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This is a suggested question by Monica Cellio, who I want to thank for providing. I hope I kept the idea in spirit as possible.
How to build a world that can still be reused if the associated work to be published is rejected?
For example, I may write a story that is incorporated into a world I built. If the story fails to publish, I do not want that failure to also make other stories associated with that world also un-publishable.
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If you've created a world, nothing can take it away from you (well, unless you sign it away). Same for your story.
Rejection by one publisher doesn't mean your story, much less your world, is dead in the water. Some authors got rejected by *every* publisher, and eventually one came back around and took a story (years later).
There are plenty of options to self-publish nowadays too.
Yes, maybe the editors are rejecting your world - in which case no story set in that world is going to sell to *that* editor. That can happen. Best I can tell you is that that's not every editor. And, unless there's a conceptual design flaw that makes your world completely break *everyone's* disbelief, someone out there will like your world (I mean, you like it right? That's one in the bag).
As advice for what type of world to build: Build one that you can write a number of different stories in. And different types/styles of story as well. That'll mean you can reuse the hard work you've put into the background, as well as make for a universe to tie all your work together.
I'd wait to do one-off worlds until you've sold a novel. (Unless the monkey on your back tells you to).
If you're just writing shorts, you're not going to go to the trouble to build a whole world.
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I'd say start with the world, not with the characters or the plot of your story.
If you start by creating a world **around** an idea for a story or a character, you will find yourself having the world indulge the needs of the story or character.
Instead, you should start by thinking of a world that makes sense not only for the characters, but for everyone living in it. Think about geography, vegetation, lifeforms existing in your world, stage of development of humanity (and/or other dominant races), political and economical system, conflicts (on a large scale; i.e. wars and such), history of the world and the people/races living in it, and stuff like that. Once you have a world that has an internal logic, you can start by thinking about what people might do, what problems they might have, which stories could develop in your world.
Of couse, this might be difficult if your story is gonna be a [Monomyth](http://en.wikipedia.org/wiki/Monomyth), i.e. a classical hero-saves-the-world story, which in many cases contains an issue that endangers a large amount of people who can only be saved by your protagonist. Take away the hero and you have a problem ...
I hope that helps you!
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What if my world had instant communication via some magical means, such as a scrying device that allows two wizards on the opposite side of the world to hold a conversation? The technology level is pretty much standard medieval Europe right as the printing press is being invented and the world is just starting down the path towards an industrial revolution.
How would instant communication affect such a low-tech world? I'm saying that some form of magical communication has been around for a while, but it's been developing over time.
Edited to provide more specifics - In my scenario, I'm thinking that only wizards, of whom there are a limited number, would be able to communicate this way. A fairly large percentage of the population has magic, but most people have very little - just enough to do a few of the simplest charms. Being a wizard is akin to being a professional - say that there's about as many wizards in the world as ours has lawyers.
Some artifact could be used, but I think that some magical input from the person using it would still be required.
The population is very spread out with many isolated rural areas.
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This is basically the same as asking what would happen if wizards had cell-phones, or wireless telegraphs. You can look at real-world reactions to those, and extrapolate back in time.
Twelfth's answer covers the **diplomatic** and **militaristic** angles, which was one of my first thoughts as well. This would allow kingdoms to more easily span larger areas. It could also be used by spies, for espionage. Which raises an interesting question: If two wizards are communicating, how secure is that communication? Could another wizard "hack into" the channel, and eavesdrop on them?
But here's some additional uses:
1. **News**. Humans seems to be fascinated with distant events, and a network of wizards could set up a sort of news-wire for distributing notable world events -- weather patterns, wars, crimes, politics, religious matters, sporting events, etc... Of course, a more nefarious media might also put a "spin" on the news, to tell the narrative they want. News can also be used to facilitate:
2. **Trade**. If you were a merchant, and you got word that there was a famine in a town three days to the north, you might consider making a trip up that way with a food surplus, secure in the knowledge that you'd have a good market. You might not have been planning to make that trip before, so you'd be willing to pay someone to update you on recent changes to nearby market conditions. As user3913060 points out, they may well choose to keep economic information to themselves, and profit from it more directly (rather than sell it to merchants). This may depend on the ethics of each individual wizard. Or there may be laws in place to prevent this kind of "inside trading" (but how could such a law be enforced?). At any rate, if there's no easy way to transport goods, the wizards may well develop a currency based on promissory notes rather than physical possession. Then they could broker trades of the ownership of one commodity on one side of the globe with that of another commodity on the other side of the world, without the goods physically exchanging hands, much like commodities traders today.
3. **Correspondence**. Wizards could set up a sort of telegram post-service allowing individuals to send letters to loved ones (or business associates) who are located far away. This might encourage more long-distance traveling, and perhaps exploratory expeditions (if they can be funded). Imagine if Christopher Columbus could have instantly provided daily reports on his discovery of the New World back home.
4. **Cultural Diffusion**. "It's a small world" as the saying goes. If you can receive messages from people anywhere in the world, even if its not done frequently, or on a personal basis, you're likely to have at least heard stories of the way other people around the world act. This wouldn't be hearsay from some single adventurer's tale, but would be (relatively) factual information. Eventually, you'd probably become more accustomed to other cultural beliefs and behaviors, to where they didn't seem so strange. This could also be used to share what we would call "IP" today (intellectual property) -- music, art, literature, even theories and inventions, could all be shared much faster.
The limiting factor here is how common these wizards are, and how available they make their services (and for what price, and with what level of accuracy?).
And finally, these wizards would obviously share silly pictures of their cat familiars with each other.
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I'd imagine the only effect this would have is on a high level...well, I guess it depends on how many 'lawyers' are in this world ;) Day to day life is likely unaffected for the many, however kingdoms (or nations or whatever your setup is) would be able to conduct diplomatic actions and coordinate large scale actions much more readily.
Medieval without magic communication - emissaries was the main method that allied and enemy nations communicated with each other. The travel wasn't quick...although a single person could travel a pretty good distance in a shorter amount of time using trade routes and the sort. 2-3 weeks to get a message to another nation and another 2-3 weeks to get a response was not uncommon. Incidentally, this was often a role that Princesses would take, though definitely not limited. Armies (generals) were often given their orders and not receive new ones for several weeks (so changing directions like recalling your army or responding to an ever changing diplomatic world was not a simple thing).
Medieval with magic communication - the 2 - 3 week communication time is reduced to near instant. This will allow for quicker negotiations (potentially the ability to address a political blunder before it incites a war?) between two kingdoms. I'd suspect far closer ties between the rulers of different nations would develop...I would venture to say intrigue and political 'backstabbing' could happen much quicker and much more readily (late Byzantine empire if you want to see a real life example of how far this intrigue could develop). Military coordination between two nations could be far greater and rulers would have far greater control over their armies movements. The element of surprise may be far less if the ability to relay scouting information was nearly instantaneous. Technological advances and idea's could be shared in a much quicker time frame as well and you may see a more homogeneous tech level in the world
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They could get filthy rich, as an appetizer. By sharing current prices in different places, they could become the best arbitrageurs around -- **literal wizards of finance** -- for example buying gold where it's cheapest, selling it where it's more expensive, and being able to do this consistently because they'd have the fastest information. The world's price differentials would be their magical, bottomless wallet. From there, assuming no mortal infighting, they could go on to rule the world.
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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/3883/edit)
In a typical feudal society where lords preside over their domains and each lordship is inherited by the son I know it's typical for their children to also have titles. However I'm unclear on the traditional hierarchies involved.
What is an appropriate title for:
* The first son and heir?
* A second son who will (short of tragedy) not inherit his father's lordship
* A nephew or other similar relative
I'm toying around with them either being dukes, barons or earls but I'm unsure how these typically rank alongside lords (I'd hate to have them accidentally outrank their father). I'd rather stay away from knightly titles such as sir because of the nature of the world they live in.
Using English medieval history as a basis what are the most appropriate titles?
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Typically titles are bestowed from the king, some are hereditary some are not but historically it was very unlikely that a lord would give his son a title. It was far more common that the royal family would recognise the lordling themselves.
Firstly a lord is actually a catch all title for a member of the nobility, in England nobles were usually one of the following (descending in importance):
* Duke (some are royal and some not)
* Marquis
* Earl
* Viscount
* Baron
All of these qualify as Lords although Dukes are sometimes addressed as "Your Grace". In addition children of the ruling lords were often referred to as Lords and Ladies.
Typically when the son of a lord reaches maturity they may be granted their own title but this will come from the king not from their father.
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As far as I know, hereditary titles don't have associated names for their heirs apparent (like "vice-count"). The heir of a king might automatically be a prince or duke (as the male heir to the United Kingdom is more-or-less automatically the Prince of Wales, Duke of Cornwall, Earl of Rothsay and other stuff), but none of those titles specifically means "heir to the throne".
In a heavily-aristocratic society you could see senior nobles having spare titles for their kids in a similar way. For example, the Earl of Flim wins favor and is additionally created the Duke of Zorch; he can then (depending on the law) pass on the earldom to his daughter, so she becomes Countess of Flim. When the Duke of Zorch dies, she becomes the Duchess (or Duke) of Zorch, and passes on the earldom to her son, and so on. In a living aristocracy these titles may also correspond to actual jobs in government or commerce.
Asdie from that, aristocracy being what it is, you'd expect to see a lot of heirs being given non-hereditary titles (knighthoods and baronetcies) while they wait, just so they don't have to sign their name "Mister".
So, yes, it would be realistic to have titles for most of your ruling-class characters, but children wouldn't usually hold titles outranking their parents.
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If the gravity on earth was different, how would our bodies change?
For this question, assume that gravity was five time stronger (5G) from the beginning of the Earth. Would a human-like body still be able to evolve? If so, how would it differ from the bodies we have?
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If gravity were five times as strong as it is now, I'd be more concerned with whether or not our universe still existed.
Let's assume you mean that the mass of the earth was five times greater than its present mass, so that its gravitational pull would be correspondingly higher. The effects would be environment wide, so rather that focus on humans, lets look at the general situation. Here's my guess :
* **Flying Animals** These would be extremely unlikely. The extra energy required to maintain flight would demand extra strength ( = extra mass ), and conversely, the extra mass would require extra energy. The costs may exceed the benefits, so evolution might not take hold in flying animals. Some gliding by land based animals may evolve.
* **Land Based Aminals** Smaller animals would be favoured by evolution since they would require less energy to move efficiently in a strongly gravitational environment. The skeletal mass of animals would need to be proportionately higher in order to maintain whatever reduced height was optimal. Similarly, muscle mass would need to be proportionately greater if high mobility was required. Most animals would be slow moving, with perhaps a few species of predators having speed. I would guess that a low, flat form with many supporting legs would be the most common body design, similar to bugs - think centipede.
* **Water Based Animals** Again, stronger gravity would favour bottom dwelling aquatic species. The amount of energy needed to swim freely would exceed the amount of energy available from food floating freely (plankton), and free floating food would sink faster. Again, one assumes that a flat form with larger skeletal mass would be the most common form. Localized underwater currents may provide some extra variety. Salt water is more buoyant that fresh water, so the changes would be more pronounced amongst fresh water species. The surface of the oceans may support life, perhaps in the form of a paper-thin animal with a large surface area and featuring thing tentacles descending into the waters to feed on plankton forming in the sunlit surface waters.
* **Plant Life** While height may be common, side branching would be very difficult and expensive to maintain in terms of energy consumption. Plant life would be unlikely to bend in the wind since they would require extra rigidity to support their weight. Once again, low growing, flat, well supported forms would be dominant.
* **Geology and Climate** The extra gravitational pull of the earth would make it more difficult for high mountains to form. This would mean the surface would tend to be flatter which may imply less dry land and more surface area covered by ocean. Rivers would be less mighty. The climate would be hotter. This is because the earth itself would be denser so its core would be hotter. Also contributing to a hotter planet would be the extra energy required to lift water vapour from the seas into the atmosphere, perhaps resulting in fewer clouds and less rain. This extra energy could come from a more turbulent atmosphere, but that seems unlikely since a smoother planetary surface (no big mountains) would actually reduce atmospheric turbulence.
So ya, things would be shorter and fatter. Kind of like living in Alabama.
**EDIT**
Reading sixfootersdude's comments below, I think I have overlooked an atomospheric consequence of this scenario. The atmosphere would hug the earth much closer than it does currently. This added density would result in added heat since molecules would collide much more frequently. It this is the case, then one would expect to see many more cloud and much more rain, rather than the drier climate I had originally assumed. One suspects that visibility would be severely restricted.
I don't see how a denser atmosphere would be more helpful for flight. Gram for gram, animals would weigh five times as much. The atmosphere would need to be many thousands of times denser (possibly more) to allow for the type of flight described. This would make the atmosphere much more difficult to move through, further hindering flight and all types of motion by animals.
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Bigger and slower (though to that creature, it'd be normal and we'd be smaller and faster).
5G doesn't simply effect the weight of creatures...it effects every element on the globe. Air pressure become significantly stronger and heavily impacts the resistance of the atmosphere to movement. Rain becomes heavier, but has to battle the higher pressure of the atmosphere to fall (terminal velocity changes). Oxygen at 5g (assuming this results in 5x the atmospheric pressure) actually becomes toxic to life as we know it at, just from the pressure of the atmosphere. Water boils at 120 degrees from simply doubling the pressure on it, however the increased pressure would also force down the melting point of water significantly.most of the equilibrium's that balance our body change under pressure as well. Life would have to be fundamentally different at a chemical level...pressure heavily effects photosynthesis, so chlorophyll plants may never come to dominate. Blood pressure would have to be significantly higher to ensure circulation...Oxygen content in your blood (both from regular content vs oxygen saturated) is heavily based on pressure. In short, pressure effects the equilibrium of nearly every chemical process known life relies on.
My guess is creatures would be larger and slower. Not sure if I can speculate beyond that. This is also my answer to speculation on what other chemistrys life could be based on...in different gravitys when chemical properties change, we really have no clue what chemical processes can drive life.
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While it is difficult (read: impossible) to predict what this would mean for a world, I'm going to go ahead and guess a 'no' on humans existing. Human ancestors were primarily tree-dwelling mammals and in a world with 5G, trees become pretty darn dangerous.
Imagine falling out of a tree. That hurts right, you might even kill yourself. Now imagine falling out of a tree weighing 400 kg. You're going to hurt yourself, a lot.
Massive dinosaurs would also be unfeasible in high gravity environments, and their lack may very well mean mammals end up dominant way earlier. I would assume that in a high gravity environment, almost all life will be low-to-the-ground to avoid falling related injuries.
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Here is a late answer: most life would be in water as water based life would have no problem with gravity. Buoyancy is not affected by gravity. Additionally, internal and external pressures would be balanced. Circulation systems would need more pressure to work against higher pressures. But then again, water cannot be compressed much. Resulting in a manageable change.
All in all, the ones that got hit would be land animals. Being on land could be so costly that in your world there might be no land animals at all. Or just small bug type animals with short plants would cover the face of the earth.
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The planet is a barren rocky dwarf planet which orbits at 0.05 AU from its star of 0.9 solar masses, at 6 billion years old. Because of this, it’s surface is melting and evaporating, forming a thin atmosphere, which is continually being blown off by solar wind, recondensing into dust which is spread throughout the star system.
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Yes hot hotness. Rock comets are close to what you describe. From previous answer:
[The plausibility of Rock comets and Molten Asteroids](https://worldbuilding.stackexchange.com/questions/223985/the-plausibility-of-rock-comets-and-molten-asteroids/224050#224050)
<https://astronomy.com/news/2021/09/sodium-may-make-asteroid-phaethon-fizzle>
>
> Aptly named after the son of the Sun god in Greek mythology, Phaethon
> has a 524-day orbit that brings it within just 0.14 astronomical units
> — where 1 AU is the average distance between the Earth and Sun — of
> our star, well within Mercury’s orbit. At that distance, the Sun heats
> the asteroid’s surface to about 1,390 degrees Fahrenheit (750 degrees
> Celsius). While any water, carbon dioxide, or carbon monoxide ices
> just under the surface would have evaporated long ago, sodium — an
> element abundant in asteroids — could be fizzling just under its
> surface.
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>
>
Phaeton and the similar ["rock comet"](https://earthsky.org/astronomy-essentials/rock-comet-3200-phaethon-geminid-meteor-shower/) [Icarus](https://adsabs.harvard.edu/full/1992JIMO...20...20S) are stony bodies that get very close to the sun. Each of these bodies is thought to have given rise to a cloud of little fragments that rain down on the Earth as meteor showers - The Geminids from Phaeton and the Areitids from Icarus. They get so close to the sun that comety stuff like ice is long gone. There is a thought that boiling sodium inside them might blast off fragments that turn into the meteors which is what you are thinking about - stony stuff melting because of the heat.
But Phaeton is twice the distance from our sun as your planet is from its star. The Parker solar probe is going to get as close as you want: 0.04 AU
<https://www.nasa.gov/content/goddard/parker-solar-probe-humanity-s-first-visit-to-a-star>
The spacecraft will fly through the Sun’s atmosphere as close as 3.8 million miles to our star’s surface, well within the orbit of Mercury and more than seven times closer than any spacecraft has come before. (Earth’s average distance to the Sun is 93 million miles.)...
>
> At closest approach to the Sun, the front of Parker Solar Probe's
> solar shield faces temperatures approaching 2,500 F (1,377 C). The
> spacecraft's payload will be near room temperature.
>
>
>
>
> To perform these unprecedented investigations, the spacecraft and
> instruments are protected from the Sun’s heat by a 4.5-inch-thick
> (11.43 cm) carbon-composite shield, which needs to withstand
> temperatures outside the spacecraft that reach nearly 2,500 F (1,377
> C).
>
>
>
Sodium and sulfur will be long gone. What remains would be nickel and iron and silica. Oxides of aluminum and magnesium will not melt at 1377 but the metals will. The thin atmosphere you describe will be metal gases.
Note that so close to the star your planet will be tidally locked. It will have a cooler dark side. The evaporated metals may rain down on the dark side. Like this giant exoplanet which is hot and close to its star like your planet.
<https://earthsky.org/space/wasp-76b-exoplanet-iron-rain-espresso/>
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# It's a napkin stretch, so not much information
What is the surface temperature of the planet? If it is high enough, then the rocks can get hot enough to evaporate and outgas from the planet.
If your planet has a sufficiently high escape velocity, then it can retain rock vapor on its surface. That means you need to specify the mass of the planet, so that the escape velocity can be calculated.
What is the loss rate of the planet's mass? This is useful in determining the lifespan of the planet. Too high and the planet evaporates away in just a few million years. Too low, and the planet is going to last for billions of years.
0.05 AU sounds too small for a orbit. Although there are a few planets that orbit much closer (WASP-12B at 0.02 AU), their orbits tend to be highly unstable and they quickly fall into the parent star. You need to make the orbit a bit bigger, and a bit stabler. Still hot as lava, but less chances of falling into parent star.
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**Don't worry about the distance**
Don't both trying to calculate the distance to the Sun. The exact number of astronomical units has no qualitative effect on the world or story.
What I can tell you is that a suitable distance certainly exists. And I'll tell you how I know too:
Put your planet too far away and it will not evaporate at all. Put it too close and it evaporates in ten minutes. Somewhere in between is a distance where it takes 10 billion years to evaporate fully.
Put your planet there.
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Silicate rock starts melting at around 1,200 °C. Mercury has a surface temperature as high as 430 °C. Your planet is around 9.5x closer to its solar analogue than Mercury is to the Sun. If mean solar output is roughly the same, your planet recieves something like 90x the insolation that Mercury does.1
Without going into much math, I think it's safe to say there will be a lot outgassing coming from your world.
1 that's likely an overestimate because at these distances the disk of the star takes up an appreciable fraction of the sky. But, it'll still be a *heck* of a lot.
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## Story in the present, something happened in the distant past
**Think of your story time window**
How much "past" would you need ? You can have a planet that age, but you don't need this "lava planet" to exist there for 6 billion years. You just need a planet that is 6 billion years old. When your story has a time window of say, thousands of years, the situation can have developed like you describe. Just put an explanation for it, e.g.
**Unfortunate stellar dynamics in the distant past caused this**
Something happened a few million years ago. Due to a near-collision with a neighboring planet, your poor dwarf was moved into its current apocalyptic orbit. At first, when the near collision happened, it need not be a mass extinction event: apart from the view, the unusual irregular temperatures and seasons, no one on your planet noticed what had happened, until it got very warm. Nowadays, everything turned into lava and the dwarf planet is approaching its definite end: but your planet *could* exist for another, say 100 thousand years, before it has evaporated, or spiraled into the sun. Your story will have a lot of time to develop, your lava planet age (and its past) can be maintained.
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Just wanted to check the scientific feasibility for a method of moving a shuttlecraft from the surface of an earth-like planet into space. This more for a space opera style setting, rather than strict hard sci-fi.
In many works of science fiction, ascending into space in a small craft without the aid of a rocket loaded with several tonnes of fuel is made to seem trivially easy. Could one way to achieve this, without having to rely on any sort of hand-wavey "anti-gravity" technology, be to have the small craft equipped with a force field generator that can repel air molecules, thus creating a bubble of vacuum around the craft? Would this vacuum bubble surrounding a shuttlecraft float up to the top of the atmosphere once a mass of air greater than the mass of the craft has been repelled? Basically what I'm imagining is a craft that takes off from the ground in a way similar to modern planes, but then once it's at a certain distance off the ground, it starts projecting this force field and growing its radius until the effect of gravity on craft begins to weaken and then neutralise, allowing the engines to only need to engage once the craft "floats" out of the atmosphere.
Is there any obvious problem with this idea that I'm missing?
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**Yes, there are problems**
First, getting out of the atmosphere is the comparatively easy part of going into orbit. Getting a rocket to travel a hundred or so km straight up so that it is effectively out of the atmosphere is not that difficult, getting it to travel "sideways" at the 7.8 km/s required to achieve low earth orbit (LEO) requires enormously more delta v. If you look at the [old Space Shuttle launch profile](https://www.nasa.gov/pdf/466711main_AP_ST_ShuttleAscent.pdf), the Shuttle was outside the denser sections of the atmosphere (altitude approximately 50 km) at the point of solid rocket booster (SRB) separation but "only" travelling at 1279 m/s. It needed to accelerate for a further six-and-a-half minutes to (almost) achieve LEO. (A final correction burn was required in order to achieve a stable orbit.)
(Note that while the SRBs made it to an altitude of 50 km under thrust and continued to a peak altitude of 67 km on inertia, they then fell back to Earth and were recovered for recovery. Getting to altitude did not get them into orbit.)
The two SRBs combined massed 1,180,000 kg and were more than half the mass of the shuttle at launch. So can you equate your forcefield generator to the SRBs and say it does the same job? Unfortunately, no - the SRBs also provided structural support to the fully-fueled orbiter + external tank and provided most of the thrust to not only clear the lower atmosphere but to get the shuttle up to almost a sixth of the necessary speed to make orbit. The rocket equation is painful - you need more fuel at the start to accelerate not only the payload but also the fuel you will need later. Unlike the SRBs, the forcefield generator is presumably retained as part of the shuttle, which means that more fuel will be required in order to accelerate the shuttle later in its flight profile, offsetting any savings in the early part of the launch. So unless the forcefield generator has a negligible mass, it probably isn't going to help much.
A second problem is structural. While the lander was designed to glide and land like a conventional aircraft, the combined structure at launch could only withstand very limited lateral forces. You cannot simply weld a big ring onto the top of the shuttle and lift the combined mass from that point, the craft would disintegrate. In order to make the structure "liftable" from some arbitrary point where the forcefield generator is mounted, a huge amount of structural reinforcement will be required, which will increase the total mass of the craft, which will increase the fuel required to accelerate it, which will increase the mass further... This is one of the main reasons why various real-world proposals for piggybacking launch vehicles into the upper atmosphere using balloons or conventional aircraft have been abandoned as infeasible.
Third, in order for any decent size shuttle to become buoyant, it needs to be displacing a truly huge quantity of air. If we continue to use the old [space shuttle](https://en.wikipedia.org/wiki/Space_Shuttle) as an example it had a mass of over 2,000,000 kg at launch. Given that a cubic metre of air at sea level has a mass of 1.29 kg, this means that the force field needs to push the air out of around 1,550,000 cubic metres of space at sea level.
As it ascends and the atmosphere becomes thinner the forcefield needs to keep increasing in size to compensate. At a height of 50 km, the atmosphere is approximately 1/650th as dense as at sea level, so it will need to maintain around 1,000,000,000 cubic metres of vacuum.
Assuming that the forcefield is spherical and centred on the shuttle - what happens when the shuttle is sitting on the ground and the forcefield is turned on, with half the sphere underground? What happens if solid objects impinge on the forcefield? (Maybe the bottom of the sphere should always be just above the shuttle, just an idea.) A significant issue if the shuttle is *inside* the sphere, as described, is that it is totally at the mercy of the weather during a long ascent. If it fires its engines at all it is effectively just redistributing its mass within the sphere rather than actually changing its vector. Along the same lines - *very* important to turn the forcefield off before firing the main engines!
In summary - even if this technology did exist, unless it had negligible weight and power requirements it would probably cause more problems than it solved in launching a shuttle. There are plenty of potentially great applications of this technology, but that is outside the scope of the question.
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While the vacuum bubble is indeed an important part of this drive's operation, it's actually not the most important application of the force field for the process of escaping a planet's gravity well. The main goal of the relatively passive vacuum bubble phase is just to get high enough into the atmosphere that it's safe to extend the fields and start pulling atmosphere to gain thrust in a way akin to ancient jet engines, but with the ability to gather much more air and accelerate it to much higher speeds. In the process it creates a vacuum bubble in front of the accelerating ship, clearing the way for rapid acceleration despite a relatively thin atmosphere. In principle the drive's jet function can be operated in the denser lower atmosphere, but all vacuum jet drives are legally required to have safeguards to prevent this, as the consequences can be extremely destructive.
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I see two problems with your theory, but don't let these stop you as you have already said it is a space opera story. My concern is always the suspension of disbelief.
Problem #1: Your forcefield can push the air molecules away from your craft. This is fine, but as your craft moves, it has to push the forcefield that is pushing the air, so you have effectively increased the air resistance as presumably the forcefield is larger than the hull of the craft.
Problem #2: You still have to fight gravity which is a bigger problem than the air. Your craft will not just float up because of your vacuum bubble. The air on earth applies an average of 15 lbs per square inch under STP (Standard Temperature and Pressure) at sea level. Of course your forcefield is still having to repel that air so it is still effecting the craft generating the forcefield. Unless your forcefield also acts as an anti-gravity field, you still have to provide enough thrust to reach escape velocity.
I agree with KerrAvon2055 that your forcefield could have other applications, but outside the scope of your question.
Remember when writing your story that you don't want to necessarily allow facts and science to screw up a perfectly good story. As mentioned at the beginning, you have to guage how far you can push the suspension of disbelief without breaking it. Once that is broken, the story will suffer in the eyes of the readers because they will get hung up on the "fantasy" aspect you have introduced.
Good luck and have fun with your writing !!!
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Let us suppose that ten high kiloton to low megaton range fission/fusion weapons are being detonated between three and five kilometers under the surface of the sea on a planet much like earth, in a solar system much like our own. The detonations occur within a distance of several kilometers of one another, within the span of five minutes. For the sake of this question, please assume modern day Earth and our solar system.
Now, let us suppose that there is a spaceship entering the solar system from interstellar space, carrying and employing the most sensitive space-based devices designed by humans to date to detect atomic detonations, and that the detonations occur on the side of the planet facing toward the spacecraft.
How far away from earth could the atomic detonations be reliably detectable?
[Answer]
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> between three and five kilometers under the surface of the sea
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Well, that will cover up almost everything, I'd say.
There was a US nuclear test, [operation wigwam](https://en.wikipedia.org/wiki/Operation_Wigwam), that involved a modestly sized warhead (~30kT) at 600m depth. There's some [footage of the test on youtube](https://youtu.be/fYUNAFVIAK8?t=526). There was a big splash on the surface:
[](https://i.stack.imgur.com/P27rD.png)
with disrupted water in an area a couple of hundred metres across, but no mushroom cloud, fireball, etc. A bigger bomb will be more dramatic, but you're talking about tests in several times the depth of water.
What you'll see from space will be some big, brief splashes, and some transiently warmed water. Unless you have seismic sensors or hydrophones on the planet itself, or radiation sensors in the atmosphere, there's no guarantee that you'd be able to identify that the event was caused by a nuclear blast even if you did manage to see it. You could probably tell that it wasn't caused by a meteorite strike, but I'm not sure you could rule out submarine volcanism.
Lets assume you have a nice [diffraction-limited](https://en.wikipedia.org/wiki/Diffraction-limited_system) telescope with a collecting element of size $d\_t$ that's looking at the right place at the right time in good weather. According to [Rayleigh's criterion](https://en.wikipedia.org/wiki/Angular_resolution), you could resolve a feature with diameter $d\_f$ in light with wavelength $\lambda$ at range $r = {d\_td\_f \over 2.44\lambda}$. A 20m aperture telescope would see a 200m feature in 500nm light about 3 million kilometres away, which is about 8.5x the distance between the Earth and the moon. A 100m aperture scope could see a 10km feature from half an AU away. That ain't too far on the grand scale of space... chances are good that the bomb-builders will see your starship braking into the system before you see their deepwater blasts, unless you have reactionless drives and fancy heatsinking. Remember also that if the thing you're searching for is about the same size as the resolution of your scope, then you're going to end up with "a blue pixel turned white for a few seconds and then turned blue". Not quite a smoking gun!
With atmospheric and surface tests there's a reasonable chance you'd be able to see the flash which will be quite distinctively unnatural. Humans had things like [Project Vela](https://en.wikipedia.org/wiki/Project_Vela) that could detect nuke x-ray flashes from [high earth orbit](https://en.wikipedia.org/wiki/High_Earth_orbit) (100000km up) in 1963. Anyone capable of building and operating an interstellar spaceflight will likely have the ability to detect those flashes from much further away... the mere presence of a signal would be enough to raise eyebrows (or the spacefaring species equivalent thereof), even if it couldn't be localised to anything more precise than "probably that planet over there".
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*edit*
As a footnote on short-wavelength (eg. gamma and x-ray) detection:
* X-ray telescopes do exist, as [focussing x-rays is possible](https://en.wikipedia.org/wiki/X-ray_optics)! We already have the technology to make x-ray optics that can work with 80keV x-rays (17.7pm).
* [Gamma ray astronomy](https://en.wikipedia.org/wiki/Gamma-ray_astronomy) is a thing, but focussing gamma rays is impractical, probably even for starfarers, absent some magical new unobtanium or technology which is out of the scope of this answer. Shielding gamma rays *is* possible though, which means that observing a narrow region of sky can be done, and larger pictures built up by changing the orientation of the detector.
A gamma-ray detector on the [CGRO](https://en.wikipedia.org/wiki/Compton_Gamma_Ray_Observatory) (launched in '91, so it is *old tech*!) took this image of the moon from low Earth orbit using only photons with energies >20MeV:
[](https://i.stack.imgur.com/yjiLN.png)
It is an open question as to how far away one could be and detect the gamma-ray signature of a nuclear blast, but localising a signal to a particular planet would not be impossible, so long as that signature could be distinguished from background noise.
The [Vela](https://en.wikipedia.org/wiki/Project_Vela) satellites used x-ray and gamma ray detectors in tandem as part of their nuke detection strategy, so clearly enough radiation *can* escape the atmosphere to be detected 100000km away by 1960s technology. You can extrapolate modern and future detection capabilities as you wish. Your spacefarers might not be able to detect the gamma ray signature, but a combination of x-ray telescope observations and visible-light [bhangmetrology](https://en.wikipedia.org/wiki/Bhangmeter) seems like it should do the job in spotting nuclear fireballs, or things suspiciously like them.
Nuke blasts that do not generate a visible fireball will not be producing detectable amounts of short-wavelength radiation. This includes sufficiently deep underwater blasts and buried blasts.
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*edit 2*
A footnote on antineutrino detection. The fission primary of a Ulam-Teller style staged thermonuclear bomb generates a hefty dose of electron antineutrinos. These are somewhat unusual on Earth, and as such seem like they'd be an interesting way to detect a nuclear blast.
Unfortunately for your spacefarers:
* neutrino detection is extremely hard, and detectors need to be very large.
* false positive antineutrino signals are generated by cosmic ray interactions, and require massive shielding to reduce even on Earth.
* anyone using nukes can (or soon will be able to) build nuclear reactors, which generate similar antineutrino fluxes to bombs going off
* the neutrino detector on Earth is not going to be more than ~12700km away from a blast on or under the surface. The inverse square law means that distant detectors will receive vastly fewer neutrinos from the event.
* the earth itself is hella radioactive, and produces a lot of antineutrinos. The sun, too, produces some. This noise makes it even harder to detect small distant sources like a small nuke going off.
* the starfarer's own spacecraft likely has some kind of nuclear propulsion and power supply, which will inevitably generate its own neutrinos of various kinds.
There's more information to be had if you read [Antineutrino Detectors Remain Impractical for Nuclear Explosion Monitoring](https://arxiv.org/abs/2005.02756).
Between the first and last bullet points, you can see you'd have to build some huge detectors (maybe out of comet ice) and then fly away from them to let them work. And if you're doing that sort of thing, you'd probably be better off just building some bigger telescopes to observe the inner system instead.
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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 idea of potentially using Metallic Hydrogen as a replacement for smokeless powder in current day rifles as a propellant has often been thrown around. What these question don't ask is how well it would work.
So to get to the question: **How well would Metallic Hydrogen work as a propellant?**
To start with some assumptions:
* Metallic hydrogen is stable at STP
* The engineering difficulties for containing the rabid expansion inside the weapon has been solved through tougher and lighter materials etc.
To have a more defined question to answer, how much Metallic Hydrogen is needed to propel a 9mm (9x19), 5.56mm (5.56x45), 7.62 mm (7.62x51) and a 12.7mm (12.7x99) to the velocities that they typically display in modern firearms (in grams).
Calculations and the formulas would be appreciated so that I and any world builder who would like to use metallic hydrogen as a propellant have the nessacary resources.
[Answer]
Here's a crude, back-of-the-envelope estimate:
This source ( <https://www.nasa.gov/pdf/637123main_Silvera_Presentation.pdf> ) estimates the recombination energy of metallic hydrogen at 216 MJ/kg. For comparison, the same source estimates the energy for TNT at 4.2 MJ/kg and from <https://en.wikipedia.org/wiki/Dynamite#Form>, one megajoule is roughly equivalent to the energy of a stick of dynamite, so metallic hydrogen is pretty energetic stuff. Converting 216 MJ/kg to more reasonable units gives us 216 kJ/g.
The muzzle energy (<https://en.wikipedia.org/wiki/Muzzle_energy>) of various projectiles can be looked up easily. For example, a NATO 7.62x51 round seems to have a muzzle energy of about 3.5 kJ.
We can find an estimate for energy efficiency of about 33% for small arms sourced from <https://en.wikipedia.org/wiki/Physics_of_firearms#Firearm_energy_efficiency>, meaning that we need to triple the muzzle energy to get the necessary propellant energy. (Yes, the estimate is for a combustion firearm but it will serve for illustrative purposes. The actual efficiency would depend on the specific mechanics of this hypothetical gun.) Doing the math, (3.5kJ \* 3) ÷ 216 kJ/g gives us roughly 0.05 grams of metallic hydrogen as the minimum that delivers the necessary energy.
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[Question]
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One of the most overlooked traits of vampire biology is superhuman strength. In fact, Dracula himself was described as having the strength of twenty men. Now, this description posed a physical problem because this is how the Count originally looked:
[](https://i.stack.imgur.com/YU80T.png)
And this is how a man might really look if he were twenty times stronger:
[](https://i.stack.imgur.com/zC5OW.png)
Lately, I've been exploring a brainstorm in which vampiric superstrength can be possible without resorting to making the subject as big or dense as Kong. Using genetic engineering, how can this be achieved?
*For further clarification, he could easily be mistaken for an ordinary human being unless he demonstrated his strength...or his long, baboon-like canines.*
[Answer]
Human muscular strength stems from two factors: a mechanical one (the myosine-actine fibers that contract) and an electrochemical one (the innervation that controls said fibers). If I recall correctly, humans allocate motoneurons and motor axons in a different way from chimpanzees or gorillas, trading finer motor control for brute power. A chimp is two to five times stronger than a human per unit weight, but doesn't have the same level of fine motor control.
(Humans are believed to possess a chemical bypass into this less-coordinated, more powerful muscle operation mode. In [Irish lore](https://en.wikipedia.org/wiki/C%C3%BA_Chulainn) it is called *ríastrad*, warping-spasm or battle-fury; in modern times, as @DWKraus noted, there are documented cases of the so-called "hysterical strength").
Extra nervous fibers could then be gengineered to restore the maximum theoretical mechanical strength with no need of adding significant mass. So we'd get a man two to five times stronger with no outside change.
To exceed this, our "human" needs a different "engine". There are [myosin analogues](https://en.wikipedia.org/wiki/Myosin#Myosin_classes) that have more strength than conventional myosin; it is not impossible for an even "stronger" molecule to exist. Two or three times the elementary strength, slightly more muscle mass, and twenty times overall is doable. This part is known to happen in humans due to several different mutations (with normal innervation it only brings two or three times normal strength, and even then, only if the mutations are exactly right, or you get drawbacks of all kinds: there *is* a reason if this mutation never became dominant, even if there are reports of ["weird-touched" warriors](https://en.wikipedia.org/wiki/Berserker#Berserkers_%E2%80%93_bear_warriors) capable of fearsome feats of strength).
The issues you're going to have are then oxygen and energy expenditure (up to twenty times as much during efforts, and I expect at least twice the norm when at rest), and bone structural resistance.
A tetanic contraction (chimpanzee-level strength) can break a bone in a normal man; our vampire analogue runs a risk four times higher. Bones can be reengineered quite easily making them out of slightly different materials, but that almost certainly means they won't be able to support *marrow*, and therefore blood cells can no longer be manufactured. Our vampire analogue will require blood from an external source, or a dedicated organ (a modified spleen, probably).
Then we probably have to expand a bit the thoracic cavity, to accommodate a larger, stronger heart - 100 mL of blood per heartbeat aren't going to cut it, we need at least ten times that, so a larger, fast-beating heart. This [German toddler](http://www.nbcnews.com/id/5278028) has two copies of a mutated gene for myostatin-induced strength... and a heightened heart risk factor. He might be able to strain himself into a heart attack.
Then, you also need thicker blood vessels, and/or higher haematocrite, and/or a different (way smaller) haemoglobin analogue - this last prevents the possibility of supplementing blood from an outside source though; and the haemoglobin analogue might not be the usual blood red. If it was colourless, we'd get a much stronger person, with a terribly pale skin. Make the analogue photosensitive (e.g. it will polymerize or coagulate or even dissociate exothermically when hit by UV) and the poor creature will be doomed to darkness, since sunlight is liable to make them literally burst into flames.
# do we need "twenty" men?
For a large part of human history, "strong as X men" more or less equated "able to defeat/survive X opponents in a melee".
But "X opponents" *cannot* optimally bring to bear their strength e.g. in battle for geometric reasons, because no more than, say, four or five can really grapple with their opponent at the same time.
Also, one's full force isn't always fully directed against the adversary - advertence, speed and technique all count (in several martial arts, for example, you use *your opponent's strength* against themselves).
So, a single person "just" three times as strong (*with* suitable bones), faster, nimbler and with the required endurance - all things that can be supplied with improved neuromotor system plus, as said above, bones and energy reserves - could really beat twenty or even more men, and so be classified "stronger than twenty men".
(Merlin Athrawes, an artificial construct in David Weber's *Safehold* series, is about ten times stronger and faster than an ordinary person, as well as having
practically *infinitely* more endurance on account of being nuclear powered; in several occasions he and their(\*) battle steel katana prove able to overcome a number of assailants in the order of *one hundred*).
(\*)
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> Merlin was templated after a woman, Nimue Alban. While the Merlin character is male, he later teams up with a *female* avatar of himself, Nimue Chweriau, which makes for a quite complicated use of pronouns.
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[Question]
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I've seen several people independently come up with the idea of three or more sexes where one sex is responsible for brooding the young (pregnancy, pouch, feeding, something along those lines) but doesn't actually contribute any DNA. Can you suggest some an evolutionary mechanisms that would support the development of a "brooder" sex that provides caregiving to young without passing on their genes?
[Answer]
1. Kin selection. They aren't passing on their own genes directly, but they are helping pass on the genes of their close relatives, which is almost as good. This would make the most sense in the context of eusocial creatures, like bees or ants. In situations where lots of individuals are sterile, and it makes sense because they support closely-related breeders, it would certainly work at least as well to distribute the effort of actually gestating the young as well. Perhaps if nakee mole rats (eusocial mammals) had evolved from marsupials instead, this is exactly what we'd see.
2. They aren't actually the same species. Rather, some normal disexual species parasitizes a second species to raise its young (like cuckoo birds, or parasitic wasps), which is culturally interpreted as a third gender due to their importance in reproduction and limited historical knowledge of genetics. This could easily evolve from straight parasitism to a mutually beneficial arrangement if the brood species is effectively domesticated, so their parasites actually take care of them and improve their own 0chances of reproducing.
3. A hybrid species complex. Option 2 actually requires 4 genders (one for each underlying species, so the brooders can reproduce themselves), unless the host species is either parthenogenic or hermaphroditic, but this could be eliminated with a suitable hybridization complex, resulting in one variant which is either exclusively male or exclusively female. To provide brooders, you would want an exclusively female variant. The brooders would pass on their genes either by genetic cloning which can only be triggered, for ancestral reasons, by copulation even though the donor DNA is discarded, or they can actually reproduce sexually with males as well as hosting embryos produced by non-brooding females.
[Answer]
**Nest helpers.**
[](https://i.stack.imgur.com/PtspP.jpg)
<http://www.columbia.edu/itc/barnard/biology/biobc3280/lectures/social2.pdf>
<https://en.wikipedia.org/wiki/Helpers_at_the_nest>
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> Helpers at the nest is a term used in behavioural ecology and
> evolutionary biology to describe a social structure in which juveniles
> and sexually mature adolescents of either one or both sexes remain in
> association with their parents and help them raise subsequent broods
> or litters, instead of dispersing and beginning to reproduce
> themselves.
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In your scenario, a breeding pair will produce males, females, and one or more "brooder sex" individuals. The brooder sex individuals will function like the immature jays in the scenario above - helping to feed and defend their brothers and sisters. A brooder from the prior generation would remain with its parents as these immature jays do.
Immature "nest helpers" contribute to their own genetic fitness by improving the survival rate of their little brother and sisters, who carry the same genes as the nest helper. So too the brooder sex - by improving care to the young the brooder improves the genetic fitness of these young, and so its own genetic fitness.
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One could make a case that postmenopausal females of our own species are exactly a "brooder sex" as you describe. I am a big fan of Sarah Blaffer Hrdy and her social anthropology studies about this. A postmenopausal female is not going to have more children of her own, but her genes are represented in her children and grandchildren. She improves her own fitness by keeping them alive. The presence of capable, nonreproductive individuals with a stake in the survival of babies and children improves the genetic fitness of those children.
[Answer]
The same reasons & processes that cause pack animals to babysit siblings, nieces & nephews (cf african wild dogs & wolf packs where there's only one alpha female that reproduces) & resulted in non-reproductive drones in insects (ants, termites & bees etc).
They share DNA with at least one of the sexually reproductive pair.
That's the evolutionary route to & reason for this, no other will work.
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> **That was the answer to your question / the rest is just musings on the theme.**
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> *The first offspring of a fertile female might be non-reproductive daughters that can carry further offspring so that (as she doesn't have to bring them to full term herself) their mother-queen can churn out offspring faster.*
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> *Maybe they reproduce like marsupials making it simple to transfer young to a non-fertile daughters pouch or perhaps the mother transfers the fertilised egg to their womb with an ovipositor.*
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> *Some ant species kidnap workers in egg or larval form from other ants nests & these kidnapped ants become workers for the kidnappers nest (taking advantage of their victims instincts) so the same could apply here.*
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> *In an intelligent species that originally evolved this way brooders might hire themselves out.*
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Note : If the 'brooder' doesn't share DNA with at least one of the genetic parents it's a parasitic reproductive strategy like a cuckoos' & you couldn't by any stretch of the imagination call those brooders a third sex, they're most likely a different species with their own reproductive process that's been hijacked to serve the others.
*A small pedantic niggle about nomenclature : If it's not contributing DNA it's not really a third sex biologically speaking, insect drones aren't a third sex, they're infertile females, though such drones could be infertile males in a fantasy species (as evidenced by sea horses & some other species).*
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[Question]
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Imagine a world quite like our own, except where technology took a different turn. Instead of researching communication, transportation, the cosmos, and the general nature of the universe, scientists researched biology and how to manipulate it.
Here, if you have enough money, you can get one more arm, five more arms, spider-like legs, or anything else you can find in nature for your descendants. This process works by editing your sex organs so that your children's genetic code is different from their parents'.
However, I am not interested in the meager boundaries of nature. I want something much more exotic. Specifically, I want a complex symbol to be placed on some specific part of the bodies of my descendants using genetics.
**Needs:**
* Millimeter Precision
* Can be put, at the very least, on the wrist or back of hand.
**Wants:**
* Able to Specify Different Colors
* Can be anywhere on the body that has skin.
* Can be turned on or off at will. (Least important feature. If your answer finds a way to do this I will be amazed.
**Is this possible?**
[Answer]
You have a lot of options. I'll list a few from most to least feasible (and also least to most expensive).
* **Seed the skin with melanocytes:** Graft or inject stem cells into the skin designed to become [melanocytes](https://en.wikipedia.org/wiki/Melanocyte), the pigment-producing cells responsible for skin color. Such a technique would produce millimeter precision, and tattoos designed this way wouldn't fade until death.
* **Use chromatophores:** Cuttlefish change color like chameleons, but their mechanism for doing so is arguably much more accessible to humans. Whereas chameleons have complex crystal structures, cuttlefish use [sacs of pigments](https://en.wikipedia.org/wiki/Cuttlefish#Chromatic) that they can voluntarily expand and contract. This method is complex in that it requires some serious gene editing, but helpful in that it allows for color changes and even possible voluntarily alterations / removals.
* **Hard-code pigmentation into the human genome:** If your society is advanced enough, it could genetically encode a pigment tattoo into a certain lineage, similarly to a zebra's stripes. This is speculative, untested, and infeasible, but it's the only concrete way to produce something hereditary.
[](https://i.stack.imgur.com/gAazu.jpg)
[Answer]
**Surprisingly, yes.**
Have you ever seen a Siamese cat? One of the unique features about them is the fact that they've got black fur clustering around their face. And the way this works is pretty neat too - the genetics by the black fur aren't any different from the white fur around the rest of the body. Rather the physical expression, that is the phenotype, is different because of the [lack of heat](https://www.catster.com/lifestyle/cat-facts-genes-siamese-cats-temperature-sensitive-albino) around the Siamese's cat's face, paws, and tail, which otherwise alters certain protein structures so that the fur is white.
So what you do is you whip up a batch of these proteins that create organic pigmentation with the human skin, and then you have a second batch of proteins serving as the inhibitor to the first batch. The catch? When the second batch is heated up to around 103 F, it denatures. Essentially, when you apply a mildly hot design to the skin, it will heat up that area and cause the cells there to react accordingly. Now, with the inhibitor protein out of the way, the first set of proteins whip up some pigmentation, and you've got the tattoo.
This can be done with precision, or at least as precise as you can get the heat control, to that end I'd recommend use a cold insulator wrapped around the design you're using for maximum neatness. It can be applied to the wrist or the back of the hand, really anywhere on the body, and by applying heat or cold, you can conjure it or dispel it at will. The only thing it can't do is be different colors - you can pick whatever color you want to *start* with, but this structure is binary so once you pick a color, you're stuck with it until you rewrite all the genetics in all your skin.
[Answer]
### This is easier than the other stuff you mention
...Not that it's *easy*, mind you. It's still something far beyond anything we can conceivably pull off in the near future.
Gene editing encodes proteins. Genes are activated based on their cell's position in the body, and exposure to chemicals produced by that area of the body. This causes them to produce particular chemicals of their own, triggering gene expression in nearby cells in turn.
The details are poorly understood right now, but you're talking about a society that has a deep enough understanding of developmental biology that they can make extra limbs, which is one of the hardest things to do with genetic engineering. If you can pull *that* off, creating a pattern of pigmented cells in a particular area of the body should be trivial.
Simply program the location to activate during development in a particular region of the body, like the back of the neck, triggering a genetic program that activates or deactivates the pigmentation gene based on how far it is from the initial locus and its proximity to different locations in the body. There might even be a ready-made computer program where you can draw an image and have the program put the gene together for your own custom design.
I say "simply" but this is far from simple. However, it is *far* simpler than adding extra limbs, which works according to the same basic process but where you have to account for interconnected nerves, muscles, bones, and all kinds of functional and structural elements beyond simple pigmentation.
[Answer]
*Millimeter precision*? Honestly, I don't think this is possible in exactly the way you've asked. Even current tattoos are subject to distortion as skin changes (which can happen due to changes in body composition, aging, etc.). Asking for something that will somehow manifest with such precision through the fairly radical changes that happen from conception to adulthood, given nothing but genetics, seems like a stretch. I'm not aware of *anything* in nature that comes close.
At best, you are going to have to replicate some sort of major structure, like a nose, but even stuff like that tends to vary by more than the precision you've stated. You *might* be able to get a recognizable shape out of this, if it's a very simple shape and you don't mind it varying in the ways that something like a nose varies from individual to individual. Forget about legible text, though.
Instead, I'd like to offer an alternative: *nanomachines*. A swarm of (self-replicating, self-repairing) nanomachines that lives in the host's body can "easily" accomplish what you want. Just program them to be able to locate a desired spot on the host's body, and to be able to determine their relative locations in the overall swarm with high precision. Ability to turn on and off? You can probably get them to have the capabilities of an e-ink display. They can turn on, off, change shape... They can *play video* (at low frame rates, anyway). *Changing* color might be a problem, but you can probably at least choose what color you want when you create the swarm, possibly within some limits. (This will depend on what pigments they can produce from what's available via the host body, or if they have some fancy way of manipulating light.)
As for heritability, that's easy; they also piggy-back on their host's, ah, "genetic material" and start a new swarm whenever conception occurs (and just shut down otherwise), such that their original hosts' offspring end up with their own swarms (with the same programming, of course, in order to produce the same mark).
[Answer]
**You're already far out of the boundaries of nature. You're asking for the equivalent of a reasonable laser gun for your time travelers.**
I don't have a mechanism to suggest, but would like to point out that what you're already doing is strictly harder than what you want to do. If you hand-waved the spider legs, there's no point in finding a reasonable explanation for the tattoos, hand-wave that too. If you have a reasonable explanation for the spider legs, use that.
If you can make a working human-sized spider-like leg grow from a predictable spot in the human body, arguably you have all the tools you need to make your tattoo as a vestigial limb.
Namely, engineering alien limbs, and placing them at will in a human body.
I called it an "alien limb" because an actual spider leg, grown locally but equivalent to a graft, wouldn't work. Even if you could find a way to scale one up seamlessly, the [square-cube law](https://en.wikipedia.org/wiki/Square%E2%80%93cube_law) would crush it when a human leaned on it, the biological mechanisms that work at spider scale just don't work at human scale. You need to engineer the leg to use completely different biological mechanisms. Hence, alien leg.
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[Question]
[
Alright, this will take some time to explain. There is historical context to my question.
Over the course of the period of time from 16th century to the first half of 19th century, the [European muzzleloading naval cannons](https://en.wikipedia.org/wiki/Naval_artillery#Age_of_Sail) were progressing towards more muzzle velocity(**up to 500m/s**), more accuracy and heavier projectiles. While there were some **exceptions in this development, such as [carronades](https://en.wikipedia.org/wiki/Carronade)**, excluding those unusual developments, the overall cannon qualities were obviously improving greatly. Optimal length of a cannon(which imparted most of the kinetic energy into cannonball) was found - so called "long guns", the boring of cannons allowed smaller windage etc. Eventually, shells replaced the cannonballs, **but before that, a lot of progress was made and the difference between the 16th century 32 pounder demicannon and the 19th century 32 pounder long gun was massive**.
However, during the 16th century, there also existed **completely different style of naval cannon**: in Korea. Called [Hwapo, Hwatong and later Chongtong,](https://en.wikipedia.org/wiki/Korean_cannon) these cannons could, just like their European counterparts, fire regular cannonballs, but also, more interestingly, could fire a bolt of a shape that somewhat resembles modern missiles.
[](https://i.stack.imgur.com/dpM2q.jpg)
According to partially confirmed information, largest of such cannons ["cheonja-chongtong"](https://en.wikipedia.org/wiki/Chongtong#Cheonja-Chongtong) which fired 30 kg (66 pounds) heavy bolt had a maximum range of ~ 1600 m. With help of some math, I eventually ended up estimating its muzzle velocity to be around 140-170 m/s. These cannons were being improved from 15th to 18th century but except for minor improvement, there was no major overhaul.
In fact, the bolt fining cannons were gradually pushed out by Chinese take on European [Culverins](https://en.wikipedia.org/wiki/Culverin#Field_culverins) named [Hongyipao](https://en.wikipedia.org/wiki/Hongyipao).
Muzzle velocity of 140-170 m/s that I calculated is greatly below what the potential of black powder cannon can do, so it appears there is lot of space to improve that. However, that would require a thicker cannon, that can withstand a larger charge (Cheonja Chongtong apparently used only a bit over 1kg charge to fire the 30 kg bolt) and also making the cannon longer would improve its efficiency. Actually without making the cannon longer, the improvement we can achieve is limited.
Which is where the problem is. These bolts have to have fins to have stable flight and accuracy. And so, making the cannon longer without making the bolt longer poses a problem, as in the historical version, bolt was put into cannon in a way that fins were in front of the muzzle.
In a fiction I am writing, it was my intention to have these cannons be developed with natural progression towards something like modern sabot ammunition, where the problem disappears as you're now able to fit the whole bolt into the cannon, with not even tip poking out, allowing the cannon to be as long as needed. Need for this development is justified by the existence of magically hardened wood used in naval ships.
[](https://i.stack.imgur.com/52dz2.jpg)
However, I am having doubts about realism of developing sabot ammunition with what is basically 17th/18th century metalworking. I'm thinking that there might perhaps be simpler method to reach that that I overlooked. **So, could bolt firing black powder cannons be realistically improved to have their bolts reach high (400m/s +) velocities, or is this beyond the means of the era I set this in?** Or are Korean bolt firing cannons a dead end, and bolt shaped cannon ammunition is just outright suboptimal before technology such as smokeless powder come into play?
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Here’s one option that might work. When the charge (green) is fired the main projectile (red) is blasted down the barrel of the gun (grey). The fin section (blue) is a simple hollow cylinder with fins attached of roughly the same bore as the central projectile spindle. When the charge is fired this section is hit by the back of the projectile as it leaves the cannon and sticks there jammed against some wood, wadding or piece of lead. The longer extensions to the gun are for guiding the fins and might not be needed.
[](https://i.stack.imgur.com/aKZ5K.png)
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Modern sabot rounds work for a very specific reason -- at the extreme velocities they strike, the hydrodynamic penetration process (the armor and projectile both erode away) means that a very high length/diameter ratio is more effective. This would not really apply to your scenario.
However -- they key thing will be the failure mode of magic wood. Is it brittle? Does it bend and cave in? Does it crack, or break into large/small/dust-size pieces. This will determine the best sort of projectile.
That said, a sabot projectile - which you can do perfectly well with black powder tech - is still a good way to concentrate maximum force on minimum area, so it this is what is needed the break the spell, go for it.
Archaelogists looking at the wreck of the Mary Rose have found what they claim are early amour=piercing rounds: "Powerful imaging technology has revealed cubic-shaped lumps of iron encased in the soft, lead cannonballs, which would have allowed guns to punch through the sides of enemy vessels. … The cannonballs would have worked much like a modern-day armour-piercing round — the soft outer material, in this case lead, would have deformed on impact, throwing the hard iron core through the armour plating.
The trust hopes to conduct tests at the The Royal Armouries to try to better understand the damage they would have inflicted.
Alex Hildred, of the archaeology team, said: “We first noticed something strange when the lead cannonballs began to rust. Some burst open so that rust came almost pouring out of where it had split.
“We found there were small iron cores inside. This could have been done to make the cannonballs cheaper or it may have made it easier to make while at sea if you had an iron core — you had to carry less of the heavier lead.
“But they would probably have worked like a soft-nose bullet. They could be some of the earliest examples of armour-piercing projectiles."
You could use your sabot projectiles similarly to deliver maximum force on a small area to splinter their way through..
Aerodynamics might be challenging -- but on the other hand, if they get it right, a 'winged' projectile might even have greater range and accuracy than an equivalent cannonball. Unlike other projectiles, sabot are often finned rather than relying on spin-stabilisation, so gliding wings might be viable.
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I'm not certain why you're rejecting sabot rounds. A sabot is merely a disposable piece of hardware meant to position the round correctly and seal in expanding gasses, thus maximizing the amount of kinetic energy transferred from the charge to the round. If you increase the size of the barrel to fit the entire bolt, then fit the bolt with two thick rings of (say) bamboo, with the lower one faced with iron to keep it from cracking or burning, that should suffice as a low tech but effective sabot. Just make sure each circle is split so it falls away immediately after firing.
You could also consider the possibility of spring-loaded fins, which would allow the un-saboted bolt to fit entirely in the barrel, with the fins expanding as soon as the bolt takes off. That was certainly within the technology of the day, though it adds an inconveniently breakable moving part.
I don't know how effective these bolts were in general. I imagine a cannon ball was a more effective anti-ship weapon for the period, since it produced a large-area crushing force as opposed to a pointed piercing force. But I also suspect that part of the problem was standardization. A large-bore cannon meant for these saboted bolts would be useless for cannonballs, requiring two separate cannon for the differing ammo. Part of the reason that modern sabot rounds have become established is that they allow smaller rounds to fit within common standardized barrels, and the piercing design fills a modern need for penetrating heavy armor with explosive gasses. Bolt-type ammo might make sense for penetrating your magically-hardened wood, but only if it delivers some secondary effect after penetration: an explosion (explosive rounds are a bit advanced for 18th century technology, but not impossible in a crude way), a magical effect, or anything that would damage or disrupt the ship or the crew from the inside.
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Looking at the design of the round, it seems that what is really desired is a form of "Spigot Mortar" rather than a cannon.
[](https://i.stack.imgur.com/xZxwR.jpg)
*WWII era Spigot Mortar*
The illustration shows the gun crew aiming the small, lightweight spigot (essentially a long steel rod) with the mortar shell already placed on the spigot. The propelling charge is actually in the cylindrical tube attached to the warhead, and after firing, the tube falls away exposing a set fo fins.
While a WWII era spigot mortar is designed to create a small, inexpensive and lightweight weapon, there is no reason that it cannot be scaled to larger sizes. It also provides the option for the gun crew to choose different sorts of ammunition rather than be confined to metal "shot", they could have explosive Shrapnel style shells to clear the enemy decks, or canister shot for very short ranges to repel borders.
Having an arrow shaped "dart" isn't much of an issue with a spigot mortar, and with the short ranges that naval combat took place in during the age of sail, the weapon should be relatively effective.
The main downside of spigot mortars is they exchange the weight and expense of the barrel for extra weight and complexity of the shells instead. This is most likely to be dealt with by using a mixed battery - heavy long guns or carronades in the lower gun decks, and spigot mortars on the upper deck.
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The question is just as simple as it sounds.
Would it tuck them under like a bird? make running motions like it does when running on the ground? some other movement that actually aids in flight somehow (if so, what is it?)
Assume the standard trope Pegasus, an otherwise normal horse with the exception of the added wings.
I can't think of any reason why a rider would change the answer, but if it does, please explain the difference and why there's a difference.
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To address the concern regarding the method of flight (magic vs physics), I've never seen any depiction of any 'standard trope" Pegasus with large enough wings to power it's flight through natural physics alone, so magic definitely comes in to play, but the fact that it has wings at all means physics is also involved. Use best judgement when deciding just how much of each is involved, and adjust answers accordingly.
The question was originally conceived as a bio-mechanics question, related to how the musculoskeletal system of such an animal might cause the wing motions to interact with the leg motions while in flight. But, since other considerations could certainly affect how the animal might behave, the overall question isn't specifically aimed at any single particular aspect of either flight or biology. Instead, if answerers feel that aerodynamics requirements, or any other aspect I haven't considered, would cause the animal to intentionally suppress what would otherwise be the most natural musculoskeletal motion to gain aerodynamic advantage, or vice versa, that's fine. Best answers should provide science-based explanation of why one aspect dominates any others, and causes the motion described by the answerer.
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I am assuming you want an answer about aerodynamics. I also am making a minor change to what we normally think of when we think of a pegasus. Normally we just imagine a horse with wings stuck on the back. I think the pegasus would also have small wing-like growths on its hind legs, as far down by the hooves as possible. Then, by straightening its hips such that its feet stick out behind it, it can use those hoof-wing-things just like an airplane uses its elevator or a bird uses its tail. One of many big problems traditional pegasi have is that they can't move their center of lift since they only have one lifting surface, which means they can't change pitch to fly up or down. These hoof-wings correct that
So as far as your question is concerned, they will stick their hind legs behind them and use them as a tailplane, and they will usually just pull their front legs up as tight as they can, to reduce drag. They may stick them out to increase drag; since they're in front, that will also move their center of drag forward and make them more maneuverable at the cost of efficiency.
Edit: One more thing I just realized. If they have a rider, he will shift the pegasus's center of drag *up*. Having the center of drag above the center of mass will make the pegasus want to pitch up, possibly uncontrollably. To counter this, either the rider needs to lean forward as much as possible, or the pegasus needs to keep it's front legs down to shift the center of drag down. Maybe both.
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Apart from flying in a more equilibrium-like state, as was discussed in another answer, I would like to think that the Pegasus would use its legs to keep balance and centre of mass. Sort of similar like what you do as a human when you're trying to balance, you wave your arms around in circular motions. Otherwise trying to reduce drag as much as possible.
When landing I would assume that it lands with the back-hooves first in a galloping state, which would be different from a normal horse, since they jump and land with the front-hooves first. Assuming this, it would probably strech out the back legs before landing, while keeping front legs in, in order to gain enough backwards rotation (just like a bird or plane).
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As per my answer to [**Anatomically Correct Pegasus**](https://worldbuilding.stackexchange.com/a/56125/21222), *pegasi* should have a patagium connecting each leg to their wings.
They are going to spread their legs just like a flying squirrel.
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I'd like to create a sci-fi story with a country or planet where only men are allowed to live and they use in vitro gametogenesis and ectogenesis (artificial womb) to have children without any woman.
If new reproductive technologies like in vitro gametogenesis (IVG) and artificial womb s(ectogenesis) become possible and accessible in the future, single men or/and gay male couples could reproduce alone without any women involved. Men could make eggs and sperm with their stem cells through in vitro gametogenesis and the fetus could grow in an artificial womb. Motherless babies will become possible. So men could have also more reproductive rights (the same or even more reproductive rights than women). Men could begin to think that women will lose their reproductive value and become unnecessary in a reproductive point of view. In the more distant future all male society may exist. And also all female societies.
Sterile women who cannot get pregnant at all (like women with CAIS) could also use the technology to reproduce. In fact anyone could reproduce with these things. Even old women.
These technologies may also help to decrease the social differences between men and women and make women do things they didn't do in most of humanity's history like for example fight and die in wars like men do.
Realize that I don't want to be sexist and I'm not against women at all, it's just a curiosity and I want to see other people's opinions.
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The short answer to your question is Yes, such a society is *possible*, but I suspect that the question behind the question is what such a society would look like, so I'm going to answer that in more detail.
I'm of the view that focusing on the nature of reproduction and extrapolating a culture fails to take into account the far more energy intensive aspect of reproduction; raising the child. This is (arguably) why marriage evolved from an anthropological perspective; raising a child (or children) takes a massive amount of effort and energy; women struggle to do it by themselves, but men want some surety that the effort they put into the raising of children is going to directly benefit themselves, genetically speaking. So, a contract is made whereby the man agrees to pool resources with the woman to raise her children, and the woman agrees that in return, all the children he's helping to support are his. If this contract is ubiquitously in place for all couples who procreate, then the discussion of reproductive rights of both the man AND the woman become redundant but we know we don't live in such a world and as far as the scope of the question is concerned, I digress.
In a culture where children are basically all vat grown (I'm going to use that term to differentiate between the artificial womb and a normal biological pregnancy; no offence is intended), the energy cost to the woman of gestation is negated. But, what about raising the child? Providing it with food, protection, and guidance? This is where the real cost of children is, as any parent, male or female, will tell you.
So, who ultimately raises the child?
Well, the answer is more or less the same as it has always been - the biological parents. In this case though, that could be any mix of gender really and as such, it's entirely possible that you'd see pairings that look suspiciously like marriage pop up even in a single gender society because the effort involved in raising a child will still be borne by those who contribute to the genetic heritage of the child in question because they are the ones to benefit from raising the child in the first place.
But, a note on some of your other comments - Yes, in a wartime situation historically it has been men and not women who have fought as soldiers. But, that fact doesn't justify the perpetuation of the myth of the violent male. In my experience, women can be (and often are) just as aggressive (if not more so) than men in many cases. The stereotype of a caring mother and indifferent father just isn't true and needs to be challenged at every level.
Men (on average) are larger and stronger than women, and that means that they tend to manifest their aggression physically. But, women can be just as violent, often inflicting emotional violence where they are not in a position to inflict physical violence due to a mismatch of physique.
By the same token, fathers (in my experience) love their children every bit as much as mothers do, again more so in some cases. The reason why this is not expressed the same way is that society sees the responsibility of providing for the family as belonging to the father, thus forcing him to distract himself from the effort of child raising with the effort of providing for the family as well.
This, ironically, is what is retarding modern feminism's advancement; the focus on rights has put those rights out of equilibrium with gender based responsibilities and expectations meaning that until the women's rights movements become women's responsibilities movements, they will struggle to make further progress, but again I digress.
The point of all this is that a child having two fathers, especially in a single gender environment, will in no way retard the development of the child. In point of fact, because having children is a conscious choice in such an environment, and can't occur by accident, children raised by two fathers in your world are probably subjected to even better levels of nurturing and guidance than modern children are.
Put even more simply, it is a mistake to confuse gender stereotypes and cultural expectations with gender based capabilities. Fathers are every bit as capable at being parents as mothers, and in your world, away from the current gender based expectations and responsibilities, would be more than capable of demonstrating that.
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Yes, but there are some genetic issues...
**Genetics**
DNA is packaged in Chromosomes. Each human (generally) has 46 Chromosomes arranged in 23 pairs. The two chromosomes in a pair provide the same biological utility but are not genetically identical.
In Humans gender is heavily influenced by a pair of chromosomes. They are generally refereed to as X and Y chromosomes, and they usually exist in pairs of: XX (female), and XY (male). *YX is the same as saying XY. I'll use the alphabetical ordering as the standard.*
There are other combinations of sex chromosomes but these are Rare, and my point is made with the common combinations.
The problem here is that a purely male population consists of individuals holding XY chromosomes. This means that a purely male population can produce: XX, XY, YX, and YY combinations.
This means that without intervention roughly 50% of the offspring made will be male, 25% will be female, and the other 25% would probably die.
Genetically speaking a male-only population is unstable. Without constant intervention, and murder of any female baby that accidentally survived, the population will eventual evolve into a female/male society.
**Hormones and defective Ys**
Even with such provisions in place to ensure that all individuals posses exactly one X and one Y chromosome, it is still possible for society to develop females. This occurs due to either a genetic failure in the Y-chromosome or an altered hormonal chemistry that deactivates the Y-chromosome. These things can happen entirely naturally, and can most definitely be induced via certain drugs.
These genetically male, but observable female individuals cannot be avoided without serious genetic modification to the populace. This is because to be (a human) Male means to contain all the genetic information to be (a human) Female.
**Birds** *and the bees*
Now if human gender operated like birds the story would be different. A male Bird contains ZZ sex chromosomes, and a female bird contains WZ sex chromosomes. A pure male bird society would be stable. It would only ever produce males.
It would be a female only bird society that would eventually produce a male/female society if left unchecked.
**Society**
What this would suggest is that a pure (human) male society, or a pure (avian) female society would have a draconian edge to it. Population scale genetic engineering, genetic reproductive controls, and even biological evaluations as individuals grew up with some form of enforcement (death, sterilisation, etc...) would need to occur to keep the society purely that gender.
Aside from that, chances are that such a society would be more likely to cherish their offspring. The simple fact is that purchasing, maintaining, and operating such external reproductive equipment would require wealth, and skill. This would raise a barrier to entry not found in our modern society. In fact the barrier operates in the other direction as couples in our modern society must invest in *not* having children.
Alternately such a society could organise along collective lines lowering the entry barrier by collaborating in a larger group. Think clan, community, or state birthing facilities. However these systems tend to raise artificial barriers to impede overuse...
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**A warrior society**
A society of warriors who's sole purpose is warfare. Children are made from the edited DNA from the most successful warriors. Death is no hindrance and in fact a glorious death in battle increases your chances of children as your genes are in storage and your heroics are you more likely to get you selected.
Scientists take the genes of the best warriors to produce the next generation and that generation proves itself in battle to produce the next and so on so each generation evolves into a better soldier.
Children are raised by society in a militaristic fashion by the wounded or the less successful members or lower classes. Each generation studies the feats, tactics and skills of the previous to better their own.
Societies like this exist in the [Clans](https://www.sarna.net/wiki/Clans) of Battletech Mechwarrior though not limited to males only
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It is not only possible, but it existed in many places, including monasteries, army service, prisons, mines, polar stations, etc, except reproduction.
How this society would look like?
Most likely it would involve heavy use of the hormone replacement therapy to make some males look feminine to satisfy the sexual needs. So, the society would look like normal society with men and women for an outsider.
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With the right technology available, an all-male society and an all-female society is possible to create, and maintain for long periods of time.
For an all-male society, this is how reproduction works. One man donates sperm, another man donates stem cells. The stem cells are converted into egg cells. The sperm cell and egg cell are combined to form a zygote. Gender selection is performed to ensure the fetus is male. The zygote is placed inside an artificial womb. The womb grows the fetus, but it needs electricity and nutrients. Once the baby is fully developed, it is removed from the womb. For breastfeeding, either baby formula can be used, or men can be given prolactin and breastfeed with their nipples.
For an all-female society, a very similar process to the male one can be done. Women have a uterus so they technically don't need an artificial womb or baby formula. The main difference is that stem cells are turned into sperm cells instead of egg cells (and it is easier for a man to donate sperm than it is for a woman to donate eggs).
As for what said society would look like, nobody alive currently knows (and anyone who says otherwise is just recounting gender stereotypes). This is a very artificial, high-tech society that is being crafted in both cases.
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Assuming something went wrong with the nuclear bunker and most women died and the few that lived died of various reasons and all you have left is a similar idea I had when watching the first previews of death stranding were the men must deliver the babies in artificial wombs because there are not women the first issue is the eggs unless we have males turning female or else self reproducing with themselves which the egg then randomizes the genes present to make a new child that is removed from the last one it produced then its possible.
Your males aren't males they're different and could present as male or not they don't even require their junk in this scenario because its all internal and they decide when the time is right. Feeding is an issue your males must do this. The issues is delivering it are they vaginal-ish or does their stomach slowly open and allow it to fall out? You should think on that because before they ever made C-sections birth was the way to go. C-section just like the concept of wash your hands after handling a corpses doctor before you handle delivering the baby were not invented at one point.
Now women have always gone to war allowed or not see the civil war see before that so if women exist and everyone for reasons is choosing the artificial womb and not a human there is no change to the population there is no all men some people want daughters others want sons there is a reason China is kidnapping women from other countries too many men and not enough women so when your population gets that way people will auto begin to make more women to avoid kidnappings or to sell off their made daughters (or sons if it goes in the reverse) You'd have to delete make females button on the machine and kill off women in any number of ways and this then assumes the men left will want to keep the male thing going this also changes love, relationships, sex your normal people still have a need for sex banging a machine ones will do so much for some of them. Your culture also changes say you get to the all male utopia you want no mention of women is present and also no idea of what one is after a point especially if the woman is suppressed from culture as they die off for good so its all male all the time to fill all roles a society would require. Their vocabulary and what they find sexy changes substantially. The other issue is feeding of children in the AW world must be done these men must do it via themselves (possible) or invention and if the bulk choose invention is not feeding or harming the food source of a child a crime?
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An all-male sci-fi society could theoretically exist provided that we have a way to prevent females from ever being created. One solution, which addresses the issues in Kain0\_0's answer, is to make everyone have just a Y chromosome, but no X chromosome. Then, anyone's Y chromosome will pass down to his sons, and he won't ever have a daughter.
The reason is simply because a typical human being has one X chromosome from his or her mother and either an X chromosome from her father (if she is female) or a Y chromosome from his father (if he is male). Without females, the X chromosome would become redundant.
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**Doomed to Failure.**
You focus solely on the mechanics of reproduction but fail to comprehend the fundamental nature of the human person and human society. We were made female and male for a reason: not just to reproduce but to balance and compliment one another within the context of a mixed society. A group that lacks one or the other of its two natural sexes & genders, that can not form even the most fundamental of human societies, the family, will eventually die of natural causes or else drive itself crazy or turn utterly savage.
It's an interesting premise, and, as you might suspect has been considered in literature before. You might be interested in reading Cordwainer Smith's *The Crime and the Glory of Commander Suzdal* (Amazing Stories, 1964; Galactic Empires, vol. 1, 1976) which deals exactly with this problem.
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Previously, I had asked [a question](https://worldbuilding.stackexchange.com/questions/142211/a-permanent-norse-presence-in-america) on what point of departure I would need to make the Norse's presence in North America permanent. Perhaps the best answer I got was summarized right here:
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> If one man had not fallen off his horse, if the Norsemen would have shown a minimum of diplomacy, and if the colonization attempt had been just a little more serious, a Norse empire in the west could have arisen to rival their success in the east, where the Rurikids created what would later be the Russian Empire.
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Ultimately, right at the start, it would mean interbreeding between the Europeans and Americans, potentially butterflying the physical ethnicity of the American body plan, but that is not all it would mean.
Consider the reality that the Norsemen were merchants and traders more often than the romanticized pirates who came before the romanticized Golden Age pirates (Black Bart, Blackbeard, Henry Morgan, just to name a few for clarification's sake.) Their influence had covered the whole of Europe and expanded down south to places like Baghdad. Surely, if the Norse had established a stable empire far to the west, the rest of Europe would have heard of it and wanted their share of the "western lands", thus pushing the Age of Exploration 500 or so years earlier than in our timeline. ***Would that last statement be true or false?***
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I think the best model for this would be from the east. The Norse settled in Novgorod and the Kievan Rus and while their contribution was significant, they never made an effort to rule these lands from Scandinavia or to replace or "Norsify" the locals. Instead these native realms with tight connections to the Norse, Norse traders and rulers who either came from Scandinavia or just had some Norse blood.
Similar patterns would happen in Normandy and Sicily. And England and Ireland for that matter. Even Finland. The Norse would come, build settlements, rule the land, start dynasties, have large political and cultural impact, but the country would stay native.
So what would probably have happened in the west IMHO is that the Vikings would have started settlements along the coast all the way to the Caribbean. They would have traded and mingled with the locals. The settlements would have evolved to small kingdoms with mostly native population and aristocracy of mixed blood. These kingdoms would then have founded new settlements and eventually evolved into larger kingdoms.
The response of the rest of Europe to this? Well, there would have been some travellers to the new kingdoms. There would have been interest in the trade, starting probably with the Arabs in Iberia and northern Africa then by the Hanseatic League. Things like furs and tobacco I think. This would be increased after the new kingdoms find Mexico with more advanced civilizations and precious metals.
By the time exploration of the Atlantic came practical due to better ships everybody in Europe would know about the Americas and the Norse Kingdoms there. People would rush to emigrate and trade. With better sailing ships the kingdoms would suddenly be lot more attractive.
The difference would be that Norse Kingdoms with Norse weapons and administration, populations of people who would already be resistant to European diseases would not really be something for a bunch of Spanish adventurers to topple and take over. There would be lots of trade and immigration but the Americas would stay **native** American with strong Norse influences. Local historians would probably even argue that the impact of the Norse was minimal as the underlying societies were native.
I am not sure this actually answers your question because quite frankly I think people really would not have cared about the Norse settling some faraway shores until much later.
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The norse kingdoms would be like the kievan rus, as Ville Niemi said in another answer - natives with a nobility that descended from the norse. Trade in the Atlantic would begin much earlier but would be limited due to shipping costs. Norse boats were small and had to hop from Canada to Greenland and then to Iceland so american products would be quite expensive. Which products would be traded?
From America to Europe: Tobacco, furs, ivory[from the polar fauna],whale oil, slaves, gold/silver. It would be more efficient to send the cigars then the dried tobacco leaves, the coats and capes then the raw furs, the many useful things made of ivory then the walrus and narwal tusks, and jewelry then raw gold and silver.
From Europe to America: Iron tools and weapows, horses, cloth, silk and spices (from the silk road).
The main trade hubs would be in England and, due to that, England would prosper but would still probably be a saxon christian England instead of a norse pagan England. Also, Novgorod and Denmark would prosper too, as the silk road would branch north. That would mean that when the crusaders destroy Constantinople during the fourth crusade the russians won't go bankrupt and will have better chances against the mongols. So, in europe, England, Denmark and Novgorod will be more powerful then they were. That could mean that the english might be able to conquer and keep France, the danes could keep the swedes under the danish crown and some kind of Russia would form earlier, maybe as a giant merchant republic instead of an autocratic monarchy.
The demand for better ships to do this trade would bring about big ships like the north european cogs. But true ocean ships would still take a long time to appear due to the lack of compass and good astronomical instruments. They may have galleons 2 century earlier but won't dare to do a direct cross due to lack of navigation tools, instead, they will keep doing the island hopping from Canada to England.
Also, religion: Christian (and muslim) missionaries would find their way to America much earlier. Christianity and Islam was useful to tribal societies because it gave them a worldview that favored monarchical centralization, helping the tribal petty kings become feudal kings. So, the american norses (and the native americans that interacted with them) would probably adopt christanity or islam. But there is an alternative...
"Pagan" religions began as tribal, limited to what the tribe knew about the world. As the tribe's horizons expands, the pagan religion becomes more and more universal, as the priests see the similarities between the varius spirits worshipped by the other tribes. The final result is something similar to neoplatonism, taoism or the egyptian religion: a complex religion, with a deep, developed, worldview capable of orienting it's followers in all phenomena in the world. The ancient greek religion evolved like that, from the greek dark ages to the Plato, the african religions are evolving like that today as result of the african diaspora in America, that mixed the african tribes, the american tribes and the european magical systems. So, the norses, in contact with christianity and islam, with the slavic tribes and the american tribes, could develop a new great world religion.
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# Changes could be minimal.
