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[Question]
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I've been creating a science fantasy conworld, but I'm honestly not interested as much in pre-industrial stuff. But I don't want to ignore the pre-industrial history, so I'm looking for a way for the Industrial Revolution to happen as soon as possible.
While most fantasy settings are medieval, this one is **not**. Furthermore, while most settings assume a dark ages of some sort before renaissance and industrialization, this doesn't have to be true -- the Song Dynasty of China nearly industrialized several hundred years before England, and it only didn't because the Mongols invaded. So I'd like to avoid the dark ages trope as well.
Limitations and conditions of the magic involved: magic requires a human to be performed (NB: it can be performed without humans, but that is difficult enough to be done long after industrialization), electricity and heat/fire magic is possible, alchemy/transmutation is also possible. Magic is fuelled by mana, which is found naturally in the world, generated from solar and kinetic energy. Assume the magic is more like elemental manipulation and such, not Harry Potter-esque "clean yourselves, dishes".
[Answer]
### 2 Minute Version:
"And as my third wish, I desire a complete implementation of a Kardashev Type II industrial infrastructure around the planet's primary."
### Harry Potter Version:
"Manufacturo perpetuum mobile!"
### [Dark Satanic (mana-)Mills](http://en.wikipedia.org/wiki/And_did_those_feet_in_ancient_time) version:
A century at most. Presumably, mana can be harnessed with high efficiency compared to steam or solar power by a previously agrarian civ. Moreover, magic can be used to refine tools, including tools that make magic more powerful. Since the mana resource does not need to be mined, and needs no infrastructure to develop, the magic-driven industrial revolution can proceed at accelerated pace. Even if magic is hard to master, schools of Thaumaturgic Engineers will start churning mages out on industrial scales. The artefacts they create will soon pervade every household, improving productivity at rates undreamt by our measly coal-driven industrial revolution. The only source of concern would be the social implications. How quickly would these Engineers take power, and how would the reactionary forces react against them? Think the French revolution at 10x speed.
[Answer]
Alright then, to be able to do something, you will generally need these 3 things in order to do a thing, anything in fact.
* Can you do the thing?
* Do you know how to do the thing?
* Do you want to do the thing?
## Can they do it?
Since you stated that magic can only work with a user nearby doing it, and there are no simple things like:
>
> not Harry Potter-esque "clean yourselves, dishes".
>
>
>
What I would imagine the industry of a magic society would then be a bit like the city from the Legend of Korra, where they had fire bender clock in and shoot lightning at a dynamo thing, which then powers the rest of the city via electricity. I would then imagine that if your magic is primarily elemental manipulation, than it would also likely end up like that.
Not only that, since your mana is solar and kinetic powered, your power generators would then be actually quite reasonably green and eco friendly.
So, can they create electricity? The answer would be a simple yes. If your magic using society from the far future was cast out to another planet or something, they would be very quickly be able to industrialize things. However, that is based on a fairly important thing that needs to be discussed next, which is:
## Do they know how to do it?
Very obviously not at first, so they would have to go through roughly the same progression of science in order to be able to create dynamos to generate electricity, uniform spring steel in order to build factories, and some other things.
This would probably be the factor that makes the magic using society fairly slow at industrializing, I would imagine, as there would be fairly little need for a magic using society to advance their sciences to the point of industrialization.
Your society would need to be forced into advancing their industrialization, and for that I can imagine a short and simple Dark Age where their magic simply stopped working for some time, like a century or so, would cause industrialization to happen quite surprisingly fast.
## Do they want to do it?
Well, as their population grows, subsistence and local craftsmen would simply be unable to work well enough, so of course they would see a need to increase their production of anything, from food crops to magic wands in order to be able to sustain their growing population
[Answer]
Well considering how japan in the real world was able to industrialize unto a modernist type society within two decades instead of two centuries like some sorts of the world, I think using magic as a developmental catalyst to speed up the scientific innovation process a society could industrloze to WW2/Cold war Era equipment within 10 years... if it was guided by a very smart and infutential leader who had modern knowledge and foresight
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There is a system of one star and something like an asteroid belt around it. But the distance between asteroids is much less than usual, with some perhaps within nine kilometers of each other, and sometimes even less (there can be closer proximity,
to several meters, and collisions are very frequent). Also, it is an inhabited place, so there's oxygen and something does not allow to fly it away. From inside this looks like millions of flying islands.
So how this can be possible?
[Answer]
Let's assume some area in space contained your "islands" - planetoids orbiting your sun. And somehow there was an atmosphere around them (we will get to that later). Atmosphere would have to orbit sun exactly same speed as your planetoids, otherwise they will experience drag, lose orbital speed, and fall to the sun. OK so far so good.
Any other space body passing area of your planetoids would slam into such atmosphere. Comets, meteors, you have it. Gravity from other big planets orbiting your sun (if any).
You would have hard time to keep such atmosphere where you want it - gravity of a planet keeps it around a planet in a "standard" case, but your "islands" do not have enough gravity to keep gases from dispersing in space.
So unless you use some complicated unstable construct like Niven, is "standard" universe answer would be: NO. Not without using a lot of magic or handwavium.
[Answer]
If we put many planets next to each other, going around the sun, so that it is possible to walk from planet to planet, in effect a torus shaped planet that would work. If the torus planet had huge lakes in it, then we would have actual islands orbiting the sun.
If the torus is like swiss cheese, then you could have islands and an irregular torus with missing parts, but these islands would be high mass in order to hold sufficient atmosphere for people.
So it would work, but the density of the islands would be very high, so it would be pretty warm in the torus. The density would be orders higher than an asteroid field. But then asteroids have low density.
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In the world I have been working on my planet has a gelatinous mass of cells coexisting but not a technical single creature. It bridges the gap between single celled and complex and it grows in size as it consumes organic matter (any organic matter). It divides in two like a bacteria when it reaches a large enough size. Is a creature like this possible and is there any known precedent?
[Answer]
There are real world examples. You're looking for colony organisms or a collection of single-celled organisms living as one. The [siphonophorae](http://en.wikipedia.org/wiki/Siphonophorae) is a colony organism. They're made up of individual animals though appear as a single animal.
The most familiar of these is the [Portuguese man o' war](http://en.wikipedia.org/wiki/Portuguese_man_o%27_war) (not pictured above).
Additionally there are the [slime molds](http://en.wikipedia.org/wiki/Slime_mold). These things are [terrifying to watch](https://www.youtube.com/watch?v=GY_uMH8Xpy0) in [time lapse](https://www.youtube.com/watch?v=oAIDevwe1nI).
The most shocking thing about slime molds, which keep in mind are made up of single-celled organisms, ***they learn***. They can [remember, make decisions, and anticipate change](http://www.nature.com/news/how-brainless-slime-molds-redefine-intelligence-1.11811).
[Answer]
The behavior of [slime mold](http://en.wikipedia.org/wiki/Slime_mold) is close.
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This planet is a rogue planet without any star or without being volcanically active. Antimatter continually collides with the planet, and annihilates with hydrogen in the upper atmosphere. This provides heat and light for the planet.
Alternatively, the planet could be made out of antimatter, with regular matter colliding with it. The end result is the same.
Could these conditions allow the planet to support life and allow enough time for life to evolve (10-20 million years)?
[Answer]
Let's start with a quick sanity check. Earth receives approximately
$$\underbrace{\frac{L\_{\odot}}{4\pi(1\;\text{AU})^2}}\_{\text{solar flux}}\times\overbrace{(\pi R\_{\oplus}^2)}^{\text{Cross-section of Earth}}=1.73\times10^{17}\;\text{Watts}$$
of power from the Sun, and that does a pretty good job of supporting life. If this planet got all of its energy from matter-antimatter annihilation, this extra hydrogen would be depleted at a rate
$$\dot{M}=L\_{\odot}/c^2\simeq2\;\text{kg s}^{-1}$$
If you made this hydrogen envelope the mass of Earth's atmosphere, it could last for approximately 85 billion years. Powering the planet for tens of millions of years would require only a small reservoir of hydrogen.
It's worth going beyond the numbers and thinking about what form that energy will take. Electron-positron annihilation usually simply forms a pair of gamma rays. Proton-antiproton annihilation, on the other hand, is comparatively messy. [Air showers](https://en.wikipedia.org/wiki/Air_shower_(physics)) from energetic cosmic rays or astronomical gamma rays produce short-lived pions and, secondarily, less-energetic protons, neutrons, muons, electrons, neutrinos and photons. Our influx of antimatter will not be moving at relativistic speeds, but similar principles will still apply.
My main concerns from the above are the following:
* Only a small fraction of this energy may be transferred to light at wavelengths suitable for photosynthesis (or whatever variants may be used). Air showers can produce visible light through [Cherenkov radiation](https://en.wikipedia.org/wiki/Cherenkov_radiation) from relativistic secondary particles, but as mentioned above, fewer of the particles produced will move so quickly as the hydrogen and antihydrogen will, unlike cosmic rays, be comparatively low energy.
* A non-negligible chunk of energy will be transmitted in the form of gamma rays. Many of these will not make it to the ground, as they'll collide with atmospheric molecules and produce more air showers, but the flux will likely still be significant.
* As BMF notes, some fraction of the energy -- I'm not sure just how much -- will escape to space, so the first calculation is a slight underestimate of the annihilation rate.
With the above in mind, producing a significant amount of optical or near-optical light will require increasing the rate of annihilation, requiring a larger hydrogen reservoir, perhaps closer to the Earth atmosphere-esque envelope I mentioned near the start. Unfortunately, this will also lead to the production of more gamma rays.
Additionally -- and this is an important point -- simulations indicate that it's quite difficult for terrestrial planets to hold onto primordial hydrogen envelopes for the timescales we're talking about; they tend to lose them [on timescales of tens to hundreds of millions of years after a planet's formation due to thermal escape](https://arxiv.org/abs/1401.2765). This planet would be prone to the same problem, albeit with thermal escape triggered not by a star but by the hydrogen-antihydrogen annihilation. Life would need to evolve starting basically at the formation of the planet, which is quite unrealistic.
My two cents, then, is that the numbers check out inasmuch as you could heat the planet with a reasonable amount of antimatter in a hydrogen envelope, but the forms of the transmitted energy would likely be unsuitable for life, and the phenomenon would not last long.
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**Low energy, fantastic range**
From HDE in [another topic](https://worldbuilding.stackexchange.com/questions/63251/seeing-using-gravitational-waves), I learned gravitational waves have an intensity which is inverse proportional to distance, not square distance, like in electromagnetic fields..
$$h\sim\frac{1}{R}\frac{GM}{c^2}\left(\frac{v}{c}\right)^2$$
Because of this, the gravitational wave energy becomes spread over a giant distances and their amplitude is extremely small.
Now suppose future detectors of gravitational waves will be very sensitive. I was thinking of using an array of highly sensitive gravitational wave detectors in orbit around a planet, as a long range sensor for ships that make use of artificial gravity, or Alcubierre drives.
<https://en.wikipedia.org/wiki/Alcubierre_drive>
**An approximate direction to the ships is known**
Important thing to keep in mind for this question: we know where to look, the direction: we know in what region of space these aliens are to be expected. So far, they were not particularly hostile to Earth, but we would like to know their capabilities. Distance to earth of the alien ships can be anywhere between 26 and 200 light years.
**The source of the gravitational wave used for this**
For our detector array, there is a suitable and regular gravitational wave, coming from that direction. The source of this GW is an imminent neutron star collision, which is in progress ca 600,000 light years behind our observation region, as seen from Earth. We expect to be able to use this constellation for about 100 years, before they collide.
<https://marvelcinematicuniverse.fandom.com/wiki/Gravity_Field_Generator>
**Interference patterns**
I wonder if an "obstacle" such as an Alcubierre drive, could cause a ripple in the gravitational waves, which could be found invoking interference patterns, like it happens in the water, when you put 2 sticks and disturb the surface.
[](https://i.stack.imgur.com/4Es7x.png) [](https://i.stack.imgur.com/UFzMX.png)
**Alternative method: the bending of light**
(thanks @ChristopherJamesHuff for the feedback..)
The linear artificial gravity and the Alcumbiere drive introduce excessive gradients in space time, which could be detected using other means. When the field required for the drive has enough range, it could be detected using the same methods applied for exo-planets: find a disturbance in the starlight characteristic for sudden ST-gradients, like like gravitational lensing. We've chosen to invest in the GW array, because 1) we don't know if these ships emit EM radiation, and 2) whether these ships will be be parked anywhere near a star.
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**Question**: is it plausible that a ship invoking a space time distortion may form characteristic interference patterns in gravitational waves, that can be detected by my array ?
<https://en.wikipedia.org/wiki/Shack%E2%80%93Hartmann_wavefront_sensor>
*Answers I'll vote for would explain how artificial gravity or other space-time irregularities would disturb gravitational waves, or not. The best answer would make me replace a tag.. I'd like this question to become science-based, now it is not.*
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Note 1: the goal of my detector is to find out if FTL or Alcubierre drives or artificial gravity can exist, if it is in use anywhere within our Milky Way, say 100 thousand light years. My sensor has no space-war or defensive purpose. **EDIT:** You may assume we know in what direction to look.
Note 2: science based *frame challenges* are very welcome ! When gravitational waves e.g. can't do interference patterns of any kind, please correct me.
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Gravitational waves and electromagnetic waves traveling through a gravitational field would behave basically identically in terms of lensing, Shapiro delay, etc. Both are just waves traveling at c through curved spacetime. The gravitational waves are themselves curved spacetime, but to a minuscule degree when speaking of ambient gravitational radiation from sources at astronomical distances.
So, given similar sources, any detection of warp drives or artificial gravity by lensing or other effects could likely be replicated *exactly* with electromagnetic antennas.
Worse, there are very few gravitational wave sources, and they are all very low frequency, so any instruments will have to be similarly huge to match them, and so will any disturbances you wish to detect. In electromagnetic radiation, there is a thoroughly-studied cosmic microwave background that reaches peak intensity at a wavelength of 1.9 mm, and a sky full of near-black-body stars, interstellar clouds of gas absorbing or emitting with sharp spectral lines, etc. There is far more signal to work with, and the shorter wavelengths will reveal smaller targets or provide a more detailed view of those targets, as well as improving sensitivity to small disturbances.
Gravitational sensors would be more useful for detecting the emissions **produced** by such ships, which are likely to be quite distinct from any natural ones. They could also provide information on objects that can't be seen electromagnetically due to obstructing dust clouds, though this seems unlikely to be relevant.
[Answer]
Not practically.
### Need many sensors to determine if patterns
To reconstruct a pattern you need a matrix/array of sensors. The example given, the 'Hartmann wavefront sensor' is backed by sensing devices that are millions of 1d sensors packed into a 2d array.
So to be able to create an image that makes it clear the patterns that may exist many sensors are needed ideally in 2d or 3d configurations.
Each sensor to be one pixel of an image.
How many pixels do you need to clearly determine there is a pattern? Depends on what is attempted to be observed. What frequency, what resolution. It can be assumed that spaceships have less impact then stellar object mergers. My guess Is that millions of LIGO detectors scattered throughout the solar system would be needed to get good resolution of patterns.
### Gravity-Radar (gravdar?)
Same idea as radar just with gravity. Much more practical then checking interference patterns.
To merely detect signal source magnitude and direction would require far fewer devices. Perhaps on the order of a dozen sensors. A few on earth plus a few at the L4, L5 points. This would assume they are large enough to be sensitive enough to detect smaller signals. Bare minimum would be three but large sensors in space with separation would allow for much better resolution both in detecting weak signals and for determining angle.
This is already being done. The array just needs to have bigger sensors that are not earthbound to be able to detect something like ships.
### Military applications:
Sensor array. High resolution. Enough said.
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# Maybe
The [best warp drive paper](https://arxiv.org/pdf/2104.06488.pdf) I've seen lately comes from the Heisenberg lab at the Swiss Federal Institute of Technology. She says a warp drive could be constructed with just 1/10000 the energy obtainable by converting the sun to pure energy, though this *might* be improvable by a factor of, say, 10³⁰.
The energy requirement as described, if converted to gravitational waves, is not all that much less than is dissipated in a black hole merger. So if the aliens can't tune their drive well, you might see it. If, of course, they do better than that ... well, keep watching the skies!
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I am raising dragons for my world. So far they had 4 limbs (2 legs that are also used as wings and 2 legs used for walking and grabbing things). But I started wanting to embrace the fantasy even more and now I've decided that they will have 6 limbs, 4 used for walking and 2 used for flying. But a problem arises: the anatomical conflict between the wing muscles and the leg muscles. I went researching and found this art and found it interesting, but I still don't know if it's biologically realistic:
[](https://i.stack.imgur.com/ldUdf.png)
Artist: Todd Lockwood
**Would the musculature shown in the image work on a real dragon if there was one, or would it need to be altered?** The point is, none of the legs can be stunted like a kangaroo arm and the wings have to be functional rather than ornamental. Flight is pure physics, the dragon will live in a world different from Earth with the right conditions for it to fly, so you don't have to limit it to the physics of our planet. The flight doesn't make use of magic. My dragon is horse sized. If necessary, you can tell if the wings need to be behind or in front of the front legs.
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Given the OP's statement that the dragons are horse-sized on a planet on which they can fly, a number of points regarding the illustration come to mind:
1. The *placement* of the muscles for a creature with a roughly vertebrate skeletal structure appears suitable.
2. The wings would likely need to articulate from joints in bones rigidly connected to the spine, more like the pelvis than the scapulae.
3. The bones of the wings look a little thin to support the whole creature's weight in the air if it is horse-sized.
4. The *size* of the muscles seems a little odd. Either this creature spends most of its time on the ground, and hunts large, robust prey, and flies only occasionally, requiring that it has a physique that is muscular overall, or else its non-flight muscles are slightly too large and its flight muscles are too small. Being able to fly means that it should be supremely capable of 'kinetic kills', diving to attack prey and killing by sheer impact forces, and so it should not need such bulky muscles elsewhere. Additionally, smaller non-flight muscles are lighter, and easier to lift, and for a creature that flies a lot, would have an evolutionary pressure selecting for that trait.
5. Horns would appear to be counterproductive. They would likely serve no purpose other than as a sexual attractant. I would expect the horns to be present only on males, and I would also expect them to be very light and used for display only, not for combat. They would likely be easily broken, or they may be shed and regrow in time for the breeding season, in which case, they could afford to be a bit more robust.
[Answer]
**How large is your dragon?**
Very interesting question, but there's a caveat here:
>
> I still don't know if it's biologically realistic.
>
>
>
Functional flight is heavily restricted by the square-cube law: Wing-area and muscle-area scale up (pun intended) slower than mass. So a finch-sized dragon can afford to be stringy and use far more tendon than muscle, while a house-sized dragon will need huge wings and exotic muscle materials to get off the ground at all.
**For a non-expert answer assuming that size is large enough for it to matter**: I'd consider mounting wings just aft of the ribcage, and providing a hip-like structure of buttressed bone plates for them to attach to. This will probably mean dividing the abdominal cavity. Alternatively, you could run tendons around the ribcage, which will require a secondary lung (as some birds have).
Overall, large flying dragons have handwaved/magical biology anyway, and you can lay muscles out based on aesthetics and string tendons to wherever you need the force.
(NB: This answer will become obsolete with clarification about size, but may provide a useful spark for better thoughts.)
[Answer]
the world it lives on needs a denser atmosphere and lower gravity, its wing muscles are way too small for earth. On large fliers the wing muscles start to make up a larger and larger portion of the body mass, square cube law is unforgiving. the largest animal to ever fly is larger than your dragon but also almost all wing muscle. on the upside the overall size of the wings seems good.
Ask yourself how does my dragon fly, is it a glider or strong maneuverable flier, this will tell you how much muscle it needs.
here is all the muscles on the wing of pterosaur not counting the flight muscles.
[](https://i.stack.imgur.com/8CNJp.png)
Your dragon has very cat like but has no reason to be. Its limbs are shot but powerful, yet completely useless for hunting, they are built like cat limbs, but if they try to roll around with prey like a cat they will destroy their wings, and they are far to short and angled wrong to be used in fight.
Its body is way too long and flexible for a flier keep in mind everything is essentially hanging from the wing shoulder in flight, fliers want to be compact and need a fairly rigid body, mammals are fairly weird in having a lumbar region most animals just have ribs all the way down. This makes the body stiffer but can also support more wing muscle. look at a birds, bats, and pterosaurs, shot compact bodies. long thin bodies make for good swimmers or climbers not good fliers.
Birds are probably your best model since unique to birds many birds still retain good ground locomotion, but bird wing muscles may not be a good model since they have both sets of flight muscles on the ventral side which is unique to birds.
If it is horse sized the neck is too long and weak for its head, a predator with a big head wants a necks that is shorter to support strong muscles for it, or it can have a small head and a flexible neck. lower gravity may help but you still have many competing hunting styles in the anatomy.
Ask yourself how does your dragon hunt. Does it attack from the air or ground, does it kill with claws or teeth. Remember a big animal with wings cannot rolling around with its prey, so don't use cats or crocodiles as a model.
On the other hand horns and crests are fine, both birds and pterosaurs did this grow large ornamentations on the head, but keep in mind they should probably be hollow.
[Answer]
**Flying or Walking**
A dragon is not like a flying horse. Most of the time, it will be flying. It will walk (slowly) only when is on the ground and reaching things nearby. It will never run or gallop like a horse because when it needs to move fast, it will fly instead of running.
Therefor its legs need not be as long as a horse. To capture heavy animals, it will need claws. Hooves will almost be useless.
**Wing Size**
A golden eagle has average:
* Weight = 10 to 15 pounds
* Body Length = 33 and 38 inches (84cm-96.5 cm)
* Wingspan = 6 to 7.5 feet(182cm-229cm)
* Wing width = 1.8 ft. (54 cm)
Flight muscles make up between 35 to 60 percent of the eagle's body weight.
An Arabian horse has average:
* Weight = 800 to 1,000 lb (360 to 450 kg)
* Body Length = 8 feet (2.4 m) (nose to tail)
**A dragon of the size of a horse will need a wingspan of approximately 25 feet with wing width of about 4 feet.**
Wing muscles may be similar to an eagle as shown [here](https://muscularsystem16.weebly.com/eagle.html).
[](https://i.stack.imgur.com/4TjVx.jpg)
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There are numerous other question on this site about "If oxygen production stopped...?" but all of them appear to still have humans around.
This question is different. In my scenario, we may assume that every single living thing on earth has been exterminated instantly. There is absolutely nothing left alive that either produces or consumes Oxygen using biological processes. We may presume that somehow the processes of life simply stop.
I would presume that there will be all sorts of objects remaining on earth that are not alive that will consume oxygen, such as rusting iron from the multitude of abandoned cars, dried-out deceased organisms and left-over refined fuels combusting and other natural non-biological processes.
While the world in which I am interested is not Earth, it is functionally identical to Earth, so Earth may be assumed to be the planet in question.
The questions:
1. How long will Earth retain molecular Oxygen in its atmosphere? I am looking for answers that can give a ballpark figure... for approximately how many days/weeks/months/years/centuries/millennia/aeons etcetera will there be detectable levels of oxygen in the atmosphere, i.e. >= 0.5% Oxygen? Answers with an error of up to ±10% will be considered acceptable.
2. How will the levels of oxygen decline? Will loss of oxygen occur at a constant rate, begin slowly and accelerate, or begin quickly and occur more slowly as time passes?
The purpose of this is to be able to calculate the approximate percentage of oxygen remaining in the atmosphere at any time between the extinction of all life and the point at which the amount of atmospheric oxygen is negligible (i.e. < 0.5%).
[Answer]
So assuming we're starting with an atmosphere weighing ([5E18 kg](https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Density_and_mass)) of 21% oxygen (1E18 kg), and ending about 0.5% atmosphere (about 2E16) kg), and the oxygen cycle continues functioning minus anything living:
[](https://i.stack.imgur.com/W1PCp.jpg)
At current air pressure, the lithosphere will absorb 6E11 kg of oxygen a year. Lightning also removes about 1E11 kg of oxygen a year by combining it with nitrogen. [Source](https://en.wikipedia.org/wiki/Oxygen_cycle)
It gets a bit more complicated - as the removed oxygen lowered the air pressure, which slows down the removal of oxygen.
* After 104,000 years, earth is at 20% oxygen.
* After 609,000 years, earth is at 15%.
* After 1,087,000 years, earth is at 10%.
* After 1,537,000 years, earth is at 5% oxygen.
[Spreadsheet with the maths](https://docs.google.com/spreadsheets/d/1btflI91tLDhfkUseAxPoR8TPPJiOVqAL9CIPPuy2S_M/edit?usp=sharing)
It will hit 0.5% oxygen after 1,923,000 years.
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How long would humans or aliens with human environmental requirements be able to live on the dead planet and breathe the air?
The total atmosphereic pressure at sea level is 760 mmhg, and oxygen at 21 % is 160 mmhg.
According to *Habitable Planets For Man* Stephen H. Dole, 1964, pages 13-18, humans nead a partial pressure of 60 mmhg to 400 mmgh of oxygen to survive.
[https://www.rand.org/content/dam/rand/pubs/commercial\_books/2007/RAND\_CB179-1.pdf[1]](https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf%5B1%5D)
According to ASH's answer after 104,000 years Earth would be down to 20 % oxygen or 152 mmhg, after 609,000 years down to 15 % oxygen or 114 mmhg, and after 1,087,000 years down to 10 % oyxgen or 76 mmhg, close to the lower limit.
So it should take approximately a million years for the concentration of oxygen to become so low that humans acclimitized to high altitude low air pressure environoments would not be able to function well at sea level.
Thus one can write about human space travellers returning to Earth, or time travelers from before all life was exterminated, or alien visitors with similar atmospheric requirements, and they should be able to breathe the air fairly well for about a million years.
This question and the answers are mentioned in my post number 578 at:
[https://www.trekbbs.com/threads/name-that-star-trek-object.302370/page-29[2]](https://www.trekbbs.com/threads/name-that-star-trek-object.302370/page-29%5B2%5D)
This link seems to be broken. But you can go to Trek BBS and select Star Trek - the Original & Animated Series and select Name That Star Trek Object and go to page 29 of that thread and post number 578.
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On a distant world, the atmosphere is different than ours - there is no oxygen but a high level of C02 like on Mars or the early Earth. This planet is otherwise similar to Earth but slightly warmer. The planet orbits a Red Giant as a sun. The soil is rocky, and high in Silicon.
If I want plants (photosynthetic plant-like multicellular organisms) on my planet, as similar as possible to Earth plants, how do I make them work? What would they look like and how does their chemistry function? There is no animal life, only alien vegetation.
[Answer]
**Anaerobic glycolysis.**
Under circumstances of low oxygen, aerobic eukaryotes can switch to glycolytic metabolism. Humans can do this too, temporarily.
<https://en.wikipedia.org/wiki/Glycolysis>
>
> Glycolysis is an oxygen-independent metabolic pathway. The wide
> occurrence of glycolysis indicates that it is an ancient metabolic
> pathway.[5] Indeed, the reactions that constitute glycolysis and its
> parallel pathway, the pentose phosphate pathway, occur metal-catalyzed
> under the oxygen-free conditions of the Archean oceans, also in the
> absence of enzymes.[6]
>
>
>
Anaerobic glycolysis is less efficient than aerobic, yielding a third of the energy per glucose molecule. Also there are byproducts that must be dispensed with or regenerated to glucose; lactic acid and ethanol are examples.
Maybe the original plants used glycolysis back when they could make sugar but were not assured of plentiful oxygen. They can still do it today.
[Low Oxygen Response Mechanisms in Green Organisms](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3634410/)
>
> Low oxygen stress often occurs during the life of green organisms,
> mostly due to the environmental conditions affecting oxygen
> availability. Both plants and algae respond to low oxygen by resetting
> their metabolism. The shift from mitochondrial respiration to
> fermentation is the hallmark of anaerobic metabolism in most
> organisms. This involves a modified carbohydrate metabolism coupled
> with glycolysis and fermentation.
>
>
>
So your plants would be glycolytic. That is totally legit biochemistry and not fiction. For a fiction I like the idea that they store the end product as either ethanol or lactic acid, regenerating sugar from it when there is lots of water and sun to use. Those plants might be harvested for their storage products in addition to their sugars.
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It occurs to me that plants in a low oxygen environment might store the oxygen they produce in their tissues, just as they store the carbohydrate product. Gaseous oxygen is reactive and difficult to store though could be stored as bubbles in an aquatic plant.
Animals store oxygen using heme molecules. Hemoglobin is one. Myoglobin stores large amounts of oxygen that whales use during their deep dives. Your plants could have similar pigments that capture the oxygen product of photosynthesis and keep it handy for aerobic metabolism when needed.
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Cyanobacteria consume carbon dioxide and produce oxygen as a waste product. They require water, sunlight and a few nutrients, but they do not require any oxygen at any point of their photosynthetic cycle so they could be a good starting point.
One possible candidate for your “plants” if you want to base them on Earth life forms would be Nostoc pruniforme which grows in gelatinous spheres with a smooth surface like a plum. These are typically a few mm or cm across but can get as large as 15cm or more in some cases.
[Nostoc pruniforme](https://en.wikipedia.org/wiki/Nostoc_pruniforme)
That said the possibilities within chemistry are vast beyond reckoning so there is no reason why given sufficient evolutionary pressure on an alien world with an alien biogenisis that something like cyanobacteria should not evolve into more complex plant like shapes and forms as well as developing resistence to the oxygen it is itself producing as a waste product.
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## Do what aquatic plants do
Here on Earth, plants need oxygen for respiration, just like animals and fungi. Very many plants have very successfully [adapted for life under water](https://en.wikipedia.org/wiki/Aquatic_plant), although plants cannot extract oxygen from water.
How did they do it? They make their own oxygen through photosynthesis.
Some aquatic plants are very popular with people who keep aquaria, both as a source of oxygen for the fish and as landscaping material.
[](https://commons.wikimedia.org/wiki/File:Ceratophyllum_demersum.jpg) [](https://commons.wikimedia.org/wiki/File:Freshwater_aquariums_Sharjah.jpg)
Left, [*Ceratophyllum demersum*](https://en.wikipedia.org/wiki/Ceratophyllum_demersum), a popular aquatic plant. Photograph by Totodilefan, available on Wikimedia; public domain. Right, [*Hemianthus callitrichoides*](https://en.wikipedia.org/wiki/Hemianthus_callitrichoides), an aquatic plant widely used in [aquascaping](https://en.wikipedia.org/wiki/Aquascaping). Photograph by [Ranjith-chemmad](https://commons.wikimedia.org/wiki/User:Ranjith-chemmad), available on Wikimedia under the Creative Commons Attribution-Share Alike 4.0 International license.
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The Earth's primitive atmosphere was Carbon dioxide and methane. When the first photosynthetic organisms absorbed carbon dioxide they converted it to oxygen. With few animals to consume it, the atmosphere literally converted.
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I understand how complicated constructed languages can be. I do not want that though. The language would need no grammar or syntax. But I would like to create places/people names and maybe the odd noun for the language.
But here's the kicker... I want to be able to generate these languages and quickly, one per player. Potentially hundreds of them.
It occurs to me that even though I don't know Japanese, I can recognize Japanese-sounding words because Japanese has some system of rules about what their words can sound like. And this is true as well for many other languages (probably all of them). For the Japanese example, they have a restricted number of vowels, and all syllables seem to end with a vowel. Consonants don't seem to cluster like in European languages (but for those, we only get particular clusters).
Has anyone actually created such a system/algorithm before? If not, is this something I could create myself or is this more like some PhD research project level of difficulty?
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[Awkwords](http://akana.conlang.org/tools/awkwords/) is the first one that comes to mind. You enter in a bunch of letters or short strings for each category, and then write rules for how the categories can be chained together. The program pulls one string at random for each time it sees a call to a category, so it's an easy way to get thousands of combinations out of just a few inputs.
It definitely misses a lot of the subtlety that languages really end up with, but I think it's a good starting place to get the feel of what words can end up looking like.
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Well... check out any fantasy name generator for examples. These probably do not directly suit your purposes, but they might give you some inspiration. You might also want to check out [this](https://github.com/Azgaar/Fantasy-Map-Generator); it generates maps, but part of its logic includes generating names.
As I understand it, most of these sorts of algorithms are based on having a set of potential phonemes and a set of rules (possibly, probabilities, some of which may be zero) about what phonemes may appear in succession. As noted, there are certainly extant examples of software with already-provided rules. I don't know offhand if anyone has made a general-purpose program of this nature that you can feed your own set of phonemes and rules.
...but the problem you are asking about (IIUC) is how to create these data sets in the first place, and that is a much harder problem, which can be complicated depending on your use case. For instance, are we even talking about *human* languages, or are you interested in creating "words" that are expressed as color patterns, scents, arm movements, ...?
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That being said... what you *might* try is to take a similar approach to generating *rule sets* as to generating words. You'll need your own software (or someone else's you can use as part of your own suite, i.e. awkwords probably won't help directly) that takes a rule set. Then, what I would do is create a 'master' set of all possible phonemes and possibly 'seed' rules for combinations and/or what sets of phonemes may be combined, and write an additional layer to generate a language rule set from the master set.
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**Body:**
Boron-based lifeforms that use ammonia as a solvent and respires methane & hydrogen, with an atmosphere of mostly methane, hydrogen, nitrogen and in smaller percentages, acetylene & other elements. The temperature of the lifeforms' planet is -10 Celsius, with the pressure being 25 atmospheres. We will call them boracoids. The intelligent life-forms are bipedal with four limbs but have a bird-like stature (not upright).
They're also not that big, being about twice the size of a raven.
[](https://i.stack.imgur.com/2uakh.png)
A boracoid in a desert on some planet, wearing a spacesuit.
The boracoids don't have a specialized gas transport molecule but rather rely on diffusion and solubility, with hydrogen and methane diffusing into the cells. In a reducing atmosphere, the roles of oxidizer and fuel are reversed, so the hydrogen is the fuel, and acetylene is the oxidizer. Acetylene is breathed in from the atmosphere as it can be produced through incomplete combustion of methane, although I have no idea what process makes that happen on such a planet.
On energy currency, acetylene will be used as it, or rather, a diborane molecule with some phosphorus attached. But I will rather talk about the acetylene, and how it can be used. Acetylene is converted to ethane through hydrogenation - the breathing process described above! With this, we can also convert ethane back into acetylene (i think through converting it into ethylene then converting the ethylene into ethane, not sure.).
As for encoding information, the boracoids use diborane and other boranes for it, polymerized into large chains, with phosphorus and nitrogen being used, so it's essentially just DNA, although I have no idea on whether this is a feasible encoding system.
There is an unusual abundance of boron, while oxygen and other chemicals such as chlorine, fluorine, and bromine are all either not present or locked up in minerals. Along with the boron, there exists an unusual abundance of metal & phosphorus in the boracoids' planet.
One thing is that the boracoids breed and use another type of lifeforms called meranchees, which are polyoxometalate-based lifeforms that rely on metals as their building block. The polyoxometalates can be assembled through metals in an acid solution in the presence of a heteroatom. So we just need a way for them to produce acid and etc... which the boracoids exploit, once a colony of meranchees has grown enough they will take it and break it down to pure metals.
**I have several questions:**
1. are all of the things I described above a feasible system? or just straight-up wrong?
2. the section I have issues with the most is the encoding system, second to that is how they respire - is hydrogen soluble in ammonia? what can we use as the encoding system instead of diborane?
*(note:) excuse me for my chemistry, I'm not really good at it though I do like worldbuilding and stuff like that.*
**EDIT (due to a reply from earlier):** I'd like to say dismissing unlikely biochemistries doesn't help. I posted this with knowledge that boron biochemistries are far less versatile and far more rare than organic biochemistries. I've seen this argument multiple times, but I'm not looking for an alternative to boron. I want to explore it. Thank you.
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I am going to take the acetylene metabolism piece as the question.
Your heterotrophs get energy by hydrogenating acetylene. I wish I knew a better way of figuring enthalpies besides googling endlessly! I eventually found that this is an exothermic reaction at -262kJ/mole [source](https://www.scienceforums.net/topic/18044-chemistry-enthalpy-reaction/) which is what you would expect because carbon does not much like to get so friendly with other carbon as it must in acetylene. So: a good way for heterotrophs to get energy.
Now you need an autotroph that regenerates acetylene. Probably this will be something that uses radiant (or other) non chemical energy to catalyze the energetically unfavorable stripping of hydrogen from ethane and methane. The waste product is acetylene just like plants strip the carbon from CO2 and the waste product is O2. Your plants sequester the valuable hydrogen like our plants sequester reduced sugar.
How to hang on to that squirrelly hydrogen? You know it wants to leave for space. I proposed here [What element would the hemoglobin content of methane-based life use?](https://worldbuilding.stackexchange.com/questions/70523/what-element-would-the-hemoglobin-content-of-methane-based-life-use/70525#70525) that a metal hydride could be used as a hydrogen carrying molecule. Or you could use [boranes](https://worldbuilding.stackexchange.com/questions/121374/boron-based-life-blood/121399#121399). Sulfur could be a good hydrogen carrier and it works that way on Earth, shuttling between sulfuric acid, elemental sulfur and oxidized sulfur.
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I will look at the broad aspect of a boron based life form and I suggest that any such life form is unlikely. The reason being that all examples of life we currently have experience of involve a very high level of complexity. Organic biochemistry offers more scope for complex compound formation than boron chemistry does by many orders of magnitude.
This is at least in part due to the fact that Boron only forms compounds with an oxidation state of three or less limiting its ability to connect to other atoms.
So although it can’t be ruled out entirely as the scope of even Boron chemistry is vast, it must be seen as being very unlikely. For those unfamiliar with the biochemistry of life and it’s complexity I suggest this link:
<http://biochemical-pathways.com/#/map/1>
And this is just a fragment of the full picture of reactions going on in the cells of organisms. Trying to replicate this or even part of this using an atom with an oxidation state of 3 rather than 4 would be challenging.
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So, mechanical computers are a thing, as are pneumatic and hydraulic actuators.
Combining those ideas, it's not that hard to design simple purely-pneumatic/hydraulic robots--provide them with a source of compressed fluid, and they just go (and that includes performing middling-complex mechanical calculations, e.g. to coordinate the motions of hexapod legs entirely via fluidic switching--not just, say, powering a turbine to spin wheels).
Building more complex control "circuits" to make a fluidic robot do more than justy move straight forward is obviously *possible*, with the proviso that they are likely to be much larger than electronically-controlled robots, since miniaturizing fluidic and mechanical components is difficult. But that's not very useful unless the control system actually has some input to act on.
So: what kinds of sensors would be feasible for a purely mechanical/fluidic robot, which can feed directly into a mechanical computer via mechanical or fluid linkages without any intermediate electrical stage?
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["Handbook of Fluidic Sensors"](https://apps.dtic.mil/dtic/tr/fulltext/u2/a041145.pdf) provides a list of fluidic sensors that were commercially available and their capabilities.
**Fluid flow and pressure**
a pitot probe is a simple example of how fluid flow speed may be sensed
**Sound.** For fluidics, you can more or less directly sense fluid flow and sound. All you need for a microphone is an acoustic horn to collect the sound. Fluidic circuits based on jet deflection amplifiers basically work off of acoustic signals. Although with traditional fluidic circuits it's difficult to operate at ultrasonic frequencies. Some fluid jets display sensitivity to ultrasound and ultrasound operated fluid switches have been developed. It's been proposed that such devices could be used to make [ultrasound remotely controlled toys](https://patents.google.com/patent/US3282051A/en). Although the performance of this type of ultrasound fluidic switch is a bit dubious for this application in practice.
**Proximity/Distance**
Although it's difficult to operate at ultrasonic frequencies with fluidics, fluidic proximity sensors based on [using ultrasound to transition a jet of fluid to turbulent](https://apps.dtic.mil/dtic/tr/fulltext/u2/a061435.pdf) have been employed commercially. See page 109 of the handbook for more details.
[](https://i.stack.imgur.com/2FJ63.png)
Although the above sensor provides only a boolean response. There are also fluidic devices which can [modulate and demodulate ultrasound](https://patents.google.com/patent/US3398758), meaning you could potentially make a workable sonar range finder despite not having switching elements which work at ultrasonic frequencies. Although this has never been done before and one might have to push the boundaries of what's possible with fluidics to do this. It might become more practical if we run fluidic devices off of low density gases like hydrogen and helium, which have higher speeds of sound and can thus enable higher operating frequencies. You can also measure short distances by measuring back flow from a jet and other fluid dynamic effects, see page 19 and 57 from the handbook above.
**Touch Sensors/limit switches**
One way to make a simple touch touch sensor is make something that opens a valve or hole when bumped. There are numerous examples of this in the handbook above. Another way is to have an open hole which we blow air out of with a another channel leading back to the circuitry we want to drive. When the holes open, the output is zero, when the hole's covered, the air gets redirected to the channel. This type of device is typically called a back pressure switch and is shown below.
[](https://i.stack.imgur.com/Bx8eR.png)
This same technique can be used to measure short distance too by looking at the back pressure.
**Rotation Encoders**
One can make a simple analog of an optical encoder by using a jet of fluid instead of a beam of light. One can also use a channel that changes width so that the fluidic resistance changes with rotation, enabling analog absolute encoders to be made
**Strain Gauges/force sensors**
One way strain gauges have been made is to have a pipe with a helical channel in it, sort of like a spring, and put rubber tubing in the channel. Compressing the pipe compresses the tubing and increases the resistance to fluid flow
**Temperature sensors**
When fluids heat up their viscosity, density, and speed of sound can change, which we may sense with fluidic circuits. Fluidic capillary pyrometers, which measure temperature by taking advantage of the fact gases become less viscous at higher temperatures thus decreasing the resistance of a capillary tube, have been used to measure the temperature of molten steel. Another means of measuring temperature is to take advantage of the fact that a fluidic oscillator will change in pitch as the temperature changes due to the change in the speed of sound.
**Chemical Composition**
fluid viscosity, density, and speed of sound can also change with composition. A simple example of this is that we can [sense the amount of helium/hydrogen](https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19760026387.pdf) in the air with an oscillator. The higher the pitch is, the more helium/hydrogen there is in the air. Fluidics has also been used to make a [non-electric gas chromatograph](https://pubs.acs.org/doi/abs/10.1021/ac00125a035)
**Accelerometers/Gyroscopes**
Purely fluidic gyroscopes have been made. Rotation can cause a fluid to swirl and form a vortex increasing fluidic resistance.[](https://i.stack.imgur.com/pDdls.png)
These have been used in an [aircraft autopilot](https://www.nasa.gov/centers/dryden/pdf/87760main_H-535.pdf) and have also been used to stabilize missiles and rockets. One can also take advantage of the fact that a jet of fluid will [deflect due to rotation or acceleration](https://apps.dtic.mil/dtic/tr/fulltext/u2/a134046.pdf)(see page 7). These have been used to make [fluidic tank gun stabilization systems.](https://apps.dtic.mil/dtic/tr/fulltext/u2/a084836.pdf) It's also interesting to note that the [first in car navigation system was based around this principle](https://global.honda/heritage/episodes/1981navigationsystem.html), although the jet was sensed electrically through hot wire anemometers
**Magnetic fields**
Most fluidic amplifiers are based on deflecting a jet between to ports using perpendicular fluid flows. Instead of a perpendicular fluid flow we can put a magnet on a flexible beam in the jet, so when there's a magnetic field the flexing of the beam will deflect the jet.
**Light**
Light's the most difficult thing to sense. In general it's difficult to transduce light to mechanical signals as the energy light carries tends to be low. Unless of course the light is bright. Fluidic sun sensors have been made, where we use a lens to focus sunlight on two curvy pipes painted black. Because fluid decreases in viscosity with temperature, we can look at the difference in resistance between the two pipes to figure out where the sun is. A [one axis fluidic](https://patentimages.storage.googleapis.com/8d/15/65/7a4bce591a2f19/US4964591.pdf) [attitude control system](https://apps.dtic.mil/dtic/tr/fulltext/u2/a204334.pdf) capable of tracking the sun intended for a solar probe was demonstrated using this approach. A similiar approach has been proposed for [making IR seeking railgun launched projectiles](https://patentimages.storage.googleapis.com/8d/15/65/7a4bce591a2f19/US4964591.pdf).(Fluidics can withstand the enormous EMP) Another means light can be sensed is using the photoacoustic effect. If the light is flashing on and off very fast, it will cause a cavity of air to expand and contract making sound. While this sound may be very minute, we can use fluidic amplifiers to amplify it into something we can work with. The [non-electric gas chromatograph](https://pubs.acs.org/doi/abs/10.1021/ac00125a035) mentioned above was able to amplify the photoacoustic signal from a 1 mW led into a pneumatic control signal. Continuing the trend of absolutely bonkers applications of fluidics for the SDI, a fluidic [ICBM interceptor control system](https://apps.dtic.mil/dtic/tr/fulltext/u2/a204334.pdf) was demonstrated that used a laser to control divert jets. One proposed means of sensing light with fluidics of doubtful practicality, but potentially higher sensitivity than the thermal approaches used above is to use [a chemical reaction that is triggered photochemically](https://patents.google.com/patent/US3228411A/en). For example, we have a continuous stream of hydrogen and chlorine directed into a chamber upon exposure to sufficiently bright UV or blue light, the hydrogen and chlorine will react explosively. We can then sense the pressure and flow of the explosion. Perhaps a strip of light sensitive explosive could be used. In short, it will be difficult to sense anything except bright light.
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Touch, hearing, balance, and vision if you have the chemistry.
For hearing, we already use a mostly fluid system. A vibrating membrane translates vibrating air to fluid, which then vibrate hairs. If those hairs are attached to micro-pneumatics (instead of electro-chemical receptors), they could transfer the signal to the pneumatic CPU (brain).
Balance works pretty similar, with fluid sending signals when it triggers certain points by being tipped in the inner ear.
Touch could work by having flexible outer layer of "skin" (rubber, plastic, whatever). It pushes on an array of ten thousand tiny pistons, which send pressure signals down the fluid channels to the CPU.
Vision is real tricky. But in human eyes, a photon actually changes the shape of a molecule in a rod or cone at the back of the eye, like a tiny a gear turning inside it. Perhaps you could use a chemical that expands or contracts to a large enough extent when exposed to light to effect the fluid channels. I admit this last one surpasses my chemical knowledge.
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The technology to make these sensors is used today and used in everyday consumer goods from inkjet printers to cells phones.
Micro Electro Mechanic Systems (MEMS) are microcircuits produced with the same scale of lithographic processes used in the 1970’s integrated circuits.
[](https://i.stack.imgur.com/qm8Hn.png)
## MEMS Pressure Sensor
They can easily measure temperature, pressure, fluid flows, detect bubbles in hydraulic fluid detection by creatively exploiting observable parameters of fluid dynamics using MEMS capacitance and resistive meters in combination with very standard analog to digital converters and a little math. These signals can be converted back to analog levels using standard digital to analog converters, which could then be turned to pressure levels or pressure oscillations using electromechanical transducers.
If a completely mechanical sensor is required, then basic MEMS design will still work and just the sampling mechanism will need to be altered. For instance, in the MEMS pressure sensor shown below. The diaphragm will need to be connected to a mechanical pushrod whose motion is amplified by standard means using combinations of levers or gearing. The sensors will be no larger than a grain of rice, but the mechanical signaling mechanism will be larger.
On advantage of MEMS-based solutions is that Silicon, on this scale, of a few microns, is stronger than steel, so the sensors are very robust.
The size of the mechanical amplifiers will be determined by the amount of amplification required and available materials.
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Would it be possible to have an organism to be based on alcohol, rather than water? Complexity does not matter, but a complex organism would be favourable. their environment would be in oceans of isopropyl alcohol on a relatively warm planet with very thin CO2 atmosphere and less than half earth's gravity.
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Not naturally, no.
Isopropyl alcohol is a pretty good solvent for both polar and non-polar molecules, but not salts. So, it is certainly plausible to imagine a complex engineered biosystem, maybe with ionic cell membranes, that depends on it. Maybe you've got a two-phase system where cells form from bubble of isopropyl alcohol suspended in saltwater with a monolayer membrane.
But naturally-occurring pools, let alone oceans, or mostly-isopropyl-alcohol in which abiogenesis could occur spontaneously? No. Any natural abiotic processes that could produce significant quantities of isopropyl alcohol would also produce even larger quantities of a slew of other simple carbohydrates. You would end up with an enormously complex mixture of an ocean--and sure, life might form in that ocean, using a complex solvent or multiple interacting solvent phases, and once primitive life is established it might well go on to specialize on a purer, self-produced or at least self-segregated internal solvent... but I see no strong reason for such life to prefer specialization on and biotic production of oceanic quantities of isopropyl alcohol, over much simpler substrates like methanol or formaldehyde.
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I’m sorry but isopropyl is typically used against microbial life; any bacteria (and presumably less complex Protists and Archaea, etc) and fungi are likely to be annihilated, introducing H2O will likely only seal their fate.
However comments on the web imply that a pure solution free of water (90%+) may be less destructive and allow certain spore forms to lie dormant but this is something that goes beyond my knowledge of organic chemistry and I can really only quote the Internet.
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The situation that you describe - oceans of isopropyl alcohol - are unlikely to occur naturally and if they did would be unlikely to remain uncontaminated for long.
The simple answer is we don't know and can't really tell with any certainty if organisms could evolve because the theoretical possibilities within chemistry and biology are so vast. I suspect not.
That said if the ocean was contaminated as it surely would be with water and other chemicals from erosion and reaction with the environment it is possible that a life form based on something other than isopropyl alcohol might evolve and extract the compounds that it needed from the ocean in the same way that Earth based life extracts oxygen from ours.
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Yes and no in the same time. Alcohol and water mix in all proportions, so the world you create with pure alcohol oceans would quickly change to a mixture of water and alcohol. And we know that there are organisms that thrive in this mixture. We use them to make fermented beverages.
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A spin-gravity space station, a ring-shaped structure that creates a faux gravity on the inside of the ring via inertia, has been depicted as no bigger than a house and as massive as a solar system.
However, I expect there's some real-world limitations on size. With the understanding that any given ring is for human habitation and exactly 1G is the target, what are the minimum and maximum radial size limits?
For minimum, obviously about 2 meters, as that's human height, but I think having your head spinning at the center would make you dizzy, so minimum is probably bigger.
For maximum, theoretical maximum would be whatever radius calculates to 1G with 1C angular velocity. But spinning at near C has obvious practical problems, not to mention the billion or so non time-dilated years it would take just to accelerate up to speed.
I'm looking for real science and mathematics here. I'm hoping answers can be comprehensive enough to include pragmatic human needs, but they can neglect things like material strength.
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> For minimum, obviously about 2 meters, as that's human height, but I think having your head spinning at the center would make you dizzy, so minimum is probably bigger.
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Just lie down? Little centrifuges are useful for counteracting physiological problems with extended stays in microgravity. The major issue is rotation rate rather than radius, and happily people have done various amounts of research on this sort of thing already. This diagram is take from [Artificial Gravity and the Effects of Zero Gravity on Humans](https://www.permanent.com/zero-gravity-effects-on-humans.html).
[](https://i.stack.imgur.com/gFILC.png)
The author of that page suggests that anything under 20m radius probably isn't much fun to live in, but it is hard to do experiments on that sort of thing on earth, so for better research you'll have to wait til humans have a more substantial presence in space. The source materials for the paper don't recommend going as high as 10rpm, but it is apparently possible to acclimatise to rotation rates as high as 23rpm, but again: experimental data is lacking.
Also take a look at [this question and its answers](https://worldbuilding.stackexchange.com/q/1445/62341).
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> For maximum, theoretical maximum would be whatever radius calculates to 1G with 1C angular velocity
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Well, neglecting relativistic effects (because who has the time to worry about those?) you'd get about $9\*10^{12}$km, or nearly one lightyear (worked out using the handy [SpinCalc](http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm), useful for the lazy). But even if you *could* make something that big, why would you? It would be a massive pain to heat and light, for a start. I posit that the largest you'd actually *want* to make a ring-shaped habitat is to fit the habitable zone for a star, Ringworld style.
The original Ringworld, of course, has been well discussed elsewhere. There are some [facts and figures here](http://www.alcyone.com/max/reference/scifi/ringworld.html), the key bit being the ~1AU radius so as to neatly fit into the habitable zone of its Sun-like G3Ve star.
I found this [slightly clunky and hostile](https://depts.washington.edu/naivpl/sites/default/files/hz.shtml) habitable zone calculator. The UI is surprisingly bad, given how simple it is, but I threw in the numbers for Sirius A (25.4 times the luminosity of the sun, surface temperature 9940K) and got habitable zone figures of around 6AU. That's about $9\*10^8$km, and throwing that radius into SpinCalc gets you a tangential velocity of about 3000km/s, or about 1% of lightspeed which is still comfortably below the point at which you need to worry about relativistic effects. I'll leave it to you to pick a star with a truly silly luminosity and work out how big a ringworld you'd need around it, though.
Constructing such a ridiculous thing (which, with Ringworld's width of 1.6 million km, has a surface area of something like 17 million earths) is left as an exercise for the reader. Even finding enough material to give it a light dusting of soil is going to be quite a challenge, but maybe you can dismantle Sirius B to help you make it?
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If you allow for realistic material constraints, everything becomes massively smaller, though still absolutely gigantic by any reasonable standard.
Thomas McKendree wrote a paper a while back called [Implications of Molecular Nanotechnology Technical Performance Parameters on Previously Defined Space System Architectures](http://www.zyvex.com/nanotech/nano4/mckendreePaper.html), and applied it to the classic [O'Neill cylinder](https://en.wikipedia.org/wiki/O'Neill_cylinder). He came up with a habitat with radius 461km and length 4610km, giving a habitable surface area of about a million square kilometres (remember half the area of an O'Neill is given over to windows). The Orion's Arm universe uses slightly less conservative estimates of the performance of carbon nanotubes, and gets a [somewhat larger habitat](https://www.orionsarm.com/eg-article/48473a892041c), 1000km in radius and 10000km long. Close to the limits of materials, but not quite beyond the realms of possibility.
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I think @StarfishPrime 's answer already covers almost everything relevant, however he seems douptfull that the one lightyear ringworld could be constructed. This isn't rally an answer but an extend comment about the 1 lightyear ringworld.
I'm under no illusions that building such a mega(giga? terra?)-structure is easy or trivial. Even though what I'll propose is physically possible, the engeneering, logistics, heating and lighting issues and those arising from friction or induced currents will be enormous. This is a project even a galaxy-spanning K3 civilisation will consider impressive and non-trivial. This is precisely the reason why I believe someone will attempt it in the distant future.
With that all out of the way, let's bring in the
## Active Support Ringworld
Whenever you build a structure you want it to stay stable. Buildings do this by relying on passive support, i.e. their own structure can carry their weight. This approach is limited by the ability of the building materials to resist the force the rest of the structure exerts on them. This is Newtons third law, actio = reactio. Actio is the force the structures weight delivers and reactio is usually the force the material must be able to muster. No imaginable material comes even close to having the tensile strength required for such a megastructure.
But nowhere it is said that the reactive force must be provided passively to keep the structure stable. Imagine a friend of yours is walking over a thin plank, which would break under his weight. The passive support of the plank isn't sufficient to counteract the force your friend exerts. Now you go under the plank and push it up, so that it can hold your friends weight. You are providing active support. The great thing about active support is that you aren't limited by puny compressive or tensile strength, you are dumping energy into the system to keep it stable. And you can dump infinite ammounts of energy into a system.
**Or to put it into simple terms, the ring will fly apart, no matter what we do. So we have to hold it together from the outside by providing a strong enough inwards acting force.**
So now we got two issues at hand. Firstly how do we get a force strong enough to hold the ring together and secondly how do we prevent friction between the ring and its support structure from vaporising everything. After all, the ring is supposed to move near lightspeed.
The support issue can be taken care of by placing the structure around an object with a hill-sphere with a radius significantly greater that 0.5 lightyears. We also don't want any other objects in the neighbourhood (read several lightyear radius) which could disturb the structure gravitationally. The central structure should be a sufficiently massive black hole. We want a black hole for two reasons. Firstly it is simply less dangerous than a star with the requiremened mass (those O and Wolf-Ratet stars will go supernova very quickly) and secondly it will be our energy source. Black holes are amazing for energy generation and we'll just need some hydrogen to use the [Penrose Process](https://en.m.wikipedia.org/wiki/Penrose_process) or harvest light from the accretion disc and we'll be set with energy for billions of years. The superstructure supporting the ring will mostly consist of hydrogen. It will be a gigantic storage tank full of it which is as big as the ringworld. You construct both ring and superstructure in orbit around the black hole. Then you install mind-bogglingly powerful electromagnets between the ring and the superstructure. (There will be induction issues, however I think engineers in a K3 civilisation might find a way to negate those.) The next step is to accelerate the ring up to lights peed and the supportstructure well below orbital velocity, but not to a complete standstill. One would have to plan the mass ratios of the two parts in a manner that the force of gravity pulling the superstructure down to the black hole is equal to the force with which the rings wants to fly apart. The magnets ensure that there is almost no friction and that both components keep interacting.
So here you go, this is a perfectly non-conservatively sized spin habitat.
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If your ship just got trapped inside the event horizon of an super massive black hole, could the ship "accelerate" back out with an alcubierre drive?
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Possibly, though you’d be escaping by moving the exit, potentially with hideously unintended side effects.
Basically below the event horizon of a black hole spacetime is warped such that nothing you do can alter anything above the black hole. Naturally this includes physical escape.
Alcubierre drives, on the other hand, work by warping spacetime such that you go from A to B without ever locally breaching the speed of light.
If you mix the two (and I have no maths to back me up here because nobody wants me to even think the phrase Alcubierre-Schwarzchild metric) it does weird things to time around the black hole, and may well require more energy than is present in the universe.
You’ll need some hefty hand waving to explain how your alcubierre drive functions in the first place; and if your ship has already fallen past the event horizon they you must somehow have A: explained away the tidal forces that should have torn your ship apart and B:have already dealt with the fact that from your ship’s point of view the heat death of the universe *has already occurred* by the time they reach the event horizon.
Wait. Back up. What?
Oh, yeah. As you approach the event horizon of a black hole time dilates. That’s why it’s impossible to escape: spacetime just wont let you, To an outside observer your ship *will never* breach the event horizon, instead it will become a smeared out, permanently frozen image of itself. From your point of view the universe will move faster and faster as you approach the black hole. Usually you’d be torn into incandescent plasma long before you got anywhere near close enough to see the universe end, but hey, handwaves.
So: now you’re not escaping from below the event horizon, but rather from just above it. This makes things easier, because an Alcubierre Drive (simply) expands space behind you and compresses it in front of you. Turning it on just above a black hole will ‘push’ the event horizon closer to the singularity below it, letting you get far enough ‘away’ to achieve escape velocity. Hooray!
Again: there’s some handwave here. Alcubierre drives (at least using the Alcubierre-White warp equations) act as more of a speed multiplier than a drive on their own, so you’ll need to deal with how you get enough energy to escape. Also: if you’re ‘in’ the black hole the amount of energy you’ll need to warp your way free will grow as you get closer to the black hole (sensibly, as you’ll be spending longer trying to escape).
Now for the unintended side effects.
Mathematically speaking if a black hole is spinning fast enough or has enough electric charge then it has no event horizon. This means you can see and interact with the singularity at the core of the black hole: a so-called ‘Naked Singularity’. Physicists and mathematicians don’t agree about what such a thing would look like because while it’s mathematically possible the one thing nature abhors more than a vacuum is a singularity. Our models of physics break down. Our models of mathematics break down. In many ways the feared ‘event horizon’ is a shield between us and pure unfettered ‘What?’. Nobody likes a naked singularity.
Again: I haven’t done the maths here because it’s fearsome, but if you ram enough power into your Alcubierre drive I can’t think of a reason why you would t be able to push the event horizon all the way back to the singularity - at which point my brain breaks. You also run hard into the 'Cosmic Censorship Hypothesis', which holds that naked singularities simply aren't allowed. You would be fighting the entire universe if you tried to create one.
So: you may well be able to escape the clutches of a black hole with your drive, as long as you have enough power. Just take care not to break physics.
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Well, seeing how the event horizon is the area from where the escape velocity is equal to the speed of light; an alcubierre drive *would* indeed allow one to escape, by accelerating beyond escape velocity.
The problem is that deeper into the hole, the velocity required increases quickly, and the increased mass in the gravity well makes 'warping' it take more energy, so all an alcubierre drive would do is pushing the effective event horizon back.
J.J abrams got this right in his 'star trek' reboot; the enterprise wound up in a black hole, and even with their FTL, they could only prevent falling deeper. (star trek uses a style of FTL that works just like the alcubierre. in fact: it is the inspiration for the design)
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I've read super-earths might become archipelago planets. Picture shallow seas, under a thick atmosphere that alternates between muggy and clammy. Because a bigger share of the surface would be continental shelf, there would be more room for kelp forests and other habitats propicious to photosynthesizers, who get more light in shallower waters; so would it follow that an archipelago planet would have very oxygen-rich air and big arthropods to go with it?
EDIT: Presume there could be mats of green sulphur bacteria or some other kind of photosynthetic anaerobes covering those big, sunny, shallow shelves, and that my arthropods would be about like Earth's dead eurypterids. To be clear on intent: Would an archipelago planet get to some sort of "Cambrian phase" earlier in it's history than Earth, and would my pseudo-Cambrian animals be better off with having dry land spread out more instead of closely packed together like Earth's used to be.
Thank you by your answers so far.
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**No**
There are a lot of issues with that assumption, but I'll go through it all as concisely as I can.
**Oxygen isn't the only limiting factor to arthropod size**
Arthropods are exoskeletal by definition. Ultimately, that means that they are an organic creature inside a hard shell, more or less. By comparison to endoskeletal creatures, that means that their outer carapaces have a limit on how hard and strong they can be as they scale up which is less of a limitation on a creature with a skeleton on the inside. If you're dealing with a 'super-earth' that implies higher gravity, meaning arthropods (especially on land) won't be able to grow beyond a certain size as their carapaces would collapse, or their internal organs would put too much pressure on each other lying in a pile inside said carapace; take your pick.
**It's *volume* of oxygen that counts, not percentage.**
A planet with a thicker atmosphere doesn't need as high a percentage of oxygen to support earth based life because the amount of oxygen we breathe (and that we need in each breath) is determined by Partial Pressure, which is a fancy way of saying a set amount of oxygen, regardless of the ambient pressure. The Apollo missions flew with pure oxygen environments because they were only pressurised to less than a third of sea level pressure. Conversely, deep sea divers use much thinner mixes of oxygen (filling the gap with an inert gas like Argon) because at pressure, they're breathing in so much larger a volume of air with every breath. So yes, you need a LOT of oxygen (in terms of volume) to support large arthropods, but don't think of that as a percentage as such, and in an environment with a denser atmosphere the pressure on the carapaces might become the limiting factor rather than oxygen (see above).
**Your plants must be in place for millions of years prior to animals.**
Your planet still needs a [Great Oxygen Event](https://simple.wikipedia.org/wiki/Great_Oxygenation_Event) in some form to release the molecular oxygen and put it into the atmosphere. Planets are highly unlikely to start off with such an atmosphere because oxygen reacts with so many other elements. That's what makes it so useful as an oxidiser. So, you need a constant endothermic reaction like photosynthesis going for millions of years before animals even come onto the scene, just to supply the oxygen needs they'll have. By the time your planet is ready for animals, it's probably not an archipelago anymore. Just saying.
**This is all based on our current model of life**
For all we know, on some of these worlds you could have photosynthesizing animals. Arthropods could have lungs, too. They may not have, but could have a form of gills that extract the CO2 out of the atmosphere instead, harnessing sunlight to form their own oxygen. They could have a combination of exoskeletal and endoskeletal body structures that allow them to grow bigger because of a segmented carapace and their growth model could be adding new segments as they grow. That's the thing about evolution; we really don't know what life would look like on another planet because we don't know the starting structures and we don't know the pressures in the environment that force it to evolve in order to survive.
Put simply, the existence of archipelagos and photosynthesizing plants don't in any way increase the chances of large arthropods on your planet, although there is the chance that they make the environment favourable for them to evolve. But, evolution and planetary ecology is an immensely complex and fragile interaction of billions of factors and as such, it would be wrong to say that the one follows the other as a general rule as defined in your question. It's not to say that you're wrong; merely that the process is almost infinitely more complex than that.
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Hundreds of years ago during the black plague, an individual named Howard Phillips Lovecraft started what would lead to the doom of humanity. Although a mediocre writer himself, his works of literature would inspire authors for generations. His most famous work, "The Call of Cthulu", was the first entry into a genre referred to as the cosmic horror story. This promoted the subversive idea that human beings were not loved by an omnipotent god, but were insignificant gnats in a large and uncaring universe, filled with unknowable creatures far beyond our comprehension.
For decades, he believed that these were his ideas, dug up from the dark corners of his imagination. Unbeknownst to him, these creatures that he imagined (nyalathotep, dagon, shub niggurath, etc) were actually real, and had been influencing his thoughts from the beginning. This was in order to gain a foothold in the mortal world, for the more they are known to mortals, the more power they gain, eventually giving them the strength to cross over. Lovecraft eventually went insane and died in obscurity, but various writers after him have picked up his work and added to it, eventually leading to what would be known today as the Lovecraft mythos. This has inspired various forms of media, including games (bloodborne), television, movies, and other works of art that are influenced by the subversive elements of the genre if not mentioning the mythos or the creatures directly, and thereby feeding their power.
A dictator of a small country has realized this truth and sought to end this threat to his people by controlling access to media outlets. These monsters can only cross over in nations that they have been able to successfully subvert, making the effect localized instead of global. While bigger nations like the U.S. will go to hell, this nation will be safe from the beings on the mortal world. By eliminating all knowledge of them and slowly removing their forms of influence in various outlets, they would be prevented from taking hold in a country. Certain outlets would be regulated through a number of measures meant to erase this genre from his country, similar to many dictators of the past. For instance:
1. Strict monitoring of Internet access. Monitoring search engines and eliminating key words or phrases, shutting down sites like Facebook or Twitter that connect people, limiting network access to certain places instead of in the home.
2. Book burning and erasure of articles or stories that have cosmic horror influences, as well as executing or imprisoning authors.
3. Strict censoring of movies, games, and TV programs, pruning them of certain influences and determining what can and cannot be shown.
The point is by selectively removing certain things and restricting access to information, the public will eventually forget what has been lost, closing off their minds from these beings and limiting their power over us.
By restricting access to media completely, I am looking for a way to realistically eliminate these subversive elements in this country in the quickest amount of time possible, and would judge answers based on that. How can I make this feasible?
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If I assume that the CHS is only transmitted as an ensemble of memes, and not telepathically implanted by the Ancient Ones in the current population, then censorship will never eliminate it, because it will be forced underground and spread by word of mouth in secret places. The censorship makes it forbidden knowledge, and humans love that stuff too much.
But, if the Dictator, clustered her citizens in groups of small villages that couldn’t communicate with each other, and they were encouraged to write horror stories about Lovecraftian things — The Tentacle Games — without being told anything about the Cthulu Mythos.
Then the Dictator could measure where the meme still existed. It wouldn’t be universal but might be wide spread. Then she only needs to kill every potential meme carrier — secretly — and repeat the contest, tricksie hobbittese
For safeties sake, she should kill the entire village and grind the entire village (buildings, books, bathrobes, everything) into dust.
Children born to meme free villages could be taken while still young and raised by androids until they reach sexual maturity wherein they could be grouped together to form new villages.
As long as no one knows the consequence for sharing a CHS meme is obliteration, and people are incentivized to share the meme, the dictator could eliminate the threat in as little as one generation. But each successive generation would have orders of magnitude lowerprobability of knowing it. Eventually the Tentacle Maiden’s Tail could stop since the meme would be excised.
[Answer]
Well, as a dictator you can just tell people not to publish this stuff.
But if you want something more subtle you could copy the way Disney destroyed the Grimm brothers (and others) or how Superman (fictional) defeated KKK (real).
Make your your own cosmic horror media, hire the best writers and most popular actors, fund a TV series and movies and tie-in novels. Engage foreign media from the beginning. If you can get the doomed Americans to make their own versions of your television and movies, they will be cool things to be proud of not the dictators insane and insanely expensive whim. It should be entirely possible to make money on this. Lots of money. Your money.
The exact details of this depend on how the entities get influence and how much you know of it. At the conservative end you are simply pushing the real stuff off the market by heavily promoting your own. Which might involve using money to get rights to previous cosmic horror and making sure no reprints or licensing deals happen. Or you could get away with using the actual names and lots of details but tacking them onto something you made up that is sufficiently different from the real.
Either way the goal is to change the public perception of the cosmic horror entities so that it no longer matches the real ones enough to give influence.
Does people knowing of Nyarlathotep give him influence if they also **know** he is an alcoholic ex-actor who uses low budget special effects to separate idiots from their money? I'd say not.
You can think of this as a vaccination. Inoculating people with very similar but safe "vaccine" gives them resistance to the real and dangerous thing. And if you do this enough herd immunity develops.
And this stuff works fast.
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I'm picturing a world without oceans. I'm not after Arrakis; I want a quite lush surface. I'd like no surface water at all, but I'm concerned that makes evolution impossible. (I imagined using chemotrophs to get around it.) I want a "sea level" pressure of 2-6x Earth. If there's surface water, it'd be "above sea level", no? Or do I also get superheated water/steam below that? I picture "sea level" as a "cloud deck", where water runs off continents in waterfalls & vaporizes at the heat/pressure limit, forming permanent, global cloud. This separates the world into two societies/species, above/below the deck. Any thoughts on the ecology & weather? Did I miss anything? (If it matters, my model is Earth, with no changes except as noted.)
[Answer]
**Underground Water**
[](https://i.stack.imgur.com/MXTdZ.jpg)
*Credit to Liam Morris*
If there is no surface water on your world, perhaps there are underground rivers and lakes. Plants could evolve to grow their roots into these waters and their leaves would grow on the surface. Imagine caves like these where roots hang from the ceiling as though they were stalactites all around the world.
Animals would need to go underground to get water and travel to the surface to get food if they were herbivores.
Your humans would have a heavy focus on wells and, eventually, underground water pumps.
If you wanted rain, you could say that the water the plants draw up evaporates and turns into clouds. Eventually the water would fall back down again and be absorbed back into the earth. You could also have it so rain is rare and, when it does fall, animals gather around lakes and rivers like they do when the River Nile floods.
[Answer]
Our oceans come from volcanic activity lifting gases out out of the world's core. A world like you describe naturally forming to be volcanic enough to support chemotrophs without oceans is not very likely.
The closest you could come is a runaway greenhouse world like Venus with VERY tall mountains. At 55km, Venus's atmosphere is Earth like except for all the sulfuric acid which your chemotrophs would love anyway. The regions below would be kept way too hot by the runaway greenhouse effect to support liquid water.
