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[Question]
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[Lithotrophy](https://en.wikipedia.org/wiki/Lithotroph) is a phenomenon known from microscopic life, where an organism converts inorganic substances, usually minerals, into energy.
So, we know that a single-celled life form can do this, but what about a more complex one? **Could a macroscopic, motile, animal-like organism feed on minerals, like iron or sulfur, and if so, how would it work?**
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I am asking this question for use in the construction of an alien planet, with which I want to break the trend of Earth-like aliens seen in most popular movies and books featuring complex extraterrestrial life.
The organism(s) in question shall be as large as humans or bigger, have multiple legs, and hard endoskeletons. The reason I'm asking this question is a) I'm not a biochemist, b) this phenomenon has never been observed in macrofauna, and c) I can assume that it would bring a host of side-effects and possible ramifications.
In an answer, I'm hoping for a "yes" or a "no", to indicate whether it's possible, and then hopefully a few words on things like digestion, biochemistry or any other things I need to know to *understand* how the organism works, not just know what it does.
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**Please note** that I have had a look at the question [Can anything survive by eating rocks and other ground minerals?](https://worldbuilding.stackexchange.com/questions/3338/can-anything-survive-by-eating-rocks-and-other-ground-minerals) and it does not answer my question. It asks if there are any real-life lithotrophs, which I know and made clear in the first sentence of the question. It does not proceed into the realms of speculation which I'm looking to enter, and the OP also does not want to understand how this phenomenon would work.
[Answer]
Sure. You would need the animal to harbor a population of commensal bacteria to do the metabolic work for it. One example of such an animal is the giant shipworm, a mollusk whose commensals feed it via hydrogen sulfide metabolism.
[](https://i.stack.imgur.com/fvIA8.jpg)
<https://www.straitstimes.com/asia/se-asia/scientists-find-giant-shipworm-in-philippines>
<https://en.wikipedia.org/wiki/Shipworms#Taxonomy>
>
> Instead, the shipworm does not eat, they rely on a beneficial
> symbiotic bacteria living in its gills. The bacteria use the hydrogen
> sulfide as energy to produce organic carbons that feed the shipworms.
> The process is similar to the green plants' photosynthesis to convert
> the carbon dioxide in the air into simple carbon compounds during
> photosynthesis. Scientists found that K. polythalamia cooperates with
> different bacteria than other shipworms which could be the reason why
> it evolved from consuming rotten wood to living on hydrogen sulfide in
> the mud. The internal organs of the shipworm have shrunk from lack of
> use over the course of its evolution.
>
>
>
Giant shipworms are sessile. Could such an organism be mobile? Sure - the giant shipworms relatives are very mobile - they attack the wood of ships which is how they got their name. Their commensal bacterial help them digest the cellulose of wood. Large land animals which subsist on cellulose rich plant matter also have huge populations of commensal bacteria and fungi - the rumen of cows is a giant tank of such creatures, which break down and digest the plant matter eaten by the cow. In exchange the cow keeps them safe.
Your putative creature would have a rumen-like organ which would be full of archons or commensals of a sort which can perform the type of energy metabolism you want for your creature. The creature would seek out and ingest the mineral materials, providing them to their internal commensals.
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Not marking this as a duplicate because I love of this speculative energy metabolism questions. Instead, let me suggest that for the interested, additional reading can be found on this site.
[Multicellular chemotrophs?](https://worldbuilding.stackexchange.com/questions/73665/multicellular-chemotrophs/73685#73685)
[How would digestion work for an alien species with a diet of minerals?](https://worldbuilding.stackexchange.com/questions/69755/how-would-digestion-work-for-an-alien-species-with-a-diet-of-minerals/69757#69757)
[How would giant, secluded, underground-cave-dwelling insects get enough food?](https://worldbuilding.stackexchange.com/questions/94136/how-would-giant-secluded-underground-cave-dwelling-insects-get-enough-food/94140#94140)
[Answer]
Short answer: probably not.
[This answer](https://worldbuilding.stackexchange.com/a/11642/51094) goes into some detail on how giant tube worms, which live in symbiosis with chemotrophic bacteria, work. The salient point is that they live off of waters rich in hydrogen sulfide, which is delivered to them by underwater vents.
However, from your description of the aliens in question, you don't want them to be sessile, clustered around places that happen to support them. You want them to walk around, graze, forage, what have you.
The problem there is one of energy. Humans (and other familiar animals) take in energy in the form of complex organic molecules, including fats, carbohydrates, and proteins, all of which have a substantial amount of bond energy that is (relatively) accessible. As a result, they have a lot of energy available to them for things like walking, chewing, higher brain functions, etc. Tube worms don't do much of that; nor do trees, or algae.
Lithotrophs don't have the advantage of preexisting organic molecules. They have fairly low margins in terms of the energy they get out of their environment, because the chemistry just doesn't give them as much to work with. It's actually much the same reason why animals aren't photosynthetic - it's not rewarding enough.
In other words, the problem is that rocks aren't as energetic as organic materials. Your aliens could theoretically sit atop a food chain of lithotrophic "plants", but that wouldn't make them lithotrophs any more than eating regular plants makes humans photosynthetic. (Your planet would also probably need a very strange atmosphere and crust to pull this off.)
Another way to think of it is like this: think of a human compared to the plants and other animals that human needs to eat in order to live. We can do complex things because we offload the grunt chemistry on other living things. That's just as true whether the initial source of energy is the sun, or metal oxidization, or something more exotic. (I wonder if you could have a radioisotope thermal-powered bacteria...) Baring some truly exceptional biology, an alien that is recognizably animal-like would need to similarly be higher up in its own food chain.
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In the world I'm building, a nuclear war and subsequent repressive chaos have led all satellites to be destroyed by the powers that be, around 10 years from now. A few years later, a small spacecraft, which doesn't have a heat resistant cover to allow it to enter the atmosphere, reaches Earth orbit and proceeds to gather space debris. Of course, with all the destroyed satellites, it has a lot of material, and it has a laser which it can use to change its course. It may also have other things but it has come from Mars so would need to have either made it there or have reused or re-purposed man made materials there.
Also it can use solar power to recharge said laser and keep things going as it floats along. It has as much time as is needed as the solar power can keep it going almost indefinitely. So the questions are: How much space debris would I have to collect, and how would I collect it, so that I'd have enough cover around my space ship to leave orbit without burning up, and so I can use my last bit of fuel to attempt a descent? Would this resulting debris cause a lot of havoc once I detached it from my ship before landing?
[Answer]
The problem you are trying to solve is similar to the one asked [here](https://physics.stackexchange.com/q/47754): what is the minimum size of an asteroid so that it impact Earth?
In your case you don't want to impact, but you want to go through the atmosphere with no damages, which is the same for the sake of your question.
>
> Based on approximating the problem by assuming that the matter in the path of the object is being pushed at the same velocity of the object, so as soon as the object has swiped out path containing the same mass as its own mass, it will have lost all of its initial momentum. All its kinetic energy will then have dissipated there, so if this happens in the atmosphere it will have burned up before reaching the ground.
>
>
> This is, of course, a gross oversimplification, but it will yield correct order of magnitude estimates. We can then calculate the critical diameter as follows. The mass of the atmosphere per unit area equals the atmospheric pressure at sea level divided by the gravitational acceleration, so this is about $10^4\ \ kg/m^2$. If an asteroid of diameter $D$ and density $ρ$ is to penetrate the atmosphere, it's mass of $1/6πρD^3$ should be larger than the mass of the atmosphere it will encounter on its way to the ground, which is $5π10^3D^2\ \ kg/m^2$. Therefore:
>
>
> $D>3×10^4ρ\ \ kg/m^2$
>
>
> If we take the density $ρ$ to be that of a typical rock of $3×10^3$, then we see that $D>10\ \ m$, which is reasonably close to the correct answer.
>
>
>
The correct answer is mentioned in a [NASA article](https://www.nasa.gov/mission_pages/asteroids/overview/fastfacts.html), which states
>
> Space rocks smaller than about $25\ \ m$ (about 82 feet) will most likely burn up as they enter the Earth's atmosphere and cause little or no damage.
>
>
>
To make a sphere of $25 \ \ m$ radius your crew needs to harvest at least $65449.8 \ \ m^3$ of space garbage. In mass, assuming again a density of $3000\ \ kg/m^3$ (aluminum is 2700) it would mean $ 210 × 10^6\ \ kg$.
This will protect the ship from the ablation damage of the reentry. Getting insulation from the resulting tremendous heat will be another story (aluminum and other metal are good heat conductors...)
[Answer]
# No.
### (but with a little caveat)
Space junk is, well, junk. It's essentially just the contents of some factory's dumpster. Most of it is very small, and the stuff that isn't very small is not designed for this purpose. Making matters worse, it sounds like your satellite is not designed for reentry. This means that it's not made for structural integrity. Or really anything besides sitting in microgravity. Even if you manage to collect a large cloud of space junk around you, how do you make it stay around you? The small stuff is going to have much less momentum and will fall behind you as soon as you hit the atmosphere. The large stuff has too much momentum, and any shifts in the junk heap will likely destroy your craft.
Even putting aside the ability to keep the junk steady, reentry is a chaotic procedure, only made less so by careful geometry in our reentry capsules. There is almost zero chance that you don't end up tumbling throughout reentry and destroying your satellite. If you do make a stable shape, it's probably stable in the wrong direction and you'll end up burning your satellite.
Finally, the engines on satellites are made for long, slow, efficient burns. Even if you manage to do everything right up until landing, that engine will do little besides lower your terminal velocity from, say 200 kph to 199 kph.
### But you said there was a caveat!
Okay, so this satellite went to Mars. Let's say that it has a more powerful engine for some reason (it really wouldn't, but let's roll with it). In addition, it has devices that are purpose built for grabbing and trapping space junk around the craft. Moreover, it can retract its solar panels so that they don't get snapped during reentry. And finally, there is some really really perfect space junk out there. Like your space junk grabber was designed to grab these exact pieces of space junk. Then yes, in this miracle of coincidences, you could potentially ride this space junk heap down to the surface, and maybe, ***maybe*** survive it. I just don't buy it.
[Answer]
**Use big space debris.**
[](https://i.stack.imgur.com/lVtYa.jpg)
<https://www.space.com/21122-skylab-space-station-remains-museum.html>
Depicted: a 1 ton oxygen tank from Skylab which survived re-entry and looks pretty good here in its museum.
I assert that if this bug chunk survived re-entry, you could survive re-entry behind it. It would be your heat shield.
The trick would be finding chunks this big still in orbit. I think people are more careful about this sort of thing now than they were when Skylab went up.
But maybe big stuff still does go up, just with explosives or other means to break it up before re-entry. Or you could make it so in your world. If there were a space arms race maybe there would be proton cannons or other space weapons platforms up there. Maybe some stuff already has heat shields you could scavenge - consider if you were going to fire a missile down from orbit it would need to survive re-entry. A phalanx of missile heads would make a badass MacGyvered heat shield.
My question for the comments - if during the OP's endeavor you found a full Skylab oxygen tank, would it be better to drain the oxygen into space before using it as a heat shield, or leave it full?
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The world is a steamy tropical ball reminiscient of Earth in the time of the dinosaurs. There is no permanent ice cover anywhere on Earth. An arctic continent, entirely within the polar circle, is surrounded on its seaward edge by [giant mushroom forests](https://worldbuilding.stackexchange.com/questions/59005/where-do-mushroom-forests-thrive).
These forests exhibit year-round oceanic temperatures between 10 and 20 C. There is moderate rain and heavy fog all year. The fungus that make up these forests are symbionts. Their mushroom-like fruiting structures have evolved into complex shapes filled with photosynthesizing bacteria or algae to generate energy. In this way, the biome operates much like a coral reef with the fungus taking the place of corals. During the endless days of arctic summer, the phototrophic bacteria (or [zooxanthellae](https://en.wikipedia.org/wiki/Zooxanthellae)) generate energy; in the long months of sunless winter, the fungus absorb nutrients and decompose matter in the soil.
I want my mushrooms to be able to build skeletons for themselves to take all the wierd shapes and colors seen in a reef. Corals can build calcium carbonate shells because the raw materials are [floating all around them](http://www.seafriends.org.nz/oceano/seawater.htm#salinity). Calcium ions are present at 411 ppm in seawater, while bicarbonate are 145 ppm. But calcium is not that common in a wet forest that never freezes, like these mushroom forests. For example, [studies of calcium](https://books.google.com/books?id=gsSSBwAAQBAJ&pg=PT214&lpg=PT214&dq=calcium%20concentration%20in%20rainforest%20soil&source=bl&ots=N2ZdIBNCgL&sig=WEeSpjQ3CeIruADWoeAI_DjXDBw&hl=en&sa=X&ved=0ahUKEwitwYLkleTYAhUS92MKHd7UDAMQ6AEILjAB#v=onepage&q=calcium%20concentration%20in%20rainforest%20soil&f=false) in soil and biomass in various rainforests show some forests have as few as 300 kg of calcium per hectare; while even the most plentiful rainforests only about about 4000 kg. That may seem like alot, but 4 tons of limestone equivalent is not nearly enough to decorate a whole hectare with giant mushroom-trees and intricate mushroom-brain-corals.
What can symbiotic fungi use to build hard, rock-like skeletons in the way that coral reefs do?
[Answer]
**Glass**
Glass sponges exist and you can leech an endless supply of silica from the soil, some plant already incorporate small amounts of it as a defense mechanism. Diatoms are another example of an organism that builds a skeleton of silica glass.
They would end up only growing as fast as corals not the faster speed mushrooms and plants normally manage, plants who can generate cellulose literally from the air and sunlight can grow very fast comparatively. However ground water does have higher concentrations of silica than ocean water, so it need not be too slow. Expect something made mostly of chitin with a silica skeleton, kinda like how wood is made of cellulose and lignin.
[](https://i.stack.imgur.com/OCS7D.jpg)
[](https://i.stack.imgur.com/bCTUl.jpg)
[Answer]
Cellulose is a very good terrestrial structural molecule. Very popular in forests. It can create large structures in a massive variety of shapes. Unfortunately fungi don't use cellulose as a structural molecule. You could wave your hands a bit and say that they do but there's another more plausible option.
Chitin is a polymer based off glucose with a similar structure to cellulose. Mushrooms already produce it.
If we're imagining a forest of Morrowind style giant mushrooms. We can ever so slightly wave our hands and say that they use chitin to give them their structure similar to how plants use cellulose.
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On my world sulphur dioxide makes up most of the atmosphere (42%). It comes from constantly active land-based and Hydrothermal vents. I know there are basic, or basic compared to a human, organisms that can 'breathe' sulphur dioxide. Would it be possible for a sentient and relatively large creature to breathe sulphur dioxide?
So my question is:
* Is it possible for my organism to breathe sulphur dioxide?
*Sorry if this has been asked before, I searched this site and other sites but I found little that could help. Thank you in advance.*
[Answer]
Probably.
Aerobic respiration of glucose (the primary source of energy for animal cells) proceeds according to the following formula:
6O2 + C6H12O6 -> 6H2O + 6CO2
We can approximate the energy gained in this reaction by looking at the heat of formation of each of the participating molecules; the energy gained is the difference between the total energies on each side of the reaction.
Heats of formation are as follows (all values taken from NIST Web Book):
```
C6H12O6 174 kJ/mol
H2O -285.83 kJ/mol
CO2 -393.52 kJ/mol
```
Which results in the following totals:
6\*0 + 174 = 174 -> 6\*(-285.83) + 6\*(-393.52) = 4076.1
for a net energy gain of 4250.1 kJ/mol of glucose.
If we directly replace O2 with SO2 in the above reaction, we get
6SO2 + C6H12O6 -> 6H2O + 6CO2 + 6S
Elemental sulfur has a heat of formation of 0, just like diatomic oxygen, so the only change in energetics comes from the non-zero heat of formation of SO2, which is -296.84 kJ/mol. Since there are six of those molecules involved, that takes 1781.04 kJ out of our net energy gain, leaving us with 2469.06 kJ/mol of glucose- a little over 60% of what we get by using oxygen.
Other reaction products are possible, including H2S, CS2, and COS, with the following heats of formation:
```
H2S -20.50 kJ/mol
CS2 89.41 kJ/mol
COS -139.0 kJ/mol
```
so you can try fiddling around with different ratios of reaction products, but I don't think you'll get better results than just producing elemental sulfur as a byproduct.
So, if nothing else changes about these creature's metabolism, the kinds of energy storage molecules they use, and so forth, an SO2-breathing creature would need to eat about 66% more food and breathe 66% more air to maintain the same power levels as an equivalent Earth creature. Given the enormous variability in food intake and metabolic rates among existing large animals on Earth, it does not seem at all implausible to me that you could have a large, energetic creature breathing SO2 under those constraints. *I* could certainly survive just fine having to eat *twice* as much food and breathe *twice* as quickly as I do now--and birds, for example, have much more efficient respiration than humans, so were I properly adapted for this environment, with more efficient lungs, I could probably get by just fine merely by altering my diet to increase the ratio of starch and sugars and only eating a smidge more than I have to as a normal, O2-breathing human.
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**This question already has answers here**:
[How would an avian city be different from ours?](/questions/2975/how-would-an-avian-city-be-different-from-ours)
(5 answers)
Closed 2 years ago.
I have bird-like race that I'm writing about, but I have no idea what their houses will be like. I have few things decided already, however, which are as follows :
* They are NOT migratory. Though they can fly, they prefer to live in rigid villages, towns etc.
* Agriculture is used, but not anywhere near as often as in human civilisations. There is a strong "survival of the fittest" philosophy, and anyone farming would have to take care to not have their goods taken by others.
* Magic is wielded by some religious figures, and is based heavily on puppetry. They believe in a gigantic invisible web which ensnares all living things, and priests and the like will adorn themselves in ropes dangling from the head and arms to symbolise this. They will use puppets on occasion as workers, performing menial tasks that such high persons would not stoop to themselves
EDITS:
* Their feathers are considerably dense, so insulation isn't an issue. However, they aren't watertight, so ceilings are still necessary
* The humans in the world are only at the fifteenth century, and the birds are still at something equivalent to the eleventh, but they can steal from or trade with the humans if they see fit, with some difficulty trading as they struggle with human languages
* Given their aggressive nature, they will naturally not hang out in groups larger than a few hundred. Families often dissolve quickly, and instead they live in tribe-like groups, often with only a few defining factors such as skills
* The bird-people have six limbs : two legs, a pair of wings, and two arms. Their general shape is the same to a human, and wings notwithstanding they are the same size. If you include the wings, unfurled, they are slightly larger
* The birds view humans with a cold indifference, and the humans likewise would not stoop so low as to interact with the "savage" birds. They don't have defined borders of their own, but they respect those of the humans. Occasionally, human countries might be separated by the territories of the birds, who will often try to capitalise on this by enforcing toll roads, collecting resources and very rarely uncut gems or other recognisably valuable items.
With all this in mind, what would their buildings, and indeed cities, look like?
[Answer]
I don't believe that they would have cities. Cities require agriculture and trade to produce the food surplus that the urban population eats. I doubt these people would group much larger than villages. Perhaps a hundred, if that. I would think something more like ten or twenty adults.
You don't mention how many offspring in a nest. If the number is relatively small, they might share nests.
Consider who is larger, the males or the females. An argument in favor of large females is that they might more easily pass larger eggs. The smaller, quicker males might fly into the world to fetch food, etc.
Most male birds have some kind of way of making a colorful display that they can use to attract the attention of predators away from their mates and children. They can often hide this display when they don't want to distract predators. Such a display often features in mating rituals. *Look at me; I'm healthy and well fed. I can provide for many strong children.* Think of a turkey or peacock spreading its tail.
They might engage in small scale agriculture in the home. Perhaps they might keep rabbits or similar that they can cage (or maybe a pit?) and eat when needed. A long-haired rabbit might provide something like wool. I was thinking about households that kept chickens in the house, killing them as needed. Perhaps a pig, goat, or raccoon (or something new for your world) to eat scraps, like bones. When it's fat enough, they toss it in the stewpot and get a new one.
Perhaps they bring back fruits or plant fruit trees to attract small animals. This should be safe from others, as they don't care about the fruit. It's the animals that they want. Of course, if they're fruit eaters, that won't work.
If they eat insects, perhaps an ant farm. Do they like sweets? Perhaps a beehive.
Homes could be built in locations that are only accessible from the air. E.g. on the sides of mountains. They might look for places close to a stream or even a waterfall. Perhaps they encourage streams to follow a helpful path by digging trenches.
Their doors are likely to be above ground level. Some may roost on perches off the ground, but the children are likely to be at ground level. If there is a pit, it is probably surrounded by walls (like wells are). Their ceilings are likely to be quite strong. They may even cover them with dirt. This is because an attack from above is quite conceivable to them. It will be the kind of attack they expect.
They may have a fireplace, surrounded by walls. They could then build nests around the fireplace so that the eggs stay warm without nesting adults. So all the adults can leave at once if necessary.
They might have small but multifamily households. The males and some of the females go out for food while some of the other females stay home and guard the nesting place. This might also allow more agriculture. Perhaps all the females stay home and all the males go out.
They would tend to think in terms of verticals. The land above them on the mountain is risky (people could attack from there). The land below them is vulnerable; they may attack people or creatures there. That's what they consider to be their hunting ground.
A mountain pass might be "owned" by some cooperating groups. If they see humans entering, they'll fly down and insist on their toll. Perhaps only a small group lands for negotiations while more watch from above. If the toll is often paid in food, they might group more thickly there than elsewhere. Similar behavior for a convenient stream. Want to drink the water? Pay the toll.
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Okay, I'm starting to get an image of these guys. Aggressive but territorial, proud and disdainful. I see them as being torn between several impulses... They want to spread apart and be away from competitors and lesser beings. They need to cluster together for mutual protection and cooperative industries. They want to keep their families close -- until they tire of them. These stresses might leave these folks on a hair-trigger, jumpy and easily provoked.
So...
They need space. Their buildings tend to be large and not sub-divided. Think Viking great halls, 2 or 3 stories high, one giant room. This allows room for short flights inside. There might be "sulking perches" on the periphery where proud avians can get away and calm down, to avoid the need for violence.
A dwelling is owned by one individual. When an avian takes a mate (not sure if these guys are exogamous or exandrous, either works, assume wife comes to live with husband) the mate moves in for as long as they can tolerate one another. The wife keeps her own house, if she owned one, and rents it out. Assets are not commingled. Decorations ... highly contingent, but let's imagine they are all about the puppets. I see little furniture for these guys, but lots of wall hangings; mosaic floors; and weird fetishes hanging from strings from the ceiling.
Factory / workshop buildings follow a similar pattern. Common areas are in the center, with plenty of room to escape. In fact, buildings will tend to have several exits, mostly well above ground level (suck it, ape-boys!).
This pattern of shared center / private periphery extends to the village as a whole. Public or commercial buildings will be near the center, and dwellings scattered further away. In areas where there are favorable terrain features (hat tip @Brythan ) such as cliffs or hills, buildings will perforce cluster closer together.
We note they fear predation and/or theft from one another. These guys invented the combination lock and heavy safes real early in their history... ;D
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I am writing a story (well, developing one) in which a humanoid **intelligently genetically engineered** species is effectively immortal. The creature maintains its lifespan through a thick-shelled seed about the size of a child's fist which rests below the heart. Within the seed there are exact copies of the creature's DNA and a brain-like neural structure which preserves some memories.
Upon the creature's death, the seed sprouts in a large bulb (about 3m tall and 2m in diameter) which encases the new "resurrected" form of the creature with some of its previous memories preserved. The bulb opens when the humanoid is sufficiently developed and the life-cycle continues with a new seed forming during puberty.
(NOTE: The bulb begins growing when a number of factors - circulation, brain activity, temperature - convince it that the creature is in fact dead. It also releases a chemical which breaks down the corpse of the creature into more useful components which the plant can use to sustain itself.)
The seed, of course, is vulnerable to disease while it is inside the creature and it can be broken or damaged with sufficient force, which would probably kill the creature due to seed fragments causing internal bleeding. One disease causes the seed to germinate while the creature is still alive. Another uncommon mutation causes the seed to not develop at all.
I don't really care if the creature is actually two different life forms that sustain each other in some mutually endosymbiotic way.
**How realistic is it for a complex organism to have two stages of life where one is a plant performing photosynthesis and the other being an animal similar in size and energy requirements to a human? Or how can it be made more realistic to achieve these qualities?**
[Answer]
The [Cassiopea jellyfish](https://en.wikipedia.org/wiki/Cassiopea) has a life cycle similar to what you describe (except for being human sized!)
[](https://i.stack.imgur.com/IoN48.jpg)
from <https://rollingharbour.com/2013/03/15/mangrove-jellyfish-an-upside-down-underwater-life/>
These jellyfish start life swimming around like any other jellyfish, doing jellyfish things which I consider to be fundamentally animal-type things. This is a dispersal phase. When the jellyfish finds a nice sunny shallow sandy bottom it flips upside-down and starts a sedentary plant-like life, living off the proceeds of their internal photosynthetic symbionts.
Clearly a mobile dispersal phase is of great benefit to plants (and everything else) and there are many different ways to accomplish this end. @Henry Taylor is right that the most common way is to recruit animals which are already mobile, the evolution of fruit being the crown jewel of this mutualistic endeavor. Mobile seeds are good and I think your approach must just encounter evolutionary barriers to its development. It sounds like it could be a good creature.
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Metamorphic organism are not unknown. For example, caterpillars and butterflies or the motile larvae of what become the sedentary coral polyps.
This hypothetical organism is possibly a more extreme version of an organism like a coral. The main difference is this creature metamorphoses into a plant-like that is then capable of gestating a humanoid which inherits some of the memories of its preceding humanoid life cycle stage.
There are animal that do have life cycle stages that are sedentary. Corals, as cited above, are one example. But organisms with a secondary memory storage cache are certainly unknown on planet Earth. Despite the apparent improbability of such a mechanism evolving it is in principle not necessarily impossible. Indeed this is true for the different elements of this organism's life cycle. The combination seems immensely improbable, but nature is full of remarkably improbable organisms and plants.
The plant stage may take a long time to grow the humanoid for its next phase. That's because photosynthesis isn't exactly the most energetic of processes. It might make more sense if the plant-like stage wasn't an actual plant but more of a very large sedentary animal that resembled a plant.
An organism like this could be realistic if it was a part of an environment where creatures like this were more natural. Basically this means could be other creatures with approximately similar life cycles. On planet Earth we have a considerable of metamorphic organisms.
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In my setting elves can see very well in the dark. I've suggested tapetum lucidim but that would make their vision less clear so would larger pupils make it easier to see in low light areas?
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Practical limit is the precision of the whole optical elements composing the eye.
It is well known a lens system "aberrations" (imperfections due to several reasons) increase as you move out from the center and thus with larger diaphragm (i.e. iris) aperture.
This is the reason why we can use cheap and relatively inexpensive lens systems in today's cameras (and phones): the light required is much less and the "film" (CCD retina) dimensions ar much smaller (about 3x5mm or less where a Hasselblad had 60x60mm film).
Rising "sensitivity" of the film (retina) is the way we are actually bettering out "night vision".
Having a large pupil would surely help at night, but at risk of getting a blurred image due to imperfections of various lenses composing eye.
[Answer]
Yes and no. It COULD increase night vision, but under certain conditions, and with other trade offs in acuity.
I am assuming that the sensitivity of the light-detecting elements of the eye remain the same. In biology, there are several ways of 'detecting light' in organisms. Therefore, it is possible to evolutionary select a better, more light-sensitive sensor for the eye. Even in the human eye, we have rods and cones - a trade off between color vision and night vision. In the fly eye, the eye is broken up into individual segments, each of which acts as one 'pixel'. Each 'pixel' has a given light sensitivity, so increasing the number of 'pixels' does not increase light sensitivity, it only increases the field of vision.
To increase the 'night vision' capability of the eye, you either increase the light sensitivity of the receptor, or increase the amount of light getting to each receptor. Your question seems to indicate that you want the sensitivity of the receptor to remain the same (there ARE ways to increase the light sensitivity of the receptor - 'eat your carrots').
So, that leaves increasing the amount of light that gets to each receptor. One way is to reduce any 'transmission loss' in the eye structure - the clarity of the lens and eye fluid.
The second is to increase the exposure time - allow the eye receptor to 'accumulate light' before it 'fires'. This, of course, slows down vision. It is the basis for time-lapse photography.
The third is to somehow amplify the light. Night vision goggles do this, but it means having a secondary receptor in the middle of the light path, that 'adds' light to strengthen the incoming signal. However, it means you have a very sensitive receptor in the first place, to pick up the available light in order to amplify it.
The fourth is to allow more light to hit each receptor. This is the tapetum lucidim - bouncing the same light around so more of it hits the eye sensor. However, it is also possible to do this by allowing a bigger 'cone' of light to hit each sensor. That is, each sensor picks up light from a wider area of the scene. This is accomplished by either focusing the same amount of light on a smaller area of sensors, or increasing the amount of light that enters the eye. Both methods involve changing the focal length - the distance between the lens and the light sensor. In the first case, you have lower resolution - fewer 'pixels' that each receive a greater proportion of the available light, or visual field. Making the pixels bigger (the light-sensitive elements) also accomplishes the same thing. The bigger the individual light sensing cell is, the more available light hits it. However, in any case, the resolution of the eye is decreased.
Increasing the amount of available light is the method that you have asked about - increasing the pupil size. The trick is, you have to focus all of this light onto the available retina - letting more light in is useless if it doesn't fall on the light sensitive areas. The increased light has to be re-focused on the available retinal surface - the focal length has to change. The retina has to be optically brought closer to the lens. Thus, increasing the size of the pupil only works if you change the real or virtual distance between the lens and the eye. Doing so, as every photographer knows, has the drawback of reducing the depth of field - only things that are a given distance away are in focus, objects that are closer or further are increasingly out of focus.
All of this assumes the existence of a suitable lens. In a pin-hole camera (that is, a camera with no lens, but just a pin hole to let the light through) the smaller the pin hole, the greater the focus. Making the hole larger (bigger pupil) only creates a more blurred, diffuse image, but does allow more light through.
Think of an array of one hundred different colored lights, ten across and ten high. You are positioned well behind a screen, and the screen is a great distance from the light array. You are looking at these lights through a window (hole) in the screen. If the screen has a hole (window) sufficiently small enough that you can only see one light at a time (the visual cone of only one light is observable by your eye), you will, of course, see only one color light at a time. You have to move your head around to see each other color. If you make the hole bigger, you will see more color lights at a time. The light cone is broad enough to allow you to see perhaps colors from four lights at a time (less resolution, the colors of all the lights blends together), but the light is brighter. Get further away, and you again will only see one light at a time (one color). Get closer, you will see more blended color lights at a time (but it will be brighter). Make the hole bigger, you have to move further away in order to see only one color light at a time.
Thus, there is a trade off between the size of the pupils, for increased night vision, and the acuity (sharpness) of vision, for the same receptor and the same distance from the pupil. Making the entire eye bigger (increasing the distance from the viewer to the screen, to increase the resolution), means that the amount of light reaching the sensor decreases, reducing night vision.
However, caveat emptor, as every pirate knows (this is why they wear an eye patch) increasing night vision has devastating consequences in full sunlight. Your elves would need eye shields, or filters, for daylight.
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[Question]
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I am attempting to make my species of elves more alien to humans.
My plan is to change their physiology in a very specific way.
How realistic would it be for them to have retractable claws similar to a feline?
[Answer]
As dmm said, fingers are pretty poor locations for normal claws, retractable or otherwise.
**Solution**
Your kitties have small, retractable claws on their fingers. These claws are the same size as fingernails, giving them room to retract into the elves fingers. This allows the elf to use his fingers the same way you or I do, with the addition of sharp scratchy fingernails when desired.
More importantly, your cats have much larger and more pronounced hind-limb claws. Toes are short and stubby, rarely used for fine manipulation, and are the perfect candidate for claws.
**Elvishness**
Having small fore-claws and large hind-claws would allow elves to do very elvish things. They would be much better adapted to climbing trees, much better suited to a life in the wilds. They could use them as styluses in their early writing systems. They could use them to dig into the earth as they bound through the wet and leaf-strewn forest floor.
To me, small fore-claws make a lot of sense and help with the suspension of disbelief, but if you don't like them, you could explain them away by claiming they had become vestigial and had eventually disappeared.
[Answer]
I can't think of any animals that have formidable (weapon-scale) claws that also have long, dexterous fingers like humans. Look at a cat's fingers and toes -- they are rather short. Cats would make lousy typists and pianists. Your elves would need very sturdy fingers, if their retractable claws are going to be useful as weapons. Otherwise, they'd sprain/break their fingers when clawing their enemies. However, you could claim the claws are vestigial -- still useful for slashing someone's face, or picking one's teeth, but not for serious battles. [People please correct if I'm wrong.]
[Answer]
A humanoid variant of an elf with cat claws. What an excellent idea. I would go the route that xmens wolverine takes and put the claws in between the fingers. Hidden in the webbing. That's the most logical way I can picture cat claws seamlessly integrated into a humanoid anything.
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[Question]
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I am writing a book in which criminals get their hands on a polymer which resembles chewing gum , but alters their saliva. This allows them to burn holes into walls made from plastic used as building material in an alternate future of earth.
-Is it possible to create a "gum" that alters saliva enough to burn through plastic without significantly harming the user?
* the word plastic is being used as a generic placeholder for any plastic that will allow for this situation to take place
[Answer]
[Scientists Just Discovered Plastic-Eating Bacteria That Can Break Down PET](https://www.sciencealert.com/new-plastic-munching-bacteria-could-fuel-a-recycling-revolution)
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> **Enzyme innovation**
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> Now a team at Kyoto University has, by rummaging around in piles of waste, found a plastic munching microbe. After five years of searching through 250 samples, they isolated a bacteria that could live on poly(ethylene terephthalate) (PET), a common plastic used in bottles and clothing. They named the new species of bacteria Ideonella sakaiensis.
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> You may think this is the rerun of an old story, as plastic-eating microbes have already been touted as saviours of the planet. But there are several important differences here.
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> First, previous reports were of tricky-to-cultivate fungi, where in this case the microbe is easily grown. The researchers more or less left the PET in a warm jar with the bacterial culture and some other nutrients, and a few weeks later all the plastic was gone.
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> [](https://i.stack.imgur.com/E9Rcq.png)
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> Bottle breakdown. Illustration: P. Huey. Reprinted with permission from U.T. Bornscheuer, Science 351:1154 (2016)
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> Second - and the real innovation - is that the team has identified the enzymes that Ideonella sakaiensis uses to breakdown the PET. All living things contain enzymes that they use to speed up necessary chemical reactions. Some enzymes help digest our food, dismantling it into useful building blocks. Without the necessary enzymes the body can’t access certain sources of food.
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The enzyme that the bacteria uses has been named PETase. Just as the Amylase in our saliva breaks down carbohydrates, PETase breaks down PET. It would be very similar to a hard-boiled sweet melting in your mouth, except... ya know, spitting on a wall.
I'm not sure how you would get the salivary glands to produce PETase aswell as Amylase though. Maybe through a process similar to the one used to genetically modify bacteria to produce Insulin?
If this hypothetical chewing gum had the ability to genetically modify some *(not all! You still want SOME amylase for eating purposes!)* of the cells in the salivary glands, then it could be possible to have them produce PETase.
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NOTE: On the subject of sweets melting in the mouth, it would take just as long to melt through your walls. Unless you want to stand licking a wall for hours (and accidentally ingesting small amounts plastic), it will not be a feasible choice. However, thanks to *imagination* and *suspension of disbelief*, anything can happen in a book! Maybe this is "Super Awesome PETase which melts through plastic in seconds!" and you spread it in the outline of a door and bust through?
[Answer]
Even if the gum replaced your saliva with a strong acid (that miraculously you aren't affected by) you don't have enough saliva to be able to melt through a wall.
The average human produces about [half a liter](https://www.ncbi.nlm.nih.gov/pubmed/7487581) of saliva a day. If you spent your entire day licking the wall that is the maximum amount of acid you would be able to apply to a wall.
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[Question]
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I was reading [this](https://worldbuilding.stackexchange.com/q/83750/26281) question about a soft bullet thereby getting inspired to think of how to deliver a fake insect sting. I want it to leave as little bruises as possible, to resemble a sting and nothing to remain in the wound. Ideally, it would look like someone was stung by an insect. That would be the advantage to just shooting a needle.
When I drive in a car and the car decelerates, I continue flying forward, unless I wear my seatbelt. Suppose I have a very soft bullet filled with one or several needles facing in (exactly or nearly) forward direction, loosely tied to the back of the bullet. Could the needles upon impact continue moving in the direction of motion, slightly come out of the squeezed bullet and deliver a fake insect sting? The idea is that after the sting the soft bullet falls off, pulling the much lighter needle out of the wound.
Probably the terrible aerodynamics of a soft projectile would not permit long ranges. But perhaps it's enough if the tip is soft.
How thin a needle would be theoretically possible, if I had very hard materials available? Obviously only very thin needles can leave stings delicate enough to be mistaken for the doing of insects.
To provide for more inertia, the tip of the needle could be very fine, while the body could be somewhat thicker. It would still have to be light compared to the bullet. Furthermore, I suspect it would have to be fine tuned to a very narrow distance range.
EDIT:
Let's first not focus on tricking experts! Whether it works is the main question. Imagine a world where poisonous insects sometimes occur. A man is killed using the correct venom. At worst it will take time before anyone looks at the sting with great detail.
[Answer]
One idea is to use a flechette gun, which is basically a small arrow.
[](https://i.stack.imgur.com/0lANZ.jpg)
But you don't want the flechette left in the wound, so instead you make it out of some material that dissolves when it gets wet, i.e. from blood, and thus leaves no trace that it was there.
As a bonus the material that the flechette is made from could contain a toxic chemical, maybe something that mimics the effects of a insect sting allergy.
These can be fired from a normal gun by using a sabot round.
[](https://i.stack.imgur.com/dZlzd.jpg)
[Answer]
First off you need to make your soft bullet cylindrical so it doesn't tumble or spin otherwise the needles won't be pointing in the right direction upon impact, then make it less soft so it can survive being fired from the projectile weapon of your choice, then move a single needle to the front to make a more likely hit on your target and finally add some stabilizers to make it fly straight.
You have rediscovered the tranquilizer gun dart.
[](https://i.stack.imgur.com/MV3QM.gif)
<https://en.wikipedia.org/wiki/Tranquillizer_gun>
As for your requirement for it to fall out after injection; a dart could do this with some modifications, you could provide a simple spring driven ejection system to remove the dart after the poison has been injected.
Normally these are fairly large (to deliver the required amount of tranquilizer agent) and would definitely be noticed, but there is no reason they couldn't be made smaller, and less noticeable, if you only need to inject a very small amount of material. The big problem you would have with a sufficiently small projectiles is air resistance would limit you to a very short range, likely requiring some direct contact method.
This technique reminds me of an actual assassination performed during the cold war.
<https://en.wikipedia.org/wiki/Georgi_Markov>
It is theorized he was poked with a modified umbrella: he said he felt a quick sharp pain similar to an insect sting and saw a man pick up a dropped umbrella and hurry away. The sting site contained a small hollow 1.7mm platinum pellet containing ricin, with the openings sealed with a material designed to melt in the human body releasing the poison after insertion.
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[Question]
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After a politically destabilizing incident that could lead to a regional war, a sentient android from a foreign government has offered to help the navy track down a space pirate turned fanatical warlord.
A simplistic political sketch of the three "sides" (from the POV of the Navy characters):
1. **The Navy** is the gung-ho American-style "humans first" military. More heart than brains, more firepower than diplomatic nuance, but guys and gals you'd want to have a beer with. They have varied (sometimes conflicted) feelings about Sentient AI. They aren't luddites (there's a regular AI on board for navigation) but building an AI to have it's own opinions and motivations is a little "creepy" and "dangerous". How could you ever trust it?
2. **The Sentient Android** is a "[Ninotchka](https://www.youtube.com/watch?v=2A60QcsJtlE)" a dry-humor cold war frenemy. She's from a union of star systems governed by AI. Under rigid management, they are approaching post-scarcity but they converted all habitable planets to farm-only clean worlds and moved humans to climate controlled space habitats. From the Navy's POV, she represents an ideology where humans have surrendered to machines in exchange for safety and comfort. These sentient AI are their next-generation. Her abilities are unknown.
3. **The Pirate** has exposed weaknesses in the local proxy government which is collapsing. In the ensuing power vacuum he has elevated his Robin Hood status to a potential warlord who can fight back against space colonialism. His reputation is rapidly changing from intergalactic criminal to freedom fighter. Navy brass is looking for a surgical solution, not an escalation of conflict.
I've added this extra background so you understand the tone I'm aiming for. Think: *Tom Clancy-esque Cold War era cat-and-mouse thriller, but the co-operating Soviet agent is a robot.*
* The android has a refrigerator-sized external data storage unit which she physically links to while "deep calculating", but otherwise has no special power requirements.
* She has offered to help track and predict the movements of the
pirate as a civilian consultant. She has no command
role and is not officially representing her government.
* This would involve sharing information during strategy meetings and
her presence on the bridge during encounters with the
pirate.
* She has agreed not to access ship's communications or any sensitive data, but her ability to hack the ship's systems, her photographic memory, and her ability to extrapolate probabilities from small observations make her the perfect spy.
**What precautions would a space navy crew take when co-operating with an enemy android?** My question is both officially as a matter of protocol, and unofficially out of precaution that the crew might improvise. Suggestions don't need to be overly technical. I'm more interested in an espionage spirit, and how a military command would deal with a co-operative foreign agent with unknown abilities.
[Answer]
The danger she poses is the danger of **political conversion**. Maybe the humans will start thinking it is better for humans to be governed by AIs.
When she is around she will offer her opinion on anything she is asked. She has no secrets. She may occasionally offer opinions on things that can be improved.
An offhand opinion winds up changing something that saves the lives of a group of space marines. They become suspicious about efforts by their leaders to keep the AI separate from the grunts. Surreptitiously the grunts seek her out for opinions about other matters.
The problem for the leadership is that she is very good at what she does. Keeping her quiet and separate reinforce the idea by the enlisted men that they are worried about her competence. Having her loose risks undermining command authority.
It becomes a classic Spock vs Kirk scenario - or Clinton vs Trump: how much do you let predictive modeling and logic govern your actions and how much should be from the gut and instinct. Exactly how the humans reconcile this going forward can drive the story. It will change from chapter to chapter. It has the makings of an excellent story.
[Answer]
In my answer, *we* describes navy crew, *he* is a commander, and *she* is an andriod
## Escort and guard
Since *she* is single and could be easily destroyed by our hand weapons, *she* is no more dangerous than 5 mans. So *our* usual security measures is enough if *she* try to use brute force. Just twice the patrols and put guard on key areas. *She* should be guarded by dozen mans everywhere, without exlusions and every time since *she* never sleeps.
## Restrictions
We don't know about other possible orders *she* got. So we should reduce *her* ability to do something bad fo us. Don't let her any chance!
* *She* will live in isolated appartaments. Prison for dangerous criminals is good. No energy even light, any wires is prohibited. Wall should be covered by non-conductive layer.
* Protocol like for dagerous criminals: unexpected movements to another 'room', body search at random time, communications is prohibited.
* Clean up after *she* left any room, especially command center. No chance for any bugs/tipsters.
If it needed you, my adjutant, could say any excuses and any reasons just don't bother *me* about it
## Stick without carrot
If *we* see any violation of rules then *we* destroy her 'refrigerator'. Let she know about it
## Possible spies/tipsters
*We* have to revent *she* could deal with anybody secretly
* Don't leave *her* tet-a-tet and even with only 2 people. At least 3 people every moment
* Change guard and any personnel *she* just may communicate as frequently as possible. Replace cleaners and overseers after each changing of watch.
* Get interview with anybody *she* met. Cross-check statements. Use polygraph.
* Video monitoring and recording is useful but *he* don't rely on it since *she* is android and could hack any system
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I described *him* as suspicious man with delusions of persecution. It's okay since *she* is enemy and help *us* with some strange reason.
[Answer]
Change the dynamics of the situation.
Present the scenario as an existential threat to AI civilisation. Show her how a rebel success could inspire revolt and maybe conquest dreams of their galaxy. Use impersonal, old world technologies when interacting with her, allow her to bug, spy on and look around our ship (hiding in plain sight)
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[Question]
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I'm asking this question about an already-built world, in accordance with [Are questions based on movies okay?](https://worldbuilding.meta.stackexchange.com/q/3141/34523).
One of the most famous props on the television show *Doctor Who* is the [sonic screwdriver](https://en.wikipedia.org/wiki/Sonic_screwdriver), which can do quite a lot. In the words of the Doctor, ["It is *very* good at opening doors."](https://www.youtube.com/watch?v=weQ3pafQt-Q) Many of the screwdriver's other capabilities seem far-fetched, but I'm interested in that particular one: Can a device, using near-future technology, open unlock locks (for the sake of the question, a standard [dead bolt](https://en.wikipedia.org/wiki/Dead_bolt)) using only sound waves?
[Answer]
# Possibly.
Some digging led me to [a project by the University of Bristol](http://big.cs.bris.ac.uk/projects/gauntlev-1) that uses sound waves to manipulate objects via "acoustic levitation". As I understand it from [an early paper of theirs](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.214301) on the subject, they were able to create small vortices from sound waves. Associated standing waves created "traps" in which angular and linear momentum could be transferred to target objects, thus moving them in any direction.
The paper itself deals with early versions of the devices that were only used on microparticles suspended in water - not very useful for unlocking doors! However, the devices have gotten more advanced since then (see the video [here](http://gizmodo.com/researchers-create-working-sonic-screwdriver-1777985413)), and can operate in air, while handheld. Here's a still frame from a demonstration:
[](https://i.stack.imgur.com/P4zmm.png)
There's obviously a huge difference between moving microparticles and moving dead bolts. However, it does seem *possible* that improved standing wave traps could be used to move larger objects in the near future.
[Answer]
You can [pick the lock](http://lifehacker.com/5961197/how-difficult-is-it-to-pick-a-deadbolt-lock) by jiggling some picks around inside. Whilst picking a lock is often shown in films as a delicate process of bumping up each pin individually you can use the much less elegant [bumping method](http://www.wikihow.com/Bump-a-Lock).
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> “Bumping” is a lock-picking technique that refers to the repeated striking motion used to dislodge the pins inside a lock.
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(Basically just jiggling the the pins up and down and putting a little pressure on the barrel at the same time to make them stick if they get into the right place).
Now we just need to hit the resonant frequency of the air in order to [drive air into the cavity](http://hyperphysics.phy-astr.gsu.edu/hbase/Waves/cavity.html) inside the lock and push the pins up. The now bouncing pins will act as if you're bumping them and you can use the normal technique.
You will, however, need to turn the barrel at the same time and although it isn't the standard approach in *Doctor Who*, you could still do it.
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[Question]
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> Pssst! Come here!
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Imagine an ecosystem where animals have evolved highly developed mimicry of each other’s calls (perhaps they have the [universal vocal apparatus](https://worldbuilding.stackexchange.com/questions/78151) discussed in earlier questions). So predators lure prey, prey confuse predators, and rivals confuse prospective mates and each other.
So after that, they evolve an **authentication mechanism**. Think of the difference between a cheap garage door opener that is [trivially defeated](https://en.wikipedia.org/wiki/Garage_door_opener#Cloning_garage_door_opener_remotes) by recording the signal and playing it back later; vs the [more advanced systems](https://en.wikipedia.org/wiki/Rolling_code).
The animals evolve something like “code rotation” and use it as a signature on any call or cry (and later, language) so that simply replay attacks can’t work. They need to share a secret with the sender once to authenticate that sender going forward.
That’s the selection pressure. I'm asking: what are the biological mechanisms that provide for this? It needs to provide an evolutionary path for continuous improvement. It does noot need to be proof against our modern understanding of cryptography — just against other animals that have an incentive to evolve a way to forge them.
[Answer]
In the real world, the sorts of reply attacks you mention don't exist because the threat model is different. Instead of trying to create something digital, which is hard, which has some mathematical properties to implement a signature, which is hard, they tend to rely on more affordable analog techniques.
[Fairy Wrens](https://www.wired.com/2014/06/to-beat-a-parasite-birds-teach-their-young-a-secret-password/) are an excellent example. Fairy Wrens have to worry about brood parasites: Horsfield bronze Cuckoos. If the Cuckoo eggs hatch, they're similar enough to the Wrens that they will get fed by the Wren mother. They then kick the baby Wrens out of the nest, one by one, so that they get more food from the mother.
The solution is sweet. Each Fairy Wren mother has a unique incubation song. It's the "shared secret" for the family. She sings it after the chicks have developed in-egg enough to hear the song, but before the Cuckoos can get to the nest to lay their eggs. When they all hatch, the real chicks incorporate that shared secret into their calls for food. Any chick that doesn't is assumed to be a Cuckoo and is destroyed.
This technique avoids a replay attack not using fancy mathematics, but by the raw difficulty in identifying the essential part of the shared secret before it's too late. It's simply too difficult to find the shared secret by listening to the other animal. Even with a "universal vocal apparatus," the Cuckoo would have to learn the shared secret the hard way because trying to do a perfect replay every time would immediately be detected as a replay. Unlike digital messages, our analog interactions are always within a context. It's very easy to detect when someone is just speaking to a script.
This obviously only occurs within the nest, which is a short time period. However, it would be easy to develop a constantly changing scheme which is very hard to follow unless you have the neural wiring to make the scheme work and had been raised to nurture the skill of using it.