Central Europe obviously knew about Scandinavia. A few centuries later, the Hanseatic League had [trading posts](https://en.wikipedia.org/wiki/Hanseatic_League#Kontore) in what is now Norway, Sweden, and Russia. They also knew about Iceland, which featured as a fabled foreign land in the [Nibelungenlied](https://en.wikipedia.org/wiki/Nibelungenlied#Siegfried_and_Kriemhild).
Greenland would be known as a minor land beyond Iceland. Vinland was farther still. If the Vikings were Christian, Vinland might take some aspects of [Prester John](https://en.wikipedia.org/wiki/Prester_John) and his kingdom.
Consider how Europe was, in principle, aware of lands beyond Russia and Persia. [Traders and diplomats](https://en.wikipedia.org/wiki/Chronology_of_European_exploration_of_Asia#Middle_Ages) went there. But there was no sudden rush of European kings and nobles to conquer land east, so why should they rush west? Africa was comparable to the Americas in the sophistication and size of the native populations. Yet Europeans did not go there much and Arab trade and conquest was also limited.
# Changes could be greater.
The crusades were not **just** about the liberation of Jerusalem. A significant effort was spent in [Europe](https://en.wikipedia.org/wiki/Crusades#European_campaigns). It would a relatively small point of departure to have some cleric or king direct people towards the Americas. For several centuries, Europeans might send "excess martial ambition" there. A non-inheriting second son, an ambitious underling, they could all be encouraged to carve a princedom out of the vast plains beyond Vinland.
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You could certainly have very interesting characters in your story from Europe - emissaries, pilgrims, cartographers, etc - but if you're looking for conflict, look no further than the First Nations.
The indigenous people of North America were far from a monolith; culturally, they were vastly more different than people in America today, and you can see what sort of strife current beliefs can bring. The Norsemen, with some decent trading skills and diplomacy, would very likely ally with one or more First Nations people(s). It may even over time morph into a very - though I'd argue never fully - enmeshed society. But, their new allies' enemies are now their enemies. And, indeed, in time that will mean Spain, England, et al... but the wars and battles within pre-colonized America were nothing to be sneezed at.
Many of the real-world Norse learned how fierce the "skraelings" were, and they didn't get that way without pre-existing animosities and enemies. Depending on how far south and west this alliance spreads, they're going to encounter some pretty entrenched and powerful nations like the Iroquois Confederacy or the "Mississippian Culture".
] |
[Question]
[
I've been working on a constructed world which started out as the home of an alien race from a sci-fi story I'm writing but just became a pure world building project.
As you can see from the map it has one major continent, one minor continent, and several islands. The poles are nothing but water and ice caps.
I was using artifexian's video as a guide to mapping out ocean currents but eventually, I got confused. Here you can see how far I got before giving up as well as a blank map. Thanks for the help.[](https://i.stack.imgur.com/cK6Wb.jpg)
Could someone explain what would be a realistic pattern of surface ocean currents and upwelling for this continental configuration? Thanks!
[](https://i.stack.imgur.com/gYUHh.jpg)
[Answer]
## Currents are complicated - start from the basics
It looks like you've already got the basics down. Assuming your world has similar prevailing wind currents (i.e. three circulation cells in each atmosphere, spins the same direction, and has a similar temperature gradient), you're wise to start with the equatorial currents. These transport large amounts of water along the equator. In the middle of the deep and powerful equatorial current, there's the shallower and weaker equatorial countercurrent that flows backwards along the equator. So far, so good - although it looks like the turnaround for the south equatorial countercurrent has the arrow on the wrong end.
When this equatorial current collides with landmasses, it splits and travels to the north and the south - you've also got this covered pretty well. However, because the warm water is moving toward the west, the boundary currents running along the east coast of continents will be warm, while the boundary currents running along the west coast of continents will be cool. Check out the map of Earth below to get a sense of this:
[](https://i.stack.imgur.com/sgh0y.png)
Note that the blue currents (the cold ones) are generally off the west coasts of continents (which is, confusingly, the *east* side of the ocean) and the red currents (the warm ones) are off the east coasts of the continents. Also note that red currents always point away from the equator, and blue currents always point towards it. This also answers your question about upwelling - upwelling happens largely in cold-water currents on the west coast of continents (think Peru and West Australia).
With that, you should be able to fill in the warm and cool currents on your map. There will be a cold current traveling toward the equator the left side of your main, middle continent and (probably) the left side of your smaller Australia-looking continent.
This looks like the step where you got confused - your red arrow traveling down the southwest corner of the main continent should be blue, and pointed in the other direction (towards the equator). Remember that the main water flow at the equator is to the west, so we'd be drawing water up from the south pole to keep it going.
Now that we've got three sides to our gyres, go ahead and fill in the fourth one by connecting the head of the red current to the tail of the blue one. Now we can see another point that may have been causing some confusion - the south circumpolar current is going the wrong way! It's not impossible that this would occur, but you'd have some crazy waves and some very stormy seas where they collide, and you'd need another massive energy source (giant, angry penguin?) to explain why it's going the opposite direction.
It looks like we can expect four major gyres on your planet. Downwelling will happen in the center of these gyres, as Ekman transport moves water slowly toward the center, and water will upwell on the west coasts of the continents as detailed above.
## Other recommendations
Spend some (read: a lot of, because they're beautiful) time looking at currents on Earth and how they react when running into landmasses. There's a fantastic interactive map at [earth.nullschool.com](https://earth.nullschool.net/#current/ocean/surface/currents/orthographic) which you can explore, and NASA's [Ocean Eddies](https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=3913) provides some high-resolution detail for more specific things.
I'd also recommend rotating your map projection - while it'll probably be useful for the rest of your story to have a continent-centric map, designing ocean currents will be easier if you center it on your ocean. Consider something like the Heezen-Tharp map, by brilliant oceanographer [Marie Tharp](https://en.wikipedia.org/wiki/Marie_Tharp):
[](https://i.stack.imgur.com/jU6AH.png)
Or better yet, something like the [Spilhaus projection](https://bigthink.com/surprising-science/the-spilhaus-projection-ocean-maps):
[](https://i.stack.imgur.com/6ICfG.jpg)
Actually, I went ahead and mocked up what it would look like for you because it helped me figure out the rest of the question above:
[](https://i.stack.imgur.com/PxaE0.jpg)
] |
[Question]
[
The secret police of my fictional country (unoriginally) uses sodium thiopental in medical interrogations, usually in combination with various forms of physical torture.
An antagonist (a courier of smuggled goods) who is detained by them and injected with a thiopental-based serum suddenly dies before the questioning officer arrives. The doctors determine that death occured due to the lethal effects of combining sodium thiopental with a certain substance the courier was injected prior to the mission.
**My question is:**
Which medical substance or drug is
* *lethal* (leading to a quick death) in combination with sodium thiopental (or one or more other truth serums), unleashing its effect if it is already present in the body when thiopental is injected,
* stored in the body for at least several hours after initial injection or ingestion, retaining its "latent combinative lethality" during that time and
* has no strong noticeable negative effects without the presence of sodium thiopental.
[Answer]
[Pentoxifylline](https://en.wikipedia.org/wiki/Pentoxifylline) when co-administered with sodium thiopental causes death by acute pulmonary edema - or at least [it does in rats!](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1978439/) and is reasonably well-tolerated in most humans, with serious adverse effects being [uncommon](https://reference.medscape.com/drug/trental-pentoxil-pentoxifylline-342179#showall)
Stress to the body (I think torture counts!) will increase the effects and pulmony edema sets in ~2 hours after administration.
The problems with this though are:
* **Timing:** it has a relatively short half-life in the body - only 1 - 1.6 hours, doesn't give a lot of time to work with. You could have the courier be taking regular doses of it through the mission I suppose, but if they don't get him or her shot up with Thiopental rather quickly following capture you're going to struggle to have enough to work with. You also need a plausible reason to have them get injected and *then* wait to question them for a couple of hours.
* **Dosages:** I'm not sure if the dosage of Thiopental used in a truth-serum scenario would be sufficient to interact lethally with the Pentoxifylline, the rat example I gave earlier was where the Thipental had been used as an anesthetic and since unconscious people don't answer many questions it's safe to say they aren't going to be using particularly high doses of it.
So if you're prepared to bend the rules a little bit around some of the finer details this would at least be a plausible mechanism.
[Answer]
# Self-induced acidosis
From [rxlist.com](https://www.rxlist.com/pentothal-drug.htm#dosage),
>
> Any solution of Pentothal (Thiopental Sodium for Injection, USP) with
> a visible precipitate should not be administered...Any factor or
> condition which tends to lower pH (increase acidity) of Pentothal
> (thiopental sodium) solutions will increase the likelihood of
> precipitation of thiopental acid...Solutions of succinylcholine,
> tubocurarine or other drugs which have an acid pH should not be mixed
> with Pentothal (thiopental sodium) solutions.
>
>
>
So, anything that lowers blood pH is going to be bad. In addition to the listed succinylcholine and tubocurarinine, the medical condition of [acidosis](https://www.healthline.com/health/acidosis#causes) occurs when your blood pH is too low.
So anything that causes acidosis would work. One way to do this is to take [metformin](https://www.webmd.com/drugs/2/drug-11285-7061/metformin-oral/metformin-oral/details), a diabetes medication, when you don't have diabetes. Of course, inducing lactic acidosis is really only possible if your liver isn't working that well, so this isn't the safest method, but it could be feasible for short terms treatments when you know you are about to get truth serumed.
] |
[Question]
[
So lets say that the level of the non-magic wielding species i.e. humans technology is at around the level it was in the early medieval times.
I would then introduce magic to the rest of the world in a form of a new species. The species i.e. elves would have lived within the world but hidden from the humankind. They would have long traditions with magic etc. The whole race would be peaceful (with a few exceptions).
The magic would lurk in to the world as humanity knows it, through some elves sent to live among them. And the country/ area of elves would become open for trade etc. (All of this due to the elves needing more resources etc. to live in the small area with a growing population)
There would be a few very strong elves who wouldn't have many limits on the magic, but those few would have more like a god status and have little to no interest in the happenings of this world.
Then there would be also a few powerful elves whose magic is strong enough to be the leaders of the elf country. They'd be peaceful and only use their powers when needed to defend their kind. If there was a war they would be easily the most powerful country in the world.
The average towns folk elf would be powerful compared to humans, but they wouldn't have so many spells or types of magic they can control. I.e. one could hold about 5 different spells which would be directed toward their professions and learned with long training. So lets say there was a farmer elf. That elf would probably have spells related to water, growing plants, shaping of land and around two others. On top of the main spells they would have learned a lot of weak spells etc.
Wielding magic without any magical items would still be very rare in the human countries and the average human could only learn to wield it through certain life threatening rituals and years of studying and training.
There would however, be many magic items introduced to humans trough the trade some countries open with the elves i.e. potions, weapons and lets say crystals that hold magical energy (would be needed to use magical weapons) and many other types of things. These items would be "low in magic" making the elves and few people have the real power of magic.
Magic would (very) slowly become inherited(?) to the mankind through slow mixing of the species (which would be banned at places -> very slow). It would however make the powerful magic wielders increase with time.
Problem comes with the few master crafts elves and weapon makers etc. who'd be able to make guns or something like that. And these could "modernize the world overnight" so to say.
The problem what this makes, is that (what I call) the technology level of the world would eventually increase its developing speed when I want to keep the human side of worlds era in the middle-ages (and generally not modernized) as long or possibly longer than it was in the Earth.
I really don't want the world to get to modernity any time soon, so my question is:
How do I keep the (mainly human) world from starting to develop their technology level too fast or "modernizing overnight" with the introduction of magic?
[Answer]
In my opinion, the presence of magic would have exactly the effect you are looking for; slowing down the advance of science by both interfering with the scientific method and by destroying people's motivation to find hard science-based solutions when easy magic-based solutions already exist.
This was explored pretty thoroughly in [this question](https://worldbuilding.stackexchange.com/questions/13384/would-science-emerge-in-a-world-with-magic), which I posted a while back.
To sum up the major ideas...
1). Science relies on the repeat-ability of results under experimental conditions. From this consistency, we draw theories which slowly grow more trusted with every successful repetition. Eventually, theories which have shown high reliability become a solid basis of further exploration which leads to new discoveries, new theories and a continuing cycle of knowledge growth. A single failure to repeat invalidates a theory, forcing us to find new explanations for what has occurred. ...unless magic is an option. Once magic is available, no revealing failure can be trusted, no experiment can be guaranteed to be free of magic tampering. The mere existence of magic undermines the scientific method. Without the significance of repeat-ability, which magic destroys, scientific growth flounders.
2). Science relies on real-life needs to motivate the arduous experimentation and repetition which leads to growth. When magical solutions exist for those real-life needs, the motivation falters, and scientists find other ways to spend their time. Nobody chooses the hard road when an easier road is also provided.
[Answer]
Technology's impact is felt more because it can happen on a mass scale, not a small one. We've uncovered things in archeological digs that are more advanced than the current tech for the time period was--like a calculator from a Greek shipwreck. Just because it exists doesn't mean it will spread--if it's hard or too expensive to make, or doesn't seem to have a practical purpose.
You already have limitations in place. And those limitations make magical tech RARE, and therefore expensive and not available to all.
Most magic users only have 5 spells per day, and most of what they can do isn't something that can benefit non-magical users.
Secondly, you're talking about magical guns, but I'm going to talk about magical BULLETS. So maybe you have a few magic makers who make guns. But those guns need a supply of bullets--and a gun becomes useless without them without a regular supply.
Third, if no one outside the makers understand how to make the guns and the bullets, then THE MAKERS are the resource. It's like if you introduced a gun to the Romans. They might be able to fire it, they might even understand it's metal, but they wouldn't know how to refine that metal and make a proper barrel good enough to get the same effect. And they wouldn't understand how the bullets were made either.
Fourth, you can create a guild that limits most of the "tech" to one-off or one use items. So a crystal or something can have the power to do something, or a potion might heal ONCE, but that's it, and it's expensive.
Fifth, you look at mixing as a way to up the magic in the whole of the population, but...maybe it's also a way to siphon off magic from the elven population. This can happen one of two ways. The first way would be that magical energy on a planet is a finite resource contained within PEOPLE, specifically magic users. The more magic users there are, the less magic there is to go around. Way two is that magical aptitude is found genetically within elven genes only, and if you actually quickly mix the two races (instead of slowly) then the big magic allowed gets less and less, while the little magic will be fairly common (because everyone is mixed). For the purist elves, if they are staying within their race only, because the mixing is widespread, it's difficult for them to find pure-breed elves to breed with. This means inbreeding, which can come with a host of genetic disorders, death, insanity and so on.
[Answer]
**Have incompatibilities between magic and large-scale (or often repeated) operations.**
In our world, the increase in the rate of technological progress from 1700 to 1970 was closely associated with the accumulation of physical capital. Each new technology could be used to improve a larger amount of stuff than was available to the previous technology. Many of the new technologies only made sense in the context of "factories", "pipelines", and "industries".
If magic is inherently a "craft" that can only work on a few small things at a time, then the feedback loop will not get out of control.
For example, **make magic increase inter-personal conflict.**
If it is hard to have many people work together in a magical environment, magical factories and universities will not be practical. This will prevent the feedback loop. It also explains why so many plots (that are interesting to the author) involve magic.
Another example is to have **magic users get bored easily**, so they don't like repetitive work.
**Or make magic work better in societies with very high marginal tax rates / very low savings rates.**
Communism does not work in non-magical societies. But what if magic can make communism work well enough? Communism's high marginal tax rates will inhibit capital growth, and thus slow down the feedback loop.
[Answer]
You could introduce some constraints.
1. The use of magical weapons and hand-held objects requires magic. The use of magical installations (i.e. magical dam or plumbing or whatever else) requires magic drawn from the Earth, which is not limitless, at least not without digging very deep down. And it also frequent maintenance by magical specialists.
2. Humans and elves are two different species, and while they can interbreed, their offspring will be infertile and will not have children to inherit their genetics. (i.e. horse+donkey--> mule)
3. Alternatively, humans and elves can only reproduce together with the help of magic: this magic also requires a qualified elven doctor/midwife/whatever you want to call it.
4. The only ones who can make magical objects are ones who can wield magic, i.e. elves or hybrids. They prefer to live near nature, so they dislike working in cities. Which means people living in small villages might have more technically advanced living conditions, which in turn might put a stop to the spread of large cities and keep people living in villages. On the other hand, it might mean that people who have to live in cities would develop technology based on science and not magic. This would be an interesting concept to explore, I think.
] |
[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 world, physics works exactly like on Earth, except that there is a narrow, 400 foot tall magical column sticking vertically out of the ground, which is magically always extremely cold -- I'm thinking -100 ˚F (200 K), the temperature at which dry ice sublimates, but I'm curious about other temperatures as well. I haven't decided on the exact local environment, but I'm thinking a temperate climate.
## How would a permanently cold column like this affect its surroundings?
*What I have considered so far:*
* I suspect it would become encased in frost from the surrounding humidity.
+ How far would we expect that frost to extend?
* Right at the edge of the freezing zone, I would expect there to be liquid water from the humidity, but I'm not sure how much.
+ Is there any limit?
+ Would a lake eventually form around it?
+ Would it flood the surrounding areas?
* Beyond the edge of the freezing zone, it would be cool.
+ How far would that extend?
[Answer]
For the column to permanently remain cold it would have to break the laws of thermodynamics.
I think it all depends on the how the column works but I can think of two possible outcomes.
**The column is magically isolated**
If the column never absorbs heat then it would remain cold.
That would also mean the surrounding environment would never dissipate heat to it and therefore would remain entirely unaffected.
**The column is a void for heat**
The column does in fact absorb heat, however all the heat is absorbs is magically destroyed.
If this were the case then it would absorb all the heat in the immediate area until it reached -100 also.
It would then presumably stop when the heat transfer rate of the air around the column was the same as the heat transfer rate of the sun over and around the area.
For the heat transfer rate of the column I need to take a couple of assumptions.
First I'm gonna assume the column is placed **on** the ground **not into** the ground - I know this is unrealistic but it makes it simpler.
The next assumption is a big one - size. 400ft (121.92m) tall and lets make it relatively thin with just a meter radius (3.28ft), also assuming its a perfect cylinder.
So given that the average temperature (obviously very variant) is 31 ºC or 304.15K that gives us a temperature difference of 104.15 K.
In addition the thermal transfer will be different in the ground and air.
There is lots of different thermal ratings dependant on soil.
Choosing a clay based soil the thermal coefficient is 1.1 W/mK.
For air this is 0.0262 W/mK
Plugging these into the equation Q/t = kAdT that gives us an initial transfer rate of approximately 360 W through the ground and 2.1 kW in the air.
Therefore total energy to counter balance this would be 2.46 kW
If the column is destroying heat the temperature difference will remain constant and therefore so will transfer rate.
Finally the sun gives us 1 kW/m^2 of thermal energy on the ground (assuming the surface is perpendicular the entire time).
This means the area would reach only 2.46 m^2 around the column, though this is a bit of a mean estimate. This area would 1.34m radius from the centre of the column or 0.34m around it.
**Edit - The Day & Night Cycle**
So I know it's been a few days but I've been thinking on it some more and realised I missed one pretty huge factor... the night.
For a quick recalculation the moon reflects 12% of the light of the sun.
I know this is subject to the moons phases but as with the rest of the question I'm taking large assumptions and averages.
The next of said assumptions is that the moon reflects light in the same proportions as the suns light (UV, visible, Infrared) and therefore its energy transfer is also proportional at 12% of 1kW/m^2 (120 W/m^2)
If this is correct then the 2.46kW transfer rate will need a much larger area to be countered.
This area would be 20.5m^2 around the column, 2.74m radius from centre or 1.74m out from the pole.
Obviously this would be hugely varying dependant on the cycle of the moon.
On a new moon night the area would reach as far as possible in the 12h (again avg) of no sunlight it has, with this being limited by the transfer rate.
On the flip side this area would be almost half the size on a almost full moon night, but not half on actual full moon as on a full moon the light of the sun is blocked by the earth and therefore wouldn't reach the same amount of light reflected back on the earth.
The cold area would fight a constant war between day and night expanding and shrinking.
This massive heating and cooling effect would have similar properties to large desert areas and over time I think the dry area would create a desert like effect around the cold zone.
You could include some species that would take advantage of this cycle and move into the area in the day for some of the nutrients or plants it creates.
Certain desert creatures and plants may like the area but would have to be introduced mostly.
However the area size wouldn't make much wiggle room.
If you were to also state your pillar is very thick then the area around it would increase in a square proportion to the radius of it, giving you a larger varying climate to go with it!
**Edit if you can...**
If you think my calculations are wrong or I missed something then suggest an edit.
I will double check it against sources to confirm it, if you name the source all the better.
However I know I've probably made a mistake or overlooked something so please do suggest!
The area outside of the absolute cold area would be very dry as water may be frozen out the air.
It'd gain moisture for a while then lose it again as it became water vapour.
I doubt it'd be enough to form a lake but in the middle of the cool zone you'd get a lot of snow/sleet/rain.
Also can recalculate if you give more values.
[Answer]
I'll assume a cylindrical tower 120m high and with 3m of diameter.
>
> I suspect it would become encased in frost from the surrounding humidity. How far would we expect that frost to extend?
>
>
>
If the surrounding air is not definitely dry it will be surrounded by ice without doubt. Ice won't extend a lot because ice is a [thermal insulant](https://en.wikipedia.org/wiki/List_of_thermal_conductivities):
* copper: 401 [W·m−1·K−1]
* ice: 1.6 - 2.2 [W·m−1·K−1]
Ice will transfer on average 211 times less heat (the higher number, the better heat transfer).
Because of this property igloos are actually a thing.
During sunny day Sun gives us max 1'413W per square meter, assuming surrounding air at 25°C, the ice creation/melt balance will be at no more than 130mm of ice. (assuming a flat surface, the math for a cylindrical tower is way more complicated). To estimate the ice thickness i've matched the two energy flux, the sun's one and the one that would pass through the balanced ice insulation.
[](https://i.stack.imgur.com/FXp0e.png)
At night? Well, it's really hard to estimate something in general since it will depend by a lot of unkown factor (estimated air temp?)
In any case, since ice is thermal insulant, the ice creation process is a strong self-limiting process, it won't extend a lot.
>
> Right at the edge of the freezing zone, I would expect there to be liquid water from the humidity, but I'm not sure how much. Is there any limit?
>
>
>
Yes, the same aforementioned limit. At that limit you would have an interface of melting/frozing water because you would have a perfect balance between the air melting "power" and the tower "freezing" power.
>
> Would a lake eventually form around it? Would it flood the surrounding areas?
>
>
>
Not really, and in any case this would drastically depends on the soil water permeability and the air humidity. 1138 square meters (tower esposed surface) of frozen surface won't create a lake even in a tropical environment. You have [28 grams of water per cubic meter of air at 30 °C](https://en.wikipedia.org/wiki/Humidity) . Lake Ontario, for instance, has 1,640 km^3 of water, 1.64\*10^12 m^3, 1.64\*10^18 grams of water.
You need to collect the water from 5.86 \* 10^16 m^3 of basically water saturated air to create such a lake.
5.86 \* 10^7 km^3 are 58.6 MILLION of square kilometers can't be really affected by your tower. Imagine a cube 400km wide (not to mention that at 400km high we already are in space, but this is conservative) full of saturated air.
Can you "feel" a snowy mountain -way bigger than your tower- 200km away? Is the mountain drastically influencing the air condensation near you?
Then you have the answer about the lake in our world.
>
> Beyond the edge of the freezing zone, it would be cool. How far would that extend?
>
>
>
"Cool" doesn't mean a lot, 10°C are cool?
Do we have winds near the tower? In that case you could be upwind (who cares?) or down wind (nice air conditioner during summer, annoying colder air stream during winter). In any case it won't be worst than a common central europe winter, and only in a very specific unlucky zone near the tower.
No wind: i'm actually guessing how could you effectively feel if that tower exist or not once you are only 100m away. Obviously you can't have conduction heat transfer.
Convection is quite difficult to justify at this distance (the tower itself will create convection vortexes that will "circulate" the air in the surrounding zone, but we are talking about meters).
Irradiance, despite the fact that -against the common sense- ice is a near black-body in the infrared wavelenght and humans mostly emit in the infrared spectrum, won't be appreciable by humans because of the little difference in temperature (37°C at maximum?), and the infinitesimal solid angle (steradian).
I know that this question is marked as hard-science but i guess that's not really important for the OP to know decimal figures of the irradiated power if it's something negligible in real life.
Moreover, a simple 1.2m high bush 1m far from the person will shield him from any possible effect.
[Answer]
Make the air cold at twice the tower's height, but not decreasing until it is past the 1xheight of the tower, unless there is high wind, in which case make it cold air to 1x -wind speed, in 2xMph.
The ground would also be cold according to the diameter of the tower, according to how much contact it has with the ground. give the ground the coldness of the tower, out to the radius, decreasing out to the diameter.
Close enough. You wouldn't want to try to do this by mass and diffusion.
Keep it simple. No need to go crazy.
[Answer]
A short answer:
The effect will roughly be this: It will absorb heat from adjacent matter, that matter will also absorb heat from adjacent matter. And the tower will keep its temperature even though it's behaving as if it's quite cold. If everything on the planet would remain somewhat "constant", it could freeze the entire planet down to its own temperature. It could even eternally prevent [the heat death of the universe](https://en.wikipedia.org/wiki/Heat_death_of_the_universe)... at least "officially."
However, our planet is not constant. Our sun will provide us with continuous energy, and the relatively hot winds will counteract that effect. The sunlight will also affect the area itself, and further diminish the freezing effect. The effect will have a gradual range, and it will depend on its heat conductivity, fixed temperature and mass. You can't go much into the "negative" heat as you can go into "positive" heat though (basically no limits to that) - however: Magic.
It wouldn't have a large effect on the surrounding environment, except maybe occasionally causing tornadoes and having snow instead of rainfall.
] |
[Question]
[
Let us assume a sufficiently earth-like moon, like Europa. It orbits a gas giant. The whole setup is within the star's [goldilocks zone](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone), so the moon is theoretically habitable.
'Day' is one rotation of the moon around itself, 'month', for the sake of the argument, is one rotation of the moon around its planet, and 'year' is the planet going once around its sun.
Days would be completely dark for a certain portion of the month, I guess, since the planet would eclipse the sun, right? While completely light days would work similar to the way they do on Earth, provided there's no eclipse?
**What I cannot figure out is how seasons would work, and whether they would exist at all. When would it be warmer/cooler?**
Please, I would very much appreciate an answer in layman terms. I have found answers to similar questions filled with formulae I couldn't make heads or tails of.
[Answer]
Seasons are a product of the tilt of the body's axis relative to the star.
Moons generally orbit near the equator of their parent body, so if the planet's axis is tilted relative to the star, the moon's axis have a similar tilt relative to the star. As the planet orbits the star, the moon will get the same sort of seasonal changes that the planet would get from its tilt.
[Answer]
On a planet, seasons are dictated by the axial tilt. The colder seasons located in the hemisphere furthest from the sun, and the warmer seasons in the hemisphere closest to sun. Temperatures, and hence the seasons, in the different latitudes are determined by the angle of the sunrays hitting the land. If your moon had an axial tilt, this would be affected it in a similar manner.
**However**, your moon is also orbiting around the planet, moving further away from the sun and then closer to the sun and then back around the planet again. This orbit-change in distance from the sun would be much larger than the hemispheric-change in distance from the sun, and would affect both hemispheres of the moon at the same time. *It would affect the overall climate and not just the seasons*. Ie say it was what we would consider the "summer" hemisphere on the moon. It could be colder in that summer-hemisphere during the *darker* periods of that month when furtherest away from the sun, than compared to the winter-hemisphere during the bright days on the nearest sun-side of the planet.
This monthly moon orbit would be similar to both the more long-term Annual and even longer-term Milankovich Cycles which influences Earth's *overall climate*. The planet being closer and further away from the sun, aphelion and perihelion. The Milankovich climate cycle is thousands of years long and influences the development of ice-ages etc. Your moon would be experiencing the *equivalent* of a very much smaller-scale "Milankovich Junior" Cycle every lunar month, getting closer and further away from the sun as it orbited your planet. You would then also still have both the planet's Annual and Milankovich Cycles as well.
If you combine this moon orbit (climate) with a moon axial tilt (seasons) then you can have;
* "winter" months with cooler weeks (sun-side) and very very cold *dark* weeks (far-side).
* "summer" months with warmer weeks (sun-side) and still very cold *dark* weeks (far-side).
* The moon's orbit around the planet would have much larger effect on your lunar climate than the seasonal axial tilt.
So now you just need to figure out if you want your moon to take 30 days to orbit your planet or 90 days!
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Axial tilt of the moon is the main factor when it comes to seasonal changes.
The orbit around the planet adds a small variation to the distance from the star, which is normally negligible.
Additionally this variation happens faster than the revolution around the star, therefore the thermal inertia of the planet can effectively mitigate it.
I.e. for the Moon-Earth system, the distance Moon-Sun varies of 2 light seconds around an average distance of 8 light minutes, which is $2/480 = 0.5\% $
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Enough people are discussing the tilt of the axis causing the seasons, but I'm wondering more about if the temperature disparity between lunar day and night might render such a body uninhabitable.
If, to pick a number, the moon orbits the planet in 28 days, it's going to be in complete darkness for about 8-10 days of that period, and semi-darkness a bit less than another 6-8 days. I'd be curious if such a body's atmosphere could hold enough heat for that long to remain liveable, seasons or no.
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I'm trying to develop a planet which has somehow developed sentience. By sentience I mean more of an animal intelligence than being a person. So far I've got a couple of ideas:
1. It's actually a species similar to a fungus or another type of creature that has basically merged itself over time with the planet and lives in symbiosis with its inhabitants. In this case the planet itself is just a normal planet that "merged" with a creature
2. The planet itself is a gigantic creature, travelling through space. The question in that case is how does it provide light for its inhabitants. One of my ideas was that it gathers energy when passing by a star and stores it, then releasing it over time. I am still not sure how does it spread light around its surface though.
To provide some context to this, I'm not super worried about it being 100% scientifically accurate, however I'd like it to be somewhat plausible and make logical sense as a type of animal. The setting is sci-fi, not fantasy. Ideally I'd prefer going for the planet as a creature scenario and use the other one as a backup.
EDIT: One important question if the planet itself is an organism travelling through space, is how does it provide light for its inhabitants? I'm not sure if having a small sun orbiting it (Discworld style) is really plausible. Another option is having some sort of self illumination mechanism, which I don't really have the knowledge to come up with.
I am also interested in having a symbiotic relationship between the planet and its flora and fauna. It's obvious what the planet provides for them (a suitable living environment), however what does the planet get out of this relationship?
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I will provide one example in literature for each possibility you mentioned.
# Planetary Fungus
One of my favorite games ever is Sid Meier's Alpha Centauri. It is like his Civilization games, but in a planet around Alpha Centauri rather than Earth. In this game there is a character called Planet (with a capital P). From the [SMAC wiki](http://civilization.wikia.com/wiki/Planet_(SMAC)):
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> Planet is what the living organism that dominates the planet is called. In earlier scripts it was called Chiron.
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> Its fungus acts as a giant brain. It can control all forms of native life, using them to attack any who upset it.
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When the settlers get there, they are surprised to find that the dominant likeform on the planet is a fungus. Later they discover that the fungus is psionic, that it has merged with all other lifeforms, and that it has a single mind. Some of the settlers even manage to merge with Planet itself.
Planet also has the power to direct its fungal parts' growth, in order to interact with allies and foes.
# Intelligent piece of rock flying through space
Behold Mogo:
[](https://i.stack.imgur.com/Kw0oV.png)
Mogo is an important member of the Green Lantern Corps. He is the one who forges new rings. I don't know whether he was made sentient by the guardians of the universe, but given their custom of granting GL membership only to the bravest and most honest sentient being of each sector, I believe Mogo was sentient before being made a GL.
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Other ideas about intelligent planets:
* The Overmind in Starcraft had "planetary" intelligence and tectonic size. When the planet it was on was covered in creep, we could consider the whole planet one intelligence. But the Overmind died and the planet moved on, so I don't think it fits the bill for this question.
* Gaia, which in different myths and aspects is the embodiment, soul or spirit of Earth.
* In the Star Wars universe, Death Stars are artificial planets. The literature on them never elaborates on the computer systems that run them - but if you let them be run by AI, then they could be said to be intelligent planets.
* In the MCU, Ego (Starlord's father) is a planet.
* In the Discworld universe, the planet where the stories take place is carried on the back of a Turtle that is much larger than it. Other bodies in the system orbit the turtle, not the disc. Therefore it may be said that the turtle is a planetary intelligence.
* This Perry Bible Fellowship comic:
[](https://i.stack.imgur.com/Zoe4G.jpg)
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> EDIT: One important question if the planet itself is an organism travelling through space, is how does it provide light for its inhabitants? I'm not sure if having a small sun orbiting it (Discworld style) is really plausible. Another option is having some sort of self illumination mechanism, which I don't really have the knowledge to come up with.
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[Cherenkiv radiation](https://en.wikipedia.org/wiki/Cherenkov_radiation) makes for the most beautiful blue light you will ever see in your life. However, unless you belong to a species that evolved in an environment with lots of it, staring at this beatiful blue light will tend to shorten your life.
Other than that, bioluminescent fauna, but specially flora, might do. By the way... If there is not enough starlight for your planet, then the most probable energy source for ecosystems at large in your planet is chemosynthesis. This is not renewable and the life on that planet is living on borrowed time (compared to a planet like Earth). Alternatively you can handwave a number of energy sources, i.e.: a stable wormhole brings energy from somewhere else, keeping the planet core hot, and life thrives on thermosynthesis... Or the planet orbits the galaxy core sufficiently close to it that it gets enough radiation (but that adds other problems, such as being in a nova-rich space).
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In Steven Universe, an alien species reproduces by extracting ores from planet crusts in a very predatorial, unsustainable way. Native fauna and flora might make it harder for an invading, predatory destroying species to cause damage to the planet - so the fauna and flora would act like a planetary immunoological system.
Or maybe the planet just wants to play god. In games such as Sim Earth and Sim Life, for example, for all practical purposes you are the planet itself - and there is no reason to keep the simulation going other than for the player's amusement.
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# Sources of light
A *lot* of thing produce light, not just stars. Sure, a star makes lots of light, and can illuminate massive regions, but there are also other solutions.
**Electric charge** - Imagine a [Fluorescent lamp](https://en.wikipedia.org/wiki/Fluorescent_lamp), but on a larger scale. maybe mercury vapors captured in clear ice (or anything clear) and then currents from a "nervous system" of your planet go through them, lighting them up?
It can be set up in a way that typically only one area is intensely illuminated. That way you can have day and night (or close enough).
Btw, [Neon lamps](https://en.wikipedia.org/wiki/Neon_lamp) can also serve as a model, allowing you to use more gases. Maybe a mix, giving different colors in different regions?
**Hot stuff** - Sure, hot stuff tend to be dangerous to humans, but not all creatures are born equal, and if life is to develop on a planet, it will be accustomed to it. This means (a) specie(s) may evolve on your planet, and they can survive an environment full of "hot stuff".
An important question is, what is "stuff"?
It can be constant streams of lava/magma, an [eternal flame](https://worldbuilding.stackexchange.com/a/87197/47807), or possibly you can make up a geological event that suits you better.
**Chemical reactions** - Many reactions produce light (and heat, which wasn't mentioned in the OP, but it's also quite important for life).
Generally, these are called [exothermic reactions](https://en.wikipedia.org/wiki/Exothermic_reaction), and there are [many](https://sciencenotes.org/exothermic-reaction-definition-and-examples/), *[many](https://www.thoughtco.com/exothermic-reaction-examples-demonstrations-to-try-606692)* out there.
A few things to consider with these:
* They tend to be quite quick, so its important to choose a not-very-violent one.
* They use up a lot of matter. Either that is replenished from some source, or you'll run out. It's possible that some creature might consume the products of the reaction and "re-create" it's reactants, but that's hardly plausible (thanks to thermodynamics). Though with some hand waving everything is possible.
**[Bioluminescence](https://oceanexplorer.noaa.gov/facts/bioluminescence.html)** - This one can go in a huge variety of ways. It can be a creature/plant that evolved on the planet, or parts of the planet itself, though that is more of a geological thing (and I couldn't find any on earth, far from a geologist though).
**Sentient made light** - Maybe no life evolved on the planet? What if it was colonized when near to a star. When it started moving away, the creatures realized they'd be doomed without light, and created a network of lamps (or an advanced alternative).
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### Conclusion
Lot's of things make light, so there's a variety to choose from. All of these need some development to work on a planetary scale, and that needs to be done by you (you know your planet much better then anyone else). Also, some of these (*cough*exothermics*cough*) will need more development and hand waving then others, but some can open up cool features for the planet, like the electric solution I suggested (which is why I like it the most).
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Terry Pratchett came up with an interesting one, The First Sirian Bank is the legal name of an intelligent planet, 7000 miles in diameter. A large solid asteroid/planetoid with crystalline semi/superconductor impurities, a complex of fault lines that create a massive complex of circuits. It actually celebrates the fault shift that made it sentinet. It Acts as a a central bank for the galaxy and in return they build it sensory interfaces and propulsions systems.
Replace crystal with fungal and you have the same effect.
Of course there is a wiki list of living planets you can look at for inspiration.<https://en.wikipedia.org/wiki/List_of_fictional_living_planets>
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I'm considering creating a fictional multi-national black ops unit called S.W.O.R.D [(Special Worldwide Offensive Resolution Division)](http://tvtropes.org/pmwiki/pmwiki.php/Main/FunWithAcronyms) designed in a highly organized and militarized manner such as you might find with [Ancient](http://tvtropes.org/pmwiki/pmwiki.php/Main/FantasyCounterpartCulture)
[Sparta](http://www.ancientmilitary.com/spartan-military.htm)... if the [Spartans used tanks, guns and cutting-edge technology](http://tvtropes.org/pmwiki/pmwiki.php/Main/DisSimile) supplied by DARPA.
*Spartiates* (soldiers under the command of S.W.O.R.D) wear futuristic fully enclosed combat helmets modelled after helmets worn by the real-life *Spartiates* with an incorporated skull motif and resembling scowling faces.
One such helmet includes the Corinthian-Type Helmet, which is worn by rank and file *Spartiates*. This helmet is vacuum-sealed and equipped with a variety of features such as large almond-shaped polarised lenses, small lights mounted to their lower halves and a pair of tubes connected to a re-breather in the wearer's armour. Just like their namesake, these helmets can be pushed up to on rest on the back of a *Spartiate*'s head.
How practical would such a combat helmet be?
***Visual References***
[](https://i.stack.imgur.com/2taSc.jpg)
[](https://i.stack.imgur.com/vTLdP.jpg)
[](https://i.stack.imgur.com/XnWLg.jpg)
[](https://i.stack.imgur.com/vdH98.jpg)
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# A heavy helmet makes it hard to turn your head
This might seem trivial, and it is in most situations, but if you don't need a heavy helmet, you shouldn't wear one. The more armor and electronics are packed into the helmet, the harder it is to move your head; that much is obvious. There is only so heavy a helmet can get, even on a Leonidas-neck. This is just something to keep in mind as you pack more and more gear into the helmet. The [real helmets used by SpecOps](https://www.hardheadveterans.com/products/ballistic-helmet?utm_medium=cpc&utm_source=googlepla&gclid=CjwKCAjwwuvWBRBZEiwALXqjw0QXTlY1TbTNgwwgMHo6glMb6immIduKpcNQ1p2WDX9SVbyPaMVhhxoCQCcQAvD_BwE) are barely over 1 kg.
# Why are you restricting the ability to breathe?
Do these soldiers expect to be attacked with chemical or biological weapons? Do they expect to go into the vacuum of space? If not, why would you so heavily restrict their respiration? I don't know if you've ever put a gas mask on, but if you run around in the desert with one one for a few days, it is very uncomfortable.
On the one hand, moisture and bacteria from your exhaled breath will build up in the helmet. This can have a deleterious effect on your lungs after a long period of time. On the other hand, your exhaled breath will also collect inside your helmet and make it generally hot and uncomfortable.
If you want a faceplate for protection, then consider making sure that there it is not sealed (all your pictures look sealed to me) so that there is adequate ventilation.
# Is it hot?
Speaking of running around in the desert with a gas mask on, there is a practical vision problem with that, too. Sweat from your forehead is naturally deflected by your eyebrows to the side of your face, away from your eyes. But contact between your forehead and the helmet and/or condensation within the mask can allow seat to get around that and impede your vision. And if it is hot out, a dark colored can on your head doesn't help the sweating situation. Even Darth Helmet [switched to khaki](https://www.google.com/search?biw=1600&bih=785&tbm=isch&sa=1&ei=bFbbWozSLO3p_Qao0pqIBw&q=darth%20helmet%20desert&oq=darth%20helmet%20desert&gs_l=psy-ab.3..0.3102.3825.0.4210.6.4.0.2.2.0.57.199.4.4.0....0...1c.1.64.psy-ab..0.6.204...0i8i30k1.0.fyWYAZKJY_o#imgrc=_) in the desert.
This one isn't immediately solvable by ventilation. Any faceplate will run into sweat concerns in high temperatures. If you do all your fighting in Norway, then this is probably not a big deal.
# Don't differentiate by rank
That gets senior officers shot. Even in tank combat in WWII, tanks with radio antennas looked more important and got shot more. One helmet should fit all.
# Can this mask stop anything important? Is it usable after one hit?
The point of a faceplate is to prevent damage to the face, presumably. Can this faceplate stop a bullet? Maybe 5.56, probably not 7.62 or anything larger (it all depends on angle of impact). No face plate lightweight enough to not stress your neck is going to reasonably stop such an energetic round.
So your faceplate is still useful for stopping shrapnel if you run into a lot of grenades. Do you run into a lot of grenades? Another thing to consider is what your faceplate looks like if you do stop a grenade. I imagine the see-through glass part is now completely damaged, and the helmet will have to be removed. This is the downside of a faceplate: a damaged helmet (penetrated, cracked, etc) is still mostly as useful as an intact helmet. A damaged faceplate that you can't see through is just deadweight.
# The real reason for a mask is information
The reason the modern army would consider a faceplate is to put information right in front of the operator's face. SpecOps in particular may find themselves chasing bad guys around town while on the phone with satellite operators who are using powerful tools to track the bad guy's movement. This is a thing that happens in real life.
But here the faceplate damage thing comes to the fore. If you have a cracked faceplate, then you can't even wear it and use the information displays any more. If you depend on the information to do your job, this is bad. Better off to use something like Google Glasses and keep a spare in your pack. Cheap and lightweight means you have a backup option in place.
# Conclusion
There is a reason that the modern military doesn't use such things. I can't see any reason to wear such a mask, given the downsides, unless there was an expectation of operating in an environment where you can't breathe (chemical weapons or space).
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Since such configuration seems to strongly limit lateral visibility, its practicality strongly depends on the use case.
In group combat, where the soldier's sides are guarded by companions, it might not be a disadvantage.
In combat scenarios where the sides are unguarded, the blind points on them can prove lethal for the soldier wearing it.
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There are practical real world reasons to have your characters with obscured faces.
**1. Save on animator time.**
[](https://i.stack.imgur.com/qmXiv.jpg)
<https://www.youtube.com/watch?v=doteMqP6eSc&t=69s>
This is a fine short. The priority here is clearly action and loving depiction of the ruined city with luxuriant plant growth. But humans look at faces and cheesy halfassed renditions of expressionless faces would be a turd in this punchbowl. Solution: plausibly obscure the face. Likewise animating large groups of people is easier if you do not need to do a realistic, different face for each one.
**2. Contrast for sexual effect.**
Anime, like pornography, often has hypersexual female heroines and faceless male participants. A good way to make sure your males are faceless is to enclose their heads in helmets. I was going to post an example image but was overwhelmed with choices.
**3. Facilitate actor switch .**
If you have a live action show, you easily can swap in a stunt person for your actor if the action version of the character has a helmet on. The prime example is Power Rangers. This also facilitates using footage filmed for alternate versions of the show with different actors. The same stunt people / battle sequences can be used.
**4. Dehumanize your villain.**
This is similar to #2. A mask makes a monster as personified by Darth Vader. When we look for a face and find something facelike but not a face it is creepier than seeing nothing.
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# Executive Summary
Thank you for considering **Chronograph Talent Consulting** for your talent acquisition needs. We select the best talent from all previous periods of human history and make them available to clients looking for the absolute finest talent that money and time can provide. Our talent portfolio is mainly drawn from past eras as it easy to show how effective the talent was in their own times. Our clients demand the effectiveness of the Julius Caesars, Frederick the Greats and Genghis Khans of the past.
To be considered, a prospective contractor must be mentioned in a history book that a Masters student in History might read. Exceptions are made on a case by case basis. Individual referrals by past contractors may also be considered. Talent is gathered from all continents and cultures. **CTC** maintains an extensive historical research arm to locate potential candidates.
Thus far **CTC** has specialized in bringing forward exceptional scientific minds to work on research projects. [Oppenheimer](https://en.wikipedia.org/wiki/J._Robert_Oppenheimer) and Einstein have been especially useful. Our customers have seen our success with science and have been asking for contractors able to work in politics. A little preliminary research shows that almost all political and military masterminds have varying degrees of sociopathy. We agree with the DSM that those with sociopathy or [Antisocial Personality Disorder](https://www.psychologytoday.com/conditions/antisocial-personality-disorder) are mentally ill but they're mentally ill in a way that's very valuable to us and our clients.
**What skills will these contractors bring that will transcend their native cultures and will be immediately/quickly useful to my clients?** Each contractor will have distinct skills and abilities unique to them, so **CTC** is not worried about the individual variations just yet.
# Onboarding Process
All of the contractors we bring forward receives an implant that handles language translation (the language barrier is just too high without it.) Candidates are also given an intensive six month to one-year cultural adjustment program to acclimatize them to the time and place they'll be working. Disease transferal isn't a problem either; it's managed by a highly skilled medical staff (we went forward in time to get them and the medical supplies).
The effects of taking a person out of their native time stream then putting them back has been solved in a satisfactory way. **CTC** employs very smart people to handle that problem. Other than the language translation module, no control devices or kill switches are implanted. However, there is a hard time-limit on the contract where once the contract time expires or the contract is otherwise breached, the contractor in question is removed from the area of operations to be returned to their own time or our facility (at our discretion).
Terms of employment are offered at the time the contractor is brought forward in time. If they do not accept the assignment or terms, they are immediately sent back to their own time. Contractors out on contract are granted the same rights that a citizen of that country or locality would be granted. Payment is sent back with them on completion of their assignment. Contractors are not permitted to stay in our time indefinitely (ie, no permanent resident cards to live in the 22nd century). They have to go back.
# Past Success Stories
A client required a leader for their military conquest of a competing corporation. They chose Genghis Khan for his excellent planning and logistics skill. Genghis was brought forward to the present day, offered a contract that he accepted and went to work. After utterly destroying the opposing corporation, he was sent back to his time with more gold and silk than a thousand horses could carry.
Another client needed a foreign ambassador seduced. Cleopatra was selected as the prime candidate and she accepted the contract. The ambassador was seduced and the required intelligence gathered. Cleopatra went back much wealthier than when she arrived.
*To those who want to know why we would bring such people forward? Profit. We can get 50x the rate for political contractors that we can get for science contractors (mainly because the political contractors know to negotiate instead of just taking what we offer them.)*
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SO much to say on this topic, but I'm going to try to keep it as concise as possible because if we go into the economic, philosophical, political, psychological, etc. aspects in detail, I'll blow the size of the answer field. But here goes...
Fundamentally, there's a reason most of the *famous* politicians and generals of the past have sociopathic tendencies; it's the only way to get things done on a large scale without being crippled by the weight of choice. This is still the case today. Whether we like to admit it or not, moving a country of any significant size forward means making choices that ultimately leave some of its citizens worse off. It has to. The question becomes, can you live with that?
Sociopaths can.
Other well-meaning leaders can too, but they'll pay an emotional toll which makes them less inclined to act. On balance, sociopaths are statistically more likely to be remembered for change that has impacted a great many people.
Let's start by looking at conventional contemporary politics; it's often said that the conservative side of politics cares about the economy because they want to increase opportunism. The argument is that if an opportunity exists in the economy, lower regulations, lower wages etc. increase the ability of entrepreneurs to exploit that opportunity, which generates jobs and adds to the economy in a useful way.
What is often less understood is that liberals care about the economy just as much, but do so from the perspective of increasing consumerism? That argument is that if employees are paid well, they will spend more and demand services that (in some cases) don't even exist yet, increasing opportunities for new services to be created and add to the economy in a useful way.
The truth is that you need BOTH ideas to exist in balance in order to drive a strong economy. Both sides of politics know that; their difference of opinion is in where the line should be drawn.
Either way though, you're going to make some people worse off. Workers under a conservative government are going to find it harder to make ends meet. Under a liberal government, business owners are going to retain a smaller percentage of their business profits.
If you look at modern political leaders, there's no question that they understand this model; but, they make their case for change based on the fact that it's 'acceptable losses'. These are losses that are effectively unavoidable because, in any change in a society of sufficient size and complexity, it's going to harm someone. The trick is to keep harm at a minimum while maximizing benefits to others.
Unless of course, you're a sociopath.
In that case, the only goal is the prosperity of the state, which in turn reflects your own prosperity or reputation.
Let's look at the most obvious example of this.
You're about to enter WWII. You have a pick of 3 leaders;
A) A failed naval tactician responsible for arguably the biggest military disaster of the 20th century. Lost more elections than he's won, suffers from chronic depression and drinks more than half a bottle of gin each night.
B) A failed business manager (been bankrupted more than once), who is also a womanizer and a paraplegic.
C) a Tee-totaller vegetarian decorated war hero with an economics degree.
A is Winston Churchill. B is Franklin D Roosevelt. C is Adolph Hitler.
Regardless of your emotional take on Hitler, there is one thing he did in the 30s that cannot be questioned; he turned Germany's economy around. In the space of a decade, it went from one of the poorest economies in Europe into one of the strongest. This is not a history debate and I'm not going to go into the details of the Treaty of Versailles and its impact on this economy in the first place as it's out of scope. The point is that he was doing good for the community at the time.
Thing is, that he was leaving one group of his constituency out of the prosperity and deliberately disenfranchising them is a matter of historical record. And, ultimately, because of that and his military overreach, his country was worse off in the end.
Obviously what you want from him (should you bring him forward) would be his economic understanding, not his military experience or his leadership qualities.
That said; it's understanding that we already have in today's world. In other words, there's **nothing that a famous sociopath can give us that we don't already have in terms of intellectual capability**. What he had that we lack is singular will to do what he believed needed to be done regardless of the human cost.
This is the one unique skill that he can bring back. It's also the one skill that would be counter-productive.
So; my opinion is that you're better off leaving them consigned to the pages of history. Let them have that because most of the people who would actually want him to be brought forward in time would want him here to stand trial for his crimes against humanity.
Sorry to say this, but completely amoral people are dangerous, and scare the daylights out of me. On top of that, we have more than enough of them among us today. No need to bring more of them into our present in my humble view.
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Two factors
# The ability to make a decision and deal with the consequences
This is the real big one. It's the one that says, if I do this then hundreds, maybe thousands, even hundreds of thousands, of people are going to die. And not just to be able to make that decision once, but make it over and over again. Could you leave a trail of corpses in your wake to achieve your aims? Caesar can.
# The belief that they are the person who should be in charge and should be making that decision
Your sociopath isn't going to suffer from imposter syndrome. They can happily truly believe they're the best person for the job without worrying that perhaps they're under qualified or out of their depth. Who should be emperor of the western world? Napoleon of course, who else?
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Ah, therein is the rub.
Will they have access to a good lawyer?
Methinks that the same qualities a client would want in a contractor are exactly the same qualities that would motivate the contractor to become their own operator. That is, they would soon become independent of CTC and branch out on their own, unrestrained opportunists that they would be.
No one wants followers from the past, they want leaders. And leaders want to lead, not follow. I am sore afraid that there would be some significant hesitation in such a person to voluntarily give up what they could have in modern society for whatever they would be returning to, no matter how rich.
After all, they would have ample access to history books, and they would know how things turned out for them.
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Let's suppose that a fusion bomb device with a yield of 200 megatons (4x Tsar Bomba) is detonated in Mare Tranquillitatis on the Moon.
My question is:
* Would the explosion be visible from Earth at night? I imagine that it would be a flash followed by the covering of the explosion site in dust clouds.
* Would there be any immediate or long-term effects observable from Earth?
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Let's run a few numbers. We'll assume that 10% of the energy from the explosion is radiated as visible light -- that's a good enough estimate for this purpose. 10% of 200 megatons is 84,000,000,000,000,000 joules, or 8.4E16. Figure it lasts for ten seconds, and that's 8.4E15 watts.
The Moon (and Earth) get about 1,360 watts/sq.m of solar radiation. Let's assume 50% of that is visible light, 680 watts/sq.m. The Moon's albedo is 0.12, so 12% of that gets reflected, 82 watts/sq.m. We'll call it 84, or 8.4E1, because it makes the sums ever so much easier.
So, the bomb will emit about as much light as 1E14 sq.m of lunar surface. The radius of the Moon is 1,700,000 metres, so the area of the disc of the full Moon is 9E12 square metres. Call it 1E13.
Therefore, for a few seconds the bomb will be something like 10 times as bright as the full Moon, and will thus be easily visible, but not immensely dramatic.
There won't be any dust clouds (for more than a minute or two), because there's no atmosphere to hold them up. The dust will fall back to the surface as quickly as any larger ejecta.
There would be no long-term effects other than a small (not visible without a pretty good telescope) new crater. There have been many thousands of bigger meteorite impacts on the Moon.
] |
[Question]
[
What kind of prosthetic technology would be available to a wealthy but rural aristocratic person without a leg and how would it affect their social standing? The time era is sort of pre-Elizabethan, but as it is fictional I can change certain aspects of it to fit the medical aspects of amputation if necessary.
The leg is removed from the knee down following an infection.
[Answer]
It's sad that this is before Victorian, because those fellows could amputate well and quickly--we are talking half a minute to 2 minutes for the really practiced ones. Pre-Elizabethan doctors were not so well versed in the art of amputation, because the autopsy craze hadn't taken hold, and that's where a lot of Victorians learned how--on cadavers. During the Pre-Elizabethan times, there would be less opportunity to practice such a thing.
Let's take your second question:
**How would it effect their social standing?**
Depends on several factors. If they were injured in war--or if the story of that injury is a good one rather than a mundane one (I tripped on the stairs and it got infected vs. epic fight with a boar. It took my leg, but I ate it. Vengeance is savory!) Injury in war can actually raise their standing because they gave to their country.
However, it means that they will be looking for ways to be useful in battle. They'd want to do mounted combat, of course, and will want to be in battle to prove themselves.
Since this isn't a birth defect, it might not harm their standing at all, as long as they produce heirs and or otherwise upstanding. If they are not upstanding (no pun intended) then this weakness will be used to further denigrate their reputation.
Socially it would hurt them for activities involving walking, though they may work to be able to do those just as easily.
Now let's look at question 1:
**What would be available to this fellow to replace the leg.**
That's going to greatly depend on finding a craftsmen. Today prosthetics are many and varied, but they often come from the same manufacturers, but back then, you would engage a specific craftsmen to do the work.
This is going to be limited by the fact that amputations that the person actually lived through were relatively RARE, because there's more to it than simply lopping off the limb--you've got to tie off blood vessels, leave extra skin to close it up, be careful where you cut. At the time you are talking about, most would be dead.
So because it's rare, there aren't likely to be people who are specialists in prosthetics. During America's Civil War for instance, there were enough amputees that a specialist business grew up out of it, but your noble is more likely to hire a craftsmen they know, or send for one at great expense who has been known to do such a job in the past.
Materials used, and the people hired include woodworkers, armorers and leather workers. There's evidence that wood and metal might be used together in order to fit on to the stump.
If you are wondering about a hinge or anything--while it could be possible, during this era it's not common. Possible, if the person in question pays a lot and gets the most advanced thing. Here's a snippet on the most advanced during that time period:
>
> Early 1500s
>
>
> In 1508, German mercenary Gotz von Berlichingen had a pair of
> technologically advanced iron hands made after he lost his right arm
> in the Battle of Landshut. The hands could be manipulated by setting
> them with the natural hand and moved by relaxing a series of releases
> and springs while being suspended with leather straps.
>
>
> Around 1512, an Italian surgeon traveling in Asia recorded
> observations of a bilateral upper extremity amputee who was able to
> remove his hat, open his purse, and sign his name. Another story
> surfaced about a silver arm that was made for Admiral Barbarossa, who
> fought the Spaniards in Bougie, Algeria, for a Turkish sultan.
>
>
> History Prosthetics 04Mid- to late 1500s
>
>
> French Army barber/surgeon Ambroise Paré...invented an above-knee device that was a kneeling
> peg leg and foot prosthesis that had a fixed position, adjustable
> harness, knee lock control and other engineering features that are
> used in today’s devices. His work showed the first true understanding
> of how a prosthesis should function. A colleague of Paré’s, Lorrain, a
> French locksmith, offered one of the most important contributions to
> the field when he used leather, paper and glue in place of heavy iron
> in making a prosthesis. [SOURCE](http://www.amputee-coalition.org/resources/a-brief-history-of-prosthetics/)
>
>
>
As you can see springs and hinges were possible for knee joint action and this gives you an idea of the materials used.
EDIT: By Knee Joint action, I just mean that the knee joint can be adjusted manually. It would not actually work like a regular knee during this time period, although there might be an adjustable hinge.
[Answer]
There are several types of early prostheses in history, showing that it would be possible to create one for most part of the foot and leg.
[Egyptian toe prosthesis (pre 600 BCE)](https://www.seeker.com/ancient-egyptian-fake-toes-earliest-prosthetics-1765999240.html)
>
> Exquisitely crafted from cartonnage (a sort of papier maché mixture
> made using linen, glue and plaster) the Greville Chester toe dates
> from before 600 BC and comes in the shape of the right big toe and a
> portion of the right foot.
>
>
>
[Capua leg (300 BCE)](https://en.wikipedia.org/wiki/Capua_Leg)
>
> The Capua leg is an artificial leg, found in a grave in Capua, Italy.
> Dating from 300 BC, the leg is one of the earliest known prosthetic
> limbs. The limb was kept at the Royal College of Surgeons in London,
> but was destroyed in World War II during an air raid. A copy of the
> limb is held at the Science Museum, London.
>
>
>
[Medieval foot (6th century CE)](http://www.atlasobscura.com/articles/mindblowing-archeological-find-wooden-prosthetic-for-a-medieval-foot)
>
> a burial of a middle-aged man who died in the 6th century A.D. He was
> laid to rest with a short sword and a brooch and his skeleton was
> fully intact except for his left foot and ankle, which had been
> replaced with a prosthetic device.
>
>
>
[Brief History of Prosthetics (from 424 BCE to near modern times)](http://www.amputee-coalition.org/resources/a-brief-history-of-prosthetics/)
>
> The Dark Ages (476 to 1000)
>
>
> The Dark Ages saw little advancement in prosthetics other than the
> hand hook and peg leg. Most prostheses of the time were made to hide
> deformities or injuries sustained in battle. A knight would be fitted
> with a prosthesis that was designed only to hold a shield or for a leg
> to appear in the stirrups, with little attention to functionality.
> Outside of battle, only the wealthy were lucky enough to be fitted
> with a peg leg or hand hook for daily function.
>
>
>
[Answer]
The only prosthetic leg available in Medieval Europe was the [pegleg](https://en.wikipedia.org/wiki/Pegleg).
Having a prosthesis shouldn't impact social standing, unless the story of how they acquired it was particularly scandalous.
] |
[Question]
[
I'm looking for a very grounded evolutionary justification for the existence of a hermaphroditic sapient and social species, preferably roughly mammalian but not mandatory, which is not as easy as it would appear to justify.
In the real word most hermaphrodite species are simple species, and most live in isolated areas where finding another of their species is harder thus increasing the benefit of ensuring the ability to mate with any you find, and/or yourself if none are found in some species.
There is a reason more 'complex' species don't tend to be hermaphrodites (forgive my simplification of referring to species like mammals as more complex, I'm not implying evolutionary levels, just more extensive genetic code). In theory it doesn't cost much for a female to have 'male parts' and be a hermaphrodite. However, if you have a hermaphrodite species some will be naturally better at being a 'male', and these better males will tend to produce more offspring since strong males can produce more offspring then strong females due to lower investment per child. Over time the strong males will 'realize' they benefit more from being a strong male and will focus more and more at securing mates as a male, which usually leads to the males 'losing' the ability to mate as female to instead focus on being better at out-competing others as a male to make them better at producing lots of young. Eventually males split off as separate from hermaphrodite as the only way to compete with other males and then the non-males specializes as females only to be the best at producing children and because they can't compete with specialized males for mating rights.
That's oversimplified explanation above I know it. The point is I want to avoid this issue, to justify hermaphrodite sapient that make sense evolutionary and won't diverge into separate sexes. They must also live socially with no shortage in potential mates.
I would prefer simultaneous hermaphrodites, though I'll accept sequential hermaphrodites *IF* there is an equal number of both sexes and no cast system where only the strongest/biggest etc transition to the other sex.
[Answer]
You can avoid some of your hermaphrodites going off to become polygynous males, by having a selection pressure which requires both parents present to successfully raise the offspring. Basically, have some biological quirk which imposes monogamy and/or cooperative breeding.
For instance, most birds are monogamous, because the eggs have to be incubated by a warm parent sitting on them AND because both parents can feed the chicks. Most mammals are polygynous because only mum is pregnant and only mum can supply milk, so dad can run off to find another female to mate with.
If you don't want something like an egg, then a tough environment, makes it likely that both mammal parents will be required to work their butts off to keep their kids fed and protected.
Since your creatures are hermaphrodites, both of them can provide milk for the baby. Or crop milk, like pigeons do. Or shed their skin for baby to eat, like caecilians do. Or make honey/royal jelly like bees.
Also you can make having the baby physically draining, like in seahorses. Mum seahorse accumulates the resources to make the eggs, but then passes them over to dad to incubate, while she goes off to feed up and recuperate, ready to produce the next brood.
In hermaphrodites, perhaps the parents have to take turns to give birth, because it takes so long for their bodies to accumulate enough body fat for baby's brain, or phosphate for baby's bones, or calcium for the egg shell, or whatever. So a bit like the seahorses, except it would be:
1. Herm A gives birth, passes baby to Herm B for initial few months of breast feeding while Herm A recovers from the resource drain of the pregnancy.
2. Both Herm A & Herm B breast feed the baby from month 3 onwards until it is a toddler. Herm A's fertility is suppressed as it is still recovering its reserves after the pregnancy.
3. Herm B gets pregnant and its milk dries up. Herm A continues to feed toddler for a few months then weans it just before Herm B gives birth.
4. Herm B now gives birth... Rinse and repeat.
If you want to make pregnancy really tough, or milk production equally demanding as pregnancy (in many mammals lactation is more energy draining than pregnancy, which is why births are timed to coincide with seasonal food abundance), then perhaps you require three or four hermaphrodites to successfully raise a child to weaning age.
[Answer]
The species is simultaneously hermaphroditic (but not capable of self-fertilization) because their ancestors rarely found mates and had to ensure that they would reproduce every chance they got ([Source](https://reefbuilders.com/2014/11/13/sequential-hermaphrodites-protandrous-protogynous/)). I suppose their ancestors were solitary tool users similar to cephalopods ([Source](https://en.wikipedia.org/wiki/Cephalopod_intelligence)). By the time they developed sapience and a social structure, their reproductive cycle was too entrenched to go away (similarly to how tetrapods, like us, cannot become hexapods despite the advantages).
In fact, humans are genetically hermaphrodites because males and females both have the genes for becoming male or female ([Source](https://embryology.med.unsw.edu.au/embryology/index.php/BGDB_Sexual_Differentiation_-_Sex_Determination)). Sometimes these genes are expressed incongruously and an individual will display both male and female traits, but such individuals are generally sterile.
[Answer]
**Regular, massive climate changes.**
Hermaphroditism would only be preserved in human-like vertibrates if there were regular occurrences that reduced population to the point where individuals found it difficult or impossible to find mates. In this scenario, the ability to reproduce without a sexual partner would allow individuals to repopulate after a population crash leaving only a small number of individuals, without needing to find a partner of the opposite sex. This would be especially beneficial if the environment changed from a very harsh one to a very forgiving one, in which child rearing was very easy, and benefits from having a partner to help raise children were minimal.
One way this could happen is if your creatures evolved on a planet with a long, eccentric orbit. This could produce global seasons far harsher and lasting far longer than the seasons we see on Earth. An intense summer or winter could drastically alter the climate, killing off a large portion of its inhabitants, after which a long spring and summer characterized by a near perfect climate for growing would see rapid blooms of life, fertilized by dead plants and animals killed by the previous winter.
Populations of hermaphrodites, in this scenario, could repopulate more rapidly than those comprised of single-sexed individuals, and would be more resilient to seasonal population crashes. All individuals, in good times, would be able to birth children, increasing the birth rate of their community.
[Answer]
Sexual recombination is a huge evolutionary advantage and the primary driving factor behind the complexity of organisms in which it has evolved. Separation into two sexes that are both required for mating guarantees the inclusion of additional genetic information. As you mentioned, in environments where other mates may or may not be available, hermaphrodism makes use of the benefits of sexual recombination while allowing failsafe reproduction within a single organism. However, the option for hermaphroditic self-fertilization does restrict genetic diversity and therefore development.
If changing conditions resulted in a hermaphroditic species that now found mates readily available, then need for self-fertilization would disappear, but the ability for a single organism to reproduce with itself would continue to be a hindrance to the rate and extent of evolutionary advancement. An alternative solution to two diverging sexes could be periodic sex cycles, where each individual transitions back and forth between the two sexes. The species would gain access to the benefits of sexual recombination, such as the eventual development of social behavior and sapience, while maintaining a hermaphroditic sex system. In fact, this system could actually increase the genetic diversity over binary sex systems, because any two individuals could mate. Variation in each individual's cycle duration would allow any two individuals to reproduce in either configuration at some point or another (A is male and B is female at one point and vice versa at a later point in time).
[Answer]
I think there is a fair amount of evidence for unnecessary/sub optimal organs sticking around long after the reason they were selected for has passed.
I think all that is required for humanoid hermaphrodites to believably exist is for it to have been selected for at some point in their evolutionary history and never cause enough of an issue to be selected against.
There are enough theoretical variation in environmental and genetic factors given the diversity in the universe that it is fairly likely for complex hermaphroditic species to exist somewhere (given the assumption that complex life forms aren't extremely rare)
Remember earth is one data point and there are many examples of stagnated or sub optimal evolution even here. If you are worried about readers not finding what you come up with reasonable hang a lantern on it and point out that the unlikely often happens one in a million times.
[Answer]
What if the species was hermaphrodite due to social evolution rather than natural evolution. Human hermaphrodites exist today, but are commonly surgically altered to be one sex or the other. What if hermaphrodites became popular and desirable for some reason and so became the majority sex.
] |
[Question]
[
It is the year 2055. Only 20 years after the devastating Third World War, humanity has united together to start a golden age. Overseen by a peaceful, ambitious, and global superpower called United Earth Republic, war has finally been eradicated. Technological advancement and exploration has skyrocketed to say the least. And most importantly, colonies have begun to spread like wildfire across Luna, Mars, and Titan.
However, in the wake of this exodus to across the solar system, we are in need of a new form of transport. The older, titanic colonial ships have become too slow, too crowded, too expensive and just too impractical to remain as the only link between planets. With thousands of people crossing the solar system each day, we need a transit system that could link the planets as easily as linking two cities.
As one the UER’s top architects, you have been put in charge of developing a mass transit network across the solar system dubbed “Project Voyager”. At your disposal, the UER Senate has provided you with an unlimited budget for resource mining, fuel, construction ships, and drones (alongside a huge human workforce ready for hire). However, there is a certain set of guidelines you have to follow:
• It has to move very fast, capable of traveling from the Earth to Mars at their closest points in only 2 days or less. Also even though we did crack FTL travel, it is **way** too expensive to scale up past individual star ships.
• It has to have a quick turn-around time, making it possible to unload its passengers and payloads, undergo a quick systems check, restock, reload, and depart in a matter of minutes.
• It has to be small, carrying only groups of 100 people each alongside a payload weight of only 5 metric tons each. For cargo only pods, it could go up to 10 metric tons.
• The UER is almost a type 1 civilization, so dyson sphere satellites and laser driven photonic propulsion are on the table (it’s not necessary, but recommended for cutting out fuel weight)
• Although the bulk of the colonies’ populations are planetside, there are O’Neil cylinder space colonies and space elevators around each of these colony worlds. So, the surface to ground and orbital infrastructures are already in place.
So, with everything ready to go, how do you plan to build this?
[Answer]
There are actually several ways to do this, but one consequence the people will have to accept is that they are essentially firing cannonballs across the solar system with the impact energy of nuclear weapons. This is going to make control over the system of utmost importance, and any malfunction or accident is going to have severe consequences.
In order to send cargo rapidly across the solar system, a series of orbital mass drivers will have to be established in orbit around every transit point (planet, moon or space colony). One mass driver is energized at the launch point and shoots the cargo at some massive acceleration to the destination (at an acceleration of 100g, a cargo pod could go from the Earth to Mars in about 24hr when the two planets are at their closest approach). The receiving mass driver decelerates the pod and stores the energy to help send an outgoing pod, make orbital adjustments and so on. Since no process is 100% efficient, there will also be a large set of radiators to deal with the waste heat.
Human beings don't take very well to this sort of treatment (and a mass driver which can accelerate human cargo to these sorts of speed at 3g or less will be improbably long), so if transporting people is the goal, they will need to be pumped full of oxygenated fluid to fill all the air spaces, and then stuck in a fluid filled tube to cushion the shock of acceleration and deceleration.
These mass drivers themselves will be huge structures, possibly resembling the 1970 era visions of Solar Power Satellites the size of Manhattan island (and given the energy consumption, ones in Earth orbit might well be that size to collect enough solar energy. Deep space mass drivers might have radiator panels that big to deal with the waste heat of their fusion reactors and accelerating/decelerating payloads).
But as I said, the key issue is the potential damage a pod could cause. A 3 ton asteroid interceptor described in [NextBigFuture](http://www.nextbigfuture.com./2009/02/unmanned-sprint-start-for-nuclear-orion.html) accelerated at 100g by ORION nuclear pulse charges would impact the asteroid with a *gigaton* of energy, so larger pods, and ones going faster to reach destinations to and from deep space would have the sorts of energies associated with dinosaur killer asteroids.
So the ability to track and (if needed) destroy off course pods would be absolutely part of the package. Mass drivers will probably have huge telescopes to assist in aiming the pods, which can be used to track them, and if necessary be used as beam expanders for powerful laser weapons. The power plants that energize the mass drivers will also be sufficient to power the killer laser, and [Ravening Beams of Death](http://www.projectrho.com/public_html/rocket/spacegunconvent.php) (RBoD's) are conceptually powerful enough to rapidly vaporize materials in microseconds from as far away as one light second. Since pods will be on ballistic trajectories, they could be engaged from much farther away.
Maybe your peaceful republic will suddenly discover they are sitting in the sights of interplanetary cannon if the space colonies become disgruntled by whatever political, economic or social systems the Republic is trying to implement....
[Answer]
In this setting people made many impossible things so lets make one more.
Lets made orbital tube transfer system around the sun. This system takes orbit between Earth and Mars and consist of rings. These rings forms space gas flow. The biggest speed of gas in the middle of ring and the lowest on the boundary.
Each space ship need a few fuel:
1. On the way from Earth to the Sun Ring.
2. Some fuel to smoothly reach the quickest space gas flow.
3. Smoothly goes out from Sun Ring.
4. Travel the rest of the way to Mars.
Lets see check list:
>
> • It has to move very fast, capable of traveling from the Earth to
> Mars at their closest points in only 2 days or less. Also even though
> we did crack FTL travel, it is way too expensive to scale up past
> individual star ships.
>
>
>
Actually no. This system speed up all Earth-Mars distances excluding the shortest one. So this system doesn't solve the problem but it reduces the problem just to make Earth-Mars travel by shortest way in two days.
>
> • It has to have a quick turn-around time, making it possible to
> unload its passengers and payloads, undergo a quick systems check,
> restock, reload, and depart in a matter of minutes.
>
>
>
Lets imagine letter container which can drop current letter on the fly and catch the new one. It seems possible.
>
> • It has to be small, carrying only groups of 100 people each
> alongside a payload weight of only 5 metric tons each. For cargo only
> pods, it could go up to 10 metric tons.
>
>
>
Supported, this system can't work with big freighters.
>
> • The UER is almost a type 1 civilization, so dyson sphere satellites
> and laser driven photonic propulsion are on the table (it’s not
> necessary, but recommended for cutting out fuel weight)
>
>
>
Fuel is not excluded but you don't need fuel on the ship to travel. Just for manoeuvres.
>
> • Although the bulk of the colonies’ populations are planetside, there
> are O’Neil cylinder space colonies and space elevators around each of
> these colony worlds. So, the surface to ground and orbital
> infrastructures are already in place.
>
>
>
It is possible to use it.
UPD 1. More details.
[](https://i.stack.imgur.com/Ha6Z0.png)
We have a set of tube transfer stations. They collects solar energy and speed up space gas flow in tunnel. There are container ships in gas flow which catches/drops usual space ships on transfer stations. I added Earth-Mars space ship trajectory to show how it works.
UPD 2. Shortest path.
My previous picture doesn't use the shortest path. Lets make it shortest.
[](https://i.stack.imgur.com/sWqU5.png)
Actually the ship orbit smoothness depends on speed changing possibilities. In theory we can improve the system if made satellite bus. The satellite bus is a big asteroid. This bus has elliptical orbit around the earth and can transfer smaller ships to transport ring. There is no such asteroid on picture now.
[Answer]
Sounds like a system of space planes that operate in the style of the railway system in the early 20th century. Since you said you already had space elevators in place, then you would need a series of space stations that act as rail stations near the elevators. The plane would dock at the station, which gives you quick turnaround time since they never enter an atmosphere. Since everything is in space the space station could be multilevel allowing several planes to dock at once.
As far as propulsion, I don't have an exact method, yet, but I know how to meet the "2 days to Mars at closest approach" requirement. An engine that is capable of sustaining 1g (Earth normal gravity) of constant acceleration will get a plane from Earth to Mars, assumed 65 million km separation, in 1d 21h 13m 1s. I would love to take credit for figuring that out, but alas, I can't. Check out [How fast will 1g get you there?](https://space.stackexchange.com/questions/840/how-fast-will-1g-get-you-there) for a really great set of charts, graphs, and travel times. Somebody figured out all the travels times from Earth to each major body in the solar system. That time is for constant acceleration for half the trip, then the ship flips a 180 and does a constant burn for deceleration.
Another benefit of constant acceleration is that it provides Earth normal gravity to the passengers and cargo. For more about this see [Space Travel Using Constant Acceleration](https://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration).
As I mentioned in the beginning, I would model the entire system around the railway of the early 20th century. Through a series of transfers, a person could travel across the US with little fuss.
Constant acceleration even works for interstellar travel as well. It would take 1 year + the number of light years to reach any given star. So Alpha Centauri would take 5.2 years since it's 4.2 light years away.
While I'm writing this I thought of a possible propulsion system, an EM Drive or an [RF resonant cavity thruster](https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster). I know next to nothing about the science of the drive, but my understanding is that it's a "fuel-less" drive system. An engine produces an EM field, which it needs to run the lights and whatnot anyway, it diverts a portion of the EM to the propulsion system and it produces thrust. Anyway, it's a thought.
[Answer]
Lets look at the velocity we need for the voyage. Look at our neighbor, Mars. Their farthest distance apart is 377Mkm. The two-day limit means we have 172,800 seconds to do it in--we need to be traveling 2182 km/sec.
To boost to this speed at 1g needs 223,000 seconds--more time than we have for the whole trip. Lets go up to 5g--now we are using 44,500 seconds to boost and a like time to stop--almost half the trip. Oops, our top speed needs to be even higher. Skipping to the answer, the continuous acceleration equation is A = 4D/T^2 (units are meters and seconds.) That gives 50.5 m/s all the way--probably not survivable.
Note, also, that this is merely to Mars, not the more distant worlds.
Thus we can conclude that we can't solve this by force, we have to resort to handwavium. Dream up what you want for your story because there's no real-science answer.
Some more snooping turns up a table of minimum transit times at 1g (look at the rightmost column):
<http://www.projectrho.com/public_html/rocket/appmissiontable.php>
Note that these are for the planets at their closest. Note that **no** planet is within the 2 day timespan even at it's closest.
[Answer]
Any solution requires availability of cheap and readily available energy to be used for propulsion. It works best when the energy supply is external, so you don't have to drag the fuel or reactors or solar panels with.
Let's first build gigantic solar array as close to Sun as feasible, perhaps under Mercury's orbit. The energy will be then beamed in very tight microwave beams across the solar system to anyone who requests it. If the beam divergence could not be solved better, then also build retransmission stations. This requires very precise aiming of the beams, as everything is in motion, and precise tracking of all debris in the solar system (which should be done anyway to ensure safety of ships).
With this in place, the passenger shuttles have very simple and lightweight construction: an electric thruster powered by microwave antenna. It would request energy from the system, then blast off in desired direction after receiving the beam, carefully coordinating its path with the power system so that energy supply beam is always on spot.
Delivering power this way from sun all the way to outer solar system to Jupiter and beyond is possibly impractical due to distances and communication latencies involved. However, in the orbit of Jupiter and Saturn there could be nuclear-powered power supplies that would provide the same beaming service. So the shuttle will be accelerated from inner solar system as far as practical in Jupiter/Saturn's direction, then it will coast. Near the destination it will be intercepted and decelerated using beam energy provided from Jupiter or Saturn stations.
[Answer]
In one possible scenario you'll need three elements. 1) A launcher of some type on a orbital platform 2) the Clarke elevator/skyhook to get to the orbital platform and 3) a wormhole network
Take the Clarke elevator to the orbital platform, board a launch pod, launch pod is loaded into a launcher and sent through a wormhole to its destination.
Of course if the launcher can get the pod up to FTL speed, you might not need the wormholes.
[Answer]
**Interplanetary Virtual Transport Tubes**
From [Mars Distance Interactive graph](https://theskylive.com/mars-info#distance)
```
Mars closest farthest Rough Average
Date Sep-Oct-20 Aug-Nov 21
AU 0.4 2.6 1.5
Acceleration at 10 m/s/s about 1.02 g
Velocity 250 Km/s 500 Km/s 750 Km/S
Coast
Time hours 67 125 144
Time days 2.8 3.5 6.0
Acceleration
Time hours 6:56 20:50 13:53
Energy Ratio 1 4 9
```
Venus min to max 0.6 to 1.6 Au (ignoring Sun avoidance)
Mercury min to max 0.4 to 1.4 Au (also ignoring eccentricity)
Jupiter 5 to 7 AU which would take at least 12 to 17
**Tubular Regions Of Space Reserved for Transports**
Divided by Velocity, Direction, Acceleration Requirements
Earth is ~500 cSecs (Distance Light travels per second) from Sun.
