
As shown with our own history and science, four legs seems to be the
best recipe for land-dwelling animals. Unless your creatures climb
vertically etc, then four legs would be much more beneficial.
* Furthermore, creatures with more than four limbs have not evolved in
land species. In fact the trend is to 'simplify'- as with snakes,
which lost their limbs- and horses, which instead of having arms and
hands, have hooves. Six, eight and even leggier arthropods (insects,
arachnids and crustaceans) have, of course, been extraordinarily
successful. But the fact that these creatures have exoskeletons
rather than bones inside their bodies limits their size.
* Large hexapoda animals would need Large exoskeletons to support
internal body tissues etc. However, it would be prohibitively
cumbersome and heavy, and would demand lots of energy to move and
grow. Because intelligence is strongly linked to how big, intricate
and energy-consuming an animal's brain is, that sentience is unlikely
to evolve in hexapoda like animals.
Edit: I concentrated on listing the disadvantages of having six legs, rather than directly comparing it with four legs.
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There are 13 answers already given as I write this but I think I can still make a valid contribution.
Possible disadvantages of having more legs:
1. neurological complexity - not an issue
2. genetic diseases - Parkinson's etc as more damaging?
3. speed of movement - conflicting factors
4. agility - same factors as speed
5. energy budget - bigger obviously but weight/strength ratio?
First .. is the question really ONLY about legs? My take on the Questioner's intent is that he specifying that two of limbs will be for manipulation and the other 2 or 4 will be for locomotion. SO my answer is only about method of locomotion.
As such .. all of the points made about speed difference, neurological complexity etc are irrelevant in that the ontology of the species will be *The One True Answer* to its evolutionary situation. Whatever form it has will have been dictated by its environment, and that form will be the best for species survival. For me this settles the neurological issue as the critter's brain will evolve to meet the need.
The issue of whether six or four legs make an individual faster and/or more agile is for me reduced to: is one faster with two legs or four? The clear answer is four. Real World experience shows that any four legged animal can beat a human's speed and is far more agile.
However, energy budget is clearly higher with 4 legs - you have more muscles working to achieve the same distance over ground. My reference is North American native deer-runners who used their greater endurance to hunt down the much faster deer by relentlessly pursuing their prey until it was too tired out to run anymore. Thus, a four-legged disadvantage.
But .. bigger creatures might not be strong enough to have use this advantage. Strength to weight ratio puts a hard upper limit on how fast a creature can accelerate because of the inverse square effect of conservation of momentum. To wit, it takes 4 times the energy to accelerate a body two times bigger than your reference.
Individuals in a small species move faster because they use far less energy to move or change direction, regardless of the number of legs they are using.
Elephant sized four-leggers obviously use more energy to move, but I contend would still be able to *sprint* faster than a two legged critter of like size. In IRL elephants can reach 35 MPH running, but not for long. I think a two legged pachyderm might have better endurance, but only just. Someone with a better knowledge of bio-mechanics might prove me wrong here.
Now for the final point: certainly a disease or injury that interferes with coordination, like Parkinson's or ALS will be more severe for creatures with a more complex gait. Four legged creatures can certainly sleep standing up (locking knees) but once in motion need to coordinate well, and at speed even better. Whether such diseases would be prevalent or not is something that the author must decide upon. But the possibility weighs against the four legged option here.
Thanks to the Questioner for raising an interesting topic.
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One disadvantage that I can think of is they would not be able to run fast. Take for example a Jaguar or a Deer. If you add two more limbs they would get in the way of running.
When a Jaguar runs it leaps with the front legs and catches up with the hind limbs where hind limbs cross the front legs/limbs. If you add two more in the middle they would get in the way.
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In the real world — I am from Europe — I often hear and participate in discussions about how printing a paper 2 Euro note would have an impact on micro-economy, i.e. how it would make people less psychologically prone to spend such a hypothetical note instead of the equally-valued real coin.
For reference, Euro currency is as follows:
* Coins:
+ 0.01 €, 0.02 €, 0.05 € (copper color)
+ 0.10 €, 0.20 €, 0.50 € (golden color)
+ 1 €, 2 € (gold/silver bicolor)
* Notes: 5 €, 10 €, 20 €, 50 €, 100 €, 200 €, 500 €
So my question is, what is the impact in a constructed world of having a single currency coin (like the standard gold coin often used in RPG video-games), as opposed to more than one type of coin (e.g. the 1 gold = 100 silver = 10k copper coins in D&D), or more realistic setups as described above?
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The effect of having a single coin is that quantities of it will have to be used for any transaction, no matter how large or small. This then has the effect that if it is a high-value coin, how do you use it to buy a low-value item? If it is a low-value coin, how do you carry enough of them to buy a high-value item?
The reason for multiple denominations of currency is to have the best of both worlds, i.e. high granularity (the ability to have small differences in the prices of items) and high portability (the ability to carry a lot of funds easily).
In metallist economies where the value of a coin is tied to the value of the metal it is made from, where a coin of sufficiently low denomination for everyday transactions was not available from the official mint, coin of lower value was frequently manufactured by clipping the existing coins - cutting them in half, quarters or even eighths.
The reason for having fewer denominations is that there is a setup cost involved to the state in having coins minted (making the dies), which increases as more denominations are produced. This may not matter much to some governments, but may be a matter of some importance to others.
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[
What scientifically, socially and logically plausible mechanisms allow two (or more) sapient **land-based** species (either closely placed on the phylogenetic tree, such as *Homo sapiens* and *Homo neanderthalensis*, or only distantly related) to develop and deploy tool-use on the same world in a similar evolutionary timeframe?
The situation needs to be such that one species' sapience and development of tool use does not eliminate the chances of the other to establish a similar base.
When I say land-based I mean that animals which are entirely aquatic and cannot exist on land at all are not allowed. Amphibian species which live in very wet environments and deploy tools in *both* aquatic and land-based environments are allowed.
Any symbiotic or altruistic approaches should have a suitable justification.
**Edit to add:** Simply having separate sapient species evolve on different continents and not in contact with one another is not valid since if that is the case I will have no story since at the stone age level of technology neither set of tool users are likely to be capable of crossing the sea that separates them. *I want them to have a shared history.*
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Have one common ancestor and split the range occupied by that common ancestor by something which is hard to cross but possible. For example a massive mountain range would do the trick.
During an ice age the mountain range becomes completely impassable, this separates the two populations for a period of around 20 thousand years. During this time they diverge enough to be separate species.
As the ice age ends the mountains become passable again but it is still hard work to do so. This means the two populations do have limited contact and even trade with each other but remain mostly separate.
If you wanted to reduce the separation then you can have the ice age finally ending at the time your world is set in. The mountains are now much more freely passable and the two previously separate species and cultures are now starting to interact much more frequently. How that would end up really is down to you.
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If both species have no reason to engage in conflict then it's entirely possible for them to not only learn tool use from each other but also to encourage each other and/or form social interactions with each other as a necessity.
As an example: Two almost sentient species exist in the same jungle. One is a ground dwelling porcine creature that eats low lying berries and nuts. Another is a raven-like bird that eats insects. The two have no need to compete for food or territory.
Both have sufficient manual dexterity to perform tool-based tasks. The Corvidians use sticks to hook grubs out of trees, and the Porcinoids bang rocks on fallen coconuts to open them up. Eventually, due to a random cohappenstance, a Porcinoid bangs into a tree, which shakes the trunk and disturbs the grubs, making them easier for a nearby Corvidian to hook with their stick. The Corvidian notes this, and also sees the Porcinoids banging coconuts to get them open. Cue lightbulb moment.
The Corvidian finds a sharp rock and uses it to cut a coconut free. He then rolls it under his favourite grub tree and waits. Along comes a Porcinoid and bashes open the coconut, disturbing the grubs and leading to an easy lunch for the Corvidian. Other Corvidians learn this trick, and soon the Porcinoids realise that if they turn up under a Corvidian roost then one of the birds is going to find a coconut, loosen it and wait for them to crack it open.
Interspecies co-operation established, the Porcinoid/Corvidian tribe rapidly outcompetes other herds of Porcinoids and flocks of Corvidians, until the other tribes establish the same co-operation. Now it's an arms race of which tribe can out-compete the other through co-operation. Porcinoids fashion sharp arrowlike projectiles that Corvidians can use as weapons or bombs, and Corvidians act as long range scouts for more food/better territory.
Eventually the two species are not only interdependent, but actively require social evolution and co-operative tool making in order to deal with other species. All of this arose because two species with no clashing resource requirements but a reason to co-operate happened to be in the same place at the same time.
Of course you can replace the details here: but the fundamental point remains the same. If two species get more from working together than from fighting they will eventually start working together, and with intelligent species from there it's a self-sustaining process.
**Edit:** I know that these two species are *very* distantly related, but a similar effect could be achieved with a species of ground based heavy apes and arboreal monkeys if you want them to be more closely related.
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**As long as they don't compete in the same niches or already have a symbiotic relationship before tool invention, they should be able to coexist.** If they directly compete then either there will be a forced migration or an extinction of one species.
**Competition Scenario**
Whichever species develops tools first will enjoy a huge advantage over the other species. The second species will need to be ecologically (though not geographically) isolated from the first. Having the two species meet *after* they have both developed tools simplifies the story a great deal though that's not what the OP asked for. An example of ecological isolation can be in the form of eagles and vultures. Both species fly, both eat meat, yet one makes fresh kills while the other feeds on carrion. They can inhabit the same geographical areas but don't directly compete for food.
Two tool using species will need to get their food from different sources, say one prefers fish and lives near streams, lakes and oceans while the other prefers terrestrial herbivores. Their territories may overlap and as long as neither group sees each other as food or a threat, they may peacefully coexist.
In this scenario, both species may be terrestrial or one terrestrial and one amphibious.
**Cooperation Scenario**
In the cooperation scenario, the two species already enjoy a symbiotic relationship before tools are invented. The trick in telling this scenario is to have the both species remain under evolutionary pressure to further develop tool making, even after the first has gotten the hang of tools.
An example of this would be early humans keeping chimpanzees as pets and fostering the chimp's tool use. Most importantly, somehow maintaining a situation over hundreds of thousands of years where the chimps who *don't* use tools die more frequently than the chimps who do use tools. Maybe the lady chimps love the tool-using macho chimps because they bring back more meat? (Sexual selection can do some really weird things.)
**Conclusion**
I think that either approach is plausible though I believe the competition scenario will provide richer interactions than the cooperation scenario. The two different environments and hunting adaptations make for radically different tool use while the similar environment of the cooperation scenario may lead to a tool making monoculture.
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I see as nearly impossible the probability for 2 completely unrelated species to reach huma-like intellectual/technological level in the same time frame.
having subspecies (like neandertal and maybe the homo floresiensis) coexisted in a post-agricultural age maybe is plausible just by having a different geography in an hypothetical alternative earth.
I will make some hypotheses basing of what we know about the evolution of man.
**Geographical heterogeneity**
Having more and more differentiated colonizable lands, should reduce the proportion between velocity of migration and velocity of evolution. Thus, for justify completely different species other assumptions are needed, playing with geography, timing and climatic changes.
I can’t tell how much this can be plausible, but should give some possible justification.
This are some characteristic I have though about the general geography and ambient:
* bigger planet surface (reducing density of the planet you don’t need to alter the gravity) and/or bigger proportion between lands and oceans.
* more climatic zones (you can have that by increasing the planet surface and its rotation speed, i don't know by how much exactly), so you will have more natural barriers like deserts and reduce migrations and exchanges between north and south
* more islands, less continents, this can reduce the average height of peoples (so can be like having more lands), also should increase the ecologic diversity trough regions and the probability for communities to remain isolated for long period.
* more gravity, this should lead to smaller life forms but also to increase the energetic needs for a similar species of the same size, so i don’t know if it’s usable justification.
* weird (for earth standards) ambiental diversification, for example having some common areas with toxic gasses or different air composition (secondary volcanism activity, stratified atmosphere, jungle of venefic-emitter plants…), you can make one population capable of resist in those enviroment (like sherpa can better breath at higher altitude).
* lands should be all quite closer to each other even if divided in islands or by others natural barriers. Not only for plot reasons but also because infectious diseases and technology gap. having completely isolated continent will lead one of the two population, once they have meet, to be almost completely wiped out by the one more advanced in trade, urbanization and with more domesticated animals.
So, isolated regions with different climate for help diversification but close enough to make possibile regular but sporadic contacts.
Although we have to consider that for example diseases are considered one possible reason for the extinction of neandertal, so having a single continent probably is not enough for assuming a necessary level of exchange between the two species over the time.
Also, sporadic contacts like trading I assume are more peculiar of post-agricultural civilizations.
* Migration and genetic derive are triggered by climatic changes, an overall stable climate through a long time scale should reduce the needs/possibility for migration making more likely for two already separated population to diversificate more, maybe also specializing in some partially different niches.
As far as we know both australopithecus, erectus and sapiens came out from central-east africa. Some hominids follow a separate evolution path in east asia but it seems without much success. The more you are closer to africa the more the phenotypic variation you find in human population, that means we all came from it. Maybe more isolation would have given the asian time to grow in number and become successively more resilient by natural selection.
Thus we can’t know if that can be enough for not being outrunned by sapiens. We have to consider that even small differences can be game changing and different ecosystem can probably lead to different result in evolution.
For example neandertal (that even if derived from african population was more suited for colder climates) actually has bigger brain and stronger muscles, but their anatomy make them consume a more energy than cromagnon, and probably they also lived in less numerous and less specialized groups. Living in more crowded community maybe can have making cromagnon to be more resistant to disease.
**More than one Africa**
So we can hypnotize a world with at least 1 or more region very similar to the one where the original species has developed. The regions must be well separated by space and natural barriers and should be easy to migrate through them only in some short and specific climatic era.
This way we can hypnotize 2 separated population that became functionally very similar for evolutionary convergence, but are sufficiently genetically separated for having different secondary characteristics (maybe there is no certain way of predict something like that and it can simply be a matter of probability).
You can make things more asymmetric for example making one race significantly more strong and efficient, one more technologically evolved or numerous.
Or one living in more crowded communities and the other with more domesticated animals (or having domesticated animal with which they live in closer contact), so that there is no asymmetric spread of diseases.
We can then create more morphological difference between the two species considering different ethnicities of them and further genetic derive (think about differences inside the homo sapiens sapiens like height differences between pygmies and masai or hemoglobin level of sherpa)
Also we can make very genetically diversificated population meet by having all the continents closely connected east-ovest in a ring-like shape (with some north-south shifting of course).
The first period after the contact should quite obviously be messy, one of the two species should prevail over the other, but you can think to different perfectly plausible ways for creating an equilibrium at some point between the two population, it depends on what are the main advantage of one race over the other.
* Having a sufficient large area of colonization with different natural barriers can slow down the spread of diseases, giving the time for evolving resistance to them through selection, and making more plausible for some isolated community to escape the wars.
They eventually have also to evolve culturally and technologically, this would be more relevant the more late in civilization level they meet, were instead physical differences will be less relevant to some extend.
* Making the two population meet after agriculture invention can slow down the conquering, if the technological and disease-immunitary gap is not too big.
Nomads groups are more warmonger and needs more lands, sedentary groups have more to lose, can sustain themselves with less land and are less susceptible to climatic changes. Also a better technology level could create to a certain degree a cold war effect, were the consequence of a war start becoming more and more encumbering for civilian activities.
So basically its like making alternative cromagnon and neanderthal meet like after 10bc instead of 40bc, assuming both have reached better technological level.
* If the species meet on a city-state/nation/empire level of civilization it's possible that one race will be spared and used for slavery instead of being completely slaughtered.
One race more technologically and disease-immunitary advanced and a race more physically adapted for certain role in an advanced economy (roles that don’t presumably needs the majority of working population, since the second race will probably be in less numbers, differently they will also be considered a potential menace).
For example dwarf that are more suited for mining (shorter, bulkier, better breathing ability in low oxygen environments), a race slightly stronger/resilient/faster for using as mercenaries (a simple more stronger race like giants two time bigger can be considered a menace), a race with smaller fingers for crafting etc…
* In the case of more advanced civilizations you have to look for big rivers and mediterranean seas placed in a longitudinally stretched continent as preferred locations for those civilizations.
* If the two species are too close so that they can make fertile offspring eventually the disadvantaged of the two will probably be absorbed by the other in few millenniums.
* Making them incapable to make fertile offspring can provide continuation of both if an equilibrium is reached.
* Lastly we have to consider also cultural/religious mindset, that can lead to more peaceful approach or, like indian caste system, slowing the eventually possible process of hybridization.
So I think this way we can hypothesize, maybe not as plausible but at least as possible, the coexistence of two species/subspecies which live in the same niche, having a shared history only after agriculture invention.
Closely related species that live in different niches can more likely survive, but it's hard to imagine how two species can develop post-agricultural technology and civilization without clashing: with technology humans have colonized all kind of environments, also you can have a species who eat different things but they will likely needs farmable land and freshwater for it. you can think of eating plants that live in different ambient and altitudes but i think it's more likely that the other species will eventually find something to eat almost everywhere or they will domesticate inedible plants or select edible plant that can live there.
Even a single reason for competition can be enough for leading eventually to the destroy of one population.
The closer species to us is the chimp, which actually can be considered rather sapient since they have a very early stone culture from at least some milleniums and can sometimes communicate with us.
Maybe we can imagine a world where an almost-sapient like chimp species is domesticated like dog from wolves. Dogs are quite faster than us and have a very good smell, they are good for tracking wounded prey.
Chimp can more easily stay in higher places, but we also can climb trees quite easily for what we need to do.
They can still have an advantages for hunt in forest if human give them weapons or as scout if they had better sense. So maybe an alternate chimp with stronger senses and better hunt inclination to use like scout can be feasible in dense forest ambients.
Some of them eventually will start to live closer to the advanced race becoming used for others purposes than hunt and eventually learn some of their manufacturing processes. Thus wolves has been domesticated only for 40.000 years, I don’t know if it is enough for making the second species develop a better hand for crafting, speech capabilities and a brain capable of more abstract thinking.
Also the dominating species will probably not want to select those characteristic since making them more powerful they can became a treat.
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**[Symbiosis](https://en.wikipedia.org/wiki/Symbiosis)**
Perhaps the two species evolved in parallel in such a way that they need each other, or needed each other during some portion of their evolution.
Not in the sense of parasites, but perhaps in the sense of the relationship between flowering plants and insects.
Or perhaps more of a social symbiosis as seen in the relationship between [aphids and ants](https://en.wikipedia.org/wiki/Aphid#Symbioses).
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The thing about organics is that they can very precisely build themselves up, from a molecular level. They can take various, otherwise useless stuff like goethite and chitin and, through the power of engineering, turn it into one of the strongest biogenic materials to date.
So, graphene is this wunder mátériel we can't produce in high enough quantities and quality to be useful. Graphene can also reinforce spider silk.
I would have to worry about fewer things if any creature, I'm working with, could be reinforced with this unobtanium. **The question is if it's possible for living creatures to produce it.**
Here's some research material, I looked through:
<https://www.sciencedaily.com/releases/2012/03/120321152554.htm>
...the aforementioned graphite oxide can be synthesized using the Tang-Lau method:
<https://www.youtube.com/watch?v=25tS1lmZIRw>
Unfortunately, it does involve high temperatures, which isn't good, maybe you can start by finding a relatively better alternative, or a way to reduce the required temperatures.
*And yes, I mainly want to apply this to dragons, but repurposing the method for other creatures would be important too.*
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**Yes, but it won't resemble the way we do it.**
The mechanism by which an organism will produce graphene won't resemble any of our crude chemical processes. Living things use proteins called enzymes to perform all of their chemical reactions. Enzymes are incredible molecular machines that facilitate nearly every biochemical reaction. There's no reason to think an enzymatic process couldn't produce graphene, or indeed, that there might not exist an enzyme or pathway of enzymes that make graphene already that we simply haven’t discovered. But, importantly, that enzymatic process isn’t going to resemble any of our existing methods.
An example of this would be the production of ammonia in biological and artificial processes. Most industrial ammonia today is produced by the [Haber process](https://en.wikipedia.org/wiki/Haber_process) which relies on extreme pressure and temperature to catalyze the reaction of nitrogen gas to ammonia. Meanwhile, in the soil around us, tiny bacteria produce enzymes called [nitrogenases](https://en.wikipedia.org/wiki/Nitrogenase) that make ammonia from the same nitrogen gas without the need for high pressure or temperature. Life is much better at organic chemistry then we are (it invented it after all). There likely could or does exist a biological alternative to the Tang Lau Method for the production of graphene that doesn’t require high temperatures at all.
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The dragons are ruminants with multi-part stomachs. They eat organic material, and in their first stomach burn the material at 800C until it become graphene oxide.
In the second stomach the graphene oxide flakes are mixed with a bacteria that digests the graphene oxide and turns it into graphene.
In the third and fourth stomach the graphene is processed, and which the dragons body uses in bone and muscle tissue growth.
This works for dragons, but it also works for other ruminants like sheep and cattle.
The sheep eat grass. In their four part stomachs the grass is first brought to 800C. Then in the second stomach it is mixed with bacteria that turn the graphene oxide into graphene. In the third and fourth stomachs the graphene is refined and processed. It is then used to grow the sheeps wool. Farmers sheer the sheep with diamond bladed sheers, and spin and weave it into ballistic armor.
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Yes!
There are lots of substances we (as in humans with labs) cannot synthesize in large quantities, especially if handedness (chirality) is important. For those we generally rely on microorganisms, genetically modified or plain, sometimes on cell-lines from organisms, and sometimes on cells in organisms. Graphene is only hard (for us) to produce in larger sheets, small flecks of it will be generated by simply pulling a piece of graphite over a piece of paper (also called writing with a pencil). Graphene has no properties inherently bad for biochemisry, so there is nothing stopping cells from producing it.
There are an infinite amount of different possible molecules (finite but mindbogglingly large if you restrict size to finite), and a (relatively) small finite amount of molecules synthesized in cells - this is because evolution is the driving factor that advances the cellular biochemistry - alterations of already established processes can produce different molecules, but this 'new' pathway needs to: Create a molecule that works with existing cellular machinery to create an advantage, *not* create any disadvantages on the way (other reactions that damage the cell), *not* be too costly energy-wise, etc - in sum there needs to be a positive net effect of this new pathway, otherwise evolution will not promote it.
So every biochemical pathway present (up to the point of first human geneticist's intervention) was, at one time, randomly formed from an existing pathway, netted a positive effect, and was present in an organism that did not die off.
There are a lot of reactions that do not *look* like they could be beneficial (pathways that produce oxygen as a side-product, or ones that *use* oxygen, for instance, as O2 is actually quite corrosive...) but are, if all things are tallied up. Some pathways might be very hard to evolve from preexisting ones, as they drop or use toxic molecules left and right, but on the face of it no reaction is totally impossible - high reaction temperature is usually possible to be circumvented by using enzymes, extreme toxicity is circumvented by putting a membrane around, etc.
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it's future Mephisto here.
You could try to create an "organic reaction chamber" that can produce the required conditions. Think of osteoderms, you could create a sphere of deposited minerals on the inside, with lots of air pockets in them (better insulation) and heavy vascularization on the outside, to get rid of the waste heat fast. You can also get away with ~165 °C, just keep the stuff there longer.
You have to figure the valve system out on our own, and listen, you have to banish Hillary before it gains more power, I don't have much time... Oh no, they're here, may the fourth be with you!
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Hummer's Method is a safer way of producing graphite oxide at lower temperatures (>98C) although less efficient than conventional methods(Tang-Lau). Graphite oxide is an intermediary to producing graphene. If an animal/organism can go through these the various steps to produce graphene similarly outlined in the Andy's answer (through multiple stomachs etc...) then it is possible to do so.
