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[Question]
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Antimatter annihilation is the best source of energy per weight. However, antimatter is not readily available anywhere within reachable distance, it's insanely difficult to produce and contain.
However, if a society with our current level of technology (or just slightly more advanced) discovered a source of antimatter, how could they use it?
1. Just having a big chunk of antimatter floating in space. I doubt that we could harvest it. Maybe we could bombard it with particles to make it glow, and then harvest that energy, but I guess it wouldn't be much different than harvesting solar energy directly.
2. If the first version cannot be used at all, let's make it much easier. We get the antimatter in nice self-contained packages (recovered from an alien shipwreck, or trading for it with a different civilization, it doesn't matter). In such a container, the size of a car battery, there are a few grams of antimatter, electromagnetically kept away from annihilating the walls of the container. There is a valve which can be opened to release a thin stream of antimatter, but once out, it is of course free to annihilate itself with any matter, including the container itself, as it is only protected from the inside. So it should either be opened in vacuum or the antimatter otherwise used up or guided by various means to its intended place to be annihilated.
How can such a source of antimatter provide useful work? Would it just be used to heat water which will drive steam turbines, like in a nuclear power plant? Or are there much more effective ways to extract useful work out of it? How could it be used to propel spacecraft?
How could we with our level of technology utilize such a source of antimatter? Besides threatening to use it as a weapon by breaking open the container.
[Answer]
As has been mentioned, a chunk of anti-matter in space would end up annihilating off of something, probably interstellar hydrogen. This would likely make it a bit too risky to try to harvest or use. Or it would have completely annihilated by now. Discovery of a pre-existing supply of advanced technology stored Antimatter, or discovery of a hyper efficient means of producing it would be a more likely scenario.
As for uses, here are a few.
1. Heat water, spin turbines, produce electricity. This isn't terribly efficient, because a lot of the energy from Antimatter annihilation isn't easy to capture.
2. Annihilate small (read: miniscule) quantities at a time to produce controlled explosions that can be used as propulsion. This would be a Bad Ideatm in atmosphere, as we'd be spewing Gamma Radiation all over the place. However, there's already plenty of radiation in outer space, so it could safely be used there. Refer to articles on 'nuclear propulsion' to get the idea of a design for this ([ref](http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion), [ref](http://en.wikipedia.org/wiki/Antimatter-catalyzed_nuclear_pulse_propulsion), and [ref](http://en.wikipedia.org/wiki/Antimatter_rocket)).
3. Use a smaller quantity of anti-matter to rapidly heat a propellent and expel it from the ship, producing a more controlled, less explosive propulsion system.
4. SCIENCE: Annihilating anti-matter in a controlled environment can show us a lot about the function of the universe (most energetic reaction possible). Having easy access to this would allow for a lot more experiments, that could ultimately result in some very useful knowledge
5. Anti-matter explosives: For when you don't mind making an enemy of the entire world. Or to crack asteroids apart for mining purposes (or to prevent a terrestrial impact)
6. Medical uses: Matter-Antimatter reactions have shown experimental usefulness in both medical imaging ([ref](http://en.wikipedia.org/wiki/Positron_emission_tomography)), and a potential ability to treat certain cancers ([ref](http://www.engr.psu.edu/antimatter/Papers/pbar_med.pdf)). Free access to Antimatter may expand this field.
Please note, this last bit is PURELY theoretical.
It has been theorized that Antimatter does NOT react to gravity the same way that normal matter does. While many scientists assume that gravity will effect matter and anti-matter in the same way, there are theories out there that suggest that matter and anti-matter will gravitationally repel each other. ([ref](http://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter#Theories_of_gravitational_repulsion)) We've never had our hands on a big enough chunk of antimatter, or even a small one for long enough to make any sort of experiment. If their theories are correct, Antimatter may be the gateway to anti-gravity systems...which could utterly revolutionize space exploration by reducing the energy required to break Earth's gravity well. Naturally, this would be extremely dangerous if the anti-matter containment were breached.
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Blocks of antimatter in space would go poorly. They would be lit up with annihilation events from interstellar hydrogen. You probably need something to keep the normal matter away from the anti-matter, so alien capsules are a good bet.
The annihilation of positrons with electrons (the most benign of the antimatter collisions) kick off a pair of gamma rays with an energy of 511 keV, which is quite a lot. Using a water bath to turn them to heat is not an unreasonable approach, though trying to find ways to convert them to lower energy photons for absorption via photovoltaic would be interesting.
*On a tangential note, research for the previous paragraph lead me across [Positron Emission Tomography](http://en.wikipedia.org/wiki/Positron_emission_tomography) (PET) scans. Seriously, how insane is it that we have medical uses for antimatter annihilation! Why are we bothering to write fiction anymore? The real world has us beat these days*
I do see an interesting question of why the aliens are sending us antimatter. So far we don't really know how to make new matter, so whenever we annihilate matter and anti-matter to power our steam turbines, we're losing matter that we just can't get back. Sure, it's only a few grams... but could they be playing a long game? We'll run out of planet eventually.
[Answer]
With option 2, assuming that the alien anti-matter containers are crash-proof, I'd use the anti-matter to make rockets with. Space flight is an area where a comoact, low-mass source of energy is practically paramount.
**Not** rockets that mix the matter and anti-matter at a 1:1 ratio, but rather using a very little bit of anti-matter to heat a lot of propellant. This could have twice the performance of the space shuttle's main engines.
Beyond earth orbit, using an anti-matter box to provide electrical power to a spacecraft and to ignite fusion fuel pellets could be leaps and bounds beyond any near-term interplanetary propulsion system.
It could certainly be used for ground-based power generation, by using it to to turn water into steam directly. Or by igniting fusion fuel pellets, though I imagine that'd be more complicated.
I'll leave it as an exercise for the reader how exactly we'd figure out how turning on dial lets out a little bit of anti-matter. Or how many researchers we'd need to go through to find out...
[Answer]
Antimatter is insanely dangerous. A large chunk of antimatter in space would rapidly annihilate, due to asteroids, tiny chunks of debris, interstellar hydrogen, and pretty much anything else. Even large amounts of charged particles will set it off, not to mention that no mechanical device can touch antimatter without catastrophic explosion. (this assumes the antimatter chunk is solid antimatter)
Stored in an electromagnetic container makes it far safer, but still not very safe. With sophisticated enough transport devices (like CERN's supermagnets capable of holding charged antiparticles) we could try and siphon it off to a reaction chamber where it is annihilated with air or any other matter. This, however, releases a lot of high-energy EM radiation (gamma rays) which could either be harvested by very high threshold photoelectric materials (not a bad idea) or by deflecting it at a large mass of water to heat it, vaporizing it. Or we could direct antimatter at the water itself, causing some to be destroyed while superheating the rest; but, since a large body of water's surface area to volume ratio isn't too good, it may not be the most efficient way to harvest it.
On a more mathematical note, let's find an actual energy amount of a single antimatter package. Assuming there are 3 grams of antimatter per package (bottom line) then using E=mc^2 (antimatter has 100% mass-energy conversion) yields around 2.6962655e+17 joules, compared to the Hiroshima explosion, where 700 milligrams of uranium was converted (6.2913e+13 joules). This amount of energy suddenly being released is a VERY bad idea, so a more gradual approach is a better way to harvest. Considering the amount of energy here, we can acheive power greater than a nuclear reactor.
TL;DR - antimatter explodes when it touches anything so we gradually siphon it into water and boil it to power a turbine.
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# Linked:
[What would the conditions on a methane world be like?](https://worldbuilding.stackexchange.com/questions/14312/what-would-the-conditions-on-a-methane-world-be-like)
[What would animal life on a methane world look like and how would it evolve?](https://worldbuilding.stackexchange.com/questions/14316/what-would-animal-life-on-a-methane-world-look-like-and-how-would-it-evolve)
# Background:
Okay, an intelligent race has evolved on a world like Titan where methane is the dominant solvent. There is no oxygen in this world, so you cannot use flames. How could this race get an equivalent of fire without modern technology.
**Question**
Assume that they currently lack any tech other than their bare hands and conditions are as close to those on Titan as possible. If this needs narrowing down just drop a comment.
Sorry about the 'space travel' title. I was thinking of my next question :-)
[Answer]
Amongst other categorizations, chemical reactions / reactants may be divided into two types: oxidizers and reducers.
On our planet, the reducers are stored as ready forms of energy because oxidizers are freely available to perform the reaction.
On a planet with a reducing atmosphere (e.g. a predominantly methane atmosphere), then life might store energy in the form of stable oxidizers. This stable oxidizer need not be oxygen or even provide oxygen to the reaction as the halogen gases (and other elements & compounds) also serve as oxidizers - but let's assume that this alien environment does use oxygen as its oxidizer (energy storage).
Some compounds that might serve (as energy storage / oxidizer in a reducing atmosphere):
* Hydrogen peroxide (liquid $H\_2O\_2 $)
* Ammonium perchlorate (solid $ NH\_4ClO\_4 $)
* Dinitrogen Tetroxide (liquid $ N\_2O\_4 $)
* Nitronium perchlorate (solid $ NO\_2ClO\_4 $)
* Nitrous Oxide (gas $ N\_2O $)
* Red fuming nitric acid (liquid 84% $ HNO\_3 + $ 13% $ N\_2O\_4 +$ 2% $ H\_2O $)
* White fuming nitric acid (liquid nearly pure $ HNO\_3 $ )
Some of these are hypergolic, spontaneously igniting in the presence of certain other chemicals.
* Nitronium perchlorate is hypergolic in the presence of organic chemicals.
* Dinitrogen tetroxide is hypergolic in the presence of hydrazine (an
organic chemical).
* Hydrogen peroxide is hypergolic in the presence of the liquid
C-Stoff.
* Others are more stable.
Ammonium Perchlorate is the oxidizer used in the Space Shuttle Solid Rocket Boosters and is one of the more stable of *these* chemicals.
So the inhabitants of your methane world would use their grasping manipulators to hold crystals of Ammonium Perchlorate they've collected from the nearby forest. Supplying sufficient heat would break down the crystals and begin combusting in the methane atmosphere in a self-sustaining fire.
A Side Note: the list of Oxidizers that I produced were ones specifically taken from rocket fuels, which in turn were selected because they are highly energetic. In reality, we could select from a much wider range of oxidizers that include some that are much more stable but also less energetic.
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By extremely high gravity, I specifically mean around 28 Gs. I recently asked [this question](https://worldbuilding.stackexchange.com/questions/5162/is-there-any-feasible-way-to-inhabit-the-sun) with regards to inhabiting the sun, and surviving in the sun's gravity seems like one of the major challenges.
I'm interested in what would be needed to allow humans to survive in such an environment, both in terms of what modifications can be made to a habitat for the humans to live in, as well as what modifications can be made to the settlers themselves.
I'd like to limit technology to 'things that could be achieved with technology we have either created or are working on', and reasonable extensions of those things. I'm assuming, for example, that we have fusion power (only way I can think of that we can power the cooling systems), and that we have in-situ genetic modification via viral DNA modification, since those are both research targets. I'd likewise consider some basic nanobots in the realm of possibility, but would like to stay away from things like large scale anitmatter production and gravity generators, since those require major breakthroughs in science that we aren't terribly close to.
Within those constraints, what can I do to allow humans to inhabit a 28 G environment for an extended period of time?
[Answer]
Ha! An obscure question I asked somewhere else now becomes relevant!
A while ago, I asked [this](https://biology.stackexchange.com/questions/23074/what-are-the-effects-of-long-term-liquid-breathing) question on Biology about [liquid breathing](https://en.wikipedia.org/wiki/Liquid_breathing). It's currently unanswered, and may stay that way forever, but it's now applicable here, which I think is cool. Anyway. . .
Liquid breathing is (as Wikipedia puts it)
>
> a form of respiration in which a normally air-breathing organism breathes an oxygen-rich liquid (such as a perfluorocarbon), rather than breathing air.
>
>
>
[Perfluorocarbons](https://en.wikipedia.org/wiki/Fluorocarbon) are strange compounds made out of carbon and fluorine. They can carry oxygen, and a *lot* of it. They are stable and have strong inter-atomic bonds. Almost all are liquid at room temperature. Also, they aren't flammable, which turns out to be a really good thing.
More importantly, they may be used in liquid breathing, assuming they are flooded with oxygen. There are two techniques used in liquid breathing; the one we'll have to choose is known as Total Liquid Ventilation (or TLV). It is (no surprise) the technique of completely filling lungs with oxygen-rich prefluorocarbons.
Why does this matter? Liquid breathing can help counteract G-forces. From Wikipedia,
>
> Liquid immersion provides a way to reduce the physical stress of G forces. Forces applied to fluids are distributed as omnidirectional pressures. Because liquids cannot be practically compressed, they do not change density under high acceleration such as performed in aerial maneuvers or space travel. A person immersed in liquid of the same density as tissue has acceleration forces distributed around the body, rather than applied at a single point such as a seat or harness straps. This principle is used in a new type of G-suit called the Libelle G-suit, which allows aircraft pilots to remain conscious and functioning at more than 10 G acceleration by surrounding them with water in a rigid suit.
>
>
>
Unfortunately, the limit for this technique is somewhere around 20 G (and we're being generous here). Wikipedia does say that it *might* be possible by raising the density level of the liquid, but there's still a limit.
So all you have to do is fill the planet with an ocean of perfluorocarbons, and you're set!$^1$ Of course, most of the perfluorocarbons would evaporate at the temperatures in, on or near the Sun, but hey, you can't have everything.
$^1$ *Note: The one huge downside here is that liquid breathing hasn't really been tested on humans before for long durations, so you're going to have to hope you get lucky.*
[Answer]
If you're talking about living on the Sun, (leaving aside for a second the tremendous heat-disposal problems), you have to understand that the Sun doesn't actually have a surface. [At the bottom of the photosphere](http://solar-center.stanford.edu/vitalstats.html) the density is $10^{-9} g/cm^3$, a pretty good vacuum. The reason we see a cleanish circle around the sun is a mere optical illusion (the mathematical point where a photon travels the length equal to the 2R of the Sun before it gets absorbed) so there is no clear delineation of where the Sun ends and the photosphere begins.
So any human construct (assuming the goal would not be to sink towards the center of the sun in seconds) would effectively have to be in orbit, even if that orbit is at an "altitude" of 0 km (with some extra oomph to overcome friction due to the intense solar wind). If it is in orbit, anyone on board will experience zero-G.
[Answer]
## This can't be done by anything resembling current humans
A serious re-work of the human body would be required.
Currently humans can survive very high g-forces for fractions of a second, but any sustained force over a few g will cause an untrained person to black out. A [g-suit](https://en.wikipedia.org/wiki/G-suit) can help.
>
> The resting g-tolerance of a typical person is anywhere from 3-5 g depending on the person. A g-suit will typically add 1 g of tolerance to that limit.
>
>
>
But not by much.
The record holder for maximum sustained g force goes to [John Stapp](https://en.wikipedia.org/wiki/John_Stapp) who experienced a peak of more than 46 g, with more than 25 g for 1.1 seconds on a rocket sled. While he didn't die, his vision was damaged for the rest of his life.
## Blood can't get to the brain
The big problem is keeping blood going to the brain. That's a problem very low on [Maslow's hierarchy](https://en.wikipedia.org/wiki/Maslow%27s_hierarchy_of_needs). The heart isn't strong enough to keep blood pumping against that kind of acceleration. That's the immediate problem. It might be overcome with special implants, suits, and liquid immersion. But there are more problems.
## A muscle cell isn't strong enough to even lift itself alone
If cyborg humans were able to install powerful pumps and reinforce blood vessels and capillaries to withstand the pressure required to raise blood to head level, they would still have the problem of raising a fork to their mouth. Not too much because of the fork that now weighs 20 newtons, but the arm that weighs over a thousand newtons. Unfortunately adding more muscle does not help. Humans can only lift about three times their own weight, so no matter the size of the muscle, it simply can't even lift itself.
## How to proceed?
You'll need some brains in vats connected to [super robotic bodies](http://www.gizmag.com/artificial-muscles-robots-nus/28923/). Or, ideally, human brains uploaded into supercomputers mounted on super robotic bodies. It'll be far better than the puddle that was a human body before. While there isn't any obvious paths to such the science that can allow this, I can't imagine why it wouldn't one day be possible.
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Humans cannot survive in biological form such gravitation forces, as explained by others - only after singularity, consciences uploaded to computer.
[Answer]
The real problem is that **the heart cant deliver blood against 9G**.
All fighter aircraft are red-lined at 9g (most modern fighters can do more if programmed to ignore the red-line) because there is no pilot who can survive more than 9G. And even this 9G is only possible for a short amount of time.
Overall the problem is about the force which the heart usually impinges on blood. At 9G sustained, the blood cant reach the brain. The return circulation will be prevented if the acceleration is sustained long enough, blood will concentrate on the lower parts of the body.
In WW2 Germany experimented with pilots laying prone. This allowed higher accelerations to be sustained. But practical considerations prevented the adoption of prone piloting.
Russians developed anti-G suits for their fighter pilots, those compress the lower parts of the body, to force blood up to the heart and head. But this has limitations.
All those problems are found on fighter aircraft, where aircraft and pilot are subject to intermittent maneuvering (and consequently acceleration). On a continuous situation humans would support much less than 9G.
Besides that, this 9G is rated for trained crew, common people usually pass out under much less G's.
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I'm working on a project involving the evolution of life on different hypothetical habitable planets. In imagining different atmospheres on planets of different masses, I'm wondering how a planet's size might affect volcanic activity. Would a more massive rocky world have a thicker crust? And would the thickness of the crust affect the power of volcanoes? I would assume a planet with lower gravity would have a crust that breaks more easily and the volcanoes would release their magma and gases more frequently but with less force. Does this make sense?
Also, I'm excluding moons in our solar system as examples in answering this question (f/e Io has intense volcanism because of extreme tidal forces).
[Answer]
## Rayleigh number
Copying from [a thing I did on Astronomy SE on this very subject](https://astronomy.stackexchange.com/questions/51586/geological-tectonic-thermal-etc-implications-of-rayleigh-numbers-%E2%89%A5-100-000-000):
>
> The competition between forcing by thermal buoyancy and damping by
> viscosity and thermal diffusion is characterized by a dimensionless
> ratio called the Rayleigh number.
>
>
>
In other words, a [Rayleigh number](https://en.wikipedia.org/wiki/Rayleigh_number) represents the ratio between how much hot mass in a [convection current](https://en.wikipedia.org/wiki/Convection) rises and how much the [viscosity](https://en.wikipedia.org/wiki/Viscosity) and [thermal conductivity](https://en.wikipedia.org/wiki/Thermal_conductivity) of the mass stop it from rising and bleed away its heat, respectively. In this case, the mass in question is the mantle of a terrestrial planet, and the convection current in question is [mantle convection](https://en.wikipedia.org/wiki/Mantle_convection).
Per [*Mantle Convection in Terrestrial Planets*](https://oxfordre.com/planetaryscience/display/10.1093/acrefore/9780190647926.001.0001/acrefore-9780190647926-e-109;jsessionid=E0978952D39C68EC05DEED914229758C):
>
> ùëÖùëé (Rayleigh number) needs to exceed a certain value, called the
> critical Rayleigh number [ùëÖùëéùëê], in order to excite convective flow.
> The value of ùëÖùëéùëê is typically on the order of 1,000, with the exact
> value depending on the thermal and mechanical properties of the
> horizontal boundaries, (e.g., whether the boundary is rigid or open to
> the air or space, see Chandrasekhar, 1961).
>
>
>
Therefore, it can be concluded that, if, within a body's mantle, the ratio of "stuff-forcing-its-way-up" to "stuff-being-held-down" is ≤ ~1,000, said body won't experience convective flow in its mantle. As far as I know, convective flow in the mantle is necessary for a body to have plate tectonics; this is supported by the fact that the Earth and Venus, with the highest Rayleigh numbers calculated in *Mantle Convection in Terrestrial Planets*, are fairly volcanically active, whereas Mercury, with the lowest one, is a dead rock, and Mars, with the second-lowest one, features stagnant-lid tectonics, if I recall correctly.
>
> Assuming their material properties are similar to Earth’s, we can
> estimate the Rayleigh numbers for the mantles of other terrestrial
> planets: ${10}^4$ for Mercury, ${10}^7$ for Venus, and ${10}^6$ for Mars. With the
> exception of Mercury, whose $Ra$ is at most an order of magnitude above
> critical, the mantle of the rocky planets in the solar system appear
> to be cooling predominantly by convection.
>
>
>
The equation for finding a Rayleigh number is: $Ra = \frac{ \rho g \alpha \Delta Td^3 }{\upsilon \kappa}$ where:
* $\rho$ = density of mantle
* g = planet's gravity
* $\alpha$ = [thermal expansivity](https://en.wikipedia.org/wiki/Thermal_expansion) of mantle
* $\Delta T$ = difference in temperature between top and bottom boundaries of mantle
* *d* = thickness of mantle
* $\upsilon$ = viscosity of mantle
* $\kappa$ = [thermal diffusivity](https://en.wikipedia.org/wiki/Thermal_diffusivity) of mantle
Per [the one answer](https://astronomy.stackexchange.com/a/51588/42355) to my Astronomy SE question, the largest possible Rayleigh number is within the ballpark of $3 x {10}^8$. The Rayleigh number *Mantle Convection in Terrestrial Planets* calculates for the Earth is ${10}^7$, which gets you your answer: even the most massive terrestrial planet is only going to have $3 x {10}^8$ / ${10}^7$ = 30 times more tectonic activity than the Earth.
However, consider that "30x more volcanic activity" is a *lot*. [Io](https://en.wikipedia.org/wiki/Io_(moon)), for instance, is likely less than 30 times more tectonically active than the Earth, and it's the closest thing to [Mustafar](https://starwars.fandom.com/wiki/Mustafar) in our solar system.
Without you providing specific statistics on the specific planets in question (i.e. the ones for that Rayleigh number equation) I would say that, for the purposes of your project, you can have tectonically active planets with a Rayleigh number between ${10}^3$ (defined in that paper as when tectonic activity halts) and $3x{10}^8$ (picture of hell). Note, however, that if you have something below ${10}^7$ (i.e. Earth and Venus), you're probably going to have [stagnant-lid tectonics](https://astronomy.stackexchange.com/a/40949/42355) like Mars, which aren't suitable for life as we know it but may be useful for what you're working on. I'm unsure about higher numbers.
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[Question]
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In short, please provide me with a scientifically plausible biochemical scheme for how an organism can harness the energy of long-wavelength electromagnetic radiation to produce food for itself. Thank you.
**Requirements of the answer:**
* The organism in question should synthesize energetic compounds using
the energy of incident electromagnetic waves with wavelengths over 1
mm (i.e. microwave or radio waves). It should not utilize anything
with a shorter wavelength, but it's okay if the organism can only
utilize a narrow wave band within that range.
* Such a "long-wavelength photosynthesis" process must be able to
happen at room temperature and in the earth's atmosphere. But the
chemical compounds involved in the process do not need to be
compatible with the biochemistry of life on earth.
* The organism in question should be able to handle 1000 W/m2 of
incident radiation (equivalent to intense sunlight at noon). However,
it doesn't need to be too efficient in terms of energy. I expect it
to convert at least 6% of the total energy of incident photons that
are within the wave band it can utilize. (That is lower than the corresponding efficiency of chlorophyll, which is about 9%.)
**Given condition:**
* The organism in question is unable to form any delicate macroscopic
shapes. (You can imagine it like sponges or lichens.) So it can not
grow large parabolic antennas or parts of heat engines. But it can
grow to a few centimetres thick.
**Note:** This question is not asking about how to form an environment that is abundant in microwave and radio waves, and it is not asking about how the organism in question could have evolved.
**Link to the opposite question:** [Photosynthetic life using *gamma* radiation](https://worldbuilding.stackexchange.com/questions/192460/photosynthetic-life-using-gamma-radiation/192468#192468)
[Answer]
**A Snowflake, a symphony of phonons and a shower of photons.**
The issue with longer wavelengths is twofold:
* Each photon has less energy the longer the wavelength, making it unable to function alone the way higher-energy short-wavelength photons can.
* Photons of longer wavelength are (probabilistically speaking) less likely to interact with a molecule of the same size as regular chlorophyll.
On Earth, we've chlorophyll that absorbs photons of a particular set of wavelengths converting the energy into excited electrons - the chlorophyll molecules do this by acting as little aerials, tuned to these wavelengths:
[](https://i.stack.imgur.com/wemRZ.png)
[Labproducts](https://labproducts.dhigroup.com/ProductDescriptions/PhytoplanktonPigmentStandards/ChlorophyllB.aspx), 2022, fair usage.
It's the tail of the molecule acting in concert with the ring part with the magnesium in the middle provides the tuning.
Magnesium's great, it's got just the right availability in the cosmos, and a convenient requirement of energy-levels to shed and capture electrons.
So, to counter the first sticking-point above, you need bigger molecules to capture the photons. The second point is dealt with by capturing more than one at a time.
You can do this by taking a leaf out of NASA's book when they grew genetically engineered aerials (technically, genetic algorithms evolved them, then NASA made the "survivor" with metal):
[](https://i.stack.imgur.com/PnWP3.png)
JPS, CIT [Lunar](http://www.lunar.org/docs/nasa/antennas.shtml) 1992-2022, fair usage.
The phonons come into it when you have several photons simultaneously (or nearly so) hitting the target molecule - each making a wave in the surface electrons of the substance like dropping several tiny pebbles around the edges of a puddle at the same time making ripples. These ripples all converge at the active centre where the chemistry takes-place reinforcing each-other's energy, the total energy being just right to make the magic happen.
The whole molecule would ring like a thousand tinkling bells all at once, the brighter the light, the higher and more intense the ringing.
**To sum-up.**
Keep the basic chemistry the same with magnesium, but make the surrounding structure more like a snowflake (or a version of NASA's aerial). Of course, the longer the wavelength, the bigger the molecule:
[](https://i.stack.imgur.com/BOZn6.png)
Komarechka via [fstoppers](https://fstoppers.com/originals/how-snowflake-photographer-turned-his-passion-money-286558), 2022, fair usage.
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[Question]
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Most if not all jumpjets (and jetpacks) in any genre have some kind of neural link or unexplained control mechanism that might as well be a neural link. However I want to have a controlscheme for my jumpjet with several requirements:
* it has no neural link
* its controlscheme is known and explained
* the controls leave the hands free to handle objects, such as carrying someone in their arms during a rescue\*♤
* the jumpjet needs to be able to perform the following maneuvers:
-- jump. The jumpjet launches in the air, the user needs to control how long this jump takes to make sure they reach the height necessary (or dont reach too high).
-- "hover". The jumpjet uses its propulsion to maintain height/slow down the descent and control the arc of the jump.
-- land. The user needs to be able to stop the horizontal and vertical speed for a safe landing, requiring a potential strong burst to slow down at the last moment.
-- control direction. The jumpjet user needs to be able to correct for miscalculated jumps, wind or pick an entirely different direction, possibly even backwards.
-- the user should not be at high risk of accidentally activating the jumpjet. You dont want to start a jump by accident indoors for example.
I am OK with controlschemes that do not satisfy all of these since its probably a tall order, but the question that satisfies most of these points will be accepted.
\*how and where the propulsion is located is not relevant for the question, assume its well-designed.
♤ *this means that any weight distribution controlschemes are not possible* as it would unbalance the jumpjet towards the weight you are carrying!
[Answer]
**Feet**
It's very quite simple. If hands and brain are out, then the feet is the preferable solution. To ascend, point your toes downwards. To descend, point your toes upwards. (This is based off the motion of driving a car - pushing your foot down is linked mentally towards triggering something.) To control direction, rotate your feet. Seems simple enough.
The only downside is that feet are commonly used for walking - so how do you prevent the jet from firing accidentally? The trick to this *also* seems simple enough - curling your toes. While walking/sprinting/jogging, a human does not curl his toes, it is an unnatural act. And a human *especially* will not curl all 10 of them at once unless fully deliberate. So the the trigger for the jet is to curl all 10 toes at once.
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# Tongue Operated Drive System
Frequently, when looking to solve a problem like this, it helps to take a look at how it's been solved in the real world, e.g, enabling people with quadriplegic paralysis to control devices. An interesting recent example, discussed in [Tongue-Operated Assistive Technology with Access to Common Smartphone Applications via Bluetooth Link](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4083017/) is the tongue drive system, which uses an inset-palate device like so:
[](https://i.stack.imgur.com/Yj7HQ.jpg)
Credit to The Verge
The basic set of controls here is intended for click-like interfaces, e.g, interfacing with a phone, but there's no reason it couldn't be adapted for something more like a flight control. Using a specific tongue motion (A repeated tongue click, perhaps?) to initiate the controls (along with tactical feedback when that happens to prevent accidental activation).
[Answer]
## A PID controller solve most of your concerns
Modern robotics are impossible without the use of feedback compensation systems. You cant just tell a system "do this much thrust" and ever expect it to work in the real world; instead, automation engineers use use gyro sensors, radio triangulation, and optical sensors in their their devices to detect any difference between where a part of a mechanism is in the real world, and where it should be according to its programming. (Optical sensors are especially useful in this case for determining things like when to slow down as you approach the ground for a landing.)
The [PID controller](https://en.wikipedia.org/wiki/PID_controller) changes the proportional trust of any components to get it to where it should be. So, if you were to pick up a heavy load like another person which offsets your weight, the PID controller would notice the lean caused by the extra weight and re-adjust the thrust balance appropriately to keep you flying straight and steady. So all of your concerns about a piolet needing to focus on weight distribution are easily dismissed assuming a setting with current or better technology.
If your flight is more of a single powerful impulse than a sustained thrust, you can put force sensors into your boots. That way you know your exact payload and approximate weight distribution before takeoff. Then once in the air, your flight control only needs to make minor adjustments to bring you down safely and on target.
## Fine motor control is paramount
While there are all sorts of ways to control a device without your hands (bite sensor, tongue sensor, eye movement sensor, voice command, etc.) When you are talking about a device that propels you through the air at high speeds without so much as role bars or a seat belt to save your life if something goes wrong, your top priority should be to have an interface that allows you the most precise and responsive control possible. With the user's life on the line, all other considerations should be considered secondary. When it comes to fine motor control, a persons hands will always be leaps and bounds more performant than any other physical interface you can chose. So the question then becomes not how to make the system hands free, but how to do other stuff while using your hands to control your jump jets.
While the OP does not mention why this person is using jump jets, we can generally assume it's because this person is some kind of solider, emergency responder, or tradesmen who just needs too get to a hard to reach place that people don't normally need to think about reaching in our day to day lives. So, this person likely has some tool of the trade that is already expected to occupy 1 or both hands. This could be a gun, a fireman's hook, a medical kit, a squeegee... does not matter. My point is no one ever needs to use jump jets unless they have some problem to work on when they get there, and for that they generally need a tool. So, just install the controller into whatever this tool of the trade is.
## How to design the interface
You will probably want a 3 factor safety like you see on many power tools just to make sure it does not go off by accident. So, one safety switch that is well out of the way that unlocks the system, when you know you are about to need it. Then require the pressing of two things at once to start it (Like R1 + Analogue shown below).
Once started, your control of the flight system is very similar to a half of a gaming controller. An analogue stick for your thumb lets you you steer while 2 finger buttons allow you to increase or decrease thrust/height. You could also add a few key combination macros like a double tap "up" to give your more of a jump than a controlled flight mode.
[](https://i.stack.imgur.com/KjROW.png)
As for carrying someone while using this, people like soldiers and fire fighters carry people all the time, and they do it without leaving behind their tools or weapons; so, assuming your protagonist is in decent shape, he could sling a person over his shoulders, and clamp the leg and arm with the tool in hand so as not to drop them, and then control the jump jets from more or less this stance:
[](https://i.stack.imgur.com/lpVXE.png)
If for whatever reason you do not have any tool-of-the-trade, just carry a 1-handed game pad in your pocket and you can put all the same controls onto it, and then some. You can still carry things in both arms while manipulating something like this in your one hand.
[](https://i.stack.imgur.com/dVF4O.png)
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**Skateboard style.**
[](https://i.stack.imgur.com/8WaCk.jpg)
<https://en.wikipedia.org/wiki/Ollie_(skateboarding)>
You pilot a skateboard using your legs and body, and leg motions relative to the body. Arms and hands are free though can be used to shift center of gravity.
If you need to rescue someone while skating you can keep skating.
[](https://i.stack.imgur.com/6vWYp.png)
<https://www.youtube.com/watch?v=9UcJ0MsS3fg>
Having your character ride a jump jet like a skateboard (maybe a snowboard because of the straps!) would open a range of actions that will be familiar and foreign at the same time which makes for fun fiction. Also you can borrow from the lingo of skating / boarding and apply those terms for your jumpjet corps.
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# Remote control
Someone else is doing the driving for you, so you can concentrate on other things such as shooting or holding someone else. The jumpjet is in effect a drone with a very special format, controlled by your buddy. You should hope that they know what they are doing.
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**Voice control and eye tracking**
You can give voice commands to the computer controlling the jumpjet.
It has multiple microphones so that it can triangulate all sounds and make sure commands come from the right source. You can refer to where you are looking. Even if it's not the main control method it can be used as a backup if you have your hands full.
Examples:
"Hover 20 m". "Go east". "Go to that car".
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**This question already has answers here**:
[Natural and affordable way to dye hair in medieval period?](/questions/200735/natural-and-affordable-way-to-dye-hair-in-medieval-period)
(5 answers)
Closed 2 years ago.
* The world is a sort of medieval era place with very widespread trade, so the character would have access to a range of materials from different climates
* The current colour is a blue-ish hue, but that's definitely not permanent- It could be any unnatural hair colour
* It could be clothing dye or any other sort of material accessible to commoners
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## Pick your color, if it can dye wool it will dye hair just fine.
Here is a great photo showing a list of known natural dyes, all are possible with medieval technology. several were not available in the real medieval era because they come from the Americas. You can also have things link woad, henna, and saffron for blue, reds, and orange respectively. Keep in mind as hair grow they will have to re-dye periodically no matter what, you can't dye something that does not exist yet. And of course bleaching your hair was a well known technique at the time.
Purity and boldness of color will be affected by cost of course, these would represent the more expensive dyes. keep in mind a commoner probably cannot afford expensive dye so they would be mostly limited to earth tones, nothing unnatural. These would be Henna (red/brown), Madder(red), onionskins (yellow), alderbark (orange), walnut (brown/black)
**For an unnatural color at low cost your best bet is green** which can be achieved with a variety of homemade dyes, although far fewer than you think. known ways to achieve that are.
Heather and alum
green lichen
Iris leaves
Pivet berries and salt (this can also produce a purplish red so may not be the best choice.)
[](https://i.stack.imgur.com/1oBYO.jpg)
These are also the ones that are not downright toxic, using lead (black) or lye bleaching were common at the time but were also toxic.
Note also depending on your initial hair color you may have to bleach it before dying, dye can't do much to black hair for instance.
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In medieval times dyes could be very expensive for certain tones, while being pretty common and cheap for other.
My grandmother (well past medieval times) used to dye her hair using walnuts and remembered that, while doing laundry with the old method (stacking layers of clothes and ashes, then pouring hot water multiple times), one should be careful to not use the ashes of a certain tree which would have dyed all the laundry with an unwanted color (I am not 100%, but I seem to remember it was rhododendron).
So, some dyes are surely pretty common, but don't expect any flashy or bright color: the reason why purple and red are colors associated with nobility is that in the past they were pretty expensive, so only well off people could afford paying for getting it. Unless your character is rich, they will have to settle for more dull/common ones.
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The main character in my novel-in-progress is an alien whose home planet has a yellow sky. This planet orbits Altair (an A7 main-sequence star) and has a nitrogen-oxygen atmosphere similar to Earth's, with a few notable differences:
* A much higher level of water vapor, resulting in the planet being mostly cloud-covered. (The clouds are not yellow, but clear sky, when it shows, is.)
* Higher barometric pressure. I don't have a numeric figure, but it isn't extreme. An inhabitant of this planet would likely suffer altitude sickness at the same elevation on Earth but would be unlikely to develop serious complications.
The air doesn't have to be human-breathable, but I need the reverse to be true. Toxic gas(es) would be pretty cool, but I don't know if it's plausible for the native oxygen-breathers to be unaffected. I've been told any particulate matter would settle when it rains, which isn't what I want; I'm looking for a permanently yellow sky. I've also considered the possibility of airborne microorganisms, possibly above the cloud layer (and thus not disrupted by rainfall), but I have no idea if that's plausible.
Is a yellow sky possible, given these constraints? How?
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**Yellow aurora.**
[](https://i.stack.imgur.com/Ijl8q.jpg)
<https://www.lemurialight.com/blogs/amazing-life/yellow-aurora>
Yellow is one of the colors possible for the aurora on Earth. Yellow is caused by charged paticles in the solar wind striking oxygen high in the atmosphere. The oxygen then emits yellow light.
This happens constantly on your planet. Because of the near constant haze, the pure yellow light emitted by oxygen is diffracted in the haze, such that the entire sky glows yellow.
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The air colour is caused by a [physical phenomenon](https://en.wikipedia.org/wiki/Rayleigh_scattering#Cause_of_the_blue_color_of_the_sky), the Rayleigh scattering. Absent this, the air away from the Sun would appear black, since there would be no light coming from directions others than the Sun's (basically the same that happens in space, or going high enough in the stratosphere: from the directions where no *direct* light source exists, we see no light, and therefore -- black. With stars).
Increasing the pressure will cause more scattering, the Sun will appear redder and the sky a stronger blue. Also, more light will be absorbed, so a darker shade of blue too (and finally black again, but without stars this time. You'd need a lot of atmosphere to do this, though; or lots and lots of suspended particulate matter, as in a nuclear winter).
The light arriving to the "far sky" *has no appreciable yellow component*. So, we need something to actively *produce* yellow light, for the sky to appear yellow. [Willk's answer](https://worldbuilding.stackexchange.com/a/186217/6933) has a very elegant solution to that.
The only way out *I* could see was your idea of a dispersed chemical. This would absorb the ultraviolet band, of which an A7 star has *lots*, re-radiating in the 580nm yellow band either through *frequency halving* or, much more common, yellow phosphorescence. Possibly some simple sulfur compound might do, and this could be continuously supplied by volcanism (the sky *did* have a yellowish tint after the Krakatau eruption, it is said).
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So the color of the Sky has a lot to do with Light Scattering. One Major factor for the scattering is the thiccnes (with double c !) of the Medium.
[](https://i.stack.imgur.com/6jgva.png)
As you can see here. Now what determainds the Color of the Sky on Sea Level is the "Base Color". For example, if you have a Base Color of a Light Blue, you get this:
[](https://i.stack.imgur.com/VBon7.png)
You will always end up with a Gradient no matter the base color. And lastly, another major factor is the Density of the Air. Lets incress the density to 5 Units in this example:
[](https://i.stack.imgur.com/dotAR.jpg)
So the main give away is that Density and Hight can be used to change the Gradients Intensity. You can get the color you want with both, but as you see, a higher density compresses the Gradient. And is also more Realistic.
The renders here dont take into account that the Atmosphere has a Falloff though. So Lets add that.Same base color but an Exponential Fallof for Density:
[](https://i.stack.imgur.com/xLv2B.png)
You can see how this affects things. To make a long story shot, for your Sky to be Yellow, you want the most right part of the Renders to be yellow. For that, we need to change the base color. This could work:
[](https://i.stack.imgur.com/Tzwl2.png)
To no one's supprise, an Orange Yellow with this HEX FFD115 is a good choice. But now to the interessting part, what gases would we need ? Well...
That is not so easy to say. See, Or Sky is Blue because the Blue Wave lenghts dont get Scattered that much. That is why the sky is Red during dawn because more Blue light gets scattered. So the Color actually mostly depends on the Density of the Atmosphere, and not so much the Gases inside of it. Sure they do play a big role but in the end, it matters how long the light has to travel. Or through how much. Venus and Titan both have Yellow skys. But if you Look at the Atmosphere of Venus, you see that most of it is Carbon Dioxide with some Nitrogen. Both of which are Colorless.
To answer your question, is a Yellow sky possible ? Yes. For the most part, the Density of the Atmosphere creates the Color so a very Dense atmosphere will create a Yellow sky on the Sea Level. But the Amount of Pressure needed is sort of High. You could go a different rout and just make the Atmosphere very Larg, but this creates even more problems.
But, since you create an Alien world, what is there to say that they didnt just evolve for such high Densitys?
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Your clouds are sulphur dioxide, your air is rich in S$\_8$, odourless and tasteless, and chlorine (Cl$\_2$) may make a contribution too; windborn iron-rich dust intensifies the yellow tint.
Your star is probably [K-Type](https://en.wikipedia.org/wiki/Stellar_classification#Class_K).
Source: <https://www.youtube.com/watch?v=L9MNC45Jr6Q>
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I know I can't simply scale up insect wings and place them on a human for them to work. I am creating a race that is constituted of small humanoids with dragonfly wings. How small do I have to make this race for them to both be able to fly and have moderate (or even advanced) mental aptitude? I am looking for both height and weight.
UPDATE-
I am looking for an IQ about 90 or above.
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It will depend on the conditions of the planet they live in. You see, insects breathe through a system of tracheas without the help of their circulatory system, meaning the oxygen goes from the tracheas straight to the tissues, allowing them to keep constantly oxygenated tissues and perform activities such as their fast movements and, of course, flight. The main issue to this system, however, is that this severely limits the maximum size of the insect according to the levels of oxygen available in the air. That's the reason why, in prehistoric earth, when oxygen levels were much higher, we could have 2 meter long centipedes and dragonflies which were around the size of modern crows. So, based on our own planet and [the largest dragonfly that ever existed](http://www.geologyin.com/2018/01/the-largest-insect-ever-existed-was.html?m=1) , your bugs could have a wingspan of around 2 ft (75 cm) and weight as much as 450 grams. Considering dragonflies already have very complex eyes and wing system, being the most successful predators of the modern era, with a 97% success rate when hunting), we can see that they already have a decently developed brain for an insect.
So, regarding size, your insect can grow to at least the size of a crow, maybe even larger depending on how dense is your atmosphere and how much oxygen is available in the air. Regarding shape however, I honestly think they'd look more like something between an insect and a human than a humanoid with an exoskeleton, as the dragonfly is shaped to be a fast and agile hunter. I'd expect them to maybe gain longer legs, starting to use only the two last pairs for overall locomotion, as well as other changes such as adopting the ability to fold their wings like their damselfly cousins so they don't occupy as much space and both sexes developing claspers, which could adapt to handling functions rather than just serving for the males to hold the females in place , but that's entirely up to you.
Now, regarding the brain. Dragonflies, with their independent wing control (they're each controlled separately basically, which grants them their great maneuverability) and complex eyes already indicate more well developed brains. However, it'd be very hard for an insect to develop complex thinking like we see in humans, as their brains are much simpler and smaller. That is not to say, however, that they're dumb, as they've been shown to be able to plan and memorize. They will need to go through a decent level of development to reach a more complex level that enables intelligence though, based on our own insects. The presence of a pack behavior could help reach such levels, as well as some level of emotion and empathy (insects as we know them are completely incapable of emotion or empathy, meaning that unless your race develops these abilities, they'll be essentially a race of psychopaths by our standards, with little to no concern for one another, unless they develop some sort of instinct to protect the other members of its species). Additionally, they do have the advantage of having ganglia that control vital functions, meaning that their main brains could, without too much of a stretch, become larger and more specialized to handle higher functions such as more complex thinking and understanding complex concepts, such as the passage of time and the awareness of their death. I recommend taking a look at [this](https://www.google.com/amp/s/www.atlasobscura.com/articles/i-asked-leading-entomologists-whats-the-smartest-bug-in-the-world.amp) to get a better understanding of how insect brains work. It also strengthens my point that they'd likely have evolved from a group of arthropod-like pack hunters.
So, summing up: how big can they grow? Depends a lot on the environment they live in, but with the proper oxygen levels, they can be at least as big as a small crow. Can they have moderate intelligence? Very likely, as they have not only good oxygenation of nervous tissue, but various ganglia across their bodies handling vital functions, which could allow their main brains to specialize further in order to grant them moderate intelligence. Though I don't think they'd have the complexity of our brains, they'd likely be capable of making long and short term plans, making ambushes and traps, understanding abstract concepts and symbols and living in a community at the very least, as most of these abilities can already be seen to some extent amount various arthropods. Overall, their larger size would also allow for larger brains and therefore greater potential at becoming smarter, but I don't find it likely that they'd be too engaged in things such as tool using, not. Meaning however that there's no chance that they could.
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Why not go for one of the extinct dragonflies: [Meganisoptera](https://en.wikipedia.org/wiki/Meganisoptera) had a wingspan of 71 cm (28") and was a predator just like today's...
All predators have more than moderate mental aptitude anyway, so pushing the limit a bit wouldn't be too hard...
[](https://i.stack.imgur.com/8h6Yg.jpg)
*Source:* linked Wikipedia article.
**Edit:** An IQ of 90 or above would mean a lot of handwavium as a higher IQ needs both a larger energy intake and external stimuli:
* Higher oxygen content of the atmosphere
* Parallel evolution where they became an apex predator:
+ they learnt how to capture small birds, [flying fish](https://en.wikipedia.org/wiki/Flying_fish), ...
+ Learnt to live in social groups like bees
+ ...
* And depending on your universe: *Magic can do anything...*
[Answer]
Brain size is not necessarily a good proxy for intelligence.
Humans (with some notable exceptions) are the 'smartest species' on earth, but we don't have the largest brains, whales are definitely larger and horses are a similar size. The ratio of bodymass-brain can be used as a proxy; but it isn't sufficient to explain the apparent difference in intelligence between species, with ants, birds and mice scoring better than humans.
Perhaps of particular interest is that the brain structure of warm/cold blooded animals is quite different, with reptiles being more intelligent per brain mass than might be expected. I struggled to find good information on insect brain structures, but an alternative structure could provide more oomph at a small size.
EDIT: Having done some further reading on insect brain structures, they are *vastly* different from mammals. They are much more tightly integrated to the sensory inputs (eyes, olfactory etc.) than mammalian brains. You would likely either want additional insectoid brain features not seen in earth or a mammal-like brain/body with insect-like body parts.
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If this creature only needs the appearance of insectoid wings, then they could likely have a membraneous wing like a bat, except with the 'fingers' altered to resemble the veins of an insect's wing. If you make them more avian in anatomy, then you could likely have them be the same size as a regular human
It seems that the minimum size that these creatures could be would be around 2ft tall, if they have regular human proportions with a dense avian brain. However, these small humanoids could have thinner limbs, due to the square-cube law
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I'd like to randomly generate between 1 and 20 million stars for a spiral galaxy resembling our Milky Way. This is of course far fewer than our galaxy (estimated between 150 to 300 billion), but I'd like it to resemble ours in proportion. Generating the locations so that they resemble a spiral pattern was a little challenging from a geometry standpoint, but I think I have that part settled.
Now comes the hard part. I'd like this galaxy to have a plausible mix of the various types/sizes of stars. It won't be a proper simulation (so that there might be close features that shouldn't be near each other) and I'm ok with that. But I'd like to have approximately the right number of neutron stars, singularities, red dwarfs, and giants within this galaxy
Some of these things aren't settled scientifically (how many rogue planets float around in the intergalactic void, or are there any actual quark stars), but many of these it seems like we should have reasonable estimates.
So, what are those? I'm looking for a statistical distribution of stellar masses/radii, color, spectral types, temperatures, etc. Ideally these might vary according to their distance from the galactic center, but I could live without that if it doesn't exist.
Does the information exist to accomplish this? Occasionally I'll find an offhand remark about how some large fraction of the Milky Way is composed of barely visible red dwarfs, or that there are an estimated 100 million neutron stars within MW. But these rarely provide hard numbers/ratios.
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This has actually been an area of intense research for decades now. Astronomers are quite interested in the distribution of stellar masses in a variety of different galaxies and clusters. The precise mix you're going to get of course depends on the environment you choose; galaxies with higher metal contents will produce stars with higher metallicities. In general, however, you can take your pick of different [initial mass functions](https://en.wikipedia.org/wiki/Initial_mass_function), or IMFs. An IMF is a function that tells you what fraction of stars have a mass between $m$ and $dm$, where $dm$ is some step size.
As an example, take the famous Salpeter IMF - one of the first created. The Salpeter IMF has the form
$$\phi(m)dm=\phi\_0m^{-2.35}dm$$
Therefore, if you have a given stellar population, the fraction of stars with a mass between $m\_1$ and $m\_2$ is
$$f(m\_1,m\_2)=\int\_{m\_1}^{m\_2}\phi(m)dm=\int\_{m\_1}^{m\_2}\phi\_0m^{-2.35}dm$$
Here, $\phi\_0$ is a normalization constant.
The Salpeter IMF is a simple one, and it's great as a toy model. More realistic IMFs, like the Kroupa IMF (which is quite commonly used), are piecewise functions. They're also power laws, but the exponent is different over several different mass ranges.
If you want to play around, I've put [some code on GitHub](https://github.com/HDE226868/Stellar-Populations/blob/master/Stellar%20IMFs.ipynb) to let you play around with a couple IMFs (and generate stellar populations on your own, with some randomness thrown in). Here's a comparison of how stellar masses are distributed, according to the two IMFs I discussed above. The $y$-axis shows the fraction of stars $f(<m)$ with a mass less than $m$:
[](https://i.stack.imgur.com/SZe7o.png)
$200M\_{\odot}$ is kind of an arbitrary upper limit, but in reality any population you synthesize will contain only a tiny, tiny number of stars with masses above $100M\_{\odot}$. $0.08M\_{\odot}$ *is* a realistic lower choice - it's the boundary between stars and brown dwarfs.
How do these stack up against [L.Dutch's numbers](https://worldbuilding.stackexchange.com/a/167161/627)? Using [some stellar mass range tables](http://spiff.rit.edu/classes/phys373/color_temp/EEM_dwarf_UBVIJHK_colors_Teff.txt), I found that the Salpeter IMF predicted 93.1% M stars, 3.03% K stars, and 0.926% G stars; The Kroupa IMF predicted 68.1% M stars, 13.6% K stars, and 4.2% G stars. The Kroupa model appears to be more realistic - as you might expect; after all, Salpeter came up with his IMF in 1955!
A couple things to bear in mind:
* The IMF only tells you the *initial* distribution of a population of stars. Stars of different masses age at different rates, so over time, as massive stars die, the population will skew towards lower masses. You arguably need to evolve your population over time - computationally expensive, even for basic toy approximations.
* This model assumes only one burst of star formation; in reality, most galaxies are continuously forming stars at different rates.
* As I said at the beginning, mileage may vary depending on your galactic environment. Using an IMF based on conditions in the Milky Way should give you a Milky Way-like population.
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Right today NASA, on its daily [APOD](https://apod.nasa.gov/apod/ap200131.html), has posted the following image
[](https://i.stack.imgur.com/XhEby.jpg)
accompanied by the following caption
>
> The Goldilocks zone is the habitable zone around a star where it's not too hot and not too cold for liquid water to exist on the surface of orbiting planets. This intriguing infographic includes relative sizes of those zones for yellow G stars like the Sun, along with orange K dwarf stars and red M dwarf stars, both cooler and fainter than the Sun. M stars (top) have small, close-in Goldilocks zones. They are also seen to live long (100 billion years or so) and are very abundant, making up about 73 percent of the stars in the Milky Way. Still, they have very active magnetic fields and may produce too much radiation harmful to life, with an estimated X-ray irradiance 400 times the quiet Sun. Sun-like G stars (bottom) have large Goldilocks zones and are relatively calm, with low amounts of harmful radiation. But they only account for 6 percent of Milky Way stars and are much shorter lived. In the search for habitable planets, K dwarf stars could be just right, though. Not too rare they have 40 billion year lifetimes, much longer than the Sun. With a relatively wide habitable zone they produce only modest amounts of harmful radiation. These Goldilocks stars account for about 13 percent of the stars of the Milky Way.
>
>
>
To summarize:
* G star type: 6%
* K star type: 13%
* M star type: 73%
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What is a possible event${^\*}$ that would cause a spike in the speed of $^{235}$U fission and reduce its average concentration in ore worldwide?
As I understand the physics of the process, it is impossible to alter the fission speed itself, but if there is a way to have a thermal neutron source in the ore volume or some kind of neutron moderator for neutrons which are emitted by $^{235}$U itself that will lead to chain reaction and then depletion, like in [Oklo](https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor).
The problem I am struggling with is to come up with an event that will look not completely made up.
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${^\*}$ The event should not be magic or alien-related.
P.S. This is my first question here if I am doing something wrong I will be happy to do it right.
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I agree that a possible solution would be to add in a source of high-energy ambient neutrons. [Cosmic rays are a possible neutron source](http://www.jetp.ac.ru/cgi-bin/dn/e_009_03_0511.pdf), at least at high enough altitudes and assuming the uranium does not have adequate shielding. A strong spike in cosmic rays could then provide such a neutron source; in turn, as one of the major sources of Galactic cosmic rays are supernovae and supernova remnants ([for cosmic rays below $\sim10^{15}$ eV](https://fermi.gsfc.nasa.gov/science/resources/swg/sept03/WS_DEllison.pdf)), it's possible that one or more supernovae nearby could produce enough neutrons to raise the rate of uranium fission enough to be detected.
Supernovae, of course, can be dangerous when close enough to Earth. Fortunately for us, [that critical distance is on the order of about ten light-years](https://worldbuilding.stackexchange.com/a/3616/627). However, this means that the cosmic ray flux would be lower than if the supernova was closer, so it's something of a tradeoff. That said, for an event to cause an increase in fission *worldwide*, rather than just in one spot, I suspect it would likely have to be astronomical in nature, meaning you'd need some sort of energetic phenomenon. This of course means that you'll be dealing with the same sort of issue with many of the answers you'll get.
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When does this reduction have to happen?
If it can happen in the distant past, it could be explained just by changing rates of radioactive decay. Right now, we think radioactive decay always happens at the same rate, but there have been some weird carbon dating results that may support the idea that radioactive decay rates could be variable. The current consensus is that these anomalies are just statistics problems, not a new physical phenomenon. But it wouldn't take too much suspension of disbelief to say this actually is a new phenomenon.
If radioactive decay rates can change, maybe they were higher for a short period in the distant past. This would mean less uranium would be around now.
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The Oklo Formation is believed to have been a naturally formed fission reactor, moderated by ground water levels over millions of years. When water levels were up, the ore body became critical and heated the land (and emitted radiation, of course). When ground water dropped, the criticality was lost and the ore body cooled. This apparently occurred several times, and was deduced based on the ore body being significantly depleted in U235 relative to its content of U238.
For this to happen worldwide, however, would require a very different mechanism, because there are (as far as I'm aware) no other similar high concentration ore bodies that could spontaneously become critical.
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Thinking of the parallel-universe concept implemented in Stephenson's "Anathem," perhaps some multiverse-catastrophe has caused two "Earths" to swap universes. The marginal differences in cosmological constants changes the half-life of U-235 in the new universe.
Of course, you'd have to MacGuffin away all the other things that **don't** change as a result of the change in cosmo-constants' values.
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No known process can make it happen world wide. It is possible that pockets of the process might happen.
There have been suggestions of an external neutron source. To produce fission you will need low energy neutrons, not high energy. U235 wants neutrons in the thermal range to produce significant fission.
The problem with external neutron sources is shielding. Uranium is currently mined at least [100's of meters deep](https://teachnuclear.ca/all-things-nuclear/canadas-nuclear-history/uranium-mining/uranium-mining-in-northern-saskatchewan/) in some locations. So any external neutron source that could produce significant fission would not be able to do it uniformly. 100 meters of rock is going to be a quite good neutron shield, preventing the deeply buried stuff from being affected.
Also note that, unless you have a situation with the Uranium quite closely and densely packed, you need (nearly) one neutron per Uranium fission. Without that close packing, the neutrons produced by fission are nearly all wasted.
Changing physical constants is currently at the "speculative" end of science. We don't know if it is possible, though several unification theories indicate it should be.
The problem with changing physics constants is that it might affect the thresholds for critical mass and such. But to get it to remove U235 from existing ore bodies is pretty much impossible. Ore comes in a wide variety of [concentrations](https://teachnuclear.ca/all-things-nuclear/canadas-nuclear-history/uranium-mining/uranium-mining-in-northern-saskatchewan/). And anything over 1% is probably a useful commercial product. To get 1% ore to start to fission would require such grotesque changes that it is quite likely many other things would start to fission as well. Thorium for example, which is far more plentiful than Uranium. The result would be a bright flash, and no more Earth.
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I was thinking of an interesting landmark to put on my conworld, and I went with the "large body of acid" trope. This lake would be about the size of Lake Superior, and near the equator. The atmosphere is very similar to Earth's, but with about 5% Argon comprising it. The underlying rock has high concentrations of minerals like quartz and graphite, with some other minerals like lazulite and diamond. It is a very dense rock and is good at insulating against radiation. What colour would this acid lake be?
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Given the chemical composition of the underlying rock, I'd suspect that the lake will actually be a kind of ordinary darkish brown.
The pretty blue of Earth's acid lakes is due to iron sulphate in the solution. The pretty blue of sulphur lakes is due to the flame's colour.
On this other world, the underlying rock is defined by *high concentrations of quartz and graphite, with some other minerals like lazulite and diamond*.
[Diamond](https://www.quora.com/Can-you-dissolve-a-diamond-using-sulfuric-acid) and [graphite](https://en.wikipedia.org/wiki/Graphite) (carbon) are insoluble in sulphuric acid. Quartz is highly resistant as well and [won't be dissolved](http://www.quartzpage.de/gen_chem.html) in sulphuric acid. [Lazulite](http://www.galleries.com/Lazulite) is also insoluble in sulphuric acid.
Sulphuric acid itself, like water, is clear, and will take on the apparent colour of whatever is behind it:
[](https://i.stack.imgur.com/joDAh.jpg)
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Turquoise
[](https://i.stack.imgur.com/UPxOa.png)
[Largest Acid Lake on Earth](https://news.softpedia.com/news/The-Largest-Acid-Lake-on-Earth-81388.shtml#sgal_0)
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Sulfuric Acid Lakes, like Thorne said, are presented as Turquoise.
Very Very Sulfuric Lands can be an Orange-Yellow, or Green, depending on the concentration of sulfur.
But one very important feature... Multan Sulfur, usually around Sulfur Lakes, will Light on Fire at night, producing a beautiful but deadly blue fire or blue lava
I loved the idea of adding this in, and had to mention the blue lava. its an amazing sight
[](https://i.stack.imgur.com/ALULR.png)
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I would greatly appreciate any info or resources for building an appropriate artificial mythology for a world.
For reference, I am reading "The Gods of Pegana" and I already went through the Silmarillion and the Cthulhu Mythos. I would like to do something similar for a world of mine but have trouble organising the macrostructure.
Some good sources of themes and archetypes would also be very useful.
[Answer]
* [James George Frazer](https://en.wikipedia.org/wiki/James_George_Frazer), [*The Golden Bough*](https://en.wikipedia.org/wiki/The_Golden_Bough), 1890. The Wikipedia article has links to several on-line editions. Warning! (1) It is a massive work. (2) It is addictive. (3) It is somewhat out of date anthropologically, but that shouldn't matter as a source of artistic inspiration.
* [Robert Graves](https://en.wikipedia.org/wiki/Robert_Graves), [*The White Goddess*](https://en.wikipedia.org/wiki/The_White_Goddess), 1948. Warning! It is a poetic / fantasy essay made to look as a scholarly work. *Do not* take anything in this book as serious anthropology or scholarship. It is a *great* poetical work, best compared with the *Silmarillion*.
* Joseph Campbell, [*The Hero with a Thousand Faces*](https://en.wikipedia.org/wiki/The_Hero_with_a_Thousand_Faces), 1949. Maybe not as engrossing as the previous two, and maybe a little reductionist, but indispensable. Warning! This is a massive high-density work.
* Edith Hamilton, [*Mythology: Timeless Tales of Gods and Heroes*](https://rads.stackoverflow.com/amzn/click/com/0316438529), 1942. One of the best English presentations of both Greek and Norse mythologies. (Link goes to Amazon.)
And, of course, start with the Wikipedia article on [Myth](https://en.wikipedia.org/wiki/Myth), follow the links, and consider the bibliographies. This will give you the basics of understanding what mythologies are about, and how they empowered artistic creativity through the ages.
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**The Hero with a Thousand Faces** ([wiki link here](https://en.wikipedia.org/wiki/The_Hero_with_a_Thousand_Faces)). This is **the** book to read if you want to get some interesting perspectives on the commonality of mythology and stories throughout cultures. The author's thesis is that much of mythology follows the same basic story, which he calls the "monomyth". It is comprised, basically, of the following story, quoted from the book:
>
> A hero ventures forth from the world of common day into a region of supernatural wonder: fabulous forces are there encountered and a decisive victory is won: the hero comes back from this mysterious adventure with the power to bestow boons on his fellow man.
>
>
>
Obviously the book goes into much more detail and studies the mythologies of many cultures and how the hero journeys in said mythologies. Basically required reading for myth making :-)
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In addition to Campbell's monomyth, take a look also at the [heroic paradigm](https://en.wikipedia.org/wiki/Hero%27s_journey). You can see this in action in a wide range of heroic literature from kids' stories to serious adult myth & legendary literature.
In addition to Silmarillion, I'd also recommend you look into the Letters of JRR Tolkien and perhaps Carpenter's biography. You can glean quite a lot of his thinking and process through those sources.
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The goal is to get from Earth to the Outer Solar System, preferably the Kuiper Belt, as quickly as practical, with a crew of about 12, and a not-set-in-stone dry mass around 30 tons.
The characters have access to something resembling a wormhole, whose other end is in a different universe. Both mouths can be moved without much energy expenditure. For setting-specific reasons, this requires constant attention from a specific crewmember, such that wormhole throughput effectively stops when they do anything else. It is not practical to just build a habitat on the other side and let the rest of the crew wait there, to minimize payload, but using the other side of the wormhole for storage of food, supplies, etc is possible.
I see two ways this could be used for spaceflight: either use the wormhole for fuel-storage to bypass the Rocket Equation, or point the wormhole at a star, and let the star provide exhaust. For character-related reasons, the simpler the end product, the better.
My preference is the Stellar Exhaust solution. However, if they use something like a Coronal Mass Ejection (exhaust velocity potentially approaching 3000km/s), the exhaust would be absurdly hot, include intense radiation, and possibly some other electromagnetic effects I'm less clear on. I don't expect this would be safe on or near Earth, even assuming there's a way to prevent it from frying the ship. The characters have access to handwavium that can mitigate some of this, given constant effort, but I don't know that it'd be enough to make stellar exhaust viable.
Given the fuel storage option, I'm expecting they'd need a high-quality rocket engine, whereas stellar exhaust seems like it could get away with a simple nozzle, if not less.
It's possible I've overlooked something that changes the answer dramatically from either of these.
Given the above, what would be the best way to accomplish the goal?
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**Blow ye winds!**
Stellar, schmellar. Too hot and too radioactive! I propose that the far end of the portal be dipped low into the atmosphere of a suitable planet. On the near side, a fierce cool wind will blast forth, laden with droplets of salty water.
Your starjammer will have masts and sails and will sail away propelled by the portal winds. Absent air resistance in space I here assert that the column of air will remain coherent for a long distance, providing propulsive force the whole time.
Arguably a liquid would provide even more propulsive force but then it would be something different than the awesome starjammer I am envisioning.
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It sounds like what you have is more of a portal than a wormhole, but that's just semantics really. You left the `science-based` tag out so let's see where we can take this. Apart from the portal itself, I'm going to assume that physics is mostly the same.
The idea of dropping the other side into the corona of a star and letting the energy pour out of our side would be great if you wanted the energy for something, but you'd have to do something more to get thrust that way. You can't just point your portal aft of the ship and start thrusting since the energy passing through the portal isn't actually pushing on the portal or the ship itself. It's not like in a rocket where the exhaust gasses are pushing against the rocket motor to generate thrust, and conservation of momentum doesn't really apply since the other side of the thrust is in fact in a different universe.
So instead you'll need to interact with what's coming through in order to derive some thrust from it. Point the portal forward into a set of curved tubes (of some refractory material that can handle the temperatures) that redirect the transferred material backward. Turning the mass around will generate thrust, and you can probably steer a bit if the tubes can be moved or valved in some way.
Or you could use a variation on the solar sail concept where you have a lightweight sail that you direct the flow of matter/energy into. It would probably have to be a bit tougher than the average Mylar sheet though. Perhaps a rigid parabolic or conical structure with the point aimed directly into the mouth of the portal so that it scatters as much of the material to the sides of the ship so that you don't get fried.
Depending on the nature of what's coming through perhaps you could just direct it down a tube with permanent magnets and use magnetic drag to get some thrust. It'd look weird having your apparent thrust pointing forward... but weird isn't necessarily bad.
There might be a simpler way though.
If your portal essentially joins two regions of space in different universes then things like gravity may pass through as well. You could position the other side near a suitably massive object like a neutron star and have a gravity well form on this side. Your ship accelerates in the gravity well, pushing the near side of the portal ahead of it. You control the rate of acceleration by moving the other side relative to the mass you're using. And since your ship would be essentially in free fall relative to the gravity well you wouldn't have to worry about acceleration stress on your crew. Maybe some tidal effects though, so be careful getting too close to the portal.
On the other hand, if gravity doesn't transmit through the portals then you'll have to use the lessons we all learned in Portal 2...
Take two pairs of portals. Place the far ends of both in a gravity well so that an item exiting from one will accelerate towards the other. On the near side put the portal exits inside your ship's engine so that objects cycle through a short part of local space before going back through the loop. Drop something into the 'down' portal and bleed energy off with magnets or something.
You could also push a tube through the 'down' portal and grab the end as it comes back through the 'up' portal. Fill the tube with water or something, which will immediately start to flow through the tube due to the gravity on the other end. Attach both ends of the tube to a machine that will brake the flow, extracting kinetic energy from the loop. Maybe have a turbine in-line that you can use to generate electricity at the same time. Make sure you can stop the flow when you want, and that you can rotate the whole assembly to get directional control.
Now, as long as you let the water flow you'll have both thrust and limitless energy.
Which is why we know Portal is just a fun game. Physics doesn't like it when we break the rules like that.
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I have answered quite a few questions regarding wormholes by reminding people that those things have mass. Specifically, [a one-meter wide wormhole would have a mass comparable to Jupiter](https://worldbuilding.stackexchange.com/a/103973/21222).
It is a good thing that you don't want to use the wormhole to go inside it, there would be some complications with humans inside the vessel. [Depending on the model](https://worldbuilding.stackexchange.com/a/139109/21222), it might be a longer journey than just not doing it, given the relatively short distance (in astrophysical terms).
Since you can move the mouths of the wormhole easily, you can do it like this:
1. The wormhole can't come close to Earth due to safety reasons, so have the ship go from Earth's gravity well to the wormhole's gravity well under its own power.
2. Move the wormhole towards the outer solar system with. The ship will follow since it will be orbiting the wormhole.
3. Once in the outer solar system, have the ship exit the wormhole's gravity well.
4. Profit!
You can then move the wormhole closer to Earth's orbit to rinse and repeat.
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You have control of a stable worm hole and you want to transverse great distances? I understand one end of it is stuck in a distant universe.
* you (and your ship) step from Earth into the worm hole
* move the Earth side to your desired destination
* step back through the worm hole
Maybe this doesn't fit your story line? You could limit the range that the portal can be moved and still stay under control. This would make the journey many small step-in-step-outs.
This mode of transportation would use very little fuel, be very fast, remove cargo limits, and more, all thanks to worm hole magic.
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I was thinking that the character would be a moderately active teenage girl that's 5"8 and 160 lbs. The speed itself is a super-power and she is otherwise a normal human. I'm defining safe as a speed that wouldn't kill or seriously injure her.
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There are two ways we can look at 'safe' speeds for your teenager;
1) How fast can she run and an unanticipated collision not kill her, and
2) How fast can she run without her body breaking.
Dealing with the impacts of collision first, the answer is not all that much faster than a normal human can run. If you look at Olympic sprinters for example, they run as fast as they can to get to the line, but they don't come to a dead stop afterwards. They have to slow their momentum down gradually. The race would look very different if (for example) the finish line was in fact a finish wall and the first person to touch it won. People would have to slow down at least a little because at a little over 25 Km/h the damage that running into a brick wall would do to the body would be substantial, especially depending on what part of you hit first. You could blow out a knee, damage your knuckles to the point that you put your hand out of action for at least a temporary period of recovery, and potentially even knock yourself out if you hit your head the right (wrong) way. So, at any speed faster than that, the momentum increases meaning that the damage that can be done by a collision also increases.
As for her body, there are a number of ways that being able to run that fast could go wrong. If her muscles are capable of super fast twitch actions, they could move so quickly that they could literally tear themselves away from the skeleton by ripping the tendon or other ligaments. They could tear themselves apart, or even snap bones like the Femur depending on things like bone density and muscle development. Even if all that wasn't the case, like a cheetah you're only going to have a small window of super speed because you simply cannot get the energy requirements to the muscles via the bloodstream fast enough for sustained super speed. Just like Cheetahs, you end up overheating with that short physical exertion as well, limiting the time you can run to a given period after your previous one for cool-down. Put simply, running too fast or for too long will kill you; just look at how the [Marathon got it's distance and name](https://www.livescience.com/11011-marathons-26-2-miles-long.html).
The Cheetah is in point of fact at the upper end of a biological niche for running at speed and most studies on the animals show that they could not run faster without significant sacrifices to their biology that are potentially non-viable. As such, we could say that the Cheetah's top speed is a biological limit for your teenager, but in reality it tops out much sooner because humans are simply not designed with the tendon & bone strength, and the fast twitch muscle design, and the blood supply system, to take advantage of similar speeds.
Evolution tends to favour efficiency over any other factor, so as a result our skeletons, blood supplies, muscle design, tendon strength et al are designed to support the upper limit of the average human's performance as a general rule. This means that unless you make other changes, the top 'safe' speed of your teenaged flash is actually pretty close to modern sprinters, or around 25 Km/h. The higher you go after that, the less safe it becomes and ultimately your top speed is REALLY set by the amount of risk you're willing to take. After all, even Olympic sprinters choose when they apply that kind of speed and don't run everywhere recklessly.
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I have an idea for a futuristic way to travel for my Story. People get into a capsule, and it launches itself extremely fast in the air. What would be needed to make this happen for real and what complications would exist?
Qualifications:
The people can't die.
The people must be able to be comfortable inside
It has to be somewhat reusable
It has to be FAST. Faster than airplanes now.
It has to be accurate. Landing in an airport like place.
My Ideas:
I thought a stabilizer inside would be important, so the capsule can spin, but the cabin itself can feel like it's staying upright
Any Ideas?
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Catapults have two problems:
1. You have only until the arm releases the capsule to accelerate the vessel. That means you have a fraction of a second to reach cruise speed. Such acceleration would turn your victims' insides into paste.
2. Friction would quickly deccelerate the capsule, so it wouldn't go very far. Supposing the capsule is as aerodynamic and heavy as a [Cessna 172](https://en.wikipedia.org/wiki/Cessna_172) as it reaches the highest point in its trajectory at the Cessna's cruise speed (226km/h, or 140mph), it will behave exactly the same as a Cessna 172 **with its engines off**.
A plane at cruise speed with its engines off does not drop as a stone. Rather, it behaves as a glider. It just so happens that planes that are not designed as proper gliders epically suck at gliding. You can play with Microsoft Flight Simulator or Kerbal Space Program for an approximated idea - just reach cruise speed and altitude with any self-powered aircraft, shut the engines down and try to land. It's actually possible to land a Cessna without too much damage, but if I ever had to go through that as a passenger in real life I would never fly again.
There is a way to solve 1 and reduce problem 2 if you are flexible. You wanted to use catapults, so we have been meddling in the realm of wacky engineering from the start. Let's up the ante and replace the the catapult assembly with guns.
Someone once asked Randall Munroe (a honorary god to worldbuilders) [whether it would be possible to assemble a machine gun jetpack](https://what-if.xkcd.com/21/). Mr. Munroe always researches and answers scientifically, and his conclusion was that a jetpack would be unfeasible - but a machine gun powered plane would be a no brainer.
The [A-10 Warthog](https://en.wikipedia.org/wiki/Fairchild_Republic_A-10_Thunderbolt_II) has a machine gun (the GAU-8 Avenger) that produces 62.5% of the thrust of its twin engines, so it runs the risk of stalling when firing straight forward.
If you replaced the two engines with two other GAU-8 machine guns, it would be able to accelerate and fly faster!
But we can improve it further. Mr. Munroe says:
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> As good as this gun would be as a rocket pack engine, the Russians built one that would work even better. The Gryazev-Shipunov GSh-6-30 weighs half as much as the GAU-8 and has an even higher fire rate. Its thrust-to-weight ratio approaches 40, which means if you pointed one at the ground and fired, not only would it take off in a rapidly expanding spray of deadly metal fragments, but you would experience 40 gees of acceleration.
>
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> (...)
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> But if you somehow braced the human rider, made the craft strong enough to survive the acceleration, wrapped it in an aerodynamic shell, and made sure it was adequately cooled ...
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> 
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> … with a GSH-6-30, you could jump mountains.
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Since your goal seems like giving your passengers a slightly worse experience than nowadays current airline flights, machine gun engines will at least make it survivable.
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This is a "catapult" less like the medieval siege engine and more like the device of the same name used to launch jets from aircraft carriers.
1. **Acceleration happens over a long period so as not to squash passengers with G forces.** This would be a long tube, possibly evacuated of air to reduce air resistance during launch. It could be built up the side of a mountain.
This idea from the Halfbakery is close.
<https://www.halfbakery.com/idea/Steam_20Space_20Launch_20Facility#1128447586>
Or you could use a railgun but just not maximize the acceleration this method could produce. You don't need to because you have a tunnel several km long.
2. **Cabin on gimbals.** This would allow the outer portion to spin very fast, stabilizing the vehicle gyroscopically.
<https://en.wikipedia.org/wiki/Gimbal>
>
> A gimbal is a pivoted support that allows the rotation of an object
> about a single axis. A set of three gimbals, one mounted on the other
> with orthogonal pivot axes, may be used to allow an object mounted on
> the innermost gimbal to remain independent of the rotation of its
> support (e.g. vertical in the first animation). For example, on a
> ship, the gyroscopes, shipboard compasses, stoves, and even drink
> holders typically use gimbals to keep them upright with respect to the
> horizon despite the ship's pitching and rolling
>
>
>
3. **Vehicle takes a ballistic trajectory**. This is essentially a mini-ICBM. <https://en.wikipedia.org/wiki/Ballistic_missile>. Its path is calculated with Newtonian physics. Most of its travel is in the distant reaches of the upper atmosphere where wind resistance is both more predictable and weaker.
4. **Parachute brakes.** Like an Apollo spacecraft. Nice and easy.