For Other Objects
Mercury Venus Mars Main Asteroid belt
200 360 750 1000 - 2000
Jupiter Saturn Uranus Neptune
2500 ~5200 ~10,000 14,000
Note that these, like most orbital distances can vary by at least 1 part in 16.
**Tube types** - divided primarily by cSec per hour speed.
Restricted to licensed transports as collision energy per 1200 tonnes at 1 cSec/hour
(~83 Km/sec) is 1 KiloTon equivalent.
Type FP1 FP3 FP9 10mC , 33mC 99mC
Velocity is in cSecs Per Hour - 1, 3, 9, 36 (~c/100), 108 (~c/33), 324 (~c/10)
Note Relative energy multiples 9, 81, 729 , 6561 , 58 869
Acceleration in 1-3g (people), 5g-15g Emergency Response Manned, 100g-10,000g -mass only
So to get to Mars at 1 cSec/hour (FP1) ranges from 250 closest to about 1500 hours when in opposition (including sun bypass). The time is about 11 to 66 days.
FP3 would reduce times to 4 - 22 days. That is probably the safe limit for the inner system. FP3 at 1g deceleration it takes 10 cSecs (3 million kilometers) to slow to a safe approach velocity.
FP9 and FP27 - are suitable for Asteroid, Jupiter, Saturn.
10mC 33mC outer exploration speeds, and 100mC for Generation class or Hibernation equipped interstellar.
] |
[Question]
[
I always feel like "hypothetical history of science" questions are kind of impossible, but here's a go anyway:
Imagine that, for the entirety of human history, EM radiation from anything beyond the Kuiper belt was totally obscured. No star besides the sun had ever been observed, and in particular no large scale structures like galaxies have ever been directly observed. In such a world, it's possible that we'd still be clueless about dark matter, since the relative orbital periods of stars around our galactic center were the impetus for positing such a thing.
I'm interested in the kinds of physics we'd have available if we couldn't rely on long range astronomical observations. To narrow the focus a little more as one commenter suggests: **In particular, how much of relativity would be available from local observations?** Would near-earth time dilation effects be enough impetus to develop (if perhaps more slowly) the entirety of general relativity? If not, what are the likely missing pieces?
(The specific narrative motivation here is, if the situation above held, and our intrepid protagonists stumbled across a traversable wormhole, whether they would have even the faintest idea what they were looking at.)
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There is a lot you can learn about physics with just the information available within this solar system. Lots of planets, moons, asteroids, pretty much everything you would need to explain basic Newtonian physics.
Assuming everything else leading up to human civilization is kept constant, we could reasonably conclude that the extinction of the dinosaurs was caused by an asteroid impact, and could therefore determine that there is stuff beyond this solar system. Comets could also be an indication.
Perhaps the only significant change might be a more widespread adoption of quantum theories, given that they were less-than-liked by Albert Einstein, whose General Relativity theory did a better job of explaining how big big big things like the movement of galaxies worked than how things work at the atomic and subatomic level, just as quantum physics is better at describing the tiny than it is at explaining the large. But that is still a titanic conjecture.
The overall effect wouldn't be too detrimental: people could still do plenty of research on Earth and by observing the solar system. People then as now will try to find ways to travel outside the solar system - in our case, to visit Alpha Centauri - as in theirs, just to see what might be out there. The knowledge of physics will, by necessity, expand, to meet these goals.
But, then again, we might not have stars to gaze at in the night sky, so we probably would have missed out on a Carl Sagan.
EDIT: Keeping with the theme of the modified question, I have a modified answer.
Johannes Kepler was a middling instructor when he noticed that the number of visible planetary bodies in the night sky matched the number of regular polygons. He therefore deduced that there was some kind of cosmic unity and spent quite a lot of time trying to prove it. He failed, but through that failure he came to the conclusion that the only realities that can be accepted by science are those with reproduce-able results, thereby ushering in what we commonly consider to be the scientific method.
I'm brushing over a lot of history here, but you get the point: even without the ability to see beyond the solar system, we would still have had plenty of impetus for the scientific revolution, and it is entirely possible that it would have led to extrastellar exploration to understand what is beyond the world we currently know.
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One theory that would remain is [Heliocentrism](https://en.wikipedia.org/wiki/Heliocentrism). With no (direct) evidence of other stars, the Sun would continue to be the center of the universe.
Navigation would be harder, specially in open sea, due to lack of stars for reference. The [Age of Discovery](https://en.wikipedia.org/wiki/Age_of_Discovery) (1500s to 1700s, in Portugal and Spain) would be delayed, possibly until reliable clocks were developed.
Myths and religions would be different without stars - I can't even guess how different. And myths affect the society structure, and creation of new ideas, thus driving science in different directions.
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Most of what led to special relativity were local experiments. The [Michelson-Morley experiment](https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment) tried to figure out the speed of our planet relative to the 'ether', a supposed medium that carries EM waves. That experiment turned up nothing, showing that the speed of light is constant in all inertial reference frames. Einstein took the idea of constant light speed as his starting point, and that's how we got special relativity. It's also worth noting that the Maxwell equations don't make sense very well without special relativity, so anyone who can figure those out is bound to come up with it sooner or later. I think it's safe to say special relativity is expected in your scenario.
[General relativity](https://en.wikipedia.org/wiki/General_relativity) comes from taking the idea of making physics work the same in all inertial reference frames and adds acceleration and gravity. If your protagonists can figure out their orbit around their sun (which might be hard without background stars), and especially if there are other planets in the system they can observe, then they'll probably eventually figure out Newtonian gravity, which is the starting point you need for general relativity. Einstein built from there with thought experiments, and GR was verified in part by measuring the precession of Mercury. Again, having other planets in the solar system helps. It's possible that without background stars, GR might be less proven, and so perhaps your society might take those ideas less seriously. There's no reason to think they wouldn't be around, though.
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Everything up to about the 1900s would be roughly the same in a number of fields.
Hubble's constant wouldn't be discovered
Relativity would only be discovered/evidenced if we tried to create a GPS.
Big Bang cosmology wouldn't be a thing
We couldn't find the CMB so anything from that would change
Astrology wouldn't exist and Nostradamus might be a famous doctor ^.^
Sailing would be harder thus the Americas might not be found when they were.
Plenty of religions would be changed.
Steven Hawking who? probably.
It's possible that WW2 would have ended radically different.
With Germany likely conquering all of Europe and allowing morally questionable experiments science in general could be much more advanced but also considered somewhat as terrible as the Inquisition, if not worse.
Quantum Mechanics would definitely be more accepted, but without the e=mc^2 evidence particle accelerators might not be a thing which might hold it way back.
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A common feature that we consider to be alien is the eyestalk and rightfully so. To my knowledge the only vertebrate that even comes close to having eyestalks is the hammer head shark (if you can even call them stalks). Sure, many species of insects have evolved eyestalks, but they are unlikely to evolve the sapience needed for advancement.
So, what evolutionary benefits would an animal with eyestalks enjoy? Why would they evolve them in the first place?
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Eye stalks have sort of happened in the past with vertebres. Mudskippers, rays, Crocodilians, even Frogs all have eyes that at least partially represent eyestalks. While these are more raised eyesockets than full on stalks, it can be usefull to talk about why these animals have these elevated sockets in the first place, and if it could be useful for them to be even higher.
Amphibians often have raised eyesockets when they spend a lot of time partially submerged or at the surface of the water. They have raised eyesockets both for protection from above water predators and to catch surface and above water prey.
Crocodilians and similar animals use their "stalks" in order to catch prey.
Fish, like rays, have raised sockets in order to survey the area while submerged under sand or other ground debree. Mudskippers similarly use these stalks to see above the mud.
Looking at these examples it appears that "raised eyes" among vertebrates relies on the need to see above a visually obscured medium (ie water, mud, sand etc...).
But what stops them from growing stalks further? Simplicity is one, if stalks don't need to be higher, then they won't get higher. Another, as others have commented, is a risk to vulnerability.
But shouldn't even slightly higher "stalks" be better for even deeper camoflauge on say sturdier animals like crocodilians? In crocodilians, they not only have raised eyestalks, but raised nostrils Raising eyestalks would mean possibly loosing hydrodynamic efficiency in water locomotion, as the nostrils would also need to be raised, possibly for little benefit. Nonetheless, it is a viable option of such camoflauge would bee needed.
Now at this point, you may be asking why I left an obvious example out. The Hippopotamus. Out of all these animals, [this extinct species of Hippopotamus](https://en.wikipedia.org/wiki/Hippopotamus_gorgops) actually did have quite close to actual eyestalk eyes.
Now the hippo itself already has raised sockets, and follows the previous reasoning presented for needing them (needing to see something above a medium [water]). But this species was special in that they were pretty close to actual stalks, not just slightly raised. I can't comment to why this evolved specifically, but I suspect that because the hippopotamus's nostrils are so far raised in the first place was at least what enabled such a evolutionary trait to not not carry the negatives you might see with modern crocodilians. The nostril height itself was spurred from the extra space needed for the massive canine tusks hippos sport.
If your species needed to see above an obscured surface that was not totally opaque (like water) and wouldn't lose out on another trait massively because of elevated eye-sockets, and also needed to be camouflaged by the surface, then eyestalks would be very beneficial.
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From a strictly terrestrial biology viewpoint, I am unaware of any 'higher' species that have evolved 'eyestalks'. With the same observation however is the correlation of eye type and complexity to the complexity of animal.
I have only been able to locate eyestalks in invertebrates, specifically in mollusks, and some arthropods.
I think that there is reason to believe that an enhanced 360 view would provide some advantages on the evolutionary path, but appears to be out weighed ( at least on Earth) by the need to protect complex eye structures.
Eyes are among natures most diverse sensory organs, from basic photosensors to a raptors amazing vision, to compound organs such as bees have.
The correlation between complexity of eye structure, the specialization of the eye for a species, and the need to protect the organ in a bony cover or socket lead me to feel the primary advantages would be in enhanced field of view, most likely in simpler 'prey' animals.
Purely speculation and opinion...
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Eyestalks allow wider vision without complicating the eye. Imagine the ability to look behind without turning your head. Being able to see two different locations would also be considered as a bonus.
But these types of eyes are vulnerable. If a creature is already weak and cannot risk physical damage, eyestalks may not be the weakest point. But in vertebrates, especially in mammals, the body is not very vulnerable, it can take a beating and still survive. If your aliens are physically weak (not necessarily in comparison to humans), having eyestalks might give them an edge for survival.
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Considering the skull contortions of a flounder to move both eyes to the same side of the head, the nose of cetations moving to the back of the head, and the eyes of the hammerhead shark, it is reasonable to suppose that eyes could be raised up as a periscope, or moved far apart to give an enhanced paralex.
Allowing the structure that supports the eyes to then develop a degree of movement is a separate step. Speculate here: consider how the trunk of an elephant is formed from a fusion of the upper lip and the nose. The [star-nosed mole](https://en.wikipedia.org/wiki/Star-nosed_mole) develops the eponomous organ from tissue of the cheeks and face.
So it is conceivable that the needed structures could grow from the head and face area. If the original “extension” was not bone but lightweight cartilage like the nose and ear, it might easily become flexible, and formed by fusing cheek and ear tissue. Muscles adapt to move it.
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With the exception of the stalk-eyed fly, most animals with eye stalks lack an effective way of looking around without them. Snails and slugs are slow-moving and it costs them a lot of energy to turn their head around, while crabs and the extinct trilobites are completely unable to turn their 'head' at all. For species such as this, having eyes that can look in any direction is beneficial. For most vertebrates, being able to turn the entire head around is pretty easy, so it makes more sense to keep the eyes fixed in the skull where they are well-protected.
That doesn't mean it can't happen, though. Frogs, which have rigid necks and can't turn their heads, might benefit from eye stalks, although these might be vulnerable when they jump. In fact, their bulging eyes might be a compromise solution. And speaking of frogs, any species that lived in marshy regions and hid from prey in murky water could benefit from eyes that could keep watch like a periscope.
And in a pinch, just look at the stalk-eyed fly. Their eye stalks don't seem to help them at all, and are considered to be a classic example of runaway sexual selection. That could potentially occur in any species for no real reason at all - if that's the route you want to go, of course, long eye stalks should be considered attractive to members of the species.
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The [mudskipper fish](http://www.mudskipper.it/VisMech.html) is the nearest thing to a vertebrate with eyestalks that I can think of. If mudskippers took to burying themselves in deep mud, their eyes might need to be raised up a bit more to poke out of the mud. But I suspect they'd solve the problem by positioning of their body, rather than evolving their eyes.
To get eyestalks like stalk eyed-fly or a [ghost crab](https://en.wikipedia.org/wiki/Ocypode#/media/File:FloridaGhostCrab.jpg) will take a phenomenal amount of re-engineering of a land vertebrate's skull. Basically you are going to have to turn a socket designed to be tucked away for protection into something sticking out into danger. Crustaceans protect their eyes by folding them sideways into slots in their carapace. I suppose a reptile with an incredibly kinetic skull (lots of articulation points within it), such as a snake *might* have the basic toolkit to create a hinge joint or retracting mechanism to pull the eyes into safety.
Of course you can't see properly with retracted eyes, which makes them a bit like [Joo Janta Peril Sensitive Sunglasses](http://hitchhikers.wikia.com/wiki/Joo_Janta_200_Super-Chromatic_Peril_Sensitive_Sunglasses)! :-)
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I saw a swamp fish in Guatemala that seems to have 4 eyes - two for below water vision, and two on stalks for above water vision. It appears that as they swim around, their stalk eyes watch for predators from the air. (Wikipedia telles me that they are called [Anableps Anableps](https://en.wikipedia.org/wiki/Anableps_anableps) and they a only have two eyes. The locals call them "[cuatro ojos](https://es.wikipedia.org/wiki/Anableps_anableps)" though.)
I think any species that need visual information from two different environments has a good reason to evolve eye stalks - whether to avoid predators, whether to detect pray, or maybe to gather information about nature for survival.
Why do they need separate eyes? The same reason we need goggles to see underwater: Because the index of refraction of water is different than air, so having a set of eyes that is adapted to water and another set adapted to air is understandable.
In the case of fish, they can't survive for very long in the air, but information from air is very helpful for survival.
The index of refraction changes between materials, and it even changes between temperatures of gas. So perhaps they have strong temperature gradients in their atmosphere, so having eyes on stalks or tentacles would be highly favored in all species.
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Eyestalks give 'a better field of vision' to the animal. They may have an improvement that benefits their likelihood of surviving, thermal-vision and ability to see from long-distances.
They may have a better chance of finding food, water and a mate.
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Eyestalks could be used to have a wider FOV, but they will most likely never appear on a sapient species because
* It makes them more vulnerable, the eyes in your head are inset to be protected by your cranium, eyestalks would be very vulnerable to hits from other animals or inanimate objects.
* They would not move both in the same way which destroys your stereoscopic vision.
* The eyes are the most important sensory input in humans and all the animals that come closest to sentience (that live on land, dolphins are an exception) because they can convey lots of information that is difficult to gather otherwise. They also create a lot of information for the brain to elaborate because of how complex an image is. Both of these factors mean that they are very connected to the brain, in humans the eyes are the only organ that is directly adjacent (almost inside) the brain. Having eyestalks would distantiate the eyes from the brain which means bigger input lag and slower information processing.
All of these drawbacks make it simply not worth it for the single benefit of an increased FOV, especially considering that it's not a continuous augmentation of the visual field, when it's so much easier to just move your head/body.
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Eye stalks may be a more of a benefit in a swampy/marshy region. It is also possible that an invertebrate species develops intelligence (many sci-fi universes have intelligent insects, the Tholians from Star Trek come to mind)
My first consideration is an alligator, that pops only its eyes and nose out of the water. the stalks would give them a few benefits like being able to see in a few directions, but if a bird checked out its eyes and tried to poke them out or something, the could be retraced. they could also be like lures catch birds or something like that.
Given that intelligent life on earth evolved after a group of ape-like ancestors were forced out of forested areas onto the plains of Africa, I will allow that some of the alligator like eye-stalk creatures (I'll call them alescs for short) are smart enough to notice some overcrowding and decide to move out of the swamp and onto a plains or forrest environment. they don't have much of an advantage here, so they use and develop intelligence here, in a new environment, and start using tools.
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Some fish larvae do have eyestalks. This is known as the stylophthalmine trait, and has evolved at least 4 times. However, this trait generally involves bulbous elliptical eyes, which may be hard to support on nekton or terrestrial creatures
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It already has.
Hammerhead sharks have very peculiar-shaped heads that some might describe as eye stalks.
[](https://i.stack.imgur.com/NWnuh.jpg)
[](https://i.stack.imgur.com/pXHMf.png)
And it is possible that it has occured in prehistoric times as well.
Perhaps the strangest prehistoric animal is *Tullimonstrum*, otherwise known as the "Tully monster." This bizarre animal's taxonomy is almost completely a mystery. Nothing has been positively determined beyond the clade bilateria, which includes all bilaterally symmetrical animals.
Some scientists think that it was an arthropod, some think a mollusk, others think a vertebrate.
Here's what this creature looks like:
[](https://i.stack.imgur.com/iKsy1.png)
<https://www.researchgate.net/publication/298434474>
<https://www.livescience.com/ancient-tully-monster-vertebrate.html>
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I'm still in the process of building my fictional language. However, I need some help in creating a realistic drifting effect for my language over time. *By linguistic drift, I mean the natural change in a language's vocabulary and syntax over time.* An example in English is the question **"Whom did you see?"** which is often associated with archaic English. Today, the question **Who did you see?** would be far more common. **How can I create a realistic linguistic drift effect?** (I'm only asking this question as part of my story takes place in an ancient period while the rest of the story takes place in modern day.)
If it makes any difference, I'm looking only for answers concerning the written part of a language.
Note: [How can I replicate language evolution?](https://worldbuilding.stackexchange.com/questions/25228/how-can-i-replicate-language-evolution) is a similar question, but it asks about 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. I'm asking about how I can simulate linguistic drift.
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## Start with changing the sound of your language.
To understand how sound in language changes, we need to define sound.
The linguistic term "phoneme" refers to any part of speech recognized by a native speaker as a single sound. Phonemes can be quite wide, actually. A language lacking a difference between the sounds P and B (which are articulated in the same place in the mouth) may use both in different circumstances, they are simply heard as the same sounds to a native listener.
Sound changes happen when the definition of a phoneme drifts, perhaps merging it with another one or splitting it into two.
People will speak in the absolutely easier way they can still be comprehended. A good example of this is the word "hue", at least in some forms of English.
The "hy-" sound (/ç/ in the [International Phonetic Alphabet](https://en.wikipedia.org/wiki/IPA_pulmonic_consonant_chart_with_audio)) clearly distinguishes it from the words "who" and "you" and it is, acoustically, one sound, yet it is not a phoneme as it is read as H followed by a Y (/j/ in IPA) sound. A phoneme change happens when two contextual rules like this overlap often enough and get learned by new speakers as a new distinct phoneme.
Some sounds are also just easier to produce, which is why you see them more often in languages. If your language distinguishes between P, B and an aspirated P (pronounced as with a puff of air), the aspirated P may drift into the acoustically similar, and in certain contexts easier to pronounce F, as is [what happened to Germanic languages](https://en.wikipedia.org/wiki/Grimm's_law).
Try for example to go "etetetete" and then go "edededede". The first one is much choppier, no? This is because D is voiced while T is unvoiced. When alternating between an unvoiced consonant and a vowel, you're forced to turn your vocal chords on and off, which is less efficient than having them on throughout. This is also why many languages devoice consonants at the end of words - the word is over, you turn off your voice as early as possible and the D becomes a T. A language which does this does it systematically. Having D turn into T at the end of words and then not have G turn into K in the same context would need to intersect with some other change to be believable as a phonological change. This is also why most languages form a near perfect matrix when listing phonemes by type of articulation and place of articulation.
A good thing is also just to look at how real languages evolve phonologically. Look up any language, then its ancestor language and then other languages with the same ancestor. You *will* find interesting systematic shifts this way. Looking at them is also good to shake off your bias for what would seem easier to pronounce to native speakers, like how a language would evolve "difficult" consonant clusters from simple ones:
*moróz -> mraz*
And perhaps the most obvious way of making things easier to pronounce is to just leave them out all together. Again, it's quite amazing how many sounds you can leave out and still be comprehensible.
English is a perfect example of this as it's reflected in the spelling. The vast majority (some exceptions are words that have been re-spelled to fit the modern way of reading them) silent E's at the end of words were originally pronounced. Same with French and most languages with silent letters.
What's important to understand about sound deletion however is that it's never the stressed sounds, as that's what people listen for when you speak.
Your example with "whom" works perfectly here. M is at the end of the word, with typically comes right at the end of a sentence or right before a more interesting word.
Also, what gives if you leave off the M? Is it that much harder to understand its role in the sentence?
## Grammatical changes as informed by sound changes
Leaving off the M would remove the case distinction, if it wasn't already clear from syntax. It is fairly exposed to the elements of sound reduction, so with those two factors out of the way, you have lost a grammatical case from your language.
Grammatical shifts are popularly theorized to work a particular cycle. Languages drift from being agglutinative to fusional to isolated and back to agglutinative again. ([Definitions here](https://www.youtube.com/watch?v=Ka5oH7gHOlw)). All of these stages have been observed on their own, but no language has been seen going back to square one as of yet.
The way this works is that if you slur the endings on an agglutinative language like Finnish, they will eventually merge (like in Estonian) into words having only a couple of affixes and some modifier words as in Russian, which if you slur the endings, they will eventually go away (like in Bulgarian) and turn into a language which primarily functions through syntax and use of modifier words such as prepositions, etc. As more common words, such as pronouns, get slurred, they will eventually merge around the more specific and important verbs, nouns and adjectives into long, affixed words.
One thing you may wonder about the previous paragraph is how you would get new grammar words from to replace the affixes previously filling those roles.
These are taken from regular words which get used in certain contexts often enough that they lose their original meaning (known as semantic bleaching) and are later analyzed by speakers as having some other function (grammaticalization).
A good example of this is help verbs. The verb becoming the grammatical form for the future tense usually has a meaning like "go", "come", "push", etc.
Imagine "I am going out (in order) to run" becoming "I am going to run".
Prepositions often get double roles as marking possession, telling time, even grammatical functions like marking the dative case (like "to" in English).
Even contextual sound changes become grammaticalized, which is how you get umlauts such as:
*foot -> feet*
Which is also why other Germanic languages use umlaut letters (Ü, Ö, Ä) to connect the umlaut to the original form:
German: *Fuß -> Füße*
Swedish: *fot -> fötter*
## In terms of writing
All sound changes and grammatical changes happen faster than spelling rules can adapt. This means that most spoken languages are written in a form that is more or less a 100 year prior form of the language (*very much* depending on the language). Now, what makes spelling not just an outdated form of the same language is spelling reform and the addition of new words.
Systematic spelling reform is *hard*. The more you put it off, the harder it gets and quite often, people get used to thinking in the terms of these mutated spellings. So what happens quite often is that the words which are changed are the few which don't adhere to the new norm.
This is how we get letters like C having two sounds. Everyone knows that C is S before E and I and K before everything else. It doesn't matter that it used to be pronounced only as K, if you spell a word "cing", people will not know you mean "king", even if that word may have been one of the few remnants of words sounding the same as 500 years ago.
This is how you get Spanish and French having both "Qu" and C to represent this sound.
[A good video on vowel deletion.](https://www.youtube.com/watch?v=BIu0CO2yvQ0)
[Another good video on sound changes.](https://www.youtube.com/watch?v=vzhh-HrIfb4)
[A good video on the evolution of the Latin script. Some factual incorrectness but interesting nonetheless.](https://www.youtube.com/watch?v=OGeIzmu9DSA)
Some Wikipedia articles on specific types of sound change:
<https://en.wikipedia.org/wiki/Assimilation_%28phonology%29>
<https://en.wikipedia.org/wiki/Dissimilation>
<https://en.wikipedia.org/wiki/Lenition>
<https://en.wikipedia.org/wiki/Fortition>
<https://en.wikipedia.org/wiki/Consonant_mutation>
<https://en.wikipedia.org/wiki/Syncope_%28phonology%29>
<https://en.wikipedia.org/wiki/Apocope>
<https://en.wikipedia.org/wiki/Epenthesis>
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Linguistic drift is a slow and perpetual process. The subject would require a whole book and each language has its own direction and pace of drifting, but there are some general patterns.
# 1- People like short words/phrases over long ones
People would gradually get fed up of having to speak the whole long words when there is a possibility to shorten them. For example, United Kingdom becomes UK, United Stated of America becomes USA, United Nations Organization becomes UNO.
People would also like to combine logical and other directive operators in a language. For example, "do not" has been replaced with "don't" (although both are valid, the shortened form is much more common). Similarly, "I would" has been replaced with "I'd". The list goes on. I hope you understand the point.
Then there is a common trend to merge two parts of a name (specially location names) and come up with a single, unified name. For example, Basti Qazian (a town in India) gradually became Qazian (Basti means town) and then gradually ended up as Qadian (the current name). Similarly, Boulders' Valley first became Bolder Valley, then Bold Valley and finally Boldally (current name).
For more detail, read [this document.](https://www.une.edu.au/__data/assets/pdf_file/0008/9368/WC_Language-usage-Shortened-forms-of-words.pdf)
# 2- Foreign Effect
Vocabulary of a language also takes foreign influence. This often happens as a result of:
* a conquest - in which case the conquered people's language takes the influence of the invaders
* long term trade relations - in which case two or more languages heavily trade and merge words
Notable examples include the conquest of Persia by Arabs, the conquest of India by Persians, the conquest of Spain by Arabs, the conquest of English Islands by Teutons (Germans) and the conquest of China by Mongols.
# 3- Slang plays an important role
Slang refers to the terminology of common people of a locality, which is initially different from the proper language. One language (spoken over a vast area) can have several versions of slangs in different parts (notable examples being Urdu, English and Arabic). Popular slang phrases are gradually picked up by writers and poets and hence are absorbed in the proper vocabulary set of the language.
It is interesting to note that a large proportion of slang words comes solely from profane talk of teens (or sailors :p). Urdu words like چبل، کھسماں کھانی، کلموہی etc have been taken from its slang repository. English slang words which have found their way into proper language vocabulary include *fuck, poon, moollah (Australian)* among dozens of others. Hindi slang includes words like چوتیا، ڈھکن، گھنٹا. I would not explain the meanings of these words here (dose of English slang should be enough :p)
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Craft up a bunch of other languages. Pick a few of the words from each, and substitute them into the existing words in the language of focus.
Take a handful of other words, and make them more general in meaning, more specific in meaning, or give them a meaning related to the original meaning, and have a few of them completely flip meaning.
Take a language feature that seems really complicated, and simplify it.
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Hi: To simulate the drifting, my advice would be to identify the sounds your target/currrent language can and can't make. That is, choose the sounds or phonemes your current language contains, then catalogue the list of phonemes the historical/original language contains as well. To simulate drift, go through and methodically substitute the closest sound in your current language phoneme catalogue for ones in the historical/original language, that occur. That way, you will have similar sounding words, i.e. the drift you speak of, but the changes will reflect the different sound bases and vowel patterns are key. I know you say you are only concerned with written language, but you cannot overlook the phoneme or sound-based aspect of language change. Spelling and letters are just signposts that tell you (or not, as the case may be) how to pronounce things. If you want a good example that is accessible to English speakers, look at the original version of the prologue of the Canterbury Tales by Chaucer and listen to it being spoken, too, by someone who speaks middle English. Then read and listen to the modern translation. This is tough without training and perhaps you could consult someone with linguistic background to help you because written language and spelling aren't the same as the sounds/phonemes produced in a language.
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All multi-cellular life as we know it is composed or eukarotic cells -- cells with a nucleus. Some single-celled organisms are eukarotic, some are prokaryotic (cells without a nucleus, such as bacteria.)
Brief research indicates that prokaryotic multicellular life would be unlikely.
But would some other form of non-eukarotic, but non-microscopic life be possible? If so, do we have any way of guessing what it's biochemestry might be like?
[Answer]
It is (theoretically) possible. We are talking sponges here. Since sponges don't operate as a *system*, rather are a collection of cells stuck together by collagen (which improves their chances of survival, versus lone cells). You could get the same type of structure with a prokaryote colony.
Essentially all cells would be secreting some binding protein (collagen or not collagen is your call). All cells would be the same type. No collective circulatory, respiratory, feeding or excretory systems.
There *might* already have been colonies of prokaryote cells known as ***stromatolites*** which date as back as 3.8 to 4.2 billion years.
[Answer]
**Prokaryotic multi-cellular life exists, but is very primitive.**
The earliest multicellular life forms were all prokaryotes, first appearing around 3 to 3.5 billion years ago ([Grosberg and Strathmann, 2007](http://www-eve.ucdavis.edu/grosberg/Grosberg%20pdf%20papers/2007%20Grosberg%20%26%20Strathmann.AREES.pdf)) and exhibiting cellular diversification starting over 2 billion years ago.
They aren't terribly complex, of course, looking something like this:
[](https://i.stack.imgur.com/YWJZr.jpg)
Ultimately, prokaryotes are good at forming into globs, and can even manage *globs in specific shapes*, but their evolutionary repertoire doesn't extend much beyond that, probably due to an inferior information storage system when compared to the DNA nuclei of eukaryotes. It's likely that this pattern would be seen in extraterrestrial life, as well, with *complex* multicellular life arising from creatures with the capacity to store lots of information in a DNA-like structure. These creatures wouldn't be eukaryotes, per se, since they don't share a common ancestor, but would be the alien equivalent.
[Answer]
There **is** non-eukariotic multicellular life.
For instance,
Nostoc pruniforme:
[](https://i.stack.imgur.com/TBvtx.jpg)
Spirulina:
[](https://i.stack.imgur.com/71rIO.jpg)
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When intelligent beings are first evolving and starting to explore the world there are a lot of unexplained things. Scary things, strange things, wondrous things. In trying to explain those things a natural first step is religion.
Why does thunder happen? Thor did it.
Why do people get sick? Evil spirits are attacking them.
What happens when we die? We go to a nice place.
Those explanations are seized on by people to create and maintain power for themselves. Shamans, priests, religions, all building power for individuals out of those first fumbling movements towards understanding.
But is there an alternative? We know of no human societies that have not created religion in their first attempts to explain the world, even if some have then moved on. What differences in the nature of humans or in human society would be needed to have those religions either not form or fade away rapidly as new explanations are discovered.
[Answer]
**Yes.**
I'm assuming you're looking for an early society that values the scientific approach. From your last sentence you say the people should let old explanations "fade away rapidly as new explanations are discovered". I see that as a not-religion approach mainly due to what I view as the primary difference between religion and science. Namely, science seeks new explanations to meet the facts, while religion seeks facts to explain its old explanations.
However.
What you're describing is not Religion, it's [superstition](http://dictionary.reference.com/browse/superstition). Religion is a set of superstitions that someone, or a group of people, has decided are the *correct* superstitions. Then people agree or submit to this invented authority and become a member of this religion.
Preventing superstition is much more difficult to do. I think it actually arises from the same thing that made people discover and use science in the first place. It arises from that thing inside people that keeps them looking for patterns and connections between events. The filter that people put in front of that process makes it into either superstition or science.
Preventing religion is easier to do. The change in human nature would be to value evidence over conviction of faith. Humans would need to value discussion and realize that questions are not an attack, they're a cooperative effort to determine the Truth. A stronger natural skepticism will allow humans to agree that there are some things we don't know yet, and we can have ideas about what the answers might be, but we need to be willing to let go of those ideas if they don't appear to fit new information.
An early human society that values the ideas of others as much as their own will likely not develop a religion, though they may have varied superstitions from person to person.
[Answer]
Religion is a hard word to define. It seems easy, until you actually try to do it. Consider the challenges faced in the US right now regarding what should be a "protected" religious belief, versus what is a "belief" from a sham religion.
Dictionary.com provides a [definition](http://dictionary.reference.com/browse/religion) I like:
>
> a set of beliefs concerning the cause, nature, and purpose of the
> universe, especially when considered as the creation of a superhuman
> agency or agencies, usually involving devotional and ritual
> observances, and often containing a moral code governing the conduct
> of human affairs.
>
>
>
Breaking this down:
* *"A set of beliefs concerning the cause, nature, and purpose of the universe"*
+ Religions answer the tough questions about existence
* *"especially when considered as the creation of a superhuman agency or agencies"*
+ Agency is a very particular word, implying entities which have "freewill" and can act on the universe around us
* *"usually involving devotional and ritual observances"*
+ Doing things "because the religion says so" and "to demonstrate to others our beliefs"
* *"and often containing a moral code governing the conduct of human affairs"*
+ Moral codes provide definition to "good" and "bad"
The creation of moral codes seems to be one of the sticking points. In fact, expanding the topic even larger than morality, religion seems to be one of the single most effective tools humanity has invented and/or been given by a deity. Methods of teaching soft skills such as "kindness" are often handled through religious channels because they're good at it.
However, I would like to focus on the first two points. It is human nature to wonder about the universe around them, and in fact, the more successful we are at building models of how nature works. Cultures that do not build models of the universe get overridden by those who do. Once you have a model of how the universe works, it is very difficult not to begin picking up the other traits of a religion.
Consider science. Science is often considered to be the alternative to religion. It explains much of the cause, nature, and purpose of the universe (though not all!), just like a religion. However, unlike religion, science does not include any superhuman agency... at least at first glance. Listen in on the musings of two Quantum Physics professors bantering back and forth, and you start to pick up words of agency used to describe quantum scale particles (these words are a side effect of our inability to see nor change some quantum values in tandem). Likewise, you will hear science weigh in on "when life begins," which is heavily entwined with human agency, and it is very difficult to go too far down that road before you wonder about superhuman agencies, such as those of mob mentalities and nations. These issues rapidly produce a moral code of their own!
The last step towards science meeting that definition would be the presence of devotional rituals. Consider the repetative practice at the scientific method in school or the act of blind faith of landing in a foreign city with nothing but a GPS and the internet (or perhaps even the blind faith of getting on an airplane in the first place). These may not qualify as rituals in your own lexicon, but you have to admit that they are on a slippery slope.
And if society's alternative to religion looks this much like a religion, that suggests that it would be remarkably difficult to handle the development of an early society without accidentally treading on it. In fact, I think it would be tricky to accomplish, even if you started the society with the expressed intent of sidestepping this particular definition of religion. Things just happen, especially when they are beneficial.
[Answer]
That depends on whether or not the religious beliefs are actually **true**, something people here do not seem to be considering.
If the religious beliefs are false, then sure, it is probably possible to develop society without those beliefs. I even believe it likely that religion would not develop in such a case. I won't elaborate since the point of my answer is the opposite case.
If the beliefs of a religion are **true**, then it very well might be *impossible* to develop a society without them given the nature of the religion.
Take the following case for example:
If the universe was intelligently designed, then if that designer created people, put on them on Earth, had introductions with the people, and those first people (and possibly various people thereafter for a while) interacted on a personal level with their God, and if God really was a (or the) God and made that abundantly apparent, then no, it would not be possible at all to develop initial society without the existence of these religious beliefs.
All it takes for competing religions to pop up everywhere is for usurpers to prey on their neighbors; that part is likely inevitable if there is already an initial religion, regardless of the truthfulness of that initial religion.
I would elaborate on my case, but it seems rather straightforward and self-explanatory. If religion is accurate, if God exists and demonstrates such, religious development is unavoidable.
[Answer]
Religion is created by Fear. The Unknown doesn't lead us to the religious believes its the Fear of it.
I think if a Species/Civilization has following characteristics then they are most likely not to develop religious believes:
1. They don't fear anything (They just don't posses an ability to be afraid)
2. All of them are Equal (No one is weak or strong)
3. They live in a balanced Society
As already been mentioned that fear of unknown is a factor which causes civilizations to start develop religious believes. For the sake of survival a rational mind would develop some scenario in which the subject would survive by the intervention of some powerful creature who can handle the danger which could be in the unknown so that the subject may live calmly until the danger actually presents itself.
Second point being the fear of known. If some creatures are powerful than others in that case a possibility exists that in some scenarios powerful would try to exploit the weak. In this case too creatures would develop a belief system which would result in their survival/favor. Like It happened in every Human Civilization. Weak chose someone strong & good to protect them against someone strong & evil. That could a God, a King or a Military leader.
My Last point about society being balanced. If both of the previous conditions are met then society would very much tend towards the balanced one. But if it isn't then it would be a very odd society where few who have less than others would blame the ones with more. But everyone is equally strong and no one is afraid of anything so the weak ones or even the strong ones can develop some believe system that they are being kept down by some entity or they are being blessed by some entity respectively.
NOTE: The 3rd point isn't really necessary as it happens in our civilization too. Where this unbalance is sometimes tackled by Marxist believes or Capitalistic ones where entity that is holding you back or blessing you is associated with secular entities rather than religious ones.
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[Question]
[
I am developing a world on this continent:
To know the world, I have to know how the weather works. Inside the white line is the continent. The blue arrows denote the flow of water. Up is north, down is south, left is west and right is east. The red blobs are mountain ranges. The gaps in between the mountains represent large flat areas of land that stretch for kilometers.
These separate mountains. The continent is in the equator and other global conditions are earth-like. **How would the weather on this continent behave near the entrance/exits? How about farther inland?**
The mountain ranges are probably going to stop rainfall and make the continent arid, but I am looking for a giant grassland continent with huge distances separating a few small woodlands. The gaps are there to allow moisture in and I need the mountains to limit global communications as this is a medieval world. Would this achieve the desired effect?
**EDIT:**
The continent can be compared to North America in the size department. The mountains are roughly the size of the Himalayas.
[Answer]
I'll take a stab at this. I'm not a climatologist, and it's hard to make an educated guess because there's nothing at this scale ringed by mountains on earth. How did these mountains come to be? What kind of tectonic activity could create this type of landmass?
These will be generalizations, because obviously many climates exist within a three thousand mile radius.
## Winds
At Sea: The Doldrums. Around the Equator there's an area of low wind, where it's very humid and the air just sits. Around the equator is the [intertropical convergence zone](http://en.wikipedia.org/wiki/Intertropical_Convergence_Zone) where airflow is vertical rather than horizontal. The landmass will cause uneven heating, which will create some alternating breezes depending on the time of day, but the overall wind from the ocean will be negligible.
On the continent, winds will be driven by albedo differences combined with the Coriolis effect since there are no oceans or waterbodies. The continent is very large, so within the mountain ranges, there will be winds, though they won't have time to pick up speed like they do over the ocean. I would expect a clockwise gyre inside the mountains, sucking up a bit of moisture from the openings.
At higher latitudes, the continent's shores and mountains will be forested and very moist. It will rain all the time. High winds will be the rule, with frequent thunderstorms. These storms will spawn hurricanes on the landmasses on the other side of the oceans.
Depending on the placement of the gaps, they could profoundly impact the continent's weather. If they're all at the equator, they won't do very much due to the low winds, but if placed in higher latitudes, the low pressure areas created by rising air over the land will divert the moisture laden winds inward.
## Dry
Outer Ring: Dry beaches at the tropics give way to scrub and eventually forested regions at the higher latitudes. Elevated areas go from very dry at the equator to alpine in the high latitudes.
The inner portion of the continent will be dry. Not desert dry, because the continent will presumably have springs and some moisture will be sucked into the gyre from the gaps. But, like ratchet freak suggested, probably savanna, like the southern part of Africa (which does have some elevation separating it from the ocean).
[Answer]
Looks like you want a [savanna](https://en.wikipedia.org/wiki/Savanna) biome in the valley between the mountain ranges.
You can feed the water inland through rivers fed by glaciers in the mountains and underground rivers/lakes. They will then meander though the valley and leave through one of the gaps into the ocean.
You'll need to stop trees from growing in some way, either by frequent fires or a shallow soil layer.
[Answer]
Mountains that big, and that many of them in those positions will produce deserts. Big and very dry ones. This happens everywhere on earth with areas that large and significant mountains blocking the sea winds: The western US, east of the Rockies. Western China, north of the Himalyas. Most of Australia between the coastal ranges. This happens in smaller places too, such as western Argentina, east of the Andes.
Simply put, you've got *no way* for moist, humid air to get to the interior, so it ***has*** to be a desert.
[Answer]
You might want to look at the continents on earth that actually have large grasslands for comparison.
Eurasia - temperate zone, prevailing winds from the west. No major barrier mountains, but once you get several hundred miles from the coast into Hungary and the Ukraine the grasslands start up.
North America - temperate zone, prevailing winds from the west/south in summer. Mountains block water from the west, but the Gulf winds in summer bring moisture from the southeast without any barriers. Once you get several hundred miles from the coasts, grasslands become prevalent to dominant - the Great Plains.
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[Question]
[
Well I was in the process of designing a world for my new RP. I briefly had the idea that this world could be a psuedo-sci-fi far-flung future Earth but eventually dismissed it, because I wanted too many fantasy properties in it. However, I thought I'd open up my theories on this to this stack and see if others could rationalise it better than I could.
For starters, I originally wanted this to be a semi-hard sci-fi setting with magic.
My rationale for this was that 'Magic' is actually an ability derived from manipulating nanomachines using a computer interface installed in a special glove-like apperatus. However; the tech involved has long been forgotten. Magisters in the current setting are those that have basically figured out some functions of the apperatus. In truth, the original device would have been able to do a lot more, with sufficient training.
Why has this been forgotten? Well the second big element of the setting was the fact that there was an apocalypse around 2060 (initially this was the standard nuke-a-thon with nuclear winter, but I'm open to change) that rendered everyone dead besides 3 groups: A) some people who went underground in siberia B) some people on a pre-established lunar colony and C) people on a small fleet of prototype US Navy battlecruisers who survived due to some anti-radiation measures and rescued people on other ships.
Furthermore, I went with comic-book craziness with the nuclear winter causing severe mutation of local species, including the land-based human survivors. This creates the settings 'demons'.
Anyways, the three groups survive mostly isolated for a couple thousand years, stuck in their little bubbles.
Initially, the lunar colony considers terraforming the earth, but it is dismissed due to logistical and other issues. However, many years later, this plan is revived because they figure they can apply the tech to the moon itself after test-bedding it on the earth.
The bonus is, its not gotta be proper terraforming from scratch, its more like fixing the issues. So theres that at least.
So it's created as a genesis bomb (ala. Star Trek II) and dropped into what was once central germany (now rife with demons). This rapidly and shockingly terraforms the earth, and as a nice bonus, kills a lot of the surface demons.
In the process though, it screws up alot about what we know about the planet; topography, life, etc. and somehow makes a giant Yggdrasil tree erupt on its ground zero.
So yeah, as you can see there's alot of crazy speculation here. Can I explain some of these things at all in a reasonable fashion and still keep this even vaguely sci-fi?
***EDIT:*** What are the demons? Basically I want a science justifiable reason for mutated creatures and humans that have lost most of their sense of reason and have become savages again; but have gained 'devilish' powers instead, like super strength, creating fire, flying with wings etc. As noted above, I used radioactive fallout as the handwavium filler-reason for this, but I'm suspicious of using that; as despite what comic books teach us I am aware that selective mutation to get results like this is beyond the realms of random chance. Also see below comment.
[Answer]
Let's call your nano-magic the "Interface", just so I have a single word to use throughout this answer. I'm assuming there's a central computer that controls all of it.
**Mutations**
The key is that maybe your people didn't mutate - what if the *Interface* mutated? Something like that has to be powerful and flexible. It could be coded in such a way that over time, the parameters and such would change. Add people trying to attack it, bot nets stealing CPU cycles, and clueless users screwing with the system for thousands of years, and you have a recipe for disaster.
Your "demons" are the descendants of [LARPers](http://en.wikipedia.org/wiki/Live_action_role-playing_game). Pre-apocalypse they were just pretending to be demons, using the Interface to make it extremely realistic. They originally set their powers to "active mode" to help protect them during the apocalypse. But over time, and due to some malicious code, they're now stuck - they grow and spend their entire lives that way, including the full spectrum of demonic powers based on current fantasy. You actually get the entire spectrum of fantasy creatures this way, based on the Interface accidentally giving people and their descendants powers based on our current pop-culture fantasy.
**Terraforming and the World Tree**
The key here is that the genesis bomb was designed to use the Interface to re-write the earth - it was, basically, a giant power influx + software update.
However, they didn't fully account for the changes within the Interface. So the patch wasn't perfect - instead of the direct and controlled update they were expecting, things *changed*. A literal world tree from mythology grows at ground zero, consuming much of the energy needed for other projects. Geography itself is re-written to match various fantasy settings, all twisted and smashed together. Demons are killed or re-written into new creatures, or their powers are combined and changed.
**Plot Twist**
The Interface is an old, very powerful, very complex computer. There's a very common sci-fi trope about those - the Interface could now be sentient. I don't know if you want to use it here, but I'd at least consider it.
[Answer]
I think that you can explain a lot with one central idea:
**The nanites try to keep people alive**
Thanks to the nuclear apocalypse, billions were exposed to massive doses of radiation. Without the nanites, they would have all died of radiation sickness. The nanites did their best to keep people from dying, but the radiation damage was just too much for them to fully repair. They were able to prevent many deaths, but the amount of DNA damage left the survivors barely recognizable as humans. For a few generations their DNA was still very unstable and led to extremely high mortality rates, but with the help of the nanites enough were able to survive to lead to a generation with more stable DNA. By this point they are no longer human - they are the demons.
The variations are due to not everyone's DNA being damaged in the same way, leading to the nanites attempting different strategies to repair them. One strategy could have been to include the DNA of nearby animals - a person who has bird DNA grafted in could be the ancestor of some of the winged demons.
In addition, by the time their DNA stabilized the nanites became integrated into the demons. This is how they can survive with otherwise implausible body structures, and also why they have unusual abilities. It can also have affected their reproduction rate, allowing you to make them however common or rare you want.
The survivors also have the nanites helping them stay alive, leading to them healing faster and being more durable. This means that your unrealistic RP can have a somewhat realistic explanation - in real life it would take you quite a while to heal from being shot or stabbed with a sword, but thanks to the nanites a good night's rest goes a long way to helping you fully heal.
As a side note, this also gives you a way to have an interesting and powerful "magic" curse - commanding the nanites to abandon someone/something. It would cause them to lose all their nanite enhancements, including rapid healing and increased durability.
**The Genesis Bomb**
The members of the moon colony aren't aware of the extent to which the nanites are keeping everything running, and the ways in which the nanites have updated themselves to the current situation. This is why the genesis bomb does not behave as expected. At ground zero, the nanites detect the surge of energy but misinterpret it as another nuclear apocalypse in the making. So they quickly abandon their hosts, leaving them to die, and absorb as much of the energy as they can to render it harmless. Thanks to their misunderstanding of the nature of the energy much of the energy still escapes to terraform the rest of the world.
The nanites at ground zero eventually realize the energy is of a different nature than expected, and dump it into a single life form - a tree. Filled with enormous amounts of genesis energy, the tree grows into Yggdrasil.
Away from ground zero, the nanites do not abandon their hosts, but attempt to do what they did during the nuclear apocalypse - keep everyone alive. This causes further changes to the life forms, but thanks to the energy being inherently creative (whereas nuclear radiation is destructive) there is not the same massive die-off that there was following the nuclear apocalypse.
The unusual changes to the geography of the earth come about because of the interference of the nanites. Their absorbing and redirecting of the genesis energy caused it to behave in ways that the moon colonists could not have predicted.
**An option:**
You could have the genesis bomb be the reason why the demon's DNA stabilized - if not for the genesis bomb they eventually would have died off, but the nanites somehow utilized the genesis energy to stabilize the DNA.
[Answer]
Since you mention nanomachines, check out [utility fog](http://www.wikipedia.org/wiki/Utility_fog). It would give you the ability to make things appear and form magically. The Yggdrasil tree is a giant nano factory created by the bomb, which both builds and powers the nanomachines.
The factory could also build other nanomachines. Some that take stuff apart, some that build, some that fight by entering the targets body. It would use the utility fog to transport them where they need to go. The ones that build and take stuff apart are what is doing the teraforming.
Edit to summarize the comments:
Demons are caused by things left over from the war:
Biological germ weapons that have mutated and now cause mutations, madness, copying genetic traits from one creature to another.
Biological monsters created in a lab and released onto the battlefield.
Autonomous machines created to hunt enemy soldiers, now roaming and killing indiscriminately.
Super solder programs gone wrong, biological implants with horrific destructive capability.
Parasitic machines that burrow into living creatures, take them over to create a cyborg. Once the host dies the machines cut their way out so they can hunt for a new body. (actually, this one works for being "demon possessed", with a degausser as exorcism equipment)
[Answer]
## Okay everyone, thanks for all of your great ideas!
**Below is the completed amalgamation of parts of my original origin story mixed in along with ideas from everyone here. I believe everything works together quite nicely now and this is really starting to get its grip. Please let me know what you think and if anything is still missing, in your opinion.**
## How it all began
It is now the year 5,706. In 2056, the well-established military contractor, the Nanolith Corporation, with their motto, “Building new futures from tiny pieces”, had their second major breakthrough in creating the Nanocolluder Virtual Interface System (or ‘VIS’) in conjunction with Intel.
Possibly the greatest quantum computer yet built to date, this wondrous machine finally allowed large-scale control and manipulation of nanobots on an unprecedented scale.
Nanobots were already becoming accepted at this time due to their obvious medical applications by MicroLife, and Nanolith’s own first product, the AURA (Autonomous Upgradable Reactive Armour), which was adopted by the US Military. So when the VIS was used to freely provide incredible disaster relief from a tsunami later that year, in its instant reconstruction of shelters and clearing of rubble, people only became even friendlier towards this new technology. This was a very smart business move by the company; generating a huge surge of interest and investment.
Of course, as with any advance, there will always be those that wish to use it for unsavoury things. After all, the VIS was not an intelligent machine. It didn’t consider the right and wrong of what it was ordered to do. It just did it. And despite the catastrophic potential of the technology, its newness meant it had no restraints or laws like gun control to bind it. People could buy the interface devices and crates of nanites, and do whatever they wanted to do…
There were some interesting applications to this. Somewhat innocuous ones, like Live Action Roleplayers with too much money on their hands changing themselves into beasts and demons. But also far more terrifying ones, like using nanobots to create new weapons and plagues.
By the time restraints were put into place properly, it was far too late already. A cunning terrorist with a rich benefactor got hold of a crate of nanites and an interface, and had a terrifying idea: if I can make anything with this, can’t I just make an ICBM? A deadly virus for the first world?
## The Apocalypse
A meticulously planned operation over the next year would be the start of the downfall of humanity.
An ‘accident’ occurred in a lab in midst of London, infecting the water-supply and the Thames. In just a handful of hours, half of the city died from a super-plague that warped their flesh and made them choke on their own blood. Those that were not mercifully killed instantly become enraged beasts that added fuel to the fire, tearing things apart in their pain and madness. The underground collapsed, parliament was set on fire due to a riot. But it didn’t end there. Shortly afterwards; an American submarine launched a missile at London. It was nuclear.
Despite shocked protests from the Pentagon and The White House, nobody could deny that the missile came from an American sub that was on the edge of British waters. The sub was quickly sunk by a nearby British Destroyer, and divers confirmed its allegiance. The provisional British government, rallied on by its outraged people, gave the order that evening to launch a Trident VI. The next morning, San Francisco was wiped from the map.
Needless to say, nuclear wars very rarely stop with a single savage strike from both sides. Within the next six months, the earth became a hellish nuclear wasteland.
## The Survivors in the Storms
Meanwhile, the shocked people of the nearly forgotten James Watson lunar colony looked on. The winds, rain, storms and devastation that wracked the Earth meant that it seemed as though nothing had survived (ala Millenium 2.2). Of course, that was nearly true.
Some people, reacting to the first of the strikes quickly, retreated to a repurposed underground shelter in Siberia. They would survive by sealing off the world underground, and would go on to be the source of the Engi race.
The crews of the three newest advanced US Navy Battlecruisers, with their own onboard Fusion Reactors and limited Electromagnetic plating survived as well, rescuing civilian ships and people from coastal settlements as the world broke down in chaos. They would go on to become the Great Migrant Fleet of the Usnay.
Furious dust storms laced with nuclear fallout ravaged the planet for over a hundred years following this. During that time, the lunar colonists hardened their hearts and toiled away, ever hoping to create a way to re-terraform the Earth. They felt themselves fortunate at their recent private investment that led them to have their own hydroponics and fusion reactor, without which they could never survive without the Earth’s assistance.
## The Dark Ages
When the storms stopped a century later, the remainders of the land were inhabited by foul and vicious creatures that were the ones able to survive. Miraculously, some surface humans did live on, but most were mutated by the radiation. Little did they know at the time, these survivals were entirely at the assistance of the remaining nanobots of the VIS, which had been unleashed upon the world en-masse by one of their original creators with a single command ‘Preserve as much life as you can!’. The nanobots truly, heroically tried their best to meet that demand, preserving life without being able to consider the consequences of such a poorly worded order. These ‘survivors’ would become the demons of the Usnay legends.
The Usnay, now the third generation of those original crews, were faced with the decision of braving the land once more. But it was now populated by vicious creatures and mutants and still replete with nuclear radiation, so they chose to instead stay within their ships forevermore, barring occasional missions to obtain metal scrap and other supplies. Where safer, after all?
The people of the Siberian shelter eventually forgot they ever came from the surface except in some forgotten legends. They became partially adapted to the dark; and over time, terrified of the prospect of the surface. Their leaders, pressed for space for all the people, agreed to expand further underground, starting the legacy of the warrens of the Engi that persist to this day. Their underground hydroponics supplied their diet, most notably via the Armillaria Superior, a hardy genetically engineered mushroom species made to taste like honey and grow upside down on cavern roofs to giant sizes in the soft rock conditions, consuming the dead tree roots above.
Due to politics on the moon, and a lack of ability to expand due to food, development of the Terraformer was slow. Occasional missions back to the home world for samples to aid the process was met with the demons, and the third and fourth generation Lunarians abandoned the project as hopeless. (by this point the Usnay ran radio silent; whilst the Engi had been cut off completely). Only a thousand years later did a lunar leader finally restart the project, because living space on the moon was difficult at the best of times and it would be in their best interest anyway to terraform the moon itself even if the Earth was a lost cause.
## The Fall of Heaven
So the Dark Ages passed. Much knowledge was lost. It took the Lunarians, who now called themselves the Ruto, another thousand years to figure out the process of terraforming; the breakthrough finally occurring when a bored programmer came across ancient records for the VIS: this was the answer- provide energy to the dead nanobot facility and use their capability to restore the planet. Had the Ruto historians of known the truth, they might almost laughed at the irony of this plan, since the VIS had technically been the cause of the apocalypse and the demons in the first place.
Most Ruto of this time had become of a religion that shunned un-necessary technology. Their goal became to recreate the earth and then all move there and start afresh without the old tools of man that caused this in the first place.
So they built a small fleet of ‘Angel’ class attack shuttles, and carpet bombed the remaining surface demons into oblivion. Some of the remaining Usnay tech-priests noticed but were too shocked to consider shooting down the new arrivals, considering that they were combating the demons, especially considering the Genesis device that was dropped shortly afterwards in what used to be Central Germany. The VIS roared back into life from its previous sleep mode. Dead nanobots across the globe leapt to life in rebuilding the wasteland.
There was still a slight problem, though. True, the VIS, given this large energy infusion and a massive firmware update, could indeed fix the world. But the thing was, it had been a thousand years since anyone had seen the Earth. What had it looked like? What was is supposed to look like? There were records, yes, but most were lost or incomplete. And many… guesses were made…
In the space of a month, a ripple of transformation smashed across the world. Previously ash-covered lands became lush again. The earth was certainly very different from what the Ruto remembered. But at least it was earth again. They kept their promises. They sunk the ‘Angels’ into the sea, and dropped their colony ship, the Argo, right near the landing spot of the genesis device, where a great tree had begun to grow. They didn’t actually expect the tree to grow so rapidly, though. It actually engulfed their ship and they were forced out.
Some of them sailed in ships of wood to meet the Usnay, and the Engi took the rumbles on the surface to be a sign from a prophecy, and emerged themselves into their promised land.
And so we have the world as it exists today.
[Answer]
Further idea, Luna base is like the ISS, and in concert with Siberia and the US Naval fleet is able to design the G-bomb. Dozens of prototypes are launched all over the earth with the idea of capturing released free radical energy from the existing energy supplies and converting it into broadcast power which would help power the G-bomb nanites to rescuplt the planet. The early prototypes are obviously not up to the task, and "Magic" is the result along with your mutations. "Magic" exists as a superset overlay of holoprograms given full reality interface (the G-bomb itself was designed to take advantage of this property) by the "corruption" of the software update. This would make it so that people from Luna base would have no actual ability to manipulate magic (but maybe they are psychic? from all that time spent mamipulating the Interface?). Luna base would have the ability to fire off people down to the surface into the sea near the US Navy so characters would be able to interact with each other.
] |
[Question]
[
It **finally** happened. The inhabitants of Metropolis, the capital of Our Nation, have finally had enough of the swampy lands, suffocating summers, freezing winters, spring floods, risk of surprise invasion by sea and whatever other nastiness the local geography had in store for them.
**They have decided to move Metropolis**. Since Our Nation is a glorious empire with vast, vast resources at our disposal, we will literally uproot the entire city and move it some place we like better (about 161 km away -- 100 miles away).
## How do we go about moving a city of 5 Million?
How much time, how much energy would it take? Can it be done in bulk, whole blocks at a time? Can you literally float it, in the air or on a river?
A few details:
* I would prefer near-future technology, but I won't get upset if your solution needs to specify otherwise, i.e. literally float-up into the air the whole darn city at once, as long as you can show your work (energy calculations etc).
* Metropolis has about **5.5 million people** in the greater urban area, and is the seat of administration of Our Nation. Edit: The area is **176.9 km²** or 68.3 mi².
* By law, no building in the city can be taller than the Giant Phallic Symbol of Power, a monument 169 m tall. Only a handful are taller than 60 meters.
* The move should be as quick as possible and cause as little disruption as possible to government and the lives of the inhabitants.
* As a real-life historical near-precedent, [Chicago has literally been lifted off the ground](http://en.wikipedia.org/wiki/Raising_of_Chicago), with 19th century tech at that.
* The reason we can't go the normal route (just build a new city) is because we're vainglorious and, frankly we have the technology and we want to show off.
* I softly encourage [hard science answers](http://meta.worldbuilding.stackexchange.com/questions/1891/should-science-based-henceforth-actually-be-science-based), but if you feel you have a brilliant idea but lack the time or the maths to flesh it out, please share it anyway.
[Answer]
This is probably the most destructive, tyrannical, and least glamorous answer you are going to see.
We can already relocate structures...it's simply a matter of building a metal framework solid enough to support the structure underneath the foundation. Jacking this framework up off the ground, and then putting wheels on it and pushing it to wherever you want to drop it off. The entire process must be done very, very slowly so as not to damage the building.
In order to relocate something like a Skyscraper (which has a very high center of gravity, generally compensated by affixing the structure to bedrock) you are going to be at a risk of it tipping over unless you can build a sufficiently massive framework to stabilize it.
From there, it is simply a matter of scale. Stronger frameworks, more/stronger jacks, more/bigger wheels. Heck, if you can build something strong enough, you might be able to carve out the bedrock that the city is built on, jack THAT up, and relocate the whole thing in one go.
But here's the catch. Anything between Point A and Point B is going to have to go. Anything that is not nice, flat ground. This means towns, cities, mountains, lakes, etc. The smaller of pieces you move the city in, the less widescale obliteration you need to unleash. Trying to take a skyscraper up a hill would end in a tipped-over skyscraper.
You're probably also going to have some repairs to make, regardless of how careful you were, because things are going to shift and move while being relocated. Hopefully not to the point of anything falling down entirely, but you'll have cracked walls, damaged floors, etc.
I'm sure someone else will come up with a more fantastic answer, like orbital lifting or somesuch...but I figured I would toss up the simple 'we already do this on a smaller scale' answer.
[Answer]
Space Elevator.
I once wrote a story which involved that.
There's an [elevator into space](http://en.wikipedia.org/wiki/Space_elevator) in the center of the city. The city needs to be moved (built on a volcano that was inert but the strain from the elevator reactivated it, and it will erupt soon), and they decided to use the technology in place to move the city.
First, reinforce the supporting ground through building tunnels and drawing cords of the same material as the space elevator through them, making the clump of stone and earth not fall apart from the stress. Then reinforce the elevator to support the whole mass, adding extra ropes. Then pump a lot of water up beyond the Geostationary orbit, forming a counterweight of ice in space.
Through extending the network of tunnels, separate the city from the native rock. At certain point, the counterweight will pull stronger than the mass of the city. Multiple heavy ground vehicles provide a moving anchor, so that the city doesn't just float away. They move the city towards the destination, holding it with long ropes several hundred meters above the ground.
Then a stray asteroid hits the counter-balance, and the city falls, nearly flipping over, the elevator ropes snap, twisted as they were not meant to, and the city lands on one side of the mountain, houses of the other side hanging nearly upside down over the jungle below, providing arena for my story.
[Answer]
Float the city.
Dig under it and put in structural bracing to support the buildings and then tons of pontoons. Then let the ocean in to let the city float up, and then tow it up the coast to the new destination. You haven't described the city at all (building height, materials used etc) so this may take some super materials to make possible.
**Edit** This gets you out of the swamp and 100 miles away into a better climate with hopefully milder winters, without having to level mountains. Which takes care of the seasonal flooding and malaria. Since everything is pretty solidly braced at this point, if you want to get out of the water to get to higher ground you could put wheels on the city boats pull them out. And because they are raised up, it would be pretty easy to put the utilities in underneath.
Or you could find a sheltered harbor and have a floating capital.
They'd still be near the coast, so maybe surprise attacks from the sea will still be a problem, but these are people with the technology to move a city. Seems like a fleet of warships to patrol the ocean and remove any surprises before they become a problem should be a small task.
[Answer]
# Put the whole city on wheels
Do this as follows:
1. Dig caverns into the bedrock under Metropolis.
2. Build some very strong wheels with near-future technology. Carbon buckyballs may be useful. If necessary, you could use superconducting magnets in place of bearings.
3. Quarry a pit of the right size and shape at your intended destination. Nuclear weapons may save time, if you don't mind a bit of radiation. **Alternatively**, design the wheels to be collapsible; when you arrive, they are crushed under the weight of Metropolis, which will then rest on a plateau above the surrounding landscape.
4. Build a suitable roadway. You would need to dig away all the soil and expose the bedrock, then level the ground, creating a (relatively) shallow trench several kilometers wide.
5. Very carefully dig away the last remaining pillars of rock beneath the city, so that the massive slab of bedrock rests on the wheels.
6. Propel the city 100 miles inland.
7. Wheel the city into the pit you have prepared. If the pit is very precisely shaped (requires some final precision digging, nuclear weapons not suitable) then the wheels will drop into individually prepared wells so that the slab of bedrock neatly comes to rest in its new home. (Or you can go with the plateau option above.)
8. Celebrate with a huge party at the base of the Giant Phallic Symbol of Power.
# Some engineering details
Metropolis has an area of 180 km^2. If it's roughly circular, it has a diameter of about 15 km. This is the width of the path you need to clear.
How much does the bedrock weigh? Ignoring the weight of the buildings, suppose we dig 1 km down into the rock, which is solid granite with a [density](http://www.engineeringtoolbox.com/density-solids-d_1265.html) of 2800 kg/m^3. One km^3 of granite is equal to 10^9 cubic meters, so 180 km^3 of granite weighs (1.8\*10^2)\*(10^9)\*(2.8\*10^3)\*(10^3) = 5.04\*10^17 **grams**.
Accelerating the slab to 1 m/s (a reasonable speed of 3.6 km/h) requires 5.04\*10^17 **joules** of energy (kinetic energy being equal to mass times velocity^2). If we take 24 hours to get up to speed, this implies (5.04\*10^17)/(8.64\*10^5) =~ 10^12 watts of power to within an order of magnitude, or 1 thousand gigawatts. This is roughly equal to the [total electricity grid output](http://en.wikipedia.org/wiki/Electricity_sector_of_the_United_States#Electricity_generation) of the USA. So if Our Country is of similar size, you just have to ask the citizens to give up *all* electric power for a day, which I'm sure they will be happy to do for the greater glory.
**Alternatively**, you could use [nuclear pulse propulsion](http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion) to accelerate Metropolis, by building a large blast absorbing plate behind the city and setting off a number of nuclear explosions. This would leave a radioactive wasteland at the original location of Metropolis, which might be regarded as a drawback.
At 3.6 km/h it takes about 45 hours to move Metropolis. In fact it will take a little longer, allowing time for initial acceleration, and deceleration at the other end. Metropolis is presumably moving uphill; this may increase the energy requirements, but conversely you can use gravity to help with the deceleration.
For the most part, this method has the advantage of **minimal disruption** except when the city is actually in motion, which is only for a couple of days.
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[
The setup: Near future (maximum 50 years in future) where "only" thing changed is, that company SpaceX together with NASA and ESA found out, how to get cargo and people to space *very cheap*
USA decides to build a space prison. Because - it would be nearly impossible to escape from it.
Now the question. **We hand wave away economical aspects** (basically, we have money):
What drawbacks would we face, if we would like to build a prison in space? What challenges need to be considered? What would be impact on society? And how long can I keep prisoners there?
[Answer]
By putting prisoners in a place where they wouldn't be able to survive on their own, you are taking on a larger burden of caretaking:
* What if there is a mechanical or electrical failure on the station and people die?
* How are you going to keep these distant prisoners fed and basically healthy? Do you have live-in guards and staff, or are you dropping a palette of food every week or two and letting them sort it out, prison-colony-style?
* How quickly can you respond if there's a problem?
Even if you send only your worst criminals there, there will be some socio-political unrest if people start dying. And unlike the prison down the road, it's harder for you to keep order or bring in extra enforcement when needed. Spaceflight might now be *cheap*, but is it *fast* and *widespread*?
An additional factor is economic. Yes it's much more difficult for prisoners to escape, which brings some peace of mind (unless they manage to commandeer a supply ship!). But a space station is also *much* more expensive to build and maintain than a conventional Earth prison. How are the taxpayers going to feel about that?
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TL;DR: *I don't think there would be any difference to society other than the exposure of health & safety of the people who are in space.*
This is pretty broad, so I will take a stab at the ethics.
In addition to punishment by retaining privileges, prisons are correctional facilities that should (hold on: I said, "should") be places of rehabilitation so that detainees can be reinstated properly into society.
Setting the economic requirements aside, I would be concerned about the health effects for a population in space for such a long time. There are [well-known health effects](http://%20An%20increase%20in%20cancer%20risk%20is%20the%20principal%20concern%20for%20astronaut%20exposure%20to%20space%20radiation,%20and%20it%20is%20one%20risk%20that%20persists%20after%20landing.) due to radiation that persist even after return from space. Because of the same health issues, prison staff would have to be on a rotational basis.
I can't imagine there being any other difference to your usual prison, which punishes people by isolating them from privileges, and hopefully has resources to help rehabilitate them for returning to society.
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I think the most basic challenges would go along these lines:
1. Out of sight, out of mind. A terran prison gets visitors and visitors ensure a basic threshold of civility. Not so with space prisons.
2. Suicide attempts. Inmates with no hope for the future will be tempted to breach the hull or crash the station into Earth just to make an final impression
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The problems? the biggest would be now being a prison guard is a hardship tour, unless you have shifts being brought in and out every day. Even if cheap I expect it would be a couple hour commute everyday or it would be several weeks on, several weeks off. Either way, hard on families. It would also make it harder for families to see their incarcerated loved ones.
Now if it was only used for those that should be executed but we've given that up as inhumane, then it might be more likely to happen. People we have really given up on, but don't want to kill them.
Now if there were living quarters near the prison you could shorten the commute to work but then you are putting civilians in proximity to possibly very dangerous individuals and also make it easier to 'escape'.
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[
This question was stimulated by the question [How would an aquatic race develop computers?](https://worldbuilding.stackexchange.com/questions/3722/how-would-an-aquatic-race-develop-computers).
The answers obviously were based on the aquatic civilization being earth based, but what about a totally aquatic planet. Could evolution based on different requirements be quite different than evolution on Earth, and interpretations of physics also differ?
Seems to me that the usage of light, as opposed to electricity might be more advantageous in an aquatic environment, and we understand very little about bio-luminescence other than it is chemically based. Our understanding of physics is based on our knowledge. Is it not possible that another environment might create other forms of knowledge, and therefore different understandings of physics?
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## Fluid Dynamics
I think the answer to this one is obvious. A nice theory of [fluid dynamics](http://en.wikipedia.org/wiki/Fluid_dynamics) is [Navier-Stokes equations](http://en.wikipedia.org/wiki/Navier%E2%80%93Stokes_equations), for compressible and incompressible flow. They would have to develop the common mathematical tools, which is kinda independent of the environment where you are. So, this is a successful theory they would do.
---
## Newton's Laws and Newtonian Gravity
Newton's laws can be derived from [Navier-Stokes equations](http://en.wikipedia.org/wiki/Navier%E2%80%93Stokes_equations). These equations are encoded: momentum conservation, Newton's first and second laws, mass and energy conservation. As gravity only depends on the mass, and [buoyancy](http://en.wikipedia.org/wiki/Buoyancy) depends only on the fluid displacement due to volume, it is possible to differentiate, and very likely a aquatic race would do so. Hence, a real theory of gravity like $F = mg$ would be developed. Also, gravity is predicted in Navier-Stokes equations, as a body force $\mathbf f$. Hence we can safely conclude gravity would be developed. And of course, buoyancy would be a well known consequence of Navier-Stokes equations in the static limit. They could develop optics and observe stars, and maybe figure out newtonian gravity as a whole: $$\mathbf F = -\frac{GMm}{r^2} \mathbf{\hat r}$$
---
## Electromagnetism
Electric and magnetic fields exists in a lot of media, including water. There are 4 equations describing all electromagnetic phenomena in any kind of media: [macroscopic Maxwell equations](http://en.wikipedia.org/wiki/Maxwell%27s_equations#.22Microscopic.22_versus_.22macroscopic.22). Therefore, electromagnetism does work inside media, and they could use it. The only problem is the presence of ions in the water that could trigger ionic currents (that's why some electric devices do not work in water). However, this can be predicted using this equations, particularly with the density current $\mathbf J$. It is also possible to derive a wave equation inside water, hence demonstrating the possibility of generation of electromagnetic waves inside water. So, possible to do a radio. Of course, the speed of light $c\_w$ in water would be:
$$
c\_w = \frac{1}{\sqrt{\epsilon\_0\mu\_0\epsilon\_r\mu\_r}} =
\frac{c}{\sqrt{\epsilon\_r\mu\_r}} =
\frac{c}{n}
$$
Where, $c$ is the speed of light in vacuum, and $\epsilon\_r$ the relative electric permittivity of water, and $\mu\_r$ the relative magnetic permeability of water, $n$ is the refractive index of water. This would give for water: $c\_w \approx 0.752c$. Just a curiosity.
---
## Thermodynamics and Statistical Mechanics
Thermodynamics is famous of working anywhere. We can **easily** build thermodynamics of electromagnetism, thermodynamics of Newton's laws, thermodynamics of gas, and surely, thermodynamics inside water. As for statistical mechanics, it can be done by finding out [microstates](http://en.wikipedia.org/wiki/Microstate_(statistical_mechanics)) in water. An nice application here is to develop the [diffusion equation](http://en.wikipedia.org/wiki/Diffusion_equation) to explain [hydrothermal vents](http://en.wikipedia.org/wiki/Hydrothermal_vent) or other thermal phenomena under water. Also, this could be the key for developing astronaut clothing, or I might say, "groundnaut", for exploring non-water domains, or places where oxygen concentration in water is few (assuming they breath oxygen).
---
## Quantum Mechanics
Quantum mechanics began when physicists realized that when we heat up a [black body](http://en.wikipedia.org/wiki/Black_body) it emits electromagnetic waves according to [Planck's law](http://en.wikipedia.org/wiki/Planck%27s_law). A consequence of this law says [energy is quantized](http://en.wikipedia.org/wiki/Energy_level). This is the first step for a quantum theory. Artificial local heating at large temperatures in order of 5000K is also possible using previous knowledge of electromagnetism or/and thermodynamics. So, it is possible to come up with quantum mechanics, then finally a quantized atomic model.
---
## Special and General Relativity
It was discovered as a consequence of what frame of reference are electromagnetic waves. As an aquatic race, sound waves is present. So they could postulate, like we did, that electromagnetic waves travel in a media called [aether](http://en.wikipedia.org/wiki/Aether_theories), as sound waves travels in a water media. They could do the [Michelson–Morley experiment](http://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment) below water to prove it wrong, and finally discover [relativity](http://en.wikipedia.org/wiki/Special_relativity), just like [we did](http://en.wikipedia.org/wiki/History_of_special_relativity). As for [general relativity](http://en.wikipedia.org/wiki/General_relativity), it is literally a generalization, as special relativity is only valid for inertial frames. General relativity is valid for any reference frame (including non-inertial frames). Only later Einstein noticed its close relation with gravity as curved spacetime.
---
## Nuclear Physics, QCD and Weak force
Once relativity growing, they would know: $E = mc^2$, which is a very important equation in [nuclear physics](http://en.wikipedia.org/wiki/Nuclear_physics). Several nuclear reactors are built underwater, like [ATR](http://en.wikipedia.org/wiki/Advanced_Test_Reactor) or [RRR](http://en.wikipedia.org/wiki/Reed_Research_Reactor). For instance, [pool-type reactors](http://en.wikipedia.org/wiki/Pool-type_reactor) could be common. Curiosity: You can identify when a nuclear reactor is under water: if it is emitting [Cherenkov radiation](http://en.wikipedia.org/wiki/Cherenkov_radiation). Also, a nuclear theory could be the basis for [QCD-Theory](http://en.wikipedia.org/wiki/Quantum_chromodynamics), which is the theory who explains the strong nuclear force, and the [weak force theory](http://en.wikipedia.org/wiki/Weak_interaction).
---
## QFT, Electroweak, Standard Model and String Theory
[QFT](http://en.wikipedia.org/wiki/Quantum_field_theory), [QCD](http://en.wikipedia.org/wiki/Quantum_chromodynamics), and the [electroweak force theory](http://en.wikipedia.org/wiki/Electroweak_interaction) could have being developed with the previous knowledge we have so far, on mathematical models, or experimental data: like nuclear physics. Joining all of it, we have the [Standard Model](http://en.wikipedia.org/wiki/Standard_Model) and now it just needs to be combined with general relativity to come up with unification attempts, like [string theory](http://en.wikipedia.org/wiki/String_theory), or something [nicer](http://en.wikipedia.org/wiki/Grand_Unified_Theory).
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8E&M might not be affected much at all. We spent much of our technological growth believing light traveled through a material (ether) anyways. There are major things I could see becoming dominating factors in how they learn science:
* Water is very dense, and moves a lot. It also doesn't move in straight lines.
* Water yields buoyancy.
* Water is the "universal solvent"
**Frames of Motion, and how they discover Newton's 1st law**
Swimming in a 3 dimensional world, they are subject to motions that we never notice. The human brain is generally not wired to make sense of the coreolis effect (which occurs when moving while rotating), but in a world where the water moves you around constantly, these effects would be quick to learn.
They would be much faster to learn calculus and differential equations, as mentioned above, to try to grasp these issues. **Newton's first law might be discovered as a corollary of measuring velocities in fluid flow, rather than a measurement of positions and times in air.**
Because of how complex the movement of water is, I would expect their mathematics of topology and fields to explode dramatically faster than we do. I would expect every 8yr old aquatic denzin be intuitively more comfortable with manifold topologies than your average PhD mathematician.
Gravity would likely be tied in tightly with buoyancy. It is possible they could develop their entire system of equations of motions around bouyancy. While we think life exists at (1 gee), they might think of it existing centered around (0 buoyancy). The air above them would seem to inflict negative bouyancy.
Another interesting direction: when moving in water, chaotic flow is a big deal. If your flow goes chaotic, you slow down fast. It took us to the mid 1900's before Edward Lorentz discovered chaos theory. They would have easily picked it up many years before that. **Because so many systems in the body are easier described by chaos theory than traditional models, their understanding of their anatomy and biology could be far superior**.
## An alternate viewpoint
Perhaps the most impressive change in how they approach physics and technology would be the most nuanced. Underwater, form and function are rarely separated. The cost of separating them, in terms of fluid dynamics, is too great. This could cause a society to focus more on harmony in movement. **The entire march of science and physics could be done in order to be "in harmony with nature," while much of Western science focuses more on "triumphing over nature." Their entire approach to science and physics could be more Eastern in nature because of this.**
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The hard part here would be that the medium this civilization lives in would be fairly disturbing. Ocean currents can fluctuate easily in certain spots, creating chaotic flows. Maelstroms and other disturbances would mess up the local environment, and rip currents could be devastating to creatures living near the surface. I'm not an expert in marine activity, but I do know that it would be hard for these creatures to avoid interacting with the medium around them.
That said, there are a lot of principles I would think they would figure out:
* **$F=ma$:** These creatures would realize that if you apply a force on an object, it accelerates. It would be evident after a lot of experimentation.
* **Newton's third law:** If you push on something, the object pushes on you. In still water, this would be incredibly obvious.
* **Gravity:** Only very buoyant objects would not sink after some time.
* **Conservation of energy and momentum:** I think this will follow after playing around with experiments resulting from studying the principles listed above.
Some things they would *not* figure out:
* **Newton's first law:** An object in motion might not stay in motion; an object at rest might not stay at rest. Currents will interact strongly with the environment, moving objects around.
* **Electricity (and perhaps magnetism):** In case you haven't noticed, electricity and water don't mix too well. Unless these creatures are electric eels, electricity won't be a major force (pun intended) in their lives. As for magnetism. . . How many magnetic materials can be found at the bottom of a body of water?
Figuring out more advanced principles would depend on their technological development.
[Answer]
In a technological society physics would be physics. The route to a solid understanding of the universe would be different for an aquatic species, but if they live in our universe (or one with similar physics) then the rules of the game are the same for everyone.
If you're curious about a more topical approach rather than the fundamental laws of nature, then there would be some significant differences. They would likely have an innate understanding of fluid dynamics and solution chemistry that we do not. It's likely that their understanding of biology would far outstrip their chemistry or physics, since there are a number of extremely important biological topics that can be learned with fairly rudimentary tools and a quick mind.
They would have a disadvantage with some basic concepts like inertia, gas phase chemistry, momentum, and even one dimensional motion. To solve a one dimensional motion problem underwater you have to do differential equations - math that the bulk of our population never even comes close to learning. Air is sufficiently close to a vacuum that we teach 8 year olds how to do them. Metallurgy would be difficult or impossible, as would the development of glass (an incredibly useful substance for science.)
[Answer]
The earliest attempts at codifying physical laws involved ideal equations that basically assumed bodies moving in a vacuum. This wasn't accurate, but it was close enough that we were able to start making decent predictions and gradually refine them. In water there's far too much resistance to ignore.