Another Option: Earth's atmosphere has lots of Oxygen and not much Carbon compared to the norm because our primary producers (plants) extract and sequester so much Carbon. It could be that your chemotrophs extract and sequester exceptional volumes of the Hydrogen or Oxygen from water in much the same way. They drank up the oceans over billions of years, now most water components are cyclically locked where the chemotrophs destroy the water, and the high elevation organisms reform it as their own biological byproduct, but mostly the components of water are sequestered deep underground in this world's version of fossil fuel sites.
[Answer]
[](https://i.stack.imgur.com/E4Gzo.jpg)**Rocheworld.**
Read up on Rocheworlds and their shared atmospheres here:
[Could two planets be tidally locked to each other so close they share their atmosphere?](https://worldbuilding.stackexchange.com/questions/4460/could-two-planets-be-tidally-locked-to-each-other-so-close-they-share-their-atmo/4461#4461)
Your planet starts like Mars, 500,000,000 years ago. Once wet and full of life, its internal fires have cooled and it is losing its atmosphere and water to space. It is drying, and dying. To save the planet and its inhabitants a second planet or great moon is moved into position.
This new partner is a fragment of a gas giant, made of water, ammonia and methane. It is so close that gravity pulls the gases away and down to replenish the grasslands and steppes of your dry planet. More importantly the tidal flexing caused by this planetary dance heats up your planet, restarting its protective magnetosphere.
sources for images:
<https://i.stack.imgur.com/wBCel.jpg>
<https://www.stephen-weaver.com/photo/prairie-sunset/>
[Answer]
Of course, the warmed up turnaround of the water can support lush plant life without oceans. But such intense whirling will cover all levels least the difference in height will be really great.
The target of the question can be reached also if oceans are underground ones. But then you have to invent some plants with extremely long roots that will raise the water from the depths to the surface to create new rains.
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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 4 years ago.
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Cracking knuckles has something to do with air bubbles, but would it work in the same way if there is no gravity? If not, how would it be different? Would there still be a popping sound and/or sensation?
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From [Wikipedia](https://en.wikipedia.org/wiki/Cracking_joints)
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> The cracking mechanism and the resulting sound is caused by carbon dioxide cavitation bubbles suddenly partially collapsing inside the joints.
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The collapsing of the bubbles is due to pressure differential between the inside and the outside of the bubble.
When we consider the pressure in a liquid, we can distinguish two components:
1. pressure due to the proper weight of the fluid above the measuring point
2. pressure exerted from outside the fluid (i.e. atmosphere)
In microgravity 1 would be 0, but 2 will still be present (else any liquid in microgravity would immediatly evaporate).
Therefore, if the person cracking knuckles is in microgravity but still under some atmospheric pressure, the pressure differential will be of the same order of magnitude. Therefore it is reasonable to expect the same phenomena to happen.
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If someone in the 14-15th century world had the knowledge required to build an engine for use in locomotives and ships, what kind of engine could be made using technology that already existed back then?
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**Steam engines**
[Edward Somerset](https://en.wikipedia.org/wiki/Edward_Somerset,_2nd_Marquess_of_Worcester) had a patent for one in the 1600's and [Thomas Savery](https://en.wikipedia.org/wiki/Thomas_Savery) (1650–1715) was the inventor of the first commercially used one, which is only 100–200 years past your time frame.
But the first recorded steam engine was as early as the [1st century Egypt](https://en.wikipedia.org/wiki/History_of_the_steam_engine) so the principles were known 1500–1600 years before your time-frame which means it's far from a great stretch for you to say development of steam engines that entered common usage was a little earlier in your world.
The propeller didn't come along for a while longer than that of course but paddle steamers are simply a reverse water wheel (which the Romans had) and [Archimedes' screw](https://en.wikipedia.org/wiki/Archimedes'_screw) also existed then, so that gives you two potential methods of transferring power from the engine to propel your ships.
[Paddle steamers](https://en.wikipedia.org/wiki/Paddle_steamer) are your most likely ships, especially as the Romans already had ox powered paddle boats (there's a reference to them in the link).
A simple [vertical single cylinder engine](https://www.google.com/imgres?imgurl=https%3A%2F%2Frickpdx.files.wordpress.com%2F2011%2F01%2Fnewcomen_engine.gif&imgrefurl=https%3A%2F%2Frickpdx.wordpress.com%2F2011%2F01%2F02%2Fold-year-new%2F&docid=FIZWkTcoKMhc9M&tbnid=bIln8QP8h8OORM%3A&vet=1&w=544&h=545&bih=616&biw=1280&ved=2ahUKEwjk7NiPup3gAhVIiRoKHWFOBTUQxiAoBnoECAEQGg&iact=c&ictx=1) [used to drive a wheel or paddle](https://www.google.com/imgres?imgurl=https%3A%2F%2Farchive.li%2FCOVkc%2Fb531a0e9b172e93bc1d96743f76e6311a25c0ffb.gif&imgrefurl=http%3A%2F%2Farchive.li%2FCOVkc&docid=eZ0SV3KXHE0EEM&tbnid=Tdv5eChI_Rhg8M%3A&vet=1&w=571&h=362&bih=616&biw=1280&ved=2ahUKEwjk7NiPup3gAhVIiRoKHWFOBTUQxiAoBXoECAEQGQ&iact=c&ictx=1) is probably most likely.
Though [this](https://www.google.com/imgres?imgurl=https%3A%2F%2Farchive.li%2FCOVkc%2Fb531a0e9b172e93bc1d96743f76e6311a25c0ffb.gif&imgrefurl=http%3A%2F%2Farchive.li%2FCOVkc&docid=eZ0SV3KXHE0EEM&tbnid=Tdv5eChI_Rhg8M%3A&vet=1&w=571&h=362&bih=616&biw=1280&ved=2ahUKEwjk7NiPup3gAhVIiRoKHWFOBTUQxiAoBXoECAEQGQ&iact=c&ictx=1https://www.google.com/imgres?imgurl=https%3A%2F%2Fi.pinimg.com%2Foriginals%2F32%2F02%2F83%2F320283381b3144fb15a9cd83ac687d5a.gif&imgrefurl=https%3A%2F%2Fwww.pinterest.com%2Fpin%2F378654281148844374%2F&docid=T3sMgtmaPOenhM&tbnid=LswMCaIjIuujDM%3A&vet=1&w=500&h=300&bih=616&biw=1280&ved=2ahUKEwjk7NiPup3gAhVIiRoKHWFOBTUQxiAoAXoECAEQFQ&iact=c&ictx=1) horizontal design is a touch more elegant to my eye.
[](https://i.stack.imgur.com/DlUhP.gif)
They'd probably be wood burning rather than coal.
[Answer]
in the 1300s the only sources of power that could be mobile were people and animals. Using animals on ships was almost never done because it was wildly impractical to have treadmills taking up needed cargo space and food to keep them well enough fed to be able to work.
The metallurgy needed for harnessing steam was not available in this time period, now were the machining tools needed. Lathes were not invented until the late 1700s and even an expert blacksmith would not be able to make a piston using hand tools
Steam engines can be made of brass or bronze, both horribly expensive in the 13-1400s, but only in small scale, like in model engines. These materials cannot handle the sort of pressure needed to drive pistons well enough to overcome the friction of a propeller in water, and they cannot be made powerful enough for a land vehicle able to transport any great weight. Turbines .. well no .. just no.
The Conneticut Yankee in King Arthurs court took years to build the infrastructure that allowed him to build 19th century weapons and electrical equipment .. but building the entire tool chain took him decades.
so if someone with all of the needed branches of knowledge, and a wide ranging practical experience of manufacturing, does wind up in the 1350 wanting to build a ship bigger than the Santa Maria (19 m x 9 m ) he would have to be an expert negotiator and manipulator to make it happen.
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I'm working on a story set in an Earth-like world but with rings (say, proportionately similar to Saturn's). I'm trying to get a solid handle on how these rings would affect the sky. For the purposes of this post, let's focus on *navigation*.
For a little more info, let's assume a location in the Northern Hemisphere, such as in the Midwest USA (Cincinnati, Nashville, Indianapolis, etc.). It's a generally medieval-type setting with no glow from modern city lights affecting the night sky. There are one sun and one moon. Assume similar axis tilt to Earth. There are 425.2 days per year (so a leap year every 5 years) and 28 hours per day. Moon rotation is every 24 days (a multiple of 8 was recommended for the calendar I did at fantasy-calendar.com; compare this to our own moon of about 27 days). ...Just in case any of this is helpful.
QUESTION: How would a person navigate at night in a world like this? For instance, would they be able to use something like a "North Star," or would the ring-glow block out most of the stars? Or maybe the rings would always appear in the south sky? Stuff like that. I'm interested in possible navigation tactics both by land and sea.
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Navigation is super easy: as long as you can see the rings, their center is directly south of you. Moreover, height of the rings in the sky tells you how far south you are.
Look at [these pictures](http://www.planetary.org/blogs/jason-davis/20130626-earths-skies-saturns-rings.html).
They assume Earth has Saturn's rings. Furtherthe rings are above the equator, i.e. their axis of rotation is same as for earth (and Moon), which is [how rings usually are](https://physics.stackexchange.com/questions/238653/why-do-planetary-all-rings-seem-to-be-on-the-equatorial-plane). I believe you assume the same. And I do assume Northern hemisphere.
**Rings will not take up the entire sky**. Polar regions of the sky will be still visible. They will cover up half the zodiac constellations.
**Rings will be visible from temperate and tropical regions**. They will not be visible from poles and polar regions. As you travel north, rings will be lower and lower in the sky, and will eventually disappear below the horizon. Exact point where it happens will depend on size of the rings and the planet.
**Rings will be visible even at night**. , part of the rings will be dark(er) b/c Earth casts its shadow at them, but you can still see portions of the rings are lit by the sun (see last picture). The shaded portion of the rings could be slighly illuminated by light reflected from moon or earth (just like shaded portion of the moon still gets some light). And in any case, rings will block starlight behind it.
As a bonus, you can tell time from position shadow on the rings -- it will move much like the hour hand of the clock.
**There will be no seasonal variation, or daily variation in height or location of the rings**. For that, you need rings rotating around a different axis from the the planet, which is [rare but possible](https://physics.stackexchange.com/questions/238653/why-do-planetary-all-rings-seem-to-be-on-the-equatorial-plane).
**A large rock in the rings will likely move**, kinda like our moon. It might also grow over centuries.
[Answer]
Not an expert by any means, but I did a bit of Googling around because this question is really interesting. I found this snippet in an article on the NASA website, discussing the rings of Saturn:
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> Researchers have discovered that while most of the ring particles are as small as dust and pebbles, there are a few chunks as big as mountains, and even some small moons several miles across embedded in the rings.
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This suggests that within the rings there could well be some (much) larger fragments, like moons. Perhaps on your planet, there's one such chunk of rock in the rings which always sits over a specific spot on the equator. If it's big enough and doesn't move relative to the planet's surface, it could be used to navigate.
Also if you're in the Northern Hemisphere, the rings would always be to your South. So the 'peak' of the rings in the sky (like the top of a rainbow) would lead you directly South from wherever you currently are if I'm not wrong.
**Sources:**
NASA article about Saturn's rings: *<https://www.nasa.gov/centers/goddard/news/topstory/2009/rings_equinox.html#maincontent>*
[Answer]
Day or night the rings would always be visible to the planet (assuming they full rings like Saturn)
The only point at which the rings may not be visible is if in heavy overcast or you were at a point on the planet whose position perpendicular to the ring's planar origin. (worded this way incase the planet somehow rotated different with respect to the ring) In this case they would be hidden in the horizon.
Since in just about every possible situation the rings position can be anticipated it can therefor be used for navigation. Similar in function to how the "sun rises In the east and sets in the west".
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[
I'm basically looking for advice on how to balance the magic system I'm designing for my novel.
Basically, the way it works is this:
There are six known Realms beyond this one where almost magic users draw their abilities from. Such a magician is called a Realmtapper. Each Realm is tapped into a bit differently. However, **there are Six major Kingdoms in this world, and each one taps into a different one of these Realms - that is to say, there is 'one Realm per kingdom.'** However, this Realmtapping 'energy' is the same for all Six Kingdoms. As a result, an enchanted item from the Elemental kingdom that, as an example, can be used as a heating device, can be recharged by a Realmtapper from another kingdom, but not recreated or modified in any way.
* **The Sea of Might**, Realm of Sorcery - such as psychic and telepathic
abilities, as well as teleporation. Used by drawing invisible runic
symbols into the air.
* **The Nameless Mist**, Realm of Power. This includes physically improving
the body and senses, as well as shapeshifting. Used by channeling
mentally and consistently and maintaining one's concentration.
* **The Endless Shades**, Realm of Elements such as fire and water and
whatnot. Used by performing certain physical movement patterns, akin
to martial arts moves, to do different actions with the elements.
* **The Divine Peaks**, Realm of Favors - such as blessings and curses -
and also of manipulating and solidifying light. Used by calling upon
the Peaks in a form similar to prayer.
* **The Veil of Souls**, Realm of Death, including raising the dead and all
that that entails, as well as manipulating and solidifying solid
shadow. Used by splintering the soul in pieces that are infused with
power.
* **Advah**. This is the world the story takes place on, and the magical
powers here involve infusing yourself with improvements - ie physical
strength, senses, no need to eat or drink for a while, etc - as well
as, more uncommonly, the ability to control/manipulate metals and
gravitational and electromagnetic fields.
There are, however, limitations to this.
* **Realmtapping exhausts stamina.** The more you tap, the more tired you
are. You can use several small realmtapping abilities, or perhaps
one large one, before you are exhausted to the point of stopping. If
you continue to realmtap beyond your limits, you will lose
consciousness. As a result, being in good physical shape helps
Realmtap for longer periods of time.
* **Realms have ties to certain environments.** You can expect Realmtapping
to come easily in some locations, but require much more effort in
others. The Sea of Might is connected to knowledge, and as such is
stronger in areas where knowledge is more prevalent, like libraries
or books or other places of learnings. The Shades is connected to
nature and 'uncivilized' land, etc. As a result, you may be an
excellent Realmtapper of the Shades, but there are some things you just can’t
do in a well-populate, industrialized city.
* **The Realm Barrier can vary wildly.** The barrier acts as a sort of
buffer between Advah and the space between all of the Realms - that
space being known as the mysterious Realm-Between-Realms. The
stronger the Realm Barrier is to where you are located on Advah, the
harder it is to Realmtap. However, that’s not all. The Barrier
fluctuates based on how much that Realm is currently being tapped
into at your location - as a result, the more you Realmtap in a
certain location, the more difficult it becomes, through the barrier
slowly grows more stable over time in periods of low usage.
* **Being able to Realmtap is something that approximately ~1% of the population
can do.**
Also, I can go into detail with any specific Realm if you ask me to! I just didn't want to dump too many words here at once without cause.
***I suppose my main concerns are these:***
* *How do I balance the Mist to be more in line with the others (it seems a bit weak to me?) and how do I do the same for the Peaks? (This one seems to powerful, unless I limit it somehow to only be short-term effects of something to that end.)*
* *Are there any glaring problems you guys think I might encounter with said system? Are there not enough restrictions?*
The two questions above are the main ones I'm really here to ask about. The two below are just sort of there, and it'd be really nice if someone wanted to take a stab at them :)
* *If this world was to take place in an almost early 1900's level of technological advancement, how might each Realm either improve or replace certain technologies? Some obvious ones are of course the Elemental kingdom having an easy time with... well, a lot of things, but if you have any other things you want to mention please feel free to do so!*
* *And, of course, is there anything else I should consider as I build this system up?*
[Answer]
What you need to do is get rid of the idea that these six realms are independent of each other, but rather interconnected to each other. You might think of the realms as the "gravity wells" in a much larger but much more nebulous universe, for example.
[](https://i.stack.imgur.com/7aVQd.jpg)
*Demonstrating the interaction of gravity wells can create other effects*
In the simplest version, if you imagine the size "realms" arrayed like the points of a hexagon, then tapping one "realm" causes a pull on the other realms as well. You can imagine yourself in the middle attached to each of the six points by an elastic cord; pulling towards one vertex means you will be pulled upon by the other five.
Amateur magicians try to do this all the time (which is why they tire so rapidly), but more adept magicians who understand seek to balance the various pulls for the effects they want to create, they will be somewhat offset from the centre of the hexagon, with two or more lines slack and the others trying to pull back to centre.
A "fully connected" network diagram with six nodes (i.e. six realms) could have even more interesting permutations, since each node isn't simply independently sitting in the multiverse, but also connected to every other node, allowing for a multitude of interesting permutations, connections and so on
[](https://i.stack.imgur.com/bZeeB.png)
*Fully connected network*
As you can see from the diagram, attempting to pull from the neutral position (i.e. the centre) is much more complicated and can set up a multitude of second and third order effects than a simple connection of everything to the centre.
I'm sure you will come up with other ideas as you play with the diagram (indeed, reversing the idea and having rigid connections rather than elastic or tension ones gives the idea an entirely new flavour).
[Answer]
I'll just say this is an awesome set of ideas you have so bravo
I have been told this personally so here is something to watch out for: if you are introducing whole new realms to your ordinary human readers, having a bunch of near-gibberish names (no matter how cool they may be) can confuse people and pull them out of the story when all the word become soup in their heads. I'm not saying scratch the names - cool names make things more fun for to read, at least for me - but connect the names to what they do. You did this with the death realm very well, as one could infer what the Veil of Souls has to do with without any knowledge of it based on its name. Maybe modify the other names so they are clearer representatives as well?
[Answer]
The realm of mist has major medical applications perhaps? Being able to perhaps cure bacterial infections by having a realm tapper channel energy into the patients immune system would easily make it increadably importantant in a pre-antibiotics world. Perhaps they can just as easily tap strength away from other people by touch making for an effective weapon?
Perhaps blessings and curses can be dispelled by any sufficiently powerful tapper of another discipline? Or perhaps peak tappers have an element of randomness to them accidentally giving the wrong blessing/curse from time to time.
You could always of course simply make the more powerful tapping disciplines rarer and less powerful ones more common amongst the populations that posses them.
Finally of course you could always leave them unbalanced and address this in universe this isn't a video game after all.
Edit:
As for further applications of your magic:
I'm worried about the veil of death, how easy is it to raise the dead and are they zombies or just no longer dead? If you have a realm of effectively Immortals or people who can communicate with the dead they will automatically the leading scientific power due to the fact they don't loose knowledge every time someone dies. And surely it's bound to have a religious impact?
[Answer]
It depends what you expect the magic user to be doing.
As with any power, people will find a niche for themselves. If you think of it in terms of a game then Peaks might make good healers while Mists manual labour, transport, communication. They would also make excellent spies/assassins, with enhanced hearing or shape shifting into a cat to roam around freely, to a bird that can escape sticky situations, to smell for tracking.
Since you have already mentioned several ways of limiting usage, this could extend to your realms. What if buffing someone took less toll than cursing? Or an average Mists user could shape shift several times a day (depending on location) while the average Peaks user could only curse once or twice?
Final note on location. If it is easier to use certain tapping based the environment, say for example Peaks is easier near a Church, but Mists is just enhancing the body, so instead is equally easy everywhere. This will neatly explain my previous point of an average Mists user being able to use their power more than an average Peaks user, while sitting within the bounds of your world.
**Additional**: Just having a think about the restrictions. If realms are tied to certain areas, you would expect people with matching abilities to flock their, either for training purposes or to sit with their biggest power well for example. Since everyone will want this advantage you will get a lot of people and thus, a lot of realm tapping in that area. This will then diminish its strength as its being used more.
[Answer]
* maybe tapping into the veil of souls takes years off one's life
* tapping into the realm of mist dulls one's senses if they use it to sharpen their senses, leads to serious muscle damage if they use it for increased physical ability, and leads to temporary deformation of the body and acute pain all around the body, owing to the fact that shapeshifting involves reshaping one's muscle and bone structure, not to mention height. Tapping too much might cause temporary symptoms to become permanent.
* tapping into the divine peaks might cause one to have bad luck for a certain amount of time, depending on the magnitude of the spell cast.
* tapping into the sea of might may have a variety of symptoms, ranging from acute headaches to temporarily being brain dead to straight-up going insane forever.
* tapping into the realm of shades could cause instant death or chronic illness at best if one uses them beyond their capacity or capabilities. This should cancel out its vast capabilities by dissuading a large number of Realmtappers from attempting it.Maybe making it a reserve of only elite level Realmtappers.Maybe even though one pulls such a spell off perfectly, tey could be bedridden for months.( This could be a major plot point in your story.)
\*ITS A BIT OBVIOUS BUT I FIND IT SURPRISINLY EFFECTIVE IN MY STORIES
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One of the worlds I'm creating has a planet-wide communal sentient Biosphere (similar to *Avatar*). They have evolved the ability to bio-engineer whatever they need, and they have decided to send a probe into space for exploration. I've "borrowed" Larry Niven's Stage Tree concept, using Ethanol and Pinene for fuel, and the ship itself has a thick bark/shell hull.
However, that raises the issue of how the probe would send information back to the home planet. One possibility is dropping bio-packages back to the surface, using DNA encoding, but that requires the bioship to return to the planet. Is it possible to create a Plant-based radio for telemetry? It doesn't have to be radio, I'm just looking for a way to communicate over planetary distances using organic technology.
[Answer]
In principle there's nothing stopping a plant from developing a natural radio.
Let's start with what a radio really is, in the most reductive form. A radio is nothing more than an antenna made of conductive material to particular dimensions, to make it resonant with electromagnetic waves of a particular frequency. By applying a changing electrical charge to it, we can cause it to emit signals of that frequency, and we can use it to receive signals of that frequency. Optionally, we might add a waveguide to concentrate or direct the signal.
The conductor is easy - any nervous system is already a network of conductors transmitting electrical signals. Forming a section of nerve-like tissue in the shape of a patch antenna (so named for simply being a rectangle of copper on a surface or similar), placed near the surface, would make a perfectly serviceable, if rudimentary antenna. With this alone the rocket could communicate by radio over short distances by *thinking* into the antenna. Power is an issue but not insurmountable, given your plant is intelligent and able to grow rockets.
Adding a waveguide isn't much harder. A properly shaped section of wood could easily act as a parabolic dish, and specially shaped cavities to act as resonators and waveguides is not without precedent- whales and dolphins already evolved this for their sonar. On the ground, a natural crater or dormant caldera would make for a marvellous dish - a particularly tall tree with a handful of antennae at the focal point of the dish would make for an excellent receiver.
Combining the two, you could in theory have a plant that manages to incorporate a radio. It doesn't have to be a patch and a parabolic dish, either: if your plant can engineer a rocket, it can engineer an antenna and waveguide of any kind.
In practice a lot will depend on the specific properties of the materials available to your plant. Mere wood as we know it is unlikely to be suitable for a waveguide, and the nervous system is unlikely to be up to the task of transmission. In the case of *Avatar*, the superconducting unobtanium rather dramatically solves the latter issue, though something more boring like a copper nervous system would probably be more than sufficient. Either way some exotic plant materials may be necessary to make this all work.
[Answer]
With a planet's worth of surface area, the sentient biosphere could grow enormous eyes (the size of radio telescopes) and "watch" its' bio-ships as they fly among the other planets. It could even elevate those eyes up out of the planet's atmosphere by placing them on the top of giant trees. That would afford the biosphere a much better view.
The ships could then send information back to the planet either by shifting its skin color like a chameleon or by dancing like worker bees.
[Answer]
There are many interesting phenomena in nature that, combined, could be said to contribute to a complex technological function. Take electrocytes in electric eels, sonar functions in bats and cetaceans, bees and migrating birds can read the magnetosphere, and some creatures take it [a step further](http://site.daftgadgets.com/blog1/6-animals-astounding-electric-powers/): "the elephant nosed fish detects its favorite food buried in the mud and muck in the pitch of night with an electric field it generates through its tail and senses it with its elongated chin."
Just to say, the building blocks are there to create a radio emitter and receiver organ, or at least something to manipulate the electromagnetic spectrum. You just need to create the evolutionary path that will lead to this outcome.
[Answer]
One of the things about plant bioships is the lack of some systems and functions that animals have, that can be rather impeding for sussing out the ship's systems. But, as for communication, perhaps an extremely amplified, extremely complicated soup-up of Earth plants' biolectricity. I presume you know the good old "potato electricity" trick.
So, electricity can be used as a means of communication, and is in some of Earth's bioelectric fauna. But, I believe that alien life would hold a plethora of more new, bizarre ways of communication. For now, let's just say your ship is bioelectric - basically a giant, flying space potato.
So, off the top of my head, that's the best answer I can think of (I'd say others might come up with better ones though.), unless you want to make the ship animalian, which might make things easier for you.
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What advantages would extreme longevity need to provide for it to develop in a human subspecies/humanoid species without outside tampering? I ask because elves and the like in fantasy are often depicted as living far longer than humans do, and are healthier for longer into old age, and assuming that's not just because they're more magical than humans and magic leads to a longer lifespan, what would induce the pressure to cause a species to develop this kind of longevity?
[Answer]
There are some traits in the animal kingdom that tend to be reasonably correlated (although not necessarily linear). Among those are size, birth rate, and longevity. Anecdotally, the mouse is small, lives just a couple of years, and has a big litter of pups every few months. The elephant is large, lives up to 70 years, and have one calf every five or six years. Blue Whales are enormous, live 80 to 110 years, and have one calf every couple of years. Humans seem to fall somewhere in the middle of the size range, live 70-100 years, and can have one baby every year, with occasional multiples. Note that the bigger-older-lower birth rate relationship is not perfect, but an overall pattern emerges.
Now we have a problem, as elves and humans are comparable in size, for them to follow this pattern they should also have comparable longevity and birth rate. However, if there was some event in the ancient elven past that made it part of their *mores* to not have as many children (for example, due to reduced resources to have to share with an increasing population), then evolution would have gradually favored longevity as well. This same scarcity of resources would also have favored not growing larger.
Here, Will's answer comes in, as those elves who are best able stick around to care for the few children they do have, will fare better in the long-term survival of the society. Thus, the long-lived more frequently pass on their genes for longevity.
In conclusion, have the ancient split between elves and humans happen in such a way that the humans got the lush forest, and the elves got the scrub at the edge of a desert, or something like that.
[Answer]
What advantages would extreme longevity need to provide for it to develop in a human subspecies/humanoid species without outside tampering/
<https://en.wikipedia.org/wiki/Fitness_(biology)>
>
> Fitness (often denoted w w or ω in population genetics models) is the
> quantitative representation of natural and sexual selection within
> evolutionary biology. It can be defined either with respect to a
> genotype or to a phenotype in a given environment. In either case, it
> describes individual reproductive success and is equal to the average
> contribution to the gene pool of the next generation that is made by
> individuals of the specified genotype or phenotype.
>
>
>
It is somewhat unusual that this has not evolved. Consider
1. Man A lives 65 years. He fathers 5 children between ages 20 and 40. He contributes to the welfare and survival of his children and grandchildren from ages 40 to 65.
2. Man B lives 195 years. He fathers 5 children between ages 20 and 40, 5 more from 40 to 60, 5 more from 60 to 80, 5 more from 80 to 100, 5 more from 100 to 120, 5 more from 120 to 140, 5 more from 140 to 160. For his last 35 years he contributes to the welfare and survival of his many descendants.
Man B lives 3 times longer and fathers 7 times as many children as man A. His genetic fitness is far superior.
In fact, you would need to build in some sort of low reproductive rate for the long lived elves or they would quickly overwhelm and out-compete the humans with their cumulative numbers.
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ADDENDUM
I am a little perplexed by the comments and horrified by the downvote, and so I thought I would add more mechanism to the fitness advantage of longetivity than just the weight of numbers.
Suppose there is a selective event - a plague, or a famine, or a toxin in the water. Man A and Man B are resistant and survive. Man A fathers one more child and then comes to the end of his natural life. Man B continues contributing his resistant genes to many subsequent generations. This is how it works for lots of lower animals like fish or sea urchins. Very long lived creatures who escape the mortality risks in their environments contribute offspring season after season.
[Answer]
**When in doubt use sexual selection.**
If you have already included magic then you can use that as a indirect selective pressure. Magic is how elves choose mates (or it is at least a huge part of it), based on power or displays with magic. since you set the rules for magic you can say the longer you live the stronger your magic becomes and the better you can use it, works even better if magical ability also takes a long time to develop.
Now age is roughly equal magical power which is basically how sexy you are to an elf, and evolution will create all kinds of stupid conditions in the name of mate attraction. so pushing longevity as far as it can makes sense.
This is pretty easy to see with your set up if humans can also use magic, magic is ancestral. Elves split off early by focussing on magic, where as faster breeding humans focused more on new ideas, aka technological development. I imagine elves to also be highly reliant on magic with stone age technology otherwise. Humans may have less power but may be more creative with it. Perhaps Humans don't just push the rock with magic like elves with abundant magic do, they use magic like a lever to roll it accomplishing the same thing with far less raw magical power.
this could also explain why magic in animals is rare if you so desire, most are too short lived.
[Answer]
# What advantages would extreme longevity need to provide for it to develop in a human subspecies/humanoid species without outside tampering?
This is a malformed question! Extreme longevity is the advantage! I will assume you asked:
# What evolutionary pressures would lead to extreme longevity?
To the best of my knowledge our live spans is limited by our genes deteriorating and this inevitably leads to cancer.
In any case a mechanism that would select for longer life spams would be something like:
* *longer childhood periods*
If the environment is very dangerous then development times will most likely increase due to the longer training a child will need to undergo to be able to handle themselves in the world.
* *unbalance in sexes*
If there are more females then males or vice-versa then this would favor individuals that live longer because it gives them more time to find a mate and allows them to reproduce.
*These conditions together would lead to greater health and longevity and it also fits a fantasy world with dragons, orcs, and generally more predators.*
[Answer]
With humans it typically takes 10-15 years to learn enough about their environment to be independent. Traditionally the first half of that was the most dangerous, so most strategies aimed at having only one young child per couple at a time and sequentially raising several over the peak active decades.
If elves follow the same logic but need longer to learn the basics of their environment, say because they aren't as smart as us or because there are more interesting things trying to kill them (like demons and dragons and humans) or because learning magic is hard that might be a childhood of 10-20 years minded by a couple with no other children. With 100% survival that might mean they need 40 active years just for replacement, and accidents happen so more like 60 would be needed for safety. If their enemies are more effective that might not even be enough.
The logic of grandparents might still hold if they had fields of study that still allow interesting growth after a century of study. If magic has a learning curve with no known end any individual able to live longer to study it might bring benefits to their genes long after reproduction.
Perhaps continuity of long term effort is important for some reason, say the intricacies of tending stalagmites or tending some tree through a full life cycle is valuable, but better learned by starting fresh than risking interfering with an existing project. Say it turns out if you consistently pet a pine tree in exactly the same way every morning never deviating even a little for 80 years it produces pineapples or whatever. This would make having long lived individuals valuable.
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In what I hope to be the first episode of a series, I'm going to highlight each piece of Tolkien architecture and see whether or not it's practical enough to use in real life, starting with the simplest: Orthanc, the centerpiece of Isengard.
[The original Alan Lee painting right here.](https://vignette.wikia.nocookie.net/lotr/images/b/b8/Alan_Lee_-_Orthanc.jpg/revision/latest?cb=20140526033440)
Tolkien actively described the tower as "a deep, gleaming black". In keeping true to the original description, WETA Workshop decided that Orthanc be made of obsidian, volcanic glass.
[](https://i.stack.imgur.com/spjvO.jpg)
It definitely is black, which makes it qualified, and using obsidian to build Orthanc certainly helps in giving it a sharp, uninviting look. In the movies, the obsidian tower occupied by Saruman the White does look visually impressive, but the question is: **Is it feasible, let alone practical, to construct a building out of obsidian?**
[Answer]
# Not feasible
I got information on obsidian's fracture toughness from [Husein, 2004](https://shareok.org/bitstream/handle/11244/9947/Husien_okstate_0664M_11020.pdf?sequence=1); and granite from [Jeong, et. al., 2017](https://ac.els-cdn.com/S1877705817323822/1-s2.0-S1877705817323822-main.pdf?_tid=0a3633d8-e215-11e7-9f6e-00000aab0f26&acdnat=1513396745_0321e55ec2a2a4fc04456915b2a842a3). Compare the load displacement curves, Figure 3.11 from Husein and Figure 10 from Jeong.
Granite's catastrophic failure under displacemnt takes roughly 10 times the force (read, weight) that Obsidian's does. That is, we would expect obsidian to crack under loading at 10 times less weight than granite.
The fracture toughness of the two materials is nearly equal, so as far as being blown about by high winds, obsidian would perform as well as granite. But with perhaps 1/10 of the compressive strength, you couldn't build anything obsidian that you couldn't build out of granite.
The highest Orthanc-like thing that was built in the ancient world were probably [obelisks](https://en.wikipedia.org/wiki/Obelisk), the tallest of which topped out around 40m. I don't see obsidian supporting anything bigger than that.
The biaxial strength of obsidian measured by Husein was around 35 MPa. The density of obsidian in Husein is about 2400 kg/m$^3$. The tallest an obsidian spire could potentially be before breaking under its own weight is
$$\begin{align}
P &= \rho g h\\
35000000 \text{ N/m}^2 &= 2400 \text{ kg/m}^3\cdot 9.81 \text{ m/s}^2\cdot h\\
h &= 1486 \text{ m}
\end{align}$$
Of course, that is the point at which the obsidian 'will' break. Small imperfections and crack propogation, tolerance for wind and such mean that you would never get that high, maybe not even within an order of magnitude.
All in all, you could not build Orthanc out of obsidian.
[Answer]
**PERFECTLY POSSIBLE since Orthanc is made out of a stone-like substance which looks like obsidian but is much stronger than any known material.**
The Alan Lee painting does not seem to conform to Tolkien's description of Orthanc, a description that seems far more geometrical and modernistic to me.
It would be hard for me to describe in words or pictures my conception of Orthanc.
I picture Orthanc as looking vaguely like a shiny, black, opaque combination of:
The Gherkin in London, but with no external framework showing:
<https://pixabay.com/en/the-gherkin-30-st-mary-axe-london-721886/>[1](https://pixabay.com/en/the-gherkin-30-st-mary-axe-london-721886/)
The central tower of Fonthill Abbey:
<https://en.wikipedia.org/wiki/Fonthill_Abbey#/media/File:Fonthill_-_plate_11.jpg>[2](https://en.wikipedia.org/wiki/Fonthill_Abbey#/media/File:Fonthill_-_plate_11.jpg)
The Ryugyong Hotel in Pyongyang, North Korea, but with four wings instead of three and with the central part lower than the tips of the four wings:
[https://en.wikipedia.org/wiki/Ryugyong\_Hotel#/media/File:Ryugyong\_Hotel\_-\_August\_27,*2011*(Cropped).jpg](https://en.wikipedia.org/wiki/Ryugyong_Hotel#/media/File:Ryugyong_Hotel_-_August_27,_2011_(Cropped).jpg)[3](https://en.wikipedia.org/wiki/Ryugyong_Hotel#/media/File:Ryugyong_Hotel_-_August_27,_2011_(Cropped).jpg)
The Burj Khalifa at Dubai, UAE, but with four wings instead of three and with the central part lower than the tips of the four wings:
<https://en.wikipedia.org/wiki/Burj_Khalifa#/media/File:Burj_Khalifa.jpg>[4](https://en.wikipedia.org/wiki/Burj_Khalifa#/media/File:Burj_Khalifa.jpg)
And with a floor plan vaguely similar to Fort Stanwyck, New York:
<https://en.wikipedia.org/wiki/List_of_star_forts#/media/File:Fost_areal_image007.jpg>[5](https://en.wikipedia.org/wiki/List_of_star_forts#/media/File:Fost_areal_image007.jpg)
Or Castillo de San Marcos in San Augustine, Florida:
<https://en.wikipedia.org/wiki/List_of_star_forts#/media/File:Castillo_de_San_Marcos.jpg>[6](https://en.wikipedia.org/wiki/List_of_star_forts#/media/File:Castillo_de_San_Marcos.jpg)
But enough about the architecture of Orthanc. What material is it made of?
>
> A peak and isle of rock it was, black and gleaming hard:
>
>
>
*The Two Towers* Book Three, Chapter Eight "The Road to Isengard".
The Ents could break up ordinary rock bare handed.
>
> An angry Ent is terrifying. Their fingers, and their toes, just freeze onto rock; and they tear it up like bread crust. It was like watching the work of great tree roots in a hundred years, all packed into a few moments.
>
>
>
But the Ents could not harm the substance that Orthanc was made of.
>
> Many of the Ents were hurling themselves against the Orthanc-rock; but that defeated them. It is very smooth and hard. Some wizardry is in it, perhaps, older and stronger than Saruman's. Anyway, they could not get a grip on it, or make a crack in it; and they were bruising and wounding themselves against it.
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*The Two Towers* Book Three, Chapter Nine "Flotsam and Jetsam".
>
> They came now to the foot of Orthanc. It was black, and the rock gleamed as if it were wet. The many faces of the stone had sharp edges as though they had been newly chiseled. A few scorings, and small flake-like splinters near the base, were all the marks that it bore of the fury of the Ents.
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*The Two Towers* Book Three, Chapter Ten "The Voice of Saruman".
The fury of the Ents could break up ordinary stone in moments, but the substance of Orthanc was impervious to their attacks.
Though Minas Tirith was mostly white, the outermost wall of the city was black. When Sauron's army began to set up catapults to attack Minas Tirth:
>
> At first men laughed and did not greatly fear such devices. For the main wall of the City was of great height and marvellous thickness, built ere the power and craft of Numenor waned in exile; and its outward face was like to the Tower of Orthanc, hard and dark and smooth, unconquerable by fire or steel, unbreakable except by some convulsion that would rend the very earth on which it stood.
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*The Return of the King*, Book Five, Chapter four "The Siege of Gondor".
WETA may think that Orthanc is made out of obsidian, but Tolkien described Orthanc as being built of a magical or technological synthetic or enhanced stone much superior to known materials, a substance that nobody in Middle-earth remembered how to create during the War of the Ring.
How tall was Orthanc?
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> A peak and isle of rock it was, black and gleaming hard: four mighty piers of many-sided stone were welded into one, but near the summit they opened into gaping horns, their pinnacles sharp as the points of spears, their edges keen-edged as knives. Between them was a narrow space, and there upon a floor of polished stone, written with strange signs, a man might stand five hundred feet above the plain.
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*The Two Towers* Book Three, Chapter Eight "The Road to Isengard".
So the central roof of Orthanc was five hundred feet above the ground, with four higher tips of the piers around it.
In *The Fellowship of the Ring*, book Two, Chapter Two "The Council of Elrond" Gandalf tells how he was imprisoned in Orthanc.
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> They took me and they set me alone on the pinnacle of Orthanc, in the place where Saruman was accustomed to watch the stars. There is no descent save by a stair of many thousand steps, and the valley below seems far away.
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Perhaps the stair had many hundred steps, and Gandalf said "thousand" by mistake.
If each riser was 7 inches high, 2,000 steps would be 1,166.66 feet high. Perhaps Gandalf was imprisoned over 1,200 feet high on the pinnacle of one of the four piers, over 700 feet above the central space that was 500 feet high. Or perhaps Tolkien meant to write that the central space was fifteen hundred feet high but wrote five hundred feet by mistake.
Modern technology has built buildings to heights of 500 feet, 1,500 feet, and much higher. Orthanc could be built as described with modern technology and materials. But the possibly artificial black stone of Orthanc seems to be much harder and stronger than any known construction material. Thus, since Orthanc in the novels is clearly not made of obsidian, Orthanc in the novels is clearly a possible structure.
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I've become interested in different kinds of dinosaurs lately, and have also been on a creature design kick. Let's talk about [Troodons](https://en.m.wikipedia.org/wiki/Troodontidae).
Troodons were a type of theropod dinosaur with unusually large brains and excellent senses. Some people have thought that had extinction not occurred, the Troodons could have evolved intelligence similar to humans. I've decided that I'm going to create a world where this actually did happen.
Real-life Troodons had hands and feet like raptors, maxed out at around 3ft tall and 11ft long. They also would have had feathers on their body and arms. I may push the height on these guys to around 4-5ft tall, but I haven't decided yet.
What I wanted to focus on for this question is their hands. Troodontid dinosaurs have three fingers on each hand, and I don't know if that would limit their dexterity. I think that if I change one finger to a thumb, that might make their grip stronger.
Here's what I'm asking:
**Could a three fingered dinosaur like a Troodon make tools?**
**If they could, what might they look like?**
[Answer]
this idea has been looked at before, I mean the evolution of dinosaurs into more intelligent beings, especially Troodons. The idea (thought up by Dale Russell) was that **if dinos never went extinct then Troodons or other theropods would have become the intelligent species**, evolving to look like humans. But in 2012 the idea was revised on by the website below and made another design that looked cooler.
<https://blogs.scientificamerican.com/tetrapod-zoology/dinosauroids-revisited-revisited/>
**Anyway, I think it's safe to assume that a Troodon could have evolved to have the brain capacity to make and use tools**, but what about phisically using them? A study done on hand strength in 2010 suggested that losing fingers equaled losing grip strength. But that was because each finger lost was connected muscle in the forearm that wasn't being used. A three-fingered being wouldn't have That problem though, as all the arm and finger muscles will be in use. Having extra fingers might add to grip strength, but since nothing in this world has two fingers and a thumb exclusively, there is nothing to compare to. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851460/>
Also according to the website below, **Troodon already had partially opposable fingers** <http://www.prehistoric-wildlife.com/species/t/troodon.html>
I quote the website,"Another feature that makes Troodon stand out from other dinosaurs is the presence of an opposable finger... It is unknown how much use Troodon would have given this adaptation, but the fact that it developed in the first place would suggest that there was at least one good reason for it occurring."
**So in my opinion, I'd say that a more intelligent species of Troodon could build tools that they can use.**
P.S. If you don't like the design of the dinosauroids from the website, you are free to use mine
## [Heading](https://i.stack.imgur.com/5ZJHZ.jpg)
[](https://i.stack.imgur.com/JZ9eL.jpg)
[](https://i.stack.imgur.com/7WIDh.jpg)
Sorry they are a bit shitzu
*other sources <https://en.wikipedia.org/wiki/Thumb#Other_animals_with_opposable_digits>*
[Answer]
An Octopus has no fingers and can do everything we can do with our hands. Most people only type with a few fingers anyway. Raccoons and other small mammals are very capable of doing amazing things with their hands. The biggest problem I see with the reptile brain is that it never really develop very far. Look at any large reptile, they have very small brains. Brains require lots of warm oxygen-rich blood, reptiles seem to favor cold low oxygen blood.
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Aliens build their city on Earth in such a way that it covers the entire planet but leaves the surface of the planet (including human cities) intact.
This is possible since they built their alien city on a huge platform which is supported by pillars rammed into the Earth's crust.
So with exception of the locations of these pillars the Earths surface remains as it was before the aliens arrival.
I'm interested in how such a city would impact the Earth's weather (I have intended for the alien city to be to be at a height of approximately 12 miles).
You can disregard the problem of sunlight as in how it could reach the ground since the alien city is in its way (the city will somehow let it through). Also disregard the problem of waste heat.
And a few notes: the city is built from extremely light but stable and firm material. I have intended that there are to be 12 pillars that hold up the city, which are located in the ocean and vast unpopulated areas such as deserts.
How would weather and other natural occurrences be affected in such a world? What type of weather patterns would the pillars produce?
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If the alien city you describe is located at
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> such a height that the weather of the Earth's surface would be as much similar to what it was before the construction of the pillar city as it can be
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it is therefore built above the [tropopause](https://en.wikipedia.org/wiki/Tropopause). The troposphere is the first layer of the atmosphere where most of weather phenomena take place, and above this we have the tropopause, where occasionally storms can extend
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> Vigorous thunderstorms, for example, particularly those of tropical origin, will overshoot into the lower stratosphere and undergo a brief (hour-order or less) low-frequency vertical oscillation
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Since your city also is transparent to solar radiation it will have no practical effect on the weather. It can actually protect the heart from the consequences of huge volcanic eruption, as it may keep the ashes from diffusing above the troposphere and shielding solar light.
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## The planet would boil to death.
If you want to know why, you can read the highly amusing series on <http://www.irregularwebcomic.net/396.html> which explains how a planet covering city would have no way to get rid of all the waste heat generated.
Now imagine living *under* this city. Since the alien city will somehow let the light through, which means it's basically invisible(??) you'll live in a giant glass house underneath a furnace.
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Natural weather would be restricted, since solar rays, wind and rain drops would be blocked.
So light, wind and rain would have to be artificial unless, the upper city had holes that would let the elements pass through.
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*The weather at the 12 pillars could be interesting, especially if the pillars are as massive (if we get to say they have mass, I guess) as I'm imagining.*
What I see happening in the air and water at the pillar locations is similar to the effects on the current seen in a large flowing river spanned by a bridge held up on pillars. The current rushes along its direction as usual everywhere but at the pillars. There, the water immediately downstream from the pillar swirls around and back in a very beautiful way (someone with the right scientific terminology please feel free to describe this phenomena further in case OP would like that detail).
I can then further imagine additional fun yet inexplicable phenomena such as Bermuda triangle mysteries and oddly coincidental locations of visible anchoring structures like pyramids appearing all over the world. Although the pillars themselves are invisible due to reacting differently with photons than the matter we are familiar with,
the observable effects such as strange swirling weather phenomena and anchors can provide many great plot launchers.
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I can't know for certain how much of an effect this will have, because you haven't specified the mass of the material, but by adding all this material in a shell around the earth you will be increasing its moment of inertia by enough to change its rotational period. Depending on the amount of change, this could affect global wind patterns caused by the Coriolis Effect. Regardless, if this is modern earth, it would easily be enough to be measurable by atomic clocks, so humans would notice.
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You are putting the city right about where the ozone layer is (see [this wiki](https://en.wikipedia.org/wiki/Atmosphere_of_Earth)).
Most weather would happen below the city. However, we have a heat problem. Underneath the city, we would either cook or freeze (I doubt the two sources of heat will balance evenly). We get heat from two sources, the Sun and our radioactive, molten core. The city will block the heat from the Sun and the Earth's heat will be reflected back from the underside of the city.
Now, assuming the alien's technology is good enough that they can exactly balance the two so the Earth's heat gain/loss rate remains the same, weather, as we know it will stop.
The differential heating from the Sun will no longer be a factor for driving weather. We will have convectional currents from hot air rising from the surface. So, we are likely to see a lot of vertically circular patterns. Most likely the air will rise around the pillars (since they will pick up heat from the crust and radiate it) and fall in the centers away from the pillars.
Also, they have to let enough of the right kinds of light through or plants die. Then herbivores die, carnivores die, we die, and the shrimp around the undersea vents become the inheritors of the planet.
Now the question becomes, why the heck they would bother with such a construction unless they want to fly the finger at Earth through some massive, expensive and spiteful construction.
The air pressure out there is such that it would need to be fully enclosed and pressurized unless they can operate in that low pressure. If they can survive that low of a pressure, they can build their city on the surface of Mars much more cheaply.
Less expensive still would be to just build space habitats for their population. Those would involve a lot less engineering.
From my pilot training, a pilot needs O2 at 12,000 feet if the aircraft is not pressurized to keep from falling asleep at the wheel. Pressurized airlines run at ~35,000 feet. 12 miles is 65,000 feet.
[Answer]
The sunlight radiation is very important for the climate, so I understand the answer that is saying "no change, because the sun goes through". However, I don't believe this is quite right.
**Your alien will need energy**. No way out of this. They have computer/fridges/whatever, so they need to power it. If they don't get it from the sun, they need to get it from the planet. Let's consider a few options:
## Sun
Ok, you said they won't. But the easiest way for them would be to take some solar energy. Even if they plant trees to feed themselves, trees are actually taking sun energy. And they are shading the earth below. If the sun goes 100% through their city, it means they are 100% transparent (the city and themselves). Highly unlikely.
If you can see them or their cities, they are blocking some solar radiation.
If they have vegetables, trees or solar panels, they are already using solar energy.
## Wind
Ok, let's assume they didn't touch the sunlight. Everything is transparent in their cities. The sun goes 100% to the ground.
So the first and most obvious energy source would be the wind. However, slowing the wind is not without effect. (Yes, if you take energy from it, you are slowing it). See for instance this [article](https://www.newscientist.com/article/mg21028063-300-wind-and-wave-farms-could-affect-earths-energy-balance/).
Actually, even if they don't take energy from it, it is likely that their cities in the sky are going to affect the wind.
Basically you can count on poorer energy redistribution. Warm places are going to get warmer. Cold places colder.
## Water
They could condensate the water up there, directly from the cloud, and use it as it used in dams. So let it drop through their pillars and put a turbine at the bottom of it.
The effect would be to reduce the amount of rain on much of the planet. All the water would go down through pillars, no through rain. Everywhere would turn into a desert. Only exception would be the deserts, as you said the pillars are in there. So the area around pillar basis would get too much water, the rest would be dry.
Also consider the effet of releasing a lot of non-salty water in oceans. Likely to change ocean currents, like stopping the gulf stream.
## Anything else
For instance stealing petrol or uranium from us. Will likely result in pollution and wars. Catastrophic for the climate. Just as we know it these days, just worse.
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My first post, I am sure I will have many more! I am so excited to have found this community!
I have a game called Rise: The Vieneo Province and a very old issue that I was hoping to get help with.
According to our [wiki](http://rise.unistellar.com/Vieneo) for our fictitious planet, the surface pressure is 2631 mb or 2.596 times that of Earth’s. However, in the aerodynamic work-up for the aircraft/spacecraft the scale height that is used is 8.0 km or equal to that of Earth’s.
I found a formula in which you can solve for the scale-height which requires the known variables of rho (density at a given altitude of z) and surface pressure. I don’t know how to reverse engineer from the function of e (is it ln?) or how to determine the density at a given height above the ground.
[Answer]
# How to derive the Scale Height
The [Nebraska Astronomy Applet Project](http://astro.unl.edu/naap/scaleheight/sh_bg1.html) of the University of Nebraska-Lincoln provides a complete derivation of Scale Height with respect to Planetary atmospheres which I will duplicate below. Please note that I'll hold of on explaining what each symbol means until Part 3: Calculating the Scale Height.
First we begin with the equation of hydrostatic equilibrium.
(1). $~~ dP = - \rho g dz$
Then we use the [ideal gas law](https://en.wikipedia.org/wiki/Ideal_gas_law) to simplify (1). We may use one of two forms:
(2). $~~ P = \cfrac{kT}{\mu m\_\mu} \rho$
(3). $~~ \rho = \cfrac{ kT}{\mu m\_\mu} P$
to eliminate $\rho$ or P from (1). Using (2) returns (4) and using (3) returns (5):
(4). $~~ dP = - \left( \cfrac{\mu m\_\mu P}{kT} \right) g dz$
(5). $~~ d\rho = - \left( \cfrac{\mu m\_\mu \rho}{kT} \right) g dz$
Shift P or /rho to the left hand side and you'll arrive at:
(6). $~~ \cfrac{dP}{P} = - \left( \cfrac{\mu m\_\mu}{kT} \right) g dz$
(7). $~~ \cfrac{d\rho}{\rho} = - \left( \cfrac{\mu m\_\mu }{kT} \right) g dz$
If you look closely, you'll notice that the formulas are **identical**, and therefore equivalent. It then follows that whichever we solve for, will have an identical form to the other. Taking after the University of Nebraska-Lincoln, we'll derive the scale height from pressure and continue with (6).
Integrate from the surface of the planet ($P\_i = P\_0$, $z\_i = 0$) to *some* height ($P\_f = P$, $z\_f =z$).
$\int{\cfrac{dP}{P}} = - \cfrac{\mu m\_\mu }{kT} g \int dz $
$\ln P |\_{P\_0}^P = \left(- \cfrac{\mu m\_\mu }{kT} g \right) z |\_{0}^z $
$\ln P - \ln P\_0 = \left(- \cfrac{\mu m\_\mu }{kT} g \right) (z-0) $
Use the [logarithmic identity for subtraction](https://en.wikipedia.org/wiki/List_of_logarithmic_identities) to simplify the left hand side.
$\ln \cfrac{P}{P\_0} = \left(- \cfrac{\mu m\_\mu g}{kT} \right) z $
Raise the entire formula to an exponent to eliminate the logarithm, then rearrange as a function of pressure.
$e^{\ln \cfrac{P}{P\_0}} = e^{\left(- \cfrac{\mu m\_\mu g}{kT} \right) z} $
(8). $~~ P = P\_0 e^{\left(- \cfrac{\mu m\_\mu g}{kT} \right) z} $
Lump the coefficients on z into a single coefficient. We'll call it H.
(9). $~~ H = \left(\cfrac{kT}{\mu m\_\mu g} \right)$
Then (1) simplifies to:
$P = P\_0 e^{-\cfrac{z}{H}} $
Since H is a constant coefficient, if we take z to equal it (z = H), then we'll get:
$ P = P\_0 e^{- 1} = \cfrac{P\_0}{e} $
Therefore we formally define $H$ as the height where the pressure drops to $\frac{1}{e}$ of the surface pressure, i.e. **The Scale Factor**.
# Determine Air density at a given height.
Recall earlier how the Scale Factor may be derived either from pressure or density? Using density instead of pressure, i.e. formula (7) to derive the scale factor gives us:
(10). $~~ \rho = \rho\_0 e^{\left(- \cfrac{\mu m\_\mu g}{kT} \right) z} $
using the same logic as before:
$H = \left( \cfrac{kT}{\mu m\_\mu g} \right)$
which is the scale height. Therefore (10) may be used to calculate the air density at a given height, or in your case, at the scale height.
# Calculating your scale height.
$m\_\mu$ is the [atomic mass constant](https://en.wikipedia.org/wiki/Atomic_mass_constant): $1.66 \times 10^−27 \frac{kg}{amu}$.
k is the [Boltzmann Constant](https://en.wikipedia.org/wiki/Boltzmann_constant): $1.38 \times 10^−23 \frac{J}{K}$.
g is the [surface gravity](http://rise.unistellar.com/Vieneo): $11.127 \frac{m}{s^2}$.
T is the temperature of the gas (average temperature of the atmosphere):
$\overline T = \frac{8.0°C + 2.9°C}{2} = 5.45 °C = 278.6 K $
$\mu$ is the average particle mass of the gas (our atmosphere). Similarly to The University of Nebraska-Lincoln, we compute this from the weighted composition of the atmosphere:
$\mu = 0.771 m\_{N\_2} + 0.222 m\_He + 0.004 m\_{O\_2} + 0.002 m\_{Ar}$
$\mu = (0.771)(28) + (0.222)(4) + (0.004)(32) + (0.002)(39)$
$\mu = (0.771)(28) + (0.222)(4) + (0.004)(32) + (0.002)(39) = 22.682 amu$
Plugging these values into formula (9) returns:
$H = 9176.83 m $ or $H = 9.177 km $
# Therefore the air density at a given height, z, is
$\rho = \rho\_0 e^{- \cfrac{z}{9176.83 m}} $
# Sample densities:
Since the scale factor is the distance required to reduce the pressure or density by $\frac{1}{e}$ sample pressures and densities at integer multiples of the scale factor ($nH$) are simple to calculate.
$\rho = \rho\_0 e^{- \cfrac{nH}{H}} =\rho\_0 e^{-n} = \cfrac{\rho\_0}{e^n} $
$$\begin{array}{|c|c|c|c|c|}
\hline \text{Elevation} & \text{n} & \text{coefficient} & \rho & P\\
\hline 0 & \text{0} & \left(\cfrac{1}{1}\right) & 1.000 \rho\_0 & 1.000 P\_0\\
\hline H & \text{1} & \left(\cfrac{1}{e}\right) & 0.368 \rho\_0 & 0.368 P\_0\\
\hline 2H & \text{2} & \left(\cfrac{1}{e^2}\right) & 0.135 \rho\_0 & 0.135 P\_0\\
\hline 3H & \text{3} & \left(\cfrac{1}{e^3}\right) & 0.050 \rho\_0 & 0.050 P\_0\\
\hline 4H & \text{4} & \left(\cfrac{1}{e^4}\right) & 0.018 \rho\_0 & 0.018 P\_0\\
\hline
\end{array}$$
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[Question]
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How would a medieval doctor identify a poison that was administered through a cut? Is it strictly by symptoms? If the implement is produced, would that help in identifying the poison?
The story is fantasy, but I've tried to stick closely with historical and medical facts from medieval times--14th to 15th century. The doctor is a soldier with training in medicine. The government has been allowing medical experimentation and study to an extent, so he is experienced and learned for my purposes, but limited by lack of scientific and medical technology.
Also, implement is a dagger, and yes it can be provided. Poison is a combination of plant, venom, and minerals, so symptoms would be difficult to diagnose.
[Answer]
If this happened the first time and the patient is dead without any characteristic symptoms - random luck.
If various poisons are regularly inserted through cut - thanks to some detective work.
If the poison has very specific symptoms (let's say *hair loss* and *bleeding from the nose*), he might be able to identify the poison.
Also by talking to the patient. The patient tells them he was cut by some guy and then he started having symptoms - most doctors can put 1 and 1 together. Even today doctors have trouble identifying the poison and mostly do it by the patient telling them what happened.
Also please be aware that a doctor in those times wasn't an intellectual (not that they are today, but often in fiction) that could solve hard puzzles, but rather a barber, for example, that also did some doctoring.
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There are plenty of options available, but it would depend a lot on the training of the "doctor" whether they would recognize the clues.
Some plant based poisons would have a faint smell. Some would cause a certain reaction on the skin around the wound, it might cause dilation of the pupils, a rash across their skin, etc. If they knew how long the reaction took (a witness saw the person attacked and how quickly they fell sick) that would help narrow it down.
In general though you will need the character diagnosing to have some training with herbalism. A monk might have had some training in that area. You will have to do some studying yourself to find specific poisons and their effects.
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Laboratory testing as we know it today, did not exist in medieval times. The doctor would have use his own senses, he could smell the poisoned blade or look for residue. Another option would be to apply the poison/ blade to an animal to observe the symptoms. Otherwise, it would be based on the poisoned person's symptoms. Also note that autopsies were not performed in the Middle Ages either.
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Short answer, a Medieval doctor of our world be unlikely to be able to do what you're looking asking.
Medical experimentation and autopsies were not an accepted part of culture until much later than this historically in our world. However, that doesn't mean that you can't build a world where this is possible, there will just have to be specific changes in culture and science made.
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> In the late 1400s in Padua and Bologna, Italy, the sites of the world's first medical schools, Pope Sixtus the IV issued an edict permitting dissection of the human body by medical students. Before such edicts from religious leaders, it was considered a crime to dissect the human body and criminal prosecutions for "body snatching" by students of anatomy date back to the early 1300s.
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> By the 1500s, the autopsy was generally accepted by the Catholic Church, marking the way for an accepted systematic approach for the study of human pathology. While a number of "giants" around this time, such as Vesalius (1514-1564), Pare (1510-1590), Lancisi (1654- 1720), and Boerhaave (1668-1738) advanced the autopsy, it is Giovanni Bathista Morgagni (1682-1771) who has been considered the first great autopsist. [SOURCE](http://www.medicinenet.com/autopsy/page6.htm)
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If you're talking the 1400s (which is the 15th century) there just hadn't been enough experimentation in order to really do what you're talking about. You'd need hundreds of years of acceptance and schools to get to a place where someone might be able to accurately declare the cause of death.
And what you're talking about is actually forensics. And chemistry. By the 1600-1700s, we'd started to get a grasp on chemistry, a bit, but we were not at the level of forensics.
This practice was actually born later, in the Victorian Age, when the collective observations of hundreds of doctors and students through the ages, plus a start to understanding chemistry gave it a boost. It was nowhere near as good as it is today, but this was the start. See this article on how they first figured out [arsenic poisoning](https://www.scientificamerican.com/article/arsenic-s-afterlife-how-scientists-learned-to-identify-poison-victims-excerpt/) in the 1800s. You'll notice that observational experimentation and the recording of those results, along with knowledge of chemistry was used.
**So your proto-pathologist would have to be, gosh, 300-400 years more advanced than everyone else, if you are using the real world as a basis.** Even if he's a genius, keep in mind that he cannot have seen everything, and pathologists, of this time and that relied on books published on the subject, the experimentation and observation of others.
**The answer here is that you are going to need to change your world a bit. It has to have been a) acceptable for many years (perhaps hundreds) to cut into dead people as a method of learning b) there have to be books or sources of information from which to learn c) there has to be a base scientific knowledge of chemistry, even if it isn't fully understood.**
In the Victorian era even, sharing information of this sort did not happen quickly, but you will notice a spate of landmark cases from about 1800-1900 as the science was born.
A person you might want to look at is: [Alexandre Lacassagne](http://discovermagazine.com/2010/nov/22-csi-original-the-birth-of-forensics) from France. Don't look so much at the psyche work he did. There's a lot of bunk there, although he is better than his Italian counterpart, [Cesare Lombroso](https://archive.org/stream/criminalmanaccor1911lomb#page/n15/mode/2up), who was big into equating physical body types with a predisposition for criminality. Still, it would be interesting to have a protagonist who is right about forensics but attributes criminality to something crazy like phrenology or an imbalance of the humors.
You say that:
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One of these can easily cloud the symptoms of the other, but if the combo is known--that can help. Some poisons have physical symptoms attached to them that could be easy to see--it's up to you as the author to attribute them--so the pupils normally dilate pretty quickly after death--but one of your poisons might prevent that for a few hours or it could be something like the rosy glow present in bodies that have died of carbon monoxide poisoning, or any number of purely physical tells, like body positioning as a result of muscle convulsions, that sort of thing. The quicker they get hold of the body, the more likely they can start to come to conclusions (except in the case of some poisonings, a symptom of which can be body preservation).
Your proto-forensics guy might understand that when a certain compound is present, it turns blue when mixed with urine/ammonia. He might not know why, but he could know that it's true.
The wound might be obvious or small, but an inspection of the body would reveal it. Then, he would perhaps dissect the area and test the tissue, looking for anything out of place. A great help would be the invention of the [compound microscope](http://www.history-of-the-microscope.org/history-of-the-microscope-who-invented-the-microscope.php) or something very like it, although you might be able to get away with an efficient magnifier.
The Maesters of Game of Thrones are a pretty good guide to upping science patchily. They have a repository of knowledge, and "earn their chains" by studying certain sciences. In this way, RR Martian has been able to slip in things a little beyond the day as part of the world (which is different from ours) and you can do the same.
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I am writing a story that takes place in a big desert. I've figured that I could make my desert as extensive as possible by building a Pangea-like supercontinent, since I've learned here that, given the distance, eventually the clouds from the surrounding seas will exhaust their water.
However, I want to know how far from the coast I may extend my desert. Let's assume a planet with the same conditions as Earth and let's assume that the continent is as plain as possible (so as not to have rain shadows as a confounding variable).
How far will the rain clouds travel inland? What's the distance from the coast where I may place the desertic climate?
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# Wet places stay wet
Rainfall happens in an area because of prevailing atmospheric conditions. For example, around the equator there is the [Intertropical Convergence zone](https://en.wikipedia.org/wiki/Intertropical_Convergence_Zone) (ITCZ), a zone of rising humid air that releases rain. This band is around 10 degrees of latitude wide and moves back and forth across the equator. Directly on the equator, there is heavy rainfall all year round, as the ITCZ sits on top of this area for most of the year.
For the tropical rainforests, this is the proximate cause of their enormous moisture. Rising, cooling air releases moisture over the forests. The forests themselves, that great mass of trees and vegetation, then respires the water at night, 'recycling' the water back into the air only for it to fall again. For the Amazon, Congo, and Southeast Asia this is what causes rainfall and is independent of distance from the coast.
# Dry places stay dry
On the other hand, around 20-30 degrees north and south, there is a band of descending dry high altitude air. This air is has little to no moisture and thus the land below it is dry year-round. At these latitudes around the world there are the deserts of Southwest US and northern Mexico, the Atamaca and Cuyo in South America, the Sahara and Kalahari in Africa, the Middle East and Thar in Asia, and nearly the whole of Australia.
In these regions, the land is always dry...even if there is a sea breeze! This is especially true in places with cold ocean currents. A desert with a cold ocean current is dry indeed, as you can see from the exceedingly dry conditions in [Lima, Peru](https://en.wikipedia.org/wiki/Lima#Climate) (Peru current) or [Namibe, Angola](https://en.wikipedia.org/wiki/Namibe#Climate) (Benguela current).
If there is a warmer current, then there is hope for wetter conditions; but only erratically. The best you can hope for is a seasonal burst of rain which leads to a semi-arid climate. Examples here would include scattered summer rains in [Mogadishu, Somalia](https://en.wikipedia.org/wiki/Mogadishu#Climate); or scattered winter rains in [Benghazi, Libya](https://en.wikipedia.org/wiki/Benghazi#Climate).
# Rain doesn't make it very far inland if it isn't supposed to be wet
The best example for how far rains can penetrate inland would be from Egypt. Here is a map of wind patterns in the Mediterranean.
[](https://i.stack.imgur.com/lPK0z.jpg)
Egypt sees oncoming winds from the Mediterranean all year round (the ancient Egyptians used this since they could sail up the Nile, but drift with the current back down).
Here (from [en.climate-data.org](http://en.climate-data.org/location/3392/)) is a climate breakdown for Alexandria, directly on the coast.
[](https://i.stack.imgur.com/ikzHZ.png)
Now here is one for Cairo, about 175 km inland.
[](https://i.stack.imgur.com/2SxMw.png)
Where did all the rain go? As little rain as there was in Alexandria, which is directly on the coast of a warm sea, with oncoming sea breeze all year long, it is all gone by the time the winds get to Cairo. You can tell that Alexandria is getting the sea breeze from a warm sea, because it is slightly warmer than Cairo in the winter, but much cooler in the summer. But wonderful climate aside, its still not getting any rain.
# Conclusion
Wet and dry bands are determined by rising and falling air patterns, and by mountains. Places far from the ocean or sea breezes like the [middle of the Amazon Basin](https://en.wikipedia.org/wiki/Iquitos#Climate), or [St. Louis](https://en.wikipedia.org/wiki/St._Louis#Climate), or the [center of the Congo](https://en.wikipedia.org/wiki/Kisangani#Climate), or [Chonquing](https://en.wikipedia.org/wiki/Chongqing#Climate) can get plenty of rain if they are located at the right latitudes or on the right side of a continent (the east side is generally wetter than the west; Africa is the big exception). The dryest places in the world are right on the coast in the Atamaca and Namibe deserts.
[Answer]
It's going to depend on the prevailing winds (which depend on your latitude) and topography. For instance, the Atacama desert of South America, the Namib desert of Africa, and many others are directly on the coast. The Great Basin and contiguous areas of North America are further inland, but shielded from most precipitation by the Sierra Nevada and Cascade mountain ranges. Then there's the Sahara, which extends clear across North Africa, with desert continuing in the same latitudes through the Arabian Peninsula and into the northwest of the Indian subcontinent.
OTOH, the Amazon Basin extends inland for a long distance, and is quite rainy, as is the Congo Basin.
[Answer]
Australia is a pretty flat continent with a lot of desert. The north is tropical, but there is a watershed (quite a subtle one, given the flatness of the continent) that the rain no longer reaches, so south of that watershed it is desert. The desert goes pretty much all the way to the coast in the west of the country, but it is not bare sand dunes. It has spinifex grass and little, sturdy shrubs. Along watercourses there is greenery and a fair bit of animal activity.
Bear this in mind when you place mountains - water that falls on mountains drains off the back side as well as the coastal side. Australia has a low mountain range along the east coast, and the rivers flowing west from those mountains support the entire Murray-Darling basin, which is the bread basket of the nation even though the rains are erratic. The water eventually reaches the sea in Adelaide, on average 1500 miles from where it fell.
As an idea of scale, Australia is about the same size as continental USA - it takes 5 hours to fly from one side to the other.
[](https://i.stack.imgur.com/DAjmQ.jpg)
[Answer]
The best way to make a desert is to put a big mountain range on the coast which gets the predominant winds. As moisture-laden air is blown inland it will rise, cool, and dump its moisture as rain, producing a rain forest on the rising slope. The air which makes it over the mountains will have very little moisture if the mountains are fairly high, and thus produce a desert. You can see this in Oregon, where the Cascade Mountains produce very dry country to the east.
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[Question]
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There seem to be honest scientific exploration in the field of the alcubierre warp drive if you believe some articles on the net. So to be a little bit scientific accurate in a story using it, I wonder about the following:
The warp drive deflates space in front and inflates it to the back of the ship, therefore shortening the distance to your destination and circumvent the light barrier problem.
But what now? Do I have to move in the direction by conventional thrusters and my (real) speed is multiplied by the compression factor (meaning I have to achieve either high real speed or high compression)? Do I have to "step over" the inflated space and then the drive will relax the space and inflate the next part? Do I have to do this with a very high frequency to obtain more relative speed? Or does some part of the alcubierre drive move the space bubble I'm in in the desired direction?
So, what (theoretically) would/could define the speed and direction of such a drive? What would the ship have to do to change speed and/or direction?
I know the exotic matter and "everything will be destroyed at your destination" debate. But for the sake of this question, please ignore it.
[Answer]
**Preamble**
Lets start from the beginning here.
The Alcubierre drive is a result of general relativity. This has what's known as a metric. Minkowski spacetime (lets call this 'flat') has the metric $dS^2 = -dt^2 + dx^2 + dy^2 + dz^2$ (where the speed of light has been taken to be $1$). This leads to special relativity - i.e. a spacetime with no mass.
Things are easiest to explain from this - take a 'test particle with mass $m$' (something that has a mass that somehow doesn't have an effect on spacetime for mathematical convenience. This will give you the general idea of how things work to a certain extent). Now, this 'test particle' follows what is known as a geodesic. Lets say this particle is moving in the $x$-direction: the metric becomes $dS^2 = -dt^2 + dx^2$. For a massless particle, this becomes $dt^2 = dx^2$ and so $\frac{dx}{dt} = \pm 1$. This is the velocity of a photon.
For a massive particle, this gets a little more complicated - use Lagrangian mechanics $\left(\dot{x} = \frac{dx}{d\tau}\right)$ where $\tau$ is the 'proper time' of the test particle i.e. $t$ is the time of the observer, $\tau$ is the time of the test particle: $$\mathcal{L} = -1 = -\dot{t^2} + \dot{x}^2$$ which gives $$\frac{\partial\mathcal{L}}{\partial t} = \frac{\partial\mathcal{L}}{\partial x} = 0$$ and $$\frac{\partial\mathcal{L}}{\partial \dot{t}} = -2\dot{t} = constant, \frac{\partial\mathcal{L}}{\partial \dot{x}} = 2\dot{x} = constant$$ giving $\frac{dx}{dt} = constant$. Again, the velocity of something is constant.