**If you really wanted a system where you can indoctrinate an individual once and they know their identity from there on, it would probably be easier to do a zero-information proof rather than some complex mathematical trick.** Zero information proofs are fascinating systems which involve three messages between the Subject and the Interrogator:
* First, the Subject announces a pair of related problems. The problems are chosen around a coin flip. One problem would be easy for a forger to fake, while the other would be very difficult unless you really knew the shared secret. The pair is chosen such that it should not be obvious to the Interrogator which solution is easy to forge and which one is hard.
* The Interrogator then picks one problem and demands the subject Solve it.
* If the Subject is the real, deal, they know the secret, so either problem is easy, so they announce the solution. If the Subject is a fake, then they have a 50% chance of the Interrogator asking for the easy question, and a 50% chance of them asking for the question they don't have an answer for.
This process can then be repeated many times to achieve a high level of confidence that the subject is the real deal: they know the shared secret.
**An example of this which could be reasonable for biology to act on involves a shared secret which is a Hamiltonian cycle through a graph: a path through a graph which visits each vertex once.** It's very easy to generate such a graph. All you have to do is create a cycle of the desired length, and then add enough edges to make it hard to find the cycle. As a general rule, finding a Hamiltonian cycle on an arbitrary graph is NP-complete.
The way we set things up, the graph itself is going to act like a public key (of sorts), while the Hamiltonian cycle is the private key.
Obviously, we can't just show our Hamiltonian cycle to every Interrogator, or else the Interrogator gets to know the cycle, even if they shouldn't. But we have a trick up our sleeve. There's another graph problem which is difficult: identifying an isomorphism of a graph. An isomorphism of a graph is a relabeling of a graph. You relabel all the vertexes, and you relabel all the edges. It turns out that proving whether two arbitrary graphs are isomorphisms of each other is also NP-complete.
So here's our algorithm:
* The Subject creates an isomorphism of the graph. This just involves relabeling all of the vertexes and edges and encoding that across your universal vocal device. The subject then announces "Here is my graph for this interaction. It is an isomorphism of the public-key graph, and I know a Hamiltonian cycle on it."
* The Interrogator then demands either "prove your graph is an isomorphism of the public-key graph" or "prove that you know a Hamiltonian cycle."
* The Subject then reveals what the Interrogator asked for. If they ask for the isomorphism, the subject simply reveals the isomorphism they created at the start. If they ask for the Hamiltonian cycle, the subject uses its isomorphism (which has not been shared with anyone) to convert the private-key Hamiltonian cycle into the one for this graph.
If the Subject is a fake, they would have needed to create the graph in step 1. If they created this by taking the public-key graph and making an isomorphism (like a true Subject would), then they won't know the Hamiltonian cycle for that graph because it's the shared key, and finding such a cycle is NP-complete. They have a 50% chance of the Interrogator asking for the cycle, which they cannot provide.
On the other hand, the fake Subject might instead create a Hamiltonian cycle of the correct length, add the correct number of edges to make it look like an isomorphism of the public-key. If the Interrogator asks for the cycle here, they can provide it. However, if the Interrogator asks for the isomorphism, they won't be able to provide it, because finding an isomorphism between two graphs is also NP-complete. Once again, they have a 50% chance of the Interrogator discovering them.
Now interestingly, the zero information proof also lets us consider a fake Interrogator. This is the case you are worried about where the predator learns to mimic the prey. At the beginning, the Subject provides a graph. The Interrogator is then allowed to ask either for the isomorphism or the Hamiltonian cycle. If they were given the privilege of asking for both, they would have enough information to reconstruct the private key shared secret. However, they don't get that privilege. They either get the isomorphism, or the Hamiltonian cycle, but not both.
The neat thing about this process is how little it actually requires. Graphs are easy to implement with neurons, and isomorphisms and cycles are equally easy. The hardest part is picking a good graph and cycle. The problems here are NP-complete because we can prove that there exist graphs for which these decision problems take NP time. This is not a guarantee that every graph has this property. Obviously, a boring ring graph `A->B->C->D->A` is extremely easy to find the Hamiltonian cycle for, and is extremely easy to find an isomorphism for. The arms race would be finding a good graph and cycle to use. Fortunately, this is an easy process! If a graph is broken, you can generate a new one very quickly. Then you just need to disseminate it!
[Answer]
Prey confuse predator is going to be great for prey. No evolutionary pressure for them to quit that.
Rivals confusing mates and each other means its harder to get some. But probably no-one dies.
Predator lure prey is where the selection pressure will come in. The fact that a predator can mimic the sounds of a lusty female of my species will mean it can eat me when I prance on in, if I am so hot to trot I show up for any lady noise I hear. That mimic ability does not mean it understands the context of the discourse occurring, or when a given sound is appropriate. I need to make sure the lady understand my worth.
The strategy by the prey is to modify calls into a call and response situation: each call by the prey should be answered by the appropriate response by a conspecific.
Call: where are the ladies who wants some musky male?
Response: I'm a lady and I want some musky male!
Call: Are you a lady who likes a guy with big bright eyes?
Response: I'm a lady and I want some musky male! - *wrong*. Her response should have to do with big bright eyes. She is a faker of some sort.
It is not a big step, evolutionarily. If you can make one call you can make more than one. If you wait to head over until you have heard one correct response, you can wait until you have heard 3 or 4 in a row. Instead of just repeating a call from a prey animal, the predator must repeat the correct call. If your lady messes up maybe she is young - give her another try. If she keeps getting it wrong maybe time for you to move on quietly. Maybe that's no lady.
But this can be overcome too - it is definitely a setup for an evolutionary arms race which might have very interesting end results.
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Consider crickets
>
> Male crickets create their chirps by rubbing their forewings together.
> One side of the wings contains a jagged edge. When the flat side of
> the wing rubs against the jagged side, this produces the chirp sound.
> [[1]](http://cricket-breeding.com/how-and-why-do-crickets-chirp/)
>
>
>
So have your creature be highing sensitive to the variation in noise, then make the noise based off of an external element (skin, scales, feathers, etc). The slight variations in scale patterns (we are just going to use scales from here out as an example) will allow differential between creatures, but it's also something that would be genetically passed down. So the offspring would be similar to to the parents (allowing family/species identification).
Obviously, as the animal grow their scale pattern will change, however it will be like boiling a frog, the change brought by day to day growth will not be enough to cause confusion. One problem that will arise from this is if the creature don't encounter each other for quite some time. But then it would go back to "I know this is a male/female of xyz species" but it would no longer be as precise as "Oh this is my mate"
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## Symbiotic relationship with some special bacteria
The biggest challenge to the question is the fact that a species can have a lot of biodiversity in it, and the best solution would be one that can work even with a lot of variations in the species even in one herd or pack. To help establish a randomly rotating cryptography key that can be shared amongst the species it makes sense to dump the responsibility onto something else, in this case bacteria.
### Pheromone producing bacteria
The bacteria in this relationship produce a number of unique pheromones at different levels that rotate seemingly at random, but are actually doing [math based upon the DNA](https://today.duke.edu/2016/08/analog_DNA_circuit) that result in a pheromone pattern. The bacteria when it divides keeps the random number sequence in sync. Much like cicadas can keep their cycles in sync, the bacteria likely would have similar mechanisms. With that said though different bacteria cultures may slowly drift or mutate causing a new key to form.
### Culture pouches
The species in question would have a number of pouches that feed the bacteria cultures and can release the pheromones before they broadcast a message. The other members of the species hear the message, but wait till they can smell the pheromone scent (which hopefully the wind is blowing in the correct direction). Upon picking up the scent, they sniff their own pouches to see if any match. If none match or they do not smell the scent they ignore it.
Multiple pouches allow them to keep different batches of bacteria cultures. Bacteria cultures will likely diverge as groups of animals go there own way. As such new herds or families likely would have some interesting rituals with either mixing their bacteria cultures up to generate a new mixture that all the members of a new herd or family can share or taking one of the cultures from the leader and share it with the others. Having multiple pouches allows them to keep their previous' family or herd's culture, so if others outside of their immediately family cry for help they can still authenticate the cry.
### Additional adaptations
The creatures will likely need a very keen sense of smell to pick up the subtleties in the different pheromone mixes and composition. Their culture pouches should feed the bacteria a unique formula that allows them to produce the pheromones or a fluid that is released willingly and/or upon death that kills all the bacteria cultures. This is to help prevent predators or other creatures from stealing the bacteria cultures to fake signals.
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Ok I'm not exactly sure how to tag this or where to ask, but...
**Could someone create living, breeding-viable wolf adults with the genes responsible for Siamese points (as found in the cat breed), and various breed-acceptable coat colors?**
**The end goal would be a population of otherwise normal Siamese-point wolves capable of breeding with one another and regular wild-type wolves.**
Even if a given gene already exists in dogs, **they'd have to come directly from the cats and be spliced into the wolf DNA, no actual dogs could be involved.** Any other methods of modern science and breeders are definitely on the table. The funding, time, space, food, equipment etc. are all available, and they have access to plenty of healthy wolves and cats for surrogates and such.
**I'm not asking if wolves and cats can interbreed naturally (obviously, they can't).** Nobody is going to be trying to inseminate cats with wolf sperm or vice versa, they're sticking to vectors and stuff.
**If they did create living cat-color wolves, would the colors manifest in a similar way, in the face/ears/paws/tail but not the body?** Basically if they had the exact same gene, would it show up in the wolves in a similar fashion.
**Would there be too much of a body temperature difference for it to show up at all, or would you just end up with a bunch of white or tabby wolves?** Basically would the body temperature difference between wolves and cats mess it up too much to actually get points.
**Is it even theoretically possible, or are wolves and cats too different and the embryos would never develop into pups at all?** On the off chance that the new gene or genes make something toxic to wolves and the pups would just die in utero.
**Thanks everyone!**
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**Easily.**
The point coloration pattern seen in Siamese cats and other animals actually has a fascinating cause. A protein called [tyrosinase](https://en.wikipedia.org/wiki/Tyrosinase) is responsible in most of the cases. This enzyme is necessary for oxidizing the amino acid tyrosine in the production of the pigment melanin. In humans and in other animals when this protein is fully inactive it causes a complete lack of melanin production and results in [albinism](https://en.wikipedia.org/wiki/Albinism). Animals with the point coloration also have mutant copies of the tyrosinase gene, but these [mutations](https://en.wikipedia.org/wiki/Cat_coat_genetics#Genes_involved_in_albinism.2C_dominant_white.2C_and_white_spotting) instead of completely knocking out the function of the protein are what are called temperature sensitive. What this means is that the temperature sensitive protein loses its function at high temperatures, but still works at lower, permissive temperatures. This is what actually creates the point pattern. The darker coloration occurs in the extremities of the animals like the feet, tail, and ears where the average body temperature is low. The core of the animal which is hotter is lighter in color due to the reduced function of tyrosinase.
Tyrosinase is a highly conserved protein and performs the same role in cats, dogs, and humans as well. In fact there exist analogous mutations in many other animals. See the [Himalayan mutation](http://www.oxfordreference.com/view/10.1093/oi/authority.20110803095937315) in mice, rabbits, and plenty of other mammals. There is even a report of a [human patient](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC329899/) with a temperature sensitive tyrosinase who had white hair on the scalp and armpit and darker hair on the extremities. If you wanted to make a dog or likely any other mammal with point coloration you could simply replace the animal’s tyrosinase genes with the temperature sensitive variants of the Siamese cat’s (or perhaps more simply just create the same temperature sensitive mutations in the new animals). Of course, I probably shouldn’t describe any genetic engineering endeavor as simple, but this project is fairly straightforward with currently existing genetic engineering technology.
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# Dogs are wolves
They can interbreed with wolves, they are the same species. I don't really know much about how color points work with cats, but I think that any color pattern bred into a cat has been bred into a dog at some point.
With selective breeding, a dog could be bred to maintain wolf-like characteristics while having any coloration seen on dogs (or cats) today. No genetic engineering required.
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Short answer no.
There's nothing preventing genetically engineered wolves from having the coloring of a Siamese cat. It wouldn't be done by splicing the genes for coloration from the cat into the wolf.
In overly simple terms genes control the activation of proteins. Most times when we are splicing genes from one organism to another we are doing it to have the spliced organism produce a particular protein. This has been done to create glow in the dark zebra fish by splicing in the genes to create a glowing protein found in jellyfish.
In the case of coat pattern many genes are at play and it is highly dependent on how coloration is expressed within that species. Given how far cats and wolves are apart simply splicing in the genes for color wouldn't work.
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[Siamese points](https://en.wikipedia.org/wiki/Siamese_cat), as you have noticed, is a specific pattern of [colouring](https://en.wikipedia.org/wiki/Point_coloration). Interestingly enough it has little to do with the normal pattern of hair colours but instead with the placement of the hair on the body. As you have notised, the wiki shows more than just cats. So more mammals have it...
For now I'll stick with breeding dogs, and it [looks like](http://www.doggenetics.co.uk/tan.html) colouring is kind of stable in dogs. While we might *not be able to have the same process of colouring* *(edit, we can)*, well, [there is this](http://www.doggenetics.co.uk/black.htm#seal), we can have the looks of it. Browse around [there](http://www.doggenetics.co.uk/), I think you can find a way to get what you want. Dogs are descendent of wolfs, so geneticly they are very similar.
So, **Yes**, you can. Might not be [precisely](http://www.doggenetics.co.uk/black.htm#seal) the same colouring as cats, but you can. Transferring the right (dog) genes with splicing is the fastest way to do it, probably. But you can get there by selective breeding if you have more time.
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Re: the other comments about breeding dogs and wolves, a natural hybrid between wolves and coyotes - "coywolves (sometimes called "woyotes") - have become alarmingly prevalent, as many contain ~10% of the DNA of domesticated dogs. This makes them intelligent and unafraid of people and are increasingly found in populated areas. Wolf and coyote DNA aside, this should give you the opportunity to utilize any types of dog coloration in your hypothetical beast.
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You know you don't need to splice genes to get this effect right? Just start breeding selectively, and eventually you'll get what look EXACTLY LIKE Siamese Points. Going out of your way to splice cat genes into wolves...let's just say this, if your science is sophisticated enough to do that, and you want them to interbreed with real wolves, what you'd actually do is manipulate the genes responsible for coloration in wolves. No cats needed.
But if we did splice--let's tackle your huge batch of questions as to how it would be expressed...well, the coloration is temperature dependant. **Dogs and cats fall near the same range as far as that's concerned--but you might actually want to look outwards.** As in, the outside temp DOES influence the expression of Siamese points. In a cold weather clime, they'd end up DARK all over, not white...yes, body temperature is mostly what does it, but that can be influenced by environments to some extent. Older cats tend to go darker too--as they run cooler when they get older.
There's also no guarantee that the genes will EXPRESS in the same way. The same gene sequence in a different animal might actually have a different result.
You don't have to rip the gene from dogs...I notice that you specifically state that you don't care that dogs have expressed this trait, or that dogs are more similar genetically, or that dogs can already interbreed with wolves. But, you don't have to rip the gene from dogs, because dogs do come from wolves. And what that means is, that lurking somewhere in their DNA is the ability to have similar coloration to a siamese cat--because dogs can.
You seem to be really attached to the idea of the hybridization--and that's really going to depend on your world.
The first thing I's be asking is why? Why did they bother to do this, when there are other, easier routes? What's the purpose?
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Oligosynthetic languages are languages with many suffixes and few roots, often leading to a vocabulary of only a few hundred words. While common in constructed languages, they are not found in nature.
* Is it possible for a cultures language to be oligosynthetic? If this
is not feasible, how close can I get to an oligosynthetic language?
* What traits would this hypothetical culture require to develop an
oligosynthetic language?
* How early could a cultures language become oligosynthetic?
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Abstracting above language, humans think in terms of "actors / actions" (I ate) or "adjectives" (beautiful flower).
Towards expressing thoughts in language, look at the *pro-drop* languages. Via inference by context, *pro-drop* languages use as few words as possible to express thoughts. The macro idea of using as few words as possible is inline with the idea of oligosynthetic languages.
Japanese is a *pro-drop* language. My feeling is that Japan's *cultural / social homogeny* enables an efficient language that is based on inference by context. Such homogeny would also help develop a true oligosynthetic language.
My observation is the Japanese is an evolutionary step up from Western languages. In English, we use pronouns as a pseudo pro-drop mechanism. Upon seeing a pronoun, based on context, we know who the antecedent is. The Japanese extended this idea further and said "to heck with pronouns!". Japanese rarely use pronouns because most frequently they can be inferred without even the pronoun placeholder. Japanese does have pronouns, but their overuse is indicative of non-native Japanese.
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The human speech system can issue a broad range of phonemes, so you *can* get a lot of different sounds that all have the possibility of becoming roots in their own right. At that point, a language actually *using* them (so, not oligosynthetic) will give you more "bandwidth", and will naturally be preferred from the beginning of each language family. Other pro-oligosynthetic considerations would arise only much later.
Similarly, we *could* count in binary positional, but we started using the decimal (in some case, duodecimal or vigesimal) system, and in the beginning it wasn't even positional.
Nowadays (or in the future), one possibility could be some sort of Newspeak imposed from above, for social control or politic/religious reasons. For the language to *remain* oligosynthetic, though, you would need a very controlled language and media - in short a very controlled society, probably a police or theocratic state.
Another possibility (not for humans) is if you have several signal *channels* (instead of one as humans do), but each of them has only a few symbols and next to no modulation. It is the case of cuttlefish, that have few "arm" roots and some fifty chromatophoric "suffixes". In such a situation, the longer-ranged or most widely available channels would tend to be used for the roots, if at all possible; the others would supply suffixes. This would allow for a basic meaning to be conveyed even when some channels are unavailable, not unlike what happens with human kinesics.
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I don't know if this will help, but what if the people were telepathic? Accompanying the words, the people can send images of whatever they are describing...
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I was looking at the cyperpunk genre, and I noticed that for dystopian futures, they always tend to do big, bad corporations controlling most of everything, with a mostly corrupt police force, and uncaring for the people at the bottom. No middle class, really.
I was thinking of switching it up; where there's a highly regulated set of laws (there would be other things to make it more of a dystopia, but these laws are what the main focus would be) similar to Prohibition: While a lot of people agree with the idea (for valid seeming reasons at the time) a lot, including people in power, don't. I also really like the idea of cyberpunk style zoot suits.
So it's still people fighting against the regime, but it's not just the haves vs the have nots, and people in charge vs the downtrodden. There's people on both sides of this issue, in all sorts of various places.
My question is: What could be so heavily regulated that people would want (not need, I would rather not it be a staple for living) that would make sense to ban? Alcohol has been done before, I was thinking of some futuristic/cyberpunk equivalent.
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**Ban colors**
Everyone would have to dress, paint their homes, paint their cars, etc. in gray scale. It would be more amazing in a visual medium, but still pretty cool.
**Ban sugar**
You can live without pure sugar. Echoes of modern killjoys.
**Ban tobacco**
We're coming close to that anyhow. But, suddenly dump it on lots of people and see how they'd act.
**Ban music and dancing**
There are already religious communities in the U.S. that have done this, some of which were especially vigorous in the 1920s.
**Ban pets**
Saudi Arabia has long banned dogs, although recently legalized them. And, lots of people could related having snuck in pets in places where they are banned now like apartments and dorms and barracks.
**Ban long hair**
The opposite of the Islamic don't shave thing. Everyone would be required to be clean shaven and basically bald. Like the Army, but for everyone across genders and status.
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A fusion energy source.
The story picks up after its discovery, and the mystery and intrigue that surround the death of its inventor, and the disappearances of any of its advocates. Ultimately, the prohibitive ban on the energy-source is established.
The ban could have been instituted by a shady Council of corporations in a bid to discourage common Liberty (or even just the rise of that absent middle-class you mentioned). The pseudo-rationalisation of this would be that without the precise conditions and informed oversight afforded by these corporations, any experiments with such a potent source of energy is most likely to result in large-scale disaster and irreparable damage; the outcome even likened to a nuclear holocaust. However, the truth remains that a fusion energy source, or this one at least, is especially docile, albeit containing the cosmic energy potential to liberate the under-people.
Feeding into the general tropes of the genre, this would allow you to trace the journey of a hero/collective in discovering the truth behind this conspiracy, discovering the subversive political tactics employed by the System that seeks to monopolise this resource by first inciting fear-mongering among the public about it which feeds their larger ignorance, and culminates in a submissive public that willingly submits to the 'protection' offered by these 'patriotic' and 'benevolent' Council of corporations.
On the sidelines, the government which sees the actuality of the situation but lacks the authority to enforce any change, instead covertly augments the protagonists' efforts to overthrow the capitalist oligarchy; again, unable to be in any sense obvious about this owing to the constraints enforced on the government by the corporations.
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1) Enhancements (cybernetic or otherwise) to boost intelligence [(transhumanism).](https://en.wikipedia.org/wiki/Transhumanism)
2) Immortality drugs or treatments.
3) Cloning yourself (organs harvesting or whole-body brain transplants)
4) Building an artificial intelligence (enslaving it or [paperclip maximizer)](https://wiki.lesswrong.com/wiki/Paperclip_maximizer)
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Does it have to be "banned"? Can you use the opposite "forced upon"?
In this case you can force laws upon the general population, that may seem fair, but actually cause problems.
Some examples would be:
* By law, each household should have at least one mammal pet. Yes,
sure, we all like pets and fight for their rights, but when you fight
for everyday survival (did you say dystonia setting?), having extra
expenses due to pets can be overwhelming, especially if you have no
say on that matter, due to some law.
* Health Chips must be implanted upon birth, a nice way to monitor your health, or your whereabouts. But all those conspiracy theories
of earlier decades, have become a reality now. The average person
will have other things to worry about on his everyday life, but.. a
certain percentage of the population still values the privacy.
* Handicapped people or terminal ill are put to death, as being non productive members of society. Health care expenses must be reduced for some "reasons" given.
* Drugs may be legal and forced upon people to keep them emotionless
throughout the day (for example drugs that deprive feelings, or that
causes apathy, etc). "For optimal work force" of course.
* Controlled births. You can have a child only with the permission of the state, due to whatever reason you want (lack of houses/jobs/food supplies/overpopulation etc). Sure it sounds fair, but who (and how) decides which family is allowed to have children?
All of the above can be "generally accepted" in a society.
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This is a bit out there (but that's why you asked, isn't it?):
Posit the technology for instant, point to point communication of limited length character messages (like telegrams.) But no storage, automatic routing or services beyond transmissions of "telegrams" to known addresses like a home or workplace. Like telephone numbers, they can be listed (via a paper phonebook) or unlisted. Perhaps an unread message causes that number to report busy until read. (What if new messages silently overwrote the one in the display? Lots of plot complication potential.)
The technology for automated switching (e.g. of telephones) was being developed, based on elecro-mechanical relays (magnets and coils of wire) around this time, but in *our* timeline, was not yet up to the task.
The big bad? The surveillance/reading of "telegrams" to root out terrorist/anarchist/socialist/pick-your-undesirables by the government and/or the bad guys at the Ministry of Post and Telecommunications.
Imagine inspector Lestrade (or the equivalent) being capable of reading Sherlock's private messages -- or the Prime Minister's. Who could stop such a person? (Clearly, there are no relevant parallels in our world; this is purely, *purely* for satire, drama or misc. storytelling. YMMV.)
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# Interpretation of Intellectual Property Rights
Some people think that corporations should be free to patent a business model. Others disagree. Some people think that copyright should be extended whenever Mickey Mouse is due to enter public domain. Others disagree. DRM. "Viral" open source licenses (use that nifty library and you're legally bound to publish the source code of your program -- if there is somebody to enforce it). Patents on parts of the human genome. The possibilities are endless.
Some characters might think that the patent system only benefits great companies and expensive lawyers. Others claim that it allows the little guy to profit from a clever idea and "get a fair share of the pie." Each side has honest believers and opportunists.
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[Question]
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So I am creating an Elven sub-species (working name is Techno Elf), these are elves that split off from the rest of the Elven society some time in the past. The reason for the split being that they wanted to focus on technology and machinery, and so communicated and collaborated with Dwarven societies (something the rest of the Elves didn't like). Over the course of a couple of millennia these Techno Elves managed to get to roughly modern level of technology, maybe near future. In the last millennia Humans had started taking huge leaps in technology and were close to catching up to the Techno Elves in terms of science and technology. The Techno Elves were curious about how the Humans had advanced so quickly, and discovered it was due to the shorter lifespan. because of how short lived the Humans were they had huge breakthroughs every couple of decades as brand new scientists brought new view points and ideas to the table. The Techno Elves then decided to take what they new of genetic engineering and try and artificially shorten their own lifespan to try and replicate the Humans.
## Timeline
* Techno Elves split from Elves talking and collaboration with Dwarves
* Techno Elves leave the Dwarves due to discovery of plastics, causing falling out with Dwarves
* Techno Elves get to modern/near future levels of technology
* Techno Elves notice Humans advancing in technology at super speed (compared to them)
* Techno Elves genetically engineer themselves to have a lifespan closer to that of humans (resulting in the rest of the elves always viewing them as children since they never really reach the age of majority)
## Background
### Elves
Elves physically mature the same as Humans, but are not considered adults until ~100, and normally live to between 600 and 1300 years. Don't really interact with other species at all. Traditionally have a good grasp on nature and magic.
### Dwarves
Dwarves physically mature the same as Humans, but are not considered adults until ~50, and normally live to between 300 and 700 years. Works a lot with metals and intricate cog based machinery.
### Techno Elves
After genetic engineering physically mature slightly faster than humans, and considered adults at ~20, and normally live between 80 and 120 years. Very quickly gets into far future technology (space-time warping for example).
### Humans
Basically the same as modern humans, but not aware of the other intelligent species inhabiting the world.
## Question
So my main question is: Does the Techno Elves' idea that a short lifespan will increase innovation actually hold up, would them having such a long lifespan have limited the innovation in the beginning?
[Answer]
This is a a question about skill vs. innovation, and I say: no, there are other ways to achieve higher ways of innovation without shortening lifespan that much.
## Long lived: the power of specialists
Of course, having a long life for a species does increase the time to become considered adult, but the average skill level and level of specialisation any of the members has is much higher than a relatively shortlived species.
Being that longlived, there is little pressure to procreate, which reduces population growth as a whole. Having a low growth rate with a high tech base leads to them training up specialists to a degree where only a handful of people is acting in any given area of technology. That has good and bad sides: while specialists are more likely to invent a fully novel thing from scratch (think about Einstein and his collegues), there are possibly much less applications for the daily life. Also, new ideas do need more time to take root in such an environment, as total turnovers in scientific areas usually are about half a generation.
## Short lived = fast procreation: tiny steps of innovation
Being shortlived with an average of 40 with a very very rare record of 90 for high medival humans did press them to procreate early. This increased the population numbers even if facing famine, high death rates and war slowly. At some critical point in the high middle ages, this procreation cycle started to increase the population more rapidly because of tiny inventions that would lessen the death toll due to hunger - This was NOT a major breakthrough, human advancement is powered by series of tiny changes!
It was stuff like the iron plow instead of the wooden one. Which then was changed gradually to turn the surface. Being short lived did not press them to invent more, it pressed them to procreate more and thus increase the chance someone would invent something to better their items. These tiny steps were aided with as many of these many people were proficient with the same tools and thus there was a big chance that someone of this large group would have a good idea liketaking iron for a plow or turning over the field.
Indeed, in human history in the real world, major breaktrhoughs on their own are almost unheard of and those that are are famous. Penicillin is one of these, and it is the result of the power of specialists above. Most often somebody would just take old parts and recombinate them in a novel and innovative way, especially in industrial revolution.
Diesel knew well about steam engines and had experimented with fuels combusting explosively under some conditions. Combinding and redesigning parts of a steam engine, he made the diesel engine. Daimler combined a cart with an engine.
## Techno Elf
### 1. Increase fertility
Well, there are several ways to go for the techno elves. First, they could increase their population growth, increasing pressure and capacity for innovation. That is actually a fairly easy fix, if they are genetic engineers: just feed the people fertility meds.
With the higher population growth, they achieve several goals at once:
* they increase their workforce and have a larger pool of people to draw from for military.
* they increase the chance of a new idea cropping in the head of a being familiar with the right tool to improve
* they reduce the time for ideas taking root in the scientific environments, as the numbers of these increase - younger generations copy ideas of each other and thus tilt the scales in their favor somewhat.
### 2. Fastern up maturity
Being genetic engineers, it might be easily doable to reduce the time to reach maturity from 100 to like 50 by adding meds to the diet. Going more could become really harmful for their brain development. With 45 years of training, you still retain a highly specialized workforce with a high live span of possibly something close to where they started, maybe 400-500 to 1000, makign them a bit more longlived than dwarfs.
### 3. Not reduce own longlivity
Why should the species reduce the longlivity even more? The pressure for innovation is not impeding death by age for humans, it is impeding death by hunger or other humans, so they innovate at things to fence of dying of hunger or to kill other humans before they do. For humans, 2 things bring forward advancement: hunger and war. Being as longlived as elvens are, they likely found a way past hunger long ago and the typical elven picture isn't about war all the time. So... let's create both pressures for the Tech Elfs:
### 4. Create servant race
Instead of cutting down the own longlivity, the elves and dwarfs could start to make a somewhat smart and sturdy warrior caste that is fed by the population of their techno-kingdom for nothing else but their service as warriors. It might be the reason why there are Orks: they are the warrior extension of the Dwarven/Elven coalition, designed to be bigger, stronger and harder to take down than humans, smart enough to be a good tactican and use their weaponry and give feedback to the weapon designers in their ivory towers. They don't need to have a very long live, but they have to gain a culture that takes pride in warfare. Feeding them well for little but training will result in them being mostly ok with their lot as the shield & arm of society. Even giving their most valued veterans a position in the governing council will help to prevent rebellions of this specis that might reach maturity at 12 and might to expect only to reach 30-35 (ignoring war casualties).
With such an army that grows even faster than humans (add cloning orcs?), there would be increased pressure on ther scientists to innovate food production, tailor weapons especially for the orc regiments and overall innovate in logistics.
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Yes. Is the answer. For one simple reason. If age 18-20 is maturity for humans and tech elves and age 100 is maturity for regular elves, then **basically a regular elf would be behind a tech elf by about 75 years, give or take. Add to that a lack of urgency regarding anything, because, basically, they live about 6 times longer.**
And then there's fertility. So a tech elf only has to live to about 20 in order to be sexually mature. A regular elf, much longer. **So not only is the tech elf ahead by many years in development, while the regular elf is still maturing, the tech elf could have several babies, all of whom will also be ahead of the first regular elf in mental maturity.** Trish, above says "increase fertility" but I argue that the life span and years to maturity already accomplishes that feat.
So 1 single regular elf will have to compete with the advancement of about how many tech elves? Because the **tech elves could actually have three generations come to maturity while the regular elf is still busy learning to drive. Or something.**
And, consider the way science marches on. The old guard naturally clings to beliefs, concepts, and precepts from when they came up. Science advances, very often, because people die. Just the way it is. **New ideas come from new ways of thinking, and that is very often tied to a specific generation.** Old and wrong-headed ideas are kept for as long as there are people to keep them alive.
Now, I can see a very long-lived elf being a venerated part of a science lab culture. They might know that the real innovations come from the faster-lived races, but being so long-lived, they really don't see the urgency of advancement and have trouble thinking that way.
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You mention magic in your post. Sorry, magic and logic are incompatible. In a world with magic, nothing need be logical. In a logical world, nothing *can* be magical.
Tell me, if you expected to live 900 years, would you engineer your kids to live 80 on the off chance that one of them will be a scientist? Hint: divide both numbers by 10, and ask again.
I'd suggest an alternative: one theory as to why young scientists (there is an enormous difference between a scientist, a technologist, and an innovator!!) are more fruitful than older ones, is that their neural connections are being formed at a much higher rate (between 15-25). Death isn't relevant. Why not just program techno-elves to periodically gain-lose-re-form their minds/memories?
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I'm designing a city built to take advantage of valuable mineral deposits in a large polar desert. The city is built around a Yellowstone-esque region of hot springs and geysers, where underground ice is melted by magma close to the surface. Water is easy; food is less so.
* Could chemosynthetic bacteria in hot springs produce energy that a human population could use?
* How would humans exploit that energy - directly eating the bacteria, or using microbivores as an intermediate step?
* If humans are eating the bacteria directly, what kind of preparation would they need?
I'll also be implementing other food sources, like rooftop gardens and trading for food, but I want to have a broad range of food for this city.
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The best food system would have the lowest trophic level. That is, something that gets its energy from the sun is trophic level 1. So eating beans puts you at trophic level 2. That is low, and that is good.
The hot springs bacteria would represent trophic level 1 in your scheme. I am not aware of any good ways to feed bacteria to humans, so we'll have to introduce an intermediary species.
A good candidate would be [mollusks](https://en.wikipedia.org/wiki/List_of_edible_molluscs), many of which are both filter feeders and edible. Scallops, clams, mussels, and oysters, you could have them filter the bacteria rich waters and then eat them. Obviously this would constitute a problem if the hot springs waters are too hot, but I'm going to ignore that as an engineering challenge.
Another candidate, for a more varied diet, would be to grow [tuna crabs](https://en.wikipedia.org/wiki/Pleuroncodes_planipes). These tiny crabs are one of the most common micronekton in the pacific, and prolific and efficient eaters of plankton. They could be fed to a variety of farmed fish for a perhaps more palatable diet. Alternately, you could depend on zooplankton to eat the bacteria, and then use shrimp to eat the zooplankton and be people food.
Note, this all-seafood diet would not be particularly good for the body, and it would have to be balanced out with some other things, but I believe you have accounted for that in your post.
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A closest real-life situation I know is a Mono Lake basin. It was not Yellowstone-like thermal, but fairly hot (some say, it it *the* most tectonically active area today). It supported a humongous population of flies and brine shrimp, large enough for local Kutzadika people to not only sustain themselves, but to trade with surrounging tribes.
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Basically, this is a setting in which artificial gravity generation is possible and can be confined to certain areas with different settings. There are maybe five human colonies on planets with near-Earth gravity (ie close enough to 1g as to make not much difference), but there are also human colonies on worlds with less/more gravitational pull. Artificial gravity adjustment is used on these worlds to keep the areas of human habitation closer to 1g than the rest of the planet, but humans can still travel outside of these areas and into zones where the local gravity is in effect, so people are somewhat used to moving between different areas of gravity.
There are two types of artificial gravity generators. One is used for extremely large areas such as a walled in or domed city. Others are used for smaller indoor areas, such as a the interior of a building or a spaceship. The larger one has a dissipating strength - as in the closer you are to the generator the better the effect of it is (so basically if you are generating 1g on a planet with less gravity than Earth, you'd have to be closer to the central radius of the generator to actually feel 1g, with it incrementally decreasing the further away you get). The smaller one is far more evenly spaced in its gravity distribution, with very little dissipation of effect on the edges.
So my question is what would be the effects of moving rapidly from one area of gravity to another? Say a person is in a building set at 1g, but runs out into an area that is 0.7g? Or 1.3g? I'm not talking huge increments. The maximum deviation from Earth norm on the heavy end will be 1.5g, while the low end would be maybe 0.4g or 0.3g. I am also not adverse to the idea of a dial getting messed with and having an entire area made into 0g on accident.
Basically, I'm writing a chase scene. The characters are going to be transitioning between areas of different gravity. I need to know if by doing so, if there will be puking, tripping, accidental breakage of bones, bouncing, fainting, heart attacks, muscle strain, nothing, or all of the above.
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**Immediate effects:**
If you are not prepared, the change in gravity might cause you to fall, just like when you don't watch where you're going and accidentally step onto an escalator or other moving patch of ground. Heavy -> light might cause you to accidentally propel yourself forward too much; light -> heavy might cause your legs to give out on you because your muscles aren't prepared for the suddenly greater strain.
Based on the assumption that going through a rollercoaster doesn't cause any immediate health concerns through the changing gravity (unless you have a weak heart etc.) I assume that changing gravity within the space of a step will not cause any health problems either. Small gravity changes (ca. 0.1g) can also be compared to an elevator starting / stopping. So you can probably expect a sinking / lifting feeling when crossing the boundary.
**Short-term issues:**
Until your body and brain have adjusted to the new gravity, you will misjudge what strength it takes to run / jump / throw / lift unless you concentrate on those actions.
Normal-gravity comparison: When you lift a gallon bottle, your mind and your muscles expect it to have a certain weight. However, when the bottle is empty when you expected it to be full, you might accidentally knock it on the shelf above it before your muscles compensate for the unexpectedly light weight. On the other hand, you won't be able to lift it at first when you expected it to be empty but it turns out to be full after all.
Sure, your body will compensate quickly for unexpected weights. But in a chase situation where everything depends on split-second changes I expect you will do a lot of overshooting, undershooting, etc. The body works a lot with muscle memory, and until the muscle memory has gotten the memo 'different strength needed' you will have problems when you don't concentrate.
I am not a biology expert, but I'd say it takes at least 4-5 repetitions to set the muscle memory to the new standard. So, after 4-5 steps you should have walking/running down pat in the new gravity. But when you suddenly decide to throw in a pacours wall-jump you'll probably have to do a lot of on-the-fly correcting and landing in unexpected positions. After 4-5 pacours wall-jumps, you'll probably have that one down as well. But then you might decide to do some other acrobatics. The adjustment period will get quicker since you are constantly gathering experience (2-3 tries instead of 4-5). But it will take time and practice to completely get used to the new gravity in that regard (I'd expect somewhere between 30min and several hours).
**Longterm issues:**
Since you are writing a chase scene, the longterm issues are pretty moot. Medium long-term: just like some people can't adjust to living in high altitudes, there might be people who can't adjust to living in a different gravity. Really long-term: I'm thinking of growing up in low-G and then going to a high-G environment. Gravity affects things like bone density and muscle tonus (not only of the trainable muscles like biceps but also of intestinal muscles etc.), so I'd expect a lot of potential problems coming that way. (Just imagine how many problems Astronauts have coming back to earth after a stint on the ISS, and that is despite being there for less than a year and having a special training schedule to not lose their earth-G muscles).
**Multiple gravity changes in short time issues:**
Going with the rollercoaster example as quickly changing gravity, I imagine you might get a headache or an upset stomach from multiple rapid changes. If you have any pre-existing medical conditions, they might be exacerbated.
That aside, the longer the chase lasts, the more likely it becomes that one of the characters loses concentration and misjudges something in varyingly fatal or at least chase-ending ways. The quicker you change gravity, the less you can benefit from adjusting muscle memory, and the more you need to concentrate on every single step or motion.
I think it is possible to train for that, so that you know what to watch for when entering a new gravity at a full run. So someone trained might have an advantage over someone untrained. But unless gravity-caused medical issues come into play, it will come down to who does multi-tasking better (concentrating on running in new gravity + (chasing perpetrator or escaping chaser)).
**Bonus effects:**
When you are changing the *direction* of gravity (i.e. floor and ceiling suddenly becoming walls, and the walls becoming the new floor) you will probably have to deal with a lot of disorientation. And nausea.
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One of the first things that people who experience zero gravity for the first time do is start swimming. During the "making of" video for the OK GO film clip for [Upside Down Inside Out](https://www.youtube.com/watch?v=pnTqZ68fI7Q) they recently released, where they filmed inside a [reduced-gravity aircraft](https://en.wikipedia.org/wiki/Reduced-gravity_aircraft) (a "vomit comet"), they all observed that the first thing they did when exposed to zero G was flail around like idiots trying to swim around, as if they were dropped in water. Unfortunately, as the air around them provided very little resistance, they generally just flailed around in place.
Definite puking. The feeling of zero gravity really messes up your sense of balance and your body responds to that by think it has been poisoned, and ejecting stomach contents. Again to use that video as an example, there were nearly 60 instances of vomiting during the filming.
Heart attacks would be very unlikely, as reducing gravity would take stress off someone's heart in the short term. Muscle strain would be unlikely as well because it's easier to propel your limbs when they don't weigh anything. Breaking bones would be possible if they lose control of themselves and carom into things. Going weightless results in the equilibration of bloodflow around the body, and as such would not make anyone faint.
Long term effects of zero gravity tend to be things like muscle atrophy and related heart problems, as well as loss of bone density, but these take months to years to manifest. Your eyes also change shape after a long period of time in zero gravity, but will return to normal when exposed to regular gravity within days to a week.
Note that these things really only apply to people who aren't used to zero gravity. If you have experienced operators, they will be able to switch between different gravity areas quickly. Dropping the gravity from 1.0 to 0.2G, for example, would make people go from running normally to bouncing around like they did on videos from the moon landings, except they would not have more than 100 pounds of suit attached to them and could get even higher with their jumps.
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I think [Susanne's answer](https://worldbuilding.stackexchange.com/a/38278/49) has covered most of it.
The human body is actually able to cope with a wide range of gravity already, as can be seen in any number of fairground rides where huge numbers of humans experience increased or reduced gravity with few injuries or bad effects.
Living long term in altered conditions has much more profound consequences but if you spend most of your time at 1G and then occasionally venture out I would not expect any serious problems. Movement in different gravity would take some time to get used to, especially moving in variable gravitational fields. That would be a learned skill in of itself and I'd expect it to take more than 4 or 5 steps.
In fact that's an area where someone used to the effects could have a huge advantage, if they were moving through areas where the gravity changed frequently. The native would adapt without thinking while someone not used to the effects would need to adapt each time it changed, and then as soon as they learned to run the gravity would change once more and they would be stumbling along again.
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The idea of a metal-poor science-fiction/fantasy setting has fascinated me since I first encountered it in [Dark Sun](https://en.wikipedia.org/wiki/Dark_Sun), and learning about [Tekumel](https://en.wikipedia.org/wiki/T%C3%A9kumel) just deepened it. When it came to my own setting, I didn't want to do things the "easy way" and have metal be scarce; instead, metal is as plentiful as it is on earth, maybe even more plentiful! However, the people of the world, for whatever reason, can not make use of the metallic bounty.
My first attempt in explaining this was [inaccessibility](https://worldbuilding.stackexchange.com/questions/37237/possible-explanations-for-a-world-with-hard-to-access-metal-deposites); however, that turned out not to be a good fit for the setting.
My second idea was unusability: metal is present in the world and accessible, but no one can use it. But a satisfactory explanation for what could actually do that eludes me.
The best one that I have been able to devise is:
There is a life form on the planet similar [to the metal-/synthetic-material-eating bacteria on earth](https://en.wikipedia.org/wiki/Microbial_corrosion). These metal-phages live in and consume metal, but, either as a metabolic byproduct or a defensive mechanism, produce some type of containment that is both lethal to anything not them and, for all practical purposes impossible to remove...almost like radiation.
My question is...
Without resorting to pure hand-waving, is there a way to render a planet's metal largely unusable to the people people living on it?
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Look at this map
[](https://i.stack.imgur.com/3FhqI.png)
# The Technological Development Of The People
The Africans are well aware of smelting and roasting processes.
The Asians and Arabians know all about gold and silver mining (pretty simple) but don't know about complex mining processes (for copper and iron).
The North Americans have a tech level comparable to Asians.
The South Americans even have iron foundries and roasters in place.
The Australians are a highly developed civilization otherwise but don't know a dime's worth of metallurgy.
# The Problems In Exploiting Metallic Ores And Mines
**Africa**
People here had some small iron ores which they exploited to extinction. They made some nice axes and swords until the ores ran out. They went south in pursuit of this precious metal and found out that southern Africa has vast quantities of iron along with some strange, shiny substance. They set up large foundries and roasters but then something frightful started happening. The people involved in iron mining started contracting horrible diseases which led to a very painful death (cancer). Their children were born with grotesque and frightful abnormalities (genetic mutations). They soon started realizing even the fauna of the region was slightly different than the fauna of central and northern Africa. After a misadventure of 10 years and losing a lot of people, they quit the whole region in terrible fright and never returned there again. Now this region is known as "gods' cursed land" and there are a lot of myths and legends stating that gods cursed this place for one reason or the other.
Actually that region is very rich in uranium and radium and these ores are found side by side with iron ores. People working in these ores are hence exposed to lethal doses of radiation and develop cancers and other genetic mutations.
**Asia**
The Asians employ gold and silver in few of their household objects such as axes and knives, but making swords or other larger objects with these metals is impossible due to their extreme heaviness and high malleability. Folk poems and legends tell of a another golden colored, very (comparably) lightweight metal to the far northeast (copper), but that region is cut off due to extreme weather, mountain barriers, wolf packs, frozen lakes and lack of food resources. The Asians are primarily agriculture based people. After a few failed tries to reach that far off land, the Asians have quit the efforts altogether and mind their agriculture.
The Asians also know about the most precious metal on earth (iron) that is located to the far west. Besides the same weather problems (uncrossable mountains and extreme winds and cold), that region is home to hostile locals who consider the land beyond the mountains as sacred, where the souls of their dead forefathers live (there are yetis living beyond the mountains actually). They would never let anyone through their lands no matter what. Those locals have a couple of iron axes and some arrowheads, which are considered highly sacred and a legacy of their forefathers. These are passed down in generations to tribe chiefs.
**Australia**
The Australians are quite developed in agriculture and fishing, but don't know anything of metallurgy. They are aware of something called as *copper* in the western sides of their small continent, but that area has excessive ponds and swamps where mosquitoes abound and anyone trying to reach the ores, dies a painful death of raging fever (malaria and yellow fever). They have made several attempts to exploit those reserves, but all have failed terribly with more than 80% life losses. Now they have left those regions for good and wait for Asian traders who bring gold axes and knives in exchange for highly prized Australian fabrics and obsidian.
**North America**
The North Americans are also adept in gold and silver mining (pretty simple, huh?) like Asians. They use gold axes and gold tipped javelins for hunting and use gold tipped spears in combat. Other than that, metal has no part in their lives due to its heaviness. They know of a region far off to the east (Iceland) where there is a (comparably) lightweight and very sturdy metal which is considered the most precious in the world (iron). Some foreigners tried reaching that island but they all dies within few days. Still many foreigners arrive with gifts for local chiefs in order to pass from their lands and reach that tantalizing land of iron ores and the local chiefs happily allow them to pass. No person who ever goes to that island ever returns alive.
Unbeknownst to the North Americans and the foreigners, the Iceland island contains heavy quantities of [perchlorate dust](https://en.wikipedia.org/wiki/Perchlorate). It blows with the wind and tiny particles of it are breathed. Some of it also gets to the eyes of the people. The overall result is severe toxication resulting in a painful death.
**South America**
The South Americans know about huge iron reserves in the northern region of their continent and many attempts have been made to exploit those reserves. However, there are huge swamps and ponds where mosquitoes abound. The bite of these mosquitoes is known to cause extreme fever and a painful death (malaria and yellow fever). Besides mosquitoes, the rainforests are also full of leeches and ticks, both with venomous bites! And to top that, several trees themselves are highly poisonous. Even water dripping off some of them causes extreme rash and swellings ([Manchineel Tree](https://en.wikipedia.org/wiki/Manchineel)). And to top that, the area is home to pygmy tribes who are extremely violent and utilize the most deadly arrows and blow-darts in the whole world. The dreaded curare!
There are still attempts now and then by adventurous merchants now and then, but few return alive ... and those too, dishevelled and ghastly, in rags, after losing all their possessions and suffering famine and diseases.
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## Consider a younger, less seismically active planet.
Due to the mechanics that cause the creation of oil and coal you're going to have very limited supplies of either, meaning that while you have the metals, your species is going to have a hard time both building the furnaces and achieving the temperatures required to refine and work them.
Any major attempt to do so will clear large swathes of forest, wood being the major fuel (and construction material) before coal was utilised. Once the forest is gone, that's the end of your industrial age.
Coal requires a planet to have had vegetation near water for some millions of years.
Oil requires ancient seas to have dried up, usually caused by tectonic movement.
[Sources at some point later when I can find some that aren't aimed at primary school kids]
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**The Answer Depends on Why You're Asking**
Whether for role-playing or fiction, a world building exercise must remember that plausibility alone means little. Just because a thing has an explanation, won’t necessarily make it satisfying to an audience (or players). Science and logic may have their rules, but storytelling has rules of its own. For example, storytelling hates irrelevancy and unnecessary details.
Your question seeks a way to make metals (things that players tend to find desirable, even necessary) available, yet somehow unavailable. This seems a role-playing equivalent of violating Chekhov’s gun.
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> Chekhov’s gun is the narrative principle that if a scene contains a
> loaded gun hanging on a wall, then the gun must go off later in the
> story. Otherwise why mention it?
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What we’re talking about here is irrelevancy. Story’s are not fictional transcripts listing all things and every detail. Only things germane to the plot or characters are mentioned at all. Game worlds work the same way, describing only the things that are different (from the player’s real world) and that would effect game play. Extraneous details are dangerous precisely because players assume they must mean something. Later when the plot proves them irrelevant, players tend to obsess.
So I see three possibilities for an answer to your question based on WHY you seek to have, yet not provide metals.
**Possibility 1 - You want to provide metals later.**
Initially your players will find a world largely devoid of accessible metals. Those metal items they crave (swords, armor, guns) just aren’t there. But at some later point, you want to introduce them. If this is the case, the mysterious force that’s hiding your metals is DIRT.
Like our own real world, the valuable stuff is hidden below vast amounts of undesirable dirt and rocks. Every enormous cash of metals in our own history, was at some past point unfound. Everybody living in California in the 1800’s knew there was no gold in the Russian river. Then one day, someone found gold - Bam!, gold rush. In a story or game campaign, such an event would be a plot point.
**Possibility 2 - You just don’t want metal.**
If you don’t want metals then tell the players there aren't any. I could point out that this is perfectly logical. The non-fiction book, “Rare Earth” seeks to address the requirements for life by looking at Earth and our solar system as an example. One of the issues it covered is that the Sun is unusually rich in metals compared to other stars (which is why Earth is unusually rick in metals). Surely there are other systems atypically wanting in metals. No further explanation needed.