Similarly, air pressure / density varies at different points on the Earth, but not by so much that it makes approximations impossible. If your aquatic civilization is dealing with a variety of depths or salinities, there's no way they could get the idea that all objects in all situations move following the same laws. HDE mentioned the effects of currents, which could be even worse -- but those are obvious enough that I think they'd be easier to recognize and remove from one's calculations (analogously, you don't need a complex understanding of air pressure to realize that you shouldn't perform physics experiments in a tornado).
The same would be true for any discoveries in optics that involve modeling light as a ray that travels indefinitely in a straight line. You would have to average out so much interference in order to make this observation that it would probably never occur to anyone.
Newton made the great discovery that the same law that governs a falling apple also governs the motion of the planets, which gave his physics a grand, majestic feel and an air of Platonic (or Euclidian?) purity. Underwater physics might be more context-dependent and focused on how real-world practices need to be carried out with a careful understanding of one's environment. They might lag in discovering what we consider basic physical laws, but have an advanced understanding of more complex engineering principles.
On the other hand, perhaps there are physical laws that can be more clearly perceived in water than in air. Maybe their overarching, Newtonian insights would involve temperature conduction or wave propagation.
[Answer]
It would definitely be understood differently.
Let's start with something easy: Archimedes law. Here we have our since forever, but because Archimedes loved to bath. In your society such law would probably be defined as speed of object falling to the ground.
Speaking of which. How did they discover gravity? On earth were have nice story about falling apple. But would be there trees? And also, the density of water makes this pretty hard to guess how the gravity works.
The biggest novelty to your civilisation would be anything "gas" connected. From having pure has available to the whole flying thing
[Answer]
We understand bioluminescence quite well. I also don't see how this contributes to the question. Please clarify this.
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[Question]
[
| Let's say you're in Atlantis, | which happens to be 1 km below sea level |
| --- | --- |
| It's also at equilibrium with the sea. You have been born there and are fully acclimated to the pressure, in air which is made of a mixed gas with the right proportions for human life. This is because, just like all the fictional adaptations of Atlantis, you can just swim into the submerged sea and get outside the dome. No airlocks, just equilibrium. Let's imagine their bodies have made the needed adjustments. | |
1km isn't as deep as you may think, elephant seals dive to more than twice this depth; there is a way. It's important to note, no one is going to the surface. This is STP as far as your little village is concerned. No pressure transitions; but that doesn't matter to the question, which is only about food processing. They are living there now, that's the point. And they want to cook. The problem of the question is this: They sit down to a nice meal and chat, or get up and make breakfast. Then I thought, "Would they smell bacon? Would grease boil? Can they talk over tea?" Hence, this question!
Water boils differently. Carbonation happens differently. Maybe yeast works differently?
Some things our people would like to enjoy are listed below, and I would like to know how processing these treats would be different at 1 km below sea level, on Earth.
* Tea and coffee
* Buttered toast (they have vegetable margarine, actually)
* Poached eggs
* Cooking pasta
* Ice cream (or similar - sherbet?)
* Pancakes
* Pickles
* Fruit pie
* grilled fish (deep seafish)
* Turkey bacon
I believe I can derive the implications to other recipes from this representative group of culinary preparations.
**All ingredients are local, nothing came down from the surface pressure.**
[Answer]
In most cases, we boil things because it is a convenient way to stop at around a certain, useful temperature, only in very few cases, that I can think of, is the act of boiling the liquid necessary for the preperation of the food. Tea and coffee are actually best brewed at slightly less than 100C: [90-98 for tea](https://www.tea.co.uk/make-a-perfect-brew) and [90-95 for coffee](https://www.wholesalecoffeecompany.co.uk/blog/the-perfect-cafetiere-coffee-temperature-and-brewing/#:%7E:text=For%20the%20perfect%20cup%20of,adding%20it%20to%20the%20coffee.) so this isn't a problem: take the kettle off the heat when it hits this temperature, rather than waiting for it to boil (which happens at over 300C as someone else pointed out already).
Poached eggs are also best at [around that temperature](https://www.jessicagavin.com/poached-eggs/#:%7E:text=cook%2C%20and%20float.-,Optimal%20poaching%20temperature,a%20few%20breaking%20the%20surface.), and boiled eggs are apparently best cooked [even lower](https://www.seriouseats.com/the-secrets-to-peeling-hard-boiled-eggs)
With jams and pies, as well as cooking the sugar, boiling the water serves to reduce and thicken the liquid, which would happen at a massively reduced rate when the water doesn't boil, so another way would be needed to remove the water and thicken the sauce - although I don't know enough about cooking these foods to suggest one
As @Anders Sandberg poitned out in [your similar question on physics stack](https://physics.stackexchange.com/questions/574418/how-would-cooking-change-at-1km-depth-under-sea), you would have soem issues with food where steam bubbles act to provide temperature, such as omlettes, and you would probably struggle to get a nice microfoam for your lattes. Bread might have some issues rising.
I can't think of any issues with When cooking meat or other foods, other than that the air will [conduct heat a bit better at higher pressures](https://www.engineeringtoolbox.com/air-properties-viscosity-conductivity-heat-capacity-d_1509.html)
This is all assuming, of course, that it is possible to find a mixture of gasses that are breathable and won't explode at the first sign of an open flame!
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Issue with the question: saturation diving record is only 701m, and that was stopped prematurely because they were having insomnia and fatigue issues from the depth.
We don't have any gas mix that would work for saturation diving at 1km. (Much less extended saturation diving.)
(And even that 701m figure was *one diver* with an mix of 49% hydrogen, 50% helium, and 1% oxygen. The rest of the divers stopped at 675m and had to go back to 650m.)
The main issue is this: *every* gas appears to have narcosis effects "eventually" as you increase the pressure.
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Cooking in a high-pressure hydreliox mix would be weird:
* The thermal conductivity of the atmosphere would be far higher than usual, both due to the increased density and due to the gas largely being hydrogen and helium.
* Boiling wouldn't happen until a much higher temperature than usual. Fine for temperature-based cooking, not so fine for reductions and such.
* The viscosity of the air is far higher than normal. (This is one of the constraints for diving mixes, actually.)
* Many volatiles that normally boil off, wouldn't.
* Rising agents probably just flat-out wouldn't work.
* Beating air into a mixture may still work, but hydrogen and helium both diffuse through materials far faster than air.
* I... honestly have no clue how burning/charring/etc would work. On the one hand, oxygen would still have a substantial partial pressure (although not too much, because that would be toxic to the diver). On the other hand, oxygen is a relatively small component of the overall mix. On the gripping hand: I have a visceral reaction to the idea of hot objects in a mix containing both oxygen and a nontrivial amount of hydrogen.
(I wasn't able to quickly find a chart of the UEL of oxygen in a hydreliox mix w.r.t. pressure, unfortunately.)
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If you are in a sealed building at surface pressure internally, then I think cooking would work the same. If, however the pressure was higher for some reason, maybe necessary due to weaker building materials, you'd see some differences.
When at high altitudes, water boils at a lower temperature due to less air pressure. (See this wikipedia article <https://en.m.wikipedia.org/wiki/High-altitude_cooking#Boiling_point_of_pure_water_at_elevated_altitudes>)
I think this can be extrapolated to higher pressures, such that you may need to boil tea at 120 degrees Celsius.
Air pressure seems less relevant for other dishes, like ice cream or pickling.
[Answer]
**Cooking is difficult at very high temperatures**
At sea level, boiling point of water is 100 C and cooking oil is around 300-500 C.
At the depth of 1 km, pressure is 100 atm. Boiling point of water is 316 C and cooking oil is around 1200 C.
If you put an egg in boiling water at 316 C, it may be inedible in short time. Similarly, if you try to fry something in oil boiling at 1200 C, it will burn quickly.
In high altitudes, people use pressure cookers. May be you will need a sort of **vacuum cooker** at 1 km depth.
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Countless times in science fiction I have seen civilizations that rely exclusively on biotechnology; These societies, often due to environmental factors, never invented certain basic technologies needed for a conventional industrial-age technological environment, nor any of the technologies a conventional industrial-age technological environment is generally recognised as a prerequisite for developing or developing the prerequisites for, but despite this, they have developed technologies which fulfil the much of the same functions as our technologies but which are biological in nature.
My question, then, is can such a civilization actually exist? Can a society, under the right circumstances, develop a level of industry and amenities equivalent to the 21st-Century First World without certain technologies humans would consider basic by using biological means alone (at least past the industrial level)?
Now, when I initially asked this question, I was very vague as to how advanced the civilization could get by non-biological technologies before it no longer counted, so I will give the criterion that the cut-off is the industrial revolution.
For example, the following technologies would be considered to preclude a civilization from being "biotechnology-only":
* The steam engine
* The Stirling engine
* The internal combustion engine
* Electricity
* Automated weaving machines
* Sewing machines
* Automated printing presses
* Any method for making steel cheaply enough to use as a common bulk construction material
* Complex clockwork timekeeping systems
* Typewriters
* Any form of inorganic computer, including electrical computers and mechanical logic engines
Whereas a "biotechnology-only" civilization could still have the following:
* Fire
* The wheel
* Basic metalworking and metal tools
* Pottery
* Complex large-scale construction using stone, clay, and other nonbiological materials
* Plumbing
* Aquaducts
* Canal-building, including for transport and for irrigation
* The plough
* The seed drill
* Sailing ships
* Papermaking
* Manual printing presses (including movable type)
* Hourglasses, water clocks, and other primitive but effective timekeeping systems
* Advanced knowledge of mathematics and geometry
Bear in mind that the above lists are by no means complete or exhaustive and are simply intended to serve as examples of the general kinds of technology a "biotechnology-only" civilization could and couldn't share with Earth.
I'm sorry if this question is too opinion-based, but I couldn't resist good opportunity to analyse a trope that has become a staple of science fiction...
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I think the question is a combination of path dependence and technological balance at a point in time.
Dr. Freeman Dyson described in this speech at Boston University [Freeman Dyson: Heretical Thoughts About Science and Society](https://www.youtube.com/watch?v=8xFLjUt2leM) the difference between green and gray technology. Green is biology based and gray is physics-based. Human civilization became green with the development of agriculture and swung to gray mainly through electromagnetism. But, the story hasn't ended. Technology hasn't stopped.
Looking at the economic situation around Boston, we are much more of a green tech than a gray tech.
When we moved off the farm and into cities, we switched from the green of then to the gray of today. But, the gray technology has created tools to increase the reach of green (bio) tech vastly. We have better tools to manipulate green processes and apply creativity to green processes.
In my expectation, a biotech-dominated society wouldn't eschew physics technology, but on balance, if there is a biotech method, it would tend to be used rather than a physic tech method. If you looked at that society from a distance, you might see primarily biotech. If you were writing a story set in that world, the biotech portion of that society would be more visible. With more economic activity within biotech, that would just be a more interesting story.
Unless, you were writing about some lower-tier engineer working in physics tech, the under-appreciated portion of society, you might have an idea or a conflict that could be thought-provoking and entertaining.
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Could such a society exist? Sure, why not? We would have to think of 21st century 'industries and amenities', as you put it, that only work with inorganic technologies to prove otherwise. Yet the boundary between organic and inorganic is hard to pin down. Is a lichen 'stoneworking' because it feeds on stone? Hardly, but it just goes to show you that this line is fuzzy.
Imagine a world where life evolves but 'flora' take a completely different route towards homeostasis. There is no photosynthesis. They evolve some miraculous method of extracting energy from the neutrinos coming from their star ( consider that on earth at the surface of the Earth, the flux is about 65 billion solar neutrinos, per second per square centimeter). 'Neutrosynthesis' would then be at the heart of the energy economy of life on this world in the way that photosynthesis is on ours.
We can imagine that life takes a radically different course on this world, but it is still conceivable, to my mind, that 'fauna' eventually evolve, first in the oceans and perhaps even spreading to land. Crucially, the atmosphere would not contain much oxygen (most of Earth's oxygen comes from photosynthesis, which would otherwise be depleted by oxidation reactions). So there would be no possibility of discovering fire, which you highlight as a key 'gap' for bio-only civs. But fire is clearly an anthropocentric concept when considered chemically. We don't refer to rusting as 'fire', but that's merely a convention:
>
> Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction products.[1][a]
>
>
>
And note [a] reads:
>
> Slower oxidative processes like rusting or digestion are not included by this definition.
>
>
>
Who decides how slow is too slow to be a fire? When you look at it this way, every animal with a stomach has 'fire tech'.
I suspect the concept of 'metal-working' is vulnerable to the same line of approach.
Since there is no reason to project the human definition of 'bios' onto our hypothetical alien civilization, I think it is perfectly feasible to imagine a civilization that never discovers 'fire' or 'metalworking' as we conceive of it, though they would certainly need their own means for transforming energy and matter if they are to reach modern-day earth levels of complexity.
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# Self modification makes a lot of this a lot easier.
While a lot of these technologies are tricky without self modification, but if you can self modify you can do a lot of these better. Imagine a species that has an extremely strong self repair ability and regeneration. They are one with nature, as the phrase goes. They can then emulate a lot of technologies.
This would be likely to happen on a very metal poor planet, where their only native resources were biomass.
# The steam engine can be emulated by grafting people onto animals
The main reason the steam engine is useful is because it allows you to move people very quickly a huge distance. But birds are even faster. They can graft their brains onto birds, much like the [infamous Vladimir experiment](https://en.wikipedia.org/wiki/Vladimir_Demikhov) where he grafted a head onto a dog, and move huge distances. New bodies can be grown on site with enough biomass. More advanced technology, victorian level, would let you freeze a newly grown body so you could just plop your head on it and walk around immediately.
Likewise, more advanced experiments would let you replace the brain of a large elephant like animal to move large objects.
# Automated machines could be made with factory lines of sliced out brain parts.
A lot of the inventions are really useful because they allow you to train a machine to do a regular task. This could be replaced with a factory line.
Extensive experimentation in brain removal would discover that you could remove certain brain parts, and get a body that would do a regular task on command. People would repeatdly learn how to do a task, have that part of their brain sliced out, regenerate it, and repeat. This lets you make factories which can do whatever you want.
# Computers can be replaced with sliced out brain parts.
Rather than turning sand into electronic minds, you could turn brains into automated machines. Extensive experimentation with slicing out brain parts would discover you could network them together to do particular tasks. People supplying computers could repeatedly learn the needed skills, have that part of the brain sliced out, and supply more.
# Steel production can be replaced with biosteel.
It's extremely common in the animal kingdom to do biometals. Our bones and teeth are mineralized calcium, bacteria [use mineralized iron](https://en.wikipedia.org/wiki/Magnetotactic_bacteria#Magnetosomes) and [beavers use iron to strengthen their teeth.](https://www.researchgate.net/publication/44120196_Radula_synthesis_by_three_species_of_iron_mineralizing_molluscs_Production_rate_and_elemental_demand) Biological materials are custom made with precise structures, and are often stronger than their native compounds. Spider silk say is stronger than steel.
They can find a native organism which processes bioiron, like the beaver, and extensively crossbreed and modify it to produce biosteel, so they can have widespread access.
# Biomineralized silicon lets you make inorganic computers.
Some organisms [use silicon](https://link.springer.com/book/10.1007/978-3-642-55486-5) to grow internal structures. This could be changed by extensive genetic engineering to grow computer chips.
# Historical progress.
# Prehistory
The race in question, which we shall call trolls, is extremely hardy. Harsh conditions on their homeworld have forced most organisms to get extremely strong regenerative abilities. They regenerate any lost body parts rapidly, and can quickly heal from horrific wounds. Early experiments in prehistory with captive enemy prisoners discovers that if you grow a part of a troll with a fetus of a native organism then you can then crosslink the two. Unknown to them, this depended on luck and genetic compatibility, but extensive experimentation soon domesticated a number of native organisms, allowing them to be controlled by the trolls.
Families which did this had a guaranteed income, and formed guilds around controlling particular animals.
# Iron age
In the iron age a number of organisms were discovered that used iron from meteor hits to grow shells and teeth. While iron was still extremely rare, some prized weapons were grown from such organisms, and extensive breeding allowed the shape and size of such things to be customized.
# Medieval age
The domestication of a fast herbivore and a fast large bird allowed the feudal era to expand. People could cut off body parts, grow new bodies from them, have them shipped afar, and then fly their heads to them to be re-attached. This allowed a lot of mobility and movement, and many large troll empires were formed with the increase connectivity, and many large wars happened.
# Industrial era
Extensive experimentation with captured prisoners discovered that you could remove a part of the brain, and get a brain dead troll which would follow a certain set of rules. This, along with the discovery of several large meteor impacts in more primitive regions which had a lot more iron allowed the industrial era to begin. Large machines which relied on strung together troll brains allowed the mass production of useful goods and the expansion of the economies of advanced nations, along with more extensive use of iron and steel to make powerful war machines.
# Modern era
With their biotechnology substantially ahead of our own, they quickly discovered the secrets of genetics, cells, and modification. Experimentation with the losers of wars yielded many secrets, and new techniques, like multiple eyes strung together, were used to pierce the secrets of tiny things.
With this came the discovery of microscopic organisms which had much wider arrays of biological mineral deposition. One useful one used silicon as a type of skeleton, and experimentation discovered this could make a crude brain. Over time, computers, often crosslinked with troll brains, would start to spread, and civilization would reach the same heights as our own.
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# No, because telecommunications.
Humans have a limitation called a "Dunbar number" to the number of people that a single individual can maintain a theory-of-mind for. This is the limit to the size of a community that hasn't developed written record keeping.
Once you have writing, you can have civilization, but science will progress slowly. The invention of the printing press allowed the distribution of knowledge, and this was the spark that allowed the industrial revolution.
Can you come up with a similar method of distributing knowledge that is purely biologically based? What capabilities would a society need to already have in order to generate the required biology? Could they get to that point without mechanical means?
This conundrum is multiplied when you consider telecommunications. We might be able to move goods around the planet in a reasonable period of time, but moving information around is how cultures progress their social structures and technology.
Consider the simplicity of a telegraph. It's just a pair of wires with a little electricity. To do this biologically, you'd need a single organism (or colony thereof) that was thousands of miles long. Even then, it would be many orders of magnitude slower.
This gives you a feel for the difficulty in complexity leap between hard tech and bio-tech. Hard tech's essential simplicity means that improvements can happen orders of magnitude more rapidly than biology based advancements. The real question would be why any race would do one when the other was available.
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I'd say It's possible but without electronic tech's assistance in analyzing and allowing them to come to some manner of direct genetic modification as we are able to know it's going to be slow-going indeed.
What you'd have available to you through breeding would be beasts of specific burden(fast riding beast, slow towing beast, whale-like ships, maybe huge hydrogen jellyfish for things like hot air balloons(ludicrously unlikely, but aliens, so meh)), or housing/storage(reverse of hermit crab, imagine a beast that naturally grows a hollow shell that people, or other things, live in or use to store things, living urn, living house, what have you), or light sources(bio-luminescence).
A high heat source might be possible with help from certain bio-produced chemicals(bombardier beetle's stuff being able to reach 100C for example, for boiling water, maybe higher with higher quantities), but metal processing might be out of reach unless you happen to have a scaly foot snail on hand to breed so that its shell or whatever grows into the specific metal-bearing shapes that you want.
This all assumes that your people have the patience for guiding the glacier that is evolution, only being mildly faster and being able to be steered by the tiny boat that is your civilization pulling on the glacier by a rope and powered by a few rowers. Whatever path you go, purely bio-tech will be slow-going for civilization advancement, to say the least.
As for bio-civs being typically depicted as aquatic, it's mostly because life as we know it arguably runs on water(+ reactive chem fuel(food)), and running a bio-civ would require a huge amount of it so it's better to simply have them be in the ocean and be surrounded by it(electricity would also be a problem underwater). Hydrothermal vents might also naturally help underwater civs with being slightly more advanced than hunter-gatherers, hunter-gatherers with cooking!(don't make the mistake that most do of thinking they'll help with metal processing) I imagine the coral being like a naturally growing hard structure that their cities can be built out of also plays a part, though by that logic it's easy to imagine a land-based bio-civ using and growing trees for specific structures instead.
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I doubt it. The computers and electronics in a Smart Phone compute literally millions of times faster than humans, we have supercomputers that work literally trillions of times faster.
No biological organism can possibly match that speed. Or even the pixel accuracy of a movie playing on a Smartphone. Or the accuracy we get with thousands of computers working together in a supercomputer to do quantum chemistry simulations, or weather simulations.
Neurons just don't work that way, and nothing biological will ever work that way.
It seems doubtful any animal will ever replace the cost and fuel efficiency of an 18-wheeler, or will ever be able to run with a multi-ton load at 75 mph for 24 hours straight, stopping only for 20 minutes at a time to refuel.
Or will be able to deliver an intercontinental ballistic missile to suborbital heights, or will be able to fly at supersonic speeds, or even be able to carry a few hundred humans and their luggage at 575 mph over the Pacific Ocean.
There is a lot that could be done with precise genetic engineering, to be sure, but modern society depends on all sorts of stuff that can only be done in refined metals, with parts (like computer circuits) much smaller than neurons.
The smallest transistors are now 5 nm wide, while the smallest neurons are about 4000 nm wide. It **is** estimated it would take about 1000 transistors to simulate a single neuron, but that is not the point in this question: The point is, how many **neurons** would it take to simulate, say, a double-precision floating point adder at the same precision. That is only some hundreds of transistors, and it would likely be thousands of neurons if we could even do it with neurons, and in neurons thousands of times slower than the billionth of a second it takes the electronic circuit.
These are different domains, and the modern world rests on the electronic circuitry. Without non-organic technology, including steel, steam engines, forges, and electronics, realistically the world is in the realm of the ancient Egyptians. (But even they mined and forged copper tools and such.)
And without microscopes, X-rays and other non-organic technology, I find it highly doubtful we could get very far in genetic engineering, we would be blind to cell-sized organisms altogether.
A Biotechnology-only civilization would be a primitive one, farmers and herders with sharp sticks, atlatls to throw them, and flint knives.
Wait, does flint knapping count as a non-organic technology?
How about forming and firing mud bricks in a stone kiln?
Well, I'm sure they could cook food, at least.
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There is an odd species of creature with striking resemblance to a reindeer called Rudolphie, it has a red hue on its nose due to constant exposure to the cold condition of Arctic tundra and being bred by the Yeti to pull heavy sleigh. Eyewitnesses reported they saw the nose of Rudolphie emitting alternating red and blue flashes of light in close proximity, any idea what evolutionary pressure or diet could led to this bizarre encounter?
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It's a well known phenomenon called [*chromatophorism*](https://en.wikipedia.org/wiki/Chromatophore). Rudolph's nose is externally the normal color, but when sensing danger or otherwise aroused, the nose is flared to increase airflow and sensitivity; engorged with blood, the nose swells in time with the heartbeat, and the internal layers get exposed.
They do not actually emit *light*, but they do contain a phosphorescent pigment that makes it *appear* similar to a police blinker.
It is an [aposematic](https://en.wikipedia.org/wiki/Aposematism) display meant to convey that the reindeer is now alert and may be in fight-or-flight mode, so you better step carefully around it or risk being gouged.
Some reports claim that the same signal is also used by male reindeers during mating chases, to induce fleeing females to slow down and pull over.
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If I'm understanding the chart correctly, in order for a planet with lower gravity than Earth (smaller than Earth), but with decent magnetosphere, to hold on to an atmosphere with oxygen, and water on the surface, that planet would have to be in the blue but can be close to the green (between Venus and Mars)?
[](https://i.stack.imgur.com/78jmU.png)
And if I'm way off, please don't laugh at the science noob.
But you CAN laugh at the fact that I wrote *magento*sphere in the graph, instead of magnetosphere.
[Answer]
# Correct!
Atmospheric particles are constantly moving around at enormous speed. For instance, the typical air particle (the kind you're breathing right now) at room temperature moves at around [1,000 mph](https://pages.mtu.edu/%7Esuits/SpeedofSound.html). Since there are trillions of them, all moving in random directions, there is no net motion.
## Escaping Gasses
Earth's escape velocity is around 7 miles per second. If a gas particle is at the top of the atmosphere, and it suddenly achieves this velocity (as trillions are doing at this second), it will leave Earth's orbit, never to be seen again. However, in order for a gas particle to achieve this velocity, it typically has to be smacked by some very high-speed radiation.
## Keeping Gasses
As you have surmised, Earth's magnetosphere stops atmospheric gas particles from escaping in large number. It does this by deflecting high-speed cosmic radiation before it can smack into atmospheric gas particles. If Earth's magnetosphere were more powerful, even fewer cosmic radiation particles would make it through. If Earth's atmospheric temperature were lower, the baseline speed of atmospheric particles would be lower, meaning it would require even faster cosmic radiation particles to make an atmospheric particle reach escape velocity. A similar effect would be achieved if Earth's escape velocity were higher.
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You set the temperature to be around 250K. That means -23C or -9F.
I would say that's a tad too cold to have liquid water on the planet. If there is water it will be frozen.
Remember that at 1 bar water is liquid above 273K, so if you want liquid water, you need a temperature above that (or higher pressure).
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Strictly speaking, the escape velocity would decrease, but the surface gravity wouldn't *necessarily* change, depending on your planet's parameters. The two are determined by the mass $M$ and radius $R$ by
$$v\_e=\sqrt{\frac{2GM}{R}},\qquad g=\frac{GM}{R^2}$$
with $G$ the gravitational constant. You've picked the escape velocity, but we need to know another parameter to determine the surface gravity. Picking a mass or radius would work, but I think it's better to specify a density. After all, you don't want your terrestrial planet to have the density of gas! This gives us a third formula, for the density $\rho$:
$$\rho=\frac{M}{\frac{4\pi}{3}R^3}$$
If we specify $v\_e=7\;\text{km/s}$ and $\rho=5.5\;\text{g/cm}^3$, the density of Earth, we find that the radius of your planet is $R\approx0.56R\_{\oplus}$ and the mass is $M\approx0.18M\_{\oplus}$, leading to a surface gravity of $g=5.6\;\text{m/s}$, which is indeed lower than Earth's but still fairly reasonable! So it turns out that we didn't have to be concerned after all.
In fact, if you do out the algebra, it turns out that
$$g=v\_e\sqrt{\frac{2}{3}\pi\rho G}\propto v\_e\sqrt{\rho}$$
This means that you do have to change the density significantly to get a significant effect on the surface gravity, unless you're willing to change the escape velocity a bit.
Looking at some exoplanet models ([Seager et al. 2008](https://arxiv.org/abs/0707.2895)), it seems that this would be reasonable for a planet with more iron than is found in the terrestrial planets in our Solar System. There would still be quite a lot of silicates, as is the case on Earth, but you would need iron to reach the requisite density. After all, your planet is roughly the same radius as Mars but 80% more massive.
The temperature also looks fairly reasonable. You could honestly increase it a bit to make it easier for liquid water to exist, and all that would require is making its orbit slightly smaller or making its star slightly brighter. If your current [temperature](https://en.wikipedia.org/wiki/Effective_temperature#Surface_temperature_of_a_planet) is about 250 K, you could raise it to 280 K (closer to Earth's temperature) by decreasing its orbital radius by about 20%.
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In *How the Grinch Stole Christmas*, the town of Whoville is situated between a few drooping mountains. Here's an example taken from the movie:
[](https://i.stack.imgur.com/1KVBA.jpg)
The tip droops, and the mountains can rise either straight up, or as in this case, at an angle. I find this geographical feature fascinating, and I'd love to have mountains that droop as part of my world.
What geological history would it take to have mountains predominantly be of this type?
[Answer]
You cannot make that with stone, for it would crumble away.
You can maybe start with a sloped mountain, ending in a vertical cliff. Then, the slope is colonized by vegetation: a light, but ligneous and largely epiphytic vegetation that creates enormous mats. With the prevailing winds going upslope, over the centuries the whole mountain gets covered with a thick mat tens of meters deep. Strong roots keep the whole mat together.
Then, the mat starts growing over the top. Being much lighter than stone, and much more resistant to traction (you'll need to handwave this a bit, I fear), it does crumble slightly every year, but the growth is enough to compensate.
While ill-advised to stay immediately below the droop, because there's a more or less continuous rain of debris, the area below is inhabitable.
[Answer]
# Hoodoos and hand waving
A [Hoodoo](https://en.wikipedia.org/wiki/Hoodoo_(geology)) is an unusual geological formation formed when a softer rock is protected underneath a layer of harder rock. Here's an example from Wikipedia:
[](https://i.stack.imgur.com/e9XOq.jpg)
You could conceivably imagine a gigantic mountain that is gradually eroded over time, leaving just the drooping part that's protected by the layer of tougher rock. It's not likely that a mountain exactly like the movie would exist in nature, but you can wave your hands a little to make it sound plausible.
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Glaciers will do it, e.g. Preikestolen in Norway: <https://en.wikipedia.org/wiki/Preikestolen> and Mt. Thor in northern Canada: <https://en.wikipedia.org/wiki/Mount_Thor> A search for "overhanging mountains" will give many other examples. Also consider snow cornices.
Note that the droop in the OP's picture seems more like an effect of perspective...
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In our world, humans evolved and spread to pretty much every place in the world they could reach. Would that still be the case if there were, say, a dozen different humanoid species? Would they all fan out into every place that suited them, or would they tend to stick to their own areas and avoid the others?
When I say "humanoid" I mean any species that walks upright, makes tools, and speaks words of some kind. Neanderthals, elves, vampires, lizard men with chameleon skin - whatever. (I'm guessing the specifics of any given species would affect things, but I'm looking more for general rules.)
[Answer]
Niche environments and more migration:
Based on how migrations of humans have happened, I would say the prime real estate would undergo a lot of shifting as different species and sub-species vied for control of territory. On Earth, most parts of the World have seen many ethnicities push each other around or absorb the other groups after conquering them. This can involve the disappearance of the Y chromosome specific to the displaced group - in other words, all the men are killed and all the children are descended from the invaders.
In a world where the invaded is a completely different species that is likely not compatible, it means species will often face extinction or migration. There will be lots of pressure on species to fight to the death or find new places to live, which often means displacing yet another species from territory THEY are in.
Species that thrive in less desirable niche environments where there is less competition will have refuges they can withdraw to and survive until in a position to reclaim territory. Elves and dwarves might want farm land, but if times are hard, they pull back to the mountains or the forests and kill everyone who sets foot there. This may allow them to stabilize their migration pattern and assert periodic control and expansion into the neighboring lands.
Other species will need to be more nomadic or come up with better strategies to stabilize their control. Orcs might be able to interbreed with everything and still give birth to orcs. Humans might be good castle builders and diplomats. Vampires may be able to infiltrate other species and adapt to whatever conqueror comes along.
* At a guess, species would tend to spread out and control preferred environments, leading to dispersed races (possibly with quite distinct ethnicities) while more generalist species will spread widely as they are moved along by constant shifting migrations of other aggressive generalists.
* Lots of changing factors like disease, technology, symbiotic relationships, and new magical abilities or even the vagaries of the gods will alter this. Imagine a god tied to a certain region - invaders would be hard-pressed to invade the trollish land of Moloch worshippers, but a conversion of the hobgoblins to worshipping Moloch could leave the locals in real trouble. Dwarves friendly with humans might let humans migrate to lands cut off from others by mountain ranges. Elves in forests completely surrounding a large swamp might undergo speciation into swamp-elves after the fire-newts burn the woods to the ground. Rice production might mean lizard men thrive and dominate, until humans start growing rice and invading wetter areas for agriculture. The possibilities are endless.
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**They Must Live Entirely Separated or Have a Different Niche**
The [Principle of Competitive Exclusion](https://en.m.wikipedia.org/wiki/Competitive_exclusion_principle) puts the kibosh on any humanoids living in harmony together if they share the same niche. Homo Sapiens drove Neanderthals and Desinovians to extinction within a relatively short time period after we first encountered them, and this is because competitive exclusion ensures that the species in a niche with even the most minor of advantages is going to outcompete the other to the point of extinction.
If the humanoids are in separate geographic areas without contact until they are both advanced enough that they can create intellectual and technical solutions to resource competition (so not even modern humans lmao) than they can survive.
If the humanoids somehow occupy a different ecological niche, say by being exclusive consumers of plant material indigestible to humans than it’s also ecologically feasible
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Well, we already know the disastrous end the Neanderthals met *here* on Earth. Sapiens moved in and either shagged or outcompeted them into extinction. I think it would be fair to say that, at the very least, if Sapiens is involved in your world, they'll just do the same.
I think if the creation a/o evolutionary tracks of the various kindreds are a little better spaced out, then you might find a situation where certain kinds of people who are well suited to a niche (like swamps or forests or mountain halls) could thrive.
If you left Sapiens out of the picture entirely, or make them a minority, you might wind up with a better balance into the future.
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In Earthly ecologies, ecological niches are fiercely contested. In areas where wolves have been re introduced, the wolves have driven off the coyotes who had occupied the vacant niche. Similar things can be seen with the introduction of invasive species, if the "new" species has some competitive advantage over the existing species, they will overrun the ecological niche. This even happens with vegetation, such as the Kudzu vine.
In our own history, the Ancestors displaced the Neanderthals and Denisovians, and possibly other hominid species, most likely because the Ancestors moved in larger groups and were wired to cooperate more successfully than their cousins. This allowed them to exploit the resources of the land more fully, and living in larger clans and tribes the Ancestors had larger pools of skills and genetics - tiny groups of Neanderthals might fail if their one healer or tool maker died and could not be replaced in time, or diseases caused by inbreeding crippled the overall viability of the group. One might wonder if Neanderthal and Denisovian clans welcomed the Ancestors because they created a larger pool of potential mates (We know the Ancestors seemed partial to redheads, since the ancestral gene comes from the Neanderthals).
So multiple hominid species will eventually be reduced down to one. The only way multiple intelligent species could co exist (which seems implied with the question) is if they existed in entirely different and non overlapping niches, somewhat like humans and orcas. In that case, the interaction would be much different - if they were at similar levels of development then at the interface between the niches there would be stories of the strange and magical creatures of "the other place" who seem to be able to talk, and might be enticed to exchange gifts.
The situation where multiple Hominid species co exist only lasts for a short time, ecologically speaking. In the case of the Ancestors, they coexisted with the Neanderthals for several tens of thousands of years (likely because the Ice Ages limited the mobility of the various species), but once conditions had changed to the point the Ancestors began their expansion (eventually *walking around the world*), they rapidly displaced their cousins. If this was possible with primitive stone and wooden tools available to everyone, then the situation would be even more extreme if any species had more advanced cultures or technologies.
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***This question was edited based on answers already submitted***. I am designing a universe with both time travel and alternate realities, but I don't want the whole thing resting on hand-waving and paradox. I understand just enough theoretical physics to get in trouble. To resolve the paradoxes I see with the whole thing, I have put together three dimensions of time, and use discrete time states (universes) so time does not blur together. Time is treated as a three-dimensional analog to three-dimensional space.The entire multiverse is treated like a time object, so the fact it gets wider or thicker doesn't violate conservation. The expanding multiverse displaces existing timespace,so nothing is created, only transformed from unfixed (assumedly high energy) pluripotent reality (primordial chaos) to fixed reality. My understanding is incomplete as to if this should work and not violate generally-understood current theoretical physics, but I need a reality-check to be sure it works. Does this violate physics, and if not, are there paradoxes intrinsic to the design? If this is not the correct place to address this question, please tell me where that is instead of just shutting down the question.
1. **Causality:** The first dimension of time is causality (linear time). Every universe is a one-dimensional string. Cause follows effect in a classical "timeline." You can't alter your own timeline. Each moment of time represents a discrete time state and a separate strand of time. These strands may differ in spacetime as well as timespace; I'm not sure how it would exactly behave.
2. **Synchronicity:** The second dimension is synchronicity (horizontal time). All strands are set apart by a moment of time, off-set in a diagonal, so all points of time are happening simultaneously in separate discrete time strings. Somewhen a universe is being born, and theoretically somewhen the last energy of a universe is draining away. The Now is like a wave moving across the strings. You can travel to "your" childhood and change things, but the changes only affect that discrete strand, so when you go home your universe is still the same.
3. **Probability**: This is my least worked-out dimension and the least critical for plot (vertical time). All observable possible events happen, and the more they are observed, the thicker the observed universe gets (a bit like Schrodinger's cat, a new universe is created where each event happened).
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@DisasterlyDisco raised some very good points regarding the dimensionality of space-time and @AdrianColomitchi also points out fundamental issues with the presentation. With regards to this I'd like to elaborate while providing some insight into how to properly use the terminology of quantum mechanics.
# Intro
In physics, words like "state", "dimension" and "quantum" have very specific mathematical meanings. Thus a system based upon these concepts used incorrectly, to the trained ear, will not sound coherent and hence not realistic.
In quantum mechanics, a "state" refers to a mathematical formation known as a wave-function. The wave function contains information about the probability of that system having particular quantum number. These quantum numbers correspond to things called observable, which we can measure.
Now this is all very abstract (quantum mechanics is notorious for this), and so here's an example which hopefully will clear up how to use the terminology.
# A basic example: demonstrating how to apply quantum principles
Imagine you just have one particle: If this were classical mechanics its easy, you can describe everything about this physics of the particle with a few quantities: where it is at :(x,y,z,t), its momentum ($p\_x$,$p\_y$,$p\_z$) and its total energy: H = T+V, where T is the kinetic energy you can get from its mass and momenta, and V is the potentials that the particle is under the influence of. While this seems complicated, once you know all these quantities, you know everything there is about the particle, furthermore once you know these things, you can predict exactly how the particle will move: its velocity and its acceleration.
This is not true of quantum particles, which means that they must be described with wave-function. Lets look at a really simple example:
Consider just one quantum particle which is not under the influence of any potential. We would describe it with a wave function, to really simplify it lets restrict its motion to one dimension (the x axis):
$|\Psi \rangle$
So what is this particle doing? The answer, we don't know, but we can make an educated guess. For starters the particle might be propagating (or moving) in either the +x direction or the -x direction, so we say that its total wave function is the super position of these two "states":
$|\Psi \rangle = |\phi\rangle\_+ + |\phi\rangle\_-$
Now, this does not have the meaning (which is unfortunately the most pop-sci way to talk about this) that the particle is moving *both* in the +x and -x directions, what this means is that the particle has probabilities of moving in each of the +x and -x directions, and we can't know for sure until we measure the particle.
So we have the wave function, but where is the particle at. I don't have a x coordinate yet. How do I get it? The answer is that its buried in the wave function. So to get it out of the wave function you apply the position operator and perform what is called the "inner product" over an interval [$x\_a$,$x\_b$]:
$\langle \Psi|X\Psi \rangle$
Now I know the probability that the particle is between $x\_a$ and $x\_b$. But I still don't know where it is at. That's because that as good as we can get with quantum mechanics.
But what about its momentum, the answer same thing:
$\langle \Psi|P\Psi \rangle$
Don't worry about the math of how to do these calculations. That would require taking a university level course in quantum mechanics, and fortunately is not necessary to understand *how* this work.
So if we can't know the energy here, how can we ever talk about energy in quantum mechanics if we can only get probabilities?
The answer to that is the mystery of quantum numbers: in both quantum and classical systems particles *can* be anywhere. But in quantum systems, unlike classical systems, they cannot have just any 'ol energy value but must contain specific units of energy which may increment/decrement in discrete levels.
Again however, we can't know for certain the particles exact value, but only until we "measure" it. Measuring doesn't have to involve a scientific instrument, it just refers to an interaction the particle undergoes which collapses the wave function, and the "actual" values can be observed.
Now if you were keen on the math you might have noticed something a little strange here; I stated that taking the inner product of the wave function, when an observable operator
gets applied, returns a probability for the observable. But in our example above, the inner product of the wave function would look like this:
$\langle \Psi | \Psi \rangle$
which would expand to this:
$(\langle\phi|\_+ + \langle\phi|\_- ) (|\phi\rangle\_+ + |\phi\rangle\_-\rangle)$
and expanding completely:
$ \_+ \langle\phi|\phi\rangle\_+ \ + \ \_+ \langle\phi|\phi\rangle\_- \ + \ \_- \langle\phi||\phi\rangle\_+ \ + \ \_- \langle\phi|\phi\rangle\_-$
Uh-oh...
Our math only works if, under the implication that the states are orthogonal $\ \_+ \langle\phi|\phi\rangle\_- \ = \ \_- \langle\phi|\phi\rangle\_+ = 0$
But +x and -x are clearly not orthogonal, what gives.
This is because the **states** of the particle moving in these directions are orthogonal not the actual directions themselves.
# How this applies to the question
How does this answer your question? Lets go piece-by-piece:
**I have put together three dimensions of time, and use quantum time states so time does not blur together**
Using the example as reference, quantum states refer to wave-functions and not to physical dimensions such as x,y,z. While wave-functions incorporate physical dimensionality into their construction to be sure, they they only apply to the quantum particles themselves. As shown in the example, qunatum mechanics does not imply that individual states blur together until observed, but serve to provide probabilities regarding the actual values of the observables such as position and momenta.
We would not talk about a quantum "time state", just like there is no quantum position states or quantum energy state. There is a quantum state, which may be a super-position of individual mathematically "orthogonal" quantum states.
**The entire universe is treated like a time object, so the fact it gets wider or thicker doesn't violate conservation**
There about 16 conservation laws of which 6 are *always* true. If a conservation law is broken, we say that there is conditions for the law to be violated and we refer to this as symmetry breaking. So what is a "time object"? And which conservation laws does being a "time object" prevent the universe from breaking?
**My understanding says this should work and not violate generally-understood current theoretical physics [regarding the three dimensions of time]**
The usage of the word dimension here, is not consistent with the mathematical definition. The mathematical definition of dimension reference to the most basic element required to define a single point within a mathematical space. Your three "dimensions" are really three restrictions on how time works in your story, lets examine each one of them:
**Causality: The first dimension of time is causality. Cause follows effect in a classical "timeline." You can't alter your own timeline. Each moment of time represents a quantum time state and a separate strand of time.**
I agree that to form a logical system, you cannot violate causality. Not allowing your characters to alter their own timeline would be a good way to prevent causal paradoxes. However, the last sentence, doesn't really make sense as regards the usage of the physics language. See above regarding the meaning of "quantum state". To illustrate, a moment of time would be a meaningless formation for a quantum state, equivalent to saying "the quantum states of x = 3".
**Synchronicity: The second dimension is synchronicity. All points are offset by a moment of time, so all points of time are happening simultaneously in separate quantum time strings. You can "travel" to your childhood and change things, but the changes only affect that time state, so when you go home your universe is still the same.**
A "moment of time" as measure by whom? All time is relative to specific frames of reference in our own universe. This does not mean that time does not obey certain rules, it certainly does, but these rules allow for different frames of reference to measure time intervals differently than one another.
What is a "seperate quantum time string"? Is this a fancy way of referring to one universe within the multiverse? If so, how are these multi-verses connected. Look-up Brian Green's options for how multiverses can exist if you are interested in how to construct a multi-verse which doesn't violate the known laws of physics.
**Probability: This is my least worked-out dimension and the least critical for plot. All observed possible quantum events happen, and the more they are observed, the thicker the observed universe gets.**
What is the observed universe? This is a way of saying multiverse, or talking about the literal observed universe, which IRL consists of all the stars and galaxies we can see from earth. Does this mean that the actual universe somehow gets new universes appended onto it? From the previous descriptions it seems that you want multiverse.
Is the meaning that all possible quantum events occur, just not in the same universe, but spread through out the multiverse? If so, then I'd consider the implications of this. For instance, if a probability of a quantum number, as determined by a quantum state consisting of a basis of two states, is 0.3 for state A, versus 0.7 for state B, does this mean that in one universe state A is the actual state and for another that state B is the actual state (two overall). Or, does this mean there are seven universes with state B, and only three for which state A is the actual.
Also remember, that quantum states are very distinct from human decisions (for which the physics is currently unknown). Common trophes might regard monumental and pivotal moments in history: for instance, a president ordering a nuclear strike. In one universe, the strike is called off at the last moment and the world of tomorrow appears a few years later, in another universe the planet is in the depth of a nuclear winter with human life on the brink of extinction. While it sounds good, even if the multiverse hypothesis is correct, quantum physics does not support these kind of outcomes resulting from the collapse of quantum states.
Another similar concept is found in "random" events being cast as quantum events. So for instance, the villain has the hero on his knees and is ready to vaporize him, but decides to be "merciful" and toss a coin to determine his fate. The coin lands heads and the hero lives to fight another day, but the evil mastermind cackles...knowing the hero's been vaporized in another universe...Except this isn't correct at all. Tossing a coin is a **classical** event, which only appears random from normal level of baysian inference and is not decided by collapsing quantum states. To fully explain this would require an answer all of it's own.
**The expanding universe displaces existing timespace, so nothing is created, only transformed from unfixed pluripotent reality (chaos) to fixed reality.**
How is time-space transformed, allowing multiple actualized states to exist simultaneously with the creation of independent realities? And how does this not violate the first point regarding causality? What is the mechanism by which the "unfixed pluripotent reality" becomes "fixed reality"? Does this occur for every quantum event? And if so, how are the other "time strings" kept separate?
# Conclusion
I hope this was just enough quantum mechanics to help you to understand the terminology and demonstrate how the principles are applied without being bogged down with too much math.
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Based on your post it is really hard to answer your question succinctly. This is mainly because what you are describing is big, broad, and vague enough to be somewhat flexible. None the less, let me try to give my answers and then proceed with some clarifying questions of my own.
First and foremost, you ask whether or not your idea violates physics, and to that I'll have to answer No, but also maybe Yes.
What you are describing, a 3d time-space (for lack of a better word, not to be confused with space time), is not violating any known physics in so far as it is vague enough that I can't apply my understanding of physics to debunk it. There is enough though that I see some areas that can be clarified and fleshed out better, so that we can arrive at the point where we can apply some physics to it. So let's get to that.
You call this a 3 dimensional time, analogous to 3d space. There are two points I want to hit on here.
First, your three dimensions per your descriptions don't seem to span the same "space". Each of your axis in this timespace seem to describe different effects and they are not interchangeable. Compare this to classical 3 dimensional space where we can't truly discern directions as all three dimensions are the same in function. In this way the dimensions as you describe them are to each much more like what the time dimension is to the three space dimensions in 4d spacetime. Both space and time are part of the same spacetime, but the time dimension is discernible from the space dimensions. We can not truly discern left and right from up and down, but forward and backward in time is different in some ways from left and right. Because of this we also call our spacetime a 3+1 dimensional spacetime, and in this way your idea to me describes like a 3+1+1+1 space-causality-synchronicity-probability, more than a 3+3 space-time. (This kinda starts leading down the rabbit hole of [parity and time symmetry](https://en.wikipedia.org/wiki/CPT_symmetry), which is interesting if unrelated to relativity)
On the note of spacetime, I will put forward my second point. You liken 3d time to 3d space, but do not really touch upon the more modern understanding of our 4d spacetime universe. We know that space and time are just facets of the same spacetime and that transformations in one invariably leads to transformations in the other. So, how does your idea conform to 4d spacetime? How does your time react to gravity and acceleration of massive bodies? As you describe it, your causality dimension seems to be the most analogous to modern time and could easily be shoehorned in as the time dimension in spacetime, but what of your two other dimensions? How would they react? If your setting uses 4d spacetime as a basis (and i don't know if you want to do that, but if you do) then I think you should ponder how all your time dimensions and the classical space dimensions mesh together in a cohesive whole.
It is from the above two points that the "maybe yes" stems as how your setting works within these would determine whether or not they are in violation of physics, as you put. Do note that time is a stupid beast we aren't done wrangling, and that it is one the main reasons why we a still stuck without a joint operation between general relativity modern particle physics. If you truly find something that pleases both then publish that bizz with all haste. And if not, then don't pull out your hair over it.
As for paradoxes I can't really help you yet. It seems like you at least avoid the grandfather paradox with your Synchronicity dimension if I understand it correctly, but honestly it is hard to find paradoxes at the state of your description. I would love to look for them though if you feel like expanding on your idea.
Finally I am curious what you your concepts "time object" and "quantum time state" means in regard to your setting. I would also like to hear more about what you mean about time blurring together and why that is a problem.
This has been a bit of a ramble, I'm sorry about that, but I hope some of it was useful. It is hard to rally talk about the physics of time when that is very rarely the focus of physics. I would love to hear more about your setting though and hope that you will divulge more of your ideas behind your 3d time setting - I love a good time travel story :)
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`reality-check`, eh? Nope, the "time dimensions" that you listed can not be independent.
`Synchronicity: ... You can "travel" to your childhood and change things, but the changes only affect that time state, so when you go home your universe is still the same`
That travel violates the conservation of matter/energy - the atoms that make up you-the-traveller already exist at destination in other combinations.
If you , in your "synchronicity travel", did not take a trip along "causality" dimension, you have no way to make those atoms exists at destination.
If you do need to take the trip in "causality" dimension (e.g. make new atoms at destination) to visit the "syncronicity" one, it means that "casual time" and "synchronous time" values aren't independent, thus can't act as separate dimensions.
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If no trips are possible without mixing the "time dimensions", then there are no reasons to assume they exist as such, you don't have any means to test the hypothesis.
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## Ill-Defined Adjacency
The issue that stands out to me is one of adjacency in your causality strings. The way to describe it, each string is a full timeline of a specific universe. They are all lined up into a plane, with adjacent strings being offset by one time-unit.
The place a conflict arises is that if you travel horizontally, say to a timeline 5 minutes before your original, and say smash a plate. Now that timeline has a broken plate, but the adjacent ones do not, so all of a sudden the timeline are not different just by a single time-unit but also by a whole broken plate.
Allow this to happen multiple times and there can quickly be very little correlation between time-strings, and you instead end up with a pretty standard multiverse theory instead of a well-defined 3d timespace.
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The dimension of Synchronity is a preferred frame, which can't exist in physics as we know it. Also, if there are multiple time dimensions, then the universe would be unpredictable, unless there was only 1 spatial dimension, in which case everything is a tachyon
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In my story people are traveling from somewhere beyond the opposite side of the galaxy to Earth. The distance traveled is approximately 66 million light-years. I would like the travelers to experience 2,000 years of time.
How close to the central black hole must the travelers pass and at what velocity must they travel to achieve this 2,000 period of time in the traveler's time frame?
* Assume the starting point is beyond the opposite edge of the Milky Way galaxy exactly opposite Earth. My 66 million light-year reference is for convenience only. I recognize that the actual parabolic path will change the actual distance traveled.
* Ignore the need to travel around stars, etc., especially near the galactic core. For the purposes of this question, assume the black hole and distance are the only relevant factors (e.g., there are no other gravity wells).
* Assume the time to accelerate and decelerate are effectively instantaneous. How my travelers get up to speed and back down again is not part of the question.
* Bonus points are awarded to the answer that results in a practical set of equations for estimating distance from the black hole and velocity given an arbitrary time experienced by the travelers. In other words, if someone else wants the same kind of results but for the travelers experiencing 8,278 years, those equations would get them to reasonable values for distance from the black hole and velocity. JBH has promised that 250 reputation points will be awarded as a bounty to the best answer that also achieves this goal. (He's about to move to Montana, so if he hasn't posted the bounty by Monday, he might need to be reminded.)
*It is assumed that the gravitational effects of the black hole will compound the time dilation. If this is not the case, please explain why.*
[](https://i.stack.imgur.com/dXNjy.png)
Image showing start and end points, distance between central black hole and the trajectory of the ship, etc.
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How close you pass to the black hole is almost completely irrelevant. The galaxy is only 100,000 ly across, and the Earth is only about 25,000 ly from the center. If the aliens are coming from a direction diametrically opposite the Earth across the galactic core, only 75,000 ly of their 66 million ly journey will even be within our galaxy, let alone near the comparatively microscopic supermassive black hole in the center. That's just a little over 0.11% of their journey, to cross *the entire Milky Way*. Technically, yes, if they choose to make a close pass by the central black hole, that will contribute additional time dilation effects--but at the speeds you would have to travel to make this kind of intergalactic journey, they'll only be in a region where the time dilation effects of the black hole are comparable in magnitude to the pre-existing special relativistic effects for a few minutes of their whole 2,000 year proper time journey.
So, we just need to figure out their speed using the formulas of special relativity.
If the aliens' journey takes time $\Delta t$ in our frame, the amount of time that they experience will be given by $\Delta t\prime = \Delta t\sqrt{1 - \frac{v}{c}^2}$ Meanwhile, the distance that they observe themselves travelling at relativistic speeds will be given by $L \prime = L\sqrt{1 - \frac{v}{c}^2}$
$\Delta t\prime = 2000\ years$ and $L = 66\ million\ ly$, according to the problem description. Furthemore, $v = \frac{L\prime}{\Delta t\prime} = \frac{L}{\Delta t}$; i.e., the velocity of the spacecraft is equal to the distance traveled divided by the time it took to travel it, in either frame, because our speed relative to them is the same as their speed relative to us. Multiplying both sides, we can find that $L\prime = v\Delta t\prime$, and we can use that to eliminate a variable and solve for $v$:
$v\Delta t\prime = L\sqrt{1 - \frac{v}{c}^2}$
$v^2\Delta t\prime^2 = L^2 - v^2\frac{L}{c}^2$
$v^2(\Delta t\prime^2 + \frac{L}{c}^2) = L^2$
$v = \sqrt\frac{L^2}{\Delta t\prime^2 + \frac{L}{c}^2}$
Plugging in the actual numbers, $v = \sqrt\frac{(66\ million\ ly)^2}{(2000\ years)^2 + \frac{(66\ million \ ly)}{c}^2} = ...$ something so close to $c$ that even Wolfram Alpha doesn't provide enough precision to distinguish it.
With a little extra manipulation we can, however, calculate that the isolated gamma factor ($\frac{1}{\sqrt{1 - \frac{v}{c}^2}}$) is 33023, and $\beta$ (the velocity as a fraction of light speed) is 0.99999999954.
If you intend them to travel at a more reasonable cruising velocity, no approach to the black holes will help. Trying to rely on the general relativistic time dilation effects of the black hole to compress the proper time of the trip is like travelling at 60 miles and hour for 59 miles, and then wondering how fast you need to go for the last mile to make your average speed over 60 miles equal to 100mph (i.e., it can't be done). The only way the effects of the black hole might matter is if you want them to make a stop there and hang out for some significant amount of Earth-time, while still keeping the subjective trip time under 2000 years.
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I don't have a solution; what I do have is a possible path to a numerical solution.
For the sake of simplicity and sanity, I will consider the special case of a non-rotating, chargeless, spherically symmetric black hole. This black hole causes space to take a shape described by the Schwarzschild metric. A small test particle - which in this case can be our ship - obeys [the following general relativistic equations of motion](https://physics.stackexchange.com/a/47884/56299):
$$\ddot{r}=-\frac{G\mathcal{M}}{r^2}+r\dot{\theta}^2-\frac{2G\mathcal{M}}{c^2}\dot{\theta}^2,\quad \ddot{\theta}=-\frac{2}{r}\dot{r}\dot{\theta}$$
where $r$ and $\theta$ are polar coordinates centered on the black hole and $\mathcal{M}$ is its mass. In terms of $t$, we're working in the reference frame of the ship, so when we differentiate with respect to time, we're talking about the ship's *proper time*, rather than the *coordinate time* measured by an observer infinitely far away from the black hole.
These two equations are all we need to determine the path of the ship, given the initial conditions of the system (namely, the mass of the black hole and the initial velocity vector of the ship). We can vary those initial conditions until we get the result that we want; given that the ship can get arbitrarily close to the speed of light, there's no limit on the time dilation it will experience. It's going to take a lot of trial and error to get it right, but we can get there.
All that said, here are some more details.
## How do we solve the equations of motion?
There's no analytical solution to these equations, so we have to resort to numerical methods. Fortunately, the equations of motion are a pair of coupled, second-order, nonlinear differential equations. Being general relativistic doesn't make them inherently more difficult to solve than the Newtonian versions (though they're slightly different). We can solve them via any method you please. Here are some you might consider:
* **[Euler's method](https://en.wikipedia.org/wiki/Euler_method):** This is something you'd only want to do as a sanity check, although it's quite simple to apply in, say, Python, in a few minutes. Say your ship's position, velocity and acceleration at some proper time $t$ are $\mathbf{r}(t)$, $\mathbf{v}(t)$ and $\mathbf{a}(\mathbf{r}(t))$. Then the same variables, at a time $t+\Delta t$, are
$$\mathbf{r}(t+\Delta t)=\mathbf{r}(t)+\mathbf{v}(t)\Delta t$$
$$\mathbf{v}(t+\Delta t)=\mathbf{v}(t)+\mathbf{a}(\mathbf{r}(t))$$
$$\mathbf{a}(t+\Delta t)=\mathbf{a}(\mathbf{r}(t+\Delta t))$$
Euler's method is relatively inaccurate, though, compared to the host of numerical methods at your disposal.
* **[Runge-Kutta methods](https://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods):** Runge-Kutta methods are a broader set of techniques that have much greater accuracy and are substantially more widely employed than Euler's method (though Euler's method is a special case). The fourth-order Runge Kutta (RK4) is the most common, and also not too hard to apply, but [higher-order RK methods involve smaller rounding errors](https://scicomp.stackexchange.com/q/25581).
* **[The leapfrog method](https://en.wikipedia.org/wiki/Leapfrog_integration):** This method computes temporary values of position, velocity, etc. in between timesteps and uses them for calculations of the next step, leading to better accuracy than the Euler scheme. Furthermore, it conserves energy.
## A note on time
It's simple to calculate the proper time $d\tau$ measured by a ship traveling at a speed $v$ in some other reference frame measuring coordinate time $dt$, ignoring gravity:
$$d\tau=dt\sqrt{1-\frac{v^2}{c^2}}$$
Similarly, the proper time measured by a ship a distance $r$ from the black hole is, ignoring motion:
$$d\tau=dt\sqrt{1-\frac{2G\mathcal{M}}{rc^2}}$$
To put these together, you have to do [a little bit of thinking](https://physics.stackexchange.com/a/321920/56299) to find that
$$d\tau=dt\sqrt{1-\frac{v^2}{c^2}-\frac{2G\mathcal{M}}{rc^2}}$$
It should be pointed out, though, that we're solving the equations of motion in only one reference frame - that of the ship - and so we likely don't care much about doing this conversion at every point during the integration.
## An idea of the on initial conditions
To get an idea of where we'll need to start looking, consider the case of a ship in traveling 66 million light-years without any sources of gravity nearby. This is an excellent approximation to most of the ship's journey, where it will be far from the black hole and thus essentially not affected by it. For the ship's proper time to be 2,000 years while traveling 66 million light-years, we can see that $dt$ should be close to 66 million years, so
$$\sqrt{1-\frac{v^2}{c^2}}\approx\frac{2000}{66000000}\approx3.03\times10^{-5}$$
This implies that $v/c\approx0.9999999995408633$, a difference from the speed of light of less than one part in a billion.
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[Question]
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I was recently looking at [this question](https://worldbuilding.stackexchange.com/questions/138559/how-to-prevent-superluminal-traveling-idiots-from-wrecking-half-of-the-universe), which seems to argue that FTL travel within the existing laws of physics can risk resulting in the destruction of half the universe. (Specifically, bad things occur when anything moving FTL hits anything else).
So, say you've handwaved this issue to allow for less dangerous FTL travel, by entering a separate hyperspace dimension where the rules are different, or whatever else. But say this mode of FTL is only possible under certain circumstances, or perhaps your handwavium drive is broken.
Have you noticed how in space opera when the "hyperdrive" breaks, somehow the heroes still manage to get from here to there in a reasonable amount of time? "Slower" maybe, but they still usually make it to "the nearest inhabited star system." Basically, if we don't want to risk wiping out large portions of the universe, how feasible is this?
**In a situation where you cannot use your normal "safe" mode of FTL, how fast can you travel without risking an unacceptable "universe destroying" potential?** The speed of light? Slightly slower? And following these guidelines, how long will it take you to go anywhere? How long to get to Pluto from Earth, or to Alpha Centauri? Would the valiant Captain be dead before he ever arrived at the nearest hyperdrive repair facility?
[Answer]
## Universe-Destroying Potential Isn't the Problem
The problem with the linked question is the required energy, and it's the problem here as well. If you accelerate something to fractional-C, it takes more and more energy the closer you get to lightspeed. This energy will subsequently be released if that object hits something (which is the source of the excellent Mass Effect line quoted in the question).
But *getting* the energy is the problem. It's why in most hard-science space stories, ships don't tend to move too quickly, on an interstellar scale.
So, in softer sci-fi, the solution is hyperspace/warp fields/alcubierre drives. Bend the rules, or find somewhere where they don't apply, and travel very fast for much less energy.
All this is to say that if your FTL drive breaks, your ship won't have a *means* of accelerating to anything near lightspeed. It won't have dozens of times its own mass in reaction mass, nor a power plant capable of expelling that mass at the velocities needed to get your ship up to those speeds. If the drive breaks, and you can't fix it, you're hooped.
*However...*
A potential solution is, a la the old *Star Wars Expanded Universe*, that the FTL drive isn't binary. It can break a *bit*, but keep working. You can't go a million times the speed of light... but you can go a hundred times the speed of light.
This still can result in a long journey - if your drive's high gear breaks halfway to Alpha Centauri, resulting in the ability to travel only a hundred times the speed of light, it'll take a week to get to one end or the other, rather than the 2 minutes it'd take travelling at a megalight.
*Edit:*
So that aside, you needn't worry about universe-destroying potential, because unless your ship is independently capable of generating enough power to destroy the universe, it won't do so by doing whatever its best sublight speed is.
[Answer]
**Emergency fallback FTL travel.**
[](https://i.stack.imgur.com/5c2DP.jpg)
<http://www.minecraftguides.org/end-portal/>
You hate to have to resort to it. The maps are crap. There is beaucoup weird stuff in there. Sometimes you feel like it gets on you and then weeks later, you smell it again. Those horrible portals. A distant second best to friendly streak-starred hyperspace, to be sure. But if you gotta get there fast the portals might be your only option. Tie back your hair, fill your pockets with pennies and jump in.
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[Question]
[
I have some alien creatures which are essentially land-going octopoids somewhat larger than humans. Tentacles not being a good form of propulsion on land, they have rudimentary 'legs' with one bone each (I envisage something like cuttlebone). Would this be enough for a slow, shuffling walk? Do I need any other modifications to get walking a octopus? This is supposed to be generally cephalopod/mollusk.
**\* UPDATE \***
If anyone is interested, the walking octopoids, aka Spawn, feature in my new novel War of the God Queen. Thank you all for your help -- and let me know if you'd like a review copy.
[Answer]
Why walk? You’ve got a whole set of strong, flexible appendages. What you need to do is
**slither**
Consider a snake. It has no limbs, and no issue with locomotion. Your octopoid can use its tentacles in much the same way, flexing a few strong, thick locomotion tentacles and pushing along the floor with them. This helps it stay low and camouflaged in a grassland environment.
Or consider a caterpillar. Their undulating motion would work superbly for your octopoid, who could even take advantage of their omnidirectional tentacles to let them change direction near instantly.
Or consider a worm. Reaching out with the fore tentacles, pushing with the rear ones and dragging oneself along the ground might not be the most elegant form of locomotion, but in the rainy season it could be marvellously efficient.
Finally consider the octopus. Many of the ways octop(uses/i/oids/us) move underwater are still usable on land, especially when they snake their tentacles under each other to create the impression of a rolling, roiling Mass of Tentacular Doom.
Your octopoid will probably also be pretty smart, so switching modes or temporarily hoisting itself into the air atop a column of tentacles to temporarily get better vision probably won’t be too much of a challenge for them.
[Answer]
Having rudimentary "legs" may be enough for a slow shuffle, but another option might be temporarily using the hydraulic pressure of body fluid through the tentacles, much like [how a spider walks](https://asknature.org/strategy/leg-uses-hydraulics-and-muscle-flex/). A more detailed explanation of how this works can [be found here](http://jeb.biologists.org/content/jexbio/36/2/423.full.pdf).
Unlike spiders who have joints, your creatures have tentacles (no joints). This may cause serious issues for stability and control, but this changes the specifics how how the motion works, not the underlying concept of using hydraulic pressure.
For example, a sudden "flow" of fluid in the rear four tentacles would cause them to straighten with great force, possibly propelling (as in a "jump") or lunging (as in a strut or "shuffle") forward. The front two tentacles could use the suction for landing and positioning, with the side two for stability (much like how a human might "swing" on crutches when walking).
[Answer]
This isn't exactly the answer you asked for, but I think it may work well for your purposes.
You said in a comment that your species is on open, rolling grassland/prairie-like biomes, so there's lots of walking to do. I think it's problematic to envision that this species evolved in these prairies because, evolution-wise, wide open spaces heavily reward efficiency of movement.
So my suggestion is: it rides some quadruped like a horse, donkey, camel, etc. It didn't actually evolve in the prairie, but evolved in some nearby habitat and then migrated to the prairie after it domesticated this quadruped.
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[Question]
[
Based on a previous question asking about mechanical computing (Babbage engines, etc.) I wondered how a steampunk story could present the concept of a modern computer monitor in a steam-driven mechanical world.
**Background:** While pondering the problem of shrinking or otherwise utilizing mechanical computers, I wondered if their most limiting attribute wouldn't be the display monitor. You could meet the basic expectations of suspension-of-disbelief with a pocket-watch sized computer (the small watch gears, densely packed and spring driven, whirring away inside. Let's not worry about heat.). But what would I be looking at?
When my eyes were younger, I could comfortably read 6-point Times New Roman text. Printing a wheel with minimum inter-character spacing having 26 letters, 10 numbers, and maybe 10 punctuation marks (including the space), means a wheel with 46 minimally-spaced characters. The diameter of the wheel would limit actual character spacing on the "display" (the space between the characters I read would be equal to the diameter of the wheel). I could reduce that by half if I'm willing to live with letters that jump up and down, allowing me to [interdigitate](https://en.wiktionary.org/wiki/interdigitate) the wheels.
But, in the end, there's simply no efficient way to display text in this manner. I could use something like the old 1970s-era bedside clocks that flipped panels. But 46 characters would require 23 panels, which feels mechanically yucky (and so very 1970s...).
**Idea:** I propose for a steampunk universe a very small cylinder, it's height equal to its diameter. The cylinder is painted in five1 shades of white (creating a spectrum from white to black). Kinda like this:
[](https://i.stack.imgur.com/AjCkB.png)
The mechanics would spin this sucker around at a thousand miles per hour, pausing *briefly* whenever a color must be displayed. My pocket watch may have a "display" of 30x30 small spindles, allowing text to appear to scroll across the screen.2
*Clarification: in pixelated displays, everything is a graphic image. True, in the early days of computing dedicated hardware converted the concept of the letter "A" into the picture of the letter "A," but the distinction is one of advancement, not discovery. If the make-or-break point for the believably of the idea is moving pictures and not simply scrolling text, moving pictures are an easily dispensed with concept.*
Due to the spinning, the background color of the "monitor" would be the average of the colors on the spindle (which argues against using an odd number of colors) or 50% black.3
Theoretically, the cylinder can be made of a small enough diameter to produce a reasonably smooth, if rough to look at (you'll be wishing for that 8-color TRS-80) pixel display.
*Clarification: using a [modern reference for pocket watch sizes](https://pocketwatchdatabase.com/reference/sizes), the largest watch is about 16mm or 2.3 inches. Accounting for the glass size, let's assume 1.5 inches with a 30x30 pixel display for 20 dpi. Technically, the letter "H" could be made 4 pixels wide (including white space for the next letter) and 3 pixels high, but it's not the most complicated letter. Ignoring whether or not the display could believably scale text, let's assume 8-pixel-tall letters in three rows separated by some pixels for legibility. Remember, however, that as a pixelated display, it's only limited by the technology driving it. This question is more about the believably of the display than it is whether or not you can make a purely mechanical graphics card.*
**Ignorance:**
* Ignore the fact that 99% of the mechanics in a pocket watch and far too much of a "table top" mechanical computer would be given over to interpreting and processing display information and the control of the display.4
* Ignore the fact that such a solution would last a very short time before breaking.
* Ignore the fact that you'd need ear muffs to (literally) muffle the sound.
* Ignore the fact that the gearing itself may take too much space to permit a comfortably dense display.
* Ignore the size of the spring required to drive this. At the moment, it's being stored in an attached pocket universe and you'd need a modern power drill to wind it up.
**Question:** For a steampunk story, would the presented display appear too modern, out of place, to too mechanically unsound — or would it fit neatly into the "modern conveniences in a steam-driven society" that is the steampunk world?
*Clarification: If you're familiar with the American TV show,* [The Wild, Wild West](https://en.wikipedia.org/wiki/The_Wild_Wild_West) *(the original TV show, not the horrible movie), then imagine Artemus Gordon flipping this watch open to help Jim West save the day with some critical piece of info from Washington D.C.*
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1 *Frankly, you could paint 256 colors. The problem is that you need a wide enough mark on the cylinder to be visually discernible during use while keeping the diameter of the cylinder to an absolute minimum for maximum "screen resolution." I'm having trouble convincing myself that even 8 colors would work. 5 might be a stretch.*
2 *Part of my inspiration was an episode of the* Murdoch Mysteries *that used grayscale to transmit a photograph of a mystery woman to the constabulary. If only they had this device....*
3 *You could change the behavior to "park" on white or black and only "spin" to the color that's needed in any given moment, but that's a lot harder than "pausing" while spinning. Ultra-high-speed printers in the 70s and 80s used a drum filed with spirals of characters that constantly spun with hammers that struck the paper against the drum to print. It's fast and efficient — but not quiet.*
4 *If you don't believe this, please take the time to look up the processing requirements to convert "computer-speak" (electronically: binary) into the beautiful letters and pictures you see on your monitors today. The actual electronics involved in that process is substantial. Doing it mechanically may be DaVinci-esque and cool — but I'd hate to be the one to design and build it.*
[Answer]
Mechanical displays have been invented, and are in regular, day-to-day use. There are two dominating variants:
1. [split-flap display](https://en.wikipedia.org/wiki/Split-flap_display)
2. [flip-disk display](https://en.wikipedia.org/wiki/Flip-disc_display)
You could see your rotating cylinders as an advanced version of a flip-disk display: They are turning around like the flip disks to display a pixel, but they have more than two sides, so they can display more colors.
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However, for full gray scale, I would recommend cylinders with just two colors on them. One side is painted white, the other side is black. Adjust the orientation of these cylinders such that the visible amounts of the black and the white side matches the intended gray scale value.
I.e. To display a black pixel, just show the black side. For a white pixel, rotate by 180°. To display 50% gray, rotate by just 90°. For 25% dark gray, you need a 60° rotation, 75% is at 120°, and so on.
Text displays will only ever use pure black and white, of course. But a large display viewed from afar may easily provide the impression of true gray scale.
If you want to improve gray scale display, you can use three sides of the cylinder, allowing only 1/3 of its surface to be seen by means of a mask. The third sector would be painted middle gray, of course, and light gray would be displayed by displaying a portion of the white and gray sectors. I don't think that more than three sectors make any sense, as any further sectoring of the cylinder will force a reduction of the switchable pixel surface, and having grays displayed as a combination of a gray and a black/white sub-pixel doesn't seem too bad to me.
[Answer]
Your mechanism is way too complicated, error prone and uses much too much power for displaying just 5 colors.
Why not settle for 4 colors and build the "pixels" out of cubes with a different color on each side?
**Advantages:**
* No power consumption and noise when the display is not being refreshed. The cubes simply lock into their current position.
* Reliable technology. The colors are created by moving one side of the cube to the front, not by pulsing a constant rotation.
* You could have more colors than black, white and grey.
**Disadvantages:**
* The pixels must have margins between each other to be able to move.
* Neighboring pixels must move one after another to avoid collisions (or the margins would have to be even bigger). The refresh rate is halved, since every odd pixel can move first and every even pixel after that.
If you opted for 3 or 2 colors, you could even get rid of most of the margins. Use 2-colored tiles or 3-colored prisms instead of cubes, like a [three-messages-billboard](https://en.wikipedia.org/wiki/Trivision) mechanism. Unlike a cube, these objects don't need more space to spin than they need to display their color, so all of them can refresh at the same time without collision.
[Answer]
I have an alternative for you...
Each pixel is a small white-painted metal square on the end of a slender rod. For argument's sake let's say there is a "mask" with holes in it for each pixel. The square is perpendicular to the rod. They can be "plucked" to vibrate (think [thumb piano](https://en.wikipedia.org/wiki/Mbira)) by a hidden mechanism. The "further" they vibrate, the less time they spend visible (because the mask obscures them) so due to persistence of vision an arbitrary greyscale colour can be displayed.
The main issue is the amount of blank space between the pixels. The mask could simply be in interlaced strips, or tiny holes in a checkerboard pattern. Maybe that would actually make it look more steampunk-y.
[Answer]
[Re]-watch **Man of Steel**: <https://en.wikipedia.org/wiki/Man_of_Steel_(film)> and then see if you could do it better. You are not "bound" by any laws of physics in SF, but just keep the "laws" that you introduce consistent.
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[Question]
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I've got these 2 giant apes like creatures who are too heavy to go on the ship to be taken to another continent. What are some ways that they could possibly get across the sea? This is a medieval epic fantasy so I can't really fly them etc.. My apes are 12 feet tall and weigh 18,000 kg. They have to travel 510.8 km oversea, going from a desert like climate to and normal spring like one.
[Answer]
**Ancient undersea tunnels.**
[](https://i.stack.imgur.com/V8eMs.jpg)
<http://www.soul-guidance.com/houseofthesun/serapeum.html>
In your world, there are learned individuals who are aware that there exist tunnels built by a prior civilization. Half-drunken intrepids claim to have used these tunnels to traverse the oceans by travelling beneath them, and one of these was in possession of a crude map. Some of the symbols scrawled on this map defy explanation but the gist is clear: the tunnels cross the ocean.
This is how you move your apes. They travel willingly on foot, comfortable with their keepers and the treats they are given as inducement.
Everyone knows that ancient tunnels are full of monsters. And the only thing better than ancient tunnel monsters is having giant apes show up to battle them!
[Answer]
# Chain of islands
Cuba is 1000 km from South America, and Hispanola is 600 km. Yet, both of these islands got giant ground sloths from South America in the [Oligiocene](https://en.wikipedia.org/wiki/Pilosans_of_the_Caribbean), long before the sloths got to North America (which is closer to Cuba).
How did they get to these distance islands?
[](https://i.stack.imgur.com/WBLpz.png)
Lots of little islands! Going 500 km in one swim is a tough ask for a land creature, but a bunch of smaller hops is more obviously feasible.
While the sloths that actually spread to cuba were smaller, some ground sloths were [very large](https://en.wikipedia.org/wiki/Eremotherium) and could stand 12 feet tall, though not as heavy (although 18 tons is very very large for a land animal...)
[Answer]
**Biomechanics**
It has been [estimated](http://www.andrewcaelliott.com/explorations/2016/10/27/how-much-did-king-kong-weigh), using the **square cube law** that a 24 foot 1930s King Kong would weigh around 15,500 kg. Your ape is 12 feet tall and weighs 18,000 kg.
Clearly your apes are either extremely obese or extremely dense (in terms of mass not intelligence!).
**Tow them**
If they are obese to that extent then they aren't going to be able to move at all. I suggest you simply immobilise their arms and tow them to wherever you are going. They'll float easily with a harness fitted with floats and weights to keep them the right way up.They may hate it but what are they going to do?
If they are extremely dense then no wonder they don't like water - they would sink immediately! This also explains why boats aren't a good idea. If they move around too much they're going to tip most medieval craft over.
**Walk them**
If they are denser than water and not allowed to go on boats, the only option is to provide some sort of breathing apparatus and walk them along the sea-bed. Blindfold them and accustom them to the water gradually.
**Water skiing**
This is rather unlikely but if they are intelligent enough to learn, it might just be possible. They could rest at night by floating. A trireme shouldn't have too much trouble pulling them at a decent speed. <https://youtu.be/e131NJWTeuE?t=36>
---
When I have some time I'll do the actual square-cube law calculations. There is a likelihood that the body structure won't be able to support them unless they have a special kind of muscle tissue hitherto unknown.
***Square–cube law***
This principle states that, as a shape grows in size, its volume grows faster than its surface area. When applied to the real world this principle has many implications which are important in fields ranging from mechanical engineering to biomechanics. It helps explain phenomena including why large mammals like elephants have a harder time cooling themselves than small ones like mice, and why building taller and taller skyscrapers is increasingly difficult.
<https://en.wikipedia.org/wiki/Square%E2%80%93cube_law>
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[Question]
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[Segue 2](https://en.wikipedia.org/wiki/Segue_2) is a galaxy with only about 1000 stars and is 111 light years in radius. It has a light output only 900 times that of our sun. (This is a real galaxy in our universe)
However, I want my fictional galaxy to be small but have many habitable planets.
Is it plausible for a galaxy like this to be comprised mostly of solar systems with Earth-like planets? I'm looking for at least 100 Earth-like planets in the galaxy. And any galaxy under 3000 stars is ok.
Assume an exact duplicate of our universe's physics but not an exact duplicate a.k.a. I want probabilities, not statements of "there isn't one in our universe"
If only 1 thing is stopping this from happening e.g. Size/Age of the Universe please state so I can consider changing it.
[Answer]
# Galaxy size
The first question is whether such a galaxy (less than 3000 stars) is possible. The clear answer is yes; Segue II already satisfies those requirements. [Segue I](https://en.wikipedia.org/wiki/Segue_1) and [Willman I](https://en.wikipedia.org/wiki/Willman_1) appear quite similar in terms of size, mass, and mass-to-light ratio; they're small and likely contain a lot of dark matter. With populations of a few times $10^3$ stars, you're venturing into globular cluster territory, to be honest, but the large amounts of dark matter are more indicative of low-mass galaxies. I therefore agree with [Mark's assessment](https://worldbuilding.stackexchange.com/a/117326/627); this much is possible.
# Frequency of planets
You're looking to have approximately 10% of your stars host planets. This doesn't seem too far-fetched. [Estimates of the number of planets in the Milky Way vary](https://astronomy.stackexchange.com/a/10250/2153), but it's possible that there's up to 1 planet per star (according to [optimistic microlensing measurements](https://arxiv.org/abs/1202.0903)). I wouldn't expect a dwarf galaxy to be substantially less conducive to planet formation, so 100 planets is absolutely achievable in a Segue II-sized dwarf galaxy.