Sticking something massive in there (that's not a test particle) and saying that it is stationary and static gives the *Schwarzchild Metric* $$dS^2 = -Fdt^2 + F^{-1}dr^2 + r^2d\theta^2 + r^2\sin^2\theta d\varphi^2$$ where $F = F\left(r\right) = 1 - \frac{r\_s}{r}$ is a function of the mass of the (non-test) object. If this object has a charge, then $F$ is also a function of the charge - this is known as the *Reissner–Nordström* metric. However, as there is now an $r$-dependence, the equations of motion have an additional term. This leads to what we call *Gravity* - due to the curvature of spacetime, things no longer travel in what you would normally consider to be a straight line.
**Answer**
**$t$ is the time of an observer at infinity, $\tau$ is the time of the test particle (ship), so $\frac{dr}{dt}$ is the velocity according to an observer at infinity**
Now, the [Alcubierre metric](https://arxiv.org/pdf/gr-qc/0009013v1.pdf) is formulated to have a spaceship at $x\_s\left(t\right)$ and can be written as $$dS^2 = -dt^2 + \left(dx - v\_s\left(t\right)f\left(r\_s\right)dt\right)^2 + dy^2 + dz^2$$ for a ship travelling in the $x$-direction. $f\left(r\_s\right)$ is the 'warp bubble' function. **$v\_s\left(t\right) = \frac{dx\_s}{dt}$ is the velocity of the ship** and is intrinsic to the metric being used. In other words, **the ship travels under gravity, albeit gravity created by exotic matter**. The ship stops a distance from wherever you're travelling from and creates a warp bubble using exotic matter (matter with a negative energy density), or perhaps creates exotic matter as a result of creating the bubble. This bubble propels the ship along, just like gravity, only the ship takes a much shorter time to reach the destination than light (and you don't experience g-forces as you're in free-fall). Half-way along the trip, you reverse the direction of the warp bubble so that a certain distance away from the destination, you're now stationary and can switch the bubble off. During the entire journey, you haven't violated any laws of relativity, except for the energy conditions, which can also be violated [in QFT](https://en.wikipedia.org/wiki/Casimir_effect).
It should also be noted that the speed of the ship is not constant, but the acceleration $\left(a\right)$ is. Half-way, the acceleration changes from $a$ to $-a$. The ship always remains within the bubble - either multiple bubbles are pre-set in space which are triggered by the ship, or the ship creates its own bubble which travels with the ship. A change in 'proper time' (of the ship) = A change in 'co-ordinate time' (of a distant observer) i.e. There is no time dilation or anything because the warp bubble warps the space in front of the ship giving $dt = d\tau$. This is essentially what allows the ship to appear to go FTL.
If you want to change the direction, then the best idea would probably be to reverse the direction of the bubble until you stop, then create a new bubble in the new direction you want to go in.
**Edit to answer questions from the comments:**
There are two types of co-ordinates (as far as this question is concerned anyway): That of the ship and that of a distant observer (someone so far from the bubble that they are completely unaffected by its existence or lack thereof). In the ship's frame, $dx = vdt$ and $f\left(r\_s\right) \simeq 1$ in a small area around the ship and so $d\tau = dt$, directly giving no time dilation. As it moves on a geodesic by design, the proper acceleration is $0$, just like when under free-fall in a 'gravitational field' (such as on Earth) even though the bubble (and so, ship) is accelerating from the perspective of a distant observer. In other words, you feel no acceleration (literally, you're still in 0-gravity), yet a distant observer will see you accelerating. As you're not actually accelerating, your proper velocity is also $0$, despite the fact that you're moving arbitrarily fast to a distant observer! A neat comparison to this is that distant galaxies appear to be travelling away from us at relativistic velocities, only (on average) they're not - it's the expansion of space causing this effect. That's just what's happening here - the space in front of the ship is contracting and the space behind is expanding again, so it's very like the cosmological constant.
You might be able to change direction without stopping, but the change to the metric is no longer smooth. Having said that, adding another bubble in an orthogonal direction should be OK. So, if you're travelling in the $x$-direction and want to travel in the $xy$-plane at 45 degrees to that, add an equally strong bubble in the $y$-direction, as opposed to rotating the bubble. Maybe you can rotate the bubble - it might be OK, but the changes may not be smooth, so I couldn't guarantee it. I suppose, considering that you're ignoring end effects of creating/getting rid of the bubble, it could be valid to arbitrarily rotate the bubble. Again, the whole 'ship stopping' thing is just to keep changes to the metric smooth, although, really, it should be fine to create the bubble while moving (if not, then indeed the question is what are you stationary relative to?). I don't really know what accelerating (using e.g. rockets to give a proper acceleration) would do though. It's easier to refer to the velocity it created the bubble at as 'stopped' though as creating the bubble at a different velocity to the one where it's destroyed could cause problems with the metric, so again, how exactly this would work isn't really known. I'd guess either the bubble is self-preserving, it doesn't matter or it's likely that you'd end up with a black hole or something? Certainly, the tidal forces at the edge of the bubble are massive, so you don't want to get near to the edge of the bubble.
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[Question]
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I am often fascinated by one of Earth's most magnificent beings, the mantis shrimp (also known as 1-2-3-death). These beautiful animals have sixteen kinds of colour receptive cones - compare to our measly three! **They can also see polarized light in ways that we cannot.**
Which got me thinking... What if we had eyes more like the ones of those cute creatures, and could see polarized light the way they do?
How differently would we see everyday things? Would magic tricks, specially those based on smoke and mirrors work differently for us? Would we perceive the sky and the stars any differently?
[Answer]
**What would the world look like if we could detect the polarization of light?**
For one, [we might be better at navigation](http://arthropoda.southernfriedscience.com/?p=54#more-54):
>
> Polarized light is produced a variety of ways in nature. The atmosphere and water both refract un-polarized sunlight, producing a polarized light pattern. This creates a striking pattern in the sky that many animals use as a navigational compass.
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As far as how we would interpret colors and such if we could see polarized light, you need to understand that polarization is different than other colors. For human color vision, we have cone cells that are particularly stimulated by certain wavelengths of light. For instance, [blue-detecting cones are most stimulated by light with a wavelength of around 430 nm](https://en.wikipedia.org/wiki/Color_vision#Cone_cells_in_the_human_eye). Polarization is basically which direction the light wave is vibrating. This is independent of wavelength - you can have blue light polarized the same as red light, while another source of blue light could be polarized differently than those two.
Given that wavelength and polarization are independent, I think we would interpret it separately. For comparison, think about light blue, light red, dark blue, and dark red. The darkness or lightness of the color is easily separated from the color itself. Polarization would be like that - another aspect of color that we would be able to describe and that can easily be compared across colors.
**What magic tricks, etc. would no longer work on us?**
This wouldn't prevent any magic tricks from working on us. When was the last time you saw a magician do a trick that was actually obvious because some part of the trick accidentally used two different colors when it should have used one? Being able to perceive polarized light, the magician would make sure that the materials used didn't polarize light in such a way as to give the trick away. It's entirely possible that magicians would have to be more particular about lighting and materials used, but that's not a significant change from what they do now.
**What would no longer be hidden from us?**
[Some animals use polarized light as part of their mating routines](https://en.wikipedia.org/wiki/Mantis_shrimp#Suggested_advantages_of_visual_system), so we would be able to see them wooing each other.
**What would be obfuscated?**
Nothing natural. You'd have to design something that rapidly changed the polarization of light it reflects/emits to produce a strobe-like effect. As I said earlier, polarization would be categorized differently than color, so it would not make it harder for us to perceive anything that we can currently perceive.
**How would we perceive the sky and the stars?**
As I quoted earlier, the atmosphere polarizes light from the sun, so we'd be able to see patterns in the sky that could help us navigate. Stars produce unpolarized light, so they'd look the same other than how the sky polarizes light.
[Answer]
With many more than three colour receptors, our colour TVs, using just three colours for display, would not come even close to showing all the colours of the world. Moreover, LDCs inherently work with polarized light; as is, they would probably look very unnatural. However, in principle this could be solved with a second LCD layer on the pixels; this would, however, make the displays twice as expensive, even before considering the extra colours.
It's not clear if we would really see *more* colours, as the additional dimensions in colour space might well be offset by a lower colour resolution, so while while we would see different colours for wildly different spectra that in our reality look exactly the same, similar spectra that already show different colours to us in the real world might in that hypothetical world look the same.
For a rough analogy (not to be taken *too* literally), consider a display with only two colour channels (say, red and blue) and three bits per channel, versus an ordinary three-channel display with two bits per channel. Both would have 6 bits available, therefore they both could display 64 different colours. The two-colour display could display more colour tones in the magenta segment (as the mixture of red and blue could be finer tuned), but in return could not display green at all.
[Answer]
## We do not know
The entire point of these extra cones is that they can see colors we cannot. Colors we cannot see, we cannot conceive. What you are basically asking is for us to imagine something we cannot imagine.
I, or rather no one, can tell what illusion would or wouldn't work, because we cannot even conceive what these other colors look like.
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I have a binary system in which my world orbits one of the stars, not the pair, in the habitable zone. The stars are relatively close together (because I want the secondary one to [shed significant light](https://worldbuilding.stackexchange.com/q/25318/28) on the planet too), tentatively [about 20AU apart with the secondary star in a small nebula](https://worldbuilding.stackexchange.com/a/25204/28). (I'm still open to other ways to solve my lighting problem; see the linked question.) The primary star is F- or G-class and the secondary is, tentatively, K-class.
I'd like to get an idea of how many other planets might be in this system and how they could reasonably be distributed. Might I see a mix of planets orbiting single stars and ones orbiting the pair? Would there plausibly be planets orbiting both stars or just one? Would that be different if the stars were farther apart, say 100AU?
And what about number? NASA has identified [nearly 600 multi-planetary systems](https://en.wikipedia.org/wiki/List_of_multiplanetary_systems) so far. In about half they have found two planets, in about a sixth they have found three, and it drops off from there. Our own solar system has the highest known planet count so far. Of course, there could be planets that NASA just hasn't found yet -- or eight planets for a single system might be really unusual. But, as best I can tell, none of the systems catalogued by NASA are multi-star systems, so even if we postulate that "about three" is the right number for a random system, we don't know if that extends to binary-star systems.
So, all that said, how do I figure out what number and distribution of planets is plausible in my binary-star system? Are any multi-planetary binary-star systems known? Are there sound principles that would let us extrapolate from mono-star to multi-star systems?
[Answer]
Let’s start with the easiest of your questions:
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> Are any multi-planetary binary-star systems known?
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There are, in fact, quite a few:
* **[55 Cancri](https://en.wikipedia.org/wiki/55_Cancri):** Five planets orbit 55 Cancri A (a G-type yellow dwarf). Four are gas giants, three of which orbit inside 1 AU, while the fifth is a super-Earth orbiting at about 0.015 AU. The two stars, by comparison, are separated by over 1000 AU. Stability is quite clearly not an issue here. 55 Cancri B is a red dwarf/
* **[HD 20781](https://en.wikipedia.org/wiki/HD_20781)/[HD 20782](https://en.wikipedia.org/wiki/HD_20782):** These two stars form a binary system of two G-type stars. The former has two Super-Earths orbiting it at less than 1 AU, while the latter is orbited by a gas giant at about 1.80 AU.
* **[Kepler 47](https://en.wikipedia.org/wiki/Kepler-47):** Kepler 47, a binary composed of a G-type star and a red dwarf, contains three exoplanets, all of which orbit Kepler 47A. They’re gas giants, orbiting within 1 AU.
* **[NN Serpentis](https://en.wikipedia.org/wiki/NN_Serpentis):** Composed of a red dwarf and a white dwarf (a stellar remnant, technically), NN Serpentis contains two gas giants, orbiting at 3.4 and 5.4 AU. The planets are circumbinary planets, as the two stars orbit close together.
As you can tell, there’s a mix of planets in P-type orbits (circumbinary) and S-type orbits (around just one star). The planets in S-type orbits seem to orbit close to the primary. It could be argued that this is an observational artifact; after all, it’s much easier to detect giant planets close to their parent star, using transit and radial velocity methods. I would guess that this plays a role in the lopsided data we have, just as it plays a role in the distribution of all the exoplanets we know of.1
However, there is another factor. Planets in S-type orbits do have a maximum semi-major axis, as first explored by [Graziani & Black (1981)](http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1981ApJ...251..337G). This distance is accepted to be [about one-fifth of the separation between the stars](http://www.solstation.com/habitable.htm). Likewise, for planets in P-type orbits, there is a zone of (according to the above page) one third to 3.5 times the separation in which stable orbits are not possible (see e.g. [Donnison & Mikulskis (1991)](http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1992MNRAS.254...21D)), though [Wikipedia](https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems#Circumbinary_planet) cites the more recent [Welsh et al. (2013)](http://arxiv.org/abs/1308.6328) in extending the innermost stable orbits to 2-4 time the stellar separation.
These are some basic ranges; Hypnosifl also suggested [Holman & Wiegert (1998)](http://arxiv.org/abs/astro-ph/9809315), who studied the long-term stability of both S-type and P-type orbits, allowing for non-zero values for the eccentricity $e$ of the orbits of the stars. Thus, their empirical formulae (with coefficients derived using least-squares techniques) may be more accurate than models which assume that $e=0$. I’d highly recommend consulting them if you want to do some basic calculations for your stellar/planetary system.
An even better resource might be [Jaime et al. (2014)](https://arxiv.org/abs/1401.1006). They discuss the applicability of stability to habitable zones, including the continuum between habitable zones around each star to habitable zones around both stars:
Additionally, like Holman & Wiegert, they discuss the impact of stellar eccentricity on the boundaries of stable orbits.
The authors look at the cases of three specific stellar systems and try to define whether or not a planet can orbit stably inside the habitable zone(s). Take, for instance, the case of HIP 80346:
The red line denotes the outermost stable S-type orbit, and the grey areas denote the habitable zone. The stars are shown in black. Using their analysis, they were able to show that only the secondary star can host planets in stable S-type orbits in its habitable zone, because the primary star’s maximum stable orbit is inside the inner edge of the habitable zone.
Now that we seem to have looked at the limits of orbits, let’s take a look at what you’re actually likely to find in a binary star system. [Quintana & Lissauer (2007)](https://arxiv.org/abs/0705.3444) is a good start, in terms of terrestrial planet formation. Here’s a quick summary:
* They began with a large number of planetesimals already formed. 14 compose half of the mass of the disk (each with a mass of about one tenth that of the Earth), while 140, each with a mass one tenth of *those* planetesimals, compose the other half of the mass.
* In a simulation of the Alpha Centauri system2, with a protoplanetary disk surrounding Alpha Centauri A, five terrestrial planets with masses at least that of Mercury formed in orbits with semi-major axes less than two AU that remained stable for the duration of the system, 200 million years. However, with a tiny perturbation in the initial position of one of the planetesimals, only four planets form, all within 1.8 AU. Furthermore, if the disk is given an inclination of 15 degrees, only three planets form, because mass is lost. In the simulations, 3-5 planets formed in S-type orbits around Alpha Centauri A under a wide range of conditions; for Alpha Centauri B, the range was 2-4.3
* In the case of general S-type orbits in “wide” binary systems, two factors that influenced planetary formation more than anything else: the stellar mass ratio, $\mu$4, and the periastron distance (the closest separation) of the two stars, $q\_B$.
* In the case of P-type circumbinary orbits, close binary stars yielded terrestrial planetary systems similar to the Solar System, especially if giant planets were added. However, in some wider binaries (stellar separations of about 0.5 AU), drastic mass lost led to only one planet. As would be expected, the most important factor here is $Q\_B$, the apastron distance (the furthest separation), as it determined disk perturbations.
* The masses and orbital eccentricities of the planets are not affected much given that there are two stars in the system (for both P-type and S-type orbits), given suitably stable orbital ranges for the $q\_B$/$Q\_B$.
Here’s Figure 1, the results of some of the simulations for planets around Alpha Centauri:
Here’s Figure 2, the results of some of the simulations in the same conditions but with that tiny change in the orbit of one of the planetesimals:
I’d also like to mention [Bromley & Kenyon (2015)](http://arxiv.org/abs/1503.03876), who attacked the problem analytically. If you’re into expanding potentials using Fourier series, be my guest and read it through. In this case, I, however, prefer to look at what overall trends from the simulations tell us.
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1 However, this is decidedly *not* the case for planets in P-type orbits. As demonstrated by [Pierens & Nelson (2008)](http://arxiv.org/abs/0803.2000), circumbinary planets with mass greater than that of Jupiter are likely to encounter instabilities during formation and will either be ejected or will migrate drastically, possibly ending up orbiting just one of the stars. That said, as noted in Quintana & Lissauer (2007), which I’ll discuss later, no terrestrial-mass planets have been detected so far in P-type orbits.
2 Keep in mind that the early reports of one or more planets in the system turned out to be incorrect; these are hypothetical planets.
3 Note that it's not impossible for both stars in the system to have protoplanetary disks, leading to planets in S-type orbits around each star.
4 μ is calculated as
$$\mu=\frac{M\_C}{M\_C+M\_\*}$$
where M\* is the mass of the star around which planets formed and MC is the mass of the companion.
[Answer]
A simple way to think about this problem is simply in terms of which planetary orbits are stable in a given binary star system.
[](https://i.stack.imgur.com/KBIDs.jpg)
Let's talk about S-type orbits, where a planet's orbit around its star is smaller than the mutual orbit of the two stars. There is an outer edge of stability: planet orbits that are wider than a certain distance are unstable. That distance is directly linked to the closest approach between the two stars, Rmin. The ballpark number is generally 1/3: orbits start to be stable at about 1/3 of Rmin. So, if the two stars' closest approach is 30 AU, planetary orbits are stable out to about 10 AU. This is not a really firm number, because it depends to some degree on things like the stars' masses, how eccentric the stars' orbit is, and how inclined the stars' orbit is relative to the plane of the planets. But it's a good ballpark number.
So, for your case of a binary separated by 20 AU, you could plausibly have planets orbiting both stars out to, say, 6-7 AU. If you want to be conservative put the edge at 5 AU. If the stars have different masses, then the more massive star can have planets farther out. If the binary orbit is eccentric, say with e=0.5, then the closest approach distance would be 20 AU \* (1 - e) = 10 AU, so the outer edge for stable orbits would be at around 3 AU.
Of course, you can pack as many planets as you want interior to that radius (see here for example: <https://planetplanet.net/2014/05/21/building-the-ultimate-solar-system-part-3-choosing-the-planets-orbits/>).
You could also have planets orbiting exterior to the two stars, on P-type orbits. The ballpark criterion for planets on P-type orbits is that the inner edge of stability is at least 2 times the maximum separation of the two stars. So, for the case of your binary separated by 20 AU, you could have planets orbiting past ~40 AU (or, to be conservative, past ~50 AU). If your binary has an eccentricity of 0.5, then the farthest separation of the two stars would be 20 AU \* (1 + e) = 30 AU, so you could have planets anywhere past 60-ish AU. Again, there are lots of details but this is the simple ballpark way to think about it.
And FYI see here for a summary of the effect of binary stars on planets: <https://planetplanet.net/2013/06/06/binary-stars-friends-or-foes/>
This figure shows the punchline:
[](https://i.stack.imgur.com/yqtFl.png)
Hope this helps!
ps - HDE 226868: very nice detailed answer related to formation.
[Answer]
Regarding distances between the stars, and the the light shed upon planets, the Alpha Centauri system is pretty close to the requirements that you want. Here is some useful information summarized from the wikipedia page about Alpha Centauri, [View from a hypothetical planet](https://en.wikipedia.org/wiki/Alpha_Centauri#View_from_a_hypothetical_planet)
* Alpha Centauri A ("A") is 1.5 times as luminous as the sun, and B is 0.9 times as luminous as the sun.
* A and B have an orbital period of 79 years (a human lifetime) where they go from 11 AU apart to 35 AU apart.
* For a planet circling A such that A is the same brightness as our sun, B will appear to be 190-2500 times as bright as the moon.
* For a planet circling B such that B is the same brightness as our sun, A will appear to be 580-6900 times as bright as the moon.
That last figure (6900 times as bright as the moon) is equivalent to 1/70 as bright as the sun. While that is bright, that is the equivalent of our own sun from 8 AU away, which is between Jupiter and Saturn. Bright enough to keep you up at night but not bright enough for photosynthesis or turning a planet into Arrakis.
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[Question]
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I recently finished reading the novel "Seveneves" by Neil Stevenson. The central premises of the novel is that an unknown object has caused the moon to break into several large pieces, with an immeasurable amount of smaller ones floating around.
In the novel, the quantity of objects is sufficient to cause a Kessler Syndrome type 'white sky' event, which then somehow jumps to a bombardment of the Earth with many of the smaller pieces.
Overall, my question is
A) Would breaking the moon into pieces cause a white-sky event, even in lunar orbit?
B) Would the pieces' orbits decay?
[Answer]
Some would. Basically the most likely event that would cause the moon to break up is a collision with another object. That collision would impart kinetic energy to the various pieces of the moon in different amounts and along different force vectors, which would cause the pieces to drift away from the moon's former location in various directions.
They wouldn't "suddenly" deorbit, but the force imparted by the collision to the pieces would be like a Saturn IVb rocket in orbit around Earth firing its engine to break LEO and head out to the moon; or, conversely, the CSM firing its engine to deorbit the moon and head back to Earth. The only difference is that the rocket engine imparts force gradually over time (a long "impulse") while a collision imports force in a fraction of a second (a short impulse). Well, there's another difference, and that's that the imparting of force to each piece of the former moon is much less precise, so predicting where the various pieces will all go, and thus whether and when they'll deorbit and where they'll impact, is impossible to calculate prior to the impact and very difficult for hours thereafter, by which time the smallest, fastest chunks will probably be causing a meteor shower for Earth observers.
[Answer]
If the Moon disintegrated as in *Seveneves,* certainly not all of its mass would end up hitting the Earth, but some of it would, and it'd only take a small fraction to produce catastrophic results.
In general, if something in orbit breaks into pieces moving away from each other, then by definition neither piece is still in the original orbit, because (due to conservation of momentum) neither piece has the original combination of velocity and altitude. One piece will be spiralling toward Earth, the other away from it, at a rate determined by how hard the object broke apart. As the fragments of the Moon collide and break each other into smaller and smaller bits, they will spread into a wider and wider distribution of orbits, some of which will eventually pass within the Earth's atmosphere, while others escape into deep space.
To put it another way, the Moon disintegrates, and becomes an expanding debris cloud like the Death Star exploding. That debris cloud is a disc centered on where the Moon's center of mass used to be (more or less). Sooner or later, the disc will expand to touch the Earth's atmosphere, and at that point the dust / rocks / huge boulders that make up the cloud will start falling out of the sky. Even if most of it burns up, this could easily heat up the atmosphere by tens or hundreds of degrees (which is what Stephenson calls the "white sky").
[Answer]
Decay in the classic sense the way a satellite in the upper fringes of the atmosphere decays? No. It's complicated.
When two objects interact gravitationally energy is conserved. In center of mass coordinates each leaves (assuming they miss) with the same speed they came in on. In the reference system of a large group of such interactions, the small bodies pick up speed at the expense of the large ones. This is the principle of the sling shot effect used by NASA. E.g. routing a probe by Venus to give it enough energy to get to Saturn.
In effect the cloud of mutually orbiting rocks 'boils' off the smaller rocks. SevenEves doesn't make clear how fast this can happen.
Rock has essentially no structural strength compared to it's mass when in large chunks. This is why planets are round. Even Ceres, the largest asteroid is essentially a large lumpy ball. Doesn't take much of a hit to make a big fragment into a large bunch of smaller fragments.
This is important: The rate that rocks are expelled from the cloud depends on:
* How often interactions happen.
* The difference in velocity between each rock and the center of mass of the cluster.
* The ratio of the mass of the large rock to the small rock
Complication: The moon is outside the earth's Hill Sphere. The sun is a stronger force than the earth is.
A rock that comes off the cloud toward the earth has basically one chance to hit the earth before being slung off into deep space.
If all moon were converted to gravel, and spread evenly in all directions, then a "White Sky" would certainly be the outcome. Figure out what fraction of the sphere the earth intercepts, and how long the gravel takes to arrive. All of it arrives at essential earth escape velocity.
(it's more complicated. You have to figure out the effective cross section for the earth because the gravitation will bend paths toward it.)
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[Question]
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So in my story/world I have a region that is straight up destroyed...demonic magic is nasty stuff.
So we have rings
[](https://i.stack.imgur.com/MvoTK.png)
**Ring 1 (1 is in the middle)**
This ring has a diameter of about 200 miles. At this range things got real real bad. The land that was here was completely gone, either ejected into the sky in massive chunks or sunk below the oceans. It is not on the Richter scale at all...
**Ring 2**
Ring 2 is an additional 100 miles around so the total diameter from the center would be 300 miles. At this range the entire area experienced the equivalent of a 9.0 - 10.0 earthquake per the [Richter scale](https://en.wikipedia.org/wiki/Richter_magnitude_scale).
**Ring 3**
Ring 3 adds an additional 50 miles to the radius, for a total of 350 from the epicenter and experienced 8.5 - 9.0 Magnitude quakes
**Ring 4**
This ring adds another 200 miles for a total range of 550 and its quake measurements registered 6.5 to 8.5
**Ring 5**
Ring 5 is a more general idea than a specific range. Quakes in this area which doesn't have a specific mileage ranged from 2.0 - 6.5
**Questions:**
1. How long would it take this region (by ring if necessary) to settle down to the point of human habitability?
* My goal is it should be 500 years in rings 1 and 2 before its even safe to walk around, be that lava, gas, tremors etc
* An additional 500 - 1000 years before non-human life will live there.
If my plan doesn't work in the regard, please suggest what ranges/etc could make that work.
2. What would be the hazards in the region prior to things settling down?
* Would there be magma pools, noxious gasses, steam from magma and water coming together? Stuff like that...
**Assumptions:**
* Magic was involved so there will be no nuclear winter follow on. I am purely asking about the geological stability of the region and any associated hazards spawned from that.
* The ground is scorched and dead out to around 300 miles from the epicenter (meaning all the living stuff in the dirt died)
[Answer]
## New Answer:
How do you render about 31K square miles lethal to visit for 500 years? Good question. This question will ignore the obvious "Well, if you have (demonic) magic, you can do anything." While that's true, it's not super helpful in this case.
**Nuclear Wasteland**
Whatever happened in this cataclysm has the effect of inducing monstrous radioactivity in Rings 1 and 2. The half-life of this radiation is such that by 500 years it's just below what a human can stand for days or weeks (though some unlucky individuals will still get cancer. Sorry.) From 500 to 1000 years, the radiation has subsided enough that normal vegetation can start to grow back. Keep in mind that these plants are all from outside Ring 2 since the soil is likely sterilized from the cataclysm. Explorers may see clumps of vegetation before the first 500 years are up. As radiation decreases, more species will be able to survive in Rings 1 and 2. As vegetation spreads, farmers and herders will be able to grow crops and herds on the new land.
**Lava Fields**
The cataclysm broke open the crust, expelling large cracks in the crust that just will not close. While lava itself will cool pretty quickly, [10-15 minutes](http://volcano.oregonstate.edu/how-long-does-it-take-lava-cool) it can take months or years for deeper lava to completely cool. Let's take this up to 11 then. The cracks in the crust are so immense that it takes hundreds of years for them to finally calm down and solidify. Make sure they don't get around to cooling with frequent eruptions from exploding gas pockets below the hardened lava. Having a river flow into the affected region will provide plenty of water for steam explosions and geysers later. Even after the 500 year mark when everything has cooled down enough to be stable and not cook a human who ventures in, it will take a long time for plants to take hold because there's no dirt, just hard hard basalt.
## Old Answer:
This is an answer to an earlier version of the question. While the information provided is still valid, it's not as pertinent to the current question constraints.
## Thermal Effects
It's going to take a long time for Ring 1 to cool down after injecting that much energy into such a small area. Given that the diameter of Ring 1 is 2 times the diameter of Chicxulub, as absurd amount of energy has been deposited. I calculated the blast effects of a 100 Teratons of TNT using [NukeMap Classic](http://nuclearsecrecy.com/nukemap/classic/?lat=32.7766642&lng=-96.79698789999998&zm=2&kt=100000000000) and I got a really silly picture. (I chose Houston, TX because it's on a plain.)
[](https://i.stack.imgur.com/GujT8.png)
That little ring of blue in the Indian Ocean is where the thermal effects *don't* go. Granted, these calculations assume the world is flat so the thermal effects probably wouldn't go that far.
If these kind of thermal effects hold true, it will take thousands or tens of thousands of years for the vegetation to grow back in any ring. Humans generally don't live where there's not vegetation.
## Geological Effects
If Ring 1 lies on a major fault line then I'd expect significant disruption of that fault leading to long lasting aftershocks. Without more details about the geology under Ring 1, this won't be easy to answer.
In general, aftershocks trail off according to some well understood [equations](https://en.wikipedia.org/wiki/Aftershock#Aftershock_size_and_frequency_with_time):
$$n(t) = \frac{k}{(c + t)^p}$$
where $c$ and $k$ are constants that depend on the earthquake sequence and $p$ which is the decay rate, usually between 0.7 and 1.5. Depending on the values chosen for $c$, $k$ and $p$ fall off of aftershocks could last from just a few days to years. The author has broad discretion here.
## Magical Effects
Depending on the nature of the demonic magic used, this area may never recover. Most stories treat demonic taint as a kind of permanent pollution that inhibit all but the most twisted of life.
[Answer]
Earthquakes themselves don't last very long. Typically 10 to 30 seconds according to <http://quake.utah.edu/regional-info/earthquake-faq>
If the quakes aren't happening because of a recurring effect, and the area hasn't been totally destabilized (creating new seismic activity) the area would be pretty much fine geologically.
If there will be aftershocks, though it seems like an unnatural happenstance of quakes, but they can continue for quite a while. They decrease exponentially though.
The seismic activity wouldn't normally occur since it's based on magic, so I would imagine that since the strain isn't due to tectonic movement, it would be fine the next day. It really depends on how it affects the overall seismic activity in the longer term.
That's as much as I understand! :D
I'm no expert though.
[Answer]
One thought (late I know) - what if part of the damage was due to a magically caused mantle plume, such as that which gives rise to basalt flood plains, or volcanic features such as the Galapagos or Hawaiian chains (sorry if my geology is off).
These have the advantage they are ongoing for a time, which would mean the effects could be much closer to the effects you are seeking (long term impact, uninhabitable centre while it lasts or for a few centuries, but rings not too far away which are habitable.)
[Answer]
### Geology and Obsidian
Ring 1's been destroyed and looks like a [land of stalagmites](https://upload.wikimedia.org/wikipedia/commons/thumb/d/de/Stalactite_(PSF).png/220px-Stalactite_(PSF).png). During the cataclysm, the ground itself exploded, producing this kind of geography in massive rock coated in [obsidian](http://geology.com/rocks/obsidian.shtml). Obsidian is extremely sharp and can last for a *very* long time. Walking there is like walking in a valley of giant knifes : it is technically possible, but extremely deadly. However, to reach this place, you would have to walk through the Ring 2 for 100 miles ...
Ring 2's geography is also linked to obsidian, but the blades are smaller, so Erosion will act faster. However, nobody really knows how it looks. When the cataclysm happened, huge masses of rocks flew from the impact point and formed a natural wall around it. Some people tried to climb it, but fell or did not come back. It is high enough that a medieval population has no way of bringing it down without heavy siege engines.
Natural erosion and time will create serious breaches in the wall, but not before 500 years.
### Part of the local atmosphere has been blown away
A little background on this idea: one of the main risks carried by an atomic bomb is not simply the radiation and the destructive ground power. An atomic bomb could blow the atmosphere around the impact, and possibly in the whole planet.
In your case, the atmosphere has been blown in rings 1 and 2, and has been replaced by a heavy gas which came with the cataclysm (like a non-explosive version of [Firedamp](https://en.wikipedia.org/wiki/Firedamp) or [Marsh Gas](https://en.wikipedia.org/wiki/Marsh_Gas)). If you combine this with the "natural wall" described in the previous idea, or if you assume that the original cataclysm created a large crater, this gas would stagnate and would not allow any lifeform to stay.
Given enough time (500 years ? 1000 years ? It simply depends on how deep the crater/how high the natural wall is), this gas will end up diluting itself, and people will be able to walk there again.
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[Question]
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I've come up with a couple of exoplanets for a story, and have reached the limits of my knowledge. I've googled around, and I had a space enthusiast friend look at them, but he freely admits that he's just guessing for most of this, especially the atmospheric makeup.
The other planet is [here](https://worldbuilding.stackexchange.com/questions/41169/exoplanetary-review-acid-rain).
Based on suggestions and additional research, I now have two versions of the planet.
**Hekaton (Version 1)**
This chthonian planet orbits a BHB blue giant, with an orbital period of 510.8 earth days. Its mass is 14.5 earths, and its radius is 2.1 earths, with a surface gravity of 3.28g. Surface temperatures range from 110 - 180 C, with a mean of 138. Its thick atmosphere has a pressure of 1.85 atms, and is primarily composed of hydrogen,with moderate amounts of helium, and nitrogen, and trace amounts of arsenic, carbon monoxide, and sulfur. It has three moons, with respective radii of 0.13 earths, 0.19 earths, and 0.265 earths.
Its star emits high levels of UV radiation, and despite the thick atmosphere sunlight is very strong, capable of causing 3rd-degree burns in minutes. The combination of high volcanic activity combined with atmospheric turbulence caused by volcanism results in the air being filled with large quantities of rock. Most of this is just grit, but stone rain is not uncommon, ranging in size from gravel to boulders. High winds circle the equator, bringing rock and ash with them. When channeled through mountains or ravines, they become flensing storms that can reach speeds of over 200 kph, leaving huge plains of ash and debris behind them.
A few specific concerns for version 1:
* For a star capable of causing enough atmospheric loss in a pegasid like Hekaton to form a chthonian planet, is it possible for it to transition to a phase where the chthonian planet doesn't have a surface temperature of several hundred degrees?
* Can a chthonian planet be as small as this? I read that most potential chthonian planets are estimated to be at least 30 earth-masses, but could easily be smaller, and that hot Jupiters and the like often have unusually low densities.
* Would a blue giant be too hot to support this surface temperature? I chose a BHB blue giant because of its UV output, so that Hekaton can have deadly sunlight without being too hot, but if there's a better type of star for this, I'll happily switch.
* Can it have such strong UV (especially C-band) radiation while still having an atmosphere thick and turbulent enough to support the rock storms?
**Hekaton (Version 2)**
This chthonian planet orbits a blue giant in a tidally-locked orbit at a distance of .6 AU. Its mass is 14.5 earths, and its radius is 2.1 earths, with a surface gravity of 3.28g. Surface temperatures on the hot side range from 1500 - 1900 C, and on the cool side from 60 - 170 C. Its thick atmosphere has a pressure of 1.85 atms, and is primarily composed of hydrogen, with moderate amounts of helium, and trace amounts of sulfur, nitrogen, oxygen, and neon, with large quantities of metals. It is in the process of losing the remainder of its atmosphere.
This temperature differential causes enormous atmospheric turbulence, carrying molten rock and metal from the hot side to the cool side to be deposited as rain. Volcanoes further this by pumping large quantities of ash and grit into the air, columns of which scour the surface in great storms. The portions of the cool side near the hot side also receive intense ultraviolet radiation reflected off the atmosphere.
A few specific concerns for version 2:
* I based this version off of Upsilon Andromedae b and picked a different type of atmosphere. Does the type of atmosphere I have still work?
* Can a planet become tidally locked at 0.6 AU, or should I dim the star and move the planet closer?
**Planetary System**
Its planetary system is relatively old. The inner system is two terrestrial planets (one of them less than 0.1 AU from the star), followed by Hekaton. Beyond Hekaton is an asteroid belt and a gas that has lost a large portion of its atmosphere. Beyond that is a super-Jupiter with over 65 Jupiter-masses that is near the threshold of becoming a brown dwarf. The final planet is an ice giant near the Oort cloud.
**Plausiblity**
How plausible is it that this planet and system could have developed naturally? If it's implausible, what changes would make it more realistic?
My general goal is to create an interesting exoplanet planet that is thoroughly intimidating to biological life but could reasonably be permanently colonized by a robotic civilization with technology that functions best in the -200 - 200 C range, that has access to smart materials, self-repairing buildings, and nanofabrication. Their ideal gravity range is 0g - 2g, but they can function in up to 4g. Colonization would of course be underground.
The important unique aspects of this planet are that it is a chthonian planet with strong UV sunlight and rock storms that will be used for mining. Any suggestions for changes to any other aspects that would make the core aspects more plausible are greatly appreciated.
[Answer]
**The planet**
The radius you have is perfectly fine. It is true that chthonian planets may have masses of 30-100 times that of the Earth, but this is merely because they are extremely dense. [Mocquet et al. (2014)](http://rsta.royalsocietypublishing.org/content/372/2014/20130164) put together mass-radius curves for several different compositions, with the lowest one being iron ([Fig. 1](http://d29qn7q9z0j1p6.cloudfront.net/content/roypta/372/2014/20130164/F1.large.jpg?width=800&height=600&carousel=1)). They then plotted certain planets on the graph, and found several below the iron line limit. I’ve modified it, adding in your planet:
Your planet actually falls on the curve of an ocean planet. It’s nowhere near as dense as most chthonian planets! To be frank, your planet isn’t too small for its mass; it’s way too big. The graph suggests that 1.5 Earth radii would be better.
The models of [Seager et al. (2009)](http://arxiv.org/pdf/0707.2895v1.pdf) support this. I've plotted Hekaton on their Fig. 4, which shows it close to being an ocean planet:
This corresponds to an equation of state characterized by the parameter $n\approx0.513$, which can be used in the authors' mass-radius relation (which I elaborated on [here](https://worldbuilding.stackexchange.com/a/9957/627)).
I’m going to pass on a discussion of the rock storms; that’s way out of my territory. Hopefully, someone else can give that a good treatment. All I’ll say is that I’m quite confused as to how a planet that’s had its atmosphere stripped away can maintain anything resembling an atmosphere.
**The star**
We can estimate the temperature of the planet to a decent extent using the formula for [effective temperature](https://en.wikipedia.org/wiki/Effective_temperature):
$$T=\left( \frac{L(1-a)}{16 \pi \sigma D^2} \right)^{\frac{1}{4}}$$
From a graph [here](http://physics.highpoint.edu/~bbarlow/subdwarfs.html) (originally from Heber (2009)), we can conservatively give an estimate of the star’s luminosity of roughly ten times that of the Sun. Converting its orbital period to a semi-major axis (~1.43 AU, assuming a stellar mass of ~2 solar masses), and plugging in an albedo similar to Earth’s, I get a surface temperature of 389 K, or 109° C. That actually fits your temperature range quite nicely. However, the oceans will boil away, so you won’t have an ocean planet left.
That said, the albedo will be different, because the planet will clearly not be Earth-like, so the results could actually be a lot different. Plus, I didn’t account for an atmosphere. I’ve written about the effects of warming through radiative forcing [here](https://worldbuilding.stackexchange.com/a/40054/627); take a look if you want to play around a bit.
I *suppose* you could have [planetary migration](https://en.wikipedia.org/wiki/Planetary_migration) move the chthonian planet away from the star, but to be frank, it would be hard. You could interact with the terrestrial planets in the inner system, but I would wager that in all likelihood, *they’ll* be the bodies that are scattered. Gas-disk migration won’t work, because the system is old enough that any disk should have dissipated by the time the planet was stripped of its atmosphere. Your best shot might be to try to use tidal effects to increase the semi-major axis, although as [Jackson et al. (2008)](http://arxiv.org/abs/0801.0716) found, this should really decrease the semi-major axis, not increase it.
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**Updates after edits to the question**
Your new concerns are quite simple to address. Tidal locking is certainly possible at 0.6 AU, and [the timescale is easy to calculate](https://en.wikipedia.org/wiki/Tidal_locking#Timescale). However, it may take quite some time; many tidally locked planets are much closer to their stars than this new version of Hekaton is.
Additionally, the atmosphere is fine. The planet has a high enough mass that the escape velocity should be about 30 km/s; according to [this](http://ircamera.as.arizona.edu/astr_250/Lectures/Lec_05sml.htm), conditions are just right to keep a hydrogen envelope, even at the temperatures you're talking about.
[Answer]
The Sun is a yellow dwarf, G2V type star, with surface temp ~ 5700K. A blue giant is of O,B, or A type with surface temperature greater than 10,000K.
Your planet is 1.4 AU from it's star (511 day orbit), let's look at a star with let's say 3 Sun masses.
With Earth's albedo and greenhouse effect numbers, surface temp will be around 538F or 281C. You say the planet has thick atmosphere and thus high greenhouse effect, but "sunlight is very strong" which means low albedo. That will make the planet even hotter.
You can than use this [calculator](http://www.astro.indiana.edu/gsimonel/temperature1.html) and play with mass of the star, the distance of the planet, the albedo and greenhouse effect numbers and see what the resulting surface temperature will be.
Classifications of stars:
[](https://i.stack.imgur.com/WSIpQ.gif)
Detailed info can be found [here](http://www.atlasoftheuniverse.com/startype.html)
I looked at a [list of exoplanetary host stars](https://en.wikipedia.org/wiki/List_of_exoplanetary_host_stars) I found on Wikipedia that lists about a third of detected exoplanets (about 600 out of about 2000) and I don't see any around blue giants. That doesn't mean that they don't exist, probably the Kepler telescope (which is responsible for the vast number of exoplanets discovered) is simply not targeting them as they are fairly rare.
[Answer]
I just did a [quick calculation](http://www.wolframalpha.com/input/?i=(6.674*10%5E-11)*((7.9*5.972*10%5E24)%2F(2.1*6371)%5E2)) using Newton's Law of Universal Gravitation to see whether your planet would actually have the gravity you think it has. An object experiences a force of gravity of 1.76\*10^7 N/kg on your planet. For comparison, an object experiences a force of 9.81 N/kg on Earth.
I recommend playing around with the mass and size of your planet until it has the gravity you want. To check if you've hit the mark, use the Law of Universal Gravitation. It's not 100% accurate, but for something like a planet it will be accurate to more decimal places then you will ever care about.
Of course, you always have the option of just not caring what physics says and doing whatever you want, but in that case I don't see much point in using exact numbers.
Nevermind, my math was wrong. Doing a [correct calculation](http://www.wolframalpha.com/input/?i=(6.674*10%5E-11m%5E3%20kg%5E-1%20s%5E-2)*((7.9*5.972kg*10%5E24)%2F(2.1*6371km)%5E2)) shows that the Newtonian gravity of your planet is 1.79G.
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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.
In many movies we see super heroes creating walls of ice to block explosions and bullets. How realistic is this?
In the Incredibles Frozone shoots ice at a police officer just before he shoots a gun at him and blocks bullet with ice in midair.
How much ice is needed to block a bullet?
What flow rate(volume/time) of ice would Frozone have to shoot to block a bullet midflight?
How fast would the ice need to travel to intercept the bullet?
Are there other side effects?
What else can you do with those capacities to shoot ice?
[Answer]
There have been tests of the stopping power of ice.
Only high power bullets can get through more than 3 feet of solid ice at freezing temperature. If ice is significantly colder than freezing, it is much stronger. Since ice is rarely used as a building material, data on this is relatively scare, but I seem to recall ice was about 5 times are strong at minus forty than it was at freezing.
Frozone seems to use ice that is closer to minus 40 than freezing, so I would assume 1 foot of his ice would stop most bullets.
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I watched the scene with Frozone in the jewelry store multiple times. Frozone freezes the officer first then the gun is fired - presumably when the officer realizes he has been attacked, but before the freeze attack is complete. Flow rates are not really applicable in the sense that water is not flowing from Frozone, he freezing the water out of the air, but apparently needed a small kick-start of water due to his recent escape from the burning building. He only drinks a sip of water, but there is least a gallon of ice shown in the next scene.
In the final battle with the Omnidroid, Frozone produces large quantities of ice, maybe 100-1000 cubic meters at a time. Again, flow rates are meaningless, the water is not coming from Frozone.
The movie shows Frozone using ice for travel by skating on the generated ice, structural material by forming bridges and encasing the Omnidroid, and fire-fighting. Presumably Frozone could just about anything you could image with ice, dropping a wall of ice on somebody, creating ice handcuffs to hold for a few minutes, barricades, freezing vehicles to prevent starting. If Frozone can elect to generate much colder temperature, other uses are possible. Very cold ice is more like granite, very strong and not slippery at all.
For other suggestions re: using your cryokenetic power visit the [Ice Manipulation](http://powerlisting.wikia.com/wiki/Ice_Manipulation) page of the SuperPower Wiki
---
Finding online references for stopping power of ice was surprisingly hard (I kept finding braking distance for cars on ice). I gave up finding a perfect reference, but I did find army testing that included penetration in various densities of snow, [Projectile and Fragment Penetration in Snow and Frozen Soil](http://www.dtic.mil/dtic/tr/fulltext/u2/a025972.pdf). In contains a graph, figure 12 on page 12 of the report that summarizes tests with 5.56mm, 7.62 mm and 50 cal rounds. The trend is consistent, denser (less air) means quicker stopping and even at 50% air all 3 rounds were stopped within 1 meter (39.37 inches). The only solid ice tests I could find online where not careful studies using solid ice. I did not find anything inconsistent with my original 3 foot claim (admittedly from memory). The army data is suggestive that my 3 foot claim likely was pessimistic for the stopping distance in ice. On reflection, my memory may simply be based on the Army study.
I might add that the army is more interested in the the armor afforded by snow than ice, because you can easily shovel (or plow) some snow barricades into existence.
I did some additional research on ice strength at -40 degrees. Found data suggesting that 3 to 5 times harder at -40 is more realistic. Presumably this is due to variations in how the ice was frozen, may be air embedded, whether it was same temperature throughout, etc. as well as different in the type of strength test. E.g.., static vs dynamic load.
BTW, how realistic is this? No, it is not realistic at all. Adding heat at a high rate is not too difficult, removing heat at a high rate is much more difficult. Unless you can pump water and liquid nitrogen (or such-like) in such a way that the nitrogen impacts the water when it reaches the desired location in a manner similar to a set of 3D printers I can't image how you could create the desired effect. Even this would not be as flexible as Frozone. The energy and mass requires would be incredible to produce the large quantities of ice that he uses.
To simply freeze 1 gallon of water that is just above freezing requires a lot of energy. 1 gallon H2O is 3.785 kg at 334 J/g (heat of fusion) is 1.264 MJ. A 4000 pound vehicle travelling at 80 mph has about the same energy. For his larger ice constructs, Frozone would need more energy than a fully fueled Airbus A330-300.
Such energy flows are compatible with a living person? So no, it is not realistic. Any any superpowers realistic?
[Answer]
The mass of ice needed depends on the bullet. The longer the bullet the more ice is needed.
I would not consider the strength of the ice to be high in this situation but it doesn't need to be--you can stop the bullet simply by sapping it's energy pushing aside the ice. You'll pretty much stop it by the time it's deflected as much mass as it's own mass even if the mass doing the deflection has no strength at all. (Observe the effects of bullets in water--they don't go a lot farther than they do in ice. Hollywood aside, you can very easily swim deep enough that you can laugh at people at the surface shooting at you--until you must come up for air.)
In terms of volume you'll need the volume of the bullet times the difference in the densities. As bullets are usually made of very dense material it's obviously several time the volume of the bullet.
What sort of flow rate you need is highly dependent on the geometry. If the bullet is coming right up the emitter you only need to emit the bullet's mass during the flight time of the bullet but if you must do a crossing intercept things get much worse indeed and at close range you'll actually need an emitter velocity exceeding the bullet's velocity (producing a very lethal jet in it's own right.)
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[Question]
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I have an organization that I want to have some kind of HQ without being in a country.
I was reminded of Sealand (Thanks Joel), those platforms off the coast of the UK.
I want something similar, basically a really tall tower in the Atlantic, out in the deep sea.
It obviously can't touch the bottom, but oil platforms just float out there don't they?
How tall/big could a tower get? Is it at all feasible?
I'd like for the this to be as close to reality as possible. It is happening a bit in the future and let's assume they have plenty of money to throw at this. There might even be technologies used for this that are things we've seen in development that might be in use in 10-30 years from now.
The building should support about a thousand people I'd say.
It should have some science labs, tech labs, living accommodations, and so on. The organization is a scientific one. They do a lot of research. Imagine Tesla/SpaceX/Cern. A scientific paradise free from borders. They make money because they've been providing technology to the world. Money is no issue as long as its realistic.
Jurisdiction is irrelevant in this question.
There are many examples of "new" countries starting up or groups outside laws and so on.
The only thing that matters if you want to be independent is that you can defend yourself. In the case of this society they easily can defend themselves and set their own rules without anyone being able to successfully intervene without an unnecessarily large show of force.
[Answer]
**Specifications**
Existing floating rigs and fixed platform rigs hold about the same weight; the heaviest today being the floating [Hibernia](https://en.wikipedia.org/wiki/Hibernia_Gravity_Base_Structure). It can hold 58,000 tons while in operation. With depths in international waters, a floating platform is recommended.
A plain office tower that is 10 stories high would weigh in at about 800 tons for foundation and an additional 100 tons per floor (I was an urban planner - these are high-level numbers, though) **coming to 1,800 tons**, well within Hibernia's capacity for *weight* (not structural integrity). So let's up the ante.
20 Stories will get you 1,600 ton foundation and 2,000 tons for floors. You're now at 3,600 tons. You can further the math.
*But the weight is not the issue. The height is.* After about four floors, you're going to start getting massive issues with wind and waves. With a top-heavy floating tower, you will be bobbing around all over the place.
So instead, I would recommend you flatten out your tower, and have a very wide, four story building, with extra floating 'legs' in the water. Not very sexy, I know. A four story building, weighing 58,000 tons would take up about 360m (1/4mi) x 360m square, allowing for utilities and transportation equipment. This is a nice, large block of space. We consider 350m to be 'walking distance,' for access to facilities in urban planning. You have a four story indoor city.
Bonus, you have a lot of space on the roof for gardens and solar power generation.
**Legality**
The location should be in international waters. While this does not grant you immunity from the law (any illegal action can be prosecuted by any country in international waters, although flag countries' law usually is what it's based on), it does allow some autonomy.
**Location**
Storms are very rough in the Atlantic, so I would recommend you place it just outside Portugal's jurisdiction around [the Azores](https://en.wikipedia.org/wiki/Azores), for some shelter, and access to nearby facilities (air strip), resources (port to bring food in), and emergency evacuations.
**Autonomy**
I'm guessing nobody will really bother you, but you'll have to do a lot if you intend to establish your own country and be legitimized by other states.
EDIT:
**So you want a little bit higher?**
I think you could have stability at 20 storeys now that I've done a little math. A similar 20-story structure could be 280m x 280m, and I think that would be flat enough to hold still in the winds off the Azores. Edge the sides off and onto the top to make a short-fat pyramid, and you can get greater height. /Edit
**What can this hold?**
I don't know what your breakdown of uses are, but either structure size can hold a healthy breakdown (inlcuding the utility, hallways, etc.)of:
* 200 apartments at 85m2 average (tight fit for two scientists or support staff each)
* 5,000m2 of retail/restaurant
* 10,000m2 of office/visiting educational spaces/convention areas
* 10,000m2 of lab
* 3,000m2 of clinic, etc.
* 5,000m2 of major utility/paths between wards/recreational facilities
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The problem with your requirements is that powerful countries make the rules. If your fictional organization is add odds with, say, the United States government, they won't accept that the structure qualifies as a 'sovereign nation' and that's it.
That being said, I think you were thinking of Sealand. The [wikipedia article](https://en.wikipedia.org/wiki/Principality_of_Sealand#Legal_status) talks about the legal problem. Sealand is close to the UK, so the situation will be slightly different in the middle of the Atlantic. Check the [Seasteading](https://en.wikipedia.org/wiki/Seasteading#Legal_issues) article, too.
The next question is the technical one.
* For a credible claim to being an island and not a ship, your structure needs to rest on the ocean floor. That sounds like a [fixed platform](https://en.wikipedia.org/wiki/Fixed_platform) rig, perhaps with rock-filled concrete structures. They can go deep enough today that they might be feasible in the Atlantic 30 years from now.
* A [semi-submersible](https://en.wikipedia.org/wiki/Semi-submersible) rig might be cheaper and possibly even safer, but it looks like a ship.
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There's a ridge that runs along the mid Atlantic. In the north it rises up and becomes Iceland. It also rises out of the water at the Azores. There's an area known as the [Atlantis Massif](https://en.wikipedia.org/wiki/Atlantis_Massif) where the ridge rises to within 3,000 feet of the surface. While it might be expecting too much to build a tower with a 3,000 foot basement, you might have a system of massive anchors and cables to anchor your tower. With the cables attached to huge winches in the basement of the tower, maybe the tower could be kept steady even through a category 5 hurricane or a nightmare rogue wave.
Feasibility would depend on your finances and the available technology. My guess is that the technology is here, but you're going to need a really fat wallet.
Finally, even in the open sea, there is law, known as maritime law, or [Admiralty Law](https://en.wikipedia.org/wiki/Admiralty_law). You might find your sweet tower being demolished as a hazard to navigation.
Maybe the whole thing could be winched down to the sea floor when approached by unfriendlies.
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I will second the notion of avoiding towers.
Beyond that, though--look at the existing work along these lines. A quick Google turns up:
<http://www.seasteading.org/floating-city-project/>
although I have also seen proposals for hexagons.
Basically, you build your city on tiles that consist of big concrete bins turned upside-down. If you want to be able to protect your place against breaking waves the outer layer or two of tiles consists simply of barriers with no habitation on them.
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[Uplifted Animals](http://tvtropes.org/pmwiki/pmwiki.php/Main/UpliftedAnimal) are real in this world. An miracle technology is capable of uplifting an animal to human level intelligence using a non-invasive procedure. Availability of this technology is limited to North America and Europe so far. Maximum intelligence is a function of prior brain complexity. Spiders won't get much smarter though a dolphin or primate may get much much smarter.
Historically, animals have always been considered as property, a belief/practice justified by the lesser intelligence of animals. Now that animals can be made smarter and self-aware, this basic assumption no longer holds. Legal precedent in many countries will need to shift to match what technology can do.
The court cases to decide personhood have not yet been decided, nor any new laws written, so the battles are in the court of public opinion.
*What would be the social pressures to accept uplifted animals as legal persons?*
*What would be the social pressures to deny uplifted animals as legal persons?*
Assumptions:
* Translation devices have been developed for each uplifted species so they may communicate in English. Depending on the species, learning human language approximates the learning speed of a normal human child.
* Uplifted animals have thus far been kept as research subjects.
[Answer]
This would be an incredibly entertaining legal quagmire to watch unfold.
**Pressure for Acceptance**
There is already pressure against confining certain animals (dolphins, chimps, whales, etc) in labs that are perceived to have high intelligence. When one of them gives an interview on CNN, there’s going to be a little more chaos. It’s heartbreaking to see the physical characteristics of confinement and abuse, but to hear an animal describe the experience of being experimented on is going to be difficult for many people. And it’s going to scare a lot of people.
Animal rights activists will have a heyday with this. Seeing animals speak english and have near-human level thought, even with artificially enhanced intelligence, is going to seriously affect the public’s attitudes toward all animals. People will be having some second thoughts about their hamburgers when a firsthand slaughterhouse experience suddenly sounds like Auschwitz. It certainly won’t sway everyone, but the increased empathy for animals will undoubtedly become a driving force for change.
Research opportunities could also be greatly enhanced by giving uplifted animals personhood, returning them to the wild, and observing and cooperating with them. The ocean in particular is far too large for us to adequately study safely. Imagine uplifted sperm whales that could explore the depths or the opportunity to examine what type of complex society dolphins form. Seeing high intelligence in a multitude of species could give us invaluable insight into the nature of intelligence and how physiology affects behavior
**Pressure for Denial**
There are some human beings who, through severe disability or injury, could be said to have even less intelligence than some non uplifted animals. Legally, these people are all still treated as persons (including those born without the capacity for normal intelligence) because personhood is rarely (if ever) about intelligence. It’s about being a human being.
Whether we admit it or not, humans very much like having dominion over planet Earth. Earth is often referred to as *ours*. The impact on human society of uplifted animals, especially in large numbers, could be profound. Almost all animal product industries could be catastrophically impacted. Personhood for uplifted animals is a slippery slope to either treating all non-uplifted animals in the same fashion, or a push to uplift as many animals as possible. These are terrible outcomes for massive and very politically powerful industries across the globe.
Ultimately, I suspect that this would become less about personhood, and more about usage of the uplifting technology. Seeing animals with such a high level of intelligence would scare a lot of people. There would likely be a major push to release the existing uplifted animals from research captivity, but it would be tremendously difficult to decide what to do with them next (how torturous would it be for a dolphin of human intelligence to be the only one of its kind?).
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It depends on what you define as a legal person.
Currently the punishment for animal cruelty is much less than murder. I think uplifted animals will almost immediately be seen as human for the case of being victims of violent crimes. A cute smart doggie should not be a victim.
Likely capital punishments for criminal uplifted animals will remain in place for a long time even if your setting wouldn't otherwise have the death penalty. That is the current procedure for violent animals and it is easy to argue "the procedure didn't take properly". There will be some support for even punishment, however.
There will be an even larger fight against animal-human marriage than with gay marriage (because ew).
Which ever party gains the most by supporting voting rights for animals will heavily argue in favor of it while the other party may fight it.
I essence with all this differentiation, laws will not be exactly the same for an elevated animal and a human. There are minute differences in laws for women and men (usually legal precident concerning paternity, divorce, sexual harrassment, etc.) and we pretty much the same. Between different species of animals there are differences. As a result, expect large protests fighting for these rights and a more silent majority against these changes. Expect that all species will eventually be viewed slightly differently under the laws based on intellegence potential, physical ability, and population. Insects will never be able to get an equal right to vote (can't ever be 18 anyways) while the voting age for dogs will drop to 2.5 human years (18 dog years).
Final note: if a completely new country forms after this change with large enough populations of each uplifted species, you can expect voters to be represented by species in a simular way to how they are by state in the united states. Cats can decide their own appropriate voting age but their alloted number of seats in congress will be decided by some combination of total population, potential intellegence, and lifespan.
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In medieval times, people possessed a muscular and flexible tail that is capable of manipulating objects. Everyone (regardless of race) is born with one such tail, and the tail can hold weight as heavy as 12kg for a short period of times - usually 5 minutes. A severed tail won't grow back and on average these tails is approximately 1.2m to 1.5m long with thickness roughly size of a thumb.
My questions are;
* How would the medieval battles fought out if everyone have fully
prehensile tail?
* Will there be a set of weapons specifically
tailored to tail?
* Or is the tail in the way?
Comment below if you have any doubt.
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Tail would cause some troubles: should the tail be armored or not? If yes, there should be a hole in the armor for it and the entrance should be well armored so it won't be easily cut off. This would decrease it's dexterity, as the armor has it's weight and is not flexible.
Because of a tail, humans would balance their body weight in a different way, probably using the tail itself, which also has it's weight, so sudden lost of a tail, or having some part of it cut off, wouldn't be something you wouldn't care of.
If we decided not to cover the tail, it becomes vulnerable and if you fall on your back, which happens pretty often during a fight, you may crush it or break it (your body + body armor + force of impact), as it's not very thick.
The most common use of the tail would be in hand-to-hand combat. Maybe it could be use by archers, but I can't really see how (passing the arrows?).
Since the tail is about 1,5m and starting from the top of our butt, it's potential reach while attacking an enemy in front of you would be slightly longer than your arms reach. Any slashes wouldn't be practical, because it's very light and not that strong + oppontents have armor.
Since the tail would be used to balance the body, it should be used in brief, quick attacks, so attaching a blade and using the tail as a sting would be possible. Main problem would be how to attach the blade to the top of the tail (if it's armored it wouldn't be much problem though).
I'm not sure how your humans would use the tail for balance, but let's assume **not** using it would be difficult to move around. There isn't much space in the battlefield when two opposing armies clash, so this could cause balancing problems.
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(1) One use of an armed tail is to ward off people behind you. The problem is that you can't see them. If mirrors have been invented, I suppose you could have wing-mirrors but it would be difficult to focus in all directions at once. Maybe the best tactic would be to swish your weaponed tail back and forth rapidly. The problem with that is that you might slash a friend that was standing behind you. They would have to shout to alert you of their presence - not always audible in pitched battle.
(2) The main advantage would be in forested areas. You could hang from branches and slash at ground foes with your hands. This is fine if you are fighting a race that doesn't have tails but it's cancelled out if everyone does.
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This answer is going to focus mainly on fighting with the tail.
The first thing you need to realize is that while your tail *can* grasp objects, and seems to be pretty flexible, it's probably not the best extremity you have available to hold your weapon. It won't have as solid a grip like a hand, (probably can't even wear a glove), and probably doesn't have the leverage and strength of an arm.
Thus, the tail won't be holding a sword or shield, but it would be a mistake to give it nothing to do. I imagine using flail-like weapons to take full advantage of the tail's length. The soldier would wind up their tail, then swing it 'round as fast as they can, delivering a massive blow to the side of their foe. This tactic has some good points- it'll be unexpected since it comes from behind the soldier's body, and it may have the range to get around the enemy's shield- but it will also come with its downsides, mainly that if the enemy is expecting it, they can either cut off your tail, or worse, pull on your tail, swinging you around and opening up your back for a kill shot. That's why any attacks by the tail should be quick, and infrequent. They'll be used for surprise attacks, to make an opening for the main weapon.
Another benefit is balance. Normally, humans have two feet upon which to balance their weight; adding a tail into the mix will give them many more options. For instance, a soldier could lean further back using the tail for balance, and thus evade more attacks. Similarly, a soldier could use their tail to spring further forward, perhaps hitting an enemy that would have evaded them without this advantage. More general moves can be aided using the tail as a counterweight. The end result of this is that battles should involve more movement and agility, as soldiers dodge back and forth.
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Working off the following ideas:
* A tail is an extension of the vertebra, and not mounted in a socket. So it can't swivel very efficiently to protect your sides, or hit something to the side.
* Whatever you hold in your tail, therefore, is not something you can employ in your field of vision the way you do with a sword.
* The tail can actually be a massive liability. Someone can easily sneak up on you and hack into it without you noticing.
I would suggest that the tail would be well armored. So well, indeed, that it might use up the 12kg weight budget. If any is left over, it should probably be used to attach a shield. This lets you put an additional layer of armor about a meter away from your back, which should be handy to block arrows.
If the top of the shield is sharpened and strengthened, the warrior can, if necessary swing the tail over his head as an emergency melee weapon. If the opponent doesn't have a tail, the battle is suddenly no longer symmetrical.
If the warrior is fighting multiple people at once, from different directions, he can incorporate a swing with the tail into a quick turn, to keep everybody at a distance.
I can't think of many animals that use their tails defensively (the Ankylosaurus is the only one that comes to mind). This is probably because a the more mobile it is, the more vulnerable it is.
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A tail would be useful as a trip weapon. Grab your opponent around the ankle and pull. The problem is that they are trying to do the same to you - you may end up tail-wrestling at the same time that you are fighting conventionally.
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Maybe use a small spear weapon for lightly armored enemies or a short whip like thing. Chain mail would be ideal for protecting it. Battle would also be very confusing, because now you have three "arms" to fight with. Kevlar would also be very useful, although they did not develop that until the late twentieth century.
[Answer]
**Think of fighting a 3 armed opponent**
[This video](https://www.youtube.com/watch?v=xFiIDl_mt2c) shows a father and son fighting as the Vikings did. Their style is usually to attempt to get around the shield and armor. If they were fighting opponents with heavier armor, I would think the goal would be to stab through joints in the armor, such as under the arm.
I would argue that the ability to pull away your opponents arms from their body would be a great strategy to open their front for attack. A tail armored with chain mail could aid greatly in this, if it had appropriate strength.
* When your opponent raises their arm to strike, anchor your tail to their neck and push against their inner arm.
* Use your off hand to pry away their shield.
* Stab through their open defenses.
This is only one way of course. You're introducing an entirely new fighting element to the human body, which is already capable of hundreds of fighting styles, and endless counters, and counters to those counters...
[Answer]
### Forget direct tail attacks - think about what it will mean for kicking.
A tail is not a very effective weapon for a biped. It's positioned behind you where you can't see it, and it isn't good at gripping compared to a hand. While you might be able to attach spiked or bladed armor to it and use it as a slashing weapon, you can't get very good leverage from it without exposing your back to the enemy, which is a big no-no in serious combat.
But that doesn't mean it's useless - a tail can be used for balancing and even brace the body against the ground. Depending on how strong and thick the tail is, it can even function as a "third leg" of sorts, which adds all kinds of possibilities for *kicking*. Kangaroos, for example, often spring up onto their tail to deliver a powerful kick with both feet at once. Maybe these prehensile tails are not strong enough to support the entire body in that way, but they can still be of use.
Kicking was an important part of medieval armored fighting. When both you and your enemy are basically heavy tin cans with a few tiny weak points (the eye-slit, generally), forcing your opponent to stumble and lower their guard or even knocking them onto their back is going to be a major part of claiming victory, and a kick is a good, solid way of delivering kinetic energy to a foe's body. Add a third leg to the mix, and you wind up with expanded options for both offense and defense. A tail on the ground can catch you when you stumble backwards or maintain balance when using a leg to attack. A tail might make more complex kicks and sweeps viable for heavy armored fighters - your knights might employ a sort of "3-legged judo" to try and knock opponents over in battle. An injured tail will represent a major handicap.
[Answer]
warriors could grip knives, short spears, and even arrows in their tails.Could be used to finish off enemy after shield lock and sword lock.Weighted modules could be put on a solider's tail to be used as a club.
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I would like to make a magic system that follows the laws of conservation of energy, making it so that you can use magic to do something that you can do physically, like lift things, as well as do things that you normally couldn't, like boil water or start fire. What I want to know is:
1. How much caloric energy can an average human put out?
2. What determines this number?
3. What other source(s) of energy could be used in a magical reaction?
[Answer]
Just look up what you can burn with sports; that should be about how much energy the body can provide. For example, looking at [this link](http://www.brianmac.co.uk/energyexp.htm) I get that by running you can burn up to 22 calories per minute (however that table may not be complete). Therefore the body should be able to provide those 22 calories per minute. However since the calories burnt depend on body weight, the calories that can be provided may depend on it, too. It might also depend on your training status; information sites targeted at professional athletes might also be a good source of information.
Note that at the end of the linked site there's a calculator where you can calculate the energy you burn for different types of sports depending on your weight. This should give you a good feeling about the available energy.
You'll also have to define how efficient the energy transfer from the body to magic is (that is, how much of the energy you draw from your body actually ends up in the magic). For example, the muscles are not too efficient for converting energy into work (according to [Wikipedia](https://en.wikipedia.org/wiki/Muscle#Efficiency) between 18% and 26%); a lot of the energy you put into them ends up as heat, which is why you sweat when you do sports. So if you assume a similar efficiency for magic, the 22 calories figure above will only amount to between 5 and 6 calories available for magic.
If using body energy for magic also causes waste heat, then it might well be that the ability to get that waste heat out of your body is the limiting factor. That might even mean that a magician can do more magic in cold climate.
[Answer]
A person typically burns 2000-2500 calories in a day, hence why most doctors recommend eating 2000 calories a day to sustain current weight.
What determines this number is a mix of daily activity and the metabolism/metabolic rate of that person. So in theory a person with a high metabolism would require more nourishment than average when using magic because that would increase their calorie burn.
In your world, where magic requires caloric output as opposed to mana or chakra or qi like in other worlds, the body would self cannibalize if they didn't have enough fat to produce energy and the body would start eating away at muscle mass to sustain magic without adequate fat reserves.
[Answer]
The other answers are about the chemical energy used by the body. The only restriction was conservation of energy, why limit yourself to chemical energy? This is magic!
[Your typical 65 kg human contains about 6e18 J](http://www.wolframalpha.com/input/?i=65%20kg%20*%20c%5E2) or about the amount of energy the Earth receives from the Sun in 30 seconds or about a [1500 megaton explosion](http://www.wolframalpha.com/input/?i=1500+megaton+nuclear+explosion). How much magical power you desire is up to how much of yourself you're willing to convert into energy.
A limit on magic user's power output, aside from disintegrating themselves, could be the waste heat generated. They could literally cook themselves from the inside out. High power levels could also produce harmful radiation which would damage their health. Safe magic would be learning to use unimportant parts of the body (ie. fat) and to channel the resulting energy safely.
[Answer]
I like @Schwern's approach, but I think it makes magic users too powerful if they can convert any quantity of matter directly into energy. Instead, let's stick with you're original question about *caloric* energy.
A quick [google search](https://www.google.com/search?q=calories%20in%20a%20steak) suggests there are about 679 calories in 251g of steak (or about 2700 calories per kg). Assuming the caloric density of human body tissue is about the same per-pound as a steak, then @Schwern's 65kg person contains about 176K calories of energy. 1 kCal = 4200 J: if a person sacrificed themselves for a spell, they'd have about 740 kJ of energy to work with. A good microwave oven operates at about 1000 W, or 1 kJ/s, so 740 kJ would be enough to power a microwave for about 12 minutes. Assuming your magic practitioner's don't plan to consume themselves completely, the magical exchange rate is about .011 J/g. Sacrificing a pinky (~100g) could power a 65 W lightbulb for about 1.5 min.
Where @Schwern's system is overpowered, my variant is probably too weak. Hopefully this analysis will help you come up with some kind of happy medium.
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[Question]
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# My pirates need to maximize profit from their illegal horse racing activities
But the horses are not normal, they are machines. You can ride on top with difficulty, and it may slow them down. So gamblers want excitement and lots of opportunities to bet. What race format suits these machines and the greedy gamblers best?
**Environment:**
A volcanic waste world with average temperatures over 800°F temperatures inhabited by British settlers 200 years ago has a pirate enclave engaged in horse racing (and playing the numbers, obviously). A particular genius has figured out reliable and durable articulating joints for knees, ankles, shoulders, etc., so they make steam-turbine powered gyro-stabilized horses to quickly cover the rugged terrain. They have no rubber that can survive the surface, so legs are the best mobility option. Competition for best design improvements have led to horse racing. Horse designers and inventors all try their improvement ideas at the track. People wear environment suits outside.