But this isn’t my point. The players may ask, but they don’t really care why there are no metals. They just need to know that metals are unavailable. Once they do, they’ll accept it as a reality of your world and move on.
**Possibility 3 - You’re over thinking it.**
Your goal is simply to create a world without certain things made of metal (swords, armor, guns). If that’s the case, there’s a simple answer - nobody’s invented metallurgy yet - or those particular things yet.
Or maybe you’re focusing too much on elaborate explanations for your world’s daily reality. As you said, “…I didn’t want to do things the “easy way” and have metal be scarce.” Why not? All fiction is a lie and the key to an effective lie is simplicity, not a web of interlinked elaborations begging for followup questions.
Or maybe the problem is thinking the explanations are what’s interesting to players - it isn’t - That’s YOUR interest as world-builder. What interests players are challenges and opportunities for their characters.
The world that player characters inhabit only needs to be understandable. If they smell an opportunity in the form of gold, iron, or copper then they’ll seek it. If you tell them there’s a reason they can’t, they’ll seek a work-around. Once they finally learn nothing will work, they’ll simply ask, “If we can't have the metal, why'd you say it was there?”
And they'd be right to ask. It's an irrelevancy. That's the Chekhov’s gun part.
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Firstly, your idea of metal eating bacteria isn't a bad idea. There are theories (and perhaps evidence) that microbes eat through quartz dissolving and concentrating gold. There is plenty of energy available in metal (an oxidation reaction releases a significant amount of energy) so an engineered bacteria could do exactly what you suggested. However it cannot be a natural bacteria unless there is a symbiotic relationship between it and a metal creating plant to create its preferred food supply. Another restriction is the specialization of the bacteria to the metal element. This may mean several plants and bacteria would be required.
Most metals are locked in an oxide or fluoride, or dispersed in low quantities though out an ore deposit (eg nobel metals). If the story is about an alternative history, one could contemplate making the bond strength of metals stronger, making it difficult to find before a scientific age. However, our blood chemistry relies on iron oxidation, our bones on absorbed calcium, our muscles on magnesium, and our brains require readily available copper, aluminum, sodium and other metals. So changing fundamentals of chemistry isn't a good idea.
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1) Your planet only has land in a fairly narrow ring around the equator. As a result, the temperatures encountered by the species is uniformly warm.
2) The species is herbivorous rather than omnivorous, and has extremely efficient digestion.
The result of 1 and 2 are that fire is not terribly useful, since it provides neither necessary warmth nor much added nutrition as a result of cooking. Consequently, without the widespread adoption of fire, the smelting of metal ores is never discovered. In addition, the cultural development of the species simply never latched on to the use of metal for purposes other than adornment. While this is easy to say, it's hard to justify, but it has a number of parallels in our history, specifically in the New World. The Incas, for instance, did excellent work in gold and silver, but never developed metal (native copper, bronze or brass) for use as weapons or tools, and it's not entirely clear why not.
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Your planet is naturally far more acidic than earth. There's continuous acid rain due to overabundance of sulphur and oxygen. Life has evolved differently from earth and is capable of surviving in this climate.
While the cave people ancestors of the modern sapients did learn to smelt tin and copper, they found these of little use, firstly because they were far too rare, and the resultant squabbles over ownership rights cost more than the mines were worth. Secondly, whatever metals were extracted, quickly tarnished/oxidised in the open, meaning that they couldn't be used for anything practical.
As a result, society has developed a distaste for metals in general, with a few exceptions, like gold, which is considered holy and used for small outdoor ornaments by the rich and power to display their wealth.
This has also led to counter sects, considered heretical, but usually ignored, by the mainstream, that hold metals to be an abomination which the gods seek to remove from the earth. Noble metals are seen as defiant to the divine will, thus symbolising evil.
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**Your biology is simply different that ours. All of the metals are quite toxic.**
As a result, people avoid metals because the pain, suffering and death resulting from handling metals pretty much discourages their use.
Although with careful handling, metal use would be possible, there is little incentive to overcome the fear of working with deadly poisons. For humans, beryllium is quite toxic, and as a result we rarely use it although it has some very useful applications.
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My world is a realistic post-apocalyptic revival of civilization. Thousands of years have passed, and almost all knowledge of the old world has been lost or greatly distorted. There is plentiful physical evidence, but no written records that can now be understood. This is a pre-scientific age, so the barely recognizable ruins attract no serious academic study. They are either exploited or avoided. The best historical accounts come from the rare educated elite, in turn passed down from oral tradition originating well after the fact.
Only a few things are certain and widely accepted: the ancient ones were a vastly more powerful people than any since; their downfall was sudden and catastrophic; it involved fire and earthquakes and falling stars; and the current ice age is a result of their demise.
The more learned may understand some of the following, which they may or may not wish to share depending on their ideology: that the ancients were just humans like us, but far more advanced; that the fall was at least in part due to their own destructive technology; that the final death blow came from the heavens; that much of the now populated lowlands were then under the sea.
With that limited cultural knowledge in place, how might it affect the beliefs of indigenous and organized religions, and philosophical schools of thought, in early civilization?
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There's a very good real-world analogy to this: the fall of Rome.
After the Roman Empire fell, for several hundred years people looked back on the things they had built with a fair amount of awe and wonder. They saw these great aqueducts, temples and colliseums, great works of art and literature that they could not reproduce. As late as the 1700s people were still talking about recapturing the lost science, technology, and arts. The mystique lasted long after people had surpassed the Romans in most ways.
Okay, they were not perceived as being destroyed BECAUSE of their technology in the sense that you are saying here. More like, "their wealth became so great that they became weak and decadent".
So all that said, my thoughts:
Number one: It would be simplistic to suppose that EVERYONE will have the same reaction, any more than everyone today has the same religion or political ideas or philosophy of life.
I'd suppose that some will say, They were destroyed by their technology. Technology brings destruction. Technology is evil. We must fight anyone who tries to rebuild this terrible technology.
Others will say, They accomplished great things that we are no longer capable of. We should study the ruins and surviving writings and try to recover this lost knowledge. They might add, Yes, they destroyed themselves, so we want to be careful not to repeat their mistakes. Technology doesn't kill people: people kill people.
Yet others might say, There is no point in even trying. We can never match the achievements of our ancestors, and even if we did, we see that their triumphs were fleeting. Life is hopeless.
Effects on religion? Presumably some would see their destruction as judgment from God. Depending on how much of their history is salvaged, possibly a direct divince judgment, like Sodom and Gomorrah, or judgment via human agencies, like the Babylonian Captivity. But other than being held up as a prominent example of the penalty to be paid for defying the laws of God or the gods, I don't think it would make that much practical difference. I mean different from religions as they exist today. Plenty of Jews, Christians, Muslims, and others believe that at one time God destroyed almost all humanity with a great flood. Would the knowledge of another cataclysm, with many more survivors than the Flood, fundamentally change their beliefs? It would reinforce them, but I don't see why it would change them.
I'm tempted to say that such an event would shatter the beliefs of people who have very optimistic religions. I mean, people who say, God loves us so he would never let anything really bad happen. But then, and I don't want to get into attacking other people's religion here, so let me just say that I've never understood how people can believe that sort of thing given all the bad things that happen in the world every day. Traditional Christianity says that the world is full of evil and here's why and here's what God is doing about it, and whatever you want to say about Christianity, at least its evaluation of the world is consistent with what we actually observe.
Similar things coudl be said about secular philosophies. Like the Humanist Manifesto says how people are getting better all the time and we are entering a new era of peace and love and enlightenment and we don't need any God. That was written shortly before World War I. When that war proved that so much of their optimism was unfounded, they didn't abandon humanism, they just toned it down a bit. I assume the same thing would happen to the highly optimistic at the time of a cataclysm like you describe. Some would abandon their beliefs, but most would probably simply adapt them.
You could speculate that some number of people would believe the ancients were gods and build a religion around them. I doubt it personally, I had a question myself in this general direction ([Would relatively primitive people really confuse technology with magic?](https://worldbuilding.stackexchange.com/questions/32327/would-relatively-primitive-people-really-confuse-technology-with-magic)). But it's certainly conceivable.
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I don't know about you, but I hear that an extraordinarily advanced race just like us was destroyed - most likely because they were *too* advanced - then I would become a hardcore [Luddite](https://en.wikipedia.org/wiki/Luddite). "Look what happened to the people who tried to learn too much, and build too much! They were struck down, whether it was by their own doing, by nature, or by a deity."
If I'm an important figure in a religion, I can easily use this as a stance to discourage technological development and learning. "We need to go back to a simpler time, a kinder time! Their destruction was the work of our god, whose vengeance is almighty and terrible! None should challenge his omnipotence and omniscience."
Aside from this, there will clearly be an element of god-fearing in any religion, assuming the above conclusions are drawn. The people pray to an angry god, a vengeful god, and he must be appeased! Religion will play a much more central role in life, similar to how it was in the days of the God-fearing, extremely pious Puritans.
Moving to a more secular school of thought, philosophers will draw the same conclusions as the religious folk drew in my first paragraph. See what technology brought them to! Maybe curiosity and exploration are negative parts of human nature.
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* The precursors will have cleaned out many of the easily accessible raw materials, from copper ore to coal. Mining in an area with millenia-old collapsed mines will be dangerous. On the other hand, there might be many smallish "motherlodes" in the form of buried junkyards. Does that decentralize the culture?
* Would those *barely* recognizable relics inspire architects and engineers build on the same scale? Imagine the stumps of a bridge like the [New River Gorge Bridge](https://en.wikipedia.org/wiki/New_River_Gorge_Bridge). Sometimes knowing that something is possible is halfway there. Does that centralize cultures around imperial capitals?
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Thats such a pretty topic. Still, it does feel like a mashup of Fallout and Fall From Heaven (a Civilization IV mod). But still, at least I think that what you are describing could be earth just just around 100BC.
People embrace their gods and carry on the stories unfolding during their gods... earth time to the next generation. These gods of course where pretty powerful, but somehow they were prone to fighting and cheating at each other, or going for a... ehm... date down to earth. Keep that impression for a moment.
Now fast forward to the point of your stories start. The next iteration of human rise and fall did start, but sadly these guys will have pretty hard time even coming to a second age of iron (because all the iron easy accessible was mined out centuries ago). Now they wander around, dwelling in wooden huts somewhere thousend years ago Germans and British Vacationists fought for the best chair at the pool. That area is now is a desert like area, because the Mediterranean Sea dried out, but at least there are no glaciers pushing forward downhills over here.
Its kind of cold, so they gather around a warm fire and start telling stories about the "old ones". You might hear the tales of Pot-Harald, who did beat a creature, shimmering in the sun, to death with his trusty broom while completely missing that he was parked in the friendzone by the red-haired lady he did like really. Or the tale of Mister Dom, who tamed a wild beast and used it to race other beast riders, until some day his best friend died. Or the tales of the well dressed guy which went out to fight the evil in the world while drinking huge loads of alcohol before grabbing the bad guys lady for a... walk. Hey, there are children around here!
Speaking of them; one might ask, what did happen to the old ones. Parents now start looking at each other and make space for the elder of the community, which - so tales tell - is old enough to know all the stuff he is telling first hand (weeeeell...).
So this old man places himself and start telling the story of the Old Ones, that worshiped the Apple of Awareness by carrying around small tokens with a picture of it, showing it slightly bitten off as a symbol for their own connection to Awareness and Wisdom.
But there were a mischievous group of baddies, who thought their God - the penguin machine - was far superior. Both battled for eternities, until one day, the Kraken of Information - Octogogolos its name - did awake from its slumber and took away the Old Ones connection to all their wisdom, angry that no one even thought about worshiping himself! For centuries the Old ones tried to please him by offering pictures of pretty girls with... less coth than advisable and cute kitten. But Octogogolos was way to angry to fall for more offerings any more.
Sadly by taking the knowledge away from the Old ones, they forget how to watch for the skies and missed that the minions of Eduard, the Space-Munky, started throwing mountains from outer space to earth. That wasn't even a bad scheme; the minions expected someone back home catching these mountains, because the old ones didn't look pretty any more. But with no one knowing how to catch them any more, they did fall at the heads of the Old Ones, crushing their homes, flushing away towns with water and causing general mayhem.
If you look out to the east you still can see such a mountain. In this days people try to get ore out of it, but its pretty complicated...
At least the kraken was pleased with all the water now flooding the earth, because he always needed it to keep himself cool...
"And what do we learn about this", the elder now asks. "Right: worship your fruits, because they are good for you, but forfeit the machines, because they will anger the kraken. But you can keep yourself save from him by sharing pictures of kitten and pretty girls with the cold water."
So... as said to the beginning, that did happen to humankind already I think. But now people start carrying around books of such misunderstood stories and think they are lessens from gods or stuff like this. And it will happen again; but the outcome may change based on what kind of story is passed to the people out there. Maybe there are groups, that still worship the penguin machines, or try to awake the kraken Octogogolos so it will give back the knowledge to humankind.
Its all about the stories, and who tells them. Always.
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For less educated people, it's easy to correlate anything coming from the sky as coming from a divine source. Thus, it is quite possible that technology will be considered evil, and having too much of it would be risking the wrath of God. However, a large part of how things develop will depend on who survived the apocalypse.
Religious groups surviving will believe it was the wrath of God, and will develop technology-free societies. What is deemed to be dangerous technology or not will be left up in large part to the leaders, and among those leaders you can get corrupt leaders who will classify certain technologies as safe for their own benefit, or pious leaders who may ban new things to protect their people.
Well-educated groups that survive (or groups with well-educated members who are respected) will pass down a different story to their descendants. It sounds like the apocalypse was not entirely self-inflicted ("the final death blow came from the heavens"), so there may be an element of "the wrath of God", but the focus will be on the hubris of human ambition. These groups will attempt to bring technology back, but emphasize caution, studying the negative effects of what they do, and learning from the mistakes of the past.
There is an immediate conflict between these two different ideologies—one wants to bring technology back (techies), while the other wants to prevent its return (luddites). This will encourage the techies to bring back technology faster, as they will desire to be able to protect themselves from the luddites. However, the luddites, even without technology, could easily overwhelm the techies if the luddites are more numerous and find the techies within a century of the end of the apocalypse. This could force the techies to hide, either in remote locations or secretly among the luddites.
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Imagine a setting in which small caches of learning materials were stored in such a way to survive and be recovered. A very knowledgeable person stumbling upon such a cache, might be able to use that recovered knowledge to improve his life.
Of course the written language in such materials would diverge widely from what was in common use.
The application of the knowledge in those books would also diverge widely from what was in common use.
Imagine a person inventing simple electrical and mechanical devices. In some ways this would appear to be identical to the learned wizards of fantasy settings. Having to learn an ancient language, recovering lost wisdom, controlling vast and mysterious powers that can potentially kill the careless.
Yup, sounds like wizardry to me.
And like wizardry in a fantasy setting some will fear, avoid, and/or persecute the "magic wielders" while others will try to bend those powers to their own needs/wants/wishes.
Putting it another way, people will still be people. As such there will be good people, bad people, and the majority who are somewhere in between the two.
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## **Context**
The setting of this question is basically our world, with magical creatures hiding among us. They are from different races, and can be human-like (witches, [santas](https://worldbuilding.stackexchange.com/questions/23764/what-should-be-the-limitations-of-a-gift-generating-power?lq=1), [succubi](https://worldbuilding.stackexchange.com/questions/23401/what-would-the-culture-and-traditions-of-invisible-people-look-like?lq=1)...) or not (kitsune, swamp monsters, chimeras...). Most of them are part of supernatural mafias.
Those mafias have set very lucrative [traffics](https://worldbuilding.stackexchange.com/questions/23485/cargo-of-a-supernatural-smuggler?lq=1) around the world. Like regular criminal organizations they smuggle drugs and weapons, but some of them specialize in tissues of magical creatures (flesh, brains, bones, skin, etc.).
In this world every potion, artifact or spell uses something originating from a creature, so the demand is high enough for this traffic to be very profitable. The *something* in question doesn't have to be a whole organ, it can be a few grams of dried flesh, for example.
The quantities are somewhat limited because every group protects their own members, so most of the sellers get their source materials either from their own deads or from "unaffiliated" creatures.
Recently, more and more lab-grown tissues are sold on the black market. These are produced using modern equipment, like what's used to make [in vitro meat](http://www.futurefood.org/in-vitro-meat/index_en.php) and [lab-grown human skin](http://horizon-magazine.eu/article/complete-human-skin-grown-lab_en.html), and *maybe* a little magic.
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## **The problem**
I'd like to limit the production of in vitro "magical meat" by adding some kind of extra difficulty.
For now, I've found a few options that could work, but am not sure which one is the best.
* **Need for blood**
The tissues have to be "fed" with a solution containing blood (or blood plasma) taken either from the original donor or from another member of the same race.
* **Magic decay**
Each magical cell can only produce a *limited number of equally magical cells* once placed in vitro.
As a result, 1 mm2 of natural skin can only produce 1 cm2 of equally magical lab-grown skin.
* **Consent is key**
The seed sample has to be given willingly to be able to grow.
* **Rule of proximity**
In vitro cells present magical properties only if they were *grown in the proximity of the original source*. The closer the donor is, the better the result.
So if a lab wants to produce werewolf liver, they have to lock a werewolf inside the lab, collect a sample of his liver and keep him alive for as long as the growing process last.
* **Magical support**
A witch/magician/druid must be present and reciting incantations/casting spells/maintaining pentagrams during the whole process.
* **Simple but boring option**
Cells originating from magical beings *don't reproduce as fast* as human cells.
* **All of the above**
I could use all of these options if *each race has its own rule*. In this case, I'll have to find other rules to cover every race I've included in this universe (I'd rather not).
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**What rule or set of rules is the best to complicate the production of in vitro magical tissues ?**
The limitations should reduce the production capacity of these labs enough so their products wouldn't flood the market, but not too much so they can still produce something.
Also, it's better if it sounds (at least a little) logical.
*Disclaimer :* Most of the scenes I've written for this setting so far are a bit violent and/or [gross](https://worldbuilding.stackexchange.com/questions/25347/what-would-a-village-built-out-of-human-remains-look-like), so don't hesitate if you want to propose a solution that contains a bit of violence and/or grossness.
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Why not use a sociological reason instead of a fundamental limitation of the technology? Real world examples include:
**1: It's really expensive:** The lab grown meat isn't cheap. Mostly because of the research costs associated with getting it to grow. If each new 'meat' added to the repertoire requires intensive magical/technological research, along with careful monitoring and tending once you have developed the in-vitro tech, then the costs of this are going to be astronomical. Even if the demand (and thus the price) justifies the expense, you're going to have to put up a lot of capital and be able to launder a lot of ill-gotten cash to be able to sell your product.
**2: It's really hard!:** Most of the batches of werewolf-hair just fail to grow. No idea why (could be any of your ideas above, some strange combination of the ideas, whatever). Eventually the ease with which you can go out and whack a werewolf is going to outstrip the convenience of growing your own. Hydroponics experts can charge a lot for their continuing services because it's not as easy as it seems. This might fall under the same purview.
**3: It's not easy to hide, and it is easy to demolish:** Consider Meth. It's relatively simple to make and it's got a decent street value. The reason that we're not utterly flooded with it? Meth labs get shut down, get taken out by rival dealers or just plain blow up. If I were a vampire lord trying to deal in unicorn-horn (the one on it's head, people) and I found out someone else were trying to make it on my patch? Firebomb through the window. If you add in a magical 'trace' or certain chemicals that are needed and are easy to track then this becomes even more of an issue, as your scientists will keep having to move production rather than increasing output.
**4: All of the above, plus your all of the above:** Combining everything seems like your best bet. In your 'All of the above' option, you say that you'd have to make a new set of criteria for each race. That's not quite true. If all the Fae races need to be near their flesh, all the Were-flesh grows super-slow unless attached to the host, and all the Undead cells have a nasty habit of getting up and walking around the lab, then you've got a good set of different needs for each type of creature but you haven't had to go through each one individually. You can re-use rules, or put them in other combinations.
For example:
*It took years to work out how to grow Fire-Imp nipples in the lab, and the chemicals needed for it weren't cheap! Not only that, but their tendency to combust when other imps came near was a major hazard!* (Options 1 and 3 on my list, plus some flavour for the race)
*By comparison growing zombie brains was cheap, though the smell tended to bring the Werewolves down hard on whoever tried to grow that dead meat on their turf. That, and the constant, expert Necromatic tending it needed..* (Options 2 and 3 on my list, plus the magical support from yours)
All in all: I think given your setting it would be more interesting to find social blockers to this happening than just saying 'magic doesn't let it happen'. That way you can avoid justifying why it doesn't happen much, and instead use someone trying to make it happen as a plot hook (*but why does the good doctor need so much Troll blood? There must be a reason...*).
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I would say you have to feed your tissue sample some living or recently deceased flesh of a similar creature, while a magic user influences the flesh to transform into the same material as the tissue sample. For example, let's say you have a square inch of werewolf liver. Someone slices some flesh off of a wolf then immediately places the werewolf liver on top of the sliced wolf flesh. The magic user then casts a few complicated spells on the wolf flesh and it turns into werewolf liver.
The similarities between the flesh and tissue sample influence how long the transformation takes place. So if you're making a werewolf liver, then wolf or human liver would take the least time, then other flesh of a human or wolf, then maybe a fox liver would be next. If the two types of flesh are too different, then the transformation would be impossible.
Tell me what you think of the system I suggested.
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Like the other answers mentioned, I think a combination of reasons will result in a much more realistic and interesting world. You can also include success probabilities. Say you have to seed a sample of skin along with various chemicals and a magic ritual, but everything only comes together in the correct configuration 1 out of 50 times. Suddenly, even if the process is cheap, you might have to run it 50 times to get a viable sample.
Another thing to consider is some higher mob power keeping supply low so that demand and prices stay high. Then, if one of the labs starts producing a lot more imp brain (or whatever that lab produces), the big bosses work together to either limit the lab's production or take it out altogether.
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Imagine living in the [Roman Empire](https://en.wikipedia.org/wiki/Roman_Empire) around 100 AD. The empire controls most of the known world! No foreign power could possibly defeat the empire! The Romans will be in charge forever!
... except we know that's not what happened—the empire declined and fell apart. The fall, however, did not happen overnight. The empire went from prosperous to not so hot to oblivion over the course of centuries.
It doesn't seem hard to imagine what it would be like to live in the midst of prosperity, or what it might be like to live when an empire is in clear decline.
The middle ground is where it gets interesting. The honest among "the powers that be" would be aware that their civilization is in trouble, while some others would be drunk with power and either not realize or not care that their actions are contributing to the destruction of their civilization.
But what about the people who are not in charge? **How would an average Joe realize that things are going in the wrong direction?** If he knows in advance that things are going south, then he can prepare for both himself and his family.
Some notes:
* I just used the Roman Empire as an example of an empire that declined. Your answer should be applicable to more than just that one empire.
* Examples from the decline of real-world empires are appreciated.
* Our average Joe does not have special access to information about the empire, i.e no brother who is a general in the army and gives Joe specific information about how battles have been going, but he could hear rumors of a battle going poorly.
* Our average Joe doesn't actually have to be average, but he's no Einstein.
* The civilization is still doing rather well, but in the near future (20-100 years) it will be pretty obvious that it's in decline.
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Civilizations ***usually*** decline so slowly that nobody can see it happening. Even if some people somehow realize what's happening, the time scale is much longer than the lives of their grandkids. Occasionally, a big event will cause a sudden acceleration of the decline, but even those events usually only cause sudden changes in the regime, not the civilization itself.
Some counter-examples to what I just said:
Astute observers could have predicted the collapse of the British Empire after WWI (and then even more after WWII). This collapse occurred over only decades, so it was "lightning-fast." Some colonial independence agitators successfully anticipated the collapse (e.g., Gandhi in India), and profited from it.
In the Bible, the prophet Jeremiah self-reports that God told him to buy land in Judah, just as the Babylonians were closing in to destroy Judah. Of course Jeremiah got a great deal from the owner, who didn't believe Jeremiah's prophesy that God intended to let their descendants come back 70 years later. (Obviously, in your world/story you don't need to rely on prophesy.)
In 405 or 406 A.D., the Germanic tribes finally breached the Rhine, and proceeded to ravage Gaul. It has been surmised that they were aided by an especially harsh winter that caused the Rhine to freeze solid. They were probably impelled to migrate West because of the Huns. Those are things that a far-seeing person might have anticipated and made plans against. Or even profited from!
How could an "average Joe" anticipate such turn-arounds? Some key factors from history (Roman, Persian, Chinese, etc.) include:
* repeated military defeats/successes
* repeated pull-backs from previously held territory (or opposite)
* repeated fast changes in rulership (or, rise of a gifted ruler)
* power shifting from the civil service to the military (or, vice versa)
* instability in the money supply and/or prices
* discovery of a new region or new technology
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It is easy if he can predict the way it will fall .... which even the rulers can’t tell.
So the real trick is civilizations are very multifaceted and "fall" in ways unique to that civilization's structure. The leaders of a country are usually working to prevent it from falling. So countries tend to only fall for reasons that the leaders couldn’t foresee in time to fix, and 20 -100 years is a lot of time to fix things.
Here are some indicators that sometimes work for each I’ll give an example were it works and one where it doesn’t work.
Current territory and rate of territory gain:
Roman sustained itself by promising solders land as payment and then using them to conquer more land and add it to the empire and give it to them as payment. This land cycle was key to the empire so the fact the borders stopped growing was a very bad sign. Conversely Venice and Athens both had very small territorial holdings that didn't grow, so for them territory growth is a bad indicator. Instead Venice fell from power when Portugal opened up new trade routes around Africa and cut them out from the valuable spice trade.
Access to Wealth or good trade routes:
Contrary to the Example of Venice, the Qing empire in China went through a period of steep decline when exposed to new trade routes from the west, though attacks by advanced European warships had a great deal to do with it. So maybe falling behind in technology is a sure sign of defeat.
Falling behind in Technology:
During the colonization of the Americas we see the Aztec and Inca civilizations fall when attacked by the more advanced Spanish. On the other hand, a few hundred years before during the dark ages European counties were far less advanced than the neighboring Muslim empires to the south and east, but instead of crumbling they mounted a comeback in the 14 and 15 hundred retaking the Iberian Peninsula and the Balkans. So even a technologically inferior group can win.
There is a second problem access to vital information, Joe needs to find out these things.
First in the eras before the information era getting access to military statistics, the imperial budget, and an accurate and up to date map of the country and the like is difficult. In Rome there are good odds he is illiterate.
Second, as a government collapses it tends to try to hide or suppress bad information. The weaker you are the more important it is to present an illusion of strength.
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It is remarkably hard to predict when a large powerful social group, like a nation, will fall. The reason for that shows up in game theory and drama theory. Most social structures exist so long as enough people want them to exist. If you see that the civilization is failing, you will act to pull out your part, speeding the collapse. As long as there are people who benefit from its continuation, they will act in a way to ensure you do not leave.
**This typically means they will try to figure out what you were looking for as signs of a collapse, and focus extra effort on making sure those few signs do not occur.**
Case studies can be found left and right in the stock market. We are constantly making tweaks to "ensure the stock market doesn't fail like last time," which just means it fails in new ways. Never underestimate the creativity of a human.
As it turns out, there's actually mathematical limits that can prove that it is impossible to develop any mathematically sound way to prove the civilization is collapsing. This means even scientific observation cannot tell for sure. Average Joe will probably be comfortable with a "probably going to collapse," rather than a mathematical certainty that it will collapse, but I bring up the mathematics to show that there isn't even a way to do it in a perfect world.
Of course, there are other approaches Joe might take to ensure his goals are not stymmed by an untimely fall of the empire. Rather than trying to predict when the empire will fall, and act then, he might adjust his lifestyle such that the empire cannot fall without also putting him on an acceptable life path. This is very hard to do if you treat the empire or other civilization as a monolothic block, but if you realize that society is a far more diffuse distributed concept, you can often identify sub-civilizations that are tearing away as everything falls apart, and join them. The real key to this is adjusting Joe's observations and actions so that they try to support Joe's needs directly, rather than taking actions which directly hurt someone else. As long as nobody is being hurt by Joe's actions, they have no reason to use their creativity to find ways to hide information from him, or to make him stay.
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If there is a decline in standard of living, or you start seeing more hobos on the street, or jobs are getting harder to find, if you see infrastructure and other structures decaying, or lots of businesses closing, that's how you(as an average joe) that things are going bad. Dmm's response is also good, but full information about those things could be concealed, either by government intent, or by simple fog of war. Keep in mind, even the government doesn't have full information of the situation. They often get no Intel, or bad Intel.
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Let say a asteroid hit earth and you survived in a bomb shelter. How long would you have to stay in that bomb shelter before it was safe to leave it? How would earth look when you got out from the bomb shelter, would it be hotter or cooler? would there be still be tree and other plants? What else would be different?
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Sources:
* Documentary Catstrophe (2008)
* Documentary Miracle Planet (2008)
* Radek Michalik and David Dolak impact visualization that was created in collaboration with the Science Institute at Chicago's Columbia College.
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**IMPACT A**: Catastrophe and Michalik & Dolak explore the Chicxulub impact, to which it is attributed the extinction of the Dinosaurs. The impact is described as follows (added unit convertions):
* 6 miles wide (9.656 km ~10km)
* 45000 mph (72420 km/h or 20.12 km/s) [Michalik & Dolak estimate 22 km/s (49213 mph or 79200 km/h)]
* On Yucatán Peninsula.
* 65 million years ago.
* Chicxulub impact crater is oval, suggesting a non vertical impact.
Note 1: None of the documentaries give an acurrate measue of wheight of the asteroid, although Catastrophe says it was "about a trillion tons".
Note 2: The extinction of the dinosaurs is dated thanks he an iridium layer (stata) that is uniformly tick around the world. Below the iridium layer there are dinosaur fossils, above there aren't. Iridium is otherwise rare in the Earth's crust, but it is found in meteorites... the impact that would have created the iridium layer is known as KT (Cretaceous–Tertiary) event. When discovered the Chicxulub crater was attributed to the KT event, but [other research](https://www.youtube.com/watch?v=PG3NK6-ysPo) suggest that there may have been two Dinosaur killers, being the Chicxulub the first one, and the KT even the second. Regardless of whatever that is true or not, we talk about the Chicxulub impact (which may or may not be the KT event).
**IMPACT B**: From Miracle Planet an hypotetical event in modern times with the following description is taken (added unit convertions):
* 500 km (310.7 miles)
* 20 km/s (44739 mph or 72000 km/h)
* On the pacific ocean, 1000 miles (1609 km) south of Japan.
* If the impact would happen today.
* Angle is not stated, but probably it is a vertical impact.
Note 3: I'm getting misleading information from Miracle Planet, in particular it says that the asteroid size 500 km but also that "the asteorid diameters is larger than the main island of Japan" while Honshu is larger than 500 km (with 1300 km according to Wikipedia). Also, it claims that the speed is 20 km/s which coverted to km/h is 72000 km/h but when the documentary mentions the speed in km/h it says it is 720000 km/h (10 times faster). Also - as possible artistic license - the video present the impact to the east of Japan instead of to the south. The information above prefers the more conservative measures and the spoken material of the displayed one.
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**First hours**
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> A lot of (the debris) makes it into the upper atmosphere and some of it even makes it out of the atmosphere and it orbits in space of a little bit and then re impacts into the surface of the Earth somewhere else. So this debris actually went all over the surface of the Earth, and as it was coming back in - just like when you see in a meteor shower - things heat up as they come back in to Earth's atmosphere. This debris would have heated up too, but there were so much of it that it would have heated up the entire atmosphere and start forest fires just from spontaneous combustion on the opposite side of the globe.
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-- Cathy Plesko
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> When an asteorid hits the surface Earth, the material is heated up to temperatures that get up to the point of... say, 4000 ºC to 6000 ºC. This is as hot as the surface of the sun.
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> (...) So, heat really is the killer.
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> (...) But that is only part of it, you then have the vapor that expands, and heats up the atmosphere as well.
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> (...) it will expand extreamly fast. It expands so quickly that it can cover - eventually - the entire planet.
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> So now you are not only beating the point of impact and the vapor that's created there. You now have material that is expanding, eventually some of that material is expanding and goes out of atmosphere of the Earth, then comes back down.
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> During the time when it comes back down... it's generating more radiation. So that you have the heat of the impact, then you have the material - that vapor - that heats the atmosphere. Then you have the jets that return to the surface of the Earth... and as it goes to the atmosphere it will create enough energy to literally fry - completely combust - any living organism that would exist.
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-- Peter H. Schultz
As per Michalik & Dolak model, global darkness is reached in the initial 3 weeks after the impact.
**No sunlight**
After the fast effects, it is expected to have an initial period of heat followed by drakness from dust covering the atmosphere. This period may last at least 6 months - 3 years as per Michalik & Dolak model.
In IMPACT A, the darkness period is cold as the heat disipates relatively fast. For IMPACT B, the darkness period is extremely hot, and it is said to boil the oceans.
For IMPACT B it is said that the heat travels slowly into the Earth crust - "about 1 meter or 3 feet every year".
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> Any organisms that are living deep underground like (under) one to two kilometers tick (rock), will probably safe. The heat part doesn't last long enough for the heat to propagate down to that depth.
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-- Normal H. Sleep
**Cold period**
After the darkness period, sunlight comes but the temperature stays low in a permanent winter.
In IMPACT A, the cold period means permanent snow. There is also acid rain, the cold and acid rain prevent growth of new plants. This period may last "a couple" years.
>
> So, at first you have the dust launched out of the atmosphere which blocks out the sun. That eventually falls back as the atmosphere converts and cleans itself out. But then you still got the sulfur acids up at the upper atmosphere, which reflect sunlight and cool the planet. So this prolongs the impact winter for probably another couple of years.
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> (...)
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> First you have this six month long winter when there is no sunlight at all, and then finally you get a little bit of sunlight and the plants think "oh good, finally I can sprout my seeds and grow again" and then the sulfur dioxide falls in acid rain and burns all the leaf off your plants.
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-- Cathy Plesko
In IMPACT B, since water is mostly vapor at the end of the darkness... the winter bring torrential rains.
**Restoration**
After the cold period, is probably the best moment to try to get out, as the restoration process will take centuries. In both scenarios there wouldn't be plants let alone animal life to be found.
Following the cold period, comes an warming that may last "several centuries". But the magnitud and conditions are different for each of the studied impacts.
It is not clear at waht point plants would be able to grow safetly again.
*IMPACT A*
It is said that it increased 20 ºC in 100 years. The planet is mainly desertic at this time. Snow retreats rapidly during the initial years.
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> The carbon dioxide was the last effect of the impact, and it hang on for centuries. Now warming the planet instead of cooling it. So, the climate is then artificially warmed and not returning to normal values for several centuries after the impact.
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-- Cathy Plesko
*IMPACT B*
The planet also becomes warmer, but not at the scale that it happens in IMPACT A. Since water wasn't in permanent snow - but in vapor instead - the following centuries are of heavy rain as all the water return to form the oceans again.
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Affiliation:
* Cathy Plesko is a Research Scientist in Applied Physics at Los Alamos National Laboratory.
* Peter H. Schultz is a Professor at the Department of Geological Sciences at Brown University.
* Norman H. Sleep is a Professor of Geophysics and Geology at the Stanford University.
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I read [on the cooking.stackexchange site](https://cooking.stackexchange.com/questions/64452/is-it-true-that-all-salt-is-sea-salt/64453#64453) that all natural salt on Earth was created by seas and oceans, starting with primordial oceans four billion years ago. This got me thinking about my fictional terraformed far-future worlds, where people brought organic materials to lifeless planets and engineered new Earth-like planets, [starting by seeding the planet with small Earth species](https://worldbuilding.stackexchange.com/questions/6867/how-long-would-it-take-to-terraform-a-lifeless-but-somewhat-earthlike-planet-usi) chosen to start developing a more and more Earth-like environment, and then working up with later arrivals of larger organisms, perhaps hundreds or even thousands of years later.
My concern is that there may be a need for a lot of salt all over to support an Earth-evolved animal (or even insect?) bio-mass. I understand that animals tend to have a lot of salt in them, and that they need it to do many of their life functions, notably to control the movement of all sorts of things across cell walls via osmosis.
So I'm wondering what would need to be done to get the world salty enough to support abundant animal populations and related ecologies consisting of introduced Earth-evolved animals (perhaps with a little bio-engineering).
The tech level is very far future, but preferably does not include complex nano-machines (i.e. no saying there can be microscopic intelligent self-replicating machines that cooperate and do it), the ability to just zap up anything from anything (i.e. no saying there are machines that can build anything by arranging atoms however wanted), nor genetic modification that isn't something that clearly very possible by today's understanding (i.e. no saying "use GMO" to make animals not need salt or be salt factories, unless that's a real known thing agreed to be eventually possible by today's scientists). Construction of industrial/chemical facilities is an option.
If thousands of years are needed, that's acceptable, but hopefully not many thousands of years.
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Salt is sodium chloride (NaCl) and sodium ions are indeed important nutrients for animal life.
Salt is naturally occurring and not created by seas. Sodium is very reactive and can react with chlorine in air and water to form salt.
Assuming that the planet being terraformed is somewhat similar to Earth, I would expect it to have salt.
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Where is the life in the middle of a large continent on Earth getting its salt from?
The carnivores eat herbivores. The herbivores eat plants. The plants take carbon dioxide from the air, sunlight, and groundwater. That water contains all the other elements. Those elements get there by the weathering of rocks. Weathering includes active attack by plant life as well as inorganic chemistry such as oxidation of surfaces exposed to air.
It takes a fair while for plants to establish a foothold on new volcanic barren rock. It starts with algae, lichen etc: tiny things lodged in tiny crevices. Gradually the rock crumbles and the crumbs become coated with humus: organic matter from dead plants. Then larger plants can establish, starting small and tough. Scrub comes later still, trees last.
You can study this where a volcano or retreating glacier or earthquake fault has exposed virgin rock. Or by filling a pot with crushed sterilised rocks and seeing what can grow given just sun air and rainwater.
Bottom line: plants can establish on barren rock but it takes very many human lifetimes to get to a layer of fertile soil. In river valleys where mechanically pulverised rock (silt) accumulates, the process will be faster but good fertile soil will still take a good while.
BTW local shortages of certain trace minerals can be a problem. Iodine, for animal life, and Boron for plants, are well-known issues. It all depends on the rocks.
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The oceans would already be salty on the world, even if life had not formed naturally. It washes out of rocks and weathering, and accumulates over time in the oceans. I think this is what you took to be "created". This would happen even without life.
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As we all know, Santa loads his sleigh with gifts for millions of children around the world and sets about distributing them during the night of December 24/25. To make them all fit in his stylish truck-sized sleigh, he obviously uses the same compression technology that enables him to jimmy up and down chimneys, infiltrate through A/C units, drink milk and eat cookies while evading bio-containment filters, intruder alarms, and such. We won't worry about that at the moment, but we can assume that the device does not modify mass (otherwise it would break all sorts of conservation laws, and make our physicists look silly indeed).
[](https://i.stack.imgur.com/JwwGg.jpg)
**How much does Santa's sleigh weigh when he sets off with a full load from the North Pole? Specifically, is it heavier than the USS Gerald R. Ford aircraft carrier?**
Bonus questions for extra credit:
1. Estimate the per reindeer power output level that allows the fully-loaded sleigh to perform essentially [VTOL](https://en.wikipedia.org/wiki/VTOL).
2. Total dollar value of the presents, and the size of the annuity needed to pay for them each year. (For simplicity, the manufacturing Elves can be assumed to be enslaved by Sandy Claws, to require no maintenance and to have no form of organized labor activity)
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Okay, let me take a shot at this.
Let's figure out some unknowns first:
* What is the weight of all the presents?
* How many kids in the world?
When you say Santa leaves the North Pole on a full load, let's assume he means to deliver some Christmas cheer to **every kid in the world.**
Based on this website [here](http://www.gapminder.org/news/world-peak-number-of-children-is-now/), there are 1.9 billion children in the world right now. Now, we can assume each kid gets 2 presents and that each present is 2 lbs. With that information we get:
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> 1,900,000,000 x 4 lbs. = 7,600,000,000 lbs [3,447,337.38547 metric tons]
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wow.....
That is a scenario where every kid is a good kid and none are bad...
Now the USS Gerald R. Ford aircraft carrier weighs about 100,000 metric tons. Comparing that with our calculations, Santa's sled is **WAY HEAVIER,** by about 3,347,337 metric tons.
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But in an ideal scenario, not every kid is good.
Let's say that 1 in 15 kids is on the naughty list:
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> **1,900,000,000** kids x **1/15** ratio of bad kids to good kids = 126,666,667 bad kids
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Now every bad kid gets some coal from Santa, let's say a 3 lb. lump of coal
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> 126,666,667 x 3 lbs. = 380,000,001 lbs. [172,365.1 metric tons]
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BUT there are still some good kids in the world, about 1,773,333,333 left.
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> 1,773,333,333 x 4lbs. = 7,093,333,332 [3217481.87 metric tons]
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So in all the weight in a realistic situation would be:
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> 3217481.87 metric tons + 172365.1 metric tons = 3,389,846.97 metric tons
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Which is still heavier than the USS Gerald R. Ford aircraft carrier, and the sleigh is even heavier than if all the kids were good in the world.
Note: my first answer is based on the fact every kid in the world gets a present.
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NORAD has been tracking Santa for years. According to their [website](http://www.noradsanta.org/) (under the library), Santa's sleigh weighs 75,000 gd before flight, and 80,000 gd at landing (due to snow and ice accumulation).
Additionally, Santa is 260 lbs before landing and 1260 lbs after, and the gifts 60,000 tons.
(Why Norad is using different units for each thing is beyond me.)
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Humans lay road to gain fast access to distant places until aeroplane is invented, I would presume the mermaids living underwater can make use of the strong water current to get around the ocean quickly. The issue is unlike road these currents changes shape and direction frequently so how can the mermaids get to its destination accurately without trial and error using our 21st century technology?
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One could rely on rules of thumb to determine where they go, but if you consider the challenge of mapping changing tides similar to the challenge of tracking traffic speeds to find the fastest route (not just the shortest route), then a Waze like tool could crowd-source the constant monitoring of current directions. It might even help them identify where predators like sharks might be lurking on the side of the road... I mean current.
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Temperature and salinity should be sufficient to track currents. (see <https://www.noaa.gov/education/resource-collections/ocean-coasts-education-resources/ocean-currents>)
From a strictly biological sense it may be that Mermaids have keen-enough chemosensory facilities to detect currents on the basis of "smell" (i.e the relative concentrations of distinct chemical components in a parcel of water).
Each current has a distinct smell or chemical signature that correlates not only with its source, but also, as mixing of water parcels occurs, it's previous path.
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A group of people secede from a country, form their own, and gain many allies. Their allies and their original country's allies start fighting a worldwide war. (Fantasy setting, by the way.) A small but heavily fortified city-fortress is built. Eventually, most nations are destroyed - including that city's. The city remains as only a city.
It has more than enough *crops* to support itself.
There are a few farms nearby, as well as a forest large enough that they can easily gain lumber. However, no sheep or goats.
But how would they get ore, cloth, etc.?
Is it realistic for them to get enough necessary supplies through merchants?
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You're saying that they don't have much technology, that can suggest that the setting was around the Middle Ages. The fact that it is a heavy fortified city also points in that direction, so I'm gonna focus my answer on that time.
You say that you can walk from one side to the other side of the city in about two minutes. Given that you walk 5km/h that would give you around 133 meters. Assuming that the city-fortress is square, that gives you 133^2 = 17,689 square meters. In that small area would live around 250 people if the population density would be the same as in the center of Amsterdam. The density in the middle ages would be different I guess, but I couldn't find any information about population density in cities in the Middle Ages, sorry ;-). This gives you enough people to create a small society that could survive on it's own.
What they should do first is to create a food industry that produces more than enough for all of them, if they didn't already have that. This is necessary because they can't go to another city that easy if they run out of food in the middle of the winter, and they don't have allies any more which will help them in problems. In the case of urgent clothing need, people could go hunt and make clothes from animal skins. Maybe they don't have that technology yet, but it isn't hard to acquire.
If they can support all necessary elements for survival themselves they can look into creating valuable goods that other cities and villages in the area want. The tricky part is what. They have skills in metalworking and woodworking, but only have access to wood (the question is also about how they would get ore, so I'm assuming they don't have access to that). And I don't think the cities and villages in the neighborhood would have much trouble to acquire wood too. I think they have a couple possibilities which are rather easy to realize:
* Focus on increasing their agricultural output and sell the surplus.
* Focus on hunting and sell the skins.
* Focus on cutting wood and crafting furniture and building materials and selling those (although I'm not sure if there will be a big market for it in the situation that the area is currently in).
They should try trading with cities and villages which have the ore they need to create metal tools and other objects. As soon as they can establish a continuing trade with such a city/village they can keep buying ore, turning it into valuable tools and other objects and sell it for more. If they acquire enough skill in metalworking they can become a trade-hub in the area.
So my final answer would be: **Yes, they can get enough necessary supplies through merchants.**
*This is of course a best case scenario, many things could go wrong or make it harder, I'll name a few:*
* *New wars could break out*
* *All cities and villages in the area are wiped out and you need to travel for days or weeks to get to the closest one.*
* *Cities and villages in the area doesn't need your stuff because they can provide for themselves.*
*Because the question left much to the imagination this can be the answer you're not looking for. If not, specify your question a little better please. Think about the following aspects:*
* *What year/era this is happening*
* *Peaceful or dangerous area*
* *Are the other cities and villages close or not*
* *In which area is the city located, desert, mountains, forests, fields, ...*
* *What climate does the city have, around the equator, close to the arctic, ...*
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This has happened on Earth! In South Africa, with [the Boers](https://en.wikipedia.org/wiki/South_Africa#European_colonisation). The Boers were dutch settlers whose country (in Europe) essentially dissipated. They successfully established several republics and managed to be independent for a while, until the British came along.
As this lesson from history shows, just because your nation (or parent nation) is destroyed, trade doesn't stop. One can even argue that a war causes greater trade in certain goods.
We can also see a similar situation when Rome dissolved; the main government failed, but the people in those areas overcame the lack of government and established new countries. All the while, trade was enough to get many people by.
To concisely answer your question; yes, trade happens even when governments don't.
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Based on the timeline (bronze age, medieval) in terms of analogies to technology, and the skillset of the local inhabitants, they might just be ok living off the land. Even up until the 1800's, with limited supplies, people where able to settle an area, build homesteads and support themselves.
Assuming every other person in the immediate vicinity were wiped out in this war, they might just spread out into the local area and live on subsistence farming.
Are they religious and particularly concerned with clothing from a modesty/morality perspective? Is it a cold climate? They might be able to grow hemp and use it to make clothing, or use some other fibre from the crops the grow..
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It's realistic to trade for whatever they need as long as they have abundant enough resources that others want. Ed.: The biggest issue with trade is whether or not the *other* survivors have anything that the *city* wants, given the global losses of support. Assuming this is so, and shipping isn't, itself, prohibitive, yeah. That bit where you said they have food? That is *far* from a given for survivors in your scenario, so it qualifies as an important trade good.
They can develop the productive skills and resources that they need, as well. Unless there is something that locks them out of some technology that they need, they can purchase the tools they need and possibly hire the experts that they need.
It's a war with time. Critical things would be developed *before* rebelling. This could be building productive capacity or trade deals. Trading for missing experts is actually quite reasonable. (and has been done, historically)
(The games *Colonization* actually address this whole topic quite well.)
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I believe the clothes question is a easy one, you can either hunt animals or have some sheeps in your farms in order to get wool.
The ore thing would depend on the area, if there is a mine it would make sense to eventually set camp or a new city there to get the ore. One example is São Paulo in Brazil, São Paulo was created to provide some resources that Rio de Janeiro couldn't acquire for itself.
Anyway it is possible for the city to survive but eventually they will need to set camp in other locations in order to get a wider variety of resources.
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In the [question asked by Jim2B](https://worldbuilding.stackexchange.com/q/28594/3202) regarding the legal personhood of uploaded personalities, my answer came to the conclusion that uploaded personalities of people would be regarded as children of the uploaded person (until they could support themselves).
Several disturbing thoughts come to me when thinking about this. Namely digital-rape and digital-retardation. An uploaded personality of someone could be spawned without their consent and/or an uploaded personality could be malformed. There is no possibility for a digital-abortion, as it were, the uploaded personality is immediately a fully aware digital person. The question of either deleting this entity or adjusting "mistakes" made in this person would be incredibly difficult to answer.
Focusing on the second thought: **if society recognized uploaded personalities as legal people, would the law also prevent the repair of copy "mistakes" that led to an intellectual disability of the uploaded personality?**
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From the answers and comments to my original questions, I can see a sort of legal framework forming.
When the capability is first introduced; law, economics, politics, "mental health", etc. will all be caught without a framework to deal with the situation. This will resolve slowly over time to a workable & stable system.
The period before this workable system is developed could be pretty chaotic.
In the stable system I envision:
The entity intending to make a copy has obligations similar to that of parenthood (a responsibility for providing support to the new copy for a reasonable period of time - amount tbd).
The new copy has a term of "childhood" in which its rights are protected by its guardian (the entity which decided to have the copy made).
When an upload is diagnosed with a problem, in most cases that upload will want to get the problem fixed (like with organics).
In some cases, the upload will not want the problem fixed.
In the US most (all?) states have provisions for administering medical care against the wishes of the person needing that care. This mostly happens for mental health problems. Some states require two psychologists to agree that the mental health patient is a danger to themselves or others AND a court order to get the patient admitted to the hospital and treated against their will.