# Stability from encounters
The main thing I'm worried about isn't the formation of these planetary systems, but their survival. Globular clusters are often thought to be poor places for planets because close encounters between stars are common, and dwarf spheroidals often aren't great, either.1 We can calculate the mean time between encounters in a globular cluster to get an idea of the timescales a planet can survive on. [Beer et al. (2004)](https://academic.oup.com/mnras/article/355/4/1244/992851) give a formula for the expected time before a star passes a distance $b\_{\text{min}}$ from a star of mass $M$:
$$\tau=7\times10^8\left(\frac{n}{10^5\text{ pc}^{-3}}\right)^{-1}\left(\frac{b\_{\text{min}}}{\text{AU}}\right)^{-1}\left(\frac{M}{M\_{\odot}}\right)^{-1}\frac{v\_{\infty}}{10\text{ km s}^{-1}}\text{ years}$$
where $n$ is the stellar number density and $v\_{\infty}$ is the velocity dispersion. Say we want to compare Segue II to a typical globular cluster. We're looking at an approach to the same star with mass $M$, at the same distance $b\_{\text{min}}$. Then the ratio of encounter times is
$$\frac{\tau\_{\text{Seg}}}{\tau\_{\text{GC}}}=\frac{n\_{\text{GC}}}{n\_{\text{Seg}}}\frac{v\_{\infty,\text{Seg}}}{v\_{\infty,\text{GC}}}$$
We can make a rough estimate of the mean stellar number density near the center of Segue II:
$$n\approx\frac{\mathcal{M}/2}{r\_l^3\Upsilon}$$
where $\mathcal{M}$ is the total mass of the galaxy, $r\_l$ is the [half-light radius](https://en.wikipedia.org/wiki/Effective_radius), and $\Upsilon$ is the [mass-to-light ratio](https://en.wikipedia.org/wiki/Mass-to-light_ratio). I've assumed that half of the stars are within the half-light radius. Substituting this in, we get another expression:
$$\frac{\tau\_{\text{Seg}}}{\tau\_{\text{GC}}}=\frac{\mathcal{M}\_{\text{GC}}}{\mathcal{M}\_{\text{Seg}}}\left(\frac{r\_{l,\text{Seg}}}{r\_{l,\text{GC}}}\right)^3\frac{\Upsilon\_{\text{Seg}}}{\Upsilon\_{\text{GC}}}\frac{v\_{\infty,\text{Seg}}}{v\_{\infty,\text{GC}}}$$
The discovery paper, [Belokurov et al. (2009)](http://adsabs.harvard.edu/abs/2009MNRAS.397.1748B), measured $\mathcal{M}=5\times10^5M\_{\odot}$, $r\_l=34\text{ pc}$, $\Upsilon=650$ and $v\_{\infty}=3.4\text{ km s}^{-1}$, although [Kirby et al. (2013)](http://adsabs.harvard.edu/abs/2013ApJ...770...16K) say $v\_{\infty}=2.2\text{ km s}^{-1}$ at the most, using a larger sample of stars. [A typical globular cluster](https://www.ast.cam.ac.uk/%7Evasily/Lectures/SDSG/sdsg_0_intro.pdf) might have $\mathcal{M}=10^4M\_{\odot}$, $r\_l=10\text{ pc}$, and $v\_{\infty}=13\text{ km s}^{-1}$, [along with $\Upsilon=2$](http://iopscience.iop.org/article/10.1086/309998/fulltext/5759.text.html). Plugging this all in gives me $\tau\_{\text{Seg}}/\tau\_{\text{GC}}=67$, or $\tau\_{\text{Seg}}/\tau\_{\text{GC}}=43$ using the Kirby figures. In other words, planets should only survive for an order of magnitude or so longer in Segue II than in a globular cluster - which still isn't a long time.
# Stability from tidal interactions
I would argue that encounters with other stars are the main threat to system stability, at least near the center of Segue II, but I agree with Mark that encounters with another galaxy and subsequent tidal interactions could be problematic. Indeed, it's possible that some dwarf galaxies could be the results of more massive galaxies that were subsequently torn apart by neighbors (!). [Today's Astrobites article](https://astrobites.org/2018/08/02/what-happened-to-the-milky-ways-sister-galaxy/), in fact, looks at [D'Souza & Bell (2018)](https://www.nature.com/articles/s41550-018-0533-x), who argue that [M32](https://en.wikipedia.org/wiki/Messier_32) is the remains of a larger galaxy that was ripped apart by Andromeda.
It's also been suggested that a number of stellar streams around the Milky Way were once dwarf satellite galaxies. Candidates include:
* The [Helmi Stream](https://en.wikipedia.org/wiki/Helmi_stream)
* The [Virgo Stream](https://en.wikipedia.org/wiki/Virgo_Stellar_Stream)
* The [Aquarius Stream](https://en.wikipedia.org/wiki/Aquarius_Stream)
* The [Monoceros Ring](https://en.wikipedia.org/wiki/Monoceros_Ring)
It's unclear whether planetary systems could survive this sort of catastrophic tidal encounter. I would think they wouldn't, but it's always possible. At any rate, it's yet another possible danger to face.
---
1 The one planet we know of is [PSR B1620-26 b](https://en.wikipedia.org/wiki/PSR_B1620-26_b), in the globular cluster M4.
[Answer]
That's a very interesting question! It breaks into two parts: Can you have a galaxy of only a thousand stars and, if so, how likely is it that most of its stars would have an Earth-like planet.
First the question of galaxy size. The answer is a clear "maybe." The current theory of the formation of galaxies has them forming in parts of the universe where the dark matter was more dense and formed a gravity well for the ordinary matter to collect in. (AKA, the [Cosmic Web](http://cosmicweb.barabasilab.com/).)
As far as I know, we have never observed galaxies as small as a thousand stars, and I don't think our simulations of the interaction of dark matter and ordinary matter are fine-grained enough to demonstrate that such small galaxies are likely, but it's difficult to see what would prevent them.
Perhaps the biggest issue is whether they'd be stable once formed. Galaxies are *very* close together compared with stars or solar systems and their peculiar motion is enough to mean they interact more than once in their lifetimes. (In fact, there's a lot of evidence that big galaxies like the Milky Way grow by consuming smaller galaxies which pass too close.) Because a tiny galaxy's gravity well is so shallow, I'd expect that if they form, nearly all of them get disrupted by tidal forces long before the present.
So 1000-star galaxies are possible, but very rare.
As people have commented, there is no reason to think that the distribution of planet-bearing stars would be different in a 1000-star galaxy than in the Solar neighborhood, so you'd expect the fraction with Earth-like planets to be similar also. The fraction of stars which have Earth *sized* planets seems to be around 10% or 15%. At this point we don't have a good idea what fraction of them are Earth-like, but our own Solar systems gives a hint: We have two or three Earth-sized planets, and one is Earthlike. Given the anthropic principle is in play here (there had to be at least one since we're here) that has to be a strong upper bound on the fraction.
So the fraction of stars with Earthlike planets is probably in the 1% to 10% range.
Bottom line: Your scenario is *possible* but rather unlikely.
] |
[Question]
[
[Zerg Overlords](http://starcraft.wikia.com/wiki/Overlord) are flying alien creatures that aid their broods by managing lesser members of the swarm, transporting units within their carapaces, and alerting a hive about any danger they perceive with their heightened senses.
[](https://i.stack.imgur.com/nQHY1.png)
They are also quite large:
[](https://i.stack.imgur.com/6qKUp.jpg)
*An inprisoned overlord, with a human close to it for size comparison. The overlord's head is to the right (notice glowing eyes). Some images (which I cannot paste here due to copyrights and etc. suggest they may reach sizes at least twice as large as the one in the image.*
Last but not least, they are able to survive in space for an indefinite amount of time. For this question I'd like to ignore their capacity for interplanetary travel, though.
How close to a Zerg Overlord can an anatomically-correct creature evolve to be?
P.s.: in the Starcraft series of games, the Zerg are capable of controlling and speeding up their own evolution. I would like to leave that out of the question as well. I am more than satisfied with the most basic Overlord.
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It is difficult to say if a Zerg Overlord can evolve in real life - there is such variety of life on Earth that it certainly seems almost anything is possible. Perhaps an analysis of some close living creatures may yield some results:
* Portuguese Man-Of-War: This is not a jellyfish found in Australia, this is actually a small series of Polyps / organisms living integrated together in a colony. The 'sail' is an inflated gas bag of carbon monoxide and nitrogen, and can be 30cm long and 15cm high above the water (actually quite large if you see one). They float on water and suspend stinging tentacles for food.
[](https://i.stack.imgur.com/0Kmu9.jpg)
* Ants, such as the Red Harvester Ant: can communicate with each other using a complex system of pheromones. These airborne/surface chemical compounds can convey quite complex messages allowing the colony to react to new circumstances.
[](https://i.stack.imgur.com/y3dxA.jpg)
* Arachnids such as Scorpions: Many arachnid species carry their young on themselves to increase their chances of survival. Their carapaces have coatings and hairs designed for the purpose of carrying large amounts of their young.
[](https://i.stack.imgur.com/WImjr.jpg)
It may be possible for all the above attributes of creatures (although we are talking about creatures from several different species type) to combine to form your Overlord, however there are some significant obstacles to overcome:
* Atmospheric floating: Currently no large organisms have achieved this feat. To evolve this must be quite challenging as in over 200 million years on Earth we do not have a large floating creature yet.
* Size: Insects are limited in size due to oxygen being unable to penetrate their interior as they have no lungs. A circulatory system and lung system is required to convey oxygen throughout. The larger your organism though, the more problems you have, in weight, nutrients and complexity.
* Space: Space is a hostile environment for which currently no large organisms we know of is existent and able to survive both high levels of radiation and vacuum.
However, you never know. Given billions not just hundreds of millions of years of evolution it may be possible that a creature that large, who has those attributes, and survives in space, could evolve. It may be that 'life finds a way...'.
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So the problem with the Zerg when it comes getting something close to there size is that there aren't any know insects that have achieved the size of something that big.
I know studies have shown that insects have achieved the size of 2-3 meters or (6.5 - 9.8 feet) in times of Anicent Earth, scary but still not close to a Overlord from StarCraft.
An Overlord is Overlords retain the thick outer shell of the Gargantis, and it changed little in the assimilation process. Their exoskeletons are strong enough to resist a lightning strike.
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> **Overlords:** with the correct growth stimuli, [they] can carry other zerg within hollows in their hides. In this form they become deep-space transports; the importance of their function is underlined by the sheer number of overlords found accompanying zerg forces. As spacefaring creatures, an overlord's carapace pressurizes and seals whenever the creature flies through vacuum. Two species of unidentified symbiotic organisms seem to regulate these functions, though Dominion scientists have been unable to obtain any living samples—these organisms die within seconds if removed from their host overlord. Due to their need to support many different strains of zerg at once, overlords can sometimes exhibit spontaneous adaptive mutations in order to improve their own efficiency.
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Definition taken from <http://starcraft.wikia.com/wiki/Overlord>.
However exoskeleton animals developed in the ocean and then started to come onto land. So if were trying to get a creature that is close to be anatomically correct of I would suggest the Lion Jelly Fish in terms of size when it would be close.
The largest recorded specimen found washed up on the shore of Massachusetts Bay in 1870, had a bell with a diameter of 2.3 metres (7 ft 6 in) and tentacles 37.0 m (121.4 ft) long. Lion's mane jellyfish have been observed below 42°N latitude for some time in the larger bays of the east coast of the United States.
So my idea would be to have this jellyfish mutate in the water and develop an exoskeleton from mutation. This works as well since I believe Overlords use helium-filled gas sacs and a weak telekinetic psi-ability for lift and motive power. This helium is generated through an efficient respiratory system distributed throughout the overlord's carapace. The excess helium is stored in thick sacs that contract and expand through rudimentary pulses, allowing overlords to regulate altitude and propulsion at will. They move quite slowly however (if you are looking for it to float that is)
**Lion's Mane Jellyfish**
[](https://i.stack.imgur.com/QrOzj.jpg)
**Size Compassion for all Zerg**
[](https://i.stack.imgur.com/R9URe.jpg)
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**Giant tardigrade.**
[](https://i.stack.imgur.com/KsMHW.jpg)
<https://www.mnn.com/earth-matters/animals/stories/tardigrade-new-species-teach-us>
<https://www.newscientist.com/article/dn14690-water-bears-are-first-animal-to-survive-space-vacuum/>
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> Tiny invertebrates called ‘water bears’ can survive in the vacuum of
> space, a European Space Agency experiment has shown. They are the
> first animals known to be able to survive the harsh combination of low
> pressure and intense radiation found in space. Water bears, also known
> as tardigrades, are known for their virtual indestructibility on
> Earth. The creatures can survive intense pressures, huge doses of
> radiation, and years of being dried out. …
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>
> After 10 days of exposure to space, the satellite returned to Earth.
> The tardigrades were retrieved and rehydrated to test how they reacted
> to the airless conditions in space, as well as ultraviolet radiation
> from the Sun and charged particles from space called cosmic rays. The
> vacuum itself seemed to have little effect on the creatures. But
> ultraviolet radiation, which can damage cellular material and DNA, did
> take its toll.
>
>
> In one of the two species tested, 68% of specimens that were shielded
> from higher-energy radiation from the Sun were revived within 30
> minutes of being rehydrated. Many of these tardigrades went on to lay
> eggs that successfully hatched. But only a handful of animals survived
> full exposure to the Sun’s UV light, which is more than 1000 times
> stronger in space than on the Earth’s surface.
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The captive creature there has a very tardigradoid build, I think. 8 legs? Ask the girl on the ladder; she has a better angle.
In any case, the spaceworthiness is the highest bar and tardigrades can do that. Your creatures can be scaled up tardigrades.
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This is just a superspecialized bee.
The presence of a hive mind is already present within bees, and they can already fly.
The alerting other members of the hive is somewhat akin to pheromones, used by all eusocial insects.
The part about transporting lesser members of the give can likely be paralleled by it making and carrying a small mini-hive of sorts with a few cells to support worker bees.
Obviously the biggest flaw to my idea is that this "overlord" bee would have to be massive, possibly on the order of a few inches, mini-hive and all.
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In a lot of media one can see moons or other planets that cover a significant portion of the sky (like the background on this page for example). This could be because the moon is actually large or because it's close. Presumably, though, if a moon is *too* close or *too* large it will cause catastrophic gravity related destruction.
I'm wondering if it would be possible to have a planet that's more or less exactly like Earth, whose moon would appear to be much larger in the sky? Can it be, say 90 angular minutes without coming within Roche limit or causing deadly tidal effects?
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# 69 degrees of arc
### Apparent size in the sky
The formula for the [visual angle](https://en.wikipedia.org/wiki/Visual_angle) of an object is
$$\alpha = 2\arctan{\frac{2r}{2d}},$$
where $\alpha$ is the visual angle of the object, $r$ is the radius of the object (for a sphere, which is what we will be talking about), and $d$ is the distance from the viewer to the object.
### Limit of $d$: how close can a moon be?
The [Roche limit](https://en.wikipedia.org/wiki/Roche_limit#Rigid-satellite_calculation) for a rigid spherical moon, while taking its synchronous rotation into account is
$$d\_{roche} = \left(\frac{9M\_M}{4\pi\rho\_m}\right)^{1/3},$$
where $d\_{roche}$ is the Roche limit, $M\_M$ is the mass of the planet (Earth in this case, $5.97\times10^{24}$ kg), and $\rho\_m$ is the density of the moon.
### Limit of $r$: how big can the moon be?
The limit for the size of the moon is the point where the moon becomes more massive than the planet. Thus, the mass of the moon must be, at the most, equal to the mass of the Earth.
There are many ways we can express this mass, but wish to solve for $r$ in terms of something we are already using as a variable; namely, $\rho\_m$. Thus
$$\begin{align}M\_M &= M\_m \\
&= \frac{4}{3}\pi r^3\rho\_m \\
r &= \left(\frac{3M\_M}{4\pi\rho\_m}\right)^{1/3}.
\end{align}$$
That looks surprisingly familiar...
### Putting it together
We now plug our minimum $d$ and maximum $r$ into the visual angle equation
$$\begin{align} \alpha &= 2\arctan{\frac{2r}{2d}} \\
&=2\arctan{\frac{\left(\frac{3M\_M}{4\pi\rho\_m}\right)^{1/3}}{\left(\frac{9M\_M}{4\pi\rho\_m}\right)^{1/3}}} \\
&=2\arctan{(1/3^{1/3})} \\
&= 1.213 \text{ radians}.
\end{align}$$
The density terms conveniently cancel out, so we are left with a maximum value of 1.213 radians.
# Conclusion
If there are two Earth-mass planets orbiting each other as binary planets, at the closest possible distance based on their Roche limits; they would appear to be 69 degrees of arc wide in the sky.
There are actually infinite solutions to this problem. A less dense Earth-mass 'moon' would be larger in radius, but would have to be farther away to not be pulled apart by gravity. So you can have some variation here, within the reasonable bounds of planetary density. For example, an Earth-mass moon at the distance of Luna would have to be 1320 kg/m$^3$ to be the maximum visual size. That is barely more than the density of water, so it is unlikely unless it is mostly of gas like a gas giant (gas midget?).
So this speaks to your gravitational effects problem. Since gravity falls off as the square of distance, a lower density object farther away would have minimal gravitational effects.
Also note that this minimum orbit is almost certainly not stable in the long run. Any reasonable moon would have to be smaller. But if artificial means are acceptable, then you can have a short term stable satellite take up nearly half of the sky.
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Well... here are some back of the napkin calculations for you.
Nomenclature:
* M = larger body's mass
* m = smaller body's mass
* R = larger body's radius
* r = smaller body's radius
* d = distance between the center of the two bodies
* Theta = apparent angular size of the moon/planet in the sky
From scratching at a piece of paper, the apparent size of a moon in the sky is:
Theta = 2\*tan^-1(r/(d-R))
From [Wikipedia](https://en.wikipedia.org/wiki/Roche_limit#Rigid-satellite_calculation) the Roche limit for a rigid body (this is the extreme, but the math is a little easier):
d = 1.26r(M/m)^1/3
I pulled some numbers from [this table](https://en.wikipedia.org/wiki/Roche_limit#Rigid-satellite_calculation) and plugged them in to solve for Theta.
* Earth/Moon = 58.4 deg
* Earth/Earth = 150.9 deg
* Jupiter/Earth = 110.6 deg
* Sun/Earth = 103.4 deg
For the last two, I swapped the r and R in the Theta equation since it's the larger body's Roche limit we care about but the observer is still standing on the Earth.
Well those are fun answers. For reference the Moon is [about half a degree](https://en.wikipedia.org/wiki/Angular_diameter#Use_in_astronomy) or 30' (60 arc minutes in a deg). The take away would be that the biggest thing you can put in the sky is going to be a binary planet of equal mass. If you decide to have the Earth as the smaller body you get diminishing returns. These are closest pass numbers, most orbits aren't perfect circles so the moon doesn't have to look this huge all the time. Finally the real Roche limit is going to be somewhere between the rigid and fluid satellite numbers, I just did the rigid above and that lets the moon come a lot closer. So some in between distance isn't going to look nearly as impressive in terms of moon's apparent size. I'll look at the fluid stuff later and add it as an edit.
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**This question already has answers here**:
[How would my dwarves tell time underground?](/questions/53090/how-would-my-dwarves-tell-time-underground)
(6 answers)
Closed 6 years ago.
The majority of the calendars on earth have used either lunar or solar cycles to keep track of time, ie days, months, years.
What would a civilization cut off from the sun or moon use to keep track of time? Are there any geothermal or geomagnetic cycles that are regular enough for time keeping?
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# Biological clocks for cave dwellers are driven by hunger
In [experiments on Somali Cavefish](http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001141), which have been isolated from sunlight for million of years, the fish were found to be unresponsive to artificially imposed dark light cycles, but that their circadian rhythm could be modified by feeding them at certain time intervals during the day.
[Other variables](https://academic.oup.com/icb/article/53/1/50/629499/Biological-Clocks-and-Visual-Systems-in-Cave) that can control circadian rhythms include temperature changes and social interaction. [Most fish species](http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0030868) in rest-activity cycle studies maintain a near-24 hour circadian rhythm; this is probably due to having been derived from a surface-dwelling fish and having no reason to change the activity cycle. However, one species in the last linked study changed their rhythm to 38 hours. The authors do not propose any specific reason for the change to a 38-hour schedule, but it is possible that it was driven by the food availability or social interaction mentioned in the previous studies.
Lastly, in the last linked study, the cave dwelling species that maintained a 24 hours cycle usually slept much less than their surface dwelling counterparts. Surface fish slept in 2-3 hour bouts for a total of 12+ hours. The cave fish slept for many 15 min or less segments for a total of only 2-3 hours.
# A cave dwelling civilization organizes around communal feasts
For a species of cave dwellers with absolutely no contact with the surface and the sun, a likely result would be organize a time schedule around communal meals, ticking off both the hunger and social activity blocks for maintaining schedules. These schedules could be 24 hours, or any other time unit, apparently.
These creatures would probably not sleep continuously through a 'night' but would catnap throughout the day. Every 4 to 6 hours, perhaps, there would be a community meal, where everyone gets together and eats. For a stone-age level people, this meal would be regulated by the genetic circadian rhythm of each individual; the social interaction provide a means for calibrating the internal clock with the other members of the tribe. As technology advances, water-clocks or hour-glasses would begin to be used to help time the meals more precisely, until eventually mechanical clocks are invented.
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It would be good to note here that the way we currently keep track of time is completely arbitrary in the first place. We define seconds, minutes, hours, years and so on, but the truth is that any definition would make just as much sense as long as it was consistently applied throughout your underground society.
For the sake of convenience, let's assume that they use the same units with the same hierarchy as we do. Assuming also that these creatures have 10 digits, and thus use a decimal numbering system, it would seem to make sense that their units of time follow a decimal system too - i.e. 100 seconds = 1 minute, 100 minutes = 1 hour, and so on.
In that case, the main question here would be: what consistent, reliable natural pattern would they use as the basis for their second? Since most geological phenomena happen pretty slowly, these would not be great for timekeeping. Instead, consider that your society, at some point, developed The Pendulum. Perhaps some great thinker saw a large block of stone tangled up in an underground creeper, swinging all by its lonesome, and he had an " eureka" moment.
I imagine a small group of Watchers (pun intented), people whose job is to monitor The Pendulum and to reset it to some initial state at regular intervals (for instance, every 10,000 periods) so that the rest of the society may continue ticking along.
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**Sleep cycles / Days**.
Humans isolated from outer time signals slightly shift their routines to a 25/26-hour day. So it will be days for them.
**Years**
Years and seasons have still discernible effects. Water supply will be low in summer and high in winter.
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The concept of days and years was forced onto humans due to the existence of natural cycles we have no control over. Things like the sleep cycle and impact of the seasons. Our existing calendar is a mess mathematically, we have to somehow reconcile the length of a day with the length of a year which don't factor nicely, hence hacks like leap years.
Underground though with no seasons there is no such problem. The need to organise activity around the sleep cycle would probably require some kind of "day" unit being created to synchronise society. After-all you can't organise a meeting by saying "lets meet at sunrise or noon" in that case. The need for some kind of clock system to organise future events would probably be a lot more pressing. I can imagine people scurrying around the caverns whose sole purpose is to synchronise sand timers.
Once they have a day unit they don't need anything more. They can measure time just in number of days. Any official calendar created with longer periods would probably be far more logical, say base 10. Or they might use the age of their current king in days to denote historical events.
Any faint geological cycle, or even some sort of impression from the surface - perhaps some kind of bat species migrates down in accordance to season at the surface the humans cannot see - I doubt it would affect their calendar, such things would just be of some academic interest to a few mathematicians who are the equivalent of astronomers (or astrologers), who would look at the cycles to try and find meaning and generally be frustrated at how they aren't predictable and don't align properly with their measure of a day.
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**The earths rotation** would still work. Pendulum deviation could be measured. once they built long pendulums for any reason they will notice it.
[Foucault pendulums](https://en.wikipedia.org/wiki/Foucault_pendulum) in particular are particularly noticeable.
Timekeeping is even easier. Simple sand glasses, water clocks, and other escapement based measurements still work fine as well. The first of these did not match known cycles they just made them tailor made for particular purposes.
Edit: dumped the tidal force idea, possible but too unlikely to be noticed in the first place.
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Say you are a plant-based life-form (imagine a walking tree). You have roots and leaves.
You have two main vulnerabilities:
1. You need sunlight on your leaves for photosynthesis to get energy.
2. You need to root yourself in the earth occasionally to absorb water and nutrients.
And you also face a serious challenge if, like your non-sentient cousins, you lose your leaves for the winter and must enter a period of extended hibernation.
Additionally, your offspring are numerous, extremely frail and take a long time to mature.
**How can such a race build a successful civilization? Especially if challenged by other civilizations.**
***Clarification Update:***
*By "Civilization" I mean a society with towns, cities, governments, politics, armies, etc. These are not all required, but just to emphasize what I mean by Civilization. Not just a loose collection of beings, but a whole nation as it were.*
---
Some of the main issues I see:
1. The race must always have access to nutrient rich earth and sunlight.
2. The entire race might be hibernating at the same time.
3. Dependent on seasons.
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# TLDR; The same way any tree does!
The key to any plant based life form is numbers. You'll need to decide what you want your species' main "predator" to be.
Is it herbivores that like to feed on your offspring (seeds)? Depending on the herbivore, they have their own predators to worry about, and won't be able to eat ALL of your offspring before retreating to their own home. Are they a predatory animal that uses your race for habitat but preys on animals that feed on your offspring? Chances are your offspring are safe from these, as the population of this animal can grow as yours does. The mutual benefit of not only protecting your species, but making sure that your species grows is a boon to both parties, as yours is the reason their food gravitates to them.
Regardless of what you choose, being a tree, young saplings are less likely to be feasted on by the other kingdom.
The next step for your species is to create a [symbiotic relationship with fungus](http://www.kew.org/science-conservation/plants-fungi/fungi/relationships), as the decomposition of your species' corpses will renew the nutrients and provide more fertile soil.
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> On the other end of the spectrum, plants and fungi engage in mutually beneficial relationships, the most important of which is called mycorriza (plural = mycorrhizae) where fungi live on and in the plant’s roots. In this case both the plant and the fungus depend on this relationship to develop and survive.
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So you've now solved predators, and soil/nutrients. Seasons are the last problem for you to solve, but it is admittedly the easiest. Hibernation is something that not only plants, but animals do as well. Those that don't are either predators, feasting on small animals, or [don't leave their burrows for anything but leftover food (essentially the offspring of yours that didn't make it)](https://www.reference.com/science/animals-hibernate-during-winter-3faa98fbb06b8ea8). When winter comes, the majority of animals either save their energy for other pursuits (growing fur for hunting, and saving lipids), hibernate (or frequently take naps), or migrate to warmer climates.
Your species during these winter months will do what all trees do! Stop producing offspring, shed leaves, and [go into dormancy](http://www.mnn.com/earth-matters/wilderness-resources/stories/how-do-trees-survive-winter). Sunlight in this state is not really necessary, and your species will have the "instincts" to do this as a group, similar to animals. For more information about how the tree knows when to lose it's leaves,
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> Dormancy is like hibernation in that everything within the plant slows down. Metabolism, energy consumption, growth and so on. The first part of dormancy is when trees lose their leaves. They don't make food in the winter, so they have no use for masses of leaves that would require energy to maintain. When it's time for trees to lose their leaves, a chemical called ABA (Abscisic acid) is produced in terminal buds (the part at the tip of the stem that connects to the leaf). The terminal bud is where the leaf breaks off when it falls, so when ABA gathers there, it signals the leaf to break off. (This occurs only in deciduous trees — not in coniferous trees.)
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In the end, unless you're a coniferous tree, you have nothing to worry about but living a long successful life (until humanoids.....).
**If you're species is coniferous**, [the greater number of "leaves", and the reduction in the water they need is key](https://jnewbio.edublogs.org/2014/11/16/how-do-evergreen-trees-survive-such-long-winters/). As a conifer, you also have a special substance called cutin, which when combined with the lesser amount of water, will prevent the leaves from freezing.
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> These are very small and thin needles that can be thought of as a leaf tightly coiled together. They cover themselves in a waxy substance called cutin. These needles also require less water to stay alive and perform photosynthesis than leaf. The small amount of water and protective Cutin coating stop any water from freezing and killing any pine needles.
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In the end of it all, no matter what tree you are, you'll have a larger problem uprooting yourself than survival, and will move infrequently as a result of [photosynthetic energy being less than that of other methods](http://www.softschools.com/difference/photosynthesis_vs_cellular_respiration/146/).
If you compete with other trees, it'll just be a numbers game. If you produce more offspring or [have a more aggressive root system](http://www.treehugger.com/natural-sciences/trees-use-roots-to-fight-off-other-trees-says-study.html), then your tree will take over new territory than your possibly non sentient neighbors.
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> Using computer software to predict the growth patterns in forests over time, Dr. Dybzinski and his colleagues are now reporting that the overabundant roots act as weapons to prevent other trees from growing.
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The trick of having tree civilization is why? A tree does not need other trees, it may appreciate predator warnings from its neighbors, and may co-operate in root based defenses or support for inter-plant-species competition, but more or less each is an island onto itself.
But let them band together against the ax wielders or something. Do what humans do. In the early days we used guard dogs, let the tree-people do the same. Breed big mean predators to scare off herbivores and ax wielders. Build walls to keep interlopers out of the places you sleep. Make alliances and crush your enemies before they hurt you.
Cities might work differently, for humans a city requires large hinterlands of farming to support it, but for trees that is the meaning of a house. A pond and mud patch surrounded by high walls where you can dig in and feel safe. Multistory dwellings would be kinda unlikely since sunlight is the main resource. Roofs won't be a thing.
Think about how many trees a typical tree spawns, thousands of seeds for a few sprouts for a couple mature trees. This could be vastly improved upon; human raised trees are nearly one seed to one tree which could mean you will have huge population growth. If you care for your kids. If not you could let the seed scatter and welcome back any juveniles that prove smart and strong enough to find their own way home.
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Building on @NotStoreBoughtDirt's answer, perhaps it would be helpful to explore what a civilisation of sentient mobile tree-people might look like.
At the dawn of their civilisation, say early tribal organisations and limited technology, the most important innovations would likely be things like walls and domesticated predators to fend off herbivores. These would be especially important during the winter where even if they were still active they'd have a lot less energy to spare.
As their civilisation develops into something akin to classical antiquity, the importance of walls and predators would still be present. If there is conflict between tribes of tree-people then it would probably follow a similar pattern to human conflicts of the time, with a campaigning season during the summer and an off-season during the winter. You'd have to find a suitable resource for them to fight over though. Dirt and sunlight aren't exactly limited resources.
You might expect a boom of civilisation in equatorial latitudes where tree-people could operate year-round. Either tropics or equatorial river deltas like the Nile. Perhaps that's the resource they're fighting over. If you have temperate tree-people they may try to push into more tropical latitudes. If you have evergreen tree-people then they may pose a significant threat to temperate tree-people by being better able to campaign during the winter. Another option for a resource to drive conflict or trade is high quality soil, or water in arid climates.
I'd expect cities and settlements to be one-level and sprawling, and likely difficult to defend because of that fact. The invention of the mirror may be a significant development in city construction, allowing direction of sunlight within structures, allowing for better fortification and more compact and defensible settlements. The aquaduct and draught animals for transportation of water and soil would also be important innovations (speaking of soil, perhaps they sleep in soil to absorb nutrients seeing as they'd likely be dormant then anyway).
Electricity would probably be the breakout invention of your tree-people's civilisation, enabling all tree-people to be active year-round regardless of latitude, active throughout the night, and allowing our tree-people to explore hitherto unreachable destinations on their world. It would also allow far greater urban development and population density than ever possible before.
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On an Earthlike planet with one large moon (just like Earth's), I have a large landlocked sea with one narrow exit (like the Black Sea, but much larger, something like six or eight Mediterraneans, with an exit about 10-20km wide).
How extreme will the behaviour of the water be with the changing tides?
For example, will it be possible for a shipping port to operate on a decent-sized island in the exit channel? Will there be whirlpools most of the time, or only when the tide is running strongest?
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You are right that the tidal rip through the channel will be extremely fierce, in fact the island and edges of the channel will experience substantial erosion as a result so expect the channel to widen rapidly in geological terms. Even hundreds of years would make a difference, thousands of years certainly would.
The thing is though there is always a period where the water levels on each side are equalized, "slack tide". This will normally last for 1 to 2 hours on earth, in your case it would depend on the length of your day and the orbit of the moon but I would expect it to be similar.
[](https://i.stack.imgur.com/nZq17.gif)
This image illustrates it for you. You have periods of high and low water with the current also ranging between a flow in one direction and a flow in the other. At the point in the center of the flow curve you have "slack water" and at that point ships are safe to manoeuvre. You would need a sheltered harbour to keep ships out of the currents and as you say rips, whirlpools, etc would be fierce in the area.
So ships would time their passage with their tides, using the current to carry them close but arriving during slack water. They would come into dock and make sure they were secure before the tides picked up again.
To leave again they would head out during slack water but timed for when the tides are going in the right direction. As they head out the increasing tidal flow would push them along.
[Answer]
It depends on the shape of the sea. Generally speaking, tidal range is highly dependent on the actual geography. This being said, if the sea extends in a direction roughly aligned with the orbit of the satellite then in good places the tidal amplitude will likely be similar to what we have on Earth on the shores of the Pacific, that is, about 2 meters (7 American feet). If the sea extends mostly in the direction perpendicular to the orbit of the satellite the tidal range is likely to be smaller.
Remember that ports can operate will quite large tidal ranges; for example, Cardiff in the United Kingdom has a tidal range of about 15 meters (50 feet).
A narrow channel (or a pair of narrow channels around the island) can experience very strong tidal currents even if the tidal range in general is small. Look up Euripus Strait, <https://en.wikipedia.org/wiki/Euripus_Strait>.
[Answer]
Actually, I believe tides will be very limited there, because the narrow exit will limit the flow and the large volume will dissipate it. The Mediterranean sea has very limited tides compared to some other bodies of water. Depending on shape, the tide could be internal to the water body.
] |
[Question]
[
I want to have a [star cluster](https://en.wikipedia.org/wiki/Star_cluster) of [main-sequence stars](https://en.wikipedia.org/wiki/Main_sequence) (yellow dwarfs [like our sun], orange, and red dwarfs) that are on a distance of 1-2 light years between each other, so interstellar travel is possible even with sub light speed.
The cluster should be far enough from e galaxy core, beside that I don't care is it [open](https://en.wikipedia.org/wiki/Open_cluster) or [globular](https://en.wikipedia.org/wiki/Globular_cluster) as long as it's stable, and there's a planets where life could form.
How to keep the cluster stable, since from what I read [open clusters](https://en.wikipedia.org/wiki/Open_cluster) are very loosely bound by gravity? Globular cluster on the other hand are usually very old though there are [exceptions](http://www.astronomy.com/news/2005/01/the-galaxys-youngest-globular-cluster) like [NGC 1818](http://hyperphysics.phy-astr.gsu.edu/hbase/astro/ngc1818.html#c1)
How about having [intermediate-mass black hole](https://en.wikipedia.org/wiki/Intermediate-mass_black_hole) in the center of the cluster which the stars orbit like [Messier 15](https://en.wikipedia.org/wiki/Messier_15) see [video](https://youtu.be/rgvs3dl40ko?t=5m2s) ? Would it help or it makes more problems then it solves since I want habitable planets on the stars?
Would having all the star to be orange or even red dwarfs help with keeping them closer together?
**Conclusion**
It seems that my setting though very cool, seems unstable. To finish on a positive note here's a link to [NGC 6101](http://www.sci-news.com/astronomy/ngc-6101-star-cluster-black-holes-04177.html) cluster with hundreds of black holes, if life ever evolves there their astronomers will know quite a lot about them.
[Answer]
Let’s determine some basic parameters of the cluster.
You say you want the stars to be 1-2 light-years apart. This is a little tricky because star clusters don’t necessarily have uniform densities. Globular clusters, for instance, have radial density profiles decreasing from some core density at $R=0$ to zero density somewhere further out. There are several density profiles used to model this. The [Plummer model](https://en.wikipedia.org/wiki/Plummer_model) is easily the simplest, as analytic expressions exist for density and potential. The King model (see [King (1966)](http://adsabs.harvard.edu/abs/1966AJ.....71...64K), the third in a series of papers) is more accurate, though the density must be solved for numerically, and the Michie model can be even more accurate (see e.g. [this thesis](http://physics.wm.edu/Seniorthesis/SeniorThesis2005/shervthesis.pdf)), as it can account for dark matter.
I’m going to follow a modified version of the models of [Bonatto & Bica (2014)](http://www.aanda.org/articles/aa/full/2008/03/aa8616-07/aa8616-07.html), who use a King profile (here applicable to open clusters). The fraction of the total number of stars $N$ within a radius $R$ is given by
$$n(R)=\frac{x^2-4u\left(\sqrt{1-x^2}-1\right)+u^2\ln\left(1+x^2\right)}{u^2\ln u^2-(u-1)(3u-1)}\tag{1}$$
where
$$x\equiv R/R\_c,\quad u\equiv\sqrt{1+\left(R\_t/R\_c\right)^2}$$
with $R\_t$ and $R\_c$ being the tidal and core radii of the cluster; the cluster is truncated at $R=R\_t$. The authors recommend a ratio $R\_t/R\_c\approx15$. Therefore, we just have to specify one of those two parameters (we also know that $u=226$). The tidal radius can be computed depending on the mass of the cluster and its distance from the center of the galaxy (see e.g. [Wu et al. (2009)](http://batc.bao.ac.cn/papers/BATC-papers/2009wzy-26_2_029701.pdf)). That would require us to specify additional parameters, so I’ll assume that the cluster is average, and give it a tidal radius of about 10 parsecs. Thus, the core radius is roughly 0.67 parsecs. This could be an overestimate; [Piskunov et al. (2008)](http://adsabs.harvard.edu/abs/2008A%26A...477..165P), for instance, surveyed 236 open clusters in the Milky Way and found that the tidal radius peaked at around 6 parsecs. Still, 10 parsecs is by no means unreasonable. At any rate, I’d prefer a more massive cluster, so more stars may survive for longer periods of time.
Some quick *Mathematica* gives me
```
Clear[Rt, Rc]
x[R_, Rc_] := R/Rc
u[Rt_, Rc_] := Sqrt[1 + (Rt/Rc)^2]u[Rt_, Rc_] := Sqrt[1 + (Rt/Rc)^2]
n[R_, Rt_, Rc_] := ((x[R, Rc])^2 - 4*(u[Rt, Rc])*(Sqrt[1 + (x[R, Rc])^2] - 1) + (u[Rt, Rc])^2*Log[1 + (x[R, Rc])^2])/((u[Rt, Rc])^2*Log[(u[Rt, Rc])^2] - (u[Rt, Rc] - 1)*(3*u[Rt, Rc] - 1))
Plot[n[R, 10, 2/3], {R, 0, 10}, AxesLabel -> {"Radius (Parsecs)", "Number of stars"}]
```
[](https://i.stack.imgur.com/vT2po.png)
The actual number of stars inside $R$ is simply $n$ multiplied by the number of stars in the cluster, $N$. We’ll take $N\sim10^3$, a decently sized cluster. How do we now go from $n\cdot N$ to number density, $\mathcal{N}$ (just to make things more confusing)? Well, take the formula for the mass $M$ of a sphere inside a radius $R$ with radial density $\rho(r)$:
$$M=\int\_0^R 4\pi r^2\rho(r)\mathrm{d}r$$
Simply divide $M$ by the average mass of a star (which I’ll get to later, but is unimportant for now) and we get
$$n\cdot N=\int\_0^R4\pi r^2\mathcal{N}(r)\mathrm{d}r$$
We just differentiate and divide:
$$\mathcal{N}(r)=\frac{\mathrm{d}n}{\mathrm{d}r}N\frac{1}{4\pi r^2}\tag{2}$$
In the code, we add
```
P[R_, Rt_, Rc_] = D[n[R, Rt, Rc], R]*1000*(4*Pi*R^2)^(-1)P[R_, Rt_, Rc_] = D[n[R, Rt, Rc], R]*1000*(4*Pi*R^2)^(-1)
Plot[P[R, 10, 2/3], {R, 0, 10}, AxesLabel -> {"Radius (Parsecs)", "Number density"},ScalingFunctions->"Log"]
```
where I’ve replaced $\mathcal{N}$ with $P$, and we get, with a logarithmic $y$-axis,
[](https://i.stack.imgur.com/6b57c.png)
Note that the number density goes to infinity as $R$ goes towards the center (which we can check by simply evaluating the limit of $\mathcal{N}(R)$ as $R\to0$). However, we know that $n(R\_t)$ is finite (although $\lim\_{R\to\infty} n(R)=\infty$, which is why we truncated it). I played around with `Animate` for $N$:
```
Animate[Plot[P[R, 10, 2/3, Nt], {R, 0, 10}, AxesLabel -> {"Radius (Parsecs)", "Number density"}, ScalingFunctions -> "Log"], {Nt, 10^2, 10^5}, AnimationRunning -> False]
```
and found that you can get *extremely* high number densities in the center, if you so desire, which makes sense.
[](https://i.stack.imgur.com/2mBSK.gif)
To find the average separation between two stars, we calculate the [mean interparticle distance](https://en.wikipedia.org/wiki/Mean_inter-particle_distance), scaled correctly (i.e. the [Wigner–Seitz radius](https://en.wikipedia.org/wiki/Wigner%E2%80%93Seitz_radius)):
$$r\_s(R)=\left(\frac{3}{4\pi\mathcal{N}(R)}\right)^{1/3}\tag{3}$$
We add another section of code:
```
rs[R_, Rt_, Rc_] := (3/(4*Pi*(n[R, Rt, Rc])))^(1/3)
Plot[rs[R, 10, 2/3], {R, 0, 10}, AxesLabel -> {"Radius (parsecs)", "rs"}, ScalingFunctions -> "Log"]
```
and, plotting this function, get
[](https://i.stack.imgur.com/MBYoe.png)
We see that $r\_s$ is always greater than about 2 light-years for $0\leq R\leq R\_t$. Towards the center. Therefore, the systems you’re interested in should be near the outer edge of the cluster.
Hold on a minute, though. This is a density distribution based entirely on a sphere of stars, with nothing else influencing them. We’ve guessed that this models an open cluster fairly well, but we also need to assume that the cluster, if left to its own devices, is unstable, and the stars will drift away. Let’s try adding a central object, like you suggested - an [intermediate-mass black hole (IMBH)](https://en.wikipedia.org/wiki/Intermediate-mass_black_hole). This isn’t terribly far-fetched; it’s an idea that’s been explored quite a lot in the case of globular clusters. In open clusters, we have problems because we need to explain how the black hole got there in the first place. However, we can ignore that for now.
If there’s a central, massive object in a star cluster, the cluster should exhibit a [Bahcall-Wolf cusp](https://en.wikipedia.org/wiki/Bahcall%E2%80%93Wolf_cusp). Within a distance equal to one fifth of the black hole’s [sphere of influence](https://en.wikipedia.org/wiki/Sphere_of_influence_(black_hole)), the density should obey a power law of the form
$$\rho\_{BW}(R)\propto R^{-7/4}$$
Number density, assuming a roughly homogeneous population (again, more on that later), should obey this power law:
$$\mathcal{N}\_{BW}(R)\propto R^{-7/4}\tag{4}$$
All we have to do is calculate the sphere of influence, find the number density there according to the King model we computed, and fit the two together.
The sphere of influence, according to one definition, is
$$r\_h=\frac{GM\_{BH}}{\sigma\_0}\tag{5}$$
where $G$ is the gravitational constant $M\_{BH}$ is the mass of the black hole, and $\sigma\_0$ is the central stellar velocity dispersion, which I’ll choose to be about .81 km/s - modeled after observations by [Geller et al. (2009)](https://arxiv.org/abs/1001.0033) of [M35](https://en.wikipedia.org/wiki/Messier_35), a reasonably analog to our cluster. I’m going to choose $M\_{BH}\sim10^4M\_\odot$. We then get $r\_h\approx 6.25$ parsecs, and the Bahcall-Wolf cutoff radius is roughly 1.25 parsecs.
Let’s calculate the number density at $R=\frac{1}{5}r\_h$ from the King model. We get 17.44 stars per cubic parsec - quite large! If we then assume that the cusp stars there, we know that
$$\mathcal{N}\_{BW}(R)=17.44=A(1.25)^{-7/4}$$
for some constant $A$, which we find to be $A=25.77$. All we have to do now is to plot the two together in a piecewise number density function, defined as follows:
$$\mathcal{N}(R)=
\begin{cases}
\frac{\mathrm{d}n}{\mathrm{d}R}N\frac{1}{4\pi R^2},\quad 0\leq R\leq1.25\\
25.77R^{-7/4},\quad1.25\leq R\leq10\\
\end{cases}\tag{6}$$
Plotting this on with a logarithmic $y$-axis gives us
[](https://i.stack.imgur.com/axoH9.png)
Here’s the code I used to do the calculations and generate the plots (although you can play around with various parameters, like black hole mass and total cluster mass):
```
Clear[Rt, Rc]
Rt = 10(*Tidal radius*)
Rc = 2/3(*Core radius*)
x[R_, Rc_] := R/Rc
u[Rt_, Rc_] := Sqrt[1 + (Rt/Rc)^2]
n[R_, Rt_, Rc_] := ((x[R, Rc])^2 - 4*(u[Rt, Rc])*(Sqrt[1 + (x[R, Rc])^2] - 1) + (u[Rt, Rc])^2*Log[1 + (x[R, Rc])^2])/((u[Rt, Rc])^2*Log[(u[Rt, Rc])^2] - (u[Rt, Rc] - 1)*(3*u[Rt, Rc] - 1))(*Number of stars in King model*)
P[R_, Rt_, Rc_] = D[n[R, Rt, Rc], R]*1000*(4*Pi*R^2)^(-1)(*Number density from King model*)
rs[R_, Rt_, Rc_] := (3/(4*Pi*(n[R, Rt, Rc])))^(1/3)(*Wigner-Seitz radius*)
PBW[R_, Rt_, Rc_] := 25.77*(R)^(-7/4)(*Bahcall-Wolf cusp*)
np[R_, Rt_, Rc_] := Integrate[(1/1000)*4*Pi*x^2*PBW[x, Rt, Rc], {x, 0, 1.25}] + Integrate[(1/1000)*4*Pi*y^2*P[y, Rt, Rc], {y, 1.25, R}](*Total number of stars in cluster*)
Plot[n[R, 10, 2/3], {R, 0, 10}, AxesLabel -> {"Radius (Parsecs)", "Number of stars"}]
Plot[P[R, 10, 2/3], {R, 0, 10}, AxesLabel -> {"Radius (Parsecs)", "Number density"}, ScalingFunctions -> "Log"]
Plot[rs[R, 10, 2/3], {R, 0, 10}, AxesLabel -> {"Radius (Parsecs)", "rs"}, ScalingFunctions -> "Log"]
Plot[{Piecewise[{{P[R, 10, 2/3], 1.25 < R < 10}, {PBW[R, 10, 2/3], 0 < R < 1.25}}]}, {R, 0, 10}, AxesLabel -> {"Radius (Parsecs)", "Number density"}, PlotRange -> 10^3, ScalingFunctions -> "Log"](*Plots final density*)
```
Congratulations! You just built an open cluster!
Well, we built a simplified model of an open cluster, and we made more assumptions than I’d prefer:
* All the mass of the cluster consists of stars and the central black hole, which gravitationally dominates most of the cluster. In reality, there should be gas and dust in the cluster, because the stars formed from [giant molecular clouds](https://en.wikipedia.org/wiki/Molecular_cloud#Giant_molecular_clouds).
* The stellar population is homogeneous, i.e. all of the stars are the same. In general, this isn’t the case. Stars that formed together might be similar, but often they’re quite different. Their masses should be be distributed as predicted by some sort of [initial mass function (IMF)](https://en.wikipedia.org/wiki/Initial_mass_function). This created no problems so far, but it might when you take into account things like mass segregation that are important in globular clusters. If you’re *really* interested in fixing this, you can use something like the [MASSCLEAN](http://bogdan.massclean.org/massclean3.html) packages to generate star clusters via the King model and an IMF (the default is the Salpeter IMF). It’s a pretty cool tool, and can save you a lot of work.
* A King model defines the cluster. I’d be more comfortable using a King model to describe a globular cluster, and I see no reason why you couldn’t just have a young globular cluster - like [M15](https://en.wikipedia.org/wiki/Messier_15), as you suggested - but I’m okay applying our version of it to our open cluster.
None of these, however, are fatal flaws in our model.
So, is this cluster going to be stable over long timescales? That, after all, is the question we’re trying to answer. Well, to start, there are several things in our favor:
* The cluster contains $\sim10^3$ stars, which is a decent amount for an open cluster. I think that should make it more likely to end up with a sizable number of stars.
* The black hole is quite massive compared to the cluster - more massive than the rest of the cluster, in fact. I did this on purpose, because it means that the black hole’s sphere of influence is over half the tidal radius of the entire cluster. Again, this should make it easier to retain more stars.
Let’s do a more formal assessment (based on e.g. [these notes](https://www.ethz.ch/content/dam/ethz/special-interest/phys/astronomy/astro-dam/documents/education/courses/Astrophysics%20III/A3C3dynamics.pdf)). Let the mean mass of a star in the cluster be $m\_m$. By the [virial theorem](https://en.wikipedia.org/wiki/Virial_theorem), the speed $v$ of a star at $R\approx. R\_t$ is given by
$$v^2\approx\frac{GNm\_m}{R\_t}\tag{7}$$
The time it takes a star to travel $R\_t$, the crossing time $t\_c$, is
$$t\_c=R/v\tag{8}$$
and the relaxation time $t\_r$, the time over which encounters with other stars begin to have an effect on the motion of a star, is
$$t\_r\approx\frac{0.1N}{\ln N}t\_c\tag{9}$$
Furthermore, if a percent $\gamma$ of stars have a velocity above a certain critical value, then the evaporation time of the system is
$$t\_e=\frac{t\_r}{\gamma}\approx t\_r\times10^2\tag{10}$$
So, what critical parameters have changed now that we added the Bahcall-Wolf cusp? Well, we can safely assume that $m\_m$ and $R\_t$ are the same, as we specified them. It turns out, however, than $N$ has changed. Integrating over the piecewise density distribution gives $n(R\_t)=0.89$, meaning that we have fewer stars in the cluster.
At the same time, the total mass of the cluster is much, much larger, since the black hole’s mass is substantially greater than the mass of the stars. Therefore,
$$v^2\approx\frac{GNm\_m+M\_{BH}}{R\_t}$$
Having fewer stars and adding a black hole will lead to a much shorter relaxation time. Even if we extend the tidal radius (as would be expected), the black hole still won’t help stars at the outside of the cluster. I recall one paper noting that in the case of a black hole with a mass somewhat less than that of the cluster, most of the stars in the outer regions of the cluster will behave just as if the cluster was perfectly described by a King model, with no central black hole.
At the center of the cluster, there will indeed be some significant effects - and since the number density is much greater there, a large fraction of the stars should be impacted. I’m reluctant to draw analogies between stellar clusters and galaxies, but stars near the center should be influenced just like stars near the supermassive black hole at the center of the Milky Way, [Sagittarius A\*](https://en.wikipedia.org/wiki/Sagittarius_A*), orbit the black hole. The analogy is actually fairly good: Most stars in a galaxy don’t orbit the central supermassive black hole; they orbit the total mass of the galaxy. It’s a self-gravitating system, not a set of bodies orbiting one massive one. At the very center, however, stars are clearly orbiting Sagittarius A\*. The same holds true for our open cluster.
So, to summarize:
* Stars in the outer regions of the open cluster will likely leave the cluster at the same time or earlier than if there was no intermediate mass black hole at the center.
* Stars within the sphere of influence of the black hole, especially within the Bahcall-Wolf cusp, will be influenced strongly by the black hole and may directly orbit it.
* The cluster will largely “evaporate” on the same timescale (though likely a shorter one) than if it had no central black hole. However, I think the central group of stars will remain bound to the black hole. Eventually, this will be all that remains of the open cluster, if the orbits are stable.
* Whether or not life can survive on planets orbiting these stars is another question entirely, and I’ll deal with that in a future edit of this answer, if you want.
[Answer]
## This area probably won't sustain life for long
Having lots of stars this close feels like a stellar nursery, not a stable cluster. Nurseries are highly unpleasant places: lots of dust and gas racing around, super novas as young bright stars merge and explode.
I don't see how a large black hole at the center of the cluster will help. Starting with a true glob, eventually, all the orbital material will eventually flatten out into a disk shaped spiral galaxy. Stars that orbit off of the orbital plane will eventually collide or have their orbits bent to an orbit more in line with all the other stars.
## Dark Matter to the rescue!
An ordinary cluster will collapse on itself eventually without something to hold it apart. Since every star attracts all the other stars, the stars at the edge of the cluster will slowly creep in towards the center, compressing and collapsing the cluster. No more stars, but a gargantuan bang(!).
However, if there's an outer shell of dark matter that attracts the outer shell of the cluster, preventing them from falling into the core, the other stars might survive long enough to stabilize, form planets, host biospheres and hopefully intelligent life.
This is a fairly hand-wavey answer but it at least involves concepts we see in science publications now.
[Answer]
The half-lives for open clusters are gravitationally stable are for up to about 150 to 800 million years.
>
> Clusters that have enough mass to be gravitationally bound once the surrounding nebula has evaporated can remain distinct for many tens of millions of years, but over time internal and external processes tend also to disperse them. Internally, close encounters between stars can increase the velocity of a member beyond the escape velocity of the cluster. This results in the gradual 'evaporation' of cluster members.
>
>
> Externally, about every half-billion years or so an open cluster tends to be disturbed by external factors such as passing close to or through a molecular cloud. The gravitational tidal forces generated by such an encounter tend to disrupt the cluster. Eventually, the cluster becomes a stream of stars, not close enough to be a cluster but all related and moving in similar directions at similar speeds. The timescale over which a cluster disrupts depends on its initial stellar density, with more tightly packed clusters persisting for longer. Estimated cluster half lives, after which half the original cluster members will have been lost, range from 150–800 million years, depending on the original density.
>
>
>
Placing an intermediate mass black hole would act as a gravitational stabilizer if it was centrally placed in the open cluster. The OP is correct that the presence of a IMBH could have severe adverse effects on the integrity of the cluster itself and on any lifeforms inhabiting planets in the cluster.
>
> Open clusters range from very sparse clusters with only a few members to large agglomerations containing thousands of stars. They usually consist of quite a distinct dense core, surrounded by a more diffuse 'corona' of cluster members. The core is typically about 3–4 light years across, with the corona extending to about 20 light years from the cluster centre. Typical star densities in the centre of a cluster are about 1.5 stars per cubic light year; the stellar density near the Sun is about 0.003 stars per cubic light year.
>
>
>
If the IMBH is located in the cluster's core, this could kept the core stars in the cluster formation while coronal stars dissipate. This could leave a compact cluster that is three to four light years across. With the high stellar density in this remnant cluster core interstellar travel could be readily accomplished.
The loss of nebular gases will reduce the probable of the infall of gas into the IMBH and thereby reducing the hazard of high radiation levels associated with the black hole. there are adverse events, but they don't need to happen all the time. There will be windows of opportunity for lifeforms inside an open cluster to live uninterrupted lives and develop technological civilizations accordingly.
Basically it's not inconceivable scenario for an interstellar empire in an open cluster. Of course, it also conceivable for it to be unworkable. But making certain allowances it could happen, because it's not impossible.
REFERENCES:
All quotations above can be found in the Wikipedia entry on [open clusters](https://en.wikipedia.org/wiki/Open_cluster)
] |
[Question]
[
I'm asking for a world I'm making, which orbits a red star.
According to this image, there is a star that would make the sky white.
What would the sky look like during sunrise and sunset on a planet orbiting that kind of star?
[Answer]
What you are calling a red star is most likely a red dwarf star, probably further along the classification, because a M0 red dwarf will produce a pale whitish blue sky on an Earthlike planet. So to get to white sky it might be, say, a M5 or M6 star.
The reason the sky looks white is the light from the star contains a lot more red light than the light from our Sun. The blue colour of Earth's sky is due to Rayleigh scattering and because blue is shorter wavelength it gets more scattered than colours like red. the result is the blue colour smeared evenly across the sky, so the sky looks blue. With a M6 red dwarf its light will contain more red and since both red and blue are scattered the planet's sky now looks more whitish probably with a underlying bluish tinge.
At sunrise and sunset because there is lots more red light the sky of a planet orbiting M6 red dwarf star sunsets and sunrises will blaze with reds, scarlets and crimsons. They should be magnificent.
This answer hasn't discussed the role of particulates in the planet's atmosphere and has only dealt with the effect of Rayleigh scattering on a clear sky. More information can be found [here](http://www.xenology.info/Xeno/5.4.2.htm).
[Answer]
The sunset and sunrise would be similar to our own, but the red tones would come sooner and stretch further up the sky. The light in the evenings and mornings would be yellowish instead of pale.
[Answer]
The habitable zone is so close-in for very red stars that your planet will be tidally locked and always show the same face to the star. That means that the Sun doesn't actually move in the sky at all.
[](https://i.stack.imgur.com/MPM2g.jpg)
(see [here](http://nautil.us/blog/forget-earth_likewell-first-find-aliens-on-eyeball-planets) or [here](https://planetplanet.net/2014/10/09/real-life-sci-fi-world-4-earth-around-a-brown-dwarf/) for more details)
] |
[Question]
[
## Context
Six thousand years ago, magic users from Earth managed to create a portal between Earth and another planet, far far away. This planet is Earth-like but developed no life forms whatsoever.
Its new population started to terraform it, using both magic and biology. But even with magic, the process is expected to last at least ten thousand years more, and the planet still doesn't have a breathable atmosphere.
---
## The City
**Geography**
The wizard planet's biggest city, and capital, was built on a plateau. The plateau is bordered on one side by a massive mountain range, and by the sea on the other.
A river, taking its source in the mountains, runs across the plateau, just next to the city.
[](https://i.stack.imgur.com/hf93h.png)
**City plan**
A network of canals supplies river-water to the city and evacuate the excess water toward the sea.
The city is made of thousands of small blocks, hexagon-shaped and separated by large canals. Those canals are filled with algae, producing most of the city oxygen.
A spell maintains a tiny Earth-style atmosphere over the city. It protects it from solar radiations and prevents oxygen from escaping too much.
On the outskirts of town, this spell is a bit unstable. Sudden gusts of wind coming from outside the city can turn the air unbreathable for a few minutes at a time. That's why these areas are only used for tree plantations, and people going there have to bring special equipment with them.
[](https://i.stack.imgur.com/p8K0Y.png)
## Resources
**From inside the city :**
City blocks are multipurpose, they can support a mix of housings, vertical gardens, hospitals, markets, insect farms, schools, factories, etc. The city itself produce most of what its population needs.
* Vertical gardens (buildings used as multistory greenhouses) -> Fruits, vegetables, mushrooms and oxygen.
* Rooftops gardens (with beehives) & window boxes -> Flowers, wax and honey.
* Insect farms -> Protein paste and silk.
* Floating duck farms (they feed directly from the canals) -> Meat,
eggs, feathers and leather.
* Rabbits (kept in hutches inside houses and fed with peels and leftovers) -> Meat, fur and leather.
* Tree plantations -> Bamboo, rubber, arabic gum, fruits, nuts, cork, oxygen and wood (in relatively small quantities).
* Canals -> Oxygen and bioluminescent micro-algae, illuminating the canals at night and put in glass jars to light storefronts and houses.
* River -> Fresh water and energy to power mills.
**From outside the city :**
Hundreds of *stations* are scattered around the planet and are homes to a total of more than a million habitants. Stations can take many forms, from small towns to hovering mobile factories. Their primary functions are to grow algae, jellyfish and other stuff, then inject those in the oceans, and to plant lichen and grass on the most hospitable lands. They also produce useful resources.
* Sea-side stations (practice pisciculture) -> Salt, dried sea food and algae (mainly spirulina).
* Mining stations -> Metals, gems and stone.
* Planting stations -> Lichens and herbs, used to make dyes and medicine.
The exchanges between stations and the capital city are made using flat-bottomed "boats", made of metal and able to hover a few meters above any body of water.
**From Earth**
The inter-galactic portal is still active.
It's only used to do "educational travels", allowing wizard spies to study the technological progress made on Earth, to "save" gifted babies born from Earthlings and to dump the few non-wizard babies born on the wizard planet.
The portal is a well-guarded secret and can't be used for large-scale imports, or even to bring back objects bigger than a backpack.
**Magic**
In this universe, magic can't be used to create matter or achieve nuclear transmutation.
However, it can produce heat and light, accelerate the development of life forms, make things hover, improve physical abilities, power sentient automatons, create large-scale spells, etc.
Magic is not an infinite resource, and the vast majority of the population uses it only for the bare necessities, like heating food and charging magic batteries then sold to businesses, rich families or public institutions.
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## City-design problems
I'd like the *space wizards capital city* to have between one and two million habitants and to stay sustainable for the next ten thousand years.
A few minor problems :
* The city doesn't produce cereals (Maybe legumes can take their place?), or milk.
* The only source of leather is duck and rabbit skins.
* The only available fabric is silk (And maybe some kind of rough fabric made of bamboo fiber).
* I'm not sure white paper and cardboard can be easily produced (without using chemicals) from bamboo and/or algae.
* The wood production is small relatively to the population, small enough so that lighting a fire is a luxury (But for most of its uses, wood can be replaced with bamboo, metal or stone, and in this world magic can be used to produce heat).
* I'm not sure if the city needs to have electricity. Also I don't know what would be the most effective way to produce it (water mills ? wind turbines ? centrals using magic heating instead of charcoal ? ), and how they would manufacture all the equipment needed without the use of plastic, limited supplies of rubber and no modern manufacturing tools.
Those problems are not unsurmountable, but I'm afraid I missed bigger flaws in this city design.
There are certainly important resources I forgot to provide to the city, or some potential disaster I didn't think about.
The "important resources" may not be obvious (like food, water or light) but something a million-habitants city will need to keep existing for millenias.
*Note* : I'm *not* looking for methods to accelerate terraforming.
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## Question :
**Is this city sustainable and why ?**
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**Some useless information** (it may interest someone)
I decided that the city couldn't sustain farming bigger animals (like cows, horses or pigs), but it could change if necessary.
My story starts 6 000 years after the opening of the portal, and 10 000 years before the air of the planet becomes breathable.
[Here is a somewhat related question I asked a while ago](https://worldbuilding.stackexchange.com/questions/22409/smallest-set-of-plants-to-feed-a-population)
The protagonist of the story is a "normal" human, born in an aristocratic wizard family and dumped on Earth by his/her (I still haven't decided) parents.
Years later he/she is contacted by one of his/her siblings and returns to the wizard planet, only to discover that the only reason for this return is so their siblings could perform a spell.
This spell is supposed to allow them to locate their mother, who has been missing for months. It necessitates 7 children of the missing person to work, that's why they needed to get their ugly duckling back from Earth.
They don't officially accept our protagonist back in the family but disguise him/her as a servant, which allow him/her to explore the city discreetly.
The story is mostly about the protagonist running around, trying to elucidate mysterious things happening around the city and looking for a place in wizard society.
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A basic ecological fact: for the next several hundred million years, the oceans will be uninhabitable to almost all animals. That includes jellyfish, and whatever pisciculture you had in mind. With no oxygen in the atmosphere, there is no oxygen dissolved in the oceans, either. Until the algae and other plant life have conquered the ocean (and this requires an enormous variety of both plants and bacteria), oxygen levels will remain extremely low. Once the oceans are busy cranking out oxygen, only then can the rocks begin to oxidize, and with a world full of rock waiting to be assimilated, this is going to take some time. This actually happened with the Earth - see [The Great Oxygenation Event](https://en.wikipedia.org/wiki/Great_Oxygenation_Event) Only once the Banded Iron formations (or this world's equivalent) have been laid down will the atmospheric oxygen levels start supporting higher life. There are a few animals which are close to anaerobic, and can live at very low dissolved oxygen levels, but not many.
If you want to finesse this time requirement, feel free. Yours is a magic kingdom, after all.
So, let's say you've got these stations, "Stations ... primary functions are to grow algae, jellyfish and other stuff, then inject those in the oceans". You should realize that, if the oceans are colonizable, once you seed them with even a small amount of (let's say) algae, adding more simply won't help. It's the wheat/checkerboard problem - if the algae are at all successful, they will expand exponentially, and after a few years adding more from the stations will be just a drop in the bucket. What the stations might do is to provide more and more species (imported from Earth, obviously), with the goal being to increase biodiversity. Ocean currents will disperse the algae in (relatively speaking) a very short time. Once oxygen levels are up, it will only take a few loads of animals to begin explosive growth rates on that front, too, although the initial effects will probably be wild population swings until the ecosystems reach some sort of (possibly dynamic) equilibrium.
As shown, your canals are not canals in the usual sense. The Venetian canals, for instance, are part of a lagoon, not a river. The difference is that canals are part of an essentially stagnant body of water, while your "canals" will have appreciable flow rates. This means that you can't grow algae and such, since they will be swept out to sea. Rooted water plants may be a possibility, but be aware that these usually require soil to root in (not wet rocks) and this will require considerable preparatory work to produce.
EDIT - I suspect you're grossly underestimating the amount of plants and algae you need to support your city. [Here, for instance](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC376613/) is a paper talking about an improved algal system, and note that it suggests that such a system would provide the oxygen for one person with a power input of 30 kW. That's continuous. Figure that sunlight is about 1 kW/$m^2$ for 6 hours per day, and you need about 40 square meters of pond/lagoon per person. Note that going to vertical gardens won't help - the limiting factor is solar energy. For 2 million people, you'll need about 80 million square meters of horizontal surface, or 80 square kilometers.
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I think your city could be sustainable with a few tweaks.
For plant and animal resources, you could have your wizards introduce plants and animals that can exist in the planets atmosphere. These plants and animals could either be created by magic, or brought in from another planet (with another portal), or taken from Earth and manipulated in some way.
Perhaps these plants and animals cannot breathe our atmosphere, and they avoid the city and stations (but with the potential for attacks on your boats as they travel between the city and the stations).
If the planet could sustain its own ecology, most of your resource issues would be solved.
As for an energy source for electricity - maybe consider geothermal power, its potentially limitless and clean, and would work on the planet regardless of its current state. Perhaps you could have some Iceland-style hot springs inside your city's hexagon network. Or you could use the river itself as a source of hydro-power (I assume a station would be built to operate and maintain the hydro power station on the rivers banks).
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**A few problems you may have missed**
Medicine - What do the wizards do if they get ill? Magic it away?
Contraceptives - If these wizards have casual sex they will end up with a lot of babies to dump and people may get suspicious.
Transport - How do you get to the outposts? You may have mentioned this and I missed it.
Criminals - What do they do with criminals? Prison? Death penalty?
Drink/Drugs - Do wizards drink alcohol, I guess they could drink femented algae or something.
Rubbish removal - Is it just thrown through the portal because 1 million people will produce more than 1 backpacks worth of rubbish.
Dead bodies - Dumping dead through the portal is not a good idea. And throwing them in the sea seems harsh.
**Solutions**
Overall I think that your society would be sustainable if the wizards impose a few rules:
All rubbish must be reused or recycled as much as possible.
Only take people from Earth who don't drink or take recreational drugs. With no drink or drugs in your new world the next generation won't have even heard of drink and drugs.
Casual sex is banned. See my section on crime for the punishment.
Transport- Small scale, temporary atmospheres around boats on the river. For land travel you would need either some form of fuel for cars or as the wind seems quite powerful you could use ailing carts or goat pulled carts.
All dead must be cremated so that there remains can be kept hygienically or put through the portal without suspicion.
**Law**
Criminals breaking minor laws (theft, casual sex etc) should have to do community service maybe on one of the far flung outposts without the city comforts. Criminals breaking major laws should be killed, cremated and returned to Earth.
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Strictly speaking, it may be sustainable, but is it economically advantageous? I doubt that.
People don't just colonize for no reason. Europeans colonize to find spice and land (for agriculture, desert doesn't count). Space colonies in real life may have exported solar power, mined rocks, Helium-3, etc.
Your Earth isn't in danger, there is no resource that cannot be efficiently produced on Earth, etc. So, colonizing that planet would be hard work for no gain.
Your planet should leave the portal wide open, because food is more efficiently produced on Earth while you should think what is so special about this planet so mages want to live here. It can be free mana, or the fact that the planet is (initially) barren plus the star is brighter here, you can build massive solar panels here.
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Would it be possible to have a planet made up of about 60-70% water with no landmasses larger than Australia? I would like this planet to be as earth like as possible, but I'm open to changing aspects of it, such as rock composition, size of tectonic plates, etc.
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Yes it is possible to have a planet like that. But it will be different from Earth in a couple crucial ways.
You can have it in the habitable zone. You can have it near-Earth sized. You can have the same elemental composition. But you cannot have it tectonically active. Tectonic activity comes with high probability that the [cratons](https://en.wikipedia.org/wiki/Craton) would collide and merge to form larger landmasses.
The most primitive *continents* on Earth after the coming of water, were the size of large Japanese/Indonesian islands. There were a lot of them and they were moving around rather fast (due to tectonic plates motion). [Wikipedia article](https://en.wikipedia.org/wiki/History_of_Earth#First_continents) says:
*Although a process similar to present-day plate tectonics did occur, this would have gone faster too. It is likely that during the Hadean and Archean, subduction zones were more common, and therefore tectonic plates were smaller.*
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EDIT TO ADD
There is no such thing as *adverse* effects. What is beneficial and what is adverse is a completely subjective perspective. You may have a planet with a molten core and static crust. But you would have to heavily tweak several geologic features of your planet (especially the composition of the core and the thickness of the crust, along with the percentage of water and land). These changes are in their own right another subject of discussion.
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While Youstay Igo is essentially he correct that does sort of miss the point that for millions of years the planet can have the configuration you need.
While earth can have the layout you want you can make it more likely by a few simple adjustments. Essentially all you need is for there to be a little more water on the planet, or for the oceans to be a bit shallower, and then to split up the continents a bit more.
So far as we know there are no hard rules restricting the amount of water on a planet so you can adjust that along with the landmass positions to get your desired result for a few hundred thousand or even millions of years.
Eventually your landmasses will merge, but then they will split apart again. You have plenty of windows to visit the planet in where you get the layout you want.
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Early earth, pre-Pangaea and even pre-Laurasia, was kinda what you are suggesting here... so ya - it's not only possible - it has happened on our planet. Mind you, plant life had yet to alter our atmosphere to nitrogen/oxygen and the air was outright toxic to what we consider life now.
Major note is: you either need a relatively young planet with tectonic plate movement, or one without these plates (no plates will cause a very shallow ocean with a few islands poking out from volcanoes). Young tectonic plates works as well, though a few million years will see the rise of mountains as the plates crash.
I'd say it's easiest to go with no plates for this setup. Volcanoes will be the majority of your landmass... and they can grow really large (think Olympus Mons on Mars). That said, I'd have no idea what impacts to larger climate that would have. It'd be really weird to be in the middle of the ocean... and have it be 16 feet deep.
Added - remember you will not get island chains very easily in this setup. Island chains are created by a volcano as the plate slowly drifts over it...first island created by volcano, continent drifts and relocates the volcano island from the volcano,same volcano creates another island beside it and so on. Instead, you will likely have single landmasses (islands) that have a central volcano / mountain in the middle and overtly lush green lands down from there, desert for a bit, then ocean (use the large island of hawaii as an example). Volcanos should be decently regular as a planet without plates only has volcanic activity to release energy.
As an adverse effect..there will be a risk that the increased volcanic activity will poison the atmosphere with sulphur and other gasses that are not life friendly.
A second effect will be drastically varying life forms as each island is badly isolated. Each island could have its own very unique plant and animal life. Possible that introducing a creature from one island to another would collapse the entire islands ecosystem....tad bit more fragile.
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In early 15th century Europe, a cataclysmic event causes a tropical jungle to cover the whole world. The jungle is populated by very dangerous, aggressive monsters (think [Pitch Black](https://en.wikipedia.org/wiki/Pitch_Black_%28film%29)).
For unknown reasons, there are some safe zones of variable size that the monsters will avoid. In the larger safe zones, villages and towns have been founded, where the human race survives. Heavily guarded caravans travel between them, ensuring some trade. Each township is visited every 3-10 years (times vary wildly).
I'm interested in a village of 1000 people. This is the amount of people it can feed with the land it has. Before the Cataclysm, there were engineers, doctors, architects, and philosophers, but after the cataclysm, priorities and values have certainly changed.
After several centuries and countless generations, what impact would the limited space have? I'm especially interested in how their technology would evolve, and what values the society would embrace.
Maybe they will discard some specialized skills in favor of more practical concerns, like agriculture, or construction (space is the most precious resource)? I'm also interested in what technology they would *lose*.
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As @Hanko Tanks brilliantly wrote, agriculture and construction would be surely preserved. However, there's also something they would probably preserve and develop in different ways. What? **WEAPONS**. The monsters are a big problem, and the less the monsters can be a danger for the caravans, the more trade can be developed, the better is the life. Bows and knifes are too slow to use or need proximity, so the technology to build guns would be probably considered valuable, not just because it makes the people be safer, but also because, allowing more trade, it could help to share knowledge and products.
Another thing to keep in mind: **ELECTRICITY**. Why? If your monsters are like the ones in Pitch Black, then the fear light. Electricity (if provided by rivers) can light the night without exhausting resources like wood, which could be useful for constructions. It also provides energy for little machines that can have survived from the apocalypse. It' something people are very used, they wouldn't give it up so easily.
What would surely be lost?
* **Advanced medicine**. It requires special instruments, drugs that are difficult to produce, specific and complicated knowledge they needs years to be learned. Basic surgery would surely be saved, and some plants in the jungle could have medical properties, but everything that is not easily accessible would be lost.
* **Advanced technology of any type**. Every kind of tech needs complicated machines, lots of knowledge and much space where to build it. The first goal for the survivors is to survive and then to guarantee themselves the best chances to survive in the future, the quality of the life is an optional.
How could the limited space influence it? Main value: **life**. Risk would be considered silly (much more than in our society) and everyone who likes it an ill person. The limited space would impede growing: adding the difficulties to travel, it may rise a group identity similar to the one of some tribes or of an ancient city-state (with lots of differences, of course).
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### You're completely right as far as technological advances.
Two of the most notable technologies that would develop *in lieu* of other technologies would be agriculture and constructions, just as the OP mentioned in the question.
**Agriculture:**
These colonists have very limited space, as you stated in the question. Therefore, in order to increase their numbers, they will need to find ways to produce the most food in the least amount of space. As our time period is 15th century, it seems unlikely that these colonists will be developing advanced hydroponics for a few centuries. So, depending on how long you intend for them to remain 'trapped' in their safe haven, their best bet are crops with high caloric content.
Some examples of these crops might be *[potatoes](https://en.wikipedia.org/wiki/Potato)* or *[corn](https://en.wikipedia.org/wiki/Maize)* (maize). Also, these crops have high energy per unit. For example, potatoes release $321kg$ and corn releases almost $40kg$ more than that.
Growing these crops depletes the soil however, so you may need to cycle through certain crops to help replenish the depleted soil after a few seasons.
*All in all, this is probably your best bet for agriculture.*
**Construction and Architecture:**
In the 15th century, buildings did not extend more than 2 stories into the sky (3 may have been a rare occurrence, but was not unheard of).
The structural integrity of the building would limit these survivors more than their ability to produce food for their growing population. If their ground area is fixed and cannot be expanded, then the population will eventually reach a comfortable peak, after which quality of life will begin to decrease, reducing the population slightly.
### Unneeded or unsustainable technologies
**Animal Husbandry:**
I do not mean to say that livestock breeding will suddenly become a dead art, but it will be very localized and small in scale. Unlike the other two fields above, there really isn't too much in the way of consolidating animal breeding into a smaller scale. *For example: only one to two cows can reliably sustain themselves on around $5$ acres of grassland.* Keyword here is grassland.
Jungles do not offer much in the ways of lush grasses for livestock, usually undergrowth consists of [hearty ferns and plants that need little sunlight](https://en.wikipedia.org/wiki/Rainforest), because taller trees block the majority of the light coming in, and replaces it with shade.
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Since @HankoTanks has covered the food, I'm going to take a look at lost technologies.
A lot of Roman era technology has already been lost by the 15th C. Plumbing, Concrete and Large scale architecture being the most obvious. You're now going to start losing a few others before they really develop, the biggest of these being key to the period.
**Mining, Quarrying, Masonry, Blacksmithing.**
These are going to become very regional skills at best. Of course Mining is always regional, there's no point having the skills away from the mines, but quarrying for stone, dressing that cutting that stone for constructing large buildings is going to be lost. Why? Population pressures and a lack thereof.
The primary use of stone was defensive fortifications and religious structures. Without human conflict there's no need for stone fortifications, wooden ones will keep out animals. Without high population, you can't afford grand religious structures. These key skills would slowly reduce in spread to the point where they're effectively lost to the population. Not entirely lost mind you, given the nature of nasty beasts in the woods, spearpoints and arrowheads would among the most valuable of trade goods.
and one that's liable to be more widespread than it was.
**[The English Longbow](https://en.wikipedia.org/wiki/English_longbow)**
You're right on the button for something like this to become a more widespread technology as opposed to the crossbow which superseded it by virtue of not needing a highly trained archer. In a smaller group, hunting is liable to become a more widely required skill, both for adding to your food supplies and dealing with nasty things in the forest.
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Hopefully they won't lose agriculture, but I'd expect the low populations to slowly revert to stone age hunter/gatherer lifestyles, especially in wooded rather than rocky areas. Localised advances in hunting and fishing techniques offset by the loss of "advanced" technologies that require separate stages of production, mining/smithing, quarrying/masonry.
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[History of the Longbow](http://www.ryelongbowmen.org/history-of-the-longbow/)
The English Archery Law of the 13th century ensured that English men would be come experts with the bow and arrow. In 1252 the ‘Assize of Arms’ ensured that all Englishmen were ordered, by law, that every man between the age of 15 to 60 years old should equip themselves with a bow and arrows. The Plantagenet King Edward III took this further and decreed the Archery Law in 1363 which commanded the obligatory practice of archery on Sundays and holidays! The Archery Law “forbade, on pain of death, all sport that took up time better spent on war training especially archery practise”. King Henry I later proclaimed that an archer would be absolved of murder, if he killed a man during archery practise! The victories over the French at Crecy, Agincourt and Poitiers were directly due to the expertise of English archers and the longbow. Skill in the use of the longbow took considerable time. The English invested in the time required – the French did not. Up to this point the skills and weapons used by a Knight were deemed to be worth 10 ordinary soldiers – hence the French reaction to defeats by the common peasant.
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1000 people is not enough for any meaningful level of scientific research to happen, you may have 1 or 2 people who retain some scientific knowledge but there is no way they would have the resources needed to advance it. Instead they would act like librarians preserving knowledge for future generations and providing what advice they can to others.
15th century is both a good and a bad time for something like this to happen. It's good because most people are already subsistence farmers, and for those people very little would change. If something like this were to happen in the modern world a lot of people would starve to death very rapidly.
However it's bad because a lot of the scientific progress we currently enjoy has not yet happened, and even those advances that had been made were not commonly known. Your society will need everyone growing food, treating the injured, defending the village from monsters, etc. There will be no spare capacity for anyone who isn't providing immediate benefits, and scientific research does not provide immediate benefits.
So in other words technology would stagnate at whatever point it was at when this happened. There might be minor tweaks or improvements and adaptation to the new environment but in general everything would continue as before but without any substantive progress being made.
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**Slash and burn agriculture**
While the colonists are likely unable to penetrate the dense jungles directly, they will often need to fight off the dangerous supernatural jungle beasts. Since limited trade is possible, the beasts are almost certainly not invincible.