<https://wikipedia.org/wiki/Hummers%27_method>
Certain bacteria such as thermophiles can survive extreme temperatures up to 122C so it is entirely possible. If you want this to be a part of your story you can mention that the bacteria live in underwater vents and the fish around the vents absorb the bacteria in significant enough quantities to produce a meaningful amount of graphene.
<https://en.wikipedia.org/wiki/Thermophile>
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Graphene and carbon fibers have a lot of implications, first of all a problem that some investigations suggest that graphene rib the celular membrane.
Other problem is that graphite to create graphene requires petroleum coke which is obtained heating the petoleum to up than 1400 °C no one living organism is able to resist that temperatures and obviosuly not able to produce that temperatures because proteins are denatured at even lower temperatures.
But here are the good points
<https://chemistry-europe.onlinelibrary.wiley.com/doi/full/10.1002/cssc.201901404>
<https://phys.org/news/2019-07-graphene-carbon-dioxide.html>
Producing graphene from CO2, inspired in the ability of the plants to transform atmospheric CO2 to biomass using water, so the CO2 conversion to graphene is able using metalic enzymes and metalic plates based on copper and paladium, the current problem is the low efficiency with high energy required at temperatures of more than 1000 °C (notoriously less than the current coke process).
<https://www.nature.com/articles/s41467-019-08824-8>
CO2 reduction to solid carbon alotropes, using liquid metalic electrocatalizers can transform the atmospherical CO2 to solid carbon, with a current low efficiency producing so few quantities.
<https://pubs.acs.org/doi/10.1021/acs.nanolett.5b02427>
Carbon nanofibers from CO2 using carbonate based electrolytes and iridium and niquel electrodes, apparently using a low energy got using a photovoltaic galvanic cell with a maximum of 2.5-2.7 volts and 2 amperes. This is a very positive option.
If you want there are bacterias synthesizing silicon composals <https://pubs.rsc.org/en/content/articlelanding/2008/jm/b719528a#!divAbstract> if you want to use things based of silicon like silicon carbide.
But someone with more chemistry knowledge can explain this better maybe I have misunderstood some things.
But this <https://newatlas.com/bacteria-make-graphene/60529/> is the most positive way, bacterias synthesizing graphene with higher purity thatn chemical reduction process.
But you still having a big problem in the process:
heat petroleum or mineral carbon>>>get graphite>>>refine graphite>>>oxide graphite>>>reduce the oxide graphite>>get graphene>>>refine graphene
With the provived information you practically have solved the last three steps, so I would be focused on find how a living creature could produce graphite a lower temperature, but it is to be expected that, as another user mentioned, a biological process would be very different from an industrial process.
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Could a moon or planet with otherwise no atmosphere maintain gas pockets in sufficiently deep craters, and could it be habitable by humans without pressure or space suits?
I found this similar question [Would oxygen pool in sink holes if the upper atmosphere was helium, hydrogen and methane?](https://worldbuilding.stackexchange.com/questions/19224/would-oxygen-pool-in-sink-holes-if-the-upper-atmosphere-was-helium-hydrogen-and) but it focusses on a planet with a full atmosphere, I want to know if it would be realistic for a planet without enough gas to maintain a breathable atmosphere beyond depressions
to exist.
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Yes, it could (or at least reasonably enough for a story).
For life to develop or be habitable by colonists, the gasses would have to be continually be replenished from some source because it will eventually dissipate for the same reason that our atmosphere continuously leaks into space.
<https://en.wikipedia.org/wiki/Atmospheric_escape>
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> One classical thermal escape mechanism is Jeans escape.[2] In a quantity of gas, the average velocity of any one molecule is measured by the gas's temperature, but the velocities of individual molecules change as they collide with one another, gaining and losing kinetic energy. The variation in kinetic energy among the molecules is described by the Maxwell distribution. The kinetic energy and mass of a molecule determine its velocity by $E\_{kin}=$$1 \over 2 $$\cdot mv^2$
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> Individual molecules in the high tail of the distribution may reach escape velocity, at a level in the atmosphere where the mean free path is comparable to the scale height, and leave the atmosphere.
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> The more massive the molecule of a gas is, the lower the average velocity of molecules of that gas at a given temperature, and the less likely it is that any of them reach escape velocity.
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If you look at Mars, you will find that the atmosphere in the deeper craters is different to that on the high surface. There's no need to ask if it could exist - because it does.
<https://en.wikipedia.org/wiki/Atmosphere_of_Mars>
"It ranges from a low of 30 pascals (0.0044 psi; 0.30 mbar) on Olympus Mons's peak to over 1,155 pascals (0.1675 psi; 11.55 mbar) in the depths of Hellas Planitia"
The only question left to ask is "could this atmosphere sustain life" - and while the answer for Mars is no; there's no reason why, if the chemical composition of it was different, it wouldn't.
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**Kind of, if it doesn't need to be a crater**
Here is a very long article talking about helium production: <https://www.chemistryworld.com/news/scientists-unearth-one-of-worlds-largest-helium-gas-deposits/1010122.article>
The interesting tidbit: after the helium is produced (by radioactive decay; beta radiation is basically a helium nucleus expelled at high speed), in the right spots it gets trapped because it can't penetrate the rock layers above it. Whereas when helium gets into the atmosphere, it's so light it just drifts up through the atmosphere and leaks into outer space.
If your settlement does not need to have an open roof, then this will work just fine. Craters typically have denser material from whatever impact created them. It could easily trap enough gas to hold a pocket of livable atmosphere.
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Yes, it is possible. Consider that at the bottom of a valley one is closer to the center of mass of the planet, [thus](http://web.ncf.ca/jim/misc/rockDrop/index.html) gravity can be relatively stronger, and this could reflect on the local atmospheric pressure.
[](https://i.stack.imgur.com/DlIyd.png)
On Earth we don't have valleys deep enough to experience dramatic difference, but we have such feature on Mars: Valles Marineris.
Up to 7 km deep, the pressure at its bottom is about 0.168 psi, while the average atmospheric pressure on Mars is 0.087 psi. About double, as you see.
Still not high enough to take a walk in T-shirt, but if the atmosphere on Mars would be more dense, it would be first spot to achieve habitable conditions.
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It is absolutely possible for a body to have breathable atmospheres in some places but not others. Earth already has that actually. Look at Mount Everest, you cannot survive at the peak for an extended period of time without supplemental oxygen. Now imagine if Earth's atmosphere was 1/10th as dense as it really is. You would then have that same low pressure 1/10th of the way up Everest. This would mean places as low as Denver, Colorado would not have enough air to breathe. Push it further, and you'll get isolated low areas with breathable atmospheres with barren wastelands between them. Places like Death Valley, New Mexico, or the Great Rift Valley in Africa would be breathable.
One problem is that if the air really is so thin the only breathable areas are deep in valleys or craters is that it will slowly bleed off into space. Every atmosphere, even our own, loses atoms to space. As the sun heats the atmosphere, some atoms gain enough energy to reach escape velocity. Some of these are stopped by running into other atoms, but some escape. With so much less atmosphere above these craters, this proportion will probably be a lot higher. The craters will not have a breathable atmosphere for long, at least not on geologic timescales.
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Factor in life. A natural evolved or genetically engineered amoeba like entity (ALE) which has adapted to living on the edge of a pocket of gas in colonies. The ALE secretes an airtight liquid which hardens into an airtight shell at the edge of the colony.
As the colony expands, it expands the shell, sealing a larger and larger pocket.
Inside or under this pocket more complex life prospers.
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Yes and no.
As the question is asked in the **title** the answer is yes--you can perfectly well have a body whose atmosphere is only dense enough at the lowest altitudes.
As the question is asked in the **body**, however, the answer is no. You simply need too much distance between the airless surface and the habitable pocket--more distance than the strength of the rocks of which your planet is made. Any pocket deep enough to hold a breathable atmosphere collapses.
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Winter is finally upon us! With winter comes a delightful break from the year-round torment of bugs flying your face.
Winter is cold - as a result, you can peacefully breathe the winter air without having to worry about inhaling swarms of bugs. Then the thought occurred to me:
# Could there be a world without bugs?
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Two major problems I though of:
### [Insects are, either directly or indirectly, the most plentiful source of flesh for animals that don’t eat plants.](http://www.motherearthnews.com/nature-and-environment/wildlife/importance-of-insects-ze0z1205zsie?pageid=1#PageContent1)
This could be rather problematic, because essentially removing the base of the food chain would require a lot of re-working in this area. Some birds whose diet consists entirely of insects could be handwaved into eating seeds and berries, but I don't know if there could even be enough seed and berry producing plants to realistically sustain (year round) all of the small animals that now eat insects. Besides, having all the smaller animals eat plants leads into another problem:
### Plants need pollination, and if you get rid of the bees, the plants won't be able to produce fruit or seeds.
This isn't necessarily a problem, as there are already a lot of plants that get pollinated via [Anemophily](https://en.wikipedia.org/wiki/Anemophily). Such plants include grasses and larger trees, but I don't see any reason why a little handwaving couldn't extend this to all plants.
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Are there any other serious obstacles to creating a world without bugs? This world should be as close to Earth as possible, but I'd be fine with some pretty big changes, provided that it stays habitable for humans, and the nice animals humans are familiar with. How this world originated with its delightful insect-free ecosystem is irrelevant.
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## Bugs are replaceable but their roles must be preserved
You must have some species to do their jobs if they are not present.
These may include
* **Pollination**. While plants may develop mechanisms that don't rely on animal life, or rely on mammals, birds, etc. bugs make up an *extremely significant* percent of all pollinators. It's not impossible to live without them, but they sure do help.
* **Being abundant primary consumers**. As the question mentions, bugs help process plant matter, and they, in turn, are eaten. There is no reason why herbivores of other families (mammals, birds, fish) couldn't become the primary consumers instead; if they're plentiful and widespread they will work just as well. Consider sheep, which eat grass, that are hunted by coyotes, which are in turn sometimes eaten by bears - etc. Dozens of other interactions occur within this ecosystem, which relies on mammals, and not insects, and remains healthy.
* **Refining nutrients**. Bugs, as a group, can eat almost anything in nature given enough time (*citation needed*). Animals that in turn consume them receive the processed nutrients from substances they otherwise *could not digest*. If you seek to replace bugs, a large group of organisms with a similar ability must be present - or food must be plentiful virtually everywhere.
* **Aiding decomposition**. While bacteria may be great when it comes to breaking down dead tissue, maggots, flies, worms, isopods, and other "bugs" boost the speed of decomposition in nature. Increased bacteria or increased scavenger populations may solve this problem in a bug-free world, but nonetheless, it will be different from our own.
* **Influencing civilized societies**. Numerous food and textile products come from bugs, they have many practical applications (removing other species, draining wounds, to name a few), and they influence engineering (by building structures and moving in efficient or interesting ways). These are all replaceable, but society may be different in a bug-free world.
## However
It's difficult to evolve a world without something *like* bugs. They're **small**, **diverse**, **adaptable**, and **reproduce often and in great numbers**, making them very fit to survive; they *work* and it doesn't take a lot of time to make them, so they probably will occur.
I cannot promise that every alien world out there has bugs exactly like ours, but I imagine many, if they exist, do.
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You would need other animals to fill the same ecological niches, or leave them empty.
* Perhaps some of them can be filled by small mammals, birds, or reptiles. Consider tiny variants of the [colibri](https://en.wikipedia.org/wiki/Smallest_organisms#Birds) to pollinate plants, or tiny scavenger [lizards](https://en.wikipedia.org/wiki/Smallest_organisms#Reptiles).
* Other niches may be filled by worms.
Compared to bugs they're still large.
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The issue I see is that there are some roles that the bugs (I assume you are including all insects like beetles etc.) are very good at and have become specialised in.
For example: Dung beetles. They consume manure from a wide variety of sources, however one of the huge impacts they have is in parasite reduction, they mess up and dry out the manure as well as stealing it, this means parasite eggs (such as nematodes etc) generally dry out and die. if the insect population dies out relatively quickly then you would have a period where meat production would be massively impacted, not to mention greenhouse gas emission from the animals and the manure would be altered, less of the gasses like nitrogen being buried and so on and so forth.
The world would survive (whether we do or not is another thing) but it would be drastically altered.
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The song *Diggy Diggy Hole* makes some questionable assertions about dwarven anatomy. Specifically:
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> Born underground
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> **Suckled from a teat of stone**
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> Raised in the dark
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> The safety of our mountain home
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> **Skin made of iron**
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> **Steel in our bones**
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> To dig and dig makes us free
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> Come on, brothers, sing with me!
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Now we *could* interpret that all metaphorically... but where's the fun in that?
So, how do we design a dwarf that actually meets those criteria?
"Skin made of iron" might have something to do with [iron sulfide scales](https://en.wikipedia.org/wiki/Scaly-foot_snail) or similar. And I am willing to posit that the "teat of stone" *may* be merely superficially similar to stone, rather than literally made of rock. But the closer an answer gets to a straightforward literal interpretation of the song, the better.
[A list of all Anatomically Correct questions](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798)
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**Suckled from a teat of stone.**
the teat is a stalactite, stalactites you see are formed form water-filled minerals slowly dripping off of rocks. which your dwarves drink to gain their nutrients at a young age.
**Skin made of iron.**
your iron sulfide theory works perfectly, they have a relationship with bacteria on their skin that lives of them and in return they produce iron.
***Steel in our bones.***
Steel is just iron and carbon. Carbon is everything and everywhere, so they have these bacteria that make the iron for their skin. They then have an organ of acid like substances similar to our stomach that heats up the iron and adds the carbon that is then built into the bones.
Go WIND ROSE!!!
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Make the dwarves automata (sorry for not anatomically/scientifically correct, but I loved the parameters and had to share).
They grow from a seed of seemingly randow gears and sprockets, strategically placed under stalactites by older dwarves who are ready to settle down and have a kid.
Their minerals are deposited by stalactites for eons, hidden waterwheels and reduction gears gently unfolding the shape of a dwarf out of water and rock- until the Bootstrap day, when the finished dwarf spits out the stalactite and starts staggering around and asking the older dwarf to borrow it's car.
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**Idea**
Is the following alternate history setup conceivable:
* Central Mexico has been converted to Buddhism by missionaries arriving from East Asia or South-East Asia hundreds of years before European conquistadors arrive.
* By the time of European conquest of the Caribian, Central Mexico is organized as a centralized and predominantly Buddhist state.
* The missionaries brought scriptures (naturally) and some knowledge of East Asian technology (advanced metal working, steel, the wheel, siege weapons, etc.).
* There is no continued political interference from Asia in the Americas, certainly no military interference.
* With the Pre-Columbian contact, Native Americans have acquired some immunity against Eurasian diseases.
Note that with a very different timeline, the people in Central Mexico would not be called Aztecs; I am just calling them that for want of a better universally understandable term. (In fact, they were not called Aztecs; this term is an invention of 19th century scholars.)
**What it could look like**
*On Holy Thursday, the anniversary of the Last Supper of Our Lord, in the year of Our Lord 1519, the Captain-General ordered us and all his fleet to disembark in this strange new land. While we made camp between the dunes we noticed a shrine with a heathen idol nearby, a gilded statue showing a monstrous sitting figure with six arms and a serene if gloating smile. The Captain-General ordered the false idol removed and replaced by the likeness of Our Lady.*
*For some days, the Indians native to this country avoided us, until an embassy arrived on Easter Sunday. The embassy was led by an Indian of noble birth, Teuhtlilli, Governor of Cuetlaxtla, accompanied by many servants and warriors. Teuhtlilli brought presents of fowl and vegetables and greetings of the prince of this country, who was called [Ahuitzotl the Enlightened](https://en.wikipedia.org/wiki/Ahuitzotl). Among Teuhtlilli's people, there were several barefooted men with stoic expressions clad in nothing but an orange robe. We learned that they were heathen monks, learned in religion and all the arts and the Indians greatly valued their council. The warriors, on the other hand appeared in full metal armor, with lances and steel swords and steel helmets adorned with golden images of snakes and dragons and terrible monsters. They assured us that there were indeed fire-breathing dragons that inhabited the mountains of the lands ahead.*
*The Captain-General ordered an altar made. Fray Bartolome de Olmedo celebrated the Holy Mass in the presence of the Captain-General and his men and the Indian embassy, for the Captain-General wanted to show the heathens the way of the true religion. Afterwards, the Captain-General dined with the Indian ambassador. He also arranged a demonstration of the cannon so that the ambassador should see it fired. The ambassador was thoroughly unimpressed. He seemed insulted and demanded to know why we had defiled the shrine to the [Bodhisattva](https://en.wikipedia.org/wiki/Bodhisattva) [Quetzalcoatl](https://en.wikipedia.org/wiki/Ce_Acatl_Topiltzin). The Captain-General tried to explain our holy faith, but Teuhtlilli would not hear it. He demanded that we re-embark and leave this country immediately; then he departed abruptly.*
*The next day, we learned that an Indian army had arrived and was encamped not far from where we had made landfall. They numbered in the tens of thousands, all with formidable armor and weapons made of steel. They also brought a number of trebuchets; one of our ships that came too close to the Indian camp was hit by a flaming projectile and set ablaze...*
(Note that style and some of the wording and context is adapted from [Bernal Diaz' account of Hernan Cortes' conquest of Mexico](https://archive.org/stream/tesisnoqueprese00garcgoog/tesisnoqueprese00garcgoog_djvu.txt).)
**How it could have happened**
For a time, Buddhism was aggressively prosetylizing everywhere from Japan, to Central Asia, to modern Indonesia, to Egypt and Greece. An [apparent Buddhist missionary](https://en.wikipedia.org/wiki/Zarmanochegas) who came with an Indian embassy burned himself to death publicly in Athens in 22/21 BCE to demonstrate his faith. Buddhist missionaries may have been government-sponsored but were happy to work alone, under hardship, and far away from their countries of origin. They would certainly have been willing to go to Mexico, had they known how.
There was speculation about whether Buddhist missionaries may actually have reached the Americas in Pre-Columbian times. Around 500 CE, a group of Buddhist monks traveled from China to a country called [Fusang](https://en.wikipedia.org/wiki/Fusang), across the sea 20000 li East of China. One li is between 300 and 600 meters (depending on where and when), which is not quite far enough to be America but much further away than Japan. Traditionally, it has nevertheless been interpreted to refer to some part of Japan or Sakhalin or other islands.
Further, in later times, it happened frequently that [Japanese fishing boats were driven out into the ocean and across](http://staff.royalbcmuseum.bc.ca/wp-content/uploads/2013/08/JapaneseShipwrecks-Grant-Keddie.pdf) the Pacific. [Some Japanese sailors](https://en.wikipedia.org/wiki/Otokichi) survived and were taken captive by Native Americans in the 19th century. It seems conceivable that this might have happened in a similar way 1000 years earlier to Buddhist missionaries bound for Japan, China, or Korea.
**Potential Problems**
* While Japanese fishermen carry potentially enough food (or at least the tools to acquire some) for the long journey across the Pacific, a ship sailing the rather short way between Korea and Japan, or even between South-East Asia and Japan would probably not.
* Buddhist missionaries in other regions were most successful when relying on a network for ideological (perhaps also material) support. Buddhist states and Buddhist monasteries could provide that across Asia, but not in the Americas. Especially when considering that the missionaries would not have had any way of knowing where they are, how to get home or write home and report about their success, etc. Even with nautical knowledge, traveling reliably across the Pacific (in order to get back, even if you understand where "back" is), requires understanding the [volta do mar](https://en.wikipedia.org/wiki/Volta_do_mar). The [Spanish had to try for a while](https://en.wikipedia.org/wiki/Manila_galleon#Discovery_of_the_route) and lost many ships before they got it right.
* The religious establishment in Central Mexico would not be amused.
* Technological knowledge is difficult to transfer. The Mongols for instance had to bring in Persian engineers to [build counterweight trebuchets and reduce the Song fortresses](https://en.wikipedia.org/wiki/Battle_of_Xiangyang#Role_of_the_counterweight_trebuchet). Buddhist missionaries may not be concerned with either steel or siege warfare or anything of the sort. Even if they had seen this in Asia and were willing to help by reproducing this technology in Mexico, they may not succeed. Or possibly they would produce very crude versions of it.
* The wheel may not be useful enough without large draft animals. But missionaries would not accidentally bring horses or water buffalo (or perhaps they would eat those when starving at sea).
* It may be impossible to move a trebuchet without draft animals.
* A one-time or two-time contact with a few missionaries may not have been enough to spread Eurasian diseases to the Americas and cause immunity to develop.
* Iron ore may not be easily to find in or around Central Mexico.
[Answer]
**Yes, this could totally happen.**
Essentially, three things need to happen for this scenario:
1. **Contact -** Some East Asian exploration of the Americas centuries before 1492.
2. **Religion -** Those explorers/missionaries convert the local population.
3. **Disappearance -** East Asia is no longer involved on the continent.
Let's take a look at each requirement.
**Contact** - completely plausible. Chinese explorer [Zheng He](https://en.wikipedia.org/wiki/Zheng_He) reached Africa, and probably had the ability to travel further. In fact, the European explorers of the 15th century did not posses any [uniquely advanced technology](https://en.wikipedia.org/wiki/Kon-Tiki_expedition), the deciding factor was motivation (rising prices of spices). If for some reason China *really* wanted to sail east - they could do this.
**Religion** - the easiest part. Christian missionaries easily (and rapidly) converted the local population, Buddhism could do the same.
**Disappearance** - this is the least likely bit of this, but not impossible. Why would you leave a continent in which you are the only overlord. However, we are talking about China. Thorough the previous millennium they knew repeating periods of expansion followed by closing the borders and focusing on the internal affairs.
**A (reasnbly) viable background story could be something like:**
*One Chinese emperor was possessed with exploration, his ships sailed east and discovered the Americas. Afterwards, the emperor supported the American presence enough to promote a technological, religious and biological exchange. However, his successors were extremely isolationists, and thus stopped all transpacific contacts. Then some crisis happened (civil war/Mongol invasion), and by the time the country became stable again the tales about the American escapades were seen as legends.*
[Answer]
Why not have an even earlier point of departure? Genetic mapping studies by Cavalli-Sforza have shown a pattern of genetic expansion from the area of the Sea of Japan towards the rest of eastern Asia. This appears as the third most important genetic movement in Eastern Asia (after the "Great expansion" from the African continent, and a second expansion from the area of Northern Siberia), which suggests geographical expansion during the early Jōmon period. These studies also suggest that the Jōmon demographic expansion may have reached America along a path following the Pacific coast, via the Kuril Islands and Aleutian islands, and that the natives of the Pacific Northwest have significant genetic admixture with the original natives of Japan.
But this expansion, the 'Jōmon Exchange', happened too early on IOTL, and ended too soon, for any of the technological, agricultural and social developments which Japan picked up later on in the Yayoi period to make it across to the Pacific Northwest, or for any prospect of extending the Japanese branch of the Maritime Silk Route, which was only established c. the 4th-5th century CE. Contact wasn't maintained, and neither was maritime trade; as such, it took until the late 1700s for the Russians to establish the Maritime Fur Route, by which stage it was far too late.
So, why not have this maritime fur trade route established earlier, either by the Japanese or by the Pacific Northwesterners themselves? In so doing, the transmission of Buddhism to the Americas is via the Japanese branch of Silk Road, just like the trasmission of Buddhism to Japan was. During the fifth and sixth centuries C.E., merchants played a large role in the spread of religion, in particular Buddhism. Merchants found the moral and ethical teachings of Buddhism to be an appealing alternative to previous religions. As a result, Merchants supported Buddhist Monasteries along the Silk Roads, and in return the Buddhists gave the Merchants somewhere to stay as they traveled from city to city.