I imagine some similar digital equivalent to force treatment of the upload against its will.
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I would say that a 'repair' would happen if it was possible. Even now we try to repair people with mental disorders, only we generally use drugs and counseling which are much less exact as changing a "few bits".
The things that would prevent it happening would start with "Is this problem repairable?" And then the next question is, "Is the individual sound enough to make a decision on if they WANT to go through with the 'fix'. And last, without the 'fix' is the individual a danger to themselves or others? Any one of those things would be part of the decision.
Though after a few screw ups, I imagine that future 'uploads' will be put into a static buffer and be double checked before actually given 'life'. So it could be erased if major issues exist and reloaded or repaired if small issues exist.
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I'd like to have an advanced civilization that lives in a ring around their sun, but a ring planet just can't work. In this case, they are among densely agglomerated asteroids (with life support, there's no atmosphere or anything) about as far out as our first asteroid belt, and have built bridges, etc. between the asteroids, many of which have been hollowed out for habitats.
**Could there be a 'thick,' densely packed ring of asteroids that form a belt around the sun**, or how long could that last. Could they be orbiting in a manner that keeps them from clumping together at least for a while? I'm imagining the distance to be like something out of Star Wars, whereby they have managed to stabilize and bridge those rocks.
EDIT: (Additional, maybe superfluous information), as requested.
The intent is to have a continuous civilization (could be far-future human) in a ring around a star. A ring-planet that is not the inevitably impossible ring-planet. The geography is flexible, but to keep it scientifically possible (it might not be), I'll venture a ring of large rocks the majority of which range between 10-20km of size, and several times that distance between each other.
The very basic question (hence the science-based tag), is if this is remotely possible. It sounds like it won't be, at least around a star.
EDIT2: I wonder, if I reduce the size of the rocks to mere meters (e.g. - 20m diameter) orbiting, if it allows for bouncing off each other, but remaining dispersed such as this, for at least human scales of time, say 30,000 years. If this introduces a new question, please let me know, and I'll remove this edit and add a new question.
[](https://i.stack.imgur.com/aa8Dw.jpg)
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**This won't work.**
The reason that asteroid belts can persist is that they don't have enough mass to accrete into a planet. If an asteroid belt had the density depicted in typical science fiction (meters or kilometers apart) there would be far more than enough mass to collapse into a planet. Which they would promptly (on an astronomical scale) do.
In our asteroid belt the distance between asteroids is, on average, [about *2 million miles*](https://physics.stackexchange.com/a/26717/45770) and its entire mass is [about 4% that of our moon](http://www.sciencedaily.com/terms/asteroid_belt.htm).
The solution is to have these aliens inhabiting a ring system of a planet. Saturn's rings, for instance, are made up of rocks that are [on the order of meters apart](http://classroom.synonym.com/close-rocks-saturns-rings-13152.html).
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No. Not like in the picture. Even Saturn's rings are usually enhanced for dramatic effect when shown up close in movies. The real universe is really sparse and boring.
The asteroid belt in our solar system is a good example of an actual astroid belt around a star. Some people say that it was created by two planets with intercepting orbits smashing together. The asteroids are so far apart that you cannot see two of them at the same time with the naked eye. The real universe is not going to deviate far from here.
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If you want a dense ring like that to live on you'll need to go within the Roche limit of a degenerate body.
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The picture above is a representation of a Methane Earth. I pulled it from [this Wikipedia article on alternative solvents](http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry#Non-water_solvents).
Several questions deal with whether life would be possible on a world with alternative biochemistry and the answer is a resounding yes. However very few explore what conditions for life on such a world would be like so...
# Question:
What general environmental conditions would need to be met for a world where, rather than using H2O as a solvent, we use liquid CH4 commonly known as liquid methane as a solvent, to exist?
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I doubt there would be much for available oxygen on a planet like this...a presence of oxygen would likely see combustion occur, leaving behind water and CO2. I'd go as far as saying that a methane planet with oxygen wouldn't be stable and would settle into a methane/co2/water mixture (assuming there was less oxygen than methane...an abundance of oxygen would see an oygen/co2/water atmosphere).
The first attribute of this planet would be rather volatile conditions. Water is what moderates Earths temperature, in 2 methods. Water takes an relatively extreme amount of energy to warm up, and an even more extreme amount of energy to change phases from solid to liquid to gas. This has the effect of insulating the earth from extreme temperature changes.
Methane isn't quite so...it requires about half the energy to raise a degree in termperature, but moreover it only requires about 1/6th the energy to change states. It's also worth noting that it is liquid at 90K (varies with pressure), so unless your planet is exceedingly cold, the methane is going to be a gas on most of the surface (oceans will be this weird mix of gas methane down until the pressure is high enough that it condenses into a liquid). If your methane world is receiving the same amount of energy from the sun as Earth is, then you'll see far more drastic temperature changes...a low of 5 degrees C and a high of 20 degrees C might very well translate to a low of 5 degrees C to a high of over 60 degrees C.
Water ice floats, which gives us ice on the surface of water...while methane liquid/ice is more dense and will sink to the bottom of the ocean. This will give the bottoms of the ocean a very cold and most likely lifeless nature (I'm not too sure if life can survive in -100C temperatures stuck in solid methane). This means that the process of ice metling to keep the globes temperature moderated does not exist on the methane world, potentially making the 60 degree estimate above a little too low.
Weather in a nut shell can be called the redistribution of energy in an unevenly distributed environment. More extreme temperature differences will spawn more extreme wind conditions, I would not be surprised if this is a very windy world.
I suspect you'd get a form of 'rain', but very little if at all would ever reach the ground. Methane in the upper atmosphere would cool to the point of condensing and forming droplets of methane that would fall towards the ground. However the act of falling would evaporate it and it would be highly unlikely that the 'rain' would ever reach the surface.
I also think the pressures will be significantly different...methane isn't as dense as our nitrogen heavy atmosphere and the pressures wouldn't be the same for the same volume of atmosphere...however pressure is mass related and if the atmospheres masses were the same, there'd be little difference here. I'm not quite sure if a planet would be able to retain it's methane or if it'd slowly leach into space though.
Geologically speaking...in cold portions of the world (very cold) you could potentially see methane rivers and lakes form that would carve out river valleys and show signs of erosion via rain...but for the most case, the land is going to be defined by wind patterns and wind erosion. I'd expect significant amounts of dust to be in the air which, when combined with high wind speeds, will have an abrasive effect on rocks and the land in general.
A volcano eruption might be an interesting thing...if there was any oxygen content in the land beneath, it could cause an eruption to ignite the atmosphere and burn until all the oxygen spewed forth in the volcanic event is consumed.
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What would the planet be like?
Cold. Very cold.
Methane is liquid between −182.5°C(−296.4°F, 90.7 K) And −161.49°C(−258.68°F, 111.66 K), so very, very cold.
On "warm" days the seas would boil.
You'd have some interesting snow around, like radon and xenon.
Fire would be very bad, because liquid methane is warmer than liquid oxygen, so any fire would instantly boil then ignite the methane...
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Most natural satellites in our Solar System are expected to contain fission furnaces at their cores, and some of these moons do have a striking resemblance to an asteroid. I'm wondering if we could establish a colony on an asteroid and harvest the "aster-thermal" energy (if there is a proper term for it) or rather create a space tourism hotspot for people to enjoy a relaxing bath in the hot spring. Is it possible for an asteroid to contain a molten core or do I need to look elsewhere to locate my "colony"?
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**Yeah, entirely possible.**
There are a couple of examples of asteroids that we've identified which may have, or recently had, molten cores. [21 Lutetia](http://www.space.com/13421-asteroid-lutetia-hot-melted-heart-rosetta.html) is a notable example. [Vesta](http://arstechnica.com/science/2012/10/large-asteroid-vesta-once-had-molten-core-magnetic-field/) is another.
The main issue is that because of their size, the ratio of surface area to volume is higher than the average planet. This means it cools much faster. So while some may have molten cores, they won't stay that way for as long as a planet might. Additionally, most aren't very near large gravity wells like a moon might be, so they don't have the same tidal forces adding energy to their interiors.
All this makes it less likely to find an asteroid with a molten core, but it's not impossible.
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[Ceres](http://www.hou.usra.edu/meetings/lpsc2015/pdf/2360.pdf) is the largest asteroid (or smallest dwarf planet, whatever); the core isn't molten based on best current data and modeling, but new data is forthcoming soon, in the sense of Earth, Io; but it may be warm enough to have liquid water. Note that [Mars](http://beamartian.jpl.nasa.gov/towhnall/question/186/does-mars-have-a-molten-core) also doesn't have a molten core and that Io and the Moon, etc. have molten cores due not to nuclear decay or to primordial heat but gravitational energy primarily.
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What would be more valuable in a post-apocalyptic world and/or more suitable to be used as currency: plastic or metal bottlecaps?
The Fallout video game series popularized the use of metal bottlecaps as a form of currency in a post-apocalyptic world as they are, supposedly, difficult to forge. However, wouldn't it be more difficult to assemble the tools for plastic injection moulding than metalsmithing? Thus forging plastic bottlecap currency would be more difficult, not to mention the ubiquity of plastic bottlecaps means they'd be more common (scarcity is probably not something you want for a medium of trade).
On second thought, I considered the fact that the imitation-proof quality of the proposed currency would most likely be pointless as a post-apocalyptic society would probably not use a fiat currency, the value of which is derived from the government, but revert to some form of barter-and-trade where the selection of a common currency of exchange would be more dependent on its inherent value than any government fiat. Would then the currency be metal bottlecaps, which have more utliliarian value since they can be melted down be used for other purposes?
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For starters, why do you need plastic currency? I mean, if you wanted a meaningful currency why not just use already-forged money as stated in other answers? If you really insist on this plastic currency I feel the need to keep you informed.
# MELTING TEMPERATURES
The following are the melting temperatures of several currency alternatives
* Iron-2,800°F (1,538°C)
* Plastic- [Wikipedia article on plastic](http://www.wikipedia.org/wiki/Polyethylene):120 to 180 °C (248 to 356 °F) or 105 to 115 °C (221 to 239 °F) depending on the grade.
* Gold- 1,948°F (1,064°C)
* Silver-1,763°F (961.8°C)
* Bronze-1742°F(950°C)
* Copper-1,984°F (1,085°C)
* Tin-449.5°F (231.9°C)
* Titanium-3,034°F (1,668°C)
# A BRIEF HISTORY and LIKELYHOOD
* Iron- A brittle conductive metal that has been used since the dominance of Ancient Rome thousands of years ago for a variety of things. Is now used for even more things (as a matter of fact trying to list them all is quite pointless to this answer). Just know that it is one of the most abundant of the well-known metals
* Plastic- Yep, that material that your water bottle is made out of does have some potential as currency in the short term. Since oil is required to make plastic you would have to have working oil rigs and access to industrial factories. After a global apocalypse some of the first things to go would be oil stocks.
* Gold- The oldest currencies were made out of this and it is quite likely that our final currencies will be made out of or based on this. After an apocalypse the soon-to-be-worthless computers will be stolen by a bunch of criminals. They will end up inheriting the earth because of the small amounts of gold in them and the large number of computers to be raided. This is one of the rarest minerals on Earth and as such is one of the most valuable to possess. I would imagine after we begin to return to currency the first new coins will be forged from this.
* Silver- This is pretty rare. Silver is very valuable. As a matter of fact, it saved Denocracy! Yep, the Persians were gonna invade Greece and the discovery of a new silver mine gave Athens the money she needed to repel the Persian naval forces and build a Greek empire under the guise of the Delian League…..why would things be any different?
* Bronze- A mildly strong alloy. Has some potential as currency but is more widely available than some of the others
* Copper- MAYBE……assuming whatever town decides to use it has strict regulations and backs it up with a more precious metal like gold
* Tin-I have little knowledge of this metal. It is quite useful in the creation of cans though…..
* Titanium-An extremely strong and durable alloy. Has potential due to a rareity.
* Diamond- A beautiful gem. Is extremely hard to polish and is one of the hardest known materials (I think possibly the hardest). It is a highly pressurized form of Carbon and can come in a variety of colors, but white is the rarest. A finely polished white diamond is worth more than its weight in gold and silver. The actual problem here would be scarcity compared to other alternatives.
* Other Jewels-Notta.
## Would then the currency be metal bottlecaps, which have more utilitarian value since they can be melted down be used for other purposes?
**I think if it came down to it metal bottle caps would prevail, but not in the end.** In the end we can know from the past that we **WILL** resort to gold, silver or diamond. I suppose we might use the metals and minerals needed to make computers ([rare earth elements](http://www.wikipedia.org/wiki/Rare_earth_element)) as a form of currency----or at least to back our currency. This is, of course assuming that we aren't total idiots and don't lose most of our current knowledge to make computers.
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**Scarcity is part of currency** In trade, you need scarcity. In trade, you exchange something which has value for you and get something what has value for them.
So, generally, step 1: Getting plastic should be relatively hard. In postapocalyptic world, people controlling landfills (full of valuable plastic) would be really rich, because plastic would have a value in your world
**You need strong authority accepting plastic as payment**: It boils down into who accepts what. Barter-and-trade would be still pretty in common, but also you would be willing to accept bottlecaps or plastic pieces simply because *Brotherhood of Steel* accepts them.
In realistic post-apocalyptic world, such authority would be probably military based. They have valuable things to offer (weapons and ammo) and if they accept plastic (for whatever reason), then plastic can be universally accepted tool of trade, because you know, that in worst case, you can buy ammo from the Brotherhood for plastic and barter ammo for food (if food owner is silly enough to not accept plastic in first place)
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As Burki said, currency is just a way to make bartering easier. You take something with a limited supply, and use it in place of goods. Say I have a goat, I will give you my goat if you give me 100 glass beads, because I can take those 100 glass beads over there and trade them for 14 chickens. If someone makes a glass bead factory and starts spitting them out by the thousands, my beads aren't worth anything, except as a really short necklace.
Most currency has no value in itself, it's just a symbol of value. There is a possibly of giving the symbol it's own intrinsic value, and plastic is actually really good for that. Say, I have a goat, I will give you my goat for 100 plastic ingots, because I can take them over to the guy with a 3D printer and make a tool that I can use to earn/trade for more plastic. In that case the 'money' is valuable by itself, and would be somewhat more inflation resistant.
If the mechanism for manufacturing new plastic from oil is missing, then plastic mining would be huge. Actually, landfill mining would be extremely profitable for a lot of reasons: metals, electronics, plastics, etc.
And most landfill locations are known, so they would become fortified towns where people would come and excavate for pay, like the gold/coal mines of old.
I can also see people with access to boats going out to net the floating garbage islands in the ocean for their resources.
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The reason to use money as a general trade good is flexibility. If i have a chicken and need a shovel, But the guy with a shovel needs a bucket, money is more convenient than finding someone who will trade my chicken for something i can trade for a bucket to get me the shovel i needed in the first place.
In order for a currency to work more or less reliably you need a system with little to no inflation, lest you end up with a situation like in post-WW1-Germany, where you needed to spend what money you had asap because it would be mostly useless tomorrow.
This means that scarcity of the currency is vital.
Concerning your original question: most plastics are thermoplasts, that means they can be melted. Duroplasts on the other hand disintegrate when heated, much like most organic material, so they require a solvent to liquefy.
The melting point of all thermoplasts i know of is much lower than that of most metals, so it would be easier to liquefy any plastic you fould, and pur it into a form to coin your own money.
So, i assume that a metal based currency would work best.
About the bottle caps: Why not just use the coins we use today? I think it is safe to assume that lots of coins will survive, and the price, in coins, will have to be newly negotiated to match the availability of the coins. But you would have to do the same with bottle caps, so i guess that should not be much of a problem.
EDIT
Not all plastic is made from mineral oil. Some of it is made from sugar or starch. And that is much cheaper and easier than mining, smelting and coining metals.
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See [A city to last ten million years: Construction](https://worldbuilding.stackexchange.com/questions/12266/a-city-to-last-ten-million-years-construction) for background.
Second question:
What would be the best choice of site on the planet's surface? Assume the planet is more or less Earthlike in its climate, terrain and vegetation.
Also related: [A city to last ten million years: Maintenance](https://worldbuilding.stackexchange.com/questions/12269/a-city-to-last-ten-million-years-maintenance)
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Ten million years are long enough to worry about plate tectonics, climate shifts, and so on.
* Stay away from plate boundaries.
* Make sure that your location doesn't travel towards a geological hot spot. Generally, stay away from volcanic areas.
* Stay away from rivers which might shift their course.
* Find some good, solid rock to anchor your foundations.
On top of something like Ayers Rock?
A batholith? Or are they too likely to be mountainous?
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* The Arctic circle or polar regions (if solid bedrock is present)
* Mesa or plateau (provided there are no rivers anywhere nearby)
* Slightly buried in sand in the middle of a desert (though even this location could be affected by ice ages)
* You specify on the planet's surface but depending how strict this requirement is, would inside a mountain be an option, if not a flattened mountain, above the cloud layer would be an excellent option provided there are too many millions of years.
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I think you have a problem with assuming that the planet is earth like; Drop that and the situation becomes quite doable. If I were wanting to build a city that lasted ten million years my choice of location would be a planetoid that doesn't have a molten core and is geologically stable but large enough to have sufficient gravity so that the first generations are not inconvenienced by it.
As best as possible, ensure a stable orbit for the plant in question and then bore into it to its heavy metal rich core and build most of the support systems of the city deep in the interior powering the city with radioactive isotopes such as Uranium 235 (half-life of 700 million years). Leave the outer layers of the planet actually completely devoid of anything as a radiation and impact shield.
Of course, everything is going to have to be over engineered to be completely passive, as fool proof as possible, and automatic fail safes that depend on nothing themselves to function.
Which if the surface of the planet was also inhabitable, and earth like as specified but without active tectonics, then we get something like HG Wells Time Machine probably developing, actually quite possibly over multiple iterations over the time periods in question.
The building of the city itself would take long enough to, even if it didn't start this way, become a religion, and the city would last long enough that giants and gods were the builders of the city, even if the knowledge of how the city was built is not actually lost fully.
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I don't think that this is possible in the face of technological regression. Key point here is that it has to remain habitable. That means that it has to have food and water supplies readily available for its occupants. When combined with climate shifts and geological events, this quickly becomes a huge issue. (Ok it quickly becomes a huge issue in planning, it may take thousands of years for the actual problems to manifest.)
Lakes, rivers, springs, and wells can all dry up or flood due to earthquakes and shifts in weather patterns. The change doesn't even have to be nearby. An earthquake that causes land hundreds of miles away to settle or raise can disrupt the flow of rivers and streams. New mountains and or volcanic activity along the coast will change the wind and rain patterns for the continent. What would be self sustaining farm land today may be a barren desert, or at the bottom of a sea/lake, in a couple hundred years.
Similarly, unless your planet has NO tectonic activity the ground will move and change. Building with your foundation in bed rock sounds like a good idea, until you realize that something that is flat now has a high chance of being anything but flat in one million years, much less several. (Anecdotally, there is a spot in Arizona along the highway between Phoenix and Flagstaff where they cut through a ridge rather than taking the road over it. It has stuck in my mind because you can see sedimentary rock with the bands running in 3 different directions, and distinct seams between the regions. I have never quite figured out what, but obviously something significant had to happen to the ground in that area for those layers to form the way they did.)
If the society retains enough technology to be able to import food/water supplies in the face a climate change and readjust their foundations after geological shifts, then this becomes potentially feasible.
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I am developing an antlered cat, and looking for some help determining the evolutionary advantages and disadvantages of certain physical characteristics.
The world is earth-like, and this particular species is only found on one island nation.
The creature starts off very much like a cougar: 36 in to top of shoulders, large muscular body, obligate carnivore (meaning they only consume meat). I intend to have 3 sub species a shaggy kind, a sleek kind, then a mix (think Clydesdale with a beard)
I am looking for some insight on a few of the following:
Paw vs. Hoof
Level of sociability (I don't want a solitary creature, but not a large herd either)
Advantages of different styles of antlers (can go in to gender of antlered species i.e. female reindeer keep their antlers past "molting" season whereas males do not vs. moose)
Presence of mammary glands? (I'm not even sure if I know if deer/moose suckle their young)
Since they are an animal of prey, how would humans in this world see them? Majestic creatures, something to be feared?
Could a determined young sprite domesticate them, and if so would they be beasts of burden or for the purpose of food production?
(First post, hope I'm able to get this on topic)
**Edit**
What I have discovered about this animal:
Antlers are created via keratin production (similar to the North American Pronghorn), are vestigial.
As well with the similarities to that species they are an even-toed ungulate, the toes having evolved like those of a pig (with non-retracting claws).
Humans fear them, so they are not hunted for their meat.
Not uncommon for two females to band together after litters are born,creating a small herd of 5-10 for half the year.
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# Paw Vs. Hoof
Paws are good for grabbing and going over not-flat surfaces. The ability of the digits to spread helps increase grip. Hooves, though are great for locomotion because they are tough and can dig in. You can get an almost-cross, like what you get with mountain goats, shown below.
# Social But Not
The benefits of being social are usually best seen in herd animals. Social Animals can get these benefits:
* More Eyes Looking for Predators/Food
* Support network to care for the sick, young
* More individuals to repel predators
* Multiple individuals to complete a task, such as hunting or colony-building
* Social Learning
Social animals also get these downsides:
* More mouths to feed. This can be really hard on predators, and is speculated that this drives most large cats to be solitary hunters. There are exceptions, such as lions.
* A "pecking order:" if you do not have what it takes to be on top, you're treated worse.
These creatures could be social, but simply not in large groups. They could travel in family groups like whales or elephants. Small social groups are not unknown in the animal kingdom. [Grey Wolves](http://en.wikipedia.org/wiki/Gray_wolf#Social_and_territorial_behaviors), for instance, usually have around 5-11 members in a group, but can get larger.
# Those Antlers
The wikipedia article [here](http://en.wikipedia.org/wiki/Antler#Occurrence_and_function) does a good job of describing general uses for antlers. For your cats, they could perform several functions:
* *Mating Display.* Larger (and more inconvenient) ones attract all the lady cats.
* *Residual from earlier times.* These antlers do not actually help the creature or do anything, but like wisdom teeth, are [vestiges](http://en.wikipedia.org/wiki/Vestigiality) from an earlier time. (Evolution does not occur over one generation!)
* *A Lure/Camouflage.* Perhaps these cats hunt prey which, themselves, have antlers. Having antlers to mimic your prey may help these cats get close enough to strike.
# Mammary Glands
Humans are a little odd because we're upright. The mammary glands for us are on our chests. Mammary glands for most other mammals, especially the four legged kind, appear on what we would call the stomach (between the rib cage and the pelvis). You can see this very easily on cows, who have specialized their glands to be [udders](http://en.wikipedia.org/wiki/Udder).
# Evolutionary Path For Such a Beast?
Deer themselves are [opportunistic carnivores](http://en.wikipedia.org/wiki/Deer#Biology), eating meat when they come upon a dead animal. Maybe the deer on this island decided that simply waiting for animals to drop dead was not enough, and they steadily evolved to become more catlike for hunting purposes. Something similar happened with [Entelodonts](http://en.wikipedia.org/wiki/Entelodont), known as "hell-pigs."
# Human Interactions
This is too broad to give a good answer to. There are plenty of animals which were admired by humans for various qualities throughout history. It simply depends on your society.
Domestication is a tricky issue. Jared Diamond has some [prerequisites for domestication](http://en.wikipedia.org/wiki/Domestication#Animals). According to those, I doubt your cats would get domesticated. They will either be not social enough to recognize humans as pack leaders, or simply require too many resources by being carnivorous. This is especially true since cougars are strong enough to take down a human. A captive cat of that size may consider a small human the perfect meal.
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This is a really odd animal mix-up as you are trying to combine herbivore traits with carnivore ones.
A defining trait of a cat is they can fit into some exceedingly narrow spaces. Their bodies are sleek and they make use of their whiskers to determine whether or not they can fit into a space (hence why cats with cut whiskers will get themselves stuck from time to time). Antlers would be a bit contrary to this as their wide point will now be these antlers and they lose the ability to fit into narrow spaces. It actually seems like a disadvantage to have these from a feline point of view.
Antler evolution is one of those topics that contradict 'survival of the fittest'...on an evolutionary level, it's really 'survival of those most capable of mating'. Antlers work as a show of virility in a lot of manners and are almost exclusively used in obtaining a mate. If only those with big antlers get to mate, then there's that distinct pressure to develop bigger antlers when they don't provide much of a survival advantage.
Paw vs hoof is a weird question as well. Hoofs are designed for running and long distances and are quite hardy. Paws are much more versatile in that they can support claws (a cats primary weapon) and allow for tree climbing. If these species are roaming around flat open plains with no need to climb (trees or rocks), hoof would make sense I guess?...but it seems if this creature has a hoof, you have a deer with slightly catlike qualities and not a predatory cat. With no claws, how exactly does your cat down it's prey?
Level of sociability - I'd look to lion prides and perhaps Cheetah behavior here.
There is a bit of a muscle use and energy conflict here as well. Hoofed creatures are designed to run longer distances and have an endurance component to their survival. Cats and predators tend to be quick surge but short time frame...this is a trait of their lean muscles. It suits their hunt style well and really makes them poor beasts of burden.
I really don't see this creature that capable of existing with how you describe it here...you can't take a predatory cat and give it a bunch of traits suited to a grazing plains lifestyle and expect it to fare all too well. I have the image of an awkward cat creature with extended legs and small head struggling to hold up these massive antlers as it timidly mouths the words 'kitty-deer shouldn't be'. Human interaction would be pointing and laughing I'd suppose ;)
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First I should mention that the horse/deer family and the cat family are significantly separated on the mammalian family tree. So the idea of a hybrid that comes from a cross descendant seems unlikely...though not impossible. It seems more likely to me that a cat species evolved them over time...a long time and you would need a environmental factor that makes them select-able.
Odds are a herbivore or omnivore would never develop to the point that they are obligate carnivores, most simply because there is far more food available for herbivores and omnivores.
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> Paw vs. Hoof
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If you are looking for a catlike stalking creature you have to go paw. Hooves are loud and not generally great on rough terrain nor are they good for turning in a chase for prey. Hooves are great for all out running, but paws are the way to go for agility, if this animal is a hunter, paws are the way to go. Keep in mind the feet are not simply for running but also for bringing down prey (in most cases).
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> Level of sociability (I don't want a solitary creature, but not a
> large heard either)
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Cat species are generally solitary. Lions being the notable example and I think the concept of a pride fits what you are looking for perfectly. 1-3 Adult males with a host of females and their offspring.
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> Advantages on different styles of antlers (can go in to gender of
> antlered species i.e. female reindeer keep their antlers past
> "molting" season where as males do not vs. moose)
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A cat's body type won't really support full blown antlers like you see on a deer. The deer and its relatives have a much more upright neck and head while a cat's head and neck tend to mostly stay on the same plane as the spine. This would make them very front heavy and while it might be entertaining to see that struggle (and feel bad about being entertained...) that wouldn't last the evolutionary process even if it formed in the first place.
I can however imagine a cat with horns more similar to a buffalo/cow. Shorter, sharper, potentially used for hunting large prey or of course attracting mates.
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> Presence of mammary glands? (I'm not even sure if I know if deer/moose
> suckle their young)
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Yes both animal types you mention do this so it is logical that some sort of hybrid would as well.
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> Since they are an animal of prey, how would humans in this world see
> them? Majestic creatures, something to be feared?
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I have to agree this isn't really answerable. It would be dictated by the interaction humans have with such an animal.
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> Could a determined young sprite domesticate them, if so would they be
> beasts of burden or for the purpose of food production?
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Not likely. Even house cats are notoriously difficult to train, and there is a reason private ownership of big cats is frowned upon and in some cases illegal. In a medieval...or any pre-modern setting, the cost to feed and shelter such an animal would be too high. Not to mention that fencing off an area for a big cat would be much more difficult than keeping cows in place.
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Hmm, a cat-deer.
The design depends on the climate, I am assuming temperate. The amount of fur, and foot shape(practical with snow) might differ.
My immediate thoughts are a basic mountain lionish head, but you might want to move the ears a bit to make room for the antlers. Ooh, what if you just used one, like a unicorn, but it was antler shaped? You wouldn't want very tall antler(s), I feel like that would make a cat like creature look top heavy. Are the antlers for fighting rivals? maybe something that's low on the head, with sharp points, it could have an added advantage of protecting the eyes.
I assume a basic cat body. Perhaps with the sort of patterning one finds on house cats?
I have a hard time imagining cat legs with hooves at the end. This would mean missing out on claws. You know how cats have little finger things for each claw? Maybe keep two or three of the finger things, and make them big, they could have claws and a limited gripping ability. I'm thinking of the of the feet on the X-man, Nightcrawler. Find a picture of him. A cat version of those toes might be cool.
The people's response would depend on how civilized they are. Primitive, then they would fear and respect them. They might have beliefs about seeing ones with different pelts: white is a good omen, black means death is coming, etc. The people could be a prey of the cats. the more advanced they get, the less respect it will get, probably. Hopefully it doesn't turn into a trophy animal.
It could be useful as a hunting animal, but I wouldn't be so eager to try to tame a mountain lion, antler's or no. Sounds too dangerous. Still, could be possible.
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There is some sort of (remote) evolutionary precedent the Saber tooth cat had extended incisors which gave them the ability to tear chunks of meat off dead animals.
I would imagine a cat might evolve antler-like bones in the head if there are many animals in this world that it hunts that are much bigger (if you wanna mess with the bull prepare to get the horns!)
Big cats (and consequently smaller cats) on the real world have been worshiped in the past. The [Ancient Egyptians](http://www.wikipedia.org/wiki/Ancient_Egypt) [worshiped cats to some degree](http://www.wikipedia.org/wiki/Cats_in_ancient_Egypt) because they thought cats were divine. It could be said that the Egyptians marveled at the majestic tendencies of big cats. However in many parts of the world cats have been hated and hunted because in these parts of the world they were much smaller and thieving and were thought to be evil or demons.
In the real world, lion prides can reach a maximum of [30 individuals](http://www.wikipedia.org/wiki/Lion#Group_organization) and have a minimum of 2. So it can be safely assumed that most lion prides will range in the 10-20 range.
As these big cats are [Mammals](http://www.wikipedia.org/wiki/Mammal), it is likely that they have [live birth](http://www.wikipedia.org/wiki/Vivipary) which will generally mean the children will feed off of milk. Just look at modern cats.
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I would like to have a planet in which somehow it becomes necessary to harvest aurora for energy (and maybe matter if that's feasible).
The civilization of this planet is moderately advanced -- enough to have colonized other planets in its solar system, but not enough to have travel between stars.
Which of the following would improve the plausibility of harvesting aurora:
* A planet smaller or bigger than the earth
* A planet with a weaker or stronger magnetic field
* A planet closer or further away than the earth
* A sun smaller or bigger than our sun
* A higher rate of solar activity
* A planet with a smaller or bigger atmosphere (or no atmosphere)
[Answer]
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> [Auroras](http://en.wikipedia.org/wiki/Aurora) are caused by charged particles, mainly electrons and protons, entering the atmosphere from above causing ionization and excitation of atmospheric constituents, and consequent optical emissions. Incident protons can also produce emissions as hydrogen atoms after gaining an electron from the atmosphere.
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So are you trying to collect the ionization particles or the light generated from them?
Catching ionization you'll need to have some kind of satellite, I'm not sure it be worth it. You'd need something to convert the ions to energy. We already have solar tech and it is getting better all the time. As ratchet freak said, You're going to get a lot more power from solar cells.
We capture such a small amount of energy from the sun it is almost negligible. Part of the idea behind things like the Dyson sphere and rings etc. is it is build partly to capture a lot more of the suns energy to give us more power, a [Dyson Swarm or Bubble](http://en.wikipedia.org/wiki/Dyson_sphere#Dyson_swarm) would be more likely scenario. Many smaller structures orbiting the Sun all capturing energy.
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I don't think we could directly harness the energy transferred to particles in auroras. However, we could probably captured the energy from the phenomena that *caused* auroras.
[Wikipedia](http://en.wikipedia.org/wiki/Aurora#Causes_of_auroras) notes that the primary cause of auroras is an interaction between the Sun and the Earth's [magnetosphere](http://en.wikipedia.org/wiki/Magnetosphere#Earth.27s_magnetosphere). Here are some ways we could exploit that:
* **The solar wind.** The [solar wind](http://en.wikipedia.org/wiki/Solar_wind) is the primary cause of auroras. It's a continuous ejection of particles (e.g. electrons and protons) from the outer reaches of the Sun. When these particles interact with Earth's magnetosphere, they can cause and aurora.
The obvious use of the solar wind is to propel a [solar sail](http://en.wikipedia.org/wiki/Solar_sail), and push a spacecraft across vast distances. This makes travel to distant stars possible.
However, solar sails work off of the principle of [radiation pressure](http://en.wikipedia.org/wiki/Radiation_pressure) - the idea that photons emitted by the Sun can exert a force against an object. The particles in the solar wind can also exert a force. In [this answer](https://worldbuilding.stackexchange.com/questions/4329/can-a-spaceship-traveling-close-to-light-speed-be-knocked-off-course-by-a-gamma/4331#4331), I calculated the force of a stellar wind on a spacecraft, and [here](https://astronomy.stackexchange.com/questions/8144/could-the-philae-comet-lander-be-recharged-by-laser/8145#8145), I calculated the force that a laser would exert on a comet. If you could take into account the force from particles of the stellar wind, you could calculate the force they would create if they pushed against a sort of "solar windmill".
Take a long rectangular object, and put it so that the longest side is bared against the Sun. Create a magnetic field emanating from a location 1/4 of the way from one edge that diverts the charged particles, so that only half of the rectangle is exposed to the solar wind. This means that the force will exert a torque on the rectangle, causing it to rotate. You might be able to harness the rotational energy of the rectangle.
[](https://i.stack.imgur.com/WHkn4.png)
*(Replace "bounce" with "solar wind"!)*
* **Coronal mass ejection/Solar flade.** [Coronal mass ejections](http://en.wikipedia.org/wiki/Coronal_mass_ejection), or CMEs, often change the intensity of the solar wind. They can have some [pretty bad effects](http://en.wikipedia.org/wiki/Coronal_mass_ejection#Impact_on_Earth) on Earth! They're also related to [solar flares](http://en.wikipedia.org/wiki/Solar_flare), which can also have some negative effects.
Both of these events are related to the emission of additional X-rays from the Sun. These X-rays are very energetic, and are also damaging to Earth. However, if the X-ray flux were high enough, a large amount of energy could be obtained from a small area. In essence, a satellite might be able to harness a lot of solar power - if it was properly equipped to handle it!
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[Question]
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Civilization progress has many dimensions, for example technological, moral/ethical, happiness/subjective quality of life, etc. For each such dimension we could state a purpose that reflects it, e.g.
* to obtain high technological advancement,
* to have high (average, minimal?) moral/ethical values of the inhabitants,
* to have high (average, minimal?) happiness.
However, when designing an alien civilization (perhaps a conglomerate of different races/species) what would be the dimensions of the civilization progress and purpose? Certainly technology works and so does morality (even if it is [blue and orange](http://tvtropes.org/pmwiki/pmwiki.php/Main/BlueAndOrangeMorality) one). But what about happiness, is there even such a concept for them?
Certainly, whatever these would be, they would have a huge impact on the civilization progress and where it went and will go as time passes. In other words, it has quite a big impact on designing aliens for your world (esp. if the time-span is huge).
**The question: What are the progress/purpose dimensions that we could use for creating an alien civilization?**
To give some examples:
* From Peter Watts novel [Blindsight](http://en.wikipedia.org/wiki/Blindsight_(Watts_novel)):
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> *Energy efficiency*: whatever you do, it is not important what it is or what are its implications, but what it does with regard to energy efficiency, e.g. whether you are energy efficient doing it, or whether by doing it you improve your energy efficiency; for example if somebody makes you lose energy (causes you to be less energy efficient), he would be your enemy.
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* Spread:
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> The ultimate aim of that civilization would be to have the highest number of *their* inhabitants on the largest number of planets/star systems/galaxies possible. You increase it (in the long run): you are a friend, you decrease it: you are an enemy. It could measure the progress of human civilization using the mass of all the humans currently alive.
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* *Alien-adjective-42*-ness (meta example):
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> We could make the alien race to optimize something which is impossible to translate/express in our language, something which is impossible for us to observe or measure, and the plot won't ever explain what it is.
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[Answer]
In human civilization, "greatness" is usually with reference to imperialism. e.g "the height of the british empire", "the height of roman civilization", "bringing Russia back to its former glory". Even when moral values are expressed, it's usually with imperialist power or economy in mind. For instance uniting muslims under true islamic law (by IS conquering and plundering), throwing off capitalist suppressors (and joining the Soviet Union sphere of power) or introducing democracy at gunpoint. So it wouldn't be too far-fetched for any "progress goal" of the aliens to also be a power struggle in disguise. Ideas include:
* "**Peace and intercultural understanding**".
*-We are fundamentally different. The humans will only understand us if we make them more like us!*
* "**Utilitarianism on the Kardashev Scale**".
*-Dear Earthlings. We have registered and duly considered your complaint. However, from a universal utilitarian ethical standpoint, which we can both agree on, the perceived cost of our actions for your 6 billion short-lived inhabitants, is dwarfed by the inconvenience that would be felt by our 8 quadrillion individuals, should we fail to monetize what you refer to as "your" star.*
* "**Living in harmony with nature**". Through massive genetic and geo-engineering, until the planet(s) provides an ideal habitat for the species, with nature producing a maximum of useful goods.
*-We know that earthlings value your planet's biodiversity but struggle at maintaining it. We are therefore happy to inform you that your biodiversity will be greatly increased following project
BioKarma. As a token of respect we will even offer each earth city its own
custom-made and unique species of hardy beetles. Know also that we are as
concerned as you about losing native species. It therefore delights
us to announce that we are now re-introducing dinosaurs to North
America.*
* "**Refinement of art**". In Alan Moore's sometimes god-awful "Miracleman", there is a species who's preferred form of art is "creating bodies and then wear them". Some bodies more powerful and nastier than others I seem to recall.
* "**Creating a safer, better world for our children**". The children of this species is like the seeds of some pines, which can lay dormant in the ground for years, only to wake after a forest fire makes conditions favourable for sprouting. The civilization perfects suspended animation for their children into millennia of sleep and is torn between building and protecting the world of the living and letting it be razed for the benefit of the unborn, who will inherit a post-apocalyptic or pristine planet, depending on time-scales. Who's children inherit the planet depends on how long they can sleep and when the razing occurs, which for some will be sooner rather than later. A civil war occurs, where one side's goal is simply the complete destruction of society.
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There are a lot, but besides the ones mentioned in the question, here are a few:
* **Power:** This is a big one. Power drives much of human politics, and a lot of human history. I think it is highly likely aliens would also want to obtain power too.
* **Entertainment:** Maybe the alien species just wants to have fun :D. Aliens could put an even higher value on pleasure than humans do, and so they might try to develop techniques and equipment to get pleasure.
* **Utopia:** The aliens could want a perfect world. They could have a drive to either convince or subdue other species to their "plan."
+ **Kindness:** Aliens may be perfect and just want to be kind and pleasant to other species around them (or to themselves).
* **Knowledge:** This one is related to technology, but is slightly different. Alien species may have a drive to know as much about the universe as possible. This would result in a focus on more exploration technology
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**Jaqminqi - Selfless curiosity**
*We, the people of Zhark prime, hold these truths to be self-evident: that all Zorks are created equal; that they are endowed by the Vraaagh with certain obligations; that among these are the participation in experimental studies of axiology, the sharing of knowledge, and selfless curiosity.*
To humans, "curiosity" is a positive emotion, adding enjoyment to non-repeating tasks, as well as something to pursue in your free time. The Zorks have a different viewpoint. They evolved as packs of hunter-gatherers a few steps down in the food chain, on a planet with wildly changing climates and many small continents and islands, with unreliable food sources. The pre-historic Zorks were continually on the move into new biotopes and curiosity and inventiveness were vital when the group were to learn how to survive in their new home. However, curiosity came at a cost.
Would you spend a month going hungry, trying out new techniques for hunting that elusive prey we havn't named yet, or play it safe by digging up those roots we are familiar with? What will motivate the first group of hunters to attack that heavy-looking grazer with a new hunting strategy? Who's curious enough to learn the taste of those berries which may or may not be poisonous? Who's curious enough to cross that mountain into unseen territory and report back, instead of *maybe* surviving where we are?
The Zorks have thus evolved to treat lack of curiosity in an individual with the same disgust that humans reserve for freeloaders in a group. To the Zork, the very concept of "curiosity", or "jaqminqi" in their language, is just a subset of "altruism", on par with sharing ones food or throwing yourself on a grenade.
As Zork civilization arose, the concept of jaqminqi were applied to trying out new forms of government, rules for social conduct and even new ethics. The latter, an experimental axiology in human terms, demanded that groups of zorks should force themselves to shift their very notions of right and wrong, to see if new ethical frameworks would help the group fare better than before. Zork breakthroughs in medication, mass-media industry, brain-computer interfaces and Zhark Prime wars III to VII are generally attributed to experimental axiology.
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Imagine a species that evolved on a planet where there was no metal (or not much) of any kind.
They, of course, discovered fire and were able to start building buildings and basic machinery from wood. Later their technology changed and became biology focused with a strong knowledge of DNA manipulation, so they were able to create bone-based kinetic weapons, and even computers based on nerve tissues.
However, space-faring requires strong materials for structure and combustion too.
So, is it possible for them to reach space, and if yes, how?
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If I imagine really pie-in-the-sky style, I could replace most of the metals necessary in the actual launching of ships into space. There are carbon structures, silicates and plastics which could be used as pressure vessels and heat shields, etc. necessary to get a ship into space, especially if we assume the planet has a lower gravity and thus escape velocity than our Earth. Crystalline structures could be used for a sort of radar for navigation and radio for communication...
The problem I run across though is in the precision tools necessary for the discovery process and creation of all the systems necessary. Nothing melts, forms, keeps an edge, sharpens, measures, conducts, bends or holds its form like metal. Sure we have laser and water based cutting tools as well as diamond saws, etc., but it is hard to imagine a scenario where we discovered their usage without having metals.
Also energy storage and transmission becomes an issue. Electric eels and other animals that use true bio electrics rely on iron and copper to do so (in admittedly small amounts). To cut out all metals, you would have to use a sugar based energy storage system and bio-luminescence; nerves can only maintain a signal for short distances (less than 100 meters or so), so relays would be necessary every so often, and speed becomes a factor very quickly. No speed of light approximation here.
It becomes easier if you don't rule out all metals. Salts are fairly important to the development of life as we know it and by definition a salt is a combination of one metal and one non-metal. Also calcium, since you mention bone-based science, is a metal. If you only rule out iron, copper, zinc and nickel, you could imagine a civilization that was extremely different from ours. Perhaps these metals do exist, but in such small quantities that iron is considered more valuable than gold to us? Remember that just 200 years ago aluminum was the most precious metal due to its perceived scarcity. Your civilization could have gone totally bio-based for a long time before discovering a smelting process...
Anyway, I love Tyranids/Zerg, and would like to help you out more here, but if we base this entirely in science, this is really hard to do.
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Issues that I can't get around
* Life as we know it is heavily mineral based...bone doesn't exist without zinc and other minerals that can be used as metals.
* How did they gain the knowledge of dna without the precision that metal brings? Can optics (microscopes) feasibly come to be without metal? Is the knowledge and manipulation of electricity really come to be without metals?
* how did they develop computers based on nerve tissues without discovering the metal within those cells and how to refine it?
* remember salt, the basis on how our muscles work, is a reaction that involves salt...sodium. Not exactly stable, but a metal nonetheless...
I guess the questions above come down to 'how scarce is metal'?
Can't call this life as we know it. Leaves me with a biological organism that has evolved the ability to travel in space without really knowing how they got to that stage (in the same manner a swimming dolphin is not aware of how it came to be able to swim).
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Yes. One approach would be biochemical.
**You can get pretty strong materials when you combine non-metallic advanced materials (composites, carbon nanotubes, advanced polymers, ceramics etc...)**
You can also GROW things you need (for SciFi example, see Yoozhan Vong of *Star Wars EU's New Jedi Order era series*, or tree spaceships from *Saga of the Seven Suns*).
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One open question would be whether the planet's "mostly lacks metals" imply lack of fissionable material (Uranium).
If not, you can have nuclear powered spaceflight, which by any and all estimates is vastly superior to chemical powered crap that our current civilization makes do with.
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Electricity might be a difficult issue to get around; it was discussed in another answer.
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**In the case of a world-wide plague epidemic that'll trigger the near extinction of humanity, is it possible that a virus/disease has inconsistent symptoms so that people aren't aware that it's really the same plague until it's already spread or in the later stages?**
This is assuming that the plague either originated from one part of the world or perhaps started off in several places in individual forms before it mutated as one new strain once the right conditions were met.
Is this a possibility? Bonus points if you can explain how diseases/viruses begin in the first place or mutate and become resistant - whether the disease/virus is natural or manmade. :-)
Thanks in advance!
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First things first, I am not a doctor - this is purely educated speculation.
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> Is this a possibility?
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I would say that while it is *possible* it is improbable.
Let's start on the inconsistent symptoms part first. In known diseases, symptoms are largely consistent since the diseases impact the same systems from host to host since they're tailored to attack that system. No biology will spontaneously evolve to be universally successful at attacking different systems. This is the primary reason why I say it is improbable.
So what unknown diseases may impact different systems while still having the same sort of attack vector?
* **Transmittable cancer** - Cancer is one of the few that does happen in multiple systems, even though the tumors themselves are the same sort of stuff. Assuming cancer was somehow contagious, the initial point of tumor development would dictate the symptoms.
* **Environmental variation** - A disease could behave differently (prefer different parts of the body) depending on what the environment (heat, humidity, atmospheric content, etc.) is. For warm blooded creatures, I expect this to be unlikely since their environments are largely uniform. For cold blooded creatures, or creatures in weird diverse biospheres? Plausible. It would also yield "regional" diseases, that are more likely to be considered different.
* **Transmittable genetic disorder** - The cancer may be a subset of this, but a disease that attacked random points of a creature's DNA would result in significantly varying symptoms - as well as a fairly slow development time.
That's part one of the unlikeliness. Part two is the transmission time.
Naturally developed (known) diseases are things that effect different species that mutate to impact the new species, or are existing diseases that mutate to cause different effects. In both these cases, you start with a single infection. Because symptoms are often caused by our immune system's response to the disease rather than the disease itself, you have very little time for that single person to distribute the disease before they show symptoms and become non-contagious by 1) being cured by medicine that works against the pre-mutated disease or similar, 2) dying and/or 3) being avoided by people.
Diseases can't really just "sit and wait" since they need to get energy from somewhere, which means leeching from their victim. That will be enough to trigger the immune response (and symptoms).
And the other part is that since diseases come only a short way from an existing disease, they're unlikely to be ***too*** successful at killing people, else they would burn themselves out.
As for biological warfare? It has far fewer restrictions. As do diseases introduced spontaneously to an area (think smallpox to North America).
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I don't really see biological convergence a possibility (several virus's that start off separately and somehow mutate to the same end result). A systemic virus could hit several sections of the body at once...if some people die because the effect on the kidney's takes them out first while others die because of heart issue prior to the kidney portion arising...still seems improbable.
I can see virus synergy as a potentiality possibility...several virus's that on their own display very separate symptoms but are not that deadly, however they become very deadly when combined in the same host. I might be stretching there.
I'm not sure on viral origins...but the general concept on them is one of highjacking. All cells have 'receptors' that can have molecules with the right configuration link in to that receptor (we'll call those keys). Virus's have millions of these keys and float around until it finds a cell that meets ones of it's keys (these 'keys' vary from species to species, which is why many virus's cannot jump across species). The virus uses that 'key' to get into the cell and locates the dna copy device that each cell possesses (I'm simplifying pretty heavily here). The virus then lines itself up to copy itself using the same technique your DNA uses to copy and presses the make a few billion copies button. The copies mass generate until they overwhelm the highjacked cell, which explodes, launching the copies out into the body to repeat the process. This creates an extremely high chance of mutation as each copy of that virus could be slightly 'miscopied' into something a bit different (basis of mutation)...perhaps one of these copies develops a 'key' that could infiltrate a new species for example (whether that key ever gets used is a different question). Or as an example to the question...it could accidentally mutate a slight resistance to a medicine that normally kills it. Medicine kills all the other instances of that virus, leaving only the ones with a fluky mutation making it resistant to the drug remaining...1 of those infects a cell and suddenly you have millions of copies of a virus that all retain some resistance to that particular drug.
As a side note...Our immune systems are adept at locating these virus's and clogging all of its keys that match our cells until the virus itself dies.
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I'm afraid I must go against the crowd and say it's certainly possible. The thing is we have already seen a plague that's killed millions that had this behavior: HIV.
The key here is that the disease has no obvious symptoms of it's own, but rather makes you vulnerable to other problems.
A readily-spread version of HIV meets your criteria.
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It is very possible if your disease was not caused by bacteria or viruses, but a parasitic organism.
The symptoms of the condition would be highly dependent on where the organism ended up. It could range from strokes to liver failure to an inability to breathe, the possibilities are endless.
Pros:
* parasitic infections can be very hard to find, depending on the size of the parasite and how similar the symptoms are to other diseases.
* it could look like a wide variety of diseases based on where the parasite ended up.
Cons:
* parasites are not very infectious compared to bacteria and viruses.
* a lot of parasites I know of do not develop well outside of their favorite feeding ground in the body.