As a result, it would be necessary to fight these monsters from time to time. Fighting the monsters in the jungle would be a terrible idea, just think Vietnam War, without the overwhelming technological advantage.
Burning their habitat and destroying them would greatly reduce the home ground advantage of these beasts, rendering them more easily defeated.
Limited agriculture can then be carried out on the fertile land, much like medieval walled cities having farms outside their walled boundaries. When the beasts approach, the farmers will withdraw into the safety of the force field, and pick the beasts off with ranged weapons.
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In most sci-fi literature, the 'human bias' is very visible in every aspect of fictional universes.
Here are some examples.
Future technology is just a modified version of today's items. In *2001, a space odyssey*, tablets are just minified televisions.
In the eighties, smart watches were imagined as minified fully fledged computers, **complete with tiny floppy disks and QWERTY keyboards**!
Oh, and don't forget those posters from 1900s artists imagining life on the year 2000. They're absolutely amazing!
What about extraterrestrial civilisations?
Alien species are inspired, if not almost identical to, terrestrial humans, animals and plants. Intelligent species communicate mainly by *talking* and *writing*; they eat; and not only they have feelings, but they also experience the same set of feelings as humans. And they, too, invented computers! What a coincidence!
Even alien societies aren't that *alien* after all. Just like here, they have families and they need some sort of central leadership (or any leadership, for that matter).
Needless to say, some human languages, spoken by many peoples on Earth, are more *alien* (compared to English) than invented languages.
Maybe the most tricky part is the physics. Although occasionally ignored to make room for some impressive stunts, fictional universes rely, almost always, on the same laws that rule our own (I'd love to see what would a triple-charged world look like!).
**THE QUESTION**
Is this familiarity with our own world intentional to make the audience comfortable with the whole set and make sense of it, or it's just some sort of lack of imagination?
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For most writers, SF is a tool to do two things:
a. Ask "what if" about existing trends or real or imagined technologies, or;
b. Look at their own society through a different lens.
Then there are the dreary hacks who write Westerns, detective stories, bodice rippers etc. with ray guns and spaceships thrown in to add local colour and make it seem "SF".
From those perspectives, it is difficult to write things which are truly original. Even the very best writers often are recycling or reimagining ideas which are already very old (speculative science fiction set far in the future involving human evolution and our ultimate destiny was pioneered in the *1930s* by Olaf Stapledon).
Aliens as different sorts of humans is an established trope in SF for all three of the basic SF themes (What if, society through a different lens and hack SF) to provide usable and understandable foils for the characters to play off of. The comments mention Solaris and Roadside Picnik as examples of truly alien aliens, and some writers can pull this off (in which case the story revolves more around the interaction of the characters between each other as they confront the mystery). Once again Olaf Stapledon made the path, in "Last and First Men" he describes the Martians as a collective being, with individuals the size of a virus. Only when enough of them clump together does intelligence manifest itself, and Martians typically "live" as a coating on rocks and flat surfaces. When they migrate to Earth in order to take advantage of the more intense sunlight, they are surprised and pleased to discover the myriad of flat surfaces to coat, never stopping to wonder where all the flat surfaces came from....
So when writing SF, if you are conscious of what you are trying to achieve (what if, looking at society through different lens, etc.) then you can consciously tailor your efforts and, with enough skill and practice, write some truly alien and original works.
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This would probably be a Writers SE question, but anyway...
It is **mostly** intentional and it can be considered "best practice".
Being imaginative adds information load on both the author and the reader, as such unless it directly benefits the actual story the author is trying to tell it almost invariably makes the story weaker. The author has more problems keeping the story coherent and maintain proper flow. The reader has more issues understanding and following the story. And of course any effort the author spends on being imaginative in ways that do not directly contribute to the story is generally away from resources available to doing things that do directly contribute to the story.
More specifically while in some genres being imaginative or at least creative and original has innate value in SciFi it has traditionally been the case that only a limited number of new concepts or "changes" are developed and explored per story. This is because SciFi has traditionally valued the quality over quantity. A good SciFi story explores some interesting ideas in depth in a framework readers can understand and relate to rather than tries to overwhelm readers with creativity. This naturally leads everything other than those specific ideas the author wants to explore being as familiar to the readers as practical.
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It would be a western science fiction tradition in *Solaris* and *Fiasco* by Lem and *Roadside Picnic* by Arkady and Boris Strugatsky the aliens are just that completely alien and impossible to even interact with. Some people myself included rank *Solaris* and *Roadside Picnic* among the best science fiction. (*Fiasco* is also good but the other two are tops.)
Like most things it boils down to what you want to write philosophical works about the limits of science and reason, cool space romps or a million things in between. They all have value and a place.
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The answer for movies is simple: budget. Different costs money.
For books, the answer is more complex.
If you're going to build a world, you have two choices: give people enough to get started, or have them wade through a lot of mystery before they get to the meat. Consider [Greg Egan's latest bit of worldbuilding...](http://www.gregegan.net/DICHRONAUTS/DICHRONAUTS.html) Egan is a major sci-fi author (judging by sales) AND one of those authors who really pushes the bounds of imagination. This latest world that he's proposed? He's got three essays posted so far just so you can understand how the sun moves in his world and why physics requires that no one be able to turn left or right more than 45 degrees. It's rigorous physics, as much as he can do without an actual world to test his mathematics on. But the burden on readers is going to be very high compared to Star Trek, where everyone is humanoid and where the situations are recognizable.
It really depends upon what your goal as an author is -- are you trying to push the bounds of imagination for science or the bounds of imagination for social situations? If you want people to dream of the technological possibilities for humanity, you need to do more to make the physics exotic or to imagine capabilities that we do not have today. If you want to make people dream about different ways we could all live together, you don't need a world any more exotic than The Hunger Games or 1984.
Of course, the masters of the art are the ones who can create foreign realms and make us see ourselves living in them. If you're on of those, please, feel free to stretch our imaginations!
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Imagine somebody puts a laser cannon in orbit. For my question it probably won't matter if it was a Bond-style villain or invading aliens. This laser cannon is powerful enough to destroy a tank on the surface of Earth, or perhaps even a bunker.
**What would an observer on Earth see?**
* Would a short pulse or a continuous beam be more feasible to get through the atmosphere? See [How powerful does an orbital laser cannon need to be?](https://worldbuilding.stackexchange.com/questions/24009/how-powerful-does-an-orbital-laser-cannon-need-to-be) A continuous beam could be firing long enough to be seen, a pulse is more problematical.
* Is the beam itself visible? Or is it obscured by the atmosphere heated by its passage? Would this be a line from the sky to the ground? Does it form immediately? How long does it last? Would it hurt the human eye?
* Would there be smoke or billowing clouds as the laser hits the target? Or does that depend on the nature of the target?
* A cannon in LEO would move at high speed relative to the ground, but would that be noticeable? I assuming the laser stays on target, so the movement near the ground is minimal). The laser strike should be over in a few seconds, at most...
* What is the sound and how far does it carry? Does the answer to [Pew Pew Lasers! What would directed energy weapons actually sound like?](https://worldbuilding.stackexchange.com/questions/33112/pew-pew-lasers-what-would-directed-energy-weapons-actually-sound-like) apply at this scale?
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Humans have successfully built lasers from microwave frequencies to x-ray frequencies. Some of frequency ranges wouldn't penetrate the atmosphere (e.g. ultraviolet-x-ray). Other specific frequencies (e.g. 9-13 $\mu$ wavelength for $CO\_2$) are absorbed by the atmosphere's constituent molecules.
## Ideal conditions
Under ideal conditions for the laser, the beam won't be absorbed or reflected by the atmosphere. That means the only thing you'd see is a *literally blindingly* bright spot at the target.
*If a human with unprotected vision looks at the target during the shot, there is a good chance they will be permanently blinded. If a human with unprotected vision is in LOS but not looking, there's still a chance they'll be blinded by reflected light. The effects of the atmospheric plasma will be exactly like lightning (sight & sound). The stroke will be perfectly straight and visible even during daylight. It fades from visibility almost instantly even at night. For a <1 sec duration shot the angle change will be <0.5 degrees - so no noticeable fan shape to the shot.*
* ***Humans doing lab work with even modestly powered lasers (>0.005 W) wear eye protection that is optically opaque to the lasing
frequency*** to prevent loss of eyesight.
* *Humans doing lab work with high powered lasers generally do so from bunkers/control rooms with no optical paths to the experiment.*
["The Hard Kill"](http://www.projectrho.com/public_html/rocket/spacegunconvent.php#id--Laser_Cannon) art from Atomic Rockets
[](https://i.stack.imgur.com/rWOYk.jpg)
Anyone able to see the target (whether looking or not) would be in extreme danger of permanent vision loss.
## Realistic conditions
### Beam propagation
The reality is that the atmosphere absorbs and reflects every frequency to some degree. This is partially due to the fact that the atmosphere always contains fine particulate matter (aka *aerosols*). As energy is transferred from the beam to the atmosphere it heats the atmosphere to a plasma.
Due to the difference in emissivity between the plasma and surrounding atmosphere, the plasma acts as a waveguide and channels the beam. Since the plasma is a just super heated gas, that gas will move around due to normal gas dynamic forces such as wind and convection. Which means that even with perfect aim, targeting, and beam director stability, your beam will wander around and hit objects near the target.
### Beam duration
The required beam dwell time depends upon how powerful your beam is. It's possible to incapacitate your target through lower powered, long dwell time heating shots. It's also possible for your beam to shatter or drill holes through targets using pulsed lasers. The sudden deposition of large amounts of energy in a very short period of time vaporizes a portion of the target's armor and creates a shockwave in the armor.
In general the long-dwell time lasers require less beam power than the high intensity shots. However, the high intensity shots may incapacitate with lower beam energy.
### Effects of orbital motion
Even for the lower powered longer dwell time lasers, we're talking seconds to maybe 2 minutes of dwell time. In 2 minutes a laser satellite in LEO will move approximately 500 miles which equates to about a 55 degree change in incident beam angle (about 1 degree change / 2 seconds).
### Beam power
The US military attempted to shoot an orbiting satellite with it's [Mid-Infrared Advanced Chemical Laser (MIRACL)](https://en.wikipedia.org/wiki/MIRACL). This laser is a 1-2 MW Deuterium Fluoride laser. I believe an orbital laser to destroy a tank would need to be *at a minimum* this powerful and probably something like 10x or more powerful.
### Beam sounds
For very high intensity short duration shots, the beam would appear as a perfectly straight stroke of lightning and sound like one too. If the shot managed to explosively destroy a tank or bunker, you would get that detonation sound too.
### Beam appearance
Whether your beam is pulsed or continuous won't have much affect on its appearance. Either the beam will be powerful enough to cause the atmosphere to incandesce or it won't. Even if the beam is pulsed, the pulsing will be far too fast for the human eye to detect and the atmosphere will continue to incandesce (if it is hot enough to do so) between pulses anyway.
Laser test shoots down drone:
[](https://i.stack.imgur.com/rZdCn.jpg)
Note that you can't see the beam indicated that this is a "lower powered" beam incapable of shattering a tank.
## What you don't know...
...about laser weapons can kill you. Nearly every laser technology has very low efficiencies. Most of the energy you pump into the laser gets turned into heat. Getting rid of waste heat in a laser weapon is going to be a big problem. In space, it's going to be a worse problem.
>
> Note that laser cannon are notoriously inefficient. Free-electron
> lasers have a theoretical maximum efficiency of 65%, while others are
> lucky to get a third of that. This means if your beam power is 5,000
> megawatts (five gigawatts), and your cannon has an efficiency of 20%,
> the cannon is producing 25,000 megawatts, of which 5,000 is laser beam
> and 20,000 is waste heat! Ken Burnside describes weapon **lasers as
> blast furnaces that produce coherent light as a byproduct**.
>
>
>
## Other information
From the [Laser cannon](http://www.projectrho.com/public_html/rocket/spacegunconvent.php#id--Laser_Cannon) section of the Atomic Rockets website (a must read for every world builder) - from a section on laser damage during a space battle.
>
> A single pulse with a total energy of 100 MJ would have the effect of
> the detonation of 25 kg of TNT. Everyone in the compartment who is not
> shredded by the shrapnel will have their lungs pulverized by the
> blast.
>
>
> That same 100 MJ delivered as 1,000,000 pulses of 100 J each could
> very well drill a hole. The crew see a dazzling flash and flying
> sparks. Some may be blinded by the beam-flash. Anyone in the path of
> the beam has a hole through them (and the shock from the drilling of
> that personal hole could scatter the rest of them around the crew
> compartment). Everyone else would still be alive and would now be
> worrying about patching the hole.
>
>
> Although it occurs to me that the **jet of supersonic plasma escaping
> from the hole being drilled could have the combined effect of a
> blowtorch and grenade on anyone standing too close** to the point of
> incidence, even if they are not directly in the beam. The effect would
> probably be similar to the **arc flash you can get in high power, high
> voltage electrical systems, where jets of superheated plasma can cause
> severe burns from contact with the plasma, blast damage from the shock
> waves, blindness from the intense light produced, and flash burns from
> the radiated heat**.
>
>
> A continuous beam could have enough scattered and radiant heat to
> cause flash burns to those near the point of incidence, along with
> blinding those who are looking at the point of incidence when the beam
> burns through. If it burns a wide hole, people die quickly when the
> compartment explosively decompresses, throwing everyone into deep
> space. If it burns a narrow hole, the survivors who can see can just
> slap a patch over the hole to prevent the escape of their air.
>
>
>
] |
[Question]
[
Another question for my comic: my friend has made a demand that I give one of her characters a flying mount, preferably griffin-like. I have some designs but I want them to be plausible:
* How bulky and how big can I make this creature?
* What air density and such can I change in the planet's atmosphere to facilitate this thing?
The planet so far is quite earth-like but I can change it if need be and the creature's anatomy, other than six limbs and a beak, is up for debate. I already know of things like lift, thrust, drag, high air density = easier flight and so on, so don't feel as if it needs explaining.
*Update*
The 'griffin' will have small forelimbs (front feet) that are more like arms than legs, with low muscle mass, sitting under the winged limbs, which have strong muscles anchored on a deep breastbone.
The wing membrane extends back from the wings, onto the hind legs and then onto the sides of the tail, which is a more reptilian tail, not the tiny lion tail of an earthly griffin.
The hind legs are low and short and mostly fold neatly against the body to reduce drag, but partially splayed to increase wing area.
The creature has a large chest cavity with large lungs and a light stature.
**How big do the wings have to be if it were still the size of a big cat, but significantly lighter and with these other changes? (You can twist the creature's anatomy to suit your answer if you see fit, as long as it can be ridden).**
[Answer]
Flight, and the dimensions of the surfaces that allow it, roughly follow the square-cube law. Simply stated, if you double each dimension of an aircraft's fuselage, the fuselage will intuitively look four times as big when viewed from any one angle (2\*2), but the volume the aircraft can now hold is actually eight times the original aircraft (2\*2\*2). The wings must therefore be able to provide eight times the lift of the smaller ones, and that almost always translates to a wing that is larger in proportion to the fuselage than on a smaller aircraft. So, the larger the object you have to get off the ground, the larger the wings, and the size of the wings doesn't scale linearly to any cross section of the object.
For example, the two families of vultures are among the larger flying birds. The Black Vulture, common in the Southern U.S. and Latin America, has a wingspan about 6 feet and a chord length about 2 feet, to lift a mass of about 6 pounds, giving the vulture a wing loading of about 0.5 lb/ft^2. To lift a Pegasus, mass about 1,200 lbs, with the same wing loading allowing similar flight characteristics, would require 2,400 sqft of wing area, comparable to the foundation footprint of a large ranch-style house, and if the wingspan to chord length were proportional to the vulture's we're talking a total wing about 90 feet by 25 feet, so the chord length is about 3 times that of the horse.
The three workarounds, two fairly real-world and one totally fantastic, are:
* Make the animal lighter. A griffin might be closer to the mass of a big cat, about 400 pounds. That would only require a wing area of 800 sqft, or a wing about 50 by 16 feet. Still beyond practical but not *quite* so ludicrous.
* Make the animal fly faster. Vultures and other large birds like raptors don't tend to fly all that fast, preferring to soar over their territory looking for prey or carrion (though they can reduce their wing area and increase their wing loading for less drag and greater speed; the '70s vogue of "swing wings" on military aircraft was based in part on this ability). Given a light breeze and a thermal off the ground, many of these birds can more or less hover. Humans usually use flying machines (or animals) as transports to get somewhere more quickly, so even airplanes prized for their docile handling behavior like the Cessna 152 have wing loadings closer to 10 lb/sqft, which reduces drag but increases stall speed (and thus takeoff/landing speeds). Even hang gliders and paragliders have at least double the wing loading of birds. If we increase wing loading by an order of magnitude to 5 lb/sqft, our 400lb griffin would only need 80 sqft wing area, or a wingspan about 16ft and chord about 6 feet. That's quite a bit more proportional to the size of the animal; if the wings tucked similarly to a vulture's they'd pack up into about a 3 foot span along each flank. However, in the real world the animal would need to be at a dead sprint to take off, while most depictions of these creatures allow for a bird-like takeoff from a standing start.
* Magic. Many fantasy worlds have flying creatures with ridiculously undersized wings. The only explanation for how such a creature could fly is that its ability isn't completely natural.
[Answer]
For any flying thing (living or mechanical), there are two primary concerns:
* The weight of the object should be as small as possible.
* The creature should be able to push as much air downward/backward as possible.
Birds and airplanes are best examples for that. Birds have *really* lightweight skeleton and their muscles are much more powerful (in terms of mass) than a mammal's. So for the same muscle mass, birds' muscles provide a more powerful thrust that is used to push air.
Now as for the largest flying creature in the history of Earth, I recommend reading in detail about [Quetzelcoatlus](https://en.wikipedia.org/wiki/Quetzalcoatlus) and [Hatzegopteryx](https://en.wikipedia.org/wiki/Hatzegopteryx). Both of them were pterosaurs (cousins of dinosaurs, living in their times) and both of them had wingspans more than 10 meters (33 ft) long! Their masses are a question mark, with lower limit being at ~40 kg while some scholars think they might have had masses approaching ~200 kg! Aerodynamic calculations predict that it is impossible to have a *living* creature with a larger size than that.
Anyhow, just get something in the size range of these creatures and give it a mass ~150 kg (so that it is able to fly while carrying a mass of ~70 kg on its back).
One more thing, the thicker a planet's atmosphere, the easier it becomes for the creature to lift up/forwards (although it's not as simple as that). But do *not* go for an atmosphere more than 1.5 times as dense as Earth's.
[Answer]
If you're open to messing with the gravity and atmosphere of the planet, heavy fliers become much more plausible (although at the cost of potentially making the planet less hospitable for visiting humans).
Relevant parameters:
* Lower gravity
+ Less weight for the wings to lift
+ Less weight for the bones and muscles to need to support, so the bones themselves can be lighter
* A denser atmosphere
+ Each stroke of the wings can provide more thrust, which should permit faster flight using less power
- Then again, denser air means proportionally greater pressure drag- but I do not know how much that matters
+ Gliding will provide more lift, since, again, there's more air to push off of
- Then again, less gravity probably means a slower glide speed, which may or may not cancel out the lift boost
While I am certainly not qualified to analyze all the possible effects of all those different factors, I can take a stab at some of the simpler-looking ones.
Say the ideal griffin has the body of a lion [(250 kg and 3.0 meters long, call it)](https://en.wikipedia.org/wiki/Lion), and the wings of a bald eagle scaled up to match the length and width of the lion. Typical bald eagles can have a [length of 1.02 m, a 2.3 m wingspan, and 6.3 kg mass](https://en.wikipedia.org/wiki/Bald_eagle). Scaling that up by a factor of 3 gives a bird 3.06 m long, with a 6.9 m wingspan. If I assume that lift is probably proportional to the area of the bird's wings, which is proportional to the square of the wingspan, this eagle should be able to lift 56.7 kg (9 times its Earth mass) and then some. Which is less than the mass of the bird itself (170.1 kg = 6.3 kg \* 3^3), and nowhere near the mass of our lion. That's the [Square-Cube Law](https://en.wikipedia.org/wiki/Square-cube_law) in action.
However, that's not the end of the story. If we want the griffin to be able to lift its 250-some kilograms as easily as our giant Earthbound eagle can lift 56.7 kg of its mass, we can reduce gravity and thicken the atmosphere to compensate.
To fly on the planet (call it P), we need
$$F\_{l\_P} \ge F\_{g\_P}$$
(read that as "Force of lift on P $\ge$ force of gravity on P")
Since a denser atmosphere there will give more lift as compared to Earth
$$F\_{l\_E} \cdot \frac{\rho\_P}{\rho\_E} \ge F\_{g\_P}$$
Substituting in mass \* gravitational acceleration for those forces (from Newton's second law of motion, F = ma)
$$m\_{equiv} \cdot g\_E \cdot \frac{\rho\_P}{\rho\_E} \ge m \cdot g\_P$$
where $m\_{equiv}$ is the 56.7 kg figure calculated above.
Rearranging that a bit gives
$$\frac{m\_{equiv} \cdot \rho\_P}{\rho\_E} \ge \frac{m \cdot g\_P}{g\_E}$$
After substituting in some known values
$$\frac{56.7 \cdot \rho\_P}{\rho\_E} \ge \frac{250 \cdot g\_P}{g\_E}$$
And after rearranging again
$$\frac{\rho\_P}{\rho\_E} \ge 4.41 \frac{g\_P}{g\_E}$$
So the atmosphere on this planet would need to be about 4.5 times as dense as Earth's, or gravity at its surface would need to be 4.5 times weaker, or somewhere in between. In theory.
I'd recommend reducing gravity by at least a factor of 3, if not 4. This goes back to the square-cube law: Even though the cross-sectional area (and thus the strength) of the eagle's wing bones increased by a factor of 9, the griffin weighs much more than 9 times what an eagle weighs. So the griffin's wings might just break whenever it tries to take off in Earth gravity, denser atmosphere or no.
The question then becomes: Could a planet with much less gravity than Earth actually hold onto such a thick atmosphere long enough for griffins to evolve? Sure. [Venus](https://en.wikipedia.org/wiki/Venus#Atmosphere_and_climate) and [Titan](https://en.wikipedia.org/wiki/Titan_(moon)#Atmosphere) both have much thicker atmospheres than Earth does; and Titan's gravity is much weaker as well. I do not know why these conditions exist on those worlds, but clearly they do.
Finally, would such a creature actually evolve in such an environment? I doubt it; not as I described. Lions are big and bulky; the classical griffin would surely be outcompeted by something with a smaller, lighter, more aerodynamic body- something more birdlike, in short. As for the more reptilian design in your question? Sure. Maybe. I don't know. I'm no biologist.
As for riding them: No idea, but you'll probably have better luck with birdlike wings that just attach to the griffin's shoulders than with batlike wings extending all the way to the hind legs and tail. If people are going to saddle these things, they'll need somewhere to put their feet, and bat wings would get in the way. Unless the rider was perched more on the griffin's shoulders, in which case the weight of the rider would be seriously unbalancing. Dragonriding has similar issues that have already been discussed here on Worldbuilding... somewhere.
[Answer]
In flight there are 4 forces acting in pairs:
* Weight vs Lift
* Drag vs Thrust
In order to fly, lift must equal or exceed weight and thrust must equal or exceed drag.
Ease of flight scales directly proportional to air density and inversely proportional to the value of gravity.
So [if you increase the air density (proportionally related to pressure) and decrease gravitational acceleration you can get most anything to fly.](https://worldbuilding.stackexchange.com/questions/18665/a-world-with-1-3rd-gravity-but-1-2-atmospheric-pressure-would-it-be-easier-to-f/18668#18668)
[At the Moon's gravitational acceleration with terrestrial atmospheric pressures, humans could fly with wings that slip over their arms.](https://space.stackexchange.com/questions/4701/could-you-fly-on-the-moon-in-earths-atmospheric-pressure-by-flapping-wearable)
If you're interested in a [more technical treatment, I ran through the calculations in another answer](https://worldbuilding.stackexchange.com/questions/14161/air-transport-breaks-down/14166#14166) and I could link that in.
] |
[Question]
[
Okay, so it's kind of a silly question, I think, but the idea is to design an effective timeline leading from present day to roughly one hundred and fifty years into the future.
I have a pretty good idea of what I want the world to look like (setting is science fiction/cyberpunk/dystopian/apocalyptic), so that really isn't the question.
I am trying to figure out, if I were to build a timeline for the purpose of worldbuilding, what factors would I have to take in to account at each step of the timeline?
I am presuming
* political
* sociological
* geological (Earth level/disasters and stuff)
* technological,
* time passed between events
would all be reasonable things to take into consideration.
Please let me know if the question needs more clarification.
[Answer]
If you want a realistic timeline, you need to first start with the end result. What is life like in this dystopian future? Are the residents of this world familiar with the timeline or only a select few? Is there democracy or dictatorship? Is there a caste system?
Once you have a good idea about what you want the world to be about, you rationalize in ways to explain *why* it turned out that way. If it is a dictatorship *when* did the dictator take over? Has it been like that for generations or did it happen recently? If the world is a democracy, what are some of its flaws and why does it have them? What caused the world to turn to democracy?
Now that you have a few questions, you should start being able to come up with answers. There should be many things that would have had to happen for this to be the case. What people/groups were involved in the event? Were there any heroes/villains in the event? Where are they now/What happened to them?
Sprinkle other events in with these that might follow in line with the mentality at the time. If two countries had a period of tension, then it would follow that there would have been moments similar to that of our own timeline such as during the cold war. You can use actual events like this as inspiration for similar things happening in your timeline. Were there any natural disasters? Any other noncircumstantial wars fought? Breakthrough technology that changed everything?
Your last step should be determining precise dates for these events. Keep them reasonable and make sure that these significant events in the timeline also make sense with other events in your timeline. For example a revolution didn't take place after the switch to democracy unless the democracy was a farce. For the sake of consistency, I would advise you to write down exact dates rather than general rules as you can refer to them later in your story. It also makes your timeline read much more like a history lesson like something happened.
Hope that helps!
[Answer]
This process is what I use and is essentially a "Start with the big questions and work down to the details type of effort."
*What is relevant to the story/What needs to be created?*
* How far back do I need to go and why?
* Am I working with Earth history (real or alternate) or a completely made up history?
* How much impact do past events directly play in the story being told?
These basic questions help define your goal, an answer could look something like this:
>
> I need to go back to creation, because the deities that created the
> world, and how the world was created play a role in the story being
> told. The world is completely fantasy, and while the planet is
> [earth-like](/questions/tagged/earth-like "show questions tagged 'earth-like'") it has a completely different history. Past events play a
> major role in the story being told.
>
>
>
From this sort of thesis statement you can then refine things further.
* How was the world created and (if relevant) by whom? If there is a whom you can also ask *why?*
* What past events have had the greatest impact on the world, and who were the key players?
>
> The world was created by *xxxxxx deity* as a deific science experiment to see if the gods could create life. As a test for creation deities occasionally release (once every two or three millennium) giant destroyer beasts. These beasts are fought by the great heroes of each age.
>
>
>
And then you keep going down the rabbit hole
* Why do the gods feel the need to test mortals?
* How many destroyer beasts have there been? What were their names? When were they released?
* Who defeated the beasts and how?
>
> There have been three monsters, *monsters A, B and C.* They were released in the years *x, y and Z.* Monster X was defeated by Bob the Builder with a hammer to the left nostril, Monster Y by Dora the Explorer refusing to stop talking and Monster Z by Indiana Jones chucking a glass skull down its throat.
>
>
>
And again (I could keep going more and more layers down but I am stopping here)
* What happened in the world during and after each of the monster's rampages?
* Where did the heroes come from and what did they do after their victories?
---
**Notes:**
1. This method keeps you on task and helps avoid wasting time on superfluous information as you follow the items most important to your effort down to the level of detail necessary
2. You can do this multiple times, if you want to do something like the one above and then do it again for something more specific, like a continent, or a nation a city, or heck if you need the detail even a single person (your main character perhaps).
3. How spread out? How many years have passed between major events is important to consider. In the example I used lets the author wants the population to think the destroyers are myths to scare people, well you are going to need lots of time (note the higher the technology level the more time will need to pass between events)
[Answer]
On thing that you really need to take in consideration for the next 150 years are the climate changes, especially since you mentioned it was a dystopia. People might invent technologies to suppress it but I suppose it's not a compatible option with your scenario. We can already feel it's impact but it is going to have a tremendous impact on the people living on Earth on the long run even with an optimistic scenario.
[Answer]
As Neil said, a good way would be to decide what your future would be like and take the steps leading up to it.
What I'd say is have a look at what life was like 150 years ago compared to now. Think about how things have changed, what important discoveries were made in that time and how it's impacted us today. It would be exactly the same with social and political beliefs which have changed a huge amount since 1865.
] |
[Question]
[
Bioships - biological spaceships - appear in a lot of SF, so I thought I'd have a go. However, in most books they are depicted as more powerful than conventional tech in all and any regard. This is unlikely as any given biological system can be outperformed by a mechanical or electrical one. However, if they can be 'grown' without much input then the number in a fleet is massively increased over the more effective but more expensive mechanical ships.
As I'm trying to go for a more scientifically accurate approach several problems have arisen. The most prominent is the nature of the drive system used, both for the ship and for weapons (missiles and torpedoes). So the questions is **what propulsion system could a bioship use, based on current understanding, but not necessarily on current ability**. In other words, it must not be impossible according to any known science, but very *unlikely* is fine.
**Addendum**
It has been pointed out in the comments that the 'terrain' the bioship operates in has a big impact, as does the exact requirement of performance. It will be mainly within the moon/ring systems of gas giants, along with some(rare) interplanetary travel. Definitely no need for interstellar velocities. Also, low DeltaV hohmann transfers are fine. High acceleration is good but not essential.
**Addendum 2**
All the answers people have given are helpful and complementary, so don't be offended if I didn't pick yours. From the information from this question, along with stuff from around the internet, I have put together some stuff [here](http://sfworldbuilding.blogspot.com.au/2015/07/myths-of-sf-bioships-organic-spacecraft.html) as a look at bioships for anyone interested.
[Answer]
Science fiction bio-spaceships are always either cybernetic (using technology for propulsion) or have some sort of drive that is currently unknown to us.
In fact bio-spaceships are often given to super-powerful aliens to show just how much more advanced they are than humans. For example the Vorlons in Babylon 5 had living spaceships as just one more way to signal how much ahead of everyone else they are.
The theoretical advantage for living spaceships is in crew, repair and maintenance. They can heal themselves, refuel by scooping up organic matter and processing it, they can produce new versions of themselves without needing massive amounts of infrastructure to support manufacturing. At the same time though they can be mass produced if needed. The weakness though comes from the fact that organics tend to be more vulnerable, weaker, etc than metal. In particular the high temperatures and pressures of conventional engines would be hard to deal with. In fact with currently foreseeable technology you would most likely be able to get the same cargo space for a much lighter frame using traditional technology.
To get back to the question though, in the situations you describe then most likely they would just use compressed gas jets to manoeuvre. They go into the ring around the planet and consume some ice asteroids. They take minerals and water from the asteroid to use, and then split some of the water using electrolysis into hydrogen and oxygen.
That gas is then stored pressurized in bladders all around the hull of the ship. Jets of gas or even water are released from the bladders to accelerate. Possibly burning the hydrogen and oxygen to add energy to the release.
This would not allow large amounts of acceleration but it would allow low energy manoeuvring with high precision and consuming some large ice asteroids would allow sustained thrust over time, which is plenty for moving around in space.
[Answer]
Biology isn't fundamentally more efficient, better, or different from technology. It just looks that way because it's had billions of years to develop a degree of complexity that our technology hasn't reached yet. But the reality is that to a large degree, the two are interchangeable.
From a certain point of view, a human is a self-directing, self-repairing robot that has subsystems that allow it to automatically repair itself, to take in fuel and resources from the environment for power, and to create more robots.
From another point of view, a robot is a neutered, lobotomized human that's tethered to specific power sources, can't self-repair and lacks flexibility.
Those same concepts apply to spaceships. And when it comes to propulsion, **a biological spaceship will use the same propulsion as a technological one.**
Physics doesn't change between the two. Mass and acceleration don't care what's being pushed. If a regular ship uses a light sail, that's what the bioship will use. If a regular one uses fusion, then the bioship is only viable if it can also create a fusion chamber and siphon hydrogen from gas giants. And so on.
[Answer]
Lightsail looks like a good candidate for propulsion, if to solve a problem of growing a living tissue in vacuum.
It may be easier to grow such a structure in place than to deploy it from the package, as with the usual mechanical light sail. Light could provide the energy to grow and transport nutrients to growing regions.
The ship could discard the sail before landing, and then regrow another one after take off.
[Answer]
Based on current science, the propulsion options are:
* **Rockets**: Efficient rockets require a hot, fast exhaust. Temperature and exhaust velocity go hand in hand, so steel and ceramics should be superior to biologicals.
* **Lightsails/Magsails**: A biological process might be able to produce a large, thin lightsail. A magsail would require organic superconductor loops, who knows?
When I think of bioships in science fiction, they usually go with a "magic" FTL drive which does not follow science as we know it. Hamilton's [Night's Dawn](http://tvtropes.org/pmwiki/pmwiki.php/Literature/TheNightsDawnTrilogy), [Farscape](http://tvtropes.org/pmwiki/pmwiki.php/Series/Farscape), Feintuch's [Seafort](http://tvtropes.org/pmwiki/pmwiki.php/Literature/SeafortSaga), the stardrive always levels the playing field.
] |
[Question]
[
I am writing a YA adventure novel that takes place in a domed city.
For my model of the dome, I am using the Mir mine project design: <http://www.wired.co.uk/news/archive/2010-11/17/russia-domed-city-siberia>
My story is taking place in the US and the city will have been built on the site of a rather large sinkhole somewhere in the Midwest.
The important elements to consider are:
* Everything is run by solar powered electricity (gathered from orbital satellites) and designed for the least amount of industrial activity.
* There is a larger economy that allows for trade with other domed entities.
* Enclosed world which is well ventilated and - at times- opened to the outer environment for short periods
* The dome has been in existence for over twenty years.
Mostly, I want to imagine what daily existence is like around the city. What are the sounds and smells of this environment? I imagine that even a ventilated city will have odors from the use of electricity to run everything from commuter shuttles (trains) to large theme park rides - a primary source of entertainment in this particular dome. Also, the sheer number of people milling about must have an impact on the environment no matter how clean they keep themselves. Sports are also huge. What kinds of decay are likely to have taken place that add to the sensory input? If you have any suggestions as to how I could better define my parameters, please offer them.
[Answer]
The presence of the dome would not have a huge impact on the smell of the city in of itself. There would be some incidental effects though, for example there would be no fires (whether for cooking, or entertainment), no combustion engines, etc. This will in of itself change the smell of some areas.
If the air is being recycled it could well develop a metallic or other taste that locals do not notice but visitors do. Beyond that the smell is going to be influenced more by how tightly packed in together everyone is than anything else. If the city is spread out then the smell will be like any other city. The more you pack the inhabitants together though the more intense the smells will become.
The closest analogy I can think of at the moment would be nuclear submarines.
<http://www.mirror.co.uk/news/uk-news/what-its-like-to-live-on-nuclear-757728>
<http://www.dailymail.co.uk/home/books/article-2021918/Why-submarine-crews-stinking-feeling-SUB-LIFE-ON-BOARD-WITH-THE-HIDDEN-HEROES-OF-BRITAINS-SILENT-SERVICE.html>
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> What nobody had warned him about was the smell. As a rough comparison, imagine your teenage son has just come home from three days at the Glastonbury festival where he hasn’t washed once. Multiply that by 120 (the number of men in a submarine crew) and think months instead of days, and you begin to get the idea.
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> One submariner describes his wife waiting for him at the front door when he comes home from leave with a bottle of Febreze in her hand. She insists on spraying him before she’ll let him in the house and his clothes go straight into the washing machine - even the ones he hasn’t worn.
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The main thing though is that whatever the smell, people who live there acclimatise and don't notice it any more. Visitors would also acclimatize over time.
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Twenty years into its existence, the city would probably have a neutral scent from the point of view of its residents. People who live in the constant presence of foul odors rarely smell anything after a year or so.
If your POV character is not from the city then they might experience any number of unpleasant odors, most notably human sweat and urine. Most of the negative smells would center around the human habitats. The farming level and the big tree at the core would probably smell a lot better.
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**Like a diluted smell of metro stations, Perhaps in places dominated by the smell of powdered rock and concrete dust.**
A metro station is underground and therefore never sees rain. The metro trains are electric, but this does not make them smell-free. Lubricants and heating of the brakes on the trains, as well as humans, contribute to the many metro station smells.
If lower sections or horisontal sections of the sinkhole in the story is being excavated, there may also be the distinct metallic burnt smell you get when hammering on rock. Another related smell is that of freshly laid gravel.
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Is there any conceivable way that a planet with two moons--one being visibly red to the naked eye due to its mineral composition--could align in an eclipse in such a way so that the whole effect looks like a glaring eye in the sky, with the smaller red planet as the "eye's" pupil?
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So you have 2 moons, a red one and white one.
The red one has to have a smaller orbital radius than the white one, so that it lines up "in front" when viewed from the planet's surface. Additionally, it has to be smaller than the white one so the white one isn't concealed behind it when it transits.
For a stable system the two moons' orbital radii can't be too similar or they'll pass too close to each other and attract/crash into each other eventually, so the outer white moon has to be significantly further out, and so (significantly)^2 larger than the inner red moon so that it still has a broader appearance in the sky.
If you have a small red moon on the inside and a big white moon on the outside, you'll get your red glaring eye, but it'll look like a googly eye (just white and pupil, no iris).
If you want an iris you need another disc. You could have the sun as the white of the eye, with a white iris and red pupil, but in an eclipse both moons will just look black, so that's not a great idea. For a full eye-iris-pupil system you could have 3 moons (the white, the red, and a third black one, even smaller and even closer than the other two) which line up to give a glaring red eye.
Alternatively you could have just the white and red moons, but they're really big and low-density, while your planet is extremely small and high density, such that when the sun is behind the planet and you look up at midnight, you see your planet's shadow as a round dark pupil on the red moon in front of the white moon, an angry eye glaring down.
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I'll take an idea from Henry Taylors' answer. I think that the converging moon would appear black as it transited the face of the larger, outer moon. But lets assume that the small moon is tidal locked and has a volcanic core that has emitted a permanent a lake of magma near the center of the moon. This would be invisible or nearly so when illuminated by sunlight.
So when the two moons coincide near full, the black moon appears in the 'white' background. Then when the lake appears you see the glow of the magma pool and you get concentric white - black - red.
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First set the size of the first moon by deciding its radius in degrees. That is, the angle between the lines from to point of observation to center of moon and the edges of the moon. Next set the size of the second moon by getting its radius in degrees, which is simply what you decided for the first moon plus how big you want the iris to be. It becomes quickly obvious from simple geometry that the mechanics are easier if the angles are smaller. Since no lower limit on the visible size was specified, it is possible to have the effect.
Apart from the visible size another important variable is how wide you want the area the effect is visible to be as that controls how far the moons need to be. Or the ratio of the distances between the three objects, really. Another consideration is the need for both moons to be full at the same time, which sets a minimum separation for the objects. Although the minimum distances set by orbital stability and tidal forces might be larger.
Honestly there are so many variables there is no point doing the math manually. There are probably some astronomy programs tha can simulate the model, show what it would look like, and allow you to tinker with the values until the desired result is achieved.
You'd probably want the larger moon to be relatively dim for the red to be more spectacular.
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The main issue is illumination, as it has already been pointed, but not fully accounted for.
You can have the two moons in different planes, and have them coincide only in the nodes line. This actually happens at Earth for Sun and Moon: they do not eclipse every 14 days, since they are not in teh same plane, but only when they both are at the nodes line at the same time.
In the case at hand, you can have three different planes for the two moons and the sun. The one for the sun is very important because it allow the moons to be (almost) fully illuminated from behind the planet without casting any shadow, not the planet on them nor the smaller moon on the bigger.
So for your case, you have a line with the two moons and the planet, for the eye effect being created, and the sun out of that line, illuminating the three bodies. This also implies the effect can happen only over the dark side of the planet (that is, at night). Unless there are more than one sun that creates an additional daytime.
I recommend you to test the case with [Universe Sandbox ²](http://universesandbox.com/) or any other simulator.
**TL;DR**
Yes, you can
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I think the color pallet might be inverted, but if the smaller moon somehow glowed then a four-way convergence (sun, big-moon, small-moon, planet) might appear as a giant black eye with the sun's corona glowing around the edge and a smoldering red pupil in the middle.
The trick would be to explain the small moon's glow. I defer to the gravity gurus that frequent this site, but if the small moon could have a molten core and a thin mantle, perhaps the alignments of gravities during the convergence could set off huge caldera volcanos on the planet facing side of the moon.
If the moon had no atmosphere, I can further imagine that the dust clouds from the volcanos might escape its gravity well and disperse quickly, leaving the fires below clearly visible from the planet's point of view. That part probably doesn't work, since during convergence, the big moon would be blocking any solar winds vectoring out from the sun, so maybe the aligned gravities would pull the dust clouds back down into the lava instead. Again, a task for the gravity experts to figure out.
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Would it be possible for a creature to have a nervous system working at 250 volts? What kind of physiology would it need to sustain that?
Could you use that creature as a power source, to power a television set, for example?
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**It would be infeasible to use such high voltages for the entire nervous system, but very feasible to have multiple voltages in different regions of the nervous system, some of which could be as high a voltage as you are looking for.**
**The main limiting factor for high voltages is the need for insulation.** With wires and nerves, this is manageable (though potentially inconvenient). However, within the brain's computing centers themselves, the amount of insulation needed would have catastrophic effects on the computational density of the brain. Forming a high voltage brain would simply be an evolutionary dead end. It would also prevent any "switching" style logic like that which computers use, as the heat generated during a switch would be overwhelming
*Computer CPUs show this trend. They used to operate on 24V, then 12V, then 5V, then 3V. Now some are operating on 1.7V. This was essential as the chips got smaller and densities grew*
However, the body is not so lazy. It has no qualms with having different behaviors for different parts. **Having a low voltage brain connected to a medium voltage nervous system connected to a high voltage periphery organ designed to emit an electric shock is totally reasonable** (and is visible in nature: electric eels).
If you wish to power a TV, voltage is not enough. You also need current, and current\*voltage = wattage. Those numbers work out in your favor: A LCD monitor draws about 30W. A quick conversion from watts to Calories per hour (for unit purists like me: kcal/hr) shows that to be about 25 Calories per hour. **Powering a LCD monitor wouldn't even qualify as strenuous exercise**, though I would probably want the voltage-generating organ to be reasonably large to make sure blood flow would be sufficient (don't make it a pinprick sized point on the left pinkie finger).
A plasma TV can consume around 135W, or 110 Calories. If I were powering that with biology, I would consider making the voltage generating organ on the order of a bicep, just to make sure it can get the energy and oxygen delivered to it for sustained use.
Also, do remember that electricity is a circuit. Electric eels are more than comfortable completing the circuit any-ol-way with the salt water around them. If you want to power a TV, make sure your organism has two "electrodes," so that electrons can flow out of the negative "electrode" and into the positive one. To power a TV, you would thouch those two electrodes to the TV power plug.
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Maybe.
You could have a high voltage, low current nervous system which functioned much like our own. You'd need some explanation of how the high voltage is produced and (if you care about that sort of thing) why the animal ended up with that arrangement, but since there are animals alive today which produce high voltages (though not within their nervous system) and the animal kingdom is full of ad hoc solutions to problems, that shouldn't be too hard.
To power a television set, you're talking about (relatively) high current. Within the brain, we can rule that out immediately, I think. High-voltage, high-current will produce a lot of heat when the same thought processes could be carried out at lower voltage. The same argument applies to sensory neurons. You could have an arrangement where everything is high-voltage and only the motor neurons are high-current; the neural impulse is actually what powers the muscles. That would need relatively little justification (or none) and gives you your scenario where you can tap in to the animal for electrical power.
This physiology can look just like ours, except instead of energy being supplied via chemicals in the blood to a given organ it comes from the nervous system. Presumably something in the brain/spine/whatever is consuming food to produce electrical energy.
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In human-made computers, lower voltage usually means much less power consumption and less heat dissipation.
A neural cell acts like a tiny capacitor, with inner and outer media making two electrodes separated by the rather thin membrane. The amount of energy required to charge this capacitor is proportional to the [square](http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capeng2.html#c1) of the voltage. The action potential is usually [about 150 mV](http://en.wikipedia.org/wiki/Action_potential), so making it 150 V would increase the amount of the required energy by 1000 \* 1000 so one *million* times.
Hence, even if the membrane would be able to hold such a huge potential (a membrane of the usual real world cell cannot), a "high voltage brain" is likely to be very energy inefficient. Apart from the energy consumption, cooling may become a problem. And the brain already uses lots of metabolic energy.
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Short answer: No
Longer answer: There's a question at <https://physics.stackexchange.com/questions/106966/electric-impluses-inside-nerve-cells> that explains fairly well how neurons don't carry electrons like the wires in your TV does, so at minimum you would need an adapter to convert the "bio-energy" for lack of a better word, into regular electricity. Secondly most electric gadgets not running on batteries runs on AC, so you would need to not just feed it electrons, but alternate the flow 50-60 times pr second (different countries different standards), again something the body doesn't do.
Finally neurons are not actually even sending ions along the nerves, but create an electric differential between the inside and outside of the nerve, and when it's triggered at one end, a cascade flows along the nerve releasing that differential. (Then a new electric differential is build up for the next signal that needs to be sent)
So even if we were to somehow superpower the way the nerves works with electric potential, a lot of modification would be needed to that energy to make it usable for regular electric appliances.
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Imagine someone wanted to divert a specific asteroid to impact the earth. The [Current Impact Risks](http://neo.jpl.nasa.gov/risk/) page at nasa.gov shows a list of known impact risks based on observations. Most of these asteroids are very small; this person would not be interested in them.
Some of these, however, look promising for widespread destruction if they were to impact the earth. Fortunately for us, the probability is very, very small that they would actually do so.
Take a sample one: **2011 SR52**. According to the linked page(page no longer exists), this object has a rough mass of 2.4e+13 kg and a rough diameter somewhere around 2.6 km. The page estimates the impact probability is about 2.5e-10 that it will impact the earth on 2034-03-30. And with future observations, the probability is certainly going to drop to zero.
Let's assume someone wanted to divert this particular asteroid onto a path that will guarantee a collision.
**What would it take to move this object's orbital path (2011 SR52) to collide with the earth?**
The page estimates the magnitude of the impact at 8.6e+05 MT. Assume it hits the Pacific Ocean. **Could humanity survive this impact?**
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Here's a quick guide to changing the orbit of an asteroid:
1. **Figure out where it is.** This is the crucial bit. You need to know its position, mass, velocity, orbit, size, density, and composition, and perhaps one or two other parameters. These are crucial, especially the first three. You'll need all this data to model its orbit and what will happen when you deal with it. Now, you might not have time to launch a probe to it (or divert another probe near it), so you'll have to make some educated guesses. If you can get good images of it, you should be able to figure out its size, position, and velocity.
2. **Predict its future.** You'll need a lot more than a crystal ball for this. Create a computer model (multiple ones for different scenarios, if possible) that predicts its orbit, both past and future. Create a model depicting the solar system, and put in the asteroid. Then you can figure out its closest approach to Earth in the near future. Take some measurements from this model, especially concerning its position and velocity at a certain time.
3. **Start building.** Unless you're a Jedi, you won't be able to move this thing with just the power of your mind. You'll have to send something up there to do something about the asteroid. Either retrofit an existing rocket or build one from the ground up (though again, you may not have time to start from scratch) and make sure it is capable of delivering objects beyond Earth orbit. Also, create a payload. This is going to be the thing that will interact with the asteroid.
4. **Launch.** At the proper time, launch the rocket and its payload. Make sure the payload isn't injected into Earth orbit; if this happens, it will be useless. The craft must escape from Earth's gravity if it wants to do anything. This is the only way to get it near the asteroid.
5. **Interact with the asteroid.** This is a bit of a broad title, but there are few different approaches you could take. I would ram the asteroid with the craft to transfer momentum and change the asteroid's orbit. This would have to be done with extreme precision, though. Ram it at just the wrong velocity and it could miss Earth by thousands of miles.
6. **Continue taking data.** I almost forgot - make sure you have a backup craft (and rocket). Lots of things could go wrong along the way, and if you're out to destroy civilization, you need a contingency plan. Even if you manage to hit the asteroid, you could have hit it too hard or too softly. Be prepared to launch again to correct the orbit.
Anyway, keep collecting data from the asteroid. You'll get better information as it nears Earth, which could help you if you need a second launch. If you have a lander on the asteroid, that could be a great source. Alternatively, have part of the spacecraft continue to do a flyby with the asteroid while the other half impacts.
7. **Wait.** There isn't a lot you can do from here. Just sit back, relax, and get your affairs in order. If something has gone wrong, though, make sure you have redundancy and go back to step 4. Or step 3, if you have the time and completely forgot.
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I don't know how much force it would take to move the asteroid in question. The NASA page says it has a mass of $2.4 \times 10^{13} \text { kg}$, which is quite sizable. The craft would have to be either very massive (a downside because you have to get it off Earth) or be going very fast to make a difference. The choice is yours. It also depends on just how much the asteroid's orbit must be changed in order for it to hit Earth.
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As you asked,
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I think we'd have some trouble. The largest nuclear bomb ever detonated, the Soviet Tsar Bomba, had an energy output of an astonishing $50 \text { megatons}$. This asteroid's impact (as NASA's estimates have it) would produce many times that amount - even if it didn't directly impact Earth.. Now, if we changed the orbit of the asteroid just enough so that there would be a direct hit, a lot more energy could be released. But it would have to be timed just right. Precision here is everything.
What would be the effects of this? Let me name just a few:
* **Tidal waves.** If you chuck a large rock into the middle of a pond, it makes quite the splash, right? Okay, now make that rock much bigger, and going at a much faster speed. I'd think you're going to have some issues. If it hits in the Pacific Ocean, many island nations could have severe flooding, and some minor atolls could sustain severe damage. The damage to continents would depend on just where the asteroid hit.
* **Impact winter.** We're going to have some chilly weather for a while. Clouds of gas and dust could be stirred up, although I've only heard about impact winters when asteroids (or other rocky objects) hit land. Hitting the ocean could reduce this issue. Still, I'd prepare for a long winter. You could get some serious sledding in.
I would think that's it. The water is going to absorb a lot of the energy of the asteroid. Also, it could break up upon re-entry, creating a lot of smaller rocks (yikes!). This would further dissipate the energy, although a much bigger are could be effected, and the resulting damage could be substantial.
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**Rockets. And math.**
The way you make an asteroid meet up with (read: smash into) another body is exactly the same way you make a spacecraft meet up with (read: dock with) another craft: You adjust its trajectory.
Course corrections take exponentially less energy the further out you make them: 1m/s ΔV at time T is worth far more than 1m/s ΔV at time 2T. This page doesn't appear to list the orbital parameters of the asteroid, but it's likely far away (especially given that it won't approach a possible-though-unlikely impact for another 20 years) and thus easy to change its path to hit us. How easy? Well, to know that, you need to know its mass (listed on that page), its current orbit, and where (relative to Earth) it will cross Earth's orbit; after that, it's a simple matter of calculating the [transfer burn](http://en.wikipedia.org/wiki/Hohmann_transfer_orbit) to get an intercept. Given that it's still so far out and yet (on an astronomical scale) going to pass quite close, even though it's quite massive the amount ΔV needed is almost certain to be very small.
Most likely, your antagonists would make the initial burn as far out as possible (the asteroid's [apoapsis](http://en.wikipedia.org/wiki/Apsis)). This would most likely consist simply of attaching a rocket to the asteroid and executing a controlled burn, although a shaped charged (i.e. explosion) might do it as well (just be careful you don't blow apart your asteroid in the process). Using a separate spacecraft to tow it into its new orbit would also work. Again, the key is simply the ΔV, how exactly you get it isn't that critical. After that, they'd monitor its progress towards Earth, and make correction burns as necessary (again, ideally doing them as far away as possible).
The downside (for them) to this is that we here on Earth would see its approach from a long ways off. Fortunately (again, for them), it's not likely we'd be able to do a whole lot about it, really.
Would we survive? Yes, probably -- but not all of us, not by a long shot. The page estimates the impact energy of this sucker at 850,000 MT of TNT. That's going to hurt, no doubt. But it's several orders of magnitude smaller than the estimates of the [Chixulub impact](http://en.wikipedia.org/wiki/Chicxulub_crater) that is supposed to have wiped out the dinosaurs; mammals far less intelligent than we are today survived that, so I think it's a given that we'd survive a smaller one. You'd still probably have a pretty severe [Impact Winter](http://en.wikipedia.org/wiki/Impact_winter) to contend with, but less than what wiped out the dinosaurs.
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The answer to this is that we have the technology right now to modify this object's orbit to guarantee its collision with earth.
What it would require is a major, probably unconcealable, launch of one or more multi-tonne unmanned spacecraft which would rendezvous with this object and attach itself (or more likely several sub-packages) to the object. The sub-packages would then fire their own engines to subtly alter the orbit of this object over a period of days or weeks to ensure its capture by earth's gravity well and its inevitable collision with earth. With continued operation, it would be possible to hit pretty much any desired target on Earth. It might even be possible to cause a glancing impact where the object would enter the atmosphere, scrape a city off the map, then bounce back out into space, doing far less than the maximum possible amount of damage.
This would take a lot of planning, money, labour and computer time to achieve, and would not be a one-man job, though it is possible that a handful of people (educated lunatics?) with enough money and the right skills could achieve this.
While the launch(es) necessary to divert the object would be unconcealable, since undoubtedly the US and Russia amongst others are still looking out for potential ICBM launches, there is nothing preventing a commercially funded overt launch from being a cover for the launch of this project. The commercial launch could then be declared a failure if necessary. The modification of the body's orbit is fairly likely to go unnoticed long enough for an operation to readjust its path to be unfeasible in the remaining time after discovery of its new path and destination.
Yes, humanity would probably survive an 860 GT impact, but not much of it at all. This would probably be an extinction-level event, causing major ecological damage similar to the event which finished off the dinosaurs 65 million years ago. A direct impact in an ocean would cause giant tsunamis (as opposed to the normal kind of tsunami), and throw up uncountable tons of dust and rock that would fall to earth as meteorite impacts right around the globe, raising the air temperature significantly for days, before an impact winter set in.
An impact in the pacific would wipe out the American western coast cities, as well as Japan, SE Asia and Australia's east coast from the tsunami effects alone, which would likely be a hundred meters or so high when it hit land. Collateral projectiles re-entering the atmosphere would cause global damage. It would actually be better for Earth if such an impact occurred on land.
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For diverting the asteroid: if you have sufficient time and the asteroid is not huge kinetic impactor or ion beam shepherd, depending on the type of asteroid (e.g. material porosity) and its orbit. For very large asteroid (> 400 - 500 m in diameter) or last-minute impactors a nuclear bomb is the only available option.
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I'm thinking about creating a creature that can eat *anything*. Perhaps a rock, if it looks "tasty", or a chunk of a spaceship, or even a piece of itself if it wishes.
Of course, it seems silly, so perhaps there are some materials that are impossible for it to eat (its stomach?), and the question is:
**How small the set of types of non-edible matter can be and how to explain it?**
I'm not saying that it has to be sentient, e.g. it might be a gel that just turns the matter it encounters into its own. The only requirement is that, when it eats something, that thing becomes a part of the creature, so it becomes movable. To explain this further, the creature can certainly excrete, digestion is not necessary (e.g. if it can incorporate the matter as it is), but it cannot act like a box/container (I would not consider a safe to be such a creature despite the fact it could "eat" anything that fits in it and then "defecate" its contents later when asked to).
My approach was via some mouth-like organ that would transform matter into something the creature could eat, but I had no idea how to solve the energy requirements.
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The closest thing that I have ever read about is the Dreen from John Ringo's [Looking Glass series](http://en.wikipedia.org/wiki/Voyage_of_the_Space_Bubble).
The Dreen use biological based technology rather than mechanical technology. A Dreen "Tank", for example, is a living creature with heavy weapons and armor. Even Dreen spaceships are alive and grown.
Obviously, to produce items such as tanks and spaceships, the Dreen would have to consume a tremendous variety of minerals and such, so the *can* "eat" pretty much everything. Most of the actual eating is done by a rapidly spreading complex mold-like organism that can break down any material. It is part of a vast collective consciousness and so can be controlled (so that it does not, say, try to eat the walls of the spaceship carrying it). Because their technology is biologically based, it does focus first on consuming organic products, such as human bodies.
It also contains the genetic programming to produce all of the Dreen biological forms. This means that if even a small amount of the Dreen "mold" escapes containment (and remember, it can eat anything), it can eventually produce an entire new Dreen colony entirely from scratch.
The Dreen are probably one of the nastiest and most fearsome creatures that I have ever read about in science fiction.
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An organism that does this would most likely need to have been designed specifically to do it, that means genetic engineering and possibly even cybernetic enhancements.
In general when digesting things you want to pull them inside yourself so you can control the environment. You could then have a snake-like creature that unhinges it's mouth and engulfs the object to eat within itself. It then has a series of digestive systems as the object moves through.
To break down larger items it would also be able to secrete digestive enzymes and generate a certain amount of brute force, enabling it to break up objects into smaller chunks that can then be consumed.
Each stomach would have a series of mechanisms both chemical and mechanical to break down a specific substance or set of substances and then retrieve anything useful that it finds within.
First it might dissolve and consume any organic material, then another stomach might break down plastics, then another extracts metal, and so-on through the process.
A recycling worm might be engineered that you released into a ruin, it then consumes every it finds and separates it out. Growing scales made of individual types of metal, consuming organic matter and plastics to fuel itself, etc.
You would most likely need to supplement its diet though, as there is not very much nutritional value in reinforced concrete.
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I would break the concept up into levels of "eating." Obviously the most complete version of eating is the one we are used to: between the mechanical crushing of our mouth and stomach, and the chemical reactions in the stomach and intestines, it turns the "food" into simple component molecules that can be transferred to anywhere in the body where they are needed.
For a different version, consider the human consumption of gold foil (why not?). We mechanically tear it into pieces which can travel through the digestive tract, but our chemical digestion does not occur with Gold. Instead it travels through relatively unharmed to be eliminated, with much of its physical layout intact.
The deciding factor between these is whether the creature actually gains from eating the material, or if it merely find its way into the digestive tract, to be eliminated later.
A third case would be to view "eating" as a defense mechanism. Instead of having a stinger or similar defense mechanism, if a creature could render its attacker inert by consuming it, it would be more than comfortable doing so, even if it did not gain any energy from it.
I think anything could be fair game along these lines, especially if you include defensive binge eating. A creature that can withstand massive massive heat could quickly disassemble and oxidize just about any compound (5000 degrees would be sufficient for everything shy of perhaps Tungsten). It would be an energy inefficient eating process, but it would work.
The only thing I think it could not eat would be a toxin crafted to take advantage of any digestive weakness it may have. For example, the creature would need to decide if something is food (using food processing mechanisms to acquire energy) or an enemy (using destructive mechanisms, which may cost energy). An enemy which appears to be food could subsist long enough to do internal damage. Such a toxin would have to be highly specialized.
One interesting direction to take is that "interesting" things would happened to try to eat exotic things. For example, if there was a way to turn a creature inside out without killing it, what would happen if one creature ate its inside out breatheren? (This is similar to the argument in DnD about turning a bag of holding inside out). A specialized toxin might try to emulate the sensation of eating its bretheren in hopes of preventing a destructive digestion from occurring.
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The sentient crystalline formations in Anne McCaffrey's Crystal Line, called Jewel Junk by Killashandra Ree, were capable of metabolizing almost any material they came into contact with provided there was enough energy available to the particular node to perform the molecular disassembly. It even eats through rock. The only thing it can't (won't?) manage is Ballybran Crystal which is a quartz-like material with some very strange properties that may not be strictly 3-dimensional.
In The Vortex Blasters by E. E. "Doc" Smith the loose atomic vortices are eventually discovered to be incubators for energy-based creatures. The vortices destroy pretty much everything in their surroundings until ultimately they form a molten crater. Part of the destruction appears to be the conversion of matter into energy to "feed" the incubating life. In this case not the life-form itself but the artificial (from our perspective) life support unit.
But if you want something scarier, try any of the various Grey Goo stories - Drexler's Engines of Creation, the Replicators from Star Gate, the nanoswarms in Michael Crichton's "Prey", etc. These are a form of created pseudo-life that disassemble anything with the requisite elements for reproduction, converting it to new copies of the "cells" of the goo. Add some sort of computronium to the mix and you have a potential hive mind scenario. Check out the noocytes from Blood Music by Greg Bear for a slightly more biological basis for this. Still engineered, but biologically so.
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*Robert Forward's* [Camelot 30K](http://rads.stackoverflow.com/amzn/click/0812516478).
It's not quite your description because what I'm thinking about is a plant, not an animal. The plants will process anything that's a solid in their environment (and as the "30K" in the title refers to the temperature, that's most things). While they don't actually have a use for many of the elements they process them into berries that are desired by the species that farms them.
While we never find out the true origin of the aliens it seems to me that they must be the product of some very advanced genetic engineering as there's simply no path by which they could possibly evolve. I would think the basic idea could apply to an animal as well, though--something engineered as a mining tool. Such a creature would be designed with metabolic pathways to handle as many elements as possible.
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Within the Star Wars Extended Universe, there is a science base on a small object within a near impenetrable sphere of Black Holes. Is this possible?
*The place referenced is called the [Maw Installation](http://starwars.wikia.com/wiki/Maw_Installation)*
[Answer]
Under the circumstances you describe, my immediate reaction is that it would not be possible. The issue here is that the cluster would be fairly unstable. The black holes would all be mutually attracted to each other, and would soon coalesce into one large black hole - taking the Imperial research center with it.
For this to somehow work, the black holes would have to be in some odd stable orbits around each other. They would have a common barycenter - in this case, the Imperial research center - and would continue circling around it. The tricky part here would be to have them orbit in three dimensions - that is, to not simply have all their orbits in the same plane, but to have orbits at odd angles to each other. Also, there would undoubtedly be gaps between the black holes, which would be undesirable.
The whole setup would seem to be rather unstable, and so I'm inclined to say that this would be impossible.
Let's say that the cluster and the station popped into existence one day. I know, it violates so many laws of physics, but I want to delve into the station's hypothetical downfall, so reality will just have to wait. Anyway, so we have a cluster of black holes in *stable* orbits. What will happen?
Certain systems, such as [binary neutron stars](https://en.wikipedia.org/wiki/PSR_B1913%2B16), emit radiation in the form of [gravitational waves](https://en.wikipedia.org/wiki/Gravitational_wave). A system composed of two black holes orbiting each other should do the same. We can calculate the rate at which their orbits will decay with the formula
$$\frac{dr}{dt}=-\frac{64}{5}\frac{G^3}{c^5}\frac{(m\_1m\_2)(m\_1+m\_2)}{r^3}$$
where $m\_1$ and $m\_2$ are the masses and $r$ is the distance between the two black holes. If you imagine the black holes each have a mass of about five solar masses, and are separated by about one kilometer, you can easily do the math and figure out the rate at which the orbit will decay.
Alternatively, we can integrate like so:
$$\int\_{r\_0}^r r'^3dr'=-\int\_0^t \frac{64}{5}\frac{G^3}{c^5}(m\_1m\_2)(m\_1+m\_2)dt'$$
to find the relationship between the distance between the black holes and time, and calculate how long it will take for the two black holes to meet. This gives you the solution
$$r(t)=\sqrt[4]{r\_0^4-4\frac{64}{5}\frac{G^3}{c^5}(m\_1m\_2)(m\_1+m\_2)t}$$
where $r\_0=r(0)$ is the initial radius. The time to coalescence is then
$$\tau=r\_0^4\left(4\frac{64}{5}\frac{G^3}{c^5}(m\_1m\_2)(m\_1+m\_2)\right)^{-1}$$
I'm not sure how this would all work with a system of $n$ black holes, but I would think they would still emit gravitational radiation. Perhaps you could use a modified formula (though I don't know for sure).
Finally, the Imperial research station would have to be in the exact center of the cluster. If it was off by just a bit, it would be pulled towards one side and consumed by a black hole. Perhaps the workers could somehow adjust the station's position, but they would have to be careful to keep it in equilibrium.
[Answer]
Aside from the problem of instability, which has already been mentioned and is indeed a gigantic problem, I'd like to illustrate another problem.
Everything would be torn apart by gravitational gradients. Yes, technically, you could have an unstable equilibrium where you can place a small object in the middle and it would stay there. you likely want them to be far apart though. But since You want a whole sphere of them, putting them far away either requires a lot of them, or very large one.
To calculate the mass of a black hole from its [Schwarzschild radius](http://en.wikipedia.org/wiki/Schwarzschild_radius), you can use the following [formula](http://en.wikipedia.org/wiki/Black_hole#Physical_properties): $\frac{2GM}{c^{2}}$, where G is the [gravitational constant](http://en.wikipedia.org/wiki/Gravitational_constant), M is the mass of our black hole and c is of course the [speed of light](http://en.wikipedia.org/wiki/Black_hole#Physical_properties). According to Wikipedia, this roughly translates to a 2.95 km radius per solar mass. So lets say we're working with solar mass black holes.
Now, how far do we put those black holes? Well if we have about 60 black holes in a circle, almost touching, they would be in a circle with a radius of about 35 km. To form a sphere of that size, you'd need several hundreds of black holes. I'm not sure where you're getting these, but sure.
We'll focus on just two black holes for now, 70 km apart and circling each other with a small object in the center. If we want to figure out what sort of acceleration that small object is experiencing, we can use the following formula: $G\frac{M}{r^{2}}$ Where G is the [gravitational constant](http://en.wikipedia.org/wiki/Gravitational_constant) again, M the mass of the black hole and r, the distance between the two objects (the small object and the black hole). Filling this out gives us: $6.673\times10^{−11}m^{3}kg^{-1}s^{-2}\frac{1.988\times10^{30}kg}{35000m^{2}}=108293257143 m/s^{2}$, That's quite some acceleration, by Newtonian gravity you'd accelerate to many time the speed of light in less than a second. Of course this doesn't hold, but it gives you an idea of the magnitude of the forces you're facing.
"But the other black hole is just as far away!", I hear you exclaim. That's true. But lets see what the gravitational acceleration looks like a meter further away from this one black hole. $6.673\times10^{−11}m^{3}kg^{-1}s^{-2}\frac{1.988\times10^{30}kg}{35001m^{2}}=108287069222 m/s^{2}$, That looks roughly the same. Let's have a look at the difference $108293257143m/s^{2}-108287069222m/s^{2}=6187921m/s^{2}$. That's not looking to healthy, lets put that in perspective.
If you were to lay out Peter Dinklage with his feet 35 km away from a sun mass black hole and his head 1 m further away (Peter Dinklage is roughly a meter long, right?) the imp would be the size of the mountain (who I am assuming is 3 m tall) in less than a millisecond. His euphoria would be brief however, because he would soon be [spaghettified](http://en.wikipedia.org/wiki/Spaghettification), as would your small object, your science base and everyone in it.
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I had an idea for a world where tin and copper are both easily accesible and usually found close to each other enough that it is a non-factor. Bronze is pretty much the main alloy for use in anything, since iron is very rare. It exists and people are even pretty competent at handling it and making good quality steel, but it is rare enough that only a select few people can reliably make use out of it. Hence why steel is ony used for things bronze can't reliably or realisticaly substitute for.
My question is this; what would small arms look like in this setting? Bronze is awesome, but it is not steel. It has different properties. So I am wondering what exactly bronze firearms could handle and what sort of limitations I would have to keep in mind.
I know artillery was made from bronze in the past, Austria Hungary used something called 'Steel bronze' in WW1. <https://en.wikipedia.org/wiki/8_cm_FK_M._5>
That said could you make a handgun, rifle, submachine gun or a machine gun out of bronze? And if yes, what are the limitations? I found somewhere that rifling probably wouldn't work too well due to bronze being softer, but maybe there are ways to bypass that specific issue.
**Things to keep into account;**
-This is more along the lines of a hellish dimension than a natural world. So sometimes things are the way they are, because higher powers decide they are. I am willing to handwave provided it is within reason.
-The people are in a near constant state of war due to the machinations of these higher beings. Trade happens, but cannot be relied upon.
-People aren't born into this world, they appear with amnesia. They do keep echoes of their memories. This makes it so that concepts such as heavier than air flight are known, but it's simply a matter of "How does it work exactly?"
-The tech level that I envision is around WW1 era, though if certain factions could plausibly make it I am willing to handwave it. (So no needing nuclear power or needing microchips or something like that.)
-Factions range from small clan sized (a couple dozen) to larger 'empires' whoms total manpower (not just soldiers, but craftsmen, farmers, etc as well) can go into the 10-15K range. Anything more is hard to keep together for 'longer' periods of time.
-Feel free to use bronze alloys such as manganese bronze if it helps.
-Iron and steel parts should be kept to an absolute minimum, *maybe* a bit can be excused, but weapons are competing with other important things for the limited amount of iron/steel available to most factions.
-If propellants such as smokeless powder or blackpowder are entirely impossible, would pneumatic rifles work?
[Answer]
There's a broadness to this question that sort of encompasses a lot of various engineering issues. While it's true that general bronze (and here I'll mean specifically the tin/copper version) does not match up to steel, there are still measurable values for what that bronze CAN do.
As such the firearms would be built with those limitations in mind. To keep things simple, lets just say bronze can only handle half the pressure/force of steel (and this is a simplification that ignores more rigorous details like compressive strength, hardness, etc.)
But simple example lets us get a couple of clear solutions:
* Use twice as much Bronze, double the thickness of your barrel and components (More weight, same performance)
* Reduce the powder charge of you bullets to half of what you would use for steel (Similar weight, less range and/or muzzle velocity)
We're roughly just concerned with the end results concerning forces here. It's also worth noting that the alloy itself is only a part of the end product. Reading the wikipedia article you linked on "Steel Bronze" suggests that it's basically a mechanically hardened form of (i'm guessing tin/copper, since they don't specify there) bronze.
So even if you do have to hand-wave something, you can make it sound like a scientific or industrial process with only minor explanation. "The benefit of the McGuffin process was pronounced, Bob had never held a fire arm this light weight; or this powerful in his life."
[Answer]
**Barrel pressures will be lower.**
High velocity rounds require high barrel pressures and the tensile strength of bronze may not be up to that in the way steel is.
But there is a workaround. Consider mv2 which describes the kinetic energy of a projectile. As it increases with the square of v you get more bang for your buck (so to speak) by increasing v.
In your world, they increase m. Cannons made of bronze are fine, because barrel pressures are low. And the destructive power is high because cannonballs are massive. In your world, projectiles are as heavy as they can be. Also, a long barrel allows more time for a low pressure charge to accelerate the projectile.
You can replicate to some degree the stability conferred by rifling through changes in projectile design. I am a fan of the Taofledermaus youtube channel and one of the coolest ones was this self-stabilizing dumbell shotgun round.
<https://www.youtube.com/watch?v=M7f4tEMrg4I>
[](https://i.stack.imgur.com/lXOat.jpg)
So for your world of bronze, in the interest of maximal awesomeness.
1: Long guns!
2: Massive projectiles.
[Answer]
## They will wear out faster and either be weaker or heavier (or both)
this can very easily be compared by looking at cannons and guns made of the materials. Bronze and iron cannons as well as smaller guns were produced at the same times.
Bronze is weaker, heavier, more costly (rarer materials), and softer(wears out faster), but it does work.
The big disadvantage iron had was consistency it was much harder to make iron of the right quality, and more importantly harder to tell you had made the wrong quality so early iron cannon could fail without warning. Iron is technically harder to work with but in all there regards it is a better material. but by WW1 most industrial coutries had solved this problem (although not ALL of them, a handful of nations like Austria-Hungary could not manage it for large artillery's pieces)
So you can make a bronze gun, but it will be heavier, weaker (in terms of power), more expensive, harder to get material for and, wear out faster than an iron/steel equivalent. You can make a rifled bronze barrel it just wears out quickly. A bronze machine gun will suffer extreme barrel wear, keep in mind early machine guns wore out STEEL barrels at an alarming rate bronze will probably have to be swapped after each use.
Weight and weakness can be traded for each other up to a point, (make a thicker heavier barrel to increase power or decrease power to lighten the weapon) but you can't really change the other two factors, and you still end up with more weight becasue of things like bronze springs, ejectors, and firing pins. Weight may make some of them unwieldable.
At WW1 tech levels Bronze offers no advantages, but firearms made using it can be made if you are determined enough. Also keep in mind WW1 technology requires industrialization. They will also need steel for the tools that make the firearms.
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Historically, the Byzantine Empire used ship-mounted Greek Fire throwers to defend Constantinople. These weapons were pretty advanced and horrifying for the enemy.
**The existence of these historic vehicle mounted flame throwers made me wonder if there is any good reason why the Byzantines couldn't have developed "Flamer Tanks".**
Think two heavily armored horses, a driver, a gunner and two pumpers in a small, armored war wagon. They drive up to the enemy with infantry support and unleash hell, literally, on the Muslim scourge before the melee. Send in some cavalry to help with the clean up afterwards.
I think that the biggest issue would be to develop the tactics that would make Flamer Tanks useful, since even war elephants, the closest thing to a pre-tech tank, would not be analogous in application. (What about flamethrowers mounted on war elephants...?)
The idea of tanks only became viable because of compact heavy cannons with decent reload capabilities and machine guns with decent fire rates. Yet a flamethrower offers something very similar to a machine gun, tactically speaking.
**So could the Byzantine Empire theoretically have deployed Flamer Tanks?**
[Answer]
***Yes!*** The Chinese developed something very similar, although it's disputable if they actually were made. Since the Greeks were already ahead of the curve with Greek fire projectors on ships, the basic engineering could have existed. The Chinese designs were a little more technically developed, but there's nothing there that couldn't have been invented by another Archimedes or Heron of Alexandria. I'd say the hardest part of it would be to have a chariot if you wanted the flames to go forward instead of backwards. Likely a side-mount flame would work very well as you rode across a formation of troops and sprayed them with Greek fire or the equivalent. "Illustrations and descriptions of mobile flamethrowers on four-wheel push carts were documented in the Wujing Zongyao, written in 1044 AD (its illustration redrawn in 1601 as well)" <https://en.wikipedia.org/wiki/Fierce-fire_Oil_Cabinet>
[](https://i.stack.imgur.com/BQaN8.png)
[Answer]
I would like to point out that the "Byzantines" did use medieval flamethrowers on land, although I know little about such use.
I once read in a history of the city of Baghdad a description of a "Byzantine" emissary to the Caliph. There was mention of a flame thrower mounted on an elephant being demonstrated to the envoys.
So there was at least a prototype of a flame thrower mounted on a possibly armor wearing elephant, though I don't know whether that weapon was ever used in combat.
DWKraus's answer mentions a Chinese design for fire spitting carts, although they don't know if such carts were ever built.
So a fantasy or alternate universe version of a flame throwing tank is a fairly plausible idea.
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The advanced civilization in my story is trying to reach as many galaxies as possible in the next few billions years before the expansion of space has sent those galaxies permanently out of reach without some form of FTL travel which my story does not have.
I plan to have von Neumann probe-like self replicating machines powered by laser relays from Nicoll-Dyson beams, possibly a double beam from opposite sides keeping the star in its location whilst sending probes in opposite directions.
Once in the new galaxies the self replicating machines will gather materials and turn the majority of stars into [Shkadov thrusters](https://en.wikipedia.org/wiki/Stellar_engine#Class_A_(Shkadov_thruster)), the collective thrust of the stars and the gravitational hold of the galaxy will move the whole galaxy towards the civilizations home galaxy.
This assumption that whole galaxies can be moved was taken from the following videos: <https://www.gregschool.org/gregschoollessons/2018/6/12/shkadov-thrusters> <https://www.youtube.com/watch?v=_VetAm7fCS0>
My question is what percentage of the stars need to become Shkadov thrusters to move the whole galaxy? Would there become a point where converting more stars is taking more time than it is worth for the additional speed? The civilization isn't worried about the time the journeys will take, as long as the galaxies eventually arrive to their area of space.
[Answer]
This wouldn't work.
The big issue is that stars make up only a few percent of the Milky Way's total mass - estimates vary by a bit, but I've heard numbers in the 3-5% range. For instance, [McMillan 2011](https://ui.adsabs.harvard.edu/abs/2011MNRAS.414.2446M/abstract) claims about 4.98%. Dark matter makes up a substantial amount, as do interstellar clouds - i.e. non-rigid bodies.
The point is, even if you attached a thruster to every single star in the galaxy, it wouldn't produce any significant gravitational effects on the rest of the galaxy, and it certainly wouldn't be enough to move the Milky Way.
You *could* try and find a galaxy that 1) has an extremely low amount of dark matter, like [NGC 1052-DF2](https://en.wikipedia.org/wiki/NGC_1052-DF2) or NGC 1052-DF4, and 2) is old and gas-poor, meaning most of its star formation is over and much of its mass is locked in stars and stellar remnants, not interstellar clouds. I'd have to learn more about stellar populations of these ultra diffuse galaxies to say anything intelligent on the subject, though.
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In many fantasy works, the world typically has giant caverns that house entire civilizations and ecosystems that are (mostly) disconnected from the world above. However, this concept, at least in an earth and non artificial setting, is practically impossible.
With that in mind, what I'm asking is:
**How can a system of large caverns form?**
Some requirements to base our assumptions on:
* The cave system is made up of extremely large caverns (similar or even bigger to the Hong Song Dong as to support a thriving ecosystem. I already have a good idea on how the food chain works) which are connected with a series of smaller and more numerous tunnels and crags.
* Span at least half of a Pangea sized continent if possible.
* Have multiple, smaller conations to the out side world like little cave openings and rivers.
* Can last for as long as possible to allow an ecosystem to develop underground. Though parts of the system would fall and crumble overtime of course.
[Answer]
**Salt cave**
Big caves on earth are usually in limestone. The limestone is a sedimentary rock that then slowly is worn away and dissolved by water. Caves open up.
I wondered - could there be something even more soluble covering even more area than limestone?
Salt.
[](https://i.stack.imgur.com/Axq63.jpg)
<https://www.tripadvisor.com/Attraction_Review-g946486-d9565380-Reviews-Namakdan_Salt_Cave-Qeshm_Hormozgan_Province.html>
When ancient oceans dry up the salt is left behind. Salt deposits can be hundreds of meters thick. These salt caves are immense, forming in solid salt domes that extend several kilometers.
>
> Salt domes can be very large structures. The salt cores range from 1/2
> mile to 5 miles across. The parent rock units that serve as a source
> of salt are usually several hundred to a few thousand feet thick. The
> salt domes ascend from depths of between 500 and 6000 feet (or more)
> below the surface [2]. They usually do not reach the surface. If they
> do, a salt glacier might form.