5. **Better on the moon.** Atmospheric vagaries make this less accurate than would be the case with no atmosphere, although ICBMs are still accurate enough to hit their targets a continent away.
.
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I think these are the key elements your story would need to touch on for this mode of transportation to be understandable by your audience:
1) Power Source that drives this system is too large to fit in a capsule for 2-4 people
2) A capsule can store energy to power control surfaces, navigation, etc but nothing exists that can store propulsive power required for travel range
1+2 mean all the required velocity has to be imparted by ‘catapult’
3) automated control surfaces use increased drag and spinning vanes to accurately guide capsule to destination anti-catapult or counter-catapult where the capsule is caught and slowed to a stop at a tolerable acceleration or is accelerate again and thrown at a new destination. hop-skip-jump mode of travel
4) mishaps happen, people died, corruption and incompetence uncovered, people fixed problems, safest way to travel.
5) other answers involving gimbled compartments and spinning shell are totally on point. And, same for acceleration, it needs to be long and tolerable.
6) low friction material or techniques like plasma induced low drag methods were important tech break through that made this mode of travel possible. Same for very and powerful power source
After that you can use whatever form of catapult you want — maglev, induction, artificial gravity, crazy technology harnessing weak force in inconceivable ways — other than traditional medieval siege weapon like a trebuchet or scorpion
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Security around the catapult is going to need to be pretty severe. Anything valuable within range of the catapult is vulnerable to insane people, people intent on "suicide by cop," sabotage, terrorism, what have you.
People trusted to work on, operate, and maintain any part of this system will need to be very carefully screened. No unstable people allowed. Nobody with huge gambling debts or a drug problem. Nobody with whacky political ideas who might be tempted to pull something.
There will need to be ways to remotely shut down the catapult so that any supposed "trouble makers" can't launch capsule after capsule into populated areas. That could be as simple as shutting off electricity to the launch site. Though that means that you also lose all other electrical devices, such as security cameras, smoke detectors, what have you. Maybe you need some clever method to be able to shut down the catapult, and be confident it can't be turned on again, but leave the other stuff working. Maybe the power circuits for all that other stuff have to be physically widely separated from the catapult. So any possible terrorists might need to bring kilometers of thick power cables with them to be able to re-power the catapult.
Maybe a capsule is less of a draw for putting dangerous stuff on board. Not much chance of a hijacking from inside the capsule since it's going where the catapult sends it, with only the smallest of variations. So maybe there is less need for passenger screening.
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Don't go for huge distances for the throw: Atmospheric drag dictates insane initial speeds, and thus unsurvivable (and uncomfortable ... i love that you specified it be both comfortable AND survivable - dodged the answers where you comfortably die) acceleration.
Go for serial lobbing - The lobbing stations are close to each other, minimising the error introduced by unforeseen winds. Capsules are caught and re-lobbed without slowing them, reintroducing the energy lost since the last lob.
Buildings close to lobbing station's receiving end (stations are one way) have to be built with aesthetically pleasing and extra-crumbly roofs, for emergency landing.
The lobs get increasingly fast, the angle of launch thus flattening. Reverse for approaching the destination.
[Answer]
You could do it while in space, for example when on orbit, to transfer between space stations. Your passengers climb aboard, suffer a high-g manouver for a moment as they get fired into a different orbit.
If you're willing to replace the catapult arms with electromagnetic railgun style launcher, this would be an effective way to travel and ship cargo around an airless, low gravity environment, such as a large asteroid or the moon. The lack of air makes ballistic trajectory energy efficient and accurate, requiring only very minor course corrections before landing in a specially designed capture location (maybe more rails, a big net, a runway, etc).
The only real drawback to this in an airless environment is the g-forces on launch and landing. It'd be ideal for chucking raw material around, and with a long enough wind up it'd be ok for human transport.
If you are prepared to do some scifi magic tech, you could have a forcefield around the capsule occupants, protecting them from high-g's. Then you can use a very powerful catapult to lob them long distances.
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Let's say we have an Earth-sized planet and the same general solar activity and climatology. However, the continents are much smaller, and it's effectively impossible to accomplish travel between them (due to distance, inability to navigate, lethal oceanic weather, or something). That is, any island continent is effectively cut off and isolated. What is the smallest land-mass that would be required to support a human civilization with cities and technology to the level of an ancient culture (e.g., Sumeria, Egypt, Rome)? And what is the optimal terrain and natural resources to achieve that minimum?
Note this is different from [this question](https://worldbuilding.stackexchange.com/questions/46/what-is-the-smallest-planet-that-a-civilisation-could-develop-on) which asks for the smallest *planet* that could support a civilization, in which the answers focus largely on issues of gravity difference. In my question I'm stipulating Earth-like size and gravity, but wondering what the minimal dry land mass would be required to support an organized human civilization approximately similar to something in our history.
Edit: As a point of clarification, assume that this question is about only the *support* of a human civilization with ancient-city-level technology. That is: Possibly the human civilization has been set down fully-formed by magic or advanced technology. The question subsumes the requirement that the population be large enough to maintain a healthy genetic pool over a long period of time.
A [separate question](https://worldbuilding.stackexchange.com/questions/151063/what-is-the-smallest-land-mass-to-develop-human-civilization) has been made on the topic of the smallest land area to *develop* (evolve) such a human civilization.
[Answer]
There is a view in philosophy that civilization start to grow when you have everything in excess. I think it was Władysław Tatarkiewicz who said that Roman, Greek and Egyptian culture and philosophy flourished because they had warm long days, olives and cheese to eat and wine do drink. And they just go around and wonder.
Of course they were all having wars, and a lot of seafaring which added to their resource sources.
Regarding just food here's a question about how much people you could feed from 1 km² of land. [How many people can you feed per square-kilometer of farmland?](https://worldbuilding.stackexchange.com/questions/9582/how-many-people-can-you-feed-per-square-kilometer-of-farmland)
Now, you have to remember that Romans, Greeks, Egyptian relied HEAVILY on slaves. It's estimated that in city state of Athens where they had 5000 men eligible for voting there was 50k of slaves. Conservative math of a family of 2+2 would give you 70 thousand people.
From linked question (and answer) and just simply crop rotation you would need 56 square kilometres.
Now a small reality check - Crete, an island that was a cradle of Bronze Age Aegean civilization, the Minoans only have 8 sq km.
So now you can conclude that there was way less people on the Crete than those estimated 70k for Athens. OR the Minoans relied heavy on sails. With the sea the thing is that you may fish in one spot maybe 100 metres square, but everything below is moving. So much larger ecosystem is providing food.
And now back to our first thought. Excess. People crave a little different buzz than just potatoes. Or Fish & Chips.
So your island would need to be mild in weather, allowing to grow different types of food all year round in excess for humans AND animals. I don't know the food requirement of sheep (the most popular source of meat in Greek mythology) but pig for example eat the same amount as human do daily (per *Cows, Pigs, Wars, and Witches: The Riddles of Culture by Marvin Harris*) so you can exclude those as breeding animal.
Now in those ancient cultures most common metal is bronze. So you would need some space for excavation of copper AND coal (because you don't want to waste space for trees that don't breed fruits)
So I would say that 70 square kilometres is a safe estimation WITH the requirement of being able to catch and eat seafood.
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It's not entirely a matter of size, but of natural resources. An island like Britain did fairly well in developing technology up to the Industrial Revolution level without a lot of imports, because it had a diverse geology, with lots of mineral resources. OTOH, a volcanic island like Hawai'i would have little in the way of minerals.
As comments point out, you have the problem of how your people evolved on such small islands, but let's assume they were landed by space ships, which either left or stopped working.
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[Easter Island](https://en.wikipedia.org/wiki/Easter_Island)-sized landmass is probably a reasonable minimum to sustain a civilization.
As @Klaus Æ. Mogensen reflected in a comment, the history of Easter Island can suggest that this landmass can be both sustainable and unsustainable for a civilization. It was a home for a sophisticated nation of Polynesian origin for 500-1000 years before the eventual collapse. The simplest explanation is that this land is just barely sufficient for a complex civilization. The surface area of Easter Island is 163 sq. km, or 63 sq. mi
The island inhabitants, Rapa Nui, were less developed technologically than Egyptians, and of course Romans, but, in our case, if we assume that inhabitants already possess an iron-age level technology and have sufficient population and resources, there is little reason to think that it would be abandoned.
At its peak, Easter Island had population of 15-20 thousands, which might have been unsustainable in long term. If the island was located in a more favorable climate, this population would have been sustainable. It is also worth mentioning that 15-20 thousand is adequate for a classical city-state.
There are some requirements to keep this civilization stable:
1. Availability of high yield crops, like potato, sweet potato or corn;
2. Isolation from pest and diseases;
3. Availability of minerals and ores necessary to maintain tech level;
4. Environmental awareness
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North Sentinel Island is a 23 sq km island off the coast of India which has supported an un-contacted (and very hostile) tribe estimated to be in the population range of 50-400 individuals and believed to have called the island home for 6,000 years with contact with the outside world limited to a handful of documented incidents. Their nearest cultural relatives, the Onge people, were brouht into contact with the Islanders in the 19th century by the British but found the language incomprehensible despite very similar cutural practices, suggesting the isolation had occured at some significant period in the past to affect linguistic drift. By comparison Modern English speakers can still make out similar root words to their own language in both Modern French and Modern German, near linguistic relatives to English.
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I would like to create a map with the help of tectonic plates. I didn't really care before. Can tectonic plates have all possible sizes and shapes? As an extreme example, could a continent the size of Australia have three small tectonic plates colliding with each other?
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Tectonic plates come in various sizes.
Among them there are also the so called [microplates](https://en.wikipedia.org/wiki/List_of_tectonic_plates#Microplates),
>
> These plates are often grouped with an adjacent major plate on a major plate map. For purposes of this list, a microplate is any plate with an area less than 1 million km2. Some models identify more minor plates within current orogens (events that lead to a large structural deformation of the Earth's lithosphere) like the Apulian, Explorer, Gorda, and Philippine Mobile Belt plates.
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On the other hand, the Pacific plate cover up 103,300,000 square kilometers.
So, answering your question, it is possible to have plates of various sizes.
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To answer your specific question, technically no... because it's three continents colloding at some point in the center of a land mass the size of Australia. The Land mass of Australia is in the dead center of the Austrailian Plate, and is one of the most geologically inert locations in the entire world. A continent can sit on multiple plates (For Example, most of Main Land North America is on techtonic plate from the Carribbean Plate, even though the Islands are all considered part of the Continent of North America. Same is true with anything west of the San Andreas Fault in California.
Tectonic Plates can be made up of bodies of Continental and Oceanic Crust, with the former being thicker than the latter by about 3 km. The dividing lines are given three different classifications based on interactions.
Divides are crated when two plates move away from each other. The currently most famous divides are the Atlantic Rift, which aside from Iceland, is largely submerged and is the source of almost all images of lava under water. The other one is the African Rift Valley (Birth Place of Homo Sapiens), which is a division forming in the African Continent that is still largely above sea level.
The next important divide behavior is subduction. Unlike Divides, Subduction fault are normally the result of continental crust meeting Oceanic Crust on the opposite side. Because Continental Crust is thicker as the plates collide, the Continental Crust forces the Oceanic Crust underneath of it. The most famous example is the Pacific Ring of Fire, which is a line of volcanos on the coastal nations of the Pacific Ocean that is the result of the fact that Pacific Plate grows smaller each year, pushing Asia and the Americas closer together. Volcanoes typically form several miles inland where the subducting ocean crust forces the mantle (the layer under the plates) upwards into the crust.
The Final meeting place are transform faults. These form when two crusts with similar thickness meet and exhibit different behaviors. Since neither is denser than the other, noting will be subducted but the plates will interact by trying to move around the other one. For example, the San Andreas fault is sliding against each other, creating the well know fact that Los Angeles and San Francisco are moving closer together.
Meanwhile, India is currently slamming into Asia, causing both sides to buckle upwards, creating the Himalaya mountain range.
For your continent, to have three plates meet, it would likely create large earthquake prone mountains, but if you're seeking volcanoes, there could be another way.
Hawaii, as you may notice, is right smack dab in the middle of the Pacific Plate. As I said earlier, this has made Australia famously inert... but Hawaii is home to one of the most active volcanos in the world, which is in a near constant erputpion. The reason for this is Hawaii exists over what's call a "Hot Spot" which is a particularly active area in the earths mantle for no known reason... Hawaii (specifically the big Island but all of the chain exist because area) sits on one such hot spot and all the Islands in the Chain were formed by it, and the Islands formed as the Pacific plate was dragged over the eruption area.
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**Size yes**, within reason. You can't have a plate that takes up half a planet and below a certain size its not really a plate because it does not reach the mantle, but you have a huge range in there.
**Shape no**, plate boundaries tend towards linked triple junctions (120 degree angles) at spreading centers and thus continental margins and wide shallow curves at ocean to ocean subductions zones, this is purely due to the interaction of forces and the strength and thickness of the rock. The most glaring errors I see in fake tectonic maps is long smooth lines for continental boundaries and coastlines or 4 or more plates meeting at one point.
Yes you can have three plates meeting in a australian size continent, for a given value of "in", at least one of them would have to be oceanic likely two of them, continent to continent collisions are exceedingly rare. Three plates meeting is actually quite common. Any point on a plate boundaries are almost exclusively 2-3 plates, no more, no less. But of course a plate has a boundary all the way around it so it may have more plates meeting it. The indian plate is in contact with four other plates, and the arabian plate 3.
[This video](https://www.youtube.com/watch?v=x_Tn66PvTn4) may help you, it is about building fictional tectonics.
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Assume that the events of this question begin in a current-day (2019) world. For the purposes of this question, let's base the scenario on Atlantis. The intelligent sea-creatures inhabiting the underwater city have decided to join the "world stage."
What is a realistic path of Atlantean's forming diplomatic relations with humans, from their making the decision, to "first contact," to forming treaties with other nations, to joining international bodies like the United Nations?
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Much will depend on what you mean by "intelligent sea creatures". Humans don't really have a good track record when it comes to not killing or enslaving other intelligent creatures. Humans included. In other words, if this is a civilisation of intelligent polupodes, then chances are good we'd just turn em into calamari and call it a day.
If they are humanoid in appearance, merfolk for example, then at least they'd stand a chance of not being immediately hunted or farmed.
I think a realistic path for such people to follow would be very much like the paths trodden by many countries in the past.
1. Make yourself known
2. Demonstrate that you are intelligent to a load of self-centered, short-sighted humans
3. Demonstrate that you are not a threat to the humans' navies
4. Make contact with a local government official (mayor of New York, e.g.) who will be able to bump the contacts up the political food chain (governor, president)
5. Having established friendly relations with the neighbours, risk sending a few of your folk into some kind of cultural exchange programme. Because you really don't know much about human society, culture, history or technology, you have to learn. Humans also have to learn about you, your societies and cultures.
6. Make contact with ambassadors or consuls of foreign governments residing at New York.
7. Carefully read [this webpage](https://www.un.org/en/sections/member-states/about-un-membership/index.html) and follow its general directions
Hey presto! You've done all you can to integrate yourselves into the great network of the world!
Now be prepared to be flooded (ha!) with human tourists who will want to come down into Atlantis and vacation there, take pictures of everything, pester your people for selfies, leave their trash all over the place, insist on imposing their ways of doing things on your people, etc.
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**With a big stick and a carrot**
The nation/species needs to be able to defend itself. No claim to the oceans will be recognized without the threat of war if it isn't. China is busy building fake islands to extend it's claim over the oceans. If someone told them their claims over the oceans were not valid, they'd threaten war. The species needs to be able to back their claim by force.
The other side is the carrot. Minerals, food, drugs, technology is available to their trading partners which would make them rich. All the more reason to accept their claim
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First off they want to go public as big and fast as they can. If a government or small group of people find them first it could end in bloodshed or capture. But if the global public is aware of them public good will could prevent a lot of mistreatment.
I'd say the best way to go about this is to get internet access. Then build up media attention if possible. Post videos that would be hard to fake proving you exist. Not everyone will believe but at least some will and that's a start. Next have a few members of your species show up in public at places where celebrities are and let people touch them and give some basic proof that they are real.
All of this needs to be combined with messages of peace and friendship. The goal is to get the western public on your side so that when the world governments actually do something it can't be too heavy handed or cruel. If you can get at least one powerful country to say they will protect you that should hopefully prevent any rouge nation from attacking.
Next I would say the best idea is to give the rich nations what they want. They are probably gonna want to study you and any magic/tech you have. So if at all possible give them the bodies of your dead, let them study your living and share your secrets. Basically remove any reason they would have to screw you over and further convince the public you are on their side and just want to help.
Alternatively start a religion. Tons of religions have started based around nothing more than a charismatic speaker. Imagine starting one based on an actual true honest to god alien race that you can show upper level members. If you can get enough of a start your followers will help smooth over your transition into the world and possibly give you a lot of power.
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It generally starts with what pressures are causing them to want to make contact with the outside world? Generally, depending on the species and their drive, a civilization that is healthy and self-sufficient (and is not being invaded) has no need to reach out to other nations barring general curiosity.
**Pressures**
If they are doing this because they need resources, there are two avenues they would have to explore: a) invading nations with resources they need and b) making overtures to nations with resources they need. The former would hinge on an analysis of the military strengths and allegiances of those involved. For example, if your nation had a ridiculously overpowered weapon that could wipe out another country in an instance, I don't think they'll have too much trouble invading. :)
For the second avenue, if they were really trying (and depending on how desperate they were for the resources), they could learn the language and customs of the nation in question and make overtures via a delegation. For example, let's say they need food and they wanted to approach the US (in better times), they could learn the language (listening in to broadcasts, figure out the Internet, etc.) and learn that hands in the air and a white flag are signs of surrender/peace.
If they're doing this out of curiosity or because they've decided to give up on being isolationists, I figure they'd take the peaceful route noted above. Alternately, they might decide to send agents to integrate into the destination society and bring back their knowledge to help adjust to how they need to interface with that society.
**First Contact**
In terms of first contact, it depends on who they want to interface with. If we're talking about the rough scenario you outlined above, then interfacing with the UN is probably their best bet since they're looking for an international/all-encompassing relationship with the rest of the world. If they wanted to connect with a single country, then obviously, they'd approach the capital (or perceived capital) of that nation.
A lot of this depends on how well their society syncs up with the target society. Water breathing entities that barely see the light of day might have a LOT of trouble interfacing with those floppy air breathers above. Additionally, if they are drastically different from humans, they will likely need to address that somehow, either by hiding their appearances or finding a way to make themselves look more human, which can lead to some seriously funny but scary situations.
**Separate Relations with Nations**
Again, depending on their goals and such, they may decide to do separate deals with different nations. From the outside, I'm guessing they'd do it as a sort of common sense diplomatic strategy where they want to establish embassies with various major countries to do business with them. They might start with the UN as a general starter but ultimately the UN is more of a forum than an actual entity you'd entreaty with (most countries don't like giving up their sovereignty which is why we are where we are historically).
**Additional Questions**
Going forward, you'll want to ask yourself some questions about whatever nation this ends up being to help determine how they'd approach this:
* Are they physiologically different and will that cause problems for any relationship they hope to foster?
* What are their motivators/drivers when it comes to opening relations with another country or the world? Everyone and every country has them whether they like to admit it or not.
* What is their technology level and does it work along the same lines as ours? Atlanteans might rely on chemical circuits for their technology or even light because shooting electricity through salt water may not be very effective. :)
* How far or close are they to the target civilization in terms of social norms? They may hate the idea of socializing or conglomerating in crowded conditions because the seas are so vast. Or they might be too clingy for the same reason.
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You are the leader of a far-future civilization - human or otherwise - that has endured for trillions of years doing whatever far-future civilizations do. You've surrounded stars with Matrioshka brains and gathered them up with stellar engines, pooled as much mass as you could and did all the computation theoretically possible, but energy is the real problem.
You know you're going to run out of extractable heat soon enough. Black holes radiate too slowly, and while they get stronger in their last moments, they ultimately vanish.
Luckily, your universe contains an anomaly, something totally unique, contrary to the laws of thermodynamics, and, as far as you're aware, totally indestructible and immutable. The anomaly is a single object of a certain size that constantly radiates at a specific temperature, thus producing a constant amount of power.
You wish to maintain your civilization, even if you have to upload your people to computers and shrink them down to a microscopic scale to run everything off the anomaly, for the rest of the infinite span of time past the heat death.
The minimum requirement is the continual, uninterrupted simulation of the equivalent of at least **one million human brains** for a time that **exceeds any finite value** given.
**How small and cool can the anomaly be?**
You have access to:
* The combined knowledge of a far-future civilization gathered over its lifespan. No technological holds are barred provided they make some physical sense. Super-intelligence is fair game. Assume mind uploading is practical.
* Several trillion solar masses of initial material of your choice.
* A few billion active stars and all the initial energy they can provide.
* One anomaly that is your only thermodynamics-violating object.
You may have to worry about:
* Proton decay and quantum tunnelling. How do you replace parts of your computing system as they go missing or fuse into each other? Do you synthesize new matter out of energy - and can you do that if your energy source is only at infrared or even *radio* wavelengths? (Or does it have to be brighter or hotter?)
* Logistics. Computing systems must be able to simulate everyone *and* keep track of the physical world with sensors, repairing damage and the like.
* Sanity. Can a simulation that lasts forever even provide infinite utility to its occupants? Will you resort to memory-wiping or are there other options that a sufficient amount of energy can help provide? (How much will you need?)
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## An Underclocked Civilization Is Only Constrained By Data Storage
The number and complexity of minds is irrelevant if you **adjust the processing speed**. Even if the energy trickle only allows 1 computation per trillion years, a trillion trillion stored hyperminds would still be capable of an infinite number of thoughts forever.
So I can think of 4 dangers, in increasingly disturbing order.
**A Fading Danger: Gravity Wells and Radiation** -- It will be important early on for the civilization to make a run for it from any mass-dense regions of space, because dodging black holes and hawking radiation would be dangerous in low-power mode. Once all undesirable mass has left their [Hubble Sphere](https://en.wikipedia.org/wiki/Hubble_volume) (i.e. distant enough that the expansion of space exceeds the speed of light), external sources of damage will be removed.
**An Uncertainly Fading Danger: Other Hostile Civilizations** -- How certain are they that theirs is the only such anomaly? Even if they are incredibly, highly certain, they will probably be wondering about self-defense for a while. But it'll get increasingly safer if FTL travel is impossible, as only civilizations within their Hubble Sphere would matter. But... How certain are they that instantaneous FTL travel is impossible? Even if they are super duper certain of that, they might keep worrying about that, just a little bit...
**A Constant Danger: Physical Decay** -- This is the big one for your question. Entropy will always be an issue, as well as containment of mass and energy. They must design their computer and redundant data storage to keep maintenance and uncontrollable exhaust under the anomaly's output by a huge margin of error. Mind computation can happily live only within that margin, and nobody but the maintenance janitor would notice. Unfortunately I can't seem to find any source for a theoretical minimum rate of data loss, and the capabilities of future nanotechnology may be unknowable. But Wikipedia's page on [Limits of Computation](https://en.wikipedia.org/wiki/Limits_of_computation) might be a place to start. Anyway, here are some mitigating strategies they might use:
* In case of catastrophic damage, it would be desirable to safely keep lots of backup energy, possibly stored as mass orbiting in a **Dyson Swarm** to catch exhaust.
* An indestructible immutable material would be ideal to help keep particles from whizzing off, so they might even **build among the matter of the anomaly itself** via quantum tunneling.
* Then, giving the anomaly a **relativistic spin** will cause the computer in the faster moving exterior to age slower than the core, pumping up the core's relative rate of energy output. In addition, this will store an incredible amount of energy as angular momentum, but hopefully their computer won't fly apart!
**A Growing Danger: Lack of Meaning** -- Heaven without its famous, boundlessly deep source of new awesome good stuff is, by definition, hell. Huddling next to a dim glow in endless darkness, having thought and imagined literally everything you can, and knowing there's nothing left, sounds kinda like a bad goal.
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**It is infinite.**
[](https://i.stack.imgur.com/CFeY4.png)
<https://www.youtube.com/watch?v=P7ojSW5pODk>
Your thing is not amenable to descriptions of scale. It is infinite, or perhaps has no dimension. Or both - a point opening to another plane. The notion of size does not apply.
Fortunately the notion of "where" does apply so you can find it and use it to make your coffee.
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I have a spaceship which is basically a cylinder a little less then a kilometer long. Attached to the ship by pylons connected to a hub is an inhabited ring which spins to produce a gravity-like effect. I want to get people from the hub up to the ship through one of the pylons. "Down" is the outside of the ring and the center of the ship has no gravity. What method of transport would lift them from the ring and by the time they got to the ship, cancel the momentum they would have from the spinning ring?
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Firstly... make the inner 'hub' have two walls - an outer shell that rotates with the spokes and ring, and an inner wall that is stationary and useful to the people inside. So, the elevator rides down the spokes to the hub, still spinning, and then the elevator car transfers sideways to a track that runs around the central hub... initially moving at the same speed as the rotating spokes and wheel, but gradually slowing down until it's 'stationary' - synced with whatever root motion the inner cavity has. At that point, people can move freely through the hull into the inner cavity in zero g.
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I believe the answer is ‘the same way the passangers gained their angular momentum when trqvelling down the pylon.’. They only gain ‘gravity’ if their angular velocity increases as the pylon platform descends from zero g to N g. They’d gain that motion by holding on to hand rails and having their feet in intimate contact with the floor of the uppy-downy ride. And, when they travelled upwards, they’d expend their rotational energy against the floor and railings.
Up near the top its gets dicey since low g means the static coefficient of friction is not realiable — zero times any number is zero. So, sticky floors, like post-its glue, or magnetic boots, or velco, or just hold on with both hands would be sufficent when combined with low acceleration when the uppy-downy bit neared the top low g spot.
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The elevator can rotate around an axis parallel to the station axis, allowing the people in it to stay upright during the ride, and the angular momentum transfers itself to the ring automatically when you go upwards.
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It is fairly simple if you do not care about using the "pylons" or are okay with them not connecting directly to the ring.
Simply surround the rotating ring with a non-rotating square so that the ring rotates inside the sides of the square at the their centers.
Then have an airlock inside the ring with the pressurized transport "vehicle" and release the vehicle to the square at the center point. The ring will continue rotating but the vehicle will continue along the direct line inside the side of the square. The vehicle would then go into free fall except that it decelerates preferably at a rate that sees it stop before the side of the square ends and it crashes thru the wall into vacuum.
Note that the "square" does not actually need to be one. You can make the sides whatever length gives you acceptable rate of deceleration. It can be oblong or #-shaped. You can even omit most of the sides. The ring will probably rotate fast enough that having one will be enough just like hard drives have been doing just fine with one set of heads. And just like with hard drive heads you will probably want to stack multiple "tracks" and airlocks. And you can have as many airlocks along the ring per track as you want for capacity. Since all the vehicles will decelerate at the same rate they will not collide even if they share the same track.
Anyway once the vehicle reaches the "corner" of the square or end of the deceleration track, you just connect the corner to the center with a pylon and have the vehicle move there. While the deceleration probably is best done with some sort of fairly robust tracks, normal or maglev, after this point the vehicle will be in free fall and assuming the square and pylon are pressurized it can simply fly.
Getting back to the ring just does the same thing in reverse. Fly to a corner, accelerate spinward along a track to match velocity with the ring and time it so that an airlock will catch you.
Technically if the ring rotates in a pressurized shell you might not need the airlocks and simple mechanism to catch and release the vehicles would suffice. But you probably want the airlocks for safety in which case the square will be unpressurized and there will be another set of airlocks at some point of the pylons. I'd guess at both ends of them. In that case some sort of maglev system to handle both acceleration and deceleration and the flight along the pylons would be the simplest solution. Simple rockets as a back up just in case.
EDIT: Added possible space station config to illustrate how it differs from the question.
[](https://i.stack.imgur.com/Vx5op.png)
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The simplest way is this:
* the pylons are attached to the outer ring.
* the pylons are also attached to a central pylon hub.
Now you have the pylon hub rotating (quite slowly) with respect to the rest of the ship, and you only need one airlock connected axially and capable of connecting the two rotating parts. This could be done in a lot of ways, for example with a [ferrofluidic seal](https://en.wikipedia.org/wiki/Ferrofluidic_seal).
When you go up the pylon, you experience a lateral force - the [Coriolis force](https://en.wikipedia.org/wiki/Coriolis_force). You can have the elevator car simply hinged at the "top" or mounted on a rail, and free to rotate. The Coriolis force will be maximum at mid-run, the car will rotate at an angle depending on ascension speed. It will start perpendicular to the ring, then tilt sideways, and then slowly tilt back before entering the hub.
[](https://i.stack.imgur.com/A8rkv.jpg)
For those interested, [here](https://books.google.it/books?id=_D5dDwAAQBAJ&lpg=PA52&ots=DnvE9QPjwm&dq=horizontal%20turntable&hl=it&pg=PA49#v=onepage&q=Horizontal%20turntable%20of%20mass%20M&f=false) is the mathematical solution to a very similar problem (the "pylon" has a 45° angle here, and gravity creates a lateral component, but simply assuming g=0 makes the two solutions identical).
# Rough estimate
We want one G ($9.81 \frac{m}{s^2}$) at the edge of an habitat wheel of radius R. Gravity in a spinning wheel is given by the square of the peripheral linear velocity divided by R; the PLV is the length of the circumference, $2R\pi$, divided by the time taken for one revolution in seconds - which is to say, multiplied by RPM and divided by sixty. So:
$$9.81=\frac{(\frac{2R\pi(RPM)}{60})^2}{R}=\frac{4R\pi^2(RPM)^2}{3600}$$
which should give approximately $RPM = \frac{30}{\sqrt{R}}$.
For a wheel of radius 50 meters, we need roughly 4.2 RPM.
Supposing the elevator runs at a speed of V = 1 m/s (a run takes one minute, which is reasonable), we need to shed a linear velocity of $\frac{2R\pi(RPM)}{60}$ in a time of R/V, so the **average** lateral acceleration is $\frac{2\pi(RPM)}{60V}$ and, expressed in G, $V(RPM)(\frac{2\pi}{60\times9.81})$ or approximately:
>
> **Average lateral Coriolis acceleration when going down a wheel spoke while the wheel is turning at RPM rotations per minute**
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> $C = V \* RPM$ hundredths of a G.
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Note that this is independent of the radius, because the longer the radius, the lesser the RPM needed to have one G at the border and the more time we have to shed lateral speed during the elevator run (i.e., the radius is already factored inside the RPM number).
For a V of 1 m/s, lateral speed is on average four hundredths of a G; enough to perceive a little swaying, no more. A tilting elevator might be overkill.
If you shoot down a pressurized pylon at 25 m/s, though, you experience a lateral acceleration of 105 hundredths of a G - in other words, you crash laterally, *hard*.
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Arrange the ship-hub to have a non-rotating pylon with a tube inside it that extended from the hub down into the ring-habitat to within a short distance of the rings floor. Where the pylon passes through the ceiling of the ring it would be attached to a circular band of non-rotating “ceiling”. The rotating and non-rotating parts of the ceiling would be linked via a rotatory seal.
Although the tube and pylon would be non-rotating they would appear to move from within the habitat ring because the habitat ring would itself be rotating. The pylon with the tube would appear to sweep around the surface, a little like looking at the second hand of a clock from inside the clock.
Rails would run around the entire ring on the floor of the habitat directly below the tube pylon’s path and a motorised carriage would be provided to run on these rails.
To use the device people would climb into the carriage and it would gently accelerate around the rails against the direction of the ring’s rotation.
When the carriage was directly under the tube it would stop accelerating and remain at constant angular velocity directly below the tube. At this point the occupants would have cancelled all of their angular momentum and would now be weightless. All that would remain would be to jump and they would be propelled along the tube all the way to the hub.
Obviously there are a wide range of variations on a theme here. If the ends of the habitat were to be utilized the rotatory seal issue could be simplified by using an airlock to transfer from the habitat-ring to the pylon/tube attached to the outside of the vessel. This could then be spun down to produce weightlessness and the rotatory seal could be much smaller and located on the axis of the hub.
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If time of transportation isn't an issue, then you might be able to use velcro like they do [here](https://worldbuilding.stackexchange.com/questions/141726/what-kind-of-footwear-is-suitable-for-walking-in-micro-gravity-environment "Stackexchange footwear in micro-gravity").
If the time of transportation is important, then my next guess would be something akin to a psuedo-railgun designed elevator where the person indicates where they want to end up, spend half the trip accelerating and the other half decelerating.
Due to the properties of magnets here, it would mean that they're kept in place by non-physical means, and the fluid bits of the body are the only concerns.
Downside is that they would take about the same amount of time to get anywhere inside the ship using this. And that would require your people to be wearing suits that have magnetic properties throughout them. And probably limit how quickly they can move because you don't want to sandblast people's faces off with air. And if it breaks AT ALL, you've got dead people.
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## Just Angle the Floor!
Or more precisely, rotate the elevator car.
A regular old elevator will have 2 problems: first, as the car rises or falls, changes in angular momentum give the perceived gravity force a horizontal component, as though *the floor is sloping!* Instead, **just rotate the car and that force will feel vertical again.**
Second, as the car stops or starts at the central hub, occupants will still have the same momentum/inertia and will *launch upward at the ceiling!* Instead, **just put the floor above them first!**
So let's put that all together... Both up and down cars gradually accelerate and then decelerate, as well as gradually rotate in the same direction as the ring spin, turning around until they end upside-down from where they started. For cars heading up to the hub, this gradually adds a soft sideways push from the floor to drain angular momentum, turning into an outward push to gradually settle occupants to a resting stop in microgravity. Cars heading down to the ring will start with the floor in toward the center of the hub, and occupants can just float in there. As the car accelerates, the floor will gently rise to meet them and the occupants will settle onto their feet. Then the push will gradually turn sideways to impart more angular momentum, finally stopping right-side up on the ring.
Easy as that!
[Answer]
Similar to how a transmission in an automobile switches between gears, you can have the elevator (pylon being the elevator shaft and therefore mobile) to/from the hub be a sort of 'clutch' system. The elevator would be an interface between the rotating ring section and the stationary hub, effectively forming mobile spokes. To transfer ring -> hub, the elevator would match velocity with the ring. Once the doors are closed, the pylon would decelerate in such a way as to comfortably come to a stop relative to the hub, in position to open into a hub access door. Transferring hub -> ring would be much the same, with the elevator pylon accelerating to meet the ring's velocity once the people are inside it.
EDIT: I should note that in my mind, the spokes remain equidistant from one another and move in unison, and they are the primary structural component holding the ring in place around the hub. The contact surfaces between the 3 components would be ultra-low friction or easily replaced, and the 3 components would effectively be completely 'detached' from one another, with a sort of rail (like a barn door track) holding their positions relatively constant with respect to one another.
[Answer]
There appear to be two parts to your question:
1. How to transport someone from the ring to the hub
2. How to cancel their momentum.
The pylons will need to be fixed at one end (either the ring or the hub).
**Pylons Fixed to Hub**
In this case since the hub is stationary all the pylons will also be stationary.
The ring is just moving round the pylons (possibly using some kind of track).
So in order to cancel the momentum of the person you have to "accelerate" them in the opposite direction to the spin of the ring. However what you are really doing is decelerating them since once you match the velocity of the ring they will be stationary. Ideally you should "stop" them next to the pylon so that they can transfer to the pylon then move toward the center.
The movement of the elevator doesn't need to be complicated, you could use a rack and pinion or just two cables (one to pull it to the center and one to pull it back.
**Pylons Fixed to Ring**
Ideally you would have two sections of the central hub:
* A rotating part attached to the pylons.
* A stationary part.
Since the pylons are now fixed at both ends the elevator could be even simpler (one cable) since there will always be some "gravity" as long as the elevator is slightly offset from the center of rotation.
Once the person has been transported to hub they can be moved to the center of the hub. At that point the only momentum they will have is their rotation, so if you cancel their spin, they will then be "aligned" with the rest of the stationary hub.
**Airlocks**
I am assuming you don't want the person to have to put on a space suit every time they transfer, so we have to figure out how to transfer people.
In the first case (stationary pylons) you would probably need some kind of "car" that sits on the inner edge of the ring that can run on a track next to the track the pylons run along. Initially the car would be rotating with the ring so the person could use an airlock to enter the car.
The car would then "slow down" so that it was stationary with respect to one of the pylons and the person could transfer through another airlock to the pylon.
If the entire pylon was pressurized no further airlocks would be required.
If the pylon is not pressurized you would need additional airlocks to enter/exit the elevator.
In the second case (rotating pylons) the entire structure (ring, pylons and central "rotating" part of the hub could all be pressurized avoiding the need for airlocks.
The only problem is transferring the people from the rotating part of the hub to the stationary part of the hub. Probably the easiest way to achieve this would be to have a circular room, in the middle of the hub which can be rotated independently of both the hub and the ring that way you could spin the room to match the ring, let people enter through one airlock.
Then stop the "transfer" room and let them exit into the hub through another airlock into the stationary part of the hub.
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[Question]
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## Premise
The goal is to implement a bronze age version of blockchain in ancient Egypt to introduce a layer of security for the royal tombs.
Tomb raiding was rampant, and at times even the legitimate successor would loot his own predecessor's tomb. Family looting aside, there were punishments for thieves who were caught looting. However, historical records seem to suggest there was ample opportunity for even non-royals to work the system:
>
> After some days, the district officers of Thebes heard that we had
> been robbing in the west and they arrested me and imprisoned me in the
> office of the mayor of Thebes. I took the twenty deben of gold that
> represented my share and I gave them to Khaemope, the district scribe
> of the landing quay of Thebes. He released me and I rejoined my
> colleagues and they compensated me with a share again. And so I got
> into the habit of robbing the tombs. -- Amenpanufer (11th century BC
> self acclaimed tomb raider)
>
>
>
While building tombs underground so they didn't stick out like sore thumbs did help, archaeological evidence suggests that physical security mostly just amounted to obstacles and heavy objects. This means that the stereotypical "booby-traps" were not historically accurate. Playing devil's advocate, even if they were used, the dilemma would be largely unchanged. The builders/workers would still know how to defeat them. As many great Egyptian tombs had entire towns of workers who lived nearby, this creates many potential points of failure into the "trust" system.
Our 21st century implementation of blockchain is a digital distributed ledger that has redundancy across many servers, making it hard to retroactively alter the data. I concede, given only bronze age technology, we lose important elements of blockchain such as electricity. Nonetheless, in principle, I'd like to explore further if it could be done. Given that the Egyptians had the potential for cryptography by virtue of the written word, and let's not forget they had the skill, organization, and knowledge to create massive and challenging projects like the pyramids. While blockchain in antiquity might seem outlandish, I personally believe we should not underestimate ancient Egyptians' competency. Assuming they have the resolve and expertise, the question becomes, is it possible in the first place?
Instead of a digital ledger where all transactions are recorded, perhaps a physical one could have a very similar effect. Of course it would be slower, since we are writing entries by hand. Still, perhaps a distributed array of giant monoliths could improve the security situation for royal tombs.
## Question
What should be recorded on these distributed monoliths to best deter the workers from leaking the design secrets and contents of the tomb, as well as deterring corruption and taking bribes as Amenpanufer alludes to?
**Further Clarifications:**
* **Budget:** unlimited, pharaoh spares no expense
* **Technology:** [bronze-age](/questions/tagged/bronze-age "show questions tagged 'bronze-age'")
* **Fallibility:** this is my biggest assumption, but for the sake of the concept, just humor me: the scribes inscribing the monolith blockchain entries are infallible. Perhaps they are monitored 24/7 or surrounded by crocodiles or are otherwise unwilling to bend the rules in anyway. (if you can think of an implementation that doesn't require such an elaborate assumption, please share)
* **Type of Blockchain:** I'm not requiring a strict cryptocurrency blockchain implementation. Other forms of blockchain are also favorable for transparency and traceability characteristics. In the comments I submitted that, in theory, this kind of implementation could hedge against corruption/bribes. In your answer, just briefly explain what type of blockchain you would like to assume. It can be as simple as that.
I had some extra time on my hands. Here is some concept art:
[](https://i.stack.imgur.com/mpATgm.png)
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The purpose of blockchain technology is to create **records** which are hard to alter. That is very useful when **other records** are objects of value, like bitcoins or stocks, but it is less relevant when the objects of value are physical.
Imagine you own a golden wedding ring. You make an unalterable record that you own the ring. Then a thief takes the ring and sells it to a fence. The fence sells it to a crooked goldsmith who melts it down to create a pair of cufflinks. What good does the record do?
There is some information that might help to deter tomb robbers.
Imagine there is a tomb protected by two sets of traps. One priest knows the first set of traps, another priest knows the second set of traps. To go to the tomb (e.g. to pray there) the first priest leads the blindfolded second priest past the first set of traps. Then the second priest goes past the second set of traps. Both priests would have to cooperate to rob the tomb.
Every couple of years, the priests must lead a blindfolded accountant to each tomb. Assume that this accountant cannot be bribed.
Three problems with that.
* A priest might die before he retires and passes the secret.
* Hundreds of priests are necessary for hundreds of tombs.
* The priests and the accountant might argue about the inventory.
The solution is that each secret is known to several priests and each priest knows many secrets.
* When a priest dies prematurely, the other caretakers must find out which secrets the replacement is supposed to know. That is encoded in blockchain records.
* When an accountant finds a gap, he must check which pairs of priests are possible suspects. Again, that is encoded in the blockchain records.
* When the priests deny that a robbery has happened, the tomb is checked against blockchained inventory list.
*The secrets are secret, the management of the secrets is public and must be protected against alterations.*
[Answer]
We need papyrus money for this. Pharaoh has giant stone monuments built ( so far apart they cannot sequentially be reached within a year) with patterns inscribed in a weather-safe place. Annually they get daubed in gold-ink, and transfer-prints are made from all monuments, the prints then sent to the next monument, for printing next year, in sequence. The prints specify which part of the next pattern to use. After the last print, those papyry are now money. To transfer money, you give the money to the one you are paying, sealing it with your personal seal and a handprint.
Before the printing ceremony, all current money is proved against one monument the current holder can choose at random. Should the prints not match, all sealers on that money are executed. The pattern is big, and only a small part of it is used each year, with input: last printed pattern, and days since last shooting star in a specific part of the sky (denoted by monument itself). This means a forger cannot pre-print money. Post-printing is only possible using the original monuments (natural patterns in the stone), and security there is organized by all the anxious people who'd like to seal in the future - distributed.
This resembles blockchain in that it is only really transparent to a few priests, the burden of upkeep burns an increasing lot of ressources, and the security hinges on technology never reaching certain levels.
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As per my last two questions asked, I still have a niggling query left regarding a humanoid species in production. To further support their matriarchal theme through evolution, I have decided to make them an oviparous species (egg laying). Conducting my own research, I have found that a smallish ostrich-sized egg may not contain the proper caloric content for something human-like with a similar enough brain to develop. Could it be possible, to divert this process through something akin to what monotremes or even marsupials are built for?
An idea I have had for this was the females could contain an inner 'pouch' of sorts or some type of inside organ similar to a human womb that can house and deliver nutrients and calories to the developing child and their hungry brain to account for caloric needs. Perhaps following this, could the baby be then encased in a thin weak egg during its latest stages of development and laid with an ample supply of nutrients needed inside? I feel this could leave the eggs with a few weeks or two left in development time before hatching in the nest. I apologize if this proposed concept is horribly biologically unsound, I am not that knowledgeable on these subjects.
[Answer]
I suspect that your proposal is not viable, at least not without significant deviation from the typical idea of humanoids.
**The main problem**: women are already at the limit of walking effectively while still being able to give birth to such big babies. C-sections are already a rather common operation for several reasons, one of which is the non-trivial risk that the baby will be too large for birth to be safe for mother and child. Widening the hips might sound like a good idea, but doing so seriously compromises the ability to walk upright at any reasonable pace. If you want women to be limited to waddling around slowly like penguins, it might work, but in nature they would be easy prey: natural selection would weed that out rapidly.
For egg-laying humanoids, the egg needs to be large enough to contain the baby when it is ready to emerge, which by necessity means one of two things. Either the baby will be born even less developed than human infants already are, with a probable spike in stillbirths and birth defects (likely including reduced intelligence), or the egg needs to be even larger than the baby would be, with a probable spike in maternal mortality as mothers die from laying these giant eggs. Pick your poison, but either way I don't see that ending well. I suppose evolution might provide an answer along the lines of temporarily widening the hips, narrowing the negative impact on walking and running to a day or two before and after childbirth (not ideal, but manageable) while still allowing giant eggs; it's worth considering, at least, although the necessary structure to allow that would probably come with other effects on the hip bones (I suspect that they'd be thinner and/or more fragile, since they'd have to be able to shift around).
**Another problem**: egg-laying is actually more demanding on the body than pregnancy. This might seem counter-intuitive, but you have to recognize that the egg is effectively a self-contained womb. If it's going to nurture the growing child within, it needs to hold all the necessary nutrients, calories, and so on that it will need, and the mother's body will have to provide that. Moreover, the mother's body will also need to produce the material for the eggshell (which is presumably not going to be of much nutritional value, unless the infant tries to eat the thing when it hatches), which would not be necessary in a pregnancy.
The burden might be a shorter duration, perhaps three months to produce the egg so that it can sit around for another six months somewhere suitably warm, but it's overall going to require more resources, more energy, than the usual mammalian pregnancy and live birth. There's also the question of whether the human body could even produce such an egg materially faster than nine months: I don't have a certain answer, but if it's no, then there'd be no point in laying an egg that would hatch within a day or two. Nature is ruthless when it comes to selecting for energy efficiency: there's several reasons why no animal (to my knowledge) that evolved to give live birth has ever returned to egg-laying, and that is a big one.
**Problem three**: this has more to do with the evolutionary background, and you could bypass it if you wish just by stipulating that live birth never evolved in your world (the effects of that on your worldbuilding are left as an exercise, but I'll warn you that they would be considerable). Pregnancy and live birth, overall, is generally superior to egg-laying as a practical matter. Egg-laying itself demands more energy than a pregnancy would: I've already explained that above, but that's not the only point.
Eggs have to be incubated and protected, unless you want to lose the great majority of them and thus waste significant energy on producing those eggs; this works when the investment per egg is small (fish, insects, basically most small animals that don't fly), but that lack of caring for one's young is not conducive to social behavior or the development of human-like intelligence, and humanoids would be investing too much in each egg in any case. Incubation and protection of an egg or eggs generally entail one parent spending most or all of their time guarding the nest (or both parents taking turns), which means a lot of time and energy that could have gone instead to other needs, especially finding food; in a pregnancy, both parents are left free to hunt without significant incapacitation (humans are an outlier here, but human women are usually still fit until late in a pregnancy or possibly even until labor begins), and protection is reduced to the mother ensuring her own safety, as would be obviously necessary in any case.
One more thing: the strain of producing the egg is still going to look and feel an awful lot like a pregnancy, and come with most of the same effects and complications. The mother's belly is still going to be growing larger as the body gets to work on that egg. Most egg-layers we know don't breastfeed, but most egg-layers we know hatch out young that are significantly more developed physically; as a practical matter, your egg-layers will probably still have to breastfeed to give their hatchlings enough nutrition, given how human babies don't even have teeth for a little while. If your end goal is to reduce the net strain on mothers, moving to egg-laying isn't the way to do it.
**My conclusion**: even if your egg-laying humanoids existed, conventional mammalian humans would have won the battle of natural selection by a significant margin.
None of these problems are necessarily impossible to solve, but you're going to have a noticeably different social structure, physiology, and so on than conventional humans do. It would definitely be interesting to read as a story, if done well, but it would require a lot of thought to do it thoroughly.
[Answer]
Have the brain grow after hatching, maybe long after. This would be different from the human/mammalian pattern, in which the brain has full-sized (or nearly so) at birth, but has many more connections than necessary and develops by pruning unneeded connections: <https://www.healthline.com/health/synaptic-pruning>
So your humanoid lays an ostrich-sized egg, which hatches out a hatchling with an ostrich-sized brain. Which, as the existence of ostriches demonstrates, is perfectly adequate for feeding &c. Some time later, the hatchling undergoes one or more growth spurts, as humans do, but these also enlarge the brain (and of course the bone structure of the skull &c).
[Answer]
The answer that comes to mind is "don't make the egg hard-shelled". If the egg had a flexible self-sealing rind instead of a breakable shell then the fetus could be fed from outside into the egg. The other alternative I can think of is to have the juvenile be hatched as a very small, very dumb nymph that will eventually cocoon and metamorphose into an actual sapient member of the species
[Answer]
No
Eggs need to supply all the materials and calories the offspring needs at once, pregnancy allows for far more resources to be transfered. Humans are particularly egregious and consume a tremendous amount of calories in the womb, around 84,000 calories (~300 calories per day average times 280 days). Eggs have a calorie density of about 1.44 calories/gram so that is a ~ 58 kg egg, to compare an ostrich egg weighs ~ 1 kg. so you have around 2000 calories to work with for an ostrich sized egg. So even accounting for the growth curve you are talking about a human born in its first or second month of development to get by with an ostrich egg sized egg. So this basically ***is*** the marsupial route and is unlikely to work.
[Answer]
A pregnant woman needs to eat up to 500 extra calories per day (on average, for the whole pregnancy) to sustain the fetus. If you want a woman to lay an egg that will have enough yolk to sustain a fetus until birth, there is only one way. You need yo lay an egg with 135,000 kilocalories. For comparison, an ostrich egg has 2,000 kilocalories. The human egg would be gigantic and forming it would be very taxing on the mother.
If we keep the same caloric density as the ostrich's egg, the human egg would weight approximately 100 kg. Now imagine a woman shedding that much mass off of her own body to get a pregnancy through completion outside her body.
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[Panotti](https://en.wikipedia.org/wiki/Panotti) so called from the Greek words πᾶν and οὖς for "all ears", were a mythical race of people, described as possessing large ears that covered their entire bodies.
>
> In the Natural History, Pliny writes about the strange race of people known as the Panotti who live in the "All-Ears Islands" off of Scythia. These people there have bizarrely large ears that are so huge that the Panotti use them as blankets to shield their body against the chills of the night. Their ears were used in lieu of clothing.
>
>
>
[](https://i.stack.imgur.com/nc2gF.jpg)
They seems to obviously share a common ancestor with *homo sapiens*, but how could they have evolved?
[Answer]
They aren't actually ears, they are elaborate growths of fur supported by flaps of skin and cartilage that in a similar way to peacock feathers are used for displays of dominance and status and to attract a mate. In particular they can be made to stand out from the head to make the Panotti seem much larger in order to intimidate foes or potential predators.
As they grew long enough to also be used for warmth both to shed heat on hot days and stay warm during cold nights they also started seeing practical use, but a pristine "ear" with no dirt or mess is still a massive status symbol as it means you don't need it for warmth and have the free time and resources to care for it.
[Answer]
One of the peculiar features of homo sapiens, which made it a formidable hunter despite its flimsy body when still living (and hunting) in the African savannas, is the ability to regulate its body temperature by sweating.
Having this mechanism in place allows for a better temperature regulation while performing demanding physical activities, like chasing a prey. The better the thermoregulation, the longer the chaser can pursue its target until its exhaustion.
Sweating has the disadvantage of losing liquids, which can bring the body to a collapse.
In warmer and drier climates it is reasonable that the ability to regulate the body temperature but not losing liquid would give a significant advantage.
An alternative way to increase the heat exchange is, of course, increase the exposed temperature. Ears are particularly suited for this:
* they have a large surface to mass ratio, significantly reducing their thermal inertia
* they are close to the head, helping in cooling down the brain
* they are in a convenient position for using air flow
* in a dry climate there is no dense vegetation, so having large ear lobes doesn't give a disadvantage by hampering movements.
[Answer]
**Answer from evolutionary theory**
Judging by the drawing they have very small penii. For that reason the males have to grow large ears to impress the females. It's a matter of sexual selection.
EDIT to add example
>
> *by the time Homo erectus arrived on the scene, the hominid penis was significantly longer, fatter and more bendy than our ape cousins'. It
> has even been theorised that bipedalism evolved in humans to allow the
> fashionably new, larger, flexible penis to be displayed to discerning
> females* Penis size: An evolutionary perspective - Carole Jahme
>
>
>
<https://www.theguardian.com/science/2010/may/06/women-penis-size>
Of course the above puts forward only one theory. However when our forbears ran naked, like the Panotti, the penis would have been in full view.
**Sexual selection**
*... when the males and females of any animal have the same general habits ... but differ in structure, colour, or ornament, such differences have been mainly caused by sexual selection ...* Charles Darwin.
<https://en.wikipedia.org/wiki/Sexual_selection>
The fact that their ears are now *ridiculously* large is a consequence of
**Fisherian runaway**
*Fisherian runaway or runaway selection is a sexual selection mechanism proposed by the mathematical biologist Ronald Fisher in the early 20th century, to account for the evolution of exaggerated male ornamentation by persistent, directional female choice.*
<https://en.wikipedia.org/wiki/Fisherian_runaway>
EDIT
Here's a real life example of extremes in outward facial structure that serves no purpose other than display:
[](https://i.stack.imgur.com/EavOb.png)
[Answer]
The explorers were mistaken and from a distance saw some Mongolian women in their traditional headdresses. Or they saw a Nubian goat from the front.
<http://local-moda.blogspot.com/2013/01/traditional-headdresses-of-mongolian.html>
[](https://i.stack.imgur.com/hwwgd.png)
[](https://i.stack.imgur.com/5rgWc.png)
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Geckos use the van der Waal force to stick to things, an effect that humans can replicate and make various materials that utilize such (like extra sticky gloves). My question is, would these work in a vacuum or near vacuum, as in space. The reason being I wish to use these instead of magnetic boots for astronauts as the latter only works on ferromagnetic material.
[Answer]
Geckos can stick to surfaces because their toes are covered in hundreds of tiny microscopic hairs called setae, each seta splits off into hundreds of even smaller bristles called spatulae. So they aren't actually sticky, they use the electromagnetic force from the electron on these hairs touching the electron from the surface. A scientist in germany in 1939 even showed this works when all the air is sucked out of a chamber with geckos inside. It is there for plausible to have this force work in space.
-Not an actual scientist, this is just what I compiled from many sources
Sources:
<https://www.sciencenewsforstudents.org/article/how-gecko-defies-gravity>
<https://www.livescience.com/47307-how-geckos-stick-and-unstick-feet.html>
[Answer]
**Yes**
Geckos, as Chebi Kitty explains below, stick to walls using the Setae and Spatulae to maximize the effect the Van der Waals force can achieve, and this is not dependent on an atmosphere so it does work in space...
**However...**
I'm going to call Van der Waals Force VDW as its just easier
VDW force is very very weak, Geckos weigh very little and have large feet for an animal of their size. so something as large as a human then this force wouldn't be enough to hold them upside down.
Now obviously in space you would be in Zero G and therefore the VDW force would be enough if the astronaut was standing still, but the forces/momentum a human can generate would be difficult to compensate for using VDW alone. Geckos tend not to move very fast when on a vertical surface and even slower when upside down, and they don't carry a lot of momentum when they try and stop due to their very low mass with friction playing its part as well as VDW.
So while VDW Force may work it also probably wouldn't be strong enough to be the primary adhesive force for space boots, but may work well as a backup.
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If I had complete control over the plant's appearance, what would be the best shape for it?
I need the plant to be able to float between the clouds. It doesn't have to spend its whole life cycle floating. But it should catch as much sunlight as possible. It should be able to get moisture from the air. A simple microscopic algae could probably get used to that kind of environment, but if that was the case, then we would already have green clouds. So I wanted to improve it.
At first I thought of an algae colony in a shape of a ball, but that would probably not get enough water, so then I thought about a hollow cactus filled with a lightweight gas. But that would probably not get much light.
Then I thought that I could have several smaller balls and a area between them as one big leaf. But the winds up there would probably mess with it too much.
Obviously all of these would need to be frost resistant.
I intend to use them as a minor nuisance during flying and landings on a desert planet, getting into engines and stuff.
The dead plants or probably ripe fruits would drop down and the desert creatures would feed on them. I like the idea of cactii randomly falling on someone. The colonisers should consider these things as annoying as mosquitoes or pigeons on our planet.
What would be the best shape for these algae/plants? And why?
Could plants or microorganisms produce a lightweight gas? This could be a byproduct of some sort of symbiont within the floating parts of the plant/algae.
[Answer]
You only need to look at our amazing Plant Kingdom to see the wonders of what is possible.
Most plants already use some form of airborne mechanism for both reproduction and germination. It is advantageous for plants to send their offspring as far away as the host plant as possible.
[](https://i.stack.imgur.com/IdG9O.jpg)
Seeds already commonly float through the air. Dandelions are a good example, where the seeds are so light they can be on gusts of winds and transfer between islands and even continents. Grasses use pollen and wind to fertilise itself, they float through the air and are small enough to become an airborne allergy for those in the area. Some plants also use wind to push the whole plant, such as tumbleweed, to roll to new locations.
The current forms of these indicate for your story the plant needs to be as light as possible, if absorbing both nutrients and sunlight within the atmosphere. Gas is by definition sparse in particles, getting nutrients into the plant is an issue and forming a plant cell for photosynthesis a challenge.
I can imagine however if the atmosphere is thick with airborne nitrates and water, that an organism with thousands of 'threadlike tendrils' in a large 3D web could exist. The most efficient form of cohesive cell structure is a lightweight string. These strings could grow in length, floating through the air, and branch off, in a logical way to minimise evolutionary complexity, and form webs and 3 dimensional matrixes that get caught in wind and float around the planet, like very large dandelions.
Reproduction could also occur by detaching pollen and seeds in similar ways to grass, using wind. This also is evolutionary simple, plants are actually very efficient at what they do and are finely tailored to an environment, and I can think of in air no more simpler evolutionary structure with simple genetic instructions than a lightweight string structure with branches.
[Answer]
You have a few choices for floating plants. One is the gas balloon model that you mentioned. It would likely be just a translucent balloon floating in the sky. I think that it would be translucent because the plant would not want to devote enough weight to structure to make it opaque. Also, that means the chlorophyll could run on all sides since some light would leak through to hit the opposite side. The sides do not have to be strong since internal pressure could be similar to outside pressure.
Another option would be a hot air balloon. The top is clear and the bottom of the inside is very dark with chlorophyll (or the equivalent). Since not all of the light is converted into chemical energy, the rest is absorbed and converted into heat. This heat would expand the air inside creating lift. Such plants would likely sink at night.
The final option is to go small. The plants float like dust floats. The heavier the atmosphere the bigger the plants can be and the flatter they are the better they float. In this case, the plants could be like plankton in the ocean. You might posit wind/rain/turbulence conditions that would cause the plants to clump and fall out of the sky. This might be when the plants mate.
[Answer]
A thicker atmosphere would make it easier for something filled with hydrogen gas to float. The floating plants are actually colonies of the same species with interlocking root mechanisms. The species grow in clusters in the deserts on the planet, the male plant species grows tough but lightweight fibrous root networks that fuse into the female member of the species, the female plants are giant cacti-like bladders that fill with hydrogen and methane produced as a byproduct of bacterial colonies inside the bladder like growths. As the storm season on the planet approaches the ground water content begins to dry up and the plants release their hold on the ground floating up into the sky in big colonies of males and females bound together by root systems. this is absorb as much water and sunlight in the clouds as possible while they are flowering and growing their seeding bodies. The males pollinate the females, then they grow tough spine covered seed pods. Ultimately the annual storm season begins and the lightning storms ignite the hydrogen inside the colonies to explode and toss these tough spiny seed pods over as wide an area as possible. The pods hit the ground and burst open scattering seeds everywhere, the storm season is when water is most plentiful giving the dispersed seeds the maximum chance to germinate.
These plants actually take years and years to grow into a successful colony. They are otherwise just colonies of cacti in the desert unless the very specific conditions to begin the metamorphosis into a floating balloon colony exist they are land bound.
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So I have been doing a lot of reading on space elevators/tethers for a SciFi book I am writing and unfortunately there doesn't seem to be a whole lot of info on building one on Mars rather than Earth or the moon. Despite some handwavium for the necessary material science, I imagine it would be quite a bit easier to build one since Mars has around .38 Earth's gravity.
My book would place the elevator on top of Pavonis Mons which lies nearly on top of the equator. This should give me a head start of 14 km and negate most of the tidal effects from Mars rotation. The design would be more along the lines of Halo (elevator car inside tube rather than around cable).
Although I have a long, complicated construction method that supposedly explains the structure is able to continuously transfer fuel and power through hoses that run the length of the elevator along with the 3-6 (undecided) elevator cars that it lifts magnetically like a vertical maglev train. The only thing I haven't really worked out as far as the design is concerned is how to deal with Phobos as it regularly crosses the equator at around only 9,300 km above Mars.
[](https://i.stack.imgur.com/I73Qa.jpg)
From what I understand, a cable from Earth would need to be around 35,786 km to reach the appropriate height. **Would it be as simple as multiplying by Martian gravity, giving me the simple answer of 13,599 km above Mars?**
Also, **would there be a better location to place the elevator other than near the equator so that Phobos isn't an issue?** This of course would require me to come up with something for the rotational effects.
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Depending on the exact design of your space elevator you'll be aiming for a station at or above geostationary (technically Areostationary) orbit, which is 20,428 km above Mars' surface. There must be at least enough cable and possibly counterweighting above areostationary orbit to ensure that the cable remains stable, but in theory if you're willing to put a heavy enough counterweight in place you can cap it off at geostationary orbit.
That's an engineering nightmare though, and you'll almost certainly need to extend the counterweight out further as a heavier counterweight means more stresses and more difficulty in getting material out there in the first place. If you put a construction station in geostationary orbit and then start feeding cable out of both sides to make sure the station stays in place as you build (as proposed by Jerome Pearson) then you need more cable on the outside, but again, if you add a heavier counterweight then you need less cable.
If we assume that it's 1:1 then you end up with a height of ~40000 km.
Phobos orbits inside the sweep of this structure at 9000 km, Deimos within at 23000 km. Sadly there's not much you can do about the latitude of the elevator: It requires the rotation of the planet in order to function (in fact you can show that ascending cars are really stealing orbital momentum from the planet and descending ones are giving it back). That isn't a killer though: You can design the elevator such that it doesn't directly hit either moon (they are very small compared to the area of space you can feasibly build in), but you will have to account for their gravitational effects, which is a lot more complex and will constantly drain energy from the system for corrections. If you're willing to spend enough energy they you could have the entire elevator oscillating back and forth, feeding off the gravitational energy of the two moons to ensure the cable safely weaves it's way between it's dangerous neighbours.
[This may be of interest to you](https://physics.stackexchange.com/questions/33547/space-elevator-on-mars-with-todays-technology-possible). Technically it's a discussion on using contemporary materials to build a martian elevator, but one of the answers proposes a different system that uses space elevators on Deimos and Phobos to achieve escape velocity but only taking a rocket as far as the innermost moon.
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A space elevator works by connecting a satellite in geostationary (well, on mars it's areostationary^^) orbit with a ground station. The satellite needs to be geo(areo)stationary so it's always above the same point of the planet - otherwise it would pull on the connecting cable and wrap it around the planet over time, or require the ground to hold it in position against its orbital tendencies (which would quickly destroy the cable, deorbit the satellite, or rip the ground station out... not good^^)
So for your appropriate height, we need to know how high an areostationary orbit is - luckily, [wikipedia](https://en.wikipedia.org/wiki/Areostationary_orbit) can help us there: it's 20,428 km.
Also, regarding your second question: The *only* location to reasonably place a space elevator is ON (not even "near") the equator. Because only over the equator you can have a geo(areo)stationary orbit. I'm not sure how far away that mountain is, maybe it could be doable - but you definitely can not put the elevator at some random spot on the planet to avoid phobos.
I'm not sure whether there's a spot on the equator that phobos does not cross over, if there is - that would be the best place to put your elevator :)
Otherwise... Well, phobos is going to have to be out of the way. Maybe in your future it was hit by something else and already removed? Or maybe, since you want a counterweight on the upper end of the cable anyway, your engineers pushed phobos into areostationary orbit and are using it for that? (quite a feat, but you didn't specify how high-tech we're talking here^^)
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You could give up on the beanstalk and try a skyhook dangled down from Phobos. There could be some sort of launch system to launch ships from the surface to rendezvous with the skyhook when it passes, and then be pulled up the skyhook to Phobos and beyond (or the payload transfered to elevator cars to go up the skyhook). Thus the ships will use a lot less fuel getting into Mars orbit than otherwise.
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Instead of a space elevator that is anchored to the surface of Mars, how about a modification of the Fulton surface to air recovery system? <https://en.wikipedia.org/wiki/Fulton_surface-to-air_recovery_system>
Hang a cable from Phobos and grab the end as it goes by. It's not a true space elevator in that the cargo has to get to the edge of the Martian atmosphere before it can catch a ride.
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### Space elevator
Just to clarify the other answers, the requirement is that the counterweight has to be past the aerostationary orbit level. That makes it attempt to pull the rest of the cable up and away from Mars. There are basically two approaches, although a combination is certainly possible.
1. Put the counterweight just outside the areostationary level. This involves a large, station-like counterweight. The counterweight would be located close to the areostationary level of 20,428 km (20,414 km above Pavonis Mons).
2. Run the cable about twice as far as necessary. This turns half the cable into counterweight. So the cable would be longer than 40,000 km. People would leave the cable at the areostationary level though. The rest of the cable is just counterweight.
Either way, the counterweight has to be outside the areostationary level. But it doesn't need to be far outside. It can be pulled into one lump or it can be extended out. The math works either way.
It would probably be easier to move Phobos than to move the elevator. Moving Phobos is an engineering problem. We aren't really sure of the theory behind moving the base of a space elevator.
I'm not sure that Pavonis Mons helps you enough to be worth it. Really, if you can manage a 20,415 km cable, you should be able to manage 20,430 km.
### Space catapult
You also should know that a space elevator doesn't give much benefit on a world without an atmosphere. You might be better off with a [space catapult](https://en.wikipedia.org/wiki/Mass_driver). Of course, you also may be planning on giving Mars an atmosphere, which would then make a space catapult non-feasible. The basic issue is that adding atmospheric resistance (which increases with speed) to gravity makes the speeds required at ground untenable. But without an atmosphere, you simply have to crank up the distance to make the acceleration work.
Another problem with an atmosphere is that it dilutes the amount of sunlight reaching the ground, so you have less power. Not so big a deal with an elevator, which can get its energy from space. May be a problem with a catapult, which is entirely on the ground.
A space catapult is helped significantly by increasing the distance above the ground from which it releases. So you might terminate it in Pavonis Mons. Probably not at the top, but above the normal ground level.
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Construct the elevator by extending cables down from Deimos and Phobos during the construction period, adding eccentricity to their orbit during the construction process... You don't have to have the final anchor-point directly over equator if there is a secondary anchor-point equal and opposite of the primary one on the other side of the equator attached to Phobos as well (which has presumably been lifted to areostationary orbit while lowering the initial tether.)
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Several possible solutions. First, as others said, you need the cable to run from the planet to aerostationary orbit, ~20.000km, and a counterweight beyond. This counterweight can be simply cable (not exactly the same mass as the main cable, because what you want is to cancel the force, and net gravity is not constant, but about the same order of magnitude) or it can be an asteroid. Deimos is near the aerostationary orbit (~23.000km), but it is too heavy for a counterweight. Maybe you can nuke it to have a big chunk of it to use as weight ;)
As for Phobos: it orbits mars at ~9000km, about 3 mars radii. One possible solution is to synchronize the cars up and down the cable to deform it (like the strings of a guitar), so that whenever phobos is going to crash, the cable is away from it. This needs a carefully controlled choreography, but it is possibly feasible. This is what A. C. Clarke did in The Fountains of Paradise. Another solution is not to use an equatorial cable, but an Y shaped one. It is harder to build, but I have seen proposals for this. One of the sides of the Y is anchored north (maybe latitude 45-60º) and the other, south. Then Phobos can pass through the Y. I am not completely sure this would work, because the Y wouldn't be straight, but more like a ≻- (curved). The two lower cables have to join beyond Phobos, but far below the aerostationary orbit. And lastly... if you have already nuked Deimos, why not move Phobos to another orbit?
And if you use cable as a counterweight, you have another advantage: as the whole cable is moving at the angular speed of the aerostationary orbit, when you are below that orbit you are at suborbital speed, and if you detach from the cable you fall to mars. But if you are above that orbit you are faster than aerostationary: if far enough, you have speed to leave the martian system or even the solar system without using any fuel (think of it as a sling).
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This may be a minor point but it seems too important to leave in a comment:
If anchored away from the equator, the cable will approach the equatorial plane as an asymptote.
There are three forces to consider (in the rotating frame):
* centrifugal force, away from the axis of rotation;
* gravity, toward the center of the planet;
* tension, toward the anchor.
If the anchor is not on the equator, these last two each have a component parallel to the axis of rotation, opposing each other.
This makes the cable longer and more costly, but it is a way to avoid Phobos.
Such a cable is not straight: it sags. There is a maximum latitude for the anchor, at which the cable lies flat on the ground; I do not know how to compute this.
(How massive can the cable and counterweight be without causing a measurable wobble in the planet's rotation?)
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[](https://i.stack.imgur.com/7rAq6.jpg)
Quick sketch of how I conceptualize this creature's skeleton. Sorry for the chopped off head, the jaw design and such isn't finished. The 4 yellow bones on the tip of the neck are the base of the jaws, but it's obviously unfinished.
There are other problems with this alien's skeleton too, such as the shoulder blades, highly encased "ribcage", and inflexible ventral spine/bone... but today I'd only like to focus on what's really upsetting me about the skeletal structure of this guy:
The esophagus.
I'm not sure how I can have a strong, flexible support for the neck and still have space for an esophagus that lines the underside of the neck. **I don't want food coming in through the top of his head** (such as that when he swallows, it'll look like the top of his neck is taking in the food) even though that's the most logical way to go for a ventral spine.
I also don't know how food will empty into his stomach if the esophagus is on the underside and the spine is attached to the bottom of his body. One way I could combat this is making it so that he digests food through an intricate system in his neck, like a modified, winding, slow moving intestine. There isn't much going on in this alien's neck anyhow. His neck is essentially an extension of his mouth; it doesn't house a brain or eyes, and he breathes and 'smells' cutaneously through his mouth lining. The only issues that may stem from doing this is the act of expelling waste. Unless the waste is in liquid form only (unlikely), then it'll have to move away from the neck somehow, and the problem I currently have in placing the esophagus will be repeated.
So... any suggestions? The only things I don't really want to trade off design wise are:
* The ventral 'spine'
* The long flexible neck and mouthpart that consumes food
* A bilaterally symmetrical organ placement (I don't want the esophagus 'bending left or right into' the gut)
And the problem I'm avoiding is:
* A dorsal esophagus
**EDIT**: Another problem is that this creature eats in chunks or swallows it's food whole. Yes, I know the ribcage will pose a problem with this already; this is just a sketch. The ribcage isn't all bone anyway, just the trailing edges and base of it; the center of the ribcage is a sort of stretchy ligament that calcifies at the ends, allowing it to extend horizontally.
Anyway, being that it swallows it's food whole or in large chunks, I can't have a split esophagus run up into the gut because it would need to be much narrower at the splits. The only workaround to that I see, is making the esophagus a modified intestine (sans stomach entirely) and make the waste (provided that the waste is quite small or soft initally) go through two tubes running up into the gut and expelled out through an aperture on the bottom of the creature (maybe the bottom end of it, that way the tubes act as a sort of 'small intestine' that further extracts nutrients from the waste).
**EDIT 2**: My drawing may have been unclear because of all the clashing colors, overlapping lines, and how there appears to be a dorsal spine already, so I made a less-busy drawing that I hope clears up the confusion:
[](https://i.stack.imgur.com/vRXbm.png)
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I am a little puzzled by the question. All vertebrates have ventral esophagi under a strong, flexible neck support: the spine. Lie on your belly like your ancestors did. Your esophagus is ventral to your spine. You can have a long neck and have an esophagus ventral to your spine. Giraffes do. Sauropods did.
from <https://svpow.com/2009/12/15/lies-damned-lies-and-clash-of-the-dinosaurs/>
[](https://i.stack.imgur.com/ctkKb.jpg)
Look at the cross section of the neck. Esophagus under (ventral to) spine. Here is a horse (actually it is Le Cheval). They have generous necks. Esophagus (œsophage) is ventral to the spine.
[](https://i.stack.imgur.com/4mB67.jpg)
## You can have your thing be a horse with bug legs.
ADDENDUM
I see now that the esophagus and spine maintain relative position in this creature but the body cavity is now dorsal, and so the esophagus has the spine between in and the body cavity. The esophagus will have to duck between the ribs. The subclavian artery is a big muscular tube and it does something similar, coursing over the 1st rib and under the clavicle.
This is from the human. <https://www.pinterest.com/explore/subclavian-artery/>
[](https://i.stack.imgur.com/4AtDV.jpg)
Another difference here is that instead of hanging down from the spine above, the viscera of this creature will be in a pile supported from below. That is ok I think; we humans get away with a similar deal in that when we stand erect our guts do not hang but are mostly supported from below (the pelvis) and in front (the abdominal musculature). Having the belly ribs be substantial and perform a support role is plausible.
An interesting thing about this creature is that its belly would be very tough and analogous to the backs of normal vertebrates. A typical vertebrate positions itself in a fight to protect the belly and take attacks on the durable back. I think this creature would be well served by some sort of armor or tough hide or sclerotized fat stores to protect the back in the absence of ribs.
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There are two options as I see it:
**Bifurcation.** The esophagus descends as expected in front of the spine and then splits to circumvent it. The bifurcation might take place within a muscular gizzard- or [crop](https://en.wikipedia.org/wiki/Crop_(anatomy))-like organ that helps break up food to avoid getting caught at the divide.
**Asymmetry.** Like the bifurcation option this has the esophagus dodge around the spinal structure, but only on one side. Asymmetrical internal organs aren't unusual – most of the human digestive system is asymmetrical.
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My initial idea was to use a unique bone that would attach to the neck spine and would have a hole that allows the esophagus to go trhough. Yet, that design would have limited the size of the chuncks the creature can eat... which would not be a problem if the creature were not to eat big chunks.
I did also consider the possibility of a spine split in two, one going left and one going right, and then recombine. This has the same problem.
So next, I had a look at the design of snake mouths. If the mandible limits the size of the chunks the creature can eat, the snake mouth is the solution... yet, that means to break the structure into two mobile parts, and you will end up with two spines, one before the connection and one after.
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What if the digestive system is ventral, but is basically a stretchy pouch like a hamster. That way whatever is swallowed is carried underneath, outside the ribcage, and is dissolved slowly. Maybe the creature has a way to drop the food and/or waste by opening the pouch underneath.
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The oesophagus could go around the side of the lower neck vertebrae, similar to a chiasm, but with only the oesophagus being asymmetric, or, the spine could be moved forwards in the neck, with the oesophagus going through the back of the skull and behind the spine.