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Technically there is nothing saying a disease should be caused by same virus, so take 3 different viruses spreading at same time (Ebola or whatsoever) each one with the potential of reducing population to 60%, if they spread at same time you would get a combined effect disease with the potential of reducing population to roughly 21%. While at same time you would get combinatorially 7 different range of symptoms:
* People infected by Viruses A,B,C would have all symptoms
* People infected by Viruses A,B would have symptoms combined of viruses A and B
same applies to viruses combinations (A,C) (B,C) (A) (B) (C).
Also it is possible certain symptoms could get combined into new symptoms (if one disease make your blood green and the other one make you bleeding you would have a green bleed).
There are documented cases: when a popolation is immune to a virus would get certain symptoms or no symptoms at all, if you expose a different popolation you would get different symptons and eventually death cases.
Also note that your "bold definition", could be applied to humans as well, not to viruses only (well, humanity is able to wipe out humanity in a range of ways in more places at the same time ^^ )
It could likely happens for a genetic modified virus:
* Take any lethal virus (Ebola)
* Farm the virus into different tanks
* Than modify the virus with small changes to make it non-lethal and at same time weak (this is the hardest part)
* The changes have to be different for each tank
* Spread the virus world wide
* The only chance for the virus to survive is to evolve, and the nearest evolution that it can do is to "revert" back to original status
Since it is weak it is going to "die" or to "evolve". That assume that the virus is constantly exposed to most of the population world wide requiring a governments mass action that is unlikely to happen (so even harder to happens in nature).
In all cases, if such things happen you would know that is not by any mean caused by "nature".
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Note my earlier comment on [the great imitator](http://www.wikipedia.org/wiki/Syphilis#Signs_and_symptoms).
Adding to the idea of multiple different diseases, perhaps there are several metabolic pathways that can compensate for each other, so knocking all of them out simultaneously is quickly fatal.
Similarly, some toxins work via secondary products. One diseased organ makes substance X, which another organ (or portion of) can eliminate, break down, or use up. If a different disease has knocked out that second process, then the first becomes fatal.
Now here's a more sinister variation: the *treatment* for one disease causes a second disease to be much worse or express unique symptoms. Only people in a community using medicine A will experience B as being of that particular form. Another community will see B as being a minor sniffle and not take special precautions to prevent spreading it.
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I'm going to insert something from reality (or at least my memory of a real document) - in this case a report from a researcher who was part of soviet bio-weapon research. Perhaps the model they developed will inspire...
Researchers started with a mild form of legionnaires disease. The symptoms are typically mild and flu like. It is easily transmissible for a long, several week window, after which the body's immune system fully eliminates the pathogen.
However, in this case, researchers genetically modified the legionnaires bacterium to express a protein taken from the myelin protein coating of rabbit nerve cells (insert your species of choice - presumably human).
So, this is how it plays out: Victim infected with modified bacterium. Becomes contagious, infects others. Becomes sick. Might go to hospital, but if he does, is diagnosed with mild flu or legionnaires, treated and sent home. Victim's immune system responds to modified bacterium and eliminates it. HOWEVER, the body's immune system has identified the invading agent by analyzing the proteins in the bacterial case, one of which is the myelin protein. The body's immune system now recognizes myelin as an invading agent. Over the next two weeks, the body's immune system mounts an assault on the myelin coatings of the body's nerves. First symptoms similar to multiple sclerosis appear, then closer to stroke, soon coma and death.
When these patients are in the hospital, no agent can be isolated from their blood. There is no apparent cause for their death that can be cultured from their blood, although it will be apparent to epidemiologists that this is somehow a contagious disease.
The Russian researcher said this was successful in rabbit test model. He was coy about whether this was ever tried in humans...
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If your disease is spread by self-replicating nano bots, totally.
Other than that, I would think that in the near future we'll be able to make things targeting specific DNA sequences and such. If your plague was engineered to behave differently depending on the DNA sequence observed in the host, it seems possible that it would present differently in various hosts. People with organ transplants would potentially make this harder to diagnose if the plague guessed wrong and triggered symptoms based on the transplanted organ(s).
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Edit: Originally I asked this question about "houses" in general, but several comments made it clear to me houses was too broad a scope. So I've edited this question to restrict it's scope to a certain type of dwelling, and I will ask further questions in series about other dwelling types in the future.
Say that humans are generally nocturnal, save the occasional day lark, and they have cat-like eyes which allow them to see clearly in bright and low-light conditions, though their maximum sight range is less in the dark than it is in bright light. For the purposes of this question, they receive vitamin D and other sunlight-borne health benefits from a special adaptation that isn't relevant to their architecture.
For this question, let's focus on a singular type of dwelling: the European manor house.
[](https://i.stack.imgur.com/ixJgI.jpg)
It's the seat of the lord of the manor, an important cog in the feudal system, found in the country, overlooks (hopefully fertile) grounds, and may or may not benefit from notable material affluence. Several different classes of nocturnal humans live here. The lord himself is a busy guy but is generally found at home administering his estates. So too, the lords family, who lead fairly comfortable lives with a lot of time spent at home. The lord has several servants who live in the manorhouse or nearby on the grounds and spend a lot of time in the manorhouse and surrounding yard. There are other tenants and workers of the land, but they live elsewhere and their dwellings don't factor into this question.
With all else equal to diurnal humans, what architectural innovations do nocturnal humans develop in their manorhouses to maximize the advantages and minimize the disadvantages of nocturnality? Do they use more or less windows? Do they build in different areas than diurnal humans would? Do they structure or furnish the homes differently? What innovations to they develop to maximize the utility of moonlight and starlight? Is directionality as important as it is for diurnal human homes that try to maximize the utility of sunlight? What security concerns may they have about their home, being generally asleep during midday and most active during midnight? How do they alleviate those concerns?
Below are some assumptions/deductions I've made regarding the above slew of questions. Ideal answers should fact-check and correct or expand on this list.
* Windows and directionality are *probably* still important. We diurnal humans use these tools to manipulate not only light, but temperature too. Also, we like being able to see outside places from inside places, you need windows for that, and the direction a window faces is important for seeing the outside places you are most interested in. I can't imagine why windows would take many different forms than normal, or that directionality would focus on a different axis than normal (it seems to me that the heat-modulating benefits of directionality aligned with the sun's course throughout the day are more important than the light-modulating benefits of directionality aligned with the moon's course throughout the night, but I may be wrong). Perhaps skylights would be more prominent to maximize the utility of moonlight and starlight.
* To the best of my (layperson's) understanding, colors would be dim to indistinguishable at night, even with night sight. We might assume then that differing texture and pattern is more important in furniture, so that different objects in a room can be more easily distinguished between.
* For similar reasons as above, homes may favor wide, open floor-plans with fewer confounding visual elements. Very chic.
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## Minor differences likely.
I am an architect and familiar with such residences and structures.
One needs to keep in mind that the major reasons why these types of houses are the way they are is for social, political and economical reasons. Behind architecture often exists a large amount of cultural and ritual reasons that determines its final form.
This is of course not isolated to only Manor houses, but also in all homes even today.
In the early 1800's these types of houses were usually the pinnacle of local hierarchy, being one of (if not the main) residence of a local Lord or important person, and designed accordingly. Often featuring multiple levels, spires, turrets, atriums and entrance halls, these homes are primarily intended to display wealth, give a sense of stability to local subjects, a sense of security to inhabitants, and impress local and regional dignitaries.
All of these factors are actually independent of whether your society is Nocturnal or not - if in your world English-style Manor Houses of the early 1800's exist, they exist with similar political, wealth and security imperatives, which informs their form, fenestration and articulation.
On a practical level, these homes were actually not that pragmatic. They often were cold and draughty, water leaks common, required copious maintenance, and were expensive to build. They were also dark (although later Manor houses rectified this with lots of glazing) requiring constant artificial lighting to internal rooms. In your case, as they would likely be used more at night than during the day, one can imagine small changes to their layout and configuration (requiring less exterior lighting), and perhaps more consistently opaque drapery, but most other features would likely remain the same.
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## Drab decor
Nocturnal animals tend to have poor colour vision, and that would probably be true of your humans too. Their wallpapers, rugs and drapery wouldn't have much colour, but they might like patterned designs. They would still have ancestors' portraits on the walls, but probably not other kinds of paintings. They might prefer drawings and sculptures for art.
The gardens would not be adorned by bright-coloured flowers, instead there would be plants that grow in interesting shapes, and possibly some white flowers that glow in low light.
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Imagine a space station orbiting a star.
The station is not orbiting a planet.
The station has cylinder shape and is orienting its side to the sunlight.
The station is rotating just like any [O'Neil Cylinder](https://en.wikipedia.org/wiki/O%27Neill_cylinder)
It is filled with water. Assume salt water, just like Earth seas.
Near the central rod there are radiators. Likewise in the inner part of the structure there are radiators.
The wanted result is to have:
* general cooler temperature near the bottom (around 4°C the maximumm density of water)
* water in proximity of the outer structure is going to be warmed by sunlight
* outer structure is going to be cooled by the water
* warmer water (less dense) is going to go 'up ward'
* as the warmer water reaches the central rod area it gets in contact with radiators that absorb the heat and cool the water down
* the cooled water sinks again, closing the cycle
See crude drawing:
[](https://i.stack.imgur.com/6U448.jpg)
Design aim: ***Would convection cycles actually happen?***
In other words what conditions should be adjusted to have convection?
What we want to achieve is an environment which will not develop extreme conditions (too cold / too hot).
Plus: Is the cycle in the drawing in the correct direction?
Note that my drawing is just to give a clarification of the question. To my understanding there are going to be many convection cycles of different sizes as the outer structure (and especially its radiators) is bound to have different temperatures in different places with H being the likely hottest and C the likely coolest.
Consider that:
* The star and orbiting distance can be planned to have the ideal amount for sunlight. But the station is not meant to change orbit. Just keep it stable.
* rotation speed should ensure some artificial gravity. But it is not necessary to reach 1g. Just in the 0.7 - 1 range (by the way [fishes don't do so well in space](https://www.smithsonianmag.com/smart-news/fish-dont-do-so-well-space-180961817/)).
Rotation speed and section radius can be adjusted to achieve the wanted result. Assume a minimum radius of 400 meters.
* outside structure can be engineered in order to have a variable amount of insulation / conduction. It would be possible to increase insulation on the shadow side and increase conduction on the sunlit side for instance. Still the sunlit side is going to be warmer until it rotates to shadows.
* heat at the central rod can be used for energy production though the station has other main power generators far more powerful
Costraints:
* the whole habitat should be able to sustain itself with minimal additional energy input (for instance to control the radiators and their flow).
* the structure was built with very advanced technology (imagine the feat of just bringing all the necessary materials in orbit, some of it from another star system far far away...) but is running on tech not so much more advanced than our own, e.g. nuclear fusion for main power. Consider current known physics for running operations. No magic alien tricks.
* keep the maximum size of the station within reasonable limit for narrative reasons. Let's say max length: 100km, max radius 2km. Min length: 2km, min radius 400 meters. But I don't think it matters and am not looking for the exact numbers.
Additional clarification: what you see in the drawing is just a section of the station where the water is. There are other compartments along the cylinder with the necessary equipment to run the station. For instance Fusion reactors.
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## The water will mix itself
In a rotating system of liquid where it's all the same temperature, you will eventually reach of point of equilibrium where all water will stay more or less in the layer it is in... but not in a system being heated from 1 side like this.
As water "rises" towards the middle, its angular velocity will still be that of the outer water. As you decrease radius and maintain angular velocity, your rotational period decreases. This means that this whole system will not move together like a wheel, but it will have many currents moving at different speeds at different layers. These differences will cause vortexes that will keep the warm and cool water constantly mixing; so, you don't need to over think the temperature thing. It will self regulate.
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This design is fairly bad.
Getting heat out at the central rod is a problem. You will need a set of fins at the middle with similar area to the inside of the cylinder. You will need a heat pump of some kind. You will need radiator fins somewhere outside the cylinder, to radiate the unwanted heat to space. Those will need shade from the sun, and will need an area comparable to the area of the inside of the cylinder.
And that process will use a lot of energy. Recall that, in the summer, you need to pay a lot for electricity to run your A/C. And you can't exactly generate electricity off the heat rejected by your A/C. You absolutely cannot generate power using this system. It will be a net consumer of power, by a wide margin.
Massively easier to control the desired temperature of the system by controlling how much sunlight falls on it. Say by a sunshade. And if you need to circulate the water you can just put in a fairly small pump.
If the goal is living space for aquatic life, you probably want the water to be in a layer on the inside of the cylinder. That way, the rotation can provide something useful in terms of an acceleration. You can then access the water from the inside surface, which can be uncovered if you want. The water is held to the inside surface by the rotation. You can provide heat, light, and the correct atmosphere inside the cylinder.
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**Yes it will work as you describe.**
Picture a cylinder as a centrifuge. If you centrifuge a tube with fluid and bubbles the bubbles will move towards the center, being less dense than the fluid. Note in background of image how the syringe with fluid and bubbles is laid in the centrifuge.
[](https://i.stack.imgur.com/5BGrf.png)
<https://www.youtube.com/watch?v=P_rs_Q5Z5G4>
Water warmed by the sun at the outer edge of the cylinder here plays the role of bubbles. Being less dense than cold water this warm water moves towards the center, displaced by more dense water pushed to the periphery.
At the center you remove heat. Now cold and denser the water moves back out to the periphery.
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In my world, there is a zombie pandemic that happens. The zombies are fast, but can be defeated by a large army. My world a little before the outbreak was close to having an Industrial Revolution. They had good agriculture, had a capitalist way of thinking, a system similar to the putting out system, and begun to mess a little with machinery. Is it still possible for them to industrialize, and how?
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## Going Underground
*It may help an advanced civilization to go underground to quarantine against zombie infection. Technology will develop because they will be living and working in modified mines.*
**Zombie Limitations**
Zombies may be fast, but almost certainly have lost some of their mental capacity (due to the lizard brain thing discussed by many zombie experts). They will either lay in wait or wander randomly. Zombies, like other creatures, will need some form of food to survive although they may be more able to survive on reserve capacities or in a near hibernating state when near starvation.
**Limitations of your Civilization**
Many civilizations develop mining skills quite early, and are capable of living in caves far before then. Even pre-industrialization the ideas of systematic quarantine was understood as a means to control infection. The combination of quarantine with mining, and perhaps a system of surface holes which lets in surface daylight (possibly covered with glass, which was also developed pretty early and was pre-industrialization) may allow underground agriculture.
The individual communities, because of quarantine-style community separation, will be cut off from communication and exchange with other communities. Each mining city will need to be self-sufficient in some way. If goods need to be exchanged they may have to take a risk using the basket system. Just outside the city gates the exchange product is lain, with the request for the product that is needed. The baskets must then be exchanged with no direct contact. This is supposed to reduce the threat of becoming a zombie.
**How Technology May Develop**
The earliest forms of industrialization began with water power. Underground streams, springs, and rivers can be controlled for these purposes. Metal casting and blacksmithing will eventually give way to metal hammer forges (hydraulic or steam mechanic presses), which will make robust mechanization of tasks possible. Fuel could be charcoal from trees harvested from the surface, or coal from the mines (indicating rich deposits at different layers, so it must be a geologically unique area for industrialization to work well).
Their thinking, although capitalistic, may also have to adapt to resilience and long-term resource sustainability. This is because without vast interconnected highways and waterways it is very possible to deplete resources too rapidly. This indicates that the actual pace of work within these underground cities will be slower than most modern civilizations.
The underground citizens will be very aware of the zombie threat and will be working towards various methods to keep safe and to defend themselves should zombies come within their perimeters. Eventually they may have to join with other underground cities to fight them as an army (once it becomes apparent that they have the technological means to do so). The avenue by which this happens must be nearly accidental, since this will be so different than the way in which they have done things before.
Perhaps something will cause the dynamic with the zombies to shift. This could include some person of malicious intent deciding to use them as a weapon or some kind or evolution in the zombies that cause them to be more of a threat. Whichever is the case, it will be necessary to band together to survive, which will lead to the vast overground war that you are describing.
[Answer]
Heck, the zombies might spur the industrialization, as a threat.
Think of the zombies as a kind of predator. Early farming humans built walled villages and homes, primarily to protect themselves against predators (including other humans). The walls were made of wood, mud bricks, stones, eventually tall enough and thick enough to protect them.
Industrialization is just the beginning of automation of some prevalent activity that is done frequently. The ideas of industry, assembly lines, and machine assisted mass production begins with some sort of engine.
IRL, that was capturing the natural energy of wind and rivers. The word "mill" comes from ancient roots meaning to grind, as a place it was a building to grind grain (circa 900AD) into a powder (aka flour). The first "industrialization" was indeed about using a water wheel turned by a river or stream as the power source to turn heavy stones that quickly ground grain into flour. Later this was adapted to turn saws, and became the "lumber mill". Elsewhere, on coasts where the wind was fairly reliable on most days, "wind mills" were used both for grinding and for pumping water. In essence the nature of the word "mill" came to mean something besides grinding, it was a building designed to capture energy to turn something.
Many people think textiles were the beginning of industrialization; along with steam engines, but in truth the water wheel at least a thousand years before that was a breakthrough in using non-animal power.
Amid a zombie outbreak, the primary concern of humans is to isolate and protect themselves from zombies, and some clever industrialization and automation can help that. Nobody resists the automation because they all want to live.
Building walls, digging deep ditches, routing streams. Building weapons, swords, knives and nets. Building traps. Building alarm systems. Boiling water for drinking and cooking.
Farming, fishing and hunting can be industrialized. The threat of zombies means we suddenly have far more work to do than we have people to do it; and part of the answer is turning some of that work over to machines that we build to do it. This can be the spur for some genius to invent the steam engine.
I'd begin with a small walled settlement straddling a stream, so we can use a water wheel for power, and even rig it to catch fish for food. (It scoops up the big-enough fish in woven baskets that drain out the water, then as the wheel raises them, the turn of the wheel tips the basket of still live fish into a chute leading to a shore-side pool where the fish will be easy to net as needed.)
That should solve nearly all of the daily protein problem, at least.
I'd posit that after that, the industrialization extends to extending the walls of the village, up and down the stream. Perhaps invent steam engines, and build out, away from the river. Steam engines can be used to both dig (wells, mining) and to pump water, and good well-sites are typically plentiful even a few miles from a stream or river. The reason for moving away might be to farm, but any farm needs to fenced off from zombies, and that's a huge amount of labor best done by machines.
In short, protecting ourselves from a zombie threat can be the **catalyst** for industrialization, creating factories, and multiplying the effectiveness of people by using machines. Not an impediment to industrialization at all.
Look at the USA in WW II. The entire country mobilized to fight Hitler, the men went to war, the women, for the first time, went to work en masse as factory workers producing weapons. There was enormous cognitive dissonance in the country, Rosie the Riveter and all that, females doing that kind of heavy lifting machine factory work was unheard of, and then suddenly common.
Why the sudden upending? The threat of Germany taking over the frikkin' world, conquering everything if we did not. That external threat forced changes to all of American society and the roles of men and women, permanently. And not just in America, in Europe and most of the world.
The Zombie outbreak is a similar existential threat, and a very good spur for people to consider a whole new model of their society, just to survive.
[Answer]
# Zombies are a potential source of limitless labour
If your zombies are physics busting creatures that seek brains, they can be harnessed to power devices. They can replace fuel sources like coal and help power machines to run industrialization.
Rather than destroying any chance at industrialization, they could enable it.
You can put them in wheel or cranks, dangle a brain in front of them, and power all sorts of machinery.
Anyone who dies can donate their body to industry for a good fee.
[](https://i.stack.imgur.com/COFle.png)
[Answer]
**Industrial Revolution will be delayed**
When there is threat to survival, the first thing people will do is to save their lives. As told by Amadeus, in WW II, the entire country of USA started to produce weapons. As told by the [U.S. Department of Defense](https://www.defense.gov/News/Feature-Stories/story/Article/2128446/during-wwii-industries-transitioned-from-peacetime-to-wartime-production/)
>
> Prior to World War II, factories in the United States were turning out
> automobiles, large and small appliances, and childrens' toys.
>
>
> In January 1942 — a mere month after the attack on Pearl Harbor,
> Hawaii — President Franklin D. Roosevelt ordered the establishment of
> the War Production Board.
>
>
> Its purpose was to convert the factories of peacetime industries into
> manufacturing plants for weapons and military equipment for the fight.
>
>
>
The same thing will happen in your world. All the factories will start making weapons and forget other industrial things. So even if your world "was close to having an Industrial Revolution", they will convert all industry into manufacturing plants for weapons.
**The Industrial Revolution will be delayed until the danger is over.**
[Answer]
**Just England.**
Or your equivalent island full of tea drinking scientists and engineers. Because they manage to purge the zombies from their island with the St Patrick maneuver borrowed from the Irish (they are ok too) snake ridding technique, followed by careful screening of incoming ships (each incoming crew member in turn dances naked on the poop deck under the scrutiny of the portmaster). New zombies are forbbidden entrance and industry blossoms!
On the mainland the problem is that there is a bottomless reservoir of zombies stumbling in from the benighted hinterlands and so every time they think things are under control - zombomania redux.
[Answer]
it depend how big the zombie Outbreak.
i mean if zombie infect animal ( like rat and crow biggest animal in city) or insect (like mosquito) , then human will perish.
they must find a place far far from civilization. then they can build safe zone
like island
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[Question]
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One of the more interesting facts about the biogeography of Hawaii is that mosquitoes were not always present; they only arrived in the early nineteenth century, as stowaways aboard oceangoing ships. The explanation for this is straightforward; Hawaii is not a splinter of a continent; it is a volcanic island that emerged pristine from the ocean, and is thousands of kilometers from the nearest continent; distance protected it, until that protective barrier was breached.
As far as I know, Hawaii is the only such case, i.e. the only nontrivial tropical ecosystem that is known to have been mosquito-free until recently.
Just how much distance is needed to serve as a barrier? I gather mosquitoes can only fly a couple of kilometers normally, but presumably the tail end of the distribution will be much longer thanks to the occasional one being swept up in a freak storm etc.
Or, for concrete numbers: suppose you have two continents, both with wet tropical climates, suitable habitat for mosquitoes, one of which has them, the other not. How wide a stretch of unbroken ocean would suffice for a less than fifty percent probability of mosquitoes reaching and becoming established on the second continent in a million years, assuming no surprising geological events like ice ages, and no intelligent agency?
[Answer]
Mosquitos can travel indefinitely if caught in a storm (and not killed for some reason or other). [Females can become dormant and survive for 6 months in that state](https://elevatepestcontrol.com/mosquito-faqs/how-much-time-can-a-mosquito-live-without-eating/).
But plenty of Pacific Islands didn't have them until recently, Hawaii is much closer to a continent than most of them. The Pacific is almost all volcanic Islands that rose from the sea. So it's not a common occurrence.
The problem is not so much how far they can disperse, but how far they can disperse and breed. A pregnant female only lives a few days. Males only live about a week. So even if a female makes it to an Island, quite possibly it won't find anything to eat in time. Or it lay its eggs, but they don't find anything to feed on.
[Answer]
**Iceland style?**
[Iceland does not have mosquitoes](https://www.businessinsider.com/iceland-has-no-mosquitoes-2016-11). They are not afraid to brag about it. Clearly Iceland is close enough for mosquitoes to blow there but they cant get established. Colder places like Greenland have mosquitoes.
Iceland likes to credit some circumstance of their weather. But I think the secret is midges. These flies (biting and nonbiting) occupy the same niche as mosquitoes and are very well established in Iceland. I think the midges outcompete mosquitoes in the larval stage. Also midge larvae in some places where the two flies coexist are carnivorous and eat larval mosquitoes.
Have your mosquito free continent be home to a generous variety of midges!
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[Question]
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I’m imagining a post-apocalyptic scenario as a thought experiment. It takes place 500 years after a nuclear war on the East Coast of what was the US, and is meant to roughly be a recreation of a high fantasy setting. I will lay out 5 prerequisites for what I will be defining as traditional fantasy:
**1. Magic**
Let’s say that some people known as ~~Mages~~ “Radiants” somehow developed supernatural abilities. Radiancy is on the weaker and harder sides of the Magic spectrum. It’s loosely based on the electro-magnetic spectrum.
**2. Fantasy Creatures**
While we’re at it, let’s have ~~fantasy Creatures~~ mutants. As many before me pointed out, realistically the closest thing you’d get to a mutant would be some living aberration. But I wouldn’t have Magic if I wasn’t liberal with radiation, so let’s let that slide and assume radiation will speed up evolution. Bonus points if you can come up with equivalents to fantasy races; so far I can only come up with Dwarves and cannibal Elves from Appalachia.
**3. Medieval-ish Social Structure**
I want something similar to a feudal society. With analogues to kings, nobles, knights, and peasants.
**4. Medieval-ish Technology**
I want the post-apocalyptic aesthetic to be relatively subtle but noticeable. Basically no technology that couldn’t exist in the 19th century.
**5. Adventurers**
We need people to go on adventures, different types of adventures, and reasons to do so.
**How close could we get a fantasy world from a nuclear holocaust with as little suspension of disbelief as possible?**
[Answer]
# Frame Challenge - Once You've Got Magic, Cause is Irrelevant
As you've pointed out, you've got magic in play, because "Radiants" don't make any sense inasmuch as real radiation is concerned. (Also, it's highly unlikely that gamma emitters are going to be your big problem w/r to post-nuclear apocalyptic scenarios, so having them be based on the EMR spectrum is *also* weird.)
Moreover, fantasy creatures as mutants - also unlikely in the extreme, as you've already observed.
The rest of it is... partially feasible. The major problem is that it's really hard to squash knowledge without also squashing the population. So guns, metallurgy, manufactory processes - they're all available to your population.
Feudalism makes a fair amount of sense, in that the people with the resources could effectively be kings, but it would be much more late-stage-capitalism and oligarchs than kings and knights, as one of the effects of modern weaponry was that it didn't take decades to master.
But, you're already bending the rules into something that doesn't remotely resemble the actual effects of a nuclear war, so if you want to make the result a fantasy setting, it's just a small shift further.
I would suggest, rather than "Radiants", have wizards effectively be hackers (which is, admittedly, a different trope). Through diligent study of dead languages and ancient texts, they are able to manipulate the relics of the old world. Your "mage" has a semi-functional smartphone they've cobbled together a power source for, and enough access codes to be able to reactivate bits and pieces of the ruined urban environment.
[Answer]
**500 Years of Prep**
[](https://i.stack.imgur.com/TDZyS.jpg)
You have 500 years to play with. Fill those 500 years with whatever developments help create your setting. Then blow it all up in the apocalypse.
**Feudalism:** Doesn't need much explanation. It is believable that a world that reverted to medieval-era technology also reverts to medieval-era governance.
**Adventurers:** This is a tricky one that has little to do with the apocalypse setting. There are many questions on this site about why small groups of roaming adventurers would be allowed to exist -- even in the standard fantasy setting. They did not exist in the real medieval world.
I suggest the apocalypse setting also provides a reason for adventurers to exist. In the medieval period all land was owned and most was full of farms. But in the apocalypse, the civilisation is young. Most land is wasteland dotted with settlements and ruins. There is a lot of opportunity in finding and plundering hidden caches from the old world.
Baron SkudBane may claim ownership of everything a thousand miles either way. But he simply cannot defend it all at once. He has sent out men to plunder. But there is too much space for him to cover. Loads left over for small groups of crafty adventurers to strike it rich.
Find a cache, plunder it, and sell what you find to the other side. Or sell it SkudBane and claim you found it in enemy territory.
**Fantasy Races:** Before the holocaust, genetic engineering had (cough. . .) evolved to the point where people could make themselves taller, shorter, more or less hairy, longer lived, or more emotionally volatile or calm.
These mods were all hereditary, but that's okay since you just go to the clinic and choose which mods to activate or deactivate for your foetus.
When the apocalypse hit, all the clinics were destroyed. Every short, burly, hairy, grumpy woman has short, burly, hairy and grumpy children. But it turns our being short, burly, hairy and grumpy is good for survival in the apocalypse. So these woman also have more children than otherwise. These are your dwarves.
**Your Homework:** Why is being short, burly, hairy and grumpy good for survival? Why is it good to be an elf? (**Hint:** Check other questions on this site.)
**Magic:** You need more details before I can answer this one properly. What can you do with magic and how hard is it?
Putting that aside I suggest magic is just technology in disguise. Mages are people who know how to use the surviving technology from before the apocalypse.
Again you can invent new future tech (and then blow it up) if you cannot think of how to cast a fireball using a smartphone.
Go all the way to nanomachines son if you want to go full parody. Nanobots already work by magic.
I did not "read your mind". All I did was [inject you with a serum of concentrated nanobots that scanned your genetic memory and then transposed the relevant bits of the genome into mine easy peasy.](https://www.youtube.com/embed/1LaSzmbtgIE?start=100&end=200)
Coming up with silly solutions to even sillier problems. That's what being a fantasy author is all about.
[](https://i.stack.imgur.com/v88Ac.png)
Gosh this one really came full circle. Sometimes I amaze even myself.
[Answer]
Starting with the easiest to explain and working to the harder to explain
### 3. Medieval-ish Social Structure
>
> I want something similar to a feudal society. With analogues to kings, Nobles, knights, and peasants.
>
>
>
Allow me to introduce you to your feudal lord ... er ... the CEO. Considering the power of corporations in America it would not be too big of a stretch to see that after the apocalypse a feudal structure based not on noble titles, but ranks in a corporation.
Interesting enough as corporations are basically people now, it would not be too far-fetched to imagine that the corporation itself becomes something more than its name and guiding principle once the world goes tits up.
Admittedly the corporations of today would have to diversify into doing a bit of everything. In a theoretical future before the end, maybe they did. Corporate towns of old came back into being with a government that allowed it, basically making people serfs in better clothes. After the end, with nothing to stop them, the corporate leaders basically became kings of their fiefdoms.
But really, you'll have corporate CEO-kings that demand everything of their worker-serfs and strive to take as much from them as possible without killing them outright. Bonus dystopia points if being fired in this world is literal.
Side Note: It might be interesting how much, or more accurately how twisted, the US Constitution will end up being in a world like this.
### 4. Medieval-ish Technology
>
> Basically no technology that couldn’t exist in the 19th century.
>
>
>
Large-scale access to technology needs to go anyways -- we can't have the newfound worker-serfs have anything that could possibly put them even one step closer to the elites. Conveniently, with how much of our technology is based on other technology, it may take a long time to build everything from scratch depending on the level of destruction, decay, and radiation.
Short of every library catching on fire, the *theoretical* knowledge of technology will remain and hopefully be passed down. In relation to the society, it may be that only a certain class of people get the education that could rebuild technologies and because of that, there is a marked difference in technology based on class and/or it just takes longer to rebuild.
Remember the elites will want to keep their power and will only have an interest in technology insofar as it increases their profits without endangering their situation.
In addition, scavenged relics combined with post-apocalyptic jury-rigging could be the aesthetic. Retained technologies will vary based on available resources and usefulness in daily life.
And since it is America -- yes there will be firearms. Even if they have to hand-forge muskets, they will have guns. The big question is if they could effectively forge bullets. If the skills survive, you may have 19th century firearms.
### 5. Adventurers
>
> We need people to go on adventures, types of adventures, and reasons to do so.
>
>
>
It's not inconceivable to think that trade wouldn't happen between corporation-states in this after-world. While the caravan might not be adventurers, the guards of the caravans might well be, adventuring to find a place to call home or just because it pays better.
In addition, given that the apocalyptic trigger is nuclear war, there may be areas that fared better than others because they didn't get bombed and the winds were on their side.
A story of a group of adventurers, knowing there might be resources elsewhere that can't be gotten within their lands, venture out into the wilds of the end of the trail known as I91 on the old maps to do trade with the northern mountain people with their strange language and customs.
Today, we call that driving through Vermont to Quebec but after the end, it may be an undertaking.
### 1. Magic
Fundamentally, your second point of Fantasy Creatures is based on this one, so I have to deal with this first.
Ultimately there are two broad ways to handle this -- magic as lost technology, or magic is trying to exist. As others have touched on the first, I'll hit the second.
Say that the damage caused by the bombs themselves create breaks in the ley lines of the Earth that lied dormant for a long time, allowing that power to seep into the world. But it is not unlimited power, and it too may be tainted by the radiation of the bombs.
With the nuclear war came magic, but we humans don't believe in magic. Even as society regressed, we still did not believe in magic except for one thing -- the invisible force that kills you if you venture into specific areas. Usually the largest ruins and the lands around them.
Because of that one crack in our rational worldview, magic can work on that and that alone. This is why the limited magic in the world works on the EM spectrum and is fairly rigid with rules and the like.
One might think that with enough religious belief, there would be divine miracles but there are not. But even if you have faith in your deity, it is common knowledge that your miracles do not come from ordinary humans. As one example: Christians are told of the miracles of Jesus, but they are also told that Jesus is a demigod of an immensely powerful deity. So no, they will not be miracles from the Churches ... probably.
### 2. Fantasy Creatures
The world's newfound magic does interact with the radiation from the war and strives to keep as much alive as possible. It's not pretty, but ultimately it is effective.
For us humans, well who knows what's been cooking with our sciences between now and the war? Dwarves could have been one Megacorp's idea before the war to use "precise genetic recombinations to achieve enhanced underground suitability and extended employable time frames". After the war, they live on as what we would consider dwarves.
The smaller peoples started as the suburban kids that were forever changed by the bombs that went off, orphaning many as their parents died in the nuclear fireballs that engulfed the cities. Stunted by both radiation and magic, they either wander or end up exploited by the corporate lords for their small size and physically weaker stature.
In the end, your basic formula is Animal + Mutations + Magic = Fantasy creature. There is even room for much subverting of ideas such as the unicorn's horn only have healing properties for the unicorn because it contains the radiation from the animal's food. I do not want to know what the marine life near and north of Boston would mutate into.
### Extra Notes
When planning your nuclear war, do make note of what cities get bombed and what ones may avoid a nuclear fate. While they might be hit by a potential nuclear winter, they might avoid a lot of the actual fallout.
It could end up that smaller cities will be the heart of corporate feudal power.
[Answer]
One point at a time.
1.magic: most nuclear bombs don't have any supernatural component to them so They probably wouldn't produce this effect.
2. Magical creatures. Another no, Unless some other factor is involved here, Then no radiation does not produce this effect contrary to what comic books have tried to teach us.
3. A historic feudal system, Definitely possible maybe even likely. Feudalism, Has developed in a variety of cultures around the globe Throughout history. Society would have to rebuild Itself entirely after nuclear war. It is possible that something like a fuedal system might take shape.
4. Middle ages technology: another likely Again it would definitely be some technological degression after a nuclear war This probably wouldn't be permanent but there would still be some.
There will be some technology left hanging around and probably some few people who could produce some technology at the old world. You're probably looking at something closer to medieval Tech barbarians.
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[Question]
[
For the longest time, I was unsure as to why the aliens in my story would have the anatomy they do; They were created through genetic engineering, so how they evolved is not an issue, but their anatomy is, quite frankly, not the most functional.
Now I've hit upon an idea: Their anatomy would not need to be functional for practical tasks if the only purpose for which they were created was to provide affection and companionship.
There's just one snag: These aliens believe themselves to be the absolute perfect form of sapient life, to the point that they exterminated their creators and now seek to convert all organic life in the galaxy into more of themselves.
It would be easy to just put this behaviour down to their creators not having been very talented when it came to engineering the genes that control behaviour, resulting in the pets rebelling in the name of their freedom - accidentally destroying their creators in the process - and subsequently developing a supremacist ideology, but that isn't satisfying to me; I want whatever caused them to want to eliminate all other sapient life to come as a consequence of something that made them such loyal, affectionate pets.
How is this possible? How can a trait which makes a species the most enjoyable pet also (presumably unintentionally) cause them to have a very strong tendency towards believing that they are the perfect form of life and all other living things are worthless?
Some criteria answers must meet:
* The belief in their own supremacy must be so extreme that they believe even their physical form - hindering as it is - could not possibly be improved upon
* They must be capable, if with the greatest reluctance, of deliberately wiping out other races
* The thing that makes them believe in their own supremacy should be something which at the very least would not, upon initial inspection, have seemed to make them worse pets, and should preferably be something that would have seemed to their creators to make them better pets until just before they began war on their creators
[Answer]
**Cats**
In an effort to create the perfect cute and lovable 'pet/companion', your creators decided to splice in the genetics of a cute, lovable pet - the common housecat. Unfortunately, they underestimated the innate superiority complex inherent in all felines and, combined with the other improvements already made (intelligence, etc.), they created a race of super-murder-felines, convinced of their own superiority.
Slightly disgusted by the fact that they 'owe' their creation to lowly human beings, they embark on a murder spree of global proportions, determined to eradicate all evidence of their embarrassing beginnings.
If you don't believe that this is a viable answer, take a look at your nearest pet cat, and imagine it to be the size and intelligence of an average human. It no longer needs you to feed it, or open doors for it, or empty its litter tray. How long do you think it will be before it realises it no longer needs you *at all*?
[Answer]
**The pets were developed to be hilarious.**
[](https://i.stack.imgur.com/qVRTh.png)
<https://www.youtube.com/watch?v=wyx6JDQCslE>
These engineered pets think they are so great; so awesome in every way: the cutest, the smartest, the best. They were engineered to have enormous egos totally disconnected with their pathetic malformities. Their creators never tired of the joke - these strutting, preening, egomaniacal circus freaks were the jesters of their world. The pets never ever figured out the joke. They were constitutionally unable to do so.
Of course the pets had the last laugh.
[Answer]
**A hazardous and outdated trend**
It was trending, everyone was buying the new biologicaly engineered pets. Lighthearted, playful, obedient, and the cherry on the cake : a very powerful but dangerous skill. (It can be any you can think of, I'll pick super speed)
You could point with your finger and the pet ran really fast to reach the location pointed. V1 was overconfident and self-advertising, V2 was faster, V3 was water-proof, V4 was so hard to break, V5 has more personnality, V6 was connected to the hive mind, V7 came with skin personnalisation, but V8 never came out.
This trend was finished, the controversies were too many, and the people were socializing together instead than with pets.
The thing is, they were build to sneakfully destroy or disable their master's other toys/pets/occupation to appear as **The thing that is reliable over anything else**.
But now they are killing your friends and your familly by ramming them when you don't look them, to be the only thing you play with.
The last humans inherited every pets they found. If they meet another human it's killed if the owner give the other one some attention. The owner has to play non stop, every distraction is destroyed, feeding and sleeping is almost impossible.
The humanity couldn't deal with those cute and fun creatures.
[Answer]
# Their owners were actually the greatest.
Their owners were the first sapient species in the galaxy, and by far the most advanced. They had numerous incredible accomplishments, did many impossible deeds and had a huge impact on the setting and the universe.
They were then killed. Their pets are not great at using their technology, and not anywhere near as sophisticated, but they claim all of their fame. They drive extremely expensive and dangerous weapons around bragging about their incredible power and sophistication and claiming all of the glory of their old masters.
This is intentional- the creatures were created to be very proud of their masters. Their masters didn't expect them to see themselves as the masters, and kill their old masters.
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[Question]
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In my setting, there is a massive crater that results from a divine apocalyptic event. Long story short, due to the sheer power contained within it, the water within the sea created by the crater is boiling or nearly boiling hot. There's not a natural origin for this.
I've heard that boiling wood will weaken it and saturate it, so I wanted to know if there was a way to get around this. I had the idea that pirates, using innovations other people didn't have, would use the hotter, inner regions of the boiling sea (maybe which are scaldingly hot but not boiling) as a shortcut and as a place to escape from pursuing vessels.
How far might they be able to reach into this boiling sea before it becomes too deadly?
[Answer]
## No
It's a fairly short answer, but your sailors will be dead before they've managed to cast off.
Even if you can manage to insulate their environment to take 40 Celsius off the ambient temperature they have a matter of seconds before permanent damage begins.
[Answer]
## Something tall
*(this answer assumes you have a small lake, that can be crossed within 30 minutes, the boiling water won't damage the wood of the ship..)*
You'd need to be below deck, preferably as far from the water as possible.
In medieval times, there were no ships able to do this, because they were too small. Consider upscaling..
**The Cog**
Dutch, 14th-15th century. Go below deck on the rear side (aft) and enjoy the sauna.
[](https://i.stack.imgur.com/rjFGU.png)
Before crossing this cooking crater lake, move some cargo behind the bow for balance.. and rig your sails.. enter the cabin in the aft.. and hope for the best.
[Answer]
**No, well... yes.**
First of all, "medieval" covers the range of roughly 600 C.E. to 1600ish C.E. A whole honking lot of technological development occurred during that time period. You don't specify a year (a common problem here on Worldbuilding. You should always specify a year), so I'm assuming the best tech possible. 1699.
* You have access to Asbestos, which has been used since time immemorial. Literally. It's believed to have been used a far back as 4,000 B.C. and was used to embalm Egyptians as far back as 3,000 B.C. So, insulation you have.
* You also have access to some pretty hard woods. Yes, heat and boiling water is pernicious, but that really only means that ships must be docked for maintenance more often. I'm a believer in human ingenuity. Some bloke would have figured out how to connect all that timber in a way that didn't just spring apart. The easiest idea is to use a different kind of wood as the plug (nail) holding boards together, one that expanded faster in heat than the wood used for planks.
This is going to result in thicker hulled ships than history actually saw. That's a good reason to favor later years, too.
* I also believe it's possible to reasonably seal the hulls such that crew below decks don't suffer from the steam outside. A few gears and some back-breaking labor would result in a high degree of ventilation, which might (maybe...) keep everyone from boiling while surfing along a boiling sea.
Where you run into problem is the management of sails. That requires people to be outside. The folks in the crow's nest might not suffer too badly, but a single wave over the deck will scald anyone there. Here's where my choice of 1699 is important.
>
> Two English inventors developed the first pressure-resisting diving suits in the 1710s. John Lethbridge built a completely enclosed suit to aid in salvage work. It consisted of a pressure-proof air-filled barrel with a glass viewing hole and two watertight enclosed sleeves. This suit gave the diver enough maneuverability to accomplish useful underwater salvage work. ([Source](https://en.wikipedia.org/wiki/Diving_suit))
>
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This is ***no small thing.*** But we're only looking for suspension-of-disbelief, right? So along with massive ventilation below decks, those folks breaking their backs are also providing ginormous ventilation for crewmen in asbestos-lined *diving suits,* used to work on deck.
Frankly, if you create enough pressure and move hot-steam-air fast enough, it'll cool things down, too. Not efficiently, but it would work. You're going to need a few extra crew on bilge duty to handle the extra condensation it'll cause — but let's roll with it!
*How believable is this? I suspect anyone with sailing experience would be rolling around laughing right now due to the need to handle complex ropes, deal with moving objects, and move quickly and with agility — all of which would be a real problem in a diving suit today, much less what was used 300 years ago. Plus the additional crew (and therefore supplies) to handle all the extra equipment and services work.*
But do we care? Sometimes on this site we worry a bit too much about whether or not a solution is *realistic.* Boring! The number of people who would read this story and say to themselves, "ppfhphttt! That'd never work!" is a mere fraction of the total readership.
So, I'm going with "yes!" A suspension-of-disbelief scenario can be created using late-medieval tech (and the driven-by-necessity early invention of some early 1700s tech) that would allow people to sail a boiling sea.
*I wouldn't want to be one of them.*
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**Oars**
[](https://i.stack.imgur.com/ofektm.gif)
<https://naval-encyclopedia.com/medieval-ships.php>
The water is 100c. We will say there is a lot of wind (because of the heat coming straight up from the water) and so the air is hot but not 100C. The wind would be good because it is steady on account of the steady heat but it is too hot on deck to stay up and use the sails.
The pirates go below deck. The middle deck has an air space which is insulated from the hot air above and also insulated by the hull and the air space down there from the heat below. The middle deck will stay cool for a while.
The pirates use oars. The oarlocks have sailcloth covering the holes to allow free play of oars but prevent ingress of hot air.
The problem is they are rowing blind. A periscope is an anachronism here but there is no reason the ancients could not have built a periscope - it is 2 mirrors and a tube. The pirates steer submarine style with a periscope.
--
This also sets up the scene where the pirates bundle up with many clothes to prevent being burned and go up to set the sails. Perhaps they run afoul of the things that live in this magical crater and must escape using the wind.
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For an RPG, I'm building a world that is the inverse of the fantasy world which contains ancient ruins and long-lost arcane secrets. This world will be home to the folks who built those first structures that will become ruins in future millennia, these are folks to first discover those arcane secrets, and these are the folks whose deeds are the most-revered by later generations.
There's a bit of a conflict here - there can't be too much human history behind my world, otherwise these people would be chronologically-enough removed from their own ancestors, such that there would be a clear distinction between the first age of humanity and the current age (to mitigate this, the first few generations are exceptionally long-lived like in some mythologies, and some of them will still be alive in my setting, partly to serve as a link to humanity's beginnings). But I also want these people to have built at least some things which humans could construct in the bronze age - most importantly, walled city-states.
So what is the fastest plausible time frame in which we could get from the first 100 humans to a handful of city-states? All of the knowledge required for civilization will come from an outside source, everything from fire to the wheel to agriculture to masonry. The motivation for humans to reproduce and civilize is also a given for this question, as well as a fertile environment. Little to no magic will be available to assist in the labor, so just in terms of available population and the required man-years to physically build something like Babylon, how quickly could it reasonably take?
I looked at some on-line population calculators, and using 2.2% growth just because it seemed to be in the middle of slow and extreme growth, I get 8000 humans after 200 years, 74,000 humans after 300 years, and 663,000 humans after 400 years. I'm thinking that somewhere in this time frame is when they would start building the cities. When would the earliest reasonably be, and then how long would it take to have a city more-or-less completed?
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Hmm. To provide you a decent answer, we have to make a lot of assumptions about numbers here. I won't be surprised if someone comes along after me to substitute better values.
First, for the most part humans are an invasive species outside of Africa. We tend to reproduce beyond what our environment will support, & there are few natural predators that prevent us from increasing our numbers over the long term, which drives into extinction other species. So it's reasonable to assume each generation doubles the total number of people.
Next, how many people are required to populate a viable city-state? IIRC, ancient cities had an average population of 10,000. Yes, some were much larger, but many flourishing & advanced cities were about this size. So for this experiment I will pick that number as the target size for our "prehistoric city-state". We can reach that in as few as 7 generations -- or a few hundred years.
(Note: in reality these people would be scattered over hundreds of miles, since as hunter-gatherers, they would need a lot of territory to supply their needs. If you don't have some means to gather them all in one place to start building the city-state, the time required to get to 10,000 will be longer.)
Now that you have your population, how long for them to build this archeological site? For this, I must point you to another source: a construction labor estimating reference. When bidding on a construction contract, builders need to know just how many hours this will take, & there are many books that provide this information. (Doing a Google search, I found [this one](https://www.craftsman-book.com/media/static/previews/2018_NCE_book_preview.pdf) I make no guarantees about its reliability.) They tend to be expensive, so check your local public library first for a copy. Now the time it takes to perform construction tasks without modern machinery hasn't changed much: people can only dig a cubic yard of soil so fast, & the speed of shoveling earth hasn't changed much over the centuries. So this reference will give you a rough idea of how long constructing a given building will take.
Then comes the issue of how many buildings you need for this city-state. Remember these people need somewhere to live, & estimating 5 people to a house, you need about 2,000 shelters for them. Next are the ceremonial buildings -- which really is your choice. At the minimum you'd want a temple, a meeting house or palace, & maybe some kind of stadium or theatre for entertainment. These will be substantial buildings, so calculate the time needed to construct them accordingly -- as well as preparation of their materials. Last will be the city walls; before modern times, every city had walls to protect its inhabitants from attack & wild animals.
A last issue is that most of the men of this city -- who will do most of the construction -- will need to spend time planting & harvesting crops. Say each family of 5 has 20 acres (I'm basing this on research I did about Medieval life years ago; you may choose 30 or 40 acres per family.) It takes one day to plow an acre once, & sometimes a piece of farmland will need to be plowed multiple times. Then the farmland needs to be harvested. So 2 months of the year you will not have anyone available for construction. Then there is Winter: you can't build during Winter. (If you don't believe me, try it yourself.) So knock off another 3 months. Lastly, people did not work 7 days a week in ancient times: they had various festivals & other holidays as a break from their endless labor. All of this means you only have a workforce for at most 7 months, more like 6 months, of the year.
In short, you've asked a very complex question, which really can't be answered in one go. Figure out what this city will contain, how much time it will take to build it, & you will have your answer.
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**TLDR** 100-500 years.
**bronze age** - hm, I was absolutely carried away from that one, yeah, oh well, hm, but still there is some truth in my answer, lol
* *For motivation, the answer is "motivated enough". I'm not meaning to sound flippant, but the idea is that I want this end result, and I'll tweak almost any factor that needs tweaking to get there. ...* (op)
Okay then you have an Amish-like society, an internally coherent group of people lead by Moses and nourished by the black monolith and then it is equivalent to a typical question of bootstrapping a colony on another habitable planet. There are questions of that kind here on wb and elsewhere - helping time travelers to survive, rise technologies in societies, space colonies establishing, etc. Quite scattered material and usually not that great, but suggest to look it up, for some inspirations and information.