>
>
>
[https://geology.com/stories/13/salt-domes/#:~:text=Salt%20domes%20can%20be%20very,below%20the%20surface%20%5B2%5D](https://geology.com/stories/13/salt-domes/#:%7E:text=Salt%20domes%20can%20be%20very,below%20the%20surface%20%5B2%5D).
Check the link for salt glacier info!
Salt deposits are a trip. Some are apparently really old - from the Cambrian! Before there was any life, water and earth were doing their dances.
How big could a salt deposit be? What if the whole ocean dried up?
<https://www.usgs.gov/faqs/why-ocean-salty-0?qt-news_science_products=0#qt-news_science_products>
>
> By some estimates, if the salt in the ocean could be removed and
> spread evenly over the Earth’s land surface it would form a layer more
> than 500 feet (166 meters) thick, about the height of a 40-story
> office building
>
>
>
If you had an ocean dry up then get covered with blown sediments, you could have a salt bed nearly the size of the ocean. [Salt deposits have been found on Mars](https://themis.asu.edu/news/salt-deposits-found-martian-highlands#:%7E:text=The%20scientists%20found%20about%20200,within%20ancient%2C%20heavily%20cratered%20terrain.) where ancient oceans did dry up. There could be immense and extensive salt deposits under the surface of Mars. In those deposits could be immense and extensive caves.
[Answer]
We have to assume that the composition of the soil is solid enough to support giant cave systems across the entire pangea for this to work. The natural formation of such caves seems unlikely. They would be too localized. So how about a semi-intelligent way to build these caves?
Coral reefs are build out of the materials surrounding the life there. With each lifecycle they create a larger structure that supports itself. Something like this could be extended to this world of yours.
Imagine if a similar lifecycle existed in the ground. They create airways to the surface in order to receive oxygen, but grow towards the nutrients and materials they need to survive. These airways are kept open by the life itself as it creates a layer of materials on the edge of the airway they create for themselves. The creatures living on the edge can keep living as they leech nutrients out of the still undisturbed ground, but the things living in the middle aren't that lucky and will die off. These dead parts will then degrade and eventually be consumed by the creatures on the edge which creates a hole in the middle, a cave.
This would encourage them to form an ever increasing cave as the creatures try to increase the size of the cave, but it would form only a small layer and wouldn't support much. So we introduce a symbiosis: Another set of creatures lives in the soil itself. These give nutrients they find to the creatures forming the cave wall, and the creatures forming the cave wall give back something as well. The creatures living in the soil will create a supporting structure around the cave as it forms, allowing it to support more weight.
As long as this "coral" is alive the creatures inside it can gather data from the coral. When we put stress on our bones theres a teeny tiny little electrical difference which our bodies can pick up on and through that guess how much stress the bone undergoes. This information is then used by the body to determine where and how more bone needs to grow to handle these stresses, and where bone can be taken away because it's not used that much and the body wants to be efficient. If this type of land-based Coral would use the same they could keep an eye out for structural collapse. Since a cave-in would kill the creatures living on the cave-in structure and it would potentially cut off a large section of creatures from oxygen they would evolve to prevent this. This causes them to create support structures when they detect a certain amount of stress on their coral structures.
A bit wall-of-texty but I hope it'll give you food for thought.
[Answer]
There are a few ways in which large caves can form.
The first one is [lava tubes](https://en.wikipedia.org/wiki/Lava_tube)
>
> A lava tube is a natural conduit formed by flowing lava which moves beneath the hardened surface of a lava flow. Tubes can drain lava from a volcano during an eruption, or can be extinct, meaning the lava flow has ceased, and the rock has cooled and left a long cave.
>
>
> A lava tube is a type of lava cave formed when a low-viscosity lava flow develops a continuous and hard crust, which thickens and forms a roof above the still-flowing lava stream. Tubes form in one of two ways: either by the crusting over of lava channels, or from pāhoehoe flows where the lava is moving under the surface.
>
>
> Lava usually leaves the point of eruption in channels. These channels tend to stay very hot as their surroundings cool. This means they slowly develop walls around them as the surrounding lava cools and/or as the channel melts its way deeper. These channels can get deep enough to crust over, forming an insulating tube that keeps the lava molten and serves as a conduit for the flowing lava. These types of lava tubes tend to be closer to the lava eruption point.
>
>
>
The other is through [karst](https://en.wikipedia.org/wiki/Karst)
>
> Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant rocks, such as quartzite, given the right conditions.
>
>
> The development of karst occurs whenever acidic water starts to break down the surface of bedrock near its cracks, or bedding planes. As the bedrock (typically limestone or dolomite) continues to degrade, its cracks tend to get bigger. As time goes on, these fractures will become wider, and eventually a drainage system of some sort may start to form underneath. If this underground drainage system does form, it will speed up the development of karst formations there because more water will be able to flow through the region, giving it more erosive power.
>
>
>
In both cases mind that it's very hard for an ecosystem to form here, since there is poor to no access to some energy source. Typical ecosystems forming in such places rely on wastes being carried through flowing waters, nothing too big or fancy.
Same goes for their extension, they can hardly span over extended areas.
[Answer]
**Coral reef formation over what was once a large, shallow sea, later uplifted above sea level**
What you're describing is almost word for word what happened in the east-central united states, in an area that extends from Missouri and Arkansas in the west to the Appalachians in the east and as far north as southern Indiana and Ohio. What happened was during the Paleozoic this area was a shallow epicontinental sea similar to the present-day Caribbean around the Bahamas, a vast, mostly shallow region about 10-30 feet deep. This was largely because the region was a partially submerged craton, rather than the oceanic shelf.
The buildup of coral reefs in the region due to the widespread, shallow seas resulted in huge amounts of limestone being formed. Eventually, due to falling sealevels and the buildup of this rock, the area rose above sea level, but this large area of limestone remained. The limestone was very fertile (becoming the backbone of the Kentucky-Tennessee "bluegrass region"), but it also meant that it was riddled with caves due to acid rain, and as a result this part of North America is known for its karstland (including very large caves like Mammoth Cave). Karstland is still being produced even though the rock is hundreds of millions of years old, and has been active for at least five million years if not longer (some fossil sites in the region are filled-in sinkholes and cave systems).
If you have a Pangaea-sized region that was once a shallow sea that gradually became uplifted, it would produce a similar effect. Additionally, the high production of limestone might push down on the crust, allowing for thicker limestone over time.
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A giant pacific octopus has around 250 suckers per arm that it can use to manipulate small items. If theoretically, one of these animals was given human intelligence, and of course proper medical training, would they be able to do something as delicate as surgery?
The surgery takes place in a low gravity room out of water as so the soft-bodied octopus inst crushed by its own weight. The octopus is also given a proper respirator as to breath out of water.
[Answer]
I don’t believe an octopus could use scalpels and other tools build for human hands with sufficient precision to perform surgery.
But, I think there could there be tool designs that would give the octopi sufficient control that they could be effective surgeons.
I’m of the opinion that designs accommodated three or more tentacles would let them have proper control. My reason is that the range of motion of a single tentacle is kind of like one of our fingers but they don’t have a rigid point of flexion like the palm and wrist. So the tools provide that.
A surgeon can control a blade in six to twelve degrees of freedom — (x,y,z roll, pitch, yaw, etc) — complex objects can move in space at 6N degrees of freedom, where N is the number of linkages in the system. But, an octopi tentacle is more limited, its curls between more than fingers, since it more contracts or elongates rather than flex and extending bounded by the bones in our fingers.
We can hold our fingers in fixed rigid position, whereas octopi either are relaxed, contracted, or elongated. But, tentacles can be moved in opposition to one another. So as along as the tool lets them balance the forces precisely, I think that they’d have control good enough for surgery.
And, in a world where they can be in space with lower gravity, there would be robotic surgical tools like we have today. I think the controls would be different for an octopus surgeon, like more knobs, but they’d work just as good for humans as for octopi.
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I'm creating a D&D campaign which takes place on a Mercury-sized planet, orbiting a Proxima-Centauri style red dwarf. It is tidally locked.
I would like it to make physical sense as much as possible, and only use magic or hand-waving if there is absolutely no alternative.
I would also like the sun to appear to be absolutely massive in the sky. At least 10 degrees in angular diameter, 20 if possible. This would correspond to the orbital radius of the planet to be between 5 and 11 solar radii, which is insanely small (earth's orbit is approximately 230 solar radii for comparison).
The problem is, it appears to me that it's absolutely impossible for a star to have a habitable zone this close to it. If the star is cold enough that liquid water can exist that close to it, it will be too cold to radiate in the visible. This can be fudged with a high albedo, but the trade-off there is that you won't be able to see the sun if the albedo is high enough to be in its habitable zone.
The thing is, we always model stars as blackbodies, but what would it look like if a star had a very low emissivity? This way, it could be hot enough to radiate in the visible, but its habitable zone could be extremely close. Would there be a conceivable reason/mechanism for such a thing, and would it be physically possible?
(The other concern I've glossed over here is the Roche limit, but I'm happy to say that I did the math and it's not a problem. For a star with the mass and radius of Proxima Centauri, and a very dense planet orbiting it -- sufficiently dense to be very small but have Earthlike surface gravity -- the Roche limit is only 4 solar radii)
EDIT: Oh boy, I just realized a big problem I hadn't considered, and that's that at these distances, at the surface of the planet, the gravitational force towards the planet would be LESS than the gravitational force towards the sun. I'm going to have to do some soul-searching here.
EDIT 2: Wow, thanks for all the feedback! This has metastasized to the spreadsheet stage, where I'm calculating whatever I can for red dwarfs, brown dwarfs, red giants, even white dwarfs and neutron stars (both complete nonstarters).
Yet another problem I hadn't considered until today was the actual luminance, i.e., how visibly bright the sun would appear, as opposed to the total energy the sun would be heating the planet up with. Putting all of these factors together - gravitation, heat, and luminance, makes it pretty tricky to find a solution to all of these, if I want the planet to be 5 solar radii from the sun.
Orbiting close enough for to a red dwarf, you'd be pulled towards the sun with 2.5 Gs. It would be about as bright as the Sun, but it would be receiving 340 times as much energy total.
With a brown dwarf, it would only be 0.4 Gs pulling you towards the sun, which you could deal with, and even jump twice as high as you could here, but it would be a significant game mechanic I don't want. Furthermore, it's only 5% as bright as the Sun, but it would still be 75 times as hot.
A red giant like Aldebaran would be MUCH better with respect to gravity - it has almost no effect there. And it's also visibly as bright as the sun. But it's still 350 times as hot.
So there's not really an existing star on which this would make sense. I'll take some time playing with numbers to see if I can find a temperature, mass, and radius that does let me do what I want and decide if that makes sense. Otherwise, I'll probably just fudge it with an atmosphere that's VERY reflective in all frequencies except for the visible. Or just magic, that's always cool.
EDIT 3: In response to @pluckedkiwi's comment, I'll use one specific example, in which my planet is orbiting around a red dwarf. The planet has a radius of 2500 km, and a mass *m* of about 10^24 kg. The red dwarf has a mass *M* of 10^30 kg, and the planet is in a circular orbit with a semimajor axis *a* of 700,000 km.
My conjecture: Orbital mechanics don't matter very much close to the surface of the planet, as you can predict what will happen to within a degree of error by using a rotating coordinate system. On the surface of this planet, you appear to be in a Cartesian coordinate system with the sun directly overhead. Plugging the numbers above into Newton's laws, your acceleration towards the planet's surface is 10.67 m/s/s. Your upwards acceleration, towards the sun, is 136/m/s/s. So you'll be falling upwards at a rate of 126 m/s/s.
Once you get more than a few hundred kilometers up, that very small and dense planet will be far enough away that that coordinate system doesn't hold up very well, and you'll model your movement as a keplerian orbit around the sun. From that perspective you'll be in a similar, but perturbed, orbit as that of the planet. You still have basically the same amount of tangential velocity/angular momentum as you did before, so you won't fall into the sun, but the planet's surface won't be pulling you downwards sufficiently to keep you on it. So the real way to look at it is you and the planet are in your own orbits around the sun. You're both falling into it at the same speed, but you won't feel much of an attraction to the planet at all. I think?
This is in contrast to where we are now, at 1 AU from the sun. The difference is much greater here, where the sun pulls us towards it with an acceleration of about 6 millimeters per second squared. If we were just two solar radii from it like in the scenario I describe here, that acceleration would be closer to 70 m/s/s. Our intuition breaks down because we're so much closer to the sun. It just looks like there isn't really a possible way to be this close to any sun relative to its radius, without your mechanics just completely breaking down on the planet's surface, unless the sun is very, very not dense, as in the case of a red giant.
Of course there's a lot of speculation in this and it's entirely possible I haven't thought it through enough.
[Answer]
**Instead of a red dwarf, use a brown dwarf.**
[Brown dwarfs](https://en.wikipedia.org/wiki/Brown_dwarf) can be nearly the size of a red dwarf but because they are no longer doing hydrogen fusion and just slowly cooling down, you can make them arbitrarily less hot and of lower emissivity. Really old ones might not glow much at all.
Your world would be something like a Jovian moon, if Jupiter glowed.
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If I have this right, what you want is the *effect* of a large body looming over the visible side, and perpetual daylight.
You could have your world be a moon of a large gas giant, tidally locked in L1 position between the planet and its star. The "Sun" in the sky would then actually be the gas giant.
Given a high enough albedo for the latter, and some magic to stabilize L1 for geological periods, it could be doable and would also solve your gravitation problem.
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If the point is to have a large body looming in the sky all the time, you might want to use a moon orbiting a gas giant, as LSemi suggests, but not in the L1 point between the sun and the gas giant, since that would put the moon-planet too far from the gas giant to achieve the desired visual size.
Put your moon-planet in a fairly close orbit to a gas giant a bit outside the habitable zone of the sun, tidally locked so that one face always faces the gas giant. Your moon-planet will receive additional heat from radiation from the gas giant as well as reflected sunlight when it is day on the gas giant, so it is possible to place the gas giant somewhat outside the habitable zone.
The sun will be visible at day, but the gas giant will eclipse it during midday. This will be the only time you can see stars, since it is night on the gas giant when it is day on the moon-planet, and vice versa. In fact, the terminator (day-night boundary) on the gas giant will work as a giant clock for people on the moon-planet.
The side of the moon-planet facing away from the gas giant will be colder, since it doesn't receive the benefit of reflected light and radiation from the gas giant. However, you would want a fairly thick atmosphere to shield from radiation (which also helps keeps the moon-planet warm), which will distribute the planetary heat better than on Earth. A thicker atmosphere will make airships and flying creatures/craft more efficient than on Earth, e.g. making huge dragons more realistic.
For dramatic effect, give your gas giant a ring like Saturn, perhaps slanted to make it more visible.
This isn't exactly what you are asking for, but might fulfill your purpose, while adding some cool details, like a short, deep night in the middle of every day and a ring around the huge gas giant in the sky - which might also have cool weather patterns like Jupiter, clearly visible at nighttime when the surface of the gas giant is lit.
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**Have you considered artificial stars?**
There are several ways to crate an artifical star whose parameters you can tweak with great precision. The YouTube channel [SFIA](https://www.youtube.com/channel/UCZFipeZtQM5CKUjx6grh54g) made a video on [Making Suns](https://youtu.be/ShC63MiURrc) a while back. While these solutions require some really extreme engeneering, they get you around gravitational, thermal and tidal issues. From sane to wacky my suggestions are fusion planet, penrose, stellar flashlight, penrose star and a kugelblitz. Let's take a look at each of them
* **fusion planet**
Build a planet of deuterium and helium-3 under 13 jupiter-masses (to prevent deuterium fusing with itself). Use [orbital rings](https://youtu.be/LMbI6sk-62E) to build a [mega-earth](https://youtu.be/ioKidcpkZN0) around it, place fusion reactors on the inside of the shell and whatever you consider practical for illumination purposes on the surface. This surface can be much bigger than the planet (fuel source) itself.
* **fusion flashlight**
Basically a fusion plant, but we just illuminate the planet. Since we go for a much more elaborate illusion, we can cut down on the brute force. Maybe a slightly bigger "planet" which your planet orbits like a double planet would be sufficient.
* **penrose star**
This one is similar to the first two with respect to the external structure, but insted of fusion, we dump hydrogen into a black hole and produce energy via the [Penrose Process](https://en.m.wikipedia.org/wiki/Penrose_process). This [video](https://youtu.be/pxa0IrZCNzg) is about the colonisation of black holes and might be of interest.
* **Kugelblitz**
The [Kugelblitz](https://en.m.wikipedia.org/wiki/Kugelblitz_%28astrophysics%29) is another way of using a black hole to harvest energy. It is a very small black hole which evaporates within a few billion years. It gives of [Hawking Radiation](https://en.m.wikipedia.org/wiki/Hawking_radiation) which you can absorb and use to generate the light you need.
Additionaly keep in mind that you don't really need a tidally locked planet, one whose rotation has been matched to its orbital period by other means will get you the same results.
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I'm providing an interesting twist on the Anatomically Correct series by focusing on a single body part instead of an entire organism.
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The following image depicts the average range of the cones of a normal human eye. Each cone allows the eye to see within a different range, and combining those ranges allows us to see in the way that we do.
[](https://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Cone-fundamentals-with-srgb-spectrum.svg/1280px-Cone-fundamentals-with-srgb-spectrum.svg.png)
Different animals have different cones. Some animals have less cones, and some animals have more cones. The vision in animals varies widely: some animals like birds and insects can see in ultraviolet light; some animals like frogs can see in infrared.
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For my story, I'm developing a creature that has the ability to alter the range of color perception in its eyes. For example, it might decide it wants one of the cones to extend into the range of infrared in order to identify sources of heat.
More specifically, it might take a cone that sees in the range 500-700 nm and change it to see in 600-800 nm. (notice the range is still 200 nm) Sometimes there will be a resulting gap, where colors that were previously easily identifiable become more difficult to see. (as least until it changes its eyes back)
# How might an eye with the ability to alter its range of color perception evolve?
Assume an Earth-like planet. Any neural alteration that might be required should be addressed in the answer as well. (because if the brain can't interpret the different colors, there's no point in an eye that can capture them)
The eyes should be capable of making these changes in an amount of time ranging anywhere from a few seconds to an hour or so. (the quicker, the better)
[Answer]
This is actually doable -- easy, even.
For infrared, as @overlord has noted, there would be difficulties that might make it not worth your while. On the other hand, it depends on the use case:
* infrared radiation is absorbed by water (thus, by the crystalline in the eye), so that only a fraction would reach the retina. Granted, evolutionary changes might lead to a crystalline formulation that's less absorbant in the IR range.
* body heat would create a noise background against which the IR signal would have to compete. The human ear is quite capable of recognizing sounds among the noise, and the same can be done by the eye. This capability would, for a certainty, extend to IR signal decoding, **but** would that be enough? I am quite confident that you wouldn't be able to read a newspaper printed in IR ink, but you might be able to spot [Vitons](https://en.wikipedia.org/wiki/Sinister_Barrier).
You cannot change the spectrum response of a cone because it depends on which [*opsins*](https://en.wikipedia.org/wiki/Opsin#Vertebrate_visual_opsins) it contains, and the frequency response of *those* is fixed. But there is nothing in principle preventing *supplemental opsins* to be synthesized in response to specific conditions ([this already happens, to some extent](https://www.sciencedirect.com/science/article/pii/S0014483588800745)) - or permanently.
Some fish have an opsin with λmax = 370 nm, allowing to see ultraviolet. A first mutation to create a fourth population of photoreceptors using *almost* the same opsin they already do (this, too, already happens, albeit only in human females - so called tetrachromaticity), then the extra opsin mutates and becomes sensitive to infrared, giving (for example) a night hunting advantage. The receptor would probably be continuously "photobleached" in daylight, and would slowly regenerate as soon as it's dark - not unlike how rhodopsin night vision is acquired.
Another possibility is some mechanism [enhancing the capture sensitivity of existing opsins](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4273384/). This way, the eye becomes "simply" more adept at detecting light at different wavelengths.
# Update: infrared vision
We start with a mutation similar to one that already happened in human's branch of vertebrates (and too many times in the case of the mantis shrimp): the doubling and mutation of the gene sequence for an opsin, giving rise to a fourth type of retinal cone (or rod). This new opsin has a sensitivity peak shifted toward the infrared ("Rhodopsin-X", in green), and is proportionally more sensitive, so during daytime the receptors are photobleached, and not used by photopic vision. This already happens to some extent with rod photosensors.
Then, the opsin further mutates, until its peak lies well into the near infrared range ("Rhodopsin-X", in red).
[](https://i.stack.imgur.com/GVI20.png)
When scotopic vision kicks in (at dusk, below one thousandth candle per square meter), also Rhodopsin-X starts regenerating, with relaxation time similar to normal rhodopsin, therefore between 30 and 45 minutes, which satisfies the "one hour" constraint of the OP.
We now have near-infrared vision. This will be comparatively weak, though, because infrared is significantly absorbed by water... and the human eyeball is *filled* with water. So, the retina could only detect the fraction of the IR signal which survives passage through the crystalline.
To have *voluntary* NIR vision, we would need to add a further modification: a nictitating membrane transparent to infrared, but opaque to visible light. This could take the form of a very thin membrane with a high content of a specialized melanine analogue. It would **never** be able to shut out the daylight at any significant photopic intensity, but it *could* allow to switch between mesopic vision and NIR vision. And, however, in full daylight and in the Sun's heat, most infrared information would probably be blotted out anyway.
Note that even then, closing the membrane would not have any effect for several minutes, with full NIR vision only achieved after 30-45 minutes. And in that period the membrane would need to stay closed, blocking ordinary vision. **BUT** it would be possible to close *one* membrane, regenerating vision in that eye, and using the other to see visible light.
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As, LSerni points out, the eye detects color based on what proteins are present in each cone. As far as I know, every organism that naturally exists produces more or less the same ratios of proteins in each cone indefinitely for the lifespan of the cell; however, it may be possible for a cell to either re-absorb and form new proteins (This could take as little as 20 seconds) or use a Epigenetic process to split and form new cells with new ratios, and absorb the old ones. (which would take about half an hour)
Another theoretical solution is to rearrange the proteins. Melanin is a good example of how our bodies can adapt to environmental stimuli by how it chooses to turn the pigments to block more or less light. A similar process might help a cone adjust the balance of what it detects.
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I'm not sure how relevant this is, but if you were to add an aspect like the cuttle fish and octopus ability to shrink and expand their melanin sacks on their skin to rapidly change their colour and shape, could this be applied to the cones? So have several with one type of protein in them, another with some more (etc.) and have the animal able to shrink the ones that are not needed and expand the ones that are.
Probably completely impossible, but maybe something to think about.
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If germs from the past was brought to the present/future on a person (or by some other means of transportation) and we have immunity to its descendants, like the modern germs for example, would we be immune to the germs brought to the present? I have only seen conversations about people bringing germs from the modern day to the past, but what happens when we flip the tables.
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You don't know how actual your question is: [link](http://www.bbc.com/earth/story/20170504-there-are-diseases-hidden-in-ice-and-they-are-waking-up). The melting of the polar cap might actually release long dormant viruses, bacteria and funghi.
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> In August 2016, in a remote corner of Siberian tundra called the Yamal Peninsula in the Arctic Circle, a 12-year-old boy died and at least twenty people were hospitalised after being infected by anthrax.
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> The theory is that, over 75 years ago, a reindeer infected with anthrax died and its frozen carcass became trapped under a layer of frozen soil, known as permafrost. There it stayed until a heatwave in the summer of 2016, when the permafrost thawed.
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> This exposed the reindeer corpse and released infectious anthrax into nearby water and soil, and then into the food supply. More than 2,000 reindeer grazing nearby became infected, which then led to the small number of human cases.
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About the risks
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> "Following our work and that of others, there is now a non-zero probability that pathogenic microbes could be revived, and infect us," says Claverie. "How likely that is is not known, but it's a possibility. It could be bacteria that are curable with antibiotics, or resistant bacteria, or a virus. If the pathogen hasn't been in contact with humans for a long time, then our immune system would not be prepared. So yes, that could be dangerous."
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We tend to correlate the word "evolution" with the word "improvement", but that is a false association. "Evolution" is more closely related to the word "change".
If at a particular moment in the past, a disease emerges to threaten the survival of a population, then the portion of that population which had previously "evolved/changed" to resist that disease would have a higher survival rate than the rest of the population. Then for a time, that higher survival rate would give them a propagation advantage, allowing their particular genetics to pervade a larger percentage of the population.
Once the presence of that disease decreased, the propagation advantage would fade as well. Other threats would emerge to endanger the population and other genetic changes would gain the advantage.
It is entirely possible over deep time that other genetic changes might break the historic disease immunity change in pursuit of immunity to a different threat. It is also possible that over deep time, an immunity change (which is no longer valuable because it's disease is not present) can disperse or even vanish from a local gene pool. Gene lines die out all the time for no reason greater than personal dating choices.
So yes, a historic disease can be a threat to a modern populace even if they had survived the disease in their distant past. As with wisdom and un-persisted knowledge, we tend to loose what we do not use. So if a particular version of a disease has been gone for a long enough time, we may very well be susceptible to it again.
[Answer]
## NO, But...
This is an something that has actually been tested in the long term e-coli experiment.
In bacteria separated by several generation older generations can outcompete there distant descendendants. It is not a given of course but the chances are not insignificant either. This is because the population of bacteria is constantly changing as bacteria adapt to each other and their hosts but such adaptations are not immediately lost nor always useful in the long run. For example an ancestor may have produced a toxin to help kill off competing bacteria but it may completely kill off that competing strain or other bacteria may become resistant to the toxin, so later it loses the ability to produce the toxin since the toxin takes calories to make. But put the toxin producing ancestor in with its descendants and it may wipe out is later descendants as well.
There is also an effect with diseases that causes them to become less lethal, later strains of HIV are milder for instance because living hosts are more likely to spread the disease. A reintroduction of the original strain would be devastating since it would be more virulent and kill a lot of people even as it drives itself extinct. This is not uncommon, very virulent diseases are worse off evolutionarily than less virulent descendants precisely because they are much worse for the hosts, and living hosts are better at spreading disease.
Now the but, if you go back far enough the chances of catching a compatible disease are lessened, simply because there is nothing with similar biochemistry to you around. For instance go back to the carboniferous and there are no warm blooded animals around and the chances of a comparable disease are extremely low. The worst diseases tend to be from your own species or closely related species, that or you need long contact with the species like humans and livestock.
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In our world, mountains generally only move up (while forming) or down (while eroding or sinking). Otherwise they follow the tectonic plates they happen to be on. In island chains like the Hawaiian archipelago it may seem that they are moving but actually some plate is moving apart from another one, with the islands form at the boundaries.
Would it be possible to have an actual moving mountain, though? I'm thinking of mountains that move over the tectonic plate they are on. In any direction other than up and down, at any speed - it doesn't have to be something noticeable on a lifetime, or even over millennia.
The reason I'm asking is because I dreamed about a mountain that circled its world every couple hundred million years, leaving paleonthologists and geologists baffled about the fossils and formations on and in it.
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If you consider a glacier to be a mountain of ice, then that could be an answer. Glaciers have a very slow lateral movement which is a result of melting unevenly at the base. This means that over a long period of time, the glacier will eventually be in a different location from where it was first measured to be.
If you want your mountain to be a pure magma formed one, then try this. Perhaps you could say that some event (super deep drilling, space debris collision, handwavium buildup, etc) caused an eruption in an arctic area of your world. In this way, a rock mountain formed atop a field of thick ice. This event (or the released magma) loosened the ice in the area, causing your mountain to now exist on a moving platform of ice.
Highly unlikely, but it could make for fun worldbuilding.
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**Of course!**
There used to be a very famous mountain called the Flanabjarg. Famous now only because it's in Sweden. But, you say, Sweden is full of mountains! But what makes Flanabjarg interesting is that, even now, it has a garrison of Norwegian soldiers on top, the so called Black Pillars, for it's a matter of history that Frederick V established a border garrison on Flanabjarg in in 1748. And not far from these fortifications is indeed a tall pillar of black stone.
Interestinger still, a map commissioned by King John in 1499 clearly shows that Flanabjarg is on the west coast of Norway while a massive sea weathered runestone on the mountain's eastern slopes, dedicated to a great voyage of Sverre Sigurdsson in 1187 is still plainly visible. Odd how a sea weathered stone should be inland, don't you think?
In an old saga bound up with the Snorra Edda, we find ...*eyland svartsteinn í meðal islands ok norvegs sundfœrranda ok hét flana bjargr*. An island mountain with a great black stone on top in the middle of the ocean!
In Landnámabók, the historical accounts of the settling of Iceland in the 9th and 10th centuries, we find references to a singular mountain island in the Southfjords, it's mighty black stone pillar rising up from the sea to greet the newly arrived settlers.
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Imagine a "log" of extremely resistant material maybe 100km long and several kilometers thick, floating vertically just under the planetary surface so that it protrudes into planetary mantle and is pushed by currents there. It is thus moving differently than the crust tectonic plates over geological timescales. On its top there is the mountain.
I can't think of a way this could happen naturally, or if such a material exists, wolfram metal would wear down too. Perhaps some alien artifact or splinter of exotic matter.
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After some research, I remembered that in Africa there are two dunes made of magnetized sand. Apparently you can even grab a handful of such sand and throw it away, and watch at is clamps back onto the dune.
The wind blows and erodes those dunes as it would with any other geographic feature. But the sand grains aggregate again, resulting in the whole structure moving at a speed of about seventeen meters per year.
[More on the magnetic dunes can be found in this link](https://www.atlasobscura.com/places/shifting-sand-dunes-olduvai-gorge). I imagine that given more mass of magnetized sand, such structures could become as large as mountains and still keep moving. It would be interesting to see what happens when they reach the ocean, though.
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It's a basic fact that most plants need sunlight to generate growth. Sure, they also need water and nutrients, but their reliance on sunlight is the one sole thing that separates them from animals.
Now, compare our sun to our moon. Even at its fullest, moonlight can only get to an apparent magnitude of -12.90, which is 1/400,000 as bright as our sun. To make matters worse, it's just a ball of unbreathable rock, which has a fairly low albedo, despite what the view of the moon would have you thinking. In short, moonlight is nowhere near strong enough for photosynthesis to occur.
But let's say that some alternate Earth is orbited by a Pluto-sized ball of ice, which is more reflective than rock. From a view of the night sky on that planet, this new icy moon, in its crescent, is 12,000 times brighter than our full moon. Which means that when this icy moon gets full, it's going to get even brighter. **But will it be bright enough to encourage plants to photosynthesize in the dark of night?**
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To learn how low you can go, let us consider the illustrative example of the gentle **Lampenflora**.
[](https://i.stack.imgur.com/QdkCL.jpg)
[Lampenflora](https://translate.google.com/translate?hl=en&sl=de&u=https://de.wikipedia.org/wiki/Lampenflora&prev=search) (translated page from German Wikipedia)
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> Totality of all autotrophic plants, which are located in caves in the
> field of fixed lighting fixtures
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These are plants which are adapted to very low light such as occurs in show caves. They occur on the wet surfaces around lights. They are studied because they are a nuisance and damaging to the cave. How low can light be to sustain a population of Lampenflora?
CONTROL OF LAMPENFLORA AT WAITOMO CAVES. NEW ZEALAND
<http://www.ackma.org/papers/Wait3.html>
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> Light - The restricted occurrence of lampenflora to areas directly lit
> by the fixed lamp housings in the caves clearly shows that light is
> the primary controlling factor for lampenflora development. The
> extent of lampenflora growth around any one lamp housing depends on
> the number of bulbs in that housing and on the distance of that
> housing from a suitable substrate. Light intensity measurements made
> in the Glow-worm and Ruakuri caves suggest that the minimum light
> levels required for continued growth of the different autotrophic
> lampenflora organisms are: green and blue- green algae 0.1 to 1.0u E
> /m2 /sec ( 10 to 50 lux) , mosses 1.0 to 3.5u E / m2/sec ( 50 to 180
> lux), and ferns 5.0u E/m 2/sec ( 250 lux).
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So that is how much the lampenflora need. Now how much does the moon provide?
<https://en.wikipedia.org/wiki/Moonlight>
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> The intensity of moonlight varies greatly depending on its phase, but
> even the full Moon typically provides only about 0.05–0.1 lux
> illumination.[2] When the full Moon is at perigee and viewed around
> upper culmination from the tropics, the illuminance can reach up to
> 0.32 lux.[2]
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A range of 0.05 to 0.32 lux. Our moon provides an order of magnitude less light than the lampenflora require. But the OP asserts that the glowy moon of this world provides 12,000 times the light of the moon, which means 600 to 3840 lux! Far more than the lampenflora require, even at the low end of the range, even the light hungry ferns!
So the answer is **yes. Glowy moon as described is enough light for photosynthesis**.
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As far as I know light is only necessary to release electrons making further reactions possible. So as long as there is some light it’s not impossible for a kind of plant like organism to develop the necessary organs.
That said I would expect that life will go down a path that is most efficient for its environment. That why it seems unlikely that we’d find many plant life specialized to produce energy under low light situation on earth, if it can do better at daylight. That doesn’t mean however that photosynthesis would be impossible but simply a lot slower. If a plant life has developed to cope with it ..why wouldn’t it be impossible. But as said, if it isn’t very efficient than maybe plants could use other energy sources that are easier to tap in like something that is result of volcanic activity etc...
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So, let’s say Bill wants to gain immortality. Bill is a billionaire, and so invests a large portion of his estate to Brain Transplant research. After a bit, the doctors vivisect him, and encase his brain inside of a robotic shell. My question is, since his brain is still needing of nutrients, how would they go about feeding his brain to keep it alive?
Bill lives in the late 22nd century (2290s) when is wilder science is permitted
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Searching for "How do they feed coma patients?" found [this Quora post](https://www.quora.com/How-do-people-in-a-coma-eat), which says that are two ways to feed a coma patient. One is a feeding tube to the stomach, but the other is
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> ...they receive TPN (Total Parental [sic] Nutrition) which is carefully formulated by a pharmacist once blood work is performed each week or few days, etc. this is delivered through an implanted port, or a catheter tunneled under the skin into a vein. Essentially it is intravenous and the dressing is changed using sterile technique every 7 days.
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So basically they inject food directly into the bloodstream. Presumably the robotic shell (in your story) still pumps blood through the brain to provide oxygen, so add nutrients to that blood. It's the same basic idea as with the coma patient.
[Total Parenteral Nutrition](https://medlineplus.gov/ency/patientinstructions/000177.htm).
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Reality check:
# Not Gonna Happen
Keeping a brain alive is a rather trivial exercise and Brythan's answer provides two common modes of feeding people who can't feed themselves. It's a "trivial exercise" because TPN and G-Tubes are placed in living bodies whose metabolic functions are working properly.
But Bill is looking to do something radically different indeed. He wants what appears to be an indeterminate existence of pure torture by sensory & communication deprivation. Tossing a brain into a soup of nutrient & oxygen rich fluids with a little pump attached to the circulatory system might do the trick of keeping his brain alive. And putting that into a robot, well, I don't know what the deal there is! The robot isn't going to be able to function as a surrogate body. All it could do is house Bill's brain and serve as a nutrient & waste storage receptacle.
This is similar in many respects to the experiments already done on [whole body transplant](https://en.wikipedia.org/wiki/Brain_transplant). This is where Bill's old body would be surgically removed from his neck and a donor body would be attached to his neck. The main difference is that with a body transplant, Bill would, in theory, be able to see, hear, taste, feel (at least from the skin of his head and neck) and may be able to talk. A brain in a box will be able to do none of those things.
**Why it's not going to happen:** In the case of whole body transplant, the main reason why it's not been done is medical ethics. Technically, there are no surgical barriers to the procedure. The surgery is basically a complex of disarticulating cervical vertebrae & fusing them to the donated body; severing and reanastamosing blood vessels, trachea and esophagus. Severing and reanastamosing nerves (cervical & vagus nerves) is much trickier. So far so good. But the big hurdle to whole body transplant is what the hell can we do with the spinal cord itself? Bill's nervous system comprises a delicate and intimate network of interconnectivity: nerves and impulses pass from his brain stem down to every tiniest part of his body and back again. It's like looking inside a telephone closet:
[](https://i.stack.imgur.com/BOsff.jpg)
Slice that with a sword and you'll be hard pressed to put it back together again! A telephone tech might be able to sort that rat's nest out, but the spinal cord doesn't come with convenient labels or easy to use splicers! Spinal regeneration is in its earliest infancy, and at best Bill will be a quadriplegic. He will also have to contend with a constant regimen of anti-rejection treatments. The first thing the transplanted body is going to do otherwise is set off its immune system to get rid of the foreign body, which in this case is Bill himself -- his head!
Your solution is a step in a different direction, but with even more hurdles to overcome. Bill doesn't want any part of his body to remain apart from his bare naked brain. The body transplant surgery would most likely lead to Bill's death. This surgery will lead to Bill's death.
**Why it's even more not going to happen:** Living brain excision is technically extremely challenging. As I'm sure you're aware, the brain is encased in a pretty solid mass of bone, called the skull. All of the blood vessels that serve the brain pass through the deepest, thickest part of it: the skull base.
The only way to get down there is to drill out all the bone:
[](https://i.stack.imgur.com/YEnlZ.jpg)
Drilling away the bone will expose all those nasty little arteries and veins and nerves that Bill's surgeon will need to sever in order to free the brain from the skull. All of those structures pass through bone and even the tiniest nick can cause hemorrhage that can not be controlled and will spell brain death.
Each vessel will have to be immediately identified and anastamosed to a cardiopulmonary bypass machine. Once his brain is securely tethered to that device, then it's a matter of severing the brain from the nerves: the biggest one is of course the spinal cord itself. But the surgeons will also have to deal with the optic nerves, the otic nerves, and the many cranial nerves.
The brain is extremely delicate & squishy ([see this video](https://vimeo.com/172418763)). Even very careful handling of it can cause major trauma to its tissues. The chances of getting the brain fully detached from the body, properly connected to its new mechanical receptacle and transfered to its new location all without the very slightest of mishap is just not possible even taking the best care.
**What to expect after:** I don't think anyone knows what will actually happen to a person whose entire body has been cut away and removed. Assuming Bill survives the surgery and transferal procedures, what will his "life" be like? He has no eyes, so can not see; no ears, so can not hear; he has no spinal cord and no nervous system, so can not feel.
While he does however, have a spinal cord stump and various stumps of other nerves that may occasionally become stimulated, for the most part, he will be entirely and completely sundered from all outside existence. The effects of short and medium term [sensory deprivation](https://en.wikipedia.org/wiki/Sensory_deprivation) are pretty well known and relatively innocuous. Bill, assuming her survives the surgery, will be subject to an endless session of absolute sensory deprivation and with no hope at all of recovery in the near future.
I'd suggest that if the brain could ever be reconnected, say in three or four centuries to an android body, "Bill" as a person probably will be long gone from the brain. His personality, cognitive function, memory will probably all be shot.
**What was the point:** At this point in time, the question becomes one of what did it mean to "keep the brain alive" in light of Bill's desire to "gain immortality"? Is it enough that his non-functioning mind and no-longer-existing sense of self reside in a physically maintained shell? If "keeping the brain alive" satisfies, then there's your answer. But what about the immortality? Has that been granted as well?
I am reminded of the tale of Eos and Tithonos, she a goddess and he a mortal man. She begs of Zeus that he be made immortal, which Zeus grants, and therein lies the real answer to your question:
*but when loathsome old age pressed full upon him, and he could not move nor lift his limbs, this seemed to her in her heart the best counsel: she laid him in a room and put to the shining doors. There he babbles endlessly, and no more has strength at all, such as once he had in his supple limbs.*
[Answer]
**Copy the brain to permanent storage.**
From Neuromancer, by William Gibson.
>
> He turned on the tensor beside the Hosaka. The crisp circle of light
> fell directly on the Flatline’s construct. He slotted some ice,
> connected the construct, and jacked in. It was exactly the sensation
> of someone reading over his shoulder.
>
>
> He coughed. "Dix? McCoy? That you man?" His throat was tight.
>
>
> "Hey, bro," said a directionless voice.
>
>
> "It’s Case, man. Remember?"
>
>
> "Miami, joeboy, quick study."
>
>
> "What’s the last thing you remember before I spoke to you, Dix?"
>
>
> "Nothin’."
>
>
> "Hang on." He disconnected the construct. The presence was gone. He
> reconnected it. "Dix? Who am I?" "You got me hung, Jack. Who the fuck
> are you?"
>
>
> "Ca — your buddy. Partner. What’s happening, man?"
>
>
> "Good question."
>
>
> "Remember being here, a second ago?"
>
>
> No.’
>
>
> "Know how a ROM personality matrix works?"
>
>
> "Sure, bro, it’s a firmware construct."
>
>
> "So I jack it into the bank I'm using, I can give it sequential, real
> time memory?"
>
>
> "Guess so," said the construct.
>
>
> "Okay, Dix. You are a ROM construct. Got me?"
>
>
> "If you say so," said the construct. "Who are you?"
>
>
> "Case."
>
>
> "Miami," said the voice, "joeboy, quick study."
>
>
> "Right. And for starts, Dix, you and me, we’re gonna sleaze over to
> London grid and access a little data. You game for that?"
>
>
> "You gonna tell me I got a choice, boy?"
>
>
>
<https://archive.org/stream/NeuromancerWilliamGibson/Neuromancer%20-%20William%20Gibson_djvu.txt>
Dix was copied onto a ROM before his death. His consciousness, memories, instincts, sense of humor and cognitive abilities are all there. But as the clip shows, he is frozen at that spot. It can lay down memories while powered up but on being disconnected and reconnected it reverts to the saved version.
In the story the ROM of Dix is a character. There is only one, but there is no reason there could not be many. The ROM is hardware ("firmware")and does not require energy to persist. In the story the ROM of Dix was retrieved from a vault. A good way to survive the apocalypse.
[Answer]
Without some kind of neural interface technology that can graft to the nerve endings and propagate nerve signals in a way the brain can understand, there's not much point to this. The visual cortex, the motor cortex, the hind-brain all would need to be re-connected at some stage to something or he's just a prisoner in sensory deprevation.
If Bill thought there was a chance that technology was only a few years away or was even already in its infancy it might be worth trying? There would have to be a pretty incredible medical reason that this would be considered in the patient's best interest. Acute radiation poisoning perhaps? 10 Gy of radiation exposure is enough to be fatal in a few days, but less than 30 Gy of it doesn't cause neurological damage.
<https://www.gizmodo.com.au/2012/07/giz-explains-what-nuclear-radiation-does-to-your-body/>
As elemtilas points out there are pretty serious risks to this, from the procedure and afterwords. Keeping him in a medically induced coma might mitigate them. Coma patients who recover report that they sometimes experience dreams. There's also biological impairments - give up the body and now there's no bone marrow, no blood cell production, no immune system. No ability to even filter the nutrient solution. Given that NASA can't even keep bacteria out of their clean-rooms this is extremely risky - if bacteria enter the blood stream it is game over.
] |
[Question]
[
Around Earth's equator, there's a band of low pressure called the Doldrums. 30 degrees north and south are bands of high pressure called the horse latitudes. Finally, there are more low-pressure bands in the polar regions called the polar fronts. Air moves from the horse latitudes to the low pressure areas, and is deflected by the Coriolis effect, creating the prevailing winds.
[](https://i.stack.imgur.com/H3aMZ.png)
**Would the above diagram apply to pretty much any planet in terms of prevailing wind direction?**
Correct me if I'm wrong, but as I understand it, if the planet rotated westward rather than eastward, the direction would be flipped because of the different Coriolis effect. Also, a higher speed of rotation would increase the Coriolis force (hence Jupiter's centuries-lasting storms), but that wouldn't change the *direction* of the winds to my knowledge.
[Answer]
# No, wind patterns are not always going to be the same.
Venus is a key counterexample here. [Its Hadley cells extend to 60 degrees above and below the equator](https://www.windows2universe.org/venus/venus_polar_atmosphere.html&edu=high) - double the size of Earth's Hadley cells. In other words, they extend above the subtropics and through what would be considered, on Earth, temperature zones. It's been proposed that in the past, [Earth's Hadley cells extended to the poles](https://www.seas.harvard.edu/climate/eli/research/equable/hadley.html), during periods of higher global temperatures. The cells then transported heat to higher latitudes.
Here's a diagram of what this looks like (Figure 5, [Cirilo-Lombardo et al. 2017](https://arxiv.org/abs/1709.03676))):
[](https://i.stack.imgur.com/tIubo.png)
The key point here is that there's no change in the direction of circulation on Venus at middle latitudes - like the Ferrel cells you note. Instead, in each hemisphere, there's uniform circulation until you get the poles, [where you find cooler winds](http://adsabs.harvard.edu/abs/2007Natur.450..637P), just like on Earth. [Polar vortices can be found here.](http://adsabs.harvard.edu/abs/2007Natur.450..629S)
There are [a couple other peculiarities](http://adsabs.harvard.edu/abs/2007Natur.450..633M) about the atmosphere of Venus that I should mention:
* Its atmosphere exhibits super-rotation, where the atmosphere travels faster than the planet (thanks partly because of Venus's extremely slow rotation).
* The atmosphere has a retrograde rotation, like the planet itself.
* The pressure gradient $\nabla p$ is *not* influenced primarily by the Coriolis force - which is essentially $0$ - but instead by the centrifugal force.
This last point is actually really important, and *does* contribute to wind direction.
[Answer]
**Insofar as we have data, you are correct, but...**
If the only thing you're considering is the planet and nothing else, then you are correct. All planets will experience fundamentally identical behavior (winds moving with the direction of rotation), differing only in the details (where the pressure zones are, wind force, etc.).
**However..**
If you spin the planet fast enough, I can imagine some of those rules shifting. Yes, the wind will still move generally in the direction of rotation, but ultra high rotation would begin to overcome the longitudinal wind cycles.
The rules would change even more in a binary (or more) star system where heat is applied in a much more complex manner than here on Earth.
And they'd change even more for a tidally-locked planet where the rotation might not be enough to overcome cycles over the light terminator at all. This is the case where better analysis than I can provide would be hugely interesting, because you may see no rotational effects of the wind. (A tidally-locked planet does rotate: once per orbit.)
I also don't want to rule out the axial tilt. Uranus' axial tilt (about 98°) would suggest the possibility of some wild wind changes through the course of a year. However, Uranus is so far away from the sun that images clearly show a rotational wind pattern. But if Uranus were in Earth's orbit such that annual heating (somtimes polar, sometimes equatorial) could seriously affect the winds... and if uranus were Earth-sized such that gravity had less hold for the sake of rotational patterns... that could be a fascinating analysis.
[](https://i.stack.imgur.com/HlonN.png)
*Image courtesy [Space.com](https://www.space.com/13231-planet-uranus-knocked-sideways-impacts.html)*
I also suspect that if Mercury had enough mass to host a thicker atmosphere that the heat from the sun would disrupt rotational patterns on the sun-side, but they'd reassert on the night-side. That would cause huge circum-terminator cycles. Cool.
**The problem is low data**
The universe is constantly surprising us. We're finding planets in orbits that not too ago we thought impossible. We're discovering star and galactic formations that reveal the wonderful complexity of what we call home. When it comes to wind patterns, we have basically nine datapoints all within a single stellar configuration. Any statistician worth his salt would tell you that's a sample too small to make universal (literally) assumptions.
But I think there's enough flexibility in what we do know to rationalize a story with a planet hosting non-terrestrial wind patterns.
] |
[Question]
[
I'm trying to build an underwater ecosystem under the ice crust of Ganymede. I know Jupiter emits a large amount of ionizing radiation and synchotrons and thought that would maybe be able to replace sunlight in this ecosystem. My idea is some sort of large organism that would burrow into the ice with root like tendrils to absorb the radiation and basically fit the ecological niche of trees. I've also read about radiotropic melanized fungi that are thought to use melanin to drop the wavelength of some high energy radiation to a usable level.
So my question is
1. Could these organisms use melanin to absorb a portion of the radiation as heat and output a usable wavelength of radiation for a chemical process analogous to photosynthesis where it would introduce oxygen into my ecosystem?
2. If not, then (assuming any necessary nutirent/molecule needed is naturally present) is there any theoretical chemical process for these organisms using radiosynthesis?
[Answer]
This is a very interesting question!
>
> Could these organisms use melanin to absorb a portion of the radiation as heat and output a usable wavelength of radiation for a chemical process analogous to photosynthesis where it would introduce oxygen into my ecosystem?
>
>
>
You are probably thinking about the [radiotrophic fungus](https://en.wikipedia.org/wiki/Radiotrophic_fungus) that was discovered in Chernobyl:
>
> Radiotrophic fungi are fungi which appear to perform radiosynthesis, that is, to use the pigment melanin to convert **gamma radiation** into chemical energy for growth.
>
>
>
The emphasis on gamma radiation is important. If you want to use a pigment to extract energy from radiation, it has to be electromagnetic radiation - alpha and beta radiation won't do. Unfortunately for your ecossystem, no EM radiation can reach under the ice of Ganymede. Not even gamma.
Water is a very efficient shield against it. [If you get 13 cm of water between you and a gamma source, you only get half the radiation you would otherwise](https://sciencedemonstrations.fas.harvard.edu/presentations/%CE%B1-%CE%B2-%CE%B3-penetration-and-shielding).
Even if it weren't so, you'd be hard-pressed finding a gamma source. [The sun does not emit gamma radiation](https://physics.stackexchange.com/a/142008/31264). The magnetosphere of Jupiter is [only powerful enough to generate X-rays, not gamma](https://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter). If you have a source within the liquid ocean itself, it will probably [redacted] up the ecossystem around it.
>
> If not, then (assuming any necessary nutirent/molecule needed is naturally present) is there any theoretical chemical process for these organisms using radiosynthesis?
>
>
>
We simply don't know of a way a creature could use α or β radiation for its metabolism; both tend to cause a lot of harm to DNA and organelles. Any local source of gamma would be generating a lot of those other two as well.
If you want to be realistic, you can have [chemolithotrophic](https://en.wikipedia.org/wiki/Lithotroph#Chemolithotrophs) organisms as the base of the food chain. The chemolitotrophs would thrive only around [hydrothermal vents](https://en.wikipedia.org/wiki/Hydrothermal_vent), but the rest of the ecossystem would free to roam and live elsewhere.
Last but not least, if you want to go through this route, [Europa is a better candidate than Ganymede](http://lasp.colorado.edu/education/outerplanets/moons_galilean.php):
>
> The case for Europa's subsurface ocean comes from the strong probability of tidal heating, melting the ice under the surface. Ganymede has a much weaker tidal force, and thus weaker tidal heating than Europa and Io. The level of Ganymede's tidal heating could not provide enough heat to make an ocean of liquid water. Aside from tidal heating, we are not sure where sufficient heat would come from to melt the ice.
>
>
>
I know this is in contradiction of the wiki, which states there is probably an 800 km deep ocean in Ganymede. I believe the article from LASP is older. However, the fact remains that Europa has stronger tides. Those help moving the geology of the moon around, which can provide nutrients to the subsurface ocean over time. I believe Europa is richer in salts too, so even better for chemistry to give rise to life.
[Answer]
Renan's answer highlights important facts on radiation penetration through ice (limited for gamma, functionally non-existent for beta electrons & alpha nuclei), and the greater plausibility of chemoautotrophic organisms. However, I can add a little on potential photon-centric mechanisms in case that is of interest.
## Background info
The main important piece of information is understanding that life fundamentally lives on chemical energy gradients. Get some way to acquire spare energy that can transform complex molecules and you can probably hack together some form of self-replication from those molecules.
On Earth we find life building off photosynthesis (whereby an incoming photon has its energy captured by the chlorophyll molecule, and then clever chemistry leads to that energy being redirected to do microbiological work building up complex molecules elsewhere in the cell), or chemotrophic life that leaves near (eg.) ocean volcanoes and "eats" the exotic sulphur compounds, which are highly reactive with carbon-ish molecules and thus can be used to do microbiological work.
In theory, the photons of gamma radiation could be captured and used in the same way as visible light is in photosynthesis, you just need a chlorophyll-esque molecule that is tuned to the energy of some appropriate photons (captures the photon, promoting the chlorophyll to a higher energy vibration or ionisation that can be utilised in further organic reactions). The **considerable difficulty** here is that gamma radiation generally imparts enough energy to ionise/break bonds in organic material, destroying the lifeform.
## Solutions
**Possible Solution for Gamma-feeders:** You either need an organism that is made of sturdier stuff than hydrocarbons, or invent a system where your organisms generate some shallow stabilised dendritic tunnels in the ganymedean ice, then sit at a deeper level (recall that gamma penetrates ice poorly) and pump a photosynthetic liquid through the tunnels, reabsorbing the energised compounds that come back, but not directly exposing themselves to the gamma radiation. The details are tricky --- in real-life you need to chemically utilise chlorophyll's absorbed photon in a few hundred nanoseconds or else the chlorophyll converts the energy to useless heat --- but doable.
**Possible Solution for Beta-feeders:** Beta radiation can easily ionise organics, which in principle could be used as an energy source for organic reaction, although the chemical pathway would be somewhat different. However, beta radiation is more destructive to molecules than gamma radiation (electrons carry more energy than photons), giving us far thornier versions of the destruction problem from earlier. Furthermore, any location that has beta exposure would have to be on the surface of the ice, meaning direct exposure to gamma and alpha radiation. I cannot imagine a lifeform living sensibly in such conditions without a completely novel chemical makeup to resist radiation damage.
**Possible Solution for Alpha-feeders:** None. Alpha radiation is helium nuclei getting flung around. Sure, they carry lots of energy, but trying to use them for organic reactions is like trying to catch a bowling ball with a cobweb.
[Answer]
**Water hydrolysis. And something else.**
Ionizing radiation can hydrolyze water. This is important for people storing and handling radioactive materials because products of water hydrolysis can accumulate.
<https://en.wikipedia.org/wiki/Radiolysis>
>
> Of all the radiation-chemical reactions that have been studied, the
> most important is the decomposition of water. When exposed to
> radiation, water undergoes a breakdown sequence into hydrogen
> peroxide, hydrogen radicals, and assorted oxygen compounds, such
> as ozone, which when converted back into oxygen releases great amounts
> of energy. Some of these are explosive.
>
>
>
Alpha particles are the best at hydrolyzing water because they are the most ionizing. Beta particles and gamma rays can do it too. All three types occur in the deep earth. There actually are non photosynthetic ecosystems which live off of hydrolyzed water, specifically hydrogen. Hydrogen is tasty microbe food wherever it occurs. In the deep earth it is generated by radioactive decay and consequent hydrolysis of water.
[Long-Term Sustainability of a High-Energy, Low-Diversity Crustal Biome](https://www.jstor.org/stable/pdf/20031589.pdf?casa_token=gLlF-qvC97AAAAAA:pcRphvbhfnAJTfbh3pRL1iaHGJPfd6ESiO9IH0cVvzrJu8nHj1wK_LyqJcNJk5effsGbm-MhtB4s_NYh4a_3gdkZXbdo7z0lLB64dHX-XWOXdfHvUg)
>
> The hot, reducing, gaseous water emanating from a fracture at 2.8 to
> 4.2 kmbls harbored a microbial community dominated by a single Firmicutes phylotype. The Firmicutes probably penetrated the Mponeng
> fracture zone at current depths during infiltration of paleome
> teoric water between 3 and 25 million years ago and since then have
> relied on nonphoto synthetically derived H2 and S042\_ converted from
> Archaean/Proterozoic pyrite. Nutrient concentrations have
> remained much higher than observed in shallower crustal environ
> ments, suggesting that the deep crustal bio sphere may be energy-rich,
> is not approaching entropic death, and is capable of sustaining
> microbial communities indefinitely by geological processes.
>
>
>
These organisms live off of naturally occurring hydrogen liberated from water by ionizing radiation. The stuff is just laying around. The next step for a greedy organism is to have a huge onboard water tank – the equivalent of leaves for capturing solar energy. Reactive products of water hydrolysis within the tank are captured by cellular proteins and sequestered as we sequester sugar, for later combination to produce energy and regenerate the water. The tank is an acellular film resistant to ionization. DNA is shielded deep under the water tank organ.
If this were a science fiction dealing with such creatures, the deep earth hydrogen biosphere would be the first step (established biogeochemistry), and discovery of the water tank creatures the second – a not so wild extrapolation.
One more step into fantastic fiction! Very energetic gamma rays have too much energy to hydrolyze water. They produce a different energetic substance. Positrons.
<https://en.wikipedia.org/wiki/Gamma_ray#Matter_interaction>
>
> Pair production: This becomes possible with gamma energies exceeding
> 1.02 MeV, and becomes important as an absorption mechanism at energies over 5 MeV (see illustration at right, for lead). By interaction with
> the electric field of a nucleus, the energy of the incident photon is
> converted into the mass of an electron-positron pair. Any gamma energy
> in excess of the equivalent rest mass of the two particles (totaling
> at least 1.02 MeV) appears as the kinetic energy of the pair and in
> the recoil of the emitting nucleus. At the end of the
> positron's range, it combines with a free electron, and the two
> annihilate, and the entire mass of these two is then converted into
> two gamma photons of at least 0.51 MeV energy each.
>
>
>
These lower energy gamma rays are fine for hydrolysis of water. When energetic gamma rays come, the organism captures and retains positrons for later release, to produce gamma rays during lean times. Positrons are antimatter. The creature’s storage organs for positrons are interesting, valuable and extremely dangerous.
] |
[Question]
[
## Information
I am developing the culture of the dwarves in my fantasy world, and I am interested in a calendar system for my dwarves. Yes, I am aware of the question [How would my dwarves tell time underground](https://worldbuilding.stackexchange.com/q/53090/28789), but I was wondering how dwarves would keep track of entire years/months/days and etc.
The Criteria are:
* It must be, for the most part, independent from any other calendars.
* Not based on the sun, unless this can be worked in a interesting direction
* If based on the moon, similarly only if in a new, interesting way.
## Some other Information
My dwarves revere crickets as they use them to detect poisonous/explosive gases in the mines. They keep perpetually lit forges as the draft keeps the tunnels and caves ventilated, so forges going out is bad. And they mostly eat fish, mushrooms, insects, and whatever they can trade for.
Edit: This question applies specifically to a species that lives underground (dwarves) and do not see any sunlight or moonlight, but still are affected by the outside world, in little ways, through trade and seasons. I want something that fits the dwarves specifically.
[Answer]
Based on their own biological clock. Many marine species breed during very specific times of the year, like down to a few weeks window. Mammals tend to have regular patterns for being fertile. Off spring tend to be ready to reproduce at about the same age. People sleep after so many hours awake.
So an example; dwarf short cycle is how many hours they can stay awake. The medium cycle is the time between times of fertility. The long cycle is child gestation. The life cycle is time until the next generation can reproduce.
This has the advantage of being fully unique to the dwarfs. It’ll be shaped by biology and culture and can cause issues later as culture changes (marrying age shifts by years over time, suddenly the amount of life cycles ago a king ruled is different amount of absolute time etc.)
[Answer]
There are cycles under the earth. No not bicycles!
Any repeating sequence of natural events should be helpful to your dwarves.
First thing that came to mind is rainy season. While the rain won't be falling on your dwarves heads, the water will be collecting in the mines and caves. Think of the boys trapped in the Thai caves at the moment. Authorities are worried about the oncoming rainy season flooding the caves.
If snow and ice is the source of your mines water, then spring's winter melt will be the cause of annual fluctuations in water. Even if there is no direct water source above the mines like a rainy season or snowpack you can still have fluctuations. Consider the okavango delta, which is bone dry for part of the year but then receives 11 000 billion litres of water from the Angola Highlands many miles away, not from direct rainfall over the delta itself. It takes a month for the water to travel across 1200 km of land. Now just put all that water in an underground cave system and adjust accordingly.
Secondly, as already mentioned in the comments, tide. I'm not sure how large this will be. It will typically be restricted to water sources connected to the oceans. Internal rivers and lakes don't typically have a noticeable tidal value.
Thirdly, as mentioned by Seserous, animal mating and birthing seasons. I was thinking bats, rodents, and various bugs. If there is a form of cicada in your world, you have a longer "decadal" year marker (I know, on Earth, cicadas repeat on a 7 year cycle).
Temperature doesn't seem to vary much underground, due to season.
>
> The earth temperature beyond a depth of 1 meter is usually insensitive to the diurnal cycle of air temperature and solar radiation and the annual fluctuation of the earth temperature extends to a depth of about 10 meters. In order to study the fluctuations of the ground temperature with depth we have installed a 50m deep U-tube in the ground equipped with thermocouples at various depths. The measured temperatures indicate that the short-period temperature variations are prominent to a depth of approximately 0.5 m. Because of the high thermal inertia of the soil, the temperature fluctuations at the surface of the ground are diminished as the depth of the ground increases. The annual temperature variation of the ground at a depth of 3m is between 15 to 25°C while at a depth of 25m is negligible and the temperature remains constant at about 22°C. The temperature measurements are compared to the calculated values resulting from simulations performed with TRNSYS.
>
>
>
Source. [PDF | Annual ground temperature measurements at various depths.](https://www.researchgate.net/publication/30500353_Annual_ground_temperature_measurements_at_various_depths)
For short time-keeping, I assume some sort of water-based clock would be used. Once a standard measurement of how far a water droplet should drop is defined, they can keep track of seconds. Then they can create minutes using their number system e.g. 60 or 100 seconds etc.
They can also use the classic fantasy time-keeping candle hours based on how long it takes to burn notched candles (these are typically made of standard consistencies and have a known number of hours it will take to burn through. Although this probably is affected by drafts or trimmed wick etc).
[Answer]
**Earth resonance.**
from [The Future of the Wireless Art, Nikola Tesla, 1908](https://teslaresearch.jimdo.com/articles-interviews/the-future-of-the-wireless-art-by-nikola-tesla-1908/)
>
> "When the earth is struck mechanically, as is the case in some
> powerful terrestrial upheaval, it vibrates like a bell, its period
> being measured in hours. When it is struck electrically, the charge
> oscillates, approximately, twelve times a second. By impressing upon
> it current waves of certain lengths, definitely related to its
> diameter, the globe is thrown into resonant vibration like a wire,
> stationary waves forming, the nodal and ventral regions of which can
> be located with mathematical precision. Owing to this fact and the
> spheroidal shape of the earth, numerous geodetical and other data,
> very accurate and of the greatest scientific and practical value, can
> be readily secured. Through the observation of these astonishing
> phenomena we shall soon be able to determine the exact diameter of the
> planet, its configuration and volume, the extent of its elevations and
> depressions, and to measure, with great precision and with nothing
> more than an electrical device, all terrestrial distances. In the
> densest fog or darkness of night, without a compass or other
> instruments of orientation, or a timepiece, it will be possible to
> guide a vessel along the shortest or orthodromic path, to instantly
> read the latitude and longitude, the hour, the distance from any
> point, and the true speed and direction of movement.
>
>
>
The dwarves strike the earth electrically (or mechanically) using ingenious machines, and measure the vibrations. These have a characteristic oscillation. As long as the nature of the Earth is unchanged, so too the period of these oscillations does not change. Each type of oscillation corresponds to a period of dwarf time.
---
Or they could use pendulum clocks. Not quite as cool, though.
[Answer]
A year, theoretically, wouldn't have to exist as the phenomena a year refers to, circling the sun, would be unknown to the Dwarves; same with a month and the moon. You might get something for seasons since that's likely to be noticed even below-ground but the smaller timeframes might not exist at all.
Given that they do presumably have the daily routine of a Human, based on the 8 hour sleep for example, they might well refer to a day as a "Cycle" with different Cycles dictating what part of the day it is.
"Sleep Cycle" referring to their night, "Rising Cycle" referring to their morning, and "Mid Cycle" for the in-between.
[Answer]
Whenever I think of Dwarves I think of a race that have developed science to an artform so advanced as to appear to be magic, but I digress.
They could have a calendar based on the sun, if they had a device that measured gravity and thus pointed to the largest gravitational field. They could then discern days, years and by using different machines and measurements lunar months.
Maybe the device could, by measuring gravitational forces in a given area also then be used to help predict earthquakes, useful for subterranean dwellers.
] |
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[
One of the trickiest things I had to do when coming up with my urban fantasy story full of superpowers was finding a consistent set of rules to justify why people can use powers like invisibility, wall-phasing, shapeshifting or teleportation and not have to be/become naked to do it. Eventually I managed to come up with one, but I just want to run it past the people here to make sure it actually makes sense and there's nothing I've missed.
Here's how it works:
The body of every person with powers emits an invisible aura that extends 2-3 inches away from the body in all directions. If any solid object, whether that be an individual strand of thread in a shirt or the steel of a blade, spends 5 solid minutes completely and totally within that aura without a single molecule being connected to a molecule that isn't, then that object becomes "synced" with the person in question and can be affected by any powers that are "syncable" as long as the person's aura is touching at least part of said object.
In short, as long as it's small enough that you can encase it within your aura in some way for five minutes, you can take it with you when you teleport, make it turn invisible or intangible with you, or any other of the myriad ways powers can and do extend to possessions. If it's got too many distinct and separate parts and isn't one solid piece (like, say, woven fabric), you can still make your powers affect it as long as all individual solid components are encased in the aura.
There are some exceptions: for balancing reasons some powers will only affect the parts of synced items that are actually encased by your aura at the time, and some detrimental effects that would otherwise be too easy to cheat with this system will treat all solid nonliving matter within your aura as synced for the purposes of what it does.
Can anyone see any problems with this? Any way the logic is flawed, or any unpleasant loopholes in this system that spring to mind? Or does this sound like it's good to go?
[Answer]
This is really an extended comment, but it seemed like a useful general purpose answer for people making magic within a science framework, so I've written it as an answer.
First off, in the comments I argued that there really isn't a "thing" which is a "bonded set of molecules." That's because nature doesn't have discrete states like that. There isn't "bonded" and "non-bonded." It's more accurate to look at it as a range between fully bonded and completely independent. However, there's a rather sharp transition region which we observe few molecules to be in. If we simply assume molecules never spend enough time in that state to matter, we can treat it *as if* there were two clear states: bonded and non-bonded. It isn't that those states exist in reality, its that it's effective to model things as though they did exist.
Which leads to the most important rule for magic systems like this: [Sanderson's First Law of Magics](https://brandonsanderson.com/sandersons-first-law/):
>
> An author’s ability to solve conflict with magic is DIRECTLY PROPORTIONAL to how well the reader understands said magic.
>
>
>
To this end, who cares if physics says that bonded vs. non-bonded is a non-real simplification of reality. Most readers have some fundamental concept of what it means to be bonded. As long as they understand it, that's all that matters.
Now if you never push the corner cases, you're set. However, let's say you do want to push the corner cases. You want to see whether you can "sync" with something that is in the process of sublimation. Now, your reader may not have enough of a fundamental understanding. Now you might need to dig deeper into the physics to analyze how "sync" should occur. Don't want to push it? Then you're golden! Sanderson's law is the key.
Now, if I may offer a suggestion which makes a lot of the rules-lawyery stuff go away: let magic operate on the "self." "Self" is a noun which does not have a precise physical meaning, but every human being out there has some concept of themselves. If you admit a concept of "self" into your magic, you gain access to a whole slew of natural easy to understand concepts which make these sorts of games easy.
For example, you primary concern is teleportation of clothing. Make the teleportation spell work upon what the individual sees as "themselves." Make it work on their mental image of who they are. Most people don't visualize themselves naked on a regular basis, so that means most people's sense of self extends to their clothes as well. Now there's no issue at all with syncing. You naturally will sync with your clothes, and that's a concept readers understand, so you don't have to dig the physics any further than that.
In theory one could abuse this by successfully visualizing something else as part of themselves (you can visualize anything). However, if you really truly feel that it is part of yourself, there are *serious* consequences. For example, you must protect that thing as part of your self, just like you would protect a finger or a leg. You must feel mental anguish if it is damaged. People can manipulate you simply by threatening to damage the object. If you don't have traits like these, then you didn't *really* treat it as part of yourself, and you wont sync it.
If you wanted to, you could also blur the line of what is "synced" and instead have degrees of being synced. You and your clothes may be highly synced. The pin you just picked up may be very low on this scale (but increasing continuously because it's within 2-3 inches of your self). Now make the rule that you can teleport *anything*, but it takes more energy/mana to teleport things if they aren't well synced. Teleporting with that pin might take great effort.
Now you have a very rich system. A normal person does not think of a gun as part of themselves, so they could not teleport with a gun with ease. However, a gunslinger whose life has depended on that firearm may think of it as an extension of themselves, in which case teleportation with that gun is easy peasy.
You can even bend the rules with this. Consider a Japanese warrior-monk whose family has safeguarded an heirloom katana for generations. That monk may be so synced with this heirloom that they can maintain the sync, even beyond the 2-3 inch range. They could teleport that katana right to their hand from across the room. And it won't seem overpowered because this monk has literally devoted their life to this cause.
All of this is easy because the concept of magic was allowed to operate on our mental image of ourself. There's no easy physical description of what that means, but every reader intuitively understands it.
Oh, and if you want to use it, you could consider taking advantage of the concept of [Evanescent Waves/fields](https://en.wikipedia.org/wiki/Evanescent_field). This is a real life phenomena which occurs over *very* short distances (fractions of a wavelength) where energy which is totally reflected "leaks" out of an object. It occurs because of the same issue we started with. We think of light reflecting off the edge of a prism as reflecting off a border, but the physics of light waves doesn't recognize borders like that. When you model the full wave behavior of light, you find there must be a fuzzy region "outside" of the prism where light acts funny, just like the 2-3inch region around the self where sync occurs.
[Answer]
/a consistent set of rules to justify why people can use powers like invisibility, wall-phasing, shapeshifting or teleportation and not have to be/become naked to do it. /
You have correctly pointed out that nakedness is the only pure way to accomplish this magic. Any other method will be poked full of holes by the hard core critical nerds - for being totally arbitrary if for nothing else. You know its true and you struggle with it, and rightly so.
Nakedness is the only pure way to accomplish your ends. Nakedness and also hairlessness because hair is not alive either. I will point out that with the shining exception of Terminator (and those 2 kept their head hair if not body hair) just about every other SF has hand waved its way past what you astutely observe is an issue. OK, the Invisible Man had to go around in the buff but the invisibility sort of solves the issues that nakedness would otherwise present. Otherwise everyone keeps clothes and hair and it just does not hold water.
Go with your gut - keep it naked and hairless! I mean the magic, not your gut. Although that too if you want.
[Answer]
Rather than have an aura, why not have the magic caster be able to channel magic into objects they are in contact with, which will them allow them to apply the same power to it?
To explain in detail, a magic user can channel magic into all objects they are in contact with. The magic will spread along the object allowing the magic casters power to be applied to it. The magic caster can also purposely exclude objects, so things like a coin in your wallet will be included as they are in physical contact with other objects that have been your magical power in it, while things like the ground won't be because the user will choose to not include it.
This way your casters will still have clothes, they can use their power instantly, which won't bring their clothes along, it takes them sometime to channel their magic into their clothes which allows you to set a delay before they can move away. You can also bring long things like a sword or maybe a rifle with you (since they could be further than 2-3 inches from you). You can exclude obvious objects, like maybe someone holding onto you, but things you aren't aware of, like a tracking device will still follow you through.
[Answer]
I like this concept but would make a few changes:
1. **Expand the range** beyond 2-3 inches, to a foot or two. The problem with such a short range is that it would be hard to get many items entirely into that space. For example, a bulky backpack, a staff, a rifle, a small box -- all of these you might want to sync, but it would be hard to press them against your body to get into a small 2-3 inch range.
2. For storytelling reasons, I think it makes sense to **be flexible with the distance and time**. "a few feet" and "a few minutes" should suffice. Maybe a person's aura power waxes and wanes constantly throughout the day.
3. Powered people will need to be able to **sense when something is synced** or not. This way - for example - they're not guessing whether their backpack or clothing will be teleporting along with them or not.
4. Let powered people **quickly sync** with an object through a spell or force of will. There may be times when the person is in a rush, and they may need to speed up the syncing process (e.g., someone throws you an item that need to quickly take with you while teleporting); this should be possible by casting another spell, augmenting a spell, or just sheer willpower -- and should use up mana or cause fatigue.
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[Question]
[
Imagine that, in the near future, pollution, overpopulation and war leads to a *massive* extinction where almost all chordates, some invertebrates and many plants are wiped out. Small, resilient plants, insects and the like remain, but all megafauna is dead.
Then, mere decades later, an interstellar ark arrives at Earth from another world. On board are a multitude of sapient species, which fled another warlike race that has since destroyed their homeworlds. To them, Earth was like Kepler 186f is to us. They had discovered it beforehand, confirmed it to be in the habitable zone, but did not know whether or not it had any life. So, they brought with them hundreds of species from their world (Mainly from one planet, since they would have all been completely different in physiology if they were all from different worlds.). They arrive at the barren Earth and introduce the alien creatures across the globe, in whatever environment they're best adapted to.
So, the question is: **If sapient species came to Earth after a mass exinction, and introduced hundreds of species from their own world, how long would it take for them to get a foothold?** I know that natural selection is cruel, and not all the species would survive very long. However, with supervision, help and managing from sapient species, could they have fully functional ecosystems and food-webs all over the world? One with active predators hunting saltatorial grazers and heavy browsers, their carcasses fed on by scavengers?
If you require any more clarification, just say so (Nicely, preferrably.) in the comments and I'll edit it as soon as I can.
[Answer]
**Plan for about a century or two.**
This is a case of invasive species. You have a shocked Earth ecosystem that you’re about to introduce true alien species into. There are two major things to consider here for each species you want to transplant:
1. How viable is this species within the existing ecosystem that matches its ideal climate?
2. How long does it take to propagate in said ecosystem?
The first question is the most critical. Invasive species tend to be so successful because the native species have no previous experience competing or surviving alongside them. As long as this foreign land is *familiar enough* to the invading species, it typically gains a foothold and then some. Ecological similarities might be a big sticking point for your aliens because rather than being transplanted from a separate region on the same planet, they’re from an entirely different planet. Even small atmospheric or planetary differences could prevent viability. If so, those species will die.
Propagation time depends on reproductive cycles and life spans. Invasive plants in the Americas have become immensely successful in a century or two, often in spite of active campaigns to eradicate them. You may very well be able to improve those times with active support of your flora. Fauna can take control of ecosystems even faster – Burmese Pythons in Florida have taken hold in the ecosystem in a matter of decades.
A note of caution here: you need both alien flora and fauna to have certain compatibilities with Earth life. Successful propagation of Earth plant species is often closely tied to insects and animals – if insects can’t assist in cross-pollination of your alien plants, that could be a serious problem. Likewise for animals – if they need to subsist on Earth fauna or flora, their digestive systems will need to be able to gain nutrients from the foreign materials efficiently.
Extinctions will, of course, be common. Given the general advantage of the invading species, it’s likely that native Earth species will lose the most. It’s inevitable, however, that some alien species won’t adapt well. All told this won’t be a fast process, but with active help from intelligent life, it won’t necessarily be too long either.
[Answer]
It depends a lot on:
1. how similar the ecosystem they are trying to introduce is to Earth's existing, surviving, lifeforms
and
2. how much of their "native" ecosystem in terms of both diversity and the vertical food-chain they have.
For example a species with left [chirality](https://en.wikipedia.org/wiki/Chirality_(chemistry)) will be starting from scratch with basic carbon capture etc... because all life on Earth uses *right chiral* enzymes (I'm not sure if it's even possible to have life with left chiral enzymes). Surprisingly enough if they have the necessary material, encompassing everything from primary producers in the form of their equivalent of [Cyanobacteria](https://en.wikipedia.org/wiki/Cyanobacteria) to the higher animals, this is actually the best case scenario for fuss free colonisation; their crops etc... have *no natural predators* except what they bring with them because nothing on earth can interact effectively with their molecular biology. In this case they spread as fast as their native species can broadcast off-spring since their is little competition for basic resources with so much of "our" ecosystem destroyed and none of what's left can attack the new colonists.
At the other extreme if they're right chiral and DNA based they're prey to everything left living on Earth and probably have no natural resistance to any terrestrial bacteria, fungus or virus, because being DNA based doesn't mean they have anything like a terrestrial immune system. In this case it will be *War of the Worlds* all the aliens die within a few months of landing because something basic and intrinsic to us, like [mitochondria](https://en.wikipedia.org/wiki/Mitochondrion), present a lethal pathogen.
I'd say the most likely scenario is something in-between; there are probably points of convergence in biological structure that make the aliens somewhat compatible with "life as well know it" so while they have little competition some of our native lifeforms do predate part or all of some of theirs at certain points in their life-cycle (whether that's while they're alive or one they're dead) so there will be some give and take. Colonisation will be possible but problems will crop up due to unexpected interactions.
[Answer]
# This is like the Columbian Exchange
The [Columbian Exchange](https://en.wikipedia.org/wiki/Columbian_Exchange) on Earth provides the nearest real-life analogue. Look at how various creatures on Earth survived when introduced to the New from the Old.
There was a mass extinction of megafauna in the Americas. America's former horses went extinct (along with llamas and oxen and pretty much every other horse analogue except the American Bison). Horses were reintroduced in 1519 and rapidly expanded. On the other hand, it helped that Old World horse were probably the same species as the extinct horses.
Apart from horses, the earliest and most widespread case, there are also plenty of feral wild boar in North America, and water buffalo in Australia (technically not the Columbian Exchange, but the same concept). Neither of these animals had particularly close relatives that went extinct. Wild boar seem to have occupied the niche formerly occupied by black bears; while water buffalo compete are probably the analogue of extinct giant wombats. Both these introduced species expanded relatively rapidly; since widespread introduction in the 1800s they have feral populations in the millions (for boar) and up to 350,000 for buffalo in Australia before heavy culling.
[Answer]
I believe that if these species' is spacefaring to the level of interstellar travel, they should have more advanced knowledge in genetic engineering. In that case, I do not see a problem in integration with any natural environment.
Additionally, one could argue that because of their warlike origins, they should have even better technological advances on survival aids. Therefore, I do not think they or their fauna should take more than a decade to integrate with Earth's ecosystem even if the other civilization attempts to conserve the local life and not alter that.
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[Question]
[
I have a world I've been developing whereby the entire world is locked in a cycle of perpetual winter. The "seasons" still exist but are merely a spectrum of mild cold ranging toward horrific winters. More or less it is the Antarctic but across the entire surface of the planet.
Inhabitants have created societies by living in the vast network of caves throughout the rocky surface. Geothermal energy has been harnessed to power and heat these cities. Magic in this world is normalized and minimal. There are a few artifacts of vast power but mostly magic is confined to everyday practical use (minor cantrips for household chores, ward off diseases, etc). The individuals in these cities can and do travel overland to trade, make war, pass along news.
That said, I am curious if there are real world fabrics or processes of weaving fabrics that could be used with the technology available late medieval to a early renaissance society that would be effective at warding off such extreme temperatures. The fabrics ideally would be as light weight as possible.
**Restrictions:**
* As stated above the temperature range would be -18 F (-27.7 C) in the
Summer down to -76 F (-60 C) in the Winter months.