As a result, Merchants spread Buddhism to foreign encounters as they traveled. Merchants also helped to establish diaspora within the communities they encountered, and over time, their cultures became based on Buddhism. Because of this, these communities became centers of literacy and culture with well organized marketplaces, lodging, and storage. With this trans-Pacific branch of the Silk Route, via the Bering Strait, the merchants could easily have spread Buddhism to the New World in much the same manner as they did on the Japanese archipelago, with [similar results](https://en.wikipedia.org/wiki/Buddhism_in_Japan).
[Answer]
### Buddhists would be barred from Mexico by disease
Buddhism was expanding quickly in the first centuries AD. It spread widely in China in the 200s, into Korea in the 300s, and 538 to Japan. The most likely route for a trans-Pacific voyage by missionaries would have been by skirting the edge of the land, up to Kamchatka, across Alaska, and then down the West Coast of the US. These lands are relatively rich in food sources, and there probably would have been plenty of intervening groups for the missionaries to interact with.
Ultimately, trans-oceanic voyages were probably both out of the missionaries capabilities and too expensive even if they were capable. Firstly, the Chinese had very large ships, and did a bit of exploring under Zheng He (though that was the 1400s, not the 700s). But they did not have experience with open ocean navigation the way that the Europeans had. Spanish and Portugese sailers that embarked on the voyages of exploration spent a lot of time going to Azores and Canary islands and back, and there were Basque fishermen that went to the Outer Banks near Nova Scotia. The didn't regularly sail to such far away islands; the Phillipines is probably the longest over-water crossing that they Chinese sailors regularly made. To my knowledge, there is no evidence of Chinese or Japanese contact with Guam, for example.
The second point relates to expense. Trips to the Americans were sponsored by European crowns at first, then by rich merchant groups after ~50 years once the economic potential of the region was uncovered. China (or Japan) would not have had much economic use for the Americas at that Early point, and there isn't much suggesting the Emperors would be interested in sponsoring a lot of ship traffic. Buddhist missionaries were able to spread by foot easily to China and hitch rides to Japan, just as Jesuits and Franciscans were able to hitch rides to America with the Spanish. But barring other reasons to sail the deep Pacific, even if the Chinese or Japanese had the technical knowhow to cross, the Buddhist monks couldn't afford to pay for their own ships.
So lets limit the missionaries to the coast-hugging route across the north. Let's say a Buddhist mission made the Pacific Northwest and spent some time converting the totem-pole making, fisherpeople of the area. Communicable diseases quickly strike and over-run most of the population of the the Americas (as happened in real life). The large towns de Soto saw in the 1540s were essentially gone a century later.
The problem is that now the Buddhist monks lose their stepping stones to Mexico. A successful conversion experience (as seen in China) need a set of monks to move back and forth from the mother country to the newly converted territory, bringing rituals, written documents and translating them.
With the hunter-gatherer tribal areas from Alaska to California disrupted by disease, the links back to the homeland are broken. Further missionaries can barely make it through the wilds, and once sedentary tribes that provided shelter are disrupted.
All in all, I think there are several reasons to think that a Buddhist conversion of Mexico is unlikely, barring significant changes to history.
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
**This Query is part of the Worldbuilding [Resources Article](https://worldbuilding.stackexchange.com/questions/143606/a-list-of-worldbuilding-resources).**
---
Once the geography of the world is designed, it needs a planetary system to inhabit. But how should that solar system look? The only constraint is that the system needs the new world to be placed in a habitable zone for the suspiciously Earth-like creatures that evolved there. By placed, I only mean it's made up, the system needs to have naturally formed in all respects.
The naive solution would be to make it like our planetary system, the Solar System.
That is, arrange it so that the planets orbit the same direction in the ecliptic plane, there are some rocky planets close to the star followed by an asteroid belt and some gas giants, like this: SRRHRAGGG (*incidentally, this is the sound the planetary system will make when it dies*)
```
Key:
S- Star
R- Rocky Planet
H- Habitable Planet/Moon
A- Asteroid Belt
G- Gas Giant
```
Is this the most likely arrangement, RxAxGx (rocky planet[s], asteroid belt[s], gas giant[s])? Can a massive gas giant be orbiting near the star out of the ecliptic plane? Can the habitable world be alone with some comets and asteroids?
*The main question:*
**What is the range of planetary configurations I can *reasonably* expect from a habitable system?**
*Clarifications:*
I'm interested in the ordering of planets (mass and type), the planet mass to star ratio, number of planets, orbital direction of planets (as in agreement between planets), ecliptic plane confinement, and the reasonable range of these aspects. Reasonable meaning very precisely "not, like, super rare among habitable systems".
*Restrictions:*
The system must contain a planet which has evolved Earth-like life.
The system must have been formed by natural processes.
**Magic, science fiction, and anecdotes need not apply, this is [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'"). We don't know much about other systems, let alone explicitly habitable systems, so inductive reasoning is allowed (if not required) but peer-reviewed papers should support any evidence used in that process.**
---
Note:
>
> This is related to a series of questions that tries to break down the process of creating a world from initial creation of the landmass through to erosion, weather patterns, biomes and every other related topics. Please restrict answers to this specific topic rather than branching on into other areas as other subjects will be covered by other questions.
>
>
>
---
See the other questions in this series here : [Creating a realistic world Series](https://worldbuilding.meta.stackexchange.com/questions/2594/creating-a-realistic-world-series)
[Answer]
## Ordering of planets (mass and type)
Can I start out by jokingly complaining that you picked a rather complex system? We've found a lot of exoplanets, but there are not many that reside in complex systems like this. This is going to be a tough question. [As Green predicted](https://worldbuilding.stackexchange.com/questions/21408/creating-a-realistic-worlds-map-solar-systems#comment54732_21408), Kepler data is useful here - [Fang & Margo (2012)](http://iopscience.iop.org/0004-637X/761/2/92/pdf/apj_761_2_92.pdf) found that
>
> 75%–80% of planetary systems have one or two planets with orbital periods less than 200 days
>
>
>
They also were able to plot data from a variety of parameters to come up with some graphs that could be used to make distribution curves. You can extrapolate from that, if you wish.
Anyway, I'm off track here. Mass distributions were covered in [Mazeh et al. (1998)](http://iopscience.iop.org/1538-4357/501/2/L199/fulltext/985083.text.html) (which is almost certainly outdated, but a good analysis nonetheless) and [Malhotra (2015)](http://arxiv.org/abs/1502.05011). Using some orbital spacing parameters (which you can adjust, if you want), Malhotra found that the peak value of $\log m/M\_{\oplus}$ occurs at about 0.6-1.0, with a standard deviation of 1.1-1.2. Not the greatest accuracy, but still pretty good.
[Llambay et al. (2011)](http://arxiv.org/abs/1101.3545) were able to come up with a mass-period distribution for exoplanets close to the star, which you can then use to come up with a decent distribution of masses at a given radius:
>
> Most smaller planets have orbital periods longer than P~2.5 days, while higher masses are found down to P~1 day.
>
>
>
In short, more massive planets are closer in, while less massive planets are further out. Still, Llambay et al. only considered planets extremely close to their parent stars. For the rest of the system (i.e. planets farther out), I refer you to [Jiang et al. (2007)](http://iopscience.iop.org/1538-3881/134/5/2061/pdf/1538-3881_134_5_2061.pdf). I can't copy the mass- and period- histograms they gave (relating each one to the total number observed), nor can I copy the scatter plots, but they are incredibly helpful, especially as they considered a sample size of 233 exoplanets.
This graph, complied on [Wikipedia](http://en.wikipedia.org/wiki/File:Exoplanet_Period-Mass_Scatter.png) from [the Open Exoplanet Catalogue](http://www.openexoplanetcatalogue.com/), is also helpful for an at-a-glance reference:
[](https://upload.wikimedia.org/wikipedia/commons/c/cc/Exoplanet_Period-Mass_Scatter.png)
Image in the public domain.
Something you must consider is [planetary migration](http://en.wikipedia.org/wiki/Planetary_migration). I've written several answers on it across Stack Exchange (e.g. [The Solar System Explosion in the Nice Model](https://physics.stackexchange.com/questions/160912/the-solar-system-explosion-in-the-nice-model), [Did Jupiter really make Earth (in)habitable](https://earthscience.stackexchange.com/questions/4595/did-jupiter-really-make-earth-inhabitable), [What gravitational impact would moving Jupiter to the inner solar system have on the outer?](https://worldbuilding.stackexchange.com/questions/12281/what-gravitational-impact-would-moving-jupiter-to-the-inner-solar-system-have-on/12290#12290), etc. - the first focused on only one part, because Kyle Oman was already familiar with the it, hence the question), and others have written excellent answers elsewhere on Stack Exchange. By now, I'm sick and tired of typing the same thing up, so I refer you to the latter two posts I gave, as a starter. You need to include planetary migration because it will severely impact the orbits of the three gas giants in the system. Be careful that you have enough - my answer on Physics discusses just why a certain number is needed.
---
## Planet mass to star ratio
No such ratio exists. You can have pretty much any (reasonable) combination you want. It all depends on the [giant molecular cloud](http://en.wikipedia.org/wiki/Molecular_cloud) from which the star formed and the evolution of the [protoplanetary disk](http://en.wikipedia.org/wiki/Protoplanetary_disk). Anything can happen.
---
# Number of planets
Fang & Margot are, once again, helpful. [Weissbein et al.](http://arxiv.org/abs/1203.6072?context=astro-ph) are also an excellent resource for this specific part. I once again wish I could figure out directly how to copy graphs and histogram without using imgur - I may use that later - but I can get around that. Unfortunately, they make three assumptions:
1. All planets in a system are exactly aligned
2. All of the stars and planets are identical
3. The Occupancy distribution of a planet existing at a given distance from its stellar host, f(r), is the same for all the stars which are capable of producing planets and is given by equation (1).
The third is not a problem, but the first two are (see my section on ecliptic plane confinement for a discussion on the first). Luckily, as I show later, that criterion can easily be met. The second one is the problem.
Anyway, Weissbein et al. find the probability, $P$, that a star hosts $m$ planets to be
$$P(m)=\int\_0^{\infty}\left[\frac{F(r)^m}{r^2m!}e^{-F(r)}\right]dr$$
where $r$ is radius and
$$F(r)\equiv \int\_0^r f(r')dr'$$
where $f(r')$ is a modified form of the general occupation probability function.
They then used this to create a table of the results, which I will not include at the moment, as I am not good with tables in Stack Exchange. However, predictably, the number of systems went down as the number of planets increased.
---
## Ecliptic plane confinement
"Ecliptic plane confinement" can be discussed in terms of [orbital inclination](http://en.wikipedia.org/wiki/Orbital_inclination), generally denoted by $i$. In the case of most systems, this is close to zero degrees for most of the bodies involved (although [Pluto has a high inclination](https://astronomy.stackexchange.com/questions/11360/why-does-pluto-have-a-high-orbital-inclination?lq=1)).
The planets in the Solar System [orbit in one plane](https://astronomy.stackexchange.com/questions/130/why-do-the-planets-in-our-solar-system-orbit-in-the-same-plane?rq=1), because everything formed out of a protoplanetary disk. The planets tend to [stay that way](https://astronomy.stackexchange.com/questions/1095/why-do-the-planets-in-the-solar-system-stay-in-the-same-orbital-plane) because of a conservation of angular momentum. This can change in some cases - notably, [Kepler-452b has a high angle of inclination](https://astronomy.stackexchange.com/questions/11392/how-can-a-planet-have-a-90%c2%b0-inclination) (90 degrees!). As I wrote in my answer there, this may have happened for several reasons:
* The star's rotation axis was perturbed, just as Uranus's rotation axis was perturbed (although by different objects)
* The planet was perturbed by another object, either in the system (e.g. a planetoid) or a companion star. The Sun was formed with many other stars in a cluster; this happens for many stars.
The relevant papers on this subject are [Crida & Batygin (2014)](http://arxiv.org/abs/1405.0960) and [Xue et al. (2014)](http://iopscience.iop.org/0004-637X/784/1/66/pdf/apj_784_1_66.pdf). There are other reasons for the change in orbital inclination of one planet, notably the [Lidov-Kozai mechanism](http://en.wikipedia.org/wiki/Kozai_mechanism) (see [Lidov (1962)](http://www.sciencedirect.com/science/article/pii/0032063362901290) and [Kozai (1962)](http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1962AJ.....67..591K&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf)). The Lidov-Kozai mechanism basically states that the eccentricity of an object's orbit can be changed by interactions with another (more massive) object, which also changes the orbital eccentricity of the first object. The angular momentum in the $z$-axis must be conserved here; it is the quantity
$$L\_z=\sqrt{1-e^2}\cos i$$
You can play around with this a bit to see what happens when different parameters are changed (you should be able to apply the orbital formulas given [here](https://worldbuilding.stackexchange.com/questions/9944/making-a-planet-habitable-for-humanoids-the-planet)). However, the model assumes that the perturber is much more massive than the perturbed object (Kozai's original analysis applied to perturbations of asteroids by Jupiter!). For larger bodies being perturbed, you would need a larger perturber. This makes it very difficult for planets. This could happen in a binary system where one star is more massive than another star, and the second star perturbs a planet moving around the larger star. It is, however, unlikely, and does not fit your model of one star.
It makes sense that either most or the orbits have high orbital inclinations - a result of a perturbation of the star's rotation axis or the protoplanetary disk - or low orbital inclinations. The Lidov-Kozai mechanism is not good for large systems. It is also important to note that it is periodic in nature.
Once again quoting Fang & Margot,
>
> In addition, over 85% of planets have orbital inclinations less than 3◦ (relative to a common reference plane).
>
>
>
They used a [Rayleigh distribution](http://en.wikipedia.org/wiki/Rayleigh_distribution) to describe this:
$$P(k)=\frac{k}{\sigma^2}e^{-k^2/\sigma^2}$$
where $\sigma$ is the parameter that determines the distribution of $k$. Notice the difference between a Rayleigh distribution and a [normal distribution](http://en.wikipedia.org/wiki/Normal_distribution). An distribution for orbital eccentricity can be found in [Kane et al. (2012)](http://arxiv.org/abs/1203.1631).
---
[Answer]
**Rocky/Gas Configurations**
Anything is possible but it is no coincidence that the solar system has its most dense planets at orbits closest to the sun and gas giants a lot further out. The greater temperatures and solar wind pressures nearer the star will be pushing lighter elements away more easily from inner orbits when the star's reactor fires up.
To quote <https://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System>:
>
> The inner Solar System, the region of the Solar System inside 4 AU,
> was too warm for volatile molecules like water and methane to
> condense, so the planetesimals that formed there could only form from
> compounds with high melting points, such as metals (like iron, nickel,
> and aluminium) and rocky silicates.
>
>
>
Heavy rocky planets nearer the star and gas giants further away are probably the most likely configuration with only peculiar formation events changing that.
Independent rocky planets in the zone of the gas giants don't exist in our solar system but rocky moons of those gas giants do. So, rocky things can and do exist at any distance but gas giants tend to be further away and capture or destroy anything in their path.
That gas giants don't exist beyond a certain point is probably simply a matter of the solar nebula being too thin after certain distances.
Binary to trinary systems could perhaps produce different situations. If Jupiter had been big enough to be a red dwarf then we would have a complex binary system: Still probably with rocky planets between the two stars but perhaps an even larger rocky system orbiting Jupiter. However, we expect multiple-star systems to be generally less conducive to stable orbits as close as the habitable zone.
**Orbital Planes and Directions**
All planets formed within the system will be orbiting in the same plane and in the same direction: they will be constructed in that orbit from the same rotating primordial mass.
However, collisions or gravitational interactions with a extra-stellar objects could feasibly knock a planet into a slightly different plane of orbit. It would have to be from an extra-stellar object, everything else has the same angular velocity vectors so collisions between system bodies just knock things into different motions in the same plane.
A solar system that moved too close to a particularly massive neighbor could end up with planets in orbital planes that slope and become more elliptical the further out they are. That is far more likely than a rogue extra-stellar planet crashing into one of the planets and producing a new planet orbiting in a different plane and/or direction.
**Captured Planets**
Capturing an object in orbit is extremely unlikely: they tend to follow parabolic or hyperbolic paths and leave the encounter with the same kinetic energy they arrived. Only collisions during the process can change that and they are highly unlikely to happen let alone happen in just the right way to cause the visitor to start orbiting.
However, it is possible: Neptune captured Triton (we know this because Triton orbits the opposite way to Neptune's rotation) so an extra-stellar planet could be captured and that could happen in any plane or any direction. It had to involve a collision so the result could be another planet also orbiting in a peculiar plane and direction.
**The Star(s) Itself**
Blue giants and super giants (O and B class) are almost certainly to be ruled out: they are too short lived.
Other giants are also likely to be ruled out as they tend to be dying stars: the habitable zone will have moved and that causes problems for evolution. Their lives as giants also tend to be short.
But anything else except dead stars (White Dwarfs, Neutron Stars and Black Holes) is feasible.
Only nice orange, yellow or white main sequence stars seem likely to produce habitable zones that are stable for long enough for life to evolve:
[](https://i.stack.imgur.com/mvCJi.png)
**Disclaimer**
We live in one of hundreds of billions of galaxies each with hundreds of billions of stars. I expect every imaginable configuration exists at least around one of those stars.
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
In my setting, a permanent "fog" hangs over the ocean. It is thick, granting low visibility to anyone within it. Instead of water droplets, however, this fog would consist of some substance or combination of substances, that is/are able to be harvested for, and if necessary refined into, fuel (and ideally other materials, such as plastics).
The "fog" should have the following properties:
* It exists as a heavier-than-air gas or cloud of fine droplets at sea level (temperature is open for discussion, but I would prefer an ambient temperature around 5-10°C for the sake of the rest of the worldbuilding);
* It is translucent, granting low visibility, equivalent to or less than that of a thick real-world cloud fog;
* It is usable as a fuel, or can be refined into such a form via relatively simple processes;
* It is plausible for the substance to exist in an earth-like atmosphere/biosphere.
The question: **what material would plausibly display these properties?** I'm aiming for plausibility - closer to science fiction than science fantasy.
I hope that my question is clear enough, and suits the site!
[Answer]
## Manna from... sea spray?
This is a super cool question, and entirely feasible within the realm of [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'"). The secret ingredient in such an atmosphere is going to be [sea spray](https://en.wikipedia.org/wiki/Sea_spray)!
Oceans are already foggy[citation needed] due to two related processes: midair condensation and droplet injection. Midair condensation happens when warm, moist air cools below the [dew point](https://en.wikipedia.org/wiki/Dew_point) and begins to form droplets of water suspended in the air as the Brownian motion of the air molecules outweighs the tendency to stratify by density. Droplet injection is a mechanically-intensive process that requires something to put energy into aerosolizing the seawater (or [gasoline](https://en.wikipedia.org/wiki/Carburetor), or [cheese](https://en.wikipedia.org/wiki/Easy_Cheese)).
In the ocean, especially near shore, these processes are related because the dew point is determined by humidity - and droplet injection increases the relative humidity of an area. On coasts, the mechanical effort to aerosolize the seawater comes from breaking waves. Every time a big, rolling wave comes through and white water is visible in its crest, you can be sure it's leaving behind a trail of suspended water droplets. These droplets often stay suspended long enough to spread inland and cause fog formations. This process also occurs in the open ocean when the wind is strong enough to cause whitecaps, which have the same effect as breaking waves.
However, water isn't the only thing in the ocean[citation needed] and sea spray isn't pure water. Rather, it's a collection of salts and organic matter and [little microorganisms](https://academic.oup.com/femsec/article/94/3/fiy005/4810542) that happened to be caught in the breaking wave. This means that ocean fogs are [incredibly complex](https://scripps.ucsd.edu/news/research-highlight-researchers-identify-bacteria-and-viruses-ejected-ocean) micro-ecosystems that we still don't know a lot about.
The problem as posed in the question, therefore, is how to manipulate the environment to maximize the concentration of organic materials (ideally hydrocarbons) in the surface ocean, so that sea spray, and therefore fog, will be especially valuable.
## Worldbuilding ideas
### Phytoplankton
On the highly-realistic - but less effective - end of the spectrum, we can manipulate normal Earth biology. The best option here will be microalgae, which are already found in seawater in high concentrations. If we can get lots of microalgae into the air, the resulting fog will be highly valuable not just as a [fuel source](https://en.wikipedia.org/wiki/Algae_fuel), but also for [food](https://www.livescience.com/48853-spirulina-supplement-facts.html) and [other important natural compounds](https://www.rxlist.com/consumer_chlorella_green_algae/drugs-condition.htm). Phytoplankton already have a tendency to "bloom" when conditions are right, during which time their concentrations increase [by a factor of 100-1000x](https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/96RG00986). These blooms are so dramatic that they'll discolor the surface ocean and be visible from space:
[](https://i.stack.imgur.com/rdVwP.jpg)
In order to make the sea-spray fog worth harvesting, however, the blooms will need to go beyond natural occurrence. Fortunately for us, humans have been conducting large scale nutrient fertilization experiments near the outflow of each of our rivers for some time now. Such man-made blooms can reach truly disgusting concentrations, as [China faced while preparing for the 2008 Olympic games](https://www.theguardian.com/environment/2008/jun/30/pollution.olympicgames2008). Such intense concentrations of algae, combined with large waves, could easily make fog worth harvesting for fuel.
### Oil slicking
On the more-disruptive side of ocean-engineering, we could deliberately add the useful compounds directly to the ocean surface. In fact, humans already tried this (albeit for different reasons) resulting in one of the [largest oil spills](https://en.wikipedia.org/wiki/Gulf_War_oil_spill), and [deliberate oil dumping](https://www.thenational.ae/opinion/deliberate-oil-spills-need-to-be-stopped-1.5616) continues to be a huge problem in many places.
On a world where the ocean surface is covered in hydrocarbons, it's likely that the fog would be largely hydrocarbon-based as well. This could be the result of [leaking natural deep-sea oil wells](https://www.whoi.edu/oil/natural-oil-seeps) or [pentane seeps](https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000JC000259), or something more exotic and biological like mid-ocean ridge [bacteria that produce rocket fuel as a way to avoid nitrogen toxicity](https://www.sciencedirect.com/science/article/pii/S096808961400724X).
The trick here would be balancing plausibility of the oil layer thickness against the relative proportions of oil and water in the air. The thicker the layer on the surface, the more oil in the sea spray, but also the more disruptive and implausible the oil slick. Fortunately, hydrocarbons are immiscible with water, so separating the two should be simple enough even if collected together.
### Ethanol oceans
On the far end of implausibility, it's possible to imagine the oceans themselves consisting of fuel. Ethanol and methanol oceans [have been discussed before on this site](https://worldbuilding.stackexchange.com/questions/71798/can-a-planet-have-oceans-of-ethanol), but this seems to go against the sentiment of your question; it'd be much easier to simply collect the fuel from the ocean. Unless, of course, the ocean was inaccessible [for other reasons](https://www.google.com/search?tbm=isch&q=ocean+cliffs)...
## Considerations
Having an ocean produce fuel naturally is a *terrifying* idea on any planet in which ignition sources also exist. Fuel-based sea spray is basically gasoline immediately before ignition, and equally flammable. As awesome as a novel would be that begins with humans setting a nearby planet on fire from their chemical rocket landing, I must urge caution if you'd like the inhabitants of said planet to remain alive for very long. Fuel sources requiring some refinement or distillation prior to use would be much more useful.