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This is more of a general question than a query about any specific model of arcology, but to make the question easier, let’s assume the arcology is either domed or covered by some sort pyramid made from selectively permeable solar panels, has an internal land area of about 8-10 square kilometers, and incorporates a mixture of smaller megastructures like large residential towers or farms alongside smaller buildings you can walk between via skyways. It houses a few million people, and while any location within the arcology is theoretically only a short walk away, traffic congestion in choke points and just the general need for convenience and efficiency demands a rapid mass transit system.
How would you do this?
Ideally I’m looking for practical solutions above all else, but I’m not above indulging in rule of cool (after all I’m intending for whatever transit system I end up using to be plagued by thrillseekers and its own version of punk biker gangs). One idea I’ve heard that overlaps nicely with an idea I had myself are pods that accelerate along predetermined tracks. The general idea was for the pods to be smaller, car-sized affairs, but I’m thinking more like a monorail system or cable cars that connect some or all of the more distant buildings to each other. To borrow an idea from Alistair Reynold’s Chasm City novel, perhaps the cable cars are all attached to a giant, web-like network of cables and they “crawl” along them using robotic arms like a spider, allowing them to freely change course by grabbing different cables and plot the most efficient route from one place to another using some city-wide traffic AI. Would this be safe and practical enough to pass muster, or is this too much rule of cool?
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# Pedestrian and Bicycle Lanes
Some movement is good for your health, and your arcology won't be *that* large. If you are worried about chokepoints, consider that any other system will have similar problems -- intersections, subway platforms, etc.
* The punks can be kids who hang out in some places, drink beer, play loud music, maybe sell drugs, and intimidate ordinary citizens.
* The thrillseekers can be kids on unsafe bikes, or skateboards, or whatever, riding in an unsafe way.
# Escalators
For people who do not want to climb stairs, [escalators](https://commons.wikimedia.org/wiki/File:Holborn_Tube_Station_Escalator.jpg) may be better option than lifts. They do not have to wait until a car arrives, and escalators are no faster if they stop every other floor.
* There may be etiquette that people stand on the right, walk up the moving escalators on the left, or vice versa. The options for punks and thrillseekers should be obvious.
* Sliding down the rails of an upward escalator?
As a variant, [moving walkways](https://en.wikipedia.org/wiki/Moving_walkway) even for level stretches.
# Streets for Computer-Controlled Cars
There will be situations where walking or cycling does not work. Delivery vans, fire engines, ambulances, the elderly, etc. Have roads where only robotic, networked cars are allowed to drive.
* Thrillseekers can hang on the outside of these cars, e.g. completely unmanned delivery vans.
* Even more thrillseeking people can try to get an "ambulance override" for their manually controlled car and watch how the traffic system shunts all other vehicles out of their way. Until they miscalculate and a full school bus cannot dodge them in time.
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[Arcology](https://en.wikipedia.org/wiki/Arcology):
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> Arcology, a portmanteau of "architecture" and "ecology",[2](https://i.stack.imgur.com/quXMa.jpg) is a field
> of creating architectural design principles for very densely
> populated, ecologically low-impact human habitats.
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Had to look it up!
From OP
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> perhaps the cable cars are all attached to a giant, web-like network
> of cables and they “crawl” along them using robotic arms like a
> spider, allowing them to freely change course by grabbing different
> cables
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This works fine. Cablecars do it now. The cables do not actually suspend the cars, which run on corresponding tracks below and utilize the obliging Earth for support. Cables provide power.
<http://roundaboutsanfrancisco.com/attractions/cablecars.html>
[](https://i.stack.imgur.com/JBwPj.jpg)
I propose that all buildings of any size be central and clustered. This allows one centralized heating and cooling of all of them with one plant and efficiency of scale. You mention skyways; you could also have motorized walkways or horizontal elevators. This too is not very creative and is currently done.
Here is the Atlanta airport.
<https://blooloop.com/news/alcorn-mcbride-waldeck-flight-paths/>
[](https://i.stack.imgur.com/quXMa.jpg)
I feel like having monorails and pedestrian walkways is sort of 1970s Epcot Center. I am trying to think of ways to update these ideas and make them more interesting. Before someone invokes pneumatic tubes: also I want something Futurama did not already do.
* Maybe ziplines? Everyone goes up a central tower and then ziplines down to their destination? That has not been done, to my knowledge. It might be tricky to have motorcycle gangs terrorize ziplines.
+ People movers with cars pulled along by big cables - well, San Francisco did that too back in the day.
+ Use as canals the giant sewers built for an ancient city 1000 times bigger at that site? That could be pretty cool and terrorizable.
+ City is built around fallen starship. The elevators still work, powered by the old fusion engine but now elevators run horizontally. Perfect people movers! The rest of the ship, though, is probably best avoided. A piece of wood is epoxyed over those buttons to keep people from accidentally pushing them.
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See for example, the one in Larry Niven's novel "Oath of Fealty" I think it was 1 x 2 miles, about 20 floors, but lots of multi-floor open spaces. Inverted pyramidal light wells pierced the roof, with balconies overlooking the wells. The roof was a park.
Main travel routes had 'slidewalks' -- a concept also used in Denver's Stapleton airport in real life.
While people moving can be largely on foot, bike, or roller blade, scooter, you still have to have some form of bulk transport. Imagine getting a new sofa home by escalator and bike.
I suspect that well over 50% of the floor space would "un-owned" That is, not 'mine' in the sense of 'my apartment' but would be in the form of access hallways, utility corridors, shared balconies, public spaces, shopping centres.
Note that an arcology has a rather intense cooling requirement. Most high rises have a net cooling requirement even in winter. Well designed ones, use surplus heat from the south side to warm exterior faces on the north side, but the waste heat from electrical use throughout the building imposes a need for cooling. In winter this is easy: Bring air in from outside, dilute it with inside air, and pipe throughout the building. In summer, you can use evaporative cooling in dry climates, or some combination of evaporative cooling, off peak power usage to create cold water/ice/brine to store coolth when it's cheap, to use during peak periods.
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I want to understand how the increase in population translates to order of the creation of different jobs. A very small village probably has a blacksmith, but probably does not have a jewel vendor.
Essentially, how big should a village (mostly farming) be before it has a full time miller, a tanner, a baker, a doctor, a seamstress, general store, etc.
Feel free to include other jobs I may have missed.
I know it will be different for different villages because of different needs but I'm looking for the average.
Eg) 5000 - jewel vendor
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It seems to me you are speaking about early medieval villages not particularly near to a town, but you don't state it clearly, so please feel free to correct my assumption.
Basic assumptions I see in other answers simply do not hold true for medieval life.
A few facts (concerning medieval (i.e.: 800-1400 AC), European villages, keeping in mind north, middle and south Europe were very different and, sometimes, life was very different *just a few* kilometers away):
* Moving between villages was difficult and dangerous; most people did not move much more than about ten kilometers in their whole life (beside the ones in the various armies).
* Money was not common among villagers; primary commerce was barter, even after end of Middle Age.
* Tools were valued and prized, and, as such, were cared for and often exceeded the life span of the owner becoming heirlooms. It was customary to burn houses when they needed to be rebuilt; that was to recover the nails used.
* Primary job for smiths was to build horseshoes, which were easy to lose, but that wasn't in villages where horses were almost non-existent and donkeys were without shoes.
* The limit for population growth was scarcity of food and villagers were always in the verge of starvation.
* Villagers ate what they grew, almost no commerce on food was done.
* Tools were traded, especially if village didn't have a resident smith, as often was the case. Smiths were usually in burgs, not villages (difference is a burg is near a castle of some kind and thus there was request for horseshoes, weapons, armor etc.).
* The first artisans in the village would be miller and baker, who would also act as trade-post.
* A special twist in larger settlements, especially in northern Europe, was the *need* for a brewer; reason for this is given hygienic conditions water was *not* safe to drink, so even newborns drank beer (they has a special low-grade for everyday usage) because that was boiled in the first place and the alcohol it contained prevented too much bacterial contamination); smaller villages usually had less problems.
* What came next strongly depended on what was *around* the village: if the next one had a smith it wasn't likely one would come, OTOH whatever was difficult to obtain would have a reason to.
* Church and priest were in almost any village; priest would teach whatever he could to children, while making sure they would grow God-fearing.
* Monasteries were primarily productive units, usually having knowledge and "technology" far superior to surrounding villages.
* Artisans and trading (barter) was concentrated in monasteries and burgs.
* There you would find also weavers (spinning was done in almost each house).
* Only in burgs you would find full-time carpenters and masons, everywhere else neighbors would lend a hand as required.
* Medical doctors were non-existent; old women would help in childbirth and some of them would know a bit of herbal potions and ailments (sometimes risking to be burnt at the stake); many monasteries retained some medical knowledge.
Please clarify better what period/location you are interested in.
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**It entirely depends on context.**
"Every village will be different" - despite your own acknowledgement of this fact, it is nevertheless true, and perhaps moreso than you realize.
People will form whatever jobs there are **supply and demand** for and which a profit can be made from, assuming largely unrestricted capitalism applies. If there is a market for jewelry selling, for instance, then someone will fill that gap as soon as they notice and take the initiative. This could happen whether there are 100, 1,000, or 1,000,000 citizens.
**There's no way to know a true average;** in order to do so, we'd need accurate historical records of the growth of small villages throughout history. **That kind of extensive and accurate statistical data has simply been lost to history.**
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I will qualify this as a sort of Non-Answer, but more of a guideline.
Follow Maslow's Hierarch of needs as a model, and couple it with specialization.
As has been stated, most communities are likely to have a blacksmith or farrier and a bunch of farmers. Call it 50 folks per town. I would say that around that time you will get an Inn, based on proximity to a road or navigable waterway. Flowing water will bring a mill. I suspect his might happen around 75 people.
Now we get to Maslows Heirarchy. The above is a guess at what point further specialization to begin. The first thing that individuals, and by extension the community, wants is to provide for the physiological. Food, Shelter, Etc. By the time you get specialization and the purely physical necessities are met and exceeded, maybe at 75 people, you can get further specialization with additional craftsmen. Carpenters, Wainwrights, Pottery makers, and so on. This represents the security phase. YOu have enough, it's time to make sure this state of affairs continues. You are now in a position to sell the surplus, but if you are selling, you need people to buy. You have to attract them by making sure there is more that one way to get to the inn. Waterways, build roads to other places maybe. That might be at around 150 people. As the town grows, opportunites for further specialization is going to come up. If you assume one blacksmith per 50 people, at 150 people you might get a blacksmith AND a farrier AND a weaponsmith. That takes care of tools and Horseshoes and sharp things. Take some of the apprentice metalsmiths and then you might get a silversmith out of the bunch. This launches you into civic pride, or the Love and Belonging phase.
Just remember that every specialization adds to surplus and will have a purpose based on location and local natural resources. Lots of iron might mean additional weaponsmiths. Fertile ground might mean an agricultural hub. Esay transport might give you means to start a Bazaar.
Just use a little logic.
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As populations increase specialization takes place. So everything needed and then wanted by people move from being done by ones self, to be provided by a specialist (blacksmith, baker, butcher, etc)
So I would pay a butcher for my meat, and a baker for my bread because my time would be better suited making horse shoes.
The higher the population the more specialization, production, and wealth is created.
no sources, just an MBA in Economics and Finance
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**Resources and Commerce**
All is reduced to the resources that a town has and how well this is translated into trading with other merchants or towns.
An actual example would be Venezuela, they have a resource "Oil", and they sell it to other places in exchange of their products, services and money. You can see the effect in a economy when this price change, they have millions of habitants but that isn't what springs jobs, the demand indeed exist but they don't have the means to acquire it, is a good economy what produce jobs.
Your town would get a jeweler if there is enough money in their local economy, to pay a merchant to bring the stones, to cut them and place them in a shop and for people to come and pay for them.
[Answer]
To best help you understand how this works:
**FOLLOW THE MONEY!**
The more currency/product A place generates the more chances it can have to diversify.
Say we have a wheat making village;
We make lots of wheat but we are spending alot of time hand mashing it.
random guy A invents a mill and can mash lots of wheat freeing up time for the farmers.
Random guy A makes a lot of money this way and wants to please his wife with fine jewlery.
He notices random guy B makes fine jewlery so he pays him in currency or wheat to make his wife fine jewelry.
The ladies of the village are jealous the wifes fine jewelery and demand their husbands buy them fine jewelery as well.
The cycle goes on and on till we have facebook.
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For *population increase* this is a function of **market size**. When there are only a few dozen people, chances are you cannot make a living as a blacksmith or baker or jewelry maker. You need to hunt, gather, fish, farm or whatever, and these occupations do not exist: People do their own smithing, or buy stuff from traveling vendors, or go to a bigger city, or all of those things.
They do their own milling, and baking: For example I've seen slideshows detailing how to use stones to grind your own wheat by hand. I've seen home-made foot pedal type tables for throwing your own pottery, or spinning a grinding wheel.
Specialization occurs for two (and usually three) essential reasons:
First, that long practice or expertise improves the product or outcome.
Second, that there is enough demand for the product that an individual can remain busy doing it all day.
Third, that others are willing to pay or trade enough for the product (or service, like from a veterinarian or water well locator) that the practitioner is better off than they were before becoming a specialist. For an example of this third requirement IRL, in America: practice improves musicianship, there is clearly a demand for music and a willingness to pay *something* for it, but the vast majority of musicians could earn more money as truck drivers or delivering pizza.
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[This website](http://www222.pair.com/sjohn/blueroom/demog.htm) has the following list. These are the number of people it takes to support a single business; for example it takes 150 people to support a shoemaker, so a town of 450 inhabitants will have 3 shoemakers. The authors adds that the number can vary by up to 60% in either direction.
* Shoemakers 150
* Furriers 250
* Maidservants 250
* Tailors 250
* Barbers 350
* Jewelers 400
* Taverns/Restaurants 400
* Old-Clothes 400
* Pastrycooks 500
* Masons 500
* Carpenters 550
* Weavers 600
* Chandlers 700
* Mercers 700
* Coopers 700
* Bakers 800
* Watercarriers 850
* Scabbardmakers 850
* Wine-Sellers 900
* Hatmakers 950
* Saddlers 1,000
* Chicken Butchers 1,000
* Pursemakers 1,100
* Woodsellers 2,400
* Magic-Shops 2,800
* Bookbinders 3,000
* Butchers 1,200
* Fishmongers 1,200
* Beer-Sellers 1,400
* Buckle Makers 1,400
* Plasterers 1,400
* Spice Merchants 1,400
* Blacksmiths 1,500
* Painters 1,500
* Doctors 1,700
* Roofers 1,800
* Locksmiths 1,900
* Bathers 1,900
* Ropemakers 1,900
* Inns 2,000
* Tanners 2,000
* Copyists 2,000
* Sculptors 2,000
* Rugmakers 2,000
* Harness-Makers 2,000
* Bleachers 2,100
* Hay Merchants 2,300
* Cutlers 2,300
* Glovemakers 2,400
* Woodcarvers 2,400
* Booksellers 6,300
* Illuminators 3,900
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[Question]
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I've been playing a lot of Deserts of Kharak lately, and I am wondering if landships depicted in game, which are essentially seagoing ships on tracks, would work in a Snowball Earth scenario. By Snowball Earth, I am using the classic Snowball Earth scenario, where all of the oceans are frozen, and the equatorial regions have temperatures of around modern-day Antarctica.
So would landships be a preferred method of transporting bulk cargo from one place to another in a snowball earth, say, compared to airlift? What challenges might a landship that runs on tracks or wheels might face on the glaciers other than structural issues of building such a titanic vehicle in the first place?
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I am not familiar with Deserts of Kharak, so I had to look up what their landships looked like... and I must say, those do not look like "ships" to me. They look like very big trucks or tanks. So if you're willing to call all of the things "ships" that that game chooses to identify as "ships", then sure. Just call whatever your preferred land-based mode of transportation is a "landship", and "landships" will be the preferred mode of transportation, by default. It is a trick of language, and nothing more.
So, I'm going to split the rest of this answer into two parts: what are the challenges associated with massive ground vehicles on a snowball Earth, and what would actual *ship* designed to run on ice and snow be like?
As far as massive tracked vehicles go, you'll note that powered vehicles designed specifically for travelling on ice and snow in the real world already use tracks! Some of them also use skis (i.e., snowmobiles), which are much better than tracks or wheels for unpowered support elements, but always tracks for the motive force. This is for two reasons: 1) ice and snow are slippery, and you need tracks to get enough grip (the same reason you can use skis for non-powered support); 2) ice and snow don't support as much weight as rock and dirt, so you need to spread out the weight of your vehicle over a larger area. So the tracks are a pretty good feature, and the challenges faced by a gigantic, aircraft-carrier size multitrack vehicle will be largely the same as those faced by present-day snowmobiles: distributing their weight over a large enough surface area to avoid sinking into the ground, and maintaining traction (although solving the first problem takes care of the second pretty much for free).
Tracked vehicles do have some unique problems that get worse with size, however, and are at odds with the need for traction on snow and ice: in particular, they skid when they turn. The simplest way to deal with this is to make the vehicle much wider than it is long, but that is not always practical. Another, more *flexible* option is to segment the vehicle, like a train, and/or complicate the track mounts to allow individual track sections to rotate independently for steering. Realistically, however, even with both strategies employed, these things are going to have very large turning radii, even compared to their enormous size. In that sense, they are rather like actual ocean-going aircraft carriers!
As for actual ship-like things, snowships have a big advantage over, e.g., [sand sailers](https://worldbuilding.stackexchange.com/questions/85447/what-features-might-a-wind-powered-ship-designed-for-travel-over-sand-have/85451#85451), in that snow, as previously noted, is slippery! That means you can get away with having a primary hull in direct contact with the round, stabilized by outrigger skis, and it's plausible that wind could still propel them. If sailing still proves impractical, however, snowships could propel themselves with [snow screws](https://en.wikipedia.org/wiki/Screw-propelled_vehicle), analogous to the screws / propellers of ocean-going ships. Unlike the propellers of an ocean ship, however, the propulsion screws of a noon-sailing snowship would also provide direction support and balance, taking the place of outrigger skis. On very large ships, however, a continuous line of screws from bow to stern would initially seem to present similar problems in turning as tracks do, although that could be ameliorated by simply have the screws at the back and support the front of the ship on skis, more like a traditional water-going ship. However, screws have some distinct advantages over treads, in that if you rotate both screws in a pair in the same direction.... you move sideways! I.e., these ships can *strafe*, which a tracked vehicle cannot do, and while turning around curves still involves some amount of skidding, a screw-driven snowship of arbitrary size with bow-to-stern screws could easily rotate in place with little or no skidding, which a tracked vehicle cannot do.
If sail-powered, rather than screw-powered, snowships can be made to work, then they might well be a major method of transporting bulk cargo. But, while a whole lot of cargo is moved around our world by trucking and oceanic shipping, and those options are cheaper and can carry larger loads than air transport, tracked or screw-driven vehicles are at a major disadvantage compared to contemporary trucks and ships: without power, they *stop moving*. A truck on wheels can roll for a good long ways while idling, and a ship can coast on inertia for a long while before hydrodynamic drag stops it. In either case, the engines need to provide far less power to maintain speed than they do to *get up to* speed. With tracked or screw-driven vehicles, this is not the case, and they are *far* less efficient. It thus seems far more likely that bulk cargo transport would be accomplished with trains, hovercraft, or perhaps even aircraft. Aerostatic craft (i.e., [cargo zeppelins](https://www.rt.com/news/aeroscraft-revolutionary-airship-cargo-187/)) may even be a quite reasonable option.
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Air lifting is very expensive when transporting resources across a planet. If you wan't any kind of serious trade between different locations on the planet, land travel is essential. In our world, trains are used for transporting heavy goods such as coal or grain. A world like this would need a complex rail system for trade to be practical.
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Within the next decade or two, Earth is attacked by an alien fleet. The various militaries have some forewarning and are able to destroy the attackers by launching most of their nuclear arsenal at the alien craft, but not before they are able to seed a fast-acting bioweapon that wipes out all unprotected life on earth. Survivors were able to take shelter immediately prior to the attack, and are now looking to scavenge supplies from the wreckage and rebuild stuff.
If I understand correctly, multiple nuclear blasts in the upper atmosphere/low orbit would produce a significant EMP effect, destroying most (all?) unshielded electronic devices. What I haven't been able to find is exactly what gets destroyed.
1. How widespread would the damage from an EMP (or multiple EMPs) be on a specific device? A few critical components destroyed, many components, the whole board slagged?
2. Would certain components on a circuit board be more susceptible to damage than others? IE, would capacitors be likely to blow but resistors be OK, all the microcontrollers burnt out, the PCB itself suffer damage, something else?
3. Would new parts be resistant to EMP effects? I'm particularly thinking of new computer components which are disconnected from everything and often stored in anti-static materials to prevent damage before they're installed, would this provide any protection from EMPs?
4. Could someone with a very strong understanding of electronics, proper tools and documentation, a lot of patience, and a large supply of junk electronics to cannibalize repair electronic devices to working order? Any restrictions on what sort of stuff wouldn't survive ever, what sort of components would be rare, what would be common? I'm particularly interested in scientific and medical machinery as found in hospitals and universities, vehicles, communication devices and infrastructure, and computing devices.
(Weapons weren't particularly aimed to cause EMP effects, but given the circumstances they weren't particularly concerned about them either. Assume that my survivor(s) are in a location that was specifically prepared for this eventuality, and have schematics and specifications for many of these devices/component and/or are exceptionally qualified to reverse-engineer them)
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In short: expect damage like that from surges or lightning, albeit somewhat more severe and much more widespread. I'll be answering your questions in turn, with the help of [this resource that Nex Terren dug up](http://www.futurescience.com/emp/EMP-myths.html) and some EE knowledge of my own.
## Damage spread
All surge damage, first off, is erratic in nature -- electrical breakdown is often a stochastic phenomenon promoted by impurities in materials, surface contaminants, or pre-existing subtle damage. I'd expect spot surge damage in a variety of places, some seemingly distant from others yet related electrically or mechanically (by arc blasts between mechanically nearby parts), and in components both mundane (discrete parts and PCB tracks) and critical and complex (such as ICs/chips). However, a total meltdown to the point of unrecognizability as electronics is unrealistic as the materials used as insulators in many parts are designed to withstand being baked in ovens, and just *won't* melt/burn up unless you put *extreme* heat into them -- even severe burn damage to circuit boards will not render them unrecognizable, and semiconductor mold compounds will split and crack under high energies far before they even smolder.
## Component susceptibility
Damage from surges can take a variety of forms, and much of it depends on how breakdown-resistant and surge-current-resistant the various paths and loops in the system in question are as well as the size of the surge. A surge can damage the PCB and tracks on it as well as current-sensitive components such as resistors and inductors via excess [I2t](http://ep-us.mersen.com/fileadmin/catalog/Literature/Application-Guidelines/ADV-P-Application-Information-Let-Thru-Current-and-I2t.pdf), overvoltage parts vulnerable to [dielectric](https://en.wikipedia.org/wiki/Electrical_breakdown) or [avalanche breakdown](https://en.wikipedia.org/wiki/Avalanche_breakdown) such as capacitors and semiconductors, and burn and pit contacts through air arcing.
Smaller *loops* and shorter *lines* have an advantage in that they pick up less energy from the environment, but smaller *feature geometries* on ICs especially but also in discrete parts tend to fail at lower voltages and currents, counterbalancing this and rendering modern equipment more vulnerable than say something from the 70s built using discrete transistors. In addition, dedicated suppression components such as fuses and MOVs are likely to fail first, and in a way that stops further energy flow (fuses blow, MOVs fail short) -- these sacrificial failures may help by absorbing the brunt of the surge energy incoming to the device, especially if it's being conducted in by long lines.
## Spares
Spares vary in vulnerability -- ESD-protection (especially conductive vs dissipative) bags or boxes may act as something of a shield, while ESD foam on the other hand can *increase* the vulnerability by closing loops that would otherwise not flow current. Boards are also more vulnerable than loose parts, especially for current-sensitive parts such as resistors, inductors, and of course fuses. However, spare boards may be less prone than live equipment to exhibiting certain destructive failure modes that require an existing energy source, such as [SCR latchup](https://en.wikipedia.org/wiki/Latch-up) in junction-isolated integrated circuits. Likewise, being unplugged has the advantage that you aren't vulnerable to surges coming in on long lines such as the AC mains or any sort of telecommunications wire.
## Repairing EMP damage
All types of surge (ESD/static electricity, fast transient/inductive transient/small arc transient, lightning, geomagnetic surge, and EMP) damage follow a similar repair process: find all the bits that fried and replace them. However, it's the *troubleshooting* that's a pain in the arse due to the scattershot and often seemingly spooky nature of surge damage. A recent [mikeselectricstuff video](https://www.youtube.com/watch?v=Fmcg_cVO_1s) demonstrates this vividly as a microwave oven he received was rendered nigh-unrepairable due to a chain of events that started with an expiring 12V incandescent lightbulb and ended in a fried controller chip on the front panel.
Your intrepid technicians would be doubly challenged as they would have to *test their spare parts* to make sure they aren't putting dead or badly damaged parts *in*. For discrete components, this is mostly feasible; however, most ICs can't be comprehensively self-tested without custom test fixturing at a minimum, and sometimes require expensive test equipment to test at all.
The silver lining is that ICs are almost universally equipped with I/O protection structures on their pads, which will absorb the brunt of the surge energy and fail *first*, usually as opens or dead shorts. This makes it possible to "go/no-go" test the ICs for surge damage by testing all the I/O protection structures. If they all pass with flying colors, the chip stands a good chance of functioning at least mostly as designed, although analog parts are vulnerable to low-energy surges causing parametric shifts. A failed protection device, however, is an auto-toss, as that means the pad connected to that device is shorted out or no longer protected.
## What survives, what doesn't
Most consumer electronics is liable to fail -- it's simply not designed to reject EMI well to begin with due to cost pressures, and an EMP is the ultimate expression of an EMC event. Well-designed quasi-mass-market gear (such as test equipment, two-way radios, or industrial controllers) is somewhat more likely to survive as it has better protection and shielding than bottom-dollar mass-market stuff; older equipment that relies less on IC technology is also more survivable than highly integrated stuff.
Appliances (white goods, HVAC, ...) are liable to have their fancy control functions and power controllers (inverters/...) fail, while the guts of the appliance stay mostly intact -- simple electromechanical control (relay, cam-timer) stuff has a good chance of surviving though, and is dead simple to fix, comparatively speaking, if it does break. Likewise, vehicles are likely to at least somewhat survive as they are heavily ruggedized electronically speaking and don't suffer from long-lines threats -- and even if the fancy computers fail, there are at least some fallbacks designed in to let you limp home or at least pull off to the side of the road. Aircraft will be even less plussed by this, especially if the weather's nice -- military/aerospace equipment is heavily ruggedized as well, and surprisingly few aircraft *absolutely* need electronics to fly in visual flight rules conditions.
As to components -- the major problems for component availability will be *custom parts* (normally ICs). This is a *massive* problem for mass-market gear, which relies heavily on custom ICs (whether it be a custom [ROM masked](https://en.wikipedia.org/wiki/Mask_ROM) into a microcontroller or a full custom [ASIC](https://en.wikipedia.org/wiki/Application-specific_integrated_circuit)). Specialized equipment is somewhat affected as well, especially if it relies on high-performance ASICs to achieve its level of functionality (vs. using more standard ICs along with processors or FPGAs for custom functions).
Jellybean parts (such as discrete parts, connectors, and multi-sourced standard catalog ICs), though, will still be likely to be available in part stocks and sometimes in equipment, even if they are not as available in junk as they were even 20 or 30 years ago. Hardened gear, of course, will also be likely to survive wholesale.
## Chaos, but not catastrophe
Given all that -- I'd expect emergency communications to rebound quickly albeit in improvised form as radio amateurs can build working transceivers out of jellybean and hand-made parts relatively readily even to this day, and run them off of batteries. Vehicles would be in various "limp modes" depending on the type and age of vehicle -- the worst *widespread* case would be a car that won't run. Even many aircraft would be serviceable in visual flight rules conditions provided you had fuel. Of course, *getting* fuel would be a problem -- the pipeline/terminal infrastructure would be mostly out of commission due to dead pumping systems (you can throw people and improvised comms at the lack of a SCADA system, but the pumps need power to run), forcing fuel to be railed, barged (yes, barged), and trucked around. Under the circumstances, refineries would be dead, but there would be enough fuel in tanks that you could get it into railcars or trucks in a pinch by way of gravity.
Scientific and medical machinery would vary in damage depending on sophistication (the more sophisticated it is, the more damage it'll take), while the impacted parts of our computing infrastructure would take some time to rebuild, along with the damaged parts of the packet-switched terrestrial IP backbone. Satellite comms and navigation, though, would come back relatively quickly to at least some extent as geosynchronous and medium-orbit birds are hardened against ionizing radiation and EMI *and* satellites don't have long lines hooked up.
As to powering this all? Generators themselves are still likely to be somewhat functional (you'd need to bypass or kludge around electronic controls on modern generators, but old/simpler ones are likely to be OKish or at least readily fixable) even if the grid itself suffers geomagnetic-type damage, and most power operators are at least somewhat familiar with the type of threat a geomagnetic storm poses, which'd give them some basis for responding to a wide-area contingency like this. Furthermore, mobile generation capacity is available wherever the rail network on your continent goes -- older diesel locomotives are relatively well-positioned to shrug off EMPs (unlike the Soviet experience in 1962, there are no long wires connected to the electrical system on a locomotive to aggravate EMP problems), and can easily be turned into mobile emergency gensets that could be used to supplement existing hydroelectric plants for black starting grids. Another possibility to deal with some grid damage problems (large transformers taking geomagnetic damage, to be precise) would be to *rewind the transformer onsite* to restore a limited degree of functionality until spares could be made -- the likely geomagnetic damage modes are heating based due to the sluggishness of the pulse involved, and the insulation and oil in a transformer go kaput far before the copper itself is ruined beyond reuse.
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# You can tailor this however you want it to be
Summary: **You as the author make the story. The world is not meant to drive the story**
Never let the world dictate your story. Literature and movies are full of examples where the authors have made a very interesting world.... but then do not have any proper story to tell in it. You cannot let the world drive the narrative, it just does not work. You have to drive the story. If you as the author do not drive the narrative, then you are not telling a story... you are just telling the results of a simulation of sorts. And that will make for a very boring read.
I would rather recommend you to **not** narrow down the possible outcomes too much, because that might turn out troublesome for you later on when you get to story elements that you need something else for. Choice is an asset for you as the author, a savings account of possibilities. Sometimes you make a withdrawal to invest in a story arch. But you should not start with a very limited amount on that account.
Anyway... as Shalvenay said: this is a very stochastic process and depends on a lot of factors: distance to the epicentre, the high atmosphere weather conditions of the day, the type of electronics, the resilience to damage, intentional and unintentional shielding... et cetera. You can get anything from making total junk out of all electronics, to having a substantial amount of it survive in some areas, being able to salvage up to whole computer systems.
So, unless your interest is this is to play out a simulation of how a very specific attack turned out, this gives you as the author the choice to tailor the apocalypse however you want it to be. Remember: the world that your story takes place in is merely the setting / backdrop for the story, it is not the driver of the story.
So in conclusion: own the story, write the story you want to write, and then adapt the world and the effects of this war as you see fit, because you have that option. **The origin of the apocalypse that you have chosen gives you lots of leeway, and lots of choice.** Start by stuffing as much choice as you can into your author's account and only make withdrawals from it when you need it in order to make a good story.
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[Question]
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Someone made the Earth.
They placed man on the surface and gave them plants, animals, the waters, and the mountains to make their life compete.
The Earth exists within a spherical [firmament](https://en.wikipedia.org/wiki/Firmament) upon which the Moon, planets, stars and the sun are affixed.
The firmament is, of course, an artificial construct. The Moon, stars, and planets are projections upon its surface. The Sun is a radiation source that travels around the sphere, giving light and heat to the inhabitants.
The Earth has an axial tilt, and the Sun's radiation fluctuates with the seasons. The Moon, as well as the planets and stars is a light source, one that waxes and wanes periodically.
Given a civilisation and history that mirrors our own, at what point in history would astronomers prove the actual existence of the firmament and how would they do so?
Assume that the firmament is roughly twice as far away as the Moon is now. The Sun or Moon do not visibly illuminate other items on the inside surface of the firmament.
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Ancient astronomers (at least of the Classical Greek period, maybe earlier) were aware of trigonometry and able to use [parallax](https://en.wikipedia.org/wiki/Parallax) to measure some distances in the solar system. The complete absence of (daily or yearly) parallax for celestial bodies will let some sharp people conclude that they all are at the same distance. Triangulating with some big triangle (like [Erastosthenes](https://en.wikipedia.org/wiki/Eratosthenes) did) will give them even the distance of firmament.
A firmament has probably some more side effects (including a greenhouse effect on the climate), but I doubt that such kind of effects were accessible to Ancient astronomers.
The final proof would follow after the development of the laser: With a laser, an artificial star can be projected onto the firmament.
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[Question]
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On the Life Ball of my fantasy stories, a particular species of *delphinidae*- I call them black dolphins- have evolved and advanced at least as much as humans and other intelligent races. Among other things:
* Black dolphins have a highly sophisticated language. They discuss abstract concepts, contemplate the future, and debate alternative points of view. Whether a written form exists and how it works is now the subject of [another question](https://worldbuilding.stackexchange.com/q/65299/10851).
* They have religion. The exact nature of their gods and how they worship are still in development.
* They have government and politics. Most pods are oligarchies. Larger pods have what we would call Ministries of Education, of State, of Natural Resources, and even Justice (yes, dolphins can commit crimes).
* They create art and fiction. Where there is a sandy bottom, they force water currents from their fins to create intricate crop-circle-like designs. Others grab stones and pieces of coral and stack them in sculptures. They are entirely satisfied with the ephemeral nature of these creations. They love to invent and tell folk-stories and fairy-tales.
* They have science and mathematics. Most black dolphins know the basic underpinnings of algebra and geometry, and the idea of the method of hypothesis -> experiment -> conclusion -> repeat.
Does all of this necessarily mean that the black dolphins have houses, stores, courts, theaters, churches/temples, conference halls, and so on?
On land, all of the humans, elves, gnomes, and so on, at the very least have villages with an assortment of wooden huts, all the way up to grand cities of stone and steel. As the species developed, so did its ability to erect structures to display that development. Did the black dolphins keep pace?
My question is specifically about my black dolphins, but I am also interested in the generic concept: Do the ideas of "being civilized" and "building structures" automatically go hand-in-hand? Does a species gain intelligence and sophistication only as a result of building things? Is it possible to have a species as advanced as we are, or even as we were ~4000-5000 years ago, and never even have any sort of enclosed space?
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Technically, going by the earliest meanings of the word, **Civilisation** does necessitate building. **Civilisation** came from the latin *Civitas*, which meant "City". A **Civilisation**, then, was a society that could build cities. No structures, no cities; no cities, no civilisation.
Now, having said that, it's hard to truly pin down what "civilisation" is in the modern sense, or how we could identify it among a species very different from our own. Still, let's go with Wikipedia's quick intro on the subject. A **Civilisation**...
>
> is any complex society characterized by urban development, social stratification, symbolic communication forms (typically, writing systems), and a perceived separation from and domination over the natural environment by a cultural elite.
>
>
> Civilizations are intimately associated with and often further defined by other socio-politico-economic characteristics, including centralization, the domestication of both humans and other organisms, specialization of labour, culturally ingrained ideologies of progress and supremacism, monumental architecture, taxation, societal dependence upon farming as an agricultural practice, and expansionism.
>
>
>
Let's take these one at a time, starting at the top.
## Urban Development
This is what we're asking about, so we'll give it a pass for the moment.
## Social stratification
This could simply be a result of human psychology rather than an essential trait of civilisations; after all, one could argue that by that definition, societies that are least theoretically democratic or meritocratic were not 'civilisations'. However, happily, you mentioned that most pods are oligarchic, so we can probably give this a point in favour.
## Symbolic communication forms
I would argue no on this. Ephemeral art that will be washed away with the tides really is less a form of communication, more a form of self-expression; it's about the artist, not the audience. Unless they have some more permanent way to record the thoughts of great dolphins, this is a point against.
## Perceived separation from and domination over the natural environment
Again, the ephemeral nature of their art and creations argues against this. I suppose they may farm kelp or coral to increase their food production, but there's only so much you can dominate the surface of the sea. One against.
One out of three isn't a good score. Let's go into detail with the remaining common features:
## Centralisation
Oligarchical politics and ministries for various tasks suggest this gets a point in favour.
## Domestication of both [dolphins] and other organisms
No information on their farming practices, so I can't award a point either way here.
## Specialisation of Labour
Again, unclear. The existence of ministries would suggest perhaps? Half a point in favour.
## Ideologies of progress and supremacism
Uknown.
## Monumental Architecture
No architecture at all. Point against.
## Taxation
Unknown
## Dependence upon farming
Unknown, but it's hard to imagine how pods could farm. I'll mark this as half a no.
## Expansionism
Without construction of any sort, it's hard to imagine borders that could be expanded. Still, it's possible that a large pod could forcibly integrate a smaller...I'll leave this as unknown.
## Score
2.5 in Favour
5 Unknown
3.4 against.
I would suggest that without some form of **permanence**, you cannot have a true civilisation, and that's the big problem here. These dolphins don't make permanent homes, they don't create permanent art, they don't alter their environment...these the hallmarks of civilisation, and they just don't meet them.
[Answer]
You're missing a few crucial pieces of the puzzle when it comes to your civilization:
* The ability to record past knowledge,
* The ability to effectively pass that knowledge down to new generations
* The ability to disseminate information accurately and widely
Essentially, you need written words, and the ability to keep accurate records.
When a court passes a verdict, that verdict must be recorded, so that people don't remember the details incorrectly. And someone (presumably not the person who passed the verdict) must then be informed of what should happen to the guilty party (imprisonment, banishment, etc.). Communicating all these details strictly by word of mouth is bound to end up having some pretty interesting consequences (broken telephone effect).
And written records need to be kept somewhere, right? And not only that, but there must exist a place where they are created, and posted for people to read.
Do you know the joke that Government exists only to feed the bureaucracy which spawned it? It's totally true. You can't have government without records, and paperwork.
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I want to have 3 different habitable **BY HUMANS** planets in a single system, I don't know much about physics so I bought Universe Sandbox2 and I'm trying to build solar system with 3 habitable planets in the goldilock zone. They all have separate orbits (no Lagrange points, orbiting gas giant things). From reading other threads most posters suggested they're unstable.
I want their surface gravity to be from 0.8g to 1.6g and humans to be able to live there. I don't have any other requirements hot, cold, dry whatever.
I expected to have one dry planet on the beginning of green zone (Tattoine like), 1 Earth Like planets, and one planet with thick atmosphere near the end of the green zone and beginning of blue zone (liberal habitable zone estimate).
But from my experiments I'm only able to put:
1. Earth with no CO2 on the border of the red & green zone
2. Normal Earth on the beginning of the green zone
3. Earth with 20 times more CO2 in the middle of green zone (Is it liveable?)
4. Snowball Earth no matter how much CO2 I have
I tried playing with obliquity, mass, atmosphere density nothing helps.
Could someone more knowledgeable advise what kind of planets should I put?
**EDIT**
From the comments I see that 4 is too many planets in separate orbits, so I changed it to 3. From my simulation Earth is on the beginning of the green [zone](http://www.nature.com/news/earth-is-only-just-within-the-sun-s-habitable-zone-1.14353) which is weird because I expected a [dry planet](https://www.ncbi.nlm.nih.gov/pubmed/21707386). What kind of planet should the next 2 be in order for humans to be able to live there.
Please note that I'm using Universe Sandbox 2 just to play around, **I'm interested in the general type of the planets**, something like :
* in the middle of the green zone the put planet with 4 times more CO2 and less water surface
* farthest planet should be larger then Earth, with thick atmosphere and high Volcanic activity.
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# Parent Star
Before we get to the orbits of planets, we first need to determine the most important variable in your system: what is the size and age of your star? Obviously, habitable zones around stars depend primarily on the heat emitted by the star. This, in turn is dependent on the size/mass of the star and also its age.
For the sake of convenience, lets say we have a main sequence star at the center of our hypothetical solar system. For those who don't know, a [*main sequence*](https://en.wikipedia.org/wiki/Main_sequence) star is one which is fusing hydrogen into helium in its core. This means, we are excluding stars like *red giants, white dwarfs, neutron stars* and other such types.
Out of several different types of main sequence stars, I would prefer keeping a [B type](https://en.wikipedia.org/wiki/B-type_main-sequence_star) star at the center of our solar system. They are 2 to 6 times larger than the sun and have surface temperatures ranging from 10,000 to 30,000 kelvin (as compared to 5000 kelvin for the sun).
The advantage of this excessive heat generation is the habitable zone will be all the more wider than the sun's habitable zone. For convenience sake, we would pick a star which is at the lower end of B type. That is, one that has a mass of nearly 2 solar masses and a surface temperature of 10,000 K.
# Habitable Zone Of Our Sun
Before we get to the habitable zone of our B type star, a word about the habitable zone of our own sun would be helpful. [This wikipedia article](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone) (which is quite interesting btw, unlike most wiki articles) states that the habitable zone around our sun extends from Venus' outer limit of orbit (109 million km) to as far as the inner side of the asteroid belt!
# Habitable Zone Of A B-Type Star
While I don't know with absolute certainty at which distance from our B type star, its habitable zone will begin, it should be safe to assume that distances of 1 AU to 4 AU will fall in the habitable disc.
# Planetary Distances And Composition
Of course you would want to keep the planet at the inner edge (1.2 AU) to be a small, Mars-mass object with relatively thin atmosphere rich in oxygen. Greenhouse gases as less as possible and lesser water content on the planet so that a runaway greenhouse effect has a chance to be reversed naturally. Also, make sure to keep the planet's core active (for a strong magnetic field) but make sure that there is almost no volcanism on the planet, as that may likely trigger runaway greenhouse effect.
The main risks for losing habitability for this planet would be the loss of atmosphere through solar wind. A strong magnetic field would be critical in keeping this from happening. Also, considering that this planet is the innermost of all the habitable planets in this system and the stellar type is B, you would want a thick layer of ozone to shield it from the deadly UV rays. Also, solar flares and magnetic storms would be potentially deadly.
In the middle (2.1 AU) you would want to place an Earth-sized planet with earthly atmospheric density and composition. A small proportion of greenhouse gases. Some volcanism and 55-65% water covered area.
This planet, being in the center of the habitable zone, will be the one with least risks. Even if it temporarily loses its habitability status due to a gigantic meteorite collision, it will naturally regain its habitability within a couple million years or so.
On the outer edge (3.8 AU) you would want to keep a super-Earth. A planet with 3 Earth-masses, thick atmosphere, rich in carbon dioxide and lots of volcanic activity. You would also want to have many organisms producing methane, as it would help in the greenhouse effect.
The hazards for this planet would be any perturbation in its methane production chain or too much increase of flora on the planet, that could trap most of the carbon dioxide from the atmosphere. Also, any snowball events would have a dangerous tendency to be perpetual, ending its habitability status.
**Note:**
I strongly recommend you to read [this article](http://www.solstation.com/habitable.htm). I have found it to be very knowledgeable and written in very simple language.
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Let's start with the number of planets. As you've been told, 4 orbits is almost certainly too many - their interactions will almost certainly cause instability. In the worst case you get collisions, of course, but that is wildly unlikely. Much more likely is the ejection of one or more planet from the Goldilocks zone for at least part of its year.
However, as the Navy Seals like to say, "If you ain't cheating you ain't trying." So how about finessing the problem. There is no rule saying that the planets have to be singletons. So make the planets dual systems, like the earth-moon but with equal sizes. You could have one pair close in, and one pair farther out. I wouldn't even try justifying the creation of two such pairs in a single system, but there's nothing I can think of that prohibits it. Assuming formation by collision (as is the current thinking about the Earth/Moon system) you could invoke an asymmetric distribution of volatiles as the impactor strips away the crust from the other, and the resulting water-rich debris settling preferentially on one of the two resulting objects. This will give you a wet/dry warm pair and a wet/dry cold pair.
Please keep in mind that cold/dry is going to have a lot of trouble supporting life. You are focusing on CO2 as a dominant greenhouse gas. In the case of the Earth, it's not. It's water that does the job. CO2 is much more persistent than water vapor, but there's a whole lot more water vapor in the atmosphere. Likewise, hot/wet runs the risk of runaway greenhouse as the increased temperature causes greater evaporation, leading to a closed loop with positive feedback.
Depending on vulcanism for long-term CO2 production is not a good idea. On earth, it's a mark of plate tectonics, and this will periodically produce eras of little activity. Furthermore, volcanic emission of CO2 is also accompanied by all sorts of nasties like sulfur dioxide and ash, which will make the surface not real hospitable to life. An alternative to plate tectonics is tidal friction, such as occurs on the Jovian moon Io. However, this again is not a good idea in the long run, as in the long run the two planets will become tidally locked and the volcanic activity cease.
Methane is a bad choice as a greenhouse gas. The problem is not that it doesn't work. It does. It's a good deal better at trapping heat than CO2. The problem is that it doesn't persist in the atmosphere in the presence of a biosphere. It oxidizes in very short order, decades or less compared to centuries for CO2. Worse, its effectiveness invites wild swings in concentration and resulting temperature. See the potential problems of oceanic clathrates.
You can specify whatever surface gravity you like. For a given density the surface gravity is proportional to the radius of the planet, but running in the range of 0.5 to 1.5 gs only produces planetary masses with a mass range of 27 to 1, which are probably not a real problem. Certainly the result would be nothing comparable to Jupiter and Saturn, and the solar system seems pretty stable with them in the house.
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Remembering that the setting has to match what you're trying to accomplish:
**Inhabited by whom?**
You want three or four habitable worlds orbiting the same star. Do they all have to be inhabitable by humans? If so, then the bounds are much tighter; your planet has to have water in its liquid phase on the surface at some point during the year, and have an atmosphere breathable by humans and a gravity that humans can withstand.
Will ab-humans work for your story (allows you to discuss the inter-racial issues as a metaphor for real-life racial issues)? If so, then you can get away with a somewhat broader gravity range, allowing for more variability in the other parameters.
Will completely unrelated intelligent species work? If you can have races that don't breathe oxygen, or don't breathe at all, then the goldilock zone extends out much farther. You can simply hand-wave an alien metabolism (which breaths ammonia and for whom oxygen gas is horribly poisonous), necessitating environmental suits for anyone visiting a planet with a different environment.
This last option can be adapted to serve your narrative. Maybe a system in which race A (humans), race B (an insect-like species that prefers a 55C environment), race C (ammonia breathers), and race D (non-breathing frigid species that prefer temperatures in the single-digit Kelvin range) can all live at once in relative comfort, makes it an ideal location for the headquarters of your galactic empire (in which these four races are predominant).
**How fast is travel from place to place?**
If you only want to have three or four planets in the same system because you want humans to travel from one planet to another in the space of time measured by hours or days instead of by years or generations, remember that you don't really need this for a fictional tale. You can put the planets in three star systems that are close to each other, and simply hand-wave a drive system that gets from one star to the other as quickly as you need for your narrative.
And added bonus is that by author's fiat you can establish that three closely-located star systems, with an inhabitable planet or two in each, is a rare occurrence in the galaxy, and that this makes the three systems strategically important. More grist for your plot.
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## There can be no oxygen without life
Note that a copy of Earth without indigenous life would have a CO2 and nitrogen dominated atmosphere with almost no free oxygen, just as Earth had before life formed, and a long time after that. A lifeless planet really cannot have a human-breathable atmosphere because free oxygen at that concentration is highly reactive and will simply react with the surrounding minerals.
The existence of e.g. 20% oxygen atmosphere implies the following:
* Something is producing oxygen at very large quantities, so the planet is full with life - possibly but necessarily microbial, likely but necessarily using energy from the star, but definitely a *lot* of it;
* That life has been there for a long time - it took many millions of years to saturate the eagerly oxidizing minerals (in part, rusting all the iron) until the oxygen could accumulate without being absorbed as quickly as it can be produced.
A planet with human-breathable atmosphere is not only habitable, but already inhabited.
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In just over 50 years Earth military aircraft advanced from [those that hardly could stay in the air](https://en.wikipedia.org/wiki/Vickers_E.F.B.1) at a mere 70 MPH, to a [vessel](https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird) that set a record of 2,193.2 MPH. Not only did simple speed increase by orders of magnitude, but various other aspects of aviation also surged ahead at exponential rates, and warfare technology elsewhere blossomed at rates possibly not as impressive as Aircraft's early days, but still extremely worthy of note. The growth of warfare has been so fast over the last hundred years or so that a difference of by a couple of decades would mean absolute suicide for one side for traditional warfare in almost all cases.
Despite this apparent fact in our real world, many soft-science fiction worlds, such as Star Wars, Buck Rogers, Warhammer 40k, or even Star Trek at times don't seem to suffer from this effect. Sure, when *centuries* separate technology *sometimes* that's an issue, but even then typically the warfare as the viewer sees sees hasn't advanced meaningfully; newer ships still buzz around more or less as fast, and generations of personal armament don't seem particularly more or less effective. Star Wars with the lack-of-apparent-change Old Republic to the original Star Wars trilogy being a particularly bad example of this, as *thousands* of years separate the two, yet warfare seems by-and-large just different flavors of one another.
While sometimes authors of such settings include mention that warfare has advanced over the years, but they typically have it as a footnote without real proof. Instead of hand waving such advancements in place, what if we *desire* this lack of Earth-like advancement in warfare?
In a setting of a galaxy's worth of different cultures and societies and where war isn't a scarcity or oddity, how could one explain a *lack* of scientific advancement over the years as it applies to warfare?
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Science advances in at least two ways, vertically and laterally.
Vertical advancement involves the discovery and "proving" of new theories about the nature of the universe.
Lateral advancement involves applying the ramification of discovered theories to different problem domains throughout our culture and our warfare methods.
Vertical advancement can be sporadic. The amount of time between significant discoveries within any given field can range from moments to eons. If no obvious clues can be found to point to the next discovery, then progress in that field must wait for an adequately intuitive or creative mind to breach the abyss between current knowledge and what remains to be learned.
Lateral advancement may appear more consistent (and therefore more efficient and profitable) on the surface, but ultimately it is dependent on vertical advancement to provide new technologies to apply.
Your galactic community may be suffering from an overexertion in lateral advancement with a simultaneous deficiency in vertical advancement. Across the galaxy, someone may have already found the most effective method for applying every potentially destructive technology which is known to the art of war. Then if no new technologies are being discovered (because the war mongers are too short sighted to fund pure research), then at some point, both types of scientific advancement would effectively stall.
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You have to have nations step back from TOTAL WAR. Only recently (since Napoleon, give or take) have nations been able to devote virtually ALL of their resources into military conflict and conversely, MUST DO SO, less they be completely overrun and wiped out. Previously most of the population was tied to the land and could not be professional soldiers, or rulers simply didn't have access to the money necessary to raise large armies and drive lots of military technological advancement. Industrialization and factory manufacturing is what allows for lots of precise weapons and ammunition to be manufactured, but this ties up a LOT of a nations GDP.
So what you need is a social change that forces a large decrease in military-industrial expenditure. This will effectively stagnate military development. This can come about in several ways.
1. There is an overwhelming powerful superpower. So everyone else is fairly safe from conquest and can relax on military development. This is sort of the situation here on Earth, where the US is so dominant that there is little military development by anyone else. How many ballistic subs, aircraft carriers, heavy lift bombers, advanced stealth fighters, or tanks have been developed recently? Very few. Or if they have been designed, they haven't been built in large numbers, even by the US.
2. People, across the globe, (or solar system or whatever) agree to deny governments the resources to field large armies. Obviously this is unlikely to be a grass roots movement, more like global corporations bend governments to their will in order to prevent conflict, which is over-all bad for business (assuming the MIC corps like Halliburton are put to rest). Without the money, you can't fund the development. So military tech is stagnant, and remains so due to explicit treaty (kind of like how NBC warfare is pretty stagnant) or simply due to lack of resources/interest.
3. Tech hits a wall. We are seeing this with things like the F-22 and F-35. The cost of development, paired with the costs of building and maintaining advanced weapons, simply grows too large. A F-22 (120+ million) is not the same cost as a F-15 Strike Eagle (20-30 million) or P51 Mustang ($662K in adjusted dollars). So clearly this growth can not continue, lest a nation be able to only afford 1 plane that it then can not risk in conflict.
Of course drone warfare is the new explosive growth area, a true military revolution that will most likely be a check point in future military history books (much like nuclear weapons, machine guns, tanks, and aircraft carriers are now) that delineate a change in the entire military mindset.
Naturally, if your future setting involves constant warfare, some of these stipulations won't apply, unless the warfare is LIMITED, i.e. only concerning regional areas, private affairs, or amongst very localized powers.
Settings like WH40K or Battletech postulate that extended warfare has led to an inability to reproduce earlier technological marvels, so every one is sort of running on the fumes of an earlier golden age. This explains the flat tech curve across years of conflict. This is only partially acceptable (I find it hard to believe you can maintain a war machine without the ability to build and innovate said war machine) but does sort of mirror what happened to the US space program (we can't build rockets like we used to).
I think the lack of tech development in sci-fi media is driven due to budget and designer choice. Plus I think there is a general lack of appreciation for how much historical cultures change over time. I bet most folks think a Roman army with Julius Caesar would look identical to one during the fall of Rome (400+ years later).
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How has military technology advanced over the last 50 years? In 1966 we had nuclear powered aircraft carriers, nuclear submarines, mach-2 fighter aircraft, main battle tanks, ICBMs, and the exact same infantry rifle.
So far as I can tell, during my service (in the Navy), the only things that were mission critical that were not available in 1966 were GPS and satellite internet. Even the GPS bombs we use aren't much more accurate than the Walleye TV guided bombs dropped on Hanoi.
Compare that to the difference in 50 years between the Civil War and WWI, or Spanish American war and WWII, or even WWI and 1966. Really puts the current military stagnation in perspective.
So what happened in the last 50 years to stop military technology? Well, nukes happened. Nuclear weapons mean you either a. Don't have wars or b. Start a dark ages.
Sure there are still wars, if you call that overblown police action in Iraq a war, but those wars don't spur the development of chemical weapons, motor vehicles, airplanes, rockets, or the Manhattan project, like a proper war would.
I'd like to point out that the world is plenty different from 1966, just weapons aren't. So general technology doesn't have to stagnate. Big differences in American life since then include the use of Internet and mobile phones, the universal availability of mortgages and home ownership, the distribution of almost half of Americans from dense city centers and small towns to suburbs of big cities, and most importantly, tripled workforce participation by women. Most of those changes are pretty fundamental to your everyday existence, but pretty marginal from a military standpoint. Even the internet is pretty useless, unless you like giving information and control to hackers.
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As a math person I need to warn people that somethings that look like exponential growth are actually logistic growth and as such have a ceiling. Let's look at two examples of human weapon development.
It is true that airplane technology advanced greatly during the course of WW1 and on to the jet age. Yet we had a Mach 2 fighter in 1960 (the F104) and fighter jets haven't gotten much faster in 50 years. So due the limits placed on chemical fuel, human endurance, material strength and air resistance, there is an upper limit on aircraft design.
If you look at firearm development over its history there were long periods of slow development, such as the musket which was invented in the early 16th century and was used up to the American Revolution. There was the "exponential growth" period in the 1800's with the inventions of the Minie ball, smokeless powder and metal cartridge. At the end of that growth was the Maxim Machine Gun invented in 1886. The M2 Browning Machine Gun was designed in 1933 and is still used today. It would require fantastic new materials for the barrel, bullet and propellant to make another exponential like leap in gun technology.
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I assume that it's because it's borderline impossible to predict the future, and that if your goal is to write entertaining fiction it makes sense to create a relatively fixed set of technologies and focus on building characters and stories.
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Historically, necessity is the hardest drive behind advancement in warfare. When two sides are fighting tooth and nail, and the stakes are total annihilation, every advantage is taken into account. If you have a universe where war is so common and frequent, that cultures and societies don’t spend a 1/10 of a percent of their time and energy on it, than more than likely no advancements would be made. They only way I see to naturally make a universes military tech stagnate is to create an universe that’s antipathetic to it.
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I'm looking to build a "twilight" world, where days are like twilight even when the sky is clear and nights are...very dark. Cloud cover might be able to turn day to an early night. I do envision a day/night cycle and capability of supporting advanced life. Ideally, I'd like the planet to have seasons, though I don't care if it overall skews colder or warmer than earth.
So far, my research for how to achieve such a world would be to have a planet orbiting a [red dwarf star](http://www.businessinsider.com/red-dwarf-planets-proxima-b-aliens-2016-8/#and-bathe-the-surface-in-x-ray-radiation-thats-hundreds-of-times-more-powerful-than-what-the-sun-shoots-at-earth-22). Or rather, a moon orbiting a planet orbiting a red dwarf star since I'm trying to avoid tidal locking. Gas giants are suggested, but I fear they may be too bright.
I have a basic idea of what I need (axial tilt, rotations, etc), but I'm lost in the hard planetary astronomy, such as how a gas giant might affect the brightness of the sky or might help heat a dimmmer world, or even how to keep the sky largely dark. Or if I'm barking up the wrong tree altogether.
Side note: Yes I am assuming the planet can withstand the solar flares.
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So, what you want is a planet where there's very little light, but it isn't terribly cold. There's an easier way to get this, and it's more interesting.
Take a normal F- or G-type star, pretty much like the Sun. Put your planet in orbit round it. Don't make it a moon of a gas giant, that gets complicated. Have an unusual feature: a large belt of fine dust orbiting closer in to the star than your planet. This intercepts most of the light from the star, which is dimly visible. The dust warms up, and re-radiates the energy as heat. Light comes from the star; heat comes from a large zone in the sky with blurred edges, which has the sun in its centre.
Now, how do we get that dust zone? It's like the [interplanetary dust cloud](https://en.wikipedia.org/wiki/Interplanetary_dust_cloud) in our solar system, but very much denser. I can't see how it could happen naturally. Does it work for your story for it to be artificial?
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## Make it a nuclear powered twilight planet
If the heat doesn't come from the star, it has to come from somewhere. Why not the planet itself?
Let's assume the following:
1. This is a roughly Earth like planet. Same size, same atmosphere, same orbit.
2. It orbits a dim star, red dwarf or some such. This star has very high metalicity, indicating an advanced age of the surrounding stellar neighborhood.
3. Due to the high metalicity of the solar system, there is an unusually high quantity of uranium in the core and mantle of this planet.
Due to [Decay Heat](https://en.wikipedia.org/wiki/Decay_heat), the uranium will heat up. If this decay heat is high enough, it will heat the crust sufficient to replace the heat that would have come from the Sun on Earth.
Decay Heat decreases with time so either handwaving or careful calculation will be required to figure out how much uranium it will take to keep the planet warm and how long it will be able to do so.
Interesting to note that about [half of Earth's heat](http://physicsworld.com/cws/article/news/2011/jul/19/radioactive-decay-accounts-for-half-of-earths-heat) come from Decay Heat. In this twilight world, maybe 75% or 90% of the planets heat comes from decay heat.
Heating this way should give you the clear skies and warm weather you want while keeping a dim sun.
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Unless the gas giant is large enough to be luminous, as opposed to merely reflecting light, I don't see why this is a concern.
The brightness of the sky is going to be a function of four factors split into two categories:
cat 1- amount of incoming light
1) Solar illumination, a function of the number of proximate stars, their brightness and distance
2) reflected illumination, a function of both the solar illumination and the number of proximate reflecting bodies, their albedo, and their distance
3) galactic illumination, a function of the solar system's position in the galaxy and the nature of the galaxy
cat 2- the amount of light impinging on the atmosphere that makes it to the surface:
4) atmospheric albedo of your planet, a function of the composition of the atmosphere
by using a fairly dim sun you minimize 1&2. If you want thing really dark at nights you can specify their galaxy such that their night sky has many fewer stars than ours, perhaps an older galaxy and the population of stars is mostly along the red giant branch. If you want both day and night to be darker then you can ramp up 4, meaning most of the light that reaches the planet is reflected back into space.
If you are thinking of a native ecology I would assume it would be based off some form of thermosynthesis (<https://en.wikipedia.org/wiki/Thermosynthesis>) given the relative lack of visible light while the relative abundance of Infrared.
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I've got a humanoid race living in a extremely bright and hot desert. **Would there be a plausible or realistic reason for them to develop without eyesight, due to the harsh rays of their sun?** Or, instead of eyes, developing some other form of vision (echolocation, some sort of extra sense, etc)?
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Vision has a lot of advantages as a sense. It's very long-ranged, and provides a lot of information. Eyes evolved several times in Earth's history, and take lots of different forms. Human eyes are much like those of other primates, which are similar to those of other mammals.
It seems likely that if life evolved naturally in your setting, *some* kind of vision would exist, although it might be very different from ours.
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No. Vision is by far the most important sense for a humanoid species. It would, perhaps, be plausible for a non-humanoid race to evolve a stronger reliance on other senses to survive in the desert.
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Check out other desert animals - they also have eyesight!
In general, eyesight itself is quite vital, so you may not expect for it *completely* missing, especially taking into account that albedo is not so extreme in the brown-yellow sand. (unlike the poles, where everything's white, so "snowblind" state is a general phenomena)
Reduced eyesight is perfectly possible, though I'd separate it more - our eyes are able to detect colors and light with two different types of cells(?), and having less of the latter sounds realistic for me.
I'm not an expert, so I'm not sure, how would that change the ability to see, so it may or may not be a better eyesight with less light receptors, but it's a topic for another (likely rather biology-related) question.
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I would be of the opinion that for land animals to have not have evolved eyes, the habitable land area on your planet must consist solely of this desert. If they live in an extremely bright and hot desert, would it make more sense for these creatures to be nocturnal? Or perhaps if it is too cold at night (as with Earth deserts), they are active during twilight hours. If so, eyes would most likely have evolved.
With that in mind, what is the evolutionary advantage pushing these creatures to be active during the day, and thus having no use for eyes? Are they protected from nocturnal predators when sleeping? Just something to consider.
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If your humanoids are nocturnal and live on a moonless planet orbiting a star on the galactic rim then they’ll be living in a nearly pitch black environment, in which case lacking eyesight makes perfect sense.
Maybe daylight is too hot to survive or the planet's magnetosphere is too weak to adequately protect them from ionizing particles?
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Maybe you could go with them evolving underground(Due to extreme temperatures or something similar). Then as time went on they developed an ability(Technology? depends on setting and their tech level) to go to the surface. As primarily underground creatures, they probably would not evolve eyesight (Or even loose it if they had it at some point). If days are to hot to be outside, and nights extremely dark, there would be no need for eyesight to evolve.
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i think it still depend on your race and its evolution. if your entire world is desert like this, then it possible for your species to skip the evolution of eye completely (thus avoid mirage), to develop echolocation or sense of smell, hearing, or heat (like the rattlesnake).
however, if your race came from somewhere else, or had evolved eyes already, then it s more plausible for them to add some features like an outer layer which act like sunglass, or switch their activity to nocturnal or crepuscular (at twilight) instead of devolve your eyes then evolve something else.
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I am making a world for a story and my question involves the displacement of a new technology to replace an existing one (magical). This is a medieval fantasy world with magic, but without demi-humans(i.e. no elves, dwarves, etc.)
Current level of magical technology involved the development of 'runes' to channel mana through (your standard floating magic circle with lightning shooting out of it). It can be used for a large number of mundane things as well as combat, but I will be focusing on combat. The magic circles are designed to control the flow of mana efficiently like a circuit, and manipulate it into the form the caster wishes it. Because these circles are built from pre-existing components that others have researched (requiring a lot of memorization), the flexibility isn't the best, but it gets the job done for most things. Mana circle is created by the caster on demand, and to cast magic like this requires a mana pool of a certain size.
* 2 in 3 people generally have mana pools are large enough to use that to a minimally useful level within a population(stuff like cooling yourself with a cold wind on a hot day).
* 1 in 3 people are capable of using it in personal combat to some extent (this can be very basic things such as summoning a gust of wind to throw dirt in your opponent's eyes).
* 1 in 10 people have a mana pool large enough to cast decent wizardly spells in personal combat(small fireballs and the like)
* 1 in 500 people are capable of launching magic over a long range, and are able to cover enough area to be able to hit multiple enemies (about 5 meter radius, at a distance of max 500m), these are the ones that generals consider to be of the 'mage' group in combat potential, and their general roles are usually to sit at the back and fire off artillery at the enemy ranks, while at the same time intercepting the same attacks from enemy mages when possible. Attacks are generally fatal for a direct hit, and about 30% death rate for those being splashed. 90% of those who survive generally are unable to continue fighting
* Some of those 1 in 500 people decide to undergo special training to form teams of about 20 mages, in order to work together to fire off single extra large magical artillery (20m radius blasts at a range of 1km). Highly lethal within the inner 15m radius, outside is about same as the single shooters.
* 1 in 1 million people are monsters that are blessed/cursed with great mana pools, that are capable of firing off 20m radius blasts at a range of 1km easily on their own
Generally, within the public, people require about 1.5 months of training (costs money for a tutor, or to enroll in an academy, standard education costs) to cast the most basic weak spells, about 6 months to have a usable spell for combat, 2 years to be able to use a *single* spell for the 'mage' group (generally you want 3-4 offensive and defensive spells for flexibility), and another 5-10 years to train together to form the single spell of the 20-mage combined magic.
Given that this is the current state of the world's magic, I want to introduce a new revolutionary technology into the world: a stone of crystallized mana, that can have runes engraved onto it, and used as a disposable 'bomb'. These are fist-sized stones that require about 3 days of training for your average peasant to learn how to activate them whilst not blowing themselves up in the process (results may vary). These stones on activation, have a fuse timer built-in (unless the craftsman who made it was having a bad day), which upon expiry, will detonate in about a 4m radius explosion for a decent stone. Varying qualities of stone can lead to varying degrees of destructiveness, from a simple child's toy to a blast that can wipe out an army. To create stones as a craftsman takes about 8 years of study, and a further 2-4 years of apprenticeship. Afterwards, the rate to produce stones (given that supplies last), is about 8 stones per day per craftsman, can vary up to 15 stones for the extremely skilled.
The technology will eventually become more advanced and have various other spells engraved on it for mundane uses other than explosions, and be able to eat the stone slowly instead of instantly, but on its introduction, this is what it does.
## My questions are:
* for this new stone to displace existing mages, and turn them mostly
into a research type role, how cheap would it have to be to make?
* How Abundant would the supplies need to be?
* How easily accessible would those supplies have to be?
* And, upon its introduction, how long would it take to displace mages to that point within the
country of origin, how long would it take to dominate battles within
the world in general, and how long would it take to completely
displace all battle mages within the world?
* If it is unlikely to displace current magic in its introductory form, what changes should be made so that it can?
* Edit: Also, are there any special tactics that these stones can be used in other than having your basic farmer toss them at the enemy/strapping them to arrows?
Ideally, the answer should have the barest parameters for the displacement to occur (i.e. no free unlimited magic stones), and the longest reasonable time-frame for it to happen, as I want to write a story the occurs in the middle of this displacement.
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It hard to give a definite answer to this but I'll try. When compare wizards with magic crystals. I would compare crossbows/long bows with muskets. Muskets required less training to use and were more powerful. Muskets first started to replace older projectile weapons in the fifteen century but for several reason (including the price of gun powder) muskets didn't fully replace the bows completely until the 16 century. So I would make it the same time frame for the crystals. At when first people start use them wizards are still used because there cheaper then crystals, but as time goes bye it becomes cheaper and cheaper until a hundred years later hiring a wizard is actually more expense.
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From a military standpoint, I believe that true Mages would always have value.
A well armed fortress should be well stocked enough that they would have all the resources (runestones) on hand to defend themselves. The problem is that not all fights would be fought at a base or fortress. In the case of a small team going into combat, you can only carry so much weight and so you will have to choose what you bring. There are the obvious notions of bringing stones that have curative magic or offensive magic; however, what happens when you come across a raging river that you didn't expect or something else you did not prepare for occurs. Having a trained mage whose powers can be bent to the situation at hand will be indispensable. It is more likely that mages would see their purpose change rather than their purpose extinguished.
You haven't made an advancement that eliminates the use of magic (like gunpowder eliminated the use of bows), you have effectively made it more convenient (like a crossbow). Skilled archers are still better overall due to their versatility and intensive training (in the time period) because they know what they are doing. A peasant can be handed a crossbow and given a few hours with it but when something in the mechanism breaks, they are defenseless. A fully trained archer would know how to carry spare bowstring or know how to make their own arrows as well as a new bow if needed from their environment. I would pose the question of what happens when a runestone craftsman makes a mistake. Can it be easily seen or would you find out by using the stone? What is to be done when it is too late and the stone has been used? Having a trained and experienced mage on hand who can fix the issue would be very valuable.
Overall, I see that Mages would more take a backseat to the fighting and more serve as interventionists by using their power when something goes wrong or something unforeseen occurs. If a particular base or stronghold didn't have an extremely powerful Mage at their disposal, they would definitely have a team or two on hand that could be dispatched at need. Furthermore, if actual trained Mages got involved in the crafting of the runestones, would the limit of their potential increase?
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There is potential for complications along the way. There is a technology quite a bit like this in Steven Brust's novel *The Phoenix Guards*, called "flash-stones" but it vanishes from the sequels. The in-world rationalisation was that someone found a magical way to detonate them at a distance, with sad results for anybody carrying one, so they were abandoned.
Also, what kind of world has magical combat as the major task of its magicians? It may be very important in adventure stories, but it's hard to believe that you can deduce the progress of a social change simply from that. It would be like assuming that you can understand the real world's metalworking technologies solely from the history of firearms.
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This question is quite interesting. Here is my input:
# How cheap would the stones be?
I think that this is what you meant by your first question. I assume that:
* Each Mage earns the equivalent of $100,000/year
* A mage can make 10 stones per day
* Mages use our form of time, and work 250 days per year
That is 2,500 stones per year, or $40 per stone. That's a very reasonable number. Every Mage makes a handsome salary, and nobody will "Cheat" by using too many stones, since they aren't 10 cents to the dozen.
# How abundant would the supplies have to be?
Fairly abundant. Assume that the population is big enough to have "one-in-a-million" type people, and you've probably got about a tenth of a billion people. That's 100 people who can possess such an amazing power as they do. With 100 million people, assume that people use:
* 0 stones per month for kids/poor/elderly
* 3 stones per month for farmers/laborers
* 12 stones per month for peasant (Non-mage) soldiers
If these people are evenly spread, there are about 500 million stones being used monthly. If each stone is a fist-sized kilogram, then you will need a half of a Teragram of Mana...per month.
# How easily accessible should these supplies be?
In order to extract this much material, 2.9 megagrams of mana should be mined per hour. If each employee can produce 100 Kg per hour, then 29,166 people should be employed in Mana mining. In order to extract 100 Kg per hour, it should be in huge veins, with billion upon billions of kilograms of Mana. These could be fairly deep and hard to access, and 100 Kg per hour would be most likely if it were mixed with other stones.
# How long until Mages are displaced?
Well, I would place my bets at 200 years. Here's my idea of a timeline:
>
> 0-50=Stones are considered toys of little practical use
>
>
> 50-100=Stones have become popular as explosives, small arguments/skirmishes between Mages and stones have began
>
>
> 100-150=Stones are used often, but Mages are popular still
>
>
> 150-200=Stones have almost taken over. The occasional Mage still helps. At the end, Mages are gone
>
>
>
# How will it become popular (Changes in introductory form)
The creators would create more spells on the stones, and a few small battles would be aided by the stones. Soon, military commanders would see their importance.
# Special Tactics:
* Using several stones, build small "contraptions", such as attaching a levitating stone to a bomb, and launching an air assault
* Find several spells with similar runes, and switch between them (Like turning a grow-plants-better spell into a shoot-lighting-that-turns-you-into-a-frog spell)
I hope my ideas help!
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There are two different real world analogies you can use:
**1. Soldier:**
We have had soldiers since ancient times and we still have them now. Science has evolved a lot during that time, and so have the weapons and strategies used by the soldiers. But the occupation of a soldier has never disappeared. Soldiers and armies in general have only gotten stronger as technology evolved.
**2. Engineer/Scientist**
The creators and researchers. They have been there since the beginning as well. As science and technology has evolved, they have used the existing science and technology to improve upon it more and just get better in general and understand more about the universe around us.
**Mage**
Since you replaced science with magic in your world, mages are not going disappear. They will evolve and get more powerful as the magic itself evolves. They will discover new nuances and applications of magic they did not know before. They will be able to go further faster than before. Communication speed will increase. The more menial / labor intensive work will become automated. They will create golems to do the simpler work for them while they focus on more intellectual / high-value work.
Maybe someday mages will even lead the civilization to space and beyond.
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The Eternal Emperor wants to throw a party the likes of which the galaxy has never seen. The billionth anniversary of his reign is fast approaching (a mere hundred thousand years away!). He has brought the best celestial engineers in the galaxy together to create a stellar fireworks show for the party using supernovae and possibly other phenomena (the quasar show a few million years ago was a big hit). The show should be visible from the Emperor's palace on a rogue planet. Being basically immortal, the Emperor and his guests have little concern for time, so the party will take place across an entire year.
The following considerations apply:
* The supernovae should be as visible as possible from the planet surface without utterly overwhelming their visual sensors (thanks XKCD for the [billion nukes against your eyes analogy](https://what-if.xkcd.com/73/)).
* The supernovae should be visible from the rogue planet throughout the party year
* The Empire is a Kardashev III civilization with significant energy production, space travel, and manufacturing capabilities
* Due to high quality unobtanium shields, the planet itself suffers no negative effects (i.e. immolation)
* As few other systems as possible should be disrupted by the "fireworks"
* No citizens were harmed in the making of this product
* Standard Imperial cruisers have a top speed of .9c, though cargo craft and civilian transport travel significantly slower. Most military and trade spacecraft are crewed and piloted by AI to allow for accelerations that would kill most organics
* Most long distance travel is done through the Imperial Intragalactic Wormhole Network (IIWN). The IIWN is a network of artificially created wormholes that link frequently traveled and high population systems. Most occupied systems are accessible within a short distance (say, 100 light years) from the nearest IIWN station. Of course, there will always be colonists and terraformers living out in the "sticks", but they mind being far away from civilization. The stations are currently large enough to transport a small moon, but theoretically could be built larger if the need permits.
Question:
Given the level of technology above, is it feasible to artificially create supernovae on demand so that they are visible from a point in space during the same time period? How visible could they be from the planet's surface?
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I had written up a long spiel that was going to be part of a long answer to another question, but it looks like it'll do all right here. Just so you don't think that I whipped it up in 20 minutes.