## Fuel and engines
The fuel for the society, and the horses, is called Negatite. This derives from an ore that is crushed down into a fine powder and processed with nitric acid to form the oily negatite fluid. When negatite is exposed to the outside air, it undergoes an extreme endothermic reaction, cooling down quickly to form a crystalline gell. Steam engines pump negatite into cooling tubes in the turbine condensers, drawing steam through the blades and condensing it back to water. Environment suits use negatite to cool their occupants and to run oxygen generators in the suits.
This all is important because unlike steam engines on cool worlds, the heat is the ambient atmosphere. Instead of having a steam generator, water is run through pipes along the ribcage of the horse. This brings the water to a boil to drive the turbine. All engines in the world gain heat with external piping, in fact. Turbines link to a pump which pressurizes the hydraulic tanks, and hydraulic fluid operates all mechanical apparatuses.
## The horse design
The horse is well articulated in shoulders, haunches, and the neck. Strong pins in the hooves are linked to plungers which close a small vacuum line as the hoof meets a solid surface. This signals a valve to put pressure on that leg, in the correct proportion determined by the 6-axis gyroscopes. Legs get the correct pressure to keep them running level, or, in the case that the horse needs to turn; slightly off-level. All this works together so the horse can run over fairly rough terrain without slowing down. Statistics are this:
* ### History
- Vast expanses of rugged volcanic plains and craggy desert separate ore deposits where cities formed. Before the first railroad went up, wheel bearings were impractical as they were too difficult to seal and keep lubricated in the intense heat. An articulated joint with no more than 20° range of motion became the most durable way to attach any articulated machinery extensions or limbs without exposing them to the elements, because the entire joint can be shielded and kept pressurized to prevent any sand or debris from entering. No suitable material existed to form durable axle dust covers at these temperatures. Thus a legged transportation made the most sense. The design needed a long stride to reduce the number of steps taken, and thereby reducing the wear on the joints. A tall stature allowed the vehicle to cross narrow crags or other obstacles, and the vehicle also should not be limited to staying on the ground. A vehicle which could jump over small boulders and evorsions if needed made transits much quicker, where wheels lacked the articulation to climb anything larger than half their height, and easily get stuck in holes. With precision gyroscopes perfected by brilliant machinists, the form of a horse made the most sense.
* ### Specifications:
Horses have been developed for many different applications, from heavy load hauling of ore wagons along makeshift mining roads, to rapid messenger transport "roadster" models with lighter frames and fast terrain response. Some models can be ridden on in an environment suit but straddling any horse powerful enough to carry a load would be a stretch because they are too wide for most to get legs around. Desert sleds on runners are common to be hauled behind a horse on an extended trip, where extra negatite can be carried, and any cargo the trip may need. Passenger dessert sleighs are also common, which can be fully enclosed and climate controlled. Once at a gallop, a horse can run very efficiently, as legs and stride are harmonically tuned to a specific speed. Some horses have adjustments for variable resonant speed, and these are generally very expensive and prone to problems.
* ### Racing:
Legitimate horse racing evolved to pit designs against each other, generally placing them in the natural environment where they would be operated. Winning promotes the best engineering and designs, and results in a great demand for your horses. Those courses generally run two hours with several laps around a natural course. Betting also brings in prize money for the winners, and promotes the sport. The gambling aspect of horse racing appeals to clans of outlaws living in the badlands in hobbled-together villages, where a small ore deposit may have been found. The promote their illegal events through an underground network, and high-profile people often secretly sponsor racers to compete in these events for a chance at large gains. Unlike the regulated sport, these races are "win at all costs," with the promise of some radical new advancement which they can patent and exploit to the public.
* **This question is asking help with the format for $\underline{ \textbf{illegitimate}}$, unregulated horse racing**
## The problem
There are many challenges to these horses. The horse's ribcage needs access to lots of heat. The horse doesn't have a large onboard fuel capacity due to all the complex machinery. Whoever is controlling the horse should have a good vantage point as the horse can't see, it goes or stops according to the commands of the operator. Many cities run races, but the particular race in this question is operated illegally at the pirate enclave, and is inherently quite dangerous, but by the same token, quite profitable if you win.
## Question:
## What format of horse racing would bring the best competitor opportunity, spectator excitement, and allow the maximum "house" profitability?
Base them on existing terrestrial race formats, such as harness, chariot, flat, endurance, etc. The track obviously wants a race that can guarantee a house win, or rig without too much trouble when needed. It's about control, and creating the illusion of high-stakes sports gambling.
[Answer]
I say go for tried and tested successes among hardcore gamblers.
So: Chariots. The Romans gambled on them for centuries, they're amenable to novelty races (like battles), they're amenable to rigging, and there's umpteen variations on them. They can be adapted from commercial carts too which allows any desperate young man to try his luck in a low grade race. It allows two or more characters to share a chariot which may be useful for plot or character development.
Detailed Roman chariot racing conventions are still well known and can be lifted wholesale while still seeming inventive to your readers. You could even lift some of their vocabulary / racing jargon, throw in a few references to Hades or Tartarus or Avernus or Styx and there's a coherent hell-racing 'feel' created with minimal work. Classics fans would realise that you're lifting material from the Romans but wouldn't consider it stealing and would actually like it.
See:
<https://www.quia.com/jg/274234list.html>,
<http://vroma.org/vromans/bmcmanus/circus.html>
Wikipedia's chariot racing article
Some other ideas:
You could have legged chariots that are powered by hydraulics supplied by the horse (with a vulnerable, exposed supply line and coupling which makes for easy plot devices).
Either that or stick jaws on the 'horses' and replicate greyhound racing, but with huge robotic greyhounds. Make it a chase. Think of a spectrum with simple robotic rabbit running in a line at one end and Harry Potter's Golden Snitch at the other and pick a 'rabbit' with the predictability you desire.
If we're going for maximum fun, put the tracks indoors in an iron sphere and give the horses magnetic hooves, to create a 360 degree, three axis viewing spectacular. Jockey stuffs up? He falls 50m to his death. Also, as it's indoors, it's more private. A big bowl is less spectacular but provides some of the spectacle and is more practical.
[Answer]
**Straight Line (Maybe a Loop)**
[](https://i.stack.imgur.com/0SamZ.png)
On Earth, most commercial horse racing happens on a straight track without obstacles. Sometimes the track is a loop to save space. Most races take a few minutes or less. Long enough to be exciting , short enough to fit dozens of races (opportunities to make a bet) each day. The short track also makes it easier to maintain and film the races.
Some fancier places have movable jumps for the horses to jump over. Some VERY Fancy places have unmoveable jumps like hedges and pools of water for the horses to jump over.
The difference in your world is that every part of the race is more expensive to host. The horses are more expensive. The horse food (fuel) is more expensive. Going outside is dangerous (and more expensive).
This will encourage simplicity in the races. Like commercial meat horse races, they will be straight lines or loops and only last a few minutes. The interesting question is can you possibly make the races any simpler than that?
Perhaps the ground is slightly bumpy to add the excitement of a horse falling over during the race, and make the track easier to maintain.
Or perhaps the track is perfectly flat, like a racing car track, and the different horses are sponsored by motoring companies?
**Note:** Rigging these races is easier than with meat horses, since you can secretly implant a subroutine inside each horse that tells it to win or lose the race. You can do this without the jockeys knowing. You cannot do this with real horses.
[Answer]
You want racing robots and you want the races to be illegal. This answer is inspired by a somewhat short-lived post-Soviet TV show from the 90s, where rally drivers and stuntmen from film industry showed off.
# Survival races
It's your normal race (loop or whatever), but the robotic race participants are not only not forbidden, but *encouraged* to attack each other. No weapons, but a lot of bumping, conspiring participants, and (more or less) spectacular wrecks. A crash is not a stop of the race, nor a reason not to continue. Who comes first, wins, sure. But there might be a consolation price for a most spectacular crash or best morale.
Make them fully robotic, with human drivers (but mostly safe, because they know, what they are doing), or full gladiator fight, depending on how bloodthirsty the audience is.
The whole thing is illegal either because humans are involved (duh), or because even robots fighting in a battle royal are not the best thing from the moral standpoint. Also, because of gambling, but that holds for any kind of races.
[Answer]
1)As for the position of the jockey- why don't give them a capsule IN the horse. Right where a normal horses head would be sits the jockey.
Otherwise this could be a good question for the engineers - how to reduce energy loss? Easies thing would be an enlarged surface, so maybe have people sit on high saddles that keep the jockey's legs off the heating coils but store heat themselves? Or even have the jockeys' suits heat up from the outside (with protective material on the inside).
2. The challenge of making the horse as hot as possible also gives room to risky technology that would be forbidden in a legal race. Similar to tuned cars security measures are disabled or removed, rocket start style Negatide explosions are utilized to give the horse an extra kick, materials are as light and thin as possible, making horses less stable and more prone to accidents with severe consequences.
3. There are very little rules, risky and unfair maneuvers are the standard. The biggest heroes are the one pulling the boldest and relentless stunts. There are bets not only on who wins but also on who crashes first and on how many jockeys are dead in the end.
4. a straight course is not quite risky and exciting enough. I'd also not go for long races of over two hours but rather short course elimination races-who wins the race goes to the next round. Races take about ten minutes and are very fast. From the prelims, the fastest racers go to semi-finals and then there is the big final.
5. For the spectators it would be coolest to see the racers the whole time, so a velodrome type of arena would be cool (it would also make more sense for the multiple round system and add some sensation due to limited space - more action going on, more crashes going on). I'm thinking if it would work with natural (or natural looking) obstacles - rocks, erupting mini vulcanos, attacking wild animals- it's a wild ride video game style, you never know what will happen next, not only does the favorite of the race have to deal with his biggest rival trying to push him off the track, now they also get attacked by a bunch of robo-bats.
6. the obstacles aren't all so random. Sometimes the mini vulcano will errupt just right to eliminate one of the competitors and if you look really close the robo-bats will only ever damage jockey A's horse, but jockey B they finish. Along with technical manipulation of the horses that's a great way to have the most exciting and unpredictable race that's actually nothing but a farce.
7. the only issue with the velodrome of course is that it's hard to keep secret, races being illegal. On the other hand most commercial, spectator friendly races would have to be. But maybe there is some big natural crate that's sort of secluded and not very well known that can be turned into that boiling pot style racing arena.
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[Question]
[
Let's say one had a giant insect the size of a sheep or a cow that some sapient species was raising as meat livestock. These animals would have to be butchered to be eaten and cannot simply be eaten whole like people eat shrimp, crayfish, and insects in the real world. Ignore the whole issue of a cow-sized insect being unable to physically function due to the square-cubed law for the sake of argument, this is akin to any number of fantasy settings where there are insect megafauna running around. However, the anatomy of an insect is very different from a vertebrate, and many of the limb muscles that in vertebrates would make for good cuts of meat are not very large in arthropods.
Given all this, **if someone was trying to butcher a giant insect for food, where would the best cuts of meat be?** Would the hind legs be a good source of muscle if the insect were a giant grasshopper or cricket, or would they be too stringy and elastic due to their role in jumping? Would flight muscles be a large, easily butcherable muscle if the insect had wings due to taking up much of the thorax?
The best I have been able to find out is that the jaw muscles of a giant insect might be a particularly large cut of meat that would be worth harvesting. Apparently in fungi that parasitize ants the fungi feed on the jaw muscles of the ant, rather than eating at the brain, because the ant's jaw muscles are so large they are the single largest and most nutritious organ in the head.
[Answer]
# Abdomen in general
In my culture people like to eat weaver ants. They eat the abdomen and discard the rest.
In America there are honeypot ants. Some workers are sessile and have giant abdomens - which is also what people go for.
And for cultures that eat termites, a queen's abdomen is the best part.
In the abdomen you will find the most fat and water in the beast. The gonads are also there for lots of protein. Legs and thorax may have more muscle (so more protein) but I imagine it would be hard to chew.
[Answer]
Crabs are not insects, but in Japan giant crab legs are a delicacy, and if you look at them they are not that visually different from insect legs.
[](https://i.stack.imgur.com/WrTaj.jpg)
Just as with chicken wings or spare ribs, it's not always the amount of flesh to make it appreciated, at least in cultures where eating flesh is a common experience.
A hunter-gatherer culture would surely regards ribs or wings as poor parts.
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[Question]
[
I'm currently building a world for a medieval based D&D campaign (i know super original) and I'm trying to make my cities as realistic as i can. Right now I'm planning on making a city in the middle of a large empire with roughly 100.000 people living there. But now comes the question of how big would this city be? what would be a reasonable population density and size of the city?
Currently i made the city have a rough area of 13.5 km2, which would come to a population density of ~7400 people/km2. This seems really high to me, so it would be great to get some confirmation about if this a good amount or if i should make the city bigger to get the pop. density to a more realistic level.
It would also be great if you could give a reasonable estimate density for large cities like Rome and Alexandria. And also smaller cities like Florence and Trier.
[Answer]
Medieval cities were quite densly populated.
Munich i.e had about 13,000 inhabitants on a area of 91ha according to Wikipedia.
This gives a density of about 14.000 people/km^2.
Cologne had an area of 401 ha, also according to Wikipedia with a Population of up to 50,000 people. This makes a density of 12,000 people/km^2. And as far as I know the cities walls surrounded an area that was actually to large for the population which lead to empty areas within the walls.
Now, the largest European medieval city was Constantinople. The Theodosian Wall enclosed about 12km^2. At it's maximum the city housed about 400,000 people but here the walls also were extremly overdimensioned. But we reach a density of incredible 33,000 people/km^2.
So your city is definitly not to dense.
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[
It's become a popular speculative evolution trope for the likeliest candidate of the mythological "wyvern" to be a Cenozoic family--if not **super**family--of scansoriopterygid dinosaur.
Now the first thing you'd be wondering is, "scanso-WHAT?" and I won't blame you. The name is not as memorable or catchy as "Pachycephalosauridae". So the "wyvern family", as I've decided to call it, was a group of small, arboreal theropod dinosaurs known in only the past decade or so for going around with batlike wings, demonstrated in this gorgeous portrait of *Yi* by Emily Willoughby:
[](https://i.stack.imgur.com/FFyeG.jpg)
But there is a problem with this family, one that has been criminally overlooked and frustratingly unanswered--the wyvern family, in our timeline, was hardly successful. Only four species have been unearthed from Chinese rocks, and their legacy was unnoticeable, existing from 165 to 156 million years ago. This is a big deal because the family died out at a relatively quiet point in the Late Jurassic period, rather than a sudden, dramatic catastrophe like the one that paved the way for the dinosaur empire 45 million years earlier or the one that'd end it 90 million years later.
While other people have been asking on how to make the Cenozoic wyverns biologically and physiologically plausible, mine is on how to make them chronologically successful. As in, **what *point of departure* would I need to ensure that the wyvern family made it to the Cretaceous, survived the fall of the dinosaur empire, endured the unrelenting climate changes of the Paleogene and Neogene and thrived long enough for the knights in shining armor to fight them off?**
[Answer]
**Refuge.**
As requested in the OP, the scansoriopterygids must survive extinction in the Jurassic, survive the extinction of the dinosaurs, and then avoid being outcompeted by birds and mammals. Let us assume that in our world, scansoriopterygids were outcompeted by creatures much like themselves - the protobirds, tree dwelling dinosaurs whose descendants survived the cretaceous extinction and today successfully compete with mammals.
Is there a precedent we can look too? Is there a group of animals which narrowly escaped being outcompeted by physically similar contemporaries in the Jurassic, survived the Cretaceous extinction and have made it to the present day despite the advent of rats and crows? Yes: the Rhynchocephalia.
[Rhynchocephalia](https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/rhynchocephalia)
>
> Rhynchocephalians (Sphenodontids)
>
>
> Rhynchocephalians as a group are considered the sister taxon to
> squamates, and, together, they comprise the Lepidosauria. . Based on the
> assumption that rhynchocephalians and squamates are each other’s
> closest relatives, they apparently diverged early in the Late
> Triassic, and the rhynchocephalians seemingly have always been a group
> with moderate or low diversity... Most of the rhynchocephalian radiation
> occurred during the Triassic
> and Jurassic, and by the Cretaceous, most had disappeared from the
> fossil record, suggesting that lizards may have outcompeted them.
>
>
>
There is one rhynchocephalian that still exists: the [tuatara](https://en.wikipedia.org/wiki/Tuatara).
[](https://i.stack.imgur.com/eyrD8.jpg)
The refuge of the tuatara is New Zealand, which split off from the mainland 83 millions years ago. It was never colonized by mammals or snakes, and of lizards has only geckos and skinks. The tuatara survived the Cretaceous extinction presumably the same way lizards did: it hid in burrows until things cooled off. Then in its island refuge, it was not outcompeted by its close relatives the snakes and varanid lizards, or more distant relatives the mammals.
I propose a similar outcome for the scansoriopterygids. In this alternate earth, they too had colonized Zealandia in the early Jurassic and this population was spared competition with the protobirds and ultimate extinction. They too survive the Cretaceous extinction by hiding in burrows and hollow logs.
But unlike the tuataras, the scansoriopterygids are predators. After the Cretaceous extinction the scansoriopterygids on Zealandia have a shot at becoming apex predators. On other islands without competition from mammal predators, varanid lizards became large apex predators: the Komodo dragons.
Like the Komodo dragons on their own island refuge, the wyverns do very well, preying on the moas which come to be the main terrestrial herbivore on Zealand. Wyverns are fair fliers at best, but glide well and mating rituals among the largest species entail towering high flying rituals with males and females. It is during one of these rituals that a storm catches and blows several individuals to the Australian mainland.
Here they thrive, facing no real competition from large predators. It is only a matter of time before wyverns then disperse north out of Australia to New Guinea, Southeast Asia, and the rest of the world.
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[
The year is 2100. While climate change has wrought serious damage to the biosphere, humanity has at last managed to become carbon neutral, and has even developed technology that can be used to reduce the level of carbon in the atmosphere. This has the effect of allowing humanity to set the thermostat, as it were, for the average temperature of the Earth.
Supposing that most of the world will be fed with farming practices similar in nature to what exist today, and that cities and habitation patterns will be built in a similar manner (i.e. not megastructures), what's the optimum temperature for Earth? If humans can control our average temperature, are looking to make the globe as habitable as possible, and aren't overly worried about further damage to the biosphere (because it's already been thoroughly wrecked), how warm would we want the Earth to be?
Climate control in 2100 can only affect the average temperature of the Earth. The gradient of temperatures from the equator to the poles will otherwise settle naturally, and any extreme weather that we'd expect to "naturally" form at a given temperature will be unimpeded. Furthermore, the governments of the future are open to helping populations move about the globe: the goal is to make the Earth, as a whole, as habitable as possible, without regards to maintaining or increasing food production in current population centers.
[Answer]
## **Frame challenge: a reset to normal would make the Earth most habitable.**
The question asserts that future humans:
>
> aren't overly worried about further damage to the biosphere (because it's already been thoroughly wrecked)
>
>
>
However, 80 years is not **nearly** enough time to destroy even 10% of global species. According to the [WWF](https://wwf.panda.org/our_work/biodiversity/biodiversity/), "between 0.01 and 0.1% of all species will become extinct each year." If we assume a worst-case-scenario of 0.1% extinction per year, we'll still have 92% of today's species by 2100. That's terrible, but still minimal enough to make saving what's left worthwhile.
After all, further damage to the biosphere [would](https://www.who.int/globalchange/ecosystems/biodiversity/en/) **directly cause damage to humans**.
* Loss of biodiversity threatens the very agriculture that increasing temperatures is intended to promote, because diversity keeps soils productive.
* Biodiversity ensures that adequate nutrients are available in different geographic regions, so killing more species might feed wealthy agrarian countries, but it would starve less developed ones.
* Increasing temperature changes the movement of disease vectors. As climate change progresses, we are seeing a plethora of new diseases (and old diseases in newly-warm places) even today.
Not to mention the other physical effects of injecting more energy into the Earth's atmosphere / hydrosphere:
* More tropical storms
* More floods
* More droughts
* More forest fires
These events are not only deadly, but expensive. They would threaten humanity as it expanded; less efficient soils, scarcer nutrients, worse weather, and worse diseases would combine to yield no net benefit.
Furthermore, the assertion that increasing temperatures would yield more productive land is inherently flawed. A warmer Earth may mean hospitable poles - but it would also mean **far less land near coasts**, as well as **inhospitably hot land near the equator**. I will concede that the poles are warming faster than the equator, so you might see a minimal net gain in arable land, but sea level rise may reverse even that. You would be better off engineering plants to live in salty soils or hard permafrost than to disturb ecosystems that have been stable for millions of years.
The bottom line is, we have largely only seen negative environmental impacts since the beginning of human-driven climate change. If humans are offered the technology to fix the Earth's climate in 2100 - at which point the ecosystem **will still be salvageable** - they will begin the process of rebuilding instead of worsening the damage.
**TL;DR** The optimum temperature of Earth for humans is the one we evolved with, because we are dependent on the ecosystems around us.
[Answer]
**Around 14.4o Celsius**
Looking through a massive amount of data before typing this up, there are a lot of details that come to hand and the one thing it is fair to say is that crop yields are increasing as the years progress. This is only partly related to temperature; better fertilisers, farming practices and the like are having a massive effect on how much food you can pull out of a given portion of land.
If you take a look at [this site](https://ourworldindata.org/crop-yields) you gt a very good description of what has been going on since around 1950 in terms of food production per hectare, and it's clear we're better at getting food out of land. If you do a search on largest agricultural countries, you get countries like China, India, the Netherlands, and USA - looking at this one might infer that you actually want a cold climate generally speaking in that all but India in this group sits around the 6-10 degree C average temp range. That's quite cold. But, India is an outlier, with nearly 24o C as an average temp. The trouble with these figures is that these countries are doing more farming, not necessarily getting better crop yields and the sheer force of numbers in terms of population (and a lot of land to use) means that they are going to do quite well in the food production stakes.
Ultimately, you have 3 factors to consider;
. Human comfort / survival
. Crop comfort / survival
. Extreme Weather Events
If you can control the temperature globally, you can probably prevent or at least drastically mitigate extreme weather events, so that becomes a non-issue. Plants as a general rule are hardier than humans in that trees can grow in temps hotter than we find easy to survive in, provided there is also a lot of rainfall. That means, that if the temp you set globally is comfortable to us, then it's probably comfortable for the crops we want to grow, meaning we are the most fragile factor.
So; you want to set a global average temperature, and let the variance between the equator and the poles sort itself out? Well, let's look at what the average temperature is across the world today, and it's not very high.
Looking at [this site](https://www.theworldcounts.com/stories/Temperature-Change-Over-the-Last-100-Years), you can see that the average global temp is around 14.8o C today, and was 14o C back in 1880 according to our records. While it doesn't sound like much, that small variance in temp has had significant environmental impacts, but then we are able to pull more crops out of less land today despite this.
So, let's split the difference; let's call it 14.4o C as a static global temperature, but don't let it end just there. You also have to make sure there is regular rainfall and a host of other environmental factors are preserved in order to maintain your artificial utopia. But, if you keep the temp at around that 14 and a half degrees C, you should be fine.
[Answer]
Looking at the historical record, during the European Warm Period (roughly 1000-1400 AD), Vikings had croft farms on Greenland, England was a wine growing nation and the European population was rising according to preserved parish records and so on. Since it is currently too cold to raise grapes in England or have croft farms in Greenland, we can safely conclude that the Earth's average temperature should be between 2-5 degrees warmer than currently to replicate the European Warm period.
Warmer weather is generally advantageous to agriculture, which in turn makes it easier to feed and support a larger human population. There are no preserved records of extreme weather events, so we can infer that the people living during that time had weather generally similar to what we see today.
The *real* problem comes when the climate cools, such as the "Little Ice Age" (roughly 1400-1700), leading to crop failures and catastrophic population decline due to harsher weather, and disease claiming larger numbers of ill nourished people. Given the Sun is currently entering a "Grand Minimum", similar to what early scientists described in the 1600's, so humanity will be feeling a great deal of stress wherever agriculture is unable to access large amounts of inexpensive energy as Western farmers do.
Making up the lost insolation may possibly be done through orbiting platoons of mirrors around the Earth and carefully controlling the amount of sunlight available to the atmosphere, hydrosphere and biosphere. Less ambitions plans could include hunkering down with lots of greenhouse agriculture and other intensive farming techniques, especially small "urban" farms which can exist in yards and balconies.
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[Question]
[
In a world where every human mind has been uploaded, and no organic humans remain, can we still produce offspring?
In a worldbuilding project I'm dabbling with, there are many people uploading their minds to a virtual world. I ran upon a roadblock, though. Could the people in the virtual world, who don't have physical bodies, do something in the virtual world to create real children?
To be clear, I don't mean design an artificial intelligence, as the physical world equivalent would be building a robot child (in my opinion). While some people would be fine building a kid like that, there are many who would prefer the "natural" way. If organic childbirth were not possible, and thus they had no choice, they would need another way. Something they would see as more "natural" than just creating a regular A.I.
[Answer]
# Yes - the Ghostborn
The way you describe them, for your infomorphs you are following the dichotomy of emulated uploaded minds ('Ghosts' - digital equivalent of naturally-evolved neural networks) and true artificial intelligences ('AIs' - programmed intelligent software or *artificially designed* neural network, with or without some layers of network 'evolution' on top of that, but *not* made by copying any naturally-evolved ones). That means you have the technology for the former, and you can expand it to emulating more than just adult brains.
It *will* be more CPU- and memory-intensive, as you will want to emulate the embryo's whole body to account for all the complex procedural influences required for the formation of a brain the 'normal' ways (but in emulation). It also will require sufficient prior research into human development - a lot of it. But given those two parameters, it's not physically impossible to emulate the whole process of growth from a single cell, just very computationally resource-intensive.
I don't recall the concept explored often in fiction, but I have recently found that Greg Egan's [Singleton](http://www.gregegan.net/MISC/SINGLETON/Singleton.html) does have it as a major part of the central events, and the concept is also present (but taken for granted, without as much novelty or focus, since the this story is set millennia after the events of Singleton) in his [Schild's Ladder](http://www.gregegan.net/SCHILD/00/SchildExcerpt.html).
[Answer]
Frankly, we (including top neuroscientists) have no clue how conscious works, what it is exactly, where it comes from, and how to make new ones (except the biological way).
Asking if a digital consciousness could have children is therefore impossible to answer (without wild speculation). The only reasonable guess we can make is that a digital consciousness would be able to make copies/clone itself.
Really, it's up to the plot of whatever story you're writing but if you have computers capable of simulating a human consciousness, simulating a sperm and an egg and the subsequent digital-biological child shouldn't be too difficult. Sure, that's a lot of cells and you'd need a virtual environment to "raise" the child in but it would be doable.
[Answer]
## Who maintains the virtual world's infrastructure? They can fertilize embryos.
If every human being is biologically born and then uploaded at birth, someone or something has to service the computers. If that someone or something is human, then there should be a human population capable of producing the offspring that get uploaded. I don't think that's what you're looking for, though.
My understanding is that your world has virtually zero adult humans outside the system. That's a problem, because **something** still has to keep the computers running.
You may want to build a mini-society composed of robots capable of sustaining the internet. When parts fail, spares will be manufactured and installed by automated drones. When you run out of spare parts, raw materials will be harvested and refined by mining bots. Plus, you will need someone to service the dozens of power plants that keep the system online in the first place.
You can employ some of these robots to conduct in-vitro fertilization. They can fertilize stored eggs with stored sperm, provide sustenance to developing embryos in artificial wombs, and then harvest each consciousness at the right developmental stage. It can be fully automated like the Matrix - except the bodies are composted.
One problem with this solution is that you will eventually run out of eggs and sperm. You may need a factory-sized genetics lab in which DNA is constantly recombined and distributed into lab-grown gamete cells. In this way, parents in the virtual world can have biological children.
[Answer]
Who says they have to be new? Take a copy of an existing person at random. Strip off the memories, the training, go back to the very core of a person - congratulations on your new child.
In your world, people are digital - we can copy without loss. We don't have an upper population limit.
[Answer]
**Rent-a-Body**
If this was my world I would play it like this:
(1) There are temporary bodies you can download yourself into whenever interaction is needed with the outside world. These might be androids, vehicles, spaceships, construction or mining equipment. Whenever something is needed to service the central server, these temporary bodies are used.
(2) There is little incentive to raise a child in a purely digital world. You don't get that same attachment to a newborn baby. You might as well simulate that attachment.
(3) Uploaded people live for thousands of years before they succumb to circuit decay, or voluntarily end their own lives. So there is little need to create new people.
(4) If you upload a baby's mind it never properly develops. Or rather it adapts super well and evolves to to "the next paradigm" of human development. This is looked down upon by the current less evolved generation.
So how does childbirth work?
(a) You apply for a childbirth license and register a lease on a bio-android body. Essentially a synthetic skeleton with organs grown in and around it in a vat of chemicals.
(b) You can either select a given genetic code or use the one assigned to you in the central database. Either way you get a sense of attachment to the new child.
(c) Procreate and have a baby.
(c.5) Some people do the procreation artificially, and only wake up the android shortly before or after the child is born.
(d) Raise the child to maturity in the real world.
(e) Upload the young adult into the server.
(e.5) During their upbringing the child can make *trips* into the central server. This lowers the shock value at age 18 where their biological body is obliterated and they are permanently uploaded. The parents can also switch bodies as appropriate.
**Question:** How does this change what a "household" is? Of course it removes any need for male-female parenting teams.
[Answer]
**Yes**
An uploaded mind is just a program and you can copy programs and make new programs.
A parenting program would take random features from both parents and build a base personality matrix from that. Said parents could then take the new AI and teach it just like a normal child.
Considered everyone is an AI, making a new AI is no difference.
In the Matrix, [Sati](https://matrix.fandom.com/wiki/Sati) is a child program of two other programs.
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[
Could a species with an incredibly advanced electroreceptive organ (such as that of a shark) be able to use it above water? The gas-mix in which the sense works must be breathable to humans, and it would be good if it was the same mix as in the earth's atmosphere.
[Answer]
TL;DR: no.
---
Electroreception that works underwater is fundamentally different from electroreception that works above water. You're not going to create an electric circuit in air, even if it is really misty or really rainy, unless either you, or the things you're trying to find, are generating *ridiculously* high voltages (think tesla coil, not electric eel... megavolts, not mere hundreds of volts) at which point you'll be able to detect them by the fact that they're *arcing* and your ability to sense light, heat, sound or impending frazzly doom will work just as well as electroreception if not better.
Above-water electroreception does exist, in the form of mechanosensory hairs on insects such as [bumble bees](https://www.pnas.org/content/113/26/7261) that react to electrostatic charges. These work in a similar way to the hairs on your own body which move in response to strong external electrical fields, only the insect equivalents are much more sensitive. Detecting electrostatic charges in this way is not something that will arise in a species that evolved in a conductive medium.
It *is* just about possible to detect neuromuscular activity through [sufficiently cunning sensory devices](http://sro.sussex.ac.uk/id/eprint/2407/1/Beardsmore-Rust%2C_Sam.pdf)... the creators of the Electrical Potential Sensors referenced in that paper claim the ability to detect muscular activity through walls, though doing so in anything other than an *extremely* well shielded environment is proving to be unsurprisingly problematic. I'm not certain this technique would work well underwater, but I could be wrong.
I do not know if a biological equivalent of these complex devices could arise, but it seems unlikely to appear in an underwater environment (because regular electroreception is simpler and works just as well if not better), and given the alternatives that can be used and indeed have evolved in an above-water environment ([thermoception](https://en.wikipedia.org/wiki/Thermoception), [echolocation](https://en.wikipedia.org/wiki/Animal_echolocation) and more familiar things like sight, hearing and even touch) there seems little reason to expect it would arise naturally.
[Answer]
**At close distances it could.**
I am thinking of small things in a dark world. In close proximity, electrostatic forces come into play. We can see that at work with our own bodies - if you scuff your feet on a dry day and accumulate charge, you can see the hairs on your arm stand up when they approach a conductive object. My own experiments with flies and a Teslacoil has demonstrated that fly wings will also move in response to charge.
If your creature itself kept itself charged, it could detect other objects in proximity to it according to how charge accumulated in its peripheral hair or winglike detector organs.
I do not think that this would be useful at human scale distances for which sight and hearing are useful. But at a very small scale this could be super useful; a small electrically charged organism could use this ability for things besides sensation as well, such as propulsion.
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[Question]
[
Sadly, the asteroid belt [isn't](https://tvtropes.org/pmwiki/pmwiki.php/Main/AsteroidThicket) the place to showoff your ace pilot skills. It is [so sparse](https://www.quora.com/Is-the-asteroid-belt-visible-from-Mars-with-the-naked-eye-If-not-after-astronauts-land-on-Mars-in-the-future-could-they-see-it-with-a-telescope-from-the-surface-or-in-the-orbiting-spacecraft) you wouldn't even see an asteroid most of the time if you flew through it.
But Saturn's rings! The rings [cast shadows](https://www.esa.int/Our_Activities/Space_Science/In_the_shadows_of_Saturn_s_rings) on the planet, indicating that that most photons passing through them hit something. The tidal forces of Saturn are thought to prevent the particles from condensing into moons despite the high density.
We assume contemporary technology (except with better ecosystems/life support for the colonies themselves) and we want to design a fighter to attack and defend ring colonies. I believe that the relative velocities of the boulders are low enough that collisions are harmless if you are co-moving with them, as large kinetic energies would have long ago dissipated. However, if you are maneuvering fast enough that would change.
Here are some considerations:
**Delta V**
Delta V is a problem, unless you use ring material as reaction mass. With a nuclear reactor there is almost unlimited energy to mechanically push against the ring objects, so *almost* infinite delta V.
**Hiding**
[Stealth in space](http://www.projectrho.com/public_html/rocket/spacewardetect.php) is hard due to heat emissions. But this isn't empty space. Would hiding behind ring material stealth be (at least short term) feasible? Or even *looking* like ring material to enemy radars.
**Weapons**
If an enemy is behind a large object, it may be possible to attack them by creating shrapnel in nearby objects to the side of them. Would launching ring material at them save on ammo?
**Tactics**
Space is 3D, but the rings are [only 10m thick](https://www.space.com/23235-rings-of-saturn.html)! This makes the arena *very* 2 dimensional. Attacks from above and below may have a good vantage point but you lose the reaction mass (maybe you could carry a boulder with you and push off against it, but doing so slows you down). Throwing an enemy spaceship away from the ring plane will cause them to have to expend precious fuel or wait ~5 hours (1/2 an orbit) for the tidal forces to pull them back.
**Windows**
Unlike deep space the morale boost from [the view (artists impression)](https://www.bellmedia.ca/wp-content/uploads/2017/09/Mission-Saturn_CGI_highres_ring-particles2_060_040-00316.jpg) combined with the visceral sense of being there rather than looking through sensors can't be ignored. How bad would the windows be for ionizing radiation?
Given these and other considerations, can we make a rough sketch of what a dogfight could look like?
[Answer]
>
> With a nuclear reactor there is almost unlimited energy to mechanically push against the ring objects, so infinite delta V.
>
>
>
Weeeeell... yes and no. Your reactor fuel isn't infinite, for one thing. More importantly though, your ability to *accelerate* is likely to be heavily influenced by your choice of reaction mass. You'll want to be throwing it away from you at a few km/s, and you want to be throwing it *straight* so you can't trivially just punt out any old chunk of ice. Haul it inboard, melt it via your coolant loop and then blow the water out through your engine, which will probably be some sort of [solid core nuclear thermal rocket](http://www.projectrho.com/public_html/rocket/enginelist2.php#id--Nuclear_Thermal--Solid_Core), [resistojet](http://www.projectrho.com/public_html/rocket/enginelist.php#id--Electrothermal--Resistojet) or [microwave electrothermal rocket](http://www.projectrho.com/public_html/rocket/enginelist.php#id--Electrothermal--Microwave_Electrothermal), given the sort of tech-level you're considering and given the need to be able to use water as reaction mass (which rules out other things like arcjets or ion drives).
Both kinds of engine have limited lifespans for various reasons that I shan't go into here, but do consider than infinite delta-V is basically impractical.
>
> Would hiding behind ring material stealth be (at least short term) feasible?
>
>
>
Given the thickness of the ring, there's milage in dropping off some little automonous sensor drones to look above and below and report back, so you'd have to hide *in* the ring, and that's a mildly hazardous place to be, what with all the rocks. At low speeds (relative to the material of the ring around you), this seems like it might be practical, and certainly an interesting setting for a fight. If you see a drone, even *after* they've seen you, you can pop it with some suitable weapon and your opponent only knows where you *were* and still needs to procede either cautiously, or with *force majeure* (if they have it).
>
> Or even looking like ring material to enemy radars.
>
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Unless you had the same heat signature and same average velocity as the other bits of the ring, you'll stand out like a nuclear rocket strapped to a chunk of ice. You might manage a very sloooow, long duration sneak attack if you were lucky and clever, though.
>
> If an enemy is behind a large object, it may be possible to attack them by creating shrapnel in nearby objects to the side of them.
>
>
>
Absolutely!
Moreover, other weapons that don't necessarily work well in space, like nukes, suddenly become a little more interesting. All those spare x-rays they emit will be absorbed by nearby ring material, which will probably go *bang*. It still won't be as dangerous as a nuke in an atmosphere, but it will present a considerable hazard.
>
> Would launching ring material at them save on ammo?
>
>
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This is a related problem to the infinite delta-V thing... you'll need to refine the lumps of ice in order to make practical projectiles. The means you use to propel them might have some other limitation, like carrying a finite number of sabots for railguns or coilguns.
Also... how would you launch the material? Docking with it, then pushing it with your main engines is obviously workable, but any point defences directed at the rock are going to hit you once the rock has broken up. Disengaging and slowing back down or redirecting yourself costs delta-V. Drones sent out to do the job will have limited delta-V. Laser ablation is deeply unsubtle and power hungry (which means lots of heat to dissipate) and can be countered in the same way. And so on.
On the flipside, if you *can* harvest and process ice rapidly, you can very quickly refill coolant tanks and that lets you fire your weapons harder and for longer, and heat is the number one enemy of most space weapons.
>
> Throwing an enemy spaceship away from the ring plane will cause them to have to expend precious fuel
>
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Most weapons you'll be using are of the "massive overkill" kind. There's a very narrow window between "no good as a space weapon" and "target reduced to partially ionised grit". Odds are good that if you can hit them, they'll be in big trouble. Falling away from the ring makes them a clear target, and it'll be much easier to finish them off.
>
> How bad would the windows be for ionizing radiation?
>
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It is hard to find good figures on the radiation environment around the rings. Here's a render from [some recent work on radiation belts](https://phys.org/news/2017-10-saturn-belts-stranger-solar.html):
[](https://i.stack.imgur.com/Ydx9g.png)
You may find that the rings themselves are actually fairly benign, as far as space radiation goes.
To be honest though, worrying about your windows is like worrying about your choice of sunglasses when wearing shorts and a t-shirt in the middle of the sahara. There's not much you can usefully take with you to protect yourself from most high energy cosmic radiation. Means of protecting against radiation are a bit outside the scope of this answer though!
What you might need to be more cautious about is nuke flash and laser beams, and you want something opaque between them and your eyes. Even indirect reflections and the flash of an object being zapped can blind.
[Answer]
First, two points need clarification:
DeltaV is mostly determined by exhaust velocity. Since the description of the ships suggests they are powered by a mass driver acting as a rocket engine (which also doubles as a weapon), you are ultimately limited by the velocity the mass driver can project objects.
What you are probably thinking of is [ISP](http://www.qrg.northwestern.edu/projects/vss/docs/propulsion/3-what-is-specific-impulse.html), the figure of merit for how efficient the engine is. High ISP's are generally associated with high temperature or velocity exhausts, and a low molecular weight exhaust. Since you can scoop reaction mass from the rings themselves, you have effectively unlimited ISP. However, before you celebrate, there are some considerations to think of.
[This site](http://www.projectrho.com/public_html/rocket/enginelist.php#massdriver) has most of the calculations you will need to determine things like the size and actual performance of your mass driver. One example in the site descrbes the performance of a mass driver that can accelerate reaction mass at 15 Km/sec:
>
> The reaction mass or payload is loaded into a lightweight bucket banded by a pair of superconducting loops acting as armatures of a linear-electric guideway. The thruster illustrated accelerates the bucket at 75,000 gee's, utilizing 7 GJ of electromagnetic energy stored inductively in superconducting coils. The trackway length is 390 meters. One 36kg of reaction mass is ejected each minute at 15 km/sec. The bucket is decelerated and recovered. Cryogenic 77 K radiators cool the superconductors.
>
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Even with the modest performance described, you will have a ship over 400 m long, a bit difficult to hide or disguise as a hunk of rock or ice. Another example with a 30 km/sec performance has correspondingly larger power requirements, and a very high performance spacecraft with a 90 km/sec exhaust velocity will be larger still by a factor of about 10 (10 X longer, ten times greater power consumption, 10 X more mass).
[](https://i.stack.imgur.com/hPTTF.jpg)
*What a medium performance mass driver would look like under construction*
Another issue is refueling. The ice has to be taken aboard, melted (it may be full of rocks and gasses which also need to be dealt with) and frozen in shapes that fit the sabots for the mass driver. In order to ensure the ship reacts the way you expect, every single "shot" needs to be the same size, shape and mass, otherwise your thrust will not be uniform, and it will be more difficult to manoeuvre the ship. Gathering ice will require you to be moving almost at rest with respect to the ice in the rings, which will be a moment of vulnerability. You will not be refueling in the manner of a bomber drawing from a tanker plane, although it will be much easier than condensing the drinking water out of the air of a jumbo jet in flight to supply the passengers. In many respects, you would be better off ignoring the ice and using drop tanks or a supply ship from Titan or other moon.
[](https://i.stack.imgur.com/DkPQ7.jpg)
*Ring Interior. Your 400 m long spaceship might get in a bit of difficulty*
Finally, staying in the plane of the rings makes you very predictable and easy to find and strike. A ship coming in from a highly elliptical orbit or a polar orbit will be moving much faster and at a different aspect and angle to your ship in the rings, potentially placing you at a huge disadvantage as you are showered with ice pellets moving at between 15 and 90 km/sec. An object moving at 3 km/sec already has kinetic energy equal to its weight in TNT, and the kinetic energy increases with the square of the velocity, so even one hit will be crippling. While a captain might choose to lurk in the rings for a short while as a tactical solution to a limited problem, the overall performance of spacecraft means they will want to use the entirety of the Saturn System, from skimming the edge of the atmosphere to the most distant moons.
[](https://i.stack.imgur.com/1Dsbs.jpg)
*Innermost part of the Saturn Theater of Operations. The enemy ship in the rings is about to get pummeled with some kinetic impactors moving at 90 Km/Sec*
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[Question]
[
The organisms in the oxygen based ecosystem we have today is perfectly adapted to each other. The ocean is filled with water, and on land it falls from the sky. Plants, algae and cyanobacteria split water into hydrogen and oxygen. Carbon dioxide is absorbed to produce sugars. Animals, fungus and the other non-photosynthetic organisms, as well as plants at night, use oxygen and release carbon dioxide back into the atmosphere.
This cycle is based on water as both an electron donor and a substance all living things needs to survive. And it is based on carbon and oxygen, where the consumers release carbon into the atmosphere, making it available for the primary producers, and the release of the waste product oxygen into the atmosphere, a molecule all complex forms of life depends on.
But there are other photosynthetic forms of life, bacteria that use a different electron donor than water. Are there any of these, if given the chance, that could have the potential to form a complex ecosystem regarding available electron donors, with consumers that produce an atmospheric waste product the producers requires to live, which in turn produce their own waste product the consumers depends on? Of course, the producers would also form the foundation of the food web, but that goes without saying.
[Answer]
You are aware that there exist photosynthesizers that do not use oxygen. You could read up on those.
An example is purple sulfur bacteria.
<https://en.wikipedia.org/wiki/Purple_sulfur_bacteria>
>
> The purple sulfur bacteria (PSB) are part of a group of Proteobacteria
> capable of photosynthesis, collectively referred to as purple
> bacteria... Unlike plants, algae, and cyanobacteria, purple sulfur
> bacteria do not use water as their reducing agent, and therefore do
> not produce oxygen. Instead, they can use sulfur in the form of
> sulfide, or thiosulfate (as well, some species can use H2, Fe2+, or
> NO2−) as the electron donor in their photosynthetic pathways.[4]
>
>
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The waste product consumed by the PSB is H2S or hydrogen sulfide. Hydrogen sulfide is produced by sulfur reducing bacteria. Just as we reduce oxygen with our metabolism and produce water, these bacteria reduce oxidized sulfur compounds and produce H2S.
<https://en.wikipedia.org/wiki/Sulfate-reducing_microorganisms>
>
> Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes
> (SRP) are a group composed of sulfate-reducing bacteria (SRB) and
> sulfate-reducing archaea (SRA), both of which can perform anaerobic
> respiration utilizing sulfate (SO42–) as terminal electron acceptor,
> reducing it to hydrogen sulfide (H2S).[1][2] Therefore, these
> sulfidogenic microorganisms "breathe" sulfate rather than molecular
> oxygen (O2), which is the terminal electron acceptor reduced to water
> (H2O) in aerobic respiration.
>
>
>
In these ecosystems, sulfur fills the role of oxygen. In an anaerobic environment like a sewage treatment lagoon, sulfate reducers break down solids and generate H2S. Purple sulfur bacteria then use the H2S and sunlight to do photosynthesis. H2S can be a gas too, if your question mandates a gas atmosphere.
[Answer]
Yes. In fact, there are quite a few options.
Willk has already mentioned sulfur. In this case, primary producers produce solid sulfur as an anabolic waste product, which consumers must eat along with the rest of their food, rather than breathing in. (Unless, of course, they are from the planet [Sar](https://en.wikipedia.org/wiki/Iceworld), which is hot enough that sulfur exists as an atmospheric gas, and molten copper chloride stands in for water.) Actual sulfur producing bacteria tend to accumulate crystals of sulfur in their cells, rather than releasing it all directly into the environment, so you could expect sulfur-producing plants to do the same, as they have even bigger excretion logistics problems than unicellular photosynthesizers do!
Some real-world bacteria can also perform carbon fixation using free hydrogen directly, in environments where free hydrogen exists. And there are organisms that *generate* hydrogen from the anaerobic respiration / fermentation. So, theoretically, there could be a cycle there; however, in practice, if you have a lot of hydrogen in the air, as well s carbon dioxide, they will spontaneously react over time (or not so spontaneously, as organisms can get energy by catalyzing the reaction themselves, which is exactly what methanogens do on Earth) until one or the other is depleted.
In a sulfuric acid world, plants could acquire hydrogen from sulfuric acid, producing solid sulfur trioxide or gaseous sulfur dioxide as a waste product, which consumers would then eat or breathe in place of diatomic oxygen. Such worlds are also likely to have a lot of hydrochloric and hydrofluoric acid around, which given sufficiently energetic light to work with, or photosystems which can accumulate energy from multiple photons (or work around it by just generating ATP / the local equivalent until there's enough of that around to power the reaction) could also be split to acquire hydrogen. I would not, however, expect the release of straight Cl2 of F2 gas, however, as those are highly reactive (maybe on a really cold world around an F-class star...)--rather, I'd expect to see them bound up in metal complexes (just like iron-oxidizing bacteria do with oxygen), or halocarbons--gaseous carbon tetrachloride and carbon tetrafluoride. Unfortunately, those are very stable chemicals, so they won't be very useful for completing an ecological cycle with consumers. Rather, you'd expect them to be feedstock for further exotic anabolic processes--extra sources of carbon and less-reactive forms of halogens.
Like the sulfuric acid world, but more plausible, while I am not aware of any Earthling organisms that do this, photoautotrophs could also acquire hydrogen (as carbon, and sometimes oxygen) and reducing potential from simple organic molecules, like methane, methanol, ethanol, acetate, etc., with more heavily oxidized organic molecules as the waste product. For example, in a world with a CO2/methane atmosphere, plants could rip hydrogen off of methane to produce ethane, ethylene, and/or acetylene gas as byproducts, which would be breathed in by consumers to regenerate gaseous methane for producers to consume and repeat the cycle.
Of course, acetylene is a pretty good energy storage molecule all by itself, and ethane is a good place to start building longer alkane and alkene chains, so as in the case of the sulfuric acid world these really aren't "waste" products like oxygen so much as they are additional useful products of photosynthesis, of which there is sometimes an excess which is useful to other organisms.
In a world with a slightly more heavily reducing environment, you can expect a decent amount of ammonia to be available. Stripping hydrogen from ammonia is easier than stripping it from water (although if you only go part way, you get some *very* energetic molecules, like hydrazine--the ammonious equivalent to hydrogen peroxide), so it would not be unexpected for that, rather than the less-abundant hydrogen sulfide or the more tightly-bound water to serve as hydrogen donor and source of reducing potential. The waste product in this case is nitrogen, which is famously not easily breathable,as dinitrogen is a very stable molecule that does not like reacting with anything. Except, it *does* react slightly exothermically with hydrogen to give you back your original ammonia, completing the cycle; there are no (known) organisms on Earth which can acquire energy through nitrogen reduction, because Earth is a highly oxidizing environment, and nitrogen-fixing bacteria have to expend more energy than ammonia production gains them in order to acquire the necessary reduction potential in the first place, but that situation does not hold in this hypothetical environment. So, your consumers would presumably perform hydrogenic fermentation *and* nitrogen fixation for a positive energy yield in both processes, closing the nitrogen-ammonia cycle instead of the oxygen-water cycle.
And in an even more strongly reducing environment, where excess hydrogen has destroyed all CO2 in the atmosphere, leaving behind free hydrogen, methane, water, and ammonia, your producers will be producing waste hydrogen rather than waste oxygen or nitrogen, and looking to acquire chemical oxdizing potential rather than reduction potential for anabolic processes. The consumers will not excrete any single gaseous molecular species to close the cycle, but the whole gamut of fully-reduced water, methane, and ammonia to resupply the producers with raw materials.
And of course, as a final note: in none of these cases should you necessarily expect glucose specifically, with its specific elemental ratios, to remain the go-to energy storage and structural molecule produced by alien photosynthesis. It wouldn't even be stable on a sulfuric acid world, and other types of molecules--like alkenes or organonitrogen compounds--will be competing for some of its functions in exotic chemical environments. Heck, even on Earth, there are organisms that get most of their energy from metabolism of fats and/or proteins rather than sugars, and the components of those cycles may end up more important than the basic oxygen-water cycle or its local equivalents.
[Answer]
Green sulfur bacteria are anaerobic and photoautotrophic. They use sulphide ions as electron donors. [Some species](https://ocean.si.edu/ecosystems/deep-sea/microbes-keep-hydrothermal-vents-pumping) live around deep sea hydrothermal vents from which they feed on hydrogen sulphide. They are so efficient at harvesting light that they can even grow in the absence of sunlight in the very weak radioactive glow from geothermally heated rock.
They also form one component of the food chain for more complex organisms that live in the vicinity of the deep ocean vents.
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[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
I'm working on a story involving humans looking for another habitable planet, and I have been scouring the net for days, finding lots of info on varying levels of oxygen and nitrogen, but none that really answer this question:
Earth's atmosphere is a mix of oxygen, nitrogen, argon, carbon dioxide and water vapor; are there other viable possibilities?
For instance, argon -- I know it is inert, which is important, but could it be replaced with another inert gas?
Thank you so much in advance for any info you have on the topic or anywhere you can point me where I might find the answer.
EDIT: Okay, target atmospheric pressure would be, I suppose, in the same realm as what we have on earth? Sorry, for the lame answer, but I am a writer trying to learn science here. I don't need examples of *possible* atmospheric blends; I'm assuming that is nearly infinite. I'm looking for whether, on a planet on which humans could live outside of pressure suits, etc., the atmosphere might look slightly different to what we have on earth, or should we reasonably expect it to look virtually identical? Thank you!
EDIT 2: Let me boil this down to my real question, I think. If we found an exoplanet that had the exact same gases in its atmosphere (N, O2, Ar, etc.), albeit at slightly different ratios, would we be surprised by that, or would we expect to see that? If you were reading a novel and in it a planet was discovered that fit the above parameters, would you think, no way, what are the odds? Or would you think, yeah, probably?
Thank you for bearing with me on this. I genuinely appreciate the expertise.
[Answer]
Firstly it sounds like you want to do bottom-up worldbuilding, meaning you want to get the basic science straight first. I would recommend [worldbuilding YouTuber Artifexian](https://www.youtube.com/user/Artifexian), as he has a series where he starts with constructing the solar system and has currently reached climate mapping. He breaks down the science to a very digestible minimum. For your question, I recommend watching his videos on [atmospheres](https://www.youtube.com/watch?v=9-j_JOWPLj8&t=284s), [alien atmospheres](https://www.youtube.com/watch?v=fwauz9uIl9M) and [sky and plant-color](https://www.youtube.com/watch?v=L9MNC45Jr6Q&t=450s).
**Pressure**
Pressure may vary significantly on "earthlike" planets. Mars has only about 0.006 atm, Earth has 1 atm, Titan has 1.5 atm and Venus 96 atm. Mars and Venus both experienced cataclysmic events in their pasts, the loss of the magnetosphere and a runaway greenhouse effect respectively. Thus they are out of the interesting zone. Looking at Earth and Titan no one could say you went overboard if you vary the pressure on planets you construct by an order of magnitude in both directions (0.1 atm - 10 atm). The upper and lower end might be unsuitable for unsuited humans.
**Composition**
>
> If we found an exoplanet that had the exact same gases in its atmosphere (N, O2, Ar, etc.), albeit at slightly different ratios, would we be surprised by that, or would we expect to see that?
>
>
>
Yes, and No. let me break this down in detail and give you some breathability limits for indefinite survival.
* N2 < [3 atm](https://en.wikipedia.org/wiki/Nitrogen_narcosis)
Is somewhat a given since ammonia is common in protoplanetary nebulas and will end up on most planets. As it gets broken apart the nitrogen reacts to N2 molecules, which are very stable and inert. Nitrogen will usually just accumulate over time in the atmosphere.
* O2 < 0,16 – 0,5 atm ([0.3 - 0.35 atm wildfire limit](https://www.earthmagazine.org/article/flammable-planet-fire-finds-its-place-earth-history)) [For the maximum](https://en.wikipedia.org/wiki/Oxygen_toxicity) [and this](https://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Pulmonary_toxicity_tolerance_curves.svg/1024px-Pulmonary_toxicity_tolerance_curves.svg.png) and [for the miniumum](http://www.geography.hunter.cuny.edu/tbw/wc.notes/1.atmosphere/oxygen_and_human_requirements.htm).
Free oxygen is only a surprise if you don't expect a biosphere. O2 is so reactive that it will disappear quickly if it doesn't get replenished constantly. O2 may also occur abioticly on worlds where no land is exposed to the atmospere, as nothing can be found to xidise it away with.
* Ar < 1.6 atm
>
> Nearly all of the argon in the Earth's atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in the Earth's crust. In the universe, argon-36 is by far the most common argon isotope, as it is the most easily produced by stellar nucleosynthesis in supernovas. - [Wikipedia](https://en.m.wikipedia.org/wiki/Argon)
>
>
>
Argon isn't in the atmosphere by chance but as a result of the alpha decay of potassium-40. This means that a planet with no argon in the atmosphere is either very young (not older than maybe 0.5 byr at most), in a low metallicity system (meaning it would most likely be a planet dominated by water), lost its original atmosphere in a geographically speaking recent event or is an artificial world around a gas giant or black hole or is so small (moon-sized) that it had little radioactive material, to begin with. Usually, you will find argon.
* H2O
You'll usually find out the maximum possible water content by calculating the water [vapor saturation pressure](https://www.engineeringtoolbox.com/water-vapor-saturation-pressure-air-d_689.html). Calculate your planets global average temperature for it and multiply the maximum saturation with 0.125. That's the average water content of the atmosphere. That said this rule of thumb only holds for planets with large bodies of water. Desert-planets might have significantly less moisture.
* CO2 < [0.02 atm](https://en.wikipedia.org/wiki/Carbon_dioxide#Toxicity)
Carbon dioxide too is a given and will remain in the atmosphere in moderate concentrations as long there is a functioning [carbon cycle](https://en.wikipedia.org/wiki/Carbon_cycle), which likely requires plate tectonics. A lot of carbon is stored in the lithosphere as rock. If the planet gets too hot it will be "cooked out", which is the reason for Venuses thick CO2 atmosphere
* CH4 < 0.05 atm (not toxic, but [explodes at this point](http://aetinc.biz/newsletters/2010-insights/october-2010))
Is usually generated by biological processes, so if there is life, some methane is likely. Abiotic methane is an option, too but you usally wont find it in significant quantities on Earth-like worlds.
* SO2 < 0.000005 atm
Is a short-lived gas and a sign for extremely strong vulcanism.
* O3 < [0.0000001 atm](https://www.epa.gov/indoor-air-quality-iaq/ozone-generators-are-sold-air-cleaners) i.e. 0.1ppm
A byproduct of having O2 in the atmosphere. Will shield away UV-rays and allow life to colonize the land.
**So, no one would be surprised to find very Earth-like atmospheres if the planet in question is very Earth-like. Also finding Mars and Venus-like planets should not surprise anyone, as they show paths along which an Earthlike atmosphere might develope.**
[Answer]
Today, we have examples of some radically different breathing environs. The most unique I know of are breathable liquids, made from specific perfluorochemicals;
<https://en.m.wikipedia.org/wiki/Liquid_breathing>
Science-wise, there is nothing preventing a planet from being covered in this stuff, although you’re on your own to figure out a natural process that would produce the stuff in quantity.
But as a proof of concept, this suffices to answer your question.
You should also check out nitrox breathing, an alternative mix of gasses used by deep-sea divers. (In chemistry, nitrox refers to any nitrogen-oxygen blend, including regular air, but among divers, it’s a specialty mix.) At extreme depths, regular air becomes toxic... as would occur on a planet with a very deep atmosphere. These alternate blends are not breathable at the surface but work just fine at depth.
<https://en.m.wikipedia.org/wiki/Nitrox>
[Answer]
It's an interesting consideration that you can have halometanes in the atmosphere: they are not very toxic but already make starting fire difficult at some concentrations.
<https://en.wikipedia.org/wiki/Halomethane>
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[Question]
[
I have a hypothetical world in the works and I have a rough idea of what it might be like.
My idea is that the planet was life-supporting with a widely varied biosphere. The magnetosphere failed and let particles in the incoming solar wind into the biosphere.
My question is: How might a planet quickly (relatively speaking) lose its magnetosphere? Would said loss of the magnetosphere let high amounts of radiation reach the surface? What other adverse effects might this have on my planet?
[Answer]
>
> The mantle eventually solidified, causing the magnetic field to fail and let in radiation from the star it orbits.
>
>
>
Eventually is a very, very long time scale for this to happen naturally. A planet is more likely to suffer a catastrophic asteroid impact on these times scales (themselves very rare events) that would wipe out almost all life. Political developments (i.e. war) and improper environmental management (e.g. climate change denial) could wipe out a civilization far faster - hundreds of years perhaps. On the other hand the very slow loss of the magnetic field is something that could be adapted to and ultimately a technological civilization able to survive long enough to worry about this problem would possibly be able to fix the problem by generating some kind of EMF shield itself. You're looking at a K1 or K2 civilization on these time scales. Worst case scenario - you go underground and live in large atmospherically sealed environments. Or if you have the tech (K1 or K2) you could just forget the messy planet thing and live is large space stations. Planets are for young civilizations, not mature ones.
Incidentally we have few example planets to go on for life (one) and few examples of non-life bearing (as far as we know) planets, so it's by no means a foregone conclusion that a planet without a magnetic field or even an atmosphere will not support life. Life does not necessarily require a surface environment to evolve on or continue existing on. For example it is conjectured that life might exist below the ice of Europa in a liquid ocean.
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Exactly as they do now.
As AlexP points out the time between the magnetic field stopping and their being significant impact to life would be on the order of millions of years at least. So "initially" - no problem.
The loss of the Ozone layer does not prevent life from existing. For *us* it would be catastrophic (at the rate we're screwing up I think "will be" is closer to the truth) because we lack (and will do on the relevant timescale) the technology to adapt quickly enough on a mass scale to drastic climate changes - that's a different issue from yours.
This might be different if the planet had an extremely strong magnetic field (which brings it's own problems) and was close to a star with an extremely strong particle wind. But this combination presents a number of problems for making a life sustaining planet in the first place. It seems unlikely.
The core supplies almost no power to the surface compared to the Sun so the climate would be unaffected in any realistic scenario.
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A planet orbiting a [Population I or II](https://en.wikipedia.org/wiki/Stellar_population) star would necessarily be light on metals and radioactives, compared to a Population III star like Sol. This makes them lower density and gives them very little in the way of heat reserves, they cool very quickly, [geologically](https://en.wikipedia.org/wiki/Geologic_time_scale) speaking and become geological dead. The problem is that such a world generally doesn't have much of a magnetosphere to begin with.
An alternative possibility would be a very salty [Water World](https://en.wikipedia.org/wiki/Ocean_planet) where a strong magnetic field generated by ocean circulation collapses due to a demineralisation of the oceans. The thing about this is that the evolution of life is the most probable cause, simple organisms change the chemistry of the ocean turning existing soluble minerals from the ocean into insoluble compounds that settle out of the water column and build up on the seabed. This process also generally involves out-gassing of lighter elements like Chlorine to reduce the solubility of elements like Calcium in the ocean.
The collapse of the magnetosphere on any world is the beginning of the end for the atmosphere and also for surface liquid water, this starts at the top of the atmosphere with the lightest gases, even with a powerful magnetosphere Earth loses Hydrogen and Helium to the solar winds Venus loses gases as heavy as Oxygen. The Ozone Layer will be the first victim, ionising radiation will energise and break up the unstable Ozone, then unfiltered UV will start to sterilise the planet. The stellar winds will continue to strip the atmosphere through a combination of particle collisions, magnetic disruption and ionisation reactions. Stripping off the whole atmosphere and then all the water on any world will take geological age*s*, plural, but unless something magically restarts the magnetosphere it's only going to end one way.
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**1. Nonconductive core.** Your planet is nonconductive - maybe alkanes all the way down. If you have minimal conduction it will be easier for your magnetosphere to disappear. No conduction means no resistive heating.
**2. No radionuclides.** This goes with #1 - your planet is a lightweight. It has no radioactive decay and so no inner heating.
**3. Evaporative cooling.** In with the alkanes composing your planets innards is a lot of hydrogen. No helium because of #2 but lots of hydrogen. This light molecule makes its way to the surface and leaves the planet into space, carrying away its heat.
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The strength of the Earth's magnetic field temporarily drops to near zero during a reversal of the magnetic poles. Unless you need the loss to be permanent, then the loss can be perfectly natural and normal on an Earth-like planet.
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> Reversal occurrences are statistically random, with some periods lasting as little as 200 years. There have been 183 reversals over the last 83 million years. The latest, the Brunhes–Matuyama reversal, occurred 780,000 years ago, and may have happened very quickly, within a human lifetime.
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> [Wikipedia](https://en.wikipedia.org/wiki/Geomagnetic_reversal)
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On the reduction of field strength during one such occurrence:
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> What is remarkable is the speed of the reversal: "The field geometry of reversed polarity, with field lines pointing into the opposite direction when compared to today's configuration, lasted for only about 440 years, and it was associated with a field strength that was only one quarter of today's field," explains Norbert Nowaczyk. "The actual polarity changes lasted only 250 years. In terms of geological time scales, that is very fast." During this period, the field was even weaker, with only 5% of today's field strength. As a consequence, Earth nearly completely lost its protection shield against hard cosmic rays, leading to a significantly increased radiation exposure.
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> [Ice age polarity reversal was global event: Extremely brief reversal of geomagnetic field, climate variability, and super volcano](https://www.sciencedaily.com/releases/2012/10/121016084936.htm)
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Question: Is it technically possible to make a 'Black' Whitewash?
True [Whitewash](https://en.wikipedia.org/wiki/Whitewash) is a plaster-like substance that has been used to coat stone and wooden walls for cosmetic and waterproofing purposes since the dark ages. It is made from limestone, and as far as I know it resists all manner of dyes. *I do NOT mean the paint.* [Watch this video](https://www.youtube.com/watch?v=lTlps-OZFDM) to understand what I am referring to.
Conditions:
* The resulting "blackwash" must serve the same purpose as the original [whitewash](https://en.wikipedia.org/wiki/Whitewash) in that it provides water proofing to as near the same degree as the original whitewash.
* Pitch and tar, while being black and capable of waterproofing, are not acceptable solutions as they are not as easily applied as whitewash and have undesirable traits (the smell, the adhesive qualities, etc.)
* As black as possible. The best answer will be that one that meets the previous conditions and has the darkest tint.
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There are some methods of tinting the limewash. 'Naturally' it is done with earth or clay, achieving mostly brownish, yellowish and reddish colors.
Modern manufacturers also offer black tint for limewash - <https://www.celticsustainables.co.uk/limewash-pigments-black-iron-oxide/>. It is said here it is based on black iron oxide and, as you see on the photo there, it gives dark gray, almost black color.
Black iron oxide, it seems, can occur naturally and is known as magnetite.
<https://en.m.wikipedia.org/wiki/Magnetite?wprov=sfla1>
So, it seems, if you add crushed magnetite to limewash as you prepare it, you may achieve black color.
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Whitewash was traditionally coloured by mixing it with "earths" (actually metallic oxides)
Copper(II) Oxide ([cupric oxide](https://en.wikipedia.org/wiki/Copper(II)_oxide)) is black, although producing sufficient quantities without also creating red/orange Copper(I) Oxide ([cuprous oxide](https://en.wikipedia.org/wiki/Copper(I)_oxide)) may be difficult
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**Possibly, but why would you?**
Whilst it may be possible to create this “black wash”, it would be made redundant by black paint. At the end of the day, white wash is simply a building material, like cement on bricks.
Think of it this way, if i wanted to make a blue brick house, would it make more sense for me to go out looking for blue clay to make into blue bricks? Or would it make more sense to simply paint the bricks blue when the house was built?
If you *really* wanted “black wash” though, you could just mix black paint into your white wash and, as if by magic, now you have black wash. You have also wasted a fair bit of paint as most of it you aren’t going to see, so what was the point? It would have been far cheaper to just apply the white wash and then paint it black. By painting it, you also add an additional layer of protection, any weathering would first happen to the paint, then the white wash, before finally the walls.
White wash was often painted in the Medieval period, typically with artwork. I’m not aware of any examples of entire walls being painted black but its not beyond the realm of possibility, it simply was not the fashion.
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Assume a subterranean civilization exists with technology roughly on par with the modern era. With changes due to lack of certain environmental factors being likely due to the vastly different environment. Assuming tunnels can be bored through the earth creating new routes to fit for instance trains and while keeping in mind limitations due to space.
My reasoning is that in a subterranean environment infantry would be the easiest unit to move around in tunnels and caves. Able to negotiate narrow passages, inclines,small drops,cross rivers,move along ledges,climb and still use available cover. Mecha/power armour small enough would be able to do many of those functions and augment troop power as force multipliers. Where a tank could not fit a small mecha or power armoured unit could quite easily. Not to say a tank of sorts could not be achieved with armoured carts on train tracks that also have treads in larger tunnels and caverns used as main thoroughfare.
However a squad of power armour units is much cheaper than said tank and can go where they cannot. As could smaller mecha units,not being limited to main tunnels but also able to go along side routes too narrow for them.
So my question is: would small mecha/power armour (small being 7-9ft tall being the norm; 12 ft tall being the max) be ideal for fighting in underground conditions?
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Depending on how wide how wide these smaller side tunnels are, I would imagine even the power armour units would be too large to effectively fight in these environments. Assuming that the side tunnels are bored out purposely for humans to pass through, the ceiling is probably going to be 7 or 8 feet high at best, meaning the power armour units are not going to be able to stand upright. Again, the width of these tunnels are probably suited such that people can pass 2-3 abreast. Considering that the power armour units are going to be significantly wider than the average human, plus their weapons (which I imagine are going to be quite a bit larger than the average infrantry weapon) and miscallaneous peices of kit such as radios, food, water, medical supplies, explosives etc, it's unlikely the power armour units would be able to even turn around in these tunnels easily, let alone fight.
Having a mech fight in the side tunnels is probably going to be like how the [tunnel rats](https://en.wikipedia.org/wiki/Tunnel_rat) had to fight in Vietnam. (Another real world example of people trying to navigate confined spaces with quite alot of [cave diving](https://en.wikipedia.org/wiki/Cave_diving)- getting your kit stuck on rocks in these tight spaces can be a death sentence). Imagine a small team of mechs inside one of these passages and for some reason they need to quickly fall back- likely their only option would be to shuffly backwards until they get to an opening where they have the room to turn around.
This is in addition to the lack of fine motor control mechs will have, so trying to navigate particularly narrow cave is going to be a nightmare for those troops.
Power armour troops would probably adopt similar tactics to the US in Afghanistan (instead of clearing out a cave, just use explosives to collapse all the entrances and exits, and go on your merry way while the men inside struggle to dig themselves out).
Your average squad of infantry, armed with a carbines and shotguns, would likely be much better and fighting in these confined spaces, especially considering that if the mechs can't follow them, enemy infantry will flee in to them whenever they are outgunned.
**Edited based on comment:**
Provided that the power armour troops stay within those car sized tunnels, then I imagine they probably would be well suited. They'd be a big target, and probably slower to react in close quarters than light infantry, but given that much of it will be fighting in low light environments due to smoke and debris from hand grenades, gunfire, damaged lights etc, the more sophisticated optics that I imagine they'd have in their helmets would be very useful- though on the other hand I imagine they'd have significantly narrower field of vision through their helmets, so they'd rely on light infantry for support in close quarters.
Also, considering the amount of richocets from shrapnel and bullets hitting the sides of the tunnels ([04:00 onwards in this FBI video is very informative on this](https://www.youtube.com/watch?v=mRpneRYaRNU)), as well as the amount of direct fire directed at them fighting in narrow chokepoints, having your point man as a walking shield would definitely improve the life expectancy of any light infantry following.
Depending on the amount of armoured troops that this military has, they may struggle to field enough power armour troops if there are a lot of tunnels to cover (and the power armour troops would probably be overfatigued from constant deployments in any longer term wars), though they'd definitely be a valuable resource.
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**Really small mecha: child soldiers.**
I like where you are going with this underground mech idea. But take it one step further. Tunnels bored for worker access / transit will be cramped for an individual in power armor. But not if that individual is 4 feet tall.
Your Mole Corps is comprised of prepubescent soldiers between ages 8 and 11, boys and girls both. Child soldiers are not a new thing but usually are discussed in the context of children being enslaved / coopted by conventional troops.
The Mole Corps arises out of necessity / desperation. It will make interesting writing contrasting the physical abilities of a 10 year old (flexibility, low strength, low caloric reserves, emotional immaturity but without sex hormones. Fearlessness / fearfulness) in the context of technologic augmentation.