Additionally, collecting fuel from sea spray is difficult to justify when there's a much more concentrated source nearby in the form of [sea foam](https://en.wikipedia.org/wiki/Sea_foam). Sea foam is essentially distilled sea spray, with an [incredibly high organic carbon content and lots of other goop](https://www.sciencedirect.com/science/article/pii/S0043135411003277). Collecting this would be as simple as walking along the beach with a vacuum cleaner, maybe with one of those screens on the front to avoid sucking up all the sand as well.
Good luck!
[Answer]
How about a rising column of gas, rather than a fog?
Your ocean contains swarms of a yeast-like organisms which "fart" a fuel gas out into the water as they feed. The gas, once released, bubble up to the surface and then being lighter than air, rise up and away.
Harvesting can thus best be achieved by capturing the gas right above the surface, before the winds disperse them beyond usefulness.
[Answer]
This question reminded me about the black sea. It has a has a habitable upper layer and a dead bottom layer. [Source](https://phys.org/news/2016-09-black-sea-lost-habitable-volume.html)
>
> As previously mentioned, biomass consumes oxygen as it decays. When there is no more oxygen, this biomass continues to decay, leading to the consumption of sulfates by the bacteria and the production of hydrogen sulfide (H2S), a highly toxic gas. The permanent stratification of the Black Sea acts as a lid over the deep waters, in which this hydrogen sulfide has accumulated and reaches now unprecedented concentrations.
>
>
>
This [H2S](https://en.wikipedia.org/wiki/Hydrogen_sulfide) can be [spilled](https://www.ncbi.nlm.nih.gov/pubmed/17696133) e.g. by asteroids or nuclear explosions. Or it just might get too much in the future and spill over from itself.
H2S is [denser](https://www.google.com/search?q=h2s%20density&ie=utf-8&oe=utf-8&client=firefox-b-e) than [air](https://en.wikipedia.org/wiki/Density_of_air) at above c.a. -10°C temperatures.
It can be used as [fuel](http://www.intertek.com/marine/bunker-h2s/) or converted to hydrogen. But it is poisonous to humans, so your sailor-fuelminers have a dangerous job.
[Answer]
How about ammonia? According to Wikipedia, Jupiter’s visible clouds are made from ammonia and water. It can be used as fuel as well. Although it would have to be frozen in crystal form to be opaque, as it is on Jupiter. So it’s not bulletproof.
Another possibility is hydrogen sulfide. Unfortunately hydrogen sulfide is colorless, but I have a workaround: **ammonium hydrosulfide** (which also occurs on Jupiter and contributes to its red color). It takes the form of a yellow-orange fuming liquid at room temperature and could be refined to H$\_2$S and used as a fuel. As an extra bonus, it could also be refined to ammonia to be used as fuel as well.
[Answer]
**Fortean rain.**
I am reading the Book of the Damned by Charles Fort. People are familiar with rains of fish and frogs (which continue to this day!) but other stuff comes down sometimes.
[source](https://books.google.com/books?id=D0LDAgAAQBAJ&pg=PA63&dq=%22charles+fort%22+tenacity+of+cotton&hl=en&sa=X&ved=2ahUKEwjP4oiS_a_kAhUrnOAKHcekBXwQuwUwAHoECAMQBQ#v=onepage&q=%22charles%20fort%22%20tenacity%20of%20cotton&f=false)
>
> That, March, 1832, there fell, in the fields of Kourianof, Russia, a
> combustible yellowish substance, covering, at least two inches thick,
> an area of 6oo or 700 square feet. lt was resinous and yellowish: so
> one inclines to the conventional explanation that it was pollen from
> pine trees-but, when torn, it had the tenacity of cotton. \Vhen placed
> in water, it had the consistency of resin. "This resin had the color
> of amber, was elastic, like India rubber, and smelled like prepared
> oil mixed with wax."
>
>
>
Rather than coming up from the ocean, this stuff falls from above. The recurring question in Fort's works is where these sky falls come from - his proposition is that there are unseen realms above us or perhaps in the solar system around us that contain things and these things can rain down.
Realms in the sky is pretty zany but fall of carbonaceous stuff from space is not zany. Fort has a whole category on "coal from the sky" which at the time he was writing was categorized with fish and frogs from the sky as picked up from earth by wind and redeposited elsewhere - meteorites were thought exclusively made of metal or stone. But it is now recognized that there exist [carbonaceous meteorites](https://en.wikipedia.org/wiki/Carbonaceous_chondrite) which seem coal like in their composition.
A fine candidate for your fog would be a rain of [Tholins](https://en.wikipedia.org/wiki/Tholin): reddish-yellow carbonaceous materials which are widely distributed around our solar system. Tholins are thought to be responsible for the reddish haze around Titan.
An aspect of Fortean rains is their extreme locality. One would expect stuff coming from space (or stuff transported by whirlwind a great distance) to be distributed widely but general that is not the case for Fortean rains which is why he invokes invisible realms not that far from the earths surface.
This stuff can dissolve into the water or sink, so collecting it from the ocean is not practicable.
Problems
1: Unless you too invoke invisible realms above the ocean there is no good reason this stuff should only fall over the ocean.
2: This is carbon, which it has to be because you want to use it for fuel. A finely distributed fog of tiny flammable particles presents a tremendous explosion risk, akin to a grain elevator or coal dust explosion. A lightning bolt would turn the entire area into a fireball. You could probably see the wall of flame coming (especially at night) and then hide in the hold of your ship and ride it out. When it went out there would not be oxygen left in your locality for a few minutes. Maybe an fire event of this sort is what ends the rain and the harvest every time, and the collectors count on being able to see it coming and hide in the hold.
I think you should have the fogs of this stuff come periodically, not constantly. When they come the boatmen go out (with masks on) and collect it with big nets. No smoking.
[Answer]
**Hydrogen peroxide**
Recently it was discovered that [microscopic droplets of water spontaneously produce hydrogen peroxide](https://news.stanford.edu/2019/08/26/water-droplets-spontaneously-produce-hydrogen-peroxide/) and that hydrogen peroxide was not lost when the microdroplets recombined into bulk water. Thus it is theoretically possible to collect the dew and refine the peroxide from water. It is potent oxidizer with wide application in chemistry, even as explosives/rocket propellant.
] |
[Question]
[
Undoubtedly, one of mythology's most iconic creatures is the centaur, a human being with his or her waist glued to the torso of a horse. For this post, we are avoiding the question of how evolutionarily feasible such a creature would be because if we were to talk about that, we'd be here ***forever!*** For now, let's look at my proposals on how it would look in real life because biology is never as clear-cut as mythology.
[](https://i.stack.imgur.com/0ROTc.jpg)
Let's start with the elephant in the room--**traditional centaurs are portrayed as having *two* torsos.** Why? Just...***WHY?*** No other animal on Earth has two separate torsos in one body simply because one is good enough. My proposal is that the transition between human and horse is in the midriff. That way, we can have two separate sternums fused into one. That still raises the question as to which organs will be in which ribcage. Here is my proposal:
## Human
* Brain
* Eyes (in all mythological humanoids--not just centaurs, but also satyrs, fauns, mers, angels, giants, elves and dwarves--the eyes have four types of cone cells, resulting in tetrachromacy.)
* Tongue
* Esophagus
* Lungs (in all mythological humanoids, the lungs make up 15% of the total body volume, rather than the typical mammalian 7%.)
## Horse
* Stomach (all four of them)
* Kidneys
* Heart (if it were human, we'd diagnose him with cardiomegaly)
* Liver
* Intestines
The next issue is what would a centaur eat? Would it eat grass, like regular horses? I say no and here are two reasons why not:
1. Grass isn't ideally nutritious, which is why some grazers spend the most part of the day mowing the lawns.
2. Grass grows low, far out of reach for the centaur's augmented torso.
Instead, let's put those hands to good use--leaves, fruit, nuts, eggs and even insects.
Traditional pictures put centaurs using modern horses. While I say we keep that traditional image, I propose that this not be the be-all-end-all. Some tribes would keep the ancestral three-toed design.
Classical image often portrayed centaurs as being sexually unrelenting. Fortunately, biology can justify that behavior--just look up ***musth***, a bi-annual condition in which a bull elephant's testosterone skyrockets, making him excessively aggressive.
This next issue is for anyone who wants to write a romance fantasy between a human and a centaur. Traditional centaurs are simply too tall for interbreeding to be merely as burdensome as regular breeding. My proposal is this--make the average centaur four to six feet tall. Which means structuring the centaur less like a thoroughbred and more like a pony or, even better, an Icelandic horse (the only one to have a fifth gait, ambling, which made this horse the ideal traveling companion during the Middle Ages).
(If you want to use the traditional thoroughbred, though, then go right ahead, but I'll warn you this--labor pains will reach critical.)
The final issue that needs addressing is color.
[](https://i.stack.imgur.com/xTZgR.jpg)
As you can see, the human half and the horse half are never in pigmentary sync. In nature, you have to be one color scheme or the other. So here's my proposal--the centaur's human half will be of either Caucasian, Asian or Polynesian design, but both halves will be the same color, be it:
* Bay
* Chestnut
* Grey
* Black
* Pinto
* Appaloosa
* Palomino
* Roan
* Smoky black
* Silver dapple
* Smoky cream
* White
Just as both halves will be the same color, both halves will grow the same coat in the winter. It's less clear-cut and more believable that way.
Are any of my proposals listed above sound, or have I created some unintentional side effects to the centaur body?
[Answer]
Seems quite reasonable. I would recommend a few changes/additions, both in keeping with tradition and to improve the model.
Firstly, on coat color. I agree that the human hair and the horse hair should match, but skin tone really doesn't need to. My cat has black hair and white skin, so if she were bald from the ribs up, she'd be mismatched too, but its perfectly normal. Most animals don't have stripes or spots on their skin, despite have striped or spotted coats, so a centaur might have brown hair and white skin, or even white hair and black skin, although it would probably be more visually pleasing to keep the two colors similar. Additionally, I would think that the human's hair would extend farther down his spine, like the mane of a horse. Maybe not all the way to the second shoulders, but at least down past the first shoulders.
Secondly on internal organs-
**Digestion:** As mentioned in some of the comments, a centaur really can't survive on human-sized organs, so I recommend horse guts in the horse part. Big lungs, big heart, big stomach, but only one stomach. If a centaur is really a mix of human and horse, it should have a human-esque stomach, capable of processing meat. Classical centaurs are archers, presumably not shooting at grass and berries, so give them big, horse-sized human stomachs. This also solves the problem of low-nutrition grass. If centaurs were only eating berries and leaves, they would be too busy grazing to get anything done, like teaching Achilles and Jason to fight. Side note, if Chiron had spent a little less time foraging and a little more time teaching, Achilles might have known to wear boots into battle instead of sandals.
**Heart:** Definitely a big horse heart in the horse chest, but I think a smaller, back-up heart should be in the human chest. Most mythological creatures are pretty hard to kill, so it makes sense that if you spear the centaur's horse-heart, a secondary, emergency heart could take over. Of course, this heart couldn't keep the centaur up and active, but it might be enough to keep him alive for a while in a comma-like state. It would eventually give out, but if he got a horse-heart transplant or something, he might pull through. With that in mind, a second, smaller set of lungs should be in the human half as well. If nothing else, it would increase the oxygen uptake and blood flow of the centaur.
**Brains:** Of course, centaurs are assumed to have human intelligence, suggesting a human brain, but brains do a lot more than just support consciousness. People say humans only use 10% of our brains, which only accounts for *conscious* use. 100% of the brain is used, just not for thinking. A lot of it is devoted to little things like telling the heart to beat, the stomach to churn, and the lungs to fill. Not to mention processing nerve signals, handling balance, and regulating temperature. A mouse and a rabbit have similar conscious brains, but a rabbit still needs more gray matter because the rabbit has more body to manage. A horse is less intellectual than a man, but the horse still needs a bigger noggin because the horse is much bigger, so I advise a secondary brain at the juncture of human and horse. The lower brain should handle basic functions, the higher brain should handle consciousness and personality. Another way to do this might be to extend the brain down the spine, eliminating the troublesome second brain. Some animals already have brain extending down their brain stems (that's why, if you do it right, you can cut the head off a chicken and he'll still run around) so it's not an impossible idea.
[Answer]
I'd just like to point this towards [this excavation exhibit](http://web.utk.edu/~blyons/centaur.htm) at University of Tennessee, Knoxville.
[](https://i.stack.imgur.com/UYCMR.jpg)
(This is a hoax, as detailed [here](https://www.lib.utk.edu/news/2008/07/the-centaur-excavations-at-volos/). But quite well done, I thought. (I saw this exhibit once; it was set up in one of UT's libraries. The case is full scale, and quite realistic looking.)
[Answer]
*An addition to @Aziri's answer*
# Anatomy
>
> Stomach (all four of them)
>
>
>
Horses don't have four stomachs, I would recommend a single, hybrid human/horse stomach because then they can occasionally munch on grass, and can digest meat= the ultimate omnivore.
>
> Heart (if it were human, we'd diagnose him with cardiomegaly)
>
>
>
An addition to help that single heart, [borrow from giraffes](https://en.wikipedia.org/wiki/Giraffe#Internal_systems) and place some additional helping pumps to the human part's arteries.
>
> Lungs (in all mythological humanoids, the lungs make up 15% of the total body volume, rather than the typical mammalian 7%.)
>
>
>
When I'm referring to human lungs, I'm really just referencing to air sacs in their place.
Structure it in an avian manner, where the movement of the front legs compressing and decompressing the air sack is analogous to how the bird's wing muscle compresses and decompresses the air sack. We separate the horse lung into two parts, a not compressing part, where the gas exchange occurs, and two air sacs, one type placed in front the main part and into a part of the human lungs, the other (from which, the air leaves the creature) is solely in the human lungs, that has a diaphragram. This ensures, that the air that passes into the lungs is always oxygen rich.
Also, apparently everyone overlooked the tiny little factor in [this question](https://worldbuilding.stackexchange.com/questions/7289/how-do-centaurs-get-enough-oxygen-to-run), that horses are obligate nasal breathers. So use the human mouth breathing again, but don't forget to give them some sort of a phlegm that can protect the throat from getting sore.
Human lungs and the long windpipe can be used to filter and heat the air with lesser resistance, which is a limiting factor in horses, but we can mess around with it freely, avoiding the dead space (not the necromorphs) issue.
>
> Instead, let's put those hands to good use -- leaves, fruit, nuts, eggs and even insects.
>
>
>
And meat. They were damn good hunters in mythology.
>
> Traditional pictures put centaurs using modern horses. While I say we keep that traditional image, I propose that this not be the be-all-end-all. Some tribes would keep the ancestral three-toed design.
>
>
>
If they live in the forest, why not to use deer lower bodies instead?
There's also the spine,
Solution: Snake, more precisely: it's segmented spine.
[](https://i.stack.imgur.com/sudIot.jpg)
---
# Physiology
>
> This next issue is for anyone who wants to write a romance fantasy between a human and a centaur. Traditional centaurs are simply too tall for interbreeding to be merely as burdensome as regular breeding.
>
>
>
There's another problem with this, click the link to see it, if you dare: [MR. HANDS](https://en.wikipedia.org/wiki/Enumclaw_horse_sex_case#Death) (spoiler: he died, reasons: perforated intestine)
By the way: if we're here, I would give centaurs a longer gestation period, so the human and the horse half will be equivalently developed.
>
> make the average centaur four to six feet tall. Which means structuring the centaur less like a thoroughbred and more like a pony or, even better, an Icelandic horse (the only one to have a fifth gait, ambling, which made this horse the ideal traveling companion during the Middle Ages).
>
>
>
That's [not true](https://en.wikipedia.org/wiki/Horse_gait), any breed of horse can learn gaits and imagine if those horses want to learn the moves. It's way easier, and an extra layer of narrative *fluff* if you want to detail what type of movement they use in various situations.
---
# Additional side effects:
I would also give a thicker skin and bones to the human body to explain the +1 natural armor, and the longbow usage, we've seen in D&D.
This would require stronger bones in the forelegs, but I think it's easy to come up with a solution for that.
---
# Summary:
Powerful, fast and tough, centaurs have the upper half of a human. However this part, aside from the air sacs (protected by the ribcage (this is, why centaurs have two.)), the windpipe and the esophagus, which two are both protected by a cartilage structure which is similar in segmentation to the spine.
Thus the human part is very resilient and flexible as it mostly contains muscle bone, connective tissue, and the myoglobin reserves.
The horse part is optimized for longer endurance runs. But the myoglobin reserves, the avian lung structuring, and the hybrid nasal and orofacial breathing also enables them to perform in a sprint just as well.
Their communities are mostly hunter-gatherers, occasionally farmers and a small plus: They can digest the other parts of the wheat too.
Their numbers and low, mainly because of the long gestation periods, and can only increase slowly.
] |
[Question]
[
Nagas are a half-human half-snake hybrid, similar to centaurs in that the beast has a human torso and a snake lower body. [This question](https://worldbuilding.stackexchange.com/questions/39912/if-a-naga-was-7-tall-how-long-would-it-be) provides an overview of probable physical characteristics of this creature. To quote from the accepted answer:
>
> So to start I think you need ~24' long body as a minimum [for the naga] if they can
> generally function at the 8' height. and 18' if they are normally 6'
> but can loom up to 8'. These would be minimums, and the 'tails' would
> be fairly large and thick. If they tapered down like a snake to fairly
> small diameter, then you might be doubling the length.
>
>
>
[This question](https://worldbuilding.stackexchange.com/questions/35282/how-would-a-person-who-is-a-snake-from-the-waist-down-move-around?rq=1) also asks how this creature would move around (though it uses a different term for them). From the accepted answer:
>
> [I]t would use all four types of movement [concertina, serpentine, sidewinding, caterpillar], depending on terrain;
> however, it would likely use serpentine movement the most.
>
>
>
To summarize the features I desire this creature to have:
* Human (or human-like) torso
* Snake (or snake-like) lower half
* Venom capabilities if possible (either via a bite, or spitting, or possibly venom-infused saliva like a komodo dragon, or heck all three)
**In the spirit of the [anatomically correct series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798), what would it take to make this creature exist?**
I would like an explanation that realistically explains how its biology would function. I would love to hear points on whether it could be a combo of mammalian or reptilian features verses one or the other.
[Answer]
This may be one of the simplest mythological creatures to make "real", or at least more realistic.
One way this could happen in a parallel universe is if humans (or a human like species) evolve in such a way that the genes for [sirenomelia](https://en.wikipedia.org/wiki/Sirenomelia) give them an evolutionary advantage. If this seems far-fetched, imagine that if they spend a lot of time in water, this could be a first step to develop a body that is fit for swimming. Just look at a seal's skeleton.
Later on, they either evolve to climb trees - perhaps they live in mangroves, or in a river in a rain forest - or to constrict their prey, so having a longer "tail" (actually a lower body) helps. Rather than the legs getting longer, it's the chest and abdomen that elongate.
Anatomically, a naga-like being makes more sense than a centaur. For a laysperson observing it, the humanoid side would seem to fit onto the snake side chest-on-abdomen, rathen than abdomen-on-neck as a centaur would.
Let's take a look at a snake's internal anatomy (taken from [Wikipedia](https://en.wikipedia.org/wiki/Snake)):
>
> Anatomy of a snake. 1 esophagus, 2 trachea, 3 tracheal lungs, 4 rudimentary left lung, 5 right lung, 6 heart, 7 liver, 8 stomach, 9 air sac, 10 gallbladder, 11 pancreas, 12 spleen, 13 intestine, 14 testicles, 15 kidneys.
>
>
>
Most snake organs are elongated, and those that come in pairs are placed one in front of another, rather than side-by-side. You could rearrange both human and snake organs in your naga, though I imagine the snake anatomy would be more prevalent.
This is how I picture it, supposing the creature is 20-ft long and has a navel where a human would:
* **The chest:** a naga wouldn't have a sternum, nor a diaphragm (it'll use its intercostal muscles for breathing).
* **The lungs:** at least one of them would be long, and extend way below the navel. That one would be divided in chambers, so that if punctured, that chamber can be isolated and the creature can continue breathing. The other lung may be a normal human lung, probably atrophied.
* **The heart:** it will be much bigger than a human's, and like that of a snake, can move up and down. Due to the sheer size of the naga, it may actually have a secondary heart, of maybe even three (this is not a feature snakes have, though).
* **The abdomen:** it will have ribs almost all the way down do the end. The stomach and bowels would take up most of the space of the snake body, along with powerful muscles surrounding them. This part of the body will be thicker than a regular human's.
* **The skin**: if the naga is to move like a snake, they will need a really thick skin. If the naga evolved from mammals, that would be some really thick hide, like that from a hippo or elephant. Now this is where it gets interesting: friction with the ground would damage this skin a lot, so they could be constantly secreting some oily substance (evolved from sweat) to lubricate their way around, and the snake part of their body could be covered in thick fur. If you want a more traditional snake-like naga, though, you can give it scales, since reptile scales are made of the same protein as mammal hair and nails, and rhino horns.
I am no biologist, so the figures in what I am going to say next are completely made up. If straightened up, your naga would be somewhat four times longer than a human, with a close width. For it to have the same metabolic rate, it would probably need to eat four or five times as much as a normal person. So a naga would probably fare better if it is cold blooded - or something in between, like dinosaurs are thought to be by some paleontologists. Whether it is cold, warm or semi-warm blooded, though, it should really gorge itself when eating.
Last but not least, you could have their humanoid side look human, but I think a more lizard like look is not only cool, but also more functional. A mouth that can open up to a really large size and a stretchy throat would allow it to swallow really large amounts of food whole.
One depiction of such a creature that I really like is the viper from X-Com 2:
And here with a human, for size comparison:
Not as long as the one being discussed here and in the other question you linked to, and thinner than I'd have it, but a nice starting point for you to build until you reach a more realistic design.
[Answer]
A traditional depiction of the Naga in Hindu mythology is not a reptile-mammal hybrid, but a fully reptilian with human like aspects( most notably hair in some texts). With the exception of hair, you could use fully reptilian anatomy.
Start with a upright Indian Cobra(latin Naja Naja) (the closest animal representation of a Naga), add in muscles to support the arm just under the flange. Add whatever human features to the head, remove the flange, and scale up. This will be near identical to historic depictions.
[Answer]
A naga could have evolved from an arboreal frog that grew larger to hunt larger prey. They might evolve more efficient lungs, in order to supply oxygen to the body. They would also evolve to grab onto branches, as they would be too large to stick to things. They may evolve to grab prey with their long hind-legs, as their legs would be stronger than their tongue. This might lead to the pelvis extending outwards, allowing the frog to reach further. Their skin might become thicker, in order to protect themselves against predators and drying out. They might also gain armoured scales. They might also start to practise parental care, by building nests to keep their tadpoles in. They might evolve to create nutritious secretions, which might lead to the formation of breasts. Their tadpoles might also evolve to coil around their parent if the nest is in danger, to allow them to escape. This could lead to the tail being kept into adulthood, which might free up the hind-legs for hunting. In order to hunt better, they might gain a neck to look around. They might further increase in size. In order to more effectively eat their prey, they might evolve to have stronger teeth, as well as a sharp ridge along the lower jaw, and a sturdy skull and jaw. This could lead to an increase in the amount of food they can eat, which might lead to them becoming endothermic. Due to competition from other arboreal predators, they might start to live on the ground. These ground-dwellers would likely slither using their tails, and would hold themselves up with their arms. Eventually they would be able to stay upright without using their hands. Due to their hands being free, they might evolve to use them to restrain prey. They might also evolve to lunge at prey to grab them. This might lead to the hind-legs shortening, with the tibiotarsus annd metatarsals shrinking into a wrist. This allows all four limbs, alongside the mouth, to be used to grab prey. They might also increase in size. In order to take on larger prey, they may evolve to secrete venom into their mouth, in order to gain a venomous bite. This venom would likely lead to the evolution of fangs for injecting venom. They might start hunting in packs, in order to get prey too large to kill alone. This would lead to them forming a social structure. Humans might enter their habitat, and bring new creatures. This could lead to a more abstract communication, to allow them to target new creatures. This abstraction would lead to language, which would lead to them becoming sapient. These changes would result in a creature quite close to a naga
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Well I have two interesting possible options (but the first answer above still being the best if you want totally humanoid nagas), so:
1. Cobras "recovering" arms, well I dont know much about Hindu culture, but in the images that appear when you search "naga" on google are the mentioned humanoids that you want but with multiple arms, so basically is less possible that some snake snake could recover arms like the other tetrapods, but hooded cobra could get some stragne new limbs by the ribs of the hood, with the constan use of the erected position could turn this to arthropod like limbs, this could be useful for trap preys, after this bringing to a more humanoid an squared head with the requiered stereoscopical vision and if well snakes are not very intelligent creatures and the intelligence still being and mistery, there are some intellingent reptiles like the Cuban crocodile and the tegu lizards, so eventually a sanke with a different life style could gain intelligence.