# Type Ia supernova
Let me take a detour to look at this. In a Type Ia supernova, we would need a second degenerate body, typically a white dwarf. The first issue here is capturing said white dwarf. The Sun2 is not in a binary system, but a Type Ia supernova requires one3. Therefore, we need a situation where the Sun captures a white dwarf. This means that the white dwarf had to have been part of a binary system, which interacts with the Sun, transferring the white dwarf to an orbit around the Sun - or, rather, having the two orbit a common barycenter - and ejecting the original companion star.
This is obviously possible, but for fun, I decided to try it out. I used [My Solar System](http://phet.colorado.edu/en/simulation/my-solar-system), from the University of Colorado-Boulder. After many frustrating runs with different parameters, I eventually got a couple of encounters where the Sun ends up with a binary partner while the third star - the original companion to the white dwarf - is ejected:
Notice how the semi-major axes of the new binary stars oscillates a little much later (detail from later on):
Here’s another one, which is a bit more boring:
In both cases, I set the masses of all three bodies to be the same mass - about one solar mass - as I set the units equal to solar masses. You can play around a bit and try to reproduce my results using this and other configurations, although it’s not too easy.
The unfortunate thing here is that the simulator can only handle four bodies, and with no sense of scale here, I couldn’t recreate the Solar System. Perhaps someone else can, with Universe Sandbox. The reason this is important is because planets in a planetary system may - in fact, I’ll go out on a limb and say that they most likely *will* - be ejected or have their orbits severely perturbed by both the encounter and the resulting companion white dwarf. Maybe you’re okay with that - without the star, life on the planets might be seriously screwed - but if not, then you might have a slight problem.
Anyway, let’s say that the white dwarf has been captured, the companion star has been ejected, and everything else stayed stable, if you want that to happen. We next have the issue of mass transfer (which I’ll revisit again when I later talk about triggering a core collapse supernova). At this point, we have a system similar to a [cataclysmic variable](https://en.wikipedia.org/wiki/Cataclysmic_variable_star)4. Mass transfer will likely take the form of an accretion disk *assuming that material has overflowed the Sun’s [Roche lobe](https://en.wikipedia.org/wiki/Roche_lobe)*. The issue here is that it is going to be difficult for the Sun to transfer this material. This overflow of the envelope will be more likely when it expands into a red giant, which won’t happen for billions of years. So we may have to simply sit back and wait.
There are two important things to note about a [nova](https://en.wikipedia.org/wiki/Nova):
* The white dwarf is the star mostly impacted, not the Sun. In cases of extreme mass transfer, a substantial portion of the donor may be accreted, but I doubt this will happen and have any significant effect.
* The nova doesn’t destroy either star.
But I digress. Back to the idea of a Type Ia supernova.
We can create this sort of supernova - instead of weaker, peroidic explosions, as with a cataclysmic variable - if enough mass is transferred onto the white dwarf so that its mass exceeds the [Chandrasekhar limit](https://en.wikipedia.org/wiki/Chandrasekhar_limit), while not triggering the runaway fusion of a nova. That said, it may not be reaching the limit that causes Type Ia supernovae. Rather, runaway fusion of carbon and oxygen, unstopped by electron degeneracy pressure, triggers the thermonuclear explosion (see, for example, [Hillebrandt & Niemeyer (2000)](http://arxiv.org/abs/astro-ph/0006305) and [Mazzali et al. (2007)](http://arxiv.org/abs/astro-ph/0702351)). However, we still have the problems associated with our nova idea: the Sun likely cannot yet transfer matter, and a Type Ia supernova would destroy the white dwarf, not the Sun.
This is why I feel that triggering such a supernova is unlikely to help. [One answer to the question I referred to earlier](https://worldbuilding.stackexchange.com/a/36107/627) proposed a different idea than binary mass transfer: dropping a chunk of degenerate matter on the Sun. My dry response is that you’d need to get that chunk of matter in the first place, if you didn’t just have the stars collide (which, as I have already stated, is unlikely). [Millisecond pulsars can shed some mass](https://astronomy.stackexchange.com/a/7802/2153) (referenced [Cook et al. (1994)](http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1994ApJ...423L.117C&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf)), but white dwarfs don’t spin anywhere near that fast.
# Core collapse supernova
The other type of supernova we could have here is a core collapse supernova, either Type Ib or Type II5 I imagine this is what you were originally looking for, and again, I’m surprised it wasn’t addressed in more depth.
Again, the main issue here is mass, although this time, a new companion is the donor star, not the Sun. Let’s revisit capture again, and do some more simulations. I’ve chosen to make the incoming binary consist of a 3 M$\_{\odot}$ star and a 10 M$\_{\odot}$ star6, with the former star hopefully being ejected and the latter star being retained as the donor.
Here’s one successful try:
Note that the 3 M$\_{\odot}$ companion is ejected at quite a high speed, while the Sun and the 10 M$\_{\odot}$ star form a close binary - good for mass transfer.
Here’s another good run:
This one is notable because the Sun and the 10 M$\_{\odot}$ initially form a binary system, while the 3 M$\_{\odot}$ star comes back to collide with the newly-acquired companion.
I marked out a detail of the events. The arrow marks the initial velocity of the Sun, circle A marks the approximate point where the new binary is formed, and circle B marks where the 3 M$\_{\odot}$ star collides with the 10 M$\_{\odot}$ star:
It’s clear that a Sun/massive donor binary can form. The one issue that arises here is one that also arose in the Sun/white dwarf binary formation, but which I didn’t mention: the new system’s orbital eccentricities and semi-major axes. In many cases (see runs 1-3), relatively close binaries form, but they have large eccentricities7. In other cases (run 4), the eccentricities are a bit lower but still non-negligible - and now the stars are pretty far apart for a good portion of their orbits. This means that mass transfer may not be easy - it certainly won’t be simple.
Let’s set that aside as a petty quibble. Suppose mass transfer takes place between the 10 M$\_{\odot}$ star and the Sun. What happens next? Well, not much that’s interesting. The mass transfer is entirely possible, and is responsible for the resolution of the [Algol paradox](https://en.wikipedia.org/wiki/Algol_paradox) (see [Pustlynik (1996)](http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1998A%26AT...15..357P&defaultprint=YES&filetype=.pdf)). The success here only depends on how much matter can be transferred. I’m not aware of this happening to create supergiant stars, but I don’t think that it’s impossible, either. My only main objection would be that studies have focused on mass transfer from red giants to other stars, and a supergiant may behave much differently in this respect. But I really have no idea about that.
One more thing before I wrap this up. Adding mass to a star will not necessarily make it the same as a star with the same total mass. In less confusing terms, if I add eight solar masses to the Sun, it won’t necessarily behave like a 9 M$\_{\odot}$ star. Composition and structure differ widely among different stars. This might in some way affect the fusion of heavier elements in the newer, more massive, Sun. Again, though, there’s nothing to back that worry up.
# Wrap-up
So, to summarize:
Novae are no good. They won’t hurt the system significantly. Type Ia supernovae *will*, but the endangered body there is the recipient of mass, the white dwarf. The donor star won’t be affected unless a substantial portion of its mass is transferred, and I don’t think that will be the case here. Core collapse supernovae do seem to be possible, if you can conquer some other issues. You’d still have a companion star in the system post-supernova, which by now would most likely have seriously messed up many of the orbits or the planets, but at least the Sun would be gone.
The issues you do need to conquer are related to the movements of the stars throughout this:
* The odds of a binary system encountering the Sun in just the right way are unlikely to happen naturally, and any civilization would have a hard time influencing the movement of a star artificially (see [flippant remarks I’ve made](https://worldbuilding.stackexchange.com/questions/36103/is-there-a-way-to-create-a-bomb-to-destroy-a-star/36121#comment100047_36103)).
* Post-encounter, the orbits of the final binary system may be somewhat screwy, and mass transfer might not happen easily.
* Any planetary system you had at the beginning of the whole thing will most likely not survive the event intact.
All of that said, a core collapse supernova could - *could* - work.
---
**Footnotes**
1 Core collapse supernovae are Type Ib or Type II.
2 I'm taking the Sun purely as an example.
3 Some might result for collisions between two stars, but this is generally between two degenerate bodies, and is unlikely to happen in many places besides dense globular clusters, where it may occur when a binary system encounters a lone star. For a good overview of that, see [Leonard (1989)](http://adsabs.harvard.edu/abs/1989AJ.....98..217L).
4 See also [here](http://www.mssl.ucl.ac.uk/www_astro/gal/cv_beginners.html).
5 I’m not going to discuss [hypernovae](https://en.wikipedia.org/wiki/Hypernova); the mass needed there is just ridiculous.
6 8 M$\_{\odot}$ is most likely the cutoff mass for a star to go supernova (see [Heger et al. (2002)](http://arxiv.org/abs/astro-ph/0212469)), but I need to donor star to not transfer *all* of its mass to the Sun, and I need some wiggle room.
7 This might just be an artifact of my test runs, but I don’t think so. Sure, low-eccentricity binaries can form, but they most likely aren’t common.
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It seems the question is: can a suitably advanced civilisation make a star into a firework (standing well back), and if so what is the most believable way we know of?
## Coke Gives Life
I'm going to aim for a technological solution, because all the ones where you somehow manoeuvre another star into the path of the first star seem like more effort than making a star artificially, or some other magic. We are struggling to see how to move asteroids with thermonuclear weapons, how on Earth would we move a sizeable planet, let alone a star?
This is, by the way, a plot point for Red Dwarf - the Nova 5 on which Kryten is stationed has the mission to send stars into nova for an advertising campaign spelling out 'Coke Gives Life' in twinkling letters in the Earth sky.
## What Physics can pop a star?
So we have a target star, huge and with an immensely high pressure plasma core, churning through a CNO fusion cycle (assuming it's a sizeable star). We need some Physical phenomena that has higher energy levels than fusion to make any kind of dent in it. The only one I can see here is Antimatter.
```
Stuff Sp. E. MJ/kg
Lithium ion cell <1
Petrol/Gasoline 46
Compressed H2 142 Top chemical
Uranium 81,000,000 Top fission
Fusion 300,000,000 Approx
Antimatter 180,000,000,000 2 c^2, (1 antimatter + 1 matter)
```
## Triggering nova with a squeeze
How can we use antimatter to trigger a nova event? We aren't trying to blow the star up, but tip it off the edge of equilibrium.
So if we could launch some cans of antimatter into the outer layers of the star, we might manage to do something similar to the current NIF laser-triggered fusion effort; create a spherical shockwave that squeezes the core down to raise densities there and trigger the nova.
But a near-nova star is not a balloon, is it? Well, sort of. The nova event occurs when the falling radiative pressure of the fusion process is overcome by the gravitational compression of the star's mass. Different classes of supernova seem to have different process here, but I want to look at a [Type Ia supernova](https://en.wikipedia.org/wiki/Type_Ia_supernova).
## Type Ia Supernovae are ticking timebombs
Essentially a Ia begins with a white dwarf with a mass that would usually proceed without exploding to become a neutron star. However, by feeding off a binary partner, the Ia acquires additional mass, and manages to reach higher core temperatures over a period of 1,000 years or so of convection. It is believed that at some point in this period, a deflagration ('flame') front is started, which starts C-C fusion which is both strongly exothermic and completely unsustainable, which rapidly uses up heavy elements over the course of a few seconds, raising the core temperature to billions of degrees, and generating enough energy to 'unbind' (SPLODE!) the star. I'm very hazy on all those details, so do look them up. The key phrase is [Carbon Detonation](https://en.wikipedia.org/wiki/Carbon_detonation).
The point, though, is that an end-phase overfed white dwarf like this is just waiting to pop during much of that 1,000 years, and once it does it goes nova.
## Putting it all together
Since most lower-mass stars (like the Sun) are set to become white dwarfs eventually, a significant fraction of stars are white dwarfs already; Wikipedia reckons 8 of the 100 nearest stars, for example. What proportion of white dwarfs are in binary feeder relationships is hard to know, but binaries are common, white dwarfs are common, the combination is quite conceivable, although there is a selection bias against them; the remaining ones are those that have not already popped.
Sending antimatter to a white dwarf seems vaguely plausible. The original idea to detonate inside the star is not possible with a 'normal' white dwarf, because it is essentially solid (electron degeneracy pressure). But we can instead send our antimatter canisters to crash into many points on the surface simultaneously.
I don't have numbers to give you, since it would depend on the star and a better understanding of determining the effect of a compressive wave on a convective white dwarf, but at least here we are making use of a star that is relatively small (~1.4 solar masses), relatively common, and which is already on the edge of exploding anyway; we are only trying to trigger an instability rather than create a star big enough to go nova by itself. We also get to choose the timing (although I'm not sure how predictable it would be) whereas any other type of supernova would happen in its own timescale.
The biggest downside is having to create so much antimatter that it could have any impact on a star. I have no idea how to do that. But we do know it can be done, and we are considering a civilisation more advanced than our own. Perhaps the long timescales needed to accrete so much antimatter would be acceptable, and they should have better technology for doing so.
## Dark possibilities
Antimatter is the most energetic reaction possible with matter in current Physics, as it involves complete annihilation of all the ingredients. However, currently we believe that only a small fraction of the mass of the universe is actually made of normal matter, leaving the rest to be 'dark matter' or 'dark energy'. Given that we only know about these things because of their gravitational effects, it is hard to know what new Physics we might discover as we explore it; there could be additional fields which we are as yet unaware of, higher energy phenomena, or even interactions that give us better control over things like large stars. So the massive caveat is that we do know that there is a lot more Physics to discover, and a more advanced civilisation might well have more and bigger tools available.
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I'm worldbuilding a continent that's mostly desertic (still trying to decide if sand or rocky desert, but definitely a hot desert). All the rain would fall on the edges of it, through a chain of mountain-ranges on all sides. I want said continent to have pockets of population, so I need to know how to distribute the water underground.
How can I draw a realistic network of underground aquifers (or where can I learn how to do it)? How will that translate in oases or locations where people might dig up wells?
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The key word you're looking for is **Aquifer**.
This is water present in underground rock layers. Generally you get an oasis or springs when the water present in layers of rock that water can pass through are funneled to the surface by layers of rock that water cannot pass through. This will usually be in lowland areas relative to nearby hills or mountains, as the water underground still has to flow down with gravity.
You can find a number of maps of these structures online by searching for aquifer maps:
[](https://i.stack.imgur.com/8PkuK.jpg)
The location of these aquifers depends a great deal on the local geology in the areas; depending on how in depth you want to world build you could construct a detailed local geology or just follow some existing topographical features. For example on the U.S. Aquifer map it is relatively easy to find aquifer contours running adjacent to mountain ranges, plateaus, and coastlines.
The USGS has a large amount of information on the [basics](http://water.usgs.gov/ogw/aquiferbasics/) and some detailed maps in the [US Groundwater Atlas](http://water.usgs.gov/ogw/aquifer/atlas.html)
On a related note, digging wells isn't the only way to get at underground water, in Earth's desert regions a common un-natural feature for moving water to facilitate human settlement is the [qanat](https://en.wikipedia.org/wiki/Qanat). It is basically a tunnel used as an underground irrigation canal, dug to let water flow horizontally out of a hillside aquifer.
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I don't know how to draw a realistic network of aquifers, but I do know that such things exist under the Sahara, and are being tapped to produce farms in the desert. So perhaps that may help? You'd probably need to investigate the geology behind what formed such aquifers (or perhaps rather why the Sahara formed over them).
<http://www.bbc.co.uk/news/science-environment-17775211>
<http://www.bgs.ac.uk/research/groundwater/international/africanGroundwater/maps.html>
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Large fossil water deposits depend on the climate having been different in the geologically recent past. The significant dryland aquifers in the world are not that old. There are broadly two types.
The first type is like the [Nubian Sandstone](https://en.wikipedia.org/wiki/Nubian_Sandstone_Aquifer_System) aquifer across the North Sahara, primarily in Libya. The water in this aquifer comes from the [Neolithic Subpluvial](https://en.wikipedia.org/wiki/Neolithic_Subpluvial), also called the 'Green Sahara'. This was a time period from about 7000 BC to 5000 BC. At this time, the Sahara was much smaller and the North Sahara area got signficant winter rainfall, much like the climate farther north in Tunisia or Greece. Since the land is relatively flat, it did not rapidly flow away, but tended to form chains of lakes. These lakes allowed much groundwater to seep into the bedrock. Eventually it pooled underground where the rock layers stopped it and is still here to the present...at least until thirsty humans pump it all out.
The second type is like the [Ogalla reservoir](https://en.wikipedia.org/wiki/Ogallala_Aquifer) in the High Plains. This isn't strictly a desert, but it is semi-arid and doesn't get much rain. The massive reservoir is deposited from water seeping from the many rivers coming off the Rockies. The Missouri, Plattes, Canadian, Arkansas and more rivers come down from Montana to Colorado and flow across the plains to the Mississippi. Their flow rate isn't that high, but it is enough to recharge the aquifer. So in this case, the water level is actively recharging, unlike the Nubian Sandstone.
If you are talking about a very dry desert ringed with mountains, then one of the best examples would be the Tarim basin in China. It too has a [large aquifer](http://inhabitat.com/vast-ocean-discovered-under-chinese-desert-may-be-worlds-largest-carbon-sink/) underneath it, of the Ogalla type. Ringed by high mountains like the Kunlun and Tien Shan, spring snow melts brings water into the basin every year. The water doesn't get very far, but can still be used for irrigation at famous Silk Road outposts like [Kashgar](https://en.wikipedia.org/wiki/Kashgar) or [Khotan](https://en.wikipedia.org/wiki/Hotan). What does make it to the desert sands disspaears, partly through evaporation, and partly through seepage into this aquifer. On the other hand, it is worth noting the fact that this particular aquifer is only being found today because it is at depth where where you need an oil rig to get it out. So it wasn't exactly usable to the ancients, who needed to depend on meltwater.
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Here are two mechanisms that can produce oasis (is oases the proper plural?):
Underground water forced to the surface at the edge of a mountain range. For example the "Palm Canyon Oasis" in southern california (tried to link, URL length seems to be an issue. You might try feeding that phrase into images.google.com or similar. A beautiful hike, if nothing else.) So, one might have a rain-shadowing mountain range, and along the base of the lee of that range, there could well be a series of precious, potable springs.
Faults can also direct groundwater to the surface (and faults can usefully change, to create/destroy scarce water sources, as quickly as plot requires.
Hot springs?? (Not all of them smell vile. Those associated with carbonate minerals {vs. sulphides} are usually quite pleasant and sought after.)
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# Prologue
In my current worldbuilding project, I decided to put a ban for faster than lightspeed travel, and decided that most space flights be done in slower than lightspeed travels. Assuming efficient engines had been invented in this universe (say, some sort of 80% to 90% energy efficiency), and antimatter are not that hard to farm (just say a new technology (or some) had been invented to increase antimatter productions and storages), relativistic travel is common to travel from stars to stars.
So far the setting looks nice, and ready to be filled with stories.
As I start writing, I realized that onboard clock and outside observer (assuming it as a reference frame) would experience different passage of time, and that accelerating (and decelerating) to relativistic speed would also contribute to variable time passage felt onboard the ship relative to outside observer.
# Common Space Travel Settings
1. Accelerate-ballistic-decelerate settings, where ships were accelerated to desired speed, then follows ballistic path, and then decelerates toward rest near its destination. Commonly used, as the ship could be mainly dormant during ballistic path (cruise speed), saves the most power for considerable travel time. Cruise speed varies between common 0.3-0.5 times *c* to high priority travel between 0.7-0.9 times *c*.
2. Constant acceleration-turnaround-constant deceleration toward rest, very energy consuming, usually used for urgent short-ranged distance travel (for example, interplanetary travel). It differs from the first setting only on turnaround phase, that costs nearly negligible amount of time compared to time elapsed on the whole voyages (while at the first setting most of the voyages were spent on cruise speed).
# Problems
Mainly the question revolves around relativistic effect felt onboard the ship and an observer at a planet (making a huge assumption that a planet is generally 'static').
## In case of first setting
1. How to calculate time (both from reference frame of a static observer, and the ship's reference frame) required for the ship to accelerate from rest toward desired speed (or from desired speed toward rest) given *x* gee of acceleration (ship's reference frame)?
## In case of second setting
2. How to calculate total time required (both from reference frame of a static observer, and the ship's reference frame) for the ship to cross the distance of *n* kilometers (or AU) given *n* gee of acceleration?
# Considerations
Given wide range of possible readers in term of math proficiency, I would encourage easy-to-understand formula, with terms that high-schoolers could understand (high-school education be the baseline for difficulty level). Explanations may follow after the given formula if the answerer desires (and would be appreciated when they do).
That said, square root functions, divisions, multiplications (additions and substractions too, obviously), square functions, are allowed.
# Closing Statements
The purpose of the aforementioned considerations are that everybody (with minimum of high-school education) could read and take advantage of the answers, basically any worldbuilder that requires the formula to calculate similar problem I am facing. And I have to admit that my physics were quite rusty (it had been two years since my high school), and quite lazy to figure it out on the net.
I wrote this question mainly to benefit me (let's be honest), but it could also benefits other (mainly) hard sci-fi worldbuilder or any worldbuilder facing similar problem as of me.
Thanks in advance.
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The term you'll want to google is the "relativistic rocket"--there's a good page on the idea [here](http://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html). The equations there all deal with a rocket that accelerates at a constant rate "a" (a constant [proper acceleration](http://en.wikipedia.org/wiki/Proper_acceleration) as measured by an accelerometer on board the ship) starting from rest in some inertial observer's rest frame (say, an observer at rest relative to a star), with distance "d" and time "t" and velocity "v" measured in terms of that frame, while "T" is the time on board the ship (which is different from t due to time dilation) For problem #1, you can use the equation for velocity "v" as a function of acceleration "a" along with either the onboard time "T" or the observer's time "t":
v = c th(aT/c) = at / sqrt[1 + (at/c)^2]
Note that the symbol "th" is intended to refer to the hyperbolic tangent function, likewise some other equations use "sh" which is hyperbolic sine and "ch" which is hyperbolic cosine, all three functions are available on the online calculator [here](http://keisan.casio.com/has10/Free.cgi), where they are written tanh, sinh, and cosh, and the calculator also includes their inverse functions atanh, asinh, and acosh (which are needed if you want to solve one of these equations for T). If you take the first half of the above equation, v = c th(aT/c), and solve for T in terms of v and a, then you get the following equation for T (I've put in a syntax that the online calculator will understand):
(c/a)\*atanh(v/c)
So, you can just substitute the speed of light for c (in whatever units you're using, might be easiest to use something like light-years for distance and years for time so that c=1), the acceleration for a (in units of light-years and years, a one-gee acceleration has a value of 1.03 as mentioned on the relativistic rocket page), and your desired final acceleration for v, and plug it into the calculator (*note to other editors:* this is why I'm not using the nicer-looking "MathJax" formatting for equations, I want people to be able to cut and paste into the calculator, so please don't change them). For example, with c=1, a=1.03 and v=0.5, I can plug (1/1.03)\*atanh(0.5/1) into the calculator and conclude it would take about 0.5333 years of onboard time to reach 0.5c relative to the reference frame I initially started from rest in.
And if you want to calculate the time in the observer's frame rather than the onboard time, you solve the equation v = at / sqrt[1 + (at/c)^2] for t, which gives the following equation for t:
(v/a)/(sqrt(1 - (v/c)^2))
So for the same numbers of c=1, a=1.03 and v=0.5, you'd plug in (0.5/1.03)/(sqrt(1 - (0.5/1)^2)) which gives an answer of t = 0.5605 years for the observer in the frame where the ship started at rest.
For problem #2, you'll want to start with these equations from the relativistic rocket page:
d = (c^2/a) [ch(aT/c) − 1] = (c^2/a) (sqrt[1 + (at/c)^2] − 1)
...and solve the first part for T in terms of d and a, then solve the second part for t in terms of d and a. Solving the first part for T gives:
(c/a) \* acosh((d\*a/c^2) + 1)
And solving the second part for t gives:
sqrt(d^2 + (2\*d/a))
So for example if you want to figure out the onboard time T and observer's time t for the ship to travel a distance of 10 light years at a one-gee acceleration, you'd use c=1, a=1.03 and d=10, so for T you'd plug (1/1.03) \* acosh((10\*1.03/1^2) + 1) into the calculator which gives an answer of 3.0252 years of onboard time, and for t you'd plug sqrt(10^2 + (2\*10/1.03)) into the calculator which gives 10.9278 years of observer's time.
Also, note these distance formulas are for a ship that accelerates at a constant rate, continually gaining speed relative to the inertial frame where it started at rest. If you like you can easily adapt the formulas to a scenario where you accelerate for the first half of the journey and then decelerate for the second half, coming to rest at your destination. The way to do this is just to pick the distance to the halfway point and plug that into the formulas, giving the time to get to the halfway point. Then since the acceleration and deceleration phases are totally symmetrical, you can just double the time to the halfway point to get the total time to arrive and come to rest at the destination.
## Summing up:
If you have the acceleration A and the final velocity V, plug them into the following along with the value of the speed of light c in your preferred units, and evaluate in the [online calculator](http://keisan.casio.com/has10/Free.cgi) to get the **onboard time T**:
(c/A)\*atanh(V/c)
If you have the acceleration A and the final velocity V, plug them into the following along with the value of the speed of light c in your preferred units, and evaluate in the online calculator to get the **time t in the inertial frame of an observer who saw the ship initially at rest**:
(V/A)/(sqrt(1 - (V/c)^2))
If you have the acceleration A and the final distance D, plug them into the following along with the value of the speed of light c in your preferred units, and evaluate in the online calculator to get the **onboard time T**:
(c/A) \* acosh((D\*A/c^2) + 1)
If you have the acceleration A and the final distance D, plug them into the following along with the value of the speed of light c in your preferred units, and evaluate in the online calculator to get the **time t in the inertial frame of an observer who saw the ship initially at rest**:
sqrt(D^2 + (2\*D/A))
## One last thing:
Another issue you may want to consider for worldbuilding purposes is the ratio of the initial total mass of the rocket, including both fuel and payload, to the final payload mass at the end of the acceleration when all the fuel has been expended (if it ends up being something ridiculous, like millions of tons of fuel per kilogram of payload mass, you may have to rethink your acceleration and time somewhat). I covered the equations needed to calculate this in [this post](https://scifi.stackexchange.com/a/105931/22250), if anyone's interested. The answer depends on the type of rocket and the velocity of its exhaust, with the most efficient possible case being a rocket that totally annihilates the mass of the fuel and converts it into high-energy photons that get shot out the back, in which case the exhaust velocity would be c. A bunch of exhaust velocities for rockets both existing and theoretical can be found on [this page](http://www.projectrho.com/public_html/rocket/enginelist.php), see the column for velocity in meters/second (which you need to convert to whatever units you're using for the other quantities in your equations, like light-seconds and seconds, light-years and years etc.).
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There are two different causes for time dilation. For the most part, you'll ignore General Relativity and just use Special Relativity, but I've laid out both as best as I know.
**General Relativity**
First is acceleration, whether this is a result of a gravitational field (such as sitting on a planet) or more typical acceleration (such as being in a rocket). I'm getting mixed results trying to find formulas for this, but at any acceleration a human can survive, the difference will be fairly negligible. From [this Physics FAQ article](http://math.ucr.edu/home/baez/physics/Relativity/SR/clock.html), it seems the effect of acceleration is just that it's constantly changing the relative speed, as shown below. While you're in a gravity field (such as on a planet), the time dilation has to do with how it warps spacetime to make it look like you're going different speeds.
The result is when your guys are far from any planets, you can just use the relative speed (special relativity) calculations below for various points throughout their acceleration (that is, integrate). For example, break the trip up into 50 stages as they accelerate, 1 stage of constant velocity, then 50 stages of deceleration. If acceleration is the same rate as deceleration, you can just calculate one and map it to the other.
When they're hovering near a planet (or standing on the planet), you use the following formula (from [this physics.SE answer](https://physics.stackexchange.com/questions/154617/what-is-the-correct-formula-for-gravitational-time-dilation-for-a-satellite-in-a)):
$t'=t\sqrt{1-{2GM\over rc^2}}$
where
$G$ is the [gravitational constant](https://en.wikipedia.org/wiki/Gravitational_constant), $\approx 6.674\times 10^{-11}{N\cdot m^2\over kg^2}$,
$M$ is the mass of the planet / star / black hole / small moon / Death Star in question,
$r$ is the distance from the center of the planet.
Doing this calculation [for Earth](http://www.wolframalpha.com/input/?i=sqrt%281-2*G*%28earth+mass%29%2F%28%28earth+radius%29*c%5E2%29%29), we see that time on Earth passes about 0.999999999305 times as fast as it would with zero gravity around. Which means we see about 0.7 seconds less than a spaceship in deep space would over a 30 year period. So you need a really massive planet before you start seeing a notable difference. To get $t'=0.9t$, you need $M\approx 8.2\times 10^{32}kg\approx 410 M\_\odot$ (about 410 times the mass of our sun), where you'd be experiencing about 136 million gees.
If they're *orbiting* near the same planet, you use this formula (from the same physics.SE answer):
$t'=t\sqrt{1-{3\over 2}{2GM\over rc^2}}$
I believe neither of those answers applies if you're inside a planet, but that shouldn't be an issue for the most part. Also, I presume that during a transition from hovering to orbit, you'd need to integrate between the two formulas, but I doubt your spaceships will spend enough time in this transition to really care. And about the only place it's going to matter anyways is if they're really close to a black hole or neutron star or something.
**Special Relativity**
Second is relative speed. As your spaceship gets close to light speed relative to some "stationary" object (your reference frame), its perceived time will be lower. The formula is [given by](http://dilation.1e5b.de/index.php) (click the link for a calculator):
$t'=t\times\sqrt{1-{v^2\over c^2}}$
where
$t'$ is the time perceived by the moving spaceship,
$t$ is the time perceived by Earth,
$v$ is the speed of the spaceship relative to Earth,
$c$ is the speed of light.
You get a 1% difference ($t'=0.99t$) in clocks around $v=0.14c$, a 10% difference ($t'=0.9t$) around $v=0.44c$, a 50% difference ($t'=0.5t$) around $v=0.87c$, a 90% difference ($t'=0.1t$) around $v=0.995c$, and a 99% difference ($t'=0.01t$) around $v=0.99995c$.
The above calculator gives the moving object's time as a fraction of "normal" time. If you'd like to go the other way, you can either just plug $1\over t'$ into a calculator, or use [this calculator](http://www.1728.org/reltivty.htm) that returns normal time as a (greater than 1) fraction of the moving object's time.
Technically, you could use anything, including imaginary objects, as your base reference frame, but it's easiest to use something like a star or planet so everyone can be on the same schedule. Stars do move relative to each other, and realistically your scientists would carefully analyze the differences, but for practical purposes all stars are in the same reference frame. [Barnard's Star](https://en.wikipedia.org/wiki/Barnard's_Star) is the fastest-moving star near us, moving about 143 km/s, which translates to a relativistic factor of 1.000000114, or 0.999999886, depending on whose perspective we're looking from. If someone near Barnard's Star counted 1,000,000,000 seconds passing, someone near Earth would count 1,000,000,114 seconds. That's a difference of about 2 minutes every 32 years.
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I saw this [old closed question](https://physics.stackexchange.com/questions/61113/what-happens-at-the-interface-between-two-universes-with-opposite-thermodynamic) on Physics.SE and thought it would be perfect for *here*. The original author is long gone, so I thought I'll just have to post it myself.
We can consider factors of plot and literature, not just hard science. But I do intend for it to be hard-SF.
In Greg Egan's [*The Arrows of Time*](https://en.m.wikipedia.org/wiki/Orthogonal_(novel)) he had a crew visit a region where the thermodynac arrow of time was in the opposite direction. The ambient sunlight was not visible to them and they would unmake footprints.
But I think that's not right. Consider what would happen if you prepared such a region by somehow reversing the momentum of every particle. It is very precarious with every gas molecule having to be exactly right! As soon as you observe it, you *peturb* that delecate state and time runs normally from that point forward.
Consider an experiment where a gas cloud in a large isolated chamber will rush into a bottle, because the state of every molecule is *just so*. If you go into the chamber, it won't work anymore because you mess up those perfect trajectories. (Unless the trajectories were chosen with knowledge of your exact effect in mind...!)
## The Setting
Suppose you had a wormhole that led to another part of the universe where time ran backwards or the orientation of the exit mouth were such that it dropped you into the time dimension facing the wrong way.
You don't experience the environment to be anti-matter: as in Egan's story it *would* be anti-matter if your time arrows were aligned, so you have matching matter polarity but opposite entropy gradiants and (whatever that means if it's more than just entropy) opposite time directions.
What happens? How?
Maybe you are like the gas bottle cloud and the large environment at your destination peturbs *you*. Does time do funny things? Do time and entropy break up into separate concepts? Could you go *down* in an elevator that's ascending, escaping in the same ride that the police use to arrive at the scene of the crime?
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The title of your question and the question you're asking seem to be two different things: In the title you're asking what would happen at the interface, but in the body of the question you ask what it would be like to experience such a world.
I can answer both: You wouldn't be able to experience such a world because the interface can't happen. Or more to the point, if it did happen, nothing would be able to cross it.
Consider a person trying to cross the boundary. In our universe their muscles are pushing their flesh. In the other universe? Their muscles are following. On the boundary? It's one of two things: Either there's a continuous (but tiny) change from one set of thermodynamic laws to another, or there's a straight discontinuity where the two universes meet.
In case 1 it's fairly obvious that the boundary is an area where time doesn't travel in either direction. If time isn't flowing: you can't cross the boundary, so you can't get to the other universe past the wall of particles that are undergoing an asymptotic temporal dilation as they approach the boundary.
In case 2 there's going to be an interesting moment when you cross the discontinuity. The cause of your skin crossing the boundary (the effect) will have to happen after the effect in the new universe. Sadly that can't happen, because the thing causing that effect (in this case a push from your muscles) is still in the wrong universe where time is going the other way. In this case the boundary causes causal violations on both sides, as particles try to cross but can't as they can't move over the boundary until they've already crossed on one side, and can't cross the boundary until they've moved over it on the other side. Confused? Not half as much as you would be at the boundary. By which I mean every quark in your body will be in a confused jumble floating back and forth at the boundary. They can't move back in this universe and can't move forward in the other one.
Essentially: Anything that has a temporal component can't work as it crosses the boundary. Sadly that includes everything (including spacetime. I can't even picture the Minkowski diagrams for this one.)
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Sir Arthur Eddington introduced the concept of time's arrow in thermodynamics. This is what he had to say about it, quoted from Wikipedia [Arrow of time](https://en.wikipedia.org/wiki/Arrow_of_time):
* It is vividly recognized by consciousness.
* It is equally insisted on by our reasoning faculty, which tells us that a reversal of the arrow would render the external world nonsensical.
* It makes no appearance in physical science except in the study of organization of a number of individuals.
and
* so far as physics is concerned, time's arrow is a property of entropy
alone.
From this, we gather that the arrow of time is just a vivid metaphor for entropy. It has no real physical existence apart from its alter ego, entropy.
Therefore, in the alternate universe, entropy is reversed. Nothing happens there: everything *un*happens.
So far, we've been discussing this unhappening at a macro level, except for a passing reference to quarks by Joe Bloggs. But is it conceivable at the level of fundamental particles? For example, all fusion must unhappen over time, leaving a universe of hydrogen. What would a time-reversed Schroedinger equation lead to? The implications are so bizarre that they make string theory look like elementary arithmetic.
LR's answer opines that two arrows of time pointing in opposite directions can't coexist. Since all our equations of physics are time-reversible, if one exists the other must exist. Therefore the only resolution to this paradox is that *there is no such thing as an arrow of time*. There is entropy, of course, but it would seem there is no way to reverse it: the genie just won't go back into the bottle.
Joe Bloggs' answer, considering what would happen if two areas with contrary arrows of time were to abut, seems to approach the same conclusion: there can't be an arrow of time. I think this is an interesting line of thought to pursue - and that's an understatement.
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# Crossing the interface
@JoeBloggs is right there are two scenarios for crossing the interface between two universes with opposite thermodynamic arrows of time. His case 2, where the interface is sharp discontinuity, requires anyone passing to do so quickly. Otherwise the person would be a mixture of matter and antimatter. The model of quantum tunneling through a soap film like wormhole would make for a safe passage.
What would this look like? This can be demonstrated with a thought experiment. Assume the interface lies at the mid-point of a tunnel. A small vehicle A is used to cross from one universe to another. It travels at one metre per second and the tunnel is twenty metres long. When the vehicle enters the tunnel its passengers we see an identical vehicle B enter the tunnel at the other end and moving towards them backwards. The people in the backwards will be waving hello to those in the vehicle from our universe.
The two vehicles approach each other at the mid-point and instead of colliding from the point of view of vehicle A vehicle B will vanish from in front of them while immediately reappearing behind them and heading backwards towards the entrance where vehicle A had originally entered.
Vehicle A continues forward and goes through the tunnel mouth leading the reversed universe as they do they wave goodbye to the people in vehicle B.
Obviously vehicles A and B are the same vehicle viewed at different parts of its worldline and in close proximity, spatially, to each other.
Case 1 is much more interesting. Here crossing the interface will happen gradually in small degrees. This reminded me of Kurt Godel's rotating universe solution to general relativity where a spacecraft travelling through its spacetime will gradually have its light cone tipped over until its relationship to past and future are reversed. This reversal of time is relative to the starting point of the Godelian spaceship. To anyone on the spaceship time will still go forward as if nothing had changed.
Details of the Godelian universe and its metric can be found here: <https://en.wikipedia.org/wiki/G%C3%B6del_metric>
This seems plausible. The interface between the two universes in case 2 would most likely be vast, perhaps several light years across. Perhaps, it might be as big as a universe in its own right. In that case, crossing between two universes with opposite directions in time will include an intermediate universe. Anyone travelling between the universes has to cross this intermediate universe before going from one universe to another. It would need something like this, and possibly as big as another universe to allow the progressive tipping of a traverser's light cone in being able to cross the interface. In a SF story the writer can scale down the size of a Godelian spacetime as interface for the purposes of the plot.
# Backwards O Time, Backwards
There are no surprises here. Once in the time reversed universe everything seen exactly the same in their home universe. Time would appear to go forward in exactly the same way. Entropy increases as usual. If the traversers had a viewing devices to observe what was happening in their home universe it would appear to be running backwards. This omits any possible effects of relativity on the viewer. Things become more than difficult considering how this might work.
If the traversers could cross the interface back their home universe, there might be time travel. This is more likely with an abrupt discontinuity. Whereas with the case 1 huge interface the time taken to it might cancel out any possible time travel.
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There are actually two scenarios differing in “polarity” with which two space-times would be connected.
If, when traversing the interface, a world line faces the reversal of thermodynamical time direction (but possibly travels the same coordinate time direction), namely:
```
calendar: Monday Tuesday Wednesday
(our world) →→→→→→→┑
(antiworld) ┖←←←←←←←←
```
, then Joe Bloggs is right: no one will be able to traverse the interface. The conscience (as well as physiology) is not able to run towards decreasing entropy, so a human travelling the way pictured above will essentially die. Of course, Ī̲ dismiss the possibility that a human body can maintain *its own direction of time* that defies the one of the surrounding universe — that’s anti-materialistic, at least.
Another possibility is the interface that we cross along the Arrow of Time, but reversing coordinate time direction, such as:
```
calendar: Monday Tuesday Monday Sunday Monday
(our world) →→→→→→→┑ ┎→→→→→
(antiworld) ┖→→→→→→→→→→→┙
```
There is no death upon transition, but implications will not be very different from the usual “travel to the past” stuff. If two-ways crossing is allowed, then mathematically, the first thing to be noted is that the united space-time of two interconnected universes isn’t [causal](https://en.wikipedia.org/wiki/Causal_structure) (there are closed time-like curves and no past–future partial ordering).
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In the universe that you are describing effect comes before cause, and enthropy always decreases. This is the universe where you would be stealing because the police is chasing you. Gas returns to a bottle because it is its natural behaviour. For the inhabitants of this universe, rain after the wet ground would be completely expected. They would not perceive it as abnormal.
I cannot imagine what a person coming from our universe would feel like there. Supposing he survives the journey, I think he would start functioning according to the local laws of physics. Imagine, if he comes to a place where gravity is repulsive, he might be surprised but he would still fall up. And in a place where time flies backwards the very neurosignals would be sent backwards. He would maybe be able to sonsciously understand cause before effect, but for him them it would be unnatural. He would just go along with the flow.
On large scale, I think that if two universes with different time arrows would meet, it would cause some very grave consequences. I don't know whether complete anihilation or the two would somehow mix in some very weird way, but it seems impossible that the two would be able to coexist.
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The skeleton of the average skyscraper is steel. While it does have its advantages, they tend to get outweighed by two specific faults. One is a resistance to corrosion so poor that in a Life After People, it might stand firm for only 150 years. The other is that it's too heavy. So much, in fact, that nothing could get taller than the ridiculously narrow Burj Khalifa in Dubai.
So, for a taller building or other manmade structure, are there any metals or alloys tougher but lighter and thus longer-lasting than steel? If yes, then which?
What about glass? We've come to a point where scientists have created a glass as tough, if not more so, than steel. Could a glass skeleton be a public reality in the foreseeable future?
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## Not yet, but maybe in the future.
There are a number of attributes that make materials desirable in constructing buildings. There are also various different ways to measure strength.
**Steel** has been and will remain the dominant construction framework material for the near future because it has high strength, reasonable anti-corrosion characteristics (when properly managed), and low cost. Steel has high strength in terms of both compression strength and yield strength, both are important.
What about alternatives?
**Aluminum**. Although stronger on a per mass basis, it is not as strong on a volumetric basis. A rule of thumb is that steel is twice as strong as aluminum, but aluminum only weighs about 1/3 as much as steel - both are available of alloys of different strengths. Aluminum also fails under cyclic loads and is more brittle (breaks at around 3% yield vs 20% yield for steel). Aluminum has an additional unsatisfactory problem for construction though, typical alloys lose much of their strength at 400 degrees F. This is simply a fatal flaw for building construction.
**Titanium**: Stronger per unit mass, but more expensive and considerably harder to work. Although abundant in the crust, much less than a million tons annual world production vs. over a billion tons for steel (about 10000:1 ratio overall). Does not have the high temperature strength of steel, but is better than aluminum. Titanium is very reactive, it will even burn in a burn nitrogen atmosphere. Titanium is popular where lightness and strength are dominant goals, such as fighter jets, but simply too expensive to use for building framing.
**Superglass**: Currently the superglass materials you refer to depend upon palladium. Palladium is expensive - today price 495.40 USD per ounce, 15,927 per kg. This glass will never be cheap enough for building construction unless the palladium can be replaced by something quite a bit cheaper. At which point, it may in fact become a common building material over time.
This superglass is not the same glass that we are all familiar with. The palladium allows the glass to be tough (bend without breaking) and retain its traditional strength. Some glass loses strength rapidly as temperature increases, other glasses actually get stronger for modest temperature increases. Without knowing the details for superglass, I can't guess this aspect and could not find any published detail related to strength at high temperature.
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In my world there are rings, these rings are around 9.5 meters tall and a little around 5000 kilometres wide. Their closest point is a little over 12,000 kilometres away from the surface and under 17,000 kilometres at its farthest point. For all intents and purposes this world is the same as earth. Since the best place to put a satellite is at the equator and rings appear at the equator, this creates a problem as to have wireless communication across the globe, you need satellites. How can my people incorporate satellites in orbit? If they cannot, what alternatives to satellites can they use?
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On Earth, a lot of satellites are in [low-Earth orbit](https://en.wikipedia.org/wiki/Low_Earth_orbit). This extends out to 2,000 km, which is a safe distance away from the innermost part of the rings around your world. So you can put satellites into orbit around your world in the same way that we put satellites into orbit around Earth.
[Medium Earth orbit](https://en.wikipedia.org/wiki/Medium_Earth_orbit) satellites would have to worry about the rings, but not too much. Wikipedia states "the most common altitude is approximately 20,200 kilometres", safely beyond the rings. Because the rings are not very tall, you don't have to worry much about them blocking communication with the satellites—giving their orbits a little bit of inclination relative to the rings will guarantee that communication will only be blocked for a fraction of a second at a time.
Any orbits farther out will be similarly unobstructed. Again, a little bit of inclination will go a long way.
The rings also won't make it much harder to get out to those orbits. You get into an elliptical orbit around the planet that takes your apoapsis (far point) out past the rings, then at your apoapsis you accelerate into a circular orbit.
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As has been pointed out by other answers, there are few satellites in the 12,000 to 17,000 km orbit. Most are communications satellites or Earth observation in a much higher geosynchronous orbit at 35,780 or in a much lower, and cheaper, orbit.
The closest to your ring would be various navigation satellites in a band ranging 19,000 to 23,500 km. [Galileo](https://en.wikipedia.org/wiki/Galileo_(satellite_navigation)) (EU), [GPS](https://en.wikipedia.org/wiki/Global_Positioning_System) (US), [BeiDou-2](https://en.wikipedia.org/wiki/BeiDou_Navigation_Satellite_System#Global_system) (China), and [Glonass](https://en.wikipedia.org/wiki/GLONASS) (Russia) are all in that band. It provides a roughly half [sidereal day](https://en.wikipedia.org/wiki/Sidereal_time) orbit so [each satellite is over generally the same locations every day](https://en.wikipedia.org/wiki/Global_Positioning_System#Space_segment). However, none are equatorial. Instead they're all inclined at 55 or 65 degrees to ensure every point on Earth can always see multiple satellites.
[](https://i.stack.imgur.com/UtoL4.jpg)
There's a handful of satellites which are in highly elliptical which may cross the ring. One is the [Chandra X-Ray Observatory](https://en.wikipedia.org/wiki/Chandra_X-ray_Observatory) which spends most of its orbit above the [Earth's radiation belts](https://en.wikipedia.org/wiki/Van_Allen_radiation_belt).
There's two fantastic sources to reference:
* [Union of Concerned Scientists Database of Operational Satellites](http://www.ucsusa.org/nuclear-weapons/space-weapons/satellite-database#.VF_jIlPF8Wg)
* [An Interactive Graphic of Every Active Satellite](http://qz.com/296941/interactive-graphic-every-active-satellite-orbiting-earth/)
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Depending on what the rings are made of, it may be cheaper to bounce waves off of them instead of launching satellites. Metal may be ideal.
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Wireless communication does not need equatorial orbits, unless you restrict yourself to geosynchronous satellites. Wireless phones in general don't actually need satellites, since the transmission/reception for the vast bulk of wireless phones take place at cell towers. Anything which connects the towers together (satellite, copper cables or optical fiber) can do the rest of the connection.
Other than military comm satellites, the only commercial satellite phone system I know of is the [Iridium system](https://en.wikipedia.org/wiki/Iridium_satellite_constellation) The Iridium satellite phones use LEO at about 485 miles, and would fit under your rings very nicely.
You seem to have confused geosynch satellites with wireless communication.
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I’m beginning to build a world for a story I want to write. The world consists of a planet, roughly earthsized, with a couple of natural satellites (moons), and roughly same orbit and a similar star. The difference is, if you travelled in the east-west axis you could advance infinitely without ever reaching the same point. You could tell that you’ve completed a “lap” by watching at the stars. But if you went to the poles you would find… A bizarre nexus that I’m yet struggling to find a good description for. Thing is, you could travel several “laps” in a single day if you are near the poles, or could take you more than one lifetime to do it on the equator, depending on your technologic level, access to vehicles and geography.
This “overlapping” where infinite places occupy the same space is limited to the planet. In fact, every “lap” receives light from the same sun and sees the same moons and stars.
As you can see I have the concept pretty much tied up, but I struggle with several caveats. I am aware that there is not a definitive “correct” answer as this is just outside the realms of real physics, but I guess we can find a workable solution.
## A) How would this be perceived from space?
I have a civilization that uses the moons as “repeaters” to send back radio waves and communicate with people on all laps… And a single Sun is lighting every lap… So waves coming from outside might affect all laps simultaneously… maybe? While this “lap” propagation does not occur if the wave is originated inside the atmosphere… maybe? Just making wild guesses here.
That makes me very confused, as from the space you might get an infinite amount of reflected light from the Sun… But we don’t want to blind and fry everything around our planet, so maybe I should go for another explanation here…
## B) How does one ENTER into the planet’s atmosphere, and where exactly?
My guess right now is that solid matter can’t enter into the planet as it would be dispersed at an infinite number of laps, thus getting fractioned in infinitely small infinite fragments. So, magic aside, space travel would be out of the question (you can’t get back…). But maybe there is another concept that works better here…
## Added info:
There is magic in the world, but the kind of magic accessible to sentient beings is not “world changing” or vastly defies physics. It’s mostly things that affect their own bodies, so no pocket dimensions, teleportations or things like that.
The world is infinite, but I’m not giving it infinite options. The planet will be earthlike almost always. Maybe there are some areas inhabited by different kind of organisms, or an especially volcano-ey and the atmosphere is full of other particles, etc… But I’m not going to have areas where everything is made out of new “elements”, or the earth is made of chocolate, oceans are made of flubber and deserts are made of cinnamon…
This also extends to civilizations. As per the story I want to tell, there is one civilization capable of “getting into space”, but it’s more of a steampunk kind of technology level than ours… We are going to assume that steampunk civilization is simply the most technologically advanced in the world, that they are the first ones to get to that level and the world (which has been crafted by another party) is too young to have reached any more than that.
The reason for this is, if I let there be more people that can throw junk into space, then in infinite possibilities there would be an infinite number of civilizations that can do it, and then space (that is out of the infinite physics-breaking world) would be full of infinite junk. Also, in some of those infinite civilizations there might be infinite maniacs crazy and powerful enough to destroy the planet…
You see? Infinite gives me headaches. But I have to keep it infinite for the story to work. And no, so big that seems infinite to us doesn’t work either.
I’ve been talking of “laps” but to clarify… There is not a “breaking point” of what is considered one lap or the next one, there is not a magic “line” following any meridian, so every person or group defines the start and the end of a lap from their point of origin (I guess)
There are similar questions about infinite worlds in this SE (likte [this one](https://worldbuilding.stackexchange.com/questions/27396/which-shape-for-an-infinite-world-with-usual-sun-cycles), where one of the answers suggests a world exactly like the one I'm planning), but I think my question has not been answered before. If it has been, please notify, and know that I am sorry for not having been able to find it before making my question. Also, I didn't know wich tags would work better for this... If you have any suggestion in that regard, please comment :)
If you need any more info or clarification, just ask me in the comments and I will try to fill the gaps.
Thank you.
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Several simple solutions to your singularity:
1. There's some kind of force that pushes things away from it. The closer you get, the harder it is to advance further, requiring infinite (and therefore unachievable) force to hit the center.
2. There's time dilation near the singularity, black hole style. You can walk in, but it takes infinite time (relative to the rest of the world) to get there, so nobody's ever done it.
3. There's a black-hole style vortex at the singularity. Anything near the vortex gets disintegrated and either feeds whatever energy source warps space near the planet or gets ejected into space like [relativistic jets](https://en.wikipedia.org/wiki/Astrophysical_jet), preventing people from trying to come in from above/below the poles.
In all cases, the basic answer is "we have no idea what's at the singularity", with a simple explanation of why we have no idea. It also puts a maximum limit on how fast you can traverse laps. The vortex and repulsion force ideas limit speed based on how close you can get and survive. With the time dilation idea, geometry speeds your laps per day as you get close to the pole, while time dilation slows it, and there's some point where those effects combine give you maximum speed.
* A. How is it perceived from space? Well, that depends. If every lap emanates stuff like normal Earth, then it would be perceived as an infinitely bright, infinitely dense region. Of course, infinite density means your entire world is essentially trapped inside a black hole, so it looks like a black hole to everyone else.
Alternately, there could be some kind of selective process by which stuff emanates. Anything trying to escape gets dispersed and only an infinitesimal amount makes it through per lap (as above, perhaps the rest is used as fuel for the warping), with a finite total radiance. From space, it would therefore look like pure static (any one point on the globe has light coming from every lap). Because there are infinite laps, the infinite static would average to a constant color (though perhaps the poles, with lower populations, would tend to be darker).
* B. How does one enter the atmosphere? If it's a black hole, you don't enter it; you just get sucked in and ripped apart. Because of time dilation in the black hole, your planet sees a finite time pass for an infinite amount of external time. All the light in the universe therefore converges onto the planet. If there's infinite light, the sky is just a constant, solid color. If not, the sky is just black. If the exterior universe has a finite or non-looping lifespan, the sky is just black.
If the escaping stuff gets dispersed, then perhaps incoming stuff does too. Except then the planet would never get sunlight (the light would be distributed evenly, and each lap would get an infinitesimal amount of light).
So maybe everything entering the atmosphere gets duplicated across every lap. This allows starlight and sunlight (and radio transmissions from the moon) to look the same from any given lap. It also means entering the atmosphere (or wherever the division between normal space and infinite space is) duplicates you infinitely. And further means you can never escape, unless you somehow synchronize all infinity of your copies to move out at the exact same time in the exact same way.
* C. Additional comments. I can't think of any reasonable way to connect an infinite space to a finite space without either destroying everything that tries to escape or infinitely saturating the finite space surrounding the infinite world.
Also, an infinite world means infinite races have developed an infinite variety of technology, and there would be infinite civilizations capable of space travel (if such a thing were possible at all), as you suggest. But there's really no way to be right at the cusp where the very first civilization travels to space, because in the very next moment of time, infinitely more follow.
The only thing I can sort of think of is if there are an infinite number of finite spaces outside the planet, and entering/leaving the planet basically puts you at a random lap/space relative to where you started. If it were truly random, things would be very chaotic.
But maybe it's a [normal distribution](https://en.wikipedia.org/wiki/Normal_distribution), so you generally end up finitely close to where you started. People leaving the planet would tend to be separated, though a few might end up in the same space. Perhaps enclosed objects, like spaceships, end up in one space (otherwise people would get separated on a molecule-by-molecule basis and die pretty quickly).
Then when you re-enter the planetspace, you end up within a few laps of where you started. Mostly. By re-entering near the poles, you could quickly determine which lap you were on because there would be labeled (probably numbered) signs along the way. If you're from lap 30, and you land on lap 68, you know to head west (or east, depending on convention) 38 laps, then fly south (or north, depending on which pole you entered) to get home.
Note that the sky would be very fuzzy, since you'd see light from a number of nearby spaces quite readily. Depending on the standard deviation of the normal curve, you might see one sky mainly, with others being almost invisible, or you might see dozens of skies at once.
This would allow space travel, and solve the problem of infinite space-faring races (there would be an infinite number, but they would practically never converge to the same space or lap). But it requires infinite spaces which isn't what the question asks.
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To simplify things I will remove one dimension from my explanation. Imagine a 2-dimensional universe: it's just an horizontal plane, with planets as circles. YOUR planet is actually a sphere, with its centre lying in the plane of the universe.
To build the planet imagine to take a wire. You start from the north pole, make a first loop and then you start a second loop to the right of the first one. Once you reach the south pole you cross the first loop, thus when you reach the north pole again you are on the left of the first loop. There you go on the right again, and again on the south pole you go on the left. The crossing does not overlap the existing loop, but compenetrates it. You will eventually close the sphere, but since each loop has 0 width it will require an infinite number of loops to do that.
From outside you can only see the intersection between the sphere and the universe: it's a circle, thus a perfectly legal planet, but it's made of 1 point for each half-loop. From the planet the sky you can see is just a line (the intersection between your loop's plane and the universe), but the closer you are to the pole the less you can see: at the poles you cannot see the sky at all. Only from where your loop intersects the universe you can leave your planet, 'cause from everywhere else you would go outside of the universe.
If you apply a similar concept to a 4-sphere planet in a 3D universe you can get something similar to what you want, although I think that the equator is the intersection between a loop and the universe, and you should walk through the pole to advance... But my knowledge of geometry is limited to 3D Euclidean spaces, I must leave to you how to figure out the mathematical details!
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Set in the 22nd century CE, space explorations reached maturity and the farthest human colony is on one of the moon of Neptune. So far the only voice from space that we have heard comes is our own, meaning the search for extraterrestrial intelligent life continues. Every nation still don't trust each other and race to occupy as many territories of space within the solar system as possible, current trend in designing spacecraft is to have a self destruct mechanism built in. Is there any political reason for every spacecraft manufacturers to install such a dangerous protocol or device on their products?
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Spaceships would be very valuable in the empty expanse of space. They likely wouldn't just be instruments of war, they would also be one of the primary resources that parties would be willing to fight over. By adopting a doctrine of self-destruction you can discourage enemy parties from trying to usurp control of your ships. This could be instrumental in discouraging aggression from piratical frontier groups.
Now perhaps your enemies are content with just blowing your ships up anyway; why bother with a kill switch? Well, space travel is a seriously complex problem and the solutions to that problem would be valuable intellectual property. Having a self-destruct option would prevent your technology from being studied by your enemies.
Finally, you can force the crew's obedience to their faction who holds the self-destruct codes. It would probably be prohibitively expensive and take too long to send a another ship to intercept and reign in deserters.
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Unless the nature of politics has changed drastically, in the 22nd terrorism is still a problem, and a hijacked interplanetary spaceship would be an extremely effective weapon for such purposes.
A self-destruct mechanism would make sense as a last resort to prevent a 9/11 on a grand scale.
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We have Earth. Modern Earth. Some moron with more brains than common sense designs a cordyceps strain to infect people via bites. Now we have zombies. The virus spreads across the world and in a time frame of about 6 months 75% of the global population is dead with 10% still infected, 14% healthy but still susceptible to infection, and the other 1% immune (or rather, their immune systems are still susceptible, but they have a good chance of at least 70% to fight the infection off).
The situation stabilizes here. The infected die after a month or two and the fungus continues to grow in them. Every fall and spring, the fungus releases millions of spores into the air to find new victims. The surviving population finds itself in a bad situation. The spores are not 100% virulent meaning if you inhale one! you don't definitively catch it, but about one in every thirty people will catch it.
**Assuming the survivors find a general way to stay away from the infected outside, how would society evolve as reconstruction begins with the threat of anyone you know waking up one morning a zombie within your walls?**
A few notes:
* The zombies are living people and as such anything physically possible for a person is possible for a zombie. The zombies are, however not too bright, so they probably cannot figure out how to open a door. The fungus is resistant to all known fungicides/antibiotics/whatever.
* We are talking about US society (I recognize there are slight regional differences, but it should be answerable. While I welcome commentary on how the rest of the world would respond, explicitly requiring it would make this question too broad.
* The infection remains passive (think small fever or 99/100 degrees)for 2 or 3 days, and takes over the victim shortly (30 minutes to a hour) upon becoming active.
* Spores can survive for 5 or six years outside of a host, and sometimes takes root in animals similar to humans, such as pigs and monkeys/apes.
This is not a question about the whether my scenario (and therefore type of disease) is realistic and as such I will vigorously down vote any answers that are based solely on the unreality of my scenario.
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I suppose that depends on how predictable the timetable is for when the spores are released. Is it something that can be plotted out, like the moon cycle, or even the fall foliage turning colors (which is pretty damn'd accurate, all things considered). And if you say that it's impossible for them to learn the schedule, then I say this: We, as a species, have learned the cycle of when leaves will be at their peak color, and that's not life threatening. If our survival depends on the fact that you wake up knowing that your neighbor, or wife, or child will not be a zombie, then you figure out pretty quick how to map out the fungus.
What you should consider: How easy is it for the spores to get into a "generally" closed building. For instance, do you have to be sleeping in a hermetically sealed room or is it safe enough to simply have windows closed? If no one is safe, regardless, then the only scenario I see as possible is this: They would need to set up a system where everyone sleeps in separate living quarters and is locked in from the inside, with their keys in their room. As zombies (unless you explicitly define them as tactile/intelligent zombies), they won't be able to unlock their own doors, so a quick headcount would quickly reveal the isolated zombie. Is this how our society is set up now? No, not really, unless you count prisons, but the society would have to adapt to be something like this, unless they want to gamble with losing their entire settlement each time the spores are released.
edit: You mentioned that spores can survive 5-6 years outside of a host. This can become an issue. Seeing that spores are re-released twice a year, if they don't degrade then you will end up with spores sitting on top of spores. Imagine if snow didn't melt for five/six years after it fell. You'd have five years worth of snow on top of snow before anything melted. Unless there really isn't a large amount of spore, or it is only released in small amounts, you'll end up with an ecosystem that is too laden with the spore to support any healthy animal population. I think you should rethink how long you want to spores to survive. Perhaps a month outside of a host/their plant so that there's two periods of time during the year where going "outside" is more dangerous than naught.
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[HEPA](https://en.wikipedia.org/wiki/HEPA) style masks. Worn all the time except when eating or changing out to a new one.
Unless the buildings are hermetically sealed it won't prevent the spores from entering, only slow them down. If there are specific times of the year where the spores are much thicker, then the masks AND staying indoors would be a good practice for those times.
I also agree, that burning corpses of zombies would also help reduce the risk of infection. Knowing the life cycle of the fungus is the best way to combat it. Disrupting the cycle as much as possible will slow down the spread as much as possible.
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**Understanding the Risks and Hardships**
It could be a period of a couple months that the spores are actively airborne - it doesn't really say how long in the spring and fall, but I'm guessing it wouldn't just be a day or so. Probably looking around a couple weeks to a month's timeframe in each season?
As part of the Midwest U.S. history, when people couldn't just go to the store, food was generally stored for the winter for when things were sparse. They still struggled at times. You're looking at adding two more months of time where people are unable to do things like plant crops, hunt for food, or construct additional buildings, outdoor tools, or gather resources. Considering Spring and Fall are very busy farming seasons this is going to put a severe strain on things regarding food.
This is more manageable if the location doesn't have to deal with winters, but those regions are going to have to deal with the wild hog populations - which can also turn into zombies and potentially keep active airborne spores going for a long period of time. This means our survivors will have an easier time starting out, but they'll have to either start eliminating the pig populations or continue spore-prevention strategies for generations to come.
However, it gets much worse since the spores can remain dormant. That would mean pretty much all your supplies and food would have to come from an isolated environment to completely eliminate the risk, with the same amount of protection that the people take during heavy spore activity.
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**Reduce the Risks**
Until such a time when we can get a fully isolated and self-sustaining community, they'd have to just try reducing the risks as much as possible. There would have to be some kind of decontamination method every time people came back in, especially with certain kinds of supplies.
Reducing the amount of spores in the immediate area would be possible by burning everything in a radius around the community, but won't eliminate everything. Such things are easy to get out-of-hand though and require resources to start and control the fire.
They would have to try and reduce the risk of inhalation, with masks and running air filters if possible *(though careful on changing the filter*). The more barriers there are to catch potential spores, the better.
It would be ideal if anybody with a fever for more than a day would become isolated. If it's possible to take a temperature every morning and every night, they should do that and then isolate anyone with 2 consecutive fever measurings. (measuring because, depending on how slight of a fever - it might not be visible). If they do turn into a zombie, burning would be best.
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**Overall Result**
We're looking at maybe eight to ten years of struggling for survival in the central and northern U.S, while the south will continue being a danger zone for the foreseeable future due to the wild hogs. The first year or so will wipe out the majority of people. The next 2 years will wipe out those who don't take all the proper precautions, or those who live in areas where it hadn't yet been able to spread. After the first 3 years, most people who are going to become infected have done so. Airborne spores are now highly unlikely because there are few hosts being infected, and those who are infected should be in a safe community that has figured out how to "take care of" them in the proper manner. Add in 5 to 6 years for the spores to become inactive, and then society can slowly start to rebuild normally, though fear is likely going to make some precautions a permanent piece of society for quite a while - especially since the fungus probably won't *completely* die out for a very long time.
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People should use gas masks 90% of time, have hermetical places to eat/sleep, and take care of animals.
# Gas masks
Providing gas masks for everyone shouldn't be *that* much of a problem. People would need to wear them anytime they're not sleeping/eating (even then, one could wear them while sleeping but it would cause discomfort).
# Hermetical shelters
Isolating every single home would cause a lot of trouble and would be expensive. I think that building big shelters where people could stay to eat/sleep would be the best option. It could also be used in case there's a zombie outbreak, but people wouldn't be obliged to stay in the shelter as long as there's no "alert". Shelters should be relatively small, maybe 1/20th of your population persons per shelter. That way, if a shelter is ever compromised, you "only" loose 1/20th of your population. This technique is used in giant web server farms, where computers are stored in containers. If a container burns, for example, you don't loose everything.
This part deals with the transmission via the fungus, but it still doesn't settle many other problems.
What if someone's gas mask breaks or if there's a breach in a shelter.
# If a shelter is compromised
It should be locked down. Tactical teams would be sent inside to kill the new zombies, and these zombies should be immediately burned or isolated using something that completely blocks air (Some kind of foam that hardens at the contact of air could do it pretty well and avoid the burning which stinks/is more dangerous). People would need to follow emergency procedures, which would imply to be checked one by one before they can get out of the shelter (where they'd be dispatched to another shelter until this one is "clear").
# If a gas mask breaks
Simple, kill the Batman person and burn him/her right away. (Again, maybe the foam would be better)
# Vegetation/Animals
Now, if the fungus can stay on vegetation, you need to make sure your food sources aren't compromised. Which means either **A** : Find trees that aren't infected, and transplant them in a greenhouse; **B** gather seeds that aren't infected, plant them, and burn everything once again.
For animals, the same protocol as plants would apply. Everyone could turn vegan, and wild animals would be considered extra-dangerous when seen in cities (Should be killed on spot). If the virus can spread to more animals, it would be safe to try to build a shelter for non-infected animals to keep them alive (not for food) to keep the species living. One male/one female of each species (kind of Noah's arch) would do it, and it'd be hell-of-a zoo to visit! In that case, people really should turn vegan, considering the small amount of animals that would survive, eating them would bring them to extinction pretty quickly.
# Defense
Now, to defend against existing zombies, you would need simple walls. I assume there wouldn't be **that** much zombies if everyone follows the protocols clearly, so that aspect might not be that important. Burning everything around cities would prevent fungus from being too close, and if it's possible, air sensors could be placed so we'd know when the fungus would be close.
# The dome!
If that's an option, you could build a dome over big cities to keep everything clear, air from the outside would be filtered before entering the dome.
# Small extra
Using giant fans around cities would be a "low cost" option to slow down the fungus spreading.
Also, once in awhile, planes like the one used to fight forest-fire could be used to drop acid/foam/napalm (though napalm wouldn't be good for air quality on the long scale) on the dead people's hot spot to slow the fungus from "vaporizing".
# Overall
The most important change would be a strict control of the air quality. Shelters should be 100% safe at all time, which would include maintenance. Apart from that, people living with gas masks could do everything we normally do at the moment, even navigate from city to city, but people would need to be inspected on arrival to make sure they're fungus-free. Using this control, at some point the fungus would be eradicated and everything would get back to normal.
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In [Humanity gets one wish](https://worldbuilding.stackexchange.com/questions/25388/humanity-gets-one-wish), I asked how the world would react to a god-like being offering to give humanity a wish. From the responses that question got, I seem to have misjudged how much chaos and panic it would cause. There were also concerns about needing to do "rules lawyering".
I've also done some further development on the god-like being's motivation since then. Basically, he wants to help humanity to reach a utopian Galactic civilization. There are many paths that can lead to that, but also many paths that will lead to humanity self-destructing and wiping itself out. He wants to put humanity onto one of the successful paths, but it doesn't really matter which as they are roughly equivalent. He could just pick one, but he highly values free will. As such, he wants humanity to come up with a wish, and he will put humanity on whichever path to success most closely matches that wish.
**What would be the best way to offer humanity a wish?** To be specific:
1. There should not be widespread chaos or panic. It should be clear that this is a altruistic gift to humanity and that the result will be something that we like. It's okay if a small percentage of people panic (less that 0.1%, perhaps?), as long as it's not enough to cause riots.
2. Most people should not worry about "being careful what you wish for". They should understand that no matter what they wish for it won't go badly for (most of) them - even a wish of "we wish to be destroyed" would go well for them (perhaps the removal of the biggest annoyance(s) causing them to want to be destroyed).
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**Use Aliens**
I know it sounds crazy. But think about this: there really is not going to be an effective way to avoid any panic with a wish of this nature. Additionally, for all of humanity to decide on a single wish with anything more than 51% support is unlikely, and quite possibly not even what you want (given educational disparities and other issues). Instead of presenting humanity with evidence of the divine, do something that will not only have some basis in human reality, but also encourage your goal of galactic civilization:
*Fabricate an alien ship and drop it into Earth orbit.*
Through these aliens, you offer and grant your wish. The aliens, who are clearly very technologically advanced, offer humanity a single gift of technological knowledge to help them survive and advance as a species. While there will be some chaos in the wake of discovering extraterrestrial intelligent beings, their peaceful overture and eventual offering of a grand gift to humanity should ease some of the potential panic.
You won’t automatically get consensus here, but when faced with such a situation there would need to be serious international cooperation, the basis of which is already largely defined in existing governmental protocols for handling first contact. There will also be widespread concern and paranoia about the real intentions of the aliens. This will lead to enormous long-term scrutiny of whatever “technology” is granted to humanity. While this won’t placate everyone’s paranoia, it should create a foundation for reassurance and hope.
Here is the best part: by revealing other intelligent, space-faring life to humanity you have now created an enormous goal for our species: to join the other advanced civilizations in the stars. The aliens you create don’t even need to be a real species — humanity will go forth to the stars in search of them anyway. What else they find out there is up to you.
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Open a massive virtual reality theme park. Inside, invite guests to interact with a virtual god like being who offers them one wish and then shows them how that wish would affect all of humanity. After a few years in operation, have the theme park franchise out to every country on the planet and lower its rates so that everyone can try it out.
After a few more years, once humanity has gotten used to this experience, hold a contest. Using a single elimination format and a syndicated TV show like Star Search, backed by a free telephone-based voting system. Whittle down the billions of initial players to a single planet wide champion based on popular vote.
Then fulfill that champion's wish.
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Three goals
**Establish understanding**
that that being has humanity's best interests at heart
has the power and knowledge to know if a wish is good and fulfill it
**Limit panic**
**Get a response**
The first is by far the hardest, we have trouble trusting other humans let alone something so beyond us. The being could act as a human to try and demonstrate trustworthiness, this comes up in Agent to the Stars by John Scalzi. Acting as human allows humanity to get to know and adjust gradually to the new person. The being could ask people for the wishes simply as a good and wise human and never reveal its existence but it would seem that few people would understand the implications offered by the wish, thinking is was from a human, and free will based on misleading information is not really free will.
So the being must reveal its existence slowly to the world and demonstrate power and that it is own our side.
While this might start a bit of a dispute but some of the most famous books in history describe God trying to speak to man, and I acknowledge here my knowledge base and biases will show. The being could pick an individual person to speak to directly and carry the message to others. The being could do good and miraculous this for the messenger and through the messenger to prove itself, think of Abraham and the gift of Issac. Or become part human part God, and sacrifice greatly on our behalf, "But God demonstrates his own love for us in this: While we were still sinners, Christ died for us."
**One choice vs many choices**
There is a bit of a difference, between this case and the examples in the holy books of the world. In most religions God doesn't ask for humanity to make 1 all encompassing wish that he interprets once to drive our future forever. In most religions it is an aggregate of many choices with many corrections by God over time. The single wish version makes you doubt the being's value of free will, as humans we have trouble understanding and deciding how we live today, we would be so poorly informed about billions the possible futures and possible choices our choice would be basically random.
I would recommend many pieces of advice, smaller wishes or corrections not one sudden wish, people change there minds, just in case 350 years down the road humanity has a different vision of Utopian Galactic civilization
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## Don't tell them that's what you're doing
I know Mr. Deity values free will, but one of the best ways to ensure a free choice is to appear to remove all consequence. It's *easy* to make a clear choice based on your ideals if you don't think you're going to have to live with the consequences.
As an omnipotent and super-wise god-like being, I assume Mr. Deity has the ability to run around 4.5 billion simulations at the same time, so it should visit us all in our dreams.
Dreams are pretty crazy, and we're conditioned to accept all kinds of weirdness in a dream state. Mr. Deity therefore goes to each of us in an apparent dream, and presents us with our choices. At this stage, he can beam any knowledge we need to make an informed judgement directly into our minds, and we'll accept it - we all know those crazy dreams where you know things you can't possibly know, after all - and let us run through scenarios representing our options.
He does this several times, until he reaches a consensus with as few outliers as possible, and then grants us that consensus.
If he wants to be blatant, then everyone on earth will be given the same dream on the same night. If he wants to be subtle, he'll pick out a few million each night to have the dream. If he wants to be *really* subtle, he can also ensure that we remain asleep after the dream has ended, so that we won't even remember the dream.
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> What would be the best way to offer humanity a wish?
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# Not to *offer* it at all.
I mean, this is a divine being (otherwise, there's very little chance of it actually being able to deliver). Therefore it will have lots of ways of gathering wishes from people: from simple telepathy to involving them in complex virtual simulations and wiping all memory of it from their minds afterwards, to simply omnisciently *knowing*.
Once it has sufficient information, it can simply *act*.
...unless the point is not granting a wish at all, but rather having people *decide*.
(There is this novel from the Strugatski brothers, not uncoincidentally called [*Hard to be a God*](https://en.wikipedia.org/wiki/Hard_to_Be_a_God), where the main character - an Earth operative on a backward world - asks one of the natives this very question - *what advice would you give the Almighty?*).
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**Telepathy**
Basically, the Alien beams the knowledge of what will happen if they choose any wish into people's heads or makes it so that if someone thinks of any particular wish the knowledge of what its outcome will be, will immediately pop into their heads. He could show that this information is accurate by allowing individuals to make smaller wishes before making the main wish and seeing that the outcomes of their small wishes were, as they predicted, with either no surprises or no surprises that would make them regret the wish.
Next, he could make it so that every human brain is in sync in such a way that each individual can make any decision that he/she wants with regard to what the wish will be, but it is either impossible for any two individuals to make a different decision on the wish or it is extremely unlikely that two individuals would make a different decision on the wish. This would make it so that humanity has free will with regard to the wish but there is no argument over who gets to decide what the wish will be because the wish that everyone decides on is the same.
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I'm designing a Fantasy AGE campaign and there is one place in the desert between two big kingdoms. There is a way through the desert passing though several cities. They are mostly small and serve as trading outposts, but I want them to be bigger than that: to have tunnels ways through the sand and bigger cities under the sand itself, where most people can't get.
How deep should they be, what problems can characters meet because of the tunnels and undersand cities (like big hollows under the sand? I don't know, that's why I'm posting this), can that actually exist, or should I just say "FRIKKEN MAGIC!" and don't even bother?
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If I'm picturing what you want correctly, here's what I would recommend. The source for the underground bit is from when I was an urban planner in the middle east.
**Distance**
Your settlements should be no further than a two or three days trek by camel/caravan. While you can go further, some of your perishables (dates, fish from the sea, camels milk) should be kept in a cool place, and by day, the further from the sea or your two mega-cities will get very hot even in the winter. You ideally want respite and water for camels as well after a couple days. Wayfinding for settlements much further apart gets difficult, if you're off by even 1°.