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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.
We know that Mars has a reddish color, because its ground consists of iron-based compounds. The moon is grey-whiteish because it consists mostly of silicon-based compounds.
What element should the moon in my world have in order to have a blue color?
I thought about cobalt-based compounds, but naturally this element is silver-grey.
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You don't need an element, you need a mineral.
Certain elements do tend to make things a certain colour, for example nickel will make minerals green, manganese pink, and cobalt purple.
The fact that cobalt itself is a metal is irrelevant. Whatever "element" you have will not be metallic, it will be as a cation (or anion) in the silicates.
So your question should be rephrased to:
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> **What element do I need to make the silicates the moon is made of, blue?**
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You have several options.
1. Add sodium and chlorine, in order to make [sodalite](https://duckduckgo.com/?q=sodalite&ia=images&iax=images): Na8Al6Si6O24Cl2 (with the other elements already abundantly present on the moon).
[](https://i.stack.imgur.com/g4uzi.jpg)
2. Sodium and water, at high pressure and then somehow expose those rocks on the surface. You will have [glaucophane](https://duckduckgo.com/?q=glaucophane&iar=images&iax=images&ia=images): Na2(Mg3Al2)Si8O22(OH)2. This is the main ingredient of the terrestrial rocks known as blueschists:
[](https://i.stack.imgur.com/8CgDq.jpg)
3. Tons more aluminium, so then you can stabilise corundum (Al2O3). When combined with the already abundant iron and titanium as trace elements, you end up with blue corundum. Also known as sapphire when in gem quality:
[](https://i.stack.imgur.com/VjqVq.jpg)
This should get you started. Other things you might consider are potassium and whatever makes [amazonite](https://duckduckgo.com/?q=blue%20feldspar&iar=images&iax=images&ia=images) (potassium feldspar) green-blue. [Copper](https://duckduckgo.com/?q=azurite&iar=images&iax=images&ia=images) is also a good one, but the blue requires water that isn't common on the Moon.
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The most popular type of stars are red dwarves, which regrettably tend to be flare stars. Yes, I know that geomagnetic storms and power lines do not like each other.
Technology level: More or less early 21st century equivalent.
Extra issues: No legacy issues, infrastructure and settlements are built from scratch. Low population density, so one theoretically could be picky. Cheapest and easiest to access source of electricity is hydropower.
**How to design power grids and related infrastructure in the most practical and reasonable way?**
Best answers will take in to consideration things such as:
1. Founding main settlements away from magnetic poles and away from main bodies of water (this second is also a risk factor on Earth for geomagnetic storms).
2. The decisive (or almost decisive) factor in locating the main city near the main power plant to shorten the cables
3. Special preferences concerning voltage or frequency of electric current for transmission lines (HVDC is out, if I'm not mistaken).
4. Practicality of hardening the grid (series capacitors / surge protectors / etc.), as opposed to a main line of defense of regularly (even a few times per day) turning off most of power transmission lines to prevent transformers from burning.
5. Trying to enforce construction codes to design buildings that would work as low quality Faraday cages
6. Any other key modification area that I've missed.
[Question only relates to geomagnetic storms, ignores issues of tidal lock or ultra high UV index during flares]
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High voltage DC is exactly the right technology to deal with the effects of geomagnetic storms.
Geomagnetic storms damage AC transmission lines by inducing large *DC* currents and voltages in them which damage equipment designed to handle AC power. HVDC equipment is is designed to handle DC and the surges are much less damaging. (The best thing we could do to insulate the grid from geomagnetic storms is to move to HVDC for long-distance transmission.)
(The Carrington Event damaged telegraph equipment since that all ran on *low* voltage DC and had no protection to deal with surges.)
See [this NASA paper](https://www.swpc.noaa.gov/sites/default/files/images/u33/finalBoulderPresentation042611%20%281%29.pdf) for an interesting discussion of geomagnetic storms and the US grid.
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> How to design an electrical grid for a flare star planet?
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Initial discoveries about electricity on such a planet may lead to a circumspect approach to this sort of thing, because of the unpredictable, painful and sometimes fatal effects to a(n at first) primitive society of inductances within metals.
# Frame Challenge.
**A radical shift in development of power distribution could develop, somewhat away from the idea of a grid in the electrical sense, but still a power grid.**
* Hydropower generation would be used to create a [hydrogen (and nominally oxygen)](https://en.wikipedia.org/wiki/Electrolysis) based transport and power distribution economy.
* Vehicles that relied on hydrogen ignition by [dieseling](https://en.wikipedia.org/wiki/Dieseling) not requiring a conventional electrical system would predominate. Vehicle starting cranks would be the standard way to start, and a fuel shut-off valve to stop the engine - just as they were the first half and more of the twentieth century.
* Terrestrial radio and television would be relayed - first through optical signals beamed by direct line of sight to [photoelectric sensors](https://en.wikipedia.org/wiki/Photoelectric_sensor) and multiple distribution points, then developing into fibreoptic networks.
* Hydrogen (and oxygen) powered and ([limelight](https://en.wikipedia.org/wiki/Limelighthttps://en.wikipedia.org/wiki/Limelight)) lit homes and businesses, with [thermoelectric](https://en.wikipedia.org/wiki/Thermoelectric_generator) and [Fuel Cell](https://en.wikipedia.org/wiki/Fuel_cell) electrical generation would be used to power industry, entertainment and communication - with well earthed and insulated systems (themselves comprising specialised [Faraday cages](https://en.wikipedia.org/wiki/Faraday_cage)).
* In addition to the local supply lines and the tankers providing gas to homes, the possibility of developing distributed nodes of massive aerials which collect power from the solar discharges would be evaluated for opportunistic power storage - into pumping water uphill into reservoirs ready for hydroelectric generation - into [molten salt thermal batteries](https://en.wikipedia.org/wiki/Molten-salt_battery) - into [gyroscopic inertial](https://en.wikipedia.org/wiki/Flywheel_energy_storage) systems and other means we haven't seen yet (fair to say).
*A different world from ours.*
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Ok, so, some quick background... I'm not an evolutionary biologist or anything, but I'm helping a friend with some alien design ideas, and at least one of them she designed and wanted help to somehow explain was a group that basically falls into the classic Star Trek "Humans but Kinda Weird-Looking" milieu... and while I was initially willing to handwave their existence with "Boy, space sure is wacky, what are the odds that it keeps making humans!", I kept thinking about it more and more, and I actually really *liked* the idea of something we might consider a "functional vertebrate" with seemingly mammalian- even HUMANOID- characteristics actually being a case of something we would possibly classify as an Invertebrate undergoing some Seriously Bizarre Convergent Evolution that took a completely different path from ours... Yet ended up with a Weirdly Similar Result?
So we ended up coming up with a pretty solid model for how this race evolved, why they have the adaptations that they do, and we have them pretty solidly fleshed out... Except that there's one thing that I'm not 100% sure about, and it's kind of a Big Freaking Deal if we want an alternatively-evolved "Vertebrate": given that the ancestor we envisioned for them was something akin to what might have happened if Cephalopods or other Molluscan Critters had somehow developed into Primitive Chordates, the way something like the Lancet did, How Would They Evolve A Skeletal Structure, and How different would it be from Ours?
So I looked back at something like an Ammonite, and wondered if it was possible for something that still had a vestigial mollusk-style shell after somehow developing an early [Notocord](https://en.wikipedia.org/wiki/Notochord) to sort of... Use that as a springboard for developing Vertebrae to protect it, and the rest of the skeleton following suit? Could the "chambers" in the shell maybe... start to diverge into separate nested "bands to allow for freedom of movement, or something like that?
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Basal chordates lack a jointed vertebral column, and have instead a rigid cartilaginous "notochord".
A gladius is very similar to a notochord. If chordates could
do it, so can cephalopods.
However, I doubt that squids would become terrestrial. They're pelagic specialists. Most people use octopuses or cuttlefish for their terrestrial cephalopod ancestors.
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how about this. Similar to how "whales had to wait until their noses migrated to the top of their heads" (quoting the book 'Sapiens' by Harari) in order to facilitate breathing while swimming, in your case it was the exoskeleton that migrated to the interior of the body, in order to more closely focus their protection on the nervous system. I can envision the soft tissues gradually "seeping through" to the outside of the exoskeleton in response to a shrinking exoskeleton, perhaps due to a shortage of calcium in the environment.
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On an Earth analog, assuming all the selective pressures necessary are there, how large can a flower's bloom evolve to be? I'm referring the the vegetative part of the flower, the petals! I have no clue how large a bloom could become since different species have varying petal strengths, of which I can't find any information on.
The largest bloom to evolve here on Earth is *Rafflesia arnoldii*, which can grow to be 3 feet across:
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Plants can get pretty big. The largest leaf in the world belongs to the [*Raphia regalis*](https://www.thespruce.com/what-tree-with-worlds-biggest-leaves-3269789) tree, and it can grow up to 80 feet long. Flower petals are basically just brightly-colored, specialized leaves; assuming a circular pattern, a flower with petals this size would be over 150 feet across. Two of those flowers would barely fit on a football field.
However, depending on the nature of your story, you should also address the issue of *why* such a massive flower would evolve that way. A flower's primary function is to attract pollenators, and the only part of it that's useful to a pollenator is the center. If your world is high fantasy or soft sci-fi, "a wizard/space-botanist did it" might be sufficient. If not, you'll need a reason for this massive flower's existence.
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I don't think there is a hard limit; in theory with a stiff enough cell structure and a thick enough petal said petal could be just as big as you like. I mean there's probably a *practical* limit dictated by the cellular termination cycle of the plant, the flower simply can't grow past X size because the cells die before it can get that big but otherwise the sky's the limit.
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Flowers are quite fascinating and there already exists a large variety of them. What we perceive as flowers may actually be quite different - the world of plants is quite varied.
[](https://i.stack.imgur.com/1v2Nv.jpg)
For instance the above Caca Lilly is actually not a single flower, but a conglomerate of hundreds of flowers assembled together, with not a petal but a bract (broad leaf) that is white. This allows pollinators to be attracted similar to smaller flowers, but allows the broad leaf to gain in size.
It is also not unheard of for leaves to be large - therefore it is possible indeed for flowers to grow in size commensurately if the evolutionary pressures are present to do so.
The world of plants is fascinating - take for instance Pando - a plant in Utah. Using one root system it has grown to the size of 110 hectares, and is predicted to weigh 6,000,000 kg. This is the largest and heaviest organism on Earth - although on the surface it is often mistaken for a grove of Aspen.
It is easy then to conceive of a flowering system being very large - however considering that flowers are for attracting pollinators and consume resources to do so, the greatest limitation to their size is probably that they don't need to be large to attract the insects they need to attract. If there is no evolutionary pressure to be large, then there may be no need for it to be so.
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Let's imagine some very powerful dude with absolutely ridiculous strength/speed/durability. I'm not asking about the credibility of this, let's suppose it's magic.
He's got some magical sword as durable as it need to be (probably way more than the hardest thing we can think of today. Here again, let's say it's magic). It would be 115 cm long.
Now the real question :
**If this guy strikes air with his sword at a very high speed, what would be the effects ? Sounds, shockwaves, light, sparks, fire, plasma ? In which amplitude ?**
To clear up the ambiguity left by the "very high speed" expression, please give me your advice about these 3 orders of magnitude :
1. Speed of sound (~300 m/s)
2. 10 times the speed of sound (~3000 m/s)
3. Half of the light speed (~150 000 000 m/s)
Let's say it's the instantaneous speed of the tip of the sword.
We're on earth, same atmospheric pressure, same gravity, at sea level.
I'm looking for some cool effect without obliterating the entire world, so I'm looking for the best speed for that.
I'm hungry for maths too, if possible.
Feel free to give me your advice about how to make things even funnier if possible. Keep in mind that I'm very well conscious of the ridiculousness of the situation.
[Answer]
Perhaps the best way of looking at this is to use the equation for kinetic energy:
Ke=1/2M\*V^2
Since the mass of the sword is going to be held constant, the part of the equation where we see the change in the energy delivered to the target is the "V^2" part. In other words, the energy increases as the square of the velocity.
From [other](https://worldbuilding.stackexchange.com/questions/107827/why-would-be-preferable-use-crossbows-than-firearms/107866#107866) [Stack Exchange](https://worldbuilding.stackexchange.com/questions/101449/realistic-bow-weight-and-penetration-for-a-humanoid-of-large-size-and-strength/101464#101464) [questions](https://worldbuilding.stackexchange.com/questions/103034/arrows-beyond-the-speed-of-sound/103108#103108) we can see how the effects multiply. A longbow arrow can strike a target with @ 100J of energy. A crossbow quarrel, having more mass than the arrow and moving somewhat faster from a steel crossbow can generate @ 200J of energy. An Arquebus from the period, shooting a ball at a much higher velocity, can strike a target with *1000J* of energy, an *order of magnitude* greater.
So a typical "arming sword" (which I am assuming you are referencing when you say "longsword" weighs 1.1Kg, or 1100g
300m/s, KE = 49500 J
3000m/s, KE = 4950000 J
150,000,000m/s, KE = 1.2375E+16 J
For context, we will look at the Atomic Rockets "[Boom Table](http://www.projectrho.com/public_html/rocket/usefultables.php)"
At 300m/s, you are striking with just under the energy of a 20mm cannon round, or @ 11 grams of TNT. In context, an anti personnel mine might be that powerful, removing limbs fairly easily.
At 3000 m/s, you are delivering just under the energy of a kilogram of TNT. This is like having an anti tank mine or IED explode on your body, expect shredded remains to go flying across the battlefield.
At 150,000,000, m/s, you are delivering a nuclear punch, of @ 3.5Mt of energy. No human or animal target will even remain (the amount of energy is so great even "pink mist" will have been rendered into its constituent atoms in a rapidly expanding ball of plasma).
[](https://i.stack.imgur.com/WdpzH.jpg)
*Perhaps a high block won't be so effective in this case*
Frankly, I'll just sit back with my sniper buddies and try to engage from @ [3 km away](http://nationalinterest.org/blog/the-buzz/the-worlds-longest-sniper-kill-the-enemy-shot-dead-3871-24141).
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Let's try to work this out for the lowest order of magnitude.
1. 300 m/s (aka speed of sound)
So this dude has absolutely great speed/strength, as you mentioned. So let's assume his arm accelerates at 46.2 g of force, which a [human](https://en.wikipedia.org/wiki/John_Stapp) could definetly survive. That would take $v\_f = v\_o + at = 453.07t = 300$ (bad with units, so didn't include, sorry). So it's concievable that it could accelerate in less than one second to the speed of sound. Obviously, the object would produce a sonic boom (an order of magnitude louder of a bullet, I'd guess, so wear earmuffs because 150 decibels is a lot). One side effect would be any drones/air troops fighting him would literally get knocked out of the sky if the sound is at the correct resonance frequency (140 decibels to disable a craft that was up to 130 feet away, so can disable crafts up to 1/4 mile away).
The next question is what they are doing with that momentum $p=mv$ which would probably be several hundred kilogram-meters per second.
A rule of Newtonian physics states that the impulse imparted to an object is equal to the change in momentum for that object, provided no other forces or effects are involved. This requires an impulse in the reverse direction of hundreds of Newton seconds, which would also cause massive deceleration. For the impulse to not have him black out, he would have to use hundreds of Newtons of force.
**Reader: Don't worry, he's *that* strong.**
In the meantime, "light, sparks, fire, plasma" are not likely, because if you see a plane break the speed of sound, they don't go 'lights sparks fire plasma' (unless something is *really* wrong). So a big soundwave which could cause permanent hearing damage and knock drones out of the sky is it (unless you consider what it is that he/she's *hitting*). I don't dare forecast for the second/third scenario (my physics skills aren't sturdy enough).
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[Question]
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I am trying to figure out how to make a moon (75% of Earth size) of a gas giant habitable.
To give an idea of the technological level, here are technologies the colonists have access to:
* fully automated and robotised asteroid mining;
* space travel at 1/10 of the speed of light;
* terraforming technologies (however, only one project has been completed successfully by the time of their departure);
* genetic engineering;
* suspended animation.
Some details of the planetary system chosen for colonisation:
* K-type main sequence star (about 60% of Sun size);
* large asteroid belt which can be mined for all and any necessary materials;
* there is a gas giant in the Goldilocks zone;
* this gas giant does not have a strong magnetosphere;
* it has 3 moons, the largest of which is being colonised;
* this moon is the only candidate in the entire star system for establishing a colony.
The colonists do not have contact with Earth and cannot receive supplies or technology updates. The majority of them are scientists (not just STEM, social sciences as well) and engineers. The team is very small — under 200 people. At the time of arrival at the system, almost all fuel is exhausted. While, theoretically, it is possible to set up fuel production in the asteroid belt, refuel the spaceship and look for a more inviting place, the colonists decide to stay.
The moon chosen for terraforming is very much a dead rock. There is no water, atmosphere, or life. It is a perfect blank canvas for the project. However, it does not have a magnetosphere. So, there is a huge concern that the solar radiation will strip their new home of artificial atmosphere and damage organic life.
Is it possible to create an artificial magnetosphere? How can it be done?
[Answer]
# You do not need a magnetosphere
### Theory
[Kass and Yung, 1995](https://www.researchgate.net/profile/Yuk_Yung/publication/15467566_Loss_of_Atmosphere_from_Mars_Due_to_Solar_Wind-induced_Sputtering/links/574cab2808ae061b3301e0ea.pdf) have one of the higher estimates of atmospheric sputtering (removal of gasses from the atmosphere through interaction with the solar wind) from Mars. Their work deals with loss of oxygen from Mars. For all sources of oxygen (diatomic, carbon dioxide, and water), particulate loss rate on a young Mars with a thick atmosphere is estimated to be about $4\times10^{28}$ particles. Multiplying by the mass of each particle, this works out to about 1500 kg of atmosphere per second.
This may seem like a lot but it really isn't. Lets say your planet has an atmosphere 1/10 the mass of Earth's (if it is smaller and thinner). The atmosphere is then about $5\times10^{17}$ kg. To remove 1% of this thinner atmosphere (or $5\times10^{15}$ kg) at 1500 kg/s would take 100,000 years.
Certainly, on the time scales of planets this is a big deal. But for humans? Not so much. If you have the ability to add a whole atmosphere in a few centuries, surely it isn't to hard to replace 1% of your atmosphere every thousand centuries.
### Application
This one is easy. Behold [Titan](https://en.wikipedia.org/wiki/Titan_(moon)), moon of Saturn. Titan is the only known moon with a significant atmosphere (surely of interest to the potential moon-colonizer). It also has no magnetosphere, and its parent planet Saturn is not nearly as magnetically potent as Jupiter. Finally, it is also tiny; its mass is 2.3% of Earth's and its surface gravity is 14% of Earth's.
Yet, it has a dense nitrogen atmosphere with a mass 1.2 times that of Earth's. Certainly Titan has less solar wind to deal with than Earth, but nonetheless it maintains has maintained a thick atmosphere for billions of years after its creation with only a fraction of the surface gravity of Earth.
Regarding solar wind, [Venus](https://en.wikipedia.org/wiki/Venus) is also here. It is closer to the sun and gets more solar wind. Despite having no magnetosphere, it still has a super dense carbon dioxide atmosphere almost 100 times more massive than Earth's.
# Conclusion
Worst case scenario, you have to spend some time and money repairing your atmosphere every few millenia. Best case, you find one of the myriad reasons that atmospheres are protected; i.e. whatever it is that is protecting the atmospheres of Venus and Titan.
I have no doubt that your magnetosphere-less moon's atmosphere will be removed over geological time (a few billion years), but your sun is also going to expand into a red giant in a similar time span, so lets worry about first thing first.
[Answer]
You may be interested in [this](https://room.eu.com/article/our-changing-world-and-the-mounting-risk-of-a-calamitous-solar-storm) article, which is about enhancing Earth own magnetosphere, but can obviously be applied to any other celestial body.
It has a lot if information and is a recommended reading; here is an Executive Summary (for the part of interest):
* building a magnetosphere for a planet by putting magnets on planet itself is inefficient.
* to protect a planet from solar wind/flares it may suffice a smaller shield in L1 (Lagrange Point 1, which is a *unstable* orbit between sun and planet).
* Shield must be kept in position by active (ion?) motors because of instability; needed push is very low.
* Shield should have a magnetic field charge level from 1 and 2 Tesla depending on desired coverage.
* Energy to maintain the shield can be directly extracted via solar panels (no need for autonomous generators).
This study has been adapted by NASA for a proposal for a [Mars shield](https://www.hou.usra.edu/meetings/V2050/pdf/8250.pdf).
In Your case having the shield in L1 of the satellite wouldn't help, of course, so it should be in L1 of the planet and large enough to protect gas giant and bodies orbiting it.
It may be necessary to step up magnetic field to cover a larger area, but if this is something NASA is actually evaluating *now* it should be a no-brainier for any race able to build starships.
[Answer]
science.nasa.gov:
"Earth's magnetosphere is part of a dynamic, interconnected system that responds to solar, planetary, and interstellar conditions. It is generated by the convective motion of charged, molten iron, far below the surface in Earth's outer core."
So in theory to have a magnetosphere you need a huge amount of charged molten iron. Conventionally, this is impossible to generate because the quantities of iron are on a planetary scale, difficult to obtain, as with your situation, core mining other planets and moons in the solar system would require too many resources.
However, if we are talking fully automated and robotized mining, theoretically they could mine asteroids for iron, provided there are enough iron rich asteroids in the system, the quantities in question are still very large and would require a shaft to the core of the planet, which at the given technological level would be a little difficult.
Alternatively, if vacuum energy is a thing that they have, one could go with an extremely strong electromagnet, at the surface or the center of the planet. Vacuum energy, however might again, be a bit out of the technological reach of our colonists and if it was on the surface of the planet it would severely interfere with any sort of un-shielded electronic equipment.
So, in reality, for a small team of scientists at the level of tech described, it'd be pretty darn difficult to pull a feat like that off. It would take a more advanced civilization years to gather the necessary iron and to create the conditions for a magnetosphere to be created. Without significantly more advanced tech, or the resources of a whole civilization, im afraid you'll have to look for a new planet, or simply shield your shelter from radiation. That'd probably be a lot easier than creating a magnetosphere.
On the other hand, today we are already discussing mars' magnetosphere and some info can be found here:
<https://www.hou.usra.edu/meetings/V2050/pdf/8250.pdf>
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[Question]
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One of the tropes I see very frequently on TV is having a supervillain build a huge mind controlling device that suddenly takes over an entire town, or eventually even the whole world.
So, it got me thinking, what would be the most plausible way to achieve this effect with present day / near future technology? Mind you, I know that it is not possible to do it, or else some superpower would've already done it... I mean what's the most **plausible** way of doing it, that requires the least amount of suspension of disbelief from the readers?
Whenever this trope comes up, the mechanism generally involves a variation of this:
1. Subliminal radio waves, through cell phones, network antenas or satellites
2. Nanomachines that bind to and corrupt the nervous system
3. Neurologically altering chemicals emitted to the air or to water supplies
Could any of these achieve the effect we want, in a relatively plausible way? (you can add another mechanism if you see fit).
Here are the characteristics of the effect I seek:
* It should cover a wide area, at least the size of a large city (if it affects the whole world, the better)
* Its effect should be immediate. By this I don't mean that the supervillain can't have a long preparatory period, ranging from months to years, where he distributes the chemicals or nanomachines. What I mean is that the effects will remain dormant until the supervillain *turns on the switch*. As soon as he does that, **everyone** in the area of influence should **immediately** fall under mind control, so as to avoid people escaping the process.
* By mind control, I mean that everyone affected will obey every command from the supervillain. This may range from turning people into mindless zombies... to having perfectly normal people with perfectly normal brain function and everyday activity, except for the fact that they seem unable to grasp the concept of "disobeying the leader".
For the purpose of this question let's assume the human's brains function the same as in our world. Let's also set aside the "magic factor"... I want a scientific solution.
[Answer]
First, Problems: I don't believe you can get literally everyone in the world, there is simply no reliable way to reach every person in the world, and the biological variance is so great you couldn't even do it with an airborne virus. You *might* be able to *kill* everyone in the world with some biologic particularly hardy and virulent, but to have a virtually undetectable neurological effect on them is a much taller order than just disrupting their life functions.
Another problem is that obeying an order from a specific leader is implausible. Not everyone in the world will understand such an order, and without a specific auditory signal (like a password, tonal combination, whatever) there is no way to tell whether a command came from the leader, or your sister. That virtually rules out any biological, the only item on your list that could know a command came from **the leader** is a computing device.
Given all known or expected technology in the next few decades, we are nowhere *near* understanding how the brain works well enough to implant any kind of machine, nano or not, to have any kind of a specific effect on belief systems, free will, etc. You might be able to cause some kinds of overwhelming emotional reactions (rage, sexual urges, fear) by releasing some kind of drug cocktail in the brain; but not anything as specific as "Send $1000 in cash to this address, do whatever you must to get it."
We just do not understand the brain that well.
I think your best bet, in a small town, is a biologic *excuse* to gain access to people. I presume the villain has resources. Pick a town with a singular water supply; and infect it with something fairly nasty, that gets worse with time. When people start getting sick, come to the rescue with the cure (a real one), and in the process of administering the cure, also administer a powerful hypnotic drug. THEN you can implant the suggestion in the subconscious that the leader must be obeyed.
Up to 25% of people cannot be hypnotized; the percentage is much less if drugs are used but still not zero. That said, innocuous ways of testing responses can tell the hypnotist if the hypnotism is not working for some reason. These can be disguised as normal questions to test reactions to the drug on the pretense that it affects some people differently. So the hypnotist can easily avoid implanting their control commands in people where they would not work anyway, and thus avoid raising any suspicions.
The people that do not come in for treatment will die; which is convenient for our villain. Of course he has to be smart enough to create the malady and the antidote and to position his corporation as the only one capable of saving the citizens, refusing to share their trade secrets of how this was done. He will provide the cure for free to all comers with a signed release; so it is not a commercial transaction (avoiding some laws about safety of commercial products). The rest, I'd have to leave to lawyers to make it okay for the villain to inject willing participants.
[Answer]
Chemicals, needing to diffuse through a supporting medium, are far from quick and effective. Plus, with distance their dilution increases, reducing their effect.
Assuming you have a clear and complete model of how the synaptic map of an individual to define his/her consciousness, you can use nanomachines guided by radio-waves to tweak the proper synapses and alter the thoughts (and actions) of targeted individuals.
[Answer]
Scopolamine.
People basically follow any instruction they're given under the influence.
Now getting the dose right is difficult, too much and people die - but if you give enough, you'll be left with a bunch of mindless drones and a percentage of dead people.
The effects are pretty much immediate.
There's a very interesting documentary by VICE on it,
it really is scarily effective.
It works in gaseous form, so can be distributed easily.
Of course, the dosage is a problem, but some evil supervillain would not really be too bothered with the losses...
[Answer]
We don't know enough of the brain to be able to design something within your requirements. Dormancy until the switch is thrown would require "hardware control" - you'd need to go the nanomachine way. Possibly, establishing an entire secondary personality and having it take control.
Problem is, humans don't have such nanomachines yet and don't know whether they're even theoretically possible. So it's difficult to call this a *reality check*; you'd need a hefty dose of suspension of disbelief.
Relaxing some constraints could lead to a feasible scenario though. People *not being able to conceive a disobedience to the leader* is doable enough that several nations and cultures actually came close, not with a single Dr Evil's silver bullet, but with several less powerful weapons used together.
The rationalization factor is actually already there: a human being can be induced to do something and he will concoct an explanation, and/or resent being forced to think about *why* he did something. [This has been demonstrated in "split-brain" patients](http://www.azquotes.com/quote/1572155), that had the *corpus callosum* surgically resecated to cure epilepsy. The left and right halves of the brain continued to coordinate, but imperfectly; so that it was possible to ask *in writing* the person to do something, and when asked *orally* to explain why he was doing that, the person would fabricate an answer - and *defend* it.
It remains to get the people to *obey the leader*. In a limited way this also has been demonstrated. But the leader must make himself known. For he needs first to give *suggestions* (or even *orders that can be disobeyed*), and then find a way to make people who disobeyed uncomfortable without there being an obvious explanation (subsonics could be a good choice). Lacking an explanation, the brain will fabricate the easiest explanation: *you feel discomfort because you disobeyed the leader. Because you wanted to obey the leader*.
This kind of conditioning *can* make people do things that normally they wouldn't, such as administering electric shocks to people - it is a variation of the well-known [Milgram experiment](https://en.wikipedia.org/wiki/Milgram_experiment) - but it can't make everyone into a mindless zombie. It can do that with *some* particularly vulnerable people, but nothing more.
You can build on that, using the most fanatic believers to rein in the others; several police states and "mind-control" sects did just that. Several tools are ready to be employed - psychological pressure, peer pressure, and even a made-up language (see Orwell's *1984*). Pervasive surveillance. Periodic loyalty checks with drugs and lie detectors.
[Answer]
I like how you want to create mind controlling device, and probably spend a ton on money, to control people when all you need to do is to set up an instagram account. Or youtube channel.
If you want to go the extra mile, why not start some revolution. Cuba, South Korea, China, Cambodia.
If you want to cover the whole world... enter Ozymandias. Just hang some spaceshippy thing in the space and tell people "Bend to my will and I will save you from the Aliens that want to destroy you {laugh, curl the evil moustache}".
You could also create some loveable and highly watchable cartoons and soaps where you hide brainwashing pictures. Then you just send via radio and speakers a message "the hen is in the fox, the fox is blue and lazy" to turn them into obeying the leader.
[Answer]
## Foreword
Unfortunately, it seems that most of the answers here have derailed into something I specifically have not accepted since my first comment in the OP. Namely, people have been suggesting that I should switch from the mind-controling device into more normal ideological propaganda. Unfortunately, this falls outside the scope of the question, for these reasons:
1. Propaganda doesn't work on everyone. Its mechanism is psychological and societal. I wanted a purely biological mechanism with high penetrance, irrespective of education, ideology or opinion
2. The purpose of this question was to test a particular TV trope. Propaganda falls in another genre altogether, the dystopian genre
3. In that particular TV trope, the machine is switched on and off at will (in fact, it's the super-hero's job to turn off the device, imediately saving everyone)
4. A mind-controlling device is cooler (yep, that's an objection I have, too)
Only Amadeus and a4android's answers tried to address the question, so I'll try to answer my own question piecing together what I liked most on both answers and my own knowledge on the matter.
First, I have to agree that this device is not possible using present-day technology. But I have said that near-future tech was fair game. I don't think that nanomachines that can be introduced in the organism for medical purposes are so distant in the future so as not to allow the use of nanobots on this question. The fact that we still know so little about brain function is a more significant hurdle... but maybe we can circumvent it with as little handwave as possible (which was the purpose of the question all along).
Second, I'll take into account some objections in Amadeus' answer, namely:
**Objection a.** 25% of the population is non-hypnotizable; The device should work on those people too
**Objection b.** People should be susceptible **only** to orders issuing from the leader, not from other people
**Objection c.** The instructions should be given in a way that everyone will be able to understand, irrespective of other factors, like language or IQ
Having said this, I've figured out four possible approaches, all using nanomachines. These could be spread by the supervillain in a city during months or years and could remain dormant until the *switch was activated*.
Note, these four approaches are displayed in increasing order of personal preference. Meaning I like approach #1 less and approach #4 more
---
## #1. The Puppeteer
In this approach, we have different types of nanomachines that invade different parts of the human brain. Some nanomachines would be stimulatory and others would be inhibitory. The stimulation / inhibition could be done through electrical impulses or microinjections of selected neurotransmitters.
The inhibitory nanomachines would go into the frontal lobes, where the higher funtions of the brain (like will, abstract reasoning and personality) are located. By selectively inhibiting the frontal lobes, the nanomachines could effectively *shut down* all voluntary control from the victim.
The stimulatory nanomachines would then take hold. These would nestle on various parts of the primary motor cortex (PMC). [We have a pretty reliable map of the PMC](https://academic.oup.com/brain/article-abstract/60/4/389/332082/SOMATIC-MOTOR-AND-SENSORY-REPRESENTATION-IN-THE?redirectedFrom=fulltext), such that we know which body part will move if an electrical stimulus is given to a specific region of the PMC.
[](https://i.stack.imgur.com/YvDpz.gif)
The nanobots could then be programmed with simple movements, like walking a specific number of steps or getting up if the host fell down.
**This means that the supervillain could effectively turn people into mindless puppets.**
All people would be affected, regardless of language or hypnosis susceptibility. Also, since everyone but the supervillain would be unconscious, there would be no one else to order people around. Besides, only the supervillain would have control over the nanobots.
---
**Hurdles**:
1. This is an over-complicated approach. The supervillain would have to fabricate a myriad of different nanomachines and those would have to be allocated to several different parts of the brain. All those nanomachines would have to be perfectly synchronised on the same individual, so as to obtain the desired effect
2. Even if everything went smoothly, the resulting movements would be uncoordinated and jerky. Coordination relies on the integration of the PMC with secondary motor centers. We still know little about how those work, so I think that nanomachines located in the secondary motor centers would lead to too much handwave. The puppets would not have fine motricity, so the tasks they could do would be very limited. For example, they could not do something as simple as picking an object from a table... it would be like trying to grip a prized toy with those claws from the amusement parks
3. Also, there would be no way for the nanomachines to integrate their motor stimuli with the sensory information coming from the host, like the eyes or the proprioception receptors. The nanomachines could move people around to a specific location using GPS, but wouldn't be able to detect unpredictable obstacles. The human puppets could fall on ditches or trip in one another.
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## #2. The Poisoner
Maybe the supervillain could use something like approach #1., but only in part. Namely, the part about inhibitory nanomachines in the frontal lobes that would *shut down* the conscious person.
The supervillain could then enter town and give each person a dose of the mind altering drugs that form the basis of Amadeus' answer. If, by biological variance, some slaves did not respond to the drugs, the supervillain would only need to shut them down again using the nanobots... and then kill them.
---
**Hurdles**
1. Time consuming. The supervillain would have to find ways to drug everyone in town.
2. Some people could escape, if they would be hidden from plain sight or stuck in inaccessible places when the device was turned on
3. Even more complicated than approach #1.
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## #3. The Messiah
Since approaches #1 and #2 are so complicated, maybe we could focus the nanobots on a single spot. The [limbic system](https://en.wikipedia.org/wiki/Limbic_system) is responsible for lower brain functions, namely related to emotions or primal behaviors. Also, it is well accessible... the nanomachines could crawl up the nasal cavity and then lodge themselves on the lower parts of the brain through the pores of the ethmoid bone.
[](https://i.stack.imgur.com/frb3A.png)
[](https://i.stack.imgur.com/CUvgK.jpg)
By stimulating this regions of the brain, the nanobots would cause all kinds of heightened emotions, like fear, rage or lust. These emotions would be so strong, that they would override any rational thought, like Amadeus says in his answer. But no matter how much the victims would indulge in violence or sex, their urges would not be satisfied as long as the nanomachines were activated.
It would require a level of self-discipline akin to a shaolin monk to be able to resist this kind of overwhelming sensations.
Enter the supervillain. He would place a tracker on him and the nanomachines would be programmed to change their pattern of stimuli accordingly to the GPS calculated distance from the villain. As the supervillain approached his victims, the nanobots would cease their fear / rage / lust stimuli... and could even induce pleasurable stimuli.
People would eventually be conditioned to view the supervillain as a kind of liberator. Once this was accomplished, he could tune his stimulation with finer detail, inducing pleasurable stimuli as a reward for good obedience and unpleasurable stimuli as punishment for disobedience.
Eventually, people would be conditioned to obey the leader blindly, almost in a pavlovian way. The nanomachines would then be dispensable. Propaganda and regular brainwashing would suffice, for trust on dear leader would be a non-issue.
---
**Hurdles**
The pre-conditioned victims would have unpredictable and erratic behavior. Many slaves would die before the supervillain could do anything about it. In fact, there's no guarantee that the supervillain would not be killed previously to the conditioning (maybe in a car crash or something like that).
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## #4. The Wish Seeder
This is my favorite approach. Unfortunately, it is also the one that requires the greatest amount of handwave.
I inspired myself in a4android's answer about synaptic mapping. However, synaptic mapping is pretty much beyond our reach in the near future. Also, the synaptic mapping of each individual is different, so this concept would not be able to sustain widespread mind control.
However, as approaches #1 and #3 show, we don't need a detailed synaptic map. We can focus on specific regions of the brain... what if we focused on the frontal lobes?
As I have said, the frontal lobes of the brain are the ones associated with the higher functions: will, abstract thought and personality.
Unfortunately, artificial hardware and neurological "hardware" are still largely incompatible, because they have different languages. We still do not know how to translate electronic language into synaptic language.
However, we already have rudiments of this translation in the form of [neuroprosthetics](https://en.wikipedia.org/wiki/Neuroprosthetics) and [brain-computer interfaces](https://en.wikipedia.org/wiki/Brain%E2%80%93computer_interface).
Let's imagine that the supervillain has perfected an interface that can translate an instruction from a computer into a thought via a nanotransmitter lodged in the frontal lobe of the victim.
The leader could then type the order in the computer and the person would find that instruction perfectly reasonable and/or desirable.
This is the best, because unlike all the previous approaches, the slave can perform complex tasks and behave in a predictable and reliable way.
---
**Hurdles**
Needs a high amount of handwave, because we can't explain the details of how such an interface would function. Also, in order to account for objection c, the computer instructions shouldn't be given in the form of words in a specific language, but in the form of images or such. Still, an interesting concept that could be perfected with some more imput from other commenters.
[Answer]
After many years of development, brain–machine interfaces (like those [Neuralink](https://en.wikipedia.org/wiki/Neuralink) wants to develop) are a reality. They rapidly become popular and "everyone" has one implanted.¹ After a few years, the percentage of the population with that implant is about the same as those having a smartphone nowadays (which are themselves replaced with mind-calls).
The hard part, creating the mind interface and "installing" it is done completely in the open. It is even paid by the victims themselves! (there are company benefits for installing it -so they have more enhanced employees-, as well as government subsides).
Then, a given day, *the switch is turned on*. There are multiple ways it could work:
* your implant sends you subliminal audio messages continuously
* dissenting messages are filtered out.
Supervillain runs for president? The other candidates -even assuming they were somehow immune to the mind control (for example, they grew out in an Amish community)- are blanked from what the user sees, their speeches filtered. If someone is talking bad of Loved Supervillain, the implant -which parses all conversations- cancels that 'noise'.
The ability to ignore other people is even a documented feature. No longer worry about that annoying neighbour, work/study quietly in a noisy environment… There might even be apps for using a third party blacklist (I can easily see many people configuring their implants to block all beggars in town). It was simply not expected that someone could insert their adversaries on every device.
* the implant will stimulate certain brain regions during Loved Supervillain speeches (according to what effect he wants to produce), and ones leading to rejection for opponents
You also have multiple options for Supervillain identity:
* it was the company owner the whole time
* Supervillain is a scientist / implant programmer working for the company
* Same as above, but he is a disgruntled employee that got fired for raising up how insecure their product was
* Supervillain blackmailed an employee from above to get this result
* Supervillain hacked the company and modified it to control the implants (too fictional, imho)
* mind advertisements.
This was actually unintentional. Implants are able to insert advertisements (maybe used to get you a cheaper implant?) into your life (e.g. showing a popup on you visual field, or producing a contextual ad for what it detects the user is doing). Supervillain found it works *too well*. He is simply paying for the ads he designed to play into everyone's minds (and offering high enough prices to ensure competitor don't come through)
¹ This may seem unlikely, but how believable would it have been 15-20 years ago a prediction that everyone would carry a device with them that tracked their position and almost every interaction they had with other people?
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[Question]
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In my world there are this people that live in a great jungle. They are as advanced as the other civilizations of the world (late medieval standards) with a complex society, work specialization, strong army, large cities, rich culture... But they do things in a very different way than the others, for example they don't use metal at all, instead their weapons are crafted from hardened wood, sharpened stones and animal bones and their armor is made of lamellar paper. But anyway about the question, they never developed agriculture because there is already a lot of food in the jungle. Could they get what they need to develop villages and even great cities only by gathering and hunting? If so, what kind of new techniques and technologies (corresponding to field crop rotation, plows and hoes for example) do you think they would develop? Thank you all in advance and this is my first question here so please tell me if I did anything wrong.
[Answer]
## Consider hunt-rotation, magic, or trade.
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**First, let's address *why* the civilization cannot be maintained through traditional hunter-gathering.**
As @kingledion mentioned, there is no need to develop agriculture; we have observed cultures that do fine without it and rely on the land instead. So it's possible! That's a start. However, his answer describes *small, thinly spread societies, and not cities*. If you want densely packed populations, you cannot harvest the same, adjacent land forever; biodiversity will lower, and you will eventually run out of food. Therefore, you **cannot** do it through the conventional means as he implies.
So the question is now "**how does a stationary settlement manage the nearby resources to continue using the same land**?"
---
**Magic**
You've described the use of magic to replace metal with durable wood; I don't see this why this magic couldn't be used to overpopulate the area with wildlife, draw in species from afar, or transmute existing matter into food. If magic can scale to the point where metal is completely replaceable, I'm sure food can be logistically feasible in this way.
**Land Rotation**
I wish I could provide the source for this, but I've lost it. Some Native American populations rotate around a certain point throughout the year, with a quadrant used for hunting and gathering in each season; this allows nature to replenish harvested regions before they need to be used again. Instead of moving temporary settlements into each quadrant, why not put your jungle city in the center - and restrict the legal hunting/harvest areas, while cycling yearly?
**Controlled Harvests**
An extension of the way hunting seasons work in real life, this scenario imposes laws that determine what can be gathered throughout the year. Perhaps there are "seasons" for certain berries and "seasons" for animals. This will allow biodiversity to be maintained; overharvesting during each season must compensate for the limited food supplies resulting.
**Trade**
An interesting approach. Perhaps the land the city/cities is/are in is inconvenient for agriculture - mountainous, marshy, or otherwise hard to work with. Instead of farming crops and animals, your natives may be able to gather a local resource - timber, gemstones, magic elephant tusks, you decide - and trade with visiting societies for food.
[Answer]
# There are hunter-gatherers exposed to agriculture that did not adopt it
American Indians in the Pacific Northwest and California generally did not make a transition from hunter-gatherer to agriculturalists, even though they were in trading contact with groups from the rest of North America, and almost all of those groups were agriculturalists.
The Pacific-Northwest Indians in particular were able to reach population densities similar to the agriculturalists of the Great Plains due to the richness of their environment. There is lots of available seafood, and in particular the salmon runs each year provide a huge calorie windfall. Incidentally, this is the reason that there are so many and so large grizzly bears in the same area. What is good for the bears is good for the people too.
However, this has more to do with lack of crop options than it does with the greatness of the salmon fishing. Corn was by far the dominant crop in temperate North America; the only other competitive grain was Indian rice from the Upper Mississippi and Great Lakes. Neither crop is appropriate for cultivation on the West coast. Indian rice depends on flooded marshland, and corn needs a warm wet growing season. While the eastern half of North America has warm wet summers, the Pacific Northwest has dry summer, as you can see from this graph of Seattle's rainfall (source: en.climate-data.org)
[](https://i.stack.imgur.com/xKBcA.png)
With a staple grain unavailable; there wasn't much incentive to shift to agriculture for the Northwest Indians. Other options like the potato from South American hadn't transfered that far north yet, and there were essentially no livestock options for a pastoral lifestyle (the llama, too, did not transfer that far north in pre-Columbian times). So the Indians of the Northwest had no better options than the fish that ran freely in their streams.
**Conclusion**: A sedentary civilization could prosper in a good climate, with an ample natural food source. There are real-world examples of such peoples developing religion and monuments (totem poles) and medium-sized villages and what have you. But it would primarily be because there wasn't a better agricultural option than the natural resources available to them. To develop further, these people would need little intrusion from outside agriculturalists, and a well explained source of natural bounty; like a giant swampland full of wild rice, lots of fish, etc.
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Do eskimos have agriculture? It's certainly possible for a culture to live as fishermen and not grow crops to a large extent (just a few herbs and vegetables).
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Yes, you can have an advanced civilization without having agriculture. If you have neighbours who farm and have industrial infrastructure and you can get all kinds of raw material and tools from them. Either by trading something valuable they want but don't have, or by taking it by force.
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**Grazing**
What about a cattle-like people that simply graze off whatever already grows? Maybe they can eat trees whole and their stomach is sort of a wood-burning stove?
**Atmospheric**
Perhaps they feed from molecules or even organisms in the air through osmosis?
**Steampunk**
What if their stomach is more of an engine that can be fueled by power cells of some kind? (think steampunk) Then I guess power cell manufacturing would end up being a kind of agriculture for them.
**Nature**
After all, agriculture itself (plants) make use of sunlight. What would prevent a race of beings from having green skin that does the same?
**Land of plenty**
If the forest they occupy is as vast as you say, I see no reason they wouldn't be the dominant life form (over any animals or competitors for food), and thus, they would have no trouble taking all the naturally growing fruit they could possibly eat. Maybe there are different kinds of trees so that fruit grows year round without any tending to?
**Aquarian**
Maybe the race only needs water to live - not solid food. Then any kind of rain, even seasonal, would be enough to sustain them. They would obviously be able to store it up for any dry spells if they had to, or you could have the planet/world provide continual rainfall.
**Vampiric**
Vampires don't require solid food. They obtain their sustenance through obvious other means.
**No food at all**
I thought I'd also point out that having a race of beings that require no sustenance at all could be perfectly acceptable in the realm of fiction. This question (and perhaps the food tag) seems to lean towards an inbuilt assumption that the species does require food to live. If they didn't, agriculture would be completely unnecessary. There are any number of other mechanisms that could explain their continued existence.
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Looking at the problem logically, you need a few things to support a city. You need an individual worker to be able to produce more food than s/he needs to feed him/herself, and you need to be able to preserve and transport that food.
It's true that you can't support a large city on the produce of hunting & gathering from the adjacent land - defining adjacent as what city people could walk to, produce food, and return. But you can't use agriculture to support large cities on the produce of adjacent land, either. The larger the town, the further the distance you have to transport food. For a fairly well-documented historical example, Rome depended on grain & other foodstuffs from all around the Mediterranean.
Terry Pratchett said it far better than I could: "Every day, forty thousand eggs were laid for the city. Every day, hundreds, thousands of carts and boats and barges converged on the city with fish and honey and oysters and olives and eels and lobsters. And then think of the horses dragging this stuff, and the windmills … and the wool coming in, too, every day, the cloth, the tobacco, the spices, the ore, the timber, the cheese, the coal, the fat, the tallow, the hay EVERY DAMN DAY…"
"Against the dark screen of night, Vimes had a vision of Ankh-Morpork. It wasn’t a city, it was a process, a weight on the world that distorted the land for hundreds of miles around. People who’d never see it in their whole life nevertheless spent that life working for it. Thousands and thousands of green acres were part of it, forests were part of it. It drew in and consumed…"
So that's what you need to get a city (or a society) that's not based on our ideas of agriculture. People have to be able to harvest more food than they need, preserve that food somehow, and transport it to the towns & cities. Perhaps a lot of the food is fruits & nuts from jungle trees that are too slow-growing to be amenable to conventional agriculture - certainly not the "plant in the spring, harvest in the fall" kind of farming. E.g. olive trees, which take a decade or more from planting to producing fruit, but can then go on being productive for centuries.
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Yes provided the area they live is very productive naturally. see the Native Americans that used to engage in potlatch. The pacific northwest natives had fairly large societies and engaged in huge ritualized waste of resources. normally such large populations and heavy use of resources would require either agriculture or herding. Yet they were hunter gathers, the area was so naturally productive the normal rules went out the window. Researching them can give you information on how they collected the resources and how it affected their culture.
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Let's say there's a habitable planet somewhere, covered with very deep cool water ocean. By very deep I mean thousands of km, but the exact numbers don't actually matter.
According to [water's phase diagram](https://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Phase_diagram_of_water.svg/700px-Phase_diagram_of_water.svg.png), at 0.6 GPa and 0oC, or 1GPa and room temperature denser than water ice VI becomes stable. The water is significantly salty, and I have no idea how it would influence ice formation. Say it would just drive the boundary a bit deeper. Also I see no reason for temperature to be far from 4oC where the water is densest, at least that's what we see in the [Mariana trench](https://en.wikipedia.org/wiki/Mariana_Trench). So let's say there's icy ocean floor somewhere between 60 and 100 km deep, until Titan or Neptune is actually explored.
Now there's also a layer of buoyant organic matter covering most of ocean surface. It is actually thick enough for a small human colony to survive on top of it. And that colony is desperate for metals. From the ocean composition they think there must be at least iron, copper, and gold somewhere in the sediments on the ocean floor. Also there must be a lot of sticky organic ooze there.
So the question is: **how to explore the floor and bring back samples without using too much metal?**
The colony has a few portable, reliable, efficient fusion reactors capable of using any hydrogen-rich substance. However, they don't want to risk any of those unless absolutely needed. Also they can mine nearby asteroids/moons for metals and silicates, but that's expensive and again they don't want to risk the only ship too much. They can 3D-print any material at hand into any imaginable form, let's say big crystals are out of reach though (a diamond monocrystal submarine, huh). A robot capable of any formalized, non-creative task can be programmed. Other than that, let's say they are on todays mankind level. Calling for interstellar help is prohibitively expensive, they're already in debt and they also sunk a leased spaceship.
What I could think of:
* brute force - make a very thick steel bathyscaphe. I have little idea if steel can withstand that kind of pressure.
* use graphite bricks (hello [RBMK-1000](https://en.wikipedia.org/wiki/Chernobyl_Nuclear_Power_Plant)). How do they patch the seams between bricks?
* Power - accumulators? wires? just H2+O2?
* handling the ooze - how? Freeze it with liquid nitrogen, then drill through?
* How long would the journey to the bottom take (w/o humans on board)?
Feel free to correct/criticize my assumptions here if you feel they are wrong. Links to existing similar worlds are appreciated as well.
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The Challenger Deep of the [Mariana Trench](https://en.wikipedia.org/wiki/Mariana_Trench) is 11 km deep, and that is just a small fraction of the depth you want to explore (the [tallest mountains on Earth](https://en.wikipedia.org/wiki/List_of_highest_mountains) are all less than 9 km above sea level), so you'd be three to five times the total elevation range on Earth. This is very, very deep.
**A Dredge System Won't Work**
Even a 60km to 100km cable or chain reaching from the surface to the bottom would require a lot of material and weigh a lot, and would have to be of a material that would be function at every combination of pressures and temperature from the surface to the bottom. This would be on the same order of magnitude as a cable for a space elevator (low Earth orbit is about 100 km up), and is [basically impossible](https://arxiv.org/pdf/cond-mat/0601668.pdf) (Pugno 2006) to do so, even with state of the art materials, technology and resources (one estimate cited in the linked paper was $10 billion for an approach that it determined wouldn't come close to working), so there is no way your folks could build that.
**What About A Robotic Mining Submarine?**
As noted in the comments, there is also no sensible reason to maintain a low pressure part of submarine to retrieve materials from this depth, which makes the engineering problem much greater than one in which an incompressible fluid inside the cavities in the submarine can counterbalance the exterior pressure. But, you would still need to have a control system (either wirelessly remote controlled - possibly with intermediate depth relay buoys, or AI), a power system, a propulsion system, and something to sift through the sediment to distinguish useless material from the materials needed (a non-trival task for materials you can't grab with a magnet).
*Mining Sediment Would Be Very Challenging*
Any sediment to sift through would tightly packed and might very quicky become [sandstone](https://en.wikipedia.org/wiki/Sedimentary_basin) at such high pressures, with a minimal sandy layer, in which case you'd need to break up the sandstone. And, before you got to the sandstone which might have minerals in it, you'd probably have to clear away slushy near ice and organic mud on the bottom. So, you'd need a slush shovel, then a sand mover/sifter, then a sandstone breaker that would make bits fine enough to analyze, and then something to analyze the content.
And, it is entirely possible and indeed, likely that the metals would be tens to thousands of meters under the sea floor, so you might need some underground mining of the sea floor as well to get at the good stuff.
Then, once you segregated out the good stuff, you'd need to bundle it up somehow and have enough propulsion to get it back to the surface (perhaps some sort of compressed air could adjust boyancy and float it up). Also, the good stuff in all likelihood wouldn't be pure elements. It would be, at best, rich ores or oxidates or something like that which would require further processing once you obtained it.
The materials you used would have to not corrode in cold salt water, would have to withstand sometimes strong currents, would have to be big enough to carry an appreciable amount of mined material plus everything you brought to mine it, so even if you unmanned mining sub is barely bigger than a backhoe attached to a small oceanic submarine, you'd probably need something on the order of 10,000-100,000 kg at a minimum. Air independent propulsion rather than nuclear propulsion could probably work, as the total distance travelled wouldn't have to be very great between refueling.
*A big investment mining submarine concentrates limited resources in a few high risk projects*
But, this is still a major engineering undertaking, and you only get one or two major mistakes and your efforts end up at the bottom on the unthinkably deep ocean. This is a big problem in an environment where there are necessarily lots of unknown unknowns.
**What About Filtering Water For Trace Useful Elements?**
On the whole, sieving low concentrations of materials dissolved in water (perhaps using a pump to get water from deeper parts of the ocean where mineral concentrations might be greater) seems like a better plan.
For example, on Earth, typical [seawater](https://en.wikipedia.org/wiki/Seawater) contains the following:
*Seawater composition (by mass) (salinity = 3.5%)*
Oxygen 85.84
Hydrogen 10.82
Chloride 1.94
Sodium 1.08
Magnesium 0.1292
Sulfur 0.091
Calcium 0.04
Potassium 0.04
Bromide 0.0067
Carbon 0.0028
Vanadium 1.5 × 10−11 – 3.3 × 10−11
All sorts of goodies are present in sea water [in more trace concentrations](http://unicorn.ps.uci.edu/M3LC/handouts/Seawater.pdf).
*Filtering Water Is Much Simpler And Disperses Risk Across Many Filters*
A system that filters impurities from cold high pressure water would have a lot less moving parts and would be easier to set up in multiple small units that could be planted in a line, and could be floated at different depths for different materials.
With a water filtering strategy, it wouldn't be important to land your filters right where rich deposits were found in the sediment the way that it would if you were digging for it. A filter might have five or ten bins each, fitted with balloons that would inflate with something a bit less dense than the surrounding water and float up to the surface (or at least to a manageable retrieval depth like 1-5 km from the surface), that would return collected material as it was gathered. Then, the entire filter system would float itself back up when it ran out of fuel and retrieval bins. A distributed approach would also make occasional failure of a particular filter system or retrieval bin (even say 20%) tolerable in a way that it wouldn't if you put all your eggs in one basket building a massive and complex sea floor mining system where one fail could exhaust all available resources.
*The Sea Floor Might Be A Good Place For Simple Filter Systems, Or Not*
Indeed, maybe rather than digging in the sediment, you set up an osmosis filter on the sea floor (on the same concept as an [industrial strength reverse osmosis seawater filter](https://www.freshwatersystems.com/c-1919-sea-water-reverse-osmosis-systems.aspx) except that you'd be after the contaminants rather than the filtered water itself) on the theory that mineral concentrations are greater at the interface of sediment and water, rather than actually digging at all.
If you wanted, you could even deliberately fill an area of the seabottom with lots of contaminants by dropping bombs on the sea floor to turn sediment into fine grained debris and then filter out that debris.
But, actually this intuition isn't all that sound. Empirically, [all sorts of different trace elements are found at different depths](http://www.soest.hawaii.edu/oceanography/courses/OCN623/Spring2011/trace_elements.pdf) and in different conditions. Lots of elements are most common near the surface, iron seems to be common at mid-depths, and other elements (e.g. lead) tend to favor the bottom of the ocean.
So actually, you'd want filter systems at all sorts of depths after first running probes at different depths and locations to figure out where the elements you want are at the highest concetrations.
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You don't need a submarine, remote dredging will work. Assuming that a chain to the ocean floor will work (and fail) like a space elevator is wrong. If the individual segments are buoyant, you can have the cake and eat it too. The tensile strength of the segments then only needs to cope with the dynamic stresses, and you can minimize those by moving real slow.
Whatever heavy elements you have, or gain, can be used in streamlined impactors (add explosives and propulsion as needed) that race to the bottom and mix things up to better dredge them.
If you can spare some tech, the chain segments can be made to control their own buoyancy, if not, you will need to print them from organics to fit into some specific slot on the pressure\ density\depth scheme of things. You then place them there by means of the one variable buoyancy- device that you have, or if you're extra cheap, by attaching salt crystals designed to dissolve in the needed time.
Depending on you budget and the specifics of your topside dwelling, the dredging mechanism may vary.
If there are sizeable currents, this idea goes the space- elevator way to the farm upstate...
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Posting an answer to my own question here just to share some further thoughts on the setting.
# Magnesium
[Magnesium](https://en.wikipedia.org/wiki/Magnesium) is abundant in seawater. It is also light, stiff, and hard metal, although subject to corrosion and flammable. So in the given setting it is going to become the colony's structural material of choice.
Magnesium is also quite [conductive](https://en.wikipedia.org/wiki/Electrical_resistivities_of_the_elements_(data_page)) (not as good as Al or Cu though).
# Robots
As pointed out in comments, robots needn't fight the pressure and can be filled with liquid (like gasoline) instead. I still believe that semiconductors may need casing, but that's going to be a small and easy to do one (think raspberry pi mounted inside a bowling ball).
# Acсumulators
I "invented" a galvanic cell with sodium anode slowly dissolving in organic compound, graphite cathode in the outside salty water, and polymer membrane separating the two. However, both Trieste and [Deepsea Challenger](https://en.wikipedia.org/wiki/Deepsea_Challenger) seem to just use normal batteries.
# Deep water vessels
A graphite or steel sphere with thick enough walls looks capable of withstanding the pressure, however, communication with the outside is going to be tricky. In particular, efficient heat exchange and thus submerged fusion reactor is out of question.
# Communication
As pointed out in comments, radio would be inefficient in water. Not sure if [ultrasound](https://en.wikipedia.org/wiki/Underwater_acoustic_communication) could be used at least for location, [heartbeat](https://en.wikipedia.org/wiki/Heartbeat_(computing)), and short orders.
# Wires
As pointed out in another answer, hanging wires would not bear their own weight. However, metallic wires in a thick buoyant insulator could be self suspending. But the compression profile of water and insulator is likely to differ, as water is not quite incompressible at required depths. So additional ballast/float units will have to be attached in order to balance the whole thing.
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Thinking of terraforming a localized region, how (if possible) can we create an artificial high pressure zone, whether practical or not,
Initially I thought, perhaps we can arrange heatsinks to induce a pressure trap heated with laser arrays closer to the Sun. Perhaps a tunable cyclonic system or harmonic heat waves along the equator creating an interference pattern focused toward one region. I am unsure about the merits and feasibility of different methods.
This is for a video game, so does not need to be scientifically plausible given our technology and resources, though of course it is encouraged.
Certainly there will be gas lost. In the game Mars has a ring system with any desired ices/minerals designed by tractoring astroids into collisions. And the handy space elevator is available so you don't need to worry about supplies unless you want to.
Part of the larger idea is that if you can sustainably terraform a small open area, leaked gas will passively pressurize the planet in the long run.
**UPDATE**
I find all the answers gave me good feedback and could have a place in the game setting. I've choosen Loren Pechtel's answer because
* most detail, effort and thought out specs
* not as plausible as subterranean areas but gives an open-air solution thats scientifically feasible-esque
* massively deforming mars's shape gives me some global-scale plot devices to work with
I am considering combining Loren's answer with the small neutron star and gravity tech from axsvl77's answer to reduce the size requirements and retain yet another plot device.
Finally I thought, early martian colonies will likely be subterranean due to practicality. Considering Fayth85's answer, we can have a small established underground culture have conflict with the newly formed surface culture. Perhaps different cultural movements between the time early and later technologies formed cause still greater differences.
Thanks for all the feedback!
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A solution that should "work" (there will be some leakage that needs to be replenished) but requires some truly massive engineering.
Slice off a chunk of the planet—the resulting surface is truly flat, not merely "flat" like we see the surface of the planet as.
Putting some numbers to it: The scale height of the Martian atmosphere is 11.1km, the pressure is 600 pascals, Earth normal is 101 kilopascals. Thus we need to raise the pressure by 168×. For each 11.1 km we go down the pressure goes up by a factor of e. We need 5.12× this to raise it to Earth normal. Thus the maximum depth of our slice must be 56.8 km. To get a larger area of Earth-normal pressure you might want to cut deeper but then curve the bottom of your cut to maintain this 56.8 km depth.
Supply sufficient air, you have your place where humans can walk unprotected and with no walls whatsoever. Beware that the Martian gravity is too weak to hold onto this air, it will **slowly** leak away. Note that while the ground is truly flat (unless you go with the bulge option) it will feel like you're walking slightly uphill as you walk away from the center.
Beware that this is a truly massive cut, it's going to be over 1,200 km across. Walking from the center the 600 km to the edge you fill find the pressure dropping from Earth-normal to Mars-normal. I also suspect that the crust of Mars isn't strong enough to avoid collapsing this cut.
Edit: I realize there's a problem with my numbers here. I looked up the scale height for the Martian atmosphere but it's not right. Scale height is a property of gravity and molecular weight—and we are replacing CO2 (weight 44) with oxygen (weight 32) and probably nitrogen (weight 28) for an average of 28.8. Unfortunately, I'm out of my depth at this point. I know the slice needs to be deeper but I don't know by how much.
Using argon (weight 40) in place of nitrogen will help a bit but where are you going to get that much argon?? Krypton would be even better at almost 84 (the slice is shallower) but finding enough is an even bigger issue. Xenon at 131 would be even better but still harder to find.
Unfortunately, I'm not finding element abundance in numeric form and I'm left with eyeballing it off a Wikipedia chart. Argon seems to be 1/100th as common as nitrogen, krypton 1/1000th of argon and xenon 1/10th of krypton.
Edit again: Amazingly, I find that despite it being an exponential function scale height simply has the molecular mass in the divisor.
Thus for a typical oxy-nitrogen atmosphere we have a scale height of 17.7 km and our slice must go 90.6km into Mars and now our cut is 1,560km across. At our original cut of 56.8 we are 1.9 scale heights higher up--atmospheric pressure is only 15% of Earth-normal. You'll need to be breathing pure oxygen to survive this--and that would be a Disneyland for fire.
For oxy-argon we are looking at a molecular weight of 38.4 and a scale height of 13.3km for 42% of Earth-normal pressure--like Earth at 22,000'. Barely survivable.
Oxy-krypton gives a molecular weight of 73.6 for a scale height of 6.9km for 8.2 scale heights with the same cut. 22x Earth-normal pressure--that's about 210m into the ocean. This gas mix and pressure is lethal. You will get Earth-normal pressure with a slice only 35.3km deep. Note, however, that while I can't find good data it looks like you'll get some fairly serious rapture of the deep issues from breathing this.
Oxy-xenon gives a molecular weight of 111.2 for a scale height of 4.6km. I won't even worry about the results with the same cut, they're obviously lethal. A 23.6km cut gives Earth-normal pressure but this gas mix looks like it causes lethal rapture of the deep problems.
I'm afraid you're stuck with the deeper cut.
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I've got a few scenarios for you, some of which are based on other works of fiction.
## But let's start with the WHERE After all, location, location, location, right?
There's only terraforming deep crevasses, or impact crater. This was done in 'Hoshi no Koe' (lit: 'voices of a distant star', an anime I've watched). Basically you either locate, or dig a large hole, and focus only on that. Advantages are that the walls will act as a natural insulation so that there's only one 'escape route' should failsafes... well, fail. Less damage to mitigate. I'm not overly familiar with Martian topography, but I believe there was a large canyon that might be ideal for just that, though it might well be much larger of an area than you were counting on.
## Right, so how?
A few options off the top of my head. First is the ever popular force field if you want the Sci-Fi route. It would take some major power to keep that sucker running, but it's not impossible. Do keep in mind that solar-farming is less effective on Mars than on Earth, so you'd need a solid energy source that is renewable. Though, I do remember reading the the greenhouse gases we oh so hate here on Earth, would help Terraform Mars in the long run, so maybe that won't be such a bad thing for you.
Hmm, you could always build your new 'environment' underground. Either by locating a subterranean cave system, or digging one yourself. After all, you need to contend with cosmic radiation there, so the more material between you and the cosmos, the better (unless you can think of a way to keep that out). My amateur advise would be storing the water above you, so that the rays hit the water before it hits you, but that's just me. This does have the drawback of plausible leaks, so you'd need to do something about that. And it would be an undertaking that makes building a city from scratch here on Earth look like 'the projects'.
Any thing using air directly will likely fail, purely because air is apt to escape regardless of what is tried. Keep in mind that the problem on Mars is the dangerously low atmospheric pressure (other than temperature). You could try to 'fill the planet' with air, but even that is apt to fail, simply because you'd need to heat up a pocket of it, and that will make it lighter than the surrounding air and therefore rise. Without a 'retaining wall', it's a guaranteed fail.
Hope this helps ^\_^
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## Same as the way we do it on Earth: With Gravity!
The easy way is to generate artificial gravity in your development zone. Then any air you release will stay nearby. Just need the technology to artificially increase gravity!
While you're at it, make the artificial gravity directional, so that it doesn't destabilize the structure of the planet you are on. Or even better, make the gravity specifically more attractive for gasses than non-gasses. That way, the planet will slowly pull gases in from off-planet.
It is fiction, so there are a ton of ways to vary this idea.
**Edit:** How to implement this? Realistically, at this time we (I?) don't understand the source of gravity well enough for me to speculate about how to build this.
For a story, I would use a 'graviton concentrator' to create a meta-material with semi-gravi-ductor logic control, like a silicon-semiconductor. Once the semi-graviductor operates, I would amplify the gravity wave through an ultra-dence on-board nano-sized neutron star.
For directional control, I would isolate anti-gravitons in a similar manner to create a reciprocal anti-gravity device, and position it such that creates destructive interference where I don't want increased gravity.
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By classical civilization, I mean one that form the ethical, governmental, scientific, or lexical foundation for cultures that follow. Such a civilization's impact lasts for centuries if not millennia. There are many examples of these civilizations in our own history. The most obvious examples are the Greek and Roman civilizations which have impacted Western civilizations in countless ways (the words ethical, governmental, scientific and lexical all have Greek/Latin roots). Another example I have in mind is Confucianism, which impacted the sociopolitical systems of many East Asian cultures. On the other side of things, there are have been countless civilizations who have been overshadowed by more influential cultures. Think about the Celts in Northern Europe. Though parts of their culture survived, they were largely Romanised and have little effect on today's society.
But enough history, this is about worldbuilding after all.
For my setting, I am creating several ancient cultures who flourished roughly 500-1000 years prior to the story. I want at least one of these to be a foundation for a [neoclassical](https://en.wikipedia.org/wiki/Neoclassicism) revival. **Why would an ancient civilization be "targeted" by such a movement? Or more to the point, why would one ancient culture overshadow another?** This is not to say the civilizations not chosen are completely forgotten or irrelevant. The ancient Babylonians had quite the [influence](https://en.wikipedia.org/wiki/Plimpton_322) on the more prominent Greek sciences, for example. I'm just looking for some rationale why a certain civilization's influence would be prevalent centuries after that civilization's decline.
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Breaking your questions apart I have distilled what you are asking down to:
1. Why would an ancient civilization be "targeted" by such a movement?
2. Why would one ancient culture overshadow another?
3. Why a certain civilization's influence would be prevalent centuries after that civilization's decline.
Neoclassicism relates to *the arts, architecture and culture.*
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To reword your first question: **Why would a culture choose to emulate and model a past time?** I will be using the Roman Empire as my example.
* What makes a past entity emulable? Past nations and empires worth of emulation usually did a few things.
1. They simplify the world. Rome accomplished this by conquering and implementing Roman values throughout their territory. The Empire was civilized and beyond were barbarians. This creates a natural bi-polar scenario not dissimilar to the cold war where there were two factions. Dealing with two factions is simpler than dealing with a multitude.
2. They standardize and make the world smaller. Much like McDonald's today familiarity makes things easier. When you travelled the Roman world you could count on Roman law, transportation networks, infrastructure, security and more. Throw in common coinage and language (at least among the ruling classes) and the world is vastly more accessible.
3. Peace and stability...Legacy. Sort of. To be worthy of cultural emulation you have to have made a lasting impact on the cultural world. Era's of relative peace and prosperity give people the time to delve into the arts, be that painting or sculpture or philosophy, mathematics...etc etc etc. No one can claim that the Roman era was wholly peaceful but in comparison to the times before and after it certainly was.
4. Reverence and nostalgia. *Those were better days...* If the population looks back on a time as a golden age of prosperity and knowledge, progress and promise it makes people wish for the good ol' days. This will be derived from some of the things mentioned in the above points. The empire was powerful, stabilizing and promoted growth...which people living in hard times want. Note that the times may not be as difficult by direct comparison but the ideal of the old empire may appear better than the current state even if that is not strictly true.
This should pretty well explain WHY a civilization would be emulated.
The short version is they simplify the world, making it a more familiar place, in essence making the world smaller. The empire leaves lasting cultural (government or social) institutions, maybe libraries or councils or trade groups, the empire leaves art and architecture that require generations of skill development (several lifetimes of student - teacher - student - teacher growth in knowledge to accomplish), and the current people must believe that the past glory days are something worth returning to.
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* **Why would one culture be chosen over another?** The answer to this is much simpler, and more practical.
1. Cultural Familiarity. While there are cultures worthy of emulation the world over, a people are not likely to attempt to emulate a culture that is very different from their own. Europeans are not going to choose to emulate the glory days of the Han Empire in China, nor the Shoguns of Japan simply due to a lack of familiarity and commonality in the two cultures.
2. Values similarity. Part of culture but worth singling out. The French, German and obviously the Italian nations of the renaissance era obviously have more in common with the Roman Empire than they do with the Mayan empires.
3. Timeline. What is best remembered? There are layers and layers of history in most of the world. The practical effect of what was great and happened most recently will play a role in what culture is chosen for emulation.
4. Documentation. A written, usually internally biased history of the empire being emulated helps familiarize a people with what the empire was and represented. Timeline plays a role here. The likelihood of history being preserved has dramatically increased as time has progressed.
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**Why would a civ's influence be prevalent centuries after its decline?**
* This is mostly a rewording of question #2. The short version being they leave **lasting reminders** of their greatness be that in culture, art, architecture, science, etc. If the history isn't there to see it's pretty tough to emulate.
**A final note.**
Counter culture. When you look at the neoclassical revolution in western Europe you can see that it replaced the Baroque and Rococo styles. These were very detailed, elaborate, gold leaf a-go-go styles. Neoclassicism on the other hand was all about simplicity, function and symmetry.