2. The other option is almost the same but applied to anguidae reptiles which can get large common arms from its legs.
I liked the first answer about the sirenomalian nagas the possible anatomy that could have dont convince the legs fusion and the pelvis form even the column suport dont convince to erect a body of that weight, probably needs an entire strcutural change also other problem that could bring is the reprodcution an breeding, for this reason I thought that a human based naga is hard to get.
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[Question]
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Background: I'm writing a nomadic society that lives in the shadow of their planet's rings. These rings are as wide as possible to grant them the biggest shadow. The planet has an incredibly long year to give them time to travel as the shadow moves. I know some have already asked what the sky looks like from the surface of the planet *in general*, but my story is set entirely in the shadow.
**What does the sky look like from within the shadow?** Is the sky closer to blue or black? Day or night? If the rings block a sizeable amount of sunlight, but not all, would they simply experience the equivalent of a cloudy day, with extraordinarily bright nights? If the planet has a few small shepherd moons in the ring plane, would they be visible in the shadow?
Thank you!
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I think the result will be very similar to what happens here on this Earth during a solar eclipse. I like this quote from <http://www.eclipse2017.org/2017/what_you_see.htm>:
>
> You'll get the shrinking sliver of Sun, which is kind of cool but is not the real show. As the sliver thins, though, you get the very weird atmosphere that surrounds an eclipse, which is very difficult to describe. As the sliver of sun gets thinner and thinner, the sky darkens a bit, and the light around you takes on a weird, "clearer" quality. Everything seems sharper and clearer, though darker. It's kind of like if you were squinting, and everything seemed much clearer to you. It's very strange, and it's a very powerful effect on your senses.
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>
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Whether your world gets this full effect or just a partial effect, such as what one will see if not directly on the line of the eclipse, will depend on the density and opacity of the particles in the rings. Even a partial eclipse produces a similar sensation.
I barely remember the one in 1979, and I am greatly looking forward to the one upcoming. What I do remember was that it got dark, but not really. You could still see outside, not at all like at night-time. The sky was blue, but more like navy blue than the normal azure. Like the linked article says, it's really hard to describe- it's just, *weird.*
You can try an [image search of sky during an eclipse](https://www.google.com/search?q=sky%20during%20solar%20eclipse&espv=2&biw=1658&bih=919&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjsnerC6qbRAhVD6GMKHQpYBMMQsAQIGQ&dpr=1), but the photos don't do justice to being there. If you're in the right place, you just have to wait eight months to get your full complete answer.
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For reference, here is an image of Saturn, where you can clearly see the shadow cast by the rings on the planet's surface:
[](https://i.stack.imgur.com/dBsdV.png)
As you can see, the shadow is quite dark. It's also quite wide. If you were standing in the middle of that shadow, at that time of year, the sun would be entirely covered by the rings for many miles in every direction, and you would only see whatever glimmers of sunlight were able to penetrate the icy mass of the rings. The sun would appear as though shining through a cloud - how heavy a cloud is up to you, as it depends on how thick the rings are. With the shadow as wide as it is during the time of year depicted, there would be no glow around the horizon as is described during a total solar eclipse on Earth, because everything for many, many miles around falls under the same shadow. The rings themselves, though casting the shadow, are backlit by the sun and so appear as the brightest thing in the sky, stretching from horizon to horizon in a glowing arc.
Another important thing that you'll notice in the picture is that the ring shadows do not run perpendicular to the planet's axis of spin. This means that, during the course of a day, you won't stay in the same place relative to the shadow, and will possibly experience gains and dips in brightness as you move past gaps in the rings. To illustrate:
[](https://i.stack.imgur.com/0dfA0.png)
The red dotted line shows the course that might be traveled by an observer standing on the planet's surface who is trying to stay more or less in the rings' shadow, as the planet spins around its axis over the course of a day. As you can see, in this particular case, there is a time around mid-day (just under that moon) when the sun edges close to a gap in the rings (i.e., the observer passes close to a gap in the shadow). From the surface, this would be experienced as a bright glow approaching from the southern horizon, and perhaps the edge of the sun beginning to peek out from behind the "cloud". Your nomads may want to time their travels so as to avoid any such gaps, or at least to encounter them around evening, when the sun is less bright. On the plus side, the timing of these bright spots will be a handy navigational aide to let them know if their travels are on schedule.
Of course, everything changes as the planet moves around its sun throughout the year. The rings move north to south and back again as the seasons change, growing wider and more curved as they move away from the equator and dangerously narrower as they move close. I'm guessing that your nomads are following the shadow of the rings because they don't tolerate sunlight well. In that case, there will be two times of the year which are difficult for them. During the spring and fall equinoxes, the rings will be oriented edge-on to the sun, and will probably not be wide enough to cover the whole disk. Looking up, you will see a glaring sun with a dark line through it, shining down with perhaps 90% of its full fury. At these times, it might be necessary for the nomads to travel only at night. Since they are by definition always staying on the winter side of the planet, these spring and fall times are also the hottest seasons of the year, even were it not for the waning protection of the shadows.
One more interesting thing: because the rings (Saturn's rings, at least) are largely made of ice, it's possible that you would get cool optical phenomena like this, if they're thin enough for the sun to shine through:
[](https://upload.wikimedia.org/wikipedia/commons/thumb/9/93/Halo_in_the_Himalayas.jpg/800px-Halo_in_the_Himalayas.jpg)
Expect this especially during the solstices, when the shadows (and the nomads) have traveled to near the planet's poles, and the sun passes through the rings at its most oblique angle.
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In addition to the dimming effect, also consider the effect of larger rocks/moons within the ring. Chances are the sunlight would constantly be flickering as larger and smaller satellites passed by, partially eclipsing the sun.
There might even be a cycle or pattern to the flickering/eclipses based on the orbital period of the rings. Maybe one section of the rings happens to have a greater number of large bodies, so every X days there is a day with a large partial eclipse every half-hour or so. The nomadic society could use this phenomenon as part of their calendar.
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Cobaltduck is on the right track with the idea of a solar eclipse but now that it's been a year, I can tell you how it was when I was actually at the eclipse.
For starters until the total solar eclipse it is impossible to tell that something is passing in front of the sun by looking at it. The only real "sign" is a continuous dimming that happens around you. This dimming is most equivalent to being in a sandstorm or a hazy day in that everything seems to get a little darker and redder. The exception is that usually when you get this kind of dimming your vision decreases from the particulate matter but during a partial eclipse it stays as clear as the day you had before.
The sky itself creates a fun phenomena during a total eclipse where the area covered by the shadow is dark and almost night like (stars aren't really visible to the naked eye but bright planets can be seen) but the areas outside the shadows, on the edges of the horizon, are still a bright daylight blue (assuming that the day is clear). During a partial eclipse the sky does darken a little and lose its colr but it is still mostly blue but takes on the same hazy feeling as the rest of the area. So the way the rings looks can vary from just a bit dark to black then depending on the size of the shadow the edges of the sky will still look normal.
As for Shepard moons their shadows would cause partial eclipses as the pass over the sun unless they are big enough to cause a full eclipse. Your nomads likely wouldn't see it however as Shepard moons create gaps in the rings that would create strips of lightlight your nomads would avoid.
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
I've been searching for hours, and most formulas I can find use complex/imaginary numbers or variables that I don't know or can't find out (such as the imaginary part of the planet's love number, which leads into the complex number thing). What's the "simplest" equation you guys know of?
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[Wikipedia](https://en.wikipedia.org/wiki/Tidal_heating) gives the formula for the tidal heating $\dot{E}$ as
$$\dot{E}=-\text{Im}(k\_2)\frac{21}{2}\frac{R^5n^5e^2}{G}\tag{1}$$
where $R$ is the radius of the satellite, $n$ is something weird called its [mean orbital motion](https://en.wikipedia.org/wiki/Mean_motion), and $e$ is the eccentricity of its orbit. I actually don't like this representation. [Another way to rewrite](http://large.stanford.edu/courses/2007/ph210/pavlichin2/) it uses the relation
$$\mu=a^3n^2\implies n^5=\left(\frac{Gm\_p}{a^3}\right)^{5/2}$$
where $\mu\equiv Gm\_p$, with $m\_p$ the mass of the planet. Therefore, we find that
$$\dot{E}=-\text{Im}(k\_2)\frac{21}{2}\frac{G^{3/2}m\_p^{5/2}R^5e^2}{a^{15/2}}\tag{2}$$
That's kind of ugly, but it gets rid of $n$, and so all of the other variables are either properties of the moon's orbit, or physical properties of the moon or planet.
# Calculating the [second Love number](https://en.wikipedia.org/wiki/Love_number)
I ignored that $k\_2$ - called the second Love number - because it's kind of tricky to calculate. I usually ignore it completely, and substitute in something like $0.02$ or $0.03$ for $\text{Im}(k\_2)$ for satellites like our Moon (see [1](http://adsabs.harvard.edu/full/1992EM%26P...56..193Z) and [2](https://www.jpl.nasa.gov/releases/2002/release_2002_37.html)). But if you really want to calculate it, go ahead.
My reference is [Hussman et al. (2010)](http://www.sciences.univ-nantes.fr/lpgnantes/lpg/fichiers/tobie-g/PUBLICATION/Hussmann_et_al_10.pdf), specifically, $\text{Eq. }32$:
$$k\_2=1.5\left(1+\frac{19}{2}\frac{\mu\_c}{\rho gR\_s}\right)^{-1}$$
for rigidity $\mu\_c$, surface gravity $g$ and radius $R\_s$. $\mu\_c$ can be calculated as
$$\text{Re}(\mu\_c)=\frac{\eta^2n^2\mu}{\mu^2+\eta^2n^2},\quad\text{Im}(\mu\_c)=\frac{\eta n\mu^2}{\mu^2+\eta^2n^2}$$
and
$$\mu\_c=\text{Re}(\mu\_c)+\text{Im}(\mu\_c)$$
for elastic rigidity $\mu$, viscosity $\eta$, and [mean motion](https://en.wikipedia.org/wiki/Mean_motion) $n$, defined as $2\pi$ divided by the period of the satellite's orbit. $\text{Re}(z)$ and $\text{Im}(z)$ denotes the real and imaginary parts of a complex number. In other words, if
$$z=a+bi$$
for real numbers $a$ and $b$, then
$$\text{Re}(z)=a,\quad\text{Im}(z)=b,\quad z=\text{Re}(z)+i\text{Im}(z)=a+bi$$
$\mu\_c$ is an imaginary number, and therefore so is $k\_2$. We can simplify this a bit, though. If we set
$$a\equiv\frac{19}{2\rho gR\_s}\text{Re}(\mu\_c),\quad b\equiv\frac{19}{2\rho gR\_s}\text{Im}(\mu\_c)$$, then
$$k\_2=(a+1)\frac{1.5}{(a+1)^2+b^2}-\frac{1.5bi}{(a+1)^2+b^2}$$
and so we have a much better expression for $\text{Im}(k\_2)$:
$$\text{Im}(k\_2)=-\frac{1.5b}{(a+1)^2+b^2}$$
There. I hope that was fun. Again, though - you're *much* better off just substituting in typical values. $k\_2$ has been studied and measured in a lot of detail.
# Scaling based on Io
Measurements have done on the relatively significant tidal heating of [Io](https://en.wikipedia.org/wiki/Io_(moon)), one of Jupiter's moons. A reasonable value for $\dot{E}$ [is $\sim10^{14}$ Watts](https://link.springer.com/chapter/10.1007%2F3-540-27053-1_7). We also know additional parameters:
* [$\text{Im}(k\_2)\approx0.015\pm0.003$](https://pdfs.semanticscholar.org/162c/064082104ac2d9f52d65dbaaf9e49e456226.pdf)
* $R\approx1800\text{ km}$
* $e\approx0.0041$
* $a\approx4.2\times10^5\text{ km}$
Therefore, letting $M\_J$ be the mass of Jupiter, and plugging in $G^{3/2}$, we find that, assuming a similar internal model as Io, the magnitude of $\dot{E}$ is
$$\dot{E}\approx10^{14}\left(\frac{\text{Im}(k\_2)}{0.015}\right)\left(\frac{m\_p}{M\_J}\right)^{5/2}\left(\frac{R}{1800\text{ km}}\right)^5\left(\frac{e}{0.0041}\right)^2\left(\frac{a}{4.2\times10^{5}\text{ km}}\right)^{-15/2}\text{ Watts}\tag{3}$$
which is hopefully easier to work with than $(2)$.
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[Question]
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Comics are full of superheros with super strength. These heroes punch through walls, lift and throw tanks, and wrestle with buildings.
But that's superhero physics. The fact is that without leverage, you'll likely knock yourself back from a significantly strong wall before you break it - it weighs more than you. You may punch hard, but you're not going to send people flying like meteors, because your arms just aren't that *fast*. And trying to lift a building is a good way to bury yourself in the ground.
Now for this question, I'm mostly concerned about how hard you punch/hit. So:
**If some humans are a million times stronger, but not any faster:**
**\* What factors would be most important for how hard they punch? Is it still strength, or do speed or mass become more important?**
Bonus questions:
* How hard would they actually be able to hit? Is there a formula you can use to determine this?
* How much of a difference does it make if they're braced and can apply full force, vs not being braced?
Assumptions:
* They're tough enough to take out the damage they would do to their bodies. So these humans aren't going to rip apart their bones and cartilage just by moving around.
* Define the strength of a punch as the amount of [force](http://hyperphysics.phy-astr.gsu.edu/hbase/flobi.html) impacted to the target.
* Obviously these humans would have incredible lift and grapple capabilities - I'm just concerned here about how much force they can put into a single impact.
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In comments, I suggested that we should use force instead of energy as a measure of punch strength. I'm not entirely sure it is the most useful measure, but its what boxers use when we [measure](http://www.livestrong.com/article/538379-how-to-measure-force-on-a-punching-bag/) the strength of their punches. It also yields really nifty results, which is always a bonus in worldbuilding exercises.
You made the assumption that they can keep their body together when using this super strength to punch. However, nothing says the world around them can keep together, so we're going to have to model the forces holding together objects like people and safes. There are molecular forces which try to hold together an object. If you strike an object, the object "responds," typically at the speed of sound for that medium, distributing the force across the bonds. Ideally, it would distribute the force evenly across the object, but in a real world, sometimes that doesn't work. If superman punches a safe with enough force, he can force the object to deform enough that it cannot distribute quickly enough. In that case, some of the molecular bonds fail, and we see the end result of superman punching a hole right through the safe.
So we can model everything in the world besides our superhero as a bunch of small bits (molecules or larger) rigged together with springs which can rip apart if put under too much strain. It doesn't perfectly model physics, but it does describe the world well enough to give us [hilarious slow motion videos](https://www.youtube.com/watch?v=90VyvOhPmA0).
So the question is what can they do without bracing. Because our superhero is being modeled as "tough" enough to not rip apart, we can treat them as one lump body, with a mass and a corresponding center of mass. If the superhero only uses his superhero strength in a way which does not move his center of mass (meaning his fist goes one way, and his body moves slightly the other way to keep his CM still), he can actually accelerate to any speed he pleases (and speed at impact \* mass of flying object = force). So super strength actually does help!
However, if you punch at ungodly speeds (speed of sound, relativistic speeds, etc.) the world around you may not withstand the impact. If you try to maximize your force, by maximizing speed, you don't necessarily maximize damage. If you punch Lex Luthor in the gut, you really don't want the damages to be limited to a fist-sized hole. I'm sure he'd find a way to work around that impediment. You really want to do more damage than that. Somehow you want to hit in a way that hurts his entire body!
This is harder because we've hit the limits of what you can do with just the invincible parts of your body. To do more damage, we need to start using all the resources available to us, like the soft squishy body of flesh right in front of our invincible fists. This is going to sound a bit strange, but we're going to hit softer to hit harder!
Visuals time! We need something on a human scale to capture what we're trying to do. Let's say our opponent is something soft, like a nice moist cake standing upright (maybe the cake is in the shape of a punching dummy). We want to use one of our fingers to strike the cake and do as much damage as we can. Sure, we can just ram our finger through it as hard as we can, but that only makes a 1cm wide hole in the cake. However, what if we had something soft and squishy, but bigger to help us out. Soft... squishy... tomato! For our visual, let's pretend we have a tomato in front of our finger, in front of the cake. I have no idea how this got so strange so quickly, but the visual works out. If we unleash full force, we squish a hole through the tomato, into the cake, but we can only make a finger-sized hole. However, if we can unleash *softer*, we can give the tomato to accelerate into the cake. Now we can make a tomato-sized hole! All we have to do is hold back just enough to avoid breaking the tomato's skin with our strike.
Okay, normal-human scale imagery aside, our superhero needs to punch with just enough force to accelerate the region they hit to use those molecular bonds to accelerate the nearby region. Then this region needs to accelerate just fast enough to accelerate a bigger region, and so forth. By hitting softer, we hit harder!
This means the effect of super strength is also dependent on your ability to strike wisely, not just hard. If you can strike in a direction which takes advantage of the strong directions of a bone, you can affect a much larger region. You're literally using their strength against them.
To strike harder than that, we need to work *with* our opponent. Yes, first we hit softer, then we work with our opponent. A lot of things in the body, like non-innervated muscle tissue, is really bad at transmitting forces for us. We'd do a lot better if we could convince our opponent to tense their muscles at just the right time. This is not easy. The easiest way to do this is to make them flinch before you punch them. Then they tense up, and the muscle transmits your punch better.
There is a school of thought which suggests that the most powerful punches are not the big ones, but the small ones. The smaller the punch, the more you can feel what your opponent is doing, and adapt to them. If they tense in one way, you adjust yourself to take advantage of that particular way they tensed up. This could hypothetically lead to punches which begin to use the opponent's mind against them. If you can figure out how they're thinking about the punch, and adapt what you are doing to encourage them to give up a mental high ground in return for a physical high ground, you can strike them right in their core, destroying their will to fight, rather than just their ability to.
So super strength is useful because you can generate as much force as you want. However, while a force of four tons may crush bodies, a force of four ounces, applied properly, may crush a soul.
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I agree with OP's assertion that strength and speed are essentially two different things. And there is rigidity, which is another factor in punching. Here I explain 3 levels of strength and speed.
# 1- A Punch That Shatters Bones!
This is the first order of strength and speed. People like that exist in hundreds in our world. One punch from a non-gloved heavyweight boxer and goodbye to a few ribs of the opponent. The only thing that matters here is power delivery.
# 2- A Punch That Sends People Flying!
This is the next level of strength and speed. Here you not only require much more strength, but also quite a faster transfer of energy too. Think about a person hitting another with a baseball bat. We know it shatters bones (like a boxer's punch). Now think about a baseball hit that sends the person flying 5 feet away in the air. The bones are STILL shattered but the swiftness of impact also sends the target flying back. It is sort of like a a shotgun hit. It is blunt impact, but very energetic and very quick. Surprisingly, you do not expect such a punch from boxers (enough energy, but too slow delivery) but from kungfu masters. There are some styles with open palm fighting (ba gwa and ni zhong etc) where the impact is so swift that it really sends the opponent flying 3-4 feet backwards. However, since a palm has a much larger area and is not as hard as knuckles of a punch, the bones are not broken.
With strength alone (and not speed) you **can** send your opponents *sliding* on the floor (if it is smooth and lubricated) but not *flying* in the air.
# 3- A Punch That Goes Through The Person!
Now this is the epic end of speed. Imagine a person getting hit with a M16 bullet versus a person getting hit with a shotgun shell. The person hit with shotgun pellets would go flying but the person getting hit with the rifle bullet would stay standing and have a hole through him. That is speed!
To punch through a person (or wall) you would need *extremely* fast energy transfer. You would also require *really* high levels of energy AND a truly rigid surface. There is a Filipino master who pokes through coconuts with his index finger, but there is no master who could pass his open palm through the opponent. That is too much area and the palm is too soft to crack open a gash in the opponent's skin.
# Lifting Buildings
Now that is interesting. Here we are not only talking about extremes of weight lifting (power) abilities, but also the ultimate strength of skeleton too! Weight lifters often have short, stocky physiques to compensate for carrying 200-300 kg weights. To pick up a whole building ...
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One thing the other answers didn't touch on is bracing, and it will definitely help. If you have a solid object to back against then you can apply that much extra force in the direction of your punch. For example a super strong human against a tank is not going to be able to do much, they may just about be able to dent the armour if they take a run up but even that's unlikely.
However if they get their hands in gaps in the tanks armour or get something like a wall to give them a brace then at that point they can actually apply their strength. A super-strong person against a tank with real-world physics is not going to punch their way through, even with a wall to brace against they are more likely to move themselves backwards than damage the tank.
Instead they are going to rip it apart.
Something else to keep in mind is that materials in large scale behave differently, for example think of a film where someone grabs a fire truck and hits another target with it. Is a fire truck really going to act like a solid club in that case or is it going to bend and deform with every impact?
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## Slow but unstoppable punches
(Normal) [punching power](https://en.wikipedia.org/wiki/Punching_power) is determined by about 5 factors: footwork, weight shifting, stepping in during a punch, pivoting the arm, and lack of arm punching. This mean that when impacting the arm should already be straight, as it needs to transfer the energy of the impact through the rest of the body. The stronger a person is the better they can do this.
If you're not defying physics, this means that a person's punch is always somewhat limited by their mass, and their ability to launch themselves towards their opponents using their surrounds. If the superheroes are flying, the difference in speed between the hero and it's target also equates into the impact of the punches.
If you prefer quick punches, where the punching power comes only from the speed and impact of the arm, the power is determined by the speed and arm mass on impact. Since an arm does not contain a lot of mass, the impact will be less, unless the speed is increased so much, that the mass of the arm becomes irrelevant. You could also rule that your heroes are so good at punching they can set their body's mass behind each quick punch. You might be breaking the physics a bit if you want this.
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Force is always Mass times Acceleration. For a given amount of mechanical power in the arm propelling the fist there is an upper limit on the force exerted .. the mass of the fist.
Oh .. Err; You also have to account for friction against the medium the fist is moving in. If the punches length of travel is long enough heating effects could play a role.