## A note on growth rate.
There was growth rate concern, 2 or 4 % may be too big, etc, I have to point out that, let's say 4%, is absolutely not a limit for growth rates of humans. 6 children per family, it is about 12 years in pregnancy cycles, is not something astonishing in old days(it is more a perception of mine, so as some facts, including actual growth rates and numbers for children mortality rates back then, for some places)
So 6 children per family on average, means a growth rate of 5.6%. So 2 or 4% aren't high, especially considering that simple hygiene procedures, simple disinfection means like C2H5OH, understanding of germ theory can help drastically to slash that child mortality rate, women's mortality rate, and overall. So simple procedures which do not require equipment and are just a result of education and creation of habits(like do not flush "dirty" water on the heads of pedestrians, keep rodent count low, burn or compost trash, quarantine people, trace contacts back once epidemy, etc) can lead to significant improvement of the epidemiological situation to the point being able to reduce risks of epidemics and even fight it to some degree(vaccines are better of course, but ...). Simple means can be quite effective.
Agriculture, farming(rotation of land, compatibility of plants predecessor cultures, or permacultures strategies), and selection work for plants, irrigations, etc - it also can be helpful knowledge that not necessarily requires some dedicated tools or chemistry but it more about workflow and what to do and what not to do. This knowledge helps worry less about famines and such things.
There is plenty of knowledge of that sort which is helpful to increase productivity and reduce risks as a result of rational planning and knowing what to do. And this or another way, in different shapes and forms all that had some occurrences in the past - like domestication of animals was selective breeding, etc. And as a whole system, it all can have a compound effect - having it in one place at the same time is handwavium, but elements of it are not.
In that sense, 4 percent can be a quite relax number and not stretching anything.
## bootstrapping
Technological advancement is the first goal from the very beginning. The reason for that is that it reduces efforts one spends on food production and be able to spend the rest of the time on other activities.
There are some bottleneck factors, like location and proximity for ores materials, fertile land, river energy. A good location could be a foot of a mountain with a relatively fast creek, next to a fertile flat thing next to a big enough river, with ore veins and dried up the ex-ocean bottom with [Manganese nodule](https://en.m.wikipedia.org/wiki/Manganese_nodule) and a big forest nearby. That's one of the options.
The problem of bootstrapping, or it possible to say its advantage when one knows the path of development 100 steps ahead is that it does not have to repeat the history, it can be done differently, cutting corners and much faster with much less effort as one does not have to do 95-99% percent of the R&D process, no dead-end routes, planning ahead is possible.
The chosen way affects the speed of development, not in the last place because different paths have a different set of conditions - restriction, bottlenecks, opportunities.
A hundred people can't do much in terms of technologies, they do not have enough man-hours and they have to busy themselves with food-collecting, but they can do some which will clearly distinguish them from just hunter-gatherer communities.
But you have to have some plan, a route for them, and it is not that easy to make a reasonable one. As an example making them farmers from the start maybe not be such a great idea, as fishing can be a gold mine in terms of energy return on energy invested([EROEI](https://en.m.wikipedia.org/wiki/Energy_return_on_investment)).
And the path of development has to be optimized in that regard. Not efficiency of production which we care about today, not a price which is convoluted mixing pot result of a lot of things including those which have nothing to do with EROEI. This very EROEI is the main optimization parameter.
* to give an extreme unrealistic example, if to make a first electricity generator you need 1kg of iron and you can make it in two ways spend 20x effort to get 10kg of iron, or burn a forest with ease and get just 1kg - most likely you burn a forest - a path of least resistance, laziness is a driver of progress - pretty much humanity lived with these mottos since the very beginning, and it turns out it can be a rational choice, despite the extinction of species due hunting and creation of some problems in the future.
With planning, they do not necessarily need that, but planning itself is created in the spirit of that.
* *omg, so much text already, let's move to the business, the topic has no end, very exciting...*
## stages of development, sizes
The introduction was not sufficiently comprehensive, but there are limits to how much fits in one post. The main point was development route can be optimized in terms of efforts required to achieve certain technological progress, and before knowledge which eliminates dead ends and R&D efforts is a great boost. So they are (or can be) constantly in a state of knowing what can be done with what they have exceeding their real capacities to implement things, what they actually can do. Pretty much never was a thing in our human history, and when such thing raised its head a little - we call it industrial revolution since then.
So a situation is limited by the number of people present for work doing, which is a function of the growth of population. What we may have problems with is to be able to set points on the plot which correspond to certain, known to us, technological levels.
A hundred people can advance in technological means quite a lot actually, despite it being just a typical tribe size or a village it would be wrong to make parallels with actual villages in old days, and a more correct way would be what can 10 guys of modern time do, assuming they are provided with the knowledge of what to do, and maybe some dream training by matrix(extreme case) black monolith - meaning they know what to do and skilled enough at doing it(not necessarily a stellar job, it may take a few times more than for a professional but they are motivated and dedicated enough).
So it 10 of time travelers(the rest are working on food child caring education material delivery etc)
* borrowing energy from external sources and replacing human physical labor was one of the fundamental achievements, which made farming better as it more energy expensive than hunting(if I recall it correctly, and didn't screw my numbers back then)
So domestication is one of the things which hard to speed up, effects require 50-100 years, but can they borrow river and creek energy for mechanical work - absolutely. The tools required for that can be just a stone(sort of a stone ax) or even just hands and laying trees.
Basalt or diabase can be cast similarly to iron or how other metals are cast. So as with mechanical work stone can be worked to all sorts of things. Combined with wood it can be a replacement of a lot of metal things in sense of machinery and mechanical contraptions.
* can accept a challenge to make a plan for 10 modern humans how to get from stone and wood and river to electricity and metals without prospecting for metal ores and making mine shafts and such.
Prospecting for materials is one of bootstrapping bottlenecks, but there are ways around it, so as places rich with gold also provide metals as well - so you can pan as for gold so as for iron oxides(and other metals in that black sand) so getting a little bit with a minimum of tools, isn't something unrealistic.
What is the limit for those 10 guys, it depends, electricity is achievable, practical uses(however limited) achievable, steam engines, cryogenic setups, acids, rectifications of all kinds, bearings, abrasive materials, metals, etc.
A lot can be done, but there is another problem how many things they can support running and operational at the same, with servicing and maintenance works. They can solve complex problems step by step with different means with a goal to get to some useful plateau which they are capable to support and which is more or less self-sufficient.
The level of technologies defines not only what is possible, but also the percentage of people busy with food production, less is the number more time they have to build cities.
Imho, it may look optimistic or not, but you may guess I have some reasons to be optimistic, lol
## 100 people
Limits improved 1400 A.C. level of tech maybe improved early steam era, water wheels or turbines(simple profiles, not necessarily Pelton turbine, but close to that) ones are not impossible and in terms of mechanical energy 10 - 100 kW are not impossible (if there is that mountain creek of sufficient power, quite a good location for initial energy generation)
Even 10 kW is a lot, for grinding of something, cutting stone blocks, drilling, etc - it can and will outperform the whole village if they would do that manually. Not that they need stone bricks at this point, just saying.
## 1000 people (50 people in charge of technologies, something like 20 percent of who are not kids or elderly)
It is still a village. They can expand on the variety of things they have or do, can have refrigerators may be in form of improved under earth ice storages keeping things spoil free with no gaps in time, all year round.
Overall they may have essential technologies on the level of the 1900s, not all, of them, but combustion engines are reality. So mobile energy conversion units for all sorts of works are a possibility.
Metall working shop is a thing, production of metals in sufficient quantity and parts from it.
No cities as of yet, a city requires brute force, but it starts.
## 10000 people (1500 in charge of technologies, 50% of workforce which not busy with food production, and another 1500 season workers another 50%)
At this point variety of implemented technologies can be quite decent, with exception of a lot of production and products which is not required yet (like radio, telegraph, airplanes, personal cars, a lot of chemistry, etc, etc) those guys can support a subset of 1930-40 technologies and it is a sizable workforce which is capable to build and support a city for themselves, at more or less modern standards as appearance and some functions, maybe without some bells and whistles, but with tap water, central heating, cogeneration of energy(thermal electricity). The assortment of goods may be poor or definitely not stellar, but in a sense of survivability, and medical necessities including vaccination can be advanced enough. So with sufficient laser focus on necessities, they probably can draw technologies from 1930 to 1970s. No computers, no tv, no microwaves - those are not necessities. Electric motors and their easy derivatives like blenders no problem, combustion engines, and shiny shovels.
So if you slash what can be found in some nowhere place with 10k people in it, and upgrade some things if you are looking at USA reality of such places - then it something you could expect from 10k people. If they work like one solid company, be focused, and have energy.
Energy is important, sticking to instructions step by step what needs to be done in a workplace begins to be a necessity, rare elements begin to be essential for further technological development.
Energy requirements at that point a few MW's will cover their needs, and operational activities. Biodiesel may be a thing for them, as it is more convenient than splitting activity for oil prospecting, and has some advantages over coal.
Wood for power at those consumption rates about 50 tones of air-dried wood per 24 hours, with 25% efficiency for electricity production, rest for heating drying and other low potential heat uses (keeping warm water in fish farms as an example, greenhouses, whatever)
For that it needs about 10000 ha or 100 km2 of forest(it grows that much(50t) of wood a day, kinda), so even if it is just wood - deforestation like it happened in Europe and which moved them to more coal use, is not a thing for that settlement. It is another example of the significant differences and problems which historical analogies can bring in a bootstrapping situation.
Their demands for materials still can be covered locally, and extracting 10% iron-rich ore, which we find not economical as of today(50-60 is today's norm, 80% was like 100-150 years ago norm) can be a better option for them than splitting and invest in roads and long-distance transportation.
They also still have enough mobility and if there is such a necessity or opportunity, it may be beneficial to move as a group to a new place - sure it takes time and effort, and it abandons a lot of earlier investments, but if someplace else is a better choice for a current situation they are capable to do so, same as they were capable to do so before as well, for a next stage it is a much harder choice.
## 100'000, 10% of population is food production(farming), the rest is technology(20k), building(low skill labor), kids(low skill labor) and elderly(easy labor, edication, managment, processes overseeing).
Pretty much expansion of what they could do at the previous stage, the city they can build and maintain should probably satisfy most of what one could expect from a city. Roads and satellite cities for farming. Trucks for cargo, centralized storage facilities for all sorts of things. Public transportation available([Trolleybus](https://en.m.wikipedia.org/wiki/Trolleybus) - there is some simplicity in the thing, even if it is less flexible, and has certain limitations), as personal transportation a bike probably still a thing, but it depends on how much energy they have.
## for goal stated in q it does not need that much, but as an honorable mention
* 1'000'000, Musk-time - sufficient to support modern technologies self-sufficient Mars colony
* 40'000'000 bare minimum for the modern technological country, sorry Norway.
* 1B - capable to support the production and development of all modern technologies without a pinch of black magic. The number can probably be a few times lower without the necessity to develop and research. The absence of competition as a driving force of development can probably slash the number another few times.
## if conditions are a-okay.
If there are not many factors that may cause some significant setback and limitations, which does not mean the absence of hardships, then somewhere in between 10'000 to 100'000 you will get what you want.
With 4% it is 120 to 180 years.
With 2% it is 230 to 350 years
For 1%-guys, it is 460 to 700 years.
For 5%-rabbits, it is 94 and 140 years.
So 500 years seems to be not unreasonable by any standard, and more or less it is what happened in history, I mean industrial revolution started about 260 years ago. They had different starting conditions, they had more people and less knowledge but the speed of implementing knowledge(once they produced it) was quite fast.
So from a certain point of view, a few hundred years in your situation is not necessarily an unreasonable expectation.
Lack of numbers is a problem but at the same time a blessing because they require fewer resources to implement things to be available for everyone. This means they can cut some costs and afford more inefficiencies, working with smaller ore mines or sticking to other means of resource extraction, like electrolysis of basalt which surprisingly contains plenty of stuff [Basalt::Geochemistry](https://en.m.wikipedia.org/wiki/Basalt#Geochemistry) and despite processes are more energy-intensive(not necessarily by much, but 2x) but at the same time it slashing costs on a lot of things and just saying roads and transportation does not describe situation deep enough. And one still can afford to be a little bit wasteful and still sustain this activity on local resources.
Clay bricks may require finding proper clay deposits, but the same basalt can be cast in bricks - again maybe a little bit wasteful, but hey it won't be like in Rome when buildings were crumbling cuz someone slashed costs on baking the bricks, those basalt bricks will last for ages, and if one casts them as lego blocks like wavy surface they may not even need mortar to make a building, meaning those bricks can be a reusable material.
So a little bit of creativity and unorthodox(from a modern or historical point of view) technological thinking can bring decent results.
## A city
* seems I didn't address it well enough, carried away by technologies and bootstrapping
here I have a little bit of problem in terms what do you mean by walled city and hope you may draw some estimations from technological capacities.
But let's say a middle-aged city with a wall - there is a choice to make - one can spend a hundred years to make one from nearby rocks, castles were done in that ways, or invest some time to make tools which will make the thing easier and less dependant on proper stones laying around.
Things depend on choices and the environment. if it is an outpost-like situation, when you build a wall against animals or other stuff - then things do not allow that much freedom in terms of slacking off and build tools, you start building your wall straight away.
a thousand people can build a walled city for their size, even a hundred may and in some places did.
At 100k city a wall loses its meaning if it is against an intelligent enemy.
so depends on the purpose and environment but 100 to 100k they are all capable to build this or another version of walled settlements.
when we talk about the fastest way to do so then it needs more specifics but it is not necessarily possible to say that technology is always a faster way to do so, or more technology is a faster way. it more like a balance of what makes sense and how big is the task, what the end goal is, and there is no general answer. here is plenty of examples where simpler technologies do provide a satisfactory result with much lesser efforts than more advanced one which does the same.
10k is a good population number it allows plenty of things to be done, in different ways - old old, old, modern, or bootstrapping.
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A group of 100 people is most probably too small to produce enough genetic diversity to survive in the long run. It is assumed you need AT LEAST 300 individuals to start a population that will not be killed off by genetic defects.
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A lot of cities were death traps. When you stick a ton of humans together you tend to get a much higher death rate from accidents, illnesses, and sickness. Cities don't just spring up when your population increases.
Cities spring up when you have a lot of farmers growing a huge amount of food, and an area has a lot of trade or traffic for some reason. Perhaps it's a contested border and soldiers are staying there, perhaps it's at a good river or sea area for trade from other areas.
Lets give an example. Carthage was founded supposedly in the 9th century by Dido. Her husband is killed by the king of Phoenicia, a leader of a group of city states in Lebannon, and so she and a bunch of settlers flee to build a new city with a load of wealth, buy some land from the locals. A good location at a harbour and skill at building ships means she can trade with the old city.
Two centuries later they declare independence and start their own empire, and three centuries later, there's enough of a city and a trade network there that they can start having border conflicts and wars with the greek colonists from their city states. They made a lot of money and caused immigration from the farmlands around them by trading metal cheaply from Spain and selling it to the wealthy north African empires at a huge markup, but Greece was making their own colonies which have more skilled metal smiths, so war was waged.
## If you're starting from 100 people, it's gonna take thousands of years.
To make cities you need trade. To make trade you need civilizations and agriculture. It takes a long time to domesticate animals and build a civilization which can make cities profitable.
You could speed this up by having the 100 people have suitable crops and animals with them and perhaps a map so that they can grow enough food to support a city.
## If you're starting in an empire, you can do it in a hundred years.
So long as the 100 includes lots of skilled people, you can quickly build up a large settlement. You can found profitable industries and people will rush in from outside. 200 years to build an empire.
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the first ''mega''-structure ever build was the gobekli tepe, probably the first time multiple groups of humans united their forces to build something together.
that was roughly 12.5k years ago, at that time the human population on the planet was an estimate of 2 million people, probably less.
Which doesn't mean 2 million people in a region but spread across the entire world.
Gobekli was built in turkey, right in the middle of the world map before the discovery of the americas. 1000 years ago most of humanity was living in south and east Asia, roughly 66% and only 8% was living in west asia and 15% in europe. That would be around 160k people in all west asia, of which turkey was really just a small portion.
modern Humanity comes from the hybridization of the various human species. Modern humans were born roughly 300k years ago, with an average of 30 years per generation, humanity was born 10k generations ago, and gobelki was built 416 generations ago.
Which means the if your world were to follow the same speed, the first cities will be built after 12.5k-0.4k = roughly 12.1k generations after the first human born.
From this you can see that technology and civilization takes quite a while to start but once it starts it goes into continuos accelaration like a magic rocket, cities existed for only 3.3% of humanity's chronology... and maybe in an alternate earth civilization might never have started, after all humans are just hairless monkeys, if the first hairless monkey never struck one rock against the other to make a tool or if they didn't teach it to their children... maybe today civilization would not exist.
So realistically, what happened in our planet is incredibly unlikely, and chances are that if humanity were to start again from zero, civilization would hardly repeat.
Monkeys make tools all the time, and they are yet to build a city, it was a mere miraculous chance that humans did, once, and survived to build more.
If you want to make any alternate world realistic, humans are still smashing sticks one against the other and screaming ooga booga, cause the average human is intelligent, but not intelligent enough to invent anything without an education, it takes smarter than average people with incredible absurd luck to start a civilization.
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What would a realistic space-dwelling humanoid species under these guidelines look like? It's for a setting I am working on. They are sentient and live on asteroids, typically converted into ships.
Rules:
1: Presence of a prehensile tail, to grab onto things.
2: Must be able to communicate to other asteroids naturally, and not through writing (they do not write in that sense).
3: Are capable of communicating with others of its kind on the asteroid they are on).
4: Can survive multiple hits from micrometeoroids in quick succession.
5: Can eat rocks for energy.
6: Presence of powerful claws, to grab onto rocks.
7: Can survive under gravity.
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There is plenty on this stack about space beasts. Maybe I will link up some of my favorites. But first - ideas about vacuum dwellers!
**Not boil.**
Liquids under vacuum boil away. These creatures must be able to close any aperture connecting any wet areas with the outside environment. They will have impermeable waxy exoskeletons covering everything. That is not so weird - arthropods do it.
**Everything needed is on board.**
The vacuum is resource poor. Really resource poor. We are used to taking sips of air and water from our environment but none of that in the Empty. If these creatures use biochemistry then all of the ingredients need to be housed within their bodies. Perhaps they can collect and process the rare matter that comes their way in the form of space dust and meteors.
**Energy eaters**
If your creatures never or rarely visit planets then they will have to get their energy out in space, which means radiant energy. Visible light has some energy and plants successfully collect that and convert the energy into biochemistry. Ionizing radiation packs the most energy but so much that the conversion into biochemistry is tricky but conceivable. There is plenty on the WB stack about energy eaters.
**Humanoid** This is the trickiest part. Our humanoid forms are fine for using tools and wrangling our terrestrial environment. But what need is there for hands and arms if you float in the void soaking up rays? I think maybe your creatures could be facultatively humanoid - taking on humanoid form for excursions into planetary environments where that form is useful. Other planets might call for manta ray forms, or wind jellyfish forms. Your creatures are shapeshifters.
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**If they must live long time in the void of space, they must be able to hybernate and have some kind of symbiosis with photosynthetic organisms**
It is safe to decide that a space dwelling humanoid should have no lungs and breathing system. They would be useless, plus would expose to the vacuum a lot of mucose and thin bllod vessels.
Heat should not be a problem, as long as they don't touch anything: vacuum is a great insulator, they could have problems in dissipating heat.
The true problem is how to keep the metabolism working (because they can't have access to air) and how to eat.
About metabolism, these humans would be closed loops that need only light to live: their skin should be partially transparent and there should be some photosynthetics bacteria living under their skin. These bacteria recover CO2 and waste from the blood of the man and thank to light can generate nutrients and Oxygen that are released in the blood stream. Since this photosynthesis would probably generate a small amount of nutrients for a hot-blooded creature, they should pass the grater part of their time in hybernation, in order to save energies.
Obviously, they would have no escretory system, since they can't afford to lose any not replaceable resource (aka atoms heavier tha Helium).
Unluckily, if they have to grow, there is no way to find suitable nutrients in the space: probably they would be a kind of predator of other space-dwelling species, or would work for planet dwelling humans in order to receive suitable food.
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## Vacuumorph:
This has already been done, in the book [Man After Man](https://speculativeevolution.fandom.com/wiki/Vacuumorph). It has a protective shell, pressure-sealed eyes, and highly flexible limbs with a crazy grip. In this case, it is described as being a genetically-engineered and sterile (on it's own) species, but I don't see why it would have to be. While it would be extremely awkward in gravity, I don't see any inherently impossible reasons it couldn't live in gravity.
It is an amazing series of books, and I highly recommend that anyone on a worldbuilding website seek out the *After Man* books for inspiration.
[](https://i.stack.imgur.com/RYpoj.png)
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So, I've got this setting. It's a supernatural post-apocalyptic story involving guys with superhuman abilities traveling across an America that's become a grid of 2x2 mile "squares" (technically pillars getting bigger going up and smaller towards the earth's core), each governed by a different supernatural gimmick. One square might make people fall west instead of down, another might make it impossible to tell lies, another might start to mutate you into some kind of human-badger hybrid the second you step into it. The people who have survived one year into what's come to be known as "Gridfall" have established settlements in the least dangerous squares they can find, learned as much as they can about the other squares surrounding them, and worked out the safest paths from one settlement to the next.
This, naturally, means that maps will be made that take the new grid system into account, and will need to inform the reader of what exactly they need to look out for with regards to the rules or gimmicks of each square they pass through. That's a bit tricky though, because conventional maps generally don't supply that kind of information. Maps generally work with symbols and coded lines, things that can be easily explained in a simple map key on the side of the map, things that barely even take a few words, let alone whole sentences, to explain. But these maps are going to have to say things like "people become half a foot tall in this one, but the animals stay the same size as always", or "people spontaneously combust at random when they enter this one, *avoid at all costs*. And keeping in mind that this is the post-apocalypse, where resources are scarce, they're going to want to come up with the most efficient and straightforward method of conveying this information as possible.
**What would be the most efficient way to make a map of an area that also explains how all the squares in that area work?**
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As a baseline, the map will have a color coding in each area, sort of a heat map, ranging from e.g. red for the most lethal to blue to the practically harmless.
Then there will be one or more symbols to specify the type of local gimmick, and if it applies to general or special classes. Lastly, an indicator, either a symbol of a color, on the level of confidence in the classification.
Rationale: whoever started the map obviously started in a safe square and figured out that some other squares were more dangerous and other less. Therefore it will soon be safe to assume that any other square is dangerous unless proven otherwise. Once the exploration began and whoever returned started bringing information, more confidence can be gained. However some gimmick can be intrinsically more tricky: for example a square where anything taller than 1 meter above the ground will be cut to that height will be safe for a toddler accidentally roaming into it but will kill a parent trying to recover it, unless the parent is also crawling.
The more information are gathered, the more confidence one can put in the symbolic description of the square properties.
And since it is post Apocalypse, it's perfectly normal to have maps displaying uncharted areas, with basically just a "hic sunt leones".
[Answer]
## Story Maps:
In the post-apocalypse, I doubt you'll have cartographers making proper maps. You'll be lucky if people can properly travel at all. But where people CAN travel, there will be roads or at least rivers. And where each route lies, there will be a story. Your maps will tell that story with hints and reminders.
No routes will cross anything overly lethal. The actual maps would likely be either a written or detailed oral account of what happens to you as you travel the road, or some sort of prompt that reminds you of what is along the path. Since the blocks occur in such regular intervals, you might have a string with unique knots and colors or beads, and a verbal explanation of what each knot/bead means. Literacy is likely quite low, and as a consequence people will have better memories and memorize things more. A map would be a string of mnemonics to tell you what you face on the road.
Beads or knot-patterns could have particular shapes to represent which direction you should go at each new square - like beads with hole in the sides, or knots that mean "turn right/north" vs. "turn right/west." This map could even have side-strings to either show you alternate routes, or as warnings about especially dangerous side-steps in case things go wrong. I could even see a sort of weave or patchwork quilt made for an area, where each patch represented a square. An old grandma selling a quilt might be an invaluable guide to survival in a given region!
I doubt most people would ever have a proper map, especially not one they took with them. Each town would likely have a visual representation of the local hazards and a few old folks always ready to tell the travelers what they face if they go a certain way. Crafty and evil locals might lay traps for unwary travelers, like "Enter the square and go in 100 feet, then stop for a minute and watch out for giant birds," but actually you don't get oxygen in the square and will pass out within a minute (and the locals then dash in to steal the stuff off the dead travelers).
Overall, travel would be epically challenging, but a good bard who memorizes lots of stories of travelers would be worth any ten maps.
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**Percentages.**
The mappers of old had class D personnel who would try to traverse a square. The percentage reflects how many successfully traversed the square. 100% means everyone made it (example, no lying square). 50% means half made it (perhaps the random combustion square).
This is the old big map. It unfolds to 3 square meters. Each square is a centimeter and contains a percentage. Squares are coded by X Y coordinate numbers and letters.
Your characters have a unique map - a well worn version with additional detail written into the squares by a variety of persons over the years. Some are barely literate scrawls; others have notes about how the square contents could be helpful or other details. Some have different percentages written in - the opinions of subsequent authors. Once they are far from familiar areas they have just the percentages to work with. The fact that the map still exists and has not been lost is considered a testament to its accuracy.
I like this for a story because your characters could have names for the various persons who contributed to the map. Some are known personally to them. Others are lost to time and have nicknames.
Consider making your squares 10 miles on a side instead of 2. 10 square mile squares rendered as 1 cm each is where I got the 3 x 3 meter map. It would be hard to fit all the 2x2 miles squares filling America on any reasonably sized map.
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[](https://i.stack.imgur.com/3YGz6.jpg)
I like [aircraft with multiple wings stacked atop each other](https://en.wikipedia.org/wiki/Multiplane_(aeronautics)); in an alternate world (undergoing a similar technological history to our planet but with a different aesthetic) I would like them to remain dominant for both commercial and military purposes: multiplane equivalents for everything from 747's to F-16's.
Historically, multiplanes offered considerable advantages over monoplane designs; you have more lift with a narrower wingspan, and the rigging made the wings a lot stiffer as well. But from my (layman) research it seems that multiple wings are a cause of excessive drag at greater speeds, which became available towards World War 2 as engines became more powerful.
I wonder what I could do to combat that. My first instinct is increasing the air pressure\*, which means achieving higher speeds is out of the question. That means that drag, which increases linearly with air pressure but quadratically with speed, is less of a concern, and multiplanes might remain viable; with monoplane aircraft restricted to experimental speed machines. Then it may take days for Average Joe to cross the Atlantic but with greater lift you can put more utilities like beds aboard a plane and have it remain a viable mode of public transport.
But increased air pressure might not be the best answer. A multiplane's increased lift may be a lesser advantage when everything has greater lift, including monoplanes. Hyper-manoeuvrable fighting craft would still like that edge, but no civilian crossing the Atlantic is going to want to fly in corkscrews.
My other instinct is the inverse, lowering the air pressure. Then lift becomes a greater concern and drag a lesser one, and stacking wings may be obligatory if you want to just stay aloft. But the more efficient solution to deal with lower air pressure is generally to just make your monoplane wings bigger, and as soon as there are materials as stiff as what's considered for the monoplane [flying drone that works in Mars atmosphere](https://en.wikipedia.org/wiki/NASA_Mini-Sniffer), multiplanes would again fall out of favour. I'm fine with restricting branches of technology or materials, but "anything stiff" might be too broad a category of tech to rule out, as it would be too influential on the rest of the world.
So I am open to other changes. Take as your baseline the Earth in the late 20th century; what can I change to make a dominant multiplane design believable?
\*The answers to [this question](https://worldbuilding.stackexchange.com/questions/194782/how-would-a-human-body-behave-if-the-atmosphere-pressure-were-2atm-at-the-sea-le) deem increasing the air pressure generally survivable. Of course a planet with twice our air pressure for its entire lifetime would have lifeforms adapted to those conditions, so I am fine with exceeding the pressure tolerable by humans, as long as the resultant planet would still support a humanoid lifeform that looks the way we do.
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What if you just tweaked history a bit so that while biplanes existed and monoplanes did not, air traffic became *much* more common and less controlled than it is now. Their ability to navigate a much denser sky due to their slower minimum flight speed and high maneuverability would entrench the biplane so that they could not be displaced by monoplanes. The government would have to try to take away every family's biplane. That would relegate monoplanes to trans-oceanic journeys were they take off from near the coast, and maybe a few select cross continental routes.
Monoplanes displaced biplanes when the materials and technology became available because they have less drag which lets you fly faster. For a monoplane to flower slower than a biplane you need something with long, thin wings like a sailplane but those aren't manueverable, not to mention tricky to build.
On the other hand, this same logic opens the way for things like gyrocopters which might be even more suited to the scenario than biplanes.
It's unclear to me how this would affect military aircraft though since they tend to set the rules during war time. On the other hand, no Nazi wants to fly an F16 to bomb London and collide with people just commuting to work. Well, they could just fly higher, I suppose.
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Alternatively,
Or you could also tweak history so that cheap refining of aluminum (which was very very recent) was never discovered. That would take a lot of monoplanes out of the sky leaving only wood skinned monoplanes, which you would then have to explain away somehow.
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**Dirigibletech batteries in a high density atmosphere world!**
1. Denser atmosphere makes lighter than air craft easier.
2. Powerful petrochemical burning engines are heavy and fussy and not that helpful with LTA craft and so there is less enthusiasm for developing powerful petrochemical burning engines.
3. Rechargable batteries and electric motors are very attractive for LTA craft. Much research goes into batteries and the dominant LTA craft are soon powered by lightweight electric motors.
4. Reliable lightweight battery powered engines go very well with low velocity biplanes and triplanes. LTA craft are still popular but for certain uses the maneuverability of planes makes them superior.
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### Tall Trees
A world with very tall trees. As in a setup where you have trees with height 1000m and beyond. If majority of flying fauna have multiple wings this would further push thinking to multiple wings.
Tall trees would discourage long wing span to avoid collisions. High speed below tree tops would be risky. Tree top airfields might be a thing, and small compact aircraft would be useful there as well.
Single wing fast aircraft would still eventually be a thing for longer distance travel above treetop, and above treetop air dominance. But to get down among the trunks smaller, more compact, and more maneuverable aircraft would be needed.
This would not be an overall biplane dominance. It would be a below treetop dominance. It would also mean that large biplanes wouldn't be dominant. But it allows small biplane, triplane dominance for a long time in one niche.
It would be better to have dense atmosphere and low gravity, to increase large tree plausibility and height. However, generally, low gravity and dense atmosphere don't go together.
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## A few thoughts (and lots of epically bad weather):
First, if the visibility was low, aerial hazards frequent, and radar less effective, the ability to avoid sudden hazards (or impact those hazards at low velocity with lifting power left over in case of damage) would encourage biplane and airship development. In [THIS](https://worldbuilding.stackexchange.com/questions/194392/what-armament-would-be-best-for-a-21st-century-airship/194445#194445) question, I suggested thick clouds and aerial lighter-than-air plants as natural hazards that would make high air speeds lethal. An early, really cheap and easy ultralight biplane design (filling the sky with planes) or some very logical reason for massive numbers of kites (say, for example, constant storms make kite-based or barrage-balloon-style [lightning capture](https://en.wikipedia.org/wiki/Harvesting_lightning_energy) a practical power source) would also make the skies filled with obstacles that a regular plane would have conniptions dealing with. So endless dark thunderclouds.
Secondly, biplanes ALSO require very short runways. If you can think of scenarios that require all or most runways to be very short, then biplanes, helicopters and autogiros will be strongly favored. Extraordinarily rough and irregular terrain would mean all early runways were short, twisty affairs. An extremely mountainous world would mean that you COULD build fixed-wing planes, but why would you? Maybe for REALLY long flights to REALLY big places. Strong, erratic winds would also make large planes needing long take-off times would be at a disadvantage. So a mountainous world with many small volcanic islands and atolls.
Finally, have you considered alternative biplanes? Canard designs (for example) are technically biplanes, but might not meet your criteria. [HERE](https://www.popularmechanics.com/flight/a7517/the-return-of-the-supersonic-biplane-7505124/) is a proposed supersonic biplane. It means that with appropriate acceleration first, a biplane can avoid the issues other supersonic planes have with sonic booms and have stable cruising speeds. So imagine if the original designer of this concept had lucked out and stumbled onto (or been secretly supplied...) a design allowing this concept to be carried out with existing tech and rockets for initial acceleration? You could skip the clumsy age of the monoplane and launch your biplanes into the supersonic age!
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## Power/Weight
The big factor that made biplanes and triplanes preferable in the early days of aviation was the low power to weight ratio of early engines. This made it necessary to save as much weight as possible on aircraft structure. A monoplane wing will tend to be heavier than a biplane wing for a given strength, but the increased lift-to-drag ratio will make it more efficient at higher speeds.
Given this, if you want to make biplanes more prevalent (not sure you'll be able to completely exclude monoplanes while flight is still practical enough to be useful), limit the availability of powerful engines and/or increase the gravity. You could also reduce the availability of high strength/weight materials, but that would mean no aluminum, steel, titanium, wood or composites, not just for aircraft but for this society as a whole (unless you can justify why they use them for some things, but not aircraft, where they would be most useful).
Reducing the air density alone won't exclude monoplanes until the density is so low that flight is impractical. However, it could make multiplanes more prevalent in cargo/passenger roles as long as you also restrict runway length and/or engine performance (otherwise they'll just settle for higher minimum airspeeds and long runways). Unfortunately, low air densities will also reduce maneuverability (all else being equal), so these aircraft may be more aesthetically pleasing, but they wouldn't be very fun to fly.
Higher air densities make high speeds less practical, and reduce the relative benefit of the monoplane planform. However, they also reduce the amount of wing area necessary for flight at a given speed and weight, so increasing air density without making any other changes might just make blended wing body, or "[flying flapjack](https://en.wikipedia.org/wiki/Vought_V-173)" style aircraft preferable to multiplanes instead. As such, increasing air density is best done in conjunction with other changes.
Bear in mind as well that air density decreases with altitude, so as long as cabin pressurization is possible or the pilot/crew/passengers already have their own life support systems, aircraft may simply opt to climb to an altitude where the air is thin enough to permit high speeds. Higher gravity and/or less powerful engines may make this impractical and force aircraft to remain low and slow.
## Restricting Engine Performance
Perhaps this is a world that for whatever reason (not life-bearing, recently terraformed, necessary conditions were never met, etc.) never formed hydrocarbon fuels, or perhaps they've all been used up. Either way you're left with electric powered aircraft where batteries comprise most of the aircraft's weight. Alternatively, maybe environmental restrictions have forbidden combustion based engines, or reduced their power though emission control measures. Maybe the atmosphere has no free oxygen, so the aircraft also has to carry its own oxidizer, again reducing the overall power-to-weight ratio. You just need to restrict the weight fraction available to the airframe until designers have no option but to resort to multi-plane configurations.
As far as performance targets, you wouldn't want to go below 5 W/N for a fully laden aircraft. 10-15 W/N tends to be the lower limit for practical performance (most WWI era fighters, and general aviation aircraft like the Cessna 172 fall in this range). WWII era fighters by contrast tended to range from 25-35 W/N.
## Increasing Gravity
Increasing gravity by itself would increase weight without increasing engine power, so it would allow you to dial up the minimum strength-to-weight ratio of an airframe until monoplanes were impractical. However, this would also have impacts on planetary life, and earth is already near the atmospheric escape threshold of helium (at least for surface temperatures that can support life as we know it). A planet with a higher surface gravity would require a corresponding increase in surface temperature to avoid becoming a gas giant (though there's no reason you couldn't have a Bespin-like colonized gas giant).
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The only way I can see biplanes remaining common is if they were to replace the automobile. Biplanes and triplanes have much more lift compared to a similarly sized monoplane. So maybe in your universe, nobody owns cars, they have biplanes. This is because a biplane can use very short runways, in a suburban setting they may be right in front of each home. In an urban setting perhaps each rooftop has one somewhat like a helipad.
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Decreasing the air density will reduce the available lift to any aircraft, which means aircraft must have a larger wing area and potentially fly far to achieve the required lift. Increased wing area can be provided by multiple wings.
The atmosphere on Mars has very low density, usually referred to as being very thin. To enable the [Mars helicopter](https://www.space.com/nasa-powers-up-ingenuity-mars-helicopter.html) to fly in the low density and lower pressure atmosphere of Mars, the helicopter will have two rotor blades that will rotate much faster than they would need to if the helicopter were to fly in Earth's Atmosphere.
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I'm designing an alien creature that looks insectoid and had a question about compound eyes.
The creature is about human in size, maybe a little larger, but I'm wondering if there is a size limit on compound eyes?
I know with vertebrate eyes (camera-type eyes?) there is a limit as to how large the eye can get before getting bigger won't add any benefits and therefore they don't go beyond a certain size.
In my case, the alien has a mantis-looking head with large mantis-looking eyes and is roughly the size of a man. Would this scale up fine and be functional or would my mantis-man have weirdly small eyes for its proportions in order for its eyes to still work?
Also, my insectoid alien does not have an exoskeleton, not sure if that is an automatic deal breaker for compound eyes or not.
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Some types of flies, such as dragon flies have compound eyes that are [very large in proportion to its head](https://en.wikipedia.org/wiki/Arthropod_eye).
[Bathynomus giganteus](https://en.wikipedia.org/wiki/Bathynomus_giganteus) are extant bottom dwelling marine creatures that have [compound eyes that measure 18 mm](https://www.researchgate.net/publication/19414852_Morphology_of_the_compound_eye_of_the_giant_deep-sea_isopod_Bathynomus_Giganteus).
The largest compound eye, so far discovered, was 4 cm in diameter. This was for an ancient marine creature called a [radiodonts](https://theconversation.com/freaky-frankenprawns-ancient-deep-sea-monsters-called-radiodonts-had-incredible-vision-that-likely-drove-an-evolutionary-arms-race-146104). They lived during the Cambrian Period, 541 million to 485 million years ago. They resembled "[frankenprawns](https://advances.sciencemag.org/content/6/49/eabc6721.full)" and were up to 50 cm in length. Depending on the species, each eye contained more than 24,000 lenses. If they were scaled up to be human sized (200 cm), their eyes might have been 16 cm in diameter. That would be huge!
There also the issue of how much would a large compound eye weight and would a creature be able to move its head with very eyes. I'm tending to think that large compound eyes might not be achievable.
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Large compound eyes are completely possible. The main limiting factor of vertebrate eyes is they are hollow which makes them weaker the bigger they are. compound eyes however do not have this problem they are very structurally sound. the only reason we don't see large compound eyes is we don't have any large animals with compound eyes. You will have to stop and think about how a organism without an exoskeleton supports a large compound eye.
More likely it will have several [separate compound eyes like spiders](https://www.researchgate.net/figure/Variation-in-eye-arrangement-and-field-of-view-across-spider-families-A-Typical-eye_fig1_320342986) with minimal overlapping field of view from each "eye". The main benefit of a very large compound eye is a greater field of vision, but with a big head you end up with a lot of wasted "eye" since the angle between facets will be very small. Also having your whole head covered in eye is pretty venerable. So for a big animal smaller individual compound eyes are better.
there are several kinds of compound eyes as well, in trilobites for instance the individual facets are separate and not connected to each other. this can give you a bigger eye without having a ridiculous number of facets.
[](https://i.stack.imgur.com/Iq3sh.jpg)
You can also have spider style compound eyes which works a bit more like vertebrate eye.
[](https://i.stack.imgur.com/AmfQa.jpg)
[Answer]
Well, last question first - not having an exoskeleton is no problem, since some annelid worms (Sabellidae) have compound eyes -- which apparently are a case of convergent evolution, not directly related to the arthropod ones.
"They display a surprising diversity of eyes of varying levels of sophistication, ranging from scattered single ocelli to compound eyes with up to hundreds of facets."
<https://pubmed.ncbi.nlm.nih.gov/27453305/>
On the main question - I think it is not so much 'compound eyes only work when small'. It is more 'compound eyes are not terribly good in the first place, and for something human-sized the disadvantage becomes ridiculous'.
"To give a compound eye the same (about 1 arc-minute) resolution as our eyes would require millions of lenses each as large as a human lens." Visual Acuity in Insects, Land, 1997
IE - the eye would have to be *larger than an entire human body* to have equal resolving power.
This doesn't mean that small is better, though - I actually found a reference to a *minimum* size for the more efficient 'superposition' type of compound eye:
<https://www.sciencedirect.com/science/article/pii/S0042698904001944?via%3Dihub>
So if you want compound eyes for a human-sized creature, it might be best to make it something evolutionarily-recent and still pretty crude (like the annelid ones) for a creature whose *primary* sense is something else (e.g. echolocation).
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Quetzalcoatl is the main of the cultures from the center of Mexico, like mexicas, toltecas, teotihuacans and the maya equivalent Kukulkan, known by the popular culture as the feathered flying snake or just feathered snake.
<https://www.ancient.eu/trans/es/1-12086/quetzalcoatl/> (
My question is how you could have an anatomically accurate Quetzalcoatl (and if possible, one that has the "real" characteristics) but first I need to explain some things:
Codex and sculptures prior to the Spanish colonization shows something more like a mammal face with a mouth filled with teeth, meanwhile snakes, specifically rattlesnakes just have the fangs, have a squared head and face instead of the triangle head of the rattle snakes, frontal eyes position and a differentiation between the nose and the superior mandible. But still having the capacity of open the mouth like a snake for gobble up "preys". Some persons thought that looks more like a feline, like the jaguar. But even of that way could look more like a python than a rattle snake
Here a link with some precolonial art crafts showing that <http://mediateca.inah.gob.mx/islandora_74/islandora/object/objetoprehispanico%3A23896>
<https://www.mediateca.inah.gob.mx/repositorio/islandora/object/objetoprehispanico:16881>
[](https://i.stack.imgur.com/nfGjr.jpg)
2. Were the codex after the conquest in which the shape of the head changed radically and I know that the previous representation was not an error because coatl's (snake), representations from the same age showed a common snake, with only two fangs and a flat head.
Even in some current art Quetzalcoatl is showed more like an oriental dragon
[](https://i.stack.imgur.com/mI6gH.jpg)
3. Some persons thought that this myth was inspired by the flight of a quetzal during the sunset in which the tail feathers looks like a long snake tail from a flying creature, in the other side, criptozoology thought that legends like this could be inspired in "modern dinosaurs" (Im not talk about it because its a pseudoscience), natives seeing feathered reptiles or scaled birds, whatever, dinosaurs had feathers, wings and long rigid tails, even its not necesary a big size for create a myth, so we still having the problem of the mammal head and the leg-less appearence.
[](https://i.stack.imgur.com/1w9oC.png)
<https://www.youtube.com/watch?v=aIWFgLmV4sM>
4. If well were more recent representations which added the wings, following the idea of the quetzal inspirations is necesary take part from the mayan equivalent, Kukulkan, necesary for confirm that the feathered snake could fly, because the Chichen Itza pyramid is used for religious rituals during the equinox, in which the snake descends from the sky for fertilize the earth.
[https://mediateca.inah.gob.mx/islandora\_74/islandora/object/sitioprehispanico%3A1276#:~:text=En%20los%20dos%20equinoccios%2C%20la,capital%2C%20Patrimonio%20de%20la%20Humanidad](https://mediateca.inah.gob.mx/islandora_74/islandora/object/sitioprehispanico%3A1276#:%7E:text=En%20los%20dos%20equinoccios%2C%20la,capital%2C%20Patrimonio%20de%20la%20Humanidad).
[](https://i.stack.imgur.com/sN5uJ.png)
So the passed characterisitcs are necesary for be considered Quetzalcoatl. But we can consider two things more, in myths real stories are exagerated, so of you can imagine a Quetzalcoatl that can fly but its too little is valid, could size from 30 centimeters to a titanic size (titanoboa for example).
But also I currently made my try with this:
[](https://i.stack.imgur.com/ozLBc.jpg)
could evolve from one the Northamerican subfamilies of the family anguidae that also still having limbs, like xenosauridae, gerrhontidae or diploglossiade, so this new lizard specie started to losing its posterior limbs in a "semi-convergent evolution", with the other members like the celestus genre or the own asian crystal lizards, but keeping the anterior limbs for climb over the trees for scape for the rattlesnakes that rarely tries to search their preys over the trees.
<https://www.reddit.com/r/SpeculativeEvolution/comments/jwxo8j/quetzalcoatls_return_the_pseudophis_quetzalis/>
So, those are the requirements, and these are the optional features:
1. Have a way in which people could thought that are a man coming out of the mouth or be a hard tameable creature.
2. Be associated with high buildings or structures.
3. Be known as God of the wind, probably by a strong wings move.
4. Be related with a good agriculture.
5. Have a big size.
Please note that my first language is Spanish, so all the links are in Spanish.
(Edit). Thanks to the first answer to this question, I need to say that would be convenient if a creture like this could use its long tail for "fly" (or just something lile fly), if we follow the common path og pterosaurus or birds, its inevitable think that lose or reduce the tail is a constant on flying creatures, and if you want to answer, so, what would evit the lost of the tail?
And this is not principally an analysis of my own provided drawing, you can do that, but primary it is just an example of what I'm searching with this question
Maybe this question could be part of [Anatomically correct series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/).
[Answer]
The main problem with your interpretation is that the wings seem to be very far forward of the Centre of Gravity (COG). I'm not too sure of how it effects flight but it would make flight very difficult (and would be unlikely to be selected for). Your Quetzalcoatl would find itself constantly [tipping backwards during flight](https://aviation.stackexchange.com/questions/32271/why-should-the-centre-of-mass-be-ahead-of-the-centre-of-pressure).
Take a look at a plane for example:
[](https://justaplanegirl.files.wordpress.com/2015/12/abobh.gif?w=640)
The same can be observed in birds:
[](https://i.stack.imgur.com/cWoCk.jpg)
**Wings**
I would expect the wing membrane to attach much further down the body, probably attaching to the vestigal rear limbs (it may increase manouverability too). This is the case for bats and pterosaurs. This prevents the animal from tipping backwards while flying. Since your creature seems quite stocky, I would expect the feathers to be responsible for the outline whilst the actual skeleton and muscle is much smaller and thinner (look at birds without feathers).
Bat wings appear to beneficial for high-frequency, high manouverability flight which may limit your Quetzcoatl to fairly small sizes. A pterosaur-like wing would trade manouverability for size.
**Tail**
The long tail also has no aerodynamic properties. Given the snake-like body plan, I would expect the tail and lower torso to be somewhat flexible to allow for [horizontal undulation](https://en.wikipedia.org/wiki/Undulatory_locomotion). They could exhibit the concave structure seen in [gliding snakes](https://www.nature.com/articles/s41567-020-0935-4) but this might complicate the flight mechanics some. The more typical solution is to evolve some kind of fluke or rudder-like structure seen in [microraptors](https://www.prehistoric-wildlife.com/images/species/m/microraptor-size.jpg) and [dimorphodon](https://pteros-img.imgix.net/dimorphodon-macronyx_julio-lacerda.png?w=2000&fm=jpg&auto=compress) or on the heads of other [pterosaurs](https://cdn.mos.cms.futurecdn.net/FJHCgb2Pwk8qNgcnd6QBe3-320-80.jpg). This structure would aid in aerodynamics would likely result in a more rigid tail. This might result in more of a crawling method of terrestrial locomotion.
**Phylogeny**
A lizard lineage makes sense for a snake-like animal although an archosaur (or basal/close relative of dinosaurs may be a better candidate since it would posses genes much more likely to develop feather-like integument and pneumaticised bones (the latter being very useful to flight). I'm sure these traits could emerge convergently, it just makes it slightly more contrived. A high metabolic rate is associated with powered flight. You didn't seem to specify wether you're looking for powered flight or gliding so I am asuming the former, in which case, the metabolic rate also requires added steps for your lizard ancestor. Lizard lungs are also much more poorly adapted for flight as they compress in sync with their movement, which would not be the case for a winged creature. A dinosaur-like creature would negate this hurdle as well.
**Conclusion**
All in all your wing attachment points are probably the biggest problem. If quetzalcoatl is a primitive flyer then everything else seems somewhat plausible. It definitely feels too bulky looking at it but that can be explained by feather coverage.
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Quetzalcoatl could have evolved from a flying paravis. These creatures may have become fossorial. This could explain the elongated body/tail and lack of legs, with the wings remaining to keep it able to fly. The mammalian face could be caused by it evolving into a carnivoran-like predator, with strong jaws to kill prey. It may also be very large, as its wings may have become the main moving limbs, allowing it to grow large like pterosaurs. This trait may also keep it volant, as it seems that wing-walking fliers rarely become flightless
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Follow up to this question:
[What would prevent an eldritch deity from gaining the abilities of others that it absorbs?](https://worldbuilding.stackexchange.com/questions/188741/what-would-prevent-an-eldritch-deity-from-gaining-the-abilities-of-others-that-i?noredirect=1#comment583931_188741)
Nyarlathotep, the Black Pharaoh, seeks to enter the realm of Earth to rule over mankind. Unfortunately, he is prevented from doing so by a barrier that blocks eldritch deities from crossing over. To get around this, he breaks his soul up into thousands of pieces and seeds them into thousands unborn children. These kids become immortal avatars of Nyarlathotep called Nylanders, who do battle with each other over the centuries through one-on-one engagements to the death. When one is killed, the other "eats" the loser and gains their power and memories, absorbing them into themselves. When all pieces of the deity have joined, Nyarlathotep will become whole within one body and would be reborn on the mortal plane. In the end, there can be only one.
As each child is killed/destroyed, the remaining Nylanders gain that power equally. As the Nylanders are killed over the centuries, the rate of power absorption would increase each time, with the final two battling being the strongest of their brethren. These warriors also possess a piece of the deity's consciousness hidden deep within their minds. As the souls merge with each other, the collective consciousness of Nyarlathotep gains more self-awareness, regaining its memories and sense of self. The remaining warriors become more deity than human, until the final battle in which the full mind of the god emerges within the body of the winner.