**Depth**
Water and sandstone can be found [in just 3m depth](https://en.wikipedia.org/wiki/Rub%27_al_Khali#/media/File:Water_in_shaybah.JPG) in the Rub Al Khali. Sandstone is marvelously pliable ([see this question](https://worldbuilding.stackexchange.com/questions/14435/a-city-of-sand-stone)). There are also many instances of troglodytes in desert areas, particularly the many in southern Tunisia and North Africa. For instance, [Matmata](http://www.greenprophet.com/wp-content/uploads/2013/01/matmata-caves-tunisia.jpg) has just a few entrances, but holds a whole warren of tunnels and dwelling units.
**Size**
Your size of underground caves is up to you. However, keep in mind that you need access for materials in and out, including waste. The [old oasis of Tozeur](http://www.globalwanderings.co.uk/countries/tunisia/tozeur/tamerza.jpg) was about 700m x 700m, but you want yours to be underground of course. This is because the 5min walking distance from the central mosque is considered about 350m radius in planning terms. Presumably your central entry/exit could be the same - give your underground dwellers a 5min walking distance from the entry/exit.
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**This can happen.** Because it *has* happened, thousands of years ago.
Take a look at the [Derinkuyu underground city](http://sometimes-interesting.com/2014/05/09/derinkuyu-the-underground-cities-of-cappadocia/) and its brethren. Room for 20,000 people, five levels, kilometer-long tunnels, &c. (Not much of a view, though.)
Here's a schematic from the linked article. (Note that the town above has grown up above the original cave systems.)
[](https://i.stack.imgur.com/wuhqD.jpg)
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**Problems to overcome**
1. The first problem I find when building large cities in the middle of a desert is water. If you want a lot of people, then you need a lot of water. Actually, the most important cities, regardless of climate or ecology, were almost always built near a ready source of water; but to drive that point home, you can take a look at a [map of ancient Egypt](https://en.wikipedia.org/wiki/File:Ancient_Egypt_map-en.svg).
At some point, your city cannot grow past its usage of available water. So if you want large, sprawling cities, you need a lot of water, and if you have a lot of water, then you don't *really* have a desert.
So, let's say there are giant underground water reserves. That obviates the need for surface water, but we still have to get to it. Which leads me to...
2. The second problem you'd have to overcome if you want your undersand cities is actually just digging in the sand. Take a shovel to the middle of a sandy dune and start digging...what happens? The scoop of sand you just dug out just fills back in with more sand. Of course, at some point, you'd hit bedrock, but not after a feat of civil engineering. So, you have to keep your workers alive for the time that they are working in the sand. In a hot, dry desert. The outcome of this project had better justify the crazy expenses that you are incurring. Your best bet is if the desert already has rocky hills/outcroppings...then you can tunnel in that way.
3. Other than that, you have some just general considerations to think of if you want to build underground cities. How are you going to get air? Light? Food? All of these things are harder to get underground, which is why most cities are built above ground. Typically, humans tend to fill their needs by using the path of least resistance. Underground cities present a *lot* of resistance, so there had better be a big payoff to living underground. Living in the desert also provides a lot of resistance, which is why you don't see a lot of classical cities that sprang up in the middle of a desert.
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Suppose humanity lives on for the next trillions upon trillions of years. One day we'll get to a point where no useful work can be done and hence no life can exist: the heat death of the universe.
But somewhere along the way we invent time travel and are able to travel back in time. Is it theoretically possible for humanity to survive by traveling back in time every time we get close to the heat death of the universe assuming we "escape" in time? If so, how will that work out? Could it be done indefinitely?
I might have misunderstood Worldbuilding. Let's say it's theoretically possible, and humans do end up going back in time indefinitely. How would that pan out?
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No. It is not possible according to the laws of physics.
Instead of "is this possible", perhaps you should ask how to design a fictional universe in which such a plot is possible and (presumably, or you wouldn't bother to ask) acceptable to knowledgeable "hard" SF readers.
One common time travel moodel used in literature is where time travel leads to a different clonee universe whose future is causally disconnected from the original.
An interesting story would be for the race to misinterpret which kind of time travel model their universe admits, and end up going back in a fixed-history block universe, not a mutable copy.
However, such an advanced elder race would not be "like us", so it would be difficult to make a story approchable without meeting up with "us" to tellmthe story from our point of view.
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I would say if such a thing were possible then the universe at this time would be filled with life. If even one race made it to the end and came back and kept repeating that, after a 100 times there would be at least 100 different races (assuming only one race became that intelligent to begin with). Over a trillion years, humans would likely be a hundred different races, and each one that came back would also turn into hundreds (thousands? millions? billions?) more each one spreading out into the galaxy. It would be teaming with life.
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If this was possible you would face another problem. In theory you could do this an infinite number of times but then the entire universe would be crowded with humans.
Each time they go back in time, the previous iterations of humans having done the same thing would also be there.
They cannot fight, because killing a previous copy of yourself would also kill you.
So they have to coexist peacefully but at some point there would just not be enough resources for the newcomers.
So it's a loose loose situation.
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The only way this would work is if the time travel is such that what they do when they go back already happened; it isn't sustainable if the time travelers can change history.
Humanity at the end of the universe is theoretically a very large population, saturating the available space on inhabitable planets in the universe. Even if they could send themselves back to all the other planets besides earth (and assuming they were originally uninhabited), this would only work once. When you get to the end of time the second round, there's nowhere to go.
If the group becomes extinct before humanity emerges as a species, it works. If they integrate themselves into their own history (as in [this Star Trek episode](http://en.memory-alpha.wikia.com/wiki/All_Our_Yesterdays_(episode))), it works. But either way, it only works once.
If you are dead set on making it possible, then humanity must have the capability to create a brand new universe each time they hit the reset button. If they don't, even if they can create new planets out of thin air and limit the number that goes back each time, they will eventually run out of room. Space is immensely vast, but ultimately finite. But at this point, time travel is arbitrary in making things work. They don't need to travel back in time unless they arbitrarily want all the universes running in sync together. And if they can create new universes to live in, they will do it well before the one they're living in runs out.
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As some other answers point out, the most interesting part of the question is how you handle (avoiding) meeting with current time civilizations and overpopulating because of infinite iterations.
Civilizations from an ending universe would look really different from their own specie millennia ago and wouldn't be able to integrate into their society. Also, the limited resources would mean a smaller community.
As an elder civilization that has seen the end of the universe they would be likely fatalists and if found out may force their own destruction to avoid interfering in the regular timeline.
With this setup, I would consider them living in small worlds scattered in distant stars and purposely hiding by avoiding galactic groups or clusters using stellar engines to move their whole solar system. I am supposing that if they have time travel and stellar engines, they can move their whole planet/system and would be able to "steal" suns to replenish. Ideally, they should steal the suns close to a Black Hole to avoid affecting the timeline (as objects in a black hole lose their information according to current theories)
This would allow them to handle nearly infinite recursions, but at the same time, harnessing mass from black holes (or avoiding it to get sucked in) would slowly reduce the time to heat death, so in infinite iterations, they would "eventually" end up meeting their demise.
Also want to point out that it would be OK to meet with older or newer recursions that have crossed the heat death horizon as they would simply part ways knowing better not to interact.
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What if Germany had been first to create atomic bombs in WWII?
Assume they had additional scientists and resources so that none of their other research/projects was slowed down, yet they were still able to complete two functional atomic bombs (extremely similar to fatman and little boy).
Assume they would have completed the atomic bombs in the Autumn of 1944. This is so that D-Day has already happened, but Germany is still a long way from surrendering, and the USA is not close at all to completing its own weapons.
Questions to Answer:
* Where would Germany have used the bombs?
* How would this change the direction and outcome of the war?
* BONUS: Where should Germany have used the bombs, with hindsight and knowing what we know today?
[How close Germany actually was](http://www.pbs.org/wgbh/nova/military/nazis-and-the-bomb.html)
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If Germany had the Atomic bomb *and* some of the other advanced weaponry as you suggest, I think the Germans would have started by using a jet bomber to attack Moscow. The logistic would be difficult (and essentially a suicide mission), but the speed and surprise of such an attack would have decapitated much of the Soviet Union's command and control infrastructure, and even its logistical infrastructure (many of the rail lines deliberately passed through Moscow, a legacy of the Tsarist Empire and a means of control by being able to dispatch troops and supplies from the Imperial Capital), effectively stranding much of the Red Army and blunting their ability to continue offensive operations against the Nazis in Eastern Europe.
Attacking London would be much more problematic. While it would be easier to send a jet or even a conventional fast bomber, the Germans actually had a certain amount of "respect" for the British, and Nazi "mythology" was receptive to the idea of an Anglo-German partnership in the New Order. (Like a lot of other ideas floating around in the Nazi universe, this wasn't well defined or spelled out in a lot of detail). The Nazis also knew that "decapitating" the British Empire was not going to work at one stroke the way it might against Soviet Russia. Churchill himself spelled it out in a speech ("We will fight on the beaches"):
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> We shall defend our island whatever the cost may be; we shall fight on beaches, landing grounds, in fields, in streets and on the hills. We shall never surrender and even if, which I do not for the moment believe, this island or a large part of it were subjugated and starving, **then our empire beyond the seas, armed and guarded by the British Fleet, will carry on the struggle until in God's good time the New World with all its power and might, sets forth to the liberation and rescue of the Old**.
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Bombing the UK would bring about redoubled efforts from the nations of the Empire (Canada alone had more than a million men under arms by this point, and the world's 3rd largest navy, despite being a very thinly populated nation at the time), and even with the resources of all of continental Europe under the command of the Nazi empire, they still would have been badly outmatched by the resources of the British Empire alone, much less America and the rest of the Allies as well. This does not even take into account that most of the British Empire was well beyond the reach of any conceivable Nazi war machines being built or contemplated in 1944; how would the Germans be able to stop the raising of armies and industrial plants in Australia, India and South Africa, for example?
The other point that should be noted is there were lots of notional "allies" like Brazil and Mexico, which were supporting the Allies and nominally part of the alliance for diplomatic and economic reasons. The unleashing of atomic weapons on European targets by the Nazi regime might well have been a tipping point for some or all of these nations to change from notional to "real" allies. There would have been a lot of pressure from the senior partners like the Americans to contribute (having these nations as allies up to this point was more to keep them and their resources away from the Axis), and the example of nuclear attacks could also have convinced them that the Nazis were not just a theoretical evil or threat, but a clear and present danger. (Alternatively, this could also have been enough for many nations to renounce their membership in the Alliance and become Neutral, with lots of second and third order effects. One can Imagine the Americans invading and occupying nations which could provide a springboard for Nazi shipping and aircraft, for example).
This would be a fascinating contra factual to explore in more depth. We have not even looked at how Imperial Japan or Fascist Italy would have looked on Germany newly armed with atomic weapons, for example.
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Germany had already bombed civilians in London with traditional explosives (both in WWI and WWII), so it wouldn't seem unlikely that they would bomb civilian areas with a nuclear weapon. Likely many places in England and Russia where civilian populations were high. They may have also bombed the US to stop the war, but if my memory serves, they weren't exactly on the harshest of terms. Don't quote me on that.
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Britain and Russia easily would have sued for peace. The Japanese were unlikely to come out of war before the 2 nukes that were dropped, but they surrendered almost immediately afterwards.
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> knowing what we know today?
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Probably on military areas rather than civilian areas. While it would be no skin of a Nazi's back, the people living under Nazi rule may be angry after the war that their government killed thousands of innocent civilians. It would be hard to tell if there would be a revolt, a movement, or just some online comments on the nazi-web that criticize it, but there'd be something.
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# Where would Germany have used the bombs?
Eastern front. Nothing was more important for Germany than stopping Russia. They could negotiate with Americans (especially after demonstrating on Russians how powerful bombs they have), but they knew perfectly well that with USSR they are totally and utterly screwed.
Forget about big cities. Germans had little to no chance to deliver the bomb outside the territory they controlled. Luftwaffe had lost air superiority very long time ago, V1 and V2 rockets were not dependable enough for such precious payload, and transporting the bomb on the ground would bring the risk of delivering it to the hands of the allies.
The only safe way to use the bomb was to set up a trap and detonate it in the right moment. That however, would limit it's usefulness to only a couple dozen thousand of enemy soldiers (at best). And this leads us to the next question
# How would this change the direction and outcome of the war?
Everyone would start beating the crap out of Germany even harder. After D-DAY it became more of political rather than military matter who will get to Berlin first (watch the movie "Patton" to see how it went: <https://en.wikipedia.org/wiki/Patton_%28film%29>), and Americans were kinda pulling their punches to let the Soviets grab more glory (and more casualties, but as much as Americans wanted to limit their death toll to minimum, Russians didn't care). After atom bomb, everyone would be like "OMG WTF KILL IT WITH FIRE". No more politics, just pure genocide.
# BONUS: Where should Germany have used the bombs, with hindsight and knowing what we know today?
One on Wernher Von Braun <https://en.wikipedia.org/wiki/Wernher_von_Braun>, to make sure that Americans won't get his knowledge, and the other on Simon Wiesenthal <https://en.wikipedia.org/wiki/Simon_Wiesenthal> to make sure he won't hunt Nazis down after the war. It may seem like an overkill, but like I said - using them on the actual military target would rather piss the Allies off, rather than stop them.
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Eastern front. Hitler hated the Slavs, it was one of the reason that he lost (the people of the CCCP had seen him initially as a liberator from the communism, he could have made the worst anti-communist resistance fighters from them).
Although the Soviet government moved in the war from Moscow to east, the Germans knew, where is it.
It is possible, but not probable that he had killed large cities en masse. In the beginning, the nuclear bomb production was very small even in the U.S. The strategy of the US was its deterring force: they didn't said to the Japans, that they don't have more bomb and they would require at least months to produce yet another. Probably Hitler had followed the same tactits. The problem is that Stalin hadn't fear this, he had probably fought until the last shot.
Hitler knew it, and thus he had probably attack Stalins headquesters with his very first bomb, despite that it had been in a small city.
During the war, the Russian air force was nearly not-existing at the begin. Later it overwhelmed the German, the Luftwaffe.
After defeating the Soviets, the problems had been still strong on the West, but he could have focus their forces to the western front. The western powers are also sensitive against blood loss (for example: the U.S. had lost aorund 70000 soldiers in the Western front, the Soviets has lost 20million lives in the war).
Hitler probably didn't attack England, his country were too bored already at this point. But he could have reached a de facto peace with England. A peace treaty had been improbable, Churchill were very dedicated for that.
The newborn German Empire had had probably very much problem with resistance fights overall.
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We're a lovely, ethical, near-future population of Earthlings, and prepared to begin terraforming Mars (yes, I went there: set it aside).
We have just stumbled on remnants of an alien civilization that both dates to around the same time as [our Phoenicia](http://en.wikipedia.org/wiki/Phoenicia#High_point:_1200.E2.80.93800.C2.A0BC) in terms of relative technology and social norms, though a much earlier expiry. As an aside, my story asserts that they were human-like or typical movie alien trope, and Mars was once habitable. The level of historic preservation is [similar to what we can find on Earth](http://en.wikipedia.org/wiki/Tunisia#Antiquity).
These are a really nice find, but...
What are the best practices today that can be applied to the treatment of these artifacts?
**NOTE:** I am aware [from this Meta post](http://meta.worldbuilding.stackexchange.com/questions/2348/can-hard-science-apply-to-social-sciences-and-other-academic-fields) that this may or may not apply to [science-based](/questions/tagged/science-based "show questions tagged 'science-based'"), but cited sources or examples of acceptable best-practice (changed obviously to relate to the remains of an alien civilization) in archaeology, etc., and academic resources are appreciated.
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**Prevent contamination.**
[Contamination](http://en.wikipedia.org/wiki/Interplanetary_contamination) is something that NASA and other space agencies are careful about when sending rovers to other planets (e.g. Mars). Rovers could accidentally release bacteria from Earth, thereby making it harder to tell if organic material is from Mars or from Earth. Returning samples to Earth is also a problem, as there is an even greater risk there. [Ideas have been proposed to solve this problem](http://www.nap.edu/reports/13117/App%20G%2008_Mars-Sample-Return-Orbiter.pdf). However, [it would take a while to prepare](http://www.nap.edu/openbook.php?record_id=12576&page=59):
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> It has been estimated that the planning, design, site selection, environmental reviews, approvals, construction, commissioning, and pre-testing of a proposed SRF will occur 7 to 10 years before actual operations begin. In addition, 5 to 6 years will likely be required for refinement and maturation of SRF-associated technologies for safely containing and handling samples to avoid contamination and to further develop and refine biohazard-test protocols. Many of the capabilities and technologies will either be entirely new or will be required to meet the unusual challenges of integration into an overall (end-to-end) Mars sample return program.
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We can assume that it would take quite a long time to do this on Mars, too.
The current best way to do this is to use a [clean room](http://mars.nasa.gov/mer/technology/is_planetary_protection.html) back on Earth prior to launch; this is the current protocol. [It is also hard for Earth microbes to survive in space or on Mars](http://www.space.com/12827-mars-rover-curiosity-landing-contamination-risks.html). Conditions on the red planet for Earth microbes are not good:
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> In the recent study, researchers simulated a Mars rover sitting on a landing platform for one, three and six hours while being exposed to Martian levels of ultraviolet (UV) rays. Even such short amounts of time killed between 81 percent and 96.6 percent of the Bacillus subtilis bacteria used in the experiment.
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Contamination can also be approached from an archaeological point of view, e.g. as suggested by [Yang & Watt (2005)](http://www.sfu.ca/%7Edonyang/adnaweb/Yang%20DY%20JAS2005a.pdf). This study relates more to saving ancient DNA, as opposed to stopping new material from being introduced, thereby making it easier to study any traces of old alien life. Contamination in archaeological investigations can come from many sources:
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> Sources of contamination vary considerably depending on the type of ancient remains and the types of research questions being posed:
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> 2. For ancient faunal and floral DNA studies, contamination would most likely originate from modern reference specimens that are used for detailed one-to-
> one comparisons during morphological identifications of the remains. Human DNA should not be considered a contamination source if distinctive PCR primers for ancient faunal and floral DNA studies are carefully chosen.
> 3. For ancient pathogenic DNA studies of bacterial species, contaminant DNA may also come from closely related species in soils and surrounding environments (soil samples should therefore be collected in order to determine whether soils contain closely related species). PCR techniques should also be specifically designed to use those DNA markers that can distinguish target pathogenic species from possible contaminant species.
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There are ways to combat this:
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> 1. Do not attempt to clean specimens designated for ancient DNA analysis, dirt on the specimens may serve as protection against contaminants entering into bone tissues, making in-laboratory decontamination easier.
> 2. Do not wash specimens as water may cause contaminant DNA to penetrate deeply into bone tissues and may also cause hydrolytic damage to ancient DNA.
> 3. If possible, avoid adding any preservatives to specimens as these chemicals may inhibit PCR amplifications and may cause potential contaminant
> DNA to adhere to the specimens.
> 4. Store specimens in cool, dry conditions to avoid further degradation of ancient DNA.
> 5. Store ancient specimens separately from modern reference specimens to prevent cross-sample contamination.
> 6. If possible, change gloves and clean or change tools from one specimen to another when handling. Specimens should be individually stored in plastic bags or tubes but only when they are completely dry. Otherwise, a paper bag should be used.
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These suggestions can be modified for the archaeological discoveries on Mars.
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I would be very wary of actually excavating alien technology until it has been studied for a very long time remotely. We have no idea of what level of technology the aliens actually had (or worse yet, have; they might still be in the neighbourhood) and playing around with stuff you don't understand the principles of could be extremely bad for your health.
As an example, imagine Victorian British engineers came across a nuclear reactor. They have no concept of radioactivity or nuclear fission, so when they decide to strip it down to examine the parts, or pull the cadmium control rods from the core for examination because they are the easiest part to get to, extreme mayhem will ensue.
The alien artifacts might be carriers of nanotechnology, spores of some form of life, the equivalent of DNA, mind altering algorithms or something even stranger.
Step one would be to build a control station on one opt the Martian moons, and set up a system of relay satellites, so remote investigation can be conducted with minimum light speed lag. Once that is done, spend a great deal of time staring at the find using multispectral sensors in orbit. Look at the find from as many angles as possible, by day and by night, and over a sufficient timespan that we know the item(s) don't become active at night or when the Martian seasons change. After than, send remote landers. The can gradually close in and begin scanning with passive and active sensors. The investigation is continually recorded in HD, so any event can be replayed and studied from multiple angles to ensure no mistakes are made, or if they are made, they are not repeated.
Finally, after all this is done, then you can start to move up to physically "touch" the items with the remote tools to take samples and so on. A robot lab can be sent down to do detailed testing if needed, but the humans *always remain in space* until there is enough evidence that the artifacts are inert and safe. Even then, caution is needed for the human investigators, and they may end up being exiled on Mars for the rest of their lives.
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A doctor suddenly noticed that his patient seems to be indestructible, their injection doesn't penetrate through, until they even conducted basic experiments such as small knife cuts and other blunt damages.
Upon this discovery, the indestructible person was examined thoroughly, until he was really generalized as someone who is indestructible; a person like a very hard rock. His body could also never be affected by any chemical substance that harms him. Upon the series of test, he grew fond of science. In this story, the scientists can never(and would never) understand his body's data for they seem to be changing in a random pace.
Aside from his shield-like gift, he seems to be just a normal person, i.e; he cannot lift heavy objects but cannot be crush by them. Upon reaching his perfect age state, he stopped aging.. Years later when he started to wonder what could he contribute to science given that he is indestructible.
In what field of science does the indestructible yet average person contribute the best and in what way?
Note:
1. Let us not focus on the person himself, but to the what contribution he could give. Lets just describe him as indestructible. If this question is too broad, please specify in which detail it is lacking.
2. Even if he reproduce, his offspring will never get his ability so that the story will focus on the main character.
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I would fire him at absurd velocities into things. As he is the hardest substance known to man (or at least, available on Earth - Neutronium is unstable outside of a neutron start) this would allow for truly unique experiments. At impact energies which would pulverize, liquefy or vaporize projectiles made of any other material, he would remain solid. As he in unyielding this would create tremendous shockwaves and absurdly high compression, helping to replicate conditions usually found in stars and big bangs and such.
Who knows what advances in knowledge could be had from such experiments - they are beyond what is possible with any conventional material!
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Performing experiments in dangerous environments.
Currently we use non-tripulated vehicles in order to explore environments like the oceanic floor, the proximities of volcanos, other planets.
When a scientific imagines an experiment that might be interesting, he has to design:
* The actual experiment.
* The medition tools needed for the experiment, made of a material that can withstand the conditions.
* The vehicle that will perform the experiment, which must also be shielded from the environment.
Imagine that a scientist wants to find out how much time a steak must be put into hot lava to get cooked.
He has to put the test steak in a lava-resistant experiment, and then design a machine that lowers the recipient into the lava and retires it at a determined time. What is worse, if he wants to repeat the experiment with a new steak, he will have to retire the machine from the crater and "load" a new recipient with a new steak, and then position the machine at the crater again.
To make matters worse, if through all of this process (or, seeing the results), he wants to add a variation to the experiment, probably he will have to modify the machine's design.
A person would be way more flexible. You give him pack of steaks, a heat-resistant chronometer, and tell him to perform the test. No need to spend time designing a robot1, and if you want to change something in the experiment you just need to talk to that person.
A different issue would be if such a person would like having to endure such environments...
1: Or, if a robot is needed due to precision issues, it would be way simpler and serviced by such a man "in the spot".
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**Chemistry**
Such a person, with sufficient instructions should be able to experimentally determine practical applications of extremely unstable compounds like [FOOF](http://en.wikipedia.org/wiki/Dioxygen_difluoride).
As a matter of fact there are a lot of such compounds about which scientists just speculate apparently due to their unstable and dangerous nature. Check out this [link](http://pipeline.corante.com/archives/2010/02/23/things_i_wont_work_with_dioxygen_difluoride.php) as well. Again this might not be the only case , a person who is indestructible can be employed to do any sort of dangerous experiments that a scientist can think of.
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In my fantasy novel, magic is a natural part of the world. It is not some mystical force shrouded in mystery, but rather backed by science (though only I, the author, know it's true workings).
In my world, magic is a force that by its nature changes living cells. It is similar to radiation, but different in the respect that it changes what the cell does, usually in a beneficial way. For example, if the cells of an eye were exposed to magic, the magic might make the eye also see infared light (I don't know if that's biologically possible, but it's an example).
There are those in my world that can control the change worked by the magic. (They can *force* the magic to make the eye see infared light. They can also use magic to make that same eye go blind.)
Here's my question. Using this magic, what would be the most effective way to kill a normal human? What would be the most effective way to temporarily paralyze/incapacitate one? If possible, the effect has to be near-instantaneous, as this magic would be used in combat.
Other questions, using this magic (the above is the main one, but if you can answer these too, that would be great):
Could something, like a clump of grass or the fur of a wolf, be set on fire, simply by changing what the cells do?
What would be the most efficient way to produce light? (Bioluminesence, fire, etc. A magic user could in theory just alter the cells of his hand to be bioluminescent, right?)
Could skin be made fireproof?
How would healing with this magic work? Could it be instant, faster than natural, or have no effect? Could magic keep the wound clean?
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Question 1: Infrared/UV sight: Possible. As stated above, there are animals that can see in both spectrums, though snakes actually use a different organ than the eye.
Question 2: Effective ways to kill: Severe nerve connection from the brain. This works well because you are altering very few cells (comparatively) to any other method. And the person stays alive for a bit, meaning if you used magic, you can reverse it
Question 3: Incapacitate Enemies: There are a host of ways to do this. The safest and fastest means would to play havoc with their sense organs (including balance).
Question 4: Igniting biological matter: Oh heck yes. Your body is constantly breaking apart molecules for energy. Thankfully, there are gates on that process, or else we would literally burn to death. Remove the proper safeguards in a fuel-burning cell and watch the fireworks.
Question 5: Efficient light: When oxygen combines with calcium, adenosine triphosphate (ATP) and the chemical luciferin in the presence of luciferase, a bioluminescent enzyme, light is produced. This is how fire flies do it, and they are almost 100% efficient at making light.
Question 6: Fire-Proof Biology: Totally possible. If you think about it, all you need are scales. The problem is that even scales heat up and can burn the flesh underneath, so you would need to build an efficient cooling system under the scales.
Question 7: Healing: Sort of. Increased healing speeds and even regeneration of limbs would be possible, but it would still take a long time and would require massive amounts of food and sleep. Instant healing would never happen with magic that can only affect cell makeup and function.
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The human body is a complicated set of interacting systems, with most of them needed for everyday motions, and especially needed for combat. Interrupt any one of these, and you can take a person out of a fight! Choose one system, alter a process very slightly, and watch the person succumb to their new ailment. This is especially true for the following systems: circulatory, nervous, skeletal-muscle, and respiratory.
# Killing
You're going to need a good definition for efficiency in killing. Do you mean quick or painless? Do you simply mean the method of killing which expends the least energy? I'm going to an amalgamation of all three. Not to compete with the list which bowlturner started, I will simply add to it:
* Prevent Neurons from firing. Seal up the chemoreceptors on neurons, or simply deform them, and even your most hard-boiled adversary is reduced to a vegetable or even just mere warm matter.
* Turn muscle fibers into the cooked version of themselves. This works especially well for the heart.
# Incapacitating
These are specifically non-lethal, but will still harm individuals.
* Activate (or disable) the [voltage dependent calcium gates](http://en.wikipedia.org/wiki/Voltage-dependent_calcium_channel) in people's cells. This will cause their muscles to tense up, rendering them useless until their calcium gates restore equilibrium. The alternative is just to make their nerves fire randomly or all at once.
* Change their eyes to be super sensitive to visible light. It effectively gives a [flash-bang](http://en.wikipedia.org/wiki/Hand_grenade#Stun) type effect. Yes, this is technically an enhancement, but few people will be well trained enough to adjust. When people *first* get glasses, for example, they often have trouble with visual tasks for a day or so until their eyes adjust. (I know I had trouble.)
* Stiffen the or remove [hairs of the inner ear](http://en.wikipedia.org/wiki/Cochlea). This denies your opponent their senses of hearing and balance, but can be undone with regeneration. More on that below.
# Other Questions
[Snakes see in infrared](http://en.wikipedia.org/wiki/Infrared_sensing_in_snakes). Bees and [birds see in UV](https://youtu.be/bG2y8dG2QIM). It can be done, and nature does it for different creatures. You just need to add the correct receptors.
Yes, setting things on fire can be done. You simply need to hit ignition temperatures for that thing. Spontaneously and only be modifying current cells? I doubt that. You could increase the [surface area](http://en.wikipedia.org/wiki/Surface-area-to-volume_ratio#Fire_Spread) of the items to lower the heat needed to burn that thing. I suppose you could force the cells to produce something that burns when in contact with air, but that is super dangerous!
The best way for a creature to non-destructively produce light via modification of an organism is [bioluminescence](http://en.wikipedia.org/wiki/Bioluminescence). Of course, if your magic is in the business of modifying eyes, why not just give people [tapetum lucida](http://en.wikipedia.org/wiki/Tapetum_lucidum)? Their eyes will shine like a cat and can see much better in the dark; certainly much better than if they shine like a beacon.
Can skin be made fireproof? If you could convince the skin to exude a mucus or some other non-flammable substance, this can be done. It should be noted, however, that everything burns, just not at the same temperature. Anyways, a non-flammable mucus can have the benefit of providing a layer of insulation between the skin and the flame. I suppose you could have thick scales on your skin, but then that really isn't skin, is it?
Can magic be used to heal better? I do not know; it is *your* magic. If this magic can only change people's biology, then yes, it can help heal. For instance, if you increase the number of or stimulate the production of [stem cells](http://en.wikipedia.org/wiki/Stem_cell), [regeneration](http://en.wikipedia.org/wiki/Regeneration_(biology)) becomes doable. Is it faster than normal healing? No. It still takes a while, but the benefit is that it happens, instead of remaining a dream. The creature regenerating that limb still needs energy to regenerate; it means you would need to eat ***a lot*** of food while regrowing a limb.
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**Flame on!**
Can a clump of grass or a wolf be set on fire by changing what the cells do?
Absolutely. Using your "magic" one must simply alter the cells to secrete acids or other compounds which result in a violent chemical reaction.
Example: To defend itself, the bombardier beetle produces a spray which is a combination of hydroquinone and hydrogen peroxide. Someone who wields your form of magic may be able to manipulate plant or other cells in this manner.
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I'm just going to answer the first part of the question, about using magic in battle for 'efficient' killing.
Making the heart stop would be very fast.
Stopping any blood going to the brain, blood vessels constricting.
Stopping all electrical signals in the brain(body)
Neck muscles contract to the point of breaking the neck.
Blood produce a poison/neurotoxin
paralyze the diaphragm
Even narrowing down the question I still made a list...
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The most efficient way to kill someone would simply be to stop every cell in their body from working (just get it to self-destruct). This would kill them more or less instantaneously.
As for incapacitating them, you could (as most people sugggest) mess with thier senses, or get make their body produce an aneasthtic.
Healing? Well, if you remove the limits of homeostasis and raise the metabolism and increase cell division, you could heal massive injuries in a few hours. You may also want to give the injured person the ability to photosynthisise to help meet the energy requirements. Fine control would be needed to avoid cancer (from all the rapid cell division).
Also, rasing the metabolism too much will kill the cells.
Combustion? Tricky, but possible. altering cells so they can survive extreme tempuratures, like some micro-organsisms (e.g: water bear), and then increasing the metabolism until the heat causes combustion is one way, but producing flammable compounds might be easier.
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I'm wondering if it was possible for there to be a planet pretty much exactly like earth, except the ocean isn't salt water, it's somethingelse water. Can that happen? If so, how?
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Water runs throught riverbeds and subterranean aquifers. In contact with soil and rocks, various salts and substances are dissolved in water. This water flows to the sea where it mix with the seawater. Substances dissolved in water are carried from land to the sea. To return to the river sources, water does not run upwards the riverbed as a solution. Instead, water evaporates from the ocean, rises to the upper layers of atmosphere and falls as rain. As the water has a much lower boiling point than most salts and substances - even if the evaporation of water is not a "boiling" per se - most of the evaporated substance is composed of water vapour, with very low ammounts of other substances (Iodine salts for example). So, you get a one way carry of substances from land to the sea, with a much smaller transport of substances from the sea to the land. This imbalance of transportation, increases the concentration of salts in water. The rate of evaporation and discharge regulates the salinity of water. Where a small ammount of water, feed by rivers (like say, dead sea) meets with high evaporation, large ammounts of salt concentrate on water. The ammount of substances that are carried by water are proportional to their solubility (in water - there are tables for this) and the availability of such substances on the riverbeds and aquifers that water passes throughout. This means that, besides the solubility, wich is a constant (under constant temperature and pressure) the other component that controls wich substances will concentrate at sea is the availability of them on the riverbeds.
Sodium chloride is a very soluble substance under the usual temperature found in our planet. Supposing a planet with same pressure and temperature as our own, table salt would concentrate in its sea. In order to change this, lets suppose that the planet in question has little to no disponibility of sodium chloride (table salt) in the sediments and rocks that form such planet. Even being very soluble, the low concentration of table salt in this planet will result in a sea with little to no table salt dissolved.
Solibility, availability and low evaporation - ie, the substance is unable to evaporate away with water in any significant quantity - are the factors that will determine the concentration of a substance in the ocean.
How to create a planet where the concentration of table salt is low and the concentration of other substances is high ?
Select a substance that you want to see in your oceans. Check its solubility (its usually expressed as a table where the rows are the substances and the columns are the temperatures). Find the best temperature - where the substance is most soluble. Set the climate of that planet accordingly to such temperature. Now change the rock and soil makeover to have high concentrations of that substance. Make sure the soil is low on other substances that might be carried away by the rivers. Verify if that substance, while dissolved in water, cannot evaporate away with water in any significant ammount. Verify if, under the planet climate needed to match the best solubility of such substance, there will be large evaporation of water from the oceans and subsequent rain over land. When all those criterias are meet, you get an ocean with a good concentration of the substance choosen.
You might verify that some substances are not soluble in water in any meaningfull ammount under a large interval of temperatures, or that the substance has low solubility and so on. While you can build your planet to match a certain substance as the one most present in its oceans water, you cannot change the solibility of the substance. So, in the event that the river brings more and more dissolved substance and the solubility limit is reached, the substance will start to crystalize or precipitate in the ocean floor. So, if your choosen substance has a solubility of 1 gram per 100 gram of water under 30 degress celsius, your ocean will have a max of 1 gram per 100 gram of water at 30 degress celsius, no matter what you do. In other words, you cannot foce a substance to match the ammount of salt in our ocean, because solubility is an intrinsic property of the substances (for each solute and solvent pair).
Real world example is a little more complex, because not all salt in ocean water came from rivers. Some came from sodium present in seabed being dissolved when the oceans formed, and some chloride from vulcanism (thermal vents). Its a complex process, but the general formula postulated in this post can be used to justify the creation of "somethingelse water" oceans in other planets that you need for your story plot.
TL;DR
You can have a sea of "substance X" water if the substance is soluble and the rocks and riverbeds of your planet have a good concentration of such substance and a low concentration of other, competing, substances.
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What we commonly refer to as "salt" is actually a particular salt, sodium chloride. This is simply a matter of abundance, though. Everything (except the stuff that isn't found in nature at all) is found there, though: [Concentration of elements in the ocean](http://www.mbari.org/chemsensor/pteo.htm).
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**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
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Questions about Idea Generation are off-topic because they tend to result in list answers with no objective means to compare the quality of one answer with the others. For more information, see [What's wrong with idea-generation questions?](//worldbuilding.meta.stackexchange.com/questions/522).
Closed 8 years ago.
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In my fantasy world, there are four supreme beings that even our gods can't understand, in fact they believe they were created by those beings.
Imagine that a human character would face one of those beings. How do you think the being would act? What would happen? (that does not result in the character instant death).
The most impressive situation I saw about this kind of thing was on the Japanese manga Gantz Chapter 369 and 370 where the characters meet an alien being whose intelligence/existence was beyond human comprehension
<http://www.mangareader.net/gantz/369> (You may read here, but 18+ only)
Have you ever seen this kind of situation in any book, movie, or anywhere else? If you did, give me a recommendation.
TLDR: What would it be like meeting a supreme being beyond human understanding?
Edit: Also if you can, give me ideas of what interesting things that could happen when the character meet such supreme being.
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Well, if they are beyond our understanding, how would we even recognize that we met them? Beyond that, if they are that impressive, would they even be able to notice us? We would be less than intestinal bacteria to them, maybe viruses to those bacteria.
I would say unless the being somehow deigned to give us some aspect of itself sufficiently diminished to be with in our understanding, we wouldn't even know we had the encounter. Anything that happens would be put down to some kind of strange natural phenomenon.
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It depends on the Point of View of your writing.
If you are writing in first person, with your readers perspective of your world limited by their senses, thoughts and understanding, then you would have to render any incomprehensible being as that character would perceive it. In this case, your character's emotional response to the encounter may overwhelm their ability to describe it clearly. Their sanity might even fail them, leaving the reader on a precarious perch, with their narrator slowly going insane. Check out the writings of H.P. Lovecraft and other authors of the Cthulhu mythos for more on this.
If your readers have a little distance, perhaps a limited third person point of view, you can be more "show don't tell" about it, describing the physical manifestation and its actions; then describing your character's reaction. Here you don't have to say that no common ground exists between the human and the divine, you just have to show it. Again, your character may not handle the encounter with impunity, she may become enlightened, inspired, or damaged. I seem to remember that Piers Anthony's early Xanth novels handled their divine being in this way.
Omnipotent third person is where the task becomes more challenging. Here your readers have become used to you, the god-like narrator, understanding everything and explaining it to them, as the characters perform in ignorance below. Your readers are used to a privileged vantage point where they not only get to see all that happens but also get to know why it happens. And now you have to explain the unexplainable to them. ...yet another reason to avoid this abysmal POV option.
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I like the view of the supreme being that we are a part of but incapable of understanding. The parallel that I like drawing for this is the relationship between us and our cells. Let's say a cell in your body (let's use a red blood cell as an example) suddenly became conscious through whatever means.
* Could that cell be aware of you?
* Could that cell be aware that it is a part of you?
* Could that cell comprehend that the other blood cells it see's in it's journey through your body are separate from it but still a part of you?
* Could that cell be aware that the walls of the 'tunnels' it travels through are also a part of you?
* Could that cell be aware that through it's existence it allows for your thoughts to exist? Could a braincell or neuron be aware that it's function allows for much greater thoughts to occur?
* Could a cell be aware of what it's body is doing and the purpose it's found?
I can go on with questions along these lines...to a single cell in our body that had thought, how much can it really be aware of the far greater purpose of it's body? And not to say that far greater purpose of the body is actually anything greater other than scope...for the length of that cells existence, the body it brings to life could be part of a firefighter saving anothers life as readily as it could be a part of a criminal viciously taking anothers life...or potentially more likely, the blood cell is a part of a human in front of a mildly entertaining tv program as he wastes it's life away. The greater scope and understanding of these supreme beings does not imply they are doing anything more important/valuable than we are.
The reverse is true too...how aware are you of the internal struggles of a blood cell in your being? Do you really care if you cut your finger, lick the wound, and unwittingly sentence thousands of them to die in the acid vat that is your stomach? Are you aware of how your cell would experience the world as a series of chemical inputs as it communicates with other cells?
So I would answer your question in one of us meeting a supreme being as a cell being put under a microscope and being examine by us...Perhaps a little awe in the supreme being realizing it can actually see something so little and meaningless to itself, and probably very little potential of the person even being aware of it being looked at. Interaction is near impossible as the senses the two beings are barely recognizable to each other...but maybe a little understanding that neither could exist without the other.
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# Chance Encounter Scenario:
The holographic displays were flickering, while the black outside viewing ports were either obliterated or dimmed to near zero, as the onboard AIs were routing all available power to the shielding systems. Yet the oncoming onslaught was such that Nabresh could see that rifts were starting to ...**Discontinuity**...
Nabresh blinked. "*Am I dead?*" he wondered briefly. Still in his hundred-g suit, most of his sensory implants reported back, albeit with mostly nonsensical values such as out-of-bounds readings from the temperature, pressure and neutrino monitors.
Using what he thought were his regular eyes, Nabresh could see the dark outlines of a giant hall. A narrow central corridor was lined with parallel stacks of book-cases. And he could sense presences, busily shifting through the corridors, although his eyes could not detect anyone.
Just as Nabresh started to wonder if these ghosts were simply the delayed result of the magnetic overpressure he'd been subjected to on his ship in what *seemed* like only seconds ago, there was a sudden change in the presences. They were suddenly hurried, and started to become more distant, as if they were all fleeing in the same direction. Nabresh felt the strong urge to do the same, but hesitated.
Curiosity got the better of him, and as he waited, energetic flashes of light invaded the hall much like the blue-red flashes of a space-station ambulance ship, except these were blue-gold. The hall's geometry had shifted imperceptibly, with the central corridor now a vast opening. Something was coming.
Nabresh now got an overwhelming sense of dread, and **knew** that he had to flee, but was somehow frozen in place. The flashes increased in intensity rapidly, and became almost painful. Then, suddenly, he saw it. It was near.
In appearance it seemed like a small golden globe, about the size of a grapefruit or a small basketball. Against it were pressed with unimaginable pressures two twisting dark-blue hemispheres, each rotating in a different direction.
[](https://i.stack.imgur.com/5k982.jpg)
For a brief moment, Nabresh knew he had encountered an alien god. As it neared, the sense of horror grew without limit, and Nabresh's last tought was "*I should have fled with the others*" as the sheer uncaring passing presence of the entity ripped his being to shreds and erased him, and whatever platonic-shanonic construct 28th century physicists chose to represent souls, out of the very fabric of spacetime.
TL;DR-WTHDYGTTTWTTS - (Where the heck do you get the time to write these things, seriously?) **It's big. It exists in a place so strange your mind reduces it to a more familiar sight to protect itself. It's so alien it's painful to look at. It will crush you and destroy your soul, probably without even noticing.**
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An encounter with a God like being we will never comprehend or understand would be like seeing an unexplainable flash of light, or feeling a cold chill on a warm afternoon. We can only hope they recognise our vulnerabilitys and let us exist. I suspect there attention on us will be short lived and only our impression of them will remain for very long. On the other hand it is god like and has all the power so it will determine how much we understand. For as long as we believed!
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Consider how we interact with ants.
One way we interact with ants is through surrogates. Watch a child investigating ants. He mostly doesn't poke them directly. Instead, he pokes them with a blade of grass, perhaps with a dead ant on the end, trying to get the two ants to "talk". He changes the ant's environment by removing its trail, and sometimes by moving it away from its familiar environment to a jar or tupperware container.
In visual storytelling, this is usually represented by a blank white void or white room, as you see in 2001, the Matrix, etc. Don't do that.
But it's important to remember that despite being ineffable to us, we may be equally inscrutable to the God - it may not even know we exist, nor, on knowing, might it have the least clue what our thoughts or beliefs are.
But if it did want to communicate, it would communicate on our level, by changing our environment, or poking us with sticks. So, an Avatar or angel - a collection of whatever crap the god found around, crafted into some form of approximation for us. It might or might not be able to communicate with us. Most likely, if we were inscrutable to the God, it'd just make the avatar do stuff and see how we reacted. Eventually, a God interested enough to put the work into it, would be able to understand us, especially if we made an effort to communicate back, just as we can understand the basics of animal communication (back off! I'm hungry! I'm scared! I'm wounded! etc).
The swirl of floating rocks and twigs would become more formed as the God understood us and our desires better. It might become an angelic statue. It might be a friendly or sexy human like thing. It might become a computer screen and keyboard. It might become a a rapidly descending shoe to stomp us out when it gets bored.
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Following up on this question, [Would Living Underground during Impact Winter be Ideal](https://worldbuilding.stackexchange.com/questions/2656/would-living-underground-during-impact-winter-be-ideal), I realized I have more questions.
**I was asking about an impact winter that was caused by an asteroid and leads to continuous snowfall and weather conditions that people are unprepared for.**
**The the answer I received was that underground works fine, but only for small groups and not in the long run. So then my response to that was, if an impact winter is happening, is there really another choice aside from living in a fortress if not underground?**
I ask because in my previous question, we see what the benefits/cons are with Kromey's answer for underground shelters. However, living above ground doesn't appear to have too many benefits either. Some examples of this would be:
**Above Ground Hazards:**
1. bursting pipes and frozen pipes = no heat/water, possibly flooding a place that will further cause temperature drop and hypothermia
2. collapsing buildings (poor infrastructure)
3. limited or no transportation
4. being stranded to a small area with limited supplies or reach to others
5. weak defenses for other desperate survivors or looters
6. No power if utility poles and such fall down, same with communications
I also used [this article](http://www.crh.noaa.gov/images/gid/WCM/awareness/winterdangers.pdf) for some reference. Now this is assuming that an asteroid hit during the start of an already early winter, so there's already a brewing blizzard. Let's say this asteroid happened in the mid-west of the US, and we're focusing on the east by the coasts. Here's what I imagine happening:
**The setting of this question (happens in a period of days/2 weeks?)**
1. Some stubborn workaholics will show up to work even if some people stay home and some businesses close, we know it happens even during bad weather.
2. Transportation is already limited, then the asteroid happens
3. People panic, before public transportation shuts down it's clogged with city workers trying to get home
4. Government is advising people to hunker in their homes/businesses until they can figure things out
5. Transportation shuts down due to worsening weather, those that remain or didn't make the last trains/buses stay in their businesses or homes to wait for help.
6. Worsening weather begins to cause some of the conditions I listed in the above ground hazard list
7. Now there's two choices, wait above ground or find better shelter and re-supply. Not to mention if someone is clever enough to realize that the weather is only going to get worse, they'd want to get home or to a more permanent shelter asap.
But with the beginnings of an impact winter, help isn't arriving. No helicopter is going to fly in blizzard conditions and the government has enough to worry about with the midwest of the US hit by the asteroid and wondering how they're going to deal with the new "[year without summer](http://en.wikipedia.org/wiki/Year_Without_a_Summer)".
So now with all of that, I might be exaggerating a bit, but that's the point of fiction - **is this the same thing others would envision happening to cities and how they stop functioning?**
**Update!**
Also what gives me the impression that an impact winter is bad news and can force humans to seek shelter underground is what's on [the Wikipedia page](http://en.wikipedia.org/wiki/Impact_winter) for impact winter as well:
>
> Those on land could possibly be kept alive in underground microclimates, with one such example being the Zbrašov aragonite caves, greenhouses in such underground complexes with fossil or nuclear energy power stations could keep artificial sunlight growing lamps on until the atmosphere began to clear. Those outside that were not killed by the lack of sunlight would most likely be killed or kept dormant by the extreme cold of the impact winter.
>
>
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See? "Be killed or kept dormant by the extreme cold of the impact winter."
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As Tim B points out in his answer, and I pointed out in mine to your original Impact Winter question, the temperatures are only going to drop by about 13 degrees C, or less than 25 degrees F. Yes, it will get cold, but if we're talking early-winter time period here then we're only getting to around usual mid-winter temperatures, or perhaps a bit colder-than-normal mid-winter temperatures.
This year's [polar vortex](http://en.wikipedia.org/wiki/Polar_vortex) brought colder temperatures, and yet cities didn't collapse into ruin overnight.
Over the short-term period you're talking about, we've seen worse, though of course that doesn't mean it isn't bad -- just because we've seen Category 7 hurricanes doesn't mean a Category 6 is no big deal.
Yes, you'll see some pipes bursting, disrupting water supplies, but in general those will be pretty localized, such as individual homes where the heat's already failed. But cold weather doesn't make buildings fall over -- I'd lose my home every winter if that were the case. I live in Alaska, [-40F/C is an annual week-long event](http://cdn.c.photoshelter.com/img-get/I0000kha6n5eFzWA/s/800/700/99012-03.jpg) (at least), and I've seen -60F/-50C. Lived through it even.
Now, yes, we do build up here for those temperatures. But all that means is that we stuff more fiberglass insulation in our walls, build our windows with 3 panes of glass apiece, and pay a lot more attention to the quality of our weather seals. Fundamentally though we're still using the same materials -- wood, steel, and concrete -- to build our buildings, and even those that have been abandoned and aren't being heated stay standing just as well as yours.
You will see a sharp rise in cars that won't start, and those that do will run "rough" until the engine warms up again. This will not affect cars kept in heated garages (and will be reduced even in enclosed unheated garages), nor will it have any effect on a car once it is warmed up. If you get heavy snowfall (certainly not a given, but possible), though, you'll be in pretty bad shape as cars slide off of roads, leaving motorists stranded; you'll also have people turning off their cars when they get somewhere, only to find later that the car won't start.1
What *is* going to cause problems for you is the people. A major meteor strike all by itself will send everyone into a panic. If you want to drive this up, have the big meteor be a part of a swarm, and have smaller impacts hitting all over the place, or really play up the smaller pieces that will inevitably break off of it as it punches through the atmosphere and hit up to hundreds of miles away.
The impact winter will add to this panic. Look at the near-panics around this year's polar vortex -- obviously the world didn't end, but lots of people were scared nonetheless.
The big deal with impact winter is that food will become scarce, since we won't be able to grow any. (Well, not without electric grow lights, but we wouldn't be able to scale that up in time to feed everyone.) As people start to figure that out, that will increase the panic.
Now you have riots. And you have bands of thugs intent on making sure they survive, no matter who they have to hurt to get food and supplies they think they need.
These are your real enemies. Widespread social unrest and panicked disorder. If these get too far out of hand, you'll see panicked survivors fleeing the cities to get away from the mobs. That's the real threat for your setting.
Of course, this is about the latitudes you're interested in. Way up here, we would be in trouble from the winter itself -- you take our -60F/-50C winter, and drop it to -85F/-63C, and we are in *very* serious trouble. You, though? You're fine. Mostly.
As I implied above, if this were to happen in the dead of winter, it could be a lot more devastating. But given the timing you've provided, social order would most likely be restored and people could have prepared for those temperatures by the time they come to pass; again, it will not be pleasant, and there will be deaths from exposure, but it's still not going to cause your buildings to collapse or anything like that.
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1 It's not relevant to this question, but if you're curious: Our cars are "winterized", which basically amounts to having installed electric heater pads underneath the battery and the oil pan. When we park, we plug in to the "[head bolt heaters](http://smg.photobucket.com/user/1stimestar/media/IMG00136.jpg.html)" that are liberally available all over the place. A few minutes isn't a big deal, but if you're going to be parked for a couple of hours or more you plug in, or you expect to need a jump from someone who did. Then you run your engine for a bit to let it warm up before you start driving.
[Answer]
The thing is an impact winter isn't a snowball earth scenario.
From [wikipedia](http://en.wikipedia.org/wiki/Impact_winter):
>
> These pulverized rock particles would remain in the atmosphere until dry deposition, and due to their size, they would also act as cloud condensation nuclei and would be washed out by wet deposition/precipitation, but even then, about 15% of the sun's radiation might not reach the surface. After the first 20 days, the land temperature might drop quickly, by about 13 Kelvin. After about a year, the temperature could rebound by about 6 K, but by this time about one-third of the Northern Hemisphere might be covered in ice.
>
>
>
So in other words the average temperature would drop by 13 degrees, slowly returning to a drop of 6 degrees over a year and then finally returning to normal a few years after that.
This is enough to turn temperate conditions decidedly unpleasant but not enough to freeze entire continents. So long as people could keep the power on and gas flowing to homes then people would survive, at first. This does give you the first reason not to hole up in caves though, moving south for warmth!
The problem comes when gas supplies fail, and when food starts running low, and when you realize that no new crops will be growing this year. When people start getting cold and tired and hungry. That's when the real trouble comes and how the authorities and survivors handle that is what makes the difference in how many people last and how long they last for.
[Answer]
The difference between your scenario and the one at the K-T boundary is the asteroid which hit the Earth there was orders of magnitude larger. It is thought some of the ejecta from that impact was literally blown in ballistic paths almost halfway around the Earth and caused large scale fires, for example.
Now if your true aim is to cause a civilization ending apocalypse, your impact *could* be used to trigger lots of secondary events, such as the unlocking of the San Andreas fault network on the West Coast, triggering the eruption of the Yellowstone super volcano or unlocking the New Madrid fault mid continent. These on top of the already devastating impact of the asteroid strike and a persistent winter would probably stress the Federal and local governments beyond their breaking points.
AS for the impact winter itself; as noted it is livable, although in places where power and other services are disrupted, unprepared people are going to have a very hard time of it. Even preppers will eventually run out of fuel for their generators, so if this happens in November, by February things will be a bit tight.
Your immediate problem is that without transport networks, urban areas will run out of food. Supermarkets will be stripped by panic buying, and there will be no means of bringing new supplies in from the warehouses. This will cause panic, mobs roaming the streets and looting for food and an exodus of people trying to leave the cities, making transportation networks even more stressed (cars abandoned on bridges or tunnels will block these choke points). When the spring rolls around, another issue will emerge; the same factors which caused the impact winter will create a year without summer, causing global crops to fail or be far smaller than normal. Now you have stress on societies all over the world, and the more fragile states will likely slip into anarchy. Depending on how late the impact was and how much ejecta is in the atmosphere, this could persist for several years.
As well, since you specified the United States is the locus of the impact, the effects on global trade markets, security and even political events will be very striking. Look how quickly Iraq collapsed after the Obama administration unilaterally withdrew US troops, creating the power vacuum that allowed ISIS to grow and move in. Now do that globally...
So the immediate effect, while severe for the people involved, is not civilization ending in of itself, but could trigger larger and longer term problems.
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[Question]
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If two (or more) planets are within travel distance from each other and they often trade with each other, how likely is it that these planets cultures influence(d) each other?
For example:
On planet A the dominant species is cat-people who like to do cat-things like cat-nip, yarn, etc.. They trade with the people from planet B, which is only a "short" traveling distance away and ideal for trading, a species of dog-people, who like to do dog-things like fetching and bones.
Is there a chance that the dog-people from planet B adapt the customs of the cat-people?
On earth we can often see the influence of other(often long dead) cultures, like the greek or roman, in modern cultures, but how would that apply to planets?
[Answer]
The short answer to your question is "yes, of course." Two societies that come into contact, assuming that they are able to communicate, will necessarily have an exchange: communication requires this. To put it in Star Trek terms, the Prime Directive is idealistic but utterly impossible: the only way not to influence another society is not to let them know you exist.
On the other hand, there is no reason that one has to think of such contact in catastrophic terms. To be sure, the history of European colonialism is not a pleasant one, but that needn't be the sole model.
Consider, for example, the many, many tribal peoples of the Americas, prior to the arrival of European invaders in the wake of Columbus (let's ignore the Vikings here). They talked to each other, traded with each other, sometimes fought and sometimes didn't, for an extremely long time. As a result, we can spot remarkable affinities among myth-cycles all across the Americas. If we had better longitudinal data than we do, we could chart how customs and such moved; in some cases, we can do this to a degree, especially when it comes to material culture (pottery, beadwork, etc.).
You cannot possibly model all of this, of course: it's ludicrously complex. But there are a few points that could perhaps be useful in a fictional worldbuilding context.
**1. Variable Usage and Interpretation**
Suppose one culture has a big thing about hats, where there are all these incredibly fine variations and gradations in hat shape, style, material, color, and so on, and these are a complex sort of code having to do with social station, age, sex, place of origin and/or residence, and so forth. (At various times China has had some of this kind of thing going on.)
Now along comes the other culture, and they do some peaceful trading for a while, and this other culture takes home pictures and souvenirs and stuff in addition to actual trade goods. Now at home, they might end up with a big fad for "alien hats," and suddenly the millinery industry is going through the roof. Of course, this culture either doesn't understand the hat-code system, or doesn't understand it well, or just as likely, sort of understands it but doesn't really care: the alien code doesn't apply, but the hats look cool.
**2. Reinterpretation**
But maybe that second culture, after a brief fad about the alien hats, finds itself in a situation in which everyone is wearing weird hats all the time. They have the concept of the alien social hat-code, but it's an alien system that doesn't match their own life-patterns. It could well happen that, over time, this society develops a way of coding hats that does match their life-patterns, particularly if they're constantly trading with the original hat-wearing aliens.
**3. Rejection as Adaptation**
And then a new thing sweeps our society: hat-coding is an alien thing, and it's contrary to what we're really all about (because of the gods, or pride, or whatever). So people stop wearing hats entirely. Before alien contact, they sometimes did and sometimes didn't wear hats, but it didn't mean much: it was a fashion thing, or maybe a way to keep the rain and sun off. Then there was this fashion surge, and then this new hat-code, and now nobody ever wears hats.
I realize that this may seem like a silly set of linked examples, but the point I'm trying to make is that cultural contact and adaptation is both extremely complicated and to a significant degree non-catastrophic. While it is obviously possible for "contact" to mean "convert them at swordpoint and then enslave them," it usually doesn't work that way. Usually what happens is that objects, customs, images, and so forth are exchanged, and then each culture has to make sense of the new stuff in its own terms, which in turn changes that culture -- but not necessarily to make it any more like the one it's exchanging with.
Here's a final example, in this case from real history: **Melanesian cargo cults**.
Cargo cults are (mostly were) complex and varied, but the basic phenomenon is revealing and helpful for the question at stake. To give a highly simplistic account of one type: During the Pacific War, the American navy (especially) sometimes provided various goods to local Melanesian tribes. In essence, the idea was to get these people to be friendly to Americans, such that they could be enlisted to assist against the Japanese; for example, they might tolerate an airstrip, or they might tell Americans about spotting Japanese ship movements, or whatever. Now when the war ended, so, pretty soon, did the providing of free stuff.
Now the problem is, a lot of Melanesian societies base their economic systems in social exchange. Think of it sort of like The Godfather: if I'm a big powerful dude, that's not because I have a lot of goods, but because everyone owes me favors. And to retain and increase that power, I have to keep people owing me by giving them stuff and not letting them pay me back. For my birthday, I'm going to throw a huge party and invite everyone, and I'm not only going to feed them but I'm going to give them all presents. This both demonstrates and increases my power.
So for these Melanesians, the American goodies represented a problem. The Americans gave them stuff, but didn't accept anything back. So this meant that the Americans were incredibly powerful. But when they just stopped giving stuff, what were the Melanesians supposed to do? They owed favors, but now the folks to whom they owed the favors wouldn't talk to them. So in these cargo cults, you'd get a millenarian religious movement centering around the Americans and their stuff. People built wicker airplanes, put on wooden headsets, and generally did anything they could to force the American "gods" (loosely speaking) to restore the relationship, not necessarily because the Melanesians wanted or needed the stuff as such, but because this gross absence threatened the whole system of exchange itself.
If you do a little research on cargo cults, and think about what's happening on the two ends of the exchange, you'll end up with a very wide range of ways to think about cultural adaptation.
[Answer]
So I think using cats and dogs in your example is a little misleading as they tend to be thought of as opposed forces...BUT.
From your questions I am presupposing a couple things (if I am correct please edit these assumptions into your question.
1. Space travel is fairly common
2. Trade by space is economically feasible, i.e. tech advancements have made it so that the practice is more than exploratory
3. The races on each planet are capable of communicating and understanding, truly understanding, not just communicating with each other
The meat of the question though is will they trade cultural info and the answer is yes absolutely. When any two nations/cultures/peoples interact there is an exchange of ideas and knowledge and customs. Rarely, these exchanges go evenly and things are shared evenly. Most often, one dominates the other (at least in world history). Look at US culture around the globe. The other scenario, again... easy to see around the world even today, is a backlash against the invasive culture. This is common but still doesn't wipe out the interaction or changes that come from intercultural exchange.
So not only would it occur, odds are its irreversible. Its kind of like knowing what a hot dog is made out of, once you know you can't unlearn it for good or ill.
[Answer]
Check this out:
Aztec <-> European
The European conquered South America. Most Aztecs died from European diseases which their immune systems where not able to handle.
Those who survived the epidemics, mixed up with the conquerors and evolved to one of the younger ethnicities on this planet (Hispanics).
Whoever refused to adopt christian religion, got killed by the Spanish inquisition.
Chinese <-> European
Again, the European tried to colonize an sub-continent.
First, the Chinese let the European build up harbours and cities for their settlers. But as it came to the point where the "conquerors" forced the Chinese Emperor to resign the throne, a war started in which the Chinese fought the Europeans back.
The Europeans then held only small parts of China, such as Hong Kong.
The influence of the European culture to the Chinese was very small, but the Europeans which went home again brought culture from China to Europe.
[Answer]
I dislike the theory of material trade between planets, unless it is based on very scarce resources found on one planet and not the other. In your example, why would the cat-people trade balls of yarn with the dog-people by sending it via transport from one planet to another when the materials for yarn are common on both planets? In this scenario it is more likely that the knowledge to make yarn is what is traded, not the physical yarn itself.
Consider the move from a material driven economy where material is the scarce resource in question to an information driven one where material is no longer scarce. To give an example, currently we go into a Mcdonalds and buy a burger (you go to a place to trade for a resource). Now consider a world in which the material is no longer scarce...a person can take a 3-d printer and 'print' themselves a burger on demand. The exchange for the material burger is no longer needed and instead the you buy the 'right' to use the information required to produce that burger instead (you have purchased a print one burger PDF file?).
In this light...the trade between dog-people and cat-people is not on a material level, it's trading knowledge between the two races instead. Knowledge is based on interpretation, a common set of interpretations between people is the cultural "we"...so yes, each culture would have an impact on the other as they trade knowledge. Just by 'using' the yarn, one could say the dog-people are adopting customs of the cat world.
>
> On earth we can often see the influence of other(often long dead) cultures, like the greek or roman, in modern cultures, but how would that apply to planets?
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Hard to compare...unless we were saying that the dog-people conquered the cat people and 500 years later there is still trace elements of cat culture in the conquered cat-peoples language.
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[Question]
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## Scenario
We've got a terrestial exoplanet three times the size of Earth, 1800 light years away and with an atmosphere similar in composition to Earth's. It is determined via studies that atmosphere would be able to support terrestial life without needing any life support. More studies and in greater detail are made en route to the system which would prove that the assumptions made back on Earth weren't fully right.
## Questions
* How precise information would humans be able to get about its atmosphere with current tech or with a near future tech (by near I mean no more than 4 decades into the future)?
[Answer]
I'll add my own two cents here, source: I work in the field.
**1. Technology**
The reference to 'near future' tech is problematic in this, as 2-3 decades is the typical timescale of planning & constructing (in the case of [James Webb](https://www.stsci.edu/jwst/about-jwst/history) more like 4 decades) a major observatory or space mission, given current funding horizons.
Given those timescales, technology in large observatory projects is frozen at a given, defined point (otherwise you'd keep exchanging and updating components) and then this frozen level of tech is used for the remainder of the existing mission (this is particularly true for space missions, ground observatories i.e. next generation interferometers and ELT's can be build much more modular).
Because of this, large observatories always lag a few decades behind compared to the newest standards, which are e.g. used in smaller science missions or top-secret intelligence satellites.
So with this disclaimer, it's clear that your mission will essentially use the technology which is in todays spy satellites, and be a typical factor 3-10 better (as it is usually per generation of telescopes) in angular resolution, signal-to-noise S/N, spectral capabilities, etc.
This factor 3-10 is a huge oversimplification, and particular for the light gathering capability (or sensitivity, or S/N) the size of your telescope and/or number of array telescopes play an overwhelming role. There, in principle you can just spend more money for a larger telescpe or more array elements, but the tech again limits whether you are actually able to analyse and use all the incoming data for an improvement in S/N.
**2. The science**
For what we can actually do with the data gathered, we have to distinguish between **discovery** and **characterization**. Discovery is only a factual statement, that something is there, while characterization is going beyond and actually saying what is there, how much etc.
The dividing line between those two modes of science is roughly the S/N ratio of the data you have: If you're fishing in the noise, and you barely see the signal of an Earth-like planet in the transit data, then you can only claim discovery. Your data is not good enough to say anything about its bulk properties or the existence of an atmosphere or other things we can today only vaguely dream of (like shape of continents etc.)
What determines the S/N in the end is the technique you are using and what object you are looking at:
* A self-luminous young giant planet, far away from its host star will have great S/N in the infrared, its light can be directly fiber-fed to an infrared spectrograph. This will yield a lot of spectral data, which can then be fit to determine temperature structure, abundances of atoms and molecules in the atmosphere. Currently, that's still a noisy job, but [the next generation of ELT's](https://elt.eso.org/science/exoplanets/) will do a fantastic job at that.
* A small, terrestrial planet, close to its host will have terrible S/N, and even discovery of atmospheres on those planets is extremely hard currently, and only for near-by stars, not your 1800 Lyr far away star. The ELT's are going to improve "discovery of atmosphere around Earth-like planets" into [occasionally doable](https://www.aanda.org/articles/aa/abs/2007/25/aa7085-07/aa7085-07.html) (given our understanding of how technology will evolve).
However, to do what you propose, you'd need your telescope size and tech to move into the mode of "routine characterization of atmospheres around Earth-like planets, at large distances", which would probably need another 2-3 generations, large-scale international funding and collaboration and world peace. Also those future scopes would presumably so insanely large that you couldn't take them on your generation ship ride, you'd have to keep a commlink with Earth and take the hit that your data doesn't become better, the closer you get to the target.
**3. Detection biases**
If you want to travel to a far-away 'perfect' planet, you want to first make sure that there is no other good candidate much closer, otherwise you're wasting a lot of money.
Your proposed 1800 Ly, which translate to something like 430 parsec are currently in the outer range of sensible exoplanet detectability by (transit) surveys. You would need to first step up your survey machinery dramatically to be sure to cover all stars that are closer than this with transits, and then another dramatic step up to cover all planets with direct imaging.
Transit surveys are biased towards the planets which happen to orbit on the line-of-sight, whereas direct imaging surveys would have a much higher completeness. However for this, novel coronographic techniques would need to be developed to block out the star (e.g. [Starshade](https://exoplanets.nasa.gov/resources/1015/flower-power-nasa-reveals-spring-starshade-animation/)) and deployed in large numbers.
Given world peace and all surplus funding in the next half century going into exoplanet science, this would be doable, but seeing the state of the world at the moment, this is not what is going to happen.
[Answer]
As L.Dutch answered, by measuring absorption lines you can get atmospheric composition of your exoplanet with high degree of precision. And 1800 light years is not that far away, as space is big. And since you gave us 4 decades of extra time, the job would be even easier. We wouldn't even need more advanced technologies, just bigger measurement apparatus.
But I have to point out few flaws in your question. First, you said it would be able to support terrestial life without life-support. Practically ANY atmosphere in 0-95 C can support terrestial life. Bacterial life, but life nevertheless. Even in our solar system there are places where terrestial (archea)bacteria could survive (if we provide them nutrients, and in some cases probably even without that).
But if you meant multicellular terrestial life, that would mean oxygen in your exoplanet's atmosphere. And oxygen is a byproduct of life! Naturally oxygen tend to get bound to other elements as it is far to reactive. Earth didn't have atmospheric oxyen until life figured out photosynthesis. But if your exoplanet already has life, you have another issue with supporting life without life-support: extraterrestial microorganisms. You wouldn't want to go there without life-support. And that is not unforseen complication, that is something anyone planing your expedition. And even ignoring the issue with native lifeforms, atmosphere and temperature range are not sufficient criteria for colonization. You need at least a proper gravitational field and low enough radiation levels.
[Answer]
This is science fiction, so let's start with the idea that someone is starting a project to resolve the best image we can of such a planet based on known science.
[The project](https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_I_Phase_II/Direct_Multipixel_Imaging_and_Spectroscopy_of_an_Exoplanet/) would involve using solar sails to send a probe out to 542 AU (about 3 light-days), where it can use the Sun as a gravitational lens. This project is designed to image the surface of planets out to about 100ly, so it could probably do spectral analysis of a planet at 1800ly. Certainly enough to build excitement adequate to justify an expedition, if such an expedition were feasible.
As it stands, just getting out to 3 light-days would take us almost 20 years, and that's not even considering the time required to build it. If they spontaneously came up with tech that would make an 1800ly expedition feasible, then they would probably start by sending a larger telescope to [Sirius](https://en.wikipedia.org/wiki/Sirius), which is a mere 8ly away and twice as massive as our sun, to get better pictures.
[Answer]
If they are able to measure [absorption lines](https://en.m.wikipedia.org/wiki/Absorption_spectroscopy) in the stellar spectrum, scientists will be able to measure the composition of the atmosphere, limitedly to those atomic species abundant enough to give a measurable absorption lines. This has been first done for an exoplanet in 2001.
Atmosphere in itself can be detected by measuring the decay of the light curve during an eclipse: an atmosphere gives a gentler fade, while with no atmosphere the transition is sharper.
The closer to the planet, the better and clearer information can be gathered.
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[Question]
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In my world, a race of intelligent cephalopods have created mecha similar to the Fighting Machines from War of the Worlds (long story short; it makes sense for then as they evolved and continue to live on this worlds version of a highly mountains, jungle filled Australia).
What I'm wondering is if the flexable leg pattern as depicted in the original War of the Worlds is possible to build in a 1G environment? And if so, on what principle would they function?
[](https://i.stack.imgur.com/ZEZHm.jpg)
Notes:
* Any form of technology will do. Mechanical, soft robotic, active support, ferrofluid, any thing else. All far game, these guys are very tech savvy.
* The machines typically range in size from 3 meters high to around 13 meters high. In this question, we'll focus on an average height of 8 meters.
* The number of legs depends on the job of the machine, with ones designed to carry heaver loads having 6 or more (assuming wheels can't be used, if the terrain is lenient enough), while other machines may have fewer. This question will focus on a machine with four legs.
* The legs are highly flexible, allowing the main body of the machine to hide behind cover in a variety of environments and to raise the machine to full height, or hid behind a boulder.
* The main body is non-humanoid and is more oval shaped. It contains the pilot, weapon emplacements (typically either a laser, Coilgun, missile rack or some combination), smaller manipulation arms based off of the same tech as the legs, and the power supply. Armor is present but just enough to survive a few glancing blows or one frontal attack from a sufficiently powerful weapon. The Cephalopods fighting doctrine prefers speed, mobility and stand-off line-of-sight weapons over armor and raw fire power. They do have high firepower weapons, just not on these particular mecha
[Answer]
It could be possible in an under water earthlike context.
It would work by having a neutrally or slightly buoyant head/vessel with anchor pods attached to it via flexible umbilicals.
These umbilicals are the legs, and carry power and data to each individual pod or foot.
Submarine context allows the legs to work in traction rather than compression which allows them to remain visually slim.
Each pod can propel itself in any direction and is powerful enough to tow the whole thing.
Each pod can move explore and anchor itself on the submarine floor, collectively all three pods combine in a gait to walk the tripod.
[](https://i.stack.imgur.com/xXRCh.gif)
[](https://i.stack.imgur.com/6dG66.gif)
[Answer]
A few possibilities:
1. A segmented robot arm just like the more traditional ones, with a small motor in each joint, but with far more joints.
2. Each segment has a small wire attached to it that runs up to the base where the motors are.
3. Metamaterials that expand or contract when a current passes them, arranged in origami-like complexity such that a computer can use a few dozen circuits to make it do whatever's wanted.
[Answer]
Combine [Artificial “Muscles”](https://news.mit.edu/2019/artificial-fiber-muscles-0711) With Nested Carbon Nanotubes.
[](https://i.stack.imgur.com/s7hwU.jpg)
Arrange them in sheets and parallel with each other:
[](https://i.stack.imgur.com/yRH2q.png)
along with an control system capable enough. You have a very strong artificial squid limb.
[Answer]
## Materials
I feel that this is more a material sciences question than a structural design question. We are talking about fully-formed legs here, which is relatively less exotic than hovering in air or teleporting or things like. So, in short, yes it’s possible if you have the right materials. Since this question is focusing on the leg design and its implications, I will assume that the power plant can achieve the necessary output.
Now, as for the materials and design basis, that’s the real challenge. You’re going to run into a couple of issues out the gate that would require some clever explanation if poked. The major ones I can think of are: ground pressure, leg sheer, and material flexing.
## Ground Pressure
We are taking a relatively large mechanical device with weapons and payloads and living things in and on it, and putting that thing up on stilts, basically. Those contact points are going to have a very high pressure level, unless the feet are comically large and well designed to distribute the weight of the device well. The other solution to this is, of course, to make it as light as possible, which wouldn’t be a terrible concept given that you’ve espoused the desire for these mechs to be maneuverable and fast. Also the fact that there are multiple limbs means the ground pressure can be more spread out than if there were two. Basically, aluminum alloys as the primary body and some kind of ultra-light metal for the armor and you’ll be in decent shape to handwave the ground pressure issue.
## Leg Sheer (material sheer)
Given that your mech is supposed to eventually move, the legs will need to bend at some point. This is an issue due to the fact that, while these spindly legs can hold up the weight of the mech when they are straight and bearing weight on the compression axis of the legs, once they bend, they will be bearing weight on the sheering axis. In order to counter this, the cross-section of the material used for support in the legs will need to be thick enough to resist the sheer force of the partial weight of the mech equal total weight divided by the number of legs minus one (assuming that, during travel, only one leg will be off the ground at a time). We will then need to incorporate a safety factor into that calculation because this thing will be moving, and dynamic forces are higher than static. There would be quite a bit more engineering involved here, but this is something to keep in mind with the size of the legs and materials, etc. If you want more detail on this concept, you might want to research ultimate sheer strength in a material just to get an idea of the PSI tolerances of metals.
## Flexing
I don’t know if you’ve even been in a boom lift or a scissor lift or something like that, but tall, thin metal structures have a tendency to flex with very little force input. A light breeze can cause a scissor lift that’s 20 feet in the air to deflect over 5 inches from center. No matter how stable the platform is, the thin metal appendages will experience deflection with even minor perturbations in center of mass or strong winds. Also, the device will have to maintain is axial tilt very carefully. Following the earlier lift example, a fully extended lift with an axial tilt over 3.5 degrees can be blown over completely with a decent gust of wind. These mechs we are discussion will be quite a bit more top-heavy by nature, and have less internally support leg systems, given that these legs will need to move independently. Stabilization will be a huge aspect of movement on these things. Actually, that would be a interesting visual picture, with the legs moving all over the place but the bodies appearing to glide through the air on those legs.
## Conclusion
I think if you find occasion with the description of these mechs to describe and counter the basic versions of these afore-mentioned issues with both design and material engineering, you will be in good shape to remain internally consistent and present these things as logically plausible in the story.
[Answer]
**Hydraulics.**
[](https://i.stack.imgur.com/kF9Exm.png)
Consider a flexible leg element with 2 hydraulic bodies inside. At full hydraulic body pressure (red) the elements are straight. Reducing pressure (violet) in one of the 2 hydraulic bodies shrinks the element on that side and the leg bends in that direction. Even more reduced pressure (blue) bends the element such that elements above are at 90 degrees to those below. Lowest pressure for both elements (blue) shortens the element.