We humans get tired of the same old thing, we want to be different...it's a species wide selective insanity in ways. For proof look at any teenager dealing with their parents.
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Aside from military conquests and ownership of land, I find that a significant factor to the success and cultural zeitgeist of certain civilizations (Greek, Roman, etc) to be Enlightenment eras.
The Ionian Enlightenment gave way to forward thinkers like Democritus (known for his speculation on atomic theory) and Pythagoras (who needs no introduction.) Its influence stretched into the Hellenistic period, where you had thinkers like Socrates and Aristotle.
Enlightenment eras of the past are the same as modern Enlightenment eras.
But that's what they are - cultural *zeitgeists*. It wasn't so much individuals who just put forth their hard work and had it mooched off of (you know, like today), it was embodied in the collective conscience of the people. It pervaded society, government, and church.
You need *all of society* to be in on it. Values of empiricism, ethics, and culture has to be part of the collective where everyone has a shared interest. To accomplish this, give your culture a religion, or some dogmatic (for lack of a better word) system where the primary cultural goal is to simply innovate on everything, and change lots of minds about large questions about our environment through that process of innovation.
For example, we hold on to the past few hundred years because minds have been changed drastically in terms of things like gravity, physics, and medicine (germ theory.)
Your government - which runs by the system or religion - would be more willing to fund projects that adhere to their belief system, in the same way King Ferdinand and Queen Isabella funded Columbus or that King Charles funded Magellan.
You basically have to have a government that's like an oversized Royal Society - it cares not about funding as much for military conquest or funding Guantanamo Bay, but about changing minds and literature that prove to withstand the test of time.
We can't help but think about these times of innovation because everything around us only works because of the innovations made in those times. With our knowledge of thermodynamics, we have refrigeration systems. With knowledge of gravity and relativity, we have GPS.
You would think of these times with a sense of nostalgia, of charm, of simplicity, of a fount of cultural innovation, whether it's the Renaissance or the Enlightenment, because it's tied to the present. You can't be as tied to a past civilization that didn't affect you.
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I've been mulling over the idea of nanites (microscopic machines that perform work - usually to transform one material into another). I've come to the conclusion that at a macroscopic level, nanites ought to operate as we see microbial life operating.
Whether the nanite is actually coopted microbial life (e.g. bacteria reprogrammed to do something we want) or just operates like it, is irrelevant for my question.
The nanite will need an energy source (already answered in another question) and the necessary nutrients (chemical inputs). It would probably help the nanites to be suspended in some sort of working fluid (e.g. water) too.
As the nanites work, they'll use up certain elements or chemicals that are required to do their job. In order to finish their job, they'll need those chemicals constantly replaced.
## How do you replenish the materials used by nanites when they're doing something?
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Alternative thought, you *don't*.
## The nanites *are* the materials.
At least when it comes to producing something - either a finished product, or the materials for a later finished product. This wouldn't work when you want to do something other than manufacture, but I'm struggling to think of uses for nanites that isn't in some way 'eat things' and/or 'make things'.
Replenishing materials becomes a non-issue as this answer is the answer to the question of *how do you manufacture nanites in the first place?*
I can think of two plausible nanite life-cycles. The end result is largely the same, but the order of things is swapped around slightly.
## Life-cycle A.
1. You feed your nanites, much like you feed biological cells. They grow large and flabby.
2. The nanites undergo [binary cell fission](https://en.wikipedia.org/wiki/Fission_(biology)).
3. You encourage half of your nanites to attach themselves onto the surface of the thing being built.
4. The nanites, using the same internal machinery used to initially build themselves, start *unbuilding* themselves and attaching those molecules to what's being built.
5. Repeat.
## Life-cycle B.
1. Split your nanites into two groups.
2. Feed both so they're large and flabby.
2.1. Encourage one group to attach themselves onto the surface of the thing being built. It's obvious what happens here.
2.2. Let the other group undergo binary cell fission.
3. Repeat.
Feeding, and manufacture are both going to produce waste. Needless to say that they'll be both messy eaters and inefficient builders. The above life-cycles have the advantage of being able to separate apart the two processes. This allows us to supply the nanites with resources without interfering with the work they'll do, **and** tailor clean up measures accordingly.
But it comes at the cost of having to manage them. And this is a control problem.
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## Control.
Controlling large numbers of very small things is going to be imprecise. You won't be able to select a single nanite and direct it to a specific location. You'll be relying on swarm behaviour. Splitting nanites into groups is the easier task; if you can instruct them to form a large blob, then mechanical separation is the order of the day.
If nanites naturally like being *somewhat* close to each other, then they will form a blob, but you can't control the location of the blob.
Avoidance of light is a good way to direct them around as it works in liquid (caveat:transparent liquids) and with cleverly placed orthogonal lights can work in 3D and make paths to guide them.
The hard part is telling the little blighters when it's time to turn themselves into stuff. This is hard for two reasons; the thing you're building something might be something like a computer CPU that has lots of specific and precisely placed elements, **and** you don't want your nanites to incorrectly start building too early.
The signal to build, and what to build into needs to be very salient.
Nanites won't have access to their x, y, z coordinates. So take inspiration from biology and use combinations chemical signals. Emit a chemical from one end of your product, and another from the far end. Give the nanites a sense of smell. The ratio of one chemical to the other can infer position, and hence what the nanite should turn into. This has the added benefit of no-smells-equals-no-construction.
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## Waste.
Now, dealing with the waste. The waste, obviously, is the left-over parts of the nanites that weren't used.
Wastes come in two types: soluble, and non-soluble. Soluble wastes will disperse throughout your liquid. *If* these wastes can be consumed by the nanites, then you're golden as they'll filter out and recycle them.
Soluble wastes are a problem to the health of your nanites as they'll likely change the pH levels of the liquid. They'll react with the nanite food, the nanites themselves, or both.
Non-soluble wastes will effect the [turbidity](https://en.wikipedia.org/wiki/Turbidity) of the liquid - which may influence your ability to control the nanites. Turbid water is treated two ways; mechanically, through filtration, and chemically through reagents. Both of these could be harmful to nanites. A work-around would be to heard all the nanites to another tank/vat/etc, and process the waste separately. Always having one operating vat, and one vat being cleaned.
Using @Magnanimancer's idea of having another variety of nanite that cleans the water is a nice idea. It allows you to have a mechanical process in-situ that doesn't harm the other nanites. Suppose you have a nanite that can sense two things; the presense of other nanites, and the turbidity of the water.
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It sounds like you will not only have to deal with supplying 'nutrition' for the nanites, but you'll also have to carry away whatever waste they produce after metabolizing their food. Matter doesn't like simply being destroyed, after all.
Depending on what they consume, though, I can't imagine it being much more difficult than simply dropping in the equivalent of a sugar cube every once in a while and calling it good (or, if they metabolize glucose, an actual sugar cube). Whatever remains from the process can then be collected, and through some other process (photosynthesis, perhaps?), would then be reconstituted into new glucose.
Alternatively, you could mix the nanites in with other tiny machines that actively perform the collection of excess waste and produce whatever the nanites need again. By doing this, you'll have essentially produced an artificial ecosystem. Sorta.
Eventually, though, there will be the need for some outside source of energy, but if you're using nanites as a means of production, acquiring cheap energy shouldn't be too difficult, whether through solar power, nuclear, or otherwise. Material can likely be acquired from the environment too. Glucose, for instance, is only Carbon, Oxygen, and Hydrogen, which aren't particularly difficult to find (water alone being comprised of 2/3 of those elements).
However, if you're referring to the actual materials they are building with, or altering, then, yes, that would have to be provided by some outside supply line. (Unless the nanites are permitted/instructed to deconstruct their environment when they require more minerals.) It might be analogous to providing construction workers with the wood, steel, and concrete necessary to do what they do. The ideas above are more about how the workers get their lunch, I suppose.
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The closest thing we have to this is the human circulatory system, where nutrients and cells that do work are carried around together and then replenished at certain points (lungs for oxygen, etc). It seems likely that any system using nano-machines would do something similar.
Trying to have the machines stay in one place while you supply resources to them would be very hard as the movement of the raw materials would also carry the nano machines along. Instead circulate the machines through the system and have them pick up raw materials from suitable locations as they flow around.
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Essentially a nanite workspace could arranged to operate somewhat like a hydroponic garden. The nanites are suspended in a tank of the working medium, and sunlight, lasers or microwaves shine on the tank to supply the energy.
A metering pump or pumps supplies nutrients and the raw materials for the items to be built, and another series of pumps or siphons draws the fluids out of the tank for filtering and recycling or processing (waste materials are processed out, while nutrients and raw materials that were not used in the first pass can be fed back into the system).
This also allows you to control the temperature and carry off waste heat from the millions or billions of nannies in the tank, while the finished product (if it is a macroscopic object) is simply lifted out once the production is complete.
While this implies that the working fluid is water, there is no need to limit yourself, depending on the nature of the nanites and the items to be created. Metallic objects like engine parts might need a slurry of metal suspended in oil, for example, and some processes might need a closed vessel that is charged with a gaseous mixture instead.
All that is needed is the working volume (usually a tank), a means to input nutrients, energy and raw materials and a means to eliminate wastes and excess heat while the process is going on.
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I've got a device that can change matter to energy (or energy to matter. Or any combination!) with perfect efficiency and absolute clarity of design. So far I've used it to build a [large, global company](https://worldbuilding.stackexchange.com/questions/29106/concealing-my-earth-changing-invention) with employees capable of performing [pretty much any task](https://worldbuilding.stackexchange.com/questions/29330/my-earth-changing-invention-how-can-i-hire-the-people-i-need?lq=1) I need done, and I've built my global public and political image to the point where everyone really, really likes me.
I've got a global presence and infrastructure complete enough that I could deploy various robotic designs based on my invention in a matter of weeks, rendering pretty much any industrial or resource gathering operation irrelevant. However: I'm still paranoid that the human race will tear itself apart if I do that, not least because they'd have all the material they need for materiel.
As I sit twiddling my thumbs and wondering about the next steps, I need a baseline on which to build a plan for the transition of humanity to the post-scarcity era as smoothly as possible. To that end, this is the question:
**Which market sector would take the longest to cease operations if they suddenly became irrelevant: Energy, mining/refining, or raw food production? Please provide numbers on lead/wind-down times if you have them.**
*Please note*: I haven't included construction, manufacture or food processing in the question as these sectors require a human design element that can't be made fully redundant. If you can think of a long running industry sector whose final product does not require any human design let me know and I'll add it to the list. By 'Cease operations' I mean 'no more major national/international networks designed to facilitate these markets'. Small local networks or crazy paranoid hermits don't count as part of the market (thanks Frostfyre).
I'm thoroughly expecting the answers here to be along the lines of chaos and horror, but any world that's in a post scarcity society must have dealt with this issue at some point, so the question needs asking before anybody can plan to fix it.
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Let's analyze the strengths and weaknesses of each sector (against the disruption from your device).
## Energy
**Strengths**
* All those cars, trucks, tanks, ships and airplanes need fuel for their engines, and the oil companies own the distribution network.
* Energy is vital to national security, so countries that can afford it will take measures to prevent a dependency on your machine.
* Powerful lobby in the US and other big countries. State-owned industry in Russia and China as well as the Middle East.
**Weaknesses**
* High extraction and operating costs and volatile global market makes them extremely vulnerable to a crash in oil and gas prices.
* Industry has zero popular goodwill and burning coal and oil causes global warming. Your greener alternative will be attractive.
**Predictions**
All these timeframes start from the point where you turn on your first large scale plant/factory in a market.
* Coal industry will collapse in the West and third world in exactly the time it takes for their first big contracts to expire. *Biggest concern: the state-owned industry in China*.
* Natural gas will be nationalized and put into hibernation as a strategic reserve. This could take several years. Biggest concern: *Russia depends on gas exports*.
* Oil is a tricky one. Oil futures prices will slide, but current volumes are huge and unless you start selling Mr. Fusion kits for vehicles, gasoline will still be in demand. Your choices are:
+ Decrease demand by producing batteries or entire electric cars to go along with your cheap electricity
+ Undercut suppliers by producing cheap refined oil products with your machine.
Either way, you can expect a few years of slow decline as people keep filling up their cars, industrial buyers can't risk having their plants sit idle and oil has a lead time of 6+ months. Then a tipping point will be reached as traders admit to themselves that you are for real. Panic selling will destroy oil prices as countries dependent on that income rush to sell off their reserves. *Biggest concern: Chaos and war will ensue in the Middle East as everyone tries to claim part of the suddenly finite pie. Then a humanitarian disaster of epic proportions follows.*
## Food
**Strengths**
* People would rather not eat your Frankenfood if they have a choice. See the ongoing GMO food struggle between the US and EU for reference.
* Heavy regulation and labeling requirements will work against you.
* Like energy, food is a vital strategic resource. Governments will not accept being dependent on you for food supplies.
**Weaknesses**
* A significant part of the world population does **not** have enough food.
* Food processors have less concerns about the ingredients they use, though only if it's not traceable.
* Animal feed is less regulated and consumes a large portion of the world's food production.
**Predictions**
You're not going to make food production for First World humans irrelevant in under two generations. Fortunately, you don't have to, as your main goal is an end to food scarcity.
The two likely spearpoints are outlined in the weaknesses: Feed the starving and the animals.
For feeding the starving, you can make good use of the NGO contacts you cultivated before. Have them perform thorough testing on your food, then use their credibility and network to distribute.
For animal feed, there will be interest because of the lower cost, but fear of being associated with Frankenfood. The best way to fix this is to make deals with either farms or trading companies to multiply their real shipments and share the profit. This is untraceable and works for everyone. After some of the suspicion is lifted, cattle farms will start asking about getting the feed right at the farm.
Both strategies have the same effect: They will lower food prices worldwide in 2-3 years. That includes initial testing, convincing the first countries and companies to try it and then ramping up production. Bad harvests and disasters may speed up this timeframe.
Hopefully, there will be no collapse as farmers switch from the highest yields to high quality (organic) foods, lowering output and stabilizing prices. First world farms will still struggle with the permanently low prices and may be subsidized or close down. This will probably happen over at least 5-10 years as farmers relearn their business.
## General manufacturing
The assumption here is that your machine can replicate complex components like circuitry and computer chips. A replicated smartphone may not boot, but it will after loading the software. If that's too delicate for the machine, you move one or two steps down the production chain.
**Strengths**
* Patent law, Intellectual Property rights and treaties effectively prevent you from making your own versions of products.
* Perversely, China's weakness of depending on manufacturing for its economy counts against you here, since it's likely to aggressively protect its turf.
**Weaknesses**
* The entire industry has been in a race to the bottom for many years now, sacrificing quality and durability plus social and environmental responsibility on the altar of quarterly profits.
+ Your prices are unbeatable, you will be buried under a mountain of company reps looking to outsource their manufacturing to you.
+ Consumers will be delighted with the higher quality of your products.
**Predictions**
Chaos, horror, war, massacre, bloodbath, earthquakes, volcano eruptions, meteor strikes, NUCLEAR APOCALYPSE!!!
Okay, maybe not all of those, but here is where things get grim. Unlike the food sector's soft landing, or the relatively small numbers of people affected by the energy sector's collapse, now you're instantly making a good (and labor-intensive) part of the world economy obsolete.
Quite a few countries in the world will lose a large chunk of their export income, as all that hard-won copper/steel/gold/rubber/wood/rare earth metal/you name it is suddenly worth as much as the mud under the miners' boots.
Then the countries where those materials used to get shipped and where the processing and assembly happens get hit (how badly depends on how finished a product you can deliver). This covers probably [half the world](http://data.worldbank.org/indicator/SL.IND.EMPL.ZS/countries?display=map) and could potentially leave half a billion people unemployed if you produced everything from phones to cars instantly in your machine.
It's impossible to give even a rough guess for this time-frame, since if you do it the quick way (start mass-producing iPhones, fridges and Tesla cars in plants inside the rich countries), war is all but inevitable. Even if you generously travel around the world and provide the newly unemployed with free iPhones, fridges and Teslas, they will still be stuck with no purpose in life and no way to get ahead. The social disruption will be too great and civil wars will break
out. China may try to head this off by taking you out before it happens, and unlike the Middle Eastern countries affected by the oil price collapse, China has nukes and the means to deliver them to your doorstep. (Tip: don't be home.)
The optimal strategy is to gradually work your way up the manufacturing chain. Start by offering raw materials and those semi-finished products that take a heavy toll on the environment. Leave the most labor-intensive parts (assembly) for last. Do all you can to support the most-at-risk countries, helping them transition their economies to services and consumption before their manufacturing collapses. At this rate, you may need 20-40 years, depending on just how much goes wrong along the way.
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The industries of energy production, mining, manufacturing and transport will all collapse first. As the comments under your question suggest, the FDA and its equivalents in other countries will defend the food-production industry, at least until your machine learns how to make perfect replicas of existing fruits, vegetables and other already approved food-stuffs.
Medicine production and distribution will also be a hold-out due to its heavy regulation.
What is nice is that you can create wealth directly in many forms: gold, water, food, electricity, etc. So you can buy any hold-out industries from their current owners and transform them manually into their post-scarcity equivalents. Buy all the drug companies and lower all prescription prices to zero. The analysts will insist that your companies must go bankrupt from such a move, but you can just keep sending those companies the operating money that they need, and prove the analysts wrong.
In pursuing a post-scarcity economy, your goal should be to wear down the dominance of the scarcity mindset. Once people get used to always having enough, they can be slowly conditioned out of the need to own things. Over time they might then stop hording things and stop investing their time and efforts in protecting those hordes from others. Enjoying life is a very alluring alternative compared to the effort needed to maintain a possessions. If your global company makes both options available to everyone, most will choose joy.
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I think that (raw) food production will hold out longest.
Not because of any feature the industry has, but because first, large numbers of people are very careful about food, and will not easily switch to anything "non-organic" (yes the term is bonkers, but still...), especially if they can afford the "healthy, and-picked, ecologically farmed" food, and second, the "original, ecological, (...) foods our grandparents cooked" will be regarded as much more hipster and thus sought after.
One small factor that will help the food industry is that at least some parts of the industry do not require as massive machinery as the other two sectors, which makes them easier to scale up or down, and thus quicker to respond to varying demands.
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Another area that you are kind of leaving out is globalization.
For instance, there are some really neat energy producing technologies that are starting to get traction in some parts of the world right now, like [plasma gasification](https://en.wikipedia.org/wiki/Plasma_gasification) and [molten salt reactors](https://en.wikipedia.org/wiki/Molten_salt_reactor) for instance, but they are having a hard time in the developed world because of entrenched interests, start up costs, and regulation.
Where you're technology will have the biggest impact is the developing world, because there is no infrastructure.
Cell phones in Africa is a good example of this. They are everywhere, and stuff like mobile payment is way more common than over here, because there was nothing there for cell phones to push out. No land lines, no debit cards. America probably has a few years before we catch up to what they are doing.
Or internet in South Korea (which is not a developing country), which is fast and cheap, because there was no existing regulation or monopolies to keep things from happening as fast as possible.
There are areas where you could take the food production stuff, start to explain "Yeah, this is replicated food" and they won't care because their children are starving. I'd sacrifice my own dog to keep my baby from going hungry. Replicated food? Gimme gimme!
For energy production, they'll just be happy to have lights and a way to cook stuff easier.
In the developed world it'll be different, and take a bit longer, but not much, especially if he's politically connected.
Energy falls fast and hard. It's the [1980's oil glut](https://en.wikipedia.org/wiki/1980s_oil_glut) all over again, but with electric cars. Automakers with experience in electric cars take off like rockets, and the rest scramble to catch up.
For food cheap and plentiful wins 8 times out of 10. Ramen noodles and college students, fast food chains, etc.
I think it would have a really weird effect on the economy, where industries would crash all over, and the economy would dip for a really short amount of time, and then take off again, with the wealth getting redistributed a bit. A few very wealthy people will lose their wealth (gas, oil, mining, etc), others will get a lot more (electronics) and the cost of living will go way down, meaning that people will have a lot more disposable income to spend and that will keep the economy from crashing.
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New use I just thought of. Since your device can take energy and turn it into matter, then one area this will simply revolutionize is space travel.
One of the reasons space travel is so expensive is because the biggest thing that you have to push around is the fuel to push the fuel around.
Say you want to go to Mars. Using the [Tsiolkovsky rocket equation](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) you figure out how much energy you need, then how much fuel you need to get that energy, but you also need to take into account the mass of the unburned fuel you have to move.
Energy to mass removes this problem. You simply launch a craft with the device and a reactor, and create the fuel as you burn it from energy. Now space travel is incredibly cheap.
You also have to figure out how much food you need for the trip, but that's not a problem any more either.
Once you get to Mars you need to set up a base and grow food, except that you don't. Shipping a few devices over, you convert dust into energy to produce food, produce living space, make air, whatever you want.
It would even be interesting to have devices who's only job is to eat dust and spit out atmosphere or soil (Mars soil is not good for planting. To much salt, no nutrients or microbes that plants need to grow). It would be a long, long project, but who cares. This will give earth some breathing room.
With the solar system open to you, you have the entire mass of the gas giants to build anything you want, including interstellar ships, and with the fuel problem solved, flight times wouldn't need to be as long.
You have the energy to [travel at 1G the whole way](https://space.stackexchange.com/a/5016), so you could get to Alpha Centauri in 5 years or so.
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Pretty much what it says in the question title.
**Suppose** a non-human, social species of Earth animal found itself on an evolutionary path that favored increased intelligence of a kind not completely dissimilar from that of humans.
These creatures, from the beginning, are able to plan ahead and at least to some degree anticipate the consequences of their actions. (It is not beyond them to reason like "If I do X, then do Y, then Z happens, which is good".)
**Would** such evolutionary pressure *necessarily also* lead to said species developing *an abstract language* of a similar kind as humans have in abundance?
For the purposes of this question, let's *ignore* what this species' language would be like; such a language, *if* it develops, could be based on any method of communication including vocalizations (sound), body language, or scent (or even telepathy or magic for all we care here). "Language" here pretty much just means "a method of communication between individuals".
Let's also *ignore* how humans would react to such a species and its evolution in such a direction. (In fact, if that makes you feel better, you can suppose that humans aren't around in this world.)
Seeking well-reasoned answers describing why an abstract language would or would not necessarily follow from a species achieving or evolving toward intelligence. Bonus points for answers that discuss how such a language might also evolve over time as the species evolves. Bonus points also for specific citations, but citations are not a substitute for answers being well-reasoned in their own right.
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Human language evolved for the interaction between humans. That may sound like a trivial fact, but it isn't: If there had not been social interaction between humans, humans would not have evolved language.
Therefore the question basically reduces to: Does a species need to be social in order to develop an intelligence of similar levels as humans? Of course, given that we have very little experimental basis (as far as we know, th4e number if species with human-level intelligence on earth is, well, quite limited), it's hard to say for sure, but I would risk to say: Yes.
Why? Because natural interactions are relatively simple, including the interaction with possible prey if that prey is itself not that intelligent. Human intelligence certainly did not evolve in order to hunt; the main hunting strategy of the early humans was to outrun the prey (which is why humans are the best species when it comes to extended runs; other animals may run faster on short distances, but none would beat us at a marathon). A bit of intelligence is, of course, useful in hunting, but I doubt too much would be needed.
It is IMHO exactly social interactions that drove the intelligence; that is the place where you have to be able to think several levels deep, exactly because the other one does, too. If you are facing a non-intelligent being, all you need to know is: What will be the reaction. A bit of intelligence is sufficient for that. But to interact with your just-as-intelligent peers, it is important to be able to think one step further: "What does he think about me?" Also social interaction includes coordination as well as passing on knowledge. Both also profit from higher intelligence, as you need to understand the motives and plans of the other person in order to either coordinate with or learn from that person.
Note that coordination and teaching are also the main two areas where in language is useful, therefore I conclude the evolutionary pressure of developing intelligence and of developing language come together.
Also note that the structures needed for both have a very high overlap, as evidenced by the fact that a lot of our inner thoughts are a sort of inner monologue; indeed Ludwig Wittgenstein famously declared that the limits of language are also the limits of thought.
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Abstract language **will** develop in that species, but only after they have crossed a certain level of self consciousness and inter-dependence is really high.
This has been decided on the basis of human history. It is impossible to state exactly when detailed language originated in humans, but it was certainly during a time when primitive societies were forming and humans had quit arboreal life and started living on ground level. It was a time when they were learning to work together for defense against terrible sabertooths of Africa (particularly Machairodus).
Such a stage is much more likely to arise in group-living animals living in the wild than lavishly living and well-cared-for pets and other domesticated animals. *Almost* all of evolution is driven by necessity and language is no exception.
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**Intelligence alone? No. Agriculture alone? No. Intelligence + Tool use + Cooperative Hunting + present-tense language? Yes.** We can find many examples of intelligent life or tool users or cooperative hunting but we don't see any examples where all those traits come together except in humans.
So the question becomes, what long standing situation would force the ability to comprehend future-tense concepts? I think it's agriculture. Humans had already developed a strong [cooperative hunting](https://en.wikipedia.org/wiki/Cooperative_hunting) trait and extended that cooperation to other aspects of social life.
There are many animals that cooperatively hunt (the above link has an extensive list) but none that operate on a time scale beyond what can be encoded in an instinctual memory. For example hungry->get with group->go hunting->take prey->eat->wait->hungry. Or a longer term cycle, cold days->follow herds/move south->warm days->follow herds/move north. Animal instincts are sufficient to encode that kind of "future" information. Further, the animals don't need to convey that their juveniles. Going north and then south is just how life is.
Agriculture is different though. It requires knowing "if I put [seed in ground] and [water the ground] then I get more food and more food is good." Note that there are some animals that practice agriculture such as ants with aphids or [fungus](http://www.sciencedaily.com/releases/2008/03/080324173459.htm) so developing agriculture alone isn't sufficient to develop an abstract language. The farmer ants and their fungus co-evolved together.
As pack hunters, humans already had a primitive present-tense only language for coordinating hunting attacks. Extending that language to conveying concepts about the future state of a crop isn't too large of a stretch.
*Evolution of capabilities:*
(format: initial state-[evolutionary pressure]->post-pressure state) Some capabilities will evolve in parallel. Generally, the more basic traits come first earlier in the list.
* solitary hunter gatherers-[group hunters do better than solitary hunters]->small group hunter gatherers (requires that cheaters don't profit from hunting)
* small group hunter gatherers-[prevent cheaters]->primitive social systems
* no communication system-[coordinated hunts fare better]->primitive communication systems (probably on the level of "go there" "throw spear!")
* wood tools-[stones hurt more than wood]->stone tool creation.
An observation that primitive grains tend to grow in a certain area might induce a band to stay in an area longer than they ordinarily might. Over a period of years, they might notice the effects of rain and drought on grain growth. A simple idea to divert water from a local stream to provide water to a wild wheat field might be all it takes to initiate agriculture.
Once they start planting the remaining seeds, that idea of planting a seed equals food later has to be conveyed somehow and that is an instance of a primitive future-tense idea. Dry and wet are also abstract ideas that are essential to successful farming.
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It is essential for an intelligent species of the type you describe to be capable of abstract thought.
Why? Because they must form models of reality that allows them to form and evaluate hypotheses, and encode learning by modifying existing hypotheses which exist in a suitably compressed form, based on their actual experiences. The possible permutations of events an intelligent animal must face are so vast that *compression via abstraction* into probabilistic models is the only sensible approach.
Given that abstraction is a necessity, do they need abstract language as well? Assuming that the species is social, and part of the learning process involves transfer of existing abstract models from one member of the species to another, then the answer must be yes - our species needs a way of communicating abstract concepts between them.
In humans, since we are social from day one, possibly without abstract language development we could not actually develop and hold onto abstract models in our minds. In that sense, abstract language and thought probably co-evolved. However, if the species is not social from day one but can develop hypotheses about the world before they can communicate at all, then we would say that abstract thought precedes abstract language.
Here are the attributes of the species which I think need to apply to have abstract thought but not abstract language:
* The creatures learn independently from birth. No parental coaching.
* There is no communication of *learned* concepts between members. Immediate *wants* are communicated using abstraction symbols which are baked into the mental architecture at birth. So here the mechanics of communication are inherent to their phenotype rather than developed, I would not call this a language, more like a 'fixed protocol'.
Just because learned concepts are communicated does not mean they cannot be passed on - possibly they have some kind of lamarckian evolution which allows the biologically determined communication protocol to be passed onto offspring.
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The steel that makes up the skeletons of modern skyscrapers consists of iron and carbon. The problem with both is that, if the entire city is untended for long enough, both metals betray their downsides. Iron corrodes easily, and though carbon is used to toughen the alloy, it, too, is vulnerable to rust.
The other piece of skyscraper anatomy is a mortar made from modern concrete. The "Portland Cement", as it is called, lacks the Romans' lime-and-volcanic-ash-mixture that made it endure for centuries.
For a posthuman metropolis to stand for centuries instead of decades, what kinds of metals could be added in the steel alloy to make it tougher and slow down corrosion? And could Roman concrete be reasonably reinforced?
*Please no suggestion for stainless steel. If stainless steel weren't used for skyscraper skeletons, there has to be good reason.*
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**Use materials that don't corrode such as glass or ceramics.** This being a post-modern technology, I'm going to assume that you can use whatever materials you like in an as yet unimagined manufacturing process to form tall buildings that stand essentially forever.
Glass and ceramics are ideal candidates as they don't react with oxygen and thus remain essentially unchanged for tens of thousands of years. The oldest human artifacts recovered are made of glass, stone or ceramic.
Coating steel with any non-reactive coating still leaves the reactive steel exposed should something happen to the coating. Ceramics may flake or craze under high wind or earthquake loads thus leaving the underlying steel exposed. Better to have the entire structural member made of something that doesn't corrode at all.
**Materials Difficulties**
Glass and ceramic have amazing compressive load strength but relatively poor tensile strength (ie, they laugh at you if you try to crush them but run crying to their mommies when you try to pull them apart). This hyper-advanced civilization should have the theoretical understanding to create custom ceramics and glasses with the appropriate compression, tension and ductile properties to build long-standing megastructures with.
Building with silicon makes a lot of sense on Earth as much of the crust is silicon in the form of quartz.
Besides, glass is the future material! Everyone knows that the future is made of glass.
[](https://i.stack.imgur.com/6rjSJ.jpg)
[Source](http://streets.mn/2013/04/01/planning-news-from-april-1st-2113/)
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You mentioned "stainless steel". It's not just one thing, but a general label meaning a minimum amount of Chromium.
Knifes are sometimes stainless, sometimes not. Why is a good example that extends to your use. I chose the stainless for kitchen knives because I figured I might be less prompt wiping it down *just once* and mess it up. But alloys that don't handle the environmental conditions are better in that they are sharper and stronger. It's a trade off.
If you put an emphasis on withstanding weathering by itself, it would be a tradeoff with other properties including expense, workability/fabrication, and strength.
Now I have pocket knives that are "stainless" but tougher than traditional stainless steel: they are made with Vanadium.
I also recall when bicycle frames started using "cromolly", Chromium and Molibdinum, for better weathering while being light and strong enough.
So I'm not saying "just use stainless". I'm pointing out that the alloy or mixture can involve many ingredients besides iron and carbon, with carefully tuned proportions. You would **source an alloy that has the desired properties**. It costs more than using an alloy with fewer requirements.
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*I'm going to get totally downvoted for suggesting this, but hear me out...*
# Wood.
Wood is an incredible building material but the mentality is typically to jump to "it burns," and "it rots."
**Safety**
Wood is largely being [recognized for viability](http://newbuildscanada.ca/wp-content/uploads/2010/11/FII-project-using-CUrisk-Final-Report.pdf). The reason that I point this out is that it leads to your longevity requirement. People will be quick to suggest that wood will burn during an 'apocalypse' or even a lightning strike, and not be viable over time. It's understood now that wood construction is not going to 'just burn down,' ([source](http://newbuildscanada.ca/wp-content/uploads/2010/11/FII-project-using-CUrisk-Final-Report.pdf) and [source](http://www.ufv.ca/media/assets/criminal-justice-research/TallBuildings_UFVResearchNote_FullReport.pdf)- just skip to the exec. summary if you like).
**Longevity**
Wood in buildings and towers is pressed, creating a layer up to a foot thick. Wood has been found to be [entirely the architecture](https://en.wikipedia.org/wiki/H%C5%8Dry%C5%AB-ji) of buildings 1500 years old, and has been found in elements of great former cities such as Damascus and Petra far before that. Not to mention petrified wood (which is a different situation, of course).
**Alternatives**
Yes, you will find glass, metals, ceramics, etc. hundreds of years from now: but don't discount wood as a viable alternative: in our minds it seems really vulnerable, but in fact, it's really strong and it does last just as long!
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Not a metal, but I think impregnating concrete with carbon nanotubes-- basically a molecular version of steel rebar-- would be an upgrade, provided nanotubes could be made cheaply enough.
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Here goes:
Use electroplating to add a very thick (a couple centimeters) veneer of [titanium](https://en.wikipedia.org/wiki/Titanium). You get all the advantages of steel, minus the rust and erosion part.
Or ... if you are rich enough, build the skyscrapper skeleton solely out of titanium. It is going to cost you a fortune, though.
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Assume Leonardo Da Vinci invented a scientifically wondrous piece of equipment: a vaporizer gun. The gun is able to instantly vaporize any human being or animal, leaving absolutely no trace behind - all clothes, possessions, fake teeth, etc, disappear without a trace. Since the vaporization only takes 1/1000th of a second, it is also a completely painless death.
Would this mean that murder and genocide become more acceptable in the human culture?
The massacre of the Armenians would leave no evidence behind: no photos, no graves, no horrible stories. The Holocaust would lack the concentration camps as people would be vaporized in their homes, without even realizing what is about to happen. Pol Pot would use the vaporizer guns to carry out his policy rather than starving people to death and forcing them into exile.
My thinking is that without evidence it would be impossible for the modern world to realize the horrors of genocide and it would become a rather distant triviality.
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Genocide will be more difficult to prove, but no, it will not make it more acceptable to extinguish human life on a massive scale.
Essentially, what you’ve done here is remove the gruesomeness of death. You have not, however, removed the consequences.
When a human being is responsible for the artificial shortening of another human life, it causes a lot of problems. The dead often leave family, friends, and other loved ones behind. These people will experience a deep loss and know that someone is directly responsible. A vaporizer does not remove these issues, which means that murder, no matter how “humanely” it is done, will continue to draw deep resentment and anger from victims and others.
With that said, it will become much harder to determine whether a person disappeared (and is still alive) or if they were killed. In many cases there will continue to be signs of struggle left on the environment — overturned furniture, broken windows. This would raise suspicion. Video evidence could certainly still record the act. But for the time periods you’re talking about, it would be much harder to prove that genocide had occurred. Eye witness accounts are easily discredited and during times of upheaval, especially the kind experienced in Europe during World War II, it’s very difficult to track the fates of civilians in crossfire.
Difficulty in proving genocide does not mean it would be considered “more acceptable”, though. Unsolved disappearances lack the closure of a known conclusion, and for many people it is harder to heal that wound. Large numbers of eye witnesses increase credibility. And many of the perpetrators of genocide are reviled for multiple reasons — genocide simply tends to stand out the most. Also bear in mind that the gruesomeness of death can be an important component to genocidal actions. For many of history’s murderers, suffering was part of the message.
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Scenario:
Earth men colonized a terraformed planet orbiting Alpha Centauri. There are already industries developed there, farms, mining etc. There's a large fleet of cargo ship capable of reaching 0.8C (over long distances - nuclear pulse propulsion) serving both systems (colonies both in our Solar system and the Alpha Centauri one).
Question:
What's the best way to establish communications between both systems with reliability of message delivery ?
* Assume current physics knowledge and tech.
* Messages might range from state courier, legal matters and commerce, cargo arrangements to personal messages, if possible.
* Particle entanglement allowed if you find a good excuse.
* EDIT -
If you send a ship to deliver messages about commercial transactions, you might very well send the cargo with it, so there would be no point in sending messages.
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Assuming "current physics knowledge and tech" we're strictly limited to light-speed (or less than light-speed) communication. [Superluminal communication](https://en.wikipedia.org/wiki/Superluminal_communication) can't be done with using quantum entanglement, because of the [no-communication theorem](https://en.wikipedia.org/wiki/No-communication_theorem).
From there, it'll depend on how much data you need to send.
**Small messages**
Use radio or laser.
For short messages the best bet is either radio or laser communication. The bandwidth will be small, but the speed is as good as it gets, light-speed. We've been communicating this way for years, to adapt it for interstellar communication we only need to tighten the beam and boost the power. And of course, like [Space Invaders](https://en.wikipedia.org/wiki/Space_Invaders), aim for where the recipient is *going to be* ([unlike Arecibo](https://en.wikipedia.org/wiki/Arecibo_message)).
**Big messages**
Use probes.
[Bracewell probes](https://en.wikipedia.org/wiki/Bracewell_probe) (or [Sneakernet](https://en.wikipedia.org/wiki/Sneakernet) probes) can be dispatched to ferry large amounts of information. The probes can be accelerated far faster than a ship with humans on it. If 0.8C is because of the acceleration times then you may be able to get there at an even faster speed. Even today, with a high speed internet connection (possibly higher bandwidth than interstellar transfer) simply sending a package by mail results in a [higher average bandwidth](https://what-if.xkcd.com/31/).
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# Letters
You can always send letters. Your ships are going at 0.8c, which is fast, and are delivering goods anyways. Letters could be just another one of those goods. They need not be physical letters, simply digitally stored ones.
This is slow, though, because you are sending letters. Physical and digital letters can be intercepted, tampered with, and so forth. We've encountered these problems before, so there are many solutions to them. The real problem is the time it takes to deliver a letter.
# Light Signals
This includes radios, flashlights, or any other form of communication which uses light. You would likely need some band or part of the spectrum that the stars of Alpha Centauri do not emit. The good news about these communications are that they travel at the speed of light, as fast as we can send them. Faster than your transport ships, even.
The bad news for light signals is that anyone can intercept them, so you'll need some sort of encoding so those communiques do not fall in the wrong hands. The other bad news is that Alpha Centauri, despite being super close, is [4.3 light years](http://en.wikipedia.org/wiki/Alpha_Centauri#Observation). This rules out any informal conversation between people. Communications would need to be just like letters; it will be at least 8.6 years before you get a response.
# Quantum Entangled Particles
We've learned about particles that seem to "instantly" affect each other, without regard to how far apart they are. It has been speculated in science fiction that you can use this to communicate instantly across great distances. So great, in fact, that you violate the "speed of light" rule of the universe.
The wiki article on [Entangled Particles](http://en.wikipedia.org/wiki/Quantum_entanglement#Apparent_paradox) actually talks about a paradox which prevents us from using this to communicate. [Veritasium](https://www.youtube.com/watch?v=ZuvK-od647c) does a good job of explaining this. When you look at an entangled particle, you do not realize why a spin is the way it is until you meet up with someone observing the other entangled particle later. So, you never know if the spin (which you use to communicate) is random noise or your actual message. This is not a basis for communication. *You cannot use this to communicate faster than light.*
If you forced a particle to enter one state, you would need to interact with it, and that could break the entanglement of those particles. That would ruin all the effort you put it into getting the entangled particles over to your buddy in the other system! Once again, *you cannot use entangled particles to communicate faster than light.*
# Quantum Secure Computer Message
Essentially, this forces you to use [quantum computers](http://en.wikipedia.org/wiki/Quantum_computing) to store and read information. These quantum messages are broken as soon as you read it; a one-time use letter whose self-destruct is initiated by reading it. This would be send via a letter-like system, but is possibly the most secure way to store information.
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## Radio
Radio is easiest considering distances and the issues with moving the patterns of energy we call atoms around the vastness of space. Photons are essentially mass-less, so can only go at light-speed, which makes them very convenient for information transmission.
Radio does have the difficulty that you emit in all directions, effectively wasting most of the signal energy, and potentially making the communication subject to interception and decryption by hostile parties.
## Lasers
High energy lasers can maintain beam focus over vast distances. Diffraction will still be an issue at inter-stellar distances, but the energy dilution is much less than that of radio. Transmission of course still occurs at the speed of light.
## Cargo-ships
Properly constructed cargo ships (no human crew) can accelerate at tremendous rates and approach $c$ much more quickly than a standard one gee flight plan (by standard I mean accelerate half the journey, decelerate the other half).
$$S = (2c^2/a)\times(cosh((at)/(2c)) - 1)$$
where, a is acceleration, t is (ship) time, S is distance and c is the speed of light. All units are in SI.
So for $\alpha$ Cen, at 4.37 light years away, while a standard 1 gee $9.81 m/s^2$ flight plan would take 3.6 years shipboard time to cover the distance to $\alpha$ Cen AB, a ship capable of 100g acceleration would only take 44 days (ship board time) due to time dilation onboard. Of course, *the source and destination are not in accelerated frames, so would measure something higher than 4.3 years in duration for the journey*.
Peak cargoship velocity from the home planet reference frame:
$$V= (1 - (1 + aS/2c^2)^{-2})^{1/2}c$$
Peak velocities:
With a one gee flight plan and 3.6 years total (ship-based) flight-time, you get to 0.95c.
With a 100g flight plan and 43 days (ship-based) flight-time, you get to 0.999990c.
## Caveat
[$\alpha$ Cen](http://en.wikipedia.org/wiki/Alpha_Centauri) is actually a close binary star system, with a more distant 3rd companion, and therefore rather unlikely to have habitable planets in stable orbits in anything like the goldilocks (not to hot, not too cold) range.
Also, with regards to both the 1g and 100g standard flight plan, there is no current known technology that would allow that sort of sustained acceleration, since the energy requirements are astronomical. Of course, this is moot since we're talking about the brave new future.
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I recall a talk I saw on youtube but can't find it again; it may have been SETI Seminars? It was a talk about a giant laser being planned for the military, and the guy real excited because it's only another order of magnitude to scale it up to "a flashlight" that could scan Mars from here. It is a *pulsed* laser, so the total power is concentrated in the pulses which are correspondingly brighter. But mort importantly the specific cadence can be watched for to distinguish the return signal even from a bright or noisy background.
He goes on to show that with some concrete numbers such as an 8 meter primary mirror at each end, it **could be used for interstrllar messaging**.
You can find information on how pulsed lasers can give a clear signal if you knowmwhat to watch for. This is something that could be built today, with a few years of development, given funding.
But the existance of the colony implies higher technology and command of energy *far* beyond what we use today. So a bright beam is peanuts compared to launching a relativistic colony ship.
Also, the ship could deploy communication bouys on its way. These would relay the signal.
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A human (contemporary, western) makes contact with an alien. Not wanting to engage 'governments and scientists' the human wants to communicate with the alien.
The alien is physiologically incapable of speech (and devoid of other obvious channels of communication perceptible by humans), plus devoid of any own resources (items/equipment) - "stranded". Also, lacking ability for any more expressive body language. Still, it's mentally advanced as much or somewhat more than humans, has a prehensile (if clumsy) limb (not suitable for sign language) and is able to write and draw.
Of course drawings (on provided paper) are the initial method of communication, but obviously they are very limited. The alien wants to learn the human's alphabet and written language.
What kind of resources (books, learning aids) or techniques commonly available today could the human provide? Assume budget is tight and basic secrecy is needed. There's good and good wits on both sides, but no specialist knowledge.
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I mean absolutely no disrespect to individuals who are born with extreme disabilities, nor am I insinuating that they are somehow like this alien, but there have been people who have been born, blind and deaf, and thus have been cut of from all normal means of human communication, and yet have been able to rise above that to live happy fulfilled lives with the help of very patient and loving teachers.
The story of Helen Keller jumps to mind. Though she was not born blind and deaf, she lost those abilities from illness when she was just one year old. In-spite of that she eventually earned a college degree. If I remember correctly it was actually her that began to try to communicate by making up her own signs, which those around her began to recognize by association. Later her teacher would spell words into the palm of her hand after letting her feel an object. Eventually she learned braille and even how to feel sign language shapes made by others with their hands, and of course she spoke to others using sign language.
So while your alien could maybe not make signs, if it could draw then it would make sense it could at least see or feel letters, flashes of light, or similar stimuli. People communicated internationally for a long time using nothing but a button to type out Morse code. Surely an alien capable of drawing could push a button, or even use a keyboard.
Small animals have also been taught rudimentary communication through association of objects with sounds, smells, flashes of light etc, and have learned to communicate back needs or desires by reproducing the same using things like buttons, or levers.
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Always thought a cool Star Trek series called first contact could be separate episodes related to first contacts. The 'universal translator' although an interesting concept and designed primarily to make the show watchable without subtitles in every episode would be a far fetch. However I have thought about how to first establish communication and I think the best method would involve numbers. Other words are difficult to describe without using words where numbers can be counted. The numbers 1 through 10 drawn say as domino pips with the word underneath would be a perfect way to start. We then make an alphabet so they can see we have 26 letters and see how we combine letters to make words and the words are easy to understand across any intelligent race capable of language and allows the alien or foreigner to write their word for the same number underneath and draw their language. In less than 60 minutes the two species could easily understand the words for the numbers 1-10 and what the alphabet looks like (if the other language uses an alphabet based word system and not pictographic/hyroglyphic type words). But even if they did we'd still have a common base with with to build a shared concept translator. Once both sides could see the word and hear the word and likely see the alphabet that makes up the word they can build on those 10 known words to establish a growing lexicon of translations based on harder concepts and more complex word phrases/sentances.
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>
> ... incapable of speech (and devoid of other obvious channels of communication perceptible by humans), plus devoid of any own resources (items/equipment) - "stranded". Also, lacking ability for any more expressive body language. Still, it's mentally advanced as much or somewhat more than humans ...
>
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when i read this, i remembered Dr. Steven Hawking as he was played in The Theory of Everything movie. even in his case, a non-computer-aided method of communication has been found, i.e. the "glass table with letters and colors" (sorry i don't know how it is called correct).
therefore, maybe his real primer tells you more than you could ask/imagine, and again, there are many publicly accessible information on his biography and life.
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We have a tiny robot, insect like, barely five millimetres long, but with an almost perfect AI. The sensory input consists on an array of chemoreceptors, vibrissae, and cameras. It can fly through air or swim in water.
How would the cameras work? What would be the effects and physical limitations of their small size? Would it be able to see something that a normal sized robot with equivalent technology couldn't?
We can safely assume technology as advanced as necessary, as the story is set on an future of well established interstellar travel.
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I can think of two ways of doing this. Both of which tie in with the robot's AI. One is predominantly a mechanical system, the other predominantly a digital one.
**1. Mechanical.**
If you're willing to 'see' only in a limited spectrum, you can use a tiny, narrow field-of-view, camera, with a collimated filter.
This would only let you in one very specific direction at a time. Think of peeking through a pipe or tube.
The astute world builder might point out that looking through a tube isn't practical.
But you can get around this by having a hi-speed, low-resolution sensor (hundreds/thousands of frames per second). And then waving it about really quickly to scan the environment. Couple this with the AI the robot has, and you have a plausible vision system.
These sensors exist today and, while not really affordable for the home user, they won't break the bank.
For reference, optical sensors can be made *very* small. A single sensing element (a pixel) in a [Canon EOS 7D](http://en.wikipedia.org/wiki/Canon_EOS_7D) is 4.3 x 4.3 um. *Micro*meters. Suppose you choose to have 'eyes' of 100x100 pixels, the eyes are less than 10% of your robot's size.
To point these eyes about, you wouldn't want motors. [Piezo actuators](http://www.piezodrive.com/actuators.html) would be my first guess.
**2. Digital.**
By and large, cameras need lenses, otherwise they're uselessly out of focus (trivia: pin-hole cameras are the notable exception to this, and the *mechanical* system I described parallels a pin-hole camera).
But lenses are; large, heavy, fragile, and expensive. Two of those things are entirely unsuitable for a tiny robot.
The workaround to this is; don't use a lens, capture the out-of-focus image... but on a craftily designed sensor of a particular shape. Because the image follows certain mathematical rules (both because of the sensor and because of physics), it's possible to pour mountains of maths and signal processing techniques to *reconstruct* the original image to a useful degree.
[This paper](http://www.rambus.com/assets/documents/papers/StorkGillSensorComm.pdf) is what gave me the original inspiration. It's very heavy on maths; but you can skip that entirely. The interesting sections are the **Abstract** as well as **sections 1, 3, and 4**.
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Does this *have* to be camera(s)?
What if it used a tiny device that relied on echolocation? If it just sent out constant inaudible pings that relayed information about its surroundings.
Also, when designing robots to act like wildlife, make sure you're pulling from said wildlife as much as possible. Like you said, chemoreceptors, vibrissae, these things are important. It'd be really neat for this tiny robot to have a pair of antennae like ants have that help them feel around.
If it does need to be cameras, though, I would say (assuming technology is at this point) give it a 360 camera placed in the center of its body. Also give that camera the ability to see in different spectrums. There really isn't much that would make this different than a normal sized robot, but the advantages are still apparent in its small size. I'd rather have five robots so small and well hidden you can't see them than one big one feeding me information.
I hope this helps some, the idea sounds really cool. Let me know if I've totally missed the mark.
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At this size, you'd basically have a [pinhole camera](http://en.wikipedia.org/wiki/Pinhole_camera) if there was only one or two, or you could have something like an insect's [compound eye](http://en.wikipedia.org/wiki/Eye#Compound_eyes). However, a pinhole camera suffers from underexposure problems, and would require extremely sensitive photoreceptors to be useful, though it does have the advantage of having a very good depth of field, while a compound eye suffers from resolution problems.
Adding a lens and a larger aperture to a pinhole camera that small would probably be counter-productive, as you'd then get more [optical aberration](http://en.wikipedia.org/wiki/Optical_aberration), and the solution might be some sort of ultra-miniaturised [photomultiplier](http://en.wikipedia.org/wiki/Photomultiplier)
In either case, the eyes would have to be really big (relatively speaking of course) to be useful, probably (like a fly's) taking up a quarter to a third of the available volume in order to achieve any useable resolution.
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<http://www.technologyreview.com/news/525731/lens-free-camera-sees-things-differently/>
The basic idea is that you don't need conventional optics to form an image. You can trade compute for optics and dispense with lenses and other trappings of macroscopic cameras. In theory, I would assume the type of camera described above could be made arbitrarily small.
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Something insect sized can be made now, though with little capability. You're better off hijacking an existing insect.
Ultrasonic range finders are very common for robotics from toys to vacuum cleaners and manufacturing, especially at small ranges where they can be very accurate. Additionally these devices take very little processing power to interpret. With range they loose much of their usefulness. Example:
A structured light scanner may also be used in moderately close quarters for similar functionality, at the cost of high level 3D data interpretation.
Cameras may be used with object profile identification to interpret their surroundings, but this also requires quite a bit of processing and can be very inaccurate.
Most small robots have vision systems catering to specific needs, a Roomba might use infrared or ultrasonic parallax but would be incapable of navigating outdoors or even large spaces without a secondary system (those devices record their path to allow returning to a charging station).
Animals navigate using sight, sounds, touch and equilibrium, capable robots will likewise use a fusion of sensory apparatus.
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How big a difference does the Earth's liquid outer core and mantle make for the evolution of complex life?
If all of Earth's parameters would be the same, but it had a solid interior just like Mars, would we still have an atmosphere, liquid water, and a moon? How much weaker would our magnetic field be? Or would we have none?
I seem to remember that Mars has a very thin (or no) atmosphere because it has no liquid core and thus no magnetic field, but could it be that our greater planetary mass would compensate for that? Venus has an atmosphere after all, even though its core seems to be only partially liquid.
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I agree with much of the other answer but did want to contest one point, as the effect of the solar wind on atmospheres is not fully understood. It is entirely possible that lighter gasses such as hydrogen are affected more by the solar wind than heavier ones. What is known for sure is that Venus has very little magnetic field and still has an atmosphere much much denser than Earth's.
<http://en.wikipedia.org/wiki/Atmospheric_escape>
So life would evolve much like it did here on earth, the atmosphere may be thinner. Water would be rarer (due to the lack of hydrogen), and radiation levels would be much higher. Expect most creatures to be resistant to radiation damage or have breeding strategies that avoid it. During solar storms animals may well retreat into burrows and there could well be a lot of nocturnal animals as well.
With no magnetic field compasses would not work. Electronics would be harder to develop and less reliable until proper shielding is developed.
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> *Keep in mind that I'm not an expert and I'm going with what is generally considered acceptable by the mainstream, both for what the
> planets are like and the causality we've attached to these
> characteristics. I don't necessarily agree with all these explanations
> and correlations, but it corresponds to common understanding.*
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Based on what we know about planetary formation and geology, the mantle and liquid core provide us with a magnetic field. Without one, we'd have no protection from the solar wind:
That means the Sun would evaporate the atmosphere and hence you get less protection from solar and cosmic radiation. You also get less weather, such as lightning, rain etc. - without these, you don't get much chance for evolution of complex life, though of course extremophile bacteria can still survive. So you might have "life" in the strict sense, such as bacteria landing through space, but you wouldn't call the planet "alive" in any sense.
Liquid water is somewhat related. Considering that the primitive Earth is assumed to not have water the way we have it today, but a much more toxic mix that slowly got changed into a combination of mostly water, due to environmental change which came about from terraforming bacteria (this is how I remember it roughly, not sure on the details), I'd say we're back at square one - you won't have vast populations of microorganisms doing their business on a planet unshielded from solar radiation (especially when the temperature range would be much more than 5-10 degrees Celsius between night and day - it'd be closer to 100 or more, making any adaptation difficult). You could however have ices, accumulating from space debris over a long period of time. The extra problem here is, where would it collect?
The reason we have vast oceans is due to mantle activity - tectonics, volcanos etc. Without a liquid mantle, you don't have those as far as we can understand. So you'd just be a smooth rocky planet like Mars. No basins.
The last but not least problem I can think of is the evolutionary cycle. Major extinction events have been linked to the emergence of new and more complex life. In our case it was probably related to environmental changes, correlated with environmental weather and atmosphere cycles, as well as solar cycles. This requires enough stability to preserve life after a disaster, but not enough to prevent the cycle from moving on, to allow newer life to take over. In other words, even if you got to dinosaurs, they could just stay like that for much longer (assuming extinction events are *not* caused by biological populations and instabilities inherent to evolutionary stages).
A planet without an atmosphere, no mantle movement and eruptions and little shielding would be pretty much like Mars - rocky, barren, relatively smooth and practically lifeless.
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[Question]
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Essentially, I have a flying predatory creature in my world which is roughly the size of a raven and hunts at night, relying quite a bit on sound for echolocation in tighter spaces, hearing for both prey and predators and for communication. Because of this, I wished to give them large ear-like structures, but there are some problems with the context the creature is in:
* the creature is not from earth and has many similarities with arthropods overall, with most of its head, apart from most of these ears, being covered by a hard exoskeleton, so I didn't want to give it external ears too similar to mammalian ones.
* these creatures have natural predators, so I wanted their ears to be usable to look bigger and more threatening, potentially with eye spots or bright patterns.
* I wanted the ears to be somewhat compressible, both to hide said warning patterns while trying to camouflage and to make them less likely to be damaged or get in the way when not used to actively listen for something.
The solution I thought of was a flexible frill-like structure with 2 main, flexible support "rods" on each side of the head (measuring around 5 centimeters in length) that could spread out like a satellite dish, with a net of muscles on the membranous part changing the shape of the ear to further help it amplify sound at certain frequencies of interest to the alien, like what you'd see in pterosaur wings or an octopus' skin. Rough draft of what I mean below, blue being the "ear" while retracted close to the body and orange the structure spread out and in use:
[](https://i.stack.imgur.com/S50Ow.jpg)
That being said, I haven't really heard of anything quite like this before in our world, the closest being African elephant ears, which can't quite compress and have their sized justified in part due to thermoregulation. Other than that, I couldn't find anything really saying whether such an arrangement could actually be good or just a waste of energy.
That said, **could such a type of external ear work?**.
Specifying what I need: I'd like to know if it's at least somewhat functional without being terribly impractical, and whether this design could be still salvageable to some extent in case it's not.
[Answer]
## Some notes on size and frequency
**Your creature won't fly with that one**
(Note: below will be of consideration with flying animals, but given the fact this anthropod has the size of a raven, it will be less of a concern)
The issue of the reflector in your opening's drawing is the amount of air resistance, placed in forward direction as a collar around the creature's neck, similar to Fred's lizards. A flying insect can't carry a fleece like that while flying forward.
**Go ultrasonic, to reduce the size of the receiver**
Let's assume your arthropod is a centimeter, or a few centimeters. Insects usually produce sounds around 4-12kHz (see [this article](https://songsofinsects.com/appreciation-of-insect-song)). When the sound emitted is e.g. 10kHz, your wavelength will be about 0.045 meters. A suitable parabolic antenna for that has a diameter *at least* about 0.015 meters to actually amplify the sound. Preferably it should be larger, a multiple of the wavelength. See [this article.](https://www.electronics-notes.com/articles/antennas-propagation/parabolic-reflector-antenna/antenna-gain-directivity.php) So.. choose your echolocation frequency wisely, go high up ultrasonic.. 40kHz would reduce the minimal diameter of your parabola to 3mm. With "collar antennas" of 10mm you'd have about 10x amplification.
**Flexible ears**
For echolocation and to prevent the issues with flying, you could consider introducing flexibility. Bats have that. Allow the animal to change the shape very quickly. See [this article](https://www.sciencedaily.com/releases/2011/11/111114133646.htm).
[Answer]
Frilled ears similar to the neck frills that [frilled neck lizards](https://en.wikipedia.org/wiki/Chlamydosaurus) from northern Australia have are possible. If they are shaped correctly they can be parabolic and focus the sounds to the ear hole similar to how parabolic radio dishes work.
The other option is to have expandable ears that become enlarged when bodily fluid is pumped into them.
[](https://i.stack.imgur.com/p7cvW.jpg)
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I know that many sentient robots in sci fi stuff eat food even if it is just for pleasure, energy or make them appear more like real humans and animals.
Well I was thinking how would such digestive system could work. I believe that in a far future robotics could be advanced enough to emulate a digestive system using 100% inorganic materials and maybe nanobots or a kind of artifitial endocryne system could emulate the enzymes that break down food. the trick is make the android produce chemicals continuously like humans do like salive and the stomach acid.
what kinds of technologies could make it possible?
If androids eat food along with having taste sense they could eat how much they wanted without worrying about health problems assossiated with overeating. this could make them superior to humans in more ways.
[Answer]
**Enzymes**
Biology is pretty good at getting the full efficiency you need. Energy can be extracted from food and stored. With technology we can emulate such things and sometimes improve on it. Enzymes are very efficient and we make many artificial ones already.
A robot can leverage this. Humans need a wide range of energy during their lives. A robot most likely needs only needs one kind for it's power. Most likely electricity will be used for both locomotion and thinking. Food can then be processed focusing only on the nutrients that can be used for power generation.
Besides making enzymes an efficient method is required to reduce the food to manageable bits. Both chewing, acids and slow movements of the stomach, in combination with enzymes, can break it down. Each of these can be generated and simulated.
All this is already possible. There exist full simulations to create such things. What is still missing is making it exact to reduce it to the right medium that can then be stored, as well as used as fuel at a later time.
Teeth/grinder, artificial stomach with acid and some enzymes for reducing it to mush. Then more enzymes to store it. Then more to make it usable/burn it for the energy.
[Answer]
**We need to start with one truth: Both humans and robots can eat less-than-useful things**
My suggestion will make more sense if you remember that humans can eat negative-calorie foods.
>
> Food provides your body with a variety of nutrients, including three main categories that dole out energy in the form of calories: carbs, fats and proteins. Your body has to expend energy in order to digest and process any food you eat. The amount of energy required varies based on the food. The term negative-calorie food typically refers to a food which supposedly takes more calories to eat, digest and process than it naturally contains and gives to your body. ([Source](https://www.healthline.com/nutrition/negative-calorie-foods#definition))
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Now, that article goes on the explain that there may be no such thing as foods that take more calories to consume than they provide the body as energy. Let's ignore that for a moment. Distilled water has no calories. It takes more energy to drink it and process it away (aka, urine) than it will ever give to my body. This is an important point.
But that article makes another important point. It says, "Food provides your body with a variety of nutrients, including three main categories that dole out energy in the form of calories: carbs, fats and proteins." In other words, this whole issue is *about more than just energy.* It's about all the things your robots need to survive.
What might a robot need other than energy? Lubricants. And if they're self-replicating, a whole bunch of stuff.
**But what the robot needs, we don't, and vice versa**
Humans can eat sand. It doesn't do us any good (more negative calorie food!), but we can eat it. On the other hand, your robots might need the silica! So it makes sense that your robots would want to eat sand even while humans don't - but they both could. Just as they could both eat rutabaga, but your robots probably won't get much out of rutabaga.
**But how would the digestion work?**
The human digestion system, which works with a combination of enzymes, acids, and various squishy stuff that serves to transport and filter the goods, could be called nothing more than a *material processing system.* Once you realize that, you realize that a gasoline refinery is just another form of digestive system. Crude oil goes in, magic happens, a useful energy-providing substance comes out, and gets delivered by pipes, trucks, and pumps until used to make your car go. A *macro* digestive system compared to humanity's *micro* digestive system.
What you'll be doing is miniturizing what we today know as *macro* digestive systems. You're creating a chemical processing plant the size of the human gullet the relieves the incoming mass of any useful energy-providing or other substances to be moved along to where they're needed to keep the robot going.
The result is a robot that could enjoy a meal with a human! The robot may not actually get much out of the meal... but when it comes time for the robot to cook, the human won't get much out of that meal, so they're even. And since they can both eat things that don't provide a lot of value, they'll both need sewage collection, transport, and processing systems. Just to make a point. You're robots will need toilets.
*I'll leave it as an exercise for the OP to figure out what elements the robots specifically need, look up how those elements are gathered and processed by humans, and then write the story to indicate that/those processes had been miniturized.*
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I started a Minecraft world one day and decided I'd challenge myself by setting the sea level to 100, a rise of 36m from typical. Besides the fact that the tops of mountains and plateaus are still above water, a quirk of the Minecraft world means that any water in mountain areas above a certain elevation will freeze, so I found myself with a lot of ice surrounding the few bits of land that poked above the water.
Now, I know this would probably be unrealistic if it were applied to Earth or any other planet, so I figured I'd see if Worldbuilding had any similar questions. I have not found one yet.
My question is: what might the weather and/or environment look like on Earth after it underwent a sort of Waterworld-like scenario where the water levels rose considerably? Ideally, this would be looking at a situation after whatever had caused the problem in the first place had gone away or calmed down. If whatever caused the Earth to undergo this would by its very nature need to stick around, then by all means let me know and figure it into an answer. Thousands of years may have passed.
I mention the Minecraft scenario because it made me wonder if the tree level of mountains would change, if the trees would start being able to live "further up" than they had been before. Would there be less snow on previously snowcapped mountains?
On one hand, perhaps survivable conditions would now exist where they didn't before, such as on Mt Everest. On the other hand, just because the sea level rose, it won't mean that the nutrients in the soil would have improved any.
[Answer]
**First, there are two ways to look at this question**
1. An earth-like planet that becomes a water world.
2. A world that naturally evolves as a water-world.
Those are important distinctions. An earth-like planet would either need an "explanation for the Biblical flood" solution (e.g., something squeezes all the water from the aquifers type of thing) or a "water was added to the system" type of solution (e.g., an ice asteroid hit the planet bringing enough water to flood it.) Either way, given that things are allowed to "settle down" into their new water-covered state, what would you have?
What you'd have is ice—and a lot of it. From this perspective Minecraft is right. Now you mentioned a rise of only 36 meters from typical. Let's use the [seal level simulator from Floodmap.net](https://www.floodmap.net/).
* If you set it to 36 meters, you don't have a water world. Most of the landmass is intact. You don't have ice in this scenario as the world hasn't really changed. You'd have a bit more polar ice, but that's about it.
* If you set it to 500 meters, you have more of a water world, but there's still a LOT of land. I wouldn't expect ice in this scenario, but people are at measurably higher elevation, so a colder climate would be expected. Your polar ice would be pretty big and global warming would no longer be a problem.
* At 1,000 meters I'd claim we have a true water world, but there's still enough land (go look at Greenland, the world's new superpower...) that you could save everyone on Earth today and probably feed them (that's a lot of ocean for fishing...). Except for the ice, which likely covers the earth.
The problem is that simply changing Earth means that you have the normal heating conditions of the sun and what we know of high-elevation temperatures coupled with a higher rate of cooling (a LOT more water in the atmosphere and much more evaporative cooling) and the fact that water is more thermally conductive than dirt. In other words, no more global warming. It would be a permanent ice age with a thriving underwater ecosystem because all that solar energy is still arriving and underwater vents still exist. Thus, I wouldn't predict a thick ice sheet on the ocean, but I would predict all the land covered with ice and substantial ice shelves.
**But, what about world #2?**
For a moment, let's consider the goldilocks condition for a true water world. In this case the planet is absolutely *tropical.* It's a bit closer to the sun to balance the cooling effects of the water. There's no ice, anywhere, not even at the poles. What land is exposed is either lush with life or completely barren. I'm going to ignore the analysis of deep-ocean vs. shallow-ocean. That would have a substantial effect on the plant life, but not the average planetary temperature as the orbit would simply be adjusted to balance it out. For fun, we'll assume deep oceans like ours.
That world would be teaming with happy oceanic life. Lost of elbow room.
**OK, but what about the weather?**
In both circumstances (#1 and #2), you have substantial storms. A TON of water is evaporating into the atmosphere and there's fewer blocks to wind. Ocean currents are still moving around undersea continents, but there's a lot less drama involving them. Which means you have striated currents, striated winds... You'd have a planet with whooping high winds, really BIG storms, and almost constant cloud cover.
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## An Important Message from Our Sponsor
@FinAndTonic brought up an incredibly good point that throws some of my answer into disarray (but I haven't time tonight to rework it all). As sea levels rise, they push the atmosphere up with them.
Here's the problem: the idea that things are colder at "higher altitudes" is based on thinner atmosphere. We humans ofttimes don't respect just how thin the golden biosphere really is. That two kilometer band above sea level is prime happy land: warm and inviting. Above that things start getting dicey until you reach the "death zone" [at 8,000 meters](https://theconversation.com/everest-i-interviewed-people-risking-their-lives-in-the-death-zone-during-one-of-the-deadliest-seasons-yet-118427).
But if you add water, the water pushes the atmosphere up. So the death zone is still 8,000 meters above the new sea level.
Now, there is a complication with this: the Earth's mass isn't materially changing with the addition of new water. That means that while we're pushing the atmosphere up, the loss of atmosphere to space ***increases***. At this moment I don't know if that increase is enough to lower the atmospheric density to bring the ice back into play.
But it's uber-cool to think about.
[Answer]
With water, it has a high specific heat capacity, so the temperature changes during the day would be less prounounced, and the range of naturally-occuring temperatures at its surface will be smaller. However, as there's a lot more water, there will be a lot more evaporation, which will produce a more humid atmosphere. This, combined with water's low albedo, will make the planet warmer than an Earthlike one that orbits the same sun(s) at the same orbital radius. Also, there will be more condensation, which means that there will be more cloud cover, which will do interesting things with how the planet traps heat. And, the hurricanes there will be larger, stronger, and longer-lasting than those of an Earthlike planet.
[Answer]
If the OP wants an extraterritorial experience in the story/fiction, try Ganymede where a salty ocean of water is expected. Then space exploration, terraforming, technology and manufacturing can be tied into the settings.
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The setting I've cooked up for a D&D campaign I'm running features a fair amount of buildings that have been totally abandoned by civilization for hundreds or even a thousand years. Obviously without upkeep, many aspects of such buildings will weather, rot, subside, collapse, etc. Our own history has furnished up with many examples of ruins that are centuries or millennia old, some of which have been reduced to little more than rubble and others which have stood largely intact.
One commonplace feature of adventuring sites in D&D that I can't seem to give up, and that is troubling me in terms of immersion with the premise of exploring ancient ruins, is doors. Doors are great for obscuring danger, controlling players' access to game content, and can become entertaining obstacles. I would like to have doors. But history tells us most doors or coverings of portals have been made from wood, bamboo, reeds, textiles, etc. even in buildings that are constructed from more durable materials like metal and stone.
Which brings me to my question -- how long might a wooden door remain intact under favorable conditions, and how long might a wooden door remain intact in ideal conditions?\*
\*For the most part my setting is Earth-like in terms of climate and life.
[Answer]
**As long as you need.**
There are lots of variables that affect how long wooden objects lasts, so unless you are writing for an audience with specific interest in such things the standard is simply provide a plausible excuse why it has lasted as long as it has. With your "science based" tag the bar is raised slightly for this answer but there is still no real reason to do math or provide hard numbers. Why would they know or care how old *exactly* the door is, right?
**So what do you need to consider?**
**Biological decay** by micro-organisms is the fastest and the one that you absolutely must explain away. This is probably not still important enough to justify actual exposition about the specific conditions but a few mentions scattered in descriptions will be good to do.
Bacteria and fungi need moisture. Ancient salt mines have some nice wooden objects that have survived for millennia. Similarly arid deserts can protect organic objects from bacteria. This is probably not what you want but you should have good drainage and decent ventilation in areas where you want wooden doors to survive. If everything is covered in mould and slime you'd need a very good excuse to have a door survive.
The wood used might be toxic or otherwise resistant enough to protect itself. Trees have evolved toxins and defensive structures to protect themselves from disease and parasites. While this is hard to quantify, it is a real "science based" thing and well suited for your needs.
As AlexP mentioned the doors have material value and a door made from a special kind of wood that can resist decay would be valuable enough that the characters would reasonably recognize it as valuable. And specifically valuable because it lasts long. And while players do not really care about how old your door is, they do care about how much it is worth in gold and won't mind an explanation why. It helps in finding the buyer with best price.
It might be treated with protective treatment. A wood that is properly dried and lacquered will be safer from decay from insects, fungi and bacteria. Rats too. Here you will need to consider the structure of the door. If your hinges are attached with screws, the holes will give bacteria a way in and your door will eventually fall down and decay from inside.
In general, despite it being bit off-topic, remember to think about how the door is attached. Players probably won't notice but who knows what people will notice. Your attached hardware should not compromise the door structurally and be itself resistant to decay. This would probably mean metal in dry conditions and a construction where the wooden door is essentially held within a metal gate with hinges and locks connected to the metal structure.
Next issue is **chemical decay**. A door immersed in boiling acid will not usually last that long despite being fairly safe from bacteria. Dungeons would generally be cool enough for heat not to be an issue but some fantasy dungeons have lava. Avoid that if you want wooden doors. The dungeon might also be in an area cold enough that it is always below freezing. This would slow down chemical reactions and also protect from most biological decay.