However, as the collective consciousness emerges, it competes with the consciousness of the human it is apart of. The human mind was not built to have two psyches within one body. This leads to both minds battling it out, leading to different memories, attitudes and personalities colliding with each other. An analogy would be schizophrenia, a chronic disorder which affects how a person perceives and relates to reality. The resulting winners would risk being burdened with these mental conditions. As more of these individuals come together, they can spread their illness to the emerging whole, leading to the creation of an unstable god.
A crazy elder god is not good for itself or the world it plans to rule. How can this collective mind avoid this fate so Nyarlathotep can be reborn in full capacity?
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**I love simple questions**
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> These kids become immortal avatars of Nyarlathotep called Nylanders, who do battle with each other over the centuries through one-on-one engagements to the death. When one is killed, the other "eats" the loser and gains their power and memories, absorbing them into themselves.
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**Assumption:** Somewhat like in the *Highlander* stories, the kids are driven to find one another. Otherwise they start dying off before finding one another and the whole plan kinda falls apart.
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> As each child is killed/destroyed, the remaining Nylanders gain that power equally. As the Nylanders are killed over the centuries, the rate of power absorption would increase each time, with the final two battling being the strongest of their brethren. ... As the souls merge with each other, the collective consciousness of Nyarlathotep gains more self-awareness, regaining its memories and sense of self.
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What this means is that the possibility of madness occurs early in the process, when Nyarlothotep has the least amount of influence over the host mind. As his avatars are consumed, his awareness exerts greater and greater control, imposing stability.
The problem occurs with this phrase:
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> These warriors also possess a piece of the deity's consciousness hidden deep within their minds.
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This was in reference to the last two combatants. Simply put...
***No they don't.***
They can't and keep all your other rules consistent. By the time the last two are battling, they basically know exactly what's going on. There aren't two hosts battling for reasons they don't quite understand, unless you better define just how much the buried consciousness exerts itself at each step along the way, what we have are two aspects of Nyarlothotep itself doing battle.
**So, what's your answer?**
Since the madness can only occurs early in the process when the buried consciousness can't exert actual control beyond "find the others and kill them!" the problem is, oddly, *self-solving.*
The mad hatter would be sought out and killed by the others, resolving the conflict. Or, the madness would resolve itself with each death as the consciousness of Nyarlothotep exerts more and more control over the host mind.
*In other words, what you have is an amazingly cool story element that isn't actually a problem.*
***And finally, once again, when's the dang book coming out? You're killing me! I swear, if I don't hear about a publication date soon... I'm gonna hunt you down and beat you with all the plush bunnies I can find along the way!***
Whew! I'm glad I got that off my chest!
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## Not Schizophrenia
First of all, you are not describing the precursors of a schizoid mental disorder at all, but rather of a cognitive dissonance issue. Schizoid disorders are mental disorders where your perceive things that do not really exist, or you misperceive things that do exist. This can be in the form of Hallucinations like hearing voices, seeing apparitions, etc. or they can be less obvious Delusions which are misperceptions where you internalize fantasies as truth, like believing that the person on the TV is actually talking to you. That said, a person with schizophrenia typically has just 1 personality; so, you should not look to schizoid disorders to model your mental instability after.
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> The human mind was not built to have two psyches within one body.
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This is actually an untrue statement. Human experience is very complex, as such we routinely run into situations where we are either doing something that we do not agree with or we believe something that does not make sense with something else that we believe. This causes an internal conflict (cognitive dissonance) in our personality which psychology often described as being two selves at once. Lucky for your children, the human brain actually has a whole lot of tricks for dealing with these internal conflicts such that most of them will actually not go mad at all, but rather adapt to the emerging thoughts and beliefs of the god inside of them the same why we adapt to any new thoughts, feelings, or emotions that conflict with our personality as we transition through the normal stages of life.
### Standard coping mechanisms for cognitive dissonance include:
**Repression:** Forcing the new thoughts and feelings of the god to only be experienced in the subconscious, here the gods emerging thoughts and feelings will be forced to play out in your dreams and unconsciously in your behaviors that "you are not thinking about". So, you continue to live a normal and moral life, but at night you have nightmares about murdering your loved ones, or you start to do things the dark god would want to do "in fits of anger".
**Regression:** If the influences of the god on your psyche are to powerful and confusing, you brain can revert to a less mature state of being (when things were simpler) to ignore the more complex interactions that the god is trying to force on your mind. The dark god wants you to murder your wife, but you want to give her a hug... instead you have her pull your finger and fart because that is an easier manifestation of the problem to resolve.
**Projection:** Your retain your identity, but resolve how the dark god is making you feel by making up narratives about how other people are making you feel that way. So you tell yourself you don't suddenly hate your family, but now when your kids leave their shoes in a walkway, it is no longer a minor offences, but a personal attack against you that should be responded to with maximum punishment.
**Reaction formation:** You respond to the unpleasant thoughts and emotions of the dark god by doing the opposite of what it wants in an exaggerated way. So, the dark god wants you to murder your neighbors, and you respond by baking them a cake.
**Sublimation:** This where you simply learn to verbally express to the people around you that you are having conflicted thoughts and feelings. Here you accept that you are feeling ambivalent and operate out of that state of being. People capable of sublimation often find they have to think longer and harder than other people to make decisions because they have to maintain a conscious awareness of both sides of themself and weigh the pros and cons of their choices each time they do something.
**Change:** If the god's ability to exert his will on you grows too strong to push into any of the defense mechanisms, a normal person would not go mad, but simply change to accept the new feelings as his/her new self. So, you did not used to want to drown a bag of puppies, now that is a thing you want to do.
*Note: various psychological models on cognitive dissonance have actually identified dozens of different coping mechanisms, these are just the most common ones*
### Sometimes Borderline/Dissociative Personality Disorder
In most cases, your children will begin with using any combination of the 1st 5 methods listed above until the dark god's influence becomes so strong that they simply change their own personalities to match. But occasionally a person is so resistant to changing their personality that it results in borderline/dissociative personality disorder. This is distinctly different than schizoid disorders in that a person with a borderline/dissociative disorder will switch between personalities without retaining any knowledge of what their other selves are doing whereas a schizophrenic person would perceive the hallucination of someone who wants them to do something, but the hallucination has no direct control over their actions because the hallucination is a manifested fantasy and not a part of the person's personality.
So, if your dark god "drives a person mad", because of the way the human brain is already wired to deal with this sort of conflict, the person in question will begin to live part of their life as 100% themself, and the other part of their life as 100% the dark god. As the god becomes stronger, they will begin to spend more and more of their time as the god until their human personality becomes permanently repressed.
Either way, the final state is a perfectly normal mind (or whatever the dark god would consider normal) that has simply altered the brain until the human self is fully supplanted or fully accepts the new reality of the dark god's personality.
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**By slowly training the host to think like the Nylander inside**
The Nylander knows if it instantly exerts itself the host may not like who they are becoming and take measures to control it. That's bad for the evil elder god.
The fix - the elder god keeps their mind to themselves so to speak, and only helps the host when the host is doing something evil the elder god would do anyway.
It starts small
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> I beat up the bully and convinced all the witnesses to lie and say he
> fell down the stairs.
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but builds
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> I need this, so I'm gonna take it and threaten anyone who sees into
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Until
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> It's my world - I deserve it. No one can stand in my way.
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By the time there are only a few left, the host has been trained to think and act just like the elder god. Any human emotion has been trained out of them, and since the elder god and host share the same goals and values, they are quite happy to co-exist.
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In my world I need to create a city that permanently floats in the air. My idea was to create a sort of trading center where the dirigible-like airships in my world can dock and trade. Over the course of a few decades, people slowly started expanding the city ship by ship, building more permanent houses and even hotels from decommissioned ships that could stay in the air but not really fly. And piece by piece an entire flying city was built.
The city I have in mind has around a thousand permanent residents, but almost the same number of traders come and go everyday. The people who live there would be really wealthy traders who find it easier for business and regular townsfolk whose main source of income would be accommodation, food and other things for the people who come there, as well as a tax levied on all airships that dock with the city.
My world has no magic of any sort, and though the setting is a bit medieval, they have good technology (like steampunk technology, not computers and robots). An example of this technology is a giant condenser in the city that extracts moisture from the air to provide usable water for the residents.
Is this method of building a city even possible? If so, how big could such a city be (in terms of physical size and population)?
This is my first question on this site, so if I need to fix something please tell me in the comments and I will edit the question.
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That depends on some details of your world. As you said, there is no magic in your world, there are a few problems your city would face to stay up there.
**Foodsupplies**
Space on an airship is scarce. This city will depend on supply from rural areas below it. Every medieval city depends on whide areas farmlands but here you have to keep in mind that all those ressources, not just food but also wood for building/repairing and everything else has to brought up there. You need to think about a transportation system.
**space**
As already said, there is not much space up there. Citys like Cologne have a population density of roundabout 2600 Inhabitants per squaremile and some newer studies suggest that this density was not that much lower in medieval times. But in your floating city, you want to reduce that, as you would need more than a half squaremile for what you have in mind. Even if we consider every ship the city is build of about ten meters wide and 100 long (and ignore the fact ships are not square-shaped) the city is build by 500 ships to get it that big. Every ship the city is made of costs money to keep it staying up there and not rotting to pieces. You could reduce this problem if you implement some kind of Wood in your world, which is highly resistant to rotting (or can be made that by any known process).
**keeping it up**
Most steampunk-technologies for airships depend on keeping them floating by burning things. To keep a whole city in the sky you will burn a vast amount of fuel/wood/whatever. Some realy lightweighted building materials could reduce that, but it will be your biggest problem to solve. It gets even more difficult as you have to connect all those ships, because as this city shall be a trade hub you have to be able to move high amounts of goods on stable ways and don't want to rely on cranes and knitters for transport all the way through your city.
I don't want to say it is impossible to build and maintain this city, but you have to solve some problems within your world (which depend on Details I don't know atm) so it gets feasable.
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The main problem that you face is the fact that Earth is just not a good place for lifting things into the sky as there is limited buoyancy available for a given volume and a lot of cost and maintenance.
Changing the environment would make life a lot easier and since this has not been specifically ruled out in your question, I suggest changing the atmosphere to resemble Venus. Which might sound strange but it comes with some surprising advantages for flying cities.
On Venus at about 50 km above the surface atmospheric pressure is roughly 1 bar and the temperature is 0-50 degrees C. There is still roughly one Earth’s atmosphere equivalent above protecting from cosmic radiation. But the atmosphere is composed almost entirely of carbon dioxide which is very much heavier than air.
This means that a sealed airship filled with Earth air at 1 atmosphere would float and could carry considerable cargo as well. So no need for a tiny gondola slung underneath a huge lifting bag, no need for gondolas – just live in the lifting gas (Earth air) inside the envelope.
By adjusting buoyancy it would be possible to move up and down through various wind streams so navigation would be possible to some extent. On an imaginary Venus like world (adjusting the pressure and temperature and distance from the Sun etc) it might even be possible to land on some of the tallest mountains where all mineral needed for construction could be found. And for day to day living water could be extracted from the atmosphere as well as oxygen.
Such a city could grow to huge proportions and if allowed to move with atmospheric currents would not be subject to much stress. People could even work outside without pressure suits, but a mask and oxygen supply would be needed, small tears to the envelope would not lead to catastrophic failure and such a structure should be well within the scope of a steam punk type civilization.
<https://en.wikipedia.org/wiki/Colonization_of_Venus#Aerostat_habitats_and_floating_cities>
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Buckminster Fuller speculated on this as far back as 1960 with his "Cloud 9" Tensegrity sphere. The basic idea is to continually increase the size of a geodesic sphere until the mass of the air trapped within is greater than the mass of the structure (Fuller calculated that a sphere with a radius of 1320 feet would rise if the internal temperature were 1 degree f above the ambient temperature, essentially the largest hot air balloon ever. Obviously this is the "minimum" case, so would be unable to lift very much outside of the supporting structure.
However, increasing the size of the sphere increases the volume, so more lift will be delivered. Some calculations of the effect can be found here: [Can Cloud Nine be built?](https://worldbuilding.stackexchange.com/questions/36667/can-cloud-nine-be-built)
[](https://i.stack.imgur.com/ezX0n.jpg)
*Scale models of megastructures. The Cloud 9 floating on the upper left may be the size of some proposed arcologies, but only houses about 7000 people*
<https://www.atlasobscura.com/articles/vertical-cities-exhibition-yale-architecture-skyscrapers>
[](https://i.stack.imgur.com/LopaO.jpg)
*Cloud 9 to scale with existing skyscrapers*
The real issue isn't "can this be built", although even with 1960 era technology it would be somewhat questionable, but rather the economics and logistics of operating the thing.
Given that even the largest conceivable Cloud 9's on Earth would have a limited lifting capability, virtually everything will need to be imported, and the city will require some sort of high value product or service to export in order to convince people to sell them food, manufactured products and so on. Since the Cloud 9 is extremely massive but also quite delicate (much like an eggshell), high value products or services will be at risk all the time from threats of invasion to bad weather events.
So while it is "possible" to build a Cloud 9, you really need to dig into the worldbuilding to understand "why" this was built and "how" it is sustainable over a prolonged period of time. I don't know of anyone actually trying to work out the economics or logistics of supporting a flying city like a Cloud 9, and I suspect there would be a multitude of other issues, such as the immense shadow, airspace rights and even how or if it should be tethered to the ground.
I would also have to question the idea of traders willing to pay tax to dock at an intermediate port. As a Zeppelin captain flying cargo, it seems much cheaper to fly directly to and from the cities and avoid paying surcharges to load and unload cargo at a Cloud 9. After all, how do they plan to stop me? Unless there is a very clear advantage to using the Cloud 9 as a "port", which you would have to identify, it seems like a monumental "prestige" structure which would consume a lot of resources to build, but never really pay back on the huge investment.
So yes, if someone is willing to pay the price and the technology allows it, a geodesic sphere over a kilometre in diameter would indeed function as the basis of a flying city, and can remain in the air so long as the internal temperature is higher than the ambient air temperature outside the sphere - which might be possible through solar energy and waste heat of the people and equipment inside. On the other hand, paying for and sustaining such a structure is not going to be easy, and you will need to identify the clear and compelling reasons that people will go through all that effort.
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Recently, I had an idea for a story in which a [vacuum metastability](https://en.wikipedia.org/wiki/False_vacuum#Stability_and_instability_of_the_vacuum) event occurs.
Would it be feasible in any way for an advanced civilization to alter the universal constants to prevent this or save themselves from that event?
I thought about whether it would be possible to create a shell with a thickness of say 50 meters (arbitrarily chosen number) that would keep the expanding vacuum bubble from a zone or enclose the bubble by setting the light speed constant to 0 within the 50 meters of said shell.
Or is that too much of a stretch?
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**Bizarre scifi is great! The trick is how to make it into a compelling story.**
Universe-wide existential threat countered by godlike reality manipulation - ok. Somehow with that there needs to be a story. For example
* How do they know a metastable vacuum bubble is coming towards them at light speed? If they have FTL communication did that tech somehow produce the bubble?
* If they tap another dimension to contain the bubble, will they themselves wind up within this bubble? How does bringing the rules of a different dimension affect things that exist under current rules?
* If you can bend space Alcubierre-drive style you could do what you want, which is capture the expanding bubble in a region of space where light is a different speed because space is stretched thinner or thicker. It might be a big bubble by the time you were aware of it. It might be easier to trap yourself in your bent space and let the meta vacuum bubble pass you by and the rest of the universe dissolve.
I posited an idea like this: save yourself by enclosing yourself in a time dilation field. [What weapon of mass destruction could theoretically vaporize a whole solar system?](https://worldbuilding.stackexchange.com/questions/107564/what-weapon-of-mass-destruction-could-theoretically-vaporize-a-whole-solar-syste/107826#107826)
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We know too little of physics to know whether it is indeed possible to change the cosmological constants to defeat a false vacuum collapse (which, also, is just theoretical), much less determine *how* to do it.
In Egan's *Schild's Ladder*, the expansion of the Void cannot be thwarted, but it is possible to "reprogram" matter and *colonize* the Void itself.
One possible way to set up the effect you describe might be to build a dense shell of neutronium or hide *inside* a event horizon (the latter strategy, for different purposes, is described in the *Heechee* series).
You must take into account that our very existence is tied to most of those universal constants, so manipulating them on large scales would be both exceedingly difficult and tremendously dangerous. This is one of the plot points in the [*Duchy of Terra*](https://www.goodreads.com/series/184763-duchy-of-terra) series, where
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> it turns out that the Ancients, before known Galactic history, did change some of those constants on a galactic scale to vastly improve the efficiency of their stardrive. Unfortunately, one of the side effects was to kill most forms of life in the Galaxy, themselves included, until other forms of life could evolve that were compatible with the new constants.
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As for the expansion speed of the vacuum collapse, it's anyone's guess. The hypothesis that it would proceed at the speed of light is just this -- a hypothesis. Since it would be a *phase change* in the space vacuum, it could expand at any speed between zero and c. For instance, sodium acetate trihydrate crystallisation does not proceed at the speed of sound in water, but rather quite slowly (the speed of water freezing, which can be quite high, is actually a *phase* speed and proceeds usually at the speed of the wind. There's one extreme and possibly incorrect instance (*Hector Servadac: Travels and Adventures Through the Solar System* by Jules Verne) in which it is pictured proceeding at the speed of sound in water.
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A vacuum metastability event would propagate outward at the speed of light. Nothing moves faster than that, so no one would ever know that the event was coming. So even if manipulation of the universal variables was possible to thwart the expansion or reverse it, no one would know to even attempt such a thing because there's no early warning that the universe is unraveling. By the time anyone is affected by the problem, they already don't exist.
Even if you have some form of time travel, that still doesn't help you: no one would know, "Hey, I need to travel backward in time in order to stop this vacuum event from spreading," until it was already too late.
Therefore: no, there's no way to act to stop the vacuum expansion.
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If your question is about changing 'universal constants', then the answer has to be 'yes'. The only thing that keeps constants 'constant' is the human insistence that they can not be changed.
The uncertainty principle pretty much guarantees that these constants do change or at least could be changed.
If your question is about changing them in a specific direction to achieve a specific goal, that is currently unanswerable, which means that it could happen. However, if one bases an entire story on them being changed willy-nilly, then you end up with Hitchhikers Guide to the Galaxy, wherein anything is probable, and even more likely to happen the more improbable it is.
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**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
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This question does not appear to be about worldbuilding, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help).
Closed 3 years ago.
[Improve this question](/posts/167654/edit)
This is a submission for the
[Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798])
For 30 years T Yoshi Munchakoopas has been been helping Mario out in many adventures even reuniting him with his brother when they were infants.
[](https://i.stack.imgur.com/VfAgu.png)
The question I want to ask is what would an anatomically correct Yoshi be like?
Based on the available data, though, it is clear that Yoshi species:
* come in various colors
* Are large enough to be ridden, and strong enough to support the weight of a fat Italian plumber
* are 5.5 ft tall
* have a long chameleon like tongue
* exist in large herds
* can quickly lay egg like objects which they can use as projectiles
* can temporally propel themselves in the air by quick moving their legs
* are fairly intelligent
* can store juices which they can later shoot out
so what species would Yoshi have evolved from, and what evolutionary pressures would lead to such a species?
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Yoshi’s could actually be highly evolved snails that have acquired reptile-like traits through convergent evolution.
The little red thing on their back could have once been a snail shell, but as the animal evolved, it became vestigial, and is now only used as a saddle.
But the most obvious evidence of their ancestry would be their method of reproduction. Despite being called a male, Yoshi lays eggs, which is something normally only female animals do. This could mean that like normal mollusks, all Yoshi’s are hermaphrodities, possessing both male and female characteristics.
As for why a snail would evolve into a creature like Yoshi, it could be because of the hostile conditions of the Mushroom Kingdom, that would require the snails to flee from more dangerous predators, forcing them to develop legs for running.
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If I were re-creating Yoshi, I would have him evolve from chickens. Yoshi seems very dinosaur-like with his lower hip structure, as opposed to side-leg gait of a reptile.
Of course, birds are dinosaurs: they lay eggs, they "herd," someone tried to ride an ostrich at least once, and they are fairly intelligent.
They don't have the reptilian/amphibian tongue or the ability to Jesus-Lizard through the air, and of course do not spit (I looked up the [Dilophosaurus](https://en.wikipedia.org/wiki/Dilophosaurus) from Jurassic Park, but the spitting was pure fiction, the "only serious departure from scientific veracity" in the book).
If I were re-creating Yoshi, I would have him evolve from chickens who had to grow bigger, returning in form to their Dino ancestors. They lose feathers in the newly-warmed earth while keeping their relative stockiness, toughness, and massive egg-laying ability.
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Let's say Santa got himself a new toy: a present delivery cannon. With this new cannon, he wants to deliver presents to children by shooting their presents from the cannon into their chimneys. Let's assume the cannon has 100% accuracy with a "present protection" feature, where presents shot from it can travel the world and go into chimneys safely with 0 damage to the present or its surroundings (because Christmas magic?).
Santa now wants to just sit at home shooting out the presents. He only has 1 cannon though, so he can only shoot and deliver 1 at a time.
What kind of force and speed would the cannon need to deliver all the presents in 24 hours?
Edit: The present should safely land in the chimneys without causing any damage. I do not intend to make Santa a terrorist.
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# This approach does not scale
Every aspect of this cannon requires magic to work. There are just too many presents to deliver. Of course, this is the problem with how Santa operated before the cannon, and you've already said the cannon is magic. But the cannon is *so magical* that things like 'force' and 'speed' don't really make sense when applied to it.
### Number of deliveries
There are about [two billion](https://en.wikipedia.org/wiki/Christian_population_growth) Christians in the world. Very roughly a tenth of that number will be children receiving presents. The number of presents each child receives will of course not be constant (some children want one big ticket item, others want lots of smaller items) but let's assume the cannon's magical delivery protection allows Big Red to fire the cannon once and stack all presents for a given address into a single shot.
Let us further assume everyone lives in a place with a chimney. How many deliveries per person do we need? One per family is a reasonable approximation. We will assume a nuclear family of 4 people, 2 of whom need presents, all serviced by one delivery.
Yes, there are orphanages, hospitals, statistical outlier families with eight kids, etc. but there aren't a lot of them. They will roughly cancel single parent homes, families with one child, etc.
This means each delivery services, on average, two children. Our population estimate of two hundred million happy clients therefore works out to 100M deliveries.
### Optimal delivery strategy
Santa wants his cannon to adjust its aim as little as possible. This poses a similar problem as [seek time](https://www.techopedia.com/definition/3558/seek-time) for modern disc-based data storage. Probably the optimal strategy is to deliver presents in strips running from one pole to the other, north to south back up to north, etc, in line with the rotation of the earth. That way he doesn't have to worry about wild divergences in time zones.
Roughly, the rate should work out to approximately one time zone per hour. Regardless of where you are in the world, you can expect your presents to arrive at roughly the same (local) time (say between 2 and 3 AM) because as the cannon delivery pipeline finishes one time zone at 3 AM local time, it rolls over into the next time zone, where it is one hour earlier.
So that means (1/24)th of the total number of deliveries need to be made in one hour (3600 seconds), giving us a final answer of **approximately 1160 deliveries *per second***.
### Muzzle velocity
You can turn the firing rate of a cannon into a lower bound on the speed of its projectiles. The first projectile has to clear the barrel before the cannon's aim can be adjusted to allow the next one to be fired. Google says cannons were between 3 and 6 meters in length.
Making the most optimistic assumptions possible (reloading and aiming take no time at all, the barrel is the shortest length), the projectile still has to travel 3 meters in (1/1160)th of a second or less. This is a minimum of ~3500 meters per second - approximately 7775 miles per hour. *Mach ten.*
### It just doesn't work
Firing a cannon 1160 times per second is going to destroy the cannon. Adjusting its aim 1160 times per second isn't much better. Loading the cannon in less than a millisecond is just silly. You may as well just give up and say "It's a *magic* cannon, it works *very well*, thank you very much."
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What you envision won't work and will make Santa the most destructive terrorist of all times.
Reason for this is that to reach the far end of the world with a ballistic trajectory you will need to give your projectile a large initial velocity, in the order of few km/s. For the conservative properties of the gravitational field, that same velocity will be present at the moment of delivery.
Santa has a "present protection" feature, but no receiver protection is mentioned. This means that all the kinetic energy of the present will be dissipated by the receiver, with catstrofic consequences.
Think of what would mean to stop a cannon ball just to get a raw idea.
After your edit: still cannot work on a science based way. Science requires conservation of energy, but if you don't want to damage neither the gift nor the receiver you are violating the conservation of energy.
[Answer]
First, let us define the problem: Santa wants to deliver presents ballistically, launching them from a cannon to descend down the recipient's chimney, yet not leave a crater at each present's intended destination. Santa's presents - at least those that are traditionally deliverable - share one characteristic: they are human portable, meaning that they have a maximum mass of around 100kg, and linear dimensions that at most are around 3m maximum length, 2m in the next largest dimension, and perhaps 1m at most in the smallest dimension, though most will be considerably smaller. Any bigger, and Santa couldn't lift it to get it out of his old sack. The old guy is probably far more muscular than his suit makes him look, given that he can sling potentially large, heavy presents around with such speed and ease for 24+ hours at a stretch, so something that only a very strong human could grasp and lift alone would seem to be the upper limit to a traditionally deliverable present.
Additionally, while presents in Santa's presence are immune to the extreme speeds and acceleration involved in delivering so many presents in one night by sleigh, simple experience will show that many presents are *not* immune when away from Santa's presence, as a launched present must be. Some are very fragile, so we may assume a relatively low minimum g-tolerance of about 4g, the maximum that may be expected in a modern airliner.
So... TL,DR: A present has a maximum mass of 100kg, maximum dimensions of 3m × 2m × 1m for a total of 6 cubic meters maximum, and a g-tolerance which may be as low as 4g.
In order to propel a projectile as far as possible with the minimum launch velocity, over a small scale, a launch angle of 45° is optimal, but over a global scale, where the curvature of the world becomes a significant factor, such a launch angle is no longer optimal. Using a software package such as Systems Tool Kit (available as an online or downloaded trial at <http://licensing.agi.com/stk/>), experimentation shows that the optimal launch angle to achieve a minimum launch velocity sufficient to propel a projectile to the far side of the world is around 30° to the horizontal, and requires a launch velocity on the order of 5000 meters per second.
However, a g-tolerance of 4g is incompatible with any cannon with a practical barrel length that is capable of propelling a projectile to a velocity of up to 5 kilometers per second. How can this problem be overcome? The answer lies with the [Gyrojet](https://en.wikipedia.org/wiki/Gyrojet) range of guns: Gyrojet guns appear to be traditional firearms, however they do not fire traditional cartridges, but instead launch miniature rockets. While [Jules Verne's Columbiad](https://en.m.wikipedia.org/wiki/From_the_Earth_to_the_Moon) may have turned any real human crew into paste on firing, rockets have proved to be suitable for use with g-sensitive payloads such as humans. The Gyrojet sysyem launches its miniature rockets at a low velocity and acceleration, and they continue to gain velocity after launch, making it an eminently suitable system, if scaled up appropriately. So, Santa's "Present Cannon" may in fact be more accurately described as a cannon-shaped rocket launcher.
The logistics of packing, loading and firing all these Present Projectiles would be no less impressive than delivering all those presents by sleigh. If we assume a hundred million presents and on average 3 children per household (necessitating only one delivery for all of the children in that household), and Santa's cannon fires from the moment of dusk on the earliest Christmas Eve timezone as the first recipients go to sleep until just before dawn on the latest Christmas Day timezone, a period of around 34 hours, that works out to be 273 deliveries per second. Obviously, then, one launch must contain on the order of 300 deliveries if they are launched one per second with brief pauses to realign the cannon. This means that each launch - if we consider that the average weight and volume of a present may be on the order of 3.3kg and 0.033 cubic metre - must contain a payload on the order of 1000 kg and 10 cubic meters.
I leave it as an exercise for the OP to design a tube-launched rocket capable of lifting 1000 kg and 10 cubic meters of payload at 4g maximum acceleration and propelling it to a velocity of 5 kilometers per second.
So... Santa's "Present Cannon" would in actuality be a relatively thin-walled tube (compared to a real cannon firing similar sized projectiles) with a bore of around 3 to 6 metres diameter, potentially a hundred or more metres long, and with a complex autoloading and aiming mechanism at the base.
For the final part of our design of the projectile, we need to consider the delivery of the presents. Within each rocket would be a delivery pod, somewhat similar in purpose to the multiple independent reentry vehicles of a modern nuclear armed missile, that being to deliver the payload of one rocket to multiple targets. However, presents are not typically g-tolerant, and Santa wants to deliver intact presents, not impact craters. So, the challenge is to deliver the presents at a velocity significantly less than the potential 5 kilometers per second. Fortunately, the relatively shallow launch angle means that the angle of descent will be similarly shallow. While the cannon may be directed far more vertically, and the projectiles pitch over toward their target after leaving the atmosphere, in order to minimise the amount of air it must pass through, a shallow angle of descent increases the distance the projectile passes through the air. This is useful, since the delivery vehicles can use aerobraking in order to shed speed. By using a drag-inducing device such as a [ballute](https://en.wikipedia.org/wiki/Ballute), the speed of a supersonic object can be reduced in high atmosphere without requiring an ablative reentry shield. Then, once the delivery vehicle is subsonic, it can deploy a parafoil with which it can maneuver to dock with its target chimney.
Next comes the target: the recipient's chimney. As Santa has traditionally come down the chimney to deliver any presents, even in dwellings which do not normally include such a suitable architectural feature at any time other than Christmas Eve after the residents are asleep for the night, we may safely assume that the magic of Christmas ensures that each dwelling will posses a chimney large enough to allow Santa and the largest possible traditionally deliverable present to descend down it's length. Obviously, this is larger than any chimney found in a dwelling these days, so it forms a standardized target for the delivery vehicle to dock with.
Finally, presents delivered, the virtual chimney disappears, along with the delivery vehicle still attached to it.
Of course, this system would share another problem with nuclear missiles, that of interference between delivery vehicles. This can be minimised by targeting the most distant unserviced target on any given bearing so that subsequent launches result in the projectiles not passing through the descent path of an earlier missile or Delivery vehicle.
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My 4D world's equivalent of [Tiktaalik](https://en.wikipedia.org/wiki/Tiktaalik), the ancestor of all terrestrial endoskeletal animals, is a tetralaterally symmetric octopod with two limb girdles holding four limbs in the front and four limbs in the back. (Note that because this is in 4 dimensions, the planes of radial symmetry in which the limbs are attached are fully perpendicular to the plane formed by the spinal axis and the vertical axis.)
Among 3D animals, it seems pretty much universal for jointed limbs to have a joint with maximal freedom for the shoulder / hip (a ball joint for tetrapods, and a compound hinge joint for arthropods), then a simple hinge join that can only rotate in a single plane (i.e., an elbow or knee), and then variously complicated stuff for the terminal segment of the limb--i.e., extended tarsals/metatarsals than turn the wrist/ankle into an additional or reversed elbow/knee equivalent, all sorts of different foot/fin/wing structures, etc. But all the specialized stuff aside, you pretty much always see a maximally generic joint with the body, then one or two simple hinges.
It is easy to generalize that to 4 spatial dimensions. The only big change it that you need at least 4, rather than 3, muscle groups to control the full range of motion of the shoulder / hip joints. But is that actually the ideal structure for a 4D limb? Do we need full range of motion of the shoulder / hip in 4D, or can it be limited to a 3D range (being a hybrid between a hinge and ball joint that only exists in 4 dimensions) with only 3 controlling muscle groups? And if we do need the full geometrically possible range in the shoulder and hip, how about the elbow and knee? Can those remain simple hinges anyway, or do they need greater freedom as well?
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Let us consider the needs of locomotion in 2, 3 and 4 physical dimensions of a creature with legs walking upon an n-sphere.
The simplest situation is a creature in 2 physical dimensions walking upon the edge of a solid disk. Regardless of the number of legs, the greatest efficiency of motion is achieved with 2 or more legs, each leg having a foot joint that allows the foot to align with the surface, a knee joint that allows the leg to lengthen or shorten, and a hip joint around which muscular force may produce the greatest angular movement of the whole limb for the least effort.
In 2d, all three joints need only be simple hinge joints, as there is only one degree of freedom.
In 3d, the foot must be able to pitch, roll and yaw in order to place the foot on the ground properly. The hip must also be able to flex in two dimensions as well as being able to rotate. The knee joint still only needs to flex in one plane in order to shorten the leg, though that it flexes such that it can provide assistance to forward movement is a bonus of which many but not all creatures take advantage.
So, by extension, in 4d, the foot would need to be able to rotate in order to engage with the ground and the hip would need to be able to rotate to provide motive force in all three dimensions of the ground surface. The knee would still need to flex in a single plane on order to shorten the leg, and could be oriented to provide mechanical advantage to forward movement.
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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.
[Wikipedia states:](https://en.m.wikipedia.org/wiki/Electromagnetic_induction)
"Electromagnetic or magnetic induction is the production of an electromotive force (i.e., voltage) across an electrical conductor in a changing magnetic field."
This one sentence has baffled me and raised more questions than answers. As I would strongly prefer to not have to learn an entire field of science, I decided it was time to post a question on the topic.
**Is it possible to build a device capable of charging electronic devices by using the planet's electromagnetic field as an energy source?** Is there any situation in which this might be possible, even if unlikely?
Good answers will tell me why or why not this is possible, and a "electromagnetic induction for dummies" rundown would be appreciated as well.
Bonus points to someone who can calculate how strong of an electromangetic field a planet would need to make this possible. (if even possible)
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> Electromagnetic or magnetic induction is the production of an electromotive force (i.e., voltage) across an electrical conductor in a changing magnetic field.
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This is correct, but the operative word here is "changing". Specifically, Faraday's law states
$$\nabla \times \mathbf{E} = - \frac{\partial \mathbf{B}}{\partial t}$$
If you're not familiar with vector calculus, fret not! This equation basically says that the "twistiness" of the electric field is directly proportional to how quickly the magnetic field is changing. But twistiness of the electric field can set up a voltage in a conducting loop (well, technically it's an EMF, not a voltage), since a twisty electric field can push charged particles all the way around the loop.
But as I alluded to before, the problem comes from the fact that we need our magnetic field to be changing for this to happen-- if it isn't, the right hand side is zero and the electric field has no twistiness, meaning no EMF to push charges through our circuit. Now, while the Earth's magnetic field does change over time, it does so very slowly, meaning that even with a very large loop you wouldn't be able to power much.
Now, you might ask "well, the Earth might not have a field that varies quickly enough to do this, but what about other planets?" Sadly, the answer is still that it's infeasible. You see, magnetic fields have a property somewhat like inertia, in that they don't like to change. In fact, if an object has a changing magnetic field, Maxwell's equations predict that the object will act like an antenna and radiate away energy. As a consequence, most planets have relatively stable magnetic fields-- if the magnetic field is rapidly changing, it eventually slows down as energy is expended.
There are a few examples of astronomical bodies with high magnetic fields that quickly change, but they tend to be poorly suited to life and short lived. Some of the most extreme examples are [magnetars](https://en.wikipedia.org/wiki/Magnetar), which are neutron stars with magnetic fields about 15 orders of magnitude stronger than Earth's. By virtue of having strong fields that vary quickly thanks to high rotation rates, they emit a ridiculous amount of radiation. The fields tend to decay by about 10,000 years, which is the blink of an eye by geological standards.
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[Methanogenesis](https://en.wikipedia.org/wiki/Methanogenesis) is among the most energy-dense forms of anaerobic respiration. Typically, it requires the environmental presence of hydrogen to reduce CO2; however, hydrogen can be generated from glucose in [hydrogenic fermentation](https://en.wikipedia.org/wiki/Fermentation#Hydrogen_gas), which also produces some metabolic energy.
So, suppose we have an anoxic world where the animal-equivalents breathe in carbon dioxide instead of oxygen, exhale methane, and produce [acetate](https://en.wikipedia.org/wiki/Acetic_acid), [glyoxylate](https://en.wikipedia.org/wiki/Glyoxylic_acid), and [formate](https://en.wikipedia.org/wiki/Formate) (and possibly traces of a variety of other light organic compounds) as additional metabolic wastes; effectively, carbon waste ends up having to be excreted in (the equivalent of) urine a byproduct of normal energy-producing metabolism, parallel to the excretion of nitrogenous wastes from the catabolism of proteins and nucleic acids.
Given that oxygenic phototsynthesis must be suppressed (if it exists at all, it at least must be uncommon, 'cause the whole point is that we want animals to breathe CO2, not oxygen), what does the rest of the ecosystem look like, in terms of basic anabolic / catabolic processes? In particular, what are plants doing, given that CO2 is abundant, methane reasonably common in the air, and animals are pumping out tons of other simple organics along with the methane?
Edit: For reference, the net reactions for acetogenic, glyoxylogenic and formogenic catabolism of glucose are as follows:
$C\_6H\_{12}O\_6 → 2CHCO\_2O^- + 2H^+ + 2CH\_4$ Glucose ferments into glyoxylate and 2 methanes.
$2C\_6H\_{12}O\_6 + 2H\_2O + CO2 → 4CH\_3COO^- + 4HCOO^- + 8H^+ + CH4$ Glucose is hydrolyzed and oxidized by carbon dioxide to produce 4 acetates, 4 formates, and methane.
Note that the glyoxylogenic reaction actually doesn't consume CO2--only the mixed-acid acetate / formate pathway; this is because the CO2 used in the glyoxylate pathway is actually endogenously generated during the initial breakdown of glucose via pyruvate. That pathway would be the equivalent of our anaerobic respiration. Both pathways hide a bunch of complexity where hydrogen and sometimes endogenous carbon dioxide are generated along the way, before eventually all of the hydrogen is used up creating various small organics.
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If one thing is sure, you can't have plants in such ecosystem.
Plant as we know them expel oxygen as byproduct of photosynthesis, and as you state
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If there is any photosynthetizer, it would probably follow the inverse path of methanogenyc respiration instead of
CO2 + 4 H2 → CH4 + 2 H2O + Energy
they would do something along the line of
CH4 + 2 H2O + Energy → CO2 + 4 H2
To store the species so synthesized the pluricellular organisms would need bags (Earth plants produce sugars, which are solid and easier to store), which would make them appear like large bubbles.
[Answer]
**You have flipped the scenario currently in the sunny topside of earth.**
Here, animals breathe O2 and use it to oxidize the reduced carbon fixed by plants. The animals breathe out CO2 and hydrogen (as H2O).
Plants scrounge up scarce CO2 and with hydrogen (obtained as H2O) , use the energy of the sun to fix it back into reduced carbon, as carbohydrates.
Flipping this in your scenario, your animals take in CO2 and hydrogen and expel reduced carbon as methane. "Plants" (considered as primary producers) will presumably take up the reduced carbon as methane, scrounge up scarce O2 and use some ambient energy to reform the CO2. Nice that the reduced carbon here is methane; if you are a plant there are better odds of CH4 drifting into your vicinity than glucose.
In your scenario the reduced carbon is methane; in ours we generally eat carbohydrates. It is all reduced carbon.
I think the trick is how much O2 is available. Prevalence of O2 will tip the balance one way or the other, as it presumably did in the early earth and still does in anaerobic / microaerobic environments.
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**EDIT: After looking more into the energetics, CO2-breathing probably won't work with glucose as an energy storage molecule. Some other energy-storage system that has more hydrogens available to liberate may still allow CO2 breathing, but if we stick with glucose, a methanogenic biosphere ends up quite different.**
It turns out that decomposing an/or reducing acetic acid is actually more efficient than reducing carbon dioxide... so glucose-eating animals using hydrogenic fermentation would not need to breathe CO2 after all. Cf.:
Acetoclasis: $C\_2H\_4O\_2 → CO\_2 + CH\_4 + 28 kJ/mol$
CO2 reduction: $CO\_2 + 4H\_2 → 2 H\_2O + CH\_4 + 17.4kJ/mol H\_2$
In fact, CO2 reduction is the very last phase of methanogenesis in terrestrial decomposition, after all other organic substrates are consumed.
Instead, you get a purely-fermentative metabolism that ends up shuffling hydrogens around internally, after some water-consuming hydrolysis reactions, to produce formic acid and methane. The high-level reactions are as follows:
Glycolysis: $C\_6H\_{12}O\_6 → 2 C\_3H\_4O\_3 + 4H$
Pyruvate cleavage: $C\_3H\_4O\_3 + 2 H\_2O → C\_2H\_4O\_2 + H\_2CO\_2$
Acetic acid reduction: $C\_2H\_4O\_2 + 2H → H\_2CO\_2 + CH\_4$
with the final fermentation products being 4 formic acids and 2 methanes.
Meanwhile, "plants" can construct glucose directly from methane and carbon dioxide, but only the methane gets regenerated by animals. So, rather than an oxygen crisis, this world ends up with an acidification crisis as CO2 and water are used up and replaced by formic acid and even more methane, and plants have to switch over to consuming formic acid instead of CO2 (via the reaction $2 H\_2CO\_2 + CH\_4 → C\_3H\_4O\_3 + H\_2O + 2H$, followed by re-assembly of pyruvate into glucose) and producing water as a byproduct of photosynthesis. In our world, bacteria use up energy to selectively decompose formic acid into CO2 and hydrogen to control pH, so that might limit the extent of an acidification crisis... but it would be a thing that sessile autotrophs "waste" energy on to ensure their survival, not something animals would bother doing most of the time... although replacing acetic acid reduction with acetoclasis (resulting in excess hydrogen production) in high-exertion situations where there isn't time for proper acid waste disposal might result in some atmospheric hydrogen buildup. On a small world, that would probably eventually lead to a much-delayed mass-extinction-causing oxygenation event as hydrogen is lost to space, but on a larger world it might result in the eventual conversion over to a more "traditional" hydrogen-breather ecology.
**Original Answer:**
Alright, having contemplated this some more myself, here's what I've come up with:
Glyoxylogenic fermentation can be pretty much ignored. It's a red herring. Insofar as how it interacts with the broad autotroph/heterotroph cycle, it's analogous to lactate-producing anaerobic respiration on Earth; it's a stop-gap method of energy production, and when oxidizers become available again, glyoxylate will get cleaned up through a variety of further reactions.
If we start out with a world in which both CO2 and methane are reasonable abundant, then building glucose from those materials is really cheap ($3CO\_2 + 3CH\_4 → C\_6H\_{12}O\_6$). That should allow rapid autotrophic growth, limited only by availability of other essential nutrients, which will pull gasses out of the atmosphere until either CO2 or methane become a limiting factor.
If we suppose that methane is the limiting factor, then there will still be lots of primordial CO2 still floating around that can be used in the proposed methanogenic respiration pathways to oxidize glucose. This world will therefore never have the equivalent of the "oxygen catastrophe". What advanced animals breathe will be remarkably similar to the original primordial atmosphere.
As heterotrophic life develops, though, the environment will instead be flooded with simple organic acids--primarily acetate and formate. That doesn't affect the atmosphere overly much, but it does affect the oceans and the rainfall. Conveniently, acidification can result in the release of even more atmospheric CO2, as carbonate is extracted from minerals; and microbes or fungal-like organisms with access to alternative anions could in fact use up formic and acetic acid as hydrogen sources to produce water, methane, hydrogen sulfide, etc. along with formate and acetate salts.
Much like with our oxygen crisis, though, geological mineral reservoirs capable of absorbing organic acids will eventually run out, and they'll start building up.
With methane levels being kept low by efficient autotroph absorption, eventually it will become more preferable to start using the abundant organic acids as a carbon source instead.
Conventiently, acetic acid (presumably through a complicated serious of intermediate reactions) can be rebuilt into glucose without any net external inputs, through the simple formula:
$3C\_2H\_4O\_2 → C\_6H\_{12}O\_6$
Getting glucose from formic acid is more complicated--it's got too much oxygen in it. It can be broken down in two ways, however, giving water and carbon monoxide, or CO2 and hydrogen:
$CH\_2O\_2 → CO + H\_2O$
$CH\_2O\_2 → CO\_2 + H\_2$
Which can be recombined to give formaldehyde, water, and CO2. 6 formaldehyde units ($H\_2CO$) form a glucose, so we get the net reaction:
$12CH\_2O\_2 → C\_6H\_{12}O\_6 + 6H\_2O + 6CO\_2$
which regenerates atmospheric CO2 for animals to breathe.
So, we end up with a rather complicated cycle in which "plants" consume acetic acid, formic acid, methane, and carbon dioxide to build hydrocarbons, producing water and carbon dioxide as byproducts, while "animals" consume glucose, water, and CO2, and produce acetic acid, formic acid, and methane as byproducts. Note, however, that the consumption of methane by "plants" does not result in the production of extra CO2--rather, they are consumed in a one-to-one ratio. When an "animal" uses up CO2 to oxidize glucose, the methane that results does not go on to be recycled back into CO2--rather, all of the CO2 that animals need is regenerated from their liquid waste formic acid.
Now, although the actual step-wise reactions are more complicated, we can actually separate out the production and consumption of acetic acid as its own independent cycle:
$C\_6H\_{12}O\_6 → 3CH\_3COO^- + 3H^+ → C\_6H\_{12}O\_6$
and, like glyoxalate, disregard it when considering how CO2 and methane are exchanged, which provides us with simplified equations to demonstrate how ecological equilibrium is maintained. In the CO2 metabolism, each molecule of glucose is oxidized by a single CO2 in conjunction with hydrolization by 2 waters, producing 1 acetic acid, 4 formic acids, and 1 methane, as follows:
$C\_6H\_{12}O\_6 + 2H\_2O + CO2 → CH\_3COO^- + 4HCOO^- + 5H^+ + CH4$
As indicates above, it takes 12 formic acids to produce 1 new glucose molecule, so tripling this gives us the following glucose cycle:
$3C\_6H\_{12}O\_6 + 6H\_2O + 3CO2 → 3CH\_3COO^- + 12HCOO^- + 15H^+ + 3CH4 → 2C\_6H\_{12}O\_6 + 6H\_2O + 6CO2 + 3CH4$
Note at the end that the total CO2 production by "plants" during formate-based glucose anabolism is twice as great as methane production by "animals" during methanogenic respiration. Thus, one more step (using the primitive CO2+methane glucose production pathway, eliminating all of the methane) gets us back to the beginning, with an excess of 3 CO2s left in the atmosphere for "animals" to breathe.
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Say we have an intelligent species whose body plan is inspired by walking insects (ants, beetles, etc.) and reptiles (particularly lizards).
More specifically, let's say they have four legs (I think they'd have things a bit easier with six, so I'll ask the four-leg case, because if it's solvable, six legs also should be) in a sprawling posture. Their legs don't come from the 'corners' of the torso like a vertebrate; their hips and shoulders are closer together, more like an insect (again, to make this the more difficult case). They're smaller than humans (exactly how much not defined at this point). Like an insect or a gecko, they're good climbers. In their case, all feet can grip, and thus they can use them interchangeably as hands. Like most of the animals that inspired them, they have a wider field of vision than a human, which probably helps when doing things with their back feet. They're more like a reptile than an insect insofar as their mouths aren't adapted for carrying things. And no, no prehensile monkey tail.
So, while they have the manipulatory ability to do various tasks and use tools, they seem to have some disadvantages to developing tools and civilization. How do they deal with...?
While they have hands, they don't have *dedicated* hands. They cannot walk on two legs. Stable standing requires at least two diagonally opposite legs, so other than when sitting / lying down (which are the same thing for a non-erect species), they can't pick up more than two things at once, and using two hands to pick up one object is difficult-to-impossible. Most critically, they can't spare a foot to use as a hand while walking. Moving on two legs is impossible, three is slow and awkward at best.
Their sprawling posture and limited ability to even rear up usefully (shoulders are close to hips) means they can't reach much above themselves. More critically, they can't reach their own backs. Thus, righting themselves if they land on their back is difficult; if they don't have something to grab for leverage, it may be impossible. This also makes their problem carrying things even worse, because while they can carry large loads on their backs, they can't place an object there unassisted!
So, how will their development of tools, transportation, and so on, differ from ours?
(I've seen [Could These Two Types of Reptiles Overcome Carrier's Constraint?](https://worldbuilding.stackexchange.com/questions/61722/could-these-two-types-of-reptiles-overcome-carriers-constraint) and [How could my non-bipedal intelligent species advance technologically?](https://worldbuilding.stackexchange.com/questions/86861/how-could-my-non-bipedal-intelligent-species-advance-technologically) Neither question or answers address exactly this situation.)
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Tool use (a prerequisite for developing technology) comes in all shapes and sizes:
Corvids wield sticks with their beaks.
[](https://i.stack.imgur.com/LGr4S.jpg)
Attribution - Science news
Some animals have developed specialist tools from their given attributes. An Aye-aye, "drinking" an egg using it's specially adapted finger. To be fair, the finger is more adapted for winkling out grubs from under bark.
[](https://i.stack.imgur.com/yutrZ.jpg)
Attribution Getty, via Telegraph.co.uk
Perhaps your creatures walk on their elbows of their fore-limbs, maybe using a [dewclaw](https://en.wikipedia.org/wiki/Dewclaw) that's migrated further up the limb to there, to aid with grip when climbing.
[](https://i.stack.imgur.com/TxqSe.jpg)
Attribution - laughingsquid.com
This would enable their fore-limbs to be free for tool use, perhaps aided by their mouth/beak, or perhaps even [pedipalps](https://en.wikipedia.org/wiki/Pedipalp), like spiders use which aren't limbs, but comprise part of the mouth-parts.