Strong muscles mean high acceleration is possible, as is immense pressure. Throwing a punch means propelling the fist at hundreds or even thousands of metres per second so that our hero can smash walls, pierce metal, and detonate bodies.
a point of information for Youstay Igo about punching holes in things. High level energy transfer is not needed. I can punch a hole in sheet metal by pressing a cutter head thru the sheet at low speed using only about 100 foot-pounds of pressure (my arm + a short lever) because I am creating a localised shearing action at the edge(s) of the cutter head. The "trick” is that there has to be a matching hole in a well anchored backing plate on the other side of the sheet of metal that acts to concentrate the force applied in a very narrow region of the sheet, breaking the crytalline structure of the metal and severing the plug from the surrounding metal, while resisting the pressure being applied.
To punch a hole in something that is not braced against moving you must apply the shearing force against the inertia of the rest of the object's mass .. and that means applying it at a speed to fast for the mass to respond by moving away. Consider the movie effect of punching through a plasterboard wall to surprise our hero sneaking down a hallway .. a fast punch gets through the wall, but a massive weight may be leant against the same wall, at low speed, without even dimpling the surface.
so .. the answer is complete. To calculate the force applied determine the pressure applied to the bones of the arm by the contracting muscles, and the time it takes to move the fist on the end of the arm from rest to contact with the target. If that force is greater than the shear resistance of the material impacted then the fist punches a hole in the target, if not the target moves. If the target cannot move the pressure in the material builds up and you have to think about bursting, crystaline deformations or potentially, fusion as atoms are crushed into one another.
I have revised my answer to make it better apply to the question asked.
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[Question]
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I'm designing a town in the Ozark mountain range circa 1871, and am unsure what population size to give it.
>
> River Bend is an isolated town in the Ozark highlands of Arkansas founded in 1845 on the promise of mining lead, zinc, and iron. The town made a modest profit until Chuck Goodnight hit diamonds five years later: the mining town boomed for the next eleven years until the Civil War started, and the mine was closed as the workers became soldiers.
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> The War is now six years behind us (1871). Chuck Goodnight and most of his workers are as dead as the Goodnight mine, and River Bend is dying too. Its remaining population ekes out a living through trapping and lumber, sending furs and logs downstream on the nearby river.
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* What population range would be appropriate for River Bend in its heyday just before the War?
* How small might its population be ten years later in 1871?
* Is it even reasonable for the town to not be completely abandoned a decade later?
[Links to cited sources, wherever possible, are appreciated: not because I don't trust you but because I want to add them to my own resource stockpile.]
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Before the war the population would likely have been about 1.5 to 3 times the number of miners. Most of the non miners would have been in the business of extracting the earnings of the miners. If the mine employed 2000 miners (a good sized mine no doubt), the town could have been 3000-5000. More likely however with just a single mine you are looking at 500 miners and a total population around 1000.
[Gold and silver mining towns often boasted a dozen mines](http://www.legendsofamerica.com/ca-holcombvalley.html) and quickly boomed up to 20k to 50k people and became ghost towns with in 10 years when the precious metal veins were mined out. Gems just did not have the same boom effect. Certianly it would attract miners, but metal veins tend to be easier to find than gems. Gems also require more work to get them ready to sell. For this reason these mines boomed slower and busted slower as well.
If the town is still eeking out a living I would guess it would be because there was still just enough left to mine to support a few dozen miners. Such small settlements tended to be the types that the more solitary mountain men that survive through trapping and hunting. [These men are also probably prospectors, always on the hunt for the next big strike of ore.](http://www.ushistory.org/us/41a.asp)
Unless there is a river nearby then lumber is not a viable trade as getting the lumber out to where it can be utilized at this time is not profitable. The wagons of the day just were not strong enough to handle the rocky rutted trails out of the mountains and hills while carring a few tons of logs. Since the city has busted most lumber being used in the town is going to be canabalized from the abandoned structures already in the town.
However since the town is called River Bend I am guessing there is a river nearby. So an extra 50 - 100 lumberjacks could certianly be working the area. Though even a small lumberjack crew of 10-20 could survive in the town. I would guess that the town is down to around 100-200 total inhabitants.
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This [site](http://www.encyclopediaofarkansas.net/encyclopedia/browse-entries-menu.aspx) might be of interest to you. For example, [this page](http://www.encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=884) give the historical population (based on census) of Franklin county from 1870 to 2010.
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Would a world be able to sustain a constant low pressure area such that there would be a constant wind from one side to the other?
Imagine that on one side of the world is a desert with some rocky mountains (presumably the source of the sand), over which lies the high pressure area. To the East is a liquid oxygen sea over which forms the low pressure area.
***Note:*** The atmosphere is cold enough to support a liquid oxygen sea.
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Yes, although I don't know about your liquid O2 sea. If the planet is tidally locked, such that one side is always facing its star while the other side is always facing away, it's clear that there'd be a pressure difference at first. Say, however, that that atmosphere is a very soluble gas in the oceans. If it's cold enough and the gravity of the planet is enough (to exert a larger pressure than the earth), it's possible that the atmosphere would dissolve to some extent in the ocean and sink. Since on the other side, the ocean is boiling and generally being really hot, liquid would have to replace it, which would probably be from the deep. You'd get, across the planet, a cycle of the oceans to the cold side on the top, to the hot on the bottom, and of the atmosphere, from the hot to the cold on all sides.
Of course, there's a simpler way, one quite similar to the prevailing winds on earth. Again, you'd need a tidally locked planet, but the only odd thing would be that the ocean/land would have to absorb much more heat than the atmosphere. Because of this, air close to the ground would heat drastically up. Assuming it's over an ocean, it'd also gain a lot of moisture. Colder air above would move downwards on the hot side to replace the heated air. Much like a tornado, the moist hot air would be trapped under the fast-moving higher cold air, and would have to move against the ground towards the cold side until it finds a place to punch through the cold air and get up high where it'd like to be. There, it'd precipitate, and, if the mechanisms for the creation of a tornado are understood at all (they aren't) would start a super-powerful vortex thunderhead, producing very strong storms near the middle of the planet. The air on the far cold side would be cooling, shrinking, possibly even freezing if it's as cold as you say it is, and generally pulling more air towards it.
I don't know if it'd be a global effect, but there'd definitely be a strong inclination for vast amounts of super-heated water vapor from the very hottest point to be causing winds on the sunny side. Anybody's guess to the intensity.
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Yes, on a planet where energy comes from an external source (such as the sun), it would be possible to have a persistent difference in temperature that would cause a difference in pressure.
For instance, in a cold area air condenses and falls closer to the ground, creating high pressure regions. In a hot area the opposite happens: heated air rises to form low pressure regions. This is essentially what causes [prevailing winds](http://en.wikipedia.org/wiki/Prevailing_winds) (wikipedia link) on Earth. However, there are a lot of factors that determine the direction and strength of winds. For instance, the rotation of the Earth causes prevailing winds to flow westerly and easterly, and not north-south from the poles to the equator. Also there are many local variables to consider: breezes are formed where land meets water, and mountains also have an effect on air pressure.
Shorter answer: Yes it is possible to have regions where high or low pressure is dominant. But there are so many factors that influence wind direction that I don't think a completely constant wind is possible on a planet wide scale.
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Under *normal* conditions the simple answer is unfortunately *nope*.
Longer: Eventually the pressure would equalize and the wind would stop.
However there could be something to make it work. Example would be
- an anomaly teleporting air from there to *somewhere* else.
- A tidaly locked planet possibly could have an effect like that as the one side is very cold (cold enough for liquid O2 even) while the other side is much hotter. However that would be quite generalized and would be a looping system (hot air rising in the hot half of the planet and cold air drawing into that area at the bottom whereas higher up the air would go the oposite direction)
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You can justify any local pressure gradient being permanent by simply making it globally circular, like a large hurricane. (Actually, there's at least one planet in our Solar system with a permanent hurricane - Jupiter's red dot)
To make it most plausible, just make its conditions similar to those that cause a natural hurricane, but add in conditions for it not to move - maybe there's some heat source on the surface that keeps the eye stationary, and the winds always rotate around this point.
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I am trying to make a space based strategy game, in which different factions try to take over all the planets in a solar system.
The first step anyone should take to take over a planet would be to destroy any spaceships (and surface-to-space defense installations) defending it, after this, an attacker may choose to destroy the planet from space (making it uninhabitable), negotiate a surrender, lay siege or invade the planet.
While I do have some idea as to what the first options would involve, I am not sure what exactly an invasion would look like.
My question is therefor: **What would a full-scale invasion of a planet, by a technologically equal civilization, involve?**
Based on these assumptions:
1. Invading a planet involves putting your troops on the ground, (which is the difference between invading a planet, and negotiating a surrender or destroying the planet from space).
2. The invaders want the planet as intact as possible, which includes both its infrastructure, ecosystems (if any) and the civilian population. The player may be allowed to choose how great length their troops shall go to to protect the planet, but certainly invading a planet should leave it better off than the *Drop-a-few-thousand-antimatter-bombs-from-space*-option
3. Even though the societies depicted in my game will be (significantly) more advanced than our society, their infrastructure would still look mostly like ours: They may have *fusion reactors*, *quantum computers*, *hyperloops*, *space elevators*, *mass drivers* and *superconductors*, but they will still have a physical energy, communication, and transportation grid.
4. In my game *magnetic shields* may be used on some planets to protect the inhabitants from solar radiation, but these shields are not powerful enough to provide any protection against the weapons of this time.
5. There is no teleportation technology, therefore the invaders can't just beam their troops down, and the defenders can't use a stargate to evacuate their planet or get help.
6. The weapons depicted in my game will mostly be more advanced versions of modern weapons: There may be antimatter bombs, antimatter propelled surface-to-space missiles, super-advanced stealth technology and surface-to-space artillery (possibly mass drivers), but there are no FTL torpedoes (in fact no FTL at all), no lightsabers, no hand phaser, no hand lasers, no death star, no gravitational-wave weapons, no photon torpedoes, no invisible elite soldiers and absolutely no magic.
7. (in response to comment) I assume that the attacking ships are very heavy ships build in orbit, which properly can't survive entering the atmosphere of the planet they are attacking, and won't try to land on it (since it will be unlikely that they will get off the planet again) The attackers will, however, have carriers which can send smaller lander vehicles which can take troops to the surface (and back).
8. (In response to comment) One of the main reasons for asking this question was that I wasn't sure when an invasion should be considered a success, but at this point I think the invasion would be successful as soon as all **centrally organised resistance either surrendered or was destroyed**, though when this happens on an entire planet can be extremely hard to tell, and judging by modern invasions of countries, fighting hardly ever ends when the capital is captured – just look at Afghanistan.
9. (In response to multiple answers and comments) While life-bearing planets probably will be self-sufficient in food, I think that all planets to some extent will depend on imported goods. At least because some resources aren't available on all planets and moons – of which Helium-3 probably is the most important resource.
Even though only one answer could be accepted, i have tried to take inspiration from all suggestions, thanks.
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> The invaders wants the planet as intact as possiple, which includes both its infrastructure, ecosystems (if any) and civilian population.
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Once you have control of orbit I can think of a few ways this could go down.
1. **Negotiate surrender.** After fighting, point out that the planetary government has lost and that being conquered by you would be preferable to being conquered by your adversaries. I think of the Germans at the wend of WW2 who fled west to surrender to the Americans rather than the Soviets. This sort of interaction might happen with no-one firing a shot, which means you also capture the surface to space defenses intact.
2. **Negotiate fealty**. Maybe you could control this planet without having them surrender. They come under your control as an independent allied state in your confederacy or allied to you like a feudal baron. Again the situation needs to be such that they see an advantage for themselves in the situation.
I can imagine this working in a situation where planetary government was divided. One governmental entity allies itself with the outworlders (you) and allows them to come down and set up a presence in that territory. That entity then gets help from the outworlders against its interplanetary rivals. Maybe too subtle for a game but inside help would be good in this scenario: agents who influence government to favor this sort of alliance in advance of the spaceships showing up.
3. **Show of force**. I am thinking here of Hiroshima. The alternative to the nukes was an invasion of Japan, whom the Allies thought would probably fight to the last person. The nuclear bombs demonstrated immense force superiority such that even the Japanese realized that they had to capitulate. From orbit, with planetary defenses down, a show of force should be pretty easy. Once they realize you are able and willing to make any given place a crater they will get in line.
4. **Work around.**. Find a lightly populated and defensible base of operations and just take that. Leave the rest of the world to do as it will. Especially if they are politically divided, no one entity might see an interest in taking on the formidable aliens solo.
5. **Rescue.**. In world war 2 the peoples along the western USSR initially hailed the Germans as rescuers, saving them from their Soviet overlords. For reasons unclear to me the Germans did not run with that, but crushed these people worse than the Soviets had. But you don't need to. Rescue a planet from your rival who has conquered them. They will ally with you in gratitude.
As opposed to totally crushing the populace back to the Stone Age, these "take it intact" options also offer the in game possibility of an uprising - for example if you are too draconian in taxes / food levy / drafting soldiers etc.
Just because there is resistance does not mean you cannot use the planet. An active insurgency does not mean a successful insurgency. Unfriendly polities elsewhere on planet may or may not hamper your use of territory you control.
More destructive / total war options seem less interesting: e.g. neutron bombs / plague or bioweapons etc.
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The scenario you describe is not that far off what you get in the [Warhammer 40 000](https://www.games-workshop.com/en-AU/Warhammer-40-000) universe and is covered in quite some depth in the Horus Heresy novels.
Here there are a number of degrees of planetary attack.
* Total destruction : rendering the planet permanently uninhabitable destroying it entirely by saturation bombardment and/or chemical and biological weapons.
* Extermination of the populace : typically a heavy but targeted orbital bombardment followed up by troop landings and an all out ground/air campaign involving a large range of unit types.
* Targeted Assault seizing key strategic locations eg military command centres, seats of government, infrastructure hubs and landing zones/ports for bringing additional reinforcements and equipment.
So if we generalise a bit there are a few key elements.
* Insertion vehicles capable of delivering troops direct from orbit ideally capable of operating in combat zones.
* Air superiority craft capable of protecting the troop carriers from air and ground fire.
* Close air support
* Elite infantry capable of assaulting directly from drop craft or from a landing zone a moderate distance away. These troops should be capable of operating for a moderate length of time without external support and have their own organic transport and support weapons. They should be adaptable and capable of aggressive high mobility assaults and enough tactical flexibility to adapt to unexpected or changing circumstances.
* Regular infantry and heavy armour to hold ground, consolidate gains, follow up initial assaults and provide heavy support, flank protection and security.
* Logistics capable of resupplying troops and equipment from orbit efficiently and in bulk.
This is broadly the way that modern combined arms forces work. You have specialist self contained airborne and marine units which are able to take key strategic locations rapidly and at a distance from establish bases which are followed up by heavier and more numerous units which can hold the ground which is taken initially and has the logistic capability to then apply sustained pressure on the enemy
Actually this model is not a million miles away from the allied invasion of Normandy in 1944 (as long as your technological hand-waving allows the English Channel to be reasonable analogy to 'from orbit').
Here you had initial operations by irregular and special forces to take key positions like gun emplacements and bridges and disrupt the enemy logistics and command and control, then followed up by direct infantry (and a limited amount of specialised armour) assault of the beaches in force supported by air superiority fighters, close air support, and strategic bombing. Then once you have secured an initial beach head a rapid build up of heavy armour, equipment, troops and supplies required for a rapid advance and build of of pressure to retain the initiative.
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**In response to specifically Point 8**
**Focus not on subjective "defeat of organized resistance" but instead on objectives.**
You started to get the right idea with Afghanistan, The Taliban held out for twenty years against the most powerful military in the world.
Think of ww2, individual Japanese troops held out for up to 29 years. There were German submarines captured 3-4 months after the war. All the forces who escaped occupation and fought under different flags or remained behind and conducted resistance operations. These are just from the isolated militaries of individual nations. Now think of if the entire planet had a coordinated defense from some extra-planetary force. How many decades could organized resistance last from a planetary wide army?
A person who doesn't want to be found can disappear inside a city or large town, imagine how hard a soldier with only entry-level SERE (survive, evade, resist, escape) training would be to find on a PLANET. Even with Statilites and cameras all over the skies, it will still be impossible to accomplish completely.
The key to a successful invasion lies in its objectives.
Have I captured all the Spaceports (official, improvised, AND potential sites)? Am I occupying key terrain to control the area? Do I have control of the power grid? Communications? Production of key resources that lead me to invade in the first place?
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Orbital Bombardment
Nuking the planet is unacceptable, but with this level of tech the attackers would be able to use conventional, highly accurate weapons to bombard enemy aurfields, vehicles, etc. The US millitary investigated something like this awhile back (dropping a bar of tungsten from orbit to level a small area). They determined that it wasn't cost effective, but that won't be a problem for you. Moreover, modern icbms attack from orbit, and are reasonably accurate and could be fitted with convengional munitions. This capability makes conventional resistance impossible, as any strong points could be reduced from orbit prior to the ground attack. Morover, while camouflaged and underground bases would survive the initial attack, orbital strikes would be called in as soon as the position was engaged.
The solution is for the defenders to scatter their forces and wage a guerilla campaign. This would work best in jungle or forested areas where satellites couldn't track them. Alternatively, they could hide in the civilian population, like isis is doing in Mosul at the moment. Both strategies can keep resisting for a long time, so the attacker would need to recruit a local force to patrols the planets vast areas. Moreover, they would need to engage in a Hearts And Minds campaign to win back the populace and hopefully make the resistance put down their arms. Or just use Agent Orange to clear the forests and the let Orbital weapons platforms do the rest.
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See how it done in [Civilisation](https://en.wikipedia.org/wiki/Civilization_(series)):
1. After defeating the army of defenders your army will begin to suppress
resistance
2. Amount of resistance depends on how hostile population against your army
3. The bigger your army the faster it will suppress resistance
4. During suppression it's possible that population has been reduced and/or infrastructure has destroyed
In real world [some resistance forces](https://en.wikipedia.org/wiki/Forest_Brothers) could act many years after invasion. But in fact they couldn't do anything significant because of
* their negligibility
* strong force of invaders
* willingness of most population to live in peace.
As game designer you could add details to make process more demanding on the players. But it may cause that players to prefer not to invade planets just because it's too boring.
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I think the best option is not to have outright invasions and simply have a game of diplomacy for the negotiation complete with intelligence assets, special ops, surgical strikes with orbital weapons, and so on. Less destructive and more interesting than an invasion.
Use the fact that controlling space means controlling air and surface movement. This gives invader an absolute advantage in mobility. So the planet would be given a number of strategic targets which would then be either destroyed by orbital bombardment or assaulted by a heavy concentration of elite troops with orbital bombardment preventing any counter-attacks or support by defenders outside the immediate area. This would be countered by digging in strategic targets (to defend against orbital bombardment), automated defences (to counter the concentration of force), and possibly self-destruct devices powerful enough to destroy the attacking force.
Strategic targets would typically be command infrastructure and logistics. There might also be psychological targets. Once defender loses enough command structure, logistics, or morale the resistance will collapse. Brute force probably should not be the only method here. Agents might be able to persuade some defenders to defect and hand over a target intact. Promises or threats backed by appropriate reputation allow morale warfare.
An invader with excellent diplomacy, strong reputation, and powerful network of agents should be able to invade without actual fighting. There should be (ideally) a smooth transition between negotiation and invasion. Negotiation minimises the need to fight, assaults improve negotiating position.
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If an enemy nation, race, empire, ect had achieved domination over a planet's orbital space, and the planet refused to surrender, conquest would be **incredibly difficult** if technology is roughly equivalent.
Let us assume that Planet A is being invaded by Empire Z. Planet A's space navy has been utterly destroyed and all ground-to-space weapons have been eliminated through strategic orbital strikes.
1. The first main question is: what are the logistics behind the invading force? How far is the supply line, and approximately how long can the invading force last without further resupply?
2. The second main question that must be asked before an invasion begins is, "**Is there a space elevator?**" If there is a space elevator, the first step in conquest would be seizing control of the space elevator which **DRASTICALLY** improves the logistics of supplying ground forces on the planet's surface.
3. Logistics aside if there is a space elevator the invaders will launch a smaller elite invasion force onto territory near the space elevator and then blitz to secure the space elevator's base. Think marines taking a beachhead and then sprinting to capture a port. Once the space elevator is secure all other ground forces will be sent to the planet's surface via the elevator. All major supply routes will stem from the elevator. From this point on the goal of the invader force is to capture all strategic objectives ranging from military bases, major cities, resources nodes, ect. Warfare would likely be very conventional with the one nuance being the availability of tactical orbital strikes on enemy formations and bases.
4. Without the space elevator the invasion could be drastically different. Without a supply method to defeat the gravity well of the planet's surface the amount of troops that could be deployed would be severely limited. The goal of orbital invasions would establishing "beachheads" on the surface, and then capturing areas that can produce supplies for you armies. Newly found supplies can be used to expand the invader's ground presence, but increasing the number of men on the planet is risky. If momentum is lost and the invading forces cannot capture any more supplies, than the army may collapse from supply constraints and evacuation might become necessary or else the invaders let millions of their soldiers die.
Generally speaking however let us say a planet has one billion people. They can, when push comes to shove, mobilize around around 25% of their population. When I say mobilize I mean that they can put guns in mens' hands. Their standing army would be much smaller, but it is likely that they could drastically outnumber any invading force, because it seems that putting tens of millions of soldiers on space ships and keeping them fed is a pretty difficult feat.
For an invasion force to negate these differences it should be expected that **significant** orbital strike support will be needed from the fleet in orbit. So expect large amounts of "rods from the gods" being sent down to devastate the planet's ground forces. Casualties will be high no matter what and infrastructure damage will likely be severe.
For the purposes of your game space elevators will make a drastic difference on invasion difficulty, and if the player decides to invade it should require a large investment of manpower and resources.
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I would suggest covertly landing a small well-trained force that will sabotage ground to space defenses in the LZ and causing general chaos. Sleeper agents could conceivably be used for this if you absolutely can't have a craft land before the defenses and detection systems are taken out.
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Ok, so I personally believe people forget certain things such as:
* atmosphere differences from homeworlds
* alien diseases
* climates
* etc.
But for invading it's pretty easy to be the invader. Well, unless the defender knows how your species attacks or ticks or something along those lines.
Let me make it easier:
The plan to invade an alien world is mostly a logistical problem and health and safety (other than the killing bit), so you will need to know what the alien world is a ocean world.
But what is its gravity? Or the heat? Like, are the oceans boiling or are they freezing? What is the atmosphere? Is the Alien population massive (easier to hit, but more likely to absorb that damage)?
What are your weapons? Heat based? Light based? Mass based? Are the weapons affected by the planet? Like mass is affected by gravity, light is affected by mist, fog, heat by cold or heat resistance.
And so far we haven't got into the invasion yet. So now that we've got the basics done:
An alien world with the same technology has a few space ports, and a defence fleet. The fleet is destroyed, but here is the thing... ALWAYS DESTROY ALIEN SHIPS no matter what. And I mean it: one ship could be a world ending disaster (if it is based of real life). One ship the size of a skyscraper (small I guessing) could destroy a city and the surrounding area. So destroy them. Hopefully the debris will go into the planet and cause havoc.
Now let's say all the logistics is done. How are your troops doing? If they have mechs or something anyway, you would planetary bomb them, destroy mostly defence things or even terror tactics. So let's say we want to conquer it with an occupational force. You would drop your main army in civilian areas, where their military might not be. Then you would drop special forces in military zones. Marines would combat drop anywhere on a small notice, support units, such as supply drops from space ships, drop pods, drop ships etc.
or conquer the moon (if it has one).
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One method of subjugating a planet without committing ground forces is creating an orbital blockade.
Depending on how advanced the technology is in your game and how old the planets being invaded are, perhaps some worlds have not achieved self-sustainability.