Your dungeon might also have been protected by inert gases. Oxygen is corrosive so not having any would make most things last lot longer. Low oxygen levels also protect from much of biological decay, insects, rats, and humans. Anoxic water or mud may apply but is probably not what you want your dungeon. Although having the dungeon be immersed in anoxic water for millennia until the waters subsided just last week is an option. Problem with such immersion is that while the wood can last long, its structure suffers and it may not be durable afterwards.
Physical processes also need to be considered. If your dungeon is intact after centuries it usually has environment static enough that erosion is not a major issue but even so fantasy dungeons can sometimes be weird. If your corridors have strong winds or flowing water or the doors keep moving that will cause physical erosion. I am really mentioning this for completeness since wood usually decays before physical erosion is an issue but it would be fairly embarrassing to protect your doors from bacteria and then be pointed out that the method you used to do so would have physically eroded the wood. So no fast moving gases or liquids even if they'd have a preservative effect.
Last thing to note is that you want to be clear whether the doors survive because of fortunate conditions, really good construction or because somebody went to lot of bother to preserve them. For a fantasy dungeon it is entirely plausible that the dungeon and the doors within were specifically designed and constructed to be functional six hundred and twenty-seven years from now when the prophesied redeemer enters.
Also do not be afraid to say "magic". Fantasy doors built to last would quite plausibly have some protective magic on them. And making the doors immune to normal biological, chemical decay and physical erosion would be a natural side effect for even fairly weak protective magic to have.
[Answer]
There's a side door in Westminister Abbey which is over 900 years old. There are plenty of much older timbers around in Anglo-Saxon buildings. I don't think you need to worry.
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I am developing a fictional planetary system in which a large gas giant planet (slightly less than the mass of Saturn), has migrated into the habitable zone during the formational years of the system, and hosts habitable moons.
The star in question is a K0V Orange Dwarf, which is reasonably quiet (i.e. doesn't flare often or at all anymore)
In trying to determine what colour my gas giant should be, it became clear to me that photochemical reactions in the atmospheres of these planets are a major factor in determining what compounds are present, and thus their colouration.
Most importantly, in our own solar system, Jupiter and Saturn receive more UV radiation (which breaks down methane into other compounds), than Uranus and Neptune (which are able to retain methane, and are thus bluer.)
Since my fictional gas giant is orbiting its star very closely to be within its habitable zone, my initial thought was that the planet would not be able to retain methane, and would therefore lack blue colouration. However, I then remembered that K-type and M-type stars are cooler, and therefore emit less UV radiation in the first place (except for flares).
What I am trying to determine is this; Does a quiet K-type star emit a sufficiently low fraction of its output in the UV spectrum, that a Jovian/Saturnian type planet would be blue or blue-white even at a habitable distance?
System parameters:
Star (K0V)
* 0.85 Sol masses
* 0.75 Sol radii
* 0.40 Sol Luminosity
* ~5,250K surface temperature
* Age: ~8 gya
Planet (Gas Giant)
* 82 Earth masses
* ~50,000km radius
* Semi-Major Axis: 0.85 AU
[Answer]
You have two questions to consider here: Can compounds required for blue atmospheres form in significant amounts on this planet, and are the temperatures right for them to condense and form clouds?
I talked about atmospheric composition and color in [an answer to a related question](https://worldbuilding.stackexchange.com/a/164777/627). Essentially, the question of whether or not compounds like ammonia and methane (known as volatiles) - can exist in a giant planet's atmosphere depends on the orbit of the planet in relation to the star's frost line. The frost line is the point at which, in the protostellar nebula, these compounds could condense. This critical temperature is thought to be [around 145 Kelvin](https://ui.adsabs.harvard.edu/abs/2012MNRAS.425L...6M/abstract). For a solar-type star, the frost line would have been around 2.7 - 2.8 AU. I suspect your star would have a frost line slightly lower than this, perhaps 2.5 AU. This would seem to indicate that your setup is impossible.
*However*, giant planets have been found quite far inside the frost line; notable are the gas of exoplanets known as hot Jupiters. These planets [migrated inwards](http://www.scholarpedia.org/article/Planetary_formation_and_migration) through interactions with the protoplanetary disk or planetesimals early in the system's history, allowing giant planets to orbit quite close to their parent stars. You can easily place your planet inside the frost line if you allow migration to occur.
Now we get to our second issue: condensation. In general, different gases condense and are dominant at different temperatures, and so [the color of the atmosphere depends on the planet's temperature](https://wfirst.gsfc.nasa.gov/science/preparatory/160303/Lewis.pdf). The effective temperature of a planet scales as $T\_{eff}\propto L\_\*^{1/4}$, where $L\_\*$ is the parent star's luminosity. Plugging in the numbers, this means that your planet should have an atmospheric temperature (neglecting greenhouse effects) suitable for water vapor but too hot for methane or ammonia. Water vapor clouds could lend a blue color to the atmosphere, but unfortunately it would not be aided by the presence of atmospheric methane or ammonia.
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There's an important aspect of my headworld involving volcanoes which I planned many years ago. Recently I revisited this concept to refine it further, only to run into a few questions that I've been struggling with. My geology knowledge is quite limited and I can't find much information on these matters online.
Basically, I have a creature species that has adapted to living in colonies settled inside craters of massive extinct volcanoes. The rough concept was that, although the environment around these volcanoes is extremely harsh with low temperatures and constant, powerful wind currents, the volcanoes still emanate enough heat to provide a good settlement for this species. The heat consistently melts down the accumulating snow at the top of the crater walls, then the water streams down and pools up inside the crater. These pools make for the colony's water source, and there are fissures/openings in the rock that allow for the water to stream out too. In some cases this even forms waterfalls outside.
I was wondering, is it plausible for completely extinct volcanoes to still emit heat in such ways? Some time ago I read about an extinct volcano that still has magma simmering in its chamber([link](https://www.nationalgeographic.com/science/2019/07/magma-found-simmering-under-extinct-volcano-what-that-means/)), while its own structure prevents an eruption from happening again. However, I'm not very knowledgeable on the details of these cases and couldn't find much information on how common that is.
[Answer]
Volcanoes become extinct when their magmatic chamber is no longer supplied with new magma from the mantle.
But like when you turn off the fire under a pan of boiling water its content stops boiling but stays hot for a while, so does the magmatic chamber. The heat from the molten lava will slowly diffuse outward, until, over geological time, the lava will solidify.
Meanwhile people living above the chamber might enjoy thermal baths and other related secondary volcanic activities.
An example of this is [Larderello](https://en.wikipedia.org/wiki/Larderello) in Italy.
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> The region of Lardarello has experienced occasional phreatic eruptions, caused by explosive outbursts of steam trapped below the surface. The water is contained in metamorphic rocks where it is turned to steam which is then trapped beneath a dome of impermeable shales and clay. The steam escapes through faults in the dome and forces its way out in the hot springs. It possesses a dozen explosion craters 30–250 m in diameter. The largest is the Lago Vecchienna crater which last erupted around 1282, now filled by the Boracifero Lake.
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> Larderello now produces 10% of the world's entire supply of geothermal electricity, amounting to 4,800 GWh per year and powering about a million Italian households. Its geology makes it uniquely conducive to geothermal power production, with hot granite rocks lying unusually close to the surface, producing steam as hot as 202 °C
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> In 1911, the world's first geothermal power plant was built in the Valle del Diavolo ("Devil's Valley"), named for the boiling water that rises there. It was the world's only industrial producer of geothermal electricity until 1958
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[Answer]
Yes, there are many “extinct”, or more precisely, dormant volcanos that still emit heat that drives hydrothermal activity.
Perhaps the best known example is Yellowstone. It has not erupted in a while and it’s not going to erupt in a while. However, the pools in the Yellowstone area support unique ecosystems of microorganisms and larger animals.
Hakone in Japan is another example. It is relatively dormant, compared to the neighbouring Mount Fuji. However, it is still thermally active and this activity supports, again, a unique ecosystem.
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Magnetic core memory was a critical innovation in the development of computers. Per <https://en.wikipedia.org/wiki/Magnetic-core_memory> it was the most advanced form of memory from about the mid-fifties to early seventies.
For development of a semi-steampunk setting, I'm thinking about how much earlier it could've been developed. (Setting is otherwise largely similar to our own world in relevant aspects of history, geography, economics etc. I'm just trying to figure a way for it to have early computers powered by e.g. electromechanical relays.)
What are the prerequisites? Clearly it needs electricity and a fair degree of proficiency in processing electrical signals, as well as the ability to mass produce identical parts. What other difficulties are there? Could a well-equipped R&D group that stumbled onto the right path, develop practical core memory at the 1900 tech level, say?
[Answer]
**This is outrageous, and the more I think about it, the more wondrous it gets**
For all intent and purpose, the electromechanical relay [was invented by Joseph Henry](https://history-computer.com/ModernComputer/Basis/relay.html) in the late 1820s. If that name sounds familiar, it should. The SI unit for magnetic inductance was named the *Henry* in his honor. But what's amazing is that electromagnetic relays were not used for computing for [*a century!*](https://history-computer.com/ModernComputer/Relays/Zuse.html) Heck, you didn't see them in telegraph machines until the 1860s.
*But! What if enamel-coated wire could be manufactured to a smaller gauge and more economically!*
It was the height of the Industrial Revolution! Factories were popping up everywhere! If Hollywood can be believed, Dr. James Moriarty is poised to take over the world! And all someone had to do was draw that magic line between the analytical functionality of Babbage's mechanical wonder — and a relay that would take up a fraction of the volume.
*Boom! Electromechanical computing in the mid 1800s.*
**But, why is that important?**
Because the most common reason any technological advance took place when it did is that there was a reason to look for it. *This is really important!* In many cases, it's not the technology part of the tree that's causing an advancement to take place when it did, *it was the fact that a need for it finally arose.* Necessity is quite often the mother of invention.
And if we have serious computing going on in the 1800s, we have the need for memory in the 1800s (not just registers, but serious computational memory on the order of whole Kilobytes!) Electomagnetic relay computing would do it, but it's also important to understand why.
*Speed*
Babbage's mechanical wonders had memory. Persistent memory. If you stopped turning the proverbial crank, all the gears stopped where they were and whatever had been stored would be remembered — *forever.* Why would anyone want memory that would, eventually, degrade?
Because you can only get so much out of spinning gears. Relays are *fast!* Lightening fast! And the best way to take advantage of that speed is to have memory that's just as fast as the relays are!
**Conclusion**
The necessary technological advances that would bring about magnetic core memory already existed in the mid 1800s. Electricity and magnetism. What lacked was a reason to even think about the need for this marvelous thing called "memory." And that's what we've provided by bringing electromagnetic computing to the fore a century before it did.
But even this requires a reason. Maybe. That's the wonderful thing about stories. You don't really need a reason for anything. But you might want to consider why you need faster computation in the mid 1800s. It's not like they were putting people into orbit (seriously, go watch the movie *Hidden Figures* or read the history of those amazing ladies. NASA didn't need computers as we know them today for quite some time, because human computers were fast enough. It wasn't until they needed the data faster that they started replacing the people...). What in your story needs fast computing? If you answer that, you've justified electromagnetic relay computers, which justifies researching memory, which brings MCM into the fore a century early.
*In my comments I mention that MCM likely couldn't have been brought to light more than about 15 years before it did. This is because of this dependency on the need for speed. MCM was dependent on fast computation. Bring about an early reason for fast computation and you speed up a lot of things.*
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[Question]
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Basically, I want to freeze the technology of earth at a level reminiscent of pre-Industrial Revolution Europe. I'm trying to figure out what substance or material would have to be absent from the geological makeup of the earth in order to prevent any significant technological advancement past this point, without altering the technological development of the world prior to this point.
I know that of course there will be advancements regardless, but is it possible to limit these as much as possible? If not, then is there a time period where it would be possible to halt development in the manner described above?
[Answer]
I'm approaching this from the "*reverse*": what you **cannot** remove since it has been used in pre-industrial era, and see if we can have an industrial revolution.
Cannot remove:
1. most organic material. Removing it disrupts too much life (including human life), and possible entire ecologies.
2. all the metals used in antiquity (iron, copper, tin, etc.)
3. silicon (used in glass)
Concrete has been used by Romans, so would be here.
Steel would be here. Charchoal can produce high quality steel, and can act as a fuel, on a much more limited scale. Canada and Russia would be much more relevant, similar to OPEC countries, due to their enourmous amount of wood.
Hydroelectricity would be here. The amount of hydro would be more than enough to satisfy the energy needs for industrial revolution. Electrical grids can be build. Trains will run on electricity instead of coal. Cars and trucks will be replaced by trolleybuses/trolleytrucks. Ships will continue to rely on sails.
So I would say both industrial revolutions will be there, albeit slower.
Removing rare earth would cripple the electronic industry as we know, and not that important for preindustrial techs. But even then I am not sure that this a showstopper, before asteroid mining becomes feasible.
[Answer]
The two obvious things would be coal and oil, but because they form from biogenic sources, it is hard to envisage a planet that harbours life without any fossil fuel deposits.
One could suggest that due to the various circumstances, the fossil fuels would not be readily available in Europe, delaying their exploitation. However, the European powers were colonising the world before that, with oil being found in the Middle East and coal being found just about everywhere (for example in Australia, a British colony).
One of the reasons for fossil fuels to not be adopted could be political conservatism or environmental instead. Some of us may recognise this quote attributed to Napoleon ([although of questionable authenticity](https://www.quora.com/Is-it-true-that-Napoleon-dismissed-Fultons-steamship-project-which-could-have-allowed-him-to-conquer-England)):
>
> You would make a ship sail against the wind and currents by lighting a bonfire under her decks? I pray you excuse me. I have no time to listen to such nonsense.
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The leaders could simply think it is not a good idea, delaying adoption of this technology by centuries. Alternatively, the early industrial revolution was extremely polluting. People could just object to it because no one wants to have a coal-fired plant next to their house.
This could be paralleled to modern times - some people are reluctant to adopt wind and solar and increase adoption of nuclear, because of political conservatism. People are just happy with the way things are and don't want to adopt new things. Having a few leaders in key countries that have this mind set would delay the industrial revolution.
For example, gold was a major contributor to scientific advancement. Rutherford developed his model of the atom by playing with gold foils.
---
It is also possible to get rid of some of the commonly used metals such as iron or aluminium, but as iron is essential for life, and aluminium is one of the most abundant elements in the solar system and on Earth, it is hard to envisage how Earth as we know it would function without them.
---
As to chemistry, an easy way to delay technological advancement to let's say early 20th century (albeit after the industrial revolution) is to get rid of all the noble metals. Gold, platinum, palladium, etc. Being noble metals, they are not essential for life. Life could very well evolve without them.
The fact that we even have noble metals is pretty much an accident. All of them were supposed to go to the Earth's core, but a geo-astronomical event called the late veneer (see last part of my answer [here)](https://worldbuilding.stackexchange.com/a/123951/39999) added more of them to the crust and mantle. If this event would never have happened, the development of electronics would very much slow down and stop at a very primitive level (late 19th century).
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[Question]
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I've just bought myself a shiny new spaceship equipped with the latest in FTL warp technology, the only catch is the fuel bill, this thing drinks the stuff like it's going out of fashion (still, it's better than the F150 but that's another story).
Now I'm just a humble space-cabbie but, my understanding of warp drives is that they just, well... *warp* the space around the ship. But then, if space-school physics taught me anything, it's that so does the Earth and the ***Earth*** doesn't need refueling every 38¼ parsecs so... *where's all that energy going?* I'm pretty sure you can't just burn a couple kilos of antimatter without also turning the inside of the ship into one heck of an oven... so what's going on?
[Answer]
It's like the difference between natural and artificial magnetism. A natural magnet doesn't need any input but can't be controlled. A controlled and focused artificial magnetic field takes energy to create and maintain and that energy is lost as heat and other inefficiencies in the system.
While the drive is running the energy is lost as heat radiated out as a side effect of artificially warping space. Ships would leave a detectable trail of heated areas, with increased radiation and exotic particles where they have passed through.
[Answer]
The good news is that your Shiny New Spaceship came with great tech that lets you control and manipulate the terrajoules per cubic meter that it takes to warp space! And, if you keep taking it in to the dealer for the (pricey) monthly tuneups, it’ll retain its excellent 99.9999% efficiency!
Unfortunately, that still leaves megajoules per cubic meter that have to be provided by fuel.
But next year, we’ll be offering SNS Model II that’s 0.00003% more efficient because of its new hybrid drive, which will save you a fortune. We’ll even take your 150 as a trade in!
[Answer]
Considering a warp drive is a speculative superscience tech, here's a speculative superscience answer:
The energy of the drive is spent in warping space, so other than waste heat from inefficiency, the drive itself does not need to appear to release as much energy as is input. However, that "excess" energy is then radiated from the empty space volume of the warp field as blackbody radiation (despite being essentially a realization of virtual particles out of vacuum) at a temperature determined by the deformation the drive produces at that point.
[Answer]
Most of the energy goes into twisting the fabric of space-time. While the warp drive is active, it produces heat and electromagnetic radiation that may be visible along its path (although nothing moving faster than light can be observed).
When you reach your destination, the warp drive attempts to reclaim as much energy as possible from the warp field. The remaining energy from the field collapse is radiated off into higher dimensions as X-rays or cosmic-rays.
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[Question]
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I am new at this site, but I've been creating a fantasy story for a while.
Now, I'm stuck. I would really like cat people (neko) in my story, but there is a problem! you can't just stick cat ears on someone's head! for the tail, it's easy, it goes on the tailbone, but what about the cat ears? Is it possible for the ears to be like this?:
[](https://i.stack.imgur.com/mYRG1.jpg)
(best picture I could get)
The cat hearing system:
[](https://i.stack.imgur.com/9yH8d.jpg)
Would it be possible to do this without taking space up from the brain?
[Answer]
Human ears are literally just cartilage with a specific shape. The real hearing organ is actually inside the skull. So for your cat ears to be correctly placed, just change the position in which the hearing organs reside in the skull. This would also change the place in the brain to which the nerves are wired to, but this is trivial, so the cat people are plausible.
On the other hand there are some counter arguments. First and more important, human ears are below the center of the brain, in a place at which the brain is quite thin. If you move them towards the thicker part of the brain, there's not enough space for both of them. This fix this, and in answer to your question, either the skull is enlarged or deformed to give space to these organs, or the brain shape changes and adapts to this organ's shape.
Secondly, forward facing ears are, usually, exclusive to predatorial species. So unless the cat people are genetically modified from humans, they should have evolved from a different animal.
[Answer]
Elves are known for having pointy ear lobes.
If you start with an elf like ear, add some hair to the lobe and make it more movable to make it more feline, you end up pretty much with a neko appearance, with the hear lobes in the appropriate place for a humanoid being.
Also good sight and superior earing capabilities are shared between cat-oid and elves.
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[Question]
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One major problem with living underground is you lose all of that wonderful energy provided by the sun. This energy is useful for many things including growing plants for food. A window is effectively a very short pipe for sunlight to enter a room in a normal house. Windows clearly allow enough of the right kind of light to enter to allow plants to grow. **Could someone in an underground bunker use a bunch of fiber optic cables to pipe enough light into a room to allow plants to grow?** Assuming that's possible would it be possible to use the same technique to power a solar oven?
The basic setup would be 144 strand fiber cables ranging from 100 to 300ft long attached to the bunker ceiling to provide overhead lighting. The cables would poke out from the ground to collect sunlight. Some cables would run up trees others would peer out from crevices in rocks, and some would mixed in with low vegetation like grass. The distribution of the cables would be randomized and not point directly back to the bunker in a straight line to reduce the chances of the bunker being found. The cables would have a fish eye lens attached to each end like a borescope. The idea wouldn't be to form a cohesive image but just to collect and pipe the light.
The implementation details described above can be adapted if needed. Some of my concerns relate to the general feasibility of using fiber optic cables to pipe light. Are readily available commercial fiber optic cables tuned to a certain frequency range of light and as a result severely attenuate or filter out the wavelengths I need? Would there be too much loss in the transmission to get the light output I'd need? Some quick googling showed a fiber is 50 microns, and a 144 fiber bundle is a bit under 3/4 of an inch in diameter. That means my "window" is going to have to be roughly 2.5 times bigger than a real window in normal house. This seems workable but I don't know if the losses are going to be so large that the ratio gets significantly worse. That being said I don't know how many watts typical food crops really require out of the roughly 1000 watts per square meter the sun provides (in ideal conditions). I also don't know if I'm missing something obvious and fundamental....
So to reiterate my question could commercially available fiber optic cables pipe enough light under ground to allow food crops to grow? If they can pipe enough light to grow food could they power a solar oven?
[Answer]
## Yep
[Light Pipes](https://en.wikipedia.org/wiki/Light_tube) are an established architectural thing. Breaking it up into optical fibres (effectively many small light pipes) would probably be expensive and finicky, but presumably cost is no object.
Relevant text from the wikipedia article:
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> Optical fibers can also be used for daylighting. A solar lighting system based on plastic optical fibers was in development at Oak Ridge National Laboratory in 2004. The system was installed at the American Museum of Science and Energy, Tennessee, USA, in 2005, and brought to market the same year by the company Sunlight Direct.
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**Edit:** To address issues brought up in the comments, mixed- or multi-mode fibers, while thicker than telecommunications optical fibre, are capable of transmitting many different wavelengths, which would serve to transmit at least a pseudo-daylight to the bunker.
Alternatively, light conductors are less specialized still, and are employed [in buildings today](https://www.architectmagazine.com/technology/fiber-optic-skylight-from-huvco-daylighting-solutions_o)
(Relevant text from the above:
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> The Fiber Optic Skylight by HUVCO Daylighting Solutions comprises an exterior mounted panel containing 64 computer-controlled lenses that focus sunlight into optical fibers. The fibers transport the natural light up to 60 feet (18 m) to deliver it where not previously possible.
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)
[Answer]
**Nope**
Crops need light. If they do not get enough light they whither and die. On the other hand there is a sturation point, so not every Watthour of light energy is reliably translated into sugars. The light needs to stay [between the compensation point and the saturation point](https://www.pthorticulture.com/en/training-center/influence-of-light-on-crop-growth/), to be effectively growing the plant.
How much light? The light saturation point, which we will try to stay near to, depends on the plant species and on their current developental phase. 2% - 35% of noon sunlight are values i found. So i'll round and say we need 10% of 40°N-summer-noon power. Noon, that is. Power from the sun will be diminished before and after noon. So whatever (sub-one) efficiency your fibers have, they will neccessarily curb the duration of the growth on each day. (Outside, the plants would still get, e.g., juuuust enough sunlight at 18:00, but with the light transmitted in fibers, another 10% is lost, and the plant ceases to effectivly photosynthesize; *even worse*, plants need to eat too, and the longer the stretch of no-photosynthesis, the higher the percentage of the sugars-produced during high-light-phases that they will snack on during low-light-phases)
If you want to grow a m² of crops fiber-lighted, they will either grow more slowly, or you need to bring in light from more than one m². If you go the other way, and take the light from one m² and distribute it on, say, two m², you may be able to still get some growth for a few minutes around high noon... So for every x m² of crops you need at least x \*(1+lossratio) m² of fibre optics - those might get hard to camouflage topside...
Let's be generous and say that your fibre itself looses nothing, because the distance is short enough, and the sunlight for some reason needs no specific setup to couple into the fibre in all the different sun-angles, and during overcast weather (absolutely impossible) - this still leaves the ends, which introduce 0.3dB each - meaning you would only loose about 7% of light. Thus, you would not suffer that much of a hit in terms of growth duration over the day and may be able to get away with 1:1 fibre-input:crop-area; this would mean [we need](https://iopscience.iop.org/article/10.1088/1748-9326/8/3/034015) about 1000m² of fibre input to feed one person... If the sourrounds are not greyish grasslands of fiber-y quality, this will be absolutely impossible to camouflage.
Problems with sun-angle and no real throughput during overcast conditions means that indeed you would need x\*10 or more, imo.
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[Question]
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>
> I am writing a fantasy novel centered on an Earth-like planet with icy rings like Saturn. This question deals with certain effects of having such a ring system. Assume the planet is Earth, the rings are Saturn's rings (minus the C and D rings), and Saturn's ratio of planet/ring holds true for my planet.
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[On an Earth-like planet with rings](https://worldbuilding.stackexchange.com/a/44931/6620), there would be a 'ring-shadow' constantly being cast somewhere on the planet. This shadow would only dissipate during the fall and spring equinoxes, at which point it would be centered on the equator, but be so thin as to not be noticeable. From the equinoxes to the solstices, the shadow would increase in width, and slowly travel towards the pole of whichever hemishere was experiencing winter. [Further description of the ring-behavior can be found here, with pictures.](https://worldbuilding.stackexchange.com/questions/114877/ringed-planet-reality-check-on-ring-shadow-visuals)
I don't think this shadow would fully block sunlight, but it would most likely resemble a total solar eclipse on steroids. Since no sunlight can get around the edges of the moon (because the 'moon' in this case is a ring completely covering the sun), light would necessarily be lower, though likely not at the level of night-time.
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This question deals with the effects of such ring-shadows on the local fauna. This is a fantasy novel, but assume there are no creatures besides what we already have here on Earth. I've looked at several [articles on how animals react to eclipses](http://time.com/4882733/total-solar-eclipse-animals-react/), but they all have the same issue: the eclipse is temporary, and very out of the ordinary. The animals aren't used to it.
On a planet with a ring system, they would be used to it, as unless they live at the poles, the shadow would cross them at some point twice every year. **How would fauna react to this?**
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I realize any answer is going to draw heavily on speculation, but I want to make it clear that this question is NOT primarily opinion-based. Any theories or conjectures you come up with MUST be supported by evidence-backed logic, or at the very least have a clear logical deduction trail which can be traced back to observable fact. The best answer will be the one which details the most behavior changes/differences AND is the best backed/referenced by fact.
[Answer]
So, according to the [Wikipedia page on Saturn's rings](https://en.wikipedia.org/wiki/Rings_of_Saturn), and this handy "optical depth" to transmittance [calculator](https://www.pgo-online.com/intl/optical-density-transmission-converter.html) I found, the amount of light blocked by Saturn's rings varies.
* C ring; ~12% - nearly transparant
* B Ring; ~60-100%, Structure varies heavily.
* A Ring; ~60-90% - Heavy overcast day?
Now - Saturn's rings are mainly water ice, with some dust. Therefore they couldn't exist around an earthlike planet as it would be too close to the sun, and they'd evaporate. For the purposes of this question though lets assume they're actually made of rocks and dust.
They're casting a pretty deep shadow on the planet below, although bands of sunlight do break through from time to time given the structure of the rings.
Assuming the rings are around the equator, and that the planet has a similar axial incline to Earth, this means the ring-shadow would occur during winter. The hemisphere that is closest to the sun at the time would be out of the direct line between the sun and the rungs, and receive normal light.
Based on that, I predict you'd see a much heavier reliance on the wintering strategies we already see here on Earth:
* Hibernation/Torpor
* Migration
* Food storage/hoarding
* Fat supplies
* Antifreeze blood (depending on temperature drop?)
Summer would be relatively normal, whilst winter is harsher than it already is. Most large animals would need to employ some sort of wintering strategy to ensure survival, perhaps more than one. Plants would likely use tubers to store nutrients.
The land near the equator would be even more prime real estate than it is now, because as you mentioned, besides the poles it's the only area not affected by the rings. Depending on the opacity of the rings, life may be strongly focused near the equator
[Answer]
I don't know that they would, at least not in an obvious, conscious way. The shadow will be pretty weak, lots of light will get past the thin layer of dust. It'll essentially be a season-long overcast day. Visual hunters may struggle a little more while in the shadow, since their prey will be able to hide better in low light. Herbivores may have a little more difficulty since the shadow will likely effect the length and quality of the growing season. This will be especially problematic if it coincides with summer. It'll be mostly irrelevant if the shadow coincides with winter. Some animals may use the shadow to time migrations or spawning.
[Answer]
Life on the planet would be very different.
To start, the planet would be colder on average as more light is reflected back into space.
The surface of the planet would be littered with craters, people would probably live in more fear of a meteor strike. There would be more dust in the air in general.
It's likely human development speed would be changed, both from the need for stronger houses from meteor strikes, and from the chance that someone like Newton could be the victim of an unlucky strike, setting back physics development.
You would see more northern plants under the ring. What us northerners call perennial flowers and evergreen trees as they are more suited to the colder temperatures.
Blue light deficiencies causing SAD would be more prevalent under the ring.
Gravity under the ring would be slightly different, possibly enough to create a tide.
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[Question]
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Suppose we had an Earth-like planet based on Saturn's moon [Iapetus](https://en.wikipedia.org/wiki/Iapetus_(moon)). Iapetus has an equatorial ridge, 13 km high, which runs around it. Scaling that up to an Earth-sized planet, it would have a ridge almost 120 km tall. (Handwaving things like hydrostatic equilibrium aside for now; it doesn't matter how the ridge formed, it's just there.)
Given that 120 km is over the line of "space", the two sides of the planet would be effectively cut off from each other. I know there's *some* air above that line, because the International Space Station has drag, but if the two sides of the planet had vastly different atmospheres (say, one half has a nitrogen-based atmosphere like Earth, while the other has a carbon-dioxide-based one like Venus), would that be stable for reasonably long timescales or would they just diffuse over the top?
[Answer]
Assuming roughly the same atmospheric pressure as on earth we would have significantly less than $0.001mbar$. Reference data shows [$1mbar$ at $50km$](http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/prs/hght.rxml) and [$0.001 mbar$ at $95km$](http://www.atoptics.co.uk/highsky/hmeso.htm). (Credit to @Skyler for finding the second reference)
**Ideal gas law**:
$PV =nRT$
assuming $P\_\text{new} = 10^{-6} \times P\_\text{old}$ with $V$ and $T$ unchanged we get:
$n\_\text{new} = \frac{P\_\text{new}V}{RT} = 10^{-6} \times \frac{P\_\text{old}V}{RT} = 10^{-6} \times n\_\text{old}$
So we can conclude that the density is smaller by **at least** a factor of $10^{6}$.
Then it is fair to assume that the diffusion flux $J$ with and
$J = \frac{1}{A} \times \frac{\delta{N}}{\delta{t}}$
given that particle count $N$ and particle density $n$ are proportional to one another that the new diffusion flux for the height is at least $10^{6}$ times lower than on ground level.
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## Conclusion
I'd like to point out that because of lack of data I had to use $95km$ as a reference. I am kinda eyeballing the numbers here, but it appears that we should have a factor significantly bigger than $10^{6}$ for $120km$. Meaning the diffusion speed is significantly lower than even in the calculation.
Until your atmosphere is rebalanced it would take a **very long time**. If there is any ground level process (like an underground current of chemical compounds that would dissolve into the respective atmospheres) it should be able to maintain the split atmosphere.
However I do think it is very unlikely for such an asymmetrical scenario to develop naturally.
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**Additional notice**
I just realised that in higher altitudes you do have lower temperature, but also would have a higher volume if you were to take a reference ring around the planet of same height and ground level and then elevate and expand it in circumference to fit the equator at high altitudes.
This does not exactly cancel out. Temperature at $100km$ is about $200K$ ($-72°C$) which is about $100K$ off (300K/200K = 150%), but the ring volume would expand by the power of 2 with the radius. (from $6,378km$ (earth diameter at equator) to $6,498km$ (+120km altitude)) This results in a ring volume increase of about 3%.
(I will adjust my calculation later - i don't have the time to do that right now. The difference in magnitude probably does not change. It's probably just off by 50% and not a factor of 10.)
[Answer]
This is actually not an answer to your question and I would like to simply comment it but it's way too complex. It is still an important thing to consider when building your walnut planet imo. Increasing Iapetus to the size of Earth, its gravity will also increase preventing the ridge to grow above a certain height.
Let's do some calculations:
So first off we have the formula to calculate the volume of Earth:
[](https://i.stack.imgur.com/bq4r0.png)
Inserting the Earths radius, which is [](https://i.stack.imgur.com/TXq6P.png) we'll get the following:
[](https://i.stack.imgur.com/ecCdG.png)
We can calculate the mass of an object by its volume and its density:
[](https://i.stack.imgur.com/eHZIx.png)
When we insert the density of Iapetus, which is [](https://i.stack.imgur.com/R0oFB.png) we'll get:
[](https://i.stack.imgur.com/8DR3B.png)
Now, we can take this formula to calculate the gravitational force between two objects:
[](https://i.stack.imgur.com/KmK1P.png)
and if we combine it with the formula of force, which is [](https://i.stack.imgur.com/cfO6s.png) we can eliminate the first object and get the formula to calculate the gravitational acceleration on the 2nd object's surface:
[](https://i.stack.imgur.com/FLg58.png)
Let's insert the values for our giant Iapetus:
[](https://i.stack.imgur.com/n9AVL.png)
Due to the lower density, the gravitational acceleration is significantly lower than on Earth (`9.81`) and even smaller than the one on Mars (`3.96`), which means our mountain range can indeed grow significantly larger than on Earth, assuming we have the same material. But how large exactly?
I have found [this website](http://www.hk-phy.org/articles/mount_high/mount_high_e.html) addressing this question ultimately coming up with the following formula:
[](https://i.stack.imgur.com/tHesR.png)
Now there are a lot of assumptions and simplifications made, the shape of the mountain is a square and the material it's made of is pure silicondioxide, which of course is not the real world case so it's just an approximation. I'm also not sure where some of the numbers come from as I'm not a physicist but anyway, let's calculate.
* [](https://i.stack.imgur.com/T5pns.png) is the energy required to melt a single molecule of silicondioxide
* [](https://i.stack.imgur.com/PTl5L.png) is the number of protons and neutrons in a single molecule
* [](https://i.stack.imgur.com/pvxAy.png) is the mass of a single proton (which is also about the mass of a single neutron)
* [](https://i.stack.imgur.com/B4P8F.png) is the gravitational acceleration we calculated earlier.
So this comes down to:
[](https://i.stack.imgur.com/81ZFp.png)
Now, the website states that this is
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> the **order** of the height of the highest mountain
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and calculates a maximum height of 4.9 km while Mt. Everest is about 9km high, but it also mentions the result for Mars would be less than 13km with Olympus Mons being 26km high, so it seems to be about the double with me assuming the difference comes from the shape and material simplification, so our giant Iapetus would have a maximum mountain range of
[](https://i.stack.imgur.com/YmXOS.png)
which is much less than your desired 120km. Now, I suppose you could increase the value with a rather sharp density drop-off, the inner and outer mantle being denser than the crust, which forms the mountain range, though I'm unsure as to whether this would be realistically feasible. Decrease your planet's density as a whole but again, no idea how low you can go and whether it depends on the size of the planet. Change the material to a lighter but harder one but also not sure whether this might be possible. I also was unable to find out what material Iapetus' crust is actually made of so I just took the siliconedioxide that was already simplified for Earth.
Now, even if you get a better value I actually don't think it's possible to create such an enormous mountain range realistically.
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[Question]
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We are developing a game setting and, while discussing certain aspects of the it, have stumbled upon our inability to adequately account for some phenomena due to our lack of knowledge. The thing is, in wake of a catastrophe the lower layers of the world’s atmosphere are filled with a dark almost opaque substance, thus an expansive region of the planet hardly gets any sunlight. We are uncertain to what extent such a hindrance to natural light would cool the surface and whether it is conceivably possible for a substance to only block the visible spectrum, while still allowing some portion of the heat to come through (as infrared rays or whatever it is that normally transmits it). We would like to arrive at a bearable science-ish explanation, so your comments on the relevant physical, environmental and chemical processes are welcome.
Basically, we want for climate to stay relatively the same, somehow, even with constant dusk.
**EDIT**
I think we may have asked the question in a slightly misleading way. The world we're trying to describe is not a 100% alternative Earth, as many of the suggestions seem to assume, but more of a fantasy/steampunk alternative world. So many of the problems may be solved by saying "because magic". On the other hand, we wanted to have enough understanding of the science behind the relevant natural processes so that we could plausibly explain how the population desperately attempted to at least partially fix the effects of the calamity by magical means (e.g., based on your suggestions, magically modifying wheat and some other plants, which turned dark grey/black in order to be able to absorb the remnants of the sunlight; red tint of the light coming through the substance in the sky also seems appealing for providing a more gothic undertone).
The substance blocking the sunlight is basically a result of a failed magical experiment and, as we plan it to be right now, mostly immaterial (basically, as we understand based on your suggestions, it should block 80-90% of all light sans the orange and red spectrum and above, so that the plants can somehow still photosynthesize after having been tampered with).
In the end, we want the world to be a dark and a slightly gothic one, but at the same time with populace more on the optimistic and pragmatic side (even if in the first, say 10-100 years after the calamity there were many losses and conflicts), which has found ways to influence their surrounding's bad conditions (adaptation of the flora; possibly coping with drops in temperature?). Basically, we're not very fond of desperation and decadence.
Also, the substance in question will cover approximately half of the planet, gradually thinning as we move away from the epicenter.
**EDIT**
And the world is supposed to have two suns.
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# It's definitely conceivable.
Light, as we see it, is in the wavelength band of 390 to 700 nm. This is a rather narrow band of light, but it's the *only* band you need to reflect to make your world dark. All the rest can come in as normal to heat the planet. And you wouldn't even need to completely reflect all the visible light. You wanted constant dusk, so you only need to stop 70-90%(ish) of the light from reaching Earth. The rest could be reflected... Or absorbed. (For more about that, see articles describing global warming.) When volcanoes erupt, they spew a bunch of reflective *stuff* into the atmosphere. In big eruptions, this usually lowers the global temperature for a year or so.
### Great, there's some background. Now how do I do it?
The first thing you'd wanna do is set up a big black cloud in the lower atmosphere, preferably of a greenhouse gas. This will absorb light from the sun and heat up. Unfortunately, as A. C. A. C. pointed out in comments, this absorbs a *lot* of heat, so much that your planet will cook. Well, how do you fix that? Mirrors. Right above the black cloud, if you set up *another* cloud, but this time [use something like sulfur to block the light](https://en.wikipedia.org/wiki/Stratospheric_aerosol_injection_(climate_engineering)) This will allow only a set percentage of the light to hit your black fog.
So... You've successfully destroyed our beautiful sky. What's that gonna do to the planet? (I swear, I plead [NPOV](https://en.wikipedia.org/wiki/Wikipedia:Neutral_point_of_view).) For one, your plants will change. If they don't die outright, they'll turn black. Since visible light is in such short supply, they'll try to capture as much of it as possible. Let's assume that your plants survived without a significant hit to the $O\_2$ in the atmosphere. Great, what's next? Wind. As your cloud stops most of the light from reaching Earth, but traps heat, the ground won't radiate heat like it does today. This will alter or stop the cyclical motion of the lowest atmosphere, causing weird effects.
### In summary
While it is definitely possible to selectively alter the climate (indeed, we can do it today!) be careful of unintended effects that result from it.
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Google "Nuclear Winter" including the quotes. The concensus was that a dust cloud heats at the top, creating a thermal inversion. The bulk of the material was soot from all the fires started by the bombs. Some heat gets down by radiation, but the number of interactions is sufficient that overall it is a cooling effect.
Practical tests: Mount Pinutubo dropped global temperatures for a degree for a year. Krakatoa was followed by "The year without a summer"
I've been downwind from serious forest fires -- sufficient that the sky was overcast to the point the sun wasn't visible. No heating during the day. No cooling at night.
Note: You can choose any combination of twilight and fog. For fog -- stuff disappearing in the distant (or nearby) haze you the particles are in the surface atmosphere. Give them a permanent static charge to keep them from settling. To have dusk but clear air the murk has to be higher up.
The climate below is going to be much more even -- The layer blocks outgoing as well as incoming light and infrared. Since surfaces don't absorb as much light, there is goign to be a lot less evaporation. You will get a much drier climate.
Since mass transport of parcels of hot air rising is greatly reduced, wind speed will be far less. Sailing ships will take much longer to get anywhere.
If you arne't blocking all the light, I'd expect temperatures to drop on the average 5-10 degrees -- half that of a nuclear winter. You can mitigate that by adding some extra greenhouse gasses.
But your world has no agriculture. Drop the sunlight below about 30% and crops won't mature. Oxygen productioon is way down. CO2 climbs as the bacteria keep decomposing. Don't know how long it would take for the CO2 to climb to lethal levels.
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Let's combine a few different effects. You want dark fog? You got dark fog. Great for "atmosphere" (cue psychotic laughter). So you've blocked most visible light, but IR can still come through, and any visible light that makes it will be toward the deep red. Scary place!
So, what about the heat effect? Not to worry, planet was just swinging into a glacial period anyway. Phew!
Still, there's a problem. If this change came on suddenly, plants may not be happy. There'd've been some huge die-off; only those plants lucky enough to be able to cope with missing the blue wavelengths will survive. But this sounds like a pretty dystopian world anyway.
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What you describe is like the particulate matter suspended after a volcanic eruption. The substance itself need not be black for it to scatter or reflect light. Darkness is confered by the absence of light at the eye. Your climate will be affected by the amount of energy that is directly reflected or scattered away. You should expect a severe cooling of the surface temperature with no visible light making it there to be reemitted as infra red radiation for anyone to feel. The analogy to this is the drop of temperature at night time despite the presence of greenhouse gases in our atmosphere. Greenhouse gases contribute to heating by trapping IR radiation, which doesn't happen as much if the sunlight never reaches the Earth for the visible light to be dissipated as IR radiation in the first place. The IR portion of sunlight would still have atmospheric heating effects and UV would still reach the surface. You may be able to retain more of that energy with additional greenhouse gasses, but your surface climate will not be the sames as before.
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Depends on the way the light gets "extinguished". The extreme scenarios:
1. absorption - the stuff absorbs the light and "store" the entire energy - think "black body". Gets hotter (the absorbed energy is converted lower frequency spectrum + increased thermal agitation). Cannot get hotter than the source of the radiation (the planet's star) without violating the 2nd law of thermodynamics - otherwise you'd get heat transfer from a colder body to a hotter one.\*\*
2. diffusion - i.e. reflective scattering. For a perfect scattering (no energy absorbed by the particles), you'll have an extremely cold planet and experience a drop in the radiation you can observe as you descend into the stuff (very likely an exponential decay; perfect but random-direction reflection on the particles, the light passing through a thickness of D into the stuff will result in x% of the radiation being reflected back. The next D will reflect back another x% and so on).
Pick any combination of the two phenomena and you can get quite a big range of possible temperatures.
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\*\* an interesting thing about "can't get hotter than the source of radiation" is the laser. Yeap, you can cu steel with it and the laser won't melt. That's because, from the point of view of thermodynamics, the laser have a negative absolute temperature. Even more weird is that a negative absolute temperature is higher than the infinite positive temperature. And the highest temperature one can asymptotically approach is negative zero Kelvin. <https://en.wikipedia.org/wiki/Negative_temperature#Lasers>
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Random idea I just had, would it be possible for a medieval society to pilot massive creatures from the inside? This creature is about 10 stories high, having the anatomy of a gray wolf. The society would have technology equivalent to that of Imperial China as well as our current knowledge of the body and brain. So, considering they are already inside but have access to resources through small cuts in the skin, would it be possible for this society to basically override the creature like a mech all while the thing is still alive? The people would have to make the wolf be able to do regular, wolfy, things.
Leave any questions below.
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Now that we know that it's impossible, let's take a look at the specified tech level and apply that to a fantasy world. This is what I would do, and how I might apply the workings of my own World to the question. Borrow or leave as you see fit!
**ASSUMPTION 1**
The result is a given, therefore there must be a means to accomplish the desired end.
**ASSUMPTION 2**
This is specifically a *fantasy world*. Even though the OP doesn't specifically allow magic, for the sake of argument we'll allow that it exists.
My answer will therefore be a kind of *thaumic acupuncture harness*.
**How it Works**
The harness itself is sturdy, made from leather with nicely decorated bronze fittings, heavy rope ties, etc. The largest part of the harness is where the *Lupigators* ride (in a rather spacious bamboo cabin where they can keep charts, maps, lupigational aids, a kettle and perhaps a couple bunks. Oh, and a loo.) The cabin has not only living quarters, but command deck, galley, stores, mechanical shacks, etc.
Since acupuncture is a well understood wiscrafty art, the breeders and trainers of these ponderous Beasties know well where the meridians are located on the animals' bodies. Which nerves can be stimulated where and so forth.
All around the Beast are smaller leather & rope harnesses that house the various arrays of acupuncture needles (primary system & backup). The arrays of needles are all connected to the control cabin by means of thin copper wires. All the wires meet up within increasingly large bundles of wire that enter the cabin through two apertures in the subfloor, one on each side, down in the mechanical shacks.
In the center of the command deck there is a tall throne upon which the captain sits and before which is a large wooden table with anatomical representations of the Beast artfully done and inlaid in various woods and surrounded by various images of the Twelve Immortals, and navigational poems composed by the greatest masters of the age. Bronze inlays denote all the scores of primary and secondary acupuncture circuits. on either side of the table are two junior officers, the *lupigators*, poised as if contemplating the moves of a crucial chess match. All around the command deck are various spotters, lookouts and communications officers.
Below the command deck, where the trunk lines enter the cabin, there are the mechanical shacks. Down here are bulk supplies, general storage and the rooms where the all-important *bat trees* are kept. These are the sole domain of the Alchemists, and it is their function to distill the *Spirits of Elektra City* and store these spirits in the *bat trees*. Another set of copper wires connects the Alchemists' rooms with the command deck above.
Back on the command deck, when the captain desires for the Beast to begin plodding forward, she will say the word of command and all stations will be on alert. The two *lupigators* will insert ivory & ebony statues of the Twenty Four Favorable Winds, each of which has a long bronze peg under its base, into a hole bored through the representations of the acupuncture circuits. Placing these statues in the appropriate slots will close a circuit, causing the *spirits of Elektra City* to flow from the *bat trees*, down along the wires and into the Beast's body. The appropriate nerves thus sufficiently stimulated, will engage and the Beast will begin plodding along.
The watchers and lookouts will alert the captain to any obstacles or changes in terrain, changes in weather and so forth. The communications officers are on the lookout for the fore and aft crews who man smaller lookout cabins upon the Beast's head and hind quarters. By the use primarily of a system of speaking tubes, and secondarily of colourful semaphore pennants, they can communicate any message at speed which will be relayed to the captain. The communications officers also relay voice orders and receive voice messages from other areas of the crew cabins as to status alerts and normal updates.
Altering the gait, changing direction of motion, slowing down, climbing or descending tilted land, indeed any of a hundred and forty-four other complex tasts --- all these are accomplished by a deft combination of needle stimulation and calling for an increase or decrease in the flow of *spirits* through the network. More juice = more nervous stimulation = more power and thus more speed or more lifting capacity. Adjusting the trim, that is, determining how much juice needs to flow, is also one of the *lupigators'* primary functions. They must be in constant communication with the spotters and lookouts. If a lookout spots a tree fallen across the road, he must be quick to alert the *lupigators*! They must be quick to adjust the trim setting wheels on their control table.
Those wheels, the chadburns, are connected by a system of pulleys down to the Alchemists' shack who will then reduce the flow of *spirits*. The *lupigators* may be ordered to engage in an evasive manoeuvre and they will pull unneeded Favourable Winds and place them in new slots so deftly that the Beast will gracefully turn to one side, shamble on by the tree and then smoothly turn back towards the road!
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Even with today's knowledge and study on brain, mind and anatomy, I'm afraid it's impossible. You might want to take a different approach on 'piloting' these animals though, maybe people can bond with the wolf just like we do with horses and dogs, and have him understand simple or even complex commands. Maybe you can have that people used selective breeding to make this animal as friendly and disciplined as possible, even having different breeds with specialization in different tasks, like real-life dogs.
You can also make these wolfs have pouches like some of the marsupials (kangaroos, wallabies, among others), originally designed for carrying pups, but adapted into human habitation by selective breeding.
[](https://i.stack.imgur.com/eIuDa.jpg)
Anyway, if all fails, maybe you can use the good ol' magic, if it exists in your world.
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There are any number of examples in nature of organisms exerting chemical control over other species. One example is [Toxoplasma gondii](https://www.theatlantic.com/magazine/archive/2012/03/how-your-cat-is-making-you-crazy/308873/), which alters the behavior of cat prey animals, and even humans. There are also wasps, such as [Amuplex dementor](https://en.wikipedia.org/wiki/Ampulex_dementor) who subvert the will of other insects for incubating their young (a scary concept).
All of these manipulations are achieved chemically in some fashion. As mentioned by others, our study of all the intricacies of human (or animal) brains are actually very rudimentary yet, but conceivably, one rider seated in the brain somewhere, and equipped with the right stimuli could control your giant wolf, should it's brain chemistry be suitably understood.
The ancient Chinese were masters of poisons, fragrances and other arts which might form the basis of the knowledge required to achieve control of the giant lupine. They might not know the chemical structure of dopamine, but they would know that a certain elixir, applied to a specific portion of the giant wolf's brain, would cause it to feel happy, safe and compliant, while a specific poison, used elsewhere would make the wolf defensive and/or aggressive, as it causes the wolf's adrenaline to spike.
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So my story takes place on a moon orbiting a gas giant about the size of Jupiter and I was wondering if it was at all possible for a planetary ring to exist beyond the planet's Roche limit. I understand that there are some tiny bands of dust that exist beyond the Roche limit of planets that could be considered "rings" but I was wondering about a large and easily visible ring.
The idea is that this "ring" would exist between the orbit of two of the moons in my planetary system. I guess the origin of the ring would be some kind of collision that blew a moon apart into a whole bunch of tiny pieces. I thought maybe since the moons in this system are rather big, (one is the size of earth, one the size of Mars and there are many smaller moons) that these large moons would create orbital resonances with the ring material that would prevent it from accreting into a new moon.
I was thinking this could work in a similar manner to the way that Jupiter prevents the asteroid belt from accreting. I am also wondering if these resonances could cause small bits of ring material to deorbit and cause meteor showers.
I know, a tough question for sure. Maybe I should have asked it in the astrophysics SE or something but I know there are some pretty smart people in this SE so I hope I'll get some answers. Thanks in advance! (:
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The answer is, in short, **Yes**.
[Saturn, for example](https://en.wikipedia.org/wiki/Moons_of_Saturn#Ring_moonlets), has several ring moonlets and shepherd moons.
Additionally, the Roche Limit varies depending on the size and composition of the satellite itself. One satellite can tolerate a bit more or a bit less than another one.
So, theoretically, you can have a ring between two moons. As far as the specifics of sizes go, that's well beyond what I'm capable of figuring out, but the basic premise seems sound.
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Yes, but it would be unstable beyond about an order of magnitude greater than the roche limit. The outer edge of Saturn's rings is 8.1 roche limits distant, for example.
The reason being is as soon as tidal forces wanting to spread a planet apart into a ring become negligible, a ring of matter would do the reverse and tend to gravitate into spherical bodies. Any small instability would eventually grow and sweep up the rest of the matter in the ring. Notice that Saturn's rings have a pretty well defined outer border as well as inner.
So yes it is possible, but to a limit.
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Yes.But note the Roche limit applies to celestial bodies held together only by their own gravity. As small objects such a sand grains and boulders that make up a ring are not held together by their own gravity the Roche limit does not apply to them so a ring of such material could theoretically orbit at any distance subject to other restrictions such as atmospheric drag.
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I'm trying to figure out what weather patterns and geographical conditions would exist on a habitable moon that is tidally locked to a much larger planet/gas giant. From my research, I was able to gather that:
* The side that faces the planet would always be night, and would have extreme freezing conditions
* The side that faces the sun would always be day, and would have extreme hot/dry conditions
* The area between the two extremes would be stuck in twilight, and would have more moderate conditions
However, I'm interested in having less extremes, potentially habitable conditions if possible. In order for that to occur, I found that:
* The moon would need to have oceans and an atmosphere
* The moon would need a close orbit to its host planet
* There would need to be strong winds to transfer heat to the colder side
That all being said, I'm wondering what would the weather conditions be like on either side and in the twilight belt? Would the sun-facing side have a lot of rain? Would extreme weather such as tornadoes, hurricanes, etc occur more frequently in the twilight belt? Are there any factors I may have overlooked or misinterpreted?
Regarding geographical conditions, I'm wondering kind of environment (in terms of physical features, not life) each biome would produce. Is it possible that only the poles would have extreme conditions, and the rest of each hemisphere would be more livable?
My apologies in advance if this question is a little broad, I tried to narrow my question down as much as possible.
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There are several problems with your visualization of this moon, especially concerning the day/night cycle. I think you are confusing some research about tidally locked planets with tidally locked moons. The moon shows one face to its *planet*, but from the moon's point of view the heavens still rotate and the sun rises and sets.
Wikipedia has [an entry for habitable moons](https://en.wikipedia.org/wiki/Habitability_of_natural_satellites#Orbital_stability) that discusses possible orbital periods around the planet between 10 and 60 days, but likely under 45. This is the length of your moon's "day". The shorter your day, the larger the planet will be in the sky because you are closer to it.
The same entry [also discusses tidal forces](https://en.wikipedia.org/wiki/Habitability_of_natural_satellites#Tidal_effects) potentially being a stronger factor in mantaining a living planet than proximity to the sun. The larger the planet the larger it's tidal zone will be, but it might be almost any distance from the sun so you can safely put it around 1AU. By definition of it being a moon, the majority of tidal forces will come from the planet, but the sun could play a small role.
Rather than a "night" and "day" side, there would be a "planet" and "space" side. Even directly under the planet, it would be large but would not fill the sky. The planet would wax and wane like our moon in the sky, but it would not progress across the sky. It would always be in the same position day and night. Some nights would have a spectacularly bright "full planet" depending on the albedo of your planet. Some days would have an enormous sliver of the planet in an otherwise blue\* sky (or whatever color your sky is).
[](https://i.stack.imgur.com/s0rcL.jpg)
Any companion moons will have complicated movement across the sky (pardon my artwork) alternately growing brighter and disappearing at times from the sky, although moons are unlikely to be as dramatically large as in my artwork. (Space is very big, and moons are small.) Your moon would probably not have it's own moon, at least nothing round, but it might be in a complicated [co-orbital relationship to another moon](https://en.wikipedia.org/wiki/Co-orbital_configuration#Co-orbital_moons) which is nearly in the same orbit. A co-orbital moon would appear to approach from one side then drift away, only to reappear years later on the other side of the sky.
[](https://i.stack.imgur.com/H4JsW.jpg)
The planet might be at almost any axial tilt, and it's moons presumably follow that tilt. That means the sun does not necessarily get eclipsed by the planet every "day". A series of eclipses might happen only seasonally in the fall and spring at the equinox. Your moon would experience summer and winter depending on that axial tilt, with the odd caveat that you might have uninterrupted "days" of sunshine in the winter and summer.
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Earth and Titan prove that ocean be made of water and liquid methane, respectively. Theoretical planets with oceans of liquid ammonia and sulfuric acid are believed to exist. But what about alcohol?
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There is no contradiction in a planet that has an Ethanol sea. In fact [Ethanol has been detected in interstellar clouds](http://mentalfloss.com/article/51271/there-are-giant-clouds-alcohol-floating-space). See [One possible origin of ethanol in interstellar medium: Photochemistry of mixed CO2–C2H6 films at 11 K. A FTIR study](http://www.sciencedirect.com/science/article/pii/S030101040700081X).
Futhermore, the mentioned sea of Methane is a precedent, yet we need to consider that Methane is simpler than Ethanol. What we need to see is by what process large quantities of Ethanol would have formed...
The article linked above provides an theory for its formation in outer space. yet, we shouldn't discard the more interesting explanation for worldbuilding: Fermentation. This Ethanol sea may have formed by the metabolism of microorganisms in the planet.
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It's hard to think of an inorganic process that would produce Ethanol alone in ocean size quantities - possibly Methanol if the temperature was exactly correct. It does occur in molecular clouds, but alongside methane, ammonia and water which would contaminate the whole process.
Obviously you can't have an oxygen atmosphere, so no conventional photosynthesis.
Perhaps.. if organisms evolved on a very cold planet started producing ethanol as a natural antifreeze, basing their metabolism around using H2S as a hydrogen source (so very little water - you'd need a planet much richer in carbon than oxygen), perhaps they could generate ethanol oceans.
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I don't believe it will be chemically stable. To clarify I am thinking about a >50% ethanol ocean. If you look at the formula for ethanol C2H6O - that is "more" complex than e.g. water. There are many ways to rearrange these molecules.
e.g.: 2 C2H6O -> CO2 + 3 CH4
The issue with reaction to CO2 and CH4 is that they are gaseous and will "escape" the ocean, also these molecules are way more "stable" than ethanol so the reaction back will take more time and energy.
There are similar reactions to water:
e.g. C2H6O -> H2O + C2H4 (which will probably keep reacting to something else)
Anyway water and such "carbon chains" won't mix - so again back reaction will be small.
My prediction is that an ethanol ocean will over time (I suppose we are talking centuries/millenia) turn to water/methane/CO2.
Though - I suppose an ocean containing less than 1% should be quite stable.
Of course you might have a process that will replenish the ethanol. But that would be of different nature as we have here - even for yeasts more than 10% ethanol would be toxic. Also the sheer amount of mass and energy needed might be a limiting factor.
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[Edit: I'm not looking for 100% realism. I'm looking for an explanation as realistic as possible, possible with just few exceptions to physics.]
[Edit 2: In my imagination these worlds are different universes and as such not reachable by travelling far. They are similar but not identical to our universe/earth. Parallel indicates that they kind of overlap with our universe, they are parallel to our world, I like to imagine sheets of paper overlapping, and you can just get to another sheet if you rip a hole in your sheet. Or maybe like in 'His dark materials', the universes are here and not here, you'd just need to know how to open a portal.]
I plan to write about several parallel universes, the first being very much like earth including our physics and its restrictions.
Scientists manage to open a portal. My thoughts so far:
* A huge amount of energy needs to be concentrated on a relatively small area
* This might be achieved by matter colliding with antimatter
* There are just the n parallel worlds to which a portal can be opened to, each might require discreet amounts of initial energy to be opened
* The portal/crack might stay open, get bigger or get smaller and vanish. I think the last option is the most realistic
My questions so far:
* Would this work as described above?
* How can it be stablized? My initial idea was that you can put materials through it to stop it from getting smaller, but something like a broomstick would just break or melt and you would need a material that has a high melting point.
* Does the portal need constant energy to keep from collapsing or would maybe cooling whatever material keeps it in place be enough?
* Would it be dangerous to be in proximity to it? Would there be radiation?
* How exactly do the edges of the portal look and behave?
* Did I miss problems that would appear?
* Other options or ideas?
In the end it should be possible for humans to walk through the portal without damage.
(Further info:
The other universes are about the same, but have one or two additional elementary particles (similar to ours). So the portal would open to the respective place in the selected world.)
I'd really like to make this as realistically/plausible as possible.
Thanks in advance!
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## Short Answer: You can't make this scientifically plausible
Let's be upfront about this.
Stephen Baxter, who has degrees in mathematics and engineering and writes extremely grounded, hard sci-fi, wrote about a device built as an 'escape hatch' to leave our universe.
The device was a ring made of cosmic strings, several *million* light-years across, spinning at nearly the speed of light.
For a realistic/plausible portal between universes...that's the kind of thing you'd need.
For a portal to be built between something similar to our world and another universe, you're going to need some heavy-duty *handwavium*. Perhaps you have some substance or material that is able to directly manipulate spacetime, perhaps built into a ring that 'pulls' spacetime apart at the centre.
But whatever you do, I'm afraid you're not going to find a scientifically plausible answer.
Edited to Add:
Home now, so I can expand a bit on my answer.
The problem you're going to run into in creating a 'plausible' portal in the spacetime continuum - we don't actually know what spacetime is.
We know that spacetime exists. We know that it has properties. We know that it can be curved and twisted by sufficient mass. We believe, to a high degree of certainty, that if you get enough mass in one place, you can create what is essentially a discontinuity in the universe - a place where two parts of the universe are causally disconnected from one another (a black hole). But we still don't have a really good description of what spacetime *is*.
To an extent, we're in the same sort of position regarding spacetime as chemistry was before the discovery of the atom. We had a map of what would happen in certain circumstances, but we don't have a clear idea of *why*.
**The only thing we know to be able to manipulate spacetime is mass.** All mass causes spacetime to curve, and a spinning mass causes a kind of twisting motion in space as well (called Frame Dragging). If we're going with what is known to exist in the universe, the only way to create a tear in spacetime is with enough mass, spinning fast enough. The amount of mass would be truly immense - far greater than a single galaxy - and certainly not anything that a handful of scientists could knock together in a lab.
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In order to have a bridge to just walk through, the spacetime needs to be grafted together. It’s the same as any wormhole.
Consider the case first where physics is the same, it’s just history that is different.
If the universe is infinite, then eventually things will repeat. Somewhere, vastly far away, is another copy of Earth and everything in it. Far far away is another identical copy of our entire Hubble volume. In fact, there are an infinite number of repeats.
Suppose a “normal” FTL wormhole creation actually cross-connects different copies. How would you ever know? The wormhole maker breaks through the destination point from a kind of hyperspace, which has no concept of distance (which is the whole point), so how does it find the spot to breqk through to? It has an affinity for the pattern of matter and energy surrounding it. But that is ambiguous because the universe is infinite.
The probability of cross-connecting a universe is dependent on how close of a match it is. So you may open a wormhole to another universe that isn’t some random bizzare thing, but is very nearly identical to ours, exactly as with the sci-fi trope.
Once they figure that out, they can try finding different universes on purpose by setting up the navigation pattern to what they want to find, rather than the actual destination.
As for different laws of physics, what if spacetime had infinite space but the specific laws vary on a scale that's larger than our Hubble Bubble. After all, our observable universe inflated from a tiny patch so will be uniform.
So the different universes are actually different *locations* in one continuous space. You can’t actually get there by moving normally though because of inflation.
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I'd say one would have to take something dealing with cosmic strings, revisiting Stephen Baxter, or use a wormhole, both of which are not completely proven. I'd say find a way to compress matter into a sizable black hole, find a way to stretch it open, which requires adding dark matter, mind you, then keep it open long enough to send something through.
Far in the future indeed, but tests would need to be done first to make sure this device wouldn't rip apart the earth (what if the universe we first contact is mainly antimatter?), find a way to send something through quickly enough in order to save energy (opening the portal up directly below something or at a surface it is travelling quickly towards). First, we'll have to prove multiverses even exist. I too love the many worlds theory and want to devote my future career to proving it.
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I'm not a fan of many-worlds. That said, we understand almost nothing about dark matter. The first thing we shouldn't assume is that it's all the same. Perhaps it's a zoo of different particles, different physics. Heck, maybe it exists in some dynamic equilibrium, traveling between (or existing in both) two or three or who knows how many "parallel" universes. So, what properties does it have.
Well, you need to read up on it. Mostly, it doesn't interact much with itself or anything else. If that can't be changed, then I'm wasting time, so let's assume there IS some way to manipulate it, and that by doing something with it (creating a sheet with it, a sphere, a current (flow), concentrating it, dispersing it, the list is limited only by your imagination, but if we could figure out some way to manipulate it, and if that manipulation moved it between universes and if it produced, say, a wake, pulling other things with it, then...there you go.
The problem I have with most fantasy disguised as sci-fi which assumes interdimensional doors, time travel, FTL, etc. is (among other issues) you need to justify why in the world such doors would be pinned to the Earth. Dr. Who had it right long ago; the TARDIS moves in both space and time. I forget how far the Earth travels in a year, but it's a significant distance in terms of light-seconds. It would be really difficult to target a place on the surface of a different planet from ours to put the other end of any hole we make. And keeping that hole fixed there would be another several of orders of magnitude more difficult.
So, there's two ideas I have to manipulate dark matter:
1. Massive spinning objects in some sort of pattern create a resonance
2. Neutrino oscillations.
That's all I got. I like the idea of (Farscape) a spaceship going through the "door", having it open up on or even near the surface of a Earth-like planet is not credible (without a huge technology and history behind it)
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I would guess in an incredibly simplified sense, if you wanted to crack open space time, you'd need to find a point in space that would be susceptible to such cracking, where two realities overlap or cross. This is sort of theoretical, but the closest thing we have to this would be the CMB Cold Spot, an area in space about 70-140 μk(micro kelvin) colder than average, that in 2013 was proven to not be a glitch or artifact of the probe observing it(Wilkinson Microwave Anisotropy Probe, which discovered it in 2004, and was observed by the Planck Satellite in 2013), and in 2017 was deemed likely to not be a supervoid(<https://phys.org/news/2017-04-survey-hints-exotic-cold.html> for proof). One of the most persistent theories to date since its discovery in 2004 has involved Everettian quantum mechanics, or the multiverse theory in Layman's terms. In this theory, the Cold Spot is an imprint of sorts left by another universe. This could technically mean enough spacetime bending properties(gravity, exceptionally high energies or speeds) could possibly(and quite literally depending on the legitimacy of string theory regarding quantum foam) "rip" through the universe and into another.
However, the imprint theory falls short on terms of prediction basis, as the theory requires a similar imprint to be on the opposite hemisphere of the Celestial Sphere(paraphrased from the Wikipedia page, I'm no expert on this particular part), and to date, little evidence has been found for it.
Secondly, you need to make some sort of artificial star or dense matter that would use its gargantuan mass to warp, and later rip through, the fabric of spacetime. Another problem is the singularity of the black hole that would inevitably form. You have to figure out how to open it up, so that whatever gets near it at high enough speeds would travel through it to another side, rather than be ruthlessly destroyed and ripped to subatomic bits by the immense and inescapable tidal forces.
Again, the vast majority of this answer is incredibly theory-heavy. I say even with constant or even speeding acceleration of our technological advancement, at least some of these problems may be solved in anywhere from the next 100 to 1000 years.
Hope this helped.
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I am surprised nobody suggested "borrowing" the approach that the movies/ TV Shows Stargate used.
Essentially, Have a rare material of some kind, Perhaps a mineral that has been found from a meteorite strike - one that came from outside the solar system - machine it or manufacture the material in some fashion. Apply some energy to it and have it generate a stable gateway of some kind.
There are MANY well written science based alternate universe stories that use this particular trope. One by the Grand Master, Heinlein, didn't even use significant energy, just an unusual application of physics. You are possibly familiar with gyroscopes. When one has "spun up" and you push on the axis - it resists the push and therefore moves in a direction perpendicular to the push. - SO he posited - what happens if you push in 3 directions at once? Turns out - in his story - that the Gyro disappears. That book was called the Number Of The Beast, By Robert A Heinlein.
Generally something like this in a story is discovered by accident, while the slightly mad genius was trying to do something else. Then the plucky hero, or his assistant, get's sucked into a vortex of action which allows him (or her) to demonstrate all kinds of resourcefulness and brilliance denied to us lessor mortals.
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the closest you could get to this is transport within our dimension by manipulating gravity to fold the fabric of the universe in a way were two points meet. interdimensional travel isn't something we can describe with modern science that well. but cross-universal travel is
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# Description :
Even in the ⅩⅩth century, biological warfare was studying only existing diseases.
But recently [we're able to modify viruses in order to cure genetic impairments](https://en.wikipedia.org/wiki/Virotherapy). Would it be possible to use similar techniques to build the perfect weapon?
# Requirements :
According to me, that weapon would need to have got one or several of the following characteristics :
* Have a long-term nonprogressor:
Most offensive diseases *(such as the black death or the 1918 flu pandemic)* that kill their host rapidly end up disappearing because they destruct their own contagious potential. That’s why the ideal disease never kills its host.
Not showing any symptoms for years, while still being contagious, is the ideal outcome. It would also allow the virus to evolve and adapt itself to various natural defenses of its host *(HIV is starting to do it)*.
* Be a RNA based virus:
In the event the researches around the disease are discovered, it’s important to prevent any curing methods to become successful. DNA based viruses are vulnerable to vaccines. Bacteria have their own viruses and are vulnerable to antibiotics.
* Infects or attacks wild animals :
In the event that the disease is uncovered and a treatment is found, having animals infected could prevent the disease from disappearing *(smallpox would still exist if it wasn’t an human only disease)*.
Ideally it should be animals which are difficult to eradicate such as flying insects. Unlike humans it doesn’t need to kill them, but just be able to infect them.
* Have as many carriers as possible :
HIV fits several categories required to be a biological weapon, however the requirement to have sex with someone you don’t know well, or use drugs stops it from being as successful as influenza which use aerial vectors.
It’s still better to combine vectors *(for example being aerial like influenza/Sars Cov2 and being able to infect through sexual relations as well)*.
* Replicate common mammals proteins while being in the viral form:
This should trigger massive auto immune reactions that would kill the host. Research on the root causes of auto‑immune diseases tend not be on infectious causes. Once the root cause is established, doubts might be spread in medical authorities of various countries due to that characteristic *(resulting doctors trying to prevent contagion getting sued)* *(South Africa is the most well known example with AIDS)*. This should delay research results by several years: enough to kill most of the worldwide population.
As the proteins would be common in various type of cells inside bodies, the symptoms are very broad. **As it should be non detectable in half of the cases** people surviving the first week would get wrongfully sent in mental hospitals *(this idea come from the borreliosis though I agree it should be impossible to mix bacterial and viral genomes)*.
Every point above is a characteristic that already exists in today’s diseases. The issue is combining them *(it’s easier to find the gene responsible for something rather than building something from scratch)*. But there’s more that could be done to get it “right”: the etymology of Epidemiology means something that is located somewhere. Having a spot of a particular disease is a red flag for an infectious root cause.
So it should be spread in various places of the world. The infected people traveling to those places needn't volunteer *(simply pay some citizen at random the high price so they voluntarily move abroad)*
# What could lead to the creation of such weapon ?
## Purpose :
This is definitely the wrong weapon if you want to win a war :
* First, it will takes up to a decade to become effective. The war could have ended.
* Second, you rarely fight against the whole world.
* Third, in the case you win, it will end up collapsing your own state. There’s no target
However, if you are the perfect authoritarian regime with a NATO war against you, then it’s completely understandable to take revenge against the whole world when you’re about to be defeated by using what was created years before in the event you had to face that situation.
## False limiting factors :
* It’s impossible to kill everyone, a minority of peoples will survive :
The weapon should still be very efficient. If only 10 million people survive, you’ll still get a perfect collapse as their wouldn’t be anymore states for centuries. At least, not in the organized modern way we actually know.
* The biological weapons convention is soft. Much like the united nations convention against torture.
* *It’s impossible to build something that can end mankind because some characteristics are too hard to build…*
Wrong! **Just add more contagious vectors to HIV and you’ll get something usable *(HIV is starting to adapt to antiretroviral drugs)*. Maybe it would mutate back so it can infect monkeys because it would have got widespread among humans.**
## Real mitigations :
* Large states have no reason to perform such research.