This is depicted as a rectangular leg element with 2 interior hydraulic bodies but a hexagonal or octagonal leg element with more hydraulic bodies would allow more precise bending. More smaller elements produces more flexiblity. A leg element could still function with some damaged hydraulic bodies.
One could have the leg element default to maximum extension or maximum compresson if too many hydraulic bodies were damaged - the leg element thus becomes "dumb" but still can serve its structural functon.
[Answer]
According to [this discussion](https://www.engineeringclicks.com/forum/threads/force-to-bend-steel-bar.4902/) to just bend a 10 cm long, 9mm in diameter steel rod requires a force equivlent to approximately the weight of 20 kg.
So, suppose your tripod is 10 meters tall, which is 100 times as long as the indicated length here. And suppose it is 1 metric tonne in mass, 50 times as much as the 20 kg bending just mentioned. And suppose it needs to be able to stop with an acceleration of 1 g. It will need that to balance in Earth's gravity, at least occasionally. Plus, you have illustrated this thing with the legs at an angle, so they would need to support the bending just standing there.
The legs need an absolute minimum area of 5,000 times that of a 9 mm steel bar. That is, they will need to be about 0.3 meters in diameter solid steel. Not including the mechanism provided to move the leg. Or sense its current location.
Now here's the thing. This rather simple calculation does not include the weight of the legs themselves. The pod was assumed 1 tonne. But 0.3 meters diameter means about 0.3 tonnes of steel per meter of length. That is, the legs would be 5 tonnes each, compared to the 1 tonne cabin. They would need to be much thicker to support their own weight.
This thing is not going to look nearly so bendy if the legs are 2 meters thick to support a 10 meter height.
Hopefully you see the point here that steel is simply not going to cut it as a single, compact, flexible limb of this type and length. The legs will break every time this thing tries to take a corner.
If you require a long flexible limb type of thing, you are going to require something much stronger than steel. Probably something at least 50 times as strong as steel. The length of the lever that wants to bend the legs is just too long. It's not quite up to the range of space-tower strengths, but it's getting there.
Structures of this size are constructed out of some kind of truss. The purpose of a truss is to convert the bending force into some combination of compression or stretching. The [working load limit](https://factor55.com/uncategorized/how-strong-is-the-steel-cable-wire-rope-that-comes-with-your-winch/) for a 5/16 inch steel cable is typically 1 ton. Steel can handle huge compression forces, typically [20 tons per square inch.](https://www.quora.com/How-many-pounds-of-pressure-does-it-take-to-break-steel) So a truss can be constructed with very much larger bending strength than a simple steel rod of similar weight.
However, that means that the legs cannot be flexible in the fashion illustrated.
[](https://i.stack.imgur.com/Bt6aL.jpg)
Here is [Robosaurus](https://www.youtube.com/watch?v=cVSnFiB1UNo), a 40 foot (about 12 meters) tall amusement park attraction. Notice that the legs are essentially stiff except at one or two joints. Notice that the joints are very solidly constructed. And that the thing keeps most of its weight on the wheels at the back, not on very long legs. The limbs are covered in a surface covering that hides the truss underneath.
He is about as tall as the tripods and yet his legs are already very much klunkier and stiff compared to your tripods.
[](https://i.stack.imgur.com/ECrQ4.jpg)
So basically you have two choices. Give up the slender flexible tentacle-like legs. Or find a construction material drastically stronger than steel.
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[Question]
[
In my setting, kinetic firearms are the handheld weaponry of choice for most people, despite centuries of technological advancement (and stagnation, somewhat). These range from chemical-propelled guns to electromagnetic guns, each with their own advantages. In practice, except for specialized weapons, the receiving end of these firearms suffer similar amounts of damage to what one might expect from real-life guns.
In addition, a significant fraction of the human population across all inhabited star systems live in small space space stations or in spacecraft, where they often deal with low and zero gravity. There are many physiological issues that arise from these environments, but most of them have solutions or workarounds. Said solutions reflect a near-future level of technological sophistication, and include such things as lab-grown synthetic foods and nutritional/hormonal supplements, all of which I have figured out plausible explanations for. However...
Injuries do not heal well in microgravity, much less debilitating injuries, and as of now there don't seem to be any definitive real-life solution for this. But the more daring of these space-dwelling "spacers" often find themselves with such injuries, which include gunshot wounds from the previously mentioned firearms. Anything from a stray shotgun pellet to the back to a sniper round through the rib would not heal properly in microgravity without assistance, and left untreated could kill the victim, but artificial gravity sources such as centrifuges can sometimes be unavailable. After all, your ship's propulsion systems may have been damaged in the same fight that earned you a gunshot wound, leaving you stranded far form any centrifuge station. Built-in centrifuges and spin tethers can also be expensive to install on a ship, and most opt out of such features.
How, then, would spacers go about treating serious wounds during extended stays in microgravity? What sort of realistic technological solutions for this might one find in, say, a zero-g first aid kit?
[Answer]
Most of the research on this topic is very new so it's hard to say exactly why wounds heal slower in microgravity. Some seem to suggest that microgravity in general somehow leads to general health issues:
>
> Experiments performed in real and simulated microgravity revealed alterations in fibroblast and endothelial cell function, changes in ECM production and dysregulation in apoptosis. Interestingly, in astronauts, **deficient immune function, signs of chronic inflammation and insulin-resistance have been observed**. These alterations, resembling some features of systemic diseases which impair wound healing on Earth, could affect the body’s response to injury and could represent a model to study defective healing mechanisms
>
>
>
and
>
> Fibroblast behavior during wound healing is tightly regulated by mechanical forces at the site of injury and the ECM-membrane mechanoreceptors-cytoskeleton system plays a prominent role in cell signaling [[Demontis et al., 2017]](https://link.springer.com/article/10.1007/s12217-016-9532-7) (Emphasis mine).
>
>
>
In my not-a-doctor-nor-a-biologist opinion, the slowness of wound healing seems to be a combination of the general health-malaise that humans suffer from during long-term exposure to microgravity and the mechanical effects of microgravity that slow down the movement and "restructuring" process of cells. I suspect that in a gravity environment, the process of tissue growth is aided by the fact that gravity "settles" the cells rebuilding the tissue lattice, and in microgravity these just float around aimlessly.
Setting aside the general unhealthy state of space-dwellers, solving the mechanical issues of wound healing could be as simple as applying vibration. Multiple studies have been done that suggest [full-body](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8102430/) or even topical application of vibration has positive effects on long-term or chronic wounds, and I could imagine that in a microgravity environment, properly applied vibrations to the patient could induce movement in and simulate pseudo-gravity for cells at a microscopic scale.
In a first-aid or field-care scenario where centrifuges or other gravity-equipped healing stations are unavailable, first aid kits could be equipped with topical vibration modules that get taped to the patients near their wounds or larger belts that get strapped around the whole patient and shake them ever so slightly.
**All that aside,**
I'm generally of the opinion that for any serious space-exploration and long-term space colonization, some prerequisite medical breakthroughs will need to be made. The classic one is cancer: it's simply so much easier and cheaper to cure cancer than it is to completely radiation shield everything when you are talking about human colonization that covers "star systems". Either eliminate cancer from the get-go (think nanobots in the blood that are constantly vigilant or genetically engineering humans to be less susceptible) or cancer needs to be reduced to something with the severity of the common cold today: maybe dangerous to old or otherwise already compromised people, but nothing that will cause you to miss more than a couple days of work before the drugs kick in and clear it up.
This is why I suggest healing gunshot wounds in space would be simple: Simply grab the single-use medical nanobot injector syringe from the first aid kit and apply it to the wound. If you don't have nanobots, then maybe you've simply genetically re-engineered the humans to be able to heal normally in microgravity.
[Answer]
**1. Apply pressure.**
Even here on Earth healing a serious injury is no small thing. People can "just heal" from scratches and minor wounds, but major injuries like deep cuts regularly require one consistent thing.
*Pressure.*
We strap people up and apply pressure to almost everything. Twisted ankles. Broken bones. Deep cuts. Those that don't require this benefit nonetheless from gravity and our atmosphere, which are all applying some form of pressure.
Consequently, it would be believable for people in microgravity to use pressure (even up to a pressure suit so simulate 1 atmosphere force against the body or more) to overcome some of the limitations of microgravity.
*I am not suggesting that pressure is magically replacing gravity. Only that some of the problems can be overcome through pressure.*
**2. 3D Bio Printing**
>
> Skin wound healing is known to be impaired in space. As skin is the tissue mostly at risk to become injured during manned space missions, there is the need for a better understanding of the biological mechanisms behind the reduced wound healing capacity in space. In addition, for far-distant and long-term manned space missions like the exploration of Mars or other extraterrestrial human settlements, e.g., on the Moon, new effective treatment options for severe skin injuries have to be developed. However, these need to be compatible with the limitations concerning the availability of devices and materials present in space missions. Three-dimensional (3D) bioprinting (BP) might become a solution for both demands, as it allows the manufacturing of multicellular, complex and 3D tissue constructs, which can serve as models in basic research as well as transplantable skin grafts. ("[Wound and Skin Healing in Space: The 3D Bioprinting Perspective](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8575129/), Mateo & Gelinsky, 2021"]
>
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>
Humanity is working on biological 3D printing *right now.* It's in its infancy, but it's proof enough that one solution to the problem is to *replace the damaged components,* be they organs, muscles, cartilage, or pretty much anything else. It's plausible that once we can create skin grafts with 3D printing, we will eventually produce everything else.
[Answer]
**Wound putty**
Current skin grafting technology involves living cells taken from the patient and grown up in a dish. This can be applied as a sheet or as a slurry with binders / carriers.
Wound Grafts: <https://www.ncbi.nlm.nih.gov/books/NBK564382/>
>
> Currently, the most commonly used skin substitute is a cultured
> epidermal autograft (CEA). A full-thickness skin biopsy from the
> patient is obtained, and the keratinocytes are then used to develop a
> graft by expanding the cells into a neoepidermis...
>
>
> A newer therapy product requires a biopsy from the dermal-epidermal
> junction to produce autologous cells (keratinocytes, fibroblasts,
> melanocytes) that are delivered in a suspension. This suspension is
> then applied to the wound by spraying it on the wound.
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>
>
Your world has off the shelf universal donor keratinocytes, fibroblasts and assorted cells which are suspended in a gooey caulk of inorganic carrier molecules, nutrients and clotting factors. The cells are engineered (aka "transformed") to be unfazed by microgravity and resistant to native inflammatory cells. A syringeful is warmed up and injected into the wound.
The living cells and clotting factors stop bleeding and congeal into a clot which within a few hours is crosslinked into a living scar. Wound putty is usually for smaller wounds. If there are not other good options some people use several doses for larger wounds (e.g. to replace a missing eye).
In some individuals the universal donor cells are overambitious and these scars can continue to grow. Occasionally an overgrown putty scar (or puttymark) might require surgical removal down the road. Backwoods types pare down puttymarks themselves or tie them off with thread.
Or let them grow and wear arsenic rings through them as a charm to ward off any other bullets. In addition to hopefully warding off bullets the arsenic retards growth of the scar.
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[Question]
[
(BTW this is my first question, sorry if this is bad.)
So basically, in my world there is a race of octopus-like aliens who use handheld firearms, now the question is how would they design them. Now humans have effectively figured out a basic design pattern, the barrel, then the stock after the barrel and the firing mechanism under the barrel. Now my question is would this change when they are made by cephalopods.
The species:
* Are cephalopod like with 12 tentacles
* 6 of them are tough but less opposable and 6 more opposable
* They do not have a skeleton.
* They move around on 6 of their tentacles by "crawling" around (However they only require about 4.) They hold onto things with 1-3 of the other 6.
* They are about 100-150 cm in height and 80-120 cm in width on average. The mass is about 30-55 kg on average.
About the firearms, the requirements are:
* They have to be operated by only a single user.
* They are single shot muskets (Barrel loaded.)
* Have a trigger system.
* Earthlike conditions on land are presumed.
[Answer]
The first thing to note about your cephalopod friends is their lack of fingers. This means they wrap their tentacles around the firearm they are carrying. So I suggest something like a cannon barrel:
[](https://i.stack.imgur.com/g68sq.jpg)
Basically, a gun without a grip for hands. Instead it could be elongated like a rifle:
[](https://i.stack.imgur.com/j1cig.jpg)
For safety’s sake, the trigger shouldn’t be exposed. Instead it should be inside a cavity where only the tip of a tentacle could reach.
Other than that, with no bones to speak of the way they carry their guns will be different too. Small tentacle-held firearms are light enough to hold with only one limb. Larger calibers require the cephalopods to hold it firmly against their body (the human equivalent of holding a cannon under our armpit). It is advised not to hold the weapon directly in front of the body but on the side, due to recoil.
The instruction manual would go something like this:
1. Wrap your tentacle around the gun.
2. Hold it firmly. Larger guns should be held on the side.
3. Aim for the target. (If using a scope don’t press your eye against it.)
4. With the tip of your tentacle reach for the trigger inside the gun. (If your arm is too short feel free to use another arm.)
5. Pull the trigger.
Well done private! You’ve fired a gun. Now get those tentacles to work and reload!
[Answer]
## You don't need much power, air gun will do fine
Consider something like this, loaded with a small arrow, or harpoon,
[](https://i.stack.imgur.com/uXx83.png)
<https://en.wikipedia.org/wiki/Air_gun>
<https://fortnite.fandom.com/wiki/Harpoon_Gun>
There are no bones, or even thick skin. It does not have to break bones or penetrate a skull. Your weapon needs far less firepower than the usual handgun based on explosives.
[Answer]
As the others have pointed out, actually handling the guns is easy. Your problem is aim.
Octopuses handle their many, highly mobile appendages by giving each quite a lot of leeway in motor control. Each tentacle has a large ganglion - a "local brain" that handles the fine control of tentacle movement in accordance with vague instructions form the central brain. In contrast, aiming requires your visual and motor systems to flow information in a fast, highly detailed loop. Presuming your cephalopods have a single sensory centre that their eyes project to, you're stuck with most of the motor circuitry in the tentacle ganglia and most of the visual circuitry in the central brain.
### What can I do?
* **Head gun** If there is some usable muscle function in the head part of the animal, controlled by a central brain motor circuit that could be well integrated with the visual system, you could just not use the tentacles at all. I'm sort of assuming that they don't have a proper manipulating limb sticking out of their foreheads, so you'd probably have to manufacture (with your very independent tentacles!) some helmet-like device that you operate by waggling your squid-eyebrows, or some similar head muscle movement.
* **Tentacle eyes** Flip of the option above. This is perhaps more outlandish, but could make for interesting creature building. You could have specialised vision abilities on different tentacles, or only some of them. This guy, who can potentially aim and shoot 12 independent targets at the same time, is *definitely* wiping the floor with plunger-head guy above.
* **Shotgun** Who says I need aim anyway? Go for sheer, wanton, only vaguely directional destruction. Just make sure you tuck your other tentacles out of the way, and there are no snipers, friendlies, explosives or crucial structural supports in the area.
[Answer]
## It would look like a Gastraphetes
The actual design of the firearm would mostly be familiar. The barrel and trigger mechanism would be pretty much the same, the biggest difference is the stock. A human stock is designed to brace against the shoulder, but the cephalopod has no shoulder, but they do have a broad muscled section where the head meets the tentacles that they can brace the recoil into. So instead of a vertical cradle, your stock would have a horizontal one making it look a lot like a [gastraphetes](https://en.wikipedia.org/wiki/Gastraphetes).
To hold the gun, the cephalopod would use one tentacle to stabilize the stock against its "belly", one to stabilize and aim the barrel, and a third to operate the trigger. If they are dexterous enough they may even be able to wrap 1 tentacle around the stock to stabilize it and then back around into the trigger for 2-tenticle shooting instead of 3.
A second minor difference may be taller sights. Depending on how good your cephalopod's grasp is, it may need to wrap its aiming tentacle around the whole gun as opposed to how humans just grip it from the bottom. If this is the case, then taller sights may be needed so that this tentacle does not obstruct line-of-sight.
[](https://i.stack.imgur.com/nzY3f.png)
[Answer]
One little known fact about Earthian octopuses (not so sure about aliens...) is that that their suckers can revolve, rotate, and bend to grip onto something. That being said, you could create a firearm with an internal trigger that is pulled when a tiny metal circle on the outside of the gun is rotated. I'm sure some system could be fabricated to allow this.
So long as you don't make the guns too long or heavy, octopuses should be able to handle it. They are surprisingly strong creatures, as a large percent of their body is pure muscle.
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[Question]
[
**Background:**
My question would be: which bear would be the most useful for a necromancer who raises one from the dead. Since the bear is dead, temperature, stamina, injuries, aggression, all of that would be rendered moot. So a setting where most of their typical flaws are not factored in.
* Would the polar bear come out on top then, seeing as it is larger and heavier? And could work well as a swimmer, dragging enemies down in the water?
* Would the Kodiak come out on top due to its more defensive build, its thicker layers of padding and longer claws?
* Would the Kodiak come out on top due to its larger size?
**Characteristics:**
The story I am writing is about a Necromancer/Smith combination. He can take dead creatures (Bears for this example) and turn them into his servants. (More akin to an automaton).
* They do not rot.
* They do not require food, water, air.
* He can repair them completely over the course of a few hours/days, depending on the damage.
* They are smart enough to follow complex commands and orders.
* Think of them as a living weapon that he forged. More like a sword or armor, then a living creature or the undead.
* They can be temporarily destroyed. Just like a normal bear. Instead of losing HP, they would lose durability. Decapitation will instantly kill it. Cutting it enough will also kill it, etc.
He would be mostly using them to fight other monsters: from wolves, to goblins, to trolls. Possibly also other humans that have bows/arrows/swords or even rifles.
**Question:**
I would be most interested in their combat capabilities. Defense, offence. Possible specialties (Such as swimming of the polar). **In that area, pound for pound, which would be the best bear for the necromancer.**
[Answer]
You know, Polar bears are far too popular. Think the golden compass. After Pantalaimon an undead polar bear would seem a bad rip off.
I'd say go with something a bit different. I would choose the Kodiak because it doesn't appear that much in media (documentaries notwithstanding), is really big and can be pretty intimidating.
If you want something that is in great numbers, is big enough that could do heavy damage if commanded and plus can swim exceptionally well I'd suggest the black bear! It's not enormous like other Ursinae but has a beautiful black coat and can pack a punch. Also there are like 500.000+ individuals in America so even with dead ones you could build quite an army.
[Answer]
**Both?**
You give no reason the necromancer has to choose only one type of bear. Bears are rare since they are big and have large territories. If you want many bears you need to diversify.
HOWEVER! If the necromancer is going on a journey and only has one spare seat in his car, then which type of bear should he choose?
Polar bears seem the biggest. Wikipedia says adult males are in the range 7' 10'' – 9' 10'' long. While the average male Kodiak is only 8'.
They can also swim better. So they are better suited for different environments.
They are also used to killing large animals like Beluga Whales. So it is easier to get them to fight large trolls. Less so for the Kodiak.
As for defensive build, I am not sure what you mean. Both animals have thick coats. Both can be given immense levels of fat armor before slaughter due to their hibernation strategy.
[](https://i.stack.imgur.com/dPJul.png)
*Did somebody say my name?*
Kodiaks have longer claws. But bears do not claw things to death (the long claws are good for opening clams) so this is not an immediate plus. For small things like wolves and people you just swat them. For big things you grapple them and wrestle them to the ground. If anything the smaller claws are better for this job.
However if you must only choose one species for your army I suggest the common brown bear. They are smaller but there are more of them. They have smaller territories than Polar bears since they live in the woods and not the frozen wastes.
[Answer]
Panda. If someone attacks one, the Chinese military shows up. Defense, offence, they have it covered, except for arguably a blue water navy. They are also unrivalled for defense against monsters that resemble bamboo shoots.
[Answer]
## A grolar bear?
How about a grolar bear? They are the offspring of a polar and a grizzly. As big as a polar bear, found further south, and have the nasty temperament of a grizzly. Plus,they have as much of an interesting 'back story' as an animal can have.
Thought I'd try to contribute something more helpful than a panda.
Extreme outside option: A cave bear. Extinct a few thousand years ago, they were about 10 feet tall. A necromancer who found a fossilised one would have a superweapon!
[Answer]
**Lava bear.**
[](https://i.stack.imgur.com/umBpD.png)
[Lava bears](https://en.wikipedia.org/wiki/Lava_bear) are the best bears for this application because they are small and light, especially when they are dead and dried out, and so can easily be carried by the spellcaster in a backpack. Then the spellcaster can hurl the bear at enemies!
The bear will not be hurt because it cannot be hurt. It is reusable too.
GO LAVA BEARS!
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[Question]
[
In this setting, magic and the supernatural is real and acknowledged by wider society. Magic is a relatively rare ability; while it is still an issue to think about, it is too rare to expect all police forces to have a magic-using officer
The most common form of magic is inherent magic, which takes the form of specific abilities either as a natural power or as a tuned magical tool. There is also spell-casting, which is where magic is projected by the user for a wide variety of purposes. This skill must be learned, and is aided by special tools such as wands (though it does not require them)
Known magic rarely gets more powerful than a truck engine, and is usually towards the lower end of the spectrum. However, it can be used in a wide variety of ways
Magical powers, when in use, emit some energy as a form of radiation, which interacts with certain materials and can be detected by special tools. Inactive powers can also be detected, but such sensitive detectors are extremely expensive
Other than the magic, the world is much like our modern world, with similar technologies and cultures
**How would the police handle magic in this world?**
[Answer]
There are a few assumptions here, and I'll try to note them (and will update if comments point out ones I miss). Primarily, I'm going to use the perspective of a developed, relatively wealthy nation. I also assume that magic is, for the most part, legal (like personal gun ownership in many countries).
### Licensing
You mention that the world is otherwise "much like our modern world", so a robust government system that can test and license magic users would exist. This licensing would identify ability level and skill, much like different driver's licenses for different vehicle types. In order to gain "magical" employment, you must be licensed. Since it's a rare skill, many people born with the skill will get licensed (and take courses/testing) to open economic opportunity. Enforcement would include a requirement to produce your license in various situations, including during investigations where the police may show up at your door; failure to comply may speak for itself depending on the society. This leads us to...
### Detection
If magic emits radiation, and magical skills differ, I assume there is a magical fingerprint. This may be unique to an individual, or at least not universal. This would allow associating a usage to an individual. If licensing is in place, the gov would have that fingerprint on file. If fingerprints are general, the license would identify the magic users' various skills, and allow searching by fingerprint type.
### Magical societies/rights groups
Much like there is MENSA and such, I'm sure there'd be magical societies. With magic being rare, I'm sure these societies would have a vested interest in keeping magic in a positive public light, meaning they'd work with police to suss out a criminal. This can also manifest as magical rights groups that advocate for the rights and place of magic users within society.
### Suppression
Assuming magic can be detected, I'll make a very large assumption it can be suppressed (ie. anti-magic effects). While these would be expensive, rich governments/corps/individuals would implement the solution for highly sensitive areas. This could be remote or local (that is, area devices or worn devices). Magical prisons would also be outfitted with these devices, and located in areas with low risk of escape due to location (try swimming from Easter Island, or walking from the South Pole to civilization). Others have already mentioned SWAT (MWAT?) so I won't retread that.
### Legal structure
There would definitely be laws surrounding the use of magic in general society concerning contracts, public safety, legal proceedings, intelligence, etc. As others have mentioned, these would be followed by most people. Minimum sentences, or entirely unique laws, would exist for things like "Assault with a magical act". However, just like in the real world, 3-letter gov agencies would have special carve outs exempting them from the laws, and those agencies and govs would have the best stuff (as others have mentioned). As such, magic users (criminal or otherwise) would have their own concerns for safety, with fear keeping them on the straight and narrow.
### Criminals
Most of this deals with law-abiding citizens, and that is because most laws assume lawfulness. You cannot legislate people to not be criminals; you can only define what is a criminal. In that case, look to the law enforcement trends around weapons, cults, mafias, extremist groups, and such for further inspiration of how to deal with powerful criminals.
[Answer]
The police can detect it, and unless all magic somehow protects the magician from bullets, nets, tear gas, etc, they will deal with the magicians like any other armed criminal. Perhaps they have their own magic protections, like police have bullet proof vests and helmets.
And in extreme circumstances, the police DO have specialist magicians with special powers to defeat other magic. Much like the military has special forces, an elite squad of the 1% that are the best, from outright assassination to disabling and capture.
Just because magicians **can** be criminals does not mean they always **are** criminals. IRL many highly intelligent people have the skills to be good criminals, but are born with empathy and don't want to be criminals. IRL the police detectives that investigate murder really do know how to get away with murder, but they don't use that knowledge because they are not the type of person emotionally capable of murder as a tool to get ahead. Same here, magicians that could be criminals choose instead to use their powers to stop the worst of the criminal magicians.
[Answer]
Hmm personnel shortage and lack of funds.. sounds realistic !
One, or a combination of the following options:
**Option 1: Safe houses**
There are magic techniques to make sure certain places are protected. Specialists take care of that. When a person is threatened by wizards, he/she is moved into such a place
<https://en.wikipedia.org/wiki/Magic_circle>
A safe house can also be used to jail a wizard. Once dragged into a magic circle, the wizard will loose all magic abilities and not be able to escape.
**Option 2: Police have good intent, that will weaken the wizard**
Police folks are trained to perceive wizards as patients that must be helped, so they have good intent toward the wizard. Wizards need their victims to resist and be afraid, else their evil magic won't work.
**Option 3: The most powerful wizards work for the police**
Magic is hierarchical.. stronger magic will always prevail. When police encounters a hostile wizard, they call a specialist, who can solve the issue remotely. Wizard becomes paralyzed on the spot and can be arrested. Detection works in a similar way. When called, the specialist will use his talents to remotely sense magic danger threatening the caller.
[Answer]
# If the Police must protect themselves, the world would at large must be prepared as well
As mentioned by @amadeus Police would need to develop tactics much like they do in reality for people with the tools to cast "long range hole poke" from their guns. Unless the magic makes them immune to bullets, then we've gotta escalate and call in the casters much like we would a swat team or helicopter.
Beyond that though, the world would have to adjust in some ways as well. Some countries may have a gun registry system today, much like a magic user registry could be enforced in some regions. There may be teams of operatives and magic sensitives who's sole duty is to patrol areas of high population to sniff these users out if they aren't registered, where some regions may be bastions of free magic use so long as it's used for good purposes.
Much like a police radar, a magic user radar can be built, either to trace a path of residual magic toward a caster's location or to identify the properties of the magic cast for forensics. We too have DNA labs etc, but typically go unused for common criminal activity, or isn't required to be used to solve the case. Higher profile magic badness would attract this sort of attention though.
### What are they protecting themselves from?
What sort of magical limits exist?
Does Divination magic exist to remotely locate people and objects?
Could a construct be built to alter a persons ability to use magic?
In public buildings like banks, courthouses, and schools, there are signs to remove weapons before entering. Is it possible that places such as the white house would have a consistent Anti-Magic field cast over it to prevent magic assassinations or possessions from afar?
Can a caster remotely kill a person, or multiple if they were powerful enough? If a caster could see the Ethereal plane and pluck a police member's soul from their body without danger of being seen, or a fair number of other scenarios, specific an specialty equipment may need to be developed to protect the common non-magic user from such magic harm.
* A magic jammer to stop divination intrusions.
* Daily Protection spells given throughout the day by police casters.
* Concentration breakers during conflicts to make it harder to cast spells.
* Materials for armor that don't conduct heat or electricity. Innately magic resistant materials would be valuable for this.
* Specific gags or handcuffs to prevent captives from casting.
* Protocols for police magic usage, standard loadouts of spells etc.
* Casters may have specific magic auras or fingerprints that can be tracked.
### While there are a lot more good people than bad, there are plenty of bad
Some areas may become outlaw havens that don't mind the expense of life for power.
Magical super weapons may be developed if left unchecked.
Specialist teams made of multiple organizations may need to work together to keep this possibility from becoming inevitable.
On the streets, people are mugged, just like magic could be used to intimidate, even if only a false threat that a supposed caster could put you to sleep or injure you.
Would Vigilante casters form guilds to help protect their cities perhaps?
If magic could be taught, it may become a typical school subject as computer use is now to us. You wouldn't want to be the only one unable to protect yourself or build a profitable skill set from magic. This could help level the field somewhat but it sounds cost prohibitive currently.
[Answer]
If magic is as flexible as you're indicating, along with being such a rare gift, then it is probably possible for anyone with the gift to get a rather high-paying job at any number of places that has uses for it. That means that there is a low chance of magic being used for petty crimes, as the risk-reward just isn't worth it. On the other hand, it will probably be used for big crimes fairly regularly. No point in using teleportation spells to steal bills out of wallets (since you can get paid more just getting a job), but stealing stacks of them out of bank vaults would still be attractive to some. Not to mention smuggling drugs past border guards.
It is very rare for someone to commit crimes *for the sake of commiting crimes* (the exception being certain violent crimes). The majority of crime is about obtaining money, and are commited because the crimes pay a lot more than work (it's like stock markets; high risk means high payout if you win). As long as anyone with the gift of magic can get rich in a legal manner, most will choose to do so simply to avoid the risk. And those that don't, they are those that want to go "big or nothing" and they will try to rob a bank or something on that scale, not petty crimes.
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**Common sense, police tactics.**
Police have to deal with every kind of stuff. Weapons. Wild animals. People acting up. People trying to get away with things. Buildings trying to fall down. Toxins. Fires. Fires with toxins. Accidents with dangerous machines. Sick animals. Drunk people. Big holes that open in the ground. And stuff that is not dangerous but people think it might be, or are not sure because it is weird.
So add magic to the list. The police will ease into things and keep eyes open. They will keep themselves safe and keep people safe. They will assess threats and deal appropriately, most of the time, more or less. It is what police do.
I must say that along the way I hope for some demon summoning magic malefactor with starry robes and tall pointy hat to get a taser to the junk and then some pepper spray. Maybe he will accidentally summon the demon "WOOOAAAGGGGHHH! cough cough ".
[Answer]
## Magic triggered guns
The police can’t recognize when someone has magic, but they can recognize when someone uses magic. You can attach to your gun a highly directional sensor that when tripped the specific radiation of a certain intensity only found by using magic at under 10 meters will fire the gun in “magic mode”. You would still have fire and safety, but magic users will be a lot less likely to try and get the drop on you if they know using magic means you get off the first shot. The gun would pose no harm to civilians, since they don’t emit that radiation, and the sensor is directional. This is a bit of an extreme example but if your goal is escalation, not de-escalation, then this works.
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So, in my world, I have a city built in a plain surrounded by a desert. The plain got to be there by magic and general hand waving and was sustained in a similar way. At some point, that stopped being possible (the one responsible died or something, it doesn’t matter), but the plain remained.
So, the question: **how does the city get rain, or any kind of moisture for that matter?** Keep in mind I am not an expert on these things, but moisture in the air can’t go through the desert because the humidity is too low (I’m simplifying a bit), nor can it go “over” that low-humidity zone because humidity decreases higher up. I know the moisture doesn’t technically *go* anywhere, but it works for my explanation of what I know.
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There is some humidity in the air over a desert, what lacks is a way to extract that humidity. In fact at night, when the temperature drops, it's possible for moisture to condense. That's how desert life often get their water.
If your plains have a way to elevate the airflows and cool them down, they have also a mean of extracting the humidity present in the air. These means are usually mountain ranges.
For a reference, [Mount Kilimanjaro](https://en.wikipedia.org/wiki/Mount_Kilimanjaro#Climatic_zones) has bushland at its feet, while it gets a rain forest above that and even snow on the top.
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## Ground Water
You don't need your plane to receive rain, you need it to receive water. If you plane is in a low-lying area compared to the desert then it may be closer to the water table which is being feed from the far side of the desert many hundreds of miles away.
The ancient wizard may or may not have been magical, but he was smart. He recognized the usefulness of the low-lands and terraformed them with a system of aquifers and irrigation fed by ground water. He may have used magic to to expose the ground water, but the actual aquifers are replenished by natural means.
[](https://i.stack.imgur.com/28wET.png)
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# The rains on plains fall mainly in the plane
Of your planet's ring system, that is. It's not very visible from directly beneath, and the planet is no Saturn, but there actually *is* a nice bright ring around the planet as visible from anywhere else. Deorbiting ice chunks deliver periodic bursts of moisture to the air over your city. They tend to deorbit right over your city because your planet is a fairly standard oblate shape, but the ring *did not* form parallel to the equator. As the particles revolve over the equatorial bulge of atmosphere, they are slowed, and come falling out at your city's temperate location at the edge of the Hadley cell.
The plain was a good spot for deorbiting valuable mineral shipments from the ring - that was a fairly exotic asteroid that broke up, and it contains much more valuable bits than just water if you can find them and bring them down.
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You haven't specified how often the rain falls, when it falls (seasonality) or when it does fall how much falls. Neither have you specified the altitude of the plain or its latitude, or how far away from the ocean the city is.
The first source of rain is clouds blowing in from the coast, even thousands of kilometers.
The second potential source of rain, hence the seasonality factor, could be monsoons. There's a rainy season for a specific time of year. Latitudinal location will also be a factor, examples of this occur in India Australia.
The third potential source of rain, and again a seasonality factor, is the inland migration of cyclones/typhoons/hurricanes. Once cyclones start to travel over land they become rain bearing depressions dumping vast quantities of rain far inland. Taiwan is heavily dependent of typhoons for its water supply. Other examples of such rain events are south east Asia, parts of eastern Africa and Australia.
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I had an idea for a sci-fantasy story set in a far future where there are primitive human settlements at the base of Mauna Kea who are unaware that they're actually dwelling on the sea floor of the Pacific Ocean. The ocean surrounding the islands of Hawaii has been drained and there's an immense circular wall built using "advanced" technology to keep the ocean at bay.
What effect would stuff like atmospheric pressure have on people on the sea floor in this scenario? Would temperatures on the sea floor be absurdly high? What would the terrain look like after thousands of years?
What sort of flora, if any, would grow below sea level or on the drained land?
This is assuming that the Earth’s oceans have not all drained away, just within this cofferdam like structure surrounding Mauna Kea.
If the sea floor would not be suitable for settlement, what broader scenarios or technological work arounds would need to exist to make it possible?
[Answer]
### Time to make some assumptions to make the primary question easier to answer.
* Putting the radius of the wall at 100Km. The big island is very approximately 50Km radius. This will put the wall far enough away to not have the ~6Km high wall not so obvious and actually have some room to live/farm.
* Sump pumps were installed at the same time to prevent infill by water.
* Wall thickness is 1m, wall height extends 10m above mean sea level. This allows only the most extreme storm water over. Allows weather systems to pass over.
* Coffer dam extends 500-1000m into ocean floor this is to prevent water flowing under the damn.
* Coffer dam is constructed of unobtainium for its structural strength.
* After dam placement the enclosed ocean water is pumped out over the next year.
### Things to expect to happen after placement, first year
* Sea life that was living close to the surface dies.
* Many land slides as the angle of repose is much steeper below water then above.
* Due to pressure changes food availability changes, almost 90% of the life that was in the waters surrounding the island are killed.
* Many significant(7-8 mostly probably a few 9+), massive earthquakes due to changing mass distribution.
* Many rocks/minerals that were stable under ocean, no longer are. E.g. all gas hydrates would melt/sublimate
### Over the next hundred years
* Slow continued desalinization of the prior sea bed.
* Weather patterns change initially to be much drier, mass loss of biomass on the island. less water to moderate temperatures. This changes as the ocean floor warms up.
* Mass starvation of any people living there, less fish, less water for farming.
* Weird chemistry in the surrounding valley due to higher temperatures and large pressure variances.
* Some plants start colonizing down slope.
* Continued massive earthquakes as the area lifted up.
* Magma eruptions would probably start occurring around the south base of the mountain due to changing path of least resistance to release magma pressure.
* Temperature of the ocean flow starts rising, without any cooling over a 100K rise would be expected.
* The increased temperature starts driving storms. which start providing significant cooling.
### 100 to one million years
mostly skipping this.
* weather formations stabilize.
### Over the next 1-10 million years (assuming wall and pumps maintained)
* Earth quakes back to pre dam levels
* the center will have risen enough to have gentle slope down from the center to the wall.
* New volcanic cone well formed.
* Plants extend range down much of the slope. By this point plants would have reached the prior ocean floor, higher cooler spots would also be colonized.
* The valley bottom slowly greens, but high temperatures and or pressures keep most greenery and certainly farming away.
* Humans follow plant growth further down slope. But are limited due to the temperature and storms.
* The massive storm system cause the storm gods to supplant the volcano gods as being the most powerful.
* Air temperature in the bottom to start rising. This will start driving some very large storms. In theory 30K/Km or 180K above surface so without cooling temperatures will be tending to well above boiling across the valley
* Air pressure will depend on air temperature, If it is 30K/km then air pressure will be about the same as surface. If it is 0K/km air pressure will could be as much as double normal air pressure. Between temperature and pressure there is going to be some fantastically powerful weather systems happening.
last two points are derived from 'Pressure and density of air in mines'.
### Possible weather trend
Not certain but it seems that a massive doughnut shaped near perpetual storm would form. Colder moisture laden air would down draft all around the wall into the valley bottom where it would heat up, picking up more water flowing off the center then start rising. Dropping moisture as it cooled over the center. Then fall back down towards the wall. Depending on how much cloud this could really limit food crops.
### Closing
The valley floor/prior sea bed will most likely be too hot to live. It needs constant cooling to keep temperature down. The constant rain and river flow would keep it from going into the boiling range. Much if not all of valley could be well above comfortable living. If it is cool enough to live then the higher air pressure will be a complication. How much complication I am not sure.
How could the valley bottom be more viable as living space? In addition to the ocean pumps a large network of heat pumps to keep the heat below 30-40C would probably do it. Perhaps. This would also calm the storms.
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Disclaimer: The science and methodology here are going to be a little sketchy. Hopefully that's fine. IMO this kind of speculative worldbuilding really only needs to give a ballpark number figure; the important thing is the consequences of approximately where it ends up.
**Skip to the end for the most exciting conclusion.**
#### Summary:
* You might get **oxygen poisoning**.
* You might get **carbon dioxide asphyxiation and volcanic gas poisoning**.
* You might get **giant animals**, evolved to both exploit and defend themselves against the oxygen.
* Ecology will probably be limited by **nutrient availability**, following a normal ecosystem development pattern.
* Be careful how you remove the oceans, so you **don't leave a thick layer of dried sea salt** that kills everything.
* You might get surface **temperatures up to 60°C, but maybe not**, and you can improve the odds if you **shape the walls to create winds and conduct heat**.
* The **whole place will flood** with nowhere for rainfall to drain to. Fixing this probably means either lots of pumps, or a (likely arid) climate with evaporation and precipitation in equilibrium.
* **Earthquakes will probably destroy your wall** as the thin sea floor crust rises upwards to make up for the lost weight of the water above it.
* **Every global coastal city outside of the walls will permanently flood** due to the volume of water removed for your cofferdam.
* **Hydrothermal vents** will be interesting to see outside of the ocean.
* The conditions at the bottom are perfect for **biologically realistic giant fire-breathing dragons**.
---
The sea around Hawaii is apparently [up to 6km deep](https://maps.ngdc.noaa.gov/viewers/bathymetry/) in some places— Around the same difference in elevation as the surface and the peak of Mount Everest, where the air is less than half as dense. Higher air pressure with the same elements also means higher partial pressure of oxygen. This could be immediately dangerous to unadapted humans:
* [**Oxygen Poisoning**](https://en.wikipedia.org/wiki/Oxygen_toxicity) — Too much oxygen or oxygen at too high a pressure can cause disorientation and damage to a lot of organs.
Hawaii also may not be the best place for this. Carbon dioxide is aleady heavier than air, and every now and then a cloud of it will [build up in a valley and smother everyone there](https://en.wikipedia.org/wiki/Lake_Nyos_disaster). Volcanoes emit a lot of gas, lots of it more toxic than CO2.
* **Toxic Gases** — You might get a pit full of [poisonous](https://en.wikipedia.org/wiki/Volcanic_gas) or [unbreathable](https://en.wikipedia.org/wiki/Limnic_eruption) air.
Even if the gasses enough aren't enough displace all the oxygen and outright smother everything, the higher pressure might be enough to force enough of it through the lungs to [turn blood dangerously acidic](https://en.wikipedia.org/wiki/Respiratory_acidosis)— Not to mention that chronic exposure to more dangerous volcanic gasses would probably be unhealthy. With the wall hundreds of miles away you'd probably be fine, but you might have problems if it were much smaller or during a particularly volcanically active time. Maybe there will be pockets of immediately lethal gas near the lowesst parts of the sea floor, which your people will turn into myths about the underworld.
Depending on how bad all this is, species could experience some pretty harsh and aggressive/fast selection pressures to adapt.
* **Gigantism** — Growing bigger bodies is both an opportunity afforded by higher pressure and a way of coping with greater oxygen.
A lot of the biggest prehistorical organisms that would not be biologically viable today existed during periods of higher atmospheric oxygen content. [Griffinflies](https://en.wikipedia.org/wiki/Meganisoptera) and [pterosaurs](https://en.wikipedia.org/wiki/Pterosaur) peaked during the Carboniferous and Cretaceous, when the atmosphere held as [much as 50% more oxygen](https://commons.wikimedia.org/wiki/File:Sauerstoffgehalt-1000mj2.png) than it does today. Having more oxygen in the air should allow the body to consume more power without that much more expensive of a respiratory system, meaning they can grow much, much larger if there's a competitive advantage to doing so. At the same time, it may also create an advantage to doing so— If the levels of oxygen and other gasses are enough to damage the tissues and organs of a normal-sized creature, then growing a bigger body could dilute those gasses back down to safely usable levels.
* **Biodiversity** — Are you leaving nutrients in place?
As long as there's sunlight, I don't see any definite reason why there shouldn't be fairly normal flora. Evolution doesn't usually just create life from thin air though, so I think the flora that ends up growing down there will largely be restricted to the flora that's already in the region to be able to spread, and its descendants. At first you'll probably be limited by nutrient availability— There's [apparently a lot of fish and stuff in the seas around Hawaii](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2914028/#s3dtitle), so if you're willing to let that die and drop to the dry sea floor, you could get a head start. Otherwise, you might have to wait for the usual [pioneer species](https://en.wikipedia.org/wiki/Pioneer_species) like lichen, algae, and simple plants to move in and break down the rocks into soil.
* [**Salt Flats**](https://en.wikipedia.org/wiki/Salt_pan_(geology)) — If you're drying out the oceans by evaporating the water though— As opposed to pumping or otherwise moving it out— Then you'll get a thick layer of salt on the surface. In this case, obviously basically nothing will grow except for some extremophile species of [Archaea](https://en.wikipedia.org/wiki/Archaea) and such.
On your timeline of just a couple thousand years, I don't think any new species will be able to evolve, although you might be able to get pygmy and giant versions of existing species— This could be a combination of the unique challenges of higher air pressure, and the [usual gigantism and dwarfism that tends to happen in isolated environments](https://en.wikipedia.org/wiki/Foster%27s_rule).
* **Uninhabitable Temperatures** — You might need to create a permanent hurricane just to avoid cooking alive in 60° heat.
Below [10km altitude](https://en.wikipedia.org/wiki/Atmospheric_temperature), temperatures [apparently](https://www.engineeringtoolbox.com/air-altitude-temperature-d_461.html) increase by around 6.5°C for every kilometer downwards. If this trend continues below sea level, the lowest parts of the dry sea floor will be around 60°C (140°F).
To work around this, you could have very strong winds. The sharp walls of a cofferdam hold the promise of being able to create a permanent hurricane-style vortex— If the axis of this hurricane is vertical (I.E. it swirls around the center peak), then the winds could be used help animals cool off. If the axis of this hurricane is tangential to the surface (I.E. it swirls vertically up against the wall of the cofferdam), like in [Howard Taylor's Eina-Afa spaceship](https://www.schlockmercenary.com/2013-09-17), then it could serve to mix up air from hotter bottom and cooler upper atmosphere, keeping the temperature at the bottom reasonable. (Note that this would probably exacerbate the next problem of flooding, though.)
The very edges of the cofferdam will also be in shade a lot, which should reduce temperature immediately around them a a lot. But in other times of the day, they could potentially reflect extra sunlight onto the ground if they're a light colour.
Cloud cover would also provide shade, and a massive pressure and temperature gradient surrounded by ocean should have lots of chances to form it.
The ocean, as always, also holds a lot of promise as [a heat sink](https://www.sciencedaily.com/releases/2016/11/161122182458.htm). The best way to solve the potential temperature problem would probably be to ensure lots of heat transfer to and from the seas, by having strong winds and possibly building the cofferdam out of heat pipes lined with cooling fins or something.
Note that even if the temperatures do increase to 60°C in some places, Hawaii's already a diverse place with multiple biomes, and not all parts will have the same climate. The seas immediately around the islands are shallower, and should stay in the 30-40°C range even in this model.
If high temperatures do end up happening and remain unmitigated, they will obviously throw a spanner in the normal ecosystems that might otherwise be able to develop there. However, it's not quite the same as turning the entire region into a desert as it will probably have quite a bit of rainfall too.
* **Rainfall and Stability** — Draining the ocean means nothing if it fills itself right back up again. This place might have to become a desert, or be permanently filled with steam, just to stay dry.
Normal dry land isn't dry because it's been drained once. Normal dry land is dry because it's higher than sea level, so rainfall on it will flow right back down to the ocean.
That can't happen with your cofferdam country, so there will need to be some other mechanism to keep it dry. Either there are pumps, geothermal boilers, or other specialized mechanisms to actively remove water, or the rates of evaporation and rainfall are naturally equivalent to those of a desert.
[Some parts](https://en.wikipedia.org/wiki/Big_Bog,_Maui) of Hawaii apparently [already get quite a bit of rain](https://en.wikipedia.org/wiki/Climate_of_Hawaii#Precipitation). With the rapid changes in pressure and temperature caused by the cofferdam, [this could potentially get worse](https://en.wikipedia.org/wiki/Windward_and_leeward)— I don't think there would be basically any rain at all over most of the surface of the sea floor, where the higher pressure and temperature allow the air to hold an insane amount of water without it condensing, but the walls of the cofferdam and the slope of the central island and peak will probably form clouds from that moist air.
The Netherlands famously [have a lot of stuff built below sea level](https://en.wikipedia.org/wiki/Flood_control_in_the_Netherlands). They might be a good reference for how this kind of system could work.
* **Earthquakes** — Removing the weight of the ocean from the thin oceanic crust seems dangerous.
Hawaii [already gets thousands of earthquakes every year](https://www.usgs.gov/observatories/hawaiian-volcano-observatory/about-earthquakes-hawaii). The depth of the water you're removing is about the same as the thickness of [the ocean crust beneath it](https://en.wikipedia.org/wiki/Oceanic_crust), and rocks are only about 2-3 times as dense as water— In essence, you're basically stripping off a quarter of the weight of the entire surface of the Earth in that region, while doing nothing to reduces the forces of pressure and hydrostatic equilibrium that were holding up that weight before.
I would not be surprised to see the sea floor eventually rebound upwards. It would in theory have to rise by around two kilometers to make up for the lost weight of the water above it, so I'm going to say to expect up to a couple hundred meters of rise as a conservative estimate. And being made out of dense oceanic crust, it will likely do this in the violent, shaking sort of way that tends to bode poorly for large, rigid structures. Your cofferdam walls had better be built out of rubber, or something equally flexible.
* **Apocalyptic Worldwide Flooding** — All that water has to go somewhere.
A 200-mile radius volume 5 km deep is around 1,600,000 cubic *kilometers*. That doesn't account for the volume of the islands, but nor does it account for the length of the island chain, and 200 miles is the minimum radius that fits the query's description of "hundreds of miles away", so this is probably altogether a conservative estimate of the amount of water involved.
[Spread across the surface area](https://www.wolframalpha.com/input/?i=%28%28pi*%28200mi%29**2%29*5km%29%2F%280.7*4*pi*%286000km%29**2%29+in+meters) of the Earth's oceans, this will increase sea levels by at least 5 meters. Many major coastal cities are going to be flooded.
* [**HydroThermal Vents**](https://en.wikipedia.org/wiki/L%C5%8D%CA%BBihi_Seamount#Hydrothermal_vent_geochemistry) — There might be a completely unique biome. Or it might poison everything around it.
There's a couple of active hydrothermal vents around Hawaii. These [are a source of heat, and they regularly pump out chemicals that can be both nutritious and poisonous](https://www.sciencedirect.com/science/article/abs/pii/0198014989900654). I don't really know what would happen if you dried them out, and I don't suppose that's something that anyone's probably looked into too much. Maybe they'll become inactive without a source of water, maybe they'll behave the same as a normal volcanic feature on land, maybe they'll form a new type of biome around it not found anywhere else on Earth, or maybe they'll spew out so much gas that they'll fill the entire basin with poison (but probably not).
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* #### ***Flight?*** — **With great oxygen comes great power, with great pressure comes great density, and with great power and great atmospheric density comes FLIGHT!**
Pressure at the Earth's surface should be equal to the weight of the column of air above per area. Pressure below will be equal to that weight, plus the weight of any further air between sea level and the new surface.
However, the density of the air will also increase with each extra depth of pressure, which means the increase can't be modelled linearly.
Air weighs around 1.2kg/m³ at sea level, which translates to an instantaneous rate of increase in pressure per depth of 0.013kPa/m. That's (1.3/10000)/m relative to the sea level atmospheric pressure of around 100kPa, and they together map linearly to the increase of density (and thus rate of further pressure increase) further down, so I think that means I can model pressure below sea level as `100*1.00013**(depth/m) kPa`. That model gets me to a ballpark within the accuracy of the numbers I based it on when I test it with the height of mount Everest, so I'm going to assume it's good enough.
(Hawaii's small enough that I'm treating the volume of the rest of the atmosphere as infinite. Temperature and humidity aren't accounted for.)
That means that the air at the lowest parts of the ocean floor will have a pressure from 190kPa to 220kPa, about twice as high as at sea level.
It will have an effective oxygen concentration of 42%, and a density 2X that at sea level, with both more oxygen available for life and more mass for wings to push off of.
35% O2 was enough for dragonflies to grow to the size of eagles. 30% was enough for pterosaurs to grow to the size of school busses, with armoured skulls and wings that could take them across continents. And that was without any significant increase in atmospheric density.
**With 42% O2-equivalence, and air that's twice as thick? If you play your cards right, you're going to get** ***dragons.***
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**The geographical setting is a good kind of mysterious**
This reminds of Larry Niven’s Ringworld series, in that you have a cornucopia of plot mechanisms from the texture, terrain, and (possibly) crumbling “old but advanced” technology. I can’t help but wonder who built that there? And why? Are they returning, or are these “primitive humans” actually a logical consequence of advanced humans who have imploded? Great idea.
**The physics of a deep valley without water**
A quick look at Google Oceans shows Mauna Kea stretches down 6000 metres or almost 4 miles below sea level. You said the water is removed so we’re only dealing with atmospheric pressure here. This results in an atmospheric pressure of roughly double that at sea level, or about 28 psi. At this pressure water boils at 120 C. In other words not a huge difference if your settlers are using fire to cook rather than some remaining ‘ancient tech’ ovens.
**The ground is hot, but the floor isn’t lava**
According to the [British Geological Survey][1] if you were to drill 5000 m below sea level then you would find the ground temperatures hovering around 130 C or 266 F. Now this is technically open to air and not drilled so it may be a lot cooler due to the wind, rain and other elements. The ocean floor, however, is known for steaming, acidic, geothermal vents. I’d assume these remained and are still active. Active that is, unless the ancient tech is covering them to harness energy or just as safety valves. Such geysers could be useful or a danger to the society.
**The lay of the land**
It would probably look quite silty, like the ocean floor. So effectively it would be a giant beach surrounded by walls. There would probably be significant volcanic cliffs although Mauna Kea is dormant so I wouldn’t expect new lava.
**Flora and fauna**
Oof these folks would have a hard life with vegetation and farming. Although the Hawai’i islands are quite lush; many of the seeds of these plants can’t drift that far over the ocean to the next island. Except coconuts. So I’d expect palm trees and a society revolving around palm oil, coconut flesh, etc. Kind of like Easter Island. Even if other seeds did make it there, it’s anybody’s guess if they could set root in an ocean floor type of silt. Perhaps some sea kelp or amphibious plants could have adapted fast enough. For sure you’d see bacterial slime, algae, and mould like you do everywhere.
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**The dam**
Each island would get its own dam - it can best be placed on to of the Arch around the island, the dam will become a giant ring shaped structure extending 3500m to the bottom of the ocean and sticking out above the ocean, say 500-1000m, depending on safety regulations. See picture below.
Suppose mr Bezos and mr Musk are living on Hawaii and both are prepared to invest, total say 350B for the first part of the project (ca 30 years). At first it involves dumping gigatons (teratons?) of sand on the Arch, to reduce the ocean depth. The sand could be won on some nearby island groups, that will be evacuated as a result of climate change anyway. The sand from other islands will also be dumped on Hawaii itself, to prepare build the actual dam in concrete. After the first phase - Bezos long gone, there will be another billionaire sponsor - a metal mould is constructed (a cage) and remaining sand is used to fill the mould, so a concrete wall will be formed, with a pyramidal profile. On either side of the dam, at some point there will be ship elevator on either side, and a canal on top of the dam.
When the dam is finished, Hawaiians have gained 200% land.. you can live on top of the dam.. build harbours there.. Say the height of the dam needs to be 4 miles, ca 2 miles of that would be the concrete part.. the flattened pyramid profile of the concrete dam will be about 20-40 miles wide at the base, on top of the sand dropped on the Arch.. you need to wait ca 10 years before all that sand has stabilized. The structure would have a flat top of say, 5-10 miles, depending on calculations. As sea level is rising, the pressure of the surrounding ocean water will be enormous. A very rigid and strong ring dam is needed. People wouldn't be required to live down in the trough at all. The trough will remain water, at first.
As pointed out above, getting all water out of the trough would involve endless pumping.. and the result is not really a healthy environment. And also unsafe, because of the height difference and the pressure of the ocean outside the dam. The through needs to be filled up. This will be a project comparible to the dam itself, in size. Issue is.. how to get all that sand over the dam, inside the trough ? And the water should be moved *also*, in that scenario.. I regard this as an open end in my story, this submit is about the dam itself.
[](https://i.stack.imgur.com/B4uGA.jpg)
[](https://i.stack.imgur.com/nhRon.jpg)
<https://www.mbari.org/flexural-arch/>
<https://volcano.oregonstate.edu/hawaiian>
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I am going to posit a dissenting opinion.
If the wall/dam is built 200 km. from the coastal line of the islands, then a 6 km. high wall is going to be inconsequential to the 200 km. of new flat land. Methinks the other posters are thinking it would be like a canyon, perhaps like the Grand Canyon, very high walls in relation to the width. It would be exactly the opposite - a wide shallow (comparatively to the wall height) saucer. One would still get weather patterns in this basin. 400 km, from wall to wall is a substantial distance for winds to pick up and flow over the 6 km. high wall (think a four hour drive at 100 km. per hour). There would NOT be a stagnant layer of atmosphere captured within the 'valley'. The wind patterns, after all, have the entire Pacific Ocean to build up a good headway. A six km. drop over 400 km. would be hardly noticeable.
And with so much air flow, their would be no expectation for the surface to be hot, any more than there is an expectation for the surface to be hot ANYWHERE on Earth. It would not be insulated by a 6 km, thick layer of earth, such that the heat could not escape, but it would be exposed to air currents like any other land mass. Winds and rain would be constantly flowing over it.
The thing is, this 400 km. would be FLAT, according to Google maps. No mountain ranges except for the islands in the middle. I would expect the wind would scour it like the wind scours the prairies. There would be a constant replacement of the air, like any other prairie or desert area.
The land would also be extremely fertile, with abundant moisture. All of the existing sea life would have settled to the bottom as the water is pumped out. There is no where for it to go. There would be a thick layer of organic matter. I suspect plant and animal life would be plentiful. It would be an almost perfect growing environment, temperature wise.
With some clever landscaping, the wall/dam would look just like any other mountain range on earth surrounding a huge plane with a few other mountains at the center. Think Death Valley with a mountain in the middle, except with an abundance of water and lush vegetation.
**EDIT Addendum**
What's been stuck in my mind is WHY would anyone do this, what 'problem' is it the 'solution' to? I have come up with an answer.
For some story-related reason, the Earth's atmosphere has been partially blown away - say, a severe solar storm. Something that is allegedly happened on Mars. In order to save any semblance of normal living, a coffer dam is built around Hawaii, and perhaps several other areas of the oceans, such that the remaining atmosphere would concentrate in these 'saucers' sufficiently that the remaining air pressure would be around our current one atmosphere. It would explain why the residents do not try to venture out - the atmosphere density and pressure would not be viable for sustained living. Also, the radiation would be too high.
This also explains why the atmosphere density and pressure is 'normal' in the enclave. Climbing to the top of the mountains (what would be the current sea level) would be like climbing Mount Everest today. If the residents DID climb the mountain, they would obviously recognize that they were inside a coffer dam, and where the actual sea level was. The mountains are, in point of fact, higher than the sea level and higher than the coffer dam. From the top, one would definitely be able to view what was beyond the coffer dam.
This is covered by the request for a 'work-around to make it work'.
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Diseases kill people by messing up with some mechanism that is necessary for life. This generally means that they have a progression - for respiratory diseases, you will have difficulty breathing for a while; Gastroenteric diseases will give you diarrhea, acidic reflux or malnourishment; Neural diseases will deteriorate your mind or reduce your coordination and so on.
Even heart conditions usually have symptoms that could be described to or by a doctor - you will usually have abnormal blood pressure or chest pains way before having a heart attack.
What I'm looking for is a mechanism that preferrably a virus, but also a bacteria, fungus or other microbe could use that **would have no symptoms for weeks to months before causing sudden death**. The disease would be infectious and if any symptoms do manifest, it should happen no sooner than a few minutes before death. I am ok with the microbe being detectable with a simple, 20th century blood exam (let's say developed countries, circa the 1990's), but there should be no other way to find out if you have it before perishing to it.
Is such a disease realistic, and if it is, how would it most probably work?
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I did not initially mention this, but the mortality and lethality rates do not have to be 100%. It's ok to have people have the disease and never die, but those who do die should be asymptomatic until moments before their death.
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## Quite possible
To achieve this **drop dead** effect you need two factors: one is *insidious progression* of the disease and the second is an *acute shift against a vital organ*.
Insidious progression can be written off as a **latent, incubation period** of the pathogen with an unspecified threshold. Once reached, the acute shift occurs and well inevitably death follows. As a bonus I would have the virus shed during this entire period.
That is true for some *Herpes Zoster infections* for example. The virus can chronically infect nerves and manifest as the *Shingles* rash in presence of triggering factors.
So I would suggest that your pathogen **infect your target organ during the incubation/latent period** to explain the targeted acute shift.
Next, the organ choice should be made. Keep in mind how *flashy* you want the death sequence to be.
**A.** I would personally go for a **neurogenic shock caused by the virus destroying encephalic and spinal nerves**. Some protein, a **trigger** would set off the *bombs* the virus was preparing all this time, destroying the entire neural network of the host. I can picture parts of the network being cut sequentially with the host losing control of one body part at a time every few seconds or minutes to make it more graphical.
**B.** Another equally graphical approach would be to target the **heart**. In essence, as long as there destruction of myocardium (heart muscle) some things can happen:
1. Destroy a large enough part and the heart won't pump blood. The person faints, brain hypoxia follows and death.
2. Destroy part of the neural network of the heart. This would have to destroy a part to create a malignant heart rate that would speed up really fast (200-300+ beats) and then either stop or keep going. The death sequence is similar to 1, aka no blood is pumped.
3. Destroy many small tissue patches so that a malignant circuit is eventually formed, just like in a myocardial infarction. Make it so that a malignant rhythm develops and we're back to 1.
Another idea for this section is myocardial perforation.
**C.** Some other organs that would quickly lead to death if destroyed fast enough are:
1. Kidneys (25% of all blood goes through them every few minutes, bleeding to death is easy)
2. Lungs (hypoxia, simple and deadly or tension pneumothorax or bilateral pneumothorax, fancier and more graphical due to asphyxiation)
3. Large vessels: Aorta/Vena Cava (rupture them and death is guaranteed in mere minutes)
## A few considerations
From an evolutionary perspective, this seems rather improbable to occur because the pathogen could achieve absolute mortality once triggered, meaning it always kills its hosts. With no hosts, it won't be able to reproduce so its ultimate purpose is lost. *No pathogen aims for death, but reproduction.*
There should be cases where the pathogen is chronically infecting the host without it triggering a reaction. Also keep in mind that this pathogen would have to be able, to some extent, *mimic, trick or suppress the immune system*.
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# Totally realistic.
All you need is a disease (bacteria or virus or fungus or prion or parasite or... For convenience lets just call them "bugs")
that disables a vital life system of its victim.
There are many pathways this can occur:
* The bug excretes a toxin that weakens arterial walls. No symptoms until an artery ruptures, causing embolism or stroke or aneurysm.
* The bug proliferates throughout your nervous system, then only once fully established changes its diet and starts eating myelin, promptly paralyzing nerves. Including ones controlling autonomous functions like heatbeat.
* The bug has a cellwall that structurally resembles your neurotransmitters. As soon as you develop a real immune response to it, your immune system eats your own brain chemicals, shutting it down.
I'm sure there are *many* ways to kill the victim quickly and without obvious warning. The only real requirement is that the bug starts out being non-damaging, gains a solid foothold in the person, and then change mode to kill. This mode change could be as simple as a chemical trigger that each bug excretes. When the concentration in the blood reaches a suitable level, it triggers the change in the bug.
Such a bug is *very* believable. The only reason we are not swamped by such things is that it is a counter-evolutionary characteristic for the bug to have. Bugs use sick humans to reproduce and spread. If it kills its victim too quickly, then that bug fails to spread as widely as when it maintains a mobile but sick and infectious victim.
But remove the evolutionary aspect from its development, i.e. make the bug in a lab? Yes, that is very doable and realistic. You just need a lab that is suitably advanced, and an experimenter with a suitable lack of morals & common sense.
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[Rabies](https://en.wikipedia.org/wiki/Rabies) is very close to fitting the bill. You have no symptoms for 1-3 months after you catch it, and then you die within 3 days. The virus crosses the blood-brain barrier by traveling through your peripheral nerves to the central nervous system, which is what makes the incubation period so long.
So, the only difference is that it's 3 days from onset of symptoms, not minutes. Is it plausible we could have a strain that makes it minutes? I would guess so, why not? The only problem is that a few minutes is too little to transmit virus to someone, so, either the person has to become infectious while asymptomatic, or human-to-human transmission is not the main mechanism - e. g., you could have an animal host for which the disease behaves differently.
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Normally, the human retina contains four types of light-sensitive receptors (opsins): three types of cones and one type of rods. Receptors contain proteins-chromoproteins - iodopsin in rods, rhodopsin in cones. The role of the latter in bright light is insignificant, therefore for a person there are three "basic" colors: blue, red, green - all the shades we perceive are formed by their combinations. And what would the world look like if there were not three such colors, but four? (Tetrachromacy is the perception of the visible range of electromagnetic radiation by combinations of four primary colors. The eyes of tetrachromats contain four types of light receptors with different degrees of perception of different subranges of the visible spectrum) The painting "Rainbow Eucalyptus" by the Californian artist Conchetta Antico, who has functional tetrachromacy, makes it possible to appreciate the variety of colors, perceived by people with four-color vision. On the left, for comparison, is a photograph of the landscape shown in the painting.
Many insects, some fish, and most reptiles and birds have four-color vision. The extra pigments allow these animals to see in the ultraviolet range. In humans, tetrachromacy occurs only as a rare genetic abnormality. It does not affect the width of the perceived part of the spectrum, but it significantly increases the sensitivity to shades. However, by the standards of mammals, humans have excellent color vision: many mammals have two-color vision, if not even monochrome. This regression compared to the evolutionary precursors of reptiles was most likely associated with the nocturnal lifestyle of early mammals. In the dark, the effectiveness of color vision drops sharply, and the loss of two types of cones "went unnoticed." As a result, primitive animals retained only two types of receptors - red and ultraviolet. Later, when mammals "came to light" again, some groups were able to restore tricolor vision. For primates, many of whom feed on fruits, this vision is very useful: it allows you to detect brightly colored fruits among green foliage, as well as determine their ripeness. The receptor that perceives the green color arose as a result of a duplication of the “red receptor” gene and subsequent mutation, which shifted its sensitivity to the short-wave region. But the receptor for ultraviolet light for human ancestors has become useless: their lens does not transmit the corresponding wavelengths. But on the basis of this receptor, as a result of a series of mutations, a receptor for blue light arose. Such mutations, which alter the peak of the spectral sensitivity of photoreceptors, can also endow their carriers with four-color vision. However, much more often they make one or another iodopsin non-functional: as a result, dichromacy occurs - color blindness. The genes for "red" and "green" iodopsins are located on the X chromosome, which is present in two copies in the chromosome set of women and only one copy in men. That is why color blindness is predominantly a male ailment: in women, due to the presence of a "reserve" X chromosome, it develops extremely rarely. For the same reason, only women can become tetrachromats: this requires that one of the X chromosomes contains a normal copy of the gene, and the other contains a mutant gene encoding a protein with a shifted photosensitivity peak. Since each of the iodopsins makes it possible to differentiate about a hundred shades, a person with normal vision can potentially distinguish about a million color combinations. The addition of another type of receptor increases this number to one hundred million. Concetta Antico is a carrier of a mutation in the gene of "red" iodopsin, the sensitivity of which has shifted to the short-wave region. Special opportunities are best manifested when distinguishing between reddish-yellowish and violet shades: in the color scheme of her paintings, the emphasis is on these tones.
And here we return to my question: how much will the color perception of my genetically modified people change if I give more than four photoreceptors (5, 6, etc.)?
If the spectrum contains seven primary colors (red, orange, yellow, green, cyan, blue and violet), then if we add each photoreceptor to these colors, we will perceive many more shades?
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Color is a *sensation*. It exists in the *mind*. Color is *not* a physical quantity; it *does not* exist in nature.
A phrase such as "sunflowers are yellow" has meaning only for a normal-ish member of one species. It is meaningless to compare color perception between species with different visual receptors.
For example, here is one of a rather [famous series of paintings](https://en.wikipedia.org/wiki/Sunflowers_(Van_Gogh_series)) by [Vincent van Gogh](https://en.wikipedia.org/wiki/Vincent_van_Gogh):
[](https://commons.wikimedia.org/wiki/File:Vincent_van_Gogh_-_Sunflowers_-_VGM_F458.jpg)
Vincent van Gogh, *Sunflowers*, 1889. Photographic reproduction of a painting in the Amsterdam Van Gogh Museum; available [from Wikimedia](https://commons.wikimedia.org/wiki/File:Vincent_van_Gogh_-_Sunflowers_-_VGM_F458.jpg); public domain.
The sunflowers are yellow. The background is yellow. And yet, were one to examine the spectrum of the light emitted by the computer monitor displaying this picture, one would most likely notice the total absence of the wavelengths which produce the color yellow in a rainbow. Which brings about the first observation about color as perceived by humans:
For extended objects, i.e., objects which occupy a significant part of the visual field, color is determined by the power spectrum of the light emitted or reflected by those objects, but the relationship is not one-to-one. An infinite number of very different combinations of wavelengths can produce the same color. But, one specific wavelength *in isolation* will always produce one and only one color.
(For small objects, i.e., objects which cover only a small part of the visual field, there is no direct relationship between perceived color and the spectrum of light. The perception of color of small objects is a very complicated subject, as it depends enormously on the color of nearby objects; the human mind behaves *as if* it had some sort of "color sharpening" filter, which makes it impossible to predict the color perceived for small objects from the spectrum of light coming from those objects.)
For extended objects, the human mental system responsible for the perception of color behaves *as if* it had three inputs:
* A quantity called *luminosity*, which is roughly what is reproduced by a black-and-white photograph.
* A quantity on the axis yellow–blue with saturated yellow at one end, saturated blue at the other end, and completely unsaturated gray in the middle.
* A quantity on the axis red–green, with saturated red at one end, saturated green at the other end, and completely unsaturated gray in the middle.
(This is why we can imagine and understand reddish-yellow, yellowish-green, and greenish-blue, but we cannot imagine and cannot comprehend yellowish-blue or greenish-red.)
Note that I said *as if* it had three inputs. *Color is a sensation which exists in the mind.* It has no physical reality. Those *as if* signals do not exist as physical quantities anywhere in the physical realm; they are as metaphysical as the mind which perceives the color.
The good thing is, we *can* predict the color perceived by a "standard observer" given the power spectrum of the light emitted or reflected by an extended object. This allows us to design various schemes of color reproduction, which, within the limits inherent in every such scheme, allow for predictable color sensations in the mind of said standard observer.
But *only* in the mind of a standard observer.
The reproduction of Van Gogh's picture shown above looks very much like the original Van Gogh picture *when observed by a human standard observer*. It would look very different from the original Van Gogh picture when observed by an observer who is *not* a standard human observer. Such as a bird, or a bee, for example. For a human standard observer, the sunflowes in the reproduction are yellow. For a bird, or a bee, they would not have the same color as the sunflowers in the original painting; *what* color they would have we cannot say, because *it is meaningless to compare color perception between species with different visual receptors*.
When we say that a standard human observer is a trichromat, what we mean is that the standard observer can *color match* a given source of light by manipulating the intensity of three different monochromatic sources.
And here we come to the crux of the problem, namely the distinction between functional *physiological* tetrachromaticity and functional *mental* tetrachromaticity.
Since I cannot show colors as would be perceived by a hypothetical human with functional *mental* tetrachromaticity, we'll have to make do with ordinary trichromaticity.
Look at the photograph shown below, which depicts a display of colorful umbrellas, which at some point in the summer of 2020 graced AFI Palace, a large shopping mall in Bucharest.
[](https://www.flickr.com/photos/alexpanoiu/50576059106)
Colorful umbrellas, displayed at some time as a decorative element in AFI Palace, Bucharest. Own work, [available on Flickr](https://www.flickr.com/photos/alexpanoiu/50576059106) under the Creative Commons Attribution license.
On the left, the umbrellas as seen by a physiological and mental *di*chromat. In the middle, the umbrellas as seen by a physiological *tri*chromat whose mind is still operating in *di*chromat mode. On the right, the image as seen by a physiological and mental *tri*chromat.
* Looking at the image as perceived by a physiological and mental *di*chromat, we notice that what we see as red, orange and yellow umbrellas are all equally red; and green umbrellas are indistinguishable from the lavender ones.
* Looking at the image as perceived by a physiological *tri*chromat whose mind still works in *di*chromat mode, we notice that the red, orange and yellow umbrellas are now perceived as *different shades* of red, and green umbrellas begin to be distinguishable from the lavender ones.
* And finally, the image perceived by a functional physiological *and* mental trichromat contains color which the dichromatic mind could not even imagine.
Which concludes the experimental part of the answer; based on which I can confidently say that:
* A human possessing full physiological *and* mental tetrachromaticity would see the world *in a very different* way from what is seen by the ordinary human trichromatic standard observer.
* The differences would be dramatic, with objects which appear of the same color to a standard trichromatic observer gaining strikingly different colors for the hypothetical human physiological *and* mental tetrachromat.
* Our trichromatic mind cannot even imagine the colors seen by a fully functional physiological *and* mental tetrachromat.
* On the other hand, a human observer who is a functional *physiological* tetrachromat, but whose mind operates the same as the usual human standard trichromatic observer, will see the same colors we ordinary humans see, but they will be able to distinguish between objects which appear of the same color to us.
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There is essentially no limit to how many colors you could perceive by adding more kinds of photoreceptor.
Say for argument's sake that we can perceive ten different levels of intensity in each waveband; then with three primary colors, you can see a thousand (10x10x10) distinct colors. Suppose that you add a third primary color, say a "yellow" wavelength between green and red. You would now be able to see ten thousand distinct colors.
But it is important to be clear that this is not simply about being able to resolve more in-between shades; with four primary colors, you will perceive differences between things that are *exactly the same color* to other people. In other words, you will see entirely new colors.
So, as you increase the number of photoreceptors, you exponentially increase the number of colors there are to distinguish between. If you have a hundred different photoreceptors, your eyes are basically spectrometers, and every molecule has its own entirely unique color (somewhat like how smell works).
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There are documented cases of (very) rare individuals who can just see into the near/lower ultraviolet (blue end of the spectrum) and therefore perceive 'colors' differently to the rest of humanity. So if the genetics involved was characterized and copied I suppose people could be engineered with that characteristic. Beyond that?
Other frequencies? would require a total reorganization/restructuring of the human eye and brain or more likely multiple sets of 'eyes' designed each designed to detect a different part of the spectrum.
It should also be remembered that evolution has adapted our eyes (and other creatures) to take maximum advantage of the light frequencies hitting the Earth **at ground level**. That's about 44% of the relevant output, with that output trailing off (again as a % of the total) at the higher and lower edges of the spectrum. So we already *see* a large chunk of the useful energy being emitted.
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Stories like The Expanse sometimes depict building colonies places like Ganymede. There's good reason to do so, but one thing has always nagged at me; how would the icy crust respond? Ganymede, Callisto and the like are all so cold that the ice in the surface is a different type of ice crystal, one hard as rock. Not only would losing heat to the surface be a big energy drain, but if the ice warms up enough, its crystalline structure would change, possibly to the point of cracking, wouldn't it?
How much insulation would you need to build on that without causing issues? Would a typical home's insulation thickness of aerogel do the trick, or would the layer need to be quite beefy? This is not just important to note for a dome colony on the surface, but varied tunnels will need this too.
Maybe I'm overthinking this, but I've never seen this addressed before.
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**Buildings on Ganymede would not be like buildings on Earth.**
The difference is that Earth has an atmosphere. That fact leads to 2 differences relevant to building.
* Weather. Earth buildings must resist being blown away. That is not an issue on Ganymede. A building on Ganymede does not need to be firmly anchored to substrate in the way an Earth building must.
* Heat loss. There are 3 main methods of heat transfer: [convection, conduction and radiation](https://www.machinedesign.com/learning-resources/whats-the-difference-between/document/21834474/whats-the-difference-between-conduction-convection-and-radiation).
Convection is transfer of heat via movement of heated gases. That is a huge issue on Earth because there is always a huge mass of gas outside trying to equilibrate in temperature with the building. On Ganymede there is not. Outside, there is nowhere for heat to go.
Conduction is direct transfer between apposing solids - like a frying pan and a egg. Conduction is relevant on Ganymede but only where the building touches the ice. If it barely touches and only thru thermally nonconductive supports, conduction losses are minimal.
Radiation. Hot things radiate heat. Compared to the above 2, infrared radiation into space would be minimal. You could insulate the building. You have access to the best insulator there is: vacuum.
Ganymede buildings would sit on thermally nonconductive stilts to minimize contact with the ice. The stilts could be changed out if the ice moved or otherwise shifted around them. I like the idea of watching for stilt shifts with spirit levels attached to the building frame. You could jack up the building, put some new stilts underneath or reposition old ones, and settle it back down.