Once an attacking fleet has neutralized the planet's defending ships and surface-to-orbit weapon platforms, your fleet could just... camp out in orbit. Any frigates with resources would be shot down, and eventually, the planet would have no choice but to surrender.
If this isn't working fast enough, your ships could bombard key food production facilities (or other resource production facilities) so as to starve the planet, much the same way the Entente did to the Central Powers in WW1: <https://en.wikipedia.org/wiki/Blockade_of_Germany>
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The thing about invading a planet is that you seperate a step.
You say the space based attackers will destroy the assets in space and the ground-based anti-space (AS) installations before considering to invade, but a more realistic approach would be to invade simultaneously with trying to attack those assets. Ground forces would have an edge in dealing with the ground-based defenses. So any invasion would be a multi-pronged attack aimed at the space ships, orbital assets and ground-based AS weaponry.
Initially you can imagine the attackers making several passes in which they try to make an opening in the orbital defenses and land a large section of troops with ample supplies and a heading where they can secure more supplies. As the ground was starts evolving and a larger area is emptied of ground AS weapons it becomes easier to stay over that section in orbit (although missile-based defenses both in orbit and on the ground would still be able to hit you from anywhere around the planet).
Keep in mind that in a more realistic scenario the attackers will need supplies when they finally arrive. They'll need fuel, possibly food (recycling may not be up to the task for 100% of the daily needs) and most definitely they'll need new spare parts for maintenance. So capturing stuff to do so is pretty much required unless you have a pretty big supporting supply fleet. A supply fleet which would be extremely vulnerable to some ships hidden away in the system waiting for their main army to detach.
Many people think that an orbital bombardment can easily force a planet into submission, but it wont for two reasons: a realistic space army would need the infrastructure on the planet to produce maintenance parts and possibly fuel for their ships to remain operational and stragetic bombing has historically rarely been a good option. People are willing to surrender if they think their lives will be disrupted and the electricity might cut out. But if they or people near them have lost loved ones you create grounds for fighting back and accepting hardships while doing it.
Just imagine it: you bomb something and ask for surrender. The planet sends a message with "we surrender, come on down". If you come down you'll simply have forces on the ground to be engaged, forces with vengeful motivations. You cant start bombing everything, you need that stuff! And the places where you'll find military resistance is around those same installations you need. The planet defenders can also threaten you with MAD: "you bomb us, we destroy everything you need to keep your fleet alive. Then you have to come down at some point and we'll be ready to have a good discussion about it".
There's also the same problem with orbital bombardment as with nukes today: sure Russia or America could just nuke a small country into submission, but that will make their adversaries rather afraid and ask the question "maybe just maybe we should bomb them before they bomb us". Orbital bombardment will rarely, if ever, be a viable long-term solution.
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How do I figure out the population numbers in my various kingdoms?
I've seen the population growth tables for the entire world showing how the population grew and died off over time (yes Genghis, I'm talking about you).
But how do I figure out the number of people in my various kingdoms. I can't just say it was a large million people strong population with medieval society and knowledge in an area the size of say, Denmark. (this is just an example).
To work out the number of soldiers I could legitimately field, or the number of large cities, or how much farmland I need etc I need to figure out just how many people are in the country.
Is this one of the times where the answer is however many you want? Or is there a *somewhat* 'established' calculation of people per area per time period/society level?
Or is the answer the reverse? Figure out how much farmland you have, that can feed the cities and soldiers. Work it out by number of mouths I can feed?
Does anyone have a handy 'farming productivity through the ages' almanac?
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This is one of those answers that I can't write up the information on and there is a lot to, but there are really great sources of information which means I'm just going to post a link and a few tools based on that info.
[Medieval Demographics Made Easy](http://www222.pair.com/sjohn/blueroom/demog.htm)
* [Donjon's, a great PnP capaign creator tool site, tool based on the above](https://donjon.bin.sh/fantasy/demographics/)
* [Probably the 2nd best incarnation of such a tool](https://www.rpglibrary.org/utils/meddemog/)
* [The best variation on the tool](http://www.welshpiper.com/medieval-demographics-online/)
To use these most accurately you should know information about your kingdoms which you'd know from world mapping them and such. You also need area of the kingdom. To get this, if you have Photoshop, open the histogram window and select the area inside your kingdom's borders. This will give you the number pixels selected and you should know the 1 px = km^2 or miles^2 number. Just multiply and you got your area.
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See, it depends.
The high of the Medieval era lasted from about 1000 CE to about 1400 CE. From this time the entire world's population was roughly 300 million to 440 million, based on the Population Bureau Reference's estimates.
During this time Europe's population approximated at between 50 and 84 million. Unless, of course, you're dealing with the Late Medieval Age, when everyone started dying of plagues. Assuming we're in the prime of the Medieval era, however, those numbers should do fine.
This averages out to a population density of around 13-21 people per square mile.
So from here you just need to find the size of your kingdom for a good starting estimate. Your example was a region the size of Denmark, so let's start with that.
Crunching those numbers, you have a plausible population range of between 215 thousand and 350 thousand for that size and time period.
From here you can distribute your populations and arrange your kingdom accordingly.
Assuming you have various kingdoms in Europe (where the Medieval era was prominent), here's the **TL;DR** :
Multiply the population density of Europe in the Medieval Ages (13-21 people per square mile) by the size of your kingdom. From there you should increase or decrease that base population accordingly, based on the nature of your kingdom (is it a major trade center or majorly farmland? etc.)
Hope this helps!
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Taxes could be a way. If every adult male pays a certain amount of taxes every year then all you need is to count your yearly income to find out what the number of fighting men.
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[Question]
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We've all seen those awesome video games and movies and comics where people throw "*Hadokens*" and "*Hamehameha*" around like it's nothing. It's flashy, does a ludicrous amount of damage (including the surrounding landscape), and usually produces massive amounts of light. It's also often referred to as chi, but almost always only seen in battle.
# Consider the following on how this "chi" magic system works:
**Limitations:**
Any person is able to use this mystical energy - pending on the persons ability to focus and move his body. In other words, this magic can be taught to anyone.
This energy is dependent on the person's mental strength, where mental strength represents will, intent, and concentration. A person that is extremely focused on doing something will have much more success compared to someone who's doing the same thing half halfheartedly.
The magic does not allow for "super strength" situations - For example, if the person would not normally be able to lift a boulder, the chi would not allow him to lift the boulder. If the person normally could punch with 50lbs of force, a "chi punch" would also only result in 50lbs of force applied to the target.
A person must grasp the overall concept of this "chi" system in order use it. (The concept to be grasped is irrelevant). As such, one usually does not "accidentally learn" chi. It's more likely that someone teaches you the proper concept and how to think about the chi in order for you to start managing and using it.
**What it looks like:**
Flashy light is disturbing to neighbors. Which is bad.
This chi is visible to the naked eye, usually visualized as a distorted section of air based the form of the intent. For example, a punch could be either a ball of chi flying through the air, or a longer tendril extending from the arm to target, depending on intent. A palm thrust could easily be as large as the cross section of a car, where as a finger thrust could be as sharp as a needle point.
**How the chi is used:**
This chi magic is often (for lack of a better word) "Activated" through martial arts; however, simply focusing on the principles of what is trying to be accomplished is enough. Consider the following situation:
>
> As Chi master Charles walks down the street, he notices a teenager trying to open a door from a distance. He's clearly practicing how to use his chi, and is launching a furry of chi punches at the door, but it's not budging at all. Charles decides to show off a bit, and takes the place of the teen. Concentrating on his intent to twist the doorknob, he extends his hand and grasps the air. Bystanders stop and stare as a circle of distorted air grasps the doorknob and twists it in unison with Charles wrist turn. A slight chi push follows, and the door swing opens.
>
>
>
An advanced user such as Charlie was able to manipulate his chi to twist the doorknob and push instead of throwing brute force at the door. Taking this example, if the door were a well oiled 100 lbs door with a thick steel lock, even if the beginner might have been stronger physically than the advanced user, a advanced user grasped the concept better and could open the door, whereas the beginner would not have been able to make it budge.
## But doesn't this all seem too perfect and convenient?
With any advantage there must be a drawback. Use of this magic **does not drain actual physical strength** - however, excessive use of this magic can cause irreversible brain damage in children, resulting in things including but not limited to: Alzheimers, ADHD, Memory loss (Short term and long term).
Here, children are defined as anyone younger than 18. As each person nears the age of 18, the use of this magic causes less damage, but becomes harder to learn to use. Once the person has passed the age of 20, he/she is free to use this magic with no side effects other than the mental exhaustion of continuously focusing on things. However, the younger the child is, the more damage the magic does.
It's well known that children absorb information and learn a lot better than grown adults - their minds are like sponges and aren't as saturated. While this magic can be drilled into adults, it's **significantly** harder than teaching it to children. Those who have been taught to use it from a young age use it much more effectively than those who learn it later. To give a sort of comparison between the early and late learners, those who learn it late (post 18 years old) are at most able to use chi at a 20% efficiency rate compared to those who learnt it earlier. Learning it before age 6 would give 100% efficiency rate at age 18 if practiced enough and trained properly.
Unfortunately, children also tend to **not listen to adults**. Once they learn it, we can't simply tell them "don't use it, it's bad for you", or explain why it's bad for them (if they're too young to understand). They'll probably abuse it for personal reasons such as entertainment, or for mislead young adults, fighting or stealing or whatnot.
# Thus, I must ask: At what point (and how) are the children taught to use this magic, with the intent of having users that can use it at maximum efficiency without sacrificing mental health?
[Answer]
Other answers will be better at the **social implications** of what is considered an acceptable age to start learning. I'm sure a 'chi' teacher would differ in opinion from overzealous parents, and those from parents that don't want their kids to have anything to do with 'chi'. Maybe the government is even regulating this stuff in your setting (though I sure hope not, since governments are known to be bad at these things ;) )
**I'll try playing out what could be considered a responsible way of introducing children to 'chi'** in order to maximize control while minimizing negative effects on mental health.
First of all, you stated that chi can not exert any more force than the user could exert without it. That's good, that means with perfect control over your 'chi' you can still improve the power of it even after you've become an adult. So childhood would likely focus on practising that control.
# How I imagine training would actually turn out in the long run:
1. Teach the children **chi-unrelated martial arts** from a young age (~2years young) - this has, just like in our world, several positive effects in general: They will get to know their body and how to interact with it and the world, they will learn discipline (mainly because discipline is necessary to avoid injury as most people come to realize quite naturally when they do sports) and they will learn that they *are* capable of inflicting terrible injuries on themselfs and others.
(The main point of many martial arts is to gain control over power output, not increase.)
2. Around age ~4 children become increasingly aware of 'chi', probably by accidently using it - starting from this point they will incorporate it into their usual training in order to gain control of it (much like an extension of their body). Think of things like **breathing techniques** but for 'chi'; in reality we use them to gain a better understanding of our body and mind, and when you add chi to the mix it's a very safe way of getting used to this new 'body part' since the effort and output can be finely regulated rather quickly. I choose age 4 because that's given the children 2 years of time to get to know their physical body. You may think that's too early (in fact, there won't be any conflict or elaborate technique in martial arts that early on), but at such a young age children are incredibly good at grasping concepts, even if they can't explain it or seemingly don't do it right. In other words, they will understand how to move their bodies, even if they are not physically capable yet of making it look especially smooth.
3. As the children improve their control over chi and grow their minds mature as well. Before, they might have been told not to overdo it, but I'd say at age 7 it's high time to have proper discussions and explanations of the explicit dangers of overusing 'chi' and, much more important yet, **how to recognize when it has been overused** (this also means that I would afterwards start to gradually reduce any safety buffers against overuse, for them to gain experience in recognizing their limits). Much like one needs to be told that some muscle pain is perfectly okay, and some isn't. Lighter versions of these explanations will have been given throughout the years already, I'm just saying overtly simple arguments may not be enough to satisfy/convince the children anymore. Oh, **explanations will probably also get shorter and shorter as they grow older, albeit more complicated** (the simplest answers for toddlers are often the most elaborate ones one ever comes up with for a question).
4. Afterwards, since control over 'chi' is the main concern in order to improve efficiency for their later lifes, proper 'chi' practice will be included in the training plan. It is important not to neglect the original martial arts however, as it's beneficial to **balance different kinds of strains** ('chi', non-'chi' mental training, normal physical training etc).
5. Starting around age 11 children have gotten a proper foundation and understanding in both martial arts and the art of 'chi' from a fundamental control point of view. It may be time to let them have a go at the wonders of using 'chi' for things like **stitching (without touching the needle) or building LEGO castles** etc. Make sure these things are just as properly supervised in order to avoid overuse of 'chi' - the children might know their limits, but **everyone forgets their limits while having fun** (such as reading a novel all the way into the next day, always thinking "just one more page").
6. Gradually introduce a greater variety and greater specialisations of 'chi' applications, and have them get emersed in what they want. Perhaps they don't really want to use their 'chi' anyway, that should be fine too.
7. Getting closer to age 18, but at the latest then, you will need to **REDO all explanations and fundamental physical and 'chi' training methods** they've done as little children. Why? Because they have gotten sloppy at their fundamentals and are not in touch with themselfs on such a broadly deep level as they were at age 9 or 11. And why is that? 'Cause their minds are filled with a life full of experiences that overshadow such basic, now almost instinctive knowledge. This is also a point where many athletes and such fail to do an overhaul of their abilities and gradually get worse. Now, don't get me wrong - I'm mostly referring to getting worse at truly understanding what one now doesn't even thinks about. **Not having to think about it is a good thing, but that stops being true when one cannot understand it anymore**. An example, do you remember how you learned to use a fork? Even if you don't that's fine - as long as you can still explain to others how to use a fork. We want to avoid a situation where one can use a fork themself but has become incapable of explaining how one does it - just transfer that to the martial/'chi' arts and you'll see that 'chi' at least ain't something you want to get sloppy with.
8. Thanks to the previous step the children, now young adults, can pretty much use their 'chi' without any harmful side effects at great efficiency while understanding their abilities. From here on some may choose to further train their bodies and mind to increase their general capability to exert more force and more intensively focus on something. At this point they are capable of expanding their own horizons by their own strength.
# To lightly address the matter of children running around with superpowers:
Being a martial artist myself I may be biased, but I expect the risks of anything bad 'chi' related to happen to be far smaller than current common causes of grief (such as bad driving, drugs, etc).
When you understand from a young age why control over your actions is important and how to apply it you are far more likely to exert that control. Not because you're automatically a better person but because getting into trouble is a pain (not the conflict itself, but the after effects such as teachers getting angry, parents scolding you etc) and easy to avoid.
What I mean is, the better you understand your capability of seriously inflicting harm on others with less effort that you'd need to do a 50m sprint the more you shun away from situations that might make you loose control. By understanding risks and how troublesome they are most kids trained in martial arts are actually really cool about things compared to their peers. They comprehend how easy it is to make a mistake, and they have the discipline to overcome obstacles (such as uncomfortable situations) rather than try to forcefully destroy them.
**Edit:**
Regarding Aify's comment, I agree that there *will* be cases of misuse and quite a great variety of ways to annoy others thanks to the 'chi' with different grades of danger. On the lower end I'm thinking of that really bothersome feeling of someone holding a finger close to your face without touching it - now imagine another kid doing something akin to that from a 10m distance with no way to slap away their hand. There's really no limit on the terrible creativity 'chi' could be used in this setting to annoy others. Of course, that would be the harmless version - there will be fights and full-blown conflicts between youths, possibly made .. more decisive .. by the involvment of 'chi'.
Still, I want to believe that on the larger scale problems with violent 'chi' misuse would remain relatively rare. Not only because of the proper training (that they will ideally receive) but also because by the Question's premise it will still be easier for most children to use physical attacks (e.g. bare fists) than their 'chi' since these are mentally less exhaustive and require less concentration/focus.
Any kid/adult who can keep their calm in a fight has a good change of being mature enough not to participate in one, the rest will likely choose the simpler option most of the time.
Possible measures I can think of are mostly preventive - proper parenting, supportive and positive environment, and refusing to teach children that are considered too high-risk. 'Chi' trainers/teachers should have a good grasp of how they evaluate that risk in each of their pupils. Children could probably be safely removed from training up to step 3 above. I'd guess that any time later you would run the risk that the children continue to teach themself wrongly and cause themself and others great harm.
Not training high-risk children seems effective to me mainly because 'chi' is set to be extremely difficult to get right on one's own, so the earlier the better. May not make much sense from an emotional maturity point of view, though - I don't know if it is even possible to tell early on whether a child will turn out high-risk/aggressive.
[Answer]
By implication, talking about excessive use of Chi for children means that there is a relatively safe level of use, beyond which the child begins accumulating neurological damage.
Since use of Chi is a visible phenomenon involving the emission of light and/or atmospheric distortions arising from the extremities, it should be possible to develop an electronic device that can detect the use of Chi.
The solution is simple, assuming a modern-day technological level: Harness children who are in Chi-training with a Child Chi-Use Detection System (CCUDS). This would use multiple very simple CCD chips and IR light sources to detect the localised emission of Chi-light or Chi-distortion. The CCUDS would be programmed with the age of the child and the safe levels of chi-use for that age group, possibly modified according to parental-, Physician- or trainer- assessment of the child's potential.
The CCUDS might look rather like a coarse fishnet worn under the clothes, complete with net-like gloves and socks, and a slightly larger battery/CPU/GPS/transciever pack in an unobtrusive location, possibly at the small of the back.
The CCUDS' function would be to permit a certain use of Chi, and to report to the wearer the number of uses remaining. This display may be very unobtrusive so as to maintain privacy, so that a child in training who had used up his Chi-allocation could still make an effective threat of the use of Chi without the system giving away the fact that he had used up his allocation.
If a child attempted to use more Chi than was safe, the CCUDS would initially administer a mild shock, increasing in severity with continued excessive use, up to and including the point of incapacitating the wearer, though incapacitation would more likely be through an administration of a sedative that would suppress Chi-use. The CCUDS would also maintain an active encrypted data connection monitored by whatever adults or authorities were responsible for the child, who would be alerted if Chi-use exceeded safe levels or if the connection was lost, indicating damage or tampering with the CCUDS and the location of the child.
Depending on how seriously the authorities took the potential brain damage to children in training, there could well be a very prompt official response to excessive chi-use - or the loss-of-signal from a CCUDS - so children would quickly learn that if they cross the line - or tamper with their protective equipment, the authorities would show up and put a stop to things, and that is if they could overcome the negative reinforcement the CCUDS was imposing on them
With a system such as this in place, assuming that there was indeed a safe level of Chi-use for children, then children as young as five or six could be trained - pretty much as soon as they are able to begin martial-arts training.
Of course, there is the potential expense of the CCUDS to consider. It is not a terribly complicated device, and could be made by us today if there was a use for such a thing, and would not be beyond the reach of middle-class families as a one-off expense, but it could also be government -funded or -subsidised, justified on the grounds of reduced public health costs and increased child safety. If Chi-misuse by minors was a matter of concern for law enforcement as well as a public health issue, then the CCUDS could easily be modified and used as a detection and logging device that could pinpoint criminal misuse of Chi by minors.
So, yes, your kids *might* be tempted to have childish Chi-battles with the neighbourhood kids or bullies, but with the CCUDS, parents and authorities would become aware of this in near-real-time, and could intervene. The constant combat, bullying and brain damage that kids risked in the past would be just that: in the past.
So, with such a system as this in place, children as young as four to six could begin to learn to use Chi safely, their parents confident that there were a lot of safeguards against their children misusing their abilities and causing themselves permanent, debilitating injuries, as well as knowing that their kids were protected from - or protected from *being* - the local chi-using bullies.
[Answer]
The use of the term "Chi" and "Martial Arts" seems to suggest a natural (although perhaps a bit stereotypical solution) of sending children to some form of specialized academy or even monastery for the safe development of their abilities. Presumably there is some level of safe usage for Chi abilities and by learning these abilities in a controlled environment with advanced Chi users as masters/teachers the mental health risk can be managed while maximizing a child's Chi potential.
Going with a monastic approach to education opens up some other possibilities such as the parallel development of martial art skills (think Shaolin monks) as well as a focus on discipline and self-control. Perhaps the often-practiced act of meditation promotes not only mental focus (for greater Chi control) but also fortitude against the mental damage incurred by childhood Chi use.
One issue this brings up is if you intend to have the majority of the population be adept Chi users, it may not be logistically possible to send everyone to Chi schools. Even in a world where Chi has great importance and there are many Chi academies, children and parents would likely have to decide between traditional educational institutes and specialized Chi ones. I think this is fine though as not everyone needs to be a master Chi user and even unpracticed adults have some ability.
I don't know what time period you're looking at but if you are interested in a more modern-day/futuristic approach these academies could be highly technologically-advanced and employ a wide battery of tests and monitoring to ensure the mental health of their students
[Answer]
# **When they are over 25.**
To ensure proper impulse control, you need a [fully connected Frontal Lobe](http://health.howstuffworks.com/human-body/systems/nervous-system/are-teens-brains-fully-developed.htm). This area of the brain is not fully developed until [at least halfway through your 20s](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2892678). Therefore, to be assured that children and young adults do not abuse the system, teach them when they are older than 25.
(I'd also recommend this as the minimum age requirement for police enforcement, public office, and a slew of other easily corruptible or corruption-ridden jobs.)
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[Question]
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
This question is partially a spinoff of some points that came up in [another recent question](https://worldbuilding.stackexchange.com/questions/59699/wireless-power-generation-in-a-fleet-of-spaceships) at *Worldbuilding* about interstellar space travel.
**Runaway Truck Ramps**
I live in Colorado, and on the downward slopes of many of our high grade mountain roads are runaway truck ramps. The idea is that if you are driving a semi and your brakes fail and you are speeding up to unreasonable speeds as you hurl down the mountain, you can divert to the runaway truck ramp, lose some speed going uphill or along a lane with high friction soft sand, and if you are still not at a stop at the end, you can crash into a long line of trash cans full of water that are placed there.
[](https://i.stack.imgur.com/sw788.jpg)
**The Canonical Hard Science Interstellar Voyage**
Now, back to the starships. The generally accepted design plan of an interstellar starship that complies with the laws of physics is to have a ship that is mostly fuel and engines accelerate at 1 G to cruising speed, cruise for a while, and then turn around and decelerate at 1 G so that you are moving at some very low manageable speed when you reach your destination.
[](https://i.stack.imgur.com/O1ua5.png)
A [previous post in this forum](https://worldbuilding.stackexchange.com/questions/23683/what-is-the-most-effective-way-to-brake-from-interstellar-speeds) considered a few ideas for handling the deceleration phase of space travel, but had mostly only superficial answers, none of what really honed in on the issues presented in this question.
The target cruising speed at the boundaries of what seems like a medium term future engineering limit is generally on the order of 0.1c (i.e. 18,600 miles per second), although if you need more cargo and living space, and less fuel, you can always trim the intended cruising speed, and the precise cruising speed isn't really material to this question.
Another part of the conventionally accepted design plan is that in the time period starting when you are going at all fast and ending around the time you reach your destination, you don't want to hit anything that could puncture or destroy your ship, and usually, we just assume that this gets figured out somehow (because it is a rather complicated issue and requires a lot of hard to acquire information about how much stuff is in interstellar space that needs to be known to considerable precision).
In this case you can assume that our starship is built out of the strongest construction materials known to exist, or credibly hypothesized, that could be manufactured on the scale of a starship.
[](https://i.stack.imgur.com/Wwra1.jpg)
This is all good and well.
**What Could Go Wrong?**
But, Mr. Murphy being omnipresent, things don't always go according to plan.