* The technological requirement is too high for the states or armed groups/rebellions. Not to mention the funding requirement.
* Whenever you support an evil state run project, you know things should generally be fine for you. Currently, you know what you create will kill you in a horrible death.
* Nobody would dare to attack you if it’s get publicly known you have such weapon.
# Final Question :
With all the conditions above : would it be realistic for such a weapon to be created in the next decade ?
For example, what about just adding more contagion vectors to HIV ?
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Thinking about all the needed conditions our hypothetical Bioweapon needs to fulfill, I came to a conclusion that such a virus would not spread too well or might be made and set free for world annihilation - Even H5N1 could not reach a pandemic level for it burned through hosts too fast and was detected too easily. Spanish Flu and COVID-19 did reach pandemic on their own because they are highly infectious, but they were/are not nearly deadly enough for this scenario - Spanish Flu in 1920 had an incubation time of about a fortnight and an estimated death toll of 20-50 million while the world population was 1.8 billion with the medicine of that time, and quarantine like in the case of American Samoa was a highly effective way to reduce the exposition to the virus.
The distance between human population centers and the huge variety of human genome makes it improbable that one virus could keep silent long enough to infect all the population of earth before the first breakout happens. If people start to die rapidly the various health centers react pretty fast to try to start an epidemic control and isolate areas as it happened in the case of H5N1 and Ebola in the last decades and recently with COVID-19. So the only way for a virus to spread globally and infect all would be one that is not considered a threat by everybody the moment it is noticed. Common cold, for example, does that every year, there are millions of variants, but few kill - which is why no epidemic control barriers are raised because of it.
COVID-19 did raise all the alarm flags as early as January 2020, but many states did try to rely on other countries reactions and lower levels of isolation until way too late, allowing the virus to spread to and then from multiple centers, which lead to the late-march 2020 actions of pretty much shutting down the public life in Europe on multi-national level and a huge amount of travel bans to slow infection rates and buy time for cure research. Meanwhile, in all countries, people panic and self-isolate, hoard basic needs and try to stay out of crowds where the virus might be. And global panic is against the requirements.
## But how?!
So you have to eliminate the human factor of starting to panic if people start to die somewhere en masse and cut down connections to that land. To do this, the hypotetical virus would have to be either a retrovirus (like HIV) that can have years between infection and outbreak, or it has to be 'quite harmless'. The bioweapon you want however is far from quite harmless.
So, the only way the bioweapon could reach all population **before** being discovered by the illness or killing, and subsequently be isolated and/or eradicated would be to give it a long incubation time - which however only increases detection chance as it spreads for each day millions of blood samples are tested for various illnesses. If new, unidentified virii get detected in those, the isolation protocols are easily kicked in and research for a specific antibody is launched. Also, remember that human genetic variance and rule of large numbers will lead to at least one infected being studied that is at least resistant to the illness - which in turn could be the start for a working anybody! **So, unintentional spread of a deadly disease with the demanded conditions is out.** (Just like even making it!)
However, how about **intentional, controlled spread?**
Let's assume the virus might be added intentionly to food or medicine and then the rigged stuff is given out free or cheap to maximize reach all over the population. This plot is entirely different! In this case, the virus does avoid detection for a some time by the vector it is given: people assume governement given aids are checked and clean of such tricks. Thus it might manage to reach all continents before it has to go on alone because it was discovered.
Now, why pass out a deadly illness? That kind of stuff might be detected and thus isolated by the death count alone as shown above! If you want to stay under the radar, it would be wise not to kill the host but instead pass out something 'quite harmless' with more long term effects. Maybe render the victims infertile or heavily allergic to some usually harmless substance that people don't usually encounter.
I guess, something like a governement aided genetic manipulating virus could reach pandemic level within a few months to years, especially if the responsible parties manage to keep a thumb on the media and thus doom humanity to die out eventually. It doesn't even need to be an airborne virus, or able to pass from human to human at all. Just infecting enough people to bring human beings in larger areas below the 50/500 threshold\* is enough. Something like this was the plot of a [Stargate episode](http://www.gateworld.net/sg1/s4/416.shtml) by the way. So I rule:
**Only if parties actively spread the virus in a way that disguises its nature, pandemy can be achieved, and even then the virus can't be of a deadly, slow kind but would need to target survivability as a whole.**
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\*The 50/500 Rule is a concept from 30 years ago, telling these are the numbers for minimum viable population size. Nowadays the numbers 50 for short term and 500 for longer term survival are thought too small: many biologists say, that to ensure genetic diversity about 2000 or even 10000 genetically diverse individuals are needed. Read more [here](http://www-personal.umich.edu/%7Edallan/nre220/outline12.htm) and [here](https://conservationbytes.com/2014/01/28/were-sorry-but-50500-is-still-too-few/)
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I don't know enough about the biological possibility of creating it to say if it is possible but a virus that ends mankind doesn't need to actually kill anyone.
You could have a highly contagious virus with no obvious symptoms except leaving the hosts children infertile. In a few generations the last human dies peacefully of old age in a world that hasn't heard children for decades.
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Well ... maybe. This may be possible, but if so, it's right on the edge of the possible. The only way to find out for sure would be to try to develop such a weapon, and see how well you did: "try and see" projects are how technology moves forwards. I suspect that the degree of success could be significantly influenced by the individual motivations and brilliance (or lack thereof) of the scientists working on it.
For obvious reasons, people who know a lot about what you'd have to do in such a project are not talking about it.
It is not impossible to get highly talented scientists to work effectively on doomsday projects, but doing so does require that they have bought into an ideology that supports it. Some dictators manage that, and some don't.
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On reflection I say "no" as well.
To begin with, we can relax some of your assumptions. For example, viral reservoirs exist other than in wildlife (herpes uses the nervous system where we don't yet have a means of eradication but other virii use bone marrow where we are starting to have such a means). A period of asymptomatic infection (to allow spreading) followed by sudden death probably won't hinder postmortem diagnosis and discovery of the pathogen or slow down R&D into treatments once it's identified (it might even make it easier to find as it will be fairly clear there is a pathogen to locate and probably which organs it can be found in).
Mutation is a double (or triple) sided problem for your would-be genocide. It creates variants of a virus but says nothing about how likely the variants are to have similar effects or succumb to similar treatments (some pathogens keep key proteins fairly stable as they mutate, which is good for vaccines, in others like the common cold the mutation is in prime areas for targeting which makes those areas unreliable markers for a response). Also if the virus is too artificial and perfected, perhaps variants will be more successful in the sense of spreading, but not in lethality - a pathogen 'measures' 'success' by (and favours) replication above host death - the genocide may wish host death but if a milder mutation spreads more successfully then it will prevail in a moderately short time (some years to some decades, perhaps a few centuries at most), which has happened to several diseases. Additionally if it's too finely tuned to target human lethality then the parts of its DNA/RNA which do so are likely to be quite superfluous for virus replication (they don't have a replication promoting function) and this has two problematic effects: in any mutation they won't have any reason to be favoured for survival and will more easily be lost or lose functionality, and being human engineered hey are possibly quite precise in function (as many human creations are) - that's quite a problem for a virus intended to be lethal, since minor changes are more likely to cause them to lose the edge of design they have, or to"break" something and therefore to not to have the desired effect at all.
So perhaps we try a different approach. We might look for a "base" pathogen to work with, whose replication can be made highly dependent on some specific aspect of mammalian biology (much easier to accept collateral loss of a class/clade than to find some core biology that's extremely distinctive in humans). In this case its replication is deliberately tied to its lethality, because replication involves successful metabolism of some protein or cell-type which is ideally a small part of the human body and where damage/loss is lethal to human life. For example - and I'm reaching here because this isn't my field - a ferrophilic virus whose replication is tied in with breaking up of haemoglobin, or iodine, or which can somehow cross the blood-brain barrier or affects ATP metabolism or the energy cycle, or whose replication occurs in nerve cells where it can replicate with impunity.
But essentially this is a generic description of many lethal virii, and despite this none have gone the "destroy all people" route yet. Even the worst plagues with zero medical/scientific knowledge and zero hygiene haven't come close. Many virii are extremely lethal when they first "find" humans (syphillus, flu, bubonic plague, ebola) yet none came close to the effect sought here. All (except possibly the recently discovered ebola) also became milder over time as well, effectively exchanging massively acute impact for duration of host lifespan/spreading potential. The natural processes of pathogen/target/vector/mutation tends to heavily load the dice against this kind of effect (if it could, it would already). Its true that some entire species have been killed by pathogens (including some trees, not just mammals) but it seems other factors including the scale of response may have played a part in this, for example diseases of trees and wild animals don't get medical responses and knowledge rapidly piling in during an acute crisis anything like a human disease would get.
Returning to our pathogen. Suppose we do tie replication success to lethality at the start. Then we need to look at how it replicates beyond its host. The problem here is you want 2 contradictory things - extreme replication and extreme host lethality. If both were easy to obtain then syphillus/flu/smallpox/measles would have killed us all long before the concept of pathogens arose. All mutated into milder, more successful, replicators. The ones that are massive replicators and also lethal (cholera being one) are slower and in some cases symptomatically treatable.
Even indirect routes (water borne virii, destruction of some crucial part of the human food chain) won't help much - water and air can be filtered for virii, and foodstuffs (plant or animal) can be captive bred in virus-free facilities. One possible target might be the CO2->O2 cycle (virii that affected photosynthesising plankton/algae/plants) but such organisms are very widely spread and have survived geological time of pathogens, I don't think your genocide would have a hope of doing in the foreseeable future, something which 3 billion years of viral warfare has completely failed to do. That's without considering other practical issues for a pathogen, such as near-universal exposure and assuming near-zero immunity, and ignoring completely non-vaccine responses such as quarantine and isolated land masses.
Stepping outside the box, in theory there is a small loophole open, if you can find a way to deliberately infect all people at once. This approach sees the issue as one of vector not pathogen (finding a lethal pathogen is easy, finding one that can kill everyone too quickly to respond to is very hard, perhaps we could "rethink" the problem into *"given a virus that's lethal **now**, could we infect almost everyone in a very short time, so hiding/spreading/mutating/vaccine aren't relevant"*, and in this way we bypass much of the design problem). The problem with this is there just aren't vectors which get enough people, or at least none I can think of. For example, simultaneous addition of virii to worldwide water reservoirs, manufactured food, medical supplies (sneaky!), or common objects that change hands quickly such as money - none seem likely to work.
My conclusion is that it just isn't that easy - that a would-be genocide will find it immensely hard. Forget magic time-delay virii, we don't have a way to do that now or in the foreseeable future. Whatever you put out there has a replication agenda not a deathly agenda, and that's what will prevail faster than you can kill all people out there.
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What you need are so-called two-stage bioweapons, they are not only possible but it's very likely that Russia, China, North Korea and other countries are already busy working on obtaining such weapons. The use of such a weapon would be extortion to e.g. get rid of sanctions in exchange for a vaccine.
[As pointed out here](https://www.sciencemag.org/news/2017/07/how-canadian-researchers-reconstituted-extinct-poxvirus-100000-using-mail-order-dna), advances in bio-engineering has made it possible to create smallpox ab-initio in the lab:
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> Eradicating smallpox, one of the deadliest diseases in history, took humanity decades and cost billions of dollars. Bringing the scourge back would probably take a small scientific team with little specialized knowledge half a year and cost about $100,000.
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This means that it's only a matter of time before new viruses that have never existed before and which cannot arise due to natural selection, can be created in the lab. The most dangerous bioweapons imaginable can then be created. A simple way to make a very destructive bioweapon is to construct a very infectious, primary virus that itself does little harm, except that besides making copies of itself, it also makes copies of a different, secondary virus that causes a deadly disease.
The primary virus infects cells in the upper airways and spreads easily from person to person. The secondary virus is then produced by the primary virus in the upper airways, but it is not capable of entering these cells, and therefore won't spread by itself from human to human. It is designed to infect cells of other vital organs such as the liver to cause a deadly disease with an incubation time of many weeks. The idea is then that the primary virus will have spread around the world, with many millions of people infected and recovered from it unnoticed, when the disease caused by the secondary virus will start to strike, seemingly at random all around the world.
When scientist investigate this disease, they'll discover that it is caused by the secondary virus, but they'll at least initially, be at a loss to explain where this virus came from and how people got infected by a virus that isn't capable of spreading from human to human.
If North Korea was responsible for this bio-attack, then that won't be clear until they either claim the attack or when it becomes clear that there are no cases of the dreaded disease in North Korea. The North Koreans would then first have vaccinated their own population against only the secondary virus, and then they would have let the primary virus spread among their population. The limited contacts the North Koreans have with the rest of the World, e.g. via their diplomats, would spread the virus throughout the Word.
North Korea could have decided to launch such an attack in an effort to get sanctions lifted. Once the disease caused by the secondary virus starts to manifests itself, Kim would announce to the World that his country has been suffering from a terrible disease and that his heroic scientists have developed a vaccine and medicines against it. He is then willing to let the World benefit from the work of his hard working scientists, completely free of charge, with only the condition that the sanctions against his country will be lifted.
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I've got to go with the no answer (atleast, no, not within 10 years), mostly due to this constraint:
* Not showing any symptoms during years while still being contagious is the ideal overcome (but when the symptoms starts, kill the host within one week to avoid diagnosis). It would also allows the virus evolve in order to adapt itself against various natural defenses of it’s host (hiv is starting to doing it).
I get what you are going for here, you need near 100% infection rates before detection to really get a massive death toll...death too quickly results in identification and quarantining, limiting the virus's ability to infect. Seems like you've been playing that plague inc. game.
Virus's are among the most rapidly mutating 'living' organisms on the planet...their reproduction method almost always ensures mutation, even within one generation of the virus. To create a virus that goes for infection, then at a certain time mass mutates to a much more lethal version of itself isn't within the realms of what we can control.
Virus's also tend to specialize...what is good in one scenario might not be good in another scenario. A virus completely specialized to go after humans won't fare as well within other species. IE, a virus that can infect a bird has devoted some of it's resources to the ability to infect a bird (and some of it's surface area), limiting what it can direct at another species suchs as humans. You are asking for a virus that is specialized in all domains without sacrificing any ability in a different domain.
You're entering the realms of asking for a car with the turning radius of a go-cart, but the wheel base of combination truck...one advantage comes at the expense of another and you can't have both.
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This concept has already been well explored by Tom Clancy in his Rainbow Six novel (and at least one other).
The virus used there seemed believable, and the distribution method ingenious.
Little spoiler: he went for a genetically hardened version of Ebola, with a very clever way of distributing it (which I won't mention, read the book).
He touches on the same issue in Executive Orders, using a completely different distribution system.
Whether either could have worked in reality I'm not the biologist or bio war specialist to be able to say, but to the layman both scenarios sound plausible (which in fiction is really all that matters, isn't it?).
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You said HIV wasn't infectious enough to be used as such a weapon of revenge. I think that is wrong. Instead of creating a stronger, deadlier virus you could use your lab time to create ways to spread HIV.
For example condoms are treated to be slippery and (some) to kill semen. Generate something that resembles this coating but contains HIV and keeps it alive. Then have people infiltrate factories to sabotage the production.
At the same time do something similar with factories for medical supplies, blood preservation, tattooing gear.
By doing that you can infect some percentage of the population. As tests don't work at once every infected person has a good chance to infect someone else before it is noticed and even after that it will take a considerable time to suspect and test the contaminated gear.
It is a slow process but I think if disruption is all you aim for it could work.
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I'll say yes because you don't actually need something as comprehensive as you are describing. To see how to do this look to history for our guide--specifically the decimation of the new world due to old world diseases. Populations crashed, some areas were completely depopulated and that's without a lab being involved.
The key is disease**s**.
You don't need to engineer superbugs, just beef up things off the shelf.
A good starting point would be smallpox. Change it enough that the current vaccines do not work, do what you can to increase the lethality.
Now look around for other nasty bugs. Breed for resistance to vaccines and drugs. If you can up the lethality influenza comes to mind given how well it spreads.
Your bioweapon isn't one disease, it's as many deadly pathogens as you can come up with. Some people will be immune to one but that won't protect them from the next. The combination punches will be a lot more lethal than any single pathogen would have been.
Now take a play from Tom Clancy--not the stupid bug of Rainbow Six but the botched job of Executive Orders. (The pathogen was a version of Ebola that had some ability to spread by air.) Your target is trade shows. You don't have the security at trade shows that you have at airports, it will be much easier to deploy your weapon. Most attendees at a trade show are going to fly somewhere in a few days.
You're not going to get a 100% kill but you don't need one to bring us down. Once you punch enough holes (workers that are dead or hiding out instead of on the job) in the system the flow of goods that keep society working stops. Most of the world is now uninhabitable--even if you didn't kill the people they'll starve anyway. You'll have survivors in more primitive areas but you'll have more mouths than producers--fighting over the food will take priority over producing it. Once you have reduced the population below minimum densities the last ones will die out.
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As someone with a degree in biotechnology, what you want is no viable with modern day technology.
If you want something to kill people after a period of ten years, I would suggest some form of parasite that could stay dormant for longs periods of time.
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I've just written a short story about biological weapons and done a little bit (really a little bit, by far not an expert) on the topic.
You will never wipe out humanity with a virus. There is too much distance and variance and too many detections and something like a multi-year infection period with a high infection rate but no symptoms and then suddenly death all over the place just isn't realistic.
If you want to kill humans, you need multiple stages. If you are a nation state with sufficient resources, you can accomplish a very high kill rate if you are really determined to do so. Your diplomats, tourists, trade delegations, etc. can spread an infection without symptoms to every corner of the world. That will in a good scenario kill millions, maybe tens or hundreds. But anything more than that would be extreme luck.
But if you can come up with an antidote in time of need and use that to deliver a second stage - now we're entering the realm of SciFi here as I don't think the genetics exists yet to create something like that - and at least for a short time you are the only supplier of the antidote, when the need is at the highest, you can go into the billions range.
With the widespread social and economical disaster that would follow such a crisis, you can go to conventional warfare to spread a third disease (i.e. just spray an aerosol like they did with Agent Orange), and simply overwhelm the medical capabilities of whatever is left.
Of course, that assumes that your country isn't hit the hardest and your military still follows you and is still operational after all of that and your biolabs are still willing and able to produce the bad stuff in enough quantity - it's all a very big stretch, and you might vary the details, but the basic message is that something like wiping out humanity is not going to happen with a single attack, no matter what borderline-magical capabilities your virus has.
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If the intention is to basically take revenge and eradicate the human race: How about a virus that affects fertility and/or pregnancy? It seems to have almost no immediate effect, but spreads extremely well (like Covid, but only mild cold symptoms, if any) - but everyone infected becomes either infertile, or will transmit the disease to the baby, causing issues during pregnancy.
Most people wouldn't even notice the virus - maybe just some sneezing, and thus wouldn't visit a doctor immediately. Noticing infertility probably takes a while - giving the virus time to spread even further - spread through air, this could be highly effective.
Of course, it would take a long time for humanity to die off - and there's a fairly long time window in which they might research ways around it - but some problems are perhaps simply not solvable. AIDS took a long time to be able to treat medically, and there's still no vaccine...
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Let's pretend the lithosphere of Earth were smoothed somehow to fit a perfect geoid and maintained in this shape; all the water would turn into a uniform layer flowing over the ground.
According to [wikipedia](https://en.wikipedia.org/wiki/Earth), sea water volume is 1.332$\times$109 km3, and this is 97.5% of all the hydrosphere waters, which gives us 1.366$\times$109 km3 of water total. Total Earth volume is estimated as 1.08321$\times$1012 km3.
If my calculations (hopefully) are correct, thickness of the water layer should be ~3 km.
I'm just curious about two things:
* Will any piece of ground ever be exposed over the water surface even for a short periods of time due to internal or external forces, such as moon gravity, centrifugal force or for any other reason?
* Will the mean temperature on a surface of this weird world be the same as a current mean surface temperature (288 K)?
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> Will any piece of ground ever be exposed over the water surface even for a short periods of time due to internal or external forces, such as moon gravity, centrifugal force or for any other reason?
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Currently, the greatest [tidal ranges](https://en.wikipedia.org/wiki/Tidal_range), of about 16 meters, occur in the [Bay of Fundy](https://en.wikipedia.org/wiki/Bay_of_Fundy). Why is this the case? [Resonance is apparently created by an alignment of the shape of the bay and the Moon](http://www.bayfundy.net/hightides/hightides.html), which happens in very few places (see also [this paper](https://www.siam.org/students/siuro/vol1issue1/S01006.pdf)). Without the coastline to interact with the water, the tides wouldn't be nearly so drastic.
In your world, you would need tidal ranges roughly 187.5 times greater - actually, double that, since the depth of three kilometers is presumably from the mean water level. With no land above water, you won't see any tides nearly as significant.
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> Will the mean temperature on a surface of this weird world be the same as a current mean surface temperature (288 K)?
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No. The [effective temperature](https://en.wikipedia.org/wiki/Effective_temperature) - without accounting for greenhouse gases - will be different, because the [albedo](https://en.wikipedia.org/wiki/Albedo) would be different. That Wikipedia page says (citing [this paper](https://web.archive.org/web/20090920212836/http://www.mpimet.mpg.de/fileadmin/staff/smithrobin/IC_JClim-final.pdf)) that temperatures would rise 27 °C if the world was covered with water, as in your case. That's likely too hot for life.
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* Will any piece of ground ever be exposed over the water surface even for a short periods of time due to internal or external forces, such as moon gravity, centrifugal force or *for any other reason*?
**tldr**
Add more water if you wish water covered planet. Poles although, may be like it is now, icy and solid surface where live some creatures.
## Yes.
Yes, it will(may and will over geological time), for that other reason.
I'll recommend to watch 2 videos:
* [What Physics Teachers Get Wrong About Tides! | Space Time | PBS Digital Studios](https://www.youtube.com/watch?v=pwChk4S99i4)
* [Tides: Crash Course Astronomy #8](https://www.youtube.com/watch?v=KlWpFLfLFBI) at 4:52 mark is important moment
They are not strongly related to answer and question, but it builds overview on topic, and maybe some moments are related.
## Why and Which reason?
There is a picture for you to guess:
[](https://i.stack.imgur.com/jEkte.jpg)
[Sahara Desert, rippled sand dunes with Blue sky](http://www.wallcoo.net/nature/amazing%20hd%20landscapes%20wallpapers/html/wallpaper37.html)
System with is described by OP Q is not stable. At begin, Earth may be perfect geoid, mass of crust is even distributed, magma is consistent, evenly heated(no density changes from temperature), equal salty(or not), etc etc. That everything will not change the fact, it will get those ripples over time, but it may affect time needed for that.
[Origin of water on Earth](https://en.wikipedia.org/wiki/Origin_of_water_on_Earth)
* Comets, trans-Neptunian objects or water-rich meteoroids (protoplanets) from the outer reaches of the asteroid belt colliding with Earth may have brought water to the world's oceans.
* Gradual leakage of water stored in hydrate minerals of Earth's rocks could have formed a portion of its water.
Important moment for *any* earth-like planet, both of that sources internal and external adding imperfections to planet mass distribution, crust strength, craters, etc.
Tides means water movement, not imaginable movements like waves in ocean or sound waves, but real flow of water, which drags materials. That water flows will be different in different parts of earth just because geometry of earth and forces involved. Let say virtual poles in plain of moon orbit - there are slower water flows, on equator (earth cut of moon orbit plane) it will be faster.
That difference may be important, but also it may have some strange effects too, take look at [Saturn's hexagon](https://en.wikipedia.org/wiki/Saturn%27s_hexagon) which may affect material movements on bottom.
I'm not capable to say how fast will be such flows, I'm curios by my self.
## Reason
Bald earth, I mean with flat surface and water on it - is not stable system.
Water, like wind in desert, will form same ripples on bottom, and more ripples there are, more and faster will they grow and form new ones. That will lead to imperfection on earth crust, because of mass of sedimentation layer, because of they do actually have viscosity - it will compress solidify, as any sedimentary rocks do(all that stuff). It will affect crust it will be thinner ticker, crust weight will affect's magma etc. Step by step there will be more and more imperfections - it will move as dynamic system to some sort of dynamically-chaotically equilibrium.
Water is more dense then air, so it will have more effects on earth upper layer.
[Sahara](https://en.wikipedia.org/wiki/Sahara)
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> Many of its sand dunes reach over 180 meters (590 ft) in height.
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So 3km tall plateau, why not. All that process will take place long before earth-like planet gets all that water, because magma also is a fluid actually(not solid at least).
Water will evaporate differently, more salty in some places, more cold, more dense etc. That affects forming [Concretion](https://en.wikipedia.org/wiki/Concretion) with may affect differently erosion etc etc.
It so much things and complex stuff involved, so no one may say what it will be, except it will not be a bald earth geoid, just cant't happen. If you see that you may know it's artificial and fresh made, geologically speaking.
If there is already sand available, any material with small particles, some dunes may be formed pretty fast, depends on how much and which quality is surface material. 100-1000-10000 years will be enough I guess, if material is easy movable by water flows. There will be the limit, how tall they can be, as it is for the mountains.
(google) "deserts sand ripples" for science bro
## Temperature
Very important factor will be established water movements flows and air flows. Air movements will affect water and will be affected by water (tides). If it will happens to be cloudy, and it may because of lack of big chunk of land, mountains specially, it may so happen to be more cloudy. So even water is't so reflective, but clouds have potentially high albedo and may regulate temperature.
As land not drain clouds I guess average temperature may be even less then now, it depends. One is sure, frozen water as result practically no clouds. Hmm but snow ice have also high albedo. So first is't sure, depends. But clouds forming, which is water evaporation, will have buffer effect, and may regulate temperature. What I wish to say, temperature is't just matter of albedo, but properties of water too - not so simple, simple assumption shall not pass here.
Second is sure, temperature distribution will not be even, some places will be warmer some colder.
Just add more water for water world, 20km-30km layer of water for earth-mass planet, 100km for mars mass planet.
## Example
Recall one example which I definitely wish to add here.
[The Moving Island of Schiermonnikoog](http://www.amusingplanet.com/2012/09/the-moving-island-of-schiermonnikoog.html)
* Schiermonnikoog is a small island off the coast of the Netherlands that has been continuously moving to the south and the east, due to the combining effect of tidal current, prevailing wind and the sea. Just 762 years ago the island lay roughly 2 km to the north of its present position, and it had a significantly different shape. If you work out the math, that is 2.62 meters per year, on average.
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There is a behemoth creature that once swam the great oceans of a planet whose waters now run dry, and whose surface is now a sand-covered desert. The Creature is now long-dead, but it's Skeleton still remains, half-buried under the sand.
The creature in question, is a sort of whale, except is hundreds of meters long (Much, much larger than a blue whale). It is angled so that the rib-bones form a sort of () shape sticking out of the sand. The skull, fins, and other parts are all sticking out of the sand as well.
My question then is; what might be the best way to construct a settlement inside the beast's skeleton? (If it's even a good reason to do so in the first place?
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The skull is your center of power, the ribs are the highrises for the influential, and the center is the pit for the commoners.
If we assume that this creature's skeleton has some latent strength remaining, it might become an anchor for structures. Looking at the ribcage, you have hundreds of meters of flat space from head to tail, much of which is likely to be "protected" by ribs protruding upwards at various heights.
The skull, a cavity-filled but well-protected enclosure, would be the most fortified location. Along with its natural protection and space, it also has the spiritual benefit of being the head of the beast. This makes for a natural palace of sorts that is both practical and meaningful.
Stretching across the sand from skull to tail is a flatter, more open expanse lined by the ribs. This region is a likely space for commoners worshiping the monstrous skull or the rulers who take residence in it to erect initial shelters. Here you'd find markets and slums springing up, most likely with the well-off staying closest to the head and the poorest near the tail.
As the settlement grows, the ribs provide upward mobility. With some construction expertise platforms can be anchored into the ribs from the bottom up to the tips. These platforms become skyscrapers with as many floors as they can fit. Stairs, ramps, pulleys, or elevators could link them and they could be full circles or simple semicircles pointed inwards.
Even without building upwards, the ribcage provides protection for the settlement similarly to how it once protected organs. Defenses can be strung along the bones and the interior can be fortified. Given enough time, the skeleton might appear to "grow" a new artificial skin as the empty space between ribs is filled by platforms or defensive structures.
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Imagine a world like any standard RPG games. In these games characters grow stronger as they defeat opponents, long after any real-world soldier would have reached their peak possible performance. In these RPGs your level 100 PC is practically a 1 man army taking on dozens of foes at once with little risk; while in the real world even your most elite solder is only human, he can still be taken down by a few simple infantry men teaming up against them, or even die to a novice due to bad luck or one bad mistake.
I want to imagine a world closer to the RPG ideal, not just for PCs but for everyone; and people in this world are aware of it. People never reach quite the level of one-man-army as allowed in some RPGs, and it's more complex and variable then kill x foes and your certain to gain a level, but It's a known fact in the world that experience or training can let someone reach levels of [Charles Atlas Superpower](http://tvtropes.org/pmwiki/pmwiki.php/Main/CharlesAtlasSuperpower) that make them able to greatly surpass the strength of a person with basic training alone. Most will not, or could not, reach the upper echelon of power, as factors such as innate talent, severity of training etc affect how fast one will grow in power and some simply will not have the raw talent or dedication to raise to the top levels of strength. Generally as one gets better raw training alone does less, and often combat experience against real threats becomes the main way to continue to grow powerful.
Now imagine a military in this world that acknowledges and expects this level of variance in power and skill. The military has soldiers that span the spectrum of power, but of course there are more of the inexperienced weak then the elite solders. Effectively you have a pyramid of lots of new fighters, decent number of competent, some veterans, and tiny number of elites. The power of the most elite solders are quite powerful, able to take on large numbers of rookies, but they are not invincible, bad luck or mistakes can let less skilled foes beat them and numbers and team tactics can easily allow a number of skilled-but-not-elite solders to defeat a more elite one. The military's power is mostly dependent on it's large number of less experienced common solders, simply due to the vast number of them compared to the more powerful, but the power of more veteran and elite soldiers is highly valued and recognized as an important factor in battles.
I'm trying to figure out how militaries would adjust by recognizing and utilizing this power potential. How would the relative skill level of soldiers decide how they're assigned, how does one use veteran or elite solders, more powerful but increasingly less common, to best utilize their power to support their less skilled solders etc.
What about rookie solders, how does one deploy them to make the most of their numbers while recognizing that there may be soldiers of noticeably higher strength they are best not used against out there on a battlefield?
For that matter if there is an expectation that generally speaking soldiers will manage to keep growing more powerful with experience (though this is general, and significant variance on how quickly one grows in strength and maximum potential) affect how soldiers are trained or utilized? Will there be a higher focus on keeping the rookies alive long enough to get some skill under their belt?
I'm looking at your average fantasy pseudo-medieval world in terms of technology. This also means smaller military sizes of standard medieval worlds.
You can also presume some level of unorganized non-sentient monsters in parts of the world, with the military being responsible for driving back monsters which wander to close to civilized areas, meaning some degree of constant threat even outside of war, but with monsters being weak enough that the military can hold them at bay; a soldier can die to monsters as part of the hazard of combat, but no one expects monsters to actually wipe out an entire patrol...
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This is a rather complex question. It depends on different factors, but we could look at a few points
### Experience
Though Video RPG and a few others place a huge part of the experience acquiring process on combats and kills. But it isn't very realistic. The name says so: "experience". Meaning, each time you do something new, you gain experience. Killing your first goblin would make you progress, but by the 100th, it will hardly be worth it.
But other things might be interesting to accumulate experience: solving a mystery, travelling, creating something new, etc. Depending on the source of your acquired experience, you progress in one profession. A blacksmith don't need to kill anyone, but by forging various swords & co. he will be better. And get to the level of a Master Smith.
### Profession
Still inspired by some RPG, you could start as lower levels as quite generalised professions: merchants, soldier, etc. Soldier would be generally as proficient with spears, swords or bows. But as they progress in levels, they'll become more specialised (think Legolas!). You could have a Master Smith specialised in Swords, another in Armors, others in horse shoes.
That may sound random, but I think it brings some realism, and it is essential to your question.
### Army
For now, let's forget about smiths, musicians or politicians. And let's dive in the world of the Force.
They know that the more battles they do, the better they'll get.
Newer recruits and/or younger ones will be kept for menial jobs. Cooking, etc. And you use the wars and larger battles to provide experience to many. And you somehow used a natural selection to see which ones got a natural talent for it.
Once they got some experience, you'll use them to guard. The more experienced they are the more important persons/places they guard.And they participate in larger operations to accumulate more experience.
And that's about as far as you get in intermediate level. One should note that many died in the process. Battles are not particularly safe places to be.
And we come to the core of your question. What to do with the highest levels?
But as we defined earlier, they got specialised. So there's not a single answer to give. You could, for example have:
* specialised units in a battle field organised to break the strategy of the opponents (somehow like cavalry was in many Medieval European battles).
* independent units: like killers, guards for Kings, spies, etc.
* trainers, teachers: they help the peons to capitalize on their experience.
### Politics and society
Now how are they treated by the societies? The highest levels are probably famous people. Whose reputation go far beyond their own countries. Many countries will try to bring the best offers to them. Attacking a country with a big fortress and the best archer in the world, is probably going to cool some ambition down. So money, titles, husbands and/or wives. Anything they'll want.
Some would just sell themselves to the highest bidder. They would want to be the best, and accumulate experience. Others would stay in a country for a reason or another. But they are certainly the objects of many political and economical discussions.
However, depending on the power gap, they might just work as Nuclear Weapons. They are too powerful, so you don't attack an army which have any of them in it. Or you do, but only if you have one equivalent in yours, but that you leave on the side. That would be too costly to both take the death price in your ranks, and take the risk to lose your masterpiece.
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Actually, what you propose isn't too far different from what we had in our world.
A well trained knight in full armour was able to take on 10 or 20 untrained peasants and emerge victorious. Not always of course, but it was possible. Mount him on a horse and it became even more likely.
The differences you describe are ones of degree rather than absolutely game changing. Your elite units would become even more elite, your cannon fodder even more cannon fodder.
If you had population to spare you would most likely want to be in a lot of constant low grade wars and skirmishes since from those your elite start to emerge, and then more training and equipment can be lavished onto those elites since they are where the true power lies.
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Farming is the key...
You want to level up soldiers safely and cheaply. Its hard and expensive to level them up in open battle because many will die.
There are non sentient monsters that would grant you experience if you defeat them, up to a point. You should trap and bread some of these creatures as training stock to ramp up your army with, that way everyone goes into their first battle as a level 2 or 3 not a level 1. Mock combat and training can be another way to accomplish this.
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It depends on 2 factors really - you either want a large number of "sweet spot" trained troops, or a few "super" trained troops. The difference in skill will tell you which you need (ie, take football, you can have the super skilled Messi still be beaten by the less-well skilled League 2 team so you'd train all your troops to the easy-and-cheap-to-achieve League 2 level, but if the skill levels were so different that the top player could take on a team all by himself, them you'd want to specialise in having a couple of them).
So assuming that as skill levels increase, they start to plateau and the difference is not so great, then you want a training programme for troops like we already have. You can see the difference here between troops of varying skill levels: a whole company of ill-trained troops will not be a match for a platoon of trained ones, or a handful of special forces troops.
However, assuming that you have D&D style experience where a level 1 untrained grunt will easily be outclassed by a level 5 veteran, and a level 20 elite soldier will take out whole armies single-handedly, then you're n the world of superheroes, where you needn't bother with any number of ordinary armies, you'd have them for peacekeeping and civilian suppression duties, and a couple of stars. Your position in the military world would be dependant on these, a bit like any story you'd find in a Marvel or DC comic.
Of course, the difference doesn't have to be down to skill: you can use technology instead. So a reasonably trained trooper can be issued with an iron-man suit (or whatever) and be a very effective fighting force by himself. In this case, you're limited to how many suits you can manufacture and support - your military might becomes one not of soldiers but of technological industrialisation. Similarly, if you developed remote-control robot troops, you don't even need soliders as you'd want them piloted by guys sitting around all day in front of a VR monitor (though ones with a good sense of discipline). In this case your battles are better fought by experienced tacticians than soldiers and your training will be more like a war game.
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I am designing a video game in which [Alcubierre Drives](https://en.wikipedia.org/wiki/Alcubierre_drive) will be obtainable by the player. I would like this game to be somewhat scientifically accurate in this way.
Specifically, I am interested in what parts would be necessary, their function, what they may look like, and where they may be placed in or on a ship. I realize that there are many unknowns regarding the Alcubierre Drive. As such, I would like several possibilities to be listed for each of the main unknowns.
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Well it appears that there are several designs out there from people who have some idea what they are proposing.
All of them have the drive(s) as a large ring around the ship. Most of them appear to use 2 rings, and my guess is that would help with stability and maybe one ring compresses space in front and the other stretches it out behind.
[](https://i.stack.imgur.com/nWnjd.jpg)
[](https://i.stack.imgur.com/emQc1.jpg)
[](https://i.stack.imgur.com/bwfcM.jpg)
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**TL; DR:** Aliens are not previously known. An alien spaceship suddenly crashes in full view of thousands of people. All members of the crew are dead. How can we expect governments and scientific bodies to react in the short/ medium term, in the broadest sense?
Ok. We start in today's modern world, and all is well. Space agencies are perhaps preparing to send the next crew up to the ISS, the intelligence services are all happy spying on each other over boring stuff like nuclear proliferation, and the media is buzzing with the latest celebrity scandal.
Suddenly, some scientist or government astronomer detects a new near earth object decelerating to a orbital injection trajectory. The object seems to have come out of nowhere. Over the next few hours, the object's orbit decays and it enters the Earth's atmosphere in what is later considered a 'vaguely controlled manner.' As it descends, Radar makes it clear that it survived reentry, which is shortly after confirmed by social media being plastered in pictures of an object in the sky trailing smoke and brightly colored gasses.
What appears to be an escape pod is ejected from the craft and crashes in location A - To make things more interesting, let's assume this is a different country from the main, far larger, ship. When investigated, the pod is found with a sealed door and three dead (presumed members of the) crew inside.
Meanwhile, the main spacecraft is shedding parts and narrowly avoids crashing into a major city, before ditching into a river/ ocean in sight of at least a few hundred thousand people. Presumably a small handful of humans are killed in the crash, either by falling parts or a direct collision, but loss of life is minimal. Some property damage occurs.
When/ If the craft is searched by divers, another member of the crew is found dead, presumed to have drowned.
So, what I would like some opinions on, is how would our world in general, particularly governments and their agencies, scientific bodies, and civil authorities, react and handle the incident in the short and medium term?
Of more specific interest to my plot: which agency/ body would likely be able to secure control of the crash site in each time frame, and what would their intentions be?
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Well... you should be aware of the huge differences that will occur when such a craft crashes down to earth with a huge load of civil observers either in country A and in country B. And it will be completely different in country C.
So while the most common place for alien-actions (the USA) may have a plan for stuff like this happen, many other nations are not prepared for this. For example in Germany a spaceship that parks itself in front of the Bundestag (where our chancellor is dwelling around) will most likely receive a traffic ticket for not owning license plate, dangerous intervention into air traffic, parking at a disabled parking location and piloting a not TÜV-approved (TÜV forbid you to use your car if its a piece of rubbish) vehicle without a flight license. Further, the aliens may get a lawsuit for illegal immigration and running around naked in public.
But in your case you claimed that this was a crash. And its clear that everyone who did observe this did notice. So the case may develop different for they following major cases:
* industrial nations: Will deploy police and fire fighters and other emergency agencies, lock off the place of happening and trying to determine whats wrong with that stange plane. As soon as they notice that its extraterrestrial maybe their army will try to grab all the pieces and lock em away. Most likely, some time after this mutual allies, that will got news from all the civillian spectators, will be allowed to participate in scientific research of this. Meanwhile, the whole world can watch dozens of videos of the crash on youtube.
* emerging nations: May act in the same way, if the crash site is not in a desert, rain forest or tundra. In these cases some military spotter will go out and you can skip directly to "grabbing whats left", but without "sharing with allies" maybe. Civil reporting will drop sharply when you hit an area with low internet access at all.
* poor nations: A local spectacle, where a bigger nation may approach and offer "technical help", in case news travel far enough. Maybe all who did observe think it was a sign of god or something like this and carefully avoid interfering with that thing any more. When you hit a "rouge nation" chances are good that they will get the leftovers and being able to profit from this in a way that makes them a global player after some years. Don't expect any footage beside some wild shaking ones.
So... these are vague estimates. Like said before, it depends where that space ship (and the pod) did land at the end. If you want an agency to pop up and take things in their hands, you should crash that ship somewhere you know a superior intelligence service is working and a big budget is available to spend to such agencies. Russia, China and the USA of course, Europe, India, Japan, British Commonwealth as secondaries...
A global working group... oh dear, just claim Illuminates are active again. At all, they even made it into Deus Ex as a group of global rich people, so just throw together some of the more influential companies which may share a common goal and give them a Joint-Venture private security force. And for some goodwill, all your crash-events did happen close to one of their companies. Or better: right on the parking spots for their employees.
But if you are after a government agency that may get in charge of the crash-site anywhere, UN and NATO may be your group of choice. Otherwise you will spend most time doing diplomacy, which can get pretty boring.
If I could choose the landing-sites... I would place the pod at Antarctica and the UFO somewhere halfway between Europe and the USA - maybe at Iceland (which is not halfway, but... well) - so that every big player get the chance to be there first, while the local authorities are unlikely to be prepared for such a happening. Some of the Oceania-Islands (Java!) may be a good spot too: quite big cities available and most big players within two hours recon-plane-range.
At the end... when no evidence of dead alien creatures from the inside made it to the internet, a country or company will try to claim that this is in fact an earth-bound plane which happens to... well, they shouldn't have updated their flight-computer to windows 10.
Otherwise it will be a matter of hours before to much evidence is around to conceal this any more. Just take group of students with smartphones and a nearby 4G Phone Transmitter Station...
I feel like I did miss something, but maybe it pop up in my mind later... or somebody else does name it.
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If it doesn't crash in a public place, if it's out in the desert or the jungle somewhere, the government of whatever country it's in might try to keep it secret so that they can take advantage of it. But this will fail, as other countries have seen it on radar and know something happened, and in any case governments are notoriously bad at keeping secrets for a long time. (Somehow the subject of UFO conspiracy theories once came up at work, and one of my co-workers said, "If I believed that the government was capable of keeping a secret like this for 50 years, with all the people who would have to be involved, it would make me proud to be an American.")
We'd have to wonder what the civilization that built this ship is doing. Are they sending a rescue party? I've seen lots of movies where aliens land and people promptly take them prisoner, maybe even kill them so they can dissect the bodies. This would be incredibly stupid. You KNOW that these aliens have technology well beyond our own -- they can travel between stars. Who knows what weapons they have. Would you really want to make enemies of them? Not to say that people don't do stupid things, but, etc. I'd be very careful about doing anything to the corpses or the crash sight until I know whether these aliens have friends coming after them, and what they consider acceptable treatment of their property and especially of their dead. Maybe they, like us, have religious or cultural rules about the treatment of dead bodies. Maybe they want to salvage the ship and would be mad if we took it apart. Maybe they don't want primitive societies like ours stealing their technology. Etc. If I was in charge, my recommendation would be to quarantine the site until the aliens' friends arrive.
Assuming we don't care about any of that or the aliens indicate they don't care about the wreckage, people could study the wreckage and maybe learn advanced technology. It's hard to say what you could figure out. If they're too far ahead of us, it may be incomprehensible. If you dropped a modern computer on a society with 1960s technology, smart people would study it and probably figure it out. Drop a modern computer on a society with 1860s or 1760s technology, and, well, I think it's an interesting question how much they'd figure out.
There'd be people saying how this totally changes our view of the universe and how society will never be the same and so on. But unless it leads to interstellar travel -- we figure it out from studying the wreckage or the aliens' friends come and give us access to their ships or technology -- then I think in the long run most people wouldn't much care. It would be big news for a few months, until it was overtaken by the latest celebrity sex scandal or whatever. It wouldn't change most people's daily lives. Compare it to the Moon landings. I remember at the time lots of people said how the fact that men had walked on the Moon changed our view of the universe, etc. But in practice, how does this change your life? How often do you even think about it? And anyone reading this is likely someone interested in such subjects. To most people, "Wow, there is alien life! How interesting! And did you see that football game last night?! ..."
Atheists would say that this proves all religions to be false. (I say that confidently because I've often heard atheists say that when we meet aliens, this will disprove religion, though the reason why has never clear to me.) Some religious people would have to adjust their beliefs and theories, While some people say that they doubt the existence of aliens on religious grounds, no major religion holds non-existence of aliens as a doctrinal point, so it's unlikely to shake anyone's faith seriously.
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Let's give this a stab by starting to appeal to all the conspiracy theorists and consider the first possible time frame "Ground Zero".
Along with the black suit syndrome, we don't know the unknown people (organisation X) who would be at G0 seconds before the projectiles (pod and ship) hit their likely calculated impact points (Let's say X has abundant resources and power to remain hidden from us common folk - be as creative as you need ie. able to intercept satellite/government/intelligence etc. to mislead their predictions of the orbital entry or crash).
Case X - A: Assume that X somehow had prior knowledge of the existence of the newcomers. If relations were diplomatic -> a search/rescue/recovery and cleanup of evidence would take place (Lots of question about media footage with no answers still preferable to spilled beans). If relations were hostile (ship was possibly compromised by X to begin with) -> cleanup of survivors + evidence.
Case X - B: X is just caught off guard like the rest of the world but they still want the information first, and if need be contained. They would likely undergo recon with risk assessment, capture/detain/eliminate hostile survivors. And attempt to clean up the scene.
Entering slightly more realistic ground and say X doesn't exist or is otherwise occupied with more pressing concerns. Considering there was ample coverage and warning (uncompromised by X) of the craft's approach, countries or areas expecting the crash in their yard will likely have prepared a military/scientific/media resource at the site. Likely in that order. To first secure the situation and ensure the craft or its passengers pose no immediate aggressive threat. Followed by an investigation into the specifics of the craft/passengers/crash and the environmental threats they could pose. Concluded lastly by allowing/or not the media to disclose details of the event.
As to what happens afterwards and who gets custody of the evidence, it's unlikely that a single government could cover up or lay claim to such an event (A claims crash site, B claims orbital entry into their skies, C claims debris, D claims death of civilians... etc.).
I suspect a panel/convention/union of countries would be formed with regards to which decisions will be taken. Most likely these decisions will lead to scientific investigation for the most of the foreseeable future. Information released would most likely be that deemed safe enough to release to the public, or that necessary to control and keep the public calm.
On a global scale there could be religious turmoil or similar such which would claim to explain the existence of the ship.
] |
[Question]
[
Obviously, this would depend on how prevalent magic was in the world. It would also depend on not only how prevalent magic itself was, but how prevalent are people who are able to perform it. There is definitely a distinction, as you could have a world where anyone and everyone is capable of wielding magic, but it is only present in rare locations, or at certain times, or whatever it is you decide.
If you had a world then, of a roughly medieval setting (say 13th-15th century maybe), and suddenly someone discovers they can cast a spell. Likely this would happen somewhat by accident, the same way that likely people first discovered how to actually start a fire. I imagine this would happen in multiple locations around the world, probably with very different results. For example, one person might accidentally cast a spell that cursed someone, while somewhere else in the world someone might cast a spell that caused their crops to grow twice as fast. These two people's views would likely be vastly different in regards to this newly discovered magic, as would the views of the people around them who might have witnessed it, or be aware of it.
Given all of this, how long do you think it might take before magic developed to some sort of form approximating what most fantasy settings have (e.g. a wizard who can shoot flames at someone or something similar)? What milestones in the development of magic might happen, or need to happen, for this level of magical development to be reached?
I'm thinking scientific methods, what was known of them at the time, would be applied to study magic. Would it reach a level familiar in most fantasy settings while the world was still in its medieval period? If not, how long before that would magic have likely needed to be discovered to reach that point?
I'm building a world where magic is still somewhat unknown, people are still figuring out. The setting, time-wise, is a medieval one, so I'm trying to figure out how long before this might magic have needed to have been discovered. Also, how rapidly it might develop further, as that and the previous question significantly impact any discussion of magical origins and workings within the game. For instance, I can't say magic was discovered only 5 years ago, if it is likely that the best most of the world could manage in that time frame is the magical equivalent of mixing two fluids to cause them to change color.
I'm sure people will want to know ore info about the magic system, but rather than include more of a wall of text than I already have, I'd rather include that info if/as it is requested.
[Answer]
From reading your response to my comments, I gather that the two components to casting a spell are the **specificity of the thought** and **lack of any interfering thoughts**. It seems like a spell must reference some specific, desired physical result. So I suspect that to shoot flames at someone, the wizard would have to think something like, "Fire, appear in front of me now and immediately move until you hit that person over there." Also, as you said, the magic-user would have to exclude competing thoughts and desires, such as not really wanting to create a fire, not really wanting to kill someone, not wanting the fire to appear in front of them, wanting to purchase a beer at the tavern, that sort of thing.
It seems like the first element is something anyone could master fairly easily, if the other problems didn't kill them first. Excluding other thoughts, though, is hard. I suspect that most people simply could not do it at all, or at least not sufficiently well to cast a spell reliably. Of course, if you can't reliably use magic, it is probably best not to mess with it. However, some small percentage of the population would, with sufficient practice, be able to exclude other thoughts from their minds, and thus reliably cast spells up to whatever power level the magic permits.
I, therefore, think that magic could spread quite rapidly. There are two key factors: how flashy was the initial magic? And how disciplined was the original caster?
**If the initial spell was very obvious, and the caster was disciplined**:
*A local monk wishes that the blood of some enemies would turn to sulfur.* The caster will know as soon as the spell takes effect that they did it. In the case of the monk, the person targeted will smell of sulfur and die essentially instantaneously. The monk will absolutely correlate his or her thoughts with the incident. In circumstances like this, your proposed method of casting spells is what the caster will try first. If they are sufficiently disciplined, like the monk, they will succeed in casting other spells in days or weeks. After that, if they choose to share the secret, it is just a matter of how quickly information could spread by horse or ship. Five years for magic to become widely known within a range of several hundred miles, and known in cosmopolitan locations within thousands, would not be unreasonable under these circumstances.
**If the initial spell was subtle, and the caster was disciplined**
*A local monk makes some crops grow twice as fast*. It is very possible that the caster will never realize what happened. If they do, it will take years of subtle spells working, after which the caster will probably try bigger things. The situation then proceeds as in the first case.
**If the initial spell was obvious, and the caster undisciplined**
*A local farmer turns the blood of some raiders to sulfur* It will be obvious to the caster what happened, but they will be unable to reliably replicate it. Because they have no way of proving their abilities, the knowledge may never spread. There are several ways it could. If the caster tells someone better at blocking out distracting thoughts, we might then have a situation similar to the first one. If not, the story may become a local legend. Over decades or centuries, someone might be able to piece together a coherent theory from similar isolated events, and thus begin an era of systematic magic.
**The spell was subtle, and the caster undisciplined**
*A farmer makes her crops grow twice as fast.* Forget about it. The caster will most likely not figure out what is happening. Even if that does occur, they will not be able to convince anyone else, at least not reliably. I suppose they might be able to convince some villagers to burn them for witchcraft because their crops grew too quickly, but this is not going to convince anyone from out of town. If all, or nearly all, incidents of magic are like this, it won't be until reliable statistical methods and censuses are around that people will be able to discover magic.
[Answer]
I think the speed of how quickly your new magic will spread will depend mostly on socioeconomic factors, and not how easy people will be able to master it. While I think what Jonah said in his answer is mostly true, I think that the spreading of this new 'technology' will happen at speeds much, much slower than the actual learning of spells or teaching new 'magicians'.
As such, the spreading of this new technology would differ vastly depending on how progressive/conservative the society is, how well organized it is, and how it looks upon technical advance - which for the sake of the argument I'll just assume models this quite accurately.
To illustrate what I mean let me give you two examples, which try to show the possible range of how fast or how slow your newly emerging magic could spread through your world.
## Example 1: Roman empire (ca. 0-100AC)
The roman empire was governed centrally, they had strong hierarchies in place and, for the time they lived in and the means given to them, were organized spectacularly. Due to the empire spanning essentially all of Europe and parts of Northern Africa and the Middle East the Romans were also fairly experienced in dealing with all kinds of societies, cultures, new technologies, different religions, etc.
In such a setting I think it could well be possible that some Roman generals or other officials recognize the immense value and power this new magic presents. (One fireball wielding wizard in each Centuria? Hell yeah!)
If they invest some resources and immediately begin to institutionalize it, I think it is realistic that magic will spread through the core of the Roman empire in maybe 5-10 years, with some additional time until it reaches all the remote provinces.
## Example 2: remote European region during the dark ages (say Scotland/England ca. 800 AC)
Compared to the first example this society literally lives in the dark age. At best we have a localized feudal system in place governing the region, quite possibly in conflict with other surrounding feudal systems. People, including their leadership, will be poorly educated and quite frankly ignorant towards most topics outside their immediate sphere of influence. Also it is likely that the people have a very conservative (probably Christian) mindset.
This mindset will realistically prove to be a strong factor working against the quick spreading of magic. It could take a very long time for magic users to convince the Church that what they are doing is not actually the work of the devil (is it though? ;))... People were burned for far less - like knowing about herbal remedies. Suddenly being able to shoot fireballs or turn your neighbors cow into stone will *not* help your case.
In the face of the mentioned obstacles, the first magic users could be forced hide their knowledge, only passing it on in secret. It could easily take 50 or 100 or more years until they are able to 'go public'. To actually institutionalize magic and the training of new magicians they will also likely have to relocate to the biggest and most prosperous political/economical cities of the time.
[Answer]
If a caster depends only on their accumulating skill, then the magic growth could be linear. $P=kt$
But, magic can be used by a caster to impose discipline on themselves. Magic would grow in relationship to its current power, thus it would grow exponentially. $P=ke^{jt}$
The actual rate of growth hardly matters, since with exponential growth all arrows point upward at an ever-increasing pitch.
If magic can be used by a caster to entrain others to focus and dismiss unrelated thoughts and distractions, then the number of minds involved in casting each spell could also increase exponentially, perhaps yielding hyper-exponential power to spells. $P=ke^{je^{lt}}$
In an arms race of such magic, an undetectable initial advantage would grow to be insurmountable. One magic force would survive and dominate all.
] |
[Question]
[
An alien race, for reasons of their own, have decided that it's important to make the third and fourth planets in our solar system about the same size and mass. Since they have a strict moratorium on altering planets with clearly visible carbon-based life on them, Mars is the object of their "affections". As a result of their cultural biases, they love iron. Any time they need/want to increase the size of a planet, they use iron to do it. (Yeah, I don't get that either but whatever, aliens, am I right?)
On the day of the drop, they position their ultra-mega cargo freighters full of iron around Mars then let all those gigatons of iron just fall Mars-ward. As you might imagine, the fireworks are spectacular. After the freighters move away, the planet cooling ships move into position but right before they start operations, an urgent call from the Supreme Dear Leader comes in demanding that his entire planet be air-conditioned and the cooling fleet is to report, pronto!
Iron parameters:
* Initial altitude: 150km (all ingots enter freefall form this height)
* Iron initial temperature: 250K
* Speed relative to Mars' surface: 0 m/s
* Individual Iron Pieces: 100 m^3 ingots
Mars must then cool off on its own. With the cooling fleet gone for an indefinite period of time, *how long will the aliens have to wait for Mars to cool down to a comfortable temperature for carbon-based life after dumping all that mass on Mars' surface?* Assume that atmospheric insulation/cooling effects can be ignored.
Altering Mars' orbit or the orbit of any of the other planets isn't a concern for these aliens, all they care about is Mars. Besides, they have the capacity to "nudge" planets into stable orbits.
(I realize that this is a fairly fanciful way of asking how long it would take to cool off Mars if you dumped enough iron on it to make it the same size as Earth, but it's more fun to write it this way. I also realize that aliens with these logistic capabilities can do pretty much anything they want.)
[Answer]
Lets start by ignoring that for deep planetary pressures, iron is compressible and that it expands when it is heated.
**Basic facts**
```
Mars mass: 6.4171e23 kg
Earth mass: 5.97237e24 kg
Mars mean radius: 3389.5 km
Mars surface acceleration: 3.711 m/s^2
Iron density: 7850 kg/m^3
volume of a sphere = 4 / 3 * pi * r^3
radius of sphere = (volume * 3 / 4 / pi) ^ (1/3)
Mass of iron = m(Earth) - m(Mars) = 5.33066e24 kg
Volume of iron = mass / density = 6.79065e20 m^3 or 6.79065e11 km^3
Gravitational Constant: 6.67385e-11 N m^2 / kg^2
```
Let us model the required iron as a spherical shell of iron with an inner radius equal to that of mars plus 150 km. So, what is the outer radius? We know that the total volume of the hollow sphere must be the total volume of iron minus the volume of the hollow interior.
```
vMars = 4 / 3 * pi * 3389.5^3 = 1.63116e11 km^3
vInner = 4 / 3 / * pi * 3539.5^3 = 1.85744e11 km^3
vOuter = vInner + vIron = 1.85744e11 + 6.79065e11 = 8.64809e11 km^3
rOuter = (vOuter*3/4/pi)^(1/3) = 5910.31 km
vIronMars = 8.42181e11 km^3 (calculated below)
rIronMars = 5858.3 km
```
So, our iron to be dropped consists of a hollow ball of iron with an inner radius of 3539 km and outer radius of 5910 km. At the inner edge of the iron, the downward acceleration would be the acceleration due to Mars alone as the net contribution of the iron mass would be zero for all points inside the shell. At the outer radius, the acceleration would be based on the mass of the entire Earth.
```
accelInnerInitial = accelMarsSurface * (marsRadius / rInner)^2 = 3.711 * (3539.5/3389.5)^2 = 3.403 m/s^2
accelOuterInitial = accelEarthSurface * (earthRadius / rOuter)^2 = 9.8066 * (6371/5910.3)^2 = 11.395 m/s^2
```
The differences in acceleration clarify the problem with the iron shell assumption, the iron blocks would crash into each other as they fall. We'll simply ignore this problem by and large.
So, what is the impact velocity of the inner shell? Either we could do calculus since the acceleration increases as the shell falls closer to Mars, or we can take advantage of the formula for gravitational potential:
```
Gravitational Potential, V(x) = -G * M / x where G is the gravitational constants, M is the mass of the planet and X is the distance to the planets center.
```
Note that V(x) is always negative and approaches zero as distance approaches infinity. Since kinetic energy = 1/2 \* mV^2 and a falling object converts gravitational energy to kinetic energy we can figure out the impact energy and velocity without having to integrate over radius with variable acceleration.
For example, consider the case of falling from infinity to the surface of Mars.
```
F(x) = -GM/x thus F(3389500) = - 6.67385e-11 * 6.4171e23 / 3389500 = - 1.2635e7 J/kg.
```
Kinetic energy change will have the same magnitude as the gravitational potential energy change due to conservation of energy.
Solving for kinetic energy for velocity, `V = sqrt(2*E/m)`, and using -F(3389500) for E.
```
V = sqrt(2*1.2635e7/1), V=5.027e3 meters / sec -- this is in perfect agreement with the published value for the escape velocity of Mars, a useful check on our method.
```
For a mass dropped from 150 km altitude. F(3539500) = -1.20996e7 J/kg. The difference between F(surface) and F(150 km up) is 5.35e5 J/kg, which means the impact velocity is 1035 meters/second if atmospheric drag is ignored. Given the total mass of iron being dropped, this seems like a good assumption.
What about the outermost shell? similar math, but it based on total earth mass as all of the iron lies inside the outermost shell-- Mars radius is now much larger due to all of the rest of the iron already added to Mars. Again ignoring comprehensibility of the iron (and Mars itself), our new Mars planetary volume is the old volume plus the volume of all of the iron:
```
volumeIronMars = 1.63116e11 + 6.79065e11 = 8.42181e11 km^3.
```
Solving for radius yields 5858.3 km so the outer shell will fall a distance of only 52 km, however it does so with the full acceleration due to Earth mass, about 9 times Mars mass.
```
F(OuterShell) = -GM/x = -6.67385e-11 * 5.97237E+24 / 5910.308044 = -67439276 J/kg
F(IronMarsSurface) = -6.67385e-11 * 5.97237E+24 / 5858.3.303939 = -68037933 J/kg
Change in outer shell potential from falling = 5.99e5 J/kg`
```
The difference in energy gain for the inner and outer layers is close enough, that I will just use the geometric mean value of the inner and outer shells as the average energy change (instead of resorting to calculus to compute a more accurate number), i.e., 5.662E5 J/kg
So, finally what is the temperature change? Iron has a specific heat capacity of around `0.45 joules / gram * deg` or `450 J/kg*deg` so we can finally compute the temperature rise as `5.662e5/450 or 1260 degrees Kelvin,` so **the final iron temperature is about 1510 Kelvin or 1237 Celsius or 2258 Fahrenheit** - this is considered white hot though there is still a yellowish orange appearance -- about the same as a candle flame. Iron melts at 1538C so not molten iron, but it will be much softer / more plastic than iron at Earth surface temperatures.
The incandescent IronMars will be very noticeable from Earth.
Calculation time to cool off is another set of nonlinear problems too. I want to stop here because there are 2 very different solutions.
1. The iron rests upon the old mars surface or
2. the iron continues to migrate down towards Mars core due to the impact load and great pressure of the softened iron overburden.
In reality, I think that there would be major penetration of iron. It is a definite possibility that the bulk of the iron will descend further, perhaps even to join with the existing iron core. The extra heat from compressing the crust might be enough to melt all of the iron, in which case it is certainly heading to the core. If this happens (and I think it would) it will take hundreds of millions of years to become Earth-like or Mars-like. Also note that the downward migration of the iron releases additional heat, so if the effect is significant it is also unstoppable, the core size is going to increase greatly.
Note that my basic model was unrealistic from the start (assuming a solid iron shell), in reality dropping from space ships the average drop height would be significantly higher and more energetic.
One major secondary effect, Mars rotation period would become about *10 times* as long since the iron has to accelerate up to match the rotational velocity of Mars. This would add another large quantity of kinetic energy to the iron (enough to cause some iron melting near the equator)
So how long to cool? Don't know, and its late and I'm tired so I'm stopping for now.
---
The assumptions of the Virial theorem do not apply in this artificial case, i.e., we do not start with a stable gravitational bound system of widely dispersed matter. We have a collection designed to collapse upon itself within one day. Even if we allow that the iron will interact and heat up during the infall, nearly all of the radiant energy will terminate on another packet of iron during infall. To reduce this effect, it is necessary to spread out the iron -- but this raises the distance of the drop more than offsetting the increased heat loss. There is also very little time for the heated iron to radiate away its heat before impact. So I don't expect any significant percentage of the heat to radiate away during infall.
What happens to the atmosphere of Mars? It too is heated to incandescence and will remain so as long as the iron remains that hot. I don't expect much of the atmosphere to be lost quickly since the escape velocity for IronMars will be even higher than Earth and the RMS gas velocity is only about 1 km/sec.
---
I do have a quibble with the problem as posed, do the aliens have antigravity? You can't simply drop iron from orbit, a straight drop required your cargo ships to simply hover in place. If you can do that, why did you have to make such a mess in the first place?
[Answer]
I’ll take a rough historical (and non hard science) stab at an answer.
Infant Earth’s theorized impact with [Theia](https://en.wikipedia.org/wiki/Theia_(planet)) seems like an interesting model for comparison here. We don’t seem to have a particularly clear idea of what Earth looked like at the time, but this event would have introduced quite a bit of material into the Earth’s vicinity (much of it theoretically forming the moon).
At present, it’s thought that the impact event occurred around [4.4-4.45](https://en.wikipedia.org/wiki/Giant_impact_hypothesis) billion years ago. This would have stirred things up quite a bit and required a cooling period, perhaps not unlike you bombarding the surface with enough iron to double the diameter of Mars.
Determining how long you’d need to wait before the atmosphere reached “pleasant” temperatures is a bigger challenge. It seems that the Earth’s crust cooled and solidified around 4.1 billion years ago, though I’m sure it wouldn’t have been a nice place to be. Earth’s first lifeforms are believed to have developed around [3.8 billion years ago](http://www.ecology.com/2011/09/10/earths-beginnings-origins-life/) with the beginning of the Archean Period. That puts you at around 600 million years, plus a few hundred million years to get to your preferred temperatures (assuming that the Earth was still a pretty hostile environment even during the Archean Period.)
There are, of course, shortcomings to using this model.
* The giant impact hypothesis, while a leading theory, may not be fully
correct.
* Earth was most likely still molten when the impact occurred, as
opposed to the fully solidified Mars.
* Further analysis is needed between the start of the Archean period
and your target environmental temperatures (though more
specification of the target may be useful).
[Answer]
The parameter to the problem where changed midway through my calculation, so I won't finish it. I'll leave this here if someone wants to take over.
Firstly we need to know the thickness of the iron pool.
$\text{Earth's mass} = E\_m = 5.972 \cdot 10 ^{24}\text{kg}$
$\text{Mars's mass} = M\_m = 6.39 \cdot 10 ^ {23}\text{kg}$
$\text{Difference} = E\_m - M\_m = 5.333 \cdot 10 ^{24}\text{kg}$
$\text{Iron's density} = D\_i = 7850\text{kg}/\text{m}^3$
$\text{Volume of Iron} = V\_i = \text{Difference} / D\_i = 6.794 \cdot 10^{20}$
$\text{Radius of Mars} = R\_m = 3.39 \cdot 10 ^ 6\text{m}$
Volume of a spherical shell
$Vi = 4/3 Pi (R\_{mnew}^3 - R\_m^3) <=> R\_{mnew} = sqrt3(3V\_i/(4\pi) + R\_m^3) = 5.859 × 10^6\text{m} $
Height of iron is:
$h = R\_{mnew} - R\_m = 2.469 \cdot 10^6\text{m}$
which makes the radius of Mars slightly lower than Earth's. This is a quite unrealistic result, because compression would play a big role into reducing this value.
There are many things that are hard to predict accurately. What would happen to the atmosphere?
Let's assume the aliens choose the lowest temperature at which iron is liquid, it's melting point. Don't waste too much energy and the extra energy from the fall would keep it liquid to spread it evenly. Another inaccuracy, we ignore pressure.
$M\_{pi} = 1538ºC$
Due to low amount of oxygen in the Mars atmosphere, I'll assume there's just some red rust on the iron.
$\text{emissivity} = \epsilon = 0.6$
$\text{reflectivity} = Ref = 1 - \epsilon = 0.4 $
Next we want to know the equilibrium temperature of the planet.
$\text{Effective temperature of the Sun} = T\_s = 5780K$
$\text{Distance from Mars to the Sun} = D = 2.279\*10^{11}\text{m}$
Using planet's emissivity instead of a black body:
$T\_eq = T\_s \* Ref^{2/4} \* \sqrt( R\_m / (2\* D) ) = 9.97\text{K}$
Yes, it will get really really cold eventually. Let's make another assumption and consider the iron shell is empty inside. We've made so many up until now that every error will cancel out and we'll get the right result. Hopefully.
[Answer]
Since Mars' atmosphere is only 1% of earth's atmosphere (in mass) so there would hardly be any fireworks visible from earth even with powerful telescopes. There would only be ultra-large clouds of red dust flying around though (iron oxide dust, that constitutes the surface of Mars).
Having an extremely light atmosphere also means that Mars' greenhouse capability is virtually zero, and any heat generated by the event of impact would radiate away into space far quicker than it would on earth. I cannot provide an exact number though, as I am unaware of precise values in this subject.
Also, I think you forgot a very important effect which would result due to this incredible increase in Mars' mass. I am talking about the asteroid belt between Mars and Jupiter. With nearly 3 times increase in Mars' mass, the gravitational balance that keeps the asteroid belt in it's place would be severely disturbed and a lot of asteroids would be deviating from their orbits towards Mars ... and beyond it ... towards ... don't ask me. The very thought horrifies me.
---
My answer above, is written assuming that the additional iron mass was dumped on the red planet as dust and tiny iron fragments, not as a single planetary sized asteroid. If you are talking about *THAT*, then it would probably end Mars' existence as a planet as both objects would crash with a force that would crack Mars to the core and pulverize it to dust. Most of the planetoid mass would vaporize from the heat of impact. The phase-2 damage to earth would also be immensely huge. Falling debris and asteroids would end all life on earth (at least all multicellular life) and rip giant fissures on the crust.
[Answer]
I suspect the surface will actually be cold from the beginning.
Here is one way to model it. Imagine you take a pillar of iron about 2000km tall, and drop it from 150km. As the pillar strikes the surface of mars, the bottom of the pillar will heat up tremendously through lithobraking and the weight and heat will drive it deep into the surface of mars - I suspect though that being dropped from a mere 150km the 2000km pillar of iron wont embed itself all the way into mars, and the top of it will remain poking out, with the top still being cold, not having experienced any lithobraking and indeed being far away from that heat.
Now take billions of those pillars and drop them all around mars the bottoms will certainly be heated to extreme temperatures in the crunch zone, but the tops will remain cold. (you might want to imagine the pillars being slightly tapered, so when they all press together they form a neat sphere)
In this modelling the boundary between Mars and the iron is super heated to tens of thousands of degrees, but that heat is contained by the mass of iron on top, and that mass of iron on top experiences no heating as such.
And I suspect it doesn't matter whether you use billions of pillars, or trillions of iron ingots, or even a monolithic iron shell. If all the iron is placed 150km above mars, and all dropped simultaneously, that is what you'll get: A super molten layer of iron under a cold crust of iron and under that the "cold" core of mars (maybe heated by being slammed in all directions by 90% earth mass of falling iron). There might be volcanoes of molten iron emerging through fault lines in the collapsing iron, or it might be perfectly contained, nevertheless I am quite certain there will be large areas of cold iron.
Now over time the heat of the super molten layer will migrate upwards and downwards, it certainly seems there is enough heat to heat all the iron to uncomfortable temperatures.
The question is then, how quickly will it radiate out? Will it radiate out quickly enough to super heat the surface? Or will it just radiate out slowly, perhaps gently radiating over hundreds of thousands of years?
I suspect it will be like Earth. There is enough thermal energy in Earth to heat all of Earth to a most uncomfortable temperature, in fact the average temperature of Earth is much hotter than our Iron Mars would be. But the rate of heat transfer from the core to the surface is too slow to do anything more than slightly warm the surface, and even with the wonderful conductive qualities of iron, there would be still be 2000km of it to act as an insulator.
So that is my answer: that the surface of Iron Mars will initially be cold, and over time will be slightly warmed, but not uncomfortably so.
If you *want* a cataclysmic heating of the surface, then the constraint of releasing all the iron at once should be relaxed, then the iron which is released later will also have a chance to slam into the surface like meteors.
] |
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