Ganymede buildings would be insulated against radiant losses by an insulating layer of vacuum between outer shell and building outside. Another way to affect radiant loss is to maximize radiant gains. Ganymede buildings would be matte black.
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For any thermal insulation at equilibrium, if you plot the temperature vs the depth of the insulation you will see that the closer to the outside, the closer is the temperature to the outside temperature and vice versa, the close to the inside, the closer the temperature to the inside temperature.
This is why if you wear a coat outside when it's snowing, you will see that snow will deposit on it and won't melt until you go inside.
What the insulation really does is reducing the heat flow from the hot environment to the cold environment. Since we are talking about temperatures well below those encountered on Earth, also the insulation will be nothing that we have seen on Earth: some 10 cms of rock-wool or PS on a frozen planet would be like wearing a T-shirt outside the Overlook Hotel when Jack is visiting the maze for the last time.
The real structure of the insulation depends on a lot of factors, including properties of the available materials, available heat source, economic and engineering constrains.
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Ganymede is 150km of ice, then 100km of salt water, the more ice, then rock, then a core of liquid iron. <https://en.wikipedia.org/wiki/Ganymede_(moon)>
This isn't a dead world that we could inadvertently heat up. It's molten iron that has a nice insulting blanket consisting of more water than we have of Earth, frozen under a vertical stack of 75 Antarcticas.
[](https://i.stack.imgur.com/4vZJd.png)
The ice under the [Australian Antarctic research station is 2.16km](https://www.antarctica.gov.au/about-antarctica/ice-and-atmosphere/sea-ice/ice-sheet/), and our settlement hasn't melted its way through that. A 150km ice sheet wouldn't fail because of lost heat from the settlement.
Your insulation needs to be thick enough to optimise your heating - a design similar to what we're doing in Antarctica will reduce power usage and minimise the heat lost into the ice.
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Scifi describes the Mars horizon as closer than on Earth since Mars is smaller. On Earth at sea we can watch sailboats gradually drop behind the horizon. The horizon also appears to us quite clearly because it is not far enough for the atmosphere to mask it (but for bad weather). How would the horizon appear to us on a much larger Earth-like planet endowed with a similar atmosphere (in clear weather)? (This might be a theoretical impossibility considering the mass of a larger Earth and the gaseous composition of ours.) Objects would gradually recede and fade away behind the atmosphere, without neatly dropping out of sight. The horizon itself would be blurry or invisible so that we could not ever neatly distinguish Earth from sky. This might induce psychological/cultural effects in human-like observers. Are there visual depictions of and/or fiction about such a scenario?
EDIT: As suggested, I guess a sufficiently large planet would be indistinguishable from a sufficiently broad flat Earth, from the observer's perspective. I'm trying to get a more visceral, and if possible visual, feel for what such an experience would be. The referenced prior question is more about long lines of sight to singular objects on our Earth, that is almost the opposite of a broad sweeping vista of a planet's surface fading out toward an infinitely distant horizon. I don't know how to put it better than this although I realize it may not fulfill whatever criteria you have around here for well worded questions.
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**This isn't as hard as people are making it**
The perceptual effect of the arc would become less distinctive, but still be there.
1. Let's ignore atmosphere for a moment. We have an airless rock in space, plenty of light, a great telescope... what happens? The smaller the diameter of the planet the more noticeable that arc is. In other words, the smaller the diameter, the easier it is to see the gradual process of the "ship" (ok "land rover") sinking out of sight. As the diameter increases, that effect is less distinguishable (you can think of it as "there's not enough resolution to easily see the gradual sinking-out-of-sight effect), but it still happens. As the diameter increases, it will appear more and more like the land rover just *pops!* out of sight. If I'm making any sense, the effect becomes more and more *sudden* as the diameter increases because it's harder to perceive the arc in relation to the distance you're looking through.
2. Compare this to an actual flat surface where you *never* see the land rover sink out of sight. It gets smaller with distance, but so long as you use ever-better telescopes, you can see it forever. No matter how large the planet is, there will always come a moment (despite needing a honking powerful telescope) when you can't see the land rover any more.1
So... big planet, harder to see the effect... *pop!* and it's out of sight. Note that if you had a telescope with the ability to clearly observe an object at any distance, you'd still clearly see the sinking-out-of-sight effect... the problem is that the human eye itself just ain't that good.
3. Now, let's add atmosphere. For the sake of argument, let's say that no matter the diameter of the planet (or its gravity), the atmosphere density is always the same as we experience here on Earth. What happens then? As diameter increases the ability to see clearly through all that atmosphere decreases, so you're right about that. Given a large enough planet you won't see the effect at all. You'll lose sight of the land rover (ok, now it can be a ship on an ocean!) before the effect occurs due to atmospheric density.
But there are some other problems, too.
* We humans sometimes forget that light passing through a gas causes grief. That's because we evolved/grew-up in it, and so we "see" perfectly fine for the distances we generally care about. It doesn't help that when we use satellites, they take pretty clear pictures (when there aren't clouds...), but they're looking through the thinnest layer of atmosphere (perpendicular to the surface). [Rayleigh scattering](https://en.wikipedia.org/wiki/Rayleigh_scattering) is what you get when light passes through a gas — and it's what makes the sky look blue. The more atmosphere you must look through, the worse that scattering gets in the way of what you're trying to see. It's basically the reason terrestrial observatories are put on mountains or a long way from any city — because the "light pollution" (local rayleigh scattering) gets in the way of a clear image.
* Also, let's not forget gravity. We sometimes read about giant mega Earths in the news, but the problem is that nothing's free. You can reduce the planetary density only so much. From a practical perspective, as diameter increases, so does gravity. Gravity is the one thing we know of that can bend light in a homogeneous medium. Light refracts ("bends" for lack of a better word) when it passes from one medium, like air, to another, like water... that's not what we're talking about. Gravity actually causes the path of photons to arc, not unlike a bullet dropping to the ground after being fired. So, as the diameter of your planet increases, so does the fact that the light's bending ever-so-gently, which can contribute to not clearly seeing the sinking-out-of-sight effect.
**TL;DR**
As the 13th century friar William of Ockham once suggested (in a much lengthier treatiese), all other things being equal, the simplest answer is usually correct. As the diameter of a planet increases, the sinking-out-of-sight effect can still be seen — it just gets harder to see.
As for what the horizon, itself, would look like (your title question)? It would look like what it looks like now, a basically flat line, only more so and harder to see. But it would still be there.
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1 *And this is the point the flat-earthers don't get or refuse to understand. From the top of the Rockies I should be able to see the Himalayas... but I can't. And the pesky interference of atmosphere isn't the reason why. Oh well, at least they're fun to argue with.*
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The thing about Earth like atmospheres is that there is no hard answer to this because there is no constant for vapor/aerosol content. Depending on what is in the air at any given time your meteorological optical range (MOR) could be anywhere from less than 1 meter to about 240km.
Then there is the second variable which is that the distance to horizon is based on how high your point of observation is. This is found using the formula **d = R\*arccos(R/(R+h))** where d = distance to horizon, R = planetary Radius, and h = height of the observer.
For purposes of your question, I will assume you want a planet where the horizon is never visible on a perfectly clear day when you have a MOR of 240km for a person of average height (1.7m) standing on ground that is perfectly level relative to the planet's center of gravity.
For this you need a world with a radius of about 17,000,000km
**To find out if this is possible, we must now look at how big your planet can be.**
In [this related question](https://worldbuilding.stackexchange.com/a/184115/57832), I answered the question that the maximum size a naturally forming 1G planet could theoretically be is somewhere on the order of a radius of 70,000km (140,000km across) assuming you have a planetary structure similar to Hyperion. This is probably an over estimation since Hyperion is probably made of highly porous ice that would compact under its own gravity at that scale. A fully compacted ice world would have a radius of 35,000km; so, the size of a world you can stand on probably tops out somewhere in that range.
You could try playing with planets of much higher gravities, but this tends to also affect the way atmospheres are compressed against the surface; so, it would not really be an Earth like atmosphere any more. Gravity and pressure would also crush your observer long before you could get to that radius; so, this does not seem like a viable solution.
Instead the most Earth like you could get the atmosphere is to leave the light gases alone and just add more vapors/aerosols. Infact, Earth's actual average MOR is only 30km, way less than an ideal maximum; so, if you were to take a 140,000 km wide icy world with an Earth like atmosphere and add just a bit of extra vapors/aerosols to the atmosphere. You could further reduce the MOR to never exceed 15.5km in which case you would never see the horizon line... or you could keep a rocky Earth like world and reduce the max MOR to 4.7km. Either way, Earth experiences these levels of light scattering all the time under normal conditions; so, making an Earth like world that does this on the norm could still be in every way human habitable. For example, [Cloud Forests](https://en.wikipedia.org/wiki/Cloud_forest) here on Earth never approach enough visibility to see the horizon (even if those darn trees were not in the way).
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I will dive into the psychological side of the problem. Take it with a grain of salt, as we don't have enough experience especially with far horizons.
**Close horizons**
The horizon on the Moon feels unnervingly close. Visually, the horizon is as close to you on Earth only if you are climbing a hill or you find yourself at a bottom of a mild pit. That's what it probably (I haven't been there myself) feels like to look at the horizon on the Moon: You are always surrounded by non-existent hills blocking your view. Look how anticlimactic it feels [when the astronauts finally get on top of a real hill on the Moon](https://www.youtube.com/watch?v=bTQ-SmeLTl8).
With Mars, it's similar, although less noticeable than on the Moon. The horizon is unnaturally close.
Because we are programmed by evolution to like great views (you see enemies and predators from far away), this might actually be a big problem for the psychological health of the future inhabitants of Mars and the Moon.
**Far horizons**
Now, what would the horizon look like on a livable big planet (let's say Jack Vance's Big Planet)? We can describe it mathematically, but can only guess psychologically. My educated assumption is that the feeling will be similar to looking from a hill down to a valley. If the weather is good, the view will always be as magnificient as a view from a hilltop, even if you find yourself on a vast flat surface.
As mentioned, because we are programmed to enjoy those views, living on such a planet might be exhilarating, at least if there are interesting objects to see around and until the brains of the colonists get used to the effect.
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I'm designing a sci-fi videogame.
But I've many doubts about the hierarchical structure.
On a ship "the captain" is the highest authority, directs, coordinates and controls all activities, responsible for everything and is the representative of the crew.
On an interstellar journey, using a generational ship (journey of many generations) and considering that:
- The initial crew could be 60,000 people.
- The crew becomes a reflection of a society in a closed ecosystem.
In this scenario the figure of the captain is lost since we would speak of an authoritarian government, a dictatorship.
What system of government would be the most suitable for a
generational type ship
( Parliamentary, federal republic, representative democracy, athenian democracy [updated] ...)? What powers would exist?
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Why stick to old system of government? The journey is going to start in the distant future (considering we are nowhere near achieving building a generation ship and plan an interstellar voyage). So you had better start thinking of how future technology will likely alter society.
1) the rise of AI: AIs of all kinds will most likely be the best managers. They will be able to choose the best option to reach the goal set by humans (supposing they are built not to consider humans as a hindrance / nuisance / pest to deal with)
No need for a captain. An AI or a system of linked AIs will manage the ship to make sure it reaches its destination with the crew in good condition and with adequate sharing of the necessarily limited resources. Interactions with humans will stil happen both to perform necessary actions and to review mission goals if necessary (maybe not the primary as it would be unlikely the ship would be able to travel to a different destination but secondary goals along the voyage may need to be reviewed / added).
2) Brain-computer interface (BCI): humans onboard will have cerebral implants to connect with the AI and basically any device. Same will happen on Earth (at least to the higher classes of the population). Incapability of direct link with AI and devices would mean to be slower by orders of magnitude. This means that optimum decisions can be made FAST by invested officials in union with the AI. It would not be quite like a hive mind as each individual retains high capacity of complex analysis.
You can decide to what degree others can access an individual's mind as this would most probably be dictated by the kind of government on Earth that develops the generation ship.
A totalitarian government may want to go for 100% access from outside. Any unsocial thought would be immediately found and weeded out (not necessarily in a violent way).
A democracy based on strong human rights may limit access strictly. Yet there may be reasons for some access. For instance access to individual memories may lead to better interfacing. This may be done by a middleware AI that does not share said memories to the more general AI system.
TL;DR: AI and mind linking will shape the future. Figures like 'the captain', 'the mayor', etc. will be unnecessary.
Instead go for circles of technicians working together with the AI system to do the overall management (resources distribution, ship maintenance, scientific research, etc). With an upper circle supervising it all.
I don't know how well this would work in your videogame but it's an idea worth exploring.
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## A generation ship must not have a "government"
Or at-least not in the normal sense. In a nation, economies change all the time and you need legislators to come up with new rules and regulations to handle growth and changing times, but on a generation ship, there are no new industries, economic recessions, or wars to fight. Just by opening up the possibility for allowing "times to change" would guarantee the failure of the mission
Your ship only has the supplies to get from point A to point B if it adheres to the plan that was laid out when then mission began. If the first generation follows the plan and rations appropriately, and then the second generation decides they would have better lives by changing how they ration things, then the last generation would not have enough resources to survive off of and the mission would fail.
Instead, what a generation ship needs is a constitution. A formal immutable doctrine that must be enforced until they reach their destination. They will have a police force and judicial system to enforce the laws set forth by the constitution, but there would be no king or congress to change the rules.
The only duties of leadership this leaves left are those which are expected of normal naval officers. People to assign jobs to crewmen, people to monitor navigational equipment, etc. But even these needs would be very minimal since the ship is not constantly changing courses and stopping at ports like a normal ship would. Changes in crew assignments or needs to plot out new courses would be exceptionally rare in the grand scheme of things.
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If Earth invested heavily in this generation ship, they may have a stake in its leadership and success. Otherwise if they vote for a idiot and the idiot captain blow the ship up, that is their problem.
If earth has communications, it may employ and appoint people from the population into key positions in the crew or government. Or issues can be appealed to an earth authority (like with courts).
If this is the case, you earth appointed ships crew for ship control; and democracy for community issues (when does the bar close, accommodation allotment). Hierarchy of courts that reach back to earth for review.
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I think that pirates are a good source of inspiration for a big reason. Pirates have elected captains [because the ship is entirely owned by those who sail on it.](https://www.youtube.com/watch?v=T0fAznO1wA8) Merchant and naval captains have to be loyal to a higher authority, while pirates only have to be loyal to their own crew. This would obviously also apply to a generation ship. Also, it's not relevant to this question, but the reason that pirates are successful is [branding](https://www.youtube.com/watch?v=3YFeE1eDlD0).
Also, on a pirate ship, the quartermaster was actually in charge outside of tactical situations. Such a structure would be just as likely here for the same reason, as while the Captain would take charge of emergency situations and serve as the official political leader, the quartermaster is the one who decides how their limited resources are distributed and enforces contract disputes between crew members.
However, one issue is that unlike pirates, crew members who are upset can't just leave. To this end there would have to be a political system in which change can occur and grievances can be heard as desired.
Using this as an inspiration, I think elected officers makes a great deal of sense. Outside of emergency situations, free elections could be held quite easily. I think it would be interesting to have a semi-parlimentary system in which the captain and quartermaster are elected by parliment and can be removed by them at any time. MPs are elected by various sections of the ship by population, with other representitives for different parts of the crew like the engineering officers having their own MP, the agricultural officers having their own MP, and so on. Elections for officer status might also require experience as part of the crew in different departments to ensure that those in charge understand how the system works.
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# Why is the Captain's word absolute?
The tradition that a Captain's word is supreme on his ship is a naval tradition. It is weird. I was never in the navy, but it was explained to me like this: because the ship is an island unto itself, cut off from everyone and anything for vast stretches of time, the Captain's word *needs* to be final. Things simply do not work otherwise.
It is the Captain's job to interpret orders from higher command they receive, and to carry them out. Nobody else on the ship questions the Captain. Indeed, if the Captain disobeys orders from Navy Command, it is not the job of anyone on the ship to remove them. They will be removed the next time they make landfall, and a new Captain will be installed.
This is true even if a higher authority is already on the ship. Technically an Admiral cannot overrule a captain on the captain's own ship. The Admiral could fire said captain, and attempt to install a new one. I am told that any such attempt would run into a practical problem that said Admiral would have difficulty finding an officer willing to play along.
# Implications for generation ships
These concerns will be far *more* pressing for a generation ship. Generation ships will not be able to maintain radio contact for very long. Relatively quickly they will be out of range. After a few last dumps of mail (light lag means conversations won't really be possible anymore) the generation ship forever loses all contact with its parent culture. It will be alone forevermore.
The Ark theoretically could fire probes back Homeward with ship's logs and status updates; but nothing from Home will have any realistic chance of intercepting the Ark. This is likely a fools' errand anyway: generation ships are fire-and-forget. Fuel and materials spent on such probes is a waste of good resources (which will be tight).
For all intents and purposes, there is no longer any higher authority. And there will be constant threats to the life and safety of everyone on board. Things will constantly be breaking down. Naval vessels can pop into drydock when they need to perform major repairs. Generation ships have no such capability.
# A generation ship will be a maintenance and logistical nightmare
Generation ships will need to have components with a very long lifespan. They will also need the ability to manufacture new components. And things will constantly break down anyway. An army of support staff will be required to keep everything running. This staff will need to be replaced with new staff.
The logistics of keeping everyone well supplied will be equally challenging. You have what you have, and that's that. If something isn't already on board, you either make it or you do without. And no matter how well you plan, there will never be enough. People will like that just as well as they like it here on Earth.
# A revolution probably results in catastrophic mission failure
Order must be maintained on the vessel, at all costs. One person going postal on a generation ship can sabotage key equipment in a way that can't be quickly repaired (or possibly even repaired at all) and the mission is fucked. Possibly life support is also fucked, and then everybody dies.
One way a revolution succeeds is by causing trouble (or exacerbating existing trouble). Then you just watch the resulting firestorm bring down the old regime, and waltz in and take over. That's bad. A violent takeover is also bad, because of the high likelihood of damaging the ship or killing the only people who know how to fix the ship.
# Military discipline keeps the ship together
For all the same reasons military discipline keeps things running smoothly in other contexts. This forms a [stratocracy](https://en.wikipedia.org/wiki/Stratocracy) with the Captain as monarch. The ship is its own sovereign nation; its political development can be guided by the Founding Builders, but they will ultimately be responsible for its development.
# No nation has ever been stable long enough
World history reveals that literally no country has ever been recorded to survive longer than several hundred years or so without some kind of civil unrest. Some parts of the world have yet-uncontacted tribes mostly left to their own devices; they might have been around longer. But nothing large enough to be called a nation has been static for that long.
And that's a problem, because a generation ship is a small nation. I really don't see any way around this other than military discipline.
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Go with a company style organization. Everyone on the ship is 'shareholder' and is represented by a 'Board' who meet as regularly as is required to deal with ongoing planning issues and problems.
As CEO of the 'company' the Captain has complete control of day to day operations of the company's assets i.e the ship. The Captain reports to the Board at regular intervals to discuss progress/concerns. His 'term in office' is a pre-agreed length of time or an age limit. Replacements for senior officers are selected from the available talent pool after intensive AI assisted training and phych profiling.
Assuming this is not a rushed/last minute/emergency expedition the ships mission parameters will have been planned out well in advance which means lots of time for pre-launch simulations that 'game out' a full range of possible scenarios that might bring the shareholders/board/senior officers into conflict. These are all documented in 'the book' which sets out rules as to who can do what and when in each situation.
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A generation ship is essentially equivalent to a portable planet, given that it is big enough. Plants can grow using light from stars and asteroids can provide necessary resources. 60,000 people are enough to have jobs beyond essential services. With current technology, your ship needs only 400 farmers, a few hundred people to operate mining robots, 250 electricians, and 12,000 factory workers. That leaves plenty of room for other jobs. As a result, you could have any form of government that exists on Earth, preferably a democracy.
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You might be looking for a **constitutional monarchy**.
Basically a system where one person holds the power but is bound by constitution or convention to act in accordance with a parliamental structure, unless there is a strong reason against it, such as emergencies. There are some real world examples out there - Monaco and Liechtenstein might be of particular interest since they have approximately the same population size as your ship.
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I propose the *benevolent government* of:
## Big Brother
Big Brother watches for you. Big brother is not a single person, he is the product of the PR group which gives the inhabitants of the ship a common figure to unite behind... and offers relief of pent up hate and aggression through the method of projecting all the aspects that can be hated, all the treason and all the bad aspects upon the world left behind and *subversive* groups that try to re-establish this world of debauchery, of boundless consuming and destroying the earth. In effect, this generation ship is in a permanent state of rewriting its own history and keeps its inhabitants in constant fear of the *recreationists* and *hedonists* so that one could say this dystopian spaceship is in an almost war-like state all the time. Work is thrown into fortifying the ship and producing and maintaining the machinery that serves no other purpose than to wage war on *waste and hedonism*.
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I'm at the very early world building for a potential story where I have a sort of humanoid feline species that I need to have been known as expansionist and/or war-like in the past but not be aggressive in the world's present.
I'm toying with the idea that the species has regular heat cycles, which were strong enough to make it hard for a female to resist reproducing. Once society and technology developed enough that infant mortality had dropped the inability to resist reproducing started to lead to difficulty with over population. Thus the species ended up being involved in a number of expansionist campaigns trying to grab up enough territory to support their rapidly growing population, and of course the war's themselves helped to 'thin out' the excess population by removing a decent number of the young males. The species eventually discovered a way to produce a heat suppressant that is now commonly used to prevent heat, so the 'modern day' species no longer struggles from excess population and without that issue no longer needs to expand.
I'm trying to determine what the introduction of such strong heat cycles may do to the species as a whole, both in the past and in modern culture influenced by the past struggle with heat cycles. How would a culture adapt to the recognized issue that excess reproduction caused by regular heat cycles would often strain the nations ability to support it's population? Obviously I intend for expansionist conflicts to be one result, but what other impacts would there be? During times of peace, between wars, what would the species do, both on an individual level and on a governmental level, to deal with the risk of over population? Are there any implication to how this would affect more modern culture of the species?
The time during which over population was an issue would have a roughly Tolkien Lord of the rings feel, both in terms of technology and how the various species interacted with each other. Magic does exist in this world, but is relatively limited and is unlikely to provide a solution for over population.
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**Your species would likely have an easier time dealing with overpopulation issues than humanity**
Humans are unusual among animals in that they have a combination of two physiological traits which by themselves already are uncommon among animals.
* **[Concealed ovulation](https://en.wikipedia.org/wiki/Concealed_ovulation)**: Human females do not produce any visible signals of high fertility or ovulation. In most animals, females produce very visible signs that they are close to ovulating to advertise to males that they are the best choice of mate because they are most likely to bear offspring. In extreme cases you have things such as the sexual swellings of baboons and many primates, but the ovulation of most species can be easily detected by things such as the scent of certain hormones in the urine. Humans don't, and this has been suggested to be a feature, not a bug, because it encourages males to stay around females and assist in the care of offspring (which increases survivorship in such a K-selected species as humans). For all the studies of humans suggesting that exposure to pheromones put out during ovulation might *subconsciously* affect human behavior, there is no evidence that humans can *consciously* detect if another human is ovulating and modify their behavior accordingly.
* **Lack of a constrained mating season**: Unlike most animals, humans do not have a strict timetable for breeding. Humans may be more likely to breed at certain periods of time, but our species has sex throughout the year as can be evidenced by the fact that birthdays span all 12 months. So it is not like other species where desire to mate peaks in a set period during the year and then dwindles to nothing later.
**The combination of these two features makes human reproduction in general a Russian roulette among animals.** Whenever humans mate, we have no way of knowing whether it will result in pregnancy or not because there is no set season when humans are fertile and there is no way of knowing whether the female is at peak fertility. Women often track their ovulation cycles to avoid peak fertility, but the fact they have to chart it and can't just tell they are fertile demonstrates how hard it is to keep track of these things.
This is how you get things like teen pregnancies, unplanned babies, and a huge market for contraceptives in humans. Our breeding system is extremely chaotic and hard to control or plan for. If human beings had a visible estrus cycle or a set breeding season population control would be exceedingly simple, just don't have sex during the extremely forecasted breeding season. Even if the females had a hard time controlling a desire to mate during the breeding season, males would be able to easily determine whether or not they wanted offspring by taking one look at the female and going "*this female is in heat. I do not want/cannot support a child right now, so I'll just wait the few weeks until she is out of heat and there is no risk of producing a child*". **If human reproduction were as predictable as your species we wouldn't be in an overpopulation crisis right now.**
If you want there to be an overpopulation crisis but keep the distinct heat season, **the best way to do it is to have severe negative side effect for not reproducing during the breeding season**. This exists in nature. [Female ferrets will get very sick if they do not mate during the breeding season, and this cannot be cured except by having sex](https://hayvets.co.uk/is-it-true-that-ferrets-get-ill-if-they-dont-have-sex/). The rump of baboons swells during estrous, and there is evidence that in addition to individual genetics the degree of swelling is correlated to how long they have gone without mating. If they don't mate the swellings get worse and worse until they negatively affect the health of the female.
Of course, the question then becomes why doesn't the species, if they are sapient, just invent methods of contraception early given how big of an issue controlling reproduction is for their society. To go back to the ferret example, it is the *act* of mating that resolves the sickness, so male ferrets with vasectomies work just fine. Things like this (or less extreme forms of barrier or hormonal contraceptives) would probably work in other species with similar mating habits. This is the kind of species that would invent the morning-after pill before the printing press.
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**Humans also struggle with a hard-to-control urge to reproduce.**
<https://en.wikipedia.org/wiki/Birth_control>
And not just sometimes. Having children is a biological imperative and also makes economic sense in many situations. Entire disciplines could be dedicated to the topic. My summary:
1. Decrease infant mortality. You do not need to get pregnant over and over to have 1 child who will support you in your old age.
2. Long term economic viability of the family less dependent on numbers. If your subsistence farm (or whatever cat people have) works just as well with 5 family members as with 25, you will go with 5 all other things being equal. Improved food production tech can help with this.
3. Social safety net. You do not need loads of kids to support you in your old age because the state will help.
4. Put reproduction under intelligent control. Females choose when they get pregnant, both as regards biology and reproductive hormones as well as sociology and the right to choose when they copulate.
5. Educate the citizenry about how pregnancy occurs, and various ways it can be avoided. Still a controversial subject in the US.
6. Additional measure: the state could disincentivize excess offspring. The Chinese are the model for this with their one child per couple policy. There are other ways this could go too.
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a state backed contraceptive campaign should do nicely. or have contraceptives be mandatory by law once an individual of this species reaches a certain age.
the solutions to this problem are very simple.
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If chemical or barrier contraceptives are not readily available...
Infanticide, and/or abortion. It's not nice, but infanticide does solve the problem, and has been practiced by humans.
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Suppose we have a fictional water planet. Humans have discovered interstellar travel and have colonized the planet. They live in large underwater cities. Its oceans are under high pressure, say perhaps ranging from 1000 psi to pressure similar or even higher than at the bottom of the Mariana trench (some 16,000 psi). There are hostile animals on this planet that are pretty effective at attacking submarines and humans and are durable. Humans would have advanced technology and weaponry such as practical railguns and coilguns.
**So my question is, how would weaponry and submarine technology look like on this planet?**
**Further Elaboration:** Would the submarines be similar to today's deeps sea submarines? And for the weaponry side of the question, would it be feasible for people to be in suits at lower depths? And would handheld underwater firearms be even feasible, or would humans be staying inside their cities and submarines all the time? If underwater firearms and such are practical, how would they look or function at such high pressures?
**Extra information on the world in question in case it matters:**
The planet's surface is 78% water, it has two moons which create kilometer-high waves and turbulent seas. Land on the surface consists of a few small continents and thousands of islands ranging in size from a few hundred kilometers to a kilometer or two. The islands and continents on the surface are also barren, being little more than resource-empty rocks, and humans decided that it wasn't worth settling on any of the islands. The surface is practically inhospitable due to these conditions, and is all but uninhabited except for a station for spacecraft to land and take off. However, under the water, there are tunnels and large caverns, results of ancient lava flows. The planet also has a lot of radioactive ores that decay and produce most of the heat deep underwater. A result of this is some areas of the ocean are boiling and some are freezing.
The planet's inhabitants would range greatly in size from small to larger than the largest submarines. They're also hostile due to aliens (humans) entering their territory, so that would be their reason to attack. Many of them can tear through the hulls of submarines, be it through ramming, tearing, or piercing. They are also naturally very robust, due to their harsh environment. As a result of hostile fauna, submarines and their crews would be armed.
Humans came to this planet with the intention of harvesting its resources. The surface station harvests gasses such as argon and nitrogen. Its cities center around mining ores, rare earth elements, and other valuable resources. Submarines function to travel from city to city, remote station to remote station, transporting goods among other things. [In this universe] this is the first planet humans have encountered extraterrestrial life on, and thus there are also missions to hunt or capture creatures for research. and thus, they are motivated to build stations and cities at the lower depths, wherever they are after resides.
**Response to questions:**
The ecosystem's nutrient base would come from a combination of geothermal venting as well as heat created by the decay of radioactive ores and metals. The surface of the world isn't exactly uninhabitable per se, humans just aren't residing on the surface except for one installation that connects the planet to the rest of civilization because it's simply not worth it to settle on the surface. There's barely any resources and the surface is plagued by constant violent waves making it dangerous. The surface oceans are also rather barren, most life being located within the planet-wide system of tunnels and caverns. Humans settle down about a kilometer or more into the tunnels or wherever the resources are.
Also, I am asking this question under the presumption that humans would and have settled on the planet and are making technology for use on this planet. ANd humans are focusing their efforts on settling in the cave systems because the surface has a violent sea that has constant multi-kilometer waves thrashing settlements. The atmosphere is also only 13.5% oxygen.
*Please note that I am asking what would such tech look like under these conditions, not the practicality of humans settling on such a planet.*
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If I were colonizing such a world, with a strong motivation to settle there (unobtainium, lack of better real estate, whatever) I would have population centers either on the coastlines, aboard giant ships, or in underwater neutral-buoyancy cities high enough up to allow easy access to the surface. Ultra-deep enemies probably couldn't tolerate LOW pressures, so humans would have safe harbors so to speak. People would bring earth like conditions with them.
* Submarines would be jet-powered improved versions of the ones we have now, but weaponry would be primarily robotic/drone based, with few people operating large numbers of mini attack subs. Organisms in water would be very vulnerable to things like depth charges and exploding torpedos. Gravity would favor humans raining death from above.
* Open ocean would be easier to control, but extensive caves (I'd put unobtainium here) would be challenging as control of drones would be hampered and distances shortened. You can't use big explosives because you don't want to destroy the caves! I'd move people to sealed bunkers to keep them safe. Coming and going from mines would be danger points.
* Drones would use torpedos, mines and depth charges, possibly poison harpoons. Sonic weapons would be interesting; The super-whales of Earth are thought to have used sonic attacks in their hunting and may have been able to kill with them. Look to terrestrial sea life for drone designs; Octopi, puffer fish, electric eels - the possibilities are endless. There was a military sci-fi series set in the ocean, Seaquest. If you recall it, That would be good source material as well.
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# They wouldn't settle on the planet at all.
If you've got the tech to build a working underwater habitat, you've also got the tech to build working space habitats - and while the ambient environment is no less deadly, there aren't angry sea monsters trying to kill you in space. If they really felt the need to settle on any stellar body at all, rather than just setting up shop in asteroids and artificial space habitats, they'd probably decide to settle on the moons, instead. Any resources that they could conceivably get from settling in the ocean can be gained from asteroid mining.
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In my book series, there are basilisks that can kill people with their gaze.
However, I want this to be explained scientifically instead of having to use a "because magic" cop-out.
What kind of at least pseudo-scientific excuse could I use to justify people being killed just because they looked a basilisk in the eye?
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Basilisks have [irises in their eyes](https://en.wikipedia.org/wiki/Iris_(anatomy)) covered in camouflage cells like the ones in [octopuses](https://en.wikipedia.org/wiki/Octopus#Camouflage_and_colour_change). Basilisks can make their eyes change colour in patterns that provoke nervous system overload to those who stare into eyes of the basilisk. So, basilisk victims have epileptic-like seizures, but instead of shaking, it induces Tonic immobility like [L.Dutch](https://worldbuilding.stackexchange.com/a/171357/2763) said, and victims are perceived paralysed, even becoming petrified and breathless with all muscles blocked.
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Following from the [Basilisk petrification query](https://worldbuilding.stackexchange.com/questions/113648/is-petrifying-vision-plausible-in-an-animal), perhaps it's not actually the eyes per se that do the killing? Maybe your basilisks have some other kind of terminal mechanism in their arsenal?
Pliny says that basilisks are small and can kill shrubberies and split rocks and that only the weasel is impervious to their venom. ([Smithsonian](https://www.smithsonianmag.com/history/on-the-trail-of-the-warsaw-basilisk-5691840/)) Others have depicted the creature as being rather larger; some are serpentine, some are birdlike, one depiction looks like a ten legged chicken-snake. But anyway...on to death!
Perhaps the basilisks in your world can sing a [deadly song of infrasound](https://www.insidesources.com/silent-sound-kills/). According to that article, infrasound can cause, among several cacatorially amusing symptoms, rather more severe symptoms such as organ rupture and death.
I'd suggest your basilisks, apart from being immune to their own infrasound capabilities, are able to home in on the resonant frequency at which its victim will react, and then ramp up the wattage until the power of the sound itself causes its victim to collapse into a heap of disintegral ooze. The powerful infrasound of the basilisk simply shakes them to pieces, in a sense. Because the sound must be focused, it simply appears to onlookers & survivors that the basilisk is staring them to death.
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The basilisk might induce a sort of unconscious [tonic immobility](https://en.wikipedia.org/wiki/Apparent_death)
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> Tonic immobility (TI) is a behaviour in which some animals become apparently temporarily paralysed and unresponsive to external stimuli. In most cases this occurs in response to an extreme threat such as being captured by a (perceived) predator. However, in sharks exhibiting the behaviour, some scientists relate it to mating, arguing that biting by the male immobilizes the female and thus facilitates mating.
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Real TI is somehow conscious, in the case of the basilisk, being unconsciously triggered results in a deep paralysis, involving also involuntary muscles like those involved in breathing, leading thus to death by suffocation.
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Charles Stross described one possible scientific explanation in his short story The Concrete Jungle, and various of his Laundry Files novels after that.
Actually, it'd be worth reading it just to appreciate the way he pointedly glosses over the *exact* mechanism with (paraphrased) "we've learned the circumstances required to produce this effect, we can reproduce it at will, and we know that it involves some interesting goings-on at the quantum level. However, we still haven't figured out exactly *what* goes on at the quantum level."
This is a perfectly valid scientific take on something, it fits in the context of the story (and the wider set of stories) and ultimately, it doesn't really matter that the underlying mechanism isn't (yet) understood.
[Answer]
Your basilisk would need to be able to spit poison like this: when the basilisk contracts it's venom gland, it squeezes a small amount out at high pressure. The venom hits the floor of the fang hole, bounces upward and out. So when the basilisk stares straight at the victim, to calculate were to aim, it spits its poison at the eyes, killing the victim. I would suggest your basilisk be immune to their own venom, and make the best way to kill it is to smack it's head with a thick mirror, because it's head is fragile like a snake.
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The invention of the Atomic Bomb changed major conflicts basically turning them into a nuclear arms race. what I want to know is what single change would have prevent the creation of the Atomic Bomb? now such a question is quite vague and would likely get closed, therefore I list a number of disclaimers, in order to make this question fit into the topic of this site.
* The change has to ensure that the bomb is not created after the war up to at least the 2010s
* The change has to be a single event, or a collection of tightly coupled and interdependent events.
* The change should preferably happen either during the war, or not more than a few years before it. The war should, at least in the beginning, look very similar to what happened in real life
* The change should have a realistic justification (no time traveling ww2 Japaneses soldier killing Einstein or anything equally absurd)
[Answer]
**Accidental early detonation**
As stated in other answers stopping the arms race from a technological point of view is hard to impossible. Making scientist and/or the general public unwilling to fund/participate in the development is probably easier. For nuclear power this has precedent in the Chernobyl accident which has had a severe impact on all research into nuclear power that still persist today.
The accidental early detonation of the (would be) first atomic bomb while still at the production facility would cause a major set back in the research since it both destroys evidence of what has gone wrong and kills a lot of the scientist and engineers necessary to build the bomb in the first place. Since it will be hard to find out what has gone wrong it will be hard for the scientist to say if it was a minor problem or a major design flaw. The effect will be that anybody will be very hesitant to continue with the project or try to start a new project.
For the disclaimers:
* An accidental atomic explosion can be caused by a simple very small effect such as a faulty wire presumably. Although I am not sure what fail safe mechanisms they had in place during production of the atomic bomb.
* This scheme would set back the USA but not necessarily the USSR although scientist there might become quite nervous about development. On the other hand if the USA didn't develop the atomic bomb the USSR might be less inclined since there would be no mutually assured destruction arms race.
* Delaying it to 2010 might not be possible with a single explosion but should come from later treaties. The UN banning the development of nuclear weapons due to the risky nature of it linked to the explosion seems feasible.
* You could argue that an atomic explosion is in fact an atomic bomb, but I would say that for it to be a "bomb" it should be stable and controllable which was not the case in this scenario, thus it should not qualify as an atomic bomb.
* As a minor side note, but that would completely depend on the story. With no atomic weapons race between the USA and the USSR they have ample opportunities to get into conflict anywhere else, be it normal war, space or anything else. The space race could for instance give such a drain on both of their resources that they wouldn't have enough resources left for the development of an atomic bomb making the year 2010 more viable.
[Answer]
Preventing the development of the atomic bomb after World War 2 may not be possible. But if the Second World War didn't take place, then the probability of the development of nuclear weapons goes down considerably.
Anything that suppressed the rise of Nazism in Germany and especially their assumption of government in the 1930s.
A specific event set the USA on the path to building the Bomb. That was the so-called Einstein letter. This was drafted and prepared by Leo Szilard and Eugene Wigner. They persuaded Einstein to sign it. Einstein said later had he known what nuclear weapons and the arms race was like, he wouldn't have signed.
Leo Szilard was inspired in realizing that a chain reaction was possible after reading HG Wells' *The World Set Free* (1914). This was a novel about a future atomic war in the far future of 1955. Szilard read the book in, about, 1936.
Of course, most of the preliminary work about the feasibility of a nuclear bomb was done in Britain in the early 1940s. Britain and its Allies lacked the industrial capacity to build the bombs and their associated infrastructure. They had a war to fight. The USA did have the necessary industrial capacity. So the British shared their nuclear knowledge and gave the Americans a substantial leg up.
The main impetus of developing nuclear weapons was two-fold. The war with Nazi Germany and the fear that the Germans might build the Bomb first. Remove those dual factors and the atomic bomb won't be developed. The cost commitment of funds and resources is too great for almost any peacetime nation. This would be especially in a world where the Second World War and the concomitant rise of Nazi Germany didn't happen. It's not what happens after the War that's important, it's the War itself. So that's the single event that needs to be removed.
[Answer]
**We all know this is an impossible task.** Project is too complex and has too many players for it to be derailed by a single actor.
So, let's look at ways this *cán* be done...
Following from Readin's lead (excellent answer, by the way!), let's look in the other direction. What comes to mind immediately is a scientist or engineer who can somehow grasp how absolutely horrific this weapon will be. This insider will be the one to throw the game.
And lo and behold! Someone actually done it! And rather successfully. There was a short story written in 1958 and reprinted in 1986 in the anthology *Hitler Victorious*, called *Two Dooms* by Cyril M. Kornbluth.
The short version: scientist gets the news that a breakthrough has been made -- the Bomb can actually work! Maybe through some prescience or just too much bad cantina food, he withholds the information for the moment from his superiors and goes out into the desert to sort things out, because he knows what such power will be capable of in the wrong hands. To say nothing of the right hands. Basic moral dilemma. He has out there a Native American friend who feeds him some really good mushrooms and he goes on a spirit quest. There, he learns what will happen in some distant future if the bomb is delayed: obviously, a victorious Japan rules the western US and a victorious Germany rules the east. The Japanese are ruthless neofeudalists and the Nazis are wack with pseudoscience. The world is pretty much stuck with 1940s tech and civilisation is on the downward spiral. Eventually, he eats some more mushrooms that he finds in a German facility, wakes up from his spirit journey and armed with this vision of horror, goes back to his life to ensure the Bomb gets made, and the rest is history.
All you have to do is ensure that he never wakes up from his spirit journey!
[Answer]
Depending on how far back you're willing to go, you could simply have the Solar system be older. It could have formed a few billion years later, and then had the rest of history progress as normal. This would add several half-lives and significantly reduce the prevalence of U-235, the "enriched uranium" that they use for making many atomic bombs. This would make a bomb like Little-Boy nearly impossible to produce.
This would not however put a significant dent in supplies of U-238, which is the raw ingredient for making plutonium based weapons, such as Gadget or Fat-Man, and has a significantly longer half-life, but perhaps those kinds of bombs can be disabled for a separate reason.
[Answer]
As many posters have pointed out, the knowledge of nuclear physics was simply too widespread by 1930 to really obscure the idea of a nuclear chain reaction. Atomic energy was so well known that H.G. Wells postulated a form of atomic weapon for his novel "[The World Set Free](https://www.gutenberg.org/files/1059/1059-h/1059-h.htm)" in *1914*, although today we would recognize this as a "salted" or "dirty" bomb.
By the time WWII is actually under way, all the major combatants have some form of nuclear program. Imperial Japan, despite its lack of industrial capacity, actually has [*two* programs](https://www.atomicheritage.org/history/japanese-atomic-bomb-project), one conducted by the Imperial Army, and a totally separate one by the Imperial Navy.
However, the biggest problem in any nuclear program is actually getting the fissionable material. The [Germans](https://www.atomicheritage.org/history/german-atomic-bomb-project) seemed intent on using natural Uranium moderated by heavy water (D2O), a process similar to a modern [CANDU](https://cna.ca/technology/energy/candu-technology/) reactor. From the various books and documents that I have been able to read over the years, it seems fairly clear that few people had any real understanding of the difficulty needed to get fissionable uranium, and fewer still had the resource base to do so.
Only the United States had the resources and ability to do so, and even then, the Manhattan project needed to explore every possible means of enriching Uranium in order to discover which one was most suitable for industrial production of enriched Uranium for reactor fuel and bomb material.
Since none of the other Allied or Axis powers seemed to have the ability to find and scale a method of Uranium enrichment, then having either the United States sit out the War, or enter a year or two later means that only very tiny amounts of enriched Uranium are available for experiments, but never enough for power reactors or bombs. This prevents Uranium "Gun" type bombs like Little Boy, but the understanding of nuclear fission exists, and the production of Plutonium is possible, even with natural Uranium reactors.
This presents a problem, since even with 1940 era technology, the various special timers, switches, detonators and mathematical and machine tools needed to create a functioning "implosion" device exist (and this was demonstrated by "Trinity" and "Fat Man", the first and third nuclear weapons ever detonated).
Here a slight hand wave could exist. If you disallow the precision timers which create the conditions for the symmetrical implosion waves that make plutonium fission bombs possible, then the various powers will try to create Plutonium "Gun" bombs. However, [this configuration is impossible](http://large.stanford.edu/courses/2018/ph241/premutico1/), since the Plutonium will start fissioning under the presence of emitted neutrons even as the two pieces are being propelled together, creating a "fizzle" yield rather than a nuclear explosion.
[](https://i.stack.imgur.com/qUPuK.jpg)
*Plutonium "Thin Man" bomb casings. At over 17' long, they were only able to be fitted in specially modified B-29's. Even a 3000' second "shot" speed was too slow to prevent uncontrolled spontanious fission*
So essentially, all that can be done by the 1930's is to slow down the ability to create fissionable materials, and to handwave the ability to build the intricate timing and switching devices needed for implosion bombs away.
[Answer]
**Replace nukes with something else**
Initial nuclear weapons were fairly unimpressive, especially relative to the effort expended to making them. Thus the nuclear arms race can potentially be averted if their space was replaced with some other MAD weapons system. In particular mass use of chemical weapons, or bioweapons.
For example, if the Manhattan project hit hurdles and the war was instead won by Churchill's "Operation Vegetarian" anthrax bombing campaign, the immediate impetus would be for different countries to develop bioweapon arsenals for deterrence, and once the major superpowers have various death strains ready and delivery systems suitable for this, there would be much smaller an impetus to replace the system with nuclear weaponry.
[Answer]
A few years before the war, a well-known and respected scientist comes up with calculations showing that an atomic bomb reaction would not stop and entire world would be consumed. The scientist is well-respected enough that no country embarks on a program to develop an atomic bomb and nuclear energy is considered too dangerous to pursue as well. The calculations are a lie.
You could toss in a conspiracy of top scientists who agree to this deception (i.e. the scientists who read the faulty paper and are smart enough to recognize the errors in the math don't say anything) because they agree that a nuclear bomb is too powerful and don't want any country developing it.
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Many stars, including the Sun, periodically display [starspots](https://en.wikipedia.org/wiki/Starspot), cooler areas of the surface associated with higher local concentrations of the stellar magnetic field. They can sometimes be a couple thousand Kelvin cooler than the surrounding regions of the stellar photosphere. My reasoning is that because surface flux from a star is proportional to $T^4$, with $T$ the photospheric temperature, if a large portion of the star was covered by starspots, we could see a significant reduction in flux, and I'm trying to use such a star in my universe.
The thing is, I don't know just how dramatic the effect could be. I can't say that I know much about starspots, and while Wikipedia claims that up to 30% of the surface of a star can be covered,
* The claim is not backed up by a citation.
* It's not clear if that's the *theoretical* limit or just the maximum value found in observations.
* Wikipedia doesn't say in what type of stars this dramatic coverage is seen.
* [Another site](https://www.windows2universe.org/the_universe/Stars/starspots.html) claims a limit of at least 66%.
Therefore, what is the upper limit for the amount of a star's surface that can be covered by starspots at a given time? I'm hoping for main sequence stars of between $0.5M\_{\odot}$ and $3M\_{\odot}$, but I would be okay if we need to go outside those boundaries to cover a significant portion of the surface.
As a note, when I say "starspot", I'm looking for a region roughly $\sim1000\text{ K}$ to $2000\text{ K}$ cooler than the normal stellar photosphere *outside the period of starspot activity*. In other words, the spot is not necessarily substantially cooler than the regions around it at a given time, if it happens to be in a large region of magnetic activity, but it's cooler than the same location would be if there was no magnetic activity at all.
[Answer]
I will take a swipe at this.
1. Starspots are created by magnetic flux tubes that extend out past the surface of the star.
2. The center of the tube has decreased convection because the magnetic fields inside the flux tube suppress convection. Decreased convection means decreased heat transferred to outermost visible layer. That layer cools, and thus darkens: the spot.
3. Bigger flux tube = bigger center = bigger star spot.
4. I figured the theoretical maximum size of a flux tube would be one that encompassed the entire star, from axis to axis. **The diameter of such a tube could be the diameter of the star and could produce a bihemispheric starspot** occupying nearly all of the star surface. Maybe there would be a bright band at the equator. Could such a thing exist?
5. Flux tubes are caused by vortices in the star stuff. A single giant flux tube would mean the star stuff was rotating as a piece rather than countless small eddies as in our sun.
I went looking. I found this. Emphasis mine.
Doppler Imagery of the Spotted RS Canum Venaticorum Star HR 1099 (V711 Tauri) from 1981 to 1992
<https://iopscience.iop.org/article/10.1086/313195/fulltext/36316.text.html>
>
> We believe that these starspots are not measuring photospheric
> differential rotation. Instead, like solar coronal holes, their
> relatively low degree of shearing and nearly solid body rotation may
> be enforced by a multikilogauss, axisymmetric, nearly current-free
> quasi-potential global magnetic field. Our Doppler images also agree
> very closely with the Zeeman-Doppler imagery of Donati et al. and
> support their finding that regions around the edge of the polar spot
> and within bright spots show largely monopolar fields of at least
> 300700 G strength. The large, permanent cool polar spots, the very low
> observable differential rotation and shearing of starspots, and the
> evidence of strong, essentially unipolar magnetic fields associated
> with them leads us to believe that HR 1099 and other rapidly rotating
> RS CVn stars harbor quite strong (multikilogauss) axisymmetric global
> magnetic dipole fields. These fields have historically been largely
> hidden from view by their high degree of rotational symmetry, by being
> concentrated in the low surface brightness dark spots, and by these
> stars' high degree of rotational line broadening. *We propose that the
> starspots on HR 1099 and other rapidly rotating RS CVn stars are, by
> analogy with solar coronal holes, large unipolar, magnetic regions
> that are tightly frozen into multikilogauss, axisymmetric global
> dipole fields in these stars.* Since the large cool polar spots, the
> signature of these dipoles, are not present on more slowly rotating RS
> CVn stars, we believe that they must be dynamo-induced fields rather
> than remnant fossil fields.
>
>
>
So: they describe a single giant, long-lived star-spanning flux tube created as a product of rapid stellar rotation, and this associated with the largest known starspots. Yay!
I took away also that these very rapidly rotating stars might often be binaries, and owe their rapid rotation to the influence of their partner. Not sure how that factors into your fiction.
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[Question]
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I want to build a habitable desert gas-giant moon and I´m not sure how little water I can give it and still get plate-tectonics instead of an Io-like lid-tectonic setup. I want plate tectonics because continental-continental divergent (East-African rift valley) and convergent (Himalayas) plate boundaries create way more interesting geological features than the uniform mountains and plains of Io-like lid-tectonics. Additionally, plate tectonics might be necessary to keep the planet habitable. Since no two papers, I read on the subject of what mass a planet needs to sustain plate-tectonics agreed on a mass range(either Earth is at the upper or lower boundary...), I settled on 0.2 to 5 earth masses and decided to call it a day. While even the role of water as a lubricant and thus its role in enabling plate-tectonics has been challenged, most sources consider it necessary. **But how much water, specifically surface water, do I need on my planet in order to maintain plate tectonics?** Earths oceans contain a lot of water, but the mantle and the crust might hold between 2 to 25 times the amount of water found in the oceans. So is ocean water even necessary?
My planet has the following, more or less fixed parameters.
* 10 to 20% global ocean cover
* ca. 0.3 Earth masses
* heavy volcanism due to tidal heating ( not Io-like but close)
* a similar composition to Earth
* first and biggest of the three moons of a super-jovian ( 12,6 Jupiter masses)
* super-jovian orbits an early F-Type star (1,15 solar masses) near the end of its 7 byr lifetime
* desert world with habitable poles
[Answer]
# None
The prevailing theory is that plate tectonics are [made possible](https://en.wikipedia.org/wiki/Plate_tectonics#Driving_forces_of_plate_motion), in part, by the relative density of the [ocean crust](https://en.wikipedia.org/wiki/Oceanic_crust) on oceanic plates. However, there is no requirement that the denser oceanic plates be overlain by actual water. Consider that an oceanic plate is about 10km thick, with a density three times that of sea water; you get an order of magnitude more mass from the crust than you do from the ocean on top of it. You could do away with ocean, and still end up with the same geological effects.
Also, it is possible that the theory about ocean crust density as a driving force for tectonic motion is wrong, so then it wouldn't matter anyways.
So, in either case, you don't need any surface water on the planet.
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My hypothetical gas giant has five major moons. Three of those moons are icy bodies with abundant water ice and volatiles. Any of these could provide fuel for translunar spacecraft, or for spacecraft headed further afield.
However, not all of these moons are created equal. One of them is much deeper into the gas giant's gravity well, and the furthest out is very small.
Considering proximity to the host planet and to the other moons, which of the three icy moons is the best place to establish a refuelling station?
***The System:***
Planet mass - 187.36 Earth Masses
**Moon A** (Icy) - Mass: 1.93 × 1021 kg, Surface Gravity: ~0.223 m/s2, Semi-major axis: 597,520km, Period: 3.8863 days
**Moon B** (Unsuitable) - Mass: 93% Mars, Semi-major axis: 747,800km, Period: 5.4408 days
**Moon C** (Unsuitable) - Mass: 88% Earth, Semi-major axis: 1,188,200km, Period: 10.8724 days
**Moon D** (Icy) - Mass: 1.6 × 1023 kg, Surface Gravity: ~1.428 m/s2, Semi-major axis: 1,883,220km, Period: 21.7446 days
**Moon E** (Icy) - Mass: 4.28 × 1019 kg, Surface Gravity: ~0.064 m/s2, Semi-major axis: 3,588,200km, Period: 57.1901 days
[Answer]
Use moon E for interplanetary craft. It is likely the interplanetary craft don't descend into the gravity well at all, but shuttle craft come up and meet them to refuel and exchange the personal and cargo. These interplanetary ships contain the life support equipment for long voyages, which is essentially useless mass when in the giant's gravity well, and you don't want to lift that up out of the gravity well each visit. You only lift the perishables out of the well: food, water, oxygen, fuel, etc.
Moon E is not small. You didn't specify the percentage of ice, but if it's more than a few percent you have thousands of years of fuel available. On the other hand, the low gravity of moon E is a major benefit for lifting the fuel to the interplanetary carriers.
If, on the other hand, you are talking about refueling craft that only fly between the moons, then it very much depends on where the most common journeys are made. Naturally the fuel will have to come to the major spaceports. We don't all drive to Saudi Arabia to refuel our cars.
If you are only talking about a single ship, or small colony, then it's likely that the earthlike gravity of the inner moons is a more attractive reason to place a colony there than the ease of obtaining fuel.
[Answer]
**The one with the least gravity**
Gravity requires fuel to escape thus the lowest gravity requires the least amount of fuel to escape from means more fuel for the journey.
[Answer]
The best location for the fuel Depot is wherever most of the people and infrastructure in the gas giant system are.
Without knowledge of exactly what the major propulsion system of your interplanetary spacecraft it is very difficult to make recommendations, but there are two major regimes to consider:
If the delta-V potential of your spacecraft is low enough that orbital mechanics are going to be a significant factor in your space travel, you can't afford to stop somewhere that isn't a destination. You'll be arriving with a high relative velocity (bare minimum ~40% of the orbital velocity of the moon in question, and most likely much higher than that) and you're going to need to spend delta-V to brake into orbit to get refueled.
If the delta-V potential of your spacecraft is high enough that planetary orbital mechanics are vague guidelines, then the delta-v difference to reach individual moons is mostly academic, and the best place to refuel is the place where everybody already is.
As such, my recommendation is to decide whichever of the moons is the most likely to be your major colony in the Gas Giant system, and the spaceport on/over that world is where the vast majority of refueling is going to happen.
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I was thinking about how an MRI uses a strong magnetic field to align the spins of hydrogen atoms in the body. What I was wondering about was if the human body experienced a magnetic field much stronger than that from an MRI, is it possible or plausible that a greater portion of the hydrogen atoms in the body could become aligned or that they could stay aligned for a longer period of time? So that someone could become magnetized (or spin polarized) enough to attract magnets or for a significant amount of time, like a few minutes.
[Answer]
You have the mindset of a scientist.
Other scientists have had the same hypothesis as you do. [In 2000, Andre Geim put it to test:](https://www.ru.nl/hfml/research/levitation/diamagnetic-levitation/)
>
> The image of a high-temperature superconductor levitating above a magnet in fog of liquid nitrogen can hardly surprise anyone these days – it has become common knowledge that superconductors are ideal diamagnetics and magnetic field must expel them. On the other hand, **the enclosed photographs of water and a frog hovering inside a magnet (not on board a spacecraft)** are somewhat counterintuitive and will probably take many people (even physicists) by surprise.
>
>
> This is the first observation of **magnetic levitation of living organisms** as well as the first images of diamagnetics levitated in a normal, room-temperature environment (if we disregard the tale about Flying Coffin of Mohammed as such evidence, of course). In fact, **it is possible to levitate magnetically every material and every living creature on the earth due to the always present molecular magnetism**. The molecular magnetism is very weak (millions times weaker than ferromagnetism) and usually remains unnoticed in everyday life, thereby producing the wrong impression that materials around us are mainly nonmagnetic. But they are all magnetic. It is just that magnetic fields required to levitate all these "nonmagnetic" materials have to be approximately 100 times larger than for the case of, say, superconductors.
>
>
>
It may take quite the force to levitate a person:
>
> our frog levitated in fields comparable to those used in commercial in-vivo imaging systems (currently up to 10T).
>
>
>
Electromagnetism is not my forte, but if it takes an MRI machine to levitate a frog, I think it might take something between the size of a room and the size of a multistory building to impress a perceptible pull on an adult human.
Seems like It wouldn't harm you, though:
>
> In the case of living organisms, no adverse effects of strong static magnetic fields are known (...). The small frog looked comfortable inside the magnet and, afterwards, happily joined its fellow frogs in a biology department.
>
>
>
This work has won Geim a very distinguished prize, making him the only person ever to individually win both a Nobel and an [Ig Nobel](https://www.improbable.com/2010/10/05/geim-becomes-first-nobel-ig-nobel-winner/) - the latter from the very levitating frog experiment.
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[Question]
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A holy man lives down a cylindrical well that is 2 metres in diameter. There is no water in the bottom and all the walls are of solid impermeable rock. He is protected from rain by a roof on supports.
He is kept alive by the locals who believe his prayers are necessary for their well-being. They assiduously lower food and water and haul up waste products at regular intervals.
**Question**
How deep can the well be before his exhalations are sufficient to suffocate him?
**Assumptions**
There are no toxic gases leaking into the well.
There is no active ventilation to the tunnel. In order to breathe the hermit must rely on diffusion. (or convection - see below)
The well is on the equator so the Sun is directly overhead once per 24 hours. The resulting temperature changes throughout the day and night will presumably cause an exchange of air by convection. (or will they?)
[Answer]
Wells have been hand dug to a depth of 390 metres, so considerably deeper than this especially if the person was not exerting themselves. Gases are very good a defusing especially if containers are being hauled up and down the well shaft, so probably a lot deeper indeed.
The ultimate depth would probably be more restricted by temperature increase than by gas diffusion. At 4000 metres I am confident that the person would not survive due to excessive temperature and probably would not survive at considerably shallower depths for the same reason.
So a best estimate would be 1000 – 2500 metres
[Deepest hole dug by hand](https://www.bbc.com/future/story/20150327-the-deepest-holes-dug-by-hand)
[Answer]
## I doubt gas exchange would be the limiting factor.
The deeper the hole, the longer it takes to exchange the gas, true. But it also increases the size of your oxygen tank. And in terms of CO2 buildup, think about how fast a fart can spread through a room. Your hermit isn't breathing fast enough to decrease the concentration of oxygen to harmful levels, because there's so much oxygen in the well.
What I would expect to be the causes of danger (in order of the depth needed for them to occur, shallowest to deepest):
1. **10+ meters – Things falling in:** A rock falling down a deep well would be enough to kill the guy when it gets to the bottom. You could have barriers to prevent this, but they'd have to be careful lowering things down. If the rope breaks, he might get killed by a falling water jug. So they don't drop anything. In that case,
2. **50+ meters – Collapses:** At some point, it gets really hard to stop the well from caving in on itself. The bigger the hole, the more rock that has to be kept from falling in from the walls. Suppose the well is reinforced with indestructible walls. Then:
3. **600+ meters – Temperature:** The earth gets really hot down there. It doesn't really matter how much food and water you have if you live in an oven. Assume the indestructible walls are also perfect insulators:
4. **??+ meters – Gas exchange:** I'm not sure when this would start, but it would be very far down. I'm also not positive that diffusion would ever be slower than the ascetic's rate of gas exchange through breathing. Also, as you mentioned, there would likely be convection. Hot air rises, and your monk is a living radiator at the bottom of a well. The air that he breathes out will create an upward current, which would probably supply him with air for even extreme depths. My only issue is that carbon dioxide is slightly heavier than air, and as you go further down, the diffusion won't be strong enough to prevent the CO2 from settling at the bottom of the hole. Also, at that kind of depth you have another problem:
5. **15000+ meters – Air pressure:** The deeper you go, the greater the gravitational compression of air. At a few thousand meters, it would be noticeably uncomfortable and hard to breathe. At around 24-25 kilometers down you would die very quickly from nitrogen narcosis, because the air would be 4 times more pressurized than on the surface. Given the chronic exposure he's getting, I think he wouldn't be able to survive much more than 15km down, no matter how much perri-air they sent him. Beyond this, it isn't really a well if you have a pressure vessel at the bottom.
[Answer]
Sooner or later, no matter where his well is located, you're going to hit water -- the [water table](https://en.wikipedia.org/wiki/Water_table). If his well is any deeper than that, he'll be swimming, and that's as deep as he can safely go.
Whether your community can dig a well deep enough to get to, for example, the aquifers under the Sahara is another matter!
As for air, there are always microfissures and pores and splits between rock layers. (Think caves & mines.) Air circulation shouldn't be much of an issue.
Though I suppose if the monk ever complained, the community could always send down buckets of Perri-air:
[](https://i.stack.imgur.com/eP7Iz.jpg)
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[Question]
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**Night/Day Cycle**
I'm trying to make a fantasy world with a longer night cycle than day.
With the advice of Renan, 12 hours of proper night, 4 hours of near/partial dark and 8 hours of good light. Similar to earth the cycle allows for entire planet to get moon and sun light in a day, but within the parameters of 12:4:8.
With this in mind the culture of the planet would be a night culture with sleep mostly occurring during the day. The main religion will be that of a lunar system with the moon being the main symbol of god, and the sun being a lesser 'evil' god and the right hand of the moon god similar to Hades.
Therefore the fauna and flora would need to be night based due to the lack of sunlight throughout the day.
**Question**
How will this affect the way the flora would turn out?
Would the plants be more geared towards a night life cycle similar but opposite to the Morning Glory?
[Answer]
The planet has an atmosphere different than ours. The gases at the uppermost layers cause extreme refraction of visible light.
When the sun is high in the sky some light makes it into the surface of the planet. But when it is close to the horizon, very little reaches observers. It might be so dim as to seem it is not there at all.
Hence you get twelve hours of proper night, four hours of sun-above-horizon-but-light-deflected and finally eight hours of good light.
This will also make the horizon seem much closer and way distorted for an observer on the surface.
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Your flora would have to gather more energy per day than earth plants do, so they may have wider leaves, and wider tops. Most plants would be smaller than terrestrial plants, though some may be super large, taking advantage of the lack of competition to spread out very huge using a more efficient process not yet gained by other plants.
Fungus would be prevelant, owing to plants creating almost solid shade during the day. Slime molds in water bodies may be particularly common. The super large plants may have several types of parasites besides specialized predators.
More animals will become nocturnal, since they can forage more at night than day. The higher level of competition may lead to many animals choosing one specific food source and out competing generalists. That means any particular species may go extinct if their food source dies off.
The oceans, if you have them, may be a lot less lively than our oceans do to a lack of phytoplankten, but besides a decrease biomass it will probably be much the same.
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The world is flat, surrounded by incredibly high mountains, and the sun circles the world. From the time the sun drops below the top of the western mountains until the time it hits the top of the eastern mountains, it's night.
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Around the Equator, tall trees with large leaves would most likely form a very large and thick canopy. These will be heliotropic (pointing towards the sun during day). The plants will need to have high levels of chlorophyll simple to make up for the minimized sunlight. Upwards of the equator, smaller and wider plants should grow.
Since the plants can't make as much energy, more than likely some would be carnivorous or live in mutualism with other species during the nighttime. There is one example of a possible formation of a carnivorous island of algae in Yann Martel's book *Life of Pi*, which is possible on this planet. Carnivorous vines should play a role in the ecosystem. Possibly underground plant configurations will form, sustained by a chemical in the environment.
This brings up another question: If fauna can sustain itself through the normal trophic system on Earth today, or will chemosynthesis be prevalent and all fauna originate from sea vents? Life will probably have to have some photosynthetic producers and some chemosynthetic producers to have any ecodiversity at all.
Further research on life systems might be needed, but overall I hope this helps!
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All hail to the Hypnotoad!
[](https://i.stack.imgur.com/azIQs.gif)
I am interested in creating anatomically correct Hypnotoad, mainly known from the [Futurama](https://en.wikipedia.org/wiki/Futurama) series.
While in Futurama the toad itself is pretty big, but I am actually interested just in having a toad which uses hypnotic abilities to catch its prey.
---
This is my addition to [Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798).
[Answer]
The answer lies in cuttlefish. By changing the color intensity of melanin particles in their skin, they can create hypnotic patterns that serve to calm their prey and lure them towards the cuttlefish's jaws.
Interestingly, there already exist frog species that can change their skin pigment, so it may not be too big a stretch to assume that they could adapt to produce hypnotic signals through change in skin color. Sadly I don't know of any frogs that can do it with only their eyes, like hypnotoad :(
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
I've looked around the forum but didn't find an answer to this particular question. In short, what food could realistically be produced in a space station assuming current (or near future) technological constraints?
Let's assume that we want to build a space station that is entirely self-sufficient (at least in the realm of food and water production). The station will carry a commune of say 10,000 people. It rotates enough to mirror gravity on Earth.
Now we want to create farms or food factories to feed the populace, but what is the most viable crop/livestock in space?
Food pills, protein powders, or any other form of artificial supplements aren't considered, so disregard that as an option.
The way I see it, the food must meet some or all of the following criteria in order to work in such constrained settings:
* The food must be able to grow or be produced in as compact an area as possible (how much can be produced per square feet, for example)
* The food must be calorie or nutrient dense (more bang for the buck)
* The food must be energy efficient in its production (that is, not require as many resources such as light, fertilizer, water, etc.) OR take little time to produce
* The food must have a long shelf life (or require little energy for preservation)
* The food must be somewhat palatable (not tasteless or downright unappetizing, this would be subjective)
Given these criteria, I can think of a few food items that space dwellers could eat. I'll list them out to get the ball rolling.
For vegetables and fruits:
* Potatoes (they are nutrient dense, and have high calories per acre grown)
* Sweet Potatoes, Leeks, & Parsnips (high calories per acre grown)
* Quinoa (high protein concentration)
* Beans (low water intake needed)
* Blueberries (superfood, but may require lots of water)
Meats, Livestock:
* Salmon (very nutritious, but high water requirements)
* Sardines (very nutritious, but high water requirements)
* Chicken (decently high in protein, moderate calories, small livestock and less energy required versus pork and beef)
* Eggs (very nutritious, but somewhat energy intensive to produce)
Forms of Food Preservation:
* Salting (albeit obviously high in salt content)
* Pickling (possibly not efficient)
* Canning
* Drying or smoked (dried foods such as beans, pemmican, and jerky have long shelf lives and high nutrient content, also easy to store)
* Refrigeration (useful in the short run, but ultimately energy-intensive)
* Vacuum packaging (given correct packaging material, very viable option)
* Freeze-drying
Unconventional alternatives
* Seaweed (high nutrient content, necessary for thyroid health, possibly high on water content)
* Quorn/high-protein fungus
These are just a few I can come up with.
Does anyone have any thoughts on what they see a space station producing based on this criteria? Or are there any additional parts to the criteria I listed that should be considered?
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To make food, you need nonfood raw materials and energy. Raw materials include a carbon source, a nitrogen source and trace minerals. Each trophic level you step through loses efficiency. Some protein sources are better than others at feed conversion - @CreedArcon's idea of using insects is reasonable as they have the best feed efficiency of any protein source (compared to other animals like fish, fowl, etc). A problem: feed for these animal protein sources is also potentially feed for humans, and putting the animals in between.
Better is a human food source that uses energy and nutrient sources that humans cannot use. Best of all would be a food source that could do double duty: process waste materials you have in abundance (from your humans) and turn these waste materials together with energy back into food.
**I propose your space people eat bioengineered microorganisms.**
This is being tried (although with regular bacteria for now):
<https://www.newsweek.com/astronauts-living-space-can-eat-bacteria-feed-human-waste-791883>
>
> The researchers tested three species of bacteria in a reactor built
> with aquarium parts that wound up with about the same volume as a
> basketball. Two species grew well in temperatures and pH levels that
> were high enough to kill off pathogens; another species grew in the
> kind of methane-rich environment created when bacteria munch on poop.
> Best of all, the bacteria could consume about half of the solid waste
> in less than a day. "That's why this might have potential for future
> space flight. It's faster than growing tomatoes or potatoes," House
> said.
>
>
>
A variety of bacteria could be used - those similar to the above linked article that subsist on waste, photosynthetic bacterial like [spirulina](https://en.wikipedia.org/wiki/Spirulina_(dietary_supplement)) (already marketed as a dietary supplement(. Yeasts are not bacteria but fit these requirements in that they can subsist on carbon sources that humans cannot use and can synthesize all their own amino acids - yeast has long been used as animal feed and nutritional yeast is in vogue right now among the vegan set.
In space your spirulina tanks would scrub CO2 from the air and be exposed to filtered sunlight. These are your primary producers. Humans could eat this and also carbohydrate fixed by the spirulina could be fed to the bacteria and yeast tanks. The bioengineering comes in to maximize nutritional yield but also flavor: there have been forays into making recombinant organisms that produce ["beefy meaty peptide"](https://www.researchgate.net/publication/228490232_Expression_and_identification_of_a_small_recombinant_beefy_meaty_peptide_secreted_by_the_methylotrophic_yeast_Pichia_pastoris) (that is its real name). Your space folk have a variety of organisms which taste like different delicious real things - good for morale.
The problem in space is obligate loss - even with near perfect recycling it is not perfect you will gradually lose carbon and nitrogen over time just as a energetic process has obligate losses to heat. For the very long term you will need a stash of this stuff (not to mention water and oxygen). Maybe you could keep it outside as frozen CO2 and anhydrous ammonia. Wrap it up in reflective plastic.
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Entirely vegan diet.
As has been noted below, each tropic level is a massive loss in potential calories. Animals don't put all of the calories they eat into building mass; most calories consumed are burned just being alive. It takes approximately 10 calories of grain to produce 1 calorie of beef. Meat is a hugely wasteful food source.
The claim that net calories could be increased by feeding crops through insects, who can often eat more of a plant than humans can, is poorly substantiated. Although there are many insect "ranches" in the world today, mostly raising crickets and meal worms for the pet industry, none of them feed their livestock on 100% food waste. Instead, they use grain and legumes as feedstocks - things that humans could otherwise be eating. Does this improve net calories? It's debatable, and at best a narrow margin, and at what cost? Keeping humans alive in space is already a massive, expensive, treacherous endeavor: high-density rearing of livestock, and all of the diseases they bring with them, would be a massive technical challenge. A colony would want to keep things as simple as possible, considering how many other challenges they would have to face.
And really, it doesn't get you anything. The only essential amino acid that is lacking in a vegan diet is vitamin B12. B12 is required in only very ver minuscule quantities, in doses as infrequent as once a week. 1.5 pounds of B12 could supply 100 humans for 800 years. If you really prefer true self-sufficiency, B12 is easily synthesized by bacteria that might be reared in a lab on site.
Synthesis can be good for micronutrients, but might be difficult to use for bulk food production. Your question asks for current technology to the extent possible, and engineering bacteria to produce large quantities of food is not proven technology. Many of spirulina's nutrients aren't biologically available. Nutrient yeast isn't much of a nutrient source -the B12 content is fortified- and is used by vegans as seasoning, not for health benefits.
So in the end it's down to traditional crops, grown hydroponically in nutrient slurries of water mixed perhaps with human waste. Lettuce, tomatoes, and strawberries have already been grown on the ISS, but these are low-calorie luxury garden crops, not the sort of plants you can live on. Grains are probably not a good route to go because they require milling, and keeping weight down is usually a priority in space. To that extent, Mark Watney was fortunate to have potatoes: a mix of root vegetables would be a good, reliable source of bulk calories for your colonists. Legumes would be great for protein. Soy has a huge yield and very high protein content. If you are concerned about excessive soy intake, there are many other beans to choose from. Lentils and cowpeas, for example, require a lower energy input to cook in comparison to other beans.
[Answer]
**[Aquaponics](https://en.wikipedia.org/wiki/Aquaponics) is your friend**
Similar to Hydroponics, Aquaponics is the science of growing plants in a liquid medium (no soil), combined with aquaculture. They don't have to be water-borne plants, pretty much any green and leafy is very well suited for this, and with a bit of careful managing, other plants such as cucumber, tomato and peppers will work as well.
Combine these plants with edible, crowd friendly fish such as Tilapia or certain species of cod and perch. Finally, you will need nitrification bacteria to convert the ammonia produced by the fish into nitrates to be used by the plants. These can grow on any surface within the system.
After the water has passed through the hydroponics system, where nutrients, nitrates/nitrites and ammonia is taken in by the plants, is is cleaned and oxygenated then passed to the aquaculture system, before looping back around.
Yield is variable, but we will assume upper end as your world will likely have researched further into this. Thus per US gallon of water in the system, you will gain 1 square foot of farmland and 1 lb of fish stock. Lets say half of that stock goes towards rearing young fish, to ensure we get half a pound per gallon per day.
A quick google says 0.5 lb of Tilapia is 292.5 calories. According to [this site](http://www.carbon.org/senegal/sweetpotatoprotocol.htm), sweet potatoes can be grown in hydroponic conditions, and [this other site](http://www.fao.org/docrep/t0207e/T0207E04.htm) says they provide 70,000 kcal/ha/day, or 650 calories per square foot. Thus you will need approximately 2.5 gallons of Aquaponics per person.
The five main inputs to the system are water, oxygen, light, feed given to the aquatic animals, and electricity to pump, filter, and oxygenate the water. You will likely have to manage separate tanks for breeding fish, but they can all be connected into the same water cycle.
Water will be a mostly closed loop, no worse than any other system on your station. light can be rolled into electricity costs and oxygen will be provided in part by your plants, although you will likely need additional oxygen systems.
Producing the feed for your fish is amusingly similar to the rocket problem. You need plants and fish meal for your fish, the fish meal is made from fish. You need feed to produce those fish... [This site](http://www.fao.org/fishery/affris/species-profiles/nile-tilapia/feed-formulation/en/) says the average feed contains approx 25% protein (a mix of fish and meat meal, plus oils), 70% plant meal and 5% minerals. [This other site](https://lakewaytilapia.com/Tilapia-Feeding-Guide.php) says you need 360~ grams of feed per 100 talipia (found by averaging the feed requirements of a newborn and adult).
Earlier, we worked out our population are each eating 1.5 Talipia per day (at 1lb per fish), which means we are harvesting 15,000 fish per day. The feeding plan recommended will bring newborns to 1lb in 194 days, meaning we will have 291,000 fish at any given moment. Thus we will need just 1,047.6kg of feed per day. I don't know how much fishmeal you get per Talipia, but we need 261.9kg of it from 15000lb (6804kg) of fish. Thus we will need to reserve 4% of each fish for fishmeal. I think that's easily doable.
Further we need 733.32kg of plant meal per day. Google says that 1kg of sweet potato has 860 calories, and we get 650 calories per square foot. Thus, we will need an additional 870 square feet of space for growing plant meal. This will come to 870 US Gallons of Aquaponics.