* The Climate will vary across the surface of the planet with some
areas experiencing wetter snowier climes and others drier
* The fabric ideally will keep the wearer warm enough to survive
exposed during the day time temps and survive under cover during
evening temps.
* The fabric will ideally be as thin as possible so that the wearers
are able to move, work, unencumbered by massive bulky clothing.
* The flora and fauna of the world resembles a combination of that
found in the Ice Age (Pleistocene) era and that found in the present
day Permafrost climates.
[Answer]
**Asbestos cloth.**
[](https://i.stack.imgur.com/kVnn3.jpg)
<http://www.yarnmagazine.com.au/category/uncategorized/>
<https://www.asbestos.com/asbestos/history/>
>
> ... because the ancient Romans were said to have woven asbestos fibers
> into a cloth-like material that was then sewn into tablecloths and
> napkins. These cloths were purportedly cleaned by throwing them into a
> blistering fire, from which they came out miraculously unharmed and
> essentially whiter than when they went in. While Greeks and Romans
> exploited the unique properties of asbestos, they also documented its
> harmful effects on those who mined the silken material from ancient
> stone quarries. Greek geographer Strabo noted a “sickness of the
> lungs” in slaves who wove asbestos into cloth... Around 755, King
> Charlemagne of France had a tablecloth made of asbestos to prevent it
> from burning during the accidental fires that frequently occurred
> during feasts and celebrations. Like the ancient Greeks, he also
> wrapped the bodies of his dead generals in asbestos shrouds. By the
> end of the first millennium, cremation cloths, mats and wicks for
> temple lamps were fashioned from chrysotile asbestos from Cyprus and
> tremolite asbestos from northern Italy.
>
>
>
[Asbestos textiles](https://inspectapedia.com/hazmat/Asbestos_Textiles.php) were manufactured from ancient times up until the mid1900s. Of course the main attraction of asbestos cloth is that it is impervious to fire and sparks. It also protects workers against hot air as might be encountered in a foundry. The air pockets trapped between the mineral fibers are excellent insulators; slad wool or [mineral wool](https://en.wikipedia.org/wiki/Mineral_wool) to this day is used for insulating properties.
If it is a good enough insulator to keep hot air out, it can keep warm air in - next to the body. I found [an ad for asbestos clothing](https://books.google.com/books?id=1JkiAQAAMAAJ&pg=PA9501&lpg=PA9501&dq=%22asbestos+clothing%22+cold+weather&source=bl&ots=QvoXc7j1TS&sig=kRbs1364Ulalfv08TEI8lxNEMmY&hl=en&sa=X&ved=0ahUKEwjJ4JfZjsraAhWH2FMKHcHVBtoQ6AEIVDAO#v=onepage&q=%22asbestos%20clothing%22%20cold%20weather&f=false) from the 1920s that boasted of this property.
The other good thing about asbestos clothing (or slag wool clothing) for this world: it is freaking cold. There will not be silkworms. There will not be cotton. Musk ox will struggle. I am not sure what the humans will find to eat. But they will be able to dig up and refine asbestos into fabric.
[Answer]
Without knowing what sorts of fabrics are available, there is one way for lightweight materials to be extremely warm: layering.
So long as the outer shell is windproof (to prevent the wind from blowing through the layers of fabric) the multiple layers create [insulating](https://infogalactic.com/info/Thermal_insulation) layers of trapped air which serve to reduce the amount of heat transfer from the body.
The other caveat is to ensure the person wearing the ensemble does not get wet, either by being exposed to water (i.e. falling in or being splashed by large amounts of water), or by vigorous work leading to sweating. The second hazard can be mitigated by opening or delayering some of the clothing to allow excess body heat to escape.
For a fairly extreme example, when [George Mallory](https://infogalactic.com/info/George_Mallory) attempted to climb Mount Everest in 1924, he was dressed in multiple layers like this, with layers of silk between other layers in order to reduce friction and allow him to climb.
[](https://i.stack.imgur.com/6GHuU.jpg)
*Replica of Mallory's climbing gear*
[](https://i.stack.imgur.com/LAQAO.png)
*Another view of the replica gear*
>
> The layered natural materials used to construct the garments were found to be excellent at trapping air next to the skin.
>
>
> The outer layer of gabardine was hardwearing and water-resistant yet breathable. But the clothing was also lighter than modern gear - the lightest ever to be used on Everest.
>
>
> "When exposed to a cutting wind blowing off the main Rongbuk glacier, I found the true value of the Gabardine outer layers. These resisted the wind and allowed the eight layers beneath to trap warmed air between them and my skin.
>
>
> It has been a three-year project to create the replicas
> "We both got too hot working on the glacier so we felt that Mallory's clothing would have been more than adequate to climb to the top in, although it would be hard to survive a bivouac near the summit."
>
>
>
<http://news.bbc.co.uk/2/hi/science/nature/5076634.stm>
So multiple layers of fabric, a hard shell to stop the wind and avoiding exposure to moisture at all costs is the key.
[Answer]
Use an aerogel. They're superlightweight (90% air) and very insulating.
This is a Wikipedia article on aerogels. <https://en.wikipedia.org/wiki/Aerogel>
Cork is also good at insulating and natural.
If geothermal energy and a small amount of water magic is harnessed, I would believe that an aerogel would be feasible.
] |
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[
This is one of a series of questions centered around living on a giant tree. The setting/scenario is described below:
>
> In my fantasy world, elves live on a giant tree, very similar in structure to a [Banyan Tree](https://en.wikipedia.org/wiki/Banyan). The elves live on the branches of this tree, which average ~300 feet wide. The tree itself is wide rather than high, only extending 600-1000 feet up. The branches are supported by massive aerial roots, as they are in older banyan trees. The elves can descend the trees to the massive fog-covered swamp below, but rarely do, meaning they have to live off of the tree entirely.
>
>
>
This particular question deals with houses and other constructs the elves would have to build, such as a castle (or at least something that serves the same purpose). The problem is that the elves do not have access to metal, rock, or even a lot of soil. I would imagine some soil would accumulate on the tree, but not enough to start building sod houses out of. All they have access to is a *lot* of wood.
**Given their lack of resources, how would my elves build houses and fortifications?**
The obvious answer is that they will build out of wood, similar to how the Pilgrims built when they came to America - wooden houses surrounded by a wooden pallisade. I'm wondering if there is a different approach I can take.
*Notes:*
* In addition to the tree itself, a lot of additional plants are growing on the tree. These include bushes, vines, and even other small trees.
* The massive tree is home to many animals, and bones/hides are definitely available.
* Water is available, as it collects in pools on the giant tree branches.
* Metal and rock are available in very limited amounts, as the elves can trade with the occupants of the swamp below. Enough to make a few special tools out of; nowhere near enough to build anything out of.
[Answer]
First of all, look up Polynesian history. They build boats, houses and waged war without metal. Weapons were made of wood, bone and teeth.
### Castles
As for your buildings. What's the purpose of a castle?
>
> In its simplest terms, the definition of a castle accepted amongst academics is "a private fortified residence". This contrasts with earlier fortifications, such as Anglo-Saxon burhs and walled cities such as Constantinople and Antioch in the Middle East; castles were not communal defences but were built and owned by the local feudal lords, either for themselves or for their monarch.
>
>
>
Liddiard, Robert (2005), *Castles in Context: Power, Symbolism and Landscape, 1066 to 1500*, Macclesfield: Windgather Press Ltd, ISBN 0-9545575-2-2
I figure you just mean a fortification. Fortifications are dictated by the enemy and their weaponry. If your enemy is other elves living on the tree that means they too have limited access to metals. If it's far away empires that bring armored knights and trebuchets it's a very different requirement.
Where do you build fortifications? Generally along an access point. Either to a valley, on a river crossing etc. So for any outside threat that will be the trunks that lead to the ground. Now a vertical surface is easy to defend. The enemy needs to climb, either the surface itself or a flight of stairs. Elevators can be cut down. Even platforms and stairs could be destroyed under a siege.
If your fighting would be within the tree I see fortifications arise on the points used to travel between branches. Generally the trunk as it's the only thing really going vertical. So a fortification around the trunk makes sense. This needs to be a wall and a gate really.
Perhaps with small holes so our defenders can use specialized pikes to stop the enemy from simply bringing some axes.
### Buildings
I think the most sense would be to erect buildings along connections. Branches to smaller branches, branches to trunk etc. It makes little sense to build a house on the middle of a branch. You got no cover, you're in full wind. No go where you got vertical support from other branches or trunks.
I imagine them cutting into the trunk to make something akin to cellars. Then around it you build your building with wood. The important things protected deep within the bark. If you must live in the middle of a branch dig in. Carve a deep trench as the foundation of your home. Then secure a roof above it.
It makes the most sense your people import iron nails. Wooden pegs could get you far, perhaps even bone is an option. But iron nails would be treasured. Perhaps a sign of wealth even.
If your elves are long lived it would also make sense they shape the tree like a bonsai. Young thin branches are pulled and curved into support structures for future buildings. It's a slow process and needs central administration but it would be worth it for a large city.
[Answer]
First you might want to check out people who have used trees to build things. Namely [living root](https://en.wikipedia.org/wiki/Living_root_bridges) bridges in India--these are often made by Banyan trees and could be a way to connect communities.
Some techniques:
**Aeroponic culturing**
This is specifically to do with using roots for shaping. Your elves have to mist those roots with water and plant food in order to maintain and shape them.
**Instant Shaping** This works best on more flexible type trees and such, like willow.
**Gradual Shaping** This is likely most of what they will doing. In the real world growing a chair can take from 8-12 years for example. If they've gotten to be experts and/or they use magic, however subtle, perhaps the time can be cut down.
Bayan is great, but, they might find they want harder wood for fortification, in which case, they might graft on other things. I know that you said they never leave the tree, but... there are going to be resources they need, not the least of which is soil--they will likely end up planting things in the trees, and while they might have "fertilizer" they may need to harvest some soil. Same goes for water. While you say some collects in the pods, it will likely not be enough, especially if they use aeroponic culturing.
I can't say specifically how they are going to build for defense because I have no idea what you are wanting to defend against. So in general, you'll want vantage points to attack from, ways to prevent egress (pull up ladders, ways to block or even HIDE the way somehow).
Banyan trees do have one cool advantage--the hollow column that sometimes happens in the center. Because Banyans grow parasitically on host trees, they eventually kill them, the host tree rots, leaving the Banyan intact, but with a hollow center. I think that you could likely use this in some way. The holes aren't always huge, but it's possible to use mirrors and spy glasses at various points to monitor things. If a tree is cultivated over years and has a ginormous one, you can use it for other things--a secure place to attack from and move freely up and down, that kind of thing.
[Answer]
Why do they need to build? Gorillas nest in trees just fine; likewise chimps. Your elves can use natural features of their trees and bunk down in forked branches or other comfy places. If I lived in a tree I would string up a hammock at night because I worry about falling as I battle ninjas in my sleep.
Fortification means a fort which means a wall. The whole concept of a fortification changes when you live in three dimensions. Consider a squirrel. The squirrel nest is not a stronghold. It is a place for babies to keep them from falling out of the tree when they are little. If the squirrel is under attack it uses the tree - moving up, down and laterally, putting wood between itself and its attacker, going places in the tree that the attacker cannot.
[Answer]
I have loved treehouses since I read *Below the Root* to my students. In this novel, the people lived both in the trees, inside them and under them. I wonder if you should limit yourself to only one scenario. Each huge tree was devoted to a different guild or branch of services. One was the major food provider, one was a temple, and another silk/clothes...
>
> Below the Root is a science fiction/fantasy novel by Zilpha Keatley
> Snyder, the first book in the Green Sky Trilogy.
>
>
>
Houses/factories/services in and under and on trees makes your world more flexible.
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[Question]
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I'm working on a quest (Space game, but don't ask, it won't be good in anything but story and even that may be a stretch. XD), and I'm looking to use our solar system, Jupiter and Saturn specifically, as a point of farming for my main character ([He-3](https://en.wikipedia.org/wiki/Helium-3), yknow), and I want them to come to the discovery of life on the planet after an unfortunate mishap.
I understand the [huge pressures on Jupiter](https://en.wikipedia.org/wiki/Jupiter),
>
> Jupiter has the largest planetary atmosphere in the Solar System, spanning over 5,000 km (3,000 mi) in altitude. Because Jupiter has no surface, the base of its atmosphere is usually considered to be the point at which atmospheric pressure is equal to 100 kPa (1.0 bar).
>
>
>
and am unsure of what sorts of materials can survive without too much assistance at such a high temperature and pressure (the two being related in most cases). I don't necessarily need a possible life form, but something that would maintain [suspension of disbelief](https://en.wikipedia.org/wiki/Suspension_of_disbelief) (for the average Joe) would be preferred. Please include in your answer what (if any) would need to be hand-waved before the creature could be possible.
Some ideas I had:
* A gas entity, where reactions between different gases at different temperatures creates a sort of "computing" system sort of analogous to a brain (See [Chemical Computing](https://en.wikipedia.org/wiki/Chemical_computer)). The issue with this is the dispersion of the gases that make this body. Incredibly complex electron bonding maybe?
* Pure energy beings, where different energy types utilize some sort of quantum computing? I'm no scientist, so am unsure of the specifics of quantum computing, but from an outsider perspective, it seems plausible to me. I feel this would require a large amount of handwavium, but I'm not really sure where.
* A completely liquid water based flying creature. I have no idea, but water isn't compressible.....so ya?
I know [Could a Neptune like Gas Giant support life?](https://worldbuilding.stackexchange.com/questions/15047/could-a-neptune-like-gas-giant-support-life) answers about Neptune being a better gas giant for the job, having a solid core, and that [some of the moons are habitable to an extent](https://en.wikipedia.org/wiki/Habitability_of_natural_satellites), but I specifically want to create a sort of "deep sea" sort of creature on Jupiter that is replicated on Saturn (although a different species), that we have no information on, and can become sort of a mythical [Macguffin](http://tvtropes.org/pmwiki/pmwiki.php/Main/MacGuffin) for the main character to create an eventual real sighting, but not discovery of.
So the question is thus:
**What is the highest theoretical pressure that a creature of any type could plausibly (with some help from an author) survive in and what would it be composed of?)**
**Life definition:** The condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional activity, and continual change preceding death..
Edit for clarity: Please read the question asked. Regardless of that background information (which can be removed if anyone would see it making the question easier), the question is about the highest theoretical pressure, temperature and other factors nonwithstanding.
[Answer]
**It's tough to say, since we don't really know how materials interact in ultra high-pressure environments.**
Unfortunately, that's about the best answer we can give for this question. For example, consider what's probably the highest pressure environment that's stable for long periods of time: the interior of neutron stars.
In the crust of a neutron star, there is a thin layer of regular matter, followed by a layer of degenerate matter which forms a variety of different shapes, [most of which are named after different types of pasta.](https://en.wikipedia.org/wiki/Nuclear_pasta) We don't really know if the proposed shapes that our models predict actually occur, since the pressures inside a neutron star are tens of orders of magnatude higher than anything we can create in a lab. We also don't really know how they interact, or what sort of energy sources might exist within the crust of a neutron star.
However, it's not inconceivable that life could possibly form there. If there are sources of energy, and if it's possible for clumps of nucleons to form into sufficiently large aggregations, it's possible that life could evolve to take advantage of those energy sources. If life did evolve there, it would likely be far smaller than life on Earth, since the nuclear agglomerations comprising it would be far smaller than molecules. It would also have far shorter life spans, since nuclear reactions happen far quicker than molecular reactions.
Again, it's not really possible to say if any of this could happen, since we don't know for sure how much the material comprising neutron stars behaves. If it were possible, though, than life could form up to the pressures that exist within neutron stars: about $10^{34}$ Pa.
That, of course, is really only an upper limit if we assume that life can't exist within black holes, but theory as to how matter behaves at and beyond the event horizon of a black hole is far sparser even than our knowledge of matter in neutron stars.
[Answer]
[ckersch's answer](https://worldbuilding.stackexchange.com/a/65212/2800) is probably the best in the general case, but if what you really care about is whether a creature made of normal atomic matter could live in the depths of Jupiter and/or Saturn, there are other constraints to consider.
Liquid and supercritical hydrogen are pretty good solvents, so you don't necessarily need to worry about whether there's any liquid water. Hydrogen remains a reasonable biosolvent fluid at pressures where any water would be in solid crystalline form, even at very high temperatures.
Organic molecules such as compose our sort of life tend to decompose at high temperatures, so we might want to look at the highest pressures that support some sort of dense fluid environment at temperatures below a few hundred degrees celsius. In that case, you'd be looking at liquid or supercritical hydrogen between a few hundred and a thousand atmospheres.
However, if we assume that other chemistries could produce life at higher temperatures, with high pressures being not merely possible but perhaps even necessary to stabilize the solid components of, e.g., cell membranes, then fluid solvents remain available, and specifically available within those gas giant planets, at much higher pressures.
[](https://i.stack.imgur.com/IBHfU.jpg)
Note that superfluid hydrogen is expected to exist on Jupiter and Saturn up to around 300,000atm (or around 32GPa), before transitioning to a liquid metallic phase. If your creatures live in a liquid metallic hydrogen solvent, the potential pressures get several orders of magnitude higher. If you want sightings of these creatures to be possible, however, basing their biochemistry around supercritical diatomic hydrogen is a much better choice, in which case they would be expected to live *at least* tens of atmospheres, and likely hundreds of atmospheres. That's the sort of environment where it would be extremely difficult to observe them, but theoretically possible with *really* good pressure vessels to seal your cameras (and possibly people) in when sending probes down to their native depths.
[Answer]
My estimate is **A few (1..3) Gigapascal**.
The reason is that water will turn into some form of ice at that high pressure for temperatures allowing earth-like life, see the [phase diagram of water](https://infogalactic.com/info/Ice#Phases)
Short time survival of even higher pressure is possible and proven for terrestrial plants and animals: They can survive a 30 min exposure of **7.5 GPa**, which came out as a surprising result because the protein change their configuration at this high pressure, see this answer on biology.se: [What is the highest pressure at which plants can survive?](https://biology.stackexchange.com/questions/37464/what-is-the-highest-pressure-at-which-plants-can-survive/57766#57766)
[Answer]
I think you're looking at this wrong. You can have gas giant life without having to deal with extreme temperature or pressure.
While the cores certainly have both (and are almost certainly incompatible with life--I don't see how you can have complex structures in degenerate matter and the cores have a certain amount of degeneracy) the outer edge of the atmosphere is obviously both very low pressure (the next thing to vacuum) and low temperature (all the gas giants have low surface temperatures.)
That means there must be spots with reasonable pressures somewhere between the surface and the core and there must be spots with reasonable temperatures, although it doesn't prove that both will exist in the same location.
From looking at terrestrial life it's obvious that life can tolerate quite a range of pressure--AFIAK there's no environment on Earth with liquid water and no life. Life exists at the bottom of the ocean. (It's pretty barren down there due to a lack of food but not completely barren.)
Thus I find it all but impossible that there isn't an altitude where life can exist. Since the only surface of a gas giant is going to be awfully high pressure this point is going to be in the atmosphere somewhere.
You'll start with microscopic life that gets tossed around by the atmosphere. Some will be unfortunate and go too deep and die but so long as the reproductive rate is high enough that won't kill it off. The next order of life would have to be a very thin balloon of hydrogen (it's not going to have a lot of buoyancy as it's in a hydrogen-helium atmosphere.) Conceivably higher life that worked on soaring could develop but the gulf from floater to soarer is going to be awfully hard to cross. If this gap can be crossed you could even go to intelligence. (See Robert Forward's *Saturn Rukh*)
I think the biggest problem for such life is obtaining the building blocks. Hydrogen and helium will be very abundant but there's not a lot else and you basically have to have carbon to make life. (The sci-fi standby of silicon doesn't work at anything like Earth-like temperatures at least, although AFIAK it hasn't been completely ruled out in other temperature realms. The basic problem is that it doesn't like to form complex molecules. The heart of carbon-based life is long chains of carbon atoms with various things stuck to them. In Earth-like chemistry at least such chains made with silicon don't work. What you find in nature is Si-O-Si-O type chains--but once you add your bits to the side joints you have made a molecule that has a considerably lower energy state by coming apart and attaching the side chains to the oxygen. If such molecules can exist at all they are generally known as explosives.)
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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.
So, assume that you have 1m$^3$ of normal Terran seawater you can adiabatically raise to an arbitrarily high pressure/temperature *in situ* (say, by compressing it with nuclear shockwaves from all directions simultaneously).
Just how much energy would those shockwaves need to impart to said 1m$^3$, and how much energy would be released by the resulting fusion reactions, for these four cases:
* Only D-T fusion takes place, no proton-proton or deuteron-deuteron reactions, and no reactions involving heavy nuclei
* D-T and D-D fusion takes place, but no proton-proton or heavy nucleus fusion takes place
* Proton-proton (at incidence levels comparable to that found within Sol), D-D, and D-D fusion all take place, but no heavy nuclei fuse
* Proton-proton, D-D, and D-T fusion take place, sufficient to convert the entire hydrogen contents of our 1m$^3$ cube into helium, but no heavy nuclei fuse
Furthermore, if at least one of the above is net exergonic to the point where a chain reaction is plausible under the given priors, what would prevent such a fusion chain reaction from spreading throughout a water-bearing, rocky planet's oceans?
[Answer]
First, references: [Bosch and Hale, 1992](http://kfe.fjfi.cvut.cz/~valenpe7/files/12FVHE/BoschHale.pdf) has cross section and S-function values for the D and T reactions, as does [Nuclear Cross Sections for Technology](https://books.google.com/books?id=OZY8q1zXdkYC&printsec=frontcover#v=onepage&q&f=false) from the US Department of Commerce, 1979.
# D-T fusion
The natural deuterium abundance is 0.0156%. 1 m$^3$ of seawater has a mass of 1000 kg, or 5.5e4 mols of H$\_2$O. Since there are two hydrogens per water molecule, that gives us about 17 mol of deuterium per cubic meter of seawater. The atomic density of deuterium is then 1.1e25 atoms / m$^3$.
Present day tritium concentrations range from 2 TU (1 TU = 1e-18 tritium per hydrogen) in the Arctic to 0.15 TU in the Southern Ocean. Lets establish a 1 TU concentration baseline, so using the same calculations we have 1.1e-13 mols of tritium per cubic meter and 6.9e10 atoms / m$^3$.
A [nuclear reaction](http://www.nuclear-power.net/nuclear-power/reactor-physics/nuclear-engineering-fundamentals/neutron-nuclear-reactions/reaction-rate/) rate can be approximated by $$\text{Reaction Rate} = \Phi N\sigma,$$ where $\Phi$ is particle flux of the faster reactant, $N$ is the density of the slower reactant, and $\sigma$ is the cross section for interaction.
To calculate both flux and cross section for interaction we need the temperature of the plasma that we must turn the seawater into to initiate fusion. This is the relevant graph of cross sections for fusion of the various reactions based on center-of-mass kinetic energy of the plasma.
[](https://i.stack.imgur.com/qfh2X.jpg)
We can see for there that the reaction rate of D-T, the optimum temperature for cross section of fusion is 100 keV (about 1.1 billion kelvin) and at that rate the cross-section for fusion is 5 barns (1 barn is equal to 1e-28 m$^2$).
Flux is the mean speed of particles divided by density and can be calculated from thermal kinetic energy in three dimensions. We want the mean magnitude of velocity $v\_{th}$, which we can get from $$v\_{th} = \sqrt{\frac{8k\_BT}{m\pi}}$$
where $m$ is the mass of the particle. $T$ is the temperature, and can be converted to Kelvin from electron-volts as ratio of the Boltzmann constant ($k\_B$) as $$T\_K = \frac{1.6\times10^{-19} \text{J/eV}}{k\_B}T\_{eV}$$ giving us $$v\_{th} = \sqrt{\frac{8\cdot1.6\times10^{-19} \text{ J/eV} \cdot 100000 \text{ eV}}{2\mu\pi}} = 3.5\times10^6 \text{ m/s}$$ for deuterium where $\mu$ is one one atomic mass unit (1.66e-27 kg).
Deuterium flux is then $$3.5\times10^6 \text{ m/s}\cdot1.1\times10^{25} \text{atoms/m}^3 = 3.8\times10^{31} \text{ atoms / s}\cdot\text{m}^2.$$ We now have all the parts to calculate overall reaction rate: $$\text{Reaction Rate} = \left(3.8\times10^{31} \text{ 1 / s}\cdot\text{m}^2\right)\left(5\times10^{-28}\text{ m}^2\right)\left(6.9\times10^{10} \text{ 1 / m}^3\right)$$ which equals $ 1.3\times10^{15} \text{fusions / m}^3\cdot\text{s}$.
Now that we have got that tricky bit of math done, lets figure out the answer. The energy required to heat 5.5e4 mols of water to 100 keV is about 5.4e14 J. The energy produced by 1.3e15 fusions is 14.1 MeV per fusion or 2.9 kJ total, per second.
**D-T fusion costs you 5e14 J to start and produces 3e3 J per second.** So that is not worth it, even remotely. There just isn't enough tritium in the water
# D-D fusion
First, lets point something out. At the temperature for the above reaction, the cross section for reaction is much lower for D-D than D-T, but given that you have much, much more deuterium, you will get much more energy.
Using the above calculations, lets let cross section be 0.02 barns (from the chart). Deuterium flux is the same, while tritium density is replaced by deuterium density for a fusion rate of 8.4e26 fusions per second per cubic meter. D-D does two different reactions, into both tritium and helium-3. Since these each have a 50% chance of occurrence, we can average the two energies for an expected 2.73 MeV per fusion. This gives us 4e14 W of fusion output on 5e14 J of input. Almost return on investment! Of course, your plasma is so hot there is no way you would get even 1 second of output before that plasma expanded like...well...a thermonuclear bomb.
To figure out the best possible results from fusing a bunch of seawater we can plot the center-of-mass kinetic energy against output fusion power. Fusion output power can be calculated by combining the D-D fusion and D-T fusion, as calculated above.
[](https://i.stack.imgur.com/qLtZE.png)
The red line is total output, the blue line is D-D output, and the green line is D-T output. As you can see from the lack of a blue line, D-D ouptut dominates due to low availability of tritium. Generally you get more out the more you put in, up to about 3 MeV. However, it takes a lot more heat to get your plasma to 3 MeV in the first place. Let us instead plot energy input in J against energy output in J.
[](https://i.stack.imgur.com/eBHyQ.png)
Here the black line is break even: 1 J out per second per 1 J in. Again, in reality, you would never be able to hold this plasma together for even a second. Even so, you don't really get back what you put in. The closest you come is right about a 100 keV, like we calculated at the start of this section.
# P-P fusion
From [Adelberger, et al., 1998](http://www.sns.ias.edu/~jnb/Papers/Preprints/Solarfusion/paper.pdf):
>
> The rates for most stellar nuclear reactions are inferred by
> extrapolating measurements at higher energies to stellar reaction
> energies. However, the rate for the fundamental p + p $\rightarrow$
> $^2$D+e$^{+}$+$\nu\_e$ reaction is too small to be measured in the
> laboratory. Instead, the cross section for the p-p reaction must be
> calculated from standard weak-interaction theory.
>
>
>
This explains why I haven't found any good graphs of cross-section versus temperature as I was able to find for D-T and D-D reactions.
Given that most of the sun's fusion is of the pp variety, and that the sun produces less energy per volume than the human body, we can assume that this interaction will produce a negligible amount of energy in return for the terajoules necessary to start it.
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[Question]
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I have wondered what a terrestrial ecosystem would look like dominated by cnidarians and ctenophores rather than insects and tetrapods. In order to fulfill the same niches I imagine they would need to be highly derived compared to their ancestral forms. Since their physiology is so different I am having difficulty figuring the path from, say, a jellyfish to a longlimbed Savannah grazer with a mass of tentacles for a face.
[Answer]
Well you need them to evolve some kind of hard tissue to support the body, which could give you animals superficially like echinoderms. specifically sea cucumbers or sand dollars and sea urchins depending on which way you want to point the mouth. But it really depends on how long they have had, the longer they have been evolving for land the less they will look like jellyfish.
[Answer]
If they can somehow separate the hydrogen or the helium from their food or enviroment to keep it in special bladders they could gain buoyancy and float out of the water (where they breed) into the air over dry land.
If then they can detect a prey right under them and quickly release gas to drop straight down, they can substitute birds of prey in a ecosystem.
Sea animals extract oxygen from the water with gills and such, maybe they can keep the H after taking the O2 (I don't know a lot about underwater respiration so ask someone who does before taking the idea into serious account)
[Answer]
## Muscles
Developing an extensive muscle system throughout their bodies, including their tentacles, could give them mobility--instead of supporting themselves with an endoskeleton or exoskeleton, they could go entirely without skeletons and simply use muscles to hold themselves up.
## Hydraulics
Perhaps instead of using skeletons or muscles, they could develop hydraulic systems to harden and soften key points in their bodies to allow for locomotion, holding, eating, etc. Perhaps some species could have very minimal, slow moving hydraulics, like plants use to turn towards sunlight, or perhaps some could be as fast as any land animal.
## Thicker Outer Skin
To prevent drying out and keep them safe, they could develop a denser, dryer outer layer of tissue, like leather.
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[Question]
[
**Setting:**
* Partially rebuilt post apo world, normal sex ratio
* Technology: comparable to early XXIst century
* Affluence: first world equivalent
* Mixed economy, semi-authoritarian system, low level of corruption
**Info concerning aims:**
* rebuilding population possibly fast, while maintaining high educational attainment
* keeping equal rights
* maintaining any tradition is NOT an aim (as a matter of principle no one seriously minds homosexual marriage, multi partner marriage, any other polyamory system or low age of consent, as long as no one in such relationships seems to be abused)
* keeping population possibly happy
**Extra info concerning system:**
* generous child benefits tied to kid results in standardized school tests
* no child alimony money (gov already takes care), but instead of retirement system gov transfers to people a share of their descendant income
* punitive tax on childless people (with some accomodation for health conditions including both infertility and heritable conditions that would be better if were not passed on next generation)
* banned abortion, except of very good reasons (rape, damaged baby, serious risk for mother)
* surrogacy motherhood not only allowed but also subsidized for infertile people
* very good public services concerning children (childcare, healthcare, schooling) including childcare facilities at secondary schools and campuses
**Ok, so how to govern and recognize by gov polyamorous and short term relationship, while keeping everything more or less fair, not too complicated and not making divorce lawyers excessively rich?**
[Answer]
**Institute state care for all children**
A major reason that people avoid or delay having kids, as well as to enter into long-term monogamous relationships, is to ensure their financial ability to care for those kids. If you want to increase the birth rate, reduce the costs involved with having kids. An easy way to do this would be for government institutions to handle all child rearing. Parents would still be able to visit their kids, and could help take care of them, but ultimately the parents would go home to their home and children would stay in the care center.
**Reward all couples for each child**
If all couples, regardless of marriage status, receive a financial reward for having kids, there would be a major incentive for people to have lots of kids. Rather than being a financial strain that one would need to get ready for, having a kid could be a way of paying for college or putting money towards a new house.
**Allow for women to designate any number of husbands, who will all share the paternal child reward**
Finally, allow a woman to have any number of husbands, and a man to have any number of wives. When a child is born, all husbands receive a portion of the reward for being the father of that child. Men would be pressured to go out and have as many wives as possible, in order to maximize their earnings. Meanwhile, men would be required to assist their wives with living expenses, so it would be in the interest of a woman to gather as many men as possible, and to produce as many children as possible with those men, in order to increase her desirability.
**Eliminate everything else about marriage**
Marriage does not grant power of attorney and does not merge finances. There are no entangling factors, so it's easy for men and for women to enter and leave relationships. Marriage exists for the purpose of producing a ton of children and getting paid for it.
This sort of system would be optimal for polygamous and short term relationships, which would be optimal for men and for women to have as many children as possible in a short span of time.
[Answer]
Well, if keeping people happy is only a minor concern, then we have some solid options. I don't believe that such a situation will persist for long, as people are, by definition, very emotionally invested about their relationships and children. Also, your requirement for "keeping equal rights" will be almost impossible. That said, *onward!*
**Discourage partnerships to begin with**
If we assume that the government can "take care" of any number of children to any reasonable standard, people will be incentivized to produce children out of wedlock to begin with. This is really the optimal case from the legal perspective; one parent is a custodial parent and receives a government income, and the other is non-custodial, and pays taxes on their work income. In order to accommodate this:
**Marriage is disadvantageous**
To begin with, marriage will be heavily taxed. Government support will revolve around single parents; birthing classes will not accommodate non-birthers, parenting courses will avoid talking about two-parent situations, and schools, hospitals, and so forth will assume single parenthood on legal forms. Importantly, parents will receive the "baby bonus", *which is taxable*, whether or not they live with the child; this creates equality between the parents, and makes sure it is creating children that is incentivized, not child care. With the promise of comfortable government support, and no requirement for child support from a non-custodial parent, separation (or, more likely not moving in together at all), will be extremely attractive to both parties. Since separated parents should owe each other nothing, *no kind of partnership should be officially recognized to do so*. A limited list of reasonable *major* joint assets, such as *a* home or *a* vehicle, may be registered with the government for liquidation and division afterwards, but generally, *joint ownership of anything is illegal*. This means a custodial parent will likely loose out big-time on separation, and is really better off staying on their own to begin with. Since child rearing isn't really incentivized or desirable:
**State child care should be the norm**
Most people will want to have a state institution do the child rearing, and visit their child on an ongoing basis. This allows them both to maintain their careers, as well as equalizes parental time and standards of living for the children. To really encourage this, either parent should be able to veto in-home care in favour of state institutional care, right from birth. This will also keep people from abusing their children to achieve better marks to earn higher baby bonuses.
**TL;DR**
Make legal partnerships or marriages legally and socially difficult to begin, severely limit or eliminate joint asset ownership and division thereof on separation, ensure both parents are paid for creating the child regardless of the parenting arrangement, and normalize the institutionalizing of children from birth to create truly equal parenting arrangements.
Personally, I think the criteria given are ludicrously unacheiveable.
* Baby farming will be a popular choice of job. For parental (and
indirectly, gender) equality to be fulfilled, payment must be equal
to both parents regardless of their involvement in child rearing; but
this means that non-custodial parents will earn comfortable livings
for no ongoing effort, and your workforce will be hamstrung. If
non-custodial parents don't receive a payment, then a) your idea
about encouraging fair short-term or polygamous relationships will be
moot b) one gender or the other will likely be heavily disadvantaged
in proportion to the size of the baby bonus (just like now!), and c)
separation will continue to be complex and acrimonious, resulting in
enrichment of legal professionals.
* Baby farming requires no
education, but can be a comfortable living under this system (as it
indeed is to some degree now). The number of people who choose to do
this will depend on how competitive this income is, relative to other
jobs. If the payments are high enough, your workforce will be
severely disabled, but if they're too low relative to other jobs, you
create a disadvantaged population. This is historically not a
solveable problem.
* Lack of child support means that unscrupulous men
are incentivized to create babies and abandon them, placing an
inordinate load on the government system, and creating enormous
inequality for women. For the wealthy, men will especially be able to
lure women into becoming pregnant and then abandoning them as a form
of tax write-off. The ability of men to do this at a much higher rate
than women is an inequality that you will never solve without
requiring ongoing child support.
* The next generation will have the
same choices as their parents, but they'll be loaded by losing a
portion of their income to their parents. In order to insure that
children are properly cared for, baby bonuses will have to increase
to accommodate the loss of this income for the child.
* All the legal
incentives in the world won't really help with divorce much, since
division of money isn't really the worst part of separation, *it's
the division of the kids.* People are super emotional about it, and
probably won't respond in rational ways to legislation in the way you
think. This is somewhat mitigated by the above plan of minimizing
parental involvement at all, or at least restricting parental
involvement to a single parent; even so, children will be traumatized
when it happens, and your whole society will revolve around this
being very common.
* As a result of your plan to base compensation on a
child's education, teachers will gain enormous amounts of power over
people's lives, and the economy and politics of teaching will
drastically change. I won't venture to guess how this will turn out,
except to say that power has a distressing tendency to corrupt.
* Abortion will likely become more contentious, as some mothers will
want to bring babies to term regardless of the consequences, just for
the money. State control of abortion will be difficult to maintain.
[Answer]
# Use separate contracts for the different parts of the encounter.
A marriage contract has certain terms, including duration, break clauses and notice to terminate requirements. Most importantly it covers children and childcare and how to deal with assets held in common.
Anne Mccaffrey had some good ideas with this on some of her worlds where people would contract for a [body heir](http://mccaffrey.srellim.org/series/bodyheir-biblio.htm). It was primarily a reproductive and financial contract between two independently wealthy people with the single intent of producing an heir for one of them. In short, one person contracts with another to sire/bear a child to be an heir to their fortune and social position. Any lingering details of love and recreation are entirely separate to the contract.
[Answer]
Get rid of inheritance.
Human monogamy originated around the time that mankind started settling down, building homes and generally having a concept of property. They had things to pass down to the next generation, so they wanted to make sure that the next generation was actually theirs before giving over all their possessions. Hence monogamy became a thing.
By the sounds of it, in this society the actual genetic parentage doesn't matter too much and all children are pretty much taken care of, then having inheritance go to the gov rather than children would make things such as monogamy much less serious in the society's eyes.
Keeping finances separate during relationships would help in the event of 'divorce', however this is problematic if someone is a designated care giver, or stay at home parent so hasn't contributed equally to paying bills etc. This is where things get really gnarly in divorce courts at the moment. Should they also get a share of the house? But it could be that stay at home parents receive a stipend from the government in this society, so they have the potential to earn just as much as a parent who goes out to work.
[Answer]
When you dissect marriage and relationships, you very quickly understand how deeply they are rooted in culture. Specifically: Non-equal male-female cultural status.
A large part of relationship "rules" only make sense in the context of a society where males work and provide for the family, and women (and children) are dependent on them. Once you remove that, you will see relationships change, as we do in the real world.
If you build a fictional world where men and women are economically equal, no further ingredient is needed. While jealousy might have biological origins, and thus might take a lot of generations to disappear, the root cause is dependency. Men want their genes to continue, so they need to guard the woman. Women are vulnerable during pregnancy and child rearing and thus need to be sure of the man.
So how to govern this? The simple solution is: **Don't**.
If there is economic security for all, or at least to the same degree, which purpose does a state-recognized marriage serve at all?
The only thing that is left is a **family recognition**, which is useful for things like inheritance, rights such as being able to refuse testimony against your family in a court, or information and access to them in a hospital. This is not a marriage thing, it's a matter of recognising family ties (parents or children have the same rights in many cases). But once you've made that small step away from a traditional marriage model, polyamory is simply an administrative matter of changing the registration form to having multiple lines.
One more aspect of marriage is shared income or shared property. However, non-family models for such already exist - you can buy a house together with a friend, for example. They would simply be applied. Again, no additional overhead needed, just small adaptations.
We are actually fairly close to exactly what you want, once you look behind the religious and cultural taboos. We have non-married couples being able to register as partners in many countries. We have homosexual couples being able to register as partners in many countries. The step to allowing three people to register a partnership really isn't that big, and doesn't require all that much legal changes.
[Answer]
Take the libertarian route and get out of the marriage biz altogether. Existing laws would cover any squabbles over property and custody of children would be judged on an individual basis
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[Question]
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I have created a world map for a story I'm making. And it has been too long since I studied geography and geology. Assuming earth-like conditions, and a normal distribution of climate based on (approximate) lines of latitude (equator, tropics, arctics), what regions would have unique climates owing to atypical precipitation (very dry or very wet)? I'm assuming that forests are abundant otherwise.
I would most appreciate answers which can be explained in the context of our planet's climates and the underlying processes, so that it's easier to understand and extrapolate from.
Regarding scales: I don't know exactly how high the darkest bits should be, but assume Himalayan equivalents. Additionally the continents are Australian in size. The centre of the map is where the equator will be. Sorry for the lack of precise scale, I'll have to add that a bit later!
[](https://i.stack.imgur.com/D4yQc.jpg)
**UPDATE:** Given Kingledion's answer I have created a climate zone map, attempting to simplify the [Koppen climate classifications](https://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification).
Dark cyan being the coldest regions of pine forest, warming to light cyan maritime, yellow Mediterranean, dirty green savannah, bright green rain forest, orange scrub land, red desert.
[](https://i.stack.imgur.com/mFBDn.jpg)
[Answer]
First we have to assume that the planet's spin direction and orbital tilt are the same as Earth's. I would not assume Himalayan heights...the Himalayas are abnormally tall for mountains on earth, caused by a massive high speed plate collision that I don't see any evidence for in your map. Most mountain ranges probably topped out in the 4000m-6000m range through earth's history. Lets say your dark region in the Lesser Southlands is a ~4000m plateau surrounded by peaks up to 6000m, like the Altiplano of Peru and Bolivia.
**Currents**
You have a landmass that is completely exposed to the effect on oncoming currents on both coasts, so those currents will probably dominate the climate. The west coast of continents generally sees cold currents from the poles heading towards the equator (such as the California, Peru, Benguela, and Canary currents). The east coast will see warm currents from the equator to the poles (Agulhas, Gulf Stream, Brazil).
The climates that on West Coast go from Rainforest to Cool Desert to Mediterranean to Temperate Rainforest to Arctic. North America, South America, Africa/Europe, and the southern half of Africa all follow this pattern (though South Africa runs out of land in the Med zone).
The Climate son the East coast tend to go Rainforest, Wet/Dry Savannah, Humid Subtropical, Humid Cold-Winter, then Arctic. East Coast of North America is the best example. East Asia follows the patten, but has an additional monsoon bringing heavy summer rains, which I'll get into below. South America mostly follows the pattern, but doesn't have a large landmass to get the polar cold winters, after the Humid Pampas near Buenos Aires, it goes into cold dry Patagonia. Your continent would probably be this version look like this.
**Atmospheric Movement**
Another pattern that affect the earth is the Intertropical Convergence Zone (ICZ). This is a band of heavy rainfall that moves to the Tropic of Cancer (North) during the northern summer and to the Tropic of Capricorn in the southern summer.
Prevailing winds between the tropic and equator are westerly and towards the equator, prevailing winds between the tropics and arctic/antarctic circle are easterly and towards the poles.
Humid air tends to rise at the equator causing rainfall and dry air from high altitudes tends to descend around the tropics and cause reduced rainfall. This is the reason that the equator is blanketed in rainforest, but the tropics tend to go through deserts.
Monsoons are caused by proximity of an ocean to a land mass that will heat up and cool down much faster than the ocean. The three major Monsoon systems of earth are caused by the Sahara Desert (West African Monsoon), Tibetan Plateau (Indian Monsoon) and Siberia (East Asian Monsoon). I don't see anything large enough on your map to cause a true monsoon. Maybe some weak smi-reversing monsoons, as we'll see below.
**Arctic Regions**
The North Pole of earth is completely surrounded by land and acts almost like a lake. The South Pole is a continent surrounded by water which is isolated by a strong circumpolar current. Your world has neither feature, so I'm not exactly sure what would happen. I'm going to assume that permanant pack ice never reaches the continents. Winter feature strong, constant, cold south-blowing winds from the poles to 60degrees latitude. Summer features a mild poleward breeze. The poles are over water, not land, so you can't get the frigid air masses that form over Siberia or Canada. Your land masses probably never get down to -20F. A comparable situation is Trondheim, Norway, on the Arctic circle with no land north of it, the record low is -14.8C.
**Summary of Regions**
* North and West Northland (NOTE: NEED BETTER CONTINENT NAMES) are subarctic to temperate rainforest (Norway)
* Northwest Westland is Mediterranean (Spain), Central-west Westland turns to Dry Desert (Morocco).
* South Westland is tropical savannah turning to rainforest, with cloud forests on top of the mountains (like Thailand/Indochina).
* The islands between Westland and Greater Southland are rainforest.
* Northwest Greater Southland is dry savannah turning to semi-desert scrub and desert (like the Sahel of Africa). This is the largest desert in your map. The region trapped by mountains on three sides in the heart of the continent is a big sea of sand.
* South Greater Southland is cool temperate forest, like European Russia.
* The island below Lesser Southlands are Mediterranean like Perth, Australia (this is because of the cold circumpolar current coming below Greater Southlands). Best fisheries on the planet.
* The eastern side of the south coast of Lesser Southlands have a wet oceanic climate, like Sydney and Melbourne Australia. As you go west, and higher in altitude, the rain drop off quickly. On the coast the weather will be like Adelaide, Australia at higher altitudes you get a dry climate like the Karoo of South Africa.
* Southeast Eastland is the biggest rainforest on your planet.
* The central and eastern parts of Westland (inside the ring of mountains) are are dry 6-8 months of the year, and then have brief wet season brought by the ICZ, but much of the water is blocked by mountains to the south. Semi-desert scrub mixes with dry thorn forest like the Deccan Plateau in India. Against the southern mountains you get heavy rainfall as the ICZ retreats in fall, so there you get a wetter seasonal forest. Probably the best place in your planet for big safari animals.
* The basin of North Eastland, South Northland, and Northwest Westland is a steppe, and the biggest set of grasslands on your planet. The climate is like the Black Sea basin...except this is much larger and stretches much farther north to south. The south would start to be hot and dry like Phoenix, while the north will grade into forest-steppe like Kiev, Ukraine. Best agricultural area on the planet.
[Answer]
So... while there is already a fine answer, I used my lunch break to try to figure out "what is with the ocean trenches?".
They are not inserted yet, so I tried to figure out how the continental and ocean plates do look after all... which wasn't as clear as I hoped at the beginning.
[](https://i.stack.imgur.com/3tiqr.jpg)
**plate tectonics**
You have mountain ranges which look like they were created by plate uplift, you have hills that might be the result of an ice age glacier action and some might even be volcanoes, which love to pop up at plate rifts.
My picture does look... well... I have no idea how the plates are drifting and so at the moment I can't tell where rifts in the ocean might be after all.
If you extend the orange lines you should find stuff like underwater mountains (volcanoes) OR deep rifts. The read lines are much more likely to result in high places under water, but still...
I got the feeling your world rips itself apart at this long rift right in the middle, BUT because there are volcanoes this might mean that the ocean isn't pretty deep after all.
Even more, I think this might be a pangea which was struck by unexplainable hot weather which resulted in an overall rise of water. Which means: Some of the even important parts of the landmasses are hidden below the ocean surface.
So you would end up with swallow water between the continents and more deep water outside the "where the pangea had its beaches" point.
Anyway, you are beyond the point where a restructuring would make sense. When I'm right with my outlining, you will end up with a greater body of water between a northern and southern group of continents, while the mountains might grow and the land start to extent at the water ends of the red lines. In many centuries....
**weather impact**
Due to swallow water, not much currents would form between the continents, but if we insert a more deep rift at all orange lines, we might get some east-west currents which will supply water from outside the continent area. You will end up with more wet climante where this happens and more dry climate where no currents pass by. Especially that... phallic island.
At the same time northern Eastland and eastern Northland and northern Lesser Southlands will get more wet climate (warm winters, wet summers).... Aaaand... I think I cannot add very much to kingledions answer after all saldy.
To be honest, the distribution of mountains, islands and water still looks like it wasn't done by tectonic forces but... well... a god who hasn't much experience in making worlds.
But maybe I'm wrong with my interpretation.
EDiT:
While staring at it for some time I think I found a useful tectonic layout... and this is indeed a pangea breaking up.
Still the masculin monkey-wrench island is getting kind of... pressure; you will end up with salt lakes or death seas... have a look (its getting more confusing)
[](https://i.stack.imgur.com/eeuKD.jpg)
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[Question]
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Would it be possible for an asteroid in solar orbit to go near enough to the Earth that the Earth's atmosphere slows it down into an orbit that is, aside from its low perigee, stable without using a third object (such as the moon) to slow down? Or would the necessary forces destroy the asteroid?
If this is possible, could it then gravity assist off of the moon to get in a truly stable orbit? Also, if it is possible, what would happen on Earth?
[Answer]
While an aerocapture could slow an asteroid down enough to keep it from escaping back out into deep space, the problem you would face without a third body or additional applied force is that the [periapsis](https://en.wikipedia.org/wiki/Apsis) (lowest point of orbit) now lies within the atmosphere. Subsequent orbital rotations would continue to slow it down until it falls into the atmosphere for good.
[](https://i.stack.imgur.com/4HyRp.jpg)
Here's an image for reference ([source](http://ccar.colorado.edu/asen5050/projects/projects_2004/dunn/)). For every pass, the point at which it contacts the atmosphere remains nearly the same, but the apoapsis (highest point of orbit) will continue to reduce until the path becomes suborbital, and into the planet it goes.
If you do have a third body such as the Moon however, it could potentially (if improbably) temporarily stabilize the orbit. I say temporarily because in order for the Moon to have enough influence on the asteroid to stabilize the orbit, the asteroid must continue to pass close enough to the Moon's orbital path that another such encounter would inevitably occur, throwing the asteroid into a different orbital path each time. This could eventually result in an Earth or Lunar collision, but not an escape, since too much energy would have been lost during the aerocapture.
[Answer]
Yes, I would say not impossible, but highly unlikely to happen naturally.
Everything would have to happen perfectly for this to ever happen.
**How it could happen:**
The asteroid would need to be mostly a metallic variety and shaped and oriented correctly (Blunt body aerodynamic shape faced into the atmosphere, like space capsules during re-entry) to withstand the atmospheric entry and deceleration forces intact. As well as correctly aimed into the atmosphere so as to slow the correct amount, to little and it skips off the atmosphere back into a solar orbit, too much and it impacts earth.
After the initial aerocapture entry into the atmosphere the upper end of the orbit (apoapsis) would need to be oriented such that the moon's gravity would alter the orbit into a more stable configuration (it would need to accelerate the asteroid to raise the periapsis above Earth's atmosphere)
And even after that your interactions with the moon could make your orbit unstable, it would be a very complicated orbital maneuver. We have only performed aero braking on a few space missions, and have never tried an [aerocapture](https://en.wikipedia.org/wiki/Aerocapture) maneuver and that is with craft able to supply some maneuverability.
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[Question]
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A naga is a snake with a human's head and torso. I want my naga to be huge, probably seven or eight feet tall. However, if you look at a picture of a snake in real life:
[](https://i.stack.imgur.com/tI8PY.jpg)
[Source](http://pix11.com/tag/cobra/)
You quickly see that only a small part of a snake's body provides it's height. Would this limitation carry over?
So, if I want my naga to stand 7' above the ground when it lifts itself upright, how long would the entire creature need to be?
[](https://i.stack.imgur.com/Pfed5.jpg)
[Answer]
Well the King cobra can [reach 18 ft long](https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=how%20high%20can%20a%20snake%20stand) and look a person in the eye. This is about 1/3rd their body length, and likely about 1/3rd their physical weight.
Some have said about 1/3-1/2 their length.
It's not just the strength of the muscles holding up the snake, it also has to do with balance etc. If the human half is significantly more dense than the rest of the snake in body mass, then you will need more tail to help balance it out. It also will matter if you want them to move standing at 7-8' or just be able to loom. To loom they can concentrate and add height. To be moving around they need a bigger better base.
So to start I think you need ~24' long body as a minimum 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.
Otherwise you will likely have a very awkward snake man.
[Answer]
The ability of a snake to lift a portion of its body off the ground is limited by the strength and weight of that particular portion and is more or less unrelated to the total length of the snake. As long as the human portion was strong enough to lift its own weight (i.e. is anatomically similar to a human) the snake portion can be any length you want (as long as it is big enough to keep the human portion from falling over). I see no physical issue with the various artistic naga depictions you can find anywhere online.
For the legless human portion to have the height of a regular tall human including the legs, the head and torso would have to be scaled up to almost twice the size of a human. This could put a strain on the heart, muscles, and bones, so you might want to fiddle with the body part sizes and shapes, especially if your naga spend a lot of time in their 'raised' position. They might have to have Hulk-esque limb proportions. It isn't *too* big though, and the whole thing is supported by a very stable snake base instead of spindly human legs, so the square-cube law shouldn't give you such a huge problem.
[Answer]
[If a naga was 7' tall how long would it be?](https://worldbuilding.stackexchange.com/questions/39912/if-a-naga-was-7-tall-how-long-would-it-be)
Let me establish two points first that the previous answers sort of miss.
1. When a cobra looms up to be at eye level with a human it is reaching its body up higher than it does normally to be able to do so.
2. As is illustrated in the picture with the bracket, when the snake rears itself up just enough to be in an upwards posture the bracket notes that this part of the snake would be the "standing" part of the Naga and would be 7 feet tall.
With these two details, the proper height and length of a naga can be determined.
In essence you are combining two creatures together, so where and how would they do that? The upper torso and lower torso of the average human male are usually about the same length, though in most situations the lower torso area is slightly the longer of the two parts. This is usually only by a few inches though. But what this means is that of the part of the snake that is "standing" in the picture, a little less than half of that will be the upper human torso of the naga.
If the naga in its "standing" position will be reared up at about 7 feet, than nearly 3 and 1/2 ft will be the upper human torso. With that being said, we now have a solid proportion for how big the rest of the snake would need to be. Now that snake looks to be rather small, not nearly the full 14 feet its said to be able to be at full size. With an understanding of how big the "human" torso section of the snake would be, if we could find the actual size of that snake in inches, then we could gain an understanding of the naga's proper size.
Basically, lets say that the marked section of the snake is actually 7 inches, that would mean that we would have a 1 to 1 ratio: for every 1 inch the snake is, the naga would need to be 1 foot.
This is because we're trying to find the scale of the "standing" portion of the snake in regards to when its enlarged to be a naga. If that portion is 7 inches, and that section is supposed to represent the height of a 7 foot human male, then each inch would scale to be one foot.
*Now for a bit of an anatomical side note*
Even though the naga wouldn't have legs like a normal human, it would still be able to rear up and "stand" as normal human would do. Whether it would be able to move like this and slither is up to whether snakes can actually slither and move when they are reared up as well, or simply the creative liberties of the person creating the naga. BUT, and this is a big but, the lower (aprox.) 3 and 1/2 ft of the naga would still in essence act as its "feet" or legs when it comes to the proportional act of standing up
*End side note*
So what this would mean in total is that if the average cobra can become 18 feet at its full length, then the full naga would be able to *pulls out calculator*
...Oh wait, it seems I've forgotten to mention something. The example of the snake being 7 inches at "standing" was completely anecdotal. To actually calculate the height and length of a naga you would first have to find out how "tall" the standing portion of the real life snake is in INCHES, based off its individual species and current age,
*Another anatomical side note*
As a cobra gets older it also gets longer, and the "height" of its standing position will scale up. But would a naga's "standing" height also scale up, causing its upper human torso to eventually become much bigger than that of a normal human's, or would its upper torso stay the same relative size as that of a human's? Because if the upper torso does not scale with its snake body and become proportionally bigger, but rather stays the same relative size as the human body, then that means there is a bit of anatomical discrepancy between the way a snake and naga scale, and that it may not be as much of a 1 to 1 ratio as previously stated.
*End side note*
This is because half of the snake's "standing" height would be converted to the (aprox.) 3 and 1/2 ft of the upper torso of the human body. So if there was a snake that was 1 ft tall "standing" then every six inches of the snake would be (aprox.) 3 and 1/2 feet, or every 12 inches would need to be 7 ft. Meaning that a snake that was 1 ft "standing" and 18 feet long would become (7[ft] x 12[in]) 126 feet long as a naga.
And as a final anatomical note, as I previously mentioned, when a snake looms up at a humans eye level they are purposefully extending themselves up much higher than they usually do. When scaled to a naga, if a snake can loom up to a humans eye level at -let's say- 6 feet, and their total body length was 18 feet, then you would have to proportionally increase that for the naga accordingly. If the snake was 1 ft "standing" and could loom up to six feet, this being about 1/3 of its total length at 18 ft total, that would then mean that a naga could, at 7 ft tall, and 126 ft long, loom up to (aprox.) 42 ft. Which would be nearly twice as tall as a Storm Giant in the current 5e universe of dnd.
As a final note, I want to emphasize this scale only works if you are trying to scale Nagas based off real world snakes and proportions. This scale does, though, provide a good reference for how long a naga would have to be,
Final formula:
((([Length of actual snake in feet] x [12 inches]) / [Height of "standing" portion of actual snake]) x [Intended "height' of standing portion of Naga])
Example:
Snake 8in "standing" portion
18ft long total body
18 x 12 = 216
216 / 8 = 27
27 x 7 = 189 feet total
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[Question]
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You all probably know what a [starfish](https://en.wikipedia.org/wiki/Starfish) is. When a starfish is ripped in half, if each half has part of the central disk, then it can regrow into two starfish. Worms can do something similar, if they are cut in half, they regrow into two worms. I was wondering, what is the plausibility of an intelligent starfish developing on an alien planet?
I was thinking the creature could be similar in shape to a human hand. It has some arms it moves around on, which are lower down, then several it uses to manipulate objects, which would be on its sides, and none on top. Its eyes would surround its starfish mouth, in the center of one side of the disk.
Is it possible for this creature be sentient, in the same manner humans are, and still be able to regenerate into two starfish if cut in half?
[Answer]
While Erik and Bowlturner have given good answers, I will suggest that evolution would discourage such abilities.
As the starfish creature ascends to sentience, more and more brainpower is being used to manipulate symbols and concepts, and presumably manipulating appendages at the ends of each arm. A complex visual processing system is also being developed (at the simplest, I would think one eye per segment, but there might be hundreds of tiny eyes scattered across the creature). In an aquatic environment, the senses of taste and smell would also be vitally important, so a good chunk of brain is working on that as well. In addition, the creature might have other senses, for example, the ability to register electrical fields (much like sharks have to sense the presence of potential prey).
When the creature was still a primitive starfish, the sense organs would have become highly developed and lots of brain power devoted to that. Regenerating after being ripped in half made it important that the surviving part(s) could still sense possible predators while regenerating, so the Starfish ability to renew makes sense.
As the creature gets more advanced, the "frontal lobes" (or whatever the equivalent in this being) need to become more and more powerful, and take more and more of the processing power and life support. Being severed by a predatory beast or enemy starfish wielding an obsidian axe is going to be massively disruptive to the higher part of the brain, and while the human and mammalian brains are very plastic, I suspect the limits are not high enough for a full fledged separation.
The regrowing of a lot of higher order brain tissue is not going to be enough, since the surviving half(s) of the creature will also need to learn everything all over again to replace the knowledge and memories lost in the destroyed parts of the brain. The evolutionary disadvantage of devoting so much metabolic process to being prepared to regenerate is probably going to highly disadvantage the beings who retain this compared to the ones who have "streamlined" their metabolisms and nervous systems. They will be simply out-thought by any non regenerating sub species.
Of course, in the very long run, as they become technologically more advanced, they may eventually discover ways to re engage these metabolic pathways via surgery or advanced genetic engineering or stem cells, much like human scientists are working of discovering how *we* could regenerate limbs.
[Answer]
In theory, maybe. First a starfish would likely be a very different animal should it evolve to have enough brain tissue to become conscious. The brain is an organ, and for a starfish to be able to survive a conscious brain being split apart it already needs to be compartmentalized.
[Starfish are radially symetric](https://en.wikipedia.org/wiki/Starfish#Taxonomy) and this is why they can survive being cut up. They have all the needed functions and organs duplicated. So their brains would also need to have this radial symmetry to have a chance.
It also means that while current star fish are 'identical' when they have finished regrowing, their conscious cousins would be two different beings since they would keep different memories and experiences in their quadrant. Partly because there isn't a real reason for radially duplicating the same memories multiple times. It would be very inefficient use of brain matter for something that you "don't want to happen" namely being split in half.
[Answer]
I don't see why not, a couple years ago i read of a woman born without cerebellum (that's a big portion) and living a normal life, then there are surgery cases where a large portion is taken off. The brain isn't only characterized by high plasticity but lately it seems that the brain functions are more distributed between the various regions that what was thought. You can bring it to an extreme and make so their brain could have evolved and allowed separation exactly like everything else in the body. The reasons for keeping the memories is to maintain knowledge, so that one individual know all the predecessors knew
[Answer]
Several answers have mentioned that keeping a sentient brain in a state where it can be divided in two and still function would take a lot of resources, and that that does not make much sense purely in preparation for a rare event which you are endeavoring to avoid. What if, however, division was part of the creature's life cycle?
Raising a sentient creature to a self sufficient stage of life is a resource hungry process, however you go about it. Humans spend a large proportion of their resources in raising their children, after all.
Here is how such a life-cycle could work:
* Upon reaching adulthood the creature's brain begins a process of weeding out memories, keeping information and skills that are most useful. At the same time it begins to fatten up, storing resources in it's body. This time would be distressing for the creature due to it's memory loss, but at the same time it might find that key memories become much more vivid.
* The weeded out memories are then duplicated to separate regions of the brain, and the structures of the brain are duplicated. Long term memory is significantly reduced, as any long term memories are stored twice. Short term memory and other brain function is also slightly reduced, as it is now split between the two brains. The creature might be at risk of split personality disorders at this point.
* Body and brain divide. Two new young creatures are created with half the adult number of legs, organs, etc., and half the adult brain size. They have the advantage however of an adult level of experience.
* The offspring re-grow the parts they lack.
A creature adapted for this life-cycle might survive an accidental division and regrow into two new creatures after such a division. However the success of this would very much depend on how close it was reaching to it's natural point of cloning. Early in the process one or both halves would be likely to have greatly reduced chance of survival, and greatly reduced brain function.
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[Question]
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I am creating a fictional off-solar system colony. In this colony people started to use a duodecimal positional number system. The people were all cultured in science and practical with numbers. They didn't have any sort of amnesia or contact with alien cultures, their new world is similar enough to Earth to allow using the old system, they don't have to hide any technical secrets from each other.
My question is: Why would a group stop using a decimal system and start using a dozenal system?
Could it be because of an event (like a war) that happened before they started the colony (assuming they started using it only once they started the colony)?
Has it already happened in the world? What kind of results could it have in their culture, technical development and science?
Thank you for your answers
[Answer]
Picture a planet with a year of 288 days in a year which has a large near moon with a orbital period of 12 days, with a week of 6 days being measured from Full Moon to New Moon and then from New Moon to Full Moon.
It is decided to use 12 months of 24 days each.
The days coincidently measure 24 hours long.
Imperial units of measure are used, with 12 inches to a foot.
[Answer]
Easy answer: religion.
Why have people started new colonies in the past? Setting up a community with their own ideals is one historical reason, and is a good bet moving forward.
A group of people are obsessed with **12** or with ancient cultures like Babylonians that used 12/60 stuff. They *start* with this idea, and go off to found their own world.
[Answer]
Hmm.. there are still many occasions where dozens or half-dozens are used (so we already have a word for it!).
Also, while we have 10 Fingers (altogether), we have 12 Finger Segments on each Hand, not counting the Thumbs. So it is possible to show Numbers up to 12 with just one Hand.
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I can think about one idea, a political one... Let's think for a while about the French Revolution. Ignore slogans concerning human rights... Which does does not matter much when one starts new era of industrial scale extermination of political opponents... think more about revolutionary minded gov, huge concentration of unbalanced power and serious efforts to make mess tolerated under *ancien régime* finally cleaned up. No more ambiguous and impractical units...
<https://en.wikipedia.org/wiki/Units_of_measurement_in_France#Revolutionary_France_.281795.E2.80.931812.29>
Got proper mood? OK, so then rearrange all units in to more clear and logic version. As extra point for mass one may actually reuse "unified atomic mass unit" which in RL is defined as 1/12 of mass of carbon-12.
<https://en.wikipedia.org/wiki/Unified_atomic_mass_unit>
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Decimal number system originated basically because we humans have 10 fingers in our hands (total, including thumbs). Number systems arise with the need of counting originates.
A number system of 12 will originate if your alien race has 6 fingers on each hand.
Or if have 12 small protrudings on their body which can be used for counting.
Something on those lines.
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I've always thought that if humans had made a stronger distinction between fingers and thumbs, we'd have counted in eights (octal). That makes conversion to binary trivially easy and computers (mechanical ones) might have arrived a lot sooner.
Anyway, there have been other number systems in history. Babylon used base-sixty, which can be subdivided as six tens or five twelves. Both were used. Sixty can be divided exactly by two, three, four, five, six, ten and twelve (and by eight using halves), which is useful to a mercantile society.
More recently base-20 was popular, subdivided in fours and fives. Vestiges survive in various somewhat obscure shepherd's dialects ( <https://en.wikipedia.org/wiki/Yan_tan_tethera> ) and in the French for ninety (quatre-vingt dix, four twenties and ten). "Dix" is ten in many of those shepherd's dialects, showing a common origin (Celtic ).
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They were merchants who sold by the dozen and by the gross. It got to the point where they said "the heck with it" and adopted the duodecimal system as their "main" system.
If they kept all their records by computer, switching bases might well have been as easy as switching display formats.
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A lot of people have answered how or why it could happen, but only a couple touch on what the effects of a switch would be.
Besides my snarky comment about the number of failed engineering projects where the incorrect unit was assigned to a number (which correlates to switching bases because does `10` mean ten or twelve or two?), there has been at least one such case in recorded history. The Norse and Germanic tribes did not use base 10, and as such, common words ended up with different meanings. For example, the [Long Hundred](https://en.wikipedia.org/wiki/Long_hundred). This had to be [standardized in law](https://en.wikipedia.org/wiki/Weights_and_Measures_Acts_(UK)#Assize_of_Weights_and_Measures) to prevent fraud. Suppose you use 120 for the value of hundred, and suppose 1 fish sells for 1 pence. I promise to sell you 100 fish for 100 pence, and you think 'Wow! What a deal!", but then I only deliver 100 fish. You get angry and wonder where the other 20 fish are, but I point out that I sold you 100 fish, not a hundred fish.
You can also look at the various gauges for things sold in countries using Imperial and countries using Metric. Cars with analog dials have markings for both MPH and KPH. Rulers have a inch side and a centimeter side. Packages list both pounds/ounces as well as kilograms.
People who were raised using base 10 will often need cheat sheets that translates Duodecimal to base 10 numbers simply because counting is learned at such an early age that it becomes deeply ingrained in us by the time we're adults.
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Not a full answer. But in base 12 you can divide nicely through all the factors: 2,3,4,6,12 (while base 10 only has 2 and five). This also means the decimal representation of the fractions become simpler -
so is 1/3 in base 12 is 0.4 (exact) - while in base 10 it is 0.333333.... (infinte series). A computer working in this base 12 would make different rounding errors than in base 10.
On a side note - there is some research going on in [mixed radix number systems](https://en.wikipedia.org/wiki/Mixed_radix). There is hope that there are systems in which complicated numbers such as roots, pi and e will have a simple form. You might make it that your (advanced) people have found such a system and 12 is the first radix - so people would for everyday things just work with this number. And computer working in such a system would make *no* rounding errors.
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During the war, computer programmers were no more secure in their accommodations than anyone else. It's hard to program when your ship's axis of rotation changes suddenly as pieces break off, and fuel is low. So while waking up the systems from hibernation and hurriedly attempting to filter out insertions into the textual history databases, somebody typed 0-9a-b instead of 0-9a-f, and numerical records in ASCII hexadecimal representation were truncated. When people started to learn numbers again, and wanted to preserve their history, they looked to the latter day "Rosetta stone" and found the digits they need. Methusalah lived 39 years. Seemed reasonable.
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I want to create an alien life for a planet which is at about 6–8 Earth masses. It has a thick atmosphere made of hydrogen, helium, methane and nitrogen. I want that life to evolve slowly and be quite complex, and being structured enough to become intelligent. It should not follow very strictly the natural selection (I mean, no one has to have special advantages to survive to predators or something so) and be very different to earth-like life. The planet has 3 moons and orbits an orange dwarf 5 Gy old, with a luminosity of 0.38 solar luminosities, from a distance of about 1.6 AU.
What kind of biochemistry could it be made of? How could it look like? What kind of ecosphere could it develop?
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Answering the second part of the question, the ecosphere wold probably resemble the deep oceans of Earth. The upper atmosphere has a zone where enough light energy is captured to power hydrogenic photosynthesis (much like plankton in the oceans of Earth), and the detritus of dead "plant" matter drifts into the depths where deep diving "fish" eat it or prey on each other.
Some species of "fish" might swim to the surface to graze on the "plankton" directly, and so some species of predators might also evolve to live near the surface as well. Since the environment is dim and cold, one could speculate that the creatures might either evolve monster eyes to operate in the dim light, or perhaps not evolve eyes at all and utilize other senses like sonar or detecting electrical fields for long range detection of food, prey or danger.
Creatures operating near the "surface" would need some sort of insulation to retain heat, and since they all exist in a gas giant atmosphere, would probably be "hot air balloons" in principle in order to remain aloft in the environment. This might take the form of being "built" around gigantic "bladders" where the body heat keeps the lifting gasses warm, and a metabolism which concentrates hydrogen in the bladder while expelling the other elements.
It is very unlikely that such an environment will be conducive to intelligence and certainly not for technology (there are not even rocks for a stone age), so the planet will be mostly a novelty for alien astrobiologists to study, or a place to be "mined" for 3He and other elements by industrialists who are not very concerned about the "fish".
[Answer]
Since the atmosphere contains hydrogen and methane (and not oxygen and CO₂), the plants probably use hydrogenic photosynthesis. [This question](https://worldbuilding.stackexchange.com/questions/25598/hydrogenenic-photosynthesis-strategies-for-animals#comment66042_25598) has some nice answers about the feasibility.
Since the luminosity is $0.38\,L\_☉$, and the distance is 1.6 AU, the planet gets $\frac{0.38}{1.6^2} \approx 0.15$ times the insolation Earth gets from (the) Sun. It will be dim and cold. There must be either an internal heat source (such as some radioactive elements, rather probable with a super Earth) or a thick, heat capturing opaque atmosphere (probably both).
Quite within the possibilities of life, just remember the planet is dim, and the gravity probably high, the plants get however more energy from the photosynthesis, but the animals get *less* nutrition from eating the plants (compared to Earth). The rest is up to your imagination.
[Answer]
This question is essentially the same as my question linked in Radovan's answer. However I will answer your specific questions:
**I want that life to evolve slowly and be quite complex, and being structured enough to become intelligent.**
It seems that hydrogenic photosynthesis which converts methane and sunlight into hydrogen and biomass is 4-5X as efficient at building biomass as oxygenic photosynthesis but the energy gains from reducing carbohydrates with hydrogen as opposed to oxidising them (the opposite of 'reduction') is 4-5x less.
In my setting, I wish to avoid this effect. However if you are after a slower pace of life then stick with this constraint and simply have your animals need to consume 4-5x the biomass for a terran equivalent energy level or make them have much slower paced metabolisms and lives.
**It should not follow very strictly the natural selection (I mean, no one has to have special advantages to survive to predators or something so) and be very different to earth-like life.**
Dispensing with natural selection is entirely a separate question to your hydrogen based atmosphere. However, the difficulty your animals have in acquiring energy rich biomass will likely produce very different evolutionary outcomes to that we have seen on earth. Maybe you just want a different evolutionary outcome and pressures? In which case the difference should be sufficient without disposing of natural selection.
**The planet has 3 moons and orbits an orange dwarf 5 Gy old, with a luminosity of 0.38 solar luminosities, from a distance of about 1.6 AU**.
The hydrogenic photsynthesis process is 4-5 more efficient making biomass than the terran version, so at 0.4 level of insolation you could still end up with twice the amount of biomass we have on earth - but there may be few complex animals. However just because animal diversity might be lower and have slower metabolisms doesn't mean they can't develop complex intelligence - you just need to posit suitable evolutionary pressures to create such intelligence - and overcoming a lack of energy rich food sources as an excellent candidate.
**What kind of biochemistry could it be made of? How could it look like? What kind of ecosphere could it develop?**
As mentioned in my linked question, a suitable biochemistry for a hydrogen atmosphere is discussed in [this paper](http://www.mdpi.com/2075-1729/4/4/716) by Bains et al. He suggests *dimethylsulfonium propionate* as an alternative to carbohydrate based energy metabolisms but doesn't elaborate on it much further. Please also see my newly filed question [Pharbohydrates vs Carbohydrates](https://worldbuilding.stackexchange.com/questions/26943/pharbohydrates-vs-carbohydrates) which has asked exactly this specific question.
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I thought there had to be a question like this here, but I didn't find one so I figured I would give it a shot.
Within my Dungeons and Dragons campaign I invented a tiny village only with about a dozen houses and maybe twenty to thirty inhabitants, all of them of quite to really old age, assumingly between 60 and 99. The village is very poor and currently there is only one younger inhabitant, the son of the innkeeper, that does all the work around the village, like doing repairs and fishing and stuff. His only reason to keep within the village is to care for his father. But as his father *might (wink)* die soon, he is likely to leave the village soon after. So my question is, **how will the rest of the townsfolk keep themselves alive, if no younger, more viable workforce is around?**
Some information about the setting:
* Magic *is* a thing, even though no one of the townspeople has any magical powers, except for the towns-eldest, that can perform minimal magical actions, like revive a dried plant and the like.
* The village is located next to a lake in the south and a forest in the north
* The village consists of a small Inn, a little chapel, a watermill, a stable and about half a dozen smaller huts and houses.
* All inhabitants are humans, have human powers and traits comparable to average real-world humans at the given age
I considered the following:
## 1. Agriculture
The town is in possession of a small vegetable garden, growing basic food like some tomatoes or lettuce, but working there requires vitality that most inhabitants do not have anymore, however, a little garden (presumably about 100 to 150m²) would not be enough to nourish two dozens of people.
## 2. Hunting, fishing and farm animals
I figured, that old people would never be able to perform some successful hunt for deers or the like. Maybe, as the village is located next to a lake, they could catch some fish with fish traps. But would the strength of a group of retirees suffice to handle it?
Also, the village is in possesion of a small pig-enclosure but again, slaughtering them would require quite the effort I guess.
## 3. Inn keeping
I guess that probably the most promising thought would be to keep the Inn going. Passing travellers could find a rest in the old Inn and would bring valuable money. A travelling salesman passes by every two weeks, so they could buy some goods from him.
## 4. migration?
I fear that the only reasonable way to keep alive would be for them to migrate to another town or village nearby, but I would love to find some way for them to stay at their beloved birthplace.
To give you some impression, here is a kind of map/image I drew of how I imagine the town to look like:
[](https://i.stack.imgur.com/2mrAM.png)
## Why are there no more young people?
The village itself is quite apart from bigger cities, so the younger population left to the bigger seaport towns in the south, to find more people of their age, seeking for like-minded friends and possible mates.
Another reason might be the increase of dangerous creatures in the forests that happend after some (I don't want do spoil to much, in case one of my PC's might read this post) dark incident.
Some of the younger folk might have felt adventurous and tried explore the forest, died due to attacks of infested goblins, or search revenge for killed or injured relatives, stolen goods and the like.
## The Powers of the Eldest
As requested, I have put some more thought in the character of the villages eldest. Conchifera Archae is the head of the village. Her real age is unknown, but due to some elvish roots, she is much older than any other inhabitants of the village. Rumors go, she might be more than 200 years old, but nobody can assure and she keeps it secret. Her character is best to describe as generous, patient and very wise. To be more technical, her alignment is somewhere between neutral and lawful good.
Classwise, she has druidic traits. Her magical powers can be well pictured by the following druidic cantrips (taken from D&D3.5 SRD) of which she can cast one per day. (If anything contradicts the rules in a major way, feel free to tell me, as I am still learning how to play, but stay focused on the main problem, as this is not <https://rpg.stackexchange.com/>)
* **Cure minor wounds:** Cure 1 point of damage
* **Detect poison:** Gain knowledge wether (and how) a creature, object or area was poisoned
* **Purify Food and Drink:** Makes rotten, spoiled or poisonous Food and water suitable for consummation. (This one might be useful) Can restore foot up to the amount that one single adult consumes within a day.
I am willing to take additional abilities into account, as long as they do not seem to much overpowered. Think about what magical powers your granny would have, if she could ;)
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You need goats. Pretty docile, and can be easily trained to stay in a location / feeding route and return home (no shepherds needed); also fairly resistant to predators (Billy goat gruff vs. troll). Milk is easy, as is shearing. Goat slaughtering is more difficult, but can be done. Especially if you have cantrips to clean up the area / not leave the stench of death in your single-file race when you cut their throats.
Pigs can get big, and can forage in the woods (truffle-hunting), depending on the type of trees (nuts) and other things available.
You're overlooking getting a custom charm animal spell (druid or ranger default), which would aid you in getting your pig docilely in a chain noose on a crane ready for slaughter.
Your river/creek is awfully straight, which implies an elevation change. If it were more meandering (flat terrain) as it got towards the lake, maybe there would be a section of forest that's mostly contained that could be control burned off. If you can kill off the trees, you can do some scatter seeding, without plowing and make some fields that you can let your pigs and other livestock forage in.
Orchards would also be great use of labor vs. return, especially if you can a cantrip or something to bring down/drop the ripe fruit/nuts on command (ie: no climbing). Orchards are typically where you get the raw materials for liquor; plum brandy, etc, etc. Running a distillery wouldn't be bad either.
Biggest problem you're going to have is shelter. House-raising takes quite a few strong people. But your housing can deteriorate around your village's ears, as long as the weather and animals don't do a number on it.
Fishing can be great, especially if you've got the right equipment - winches to haul in some nets - AND no competition, nor over-fishing. Boat repair may be a thing. But if you had several boats, and only a couple in use - any that are down for the count could be left until a repair guy comes along.
Why would anyone come along? Cash money. What you need are some trade goods. And I'd suggest magic-item components. Your garden should be herbs, that most people can't grow, but that your elven ancient knows how to tend/make prosper (cantrip to prepare the weekly fertilizer (human bone?) required for growing? special soil? needs fish byproducts as well as whatever? constant tending: boring/tedious that young people hate to do?). Basically make it something that's hard to replicate for the PCs, and not something that's so common that everyone in the world can do it, and they've got some trade to generate money. Then they need to get it dried/prepared (low strength tasks that old people can do), then they're shipped off to that traveling salesman (why else is he coming along so often?).
Pluses: you can pay off the PCs with a bunch of their preserved stock (vs. only a few coin). Now the PCs need to take a cart-load to the city, negotiate a sale, or save it for their own use (where do you house it until you use it?). Plenty of hooks with that.
But yeah, if you don't manipulate something they're pretty much dead in the water. You need young people in a village.
If you've got income going into the village you also need a reason for the young people to have left. One way to do that is to link your threat to a curse on human fertility (maybe linked to the herbs sucking the vitality out of the area)? Or a limit on where/how housing can be expanded (maybe they're hemmed in by dryad, or treant protecting the forest from encroachment (but not use). If young people can't get land (or the land isn't worth anything), can't get (a share of the) income, can't have babies, they'll go somewhere else.
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Simply...everyone dies or leaves.
Before the modern age your "pension" was your children. You raised children and then they took care of you in your age in exchange for you helping with what you can (for example caring for grandchildren).
In this situation though it's not sustainable. All the younger people have gone and the older ones will cling on for a while but then gradually that becomes unsustainable.
Soon enough everyone either dies or leaves and you have nothing but a ghost village.
Sorry if that's not the answer you are looking for but unless they can tempt more younger people back then it's a failed settlement and everyone in it will either leave or die over the next few years. A few decades at the most.
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