Maybe you had to plough through interstellar gas on the way to your cruising speed only to realize with horror that as a result you had used more than half of your fuel by the time you hit your cruising speed.
[](https://i.stack.imgur.com/ehgCI.jpg)
Or, maybe you forgot to consider extra gravitational sling shot boosts you received in the acceleration phase, so you kept accelerating until you used up half of your fuel and have reached a cruise speed that is faster than you have enough fuel to slow down from.
[](https://i.stack.imgur.com/TRTqI.jpg)
Or, perhaps some micro-meteoroids have made some tiny holes in your fuel tanks and twenty years into your voyage when it is time to start slowing down again, you discover to your horror that 7% of the fuel you should have left to slow down with has seeped out of those holes over the course of the last twenty years.
[](https://i.stack.imgur.com/z5Cyc.jpg)
Or, maybe when you ordered 50,000,000 tons of fuel tanks from the idiot marketing guy in Chicago, he told the engineers that you needed 50,000,000 short tons (907.185 kg each) rather than 50,000,000 metric tons (1000 kg each) and nobody caught the problem until the acceleration phase of the trip was over and your were cruising along at cruise speed. (Not as unrealistic as it seems. A [real life NASA disaster](http://edition.cnn.com/TECH/space/9909/30/mars.metric.02/) was caused by an English system v. metric system screw up.)
Come up with your own scenarios. The bottom line is that shit happens and you don't have enough fuel to slow all of the way down when you need to.
**Human Factors To Consider**
Since a hard science interstellar ship is a one way trip and you need to rebuild civilization when you arrive, your ship will have 100,000+ passengers, men and women, and every age from babies to old people at the time you need to start slowing down.
[](https://i.stack.imgur.com/ozBvE.jpg)
Now, while it would be optimally comfortable to decelerate at 9.8 Newtons (a Newton is one meter per second squared for one kilogram) which is also known as 1 G, nobody is going to suffer long term ill effects is you do so at 15 Newtons/kg for a little while now and then.
But, at 50 Newtons/kg, people start passing out and frail people may suffer bodily injury. At 100 Newtons/kg your strongest people while properly cushioned in specialized chairs are struggling to stay conscious and avoid injury. At 1000 Newtons/kg, almost all of your passengers are dead, and the survivors will be seriously injured with no one to take care of them and won't have enough of a critical mass to build a society that can meet its basic needs when you arrive.
[](https://i.stack.imgur.com/zsjYf.jpg)
So, you can't slow down too fast and you have a pretty narrow window of acceptable solutions.
**Runaway Starship Ramps**
But, all is not lost.
Recall our runaway truck ramps. While there is no complete substitute for fuel when it comes to speeding up (although gravitational boosts can help a little), the universe is full of stuff that will slow you down if you crash into it - interstellar gas, gas giant and terrestrial planet and moon atmospheres, space dust, meteoroids big and small, asteroids, oceans, and solid ground on terrestrial planets, for example, via [lithobraking](https://en.wikipedia.org/wiki/Lithobraking).
[](https://i.stack.imgur.com/0q37Y.jpg)
Approaches into the gravitational fields of large objects like stars and planets at optimal angles [can also slow you down](https://worldbuilding.stackexchange.com/questions/47957/gravitational-slingshots-could-they-be-used-to-decelerate-a-spacecraft-travelin?rq=1) just as other approaches can speed you up.
So, the trick is to consider what you can crash into at various speeds to reduce your starship's speed while not destroying the starship or causing deceleration of more than 50 Newtons/kg at any one moment if you can help it.
I can also imagine some additional strategies that could help.
My intuition is that the more diffuse and less rigid the object you are impacting is, the more gentle the impact will be and the more likely it is that your ship will not be destroyed on impact. So, you may want to use lasers or missiles to break up objects in the path of your ship to soften the blow.
[](https://i.stack.imgur.com/cQ6nV.jpg)
Also, the top priority in this situation is to save the people and essential cargo on board. Towards the end of the trip, some portion of the ship can be sacrificed to make ablative barriers to protect the ship that are destroyed on impact with space debris.
[](https://i.stack.imgur.com/uGHwg.jpg)
**Budget Space Travel: A Planned Crash Scenario**
[](https://i.stack.imgur.com/VIDFI.jpg)
Finally, I have initially posed this question as a solution to an unplanned problem.
But, suppose that you have well established human colonies with advanced technology at your destination. To what extent could you limit your fuel requirements by intentionally having people on the destination set up an optimal "crash ramp" in deep space for your ship and what would that crash ramp look like.
**My Questions**
So, my questions are these:
Certainly, at some point, if you have enough fuel to go slow enough, the runaway spaceship ramp strategy for starships can work.
But, how slow do you have to get? What kind of crash targets and gravitational braking approaches are best at which parts of the controlled crash? Is it realistic to think that "runaway starship ramps" could provide any meaningful share of the needed deceleration without killing most of the passengers?
[](https://i.stack.imgur.com/EE82h.jpg)
What crash targets and gravitational braking approaches make most sense in an unplanned crash scenario?
What would you do differently if you could have technologically advanced colonists at the destination build a crash ramp in deep space to your specifications in the vicinity of the destination?
[](https://i.stack.imgur.com/zYZM5.jpg)
[Answer]
Assume a colony starship *Centauri Pilgrim* is carrying one hundred thousand plus colonists, travelling at 0.1 c to Alpha Centauri. It undergoes a catastrophic propellent containment failure losing most of its fuel to decelerate. The ship can only decelerate by one percent of lightspeed, to 0.09 c (this is a velocity of 27,000 km/s).
Using gravitational fields to slow the ship will ineffective (next to useless actually). Lithobraking is insane; basically this would mean decelerating through 27,00 km/s in a minute fraction of a second. It also requires 'magic' deceleration technology and 'magic' force-fields to survive the collateral effects of fragments of the lithobraked planet.
The sensible way to decelerate the *Centauri Pilgrim* would be an interception strategy to send repair vehicles to fix any damage and tanker ships to replace the lost fuel. But this isn't exactly an interstellar runway ramp.
There is an even better way to decelerate our runaway *Centauri Pilgrim* and that involves particle beam propulsion technology. Essentially electromagnetic launchers or mass-drivers to dispatch a stream of smart pellets to transfer momentum to the incoming ship. The pellets can be blasted with powerful laser pulses and the resulting plasma is reflected from a magnetic deflector mounted on the bow of our runaway vessel.
>
> An alternative to rockets is to push spacecraft with a reflected beam. The advantage is that it leaves most of the propulsion system mass at rest. Use of mass beams, as opposed to photons, allows great efficiency by adjusting the beam velocity so the reflected mass is left near zero velocity relative to the source. There is no intrinsic limit to the proper frame map velocity that can be achieved. To make a propulsion system, subsystems need to be developed to acquire propulsive energy, accelerate the mass into a collimated beam, insure that the mass reaches the spacecraft and reflect the mass. A number of approaches to these requirements have been proposed and are summarized here. Generally no new scientific discoveries or breakthroughs are needed. These concepts are supported by ongoing progress in robotics, in nanometre scale technologies and in those technologies needed to use of space resources for the automated manufacture of space-based solar power facilities. For mass beams specifically, work in particle sizing, acceleration, delivery and momentum transfer is needed. For human interstellar flight, a notional schedule to provide a mass beam propulsion system within a century is provided.
>
>
>
Gerry David Nordley is a major proponent of particle beam propulsion. Taking his proposal to send a probe to Alpha Centauri at a large fraction of lightspeed (0.8667 c) with an acceleration of 3 g over 122 sidereal days.
[](https://i.stack.imgur.com/pGQYm.png)
If a particle beam system is used to decelerate the runaway ship. let's use a PB system with exactly the same characteristics as Nordley's Alpha Centauri probe. It has to decelerate a ship from 27.000 km/s to relative rest with respect to Alpha Centauri.
The probe has 86.67/9 squared times the kinetic energy of the *Centauri Pilgrim* or 92.74 times if its velocity was pure Newtonian. At 0.8667 c, it has Lorentz factor of two. So multiply the value for kinetic energy by, say, nine. This gives an approximate relativistic kinetic energy of 834.6321 for the probe. Since the Nordley PB system accelerates the probe at an acceleration of 3 g, then we can multiply by another 3 to account for an acceleration of 1 g to decelerate the *Centauri Pilgrim*.
If a PB system is deployed in the Alpha Centauri to decelerate a runaway ship moving at 27,000 km/s, and with the same characteristics as Nordley Alpha Centauri probe, then it will be capable of decelerating a vessel with a mass of 2,503,896.3 tons at 1 g in a period of 31.89 days.
An interstellar vessel with a mass of 2.5 million tons can more than readily accommodate 100,000+ colonists. Using the known parameters of particle beam propulsion system and then calculating what mass vehicle it could decelerate confirms this system would be more than adequate to safely bringing a runaway colony ship to stop at its destination. The vessel turns out to have more than enough capacity to accommodate the OP's proposed complement of colonists.
REFERENCES:
Gerry David Nordley, [Particle Beam Propulsion and Two-Way EML Propulsion](http://www.gdnordley.com/_files/2way%20EML%20&%20PB%20prop.pdf)
G. D. Nordley et al., Mass Beam Propulsion: An Overview (2015), JBIS, 68, pp.153-166
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[Question]
[
I realize that [evolutionary linguistics](http://en.wikipedia.org/wiki/Evolutionary_linguistics) comprises an entire sub-field of study, but I figure I can narrow it down a bit for this question.
In [How long will it take to form a new dialect and language in underground steampunk London?](https://worldbuilding.stackexchange.com/questions/22688/how-long-will-it-take-to-form-a-new-dialect-and-language-in-underground-steampun), I asked about how long it would take for a new language to form, and how much a language would change within 50 years. In a continuation of my worldbuilding experiment, I'd like to fully simulate language evolution.
I'll break this down into a two sections: short-term and long-term. What pieces of a language are more likely to change over a short-term period of time and what pieces are more likely to change over a long-term period of time?
Here are the "pieces" I'm concerned with:
* Vocabulary/semantics
* Conjugations and declensions
* Word order/syntax
* Phonetics
* Speech rhythm
* Cadence
* Any other important bits I'm missing (?)
The reason I ask this is because I'd like to work towards a computational simulation of the evolution of a language. I've read about various methods (see, for example, a late section of [Bickerton (2007)](http://www.ucd.ie/artspgs/langevo/langevobriefly.pdf), but I'd like to figure out which bits I should focus on for short-term and long-term simulations.
[Answer]
I'm assuming you already know your linguistics so I won't go over the (not so) basics.
It's pretty easy to tell what the phonology will become because those changes already happened in the past or other languages in the language family/dialects. On the other hand, "Innovations", changes that do not happened before or happened but didn't stick for long take more time. Vowels in general change all the time.
The same principle applies to grammar and syntax, the changes that are already taking place will keep moving on until the language changes category or grammatical focus.
Assuming no significant external influences the vocabulary will change accordingly the patterns of the language's morphology and sound distribution, names are usually obvious in the context they were introduced, some languages call batteries "piles" because back in the day they were actual piles of zink people came up with the them because it was obvious for them.
You were naive on this regard on your last post, the name 'geordysword' is too long and cumbersome for an English word, it's not intuitive and it's not consistent with how words are formed, for English you would like to have either a name coming from Latin/French or a monosyllabic English word in which the sounds fit with the apparent/shape of the object. Like [ljuːm] from Latin [Lumen]. Remember that every time something new appears it usually has several names but only the most consistent (easy to learn and remember) names survive. By 'consistent' I mean matching the expectations of the people. They also need to be consistent with the object they represent, see "sound symbolism" and "[Bouba/Kiki](https://en.wikipedia.org/wiki/Bouba/kiki_effect) effect".
Take much care with slang, slang is like sperm, they are created by the thousands but only a few are actually useful and have the properties to survive.The rest dies in obscurity.
On a side note, your whole idea seems very implausible, those people have family, business, tasks to do in the big outside world which are much more appealing than the hot deeps of the mine, why they would isolate themselves to form a new society, let alone a new language?
[Answer]
**Any model for language change is going to depend on the rate of change in the surrounding society.** Changes in vocabulary can happen much faster than changes in grammar. The degree of social isolation for UnderLondon from London will play a role too. If social isolation is high then UnderLondon is free-r to evolve a new language than it is remains anchored to London's English.
Vocabulary can change very rapidly as shown in this "short" [list of words](https://aggslanguage.wordpress.com/a-z-new-words-in-the-last-fifty-years/) that didn't exist 50 years ago. So when UnderLondon starts, I would expect to see the introduction of several words to describe new circumstances that differ between a common coal mine and UnderLondon. As the rate of new experiences and objects declines, the rate of new words would also slow down.
Vocabulary
**Modelling**
I believe (and cannot prove) that changes in language will follow the s-shaped curve of the [logistics function](https://en.wikipedia.org/wiki/Generalised_logistic_function) moving from one state of homeostasis into a period of rapid change into a saturated state with low rates of change. How the various aspects of a language will interact or their rates of change over time, I'm not sure.
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[Question]
[
Let's say there exists an Earth-like exoplanet which orbits a normal star, with a similar process regarding the evolution of life on earth, yet the star became a red giant during said evolution.
Assuming the exoplanet was in the goldilocks zone during and after the transition from normal star to red giant and the red giant still having a lifespan of a billion years subsequent to the transition...
How would life adapt to take advantage of this if there were no sapient organisms?
Would the planet become dominated by photosynthetic plants due to increased efficiency from solar energy conversion rates?
Would mutations become more common due to increased solar radiation?
If the planet had a slow rate of rotation might the plants develop a new storage medium for the solar energy when left without a constant source?
Would animals tend to be cold blooded and/or would they develop photosynthetic traits, possibly with semblance to the synthesization of vitamin D in humans?
[Answer]
## Temperature and luminosity
Let's start with some calculations. For the sake of argument, I'll assume that we're talking about a planet that's identical to Earth orbiting a star that's identical to the Sun. To be as generous as possible, I'll assume that this red giant expands to only about $\sim$200 solar radii - a mere 0.93 AU - and cools to around 2800 Kelvin. Therefore, its radius has grown by a factor of 200 and its temperature has dropped to half its value on the main sequence. Now, we can approximate the star as a black body, meaning that it has a luminosity described by
$$L\propto R^2T^4$$
as per the [Stefan-Boltzmann law](https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law). Therefore, the red giant will have a luminosity $\sim$2500 times that of the Sun - near the lower end of models for our Sun's future. The [effective temperature](https://en.wikipedia.org/wiki/Effective_temperature#Planet) of a planet scales as
$$T\_{eff}\propto\sqrt[4]{\frac{L}{r^2}}$$
where $r$ is the distance to the star, and so at its current distance, the equilibrium temperature of the Earth would be about 7 times its current value, about 2029 Kelvin. Now, fortunately for any life-forms on the planet, [the radius of the planet's orbit may increase](https://astronomy.stackexchange.com/a/21171/2153) as the star loses mass, which happens significantly faster during the red giant phase. Generously, Earth could move to an orbital radius of $\sim$1.5 AU. If we were to assume an even greater mass-loss rate for this star, it's not too far out of the question that Earth could move as far away as 2 AU. Therefore, if we recalculate the temperature, we find that $T\_{eff}$ drops down to 507 Kelvin, or a mere 453$^{\circ}$ F. Hey, it's still better than Venus!
### Possible adaptations
I think the classic picture of life on a planet orbiting relatively close to a red giant involves a completely inhospitable surface. I agree; 453$^{\circ}$ F is *way* too hot for life as we know it to live without shade. Even [thermophiles](https://en.wikipedia.org/wiki/Thermophile) couldn't survive; the famous [Strain 121](https://en.wikipedia.org/wiki/Strain_121) and [Strain 116](https://en.wikipedia.org/wiki/Methanopyrus) - which can live at 250$^{\circ}$ F - would be boiled. I would argue that things won't get much better at night. Heat transfer in a planet's atmosphere is incredibly complicated, so I can't give you hard figures, but the [thermal inertia](https://en.wikipedia.org/wiki/Volumetric_heat_capacity#Thermal_inertia) of air would have to be much, much lower than it currently is for any significant cooling to take place at night. Any organisms that tried to live nocturnally would be out of luck.
We therefore have to go underground for shelter, which is a problem, because it means that photosynthesis might not be possible. [Chemosynthesis](https://en.wikipedia.org/wiki/Chemosynthesis) is a possibility, as is [thermosynthesis](https://en.wikipedia.org/wiki/Thermosynthesis) - which, [as I've talked about before](https://worldbuilding.stackexchange.com/a/102149/627), was a possible metabolic mechanism for early life on Earth. If I can invoke thermosynthesis here, then I'll point out that, as you'd need a large heat gradient for it to be effective, this planet might be just ripe for it to develop and thrive. As to how exactly it could be implemented - well, I'll leave that to you, for now.
It does seem that [cyanobacteria can live deep underground](https://www.nationalgeographic.com/science/2018/10/news-cyanobacteria-photosynthesis-mars-extraterrestrial-life/), processing hydrogen gas using a photosynthesis-like chain that doesn't use light. It's pretty incredible, and means that subsurface life is indeed possible. Perhaps these cyanobacteria could survive the extreme temperatures and conditions on the surface.
---
## Periods of rotation and revolution
Now, [Kepler's third law](https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion#Third_law_of_Kepler) states that the length of a planet's orbital period ($P$) is related to its semi-major axis ($a$) and the mass of its parent star ($M\_\*$):
$$P^2=\frac{a^3}{M\_\*}$$
Now, we assumed above that $a$ doubles and $M\_\*$ is approximately cut in half. Therefore, we can see that the new period of revolution is four years.
Now, there shouldn't be a significant change in the period of the planet's day, because that would involve a change in its rotational angular momentum. There's no source for it to offload its angular momentum to, and as its mass and radius will remain the same, so will the length of one day. The one way this could change would be if it has a moon - like Earth does. Over time, tidal forces transfer angular momentum from the planet to the moon, slowing its rotation. You haven't stated whether or not a moon exists; for simplicity, I'll assume one doesn't.
### Possible adaptations
I don't see any significant changes happening here. If the length of a day remains the same, then the only difference is that the year has doubled, which doesn't seem terribly absurd. The seasons - such as they are - will also be twice as long, although with arguably no surface life, the change could be tough to see. The only effect this would have on life here would be that the available heat reservoir for thermosynthesis would oscillate over a longer period. That change, though, should be slim, and certainly wouldn't endanger life.
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## Type of incoming radiation
[Dan Clarke mentioned something important](https://worldbuilding.stackexchange.com/questions/107040/physiological-adaptation-of-life-on-a-planet-orbiting-a-red-giant#comment324683_107040), and I'm going to expand upon it. The spectrum of a black body isn't uniform; it's peaked at some characteristic wavelength $\lambda\_{\text{max}}$. We can calculated this wavelength from [Wien's law](https://en.wikipedia.org/wiki/Wien%27s_displacement_law):
$$\lambda\_{\text{max}}=\frac{b}{T}$$
where $b$ is a constant, 2.897$\times$10$^{-3}$ m$\cdot$K. Using this, we find that the Sun has a peak wavelength of roughly 502 nm. This red giant, with a temperature half that of the Sun, has a peak wavelength of 1004 nm, in the [near-infrared](https://en.wikipedia.org/wiki/Infrared#Regions_within_the_infrared) section of the electromagnetic spectrum. Moreover, there would be less emission of ultraviolet light than from a Sun-like star.
### Possible adaptations
As [I wrote about here](https://worldbuilding.stackexchange.com/a/76237/627), different photosynthetic pigments are more effective at different peak wavelengths. For peak emission around 1000 nm, [certain bacteriochlorophylls will be efficient](http://www.life.illinois.edu/govindjee/photosynBook/Chapter9.pdf). If photosynthesis was possible, the dominant life forms would be purple and green bacteria. Now, it doesn't seem like photosynthesis could happen - the surface temperature is too high. Still, I'm wondering if there's a way around this - perhaps, somehow, the atmosphere is extremely dense and drastically reduces the amount of light reaching the surface to a reasonable amount. If so, purple and green bacteria could be the major denizens.
You asked about mutations. [Ultraviolet light is a cause of mutations](https://en.wikipedia.org/wiki/Mutagen#Physical_mutagens), and given that the temperature of the star has changed, so has the amount of ultraviolet light - it's gone down. The same goes for any x-ray and gamma-ray radiation (which would be negligible to start with, for a Sun-like star). Therefore, we should see a slight decrease in mutation rates. But then again, there won't be much light out in the open anyway. At any rate, having an ozone layer would be less important.
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## The AGB phase
The [asymptotic giant branch (AGB) phase](https://en.wikipedia.org/wiki/Asymptotic_giant_branch) of a star's life - occuring immediately after the star leaves the red giant branch - presents slightly different hazards for life on an orbiting planet. AGB stars [lose mass rapidly through strong stellar winds](https://astro.uni-bonn.de/%7Enlanger/siu_web/ssescript/new/chapter10.pdf), sometimes losing up to $10^{-4}M\_{\odot}$ per year! This is a major problem. The central stars of planetary nebulae - having just left the asymptotic giant branch - [can ablate away the atmospheres of orbiting planets](https://worldbuilding.stackexchange.com/a/1394/627), and I suspect that conditions wouldn't be more hospitable during the AGB phase. In other words, I would conjecture that it's possible that Earth's atmosphere could be stripped.
In addition to the mass-loss problem, there's still the issue of a vastly increased luminosity (perhaps $\sim10^4L\_{\odot}$) at the very end of the asymptotic giant branch. Even if the planet retains its atmosphere, and even if the planet moves far enough away to remain in the habitable zone while its parent star is on the red giant branch, it will likely be scorched during the AGB phase.
### Possible adaptations
None. Unless that thermosynthesis is working out already.
[Answer]
I believe that unless the organism had some kind of plant-based cell it would become cold-blooded, but they'd have to adapt underground to avoid extreme exaustion.
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This all kind of depends on the density of the atmosphere of said planet. Does it have a good ozone layer? If so then, radiation should not be a problem. The planet would probably mainly be populated by an invasive species of plants, as it could be hard to survive for long periods of time in the dark. Animals might also be invasive, or they could be migrational (and move towards the light were plants are still healthy (and other animals are still alive)) as of predators. Maybe there are some animals that follow the migrating plant eaters, or maybe there are some plants that will use animals as "batteries" for the long night. As of mutations, I can not say.
[Answer]
I'd say as a safe bet due to the solar radiation from the fluxing red giant, there would probably not be an ozone protecting from harmful radiation, so most life would be confined to water where the radiation is absorbed. this makes life even on the surface of the water unlikely as radiation isn't completely absorbed by the water. but eventually, the creatures in deep water could build up a resistance to radiation (if genetic stabalization was possible). and could eventually inhabit land. although a vast number of creatures would still live in the water.
I would say that the land would be relatively barren causing most creatures to be carnivorous and predatory. the prey would have to adapt to be able to run and/or hide from the predators, meaning both predator and prey would have to be fast and be able to run for a long time. the creatures able to survive would most likely survive on algae, moss, and other leeching plants that can live on no/ extremely little soil.
another consideration is the fluxes of energy from the star, turning it hot enough so send ponds to a boil one day, and cold enough to freeze rocks open the next. so everything would have to adapt to these constant temperature fluxes by developing thick skin and a way to store water to use for hot days and draw away for cold ones, expanding and shriveling the creatures slightly respectively.
the creatures would also have to adapt to the light level changes; either having large eyes to intake available light, or using another sense entirely. finally, the plants living on the planet would likely mutate from the radiation giving way to everything from spiky algae to rock hard bushes. that's really all I know for now.
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