At 45,400 lb of Talipia in our system, we'll need 45,400 US Gallons of Aquaponics, providing 45,400 square feet of growing area. This is almost double what out population of 10,000 actually needs in crop yield. By picking a more suitable crop for plant meal (as I haven't found potato being suggested anywhere) we should be able to cut that down some. Or we could use the excess space to grow utility plants, such as textiles, or less efficient, more interesting food.
This amounts to 170 m3 of Aquaponics. Let's double that to 340 m3 to take support systems, access areas etc, and you can fit the whole thing into about 5 shipping containers, or 13.6% of an Olympic swimming pool.
So, we've proven that you can sustain your population with only 9 US gallons (0.034m3) per person and it is very efficient, as the only real input is power. You could stagger your yields to allow daily production, meaning preservation is not an issue, and finally it is real plants and real fish. What could be more palatable?
[Answer]
**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.
**Insects lots and lots of Insects**
Insects would be one of the best choices for your Space Dwellers to eat. The HIGHEST in protein and can adapt very well in space (better than the humans anyway) they could also be used to combo with other foods to help in production. if you have ever grown your own food before; you would know that even if you get all the right stuff (soil, lighting, nutrients) if you don't have an ecosystem to go along with it your plants will not thrive.
**some examples:**
**Ants:** some of the most amazing little creatures around (look them up) <https://www.youtube.com/watch?v=Hc1hrvWjRQs> they can be very useful to you and not just in "meat" they also can maintain your crops and get rid of your "green waste".
**Cockroaches:** yes they can be of use, if they get the right species even if its plan "meat volume".
**Grubs and Worms:** the best friends for any garden and the most reliable in "meat volume".
So pick insects, they will help you, they will feed you, and will cost almost nothing to produce
[Answer]
I got some great recommendations and ideas, so I can't really pick the "right answer" as they're all very good ones.
I'll post the summary and credit the authors:
Willik had the most upvoted answer, proposing that space dwellers eat edible bacteria (spirulina) and use microorganisms as micro food factories to create something called "beefy meaty peptides". Look up Willik's post for the links and sources, it's interesting stuff.
Creed Arcon proposed cultivating insects for both consumption and creating bio-diversity in space farmlands. A great idea, especially since insects are protein-dense.
Pink Sweetener argued that insects might not be sustainable as they too require food to be farmed and proposed an entirely vegan diet. He argues its entirely possible to adequately feed humans in space with a healthy diet of potatoes, legumes, soy, other such beans (as they are protein-dense and have high crop yields), in addition to veggies.
Kyyshak is the most math heavy, and is therefore more convincing then other posts. Kyyshak argues for aquaponics in which crops are grown in nutrient rich slurries that pump past these plants to enrich them as they grow, then are filtered and treated to farm fish such as Tilapia before looping back around to feed the plants again. Kyyshak has the hard math to back up his claims, and its pretty convincing stuff!
Thanks to everyone who posted, you've given me a lot to sink my teeth into!
If anyone feels I didn't clarify or summarize their post correctly, please let me know and I'll edit accordingly.
Thanks again!
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I've been on the worldbuilding StackExchange for a little while now and I have yet to see a specific line of questioning. How do I design and create flora for my world? As this particular question may get closed as too broad, I will narrow it down.
Are there any online resources (preferably free) that I can use to research medicinal plants and how to combine them into tinctures and salves?
salve means:
a medicinal ointment for healing or relieving wounds and sores.
<http://www.dictionary.com/browse/salve>
As I would to use the information to help create flora to populate my world.
[Answer]
**Borrow the whole thing intact.**
<https://theherbalacademy.com/3-old-timey-herb-books-you-can-read-online/>
On looking into this I was very pleased to find Culpeppers Complete Herbal. <https://archive.org/details/cu31924001353279>
It is written in chatty period English, with commentary on the herbs, their uses and also his countrymen, foreigners and whatever else comes to his mind. It is delightful! I am going to order a paper copy for the bedside.
An excerpt on the Furze Bush:
[](https://i.stack.imgur.com/6O8GK.jpg)
Instead of making up a bunch of stuff, use the lesser known herbs exactly as they are described. The Herbal contains entry on things I recognize like fennel and burdock and cherry tree but many (like Furze Buth here) that are unfamiliar. A selection of the latter should serve your story and it will be fun if your readers later on realize that what you laid out was actually nonfiction.
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Suggestion: before going for the flora, go for the fauna. Given that you can basically come up with any solution you like, if you want more accuracy, you need to start with fauna's necessities. For example, in your world, a species of herbivores could eat both to get nourishment and to assimilate some particular microbiotics that help them become toxic for their predators. They would compensate with an inferior reproduction rate.
Certain flowers could contain a pollen that make bats phosphorescent. These bats would help pollinate these flowers and at the same time become a magnet for insects who would make for easy prey.
Then there could be climatic-driven mass pollination! A kind of plant that grows big globs containing lots of seeds. When, on a given continent, summer, hot and dry summer comes, carrying powerful gusts of foehn, the globs would explode and the seeds would fly toward their new destination...
EDIT:
as for the specific question:
[DIY: TINCTURES](https://blog.mountainroseherbs.com/guide-tinctures-extracts)
[DIY: SALVES](https://blog.mountainroseherbs.com/diy-herbal-salves)
[Answer]
I know this isn't really answering you question, sorry about that
But...
Unfortunately there are so many different types of salves, some come from the leaves of plants others from the seeds and roots and then fungi etc...
There is no real set rule, Poppies are used to create opiates, and Aloe Vera is used topically as a salve, and there are hundreds of plants in between all as different from one another as the previous ones.
maybe a simple starting point would be <https://en.wikipedia.org/wiki/Medicinal_plants>
Then next suggestion i can give you is to simply decide what illness needs treating and then go from there, obviously salves are applied topically wheres tinctures are taken orally.
As i said, there is such a vast difference in the plants used that there doesn't need to be anything special about them, just that they have X trait, and that helps Y illness.
Tinctures are usually alcohol based (normally almost 80% proof), with various herbs or other plant extracts included to give the needed benefits. so you would need a way to produce the alcohol.
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Well... I think the fastest way to answer your question would be Googling it. Look: In this link there here are some ancient medical remedies that actually work:
<https://www.foodmatters.com/article/10-ancient-medicinal-herbal-remedies-that-actually-work>
However, since your flora will be "designed", you will need a little bit more than that. For example: if we assume your alien plants will also retrieve CO2 and release O2 by means of the photosynthesis, you will need to decide what kind of sun will provide the energy, and which wavelengths will the plants will use. Here on Earth plants are green because the chlorophyll absorbs mostly the wavelengths in the blue and red spectrum, reflecting the green (the one we see). If your pigments evolved to use a different wavelengths, the color of your plants will be different.
Additionally, the evolution of the chemical substances each plant produces, is also related to the needs of the plant in the ecosystem. An alien plant could produce a toxin to protect itself from being eaten, and that toxin could be used to cure a sickness in a different species.
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In my fictional world I am planning to have a humanoid species living on an arctic continent, and I am wondering what type of biological adaptations a humanoid (as in, anatomically modern humans or our extinct close relatives) might need to survive in such an environment.
For clarity, the continent in question is an ice-capped land mass connected to other, more temperate continents so there is no issue about migration into the region and the climate will most likely be more stable than our real-life arctic due to having proper ice caps rather than just sea ice. This question is purely about biology and the types of adaptations that my hypothetical humanoids would probably develop given enough time & isolation in this environment.
The inspiration is of course the *jotunar* found in Norse mythology, but my humanoids need not be actual giants. They should however be intelligent on some level, and have some capacity for speech and language if not the cultural sophistication of humans.
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Being a giant is a good start. Scaling up from a human will get you a giant with l² surface but l³ bodymass, which is great for retaining heat. Fat is good, as is copious body hair. If you are striving for humanoid shape, go easy on the concept of "a sphere has minimal surface, thus minimal heat loss". Perhaps have fewer, thicker fingers, no individual toes. They should be able to curl up into a compact form, with much hair outside, possibly tufts of hair for the mouth- region (huskies use their tail). Young ones won't have the size, so the parents will need to feed them high energy milk, and lots of it, additionally being very plump is valuable.
The area/mass thing works against you on the issue of breaking through ice, so either they wear snowshoes, or their feet are disproportionally large.
Ability to hibernate with minimal energy usage would be great.
For hunting (no subsistence farming/gathering in climate that harsh) they need acute eyesight, and hearing. If they hunt something that lives below the ice, its helpful to have something that bridges the impendance- gap from the ice, so perhaps a claw- like nail made from really brittle material, which they can use to feel high frequency sounds in the ice.
The scarcity of trees to me says they evolved without sticks, so either make them crack shots with a stone or piece of ice, or give them a natural weapon - fangs, claws, elbow-spikes... Everything they kill will have a tough hide, so give them something razor-sharp to break open the carcass - claw, tooth, some sort of ridge...
[Answer]
You might look at creatures which have adapted to live in (ant)arctic environments.
First question is just how "arctic" you want your land to be: like Earth's regions around the Arctic Ocean, with a winter/summer cycle that allows vegetation to grow, or like Antarctica? The problem, of course, is the base of the food chain. Either you need a summer to grow land-based plants which feed grazers and ultimately omnivores & carnivores, or you need a food chain based on ocean plankton.
In the former case, you can have land-based animals. They will probably evolve to be something like a cross between grizzly & polar bears: fairly large, with thick fur and an insulating layer of fat which they build up during the brief summer, with a diet that's mostly meat & fish. They might hibernate in winter.
For an Antarctica-like habitat, your only solution is to become largely aquatic, living near the shorelines, going to sea for food, and coming ashore to rest & breed. In Antarctic, of course, your main model is the penguin. For a mammalian species, you could look at walruses & sea lions, or even polar bears.
[Answer]
Take a look at people who currently live in arctic: Eskimos. Eskimos have higher fat content in their eyelids to keep their eyes more insulated.
Here is an [article](https://www.reuters.com/article/us-science-inuit/arctic-advantage-genetic-traits-help-inuit-in-harsh-conditions-idUSKCN0RH2WY20150917) on Inuit adaptions. Im sure you can google for more.
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***CONTEXT/EVOLUTIONARY HISTORY***
A book that I'm currently writing called *Surge* features [an enemy faction called the Degenerates that are heavily inspired](http://tvtropes.org/pmwiki/pmwiki.php/Main/FantasyCounterpartCulture) [by the Scythians](http://arkhamhaus.com/scythian-scouts.html) (Indo-Iranian horse nomads that ruled the Eurasian Steppes and Central Asia from the 10th century BCE to the 3rd century CE) and consists mostly of humans parasitized by a prehistoric endoparasite called Echidna *(Aengapentastomumn corruptor)*, which parasitizes and radically alters the entire physiology of a wide variety of organisms from the phylum Chordata.
An excerpt from [an in-universe field manual that was given to the protagonist](http://tvtropes.org/pmwiki/pmwiki.php/Main/EncyclopediaExposita) (written in the vein of a scientific dossier or military briefing) implies that Echidna is a [pentastomid](https://www.academia.edu/22014789/Pentastomids_of_wild_snakes_in_the_Australian_tropics) (an endoparasitic crustacean that feeds on vertebrates) that first appeared during the tail end of the Cambrian period. While most pentastomids evolved to infect and enter a vertebrate’s lungs via an intermediate host, Echidna forewent this reproductive process by tunnelling into an animal’s brain and [hijacking their body](http://tvtropes.org/pmwiki/pmwiki.php/Main/PuppeteerParasite) for the purpose of giving birth to thousands of larval Echidnae.This was a simple, yet ingenious survival strategy since Echidnae possessed no natural defences and an organism controlled by an Echidna would be used as [a living suit of armour](http://tvtropes.org/pmwiki/pmwiki.php/Main/MeatPuppet) that allowed the parasite to sustain itself in a hostile environment until it reached sexual maturity.
Echidna originally evolved to parasitize marine arthropods inhabiting Cambrian seas. Upon locating a suitable host, Echidna would use its razor-sharp teeth to cut through the hard exoskeleton without damaging any internal organs and burrow into the host's brain. Upon locating the frontal lobe, Echidna would spread root-like tendrils that fused with the host's central and peripheral nervous systems, bringing the creature under the parasite's control. Once this was done, the host's physiology would undergo a series of changes as the Echidna ["edited" the host's genetic structure by adding, removing or substituting parts of the genome with genetic material acquired from previous hosts](http://tvtropes.org/pmwiki/pmwiki.php/Main/LegoGenetics) (e.g the excerpt mentions that the fossil of a parasitized trilobite was discovered possessing raptorial appendages like those of *Kodymirus vagans* and extremely long, hollow spines that possibly contained venom.) It was also not uncommon for Echidna to absorb genetic components from their hosts [using Horizontal Gene Transfer](http://ib.bioninja.com.au/standard-level/topic-5-evolution-and-biodi/52-natural-selection/artificial-gene-transfer.html0), which would've been incorporated into their offspring's genome.
It wasn't until vertebrates migrated onto land during the late Devonian era that Echidna made the jump from arthropods to vertebrates and truly began to thrive. As countless species came and went, Echidna evolved so rapidly that it was almost impossible for the fossil record to keep up and its genome became a vast catalogue of genetic information compiled from countless extinct species. Over time, Echidna gradually evolved to infect humans that settled on the Australian continent, some 65,000 years ago before the events of *Surge*.
But for reasons unknown, Echidna suddenly vanished from the fossil record. It wasn't until the early 21st century that Echidna returned from the brink of extinction, when human activity awakened a colony of Echidnae from their millennia-long slumber. The Echidnae wasted no time in undergoing an abrupt re-evolution in order to parasitize not just anatomically modern humans, but also Australian vertebrates that evolved in the wake of the Quaternary extinction event.
***ADAPTIONS***
Now, to the main event. The stuff I need to know what sort of adaptions would Echidnae need to:
* To enter through a vertebrate's ear canal and tunnel into their frontal lobe, without killing the host
* Successfully avoid triggering an immune system response
* Assume full control their hosts' behaviour and bodily functions
* Alter the host's physiology and genome using Horizontal Gene Transfer
[Answer]
**Background**
Pentastomids are a good candidate, but the secret to their success in this case is in their lifecycle. The ear canal is a possible entry point, but only as a means to get to the spinal column and cervical joint at the base of the skull. However, it is extremely unlikely that an adult Echidnae would ever attempt such a thing - like other pentastomids, they are obligate parasites, unable to survive long outside of a host.
They are already good at masking their presence from the immune system - that is part of their basic abilities as successful pan-species parasites, like all other pentastomid species.
**Brain control**
The frontal lobe is not a good place to control a creature from. While problem solving happens in the frontal lobes, behaviors are not governed by rational thought. Contrary to popular belief, emotions are the core of sound decision making, not rationality. Without experiencing emotions, people have great difficulty prioritizing, forming memories, or learning.
In my own case, I have problem solving capacity in the 98th percentile of the population (great frontal lobes). However, I am very slow to learn new information, and under pressure would be organically incapable of prioritizing the house over my head being on fire versus a sudden desire for a peanut butter and jelly sandwich (lack of emotional connection).
With the research into my own brain injury, I know that a relatively small section of the brain, comparable in size to the pentastomid itself, is responsible for carrying information between the region of the brain that "has" emotions and the portion that "experiences" emotions. Disruption of this section of tissue in a creature effectively gives the parasite full control of the creature, regardless of its rationality.
**Lifecycle**
Pentastomid eggs are consumed by the candidate host, and hatch in their digestive tract. The larval Echidnae migrates through the espohagus, but unlike its more common cousins, it ignores the lungs and moves higher before burrowing into the back of the the throat, seeking out the spinal column, and then migrating into the brain stem through the cervical joint. Following this route, it has no need to penetrate bone.
Once in the brain stem, the parasite latches on to a capillary bed and feeds much like its more common cousins do in the lungs. Once it is fully mature, it begins to grow neural tissue outside of its shell which forms connections with the host's nervous system.
**Genetic Changes - Horizontal Gene Transfer**
The second part of the question involves genetic manipulation. A certain portion of all animal DNA is actually viral DNA that has become embedded in the genome. The Echidnae has a retrovirus that carries with it the genetic encoding for the physiological traits desired. The virus is transmitted by exchange of fluids - as the parasite consumes blood it excretes into the cerebro-spinal fluid, releasing the virus into the host's body.
Since the virus affects the genome of the host, the changes will breed true. Even if they don't breed true in the first generation, the infant will be infected in-utero and will breed true in the second generation. Furthermore, the infant will be infected with Echidnae eggs, which will hatch and parasitise the young.
A side effect of this potential multi-infection is a higher than normal cancer rate amongst Degenerates.
[Answer]
I'm mostly focusing on the genetic/immune system questions - I don't think you can provide a scientifically coherent explanation for the other ones without a lot of handwavium.
In my opinion it would make most sense for the parasite to enter host body close to the spine and burrow from there to the stem brain. From there its much easier to take control of the central nervous system (and therefore the body) and then slowly the brain. This is also much more similar to the prehistoric parasite you describe.
>
> Successfully avoid triggering an immune system response
>
>
>
The immune system attacks anything that looks foreign to the body. Therefore, in order to not get attacked, your parasites need to look 'similar' on a molecular level. This is actually a routine procedure for it, since "its genome became a vast catalogue of genetic information compiled from countless extinct species" - it has a couple of mammalian (amongst other) looking surface markers laying around which it can quickly adapt to mask it against the human immune system.
>
> Alter the host's physiology and genome using Horizontal Gene Transfer
>
>
>
This is a bit tricky and also you don't actually mean "Horizontal Gene Transfer" - this only describes the process of one species taking up DNA from another species over the course of evolution. What you seem to want is genetic engineering of the host body (which as a single organism is not subject to evolution).
Since you can't control the DNA of cells remotely your parasite need to spread throughout the while host body (or at least to all areas it ants to modify). Then in order to change the host bodies DNA it needs a mechanism similar to the one that retroviruses use. Actually it probably uses the exact same one - retroviral elements are clustered throughout the genomes of almost all species and during the evoltuion of the parasite it didn't only pick the up, it also managed to activate them in order to use them on his host body. Since it also has an arbitrary library of genes from various species in its genome it can introduce whatever features it wants into the host.
Please not that just changing the host bodies DNA doesn't automatically mean it will grow new appendages or organs. It's much more likely that the skin (or nails) change or that pores in the skin start producing new molecules. Actually starting the growth of new organs/limbs/... will wreak havoc with the body, likely lead to cancer and in the long term kill the host body.
[Answer]
Logic says that basic characteristics would be:
* Octopus-like physiology (to be able to slip through the ear canal and maybe even very thin cuts)
* The ability to camouflage itself in some way so that the not-yet-host's immune system doesn't attack it.
* Creating carefully analyzed hormones and neurons with axons touching host axons, so that it can exert control over its host's thoughts.
I don't know how to answer the rest of your questions; these basic characteristics are just a starting point.
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[Question]
[
There are seven planets, and each one has a different coloured sky. One has red, one has orange, all the way up to indigo and violet. Of course, they don't have a sky this colour all the time, but preferably for most of the 'daytime'.
However, those aren't the only limitations. Humans must be able to survive in each of the seven without special equipment, and it must be possible for people from any one planet to be able to survive (maybe with a little special training) on any of the other planets.
These must be 'humans', with at least roughly identical anatomy to us on Earth, though the 'blue' planet doesn't have to be Earth.
The tilt, composition of the bulk of the planet, colour and kind of star, can be different if necessary, and these planets do not have to be in the same solar system.
What is the best way to achieve this?
[Answer]
Won't happen with gases. Not if you want Terran type life in the open. The blue of our sky is primarily Raleigh scattering. <https://en.wikipedia.org/wiki/Rayleigh_scattering>
This is going to be the bluish end of whatever light the atmosphere is transparent to.
Most gases aren't coloured. Exceptions:
\* Chlorine -- yellow-green
\* Bromine -- brown
\* Iodine -- purple
\* Nitrogen dioxide (NO2) -- redish brown.
But all of these are toxic.
Table with more colours: <https://en.wikipedia.org/wiki/Color_of_chemicals>
A better way to colour sky may be with dust. Mars's skies are pink due to superfine dust floating in the air.
Most of our earth dust is white or grey, so you get dull colourless skies.
Smoke is fine enough that it shows some Raleigh scattering -- hence bluish colour when lit from the front. Mountain haze (mostly organics and water) is bluish too. Lit from behind the colours are redish. The blue got scattered, and red is what's left. The more particles there are, the dimmer the light, which you perceive as being more saturated.
Gold, if fine enough (A few atoms thick) will be green in transmission, and gold in reflection. So around the sun in the sky it would be green. Away from the sun it would be gold. Raleigh scattering would add a blue component at right angles to the sun. The world would overall have a greenish look to it from the filtering. You need some interesting geology to create this.
In general any colour of dust should be usable this way:
If the particle size is large enough that it is opaque, then reflection is the only activity. The colour of the dust dominates, but is mixed with raleigh scattering.
If the particle size is small enough to be transparent, then you two colours -- the bulk colour as back scatter, and the sunlight minus the bulk colour as forward scatter, again with Raleigh scattering off the gases.
If the particle size is small compared to light, you get Raleigh scattering off of the particles too.
In addition to this, particle shape has an effect. Ice in Earth's atmosphere produces a bunch of effects from refraction, reflection and diffraction. Start here: <https://en.wikipedia.org/wiki/Halo_(optical_phenomenon)> With coloured crystals you could tint the resulting phenomena. Note that the angles mentioned in the article are specific to water ice. You may need to get more detail off the physics forums.
You're going to need to do a bunch more research, but you have to potential to put on quite a show in your story.
[Answer]
**Aurora's Are The Key**
Originally I was going to suggest there being two atmospheres, one with poisonous color giving chemicals, the other being the "safe" atmosphere, but now I have an even better idea...
All the planets could have the same atmosphere but really strong protective magnetic fields. The key is in the Sun. Each planet would be constantly hit with rays of the sun to form a consistent Aurora while certain conditions might change the color for example one planet will have a harsh sun so the sky will be red, another planet will be mountainous and the altitude will be really high and the sky will be green
More information here: <http://www.webexhibits.org/causesofcolor/4D.html>
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[Question]
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I'm making a medieval settlement of humans that reside very close to a volcano (and maybe venture into the caves surrounding the volcano), to the point of living in the caldera itself.
The humans are magically highly fire-resistant and can live there without much problem, however **I'm concerned about what kind of food I can produce** in a rather *active* volcano caldera. I'm not talking about rather greenish fertile volcano sides like we have here in Indonesia (which are made possible because of intervals between eruptions every several months), but rather imagining a black, scorched earth, with visible magma here and there, in *most* of the area. There will be steady magma flowing from the center of the caldera (I'm thinking of a Hawaiian-type eruption)
**Note:** I'm not sure if this volcano is realistic or not, or if what I describe even counts as a volcano caldera, but that is not the scope of this question.
The settlement will be inside the shallow "cup" of a volcano, with almost 10,000 people. I'm not sure about the exact dimensions of the caldera yet, but there should be plenty of room for "pastures" and improvements. There are caves that allow "one-way trading" (from the settlement to the outside world. The outside world has little interest in sending traders to this settlement).
Is it plausible for plants to live there? Cattle? There is a little magic to wiggle the requirement a bit, but I'd rather not create any plants/livestock that vastly differ from what we have in reality. **What is the most plausible method to produce food there?**
I don't think crop farming is possible there, but rather fruit trees that can withstand the heat, but I'm happy to be proven otherwise. I've read [Considerations for a Dwarven Volcano City](https://worldbuilding.stackexchange.com/questions/70624/considerations-for-a-dwarven-volcano-city) but I'm looking a more specific answer about raising livestock and "farming" there (and possibly other methods to produce food)
[Answer]
**[Bromeliads](https://en.wikipedia.org/wiki/Bromeliaceae)**
Bromeliads are a family of plants adapted to dry conditions and poor soil. Or no soil.
[](https://i.stack.imgur.com/7k0H8.jpg)
from linked wikipedia
Adaptations allow them to capture nutrients and water from the air. These are the plants you see growing high in trees or on power lines, like this picture.
>
> Bromeliads are able to live in a vast array of environmental
> conditions due to their many adaptations. Trichomes, in the form of
> scales or hairs, allow bromeliads to capture water in cloud forests
> and help to reflect sunlight in desert environments.[14] Some
> bromeliads have also developed an adaptation known as the tank habit,
> which involves them forming a tightly bound structure with their
> leaves that helps to capture water and nutrients in the absence of a
> well-developed root system.[14] Bromeliads also use crassulacean acid
> metabolism (CAM) photosynthesis to create sugars.
>
>
>
Could these austere plants produce delicious starchy, sugary crops? One has.
[](https://i.stack.imgur.com/YR8UZ.jpg)
[Answer]
I would think that it's not so much a problem with the heat as it is ground. In the scenario you're imagining, I figure that there would be little to no groundwater in that area, so any watering would have to be done by artificial irrigation. Secondly, in order to get plants established, they would have to be able to put down roots. But if you're talking about an active caldera, the ground would either be too hard for plants to take root (in the cool areas) or so hot that they wouldn't be able to find water. So really, unless your population is going to subsist off lichens, I think you'd have to make some sort of magical excuse to allow them to plant food.
Of course, one possibility is to create earthboxes. Bringing in soil and containing it in large pots and boxed-in areas would allow you to get around the hardness of the soil. Of course, this also has its limitations. Water would still have to be brought in, unless you have enough rainfall in the area. The other major drawback is that unless the earthboxes are very large, you would not be able to plant crops that require very large root systems, like some trees.
As far as raising livestock goes, the problem there is that you have to provide them with food. If you want cattle, [your cattle will need to be fed](http://beef.unl.edu/cattleproduction/forageconsumed-day). And a diet of meat is much [more inefficient](http://news.cornell.edu/stories/1997/08/us-could-feed-800-million-people-grain-livestock-eat) than a vegetarian one. If you're already extremely limited on your arable land, and you're not bringing in food from the outside, all of your produce would have to go to feeding your animals.
[Answer]
# They have a perpetual greenhouse, and they import soil
Regular humans do not like living in temperatures of about 40 degrees C. **Plants however, love it.** Heat is great to make plants grow quickly and become large and healthy. This is why we have [greenhouses](https://en.wikipedia.org/wiki/Greenhouse).
[](https://i.stack.imgur.com/OfD0Y.jpg)
*Human: "Eeewww... so balmy... I don't like it"*
*Plants: "Yaaaaay! We love it here!!"*
Now you are saying you have humans that do not mind the temperature... high temperatures do not bother them. Also this tribe lives in the "bowl" of a volcano. They have a natural **rain collector**. High temperatures, plenty of water, this means...
**Your fire-resistant humans live in a perpetual, natural greenhouse.**
This puts very few limitations on what they can grow. On the contrary: they are probably less susceptible to seasonal variations, and also they do not have to suffer frosty periods. Their farming will most likely be varied, efficient and plentiful compared to the amount of land they use. And they can go all year, as opposed to most farmers on the outside.
Temperature regulation is not very hard either: if they sprinkle water into fine droplets, it evaporates quickly and soaks heat. This lets them down-regulate the temperature as they need it for specific crops.
The thing they need and that is hard to get is [**soil**](https://en.wikipedia.org/wiki/Soil), and this is a huge plot generator for you. If you have read [the book 'The Martian' by Andy Weir](https://en.wikipedia.org/wiki/The_Martian_(Weir_novel)) (\*) you will know that making [fertile soil](https://en.wikipedia.org/wiki/Soil_fertility) from otherwise non-fertile ditto is not impossible nor a very high-tech affair.
In short: **fertile soil breeds more of itself**.
So your fire-resistant humans are **importing soil to their crater** and they are **experts on [soil quality](https://en.wikipedia.org/wiki/Soil_quality)**. They are farmers that have next to magical knowledge on what makes soil thrive and be well. They can — near instantly — make an accurate judgement on the quality of soil. They revere soil and treat it as a living thing (which it actually is, or at least the [soil micro organisms](https://en.wikipedia.org/wiki/Soil_biology)).
Also since few animals tolerate high temperatures this means that your tribe are probably vegetarians. Not out of ethics — maybe they think that meat is a rare treat and a good perk to go on soil-trading expeditions? — but they simply cannot keep animals in their steamy, balmy home. But that is quite all right because **animals as food is a huge waste of resources**. Really, you lose about 90% of the plant energy when you make animals into food. For us regular humans that is not a big issue because we have lots of resources to use (sort of.... or maybe not.... but we do it anyway). But your volcano-dwellers do not have that luxury. They need to manage what they grow carefully.
(\*) The movie does not delve deep enough into the subject of soil, but the book goes into it in great detail. I highly recommend this book, not only for that but in general. Also the audio version narrated by R.C. Bray is incredibly funny at times; he is a much better Mark Watney than Matt Damon.
[Answer]
They breed fruit bats. Bats live in the caves and fly out at night to eat fruit from the surrounding area's trees. Selective breeding made them big enough to provide food for a whole family for a day.
Or if this volcano is near the ocean, at least on one side, they could go through the tunnels to fish.
Or maybe they go out and trade whatever they can get out of the volcano (diamonds?) for all the food they need.
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I am currently reading [an eternal golden braid](https://en.m.wikipedia.org/wiki/G%C3%B6del,_Escher,_Bach), i've gotten as far as several lengthy chapters about the brain.
He talks about neurons and symbols, what 'meaning' is and there is a lot of hypothesizing going on. To me much seem like assumptions about our mind from a mind strongly affected by its knowledge about computers. Anyway it intrigues me! I got the impression that the brain is somewhat well understood on the micro level (neuron-level, not neutron level) but that it all falls apart when trying to understand it on higher levels. (this book was ofcourse written decades ago)
Given current electroengineering technology and sub-infinite resources how slow/big would our model of the neural net of the brain become? The neurons in the model should reflect our current biological understanding of them.
size/speed is all free variables in this question. I reckon doing anything close to 86billion braincells got to be too slow/memory intensive for doing in software in general unspecialized supercomputers.
By speed i mean how long a 'thought' would take compared to a human if somehow the net was constructed and jumpstarted and it actually became an 'I'. How feasible would it be for a near future megacorp to afford to try making one?
[Answer]
Simulating human brain is currently absolutely not feasible for several reasons (I'll detail later).
AFAIK the only *successful* simulations (meaning: simulated result matched what biologic Neural Network actually did to a reasonable degree) were done for very simple organisms, if memory assists the most complex was a snail with several thousand neurons.
These simulations, however, were done simulating effects of neurotransmitters and neuron membrane; Simulated Neuron Networks (SNN, the kind of Neuron Networks that are actually in use to solve many problems, including prepare weather forecasts) work in a completely different way, the abstract the actual working of a neuron in a "stylized" way which has nothing in common with real Neuron operation. They are *models* of the neuron leaving out a lot of details to capture general principles of operation.
They do a good job, enough to be real useful in building A.I.
They're powerful enough to scare people like Elon Musk and Bill Gates with perspective results.
There's a heated debate if these SNN really capture enough of neurons working to permit replication of a complex brain.
In general problems arising when trying to simulate human brain are at several levels:
* Scale Problems
+ It is unclear if SNN really behave in a way comparable with biologic systems.
+ Very large SNN contain several hundred thousand Simulated Neurons our brain is close to hundred *billion* neurons.
+ Each SN has, at most, about 100 connections; typical neuron has more than 100 *thousand* connections.
* Physiological problems:
+ We do not exactly know how neurons are connected in our brain.
+ We have only a vague idea of function localization.
+ We have understood *some* of the interaction between neurons and neurotransmitters in blood stream.
+ We are recently starting to understand neurons *not located in the brain* (such as cardiac ganglia) have an important role in long-term memorization (thus giving a completely new meaning to the phrase "learn by hart").
+ Similar importance for overall brain operation have abdominal ganglia.
* Philosophical problems:
+ There still is no universal consensus (I have definite ideas on the subject though) if brain biochemistry can fully explain our subjective and objective behavior.
+ There still is no consensus of what actually is that we call "Conscience".
+ There still is no consensus if simulation can capture the relevant parts of what we cal "I".
The cited Hofstatter's book is a very interesting one and it is what spawned my interest on the subject, mut it is, IMHO, trying to hard to demonstrate a philosophical thesis ans thus it is, in the end, rather unconvincing.
Note: I summarized my personal understanding of the matter in a [small site](http://home.condarelli.it) I wish I had more time to maintain. You'll find many references to published academic papers there.
[Answer]
Your modern computer is blindingly fast. A quad core 3Ghz i7 with hyperthreading does in excess of 12e9 computations per second. A GTX1080 GPU has ~2600 cores at ~1.6ghz, or 4,160e9 computations per second. Your brain, on the other hand, has 100e9 neurons all working in parallel. A neuron can fire about 200 times per second. giving us a rate of 20,000,e9 firings(?) per second.
So if we say that it takes 100 computer instructions (number pulled from hat) to simulate a neuron and ignore our ram requirements and lookup times. If we load that onto a single GTX 1080, and if we somehow assemble the neurons into a brain, how fast will it run?
**On a single GTX1080, it will be 500 times slower ignoring ram lookups, assuming 100 instructions per neuron.**
```
GTX1080
-> 4,000e9 instructions per second * (1 artificial_neuron_triggers / 100 instructions)
-> 40e9 artificial_neuron_triggers per second
HUMAN BRAIN
-> 100e9 neurons * (200 neuron_triggers / 1 neuron) per second
-> 20,000e9 neuron_triggers per second
```
---
So we're not that far off. Grab a couple hundred GPU's and you can be in the same order of magnitude. Why can't we (currently) simulate a brain in real time with a bunch of super-fast GPU's?
I can think of a few reasons (Also see ZioByte's answer):
1. We don't have a clue about how the brain fits together other than at the micro level (single neurons) and a touch at the macro level (eg MRI's), or if we do, I haven't heard about it (if you have, post links or edit this answer). As such, while we may be able to simulate networks of neurons, we (as far as I know) can't assemble them into a human brain.
2. A neuron is not a single calculation. A GPU is a vector processor, and just like your CPU, it can do things like adding numbers, or multiplying them. What does a neuron do? You can find pages and pages of math representing the behaviour of a single neuron. Needless to say, you will need an order of magnitude or more excess computation power to simulate an equivalent number of neurons. I assumed 100 instructions per neuron 'trigger', but I suspect that is far to low.
3. Memory lookups are really slow. If you have 100 billion neurons, you need 100 gigabytes of ram to store the system state (assuming a single byte per neuron - so you'll need more). While this is possible using caching to disk, access will be crazily slow. The slowest operation in most shaders in computer games is a texture lookup. I doubt this is any different for looking up neuron states. In a real brain each neuron stores it's own state, but we do not have 100 billion L1 caches (the really fast ones) on our GPU. We only have 2600 (one per core).
4. The architecture is all wrong. Even on a highly parelleized GPU, things are still synchronous, and your brain will be simulated in individual steps. So far as I know, a brain does not have a clock [citation needed] and is thus an asynchronous machine. It will be hard to change this in the near future, and I suspect that proper neural simulations cannot be done with current machine architectures.
5. Samwise points out in the comments that this ignores the role of synapses. These are likely to increase the required computation hugely.
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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.
I am creating a creature which uses infrasound to immobilize prey and I have done a little bit of research on the effects of Infrasound on animals, finding that 177 dB with a frequency between 0.5 to 8hz in infrasound can induce artificial ventilation in animals and cause respiration to cease.
I would like to know the frequency required to cause a human head to explode, and whether something like this could actually be achieved in real life.
(I do not care about the plausibility of such a creature's biology, how it would have evolved or any other such questions regarding its nature. Those are not the focus of this question.)
[Answer]
"[Resonance frequencies of the human skull in vivo](https://www.ncbi.nlm.nih.gov/pubmed/8176050)" by B. Håkansson, A. Brandt *et al.* (*J. Acoust. Soc. Am.*, March 1994, vol. 95 (3) pp. 1474-1481), available on [PubMed](https://www.ncbi.nlm.nih.gov/pubmed):
>
> *"Between 14 and 19 resonance frequencies were identified for each subject in the frequency range 500 Hz to 7.5 kHz. The two lowest resonance frequencies were found to be on the average 972 (range 828-1164) and 1230 (range 981-1417) Hz."*
>
>
>
That is definitely not *infrasound*. And while it might *shatter*, it won't *explode*.
[Answer]
The human head can absorb a lot of energy, resonant frequencies or not.
According to [here](https://www.extremetech.com/extreme/175996-can-a-loud-enough-sound-kill-you) the threshold of death from decibels (loudness, you have to get to ultrasonic frequencies for the frequency to matter at all) is 185-200dBA. For comparison, a modern jet liner taking off is 120dBA and a flash-bang grenade produces 150-180dBA (the threshold of death, designed to stun and incapacitate). Remember that decibels are a logarithmic scale, so power increases exponentially.
I'm guess, but my sense of math with a logarithmic scale suggests you'd need 250-300dBA to pulpify the head — and that might be low.
Now, sound dissipates according to the inverse law (1/r). So, if you're 10 meters away the sound level is 10% of what you started with, or 20dBA. So the killing effect would be good for 1:1 combat.
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In Georgia (Soviet Union) bacteriophages are used to to cure bacterial infection. In this [video](https://www.youtube.com/watch?v=_mm3GlUnGFk) one can see how they are produced. So it might be possible in an alternate timeline, that Paul Ehrlich came up with this in the late 19th century. The right filter ([Camberland filter](https://en.wikipedia.org/wiki/Chamberland_filter)) was available to get rid of the bacteria.
Then in the alternate timeline, this therapy is developed and becomes a standard treatment. Then antibiotics are discovered much later (because there already is a treatment) and later it is noticed that bacteria becomes resistant (to antibiotics) faster because of the use of bacteriophages.
Does this concept make sense?
EDIT:
Note, the bacteriophage production is very different from the today medicine production. Instead of developing one pill after extensive testing, the production is very localised, i.e. every hospital has a bacteriophage production (and interchange them with other hospital). Moreover the hospital gives them out to every medical practice. Then if you have some bacterial infection the doctor test if any of his bacteriophage kills the infection, if not you get send to hospital where they have more bacteriophage, if no one helps either they produce new one as seen in the above video from minute 33 onwards (they get water from the local river and filter the bacteria out)...
[Answer]
Bacteriophages and antibiotics use different pathways and receptors for their mechanisms of action. So in general no, antibiotic resistance shouldn't lead to bacteriophage resistance or vice versa.
Here is a quote from [an article](http://www.medscape.com/viewarticle/759866_3) discussing this.
>
> Dr. Sulakvelidze pinpoints the essential difference between phages and
> traditional antimicrobials. "The mechanisms by which antibiotics and
> lytic phages kill bacteria, and the mechanisms of bacterial resistance
> to antibiotics and phages, are fundamentally different from one
> another. Lytic phages can killbacteria that cannot be killed by
> currently available antibiotics, and the use of phages in various
> settings (including for improving food safety) does not create
> selective pressure for antibiotic-resistant strains to emerge,"
> explains Dr. Sulakvelidze. "Lytic phages are very effective in killing
> their targeted host bacteria. However, in contrast to antibiotics,
> they are very specific -- phages will lyse related strains or a
> subgroup of strains (usually within the same bacterial species or
> within closely related bacterial species), but they will not lyse
> strains of other, unrelated bacteria."
>
>
>
[Answer]
Yes, easily. Here is a article by Carol Potera discussing continued study and use of bacteriophage treatments by Eastern Europians: Phage Renaissance: New Hope against Antibiotic Resistance
<https://ehp.niehs.nih.gov/121-a48/>
This article examines the continued overuse and mis-use of antibacterial medications causing increasing resistance to them. It's explains in the 1920's and 30's use of bacteriophage for treatment of bacterial infections was discovered and used by physicians, but with inconsistent results. The much better success of antibiotics obliterated use of bacteriophage in Western medicine.
With today's much more advanced understanding of molecular biology, phage therapy is once again emerging as a valuable warrior in the medical battlefield. The article also states there are currently two companies using phage therapy products for the FDA and the USDA for use against food-borne infections.
The caveat with their use accelerating antibacterial resistance is summed up in the article's statement: "However, phages are not totally bad (for the bacteria) and even offer bacteria a fitness advantage by transferring genes for antibiotic resistance and toxins to bacteria."
In your world, perhaps molecular technology isn't advancing fast enough to overcome this limitation.
[Answer]
Bacteriophage can be used to treat illness, but bacteriophage resistance can occur just as antibiotic resistance occurs. It is a matter of the microbial arms race concept.
Bacteriophage infect cells through proteinaceous receptors, I believe, always. Antibiotics kill bacteria by targeting one of five or so different basic functions of the bacteria: Cell wall, protein synthesis, DNA synthesis, membrane cohesion, etc.
Bacteriophage may be less toxic to humans, since their receptors do not occur on human cells. But, bacteriophage are rarely (ever?) wide spectrum. They are usually species - specific. So, Penicillin was useful against many types of bacteria, but it would be unlikely to find a phage that has this sort of spectrum of effectiveness.
Your final question is whether antibiotic resistance would spread easier, if phage therapy was used. In theory, yes, because phage are vectors and can move the antibiotic resistant genes around as they grow and lyse the cells.
One big problem with some infections (like tuberculosis) is that some proportion of the cells wall themselves off and become dormant, thus antibiotics (and phage) are less useful. A combination therapy, one that gets those dormant bacteria growing, is called for, to make the bacteria susceptible to treatment.
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My question is simple: In a world where babies are born with the knowledge of an average adult, what would happen to the childhood of the child?
For example, how would this affect the learning of walking, the ability to speak, etc.
We have the following assumptions:
* Parents are aware of this phenomenon before birth, it is something normal in this world
* There is only one language in this world so there is no problem with learning foreign languages
* Growth is physiologically normal
Edit: Let's suppose the baby has all the conscious and unconscious knowledge of an adult except for his physical abilities.
For example, the baby could "inherit" a water phobia but not "inherit" being a darts champion.
**In a world where babies are born with the knowledge of an average adult, what would happen to the childhood of the child?**
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Knowledge is useless without the emotional maturity to apply it. Ask anyone married to an alcoholic or addict!
A one-year-old may know all about how electricity works, but when the impulse strikes to stick a fork in a socket, that knowledge will mean nothing. Ask the parent of any teenage male!
Up until the age of about 6, the child simply does not have the capacity for conceptual thought. (Check out [Piaget's developmental stages](https://ehlt.flinders.edu.au/education/DLiT/2000/Piaget/stages.htm).) Adult knowledge is really only useful after that age.
The one effect it will have is that in the times when the child (older than 6) is calm and able to be rational, he or she will have more ability to cause havoc, because they will know how to, for example, take apart the toaster and use the heating element to make central heating for their dollhouse.
Formal reasoning "if A is dangerous, and B leads to A, then B is dangerous" doesn't develop until around puberty.
Even then, when they are capable of formal reasoning, the ability to assess risk develops much later. Brain development isn't complete until the early 20s, and until that time, people tend to take idiotic risks, especially people with a lot of testosterone in their systems. (This is why car insurance premiums are much higher when you have a driver under 25.)
The kids would behave a bit like idiot savants, or like Rain Man - having isolated pockets of extremely detailed information, but lacking the social/emotional resources to integrate that knowledge and behave like a regular adult who knows that stuff.
Depending on your definition of "knowledge", they may also behave like sociopaths, because empathy is a physically-learned skill, based on the bodily sensations that result from the action of [mirror neurons](http://www.apa.org/monitor/oct05/mirror.aspx).
Perhaps you are not aware, but phobias are learned physically, too. They are a physiological response to a perceived threat. The circuits that trigger phobias [bypass the cerebral cortex](https://en.wikipedia.org/wiki/Amygdala_hijack) (where thinking happens) and connect the perceptual input (sight, sound, smell, etc) directly to the amygdala (reptilian complex), which triggers the "fight or flight" response. So, "knowledge" as you define it, would not include phobias.
Emotions and proprioceptive feedback are so deeply involved in learning, making decisions, and dealing with obstacles that it is difficult to imagine how a human being could have much meaningful "knowledge" if the physical aspect of the learning process was removed. For example, [children who don't crawl](http://ilslearningcorner.com/why-babies-should-never-skip-the-crawling-phase/) before they start walking have deficits in mathematical reasoning (due to poor integration of the two brain hemispheres), which can be repaired if they do a bunch of physical therapy.
As a way of resolving at least some of these dilemmas, you could consider Jean M. Auel's approach to this "inborn knowledge" in her Neanderthals in the [Clan of the Cave Bear](http://rads.stackoverflow.com/amzn/click/0553250426) series. Children have all the knowledge of their ancestors, but it is subconscious, and they can only access it consciously once they have been reminded of it by another person. These remainders come at appropriate ages - the really dangerous knowledge is only activated after they reach adulthood and can deal with it responsibly.
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# There is an error in logic here...
If a baby had all the knowledge of an adult, and then learned anything, he would then have more knowledge as an adult than he did as a baby. If every person knew more as an adult than as a baby, that would invalidate the original claim that babies are born with the knowledge of an adult.
If no one learns anything in their lifetime, then nothing new can be invented. That would include society itself (or language, religion, fire, how to use pointy sticks to kill mammoth, anything). Therefore, if a people had all the knowledge of an adult as a baby, society could never develop, and your people would just be animals.
Conclusion: such a society could not exist.
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Since blood is a fluid tissue rich in nutritious proteins and lipids that can be taken without great effort, it looks like hematophage animals would be above carnivores in the food chain.
Animal tissue (meat) has much higher energy content than plants but still needs to be broken down in proteins. Breaking down those protein through digestion costs some energy.
Blood already contains those broken down nutrients and it would seem that it s even more energy efficient than meat.
On our planet, only small animals are hematophage. I wonder if it s because it would be too difficult for a larger animal to constantly hunt bigger animals and drink their blood.
Therefore I m wondering if a human sized animal could entirely be hematophage.
Also would it be possible to modify our DNA to make our digestive system be able to digest blood? That would turn us into vampires!
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I recently saw an interview with Neil Degrasse Tyson where he mention the plausibility of adding every metabolic advantage that exist in the animal kingdom to humans. We all stem from the same evolutionary tree, so we are "compatible" in a genetic level. If there are enzymes and intestinal processes that allow animals to digest blood, then it should be possible to add them to humans. The problem would be for a grown individual to acquire enough blood to feed each day. And that blood to have all the nutrients needed in sufficient quantities, otherwise the vampire would suffer calcium insufficiencies and such. It would make more sense for a humanoid to modify their metabolism to digest as much kinds of food as possible. That way some days you'll only need to extract a litter of blood from a cow if you don't want to kill it for it's meat yet.
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Blood may be more efficient to digest than meat, but it is also in lower supply, which is a problem especially for the required calorie intake.
I wrote a rather detailed answer [here](https://worldbuilding.stackexchange.com/questions/46266/how-to-steal-hemoglobin-from-other-people-animals/46274#46274) explaining how humans could be biologically forced to vampiristic behavior (basically, by disenabling them from absorbing iron from plants and making them allergic to meat which, contradictory as it sounds, is possible (see link) thus forcing them to get it from blood. They still have to complement their diet with plants to get calories and vitamin C which blood doesn't give them enough of).
The reason why only small animals are hematophage is probably, as mentioned above, that there simply isn't enough blood to hunt for bigger animals.
In regards to the ability to digest blood we have to look at every component singularly. Our digestive system can already absorb all the nutrients in it, but not absorb any of its proteins (which makes it impossible to absorb hemoglobin, like the question I linked proposed). The ability to do so would require **very** big changes to our digestive system and would be impossible to achieve by genetic manipulation, if that's what you asked.
What can be done to facilitate a blood-based diet is developing more efficient mechanisms to dispose of iron and sodium, of which there is a relatively high amount in blood if they really have a blood-only diet, which would require consumptions of more than 3 liters of blood every day.
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## **NO**
Blood is actually one of the **least nutritious components** of the entire body. It's 92% water by volume, with only 8% composed of "stuff". By contrast meat is only 75% water by volume. In contrast to meat blood also lacks high-density nutrient components such as fat.
As an example, consider one of the only hematophagous vertebrates, the [vampire bat](https://en.wikipedia.org/wiki/Common_vampire_bat). Blood is such a poor food source that vampire bats have to feed every other night to avoid starvation, and if they fail to find a cow or a capybara to feed on they have [specialized behaviors where they beg for food from another member of their flock to avoid starving to death](https://royalsocietypublishing.org/doi/full/10.1098/rspb.2012.2573). If they don't feed within 48 hours they die. On top of that, blood is so poor in nutrients vampire bats cannot physically get enough blood into their bodies to sustain themselves. They have to eat half their weight in blood every night to survive. [In order to do this they urinate all over themselves as they feed, trying to remove as much liquid water from their meal as possible before they take off.](https://www.semanticscholar.org/paper/Intestinal-Water-Absorption-Varies-with-Expected-Price-Brun/2df15663e4893497359f4d3f8563fd2f996542a6)
This is bad enough, but now scale this up to the size of a human being. Someone actually crunched the numbers and found that a human-sized vampire would [need 55 liters of blood a day](http://omgfacts.com/how-much-blood-would-a-vampire-really-need-to-survive/), or in other words **10 peoples worth of blood per day**, in order to get enough energy to survive. Notably, this link's value is probably wrong, because it doesn't take into account the square-cube law and doesn't take into account the fact that basal metabolic rate scales to the 0.75 power of body mass. The actual value is likely higher. The human metabolic rate is also [twice what is predicted based on body mass](https://www.pnas.org/content/100/7/4046), likely due to our large, energy-hungry brains. I have no idea if vampire bat metabolism is high or low relative to their body size, though there is some evidence they have adaptations to fasting.
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Due to how nutrient-poor blood is, being mostly water, I believe that such an adaptation would require a world with more megafauna. If we go with blood that has a glucose concentration of 1.30 g/L, and glucose has an specific energy of 15.6 kJ/g, that means that each liter of blood contains 20.2 kJ/L, or 4.83 kcal/L. Thus, the bloodsucker would need 414 L of blood a day, which is equivalent to 82.8 human bodies' worth of blood. Assuming that the megafauna's adults have a blood concentration identical to human blood, they would need about 414 L of blood each for the bloodsuckers to survive via draining one completely dry a day.
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On Earth, we experience seasons because of our planet's axial tilt.
[](https://i.stack.imgur.com/usSHK.png)
It is a common misconception that the seasons are instead caused by our planet's distance from the sun changing as it orbits. The Earth's distance from the sun does change throughout the year, but the change is far too small to have any effect on the planet's temperature. In fact, in the northern hemisphere, the Earth is actually furthest from the sun during *summer.*
[](https://i.stack.imgur.com/RJj6I.jpg)
Imagine an earthlike, inhabited planet with zero axial tilt (ignoring wobble) and a much higher orbital eccentricity than Earth (exact values aren't important at this point but feel free to calculate them for extra kudos). For this planet, "summer" is the time spent closest to the sun and "winter" is the time spent furthest from the sun.
[](https://i.stack.imgur.com/mmKcA.png)
# Is this setup a feasible explanation for the seasons of a fictional planet?
If so, how would the planet's seasonal cycle differ from Earth's (all other things being equal)?
Would there be any notion of an equinox?
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Yes, more eccentric orbits are possible and you can find or handwave reasons for it to stay that way (e.g. pumping from gas giant). In fact, this is expected to be the case for inner planets around dim red stars (much closer than Earth is to our sun to get the same total light) when a giant is also present farther out. Interestingly, the *day* will be synchronized with the year, and the year will only be a few Earth days, so we would call that part of the diurnal cycle and not *seasons*. Anyway, you can plausibly say that an Earth-like system has a more eccentric orbit, and only the most advanced readers will question the long-term dynamics and reconcile it against current formation models.
The big difference you find will be the **lengths** of the seasons. The planet moves slowest at the far end of the orbit (and vice versa), so you’ll have a long winter and a brief summer.
In general, you’ll have axial tilt *also* giving a combination effect. This will change in relative phase over thousands of years as the axis precesses. And the planet’s axis changes over tens to hundreds of millions of years, wondering every which way, so finding it where it happens to be vertical is a temporary condition and life would evolve to match because it’s such a long time scale, but would show the history of other tilts.
To *stabilize* the planet’s tilt, you need something like our own large moon.
To learn much more about these interrelated subjects, I suggest you check out the SETI Weekly Colloquium series. You can find them posted on Youtube.
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So, on the Planet of the Aves, [Tres' sapient crows](https://worldbuilding.stackexchange.com/questions/53098/planet-of-the-aves-low-tech-weaponry) are the dominant sapient species. Given that your average bird spends plenty of time on the wing, how intuitive would they find subsonic aerodynamics, compared to us ground-bound humans, who have to crunch all sorts of numbers just to figure out how well a wing design will work? (Nowadays, we let a PC do that for us, but the idea doesn't change.)
Furthermore, assuming they can fly high enough and long enough for weather to be a factor, would they have an easier time understanding weather phenomena than we do? Could they simply glance at a storm and tell if it's a minor rainshower or a baby microburst being born? Would they be able to tell us things about icing layers that we haven't figured out yet?
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A list of all Planet of the Aves questions can be found [here](https://worldbuilding.meta.stackexchange.com/questions/3939/planet-of-the-aves-series/3940#3940).
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Birds can hear infrasound which tells them lots of stuff about storms which we can't perceive until the storm is practically on top of us. These birds [fled a storm which was hundreds of km away.](https://www.theguardian.com/science/2014/dec/18/birds-storm-infrasound-warblers) While [these birds avoid storms on their migration roue](https://ww2.kqed.org/science/2014/12/19/uc-berkeley-study-says-migratory-birds-use-infrasound-to-avoid-storms/) and it has been suggested that Australian birds head towards the arid centre (e.g. Lake Eyre) to breed when they hear a storm - and thus know that rain has fallen there.
So there will be a lot of weather phenomena which your birds will be able to sense directly.
Aerodynamics... just as humans since time immemorial have been making wooden legs and artificial arms for people who have lost a limb, your birds will doubtless have been experimenting with artificial wings. So they may have worked out a lot of the principles of aerodynamics even when they were a pre-literate/pre-numerate society. They'll crunch the numbers later, when their scholars are trying to explain what they already know in scientific terms.
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I suspect that Aves would have an entire subset of language for understanding aviation, similar to the extended vocabulary that high latitude cultures [tend to have about snow](https://en.wikipedia.org/wiki/Eskimo_words_for_snow):
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> The claim that Eskimo languages have an unusually large number of words for snow is a widespread idea based on the work by anthropologist Franz Boas and has become a cliché; it is often used to illustrate the way in which language embodies different local concerns in different parts of the world. Boas didn't make quantitative claims but rather pointed out that the Eskimo–Aleut languages have about the same number of distinct word roots referring to snow as English does, but the structure of these languages tends to allow ***more variety*** [emphasis mine] as to how those roots can be modified in forming a single word.
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The significance of this is in the ability to express and share ideas. With a broader vocabulary, or more nuanced phrasings, as seems to be the case above, people have the ability to express more complex and subtle ideas. It is experience and practice plus thought on a subject matter that promotes these extensions to language. And likewise the extensions to the language promote deeper thought and clearer communication on the subject matter.
Similarly, weather knowledge can be thought of from an experiential perspective. Farmers who have lived and worked in the same area for a period of time can often look at the sky, feel the air and predict with greater accuracy the weather in their local area than meteorologists whose job it is to track and predict weather on larger scales than what concerns a local farmer.
Aves, also I suspect, would have visual knowledge of the sky, but unlike a farmer they would have a physical sense of the sky from up in the sky. They could fly through turbulent air, taste it, feel the intensity of it, whether it is large and flowing turbulence, less chaotic turbulent air, or smaller, roiling turbulence, hotter, colder, wetter, drier, charged, etcetera. There would likely be an entire area of language that farmers or perhaps even meteorologist do not possess to such an acute degree.
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Every culture has its armor and their armors always, without exception, fit in with the culture they belong to. Even more than [weapons](https://worldbuilding.stackexchange.com/questions/22176/process-for-creating-cultural-weapons), armor makes or breaks a cultures feel and theme, you would not expect to see a Germanic Barbarian Wearing samurai armor, nor would you ever think of seeing Native Americans wearing Aztec wear.
Needless to say the armor a culture wears is are as important as their [beliefs](https://worldbuilding.stackexchange.com/questions/22445/how-to-create-a-myth-that-fits-in-well-with-your-culture) and necessary to keep the feel of that culture and many works of fantasy show great design that fits the feel of their armor; such as the Thalmors armor in Skyrim, or the Orcish armor in Lord of the Rings. What things should you keep in mind when designing cultural armor?
[All Culturally Correct Questions](http://meta.worldbuilding.stackexchange.com/questions/3960/culturally-correct-series/3961#3961)
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There's many factors that go into a good armor but let me throw some bullet-points out. These all must be considered at the very least:
* Resource availability, you need a decent amount to make armor so this is going to reflect economy (you wouldn't have a standard armor made out of gold on earth).
* Resource shape-ability, the easier the more intricate work is allowed and the more culturally adapted it can be.
* Resource protect-ability, does it actually guard against anything for its weight cost? Really heavy cotton candy does not a good armor make.
* Resource significance, are we culturally allowed to use said resource?
* Climate adapted design, you can't wear plate mail in the desert. Moisture and cold aren't much better pairings either.
* Culturally adapted design, your god protects the left hand of righteous people, so why cover it in armor? If pictures are forbidden use spirals and knots. If combat is about fear maybe make armor imposing at the cost of being practical (Vlad would approve). Is armor mainly ritualistic/ceremonial? Then it doesn't need to be practical at all but entirely reflect its cultural purpose.
* Military adapted design, is it mass producible? We're not thinking about resources now, we're thinking about time to create a single unit. Armor would tend to be trendy or radically individualistic if not for a "common" armor.
* Combat adapted design, in the rock-paper-scissors of weaponry and tactics: what's the current trend and what best protects against it? Are me aiming for mobility? Are me adapted for mounted units? Are we opting for maximum protection on each unit? Curved surfaces deflect blows but really soon we could optically camouflage a flat surface. There's almost a need for a *History of Wars* here.
There's almost certainly more points I haven't considered here. Definitely make sure it's consistent though. Cultures tend to bleed across political boundaries for example.
**Edit:**
I talked with an armor smith. A major additional point under the military bullet is the fact that you live in your armor at war, so ceremonial/tournament armor would be designed differently than war armor.
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Weapons, industry, social and political organization, technology, resources and materials. Basically what shapes a culture and its choice of armour is the world in which it exists and the ways in turn that culture influences that world.
Essentially what determines the design of armour isn't purely cultural expression (the symbols and iconography the armour represents) but its utility in warfare.
Native Americans didn't wear armour because their cultures lacked the industry and technology. They weren't engaged in conflict where wearing armour was an advantage. The wearing of armour was discarded when new weapons made armour a disadvantage. For example, wearing a full suit of armour isn't very useful in going up against machine guns.
Culture is only an expression of all these factors. Once armour is useless people hang it on their walls and get on with using weapons and protective gear that give them the advantage in war they need.
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The vast, vast majority of food chains of earth use photosynthesis as a base for the food chain. But theoretically we as a community have talked about other ideas such as; Radiosynthesis (based on radioactive elements), Chemosynthesis(based on miscellaneous chemicals) and Mangetosynthesis (using Earth’s magnetic poles).
Obviously in a manner of likelyhood, evolution will favour photosynthesis, but let's say that for some reason they are all possible candidates for my world. What are the pros and cons of different syntheses?
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Remember the most important rule of a food-chain: **the source of energy at the base *must* be renewable.**
Photosynthesis has always been the base of all major food chains (major as in involving transitions of great amounts of energy) because it is based on the free, easily available and longest lasting source of energy: sunlight.
# Chemosynthesis
This is usually believed to be the earliest type of respiration on Earth. The primitive beings, the ancestors of archaea used to live by [eating sulfurous compounds](https://en.wikipedia.org/wiki/Sulfate-reducing_bacteria) found abundantly in the oceanic hot springs.
It has happened once, it can happen again on another planet. The advantages are:
* The process is very simple and does not require complex digestive system. Highly suitable for simple life forms.
* Creatures relying on this method of respiration can (and do) populate closed places where sunlight never reaches (deep, closed caverns and endemic habitats on seafloor). Simple food webs can be designed for such localities, with these creatures on the base.
* Also provides an excellent biological channel for converting these compounds into products which are more easily utilized by intelligent life forms (humanoids?) on the planet. For example, archaea eating hydrogen sulfide would convert it to sulfur dioxide, which disperses into the air. At other locations strong reducing agents would reduce sulfur dioxide back to amorphous sulfur, creating sulfur ores. This would help assemble all crustal sulfur into ores which are easily utilized by the humanoids. On the contrary, it would be practically impossible for your humanoids to go on collecting small amounts of hydrogen sulfide from several cave systems and deep-sea vents.
However, this might not be a very good idea for serving as the base for *all* food webs on your planet. Here are some of the disadvantages of this method:
* It does not create large amounts of energy (as compared to glucose combustion) which means that it cannot power complex, multicellular organisms.
* Another reason for not supporting complex life is that the waste products of most chemosynthesizing processes (specially those involving sulfur and nitrogen) produce highly toxic waste products (anywhere from sulfur powder to sulfuric and nitric acids). While it is easy to quickly expel such disastrous chemicals from a single cell, it would be impossible to collect and expel all the toxic waste created by all the body cells in a complex organism.
* High-energy chemical can be present on a planet in large quantities, but without any proper cycle, they are always exhaustible and non-renewable. This means that in the long run, most of chemosynthesizing organisms would go extinct (as their food sources deplete and vanish), ultimately leaving on small, isolated population around limited locations where natural process recreate some of the high-energy chemicals.
# Radiosynthesis
I don't even know where this idea came from and how it is supposed to work. There are only two (possible) advantages of this method:
* Radioactive decay is usually orders of magnitude more energetic than chemical reactions (1 kg atomic bomb versus 1 kg TNT) so a creature relying on this method would require very minute amounts of food for sustenance. If a creature is somehow able to power itself through fusion (instead of fission) it would only require to eat once in its entire lifetime (violent pun intended).
* It would be extremely cool to have such creatures around!
However, powering a biological engine by this method does not come without some nuisances. Few that I can think of, right now, are following:
* It happens that nuclear decay does not only release huge amounts of energy, but also creates deadly radiation including gamma and X-rays. These rays are known to irrepairably damage DNA. A population of radiosynthesizing creatures would gradually sterilize the whole area of all life. There is no question of a food-chain appearing in the first place.
* Without thick sheets of radiation absorbing material (lead comes to mind), the creatures *themselves* would be at risk of severe mutations, hereditary diseases and cancers. We are basically talking about a creature which has a lead-shield around each of its organs. Note that there are types of [radiation-resistant bacteria](https://en.wikipedia.org/wiki/Radioresistant), but they are all bacteria (single celled). No complex life form has ever been seen to be able to cope with high energy radiation.
* Such organisms and the food chains based on them, would only be active in regions where there are at least moderate concentrations of radioactive elements in the soil. This means that like chemosynthesis, radiosynthesis can also only support limited, endemic populations of simple creatures.
# Magnetosynthesis
This comes even crazier than radiosynthesis. Earth has a colossal magnetic field. But how *on Earth* can an organism utilize this magnetic field to obtain energy is anybody's guess. Rotating an electricity-conductive coil in a magnetic field induces the flow of current in the coil, true. But how can a creature generate such a coil and how is it going to rotate that coil without applying *more* mechanical energy than electrical energy it is going to obtain?
Despite all the absurdities and impossibilities regarding the origin and biology/physics of such a creature, there is still one advantage of such a (hypothetical) creature:
* It will baffle the scientists out of their wits and someone will receive a nobel prize for disproving the law of conservation of energy.
However, there is also a downside of this scenario:
* It wouldn't happen.
# Other (Hypothetical) Possibilities
By this term, I mean using sunlight for creating high-energy compounds without the complexities of chlorophyll-related processes. The possibilities include:
* Creatures which convert sunlight into electrical energy through biological solar cells.
* Creatures which create glucose through a process not involving chlorophyll.
* Creatures subsisting on chemosynthesis, but replenishing their exhausted chemical supplies by reconverting spent chemicals back into high-energy chemicals, using sunlight. For example:
Hydrogen Sulfide + Oxygen => Hydrogen oxide + Sulfur dioxide + energy
Hydrogen oxide + Sulfur dioxide + sunlight => Hydrogen Sulfide + Oxygen
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In the story I'm writing, a gas dwarf (named Eden) is discovered in a triple star system. Its atmosphere is mainly oxygen and water based, and its gravity is slightly higher than Earth's.
Unlike our gas giants, however, Eden has 2 "surfaces". The upper layer is made up of millions of floating islands hovering just above its cloud layer. (A moon or a passing planet probably broke as it passed Eden and was lock in its magnetic field). Known as the Aether, most of the planet's population lives up here. There are even cities built in the sky that simply hover from the planet's magnetic field.
Far below, however, is an unstable icy crust known as the shell, which is constantly changing due to the forces of the water and oxygen ocean layers below it. Shell quakes and rifts occur on a daily basis here, dramatically changing sections of the Shell in an instant.
Could such a world exist, and am I missing any important details?
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**Short answer: As described Eden could not exist naturally, you need a consult with [Magrathean engineers](http://hitchhikers.wikia.com/wiki/Magrathea) to see if they could build it for you.**
Magnetic levitation of millions of islands cannot occur naturally. The conditions necessary for magnetic levitation are very strict. You need carefully balanced magnetic fields of opposite polarity to support the floating object. A small imbalance and the floating object will tend to flip over and then the magnetic repulsion becomes magnetic attraction and you quickly plummet.
As your moon crumbles, the pieces descending would almost always naturally orient themselves such that they would crash into Eden.
As I type, I see that HDE 226868 has already answered the impossible field strength required aspect. I would also add that unless you manage a monopole somehow, the magnetic field cannot be in the same direction all over the planet, you could in theory have islands hovering over the north pole and others hovering over the south pole, but really nothing in between. Such hovering would not be stable as they would all tend to crash together directly over the magnetic poles.
You could get more stable magnetic support by making the floating islands superconducting magnets due to [flux pinning](https://en.wikipedia.org/wiki/Flux_pinning), though unless your planet is extremely cold (where oxygen would be solid) they would not be superconducting naturally.
Lighter than air islands are the only *"realistic"* way to have floating islands. Perhaps you could have a large scale biological source of aerogels that are somewhat stronger than ones we can currently make and are filled with a lighter gas, perhaps methane (hydrogen and helium are very difficult to contain over time due to diffusion). Aeorgels are not very strong as construction materials though. You definitely need a stronger platform than any aerogel we have. If you add natural clumping of the floaters, you might have respectably large stable floating platforms, though clumping behavior does not result in a strong bond. An aerogel of graphene or similar fullerene structure might be a good place to start. You also have the problem of your islands catching on fire due to lightning strike, etc. but hey stuff happens.
For high buoyancy, a dense atmosphere is desirable, Oxygen toxicity limits the amount of oxygen, Nitrogen narcosis limits the amount of nitrogen and the narcosis problem is more general, essentially all of the heavy inert gases have the same problem, so there are definite limits of habitable atmospheric density.
Overall, it seems to me that Eden is not aptly named.
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The tendency to flip over is much more pronounced that you might imagine. You pretty much have to cheat in one way or another to achieve magnetic levitation. According to [Earnshaw's Theorem](http://math.ucr.edu/home/baez/physics/General/Levitation/levitation.html), static levitation is impossible for the most common types of simple magnetic materials. I apologize for being far too generous when I simply described it as a tendency to flip.
Superconducting magnets are not subject to Earnshaw's because of the way the flux lines penetrate the floating magnetic - causing flux locking. Rotating floating objects also bypass the assumptions of Earnshaw's. You can also construct a composite of a number of different magnetic sources on the ground and the floating object that don't match Earnshaw's model.
However, when you are talking about Eden as described, Earnshaw's is a pretty good model of what must occur. Since the model is not 100% accurate in this physical case, I described it in weaker language assuming that an edge case might float. It would almost certainly flip over due to perturbations from storms, etc. even when carefully balanced initially. So, floating for any length of time would be extremely rare at best.
Without going into the physics, you can levitate some things (such as a frog) using very strong fields that is diamagnetic (again, Earnshaw's does not apply), but as you can see [it is not stable](https://www.youtube.com/watch?v=A1vyB-O5i6E)
Of course, the other problems such as the impossible field strength, etc. would still prevent Eden from existing.
[Answer]
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> In the story, a gas dwarf (named Eden) is discovered in a triple star system. Its atmosphere is mainly oxygen and water based, and its gravity is slightly higher than Earth's.
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You don't need to resort to [gas dwarfs](https://en.wikipedia.org/wiki/Gas_dwarf) if you want gravity slightly higher than Earth's. While Jupiter is a heavy beast, Saturn has a gravitational pull only [6.5% greater than Earth's](http://nssdc.gsfc.nasa.gov/planetary/factsheet/saturnfact.html) at depths with 1 bar of pressure (slightly less than one atmosphere of pressure at Earth sea level). The level in gas giants where pressure equals 1 bar is often used as the level for surface gravity since gas giants have no surface.
If you want an oxygen and water heavy giant, consider an [ice giant](https://en.wikipedia.org/wiki/Ice_giant). Uranus and Neptune are ice giants. Although, don't be confused by the name. They aren't made of ice or mostly made of water. They simply have a larger ratio of volatile compounds (colloquially known as "ices") than gas giants. For comparison, gas giants are about 90% hydrogen and helium, whereas ice giants are only about 20%.
On the issue of atmospheric composition, don't worry too much about how much molecular oxygen the planet naturally had from its formation. Earth didn't have much O₂ in the air until the [Great Oxygenation Event](https://en.wikipedia.org/wiki/Great_Oxygenation_Event). It was originally closer to that of Titan than the Earth of today. Photosynthetic life nearly suffocating itself on its own waste is what changed that for us. So, there's more than one way to skin this particular cat.
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> Unlike our gas giants, however, Eden has 2 "surfaces".
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> Far below, however, is an unstable icy crust known as the shell, which is constantly changing due to the forces of the water and oxygen ocean layers below it.
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This wouldn't be possible in any of the gas/ice giant observed and I can't think of any math to make such a thing work. Physics has limits.
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> The upper layer is made up of millions of floating islands hovering just above its cloud layer. (A moon or a passing planet probably broke as it passed Eden and was lock in its magnetic field)
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This is something else the physics isn't amenable to. If they were magnetically attracted to the planet, they wouldn't be locked in place. They would fall in. Anything else just wouldn't be thermodynamically stable.
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> Known as the Aether, most of the planet's population lives up here. There are even cities built in the sky that simply hover from the planet's magnetic field.
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While I suppose the cities could [magnetically hold themselves in place](https://en.wikipedia.org/wiki/Flux_pinning) if they have the power to super cool massive supermagnets built into the city foundations/superstructure, that would be obscenely power intensive. A more sane solution might be buoyant cities, similar to what some people have proposed [doing on Venus](http://motherboard.vice.com/read/why-we-should-build-cloud-cities-on-venus).
In short:
* Ice giants might be the sort of planet you want.
* Their formation alone could be enough to give a good atmosphere, or you could use life (or intentional terraforming) to get the rest of the way there.
* Floating rocks in the upper atmosphere is almost impossible to imagine and an ice shell nested between layers of a gas/ice giant's atmosphere would be an impossible natural phenomenon.
* Floating cities are conceivable. Magnetism can work, but conventional floating is already considered plausible for even modern technology. (So, you have multiple options there, too.)
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Here are some jumbled thoughts I had:
There's no way the planet can have a magnetic field strong enough to levitate rocks. In [my answer to Can there be planets with extremely strong magnetic fields?](https://worldbuilding.stackexchange.com/a/33528/627), I calculated that for Earth to have a surface magnetic field as strong as a kitchen magnet, it would need to have a magnetic moment stronger than a [magnetar](https://en.wikipedia.org/wiki/Magnetar), by a factor of about 1.5. You'd need to have an even larger magnetic moment here, because the radius would be bigger because
$$B\propto\frac{p}{r^3}$$
where $B$ is the magnitude of the magnetic field, $p$ is the magnetic moment and $r$ is the radius, and also because you would need a stronger magnetic field to levitate the rocks.
This would seem to indicate that the planet cannot be colonized; the cities cannot be built.
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The closest valid thing I can think of would be a nebula in which the gases create a deep enough gravity well for it to be compressed to a life sustaining pressure but there's not enough mass for the gravity well to become any deeper than that.
There may be asteroids in this nebula and as long as they don't have enough mass to disrupt the gravity/pressure balance they wont form a planet, but you wouldn't be able to walk on them, not unless all non-gaseous matter had some sort of alternate gravity.
Inside the nebula would be warm, indeed the denser depths may be quite hot, great columns of hot/moist air rising from the depths, while any free-floating moisture near edges would condense to frost and fall back in, I leave it up to you to figure out where all this heat is coming from.
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[Question]
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The main reason I ask this is because my world's moons both have long periods of darkness based on their phases (see [here](https://worldbuilding.stackexchange.com/q/33563/8928)) so plant life needs to have a way to persist through such a lack of light. I know chemosynthetic bacteria can thrive without light, and there are already [species of tube worms](https://en.wikipedia.org/wiki/Giant_tube_worm) that rely on these bacteria in favor of a digestive system. So, what I want to know is, could a plant theoretically rely on chemosynthetic bacteria in the absence of light, and if so, what are the requirements for it to occur? Or, if possible, could plants that can simply conduct both photosynthesis *and* chemosynthesis exist?
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Yes. I think it would work the same as the stuff that's in the soil now. In fact, isn't nitrogen-fixing bacteria an example of *bacteria* (not fungi) that don't use light?
I think the point you want is to use *autotrophs* that are not photosynthetic, rather than something that *eats* and breaks down other material.
Now I see the problem. Chemosynthetic life typically lives in environments that normal stuff doesn't. Where is non-biological energy chemicals going to come from in normal soil?
These chemical energy sources are not very rich, in comparison. So they would *become food* and not complete well in a mixed situation.
But, you're talking about an alien ecosystem. So work out what's needed so it *does* work. You mentioned the long darkness. Also, why *plants*? Maybe think of a lichen-like thing that can host varied and *changing* populations of autotrophic symbiotes. The green stuff does well in the day; it is *replaced* with chemosynthetic bacteria at night. Perhaps different ecosystems *within* the host complete for the best breed based on the particular details of food sources and temperature.
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You need one of two things.
1. Better carbon storage and ability for dormancy in the plants. Then they can synthesize sugar when there is light, and respire when it is dark (as our plants do).
2. An organelle in the plants different from chloroplasts. They would use H2S (which has higher energy electrons that H2O) to provide the electrons to fix CO2 into sugar.
These plants will not be green, as the purpose of chlorophyll is to collect light. If they conduct both types of autotrophy, (which is certainly possible, some invertebrates have five organelle-like symbionts and plants have two), then they would be (red or) green again.
Indeed, this would be analogous to *Riftia* and similar tubeworms, or *Bathymodiolus* mussels, or other benthic invertebrates.
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