[](https://i.stack.imgur.com/6XegO.jpg)
Attribution - arachnipedia.fandom.com (sic)
To address the **civilization** part of your question, what is required is **[cooperation](https://en.wikipedia.org/wiki/The_Evolution_of_Cooperation)**, there are many theories about how it might have evolved, to do with child raising, education (ie. passing on of knowledge) and hunting, none of which stand alone. It seems that several characteristics of a species synergistically function to enable the evolution of a civilization. The linked wiki article should provide you with some context. Without copying and pasting the whole thing, I can't see another way to cover the breadth of the question without forum blow-out.
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The obvious answer is "they'd evolve grippers" and possibly "they'd evolve bipedal locomotion". After all, the distant ancestors of humans were quadrupeds, and yet modern humans are able to do things like touch-typing so it clearly hasn't held them back.
If you can't hold, carry and manipulate stuff whilst moving you're not much of a tool user, and if tool usage is useful in an evolutionary way (it seems to have been for humans) then you'll end up evolving away from a bodyplan that hinders tool use.
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A climbing species that can't self-right after a fall does not sound like a species which will evolve intelligence.
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Here are some alternatives to hands, following the example of CBBF.
Here's a splendid example of a partially-uplifted quadruped with non-grasping feet using tools:
[](https://i.stack.imgur.com/mTZn7.jpg)
There are of course other kinds of [muscular hydrostat](https://en.wikipedia.org/wiki/Muscular_hydrostat) that might be adaptable:
[](https://i.stack.imgur.com/D1Cmv.jpg)
Why not have a prehensile tail? Have another chameleon:
[](https://i.stack.imgur.com/QW5mj.jpg)
A tail is a useful thing in a climbing species, and given that it can be used as an extra limb for locomotion it would be very useful for moving whilst holding things, either by itself or by freeing up a gripper on another limb. Howler monkeys use their tails to provide support whilst foraging using their hands, for example.
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Ants and dolphins also manage with their mouths. And speaking of ants, how well do they work together? With a little cooperation, every individual having just one "hand" is hardly a hindrance.
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**This question already has answers here**:
[Why might humans and aliens be able to produce viable offspring? [closed]](/questions/122130/why-might-humans-and-aliens-be-able-to-produce-viable-offspring)
(6 answers)
Closed 4 years ago.
I had an idea for a planet which, millions of years ago, was accidentally contaminated with various animals, plants and microbes from Earth, and - via the planet's native aliens' bizarre reproductive biology - the two independent lineages hybridized and produced fertile descendants.
**Is there any conceivable reproductive mechanism, however alien, which could allow these organisms to interbreed with Earthly ones?** One of the first problems is that of DNA - however, it's not statistically *impossible* that it would be used by the aliens too, coincidentally. Or maybe you can think of a way to do it without DNA.
One very hazy idea I had was something loosely based on the reproduction of lysogenic viruses, so you can try that if you want, but I didn't expand on it much more.
**EDIT:** In response to a comment on L.Dutch's answer; horizontal gene transfer, though not technically interbreeding, is fair game, as is any other method which produces chimeras rather than true hybrids.
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Life on Earth reproduces using nucleic acids (DNA or RNA). Thus a prerequisite for this to happen with an extraterrestrial life form is that it also used nucleic acid.
On Earth bacteria are able to exchange genetic information among them, regardless of their species, by exchanging plasmides. Think of them like "macro" which serve specific scopes (i.e. degrade an antibiotics molecule to make it non toxic) and which can be executed under different software.
Most of the times, when it happens with higher life forms, genetic instruction can be executed (that's how bacteria and viruses infects), but rapidly removed from the system, either by healing or by death of the host. Sometimes they are kept and transmitted.
If somehow your alien has:
* capability of taking genetic sequences from the outside
* capability of integrating at will said sequence in its own nucleic acid and executing them
* capability of not destroy the carriers of the imported sequences
then it becomes viable that the alien organism, after importing and embedding genetic sequences from an other organism, becomes a chimera and, upon reproducing, transmits those sequences to the offspring.
Mind that the second bullet can backfire if not controlled properly: you don't want to embed the genetic material of everything you eat, for example.
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Something to consider are aliens roughly akin to something like [Tardigrades](https://en.wikipedia.org/wiki/Tardigrade), which are both cool and freaky. They are believed to have *survived the last five mass extinctions*. They can survive in crazy conditions, even temporarily in dead space.
Ignoring the title of [this article, it states](https://www.iflscience.com/plants-and-animals/tardigrades-didnt-steal-16-their-dna-other-organisms-after-all/)
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> In the case of these tardigrades, when they're dried out, their cell membranes are often broken and leaky. This allows DNA from the environment to sneak inside, allowing them to make it part of their DNA when they rehydrate and repair themselves. It’s possible that it’s this successful DNA acquisition that’s allowed them to become so adaptable to so many environments.
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In such a situation, blood or other sources of human DNA could "leak into" the dried Tardigrades. When they re-animate, so to speak, the human DNA would be integrated into them, and therefore replicate during reproduction.
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**Hybrid: 2. a thing made by combining two different elements; a mixture.
"the final text is a hybrid of the stage play and the film"**
Is it possible to make a "hybrid" creature which combines prokaryotic and eukaryotic methods of handling DNA? Or a hybrid which combines evolved fungal and algal elements? Yes - this is possible via symbiosis. Mitochondria are prokaryotic organisms that developed a symbiotic relationship with ancient eukaryotes. It is possible to accidentally kill your mitochondria with antibacterial antibiotics. Lichens are ancient symbiotic organisms combining elements of fungus and algae. In both these situations, the symbiote cannot exist without both partners.
A stable symbiosis sidesteps very different methods of handling the genome, DNA, cellular housekeeping or what have you. In a symbiotic relationship, earth beasts keep ours and aliens keep theirs. But we move in together and work together for the common fitness of the symbiotic organism. Perhaps an earth creature takes up alien symbiotes that interface with the cells and organs of the earth creature. Or vice versa: an alien creature picks up commensal earth creatures which contribute to the alien creature's fitness.
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The alien has a complex hybridized reproductive and immune system. Using reproductive cells (or not) from the donor female or male, it uses stem cells to systematically copy the host cell(s) thousands of times for systematic evaluation. It randomly splices segments of its own DNA into the host's cell. The alien checks if the cloned organism is a viable, healthy being (capable of sexually reproducing like either the host or the alien itself). What's a healthy, viable being? The alien DNA has a complex corpus of "match" and "reject" sequences that show if a certain genome is likely to produce a viable offspring. By transcribing RNA from the cloned DNA, then matching those RNA sequences from the alien's corpus to the candidate zygote, the immune system will reject or keep that particular copy. Polybirth is common.
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My story takes place in a medieval/fantasy setting. The main part plays out on a locked-off island with a fairly uniform population I'd call Asian to keep this question to the point (look Asian and have those genetics, but of course there is no Asian continent nor culture in that world). They keep to themselves, but of course there is some interaction with the outside world, mainly a nation of seafarers (Caucasian face shape, mostly varying shades of blond, blue or other very low-melanin eyes, white or freckled skin).
What I am looking for is, in a setting that has a very 'pure' racial background (in this case, an island largely locked of from the rest of the world), how would I describe the visual characteristics of children with a mixed background, aka if someone four generations down was rumored to have had intercourse with an 'outsider', what characteristics would they most likely show that people could point at to prove their point? I'd go by simple Mendelian genetics, which is what I learned in school, but the traits most easily describing a human (hair, eye and skin color) are sadly a bit more complicated in their inheritance, which is the core of my problem.
Another question in the same setting: With how melanin (eg. skin/eye/hair color) inheritance goes, how would a condition like albinism affect genetics? Albinism in itself is recessive and would disappear if 'bred' to a healthy partner. But what if the partner is fair skinned, blue-eyed and blond?
In context: There is this young woman, an islander (Asian characteristics), who is an albino. She's carrying the child of one of the seafarers (blond, blue eyed, freckles).
Would the dark hair and eye color the albino mother would have had without her condition 'return' in the absence of the albinism, or would the child still be paler than its already light-blond father? And, if she marries an islander, would she be able to pass the child off as his (the man himself is completely informed and supportive), assuming the general public (villagers, gossipers, you know the kind) is not too knowledgeable?
Edit: I deleted the first part because it was misleading. Also edited the last part and added more context to hopefully be more clear.
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* *[A] young woman, an islander (asian characteristics), [...] is an albino. She's carrying the child of one of the seafarers (blond, blue eyed, freckles). Would the dark hair and eye color the albino mother would have had without her condition 'return' in the absence of the albinism, or would the child still be paler than its already light-blond father?*
Albinism won't carry to the child; the child will look as if they were the child of a non-albino islander mother and a foreigner.
I've never ever heard of a first-generation inter-racial child looking entirely like one of the "races" of their parents. The vast majority of human phenotypical characteristics are polygenic, so that in the first generation inheritance appears to be blending.
Most likely the child will exhibit a typical Eurasian phenotype, that is, their eye shape would look intermediate between Europoid "wide eyes" and Mongoloid "slanted eyes", their nose would be intermediate between their father's and their mother's. The hair may be blond(ish) or black(ish), and its texture will most likely be like their mother's and not silky smooth as their father's. They will most likely have freckles (which are usually the manifestation of a dominant allele). Likely the child will grow to be taller than the islanders. The child may or may not have blue eyes; the most likely outcome is typical human brown eyes.
Skin tone is much more complicated. First of all, the skin tone of most East-Asian people is well within the normal variation of the skin tone of "white" people. I have met people from central Asia and China whose skin tone was if anything *lighter* than that of most Europeans. (Not as light as the stereotypical Swede, but definitely lighter than the stereotypical Greek.) Second, even in countries populated by stereotypical pale northwesterners, people with darker skin tone exist and have always existed.
* *And, if she marries an islander, would she be able to pass the child of as his?*
Basically any Englishman will most likely be able to tell that the child is Eurasian and any villager will be able to tell that the child has foreign blood. What's interesting is that it is likely that some *their* children or grandchildren or grand-grandchildren will show blue eyes, or blond(ish) hair...
But...
1. Humans exchange genes at each and every opportunity. It may be the case that the sea-faring Englishman is carrying East-Asian genes -- maybe from the Huns, or from the Mongols, or from who knows what ancient migration. So it is *possible* (although not likely) that instead of showing a typical Eurasian phenotype the child will look closer to a typical East-Asian, just maybe taller, or with a little wider eyes than usual, or with a nose a little more protruding than usual, or with hair less lustrous black than usual.
2. The pure East-Asian populations are purely mythical, as are the pure [North-West Block](https://en.wikipedia.org/wiki/Nordwestblock) populations. There are occasional blue eyes in Afghanistan, and occasional blond and even red hair in China, and didn't the Ainu population of Japan look pretty much like Europoids, with wide eyes and curly brown hair and bushy beards?
In all human populations children are occasionally born showing characters not typical for the area. For example, in Romania we have a Hungarian-speaking population, the [Székelys](https://en.wikipedia.org/wiki/Sz%C3%A9kelys), whose distant ancestors came from central Asia more than a thousand years ago: and to this day some Székely children are born with almond eyes (which we find quite attractive).
The point being that it may be perfectly possible to explain some of the physical attributes of the child as a throwback to one of the grandparents or grand-grandparents of the woman or her husband. Oh, they have curly hair like the barbarian bride the grand-grandfather of the woman brought back from that epic battle! Oh, their eyes are steel-blue like the father's great-uncle had, and they are tall like him too!
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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.
An interstellar traveller stands upon the surface of an alien planet beneath the light of an unfamiliar sun. The planet upon which he stands orbits one star of a binary system in which one is a G-class yellow dwarf and the other is an M-class red dwarf.
While they are indeed orbiting their common barycentre, the stars are sufficiently distant from one another that the red dwarf companion does not interfere with the orbit of the planet, nor does it contribute sufficient insolation to affect the planet's climate.
My question is this: How close must the companion star be for it to appear noticeably more prominent in the sky compared to background stars?
(My assumption here being that at a certain distance a red dwarf will simply blend in with the stars behind it.)
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A really bright early M-type main-sequence star (something like M0V spectrally, [Lacaille 8760](https://en.wikipedia.org/wiki/Lacaille_8760) being a good example) might have a visual absolute magnitude of around +9. While I don't know *exactly* how bright you need this star to be relative to the background, I think a good requirement would be that it is visible during the day, which isn't true of any non-Sun stars visible from Earth and might stand out as unusual. This occurs at an *apparent* magnitude of about -4, which is also about as bright as Venus.
The equation relating difference in absolute magnitude *M* and apparent magnitude *m* to distance *d* (in parsecs) is:
$$5 + (m-M) = 5\*log\_{10}(d)$$
so the distance to the red dwarf star we need to achieve this is about 0.025 parsecs, or just over 5,100 AU. (This is well over one hundred times the Sun-Neptune distance, for comparison — as far as I know, this shouldn't cause any stability problems in the system whatsoever.)
If you have a fainter star, you need to move it proportionally closer — quartering the intrinsic visual-band luminosity of the star will drop its distance by a factor of two.
If you want the star to appear brighter, an increase in brightness by one magnitude requires the star to be $\sqrt[5]{100}$ times as bright, which mandates a reduction in distance by a factor of $\sqrt[2.5]{100}$ or about 6.3.
At some point, one or both of these factors will bring the star too close to the inner system to keep it stable, but for your purposes it can probably be quite a long ways out.
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I am currently working an a magic system that involves Photokinesis. However, I am having difficulty understanding its limits and its capabilities.
[Visual example](https://i.stack.imgur.com/rB89A.jpg)
The best definition for this type of magic comes from [Fandom](https://powerlisting.wikia.com/wiki/Light_Manipulation):
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> Light Manipulation - The user can create, shape and manipulate visible light, commonly referred to as light, is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight.
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> Primary properties of visible light are intensity, propagation direction, frequency or wavelength spectrum, and polarization, while its speed in a vacuum (299,792,458 meters per second/186,000 MPS) is one of the fundamental constants of nature. Visible light, as with all types of electromagnetic radiation (EMR), is experimentally found to always move at this speed in a vacuum.
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> In common with all types of EMR, visible light is emitted and absorbed in tiny "packets" called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality. The study of light, known as optics, is an important research area in modern physics.
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The area I am having an issue with is how any kind of light can affect matter, like a small rock.
Question: Can light manipulate matter in any other way beyond its temperature? Can light move matter, like it does with DC's Green Lantern's ring?
The capabilities and limitations of this Magic ability are important to me, because the magic system I am making is supposed to follow the laws of physics as closely as I can make it.
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Given enough light, enough protection, and the right conditions, light can move objects. Consider the [solar sail](https://en.wikipedia.org/wiki/Solar_sail), which can move objects not unlike a sail boat. Or any of the questions asked on this site about [laser ploughs](https://worldbuilding.stackexchange.com/questions/103155/how-well-will-interstellar-ploughs-work) (laser trains/freight/etc), where a substantial laser beam is used to move cargo.
It's worth remembering that all electromagnetic radiation is photonic. Or, said another way, it's all light. Radio waves are a form of light.
So, yes, it's "doable" (in that we can mathematically model the theories... none of this is reality). However, considering the affect of the [solar wind](https://en.wikipedia.org/wiki/Solar_wind) on Earth's [magnetosphere](https://en.wikipedia.org/wiki/Magnetosphere), it's not beyond belief.
*Keep in mind that you're trying to develop a magic system, which is 100% fictional, and keep it as closely related to physics as possible. We get these questions from time to time. Obviously, magic having nothing at all to do with physics, there's ony so much you can do to achieve this goal. Remember to be flexible and creative. Your story is often more about how well you write or present your ideas than it is how fact-based it is.*
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There are recent discoveries that points to the possibility of photons interacting with each other to form "bounds", so hard-light may not be too far fetched.
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> It’s a glimpse of science fiction made fact: Scientists have created a new form of light that could someday be used to build light crystals.
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* <https://www.smithsonianmag.com/smart-news/scientists-link-photons-and-create-new-form-light-180968184/>
Does this photokenisis extend to only visible light, or does any EMR count? There are many uses of radio waves, for example. You could interfere with communications or see through walls ([this video](https://www.youtube.com/watch?v=fujdEiRR-K8) explain how X-ray vision wouldn't work, but WiFi radio vision would). With infrared, you could get thermal and night visions.
Depending on how closely related to electricity this all is, photokenisis and electrokinesis could be essentially the same power, but I don't know if you want those two to be separate entities.
If all else fails, photokinectics could be walking flashlights and flash-bangs.
Edit: After researching more about the topic, like Logan said, 'light crystals' are not actually solid. I should warn you, there are many "scientific" articles out there that made the same mistake as I did when describing a light crystal, so always check for the source. Hopefully the article was still helpful to you.
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[Pulse laser powered propulsion](https://www.youtube.com/watch?v=LAdj6vpYppA) has been around for a while aspects going back to the 1950s.
For the [Lightcraft](https://en.wikipedia.org/wiki/Lightcraft) to work lasers or masers (microwave versions of the same thing) are focused:
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> to **heat the air** at an extremely high temperature up to 30,000 degrees,
> transforming it in a plasma that violently expands .... acting as an
> external pulse detonation engine producing thrust.
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Emphasis mine.
I see no reason that your characters could not work hard on their ability and learn to create intense focused pulses of light to manipulate objects. Plus there might be a cool TszszszsT sound to accompany it.
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I see a lot of historical and fictional illustrations of walls that do not have wall walks. My understanding of medieval tactics is largely based on cinema and *some* wikipedia, so as far as I know a wall is mostly only good for standing on top of, to fend off attackers using ladders. In my mind, when I imagine a wall without a wall walk, I see people scaling the wall with ladders, with the defenders in a courtyard now in a lower vantage point as people pour over from above. This seems less than ideal, so I assume I'm missing something.
Does a wall without a wall walk only serve as a very preliminary defense, or a privacy screen, rather than a defense against a true raid or invasion (or anyone with a ladder)? Or is there some other tactical advantage that I'm missing?
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It depends on who or what you are defending against.
If you are trying to defend against an army in an area where wood is common, I agree that you need a wall walk.
However, there are situation where just a reasonably tall wall is useful:
1. You are just trying to keep out the local wildlife. The wall is
enough to deter most of them.
2. You only have to worry about small bands of bandits. The wall not
only makes it harder for them to enter but then they have to get
back over the wall with whatever they grabbed. It's not foolproof
but it might get them to try for easier targets. Also, presumably,
by the time you have enough to be a good target, you will have
enough for a better wall.
3. There is little wood around. In desert areas, it may be too
expensive to build a large number of ladders.
4. You are just interested in slowing down the enemy. If you have the
high ground (the top of a hill), you can build walls on the hill
that will slow down charges and give your archers more time to pick
them off.
5. To channel attacking infantry into kill zones. Somewhat an
extension of the of the one above. The Japanese used these a lot,
making infantry make several sharp turns to get to the gates,
slowing down the charge and making them easier to deal with.
6. Slow down siege equipment. If they need to breach walls to get
their equipment to you, it gives you more time to prepare.
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Would it be possible for a human to survive on a diet of modified yeast as seen in many fictional stories? Not necessarily be able to get perfect nutrition from, or live healthily on, but simply live off of.
This is usually some kind of raw yeast grown off of sewage or some such. An example would be Dole Yeast in Larry Niven's "Known Space" series. But this is meant to cover the concept of yeast as a bare bones food in general.
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The fungus *[Fusarium venenatum](https://en.wikipedia.org/wiki/Fusarium_venenatum)* is used as the basis of the meat substitutes marketed under the [Quorn](https://en.wikipedia.org/wiki/Quorn) brand. To be nutritionally complete such foods would need serious [fortification](https://en.wikipedia.org/wiki/Food_fortification) which can be done either artificially during processing using synthesised vitamins or possibly with a little genetic tampering the fungus could be altered to produce the necessary compounds.
So I'd say yes a yeast based diet is almost certainly possible.
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According to the [NHS](https://www.nhs.uk/live-well/eat-well/what-are-reference-intakes-on-food-labels/) in the UK healthy eating guidelines for the average UK Citizen are:
* Energy: 8,400kJ/2,000kcal
* Total fat: less than 70g
* Saturates: less than 20g
* Carbohydrate: at least 260g
* Total sugars: 90g
* Protein: 50g
* Salt: less than 6g
This varies dependent on several factors including age, height, weight, gender etc but a baseline average is the above. there are also a huge number of different vitamins and minerals that are needed but i haven't stated them as it would make this answer approximately 600 miles long...
According to Wikipedia the average nutritional values of Yeast per 100 grams are:
* Calories 325
* Total Fat 8 g 12%
* Saturated fat 1 g 5%
* Polyunsaturated fat 0 g
* Monounsaturated fat 4.3 g
* Cholesterol 0 mg 0%
* Sodium 51 mg 2%
* Potassium 955 mg 27%
* Total Carbohydrate 41 g 13%
* Dietary fiber 27 g 108%
* Sugar 0 g
* Protein 40 g 80%
* Vitamin A 0%
* Vitamin C 0%
* Calcium 3%
* Iron 12%
* Vitamin D 0%
* Vitamin B-6 75%
* Vitamin B-12 1%
* Magnesium 13%
The % are compared to the daily recomended intake, as we can see that 100 grams of yeast doesn't provide enough calories, so we'd need about 600 grams, this would put us still below on several factors but it doesn't appear to provide an excess of anything harmful. namely Salt and Saturated Fat. too much fibre which would definitely be provided can cause issues however. so actually its not *that* bad a resource if it could be harvested in sufficient quantities. the parts that do provide too much are mostly vitamins and minerals that the human body would just use what was needed and "dump" the rest.
After that its just the other missing vitamins and minerals, some of which are provided in water, The others would need to be provided in some form of supplement form to provide a reasonable diet.
It would most likely be nothing more than a bland cruel but it could indeed be lived on. after that its only the fibre that could be an issue, perhaps some of this could be removed in the refining process.
**Extras**
Vegetable extract products like the Glorious and beautiful tasting Marmite are also of interest as they have been fortified with other vitamins to provide a healthier sandwich spread.
Although i will admit its probably not to America taste, just go on YouTube and search Americans try Marmite and you'll see what i mean. its one of those Love or Hate foods, i am very much in the former grouping.
**TLDR: on face values it could be survived on although it wouldn't make you happy**
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So on a planet with a chlorine based atmosphere and only a small amount of oxygen, here is my proposed mechanism for chlorine based photosynthesis.
Carbon tetrachloride, since it is a liquid at 70 degrees Fahrenheit or 23 degrees Celsius, needs to be absorbed through the soil mostly though some does come from the air. HCl vapors and HOCl vapors are also absorbed into the black leaves. The leaves are black because since Chlorine absorbs UV and violet and blue light, all that is left for the plants is the range from red light to green light. As a result, they evolved a black pigment to absorb as much as they can of this light.
This also means that the plants get hot because they absorb a ton of infrared and then release some of it. So animals have evolved infrared vision to find these plants in the dark.
But anyway, back to what I was saying about photosynthesis.
HCl and HOCl are both hydrogen sources, HOCl is an oxygen source, and CCl4 is a carbon source. 6 of each are required to make 1 glucose. I haven't figured out exactly how this occurs but the black pigment that makes the plants get hot and release some infrared definitely helps this process by absorbing a lot of energy which can then be used to split the chlorine off of these molecules.
So you get this equation for chlorine based photosynthesis:
${6HCl + 6HOCl + 6 CCl\_4 + light -------> 1 C\_6H\_{12}O\_6 + 18Cl\_2}$
Cellular respiration would essentially be the reverse of this except that the energy would be in a different form. So is this a plausible form of photosynthesis for plants adapted to living on a planet with a chlorine based atmosphere or is there a better alternative that still produces the glucose and chlorine but requires less energy for it to happen?
[Answer]
**I feel like oxygen is kind of crashing the chlorine party here.**
On our world, oxygen is the readily available oxidizer and carbon is the energy currency. CO2 is the maximally oxidized carbon and CH4 the least oxidized. Some creatures oxidize CH4 to CO2. Eukaryotic life uses partly oxidized carbons like sugars and fats and alcohol - presumably because it is easier to handle metabolically. Glucose makes sense in an oxygen world. Alkanes or aromatics would also be good fuel - and are good fuel for internal combustion engines.
I think that in a chlorine world, chlorine should take the place of oxygen altogether. The chlorine analogs would be chlorocarbons not terminally chlorinated like carbon tetrachloride - chloroform, dichloromethane. You could make a long chain of these with chlorine hanging off, like a chlorine fat. You could not close a ring with chlorine like you can with oxygen.
I like the idea of a chlorinated aromatic filling the glucose role.
[](https://i.stack.imgur.com/6u94w.jpg)
A molecule like tetrachlorobenzene would be stable and would have loads of energy to be released on chlorination back to carbon tet.
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**This question already has answers here**:
[Is a planet with a primarily reddish/pinkish sky a plausible place for humans to live on?](/questions/42426/is-a-planet-with-a-primarily-reddish-pinkish-sky-a-plausible-place-for-humans-to)
(2 answers)
Closed 5 years ago.
I recently came across a planet that I found pretty interesting but I can't seem to find much information about its characteristics. Its atmosphere is pink in appearance. After looking at the picture a bit, you can see that the pink hue couldn't be caused by the color of a gas in the atmosphere because that would make the planet appear slightly opaque.
[](https://i.stack.imgur.com/8G4lN.png)
On earth, when sunlight reaches its atmosphere, it's scattered in all directions by all the gases and particles in the air. Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves.
**So If the same process happened on this planet, what gases in its atmosphere could scatter light to make the atmosphere pink in hue when the parent star is behind it?**
I didn't make this picture. I didn't add anything to it before posting this question. From what I found, this picture was created by a google plus user named Lerne Seref
If I need to change anything about this question, let me know.
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**The magenta is a sunset as seen from space.**
In situations where the light that comes to your eye is not direct from the source, that light is scattered or bounced off of the medium it is traveling through. The more the light scatters and bounces, the more of it can change path and make it to your eye. Short (blue, indigo, violet) wavelengths scatter and bounce more. That is why the sky is blue - it is lit indirectly and more of the blue bounces back down to your eye. That is why water is blue - of all the light entering the water, the short wavelengths come back out to your eye.
(I just realized this phenomenon explains why a pure note whistled in a stairwell will echo slightly sharper! Woo!)
The converse is true for a sunset or sunrise. The light is coming straight at your eye from the source. When coming through an atmosphere, shorter wavelengths scatter away but the long wavelengths (reds) punch through whatever is scattering the light and keep going. That is why sunsets are red and smoke / dust make redder sunsets.
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The planet - I conclude it is being lit from behind and we are seeing the equivalent of a sunset refracted around through the atmosphere. The refracted light has travelled a straight (although refracted) path and so is redder. Some of the blue is still present scattering back which tints the red towards magenta. You can sometimes see this in the sunset.
[](https://i.stack.imgur.com/veM9D.jpg)
<http://lightexhibit.org/bio_image80.html>
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> At sunrise and sunset, light from the Sun must take a much longer path
> through the Earth's atmosphere than it does during the middle part of
> the day. This means more of the blue and indigo light of sunlight is
> scattered away because these shorter wavelengths of visible light are
> more affected by air molecules in the atmosphere. This often allows
> more of the red and orange light to reach the Earth's surface. Other
> factors -- including dust, pollution, haze, and cloud formations – may
> also affect the colors of a sunset, creating a more complicated
> palette of light as the Sun dips below the horizon
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What a great picture. I think it is unmodified because they are using it as exactly the example I want.
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Being pedantic - I do not think we would see the illuminated swath at 10 oclock if the only available light were such as to produce the magenta sunset effect. I conclude that this celestial body must have 2 light sources - one illuminating the top left and the other almost completely behind the body, refracting around the edge as the sunset. A star and large reflective moon could team up this way.
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When Mt. Pinatubo erupted the sky and sunsets were noticeably pinker than usual, although this won't be the driver of your photo. Similar phenomena were reported after the 19th century eruption of Krakatoa. If you really want a pink atmosphere, though, you could have a world with substantial volcanic activity maintaining levels of dust in the atmosphere.
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The most probable cause of the pink is artistic licence since this is not an unadulterated picture of a real planet.
Alternatively and very unlikely is that it is part of an eclipse where the light from the star is pink. In which case it's extremely badly drawn.
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A CO2 atmosphere scatters longer wavelengths of light than our Oxy-nitro atmosphere, and the suspended dust particles make it even redder.
In the case of this image, if taken from the Earth, the "atmosphere" could easily be an artifact of Earth's own atmosphere, and the colors an artifact of diffraction. I have also seen this effect when viewing the moon through a telescope on a clear summer evening, due to a combination of optics and atmospheric diffraction.
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I'm attempting to create a world that has very brutal, hard swinging weather and environments, leaving much of the planet desert-like. The world I've designed is a moon of a gas giant.
## The Parent Planet
This planet is a gas giant orbiting a sun smaller and cooler than our own. It's closer than the goldilocks zone of this star, so it is quite warm. It has a wide band of rings, and a single moon orbiting closer to the planet than the rings.
## The Moon World
The moon is earth sized, not tidally locked, and experiences days similar in length to earth days, and its orbit is about 40 of these days. Most of the year, due to the rings, this planet has a band at the equator of essentially arctic tundra, never seeing sunlight. However, due to the axial tilt of the parent planet, and the moon's slightly erratic orbit, each hemisphere spends a quarter of the year (Each year being about four orbits, or 160 days) more and more in the shadow of the rings, making for one very, very cold orbit (-40F, -40C at night). On the other side of the year, with one hemisphere out of the shadow of the rings entirely, the surface becomes blazing hot, reaching regular temperatures of 120F (49C) During the day. During the other two orbits, with some shadow from the outer rings, temperatures are more stable and around 80-60F (27-16C) high and 60-40F (16-4C) low.
## Question
Is this proposed moon possible? Would it act how I expect it to? If not, can I fix it? Bonus points for pointing out any cool and unexpected visual effects.
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> **(In answer to the [original question](https://worldbuilding.stackexchange.com/revisions/ca879376-f7a0-41ab-aedd-a09acbb59b85/view-source): *Is it possible to have a planetary moon closer than rings?*)**
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**It doesn't really make sense.**
Rings and moons aren't unrelated features that just happen anywhere around a planet. Rings are what happen when a moon is too close to its parent planet, i.e., when it is inside its [Roche Limit](https://en.wikipedia.org/wiki/Roche_limit)
It's *theoretically possible*, if you had a really, really dense moon (e.g., pure osmium) orbiting just inside the rings that resulted from a really, really light moon (water ice), but it would be a very contrived situation.
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So... the moon's existence might be possible given the planet's own position and composition. But for the smaller details like the tidal lock and the temperature, I'm not so sure about.
Planets form from leftover debris from the formation of a star; rocks and solids usually orbit closer to the star as further out the gravitational field would be too weak to lock them in orbit. However, gas giants can only form within the larger clouds of gas and ice further out as only there are the materials abundant enough to make them 'giant'; like the gas giants within our own solar system.
There would have had to be some kind of push from another celestial body to nudge it that close to the star.
And yeah, there's a precedent for this happening:
<http://hubblesite.org/hubble_discoveries/discovering_planets_beyond/how-do-planets-form>
So now you need a large celestial body to give a gravitational nudge to the planet. And there you might be able to explain some of the rings; some pieces from a nearby asteroid belt were thrown away by its gravitational field and nudged it ever closer to the star while others were trapped in the field and began orbiting it as rings.
The moon could be what's called a "Shepherd Moon"-- one that orbits in the very inner or outer circle of the rings. After some more research I don't think it's possible for a moon to form any closer than the shepherd moons in the rings (which keep them from clumping and collapsing onto the planet), there's a lot that can happen in space and the possibility it could occur might be very unlikely but still possible with some extreme circumstances and a bit of glossing over.
<https://www.iflscience.com/space/how-saturns-shepherd-moons-herd-its-rings/>
<https://physics.stackexchange.com/questions/26643/why-arent-saturns-rings-clumping-into-moons>
<https://en.wikipedia.org/wiki/Ring_system>
It's not the best explanation, but this could suffice as a placeholder until something better comes along.
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# There is no 'shadow of the rings'
Saturn's majestic A ring is 10-30 meters thick; overall the rings of that planet range from 10 meters to 1 km thick.
The asteroid belt is a 'ring' around the Sun. That, too, is not dense enough to block the sun. In [this answer](https://worldbuilding.stackexchange.com/questions/123819/could-an-astronaut-in-a-near-future-space-ship-survive-transit-through-our-aster/123841#123841), I show that if the asteroid belt was ground down into particles 100g in mass, each particle would have 1530 km$^2$ of space to itself; each particle would be about 14 km from the next particle.
Rings just aren't thick enough to create an appreciable shadow.
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So I've been working on a low magic world where magic is actually just another form of energy that can be actualized, similar to alchemy in Full Metal Alchemist. Although development has taken a different course in this world, it resembles a late middle age to pre-industrial age period in time.
This world is slightly more dangerous than ours, with monsters running around here and there which may become a great pay day for an adventurer commissioned to clear it out, or a threat that jeopardizes an entire town despite them rolling out the entirety of their guards to stop it.
Among the various races and creatures that are in this world, I have one that still needs help figuring out. I would like to have slimes included as part of my fantasy world. I want slimes to work on a principle of acid digestion, in which stepping on one or having one latch onto your foot may compromise your leg, the bone in it, or even your life. They get to have the nickname "Farmers Bane" and are known as a threat to unsuspecting people who step on them.
So far I've envisioned my slimes as a type of extremely large protozoa, either single celled or a colony. When stepped on they encapsulate the foot and release a strong acid which greatly impacts the creature that has stepped on it. In particular, it's best if they can cause bone failure which has a potential for incapacitating their prey. Then, small deposited forms of the slime grow using the prey as nutrients once the flesh in the area is dead, or devouring the entire creature to form new cells if possible.
My question is simply this: **Can a creature exist that can use hydrofluoric acid without destroying itself, and what kind of structures would it have?**
I thought maybe a silicone based organism would work, but I don't know enough about chemistry to understand how hydrofluoric acid can or cannot react with something, and whether or not that something could be a living being.
I have other less important questions that I would love answered if the above is possible:
* Is it possible to have a single cell organism that functions in this way, or does it need to be multicellular? (Or symbiotic with another organism)
* Does chloroplast react to hydrofluoric acid?
* If flesh is broken down by hydrofluoric acid can it still be used as nutrients?
Or if the above is impossible:
* What are possible substitutes for hydrofluoric acid that I can look in to?
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Hydrofluoric acid is not actually that acidic (pKa of HF*aq* ~ 3 vs. pKa of HCl*aq* ~ -6). The main issue for, well, most multicellular creatures on earth really is that it can easily penetrate tissue and bind with Calcium in our blood and nervous system. Calcium Fluoride is highly insoluble in water. This effectively leaches out Ca2+ ions from the body which can lead to serious medical problems and even death (read about HF burns starting at e.g. [the wikipedia article](https://en.wikipedia.org/wiki/Hydrofluoric_acid)). Also; HF*aq* releases gaseous HF which can cause heavy eye irritation and blindness by attacking the cornea.
If your slime's biochemistry does not rely on Calcium (or Magnesium) you should be better off. The problem is that [most fluorides are poorly soluble in water](https://pubs.acs.org/doi/pdf/10.1021/ie50227a024). You're basically limited to small cation compounds (basically only Sodium. Lithium binds strongly) or some fancy metal-ligand binding of your metals in the slime's proteins.
If, however, your slime is not inherently water based, you might be better off. I could not find any studies about solubility of HF in solvents other than water (short of one rather dubious mention of it not being very soluble in liquid butane...), but from experience may I suggest something like methanol/ethanol (leaning towards he former)? They are both highly polar and will for certain support large dissolved concentrations of HF. The things to worry about then are: evaporation and environmental water leaching into the slime. The first is going to be a problem with slime design either way, and the second could be dealt with in a similar way to which many creatures living in slaty environment deal with large salt concentrations - actively removing it from the slime's body. Maybe some thick-yet-malleable skin on the slime which deals with both the evaporation of it's body and houses water pores? [Polivinyl alcohol](https://en.wikipedia.org/wiki/Polyvinyl_alcohol) gloop e.g.?
Non of this of course touches on the most important part of the design: **Why would a slime have an evolutionary need for HF in it's body(?) and how would it get it's (in this case) nutrient fluoride?** These are your questions to answer, but if all you need is a tough enemy and not necessarily a species, then the easiest way to solve all these problems is to go with a "normal" water-based slime who's biochem is only very loosely based on insoluble-in-fluoride-form ions. The slime has been roaming under a chemical factory (or equivalent thereof in your world, e.g. in the swamps surrounding the age old tavern - *The Alchemist's Refuge*) and thus has absorbed a large amount of HF*aq*. The slime is slowly dying and is therefore enraged, at least to whatever degree the state of the slime's consciousness allows.
Edit:
Also; further to your comment: Even a large amount of HF does not act fast. It usually takes a day or so for the symptoms to arise. The prey could just wander away after stepping into the slime unless otherwise constrained.. If you want to paralyze or disable living creatures there is a plethora of easy to make in cell nerve agents / fast acting poisons and toxins.
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Our stomach uses hydrochloric acid for digesting whatever we eat. And, as you might notice, the stomach doesn't digest itself in the process (not in healthy subjects, at least).
This happens thanks to a layer of mucus covering the layer of the stomach in contact with the acid solution, therefore the same solution can be used by your slime, which also happens to be slimy, to it fits the character!
Not all the substances are digested by the acid alone, if I remember correctly lipids need a different environment to be broken down. Otherwise, the broken down molecules are exactly the expected outcome of the digestion.
In principle the same adaptation could be used with hydrofluoric acid. However, the main reason for not using hydrofluoric acid is that it is the weakest of the acids having an halogen: its acid dissociation constant is 11 orders of magnitude lower than hydrochloric acid. So, in light of this your slime could be easily outcompeted by other slimes using hydrochloric acid.
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In the National Geographic mini-series *Extraterrestrial* or *Alien Worlds*, they featured a hypothetical gas giant moon called the Blue Moon. The Blue Moon orbits a binary star, has a very dense atmosphere with lots of carbon dioxide and oxygen, and a slightly lower gravity than Earth.
The Blue Moon's landscape is dominated by giant plants called "pagoda trees":
[](https://i.stack.imgur.com/h9K30.jpg)
Instead of drawing up water from the ground and having to pump it upwards, the pagoda trees collect rainwater in "sky-ponds", and are interconnected so that they do not collapse. Because they can just let gravity do its job, they can grow very high, up to 1 kilometre in fact.
My question is: **Could trees that collect water like this grow to be 1 kilometre tall? Are there any other inaccuracies or implausibilities with these plants, perhaps in relation to the atmospheric conditions given?**
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Bromeliads are a group of plants which gather water in much the same way as these pagoda trees. You can see the central tank with water in this image.
[](https://i.stack.imgur.com/PM4yu.jpg)
<https://homeguides.sfgate.com/bromeliads-brown-90776.html]>
<https://en.wikipedia.org/wiki/Bromeliaceae#Adaptations>
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> 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.
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Bromeliads need to do this because their use their roots to hang on and that is about it. I could imagine on a rocky substrate where there was no possibility of finding water, the ancestors of pagoda trees would spread out laterally and catch water like a bromeliad. Just as for photosynthesizers a small height advantage means shading your neighbor / eating his lunch, so too a slight height advantage would mean catching water before it landed on your shorter neighbor. There ensues a race to the sky, as with rainforest trees.
Why would the trees interlace and "cooperate"? Maybe it is happenstance. Or maybe huge patches of these pagoda trees are actually a single organism - a huge multitrunk organism like [Pando](https://en.wikipedia.org/wiki/Pando_(tree)) the giant clonal aspen tree(s?). In the latter circumstance one might see a small no-man's land between individual clones because unrelated trees cannot interconnect.
Super high trees in low gravity / dense atmosphere world - why not? A cool thing would be if the trees used floats like giant kelp. Buoyant structures full of some lighter gas would be neat. Maybe these trees sequester atmospheric argon and use it for their floats.
No mention is made of energetics; I will assume that to be outside the scope of the question.
I see in the image there is some vaguely cthluloid critter perched on the edge of one of the trees. That tree top must be made of stern stuff to not tip at all with that thing on it.
Bromeliad tanks are full of life. The bromeliads must have some adaptation to discourage mosses and other freeloaders that want that water, but frogs and crabs and all sorts of things hang out in the fresh water. So too the pagoda trees.
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Life is very varied, and if anything teaches us about life on Earth it is that anything is *possible*, but this is different to being *probable*.
My question would be: How would such plants evolve? What did they evolve from?
Presumably the events that have occurred on the Blue Moon is the same events of that of Earth - a spark of single celled life, invention of photosynthesis (and thus plants), a great Oxygenation event and perhaps sexual reproduction to push evolution to its current state through sexual selection, and a symbiotic balance of perhaps animals and other carbon dioxide producing mechanisms to create an environment of stability in which advanced species like this could evolve.
Considering it is a plant, presumably it is using photosynthesis to grow. This would normally then be green, not blue, and indeed blue light is not an efficient light for photosynthesis to be an efficient method of converting carbon dioxide to carbon.
It is true that capillary action from the ground limits the height of trees, access to water top down would reduce this impediment. A kilometre is a long way though, one would expect stability to be a major issue (especially for the first) - I would not expect this likely unless gravity and wind is a lot less.
Also, not sure of the utility of the elevated lily ponds evolutionarily, besides that of obstructing your neighbours access to light to give you the best advantage possible. However if this was the case, others would grow taller to compete with you, I would expect the plants therefore to be jostling and quite varied in heights, eventually reaching an uneven, but dynamic, loose equilibrium (much like the Congo in Africa).
Evolutionarily, there would be a varied and divergent series of other species either along the way or in parallel, these would also compete for light too. Like the Congo, it would result in a morass of different colliding species, for which this would be only one.
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It depends how tree like these trees actually are but potentially yeah that could work. Trees on Earth have a vertical growth limit which is pretty much the maximum height of the biggest trees currently around, the [giant sequoia](https://en.wikipedia.org/wiki/Sequoiadendron_giganteum), 130m. Beyond that water costs more energy to raise than what the plant gets from the leaves/needles that the water supports, but it's not a limit based on structural strength. Structurally, at least in theory, there is no growth limit; so with top-down water sourcing it could work for large structures that are biochemically identical to Earth's trees if they were big enough. It'll work even better with something a bit less Earthly, a tree that uses silica as a tissue stiffener could have far greater compressive strength making the 1000m mark easier to reach.
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From watching the movie (through Youtube), I wondered the same thing: The pagoda tree is extremely high, and the winds are strong due to the dense atmosphere and long day/night cycle. I see all the pictures depicting entangled branches. This may be a strategy to deal with the strong winds. The branches do not diverge from a main trunk, but split and re-join forming a [space frame](https://en.wikipedia.org/wiki/Space_frame) instead. It may be possible the whole structure is not a single tree, or a single trunk, but a colony of interconnected trees. (A single trunk holding this against the wind will be useless)
A second point to consider, is capillary action: All trees on Earth, from grass to the giant sequoias of California rely on capillary action to draw the water from the roots up to the leaves. This may work up to a certain height, and [an upper limit for capillary action](https://www.sciencedirect.com/science/article/pii/S0038080614001358) does exist. I couldn't find that number but I suppose the pagoda tree did exceed it. Beyond that limit, the tree has to adapt an epiphytic growth habit: The leaves will catch water and nutrients just like the bromeliads depicted in the picture above. It is amazing, but ordinary plants may also catch water through the leaves. Do a simple experiment and put a wilted branch inside a bag and seal it. In a few hours you will notice that the leaves have been restored to their original condition. Foliage feeding, is another technique to mist water with dissolved fertilizers on the leaves, and plants seem to benefit from that as well, so most plants may draw water and nutrients from their leaves to some extent. Epiphytes have taken this to a higher level.
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I am designing a solar system, with the first planet located very close to the parent star. This planet has become tidally locked to the star. Is it possible to have a molten lava ocean on the side that is facing the sun?
What would the conditions be like for on the other (solid) side of the planet?
Could a settlement be built on the side facing away from the sun?
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Probably start with the basic "ballpark" expression for a planetary surface temperature ( the [Effective Temperature](https://en.wikipedia.org/wiki/Effective_temperature) ) :
$$T\_{eff}=\left[ \frac {A\_{abs}}{A\_{rad}} \frac {L(1-\alpha)}{4\pi\sigma\epsilon D^2} \right]^{\frac 1 4}$$
For a tidally locked body $\frac {A\_{abs}}{A\_{rad}} = \frac 1 2$
It's a little easier to work with quantities related to Earth and the Sun :
$$\frac {T\_{planet}}{T\_{earth}} = \left[ 2 \frac {L\_{star}}{L\_{sun}} \frac {1-\alpha\_{planet}}{1-\alpha\_{earth}} \frac 1 {R^2\_{planet}}\right] ^ {\frac 1 4}$$
where the distance from the star ($R\_{planet}$) is in AU and the $\alpha$ values are albedo values and the luminosity values ($L$) can be in any unit as long as it's the same for both (it's common for these values to be quoted relative to the Sun in astronomy).
The factor of two comes from Earth having not being tidally locked compared with your planet which is.
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In short yes, the central area will certainly be able to do this, although the boundaries for the end of this ocean would depend on a lot of details (it's practically a science paper in itself to calculate for any given body).
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Solid but what temperature ? This is tricky, but there's a more significant problem.
Remember you have to have an atmosphere (and would have a ghastly one) for such a body to exist with any possibility of having life.
The closest thing in real life to such a body would be an exoplanet called [Trappist-1f](https://en.wikipedia.org/wiki/TRAPPIST-1f) although it's not quite what you're looking for.
The "hotspot" would be ballpark 1400 K and the opposite side's "cold spot" would be of the order of 219 K (i.e. extremely cold). Somewhere along a narrow band there *might* be a region where it's livable.
However the atmosphere is a problem. It's going to generate extremely strong winds (on that exoplanet and on yours). It has to - you've searing heat on one side and freezing cold on another. The resulting atmospheric circulation (which has to happen) would be violent.
It would also transport gases from the lava ocean (none of them friendly to human-like life) to the otherwise habitable regions. I can't see a way to avoid this. Given you're looking for an ocean sized hotspot of lava, this would be really hellish even in the "temperate" regions.
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Maybe, but probably a lot, lot easier (and safer) to build an larger orbiting settlement. Any settlement (for human like species) would be essentially sealed and would need excellent climate control internally to cope with fluctuations in climate.
There's also a potential issue with seismic activity. You've a planet heated to molten temperatures for the crust at one side and cold as the worst of Earth's polar conditions on the opposite side. This is bound to generate seismic (tectonic) activity on a significant scale. I'd imagine the "temperate" region to be worst affected as this is the region where the cold plates meet the warm plates.
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Yes it's very possible but not likely to be a life bearing planet. Life can really only survive at the boundary between zones.
One side has extremes of heat and the other side frozen. Any settlement would at the edge so the heat and cold balance out and there is light. Any further into the cold and it is darkness 24/7.
I'm not sure about completely molten. I suspect you need a large moon to keep the core molten
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Imagine a large chunk of land about half the size of the size of the United States cracked away from the main landmass and floated up into the sky for as high as a mountain (say, 2,800 meters, not as high as mount Everest or some of the highest ones so the condition would still be inhabitable). The continent left a massive crater in the ground, meaning massive cliff sides face in all directions. The landmass is about a thousand metres thick.
This continent has been around forever, has its own ecosystem and resources, and humans have been born and built civilizations both on it and throughout the rest of the world.
I'll try to keep the pretext simple: let’s say that one day the people of the floating continent decided to unite themselves into one single country, and started to act all xenophobic, and eventually a war break out between them and one of the world superpowers below but nearby. The protagonist is a high ranking officer of this superpower’s military force who will have to figure out the logistics and plan of attack. Technology is equivalent to today's NATO countries/forces here on Earth, but nukes are not in play from either side.
## The “Ascended” people
* Since the country is landlocked, and seafaring vessels cannot reach them, the people of the floating continent are renowned for building some of the largest cargo planes and even helicopters with powerful engines, that can easily transport large amounts of supplies along with some of the most advanced airports in strategic locations all over the continent. This acts as their lifeline. They are still trading with the other countries. So, they don’t have a two front war to contend with and can't be starved into submission.
* They can’t overpower the superpower economically or militarily, but they sure can put up a fight and can easily wage a protracted war with their control of the skies. Their soldiers are fanatical due to a belief in racial and geographical superiority. They are not afraid to enact scorched earth policies on some of their own infrastructures.
* They have fortified the cliffside facing the superpower's border with a wall of guns in an extended cave system (think of the Maginot line, but they have both dimensions to work with).
* They do depend on trade to remain viable economically and with resources.
## The superpower
* For simplicity, imagine a clone of America's army today with all of its equipment and ordnance. They have a coast line open to trade, are a juggernaut both militarily and economically, and possess some of the best air force and airborne units in the world, second only to the Ascended. They have no allies.
* The superpower’s goal is not to completely occupy the continent, but to control a sizable portion of territory on it (cities or provinces) and shatter the image of superiority of the Ascended people, weakening their position and hopefully bring more allies to their side in the case of any future conflict.
I've planned to have the superpower neutralize the cliff side defenses after an epic battle, but what troubling me the most is the logistics following the battle once they’ve establish footholds on the landmass. Since the superpower can’t bring its massive navy and cargo ships to deliver supplies like the US did at Normandy, everything must be transported by air.
**Question:** Is there a more efficient solution than aircraft to supply a beach head operation in the sky given the parameters outlined above? Efficiency is the key to the best answer. Efficiency in terms of speed, cost, and defensibility.
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Your scenario actually doesn't change much of how logistics are handled in modern wars, as a lot of the countries that the U.S. and its allies fight in, primarily in the middle east, are landlocked. As such, a large portion of the supplies are delivered via cargo plane. C-17's as mentioned in user's comment above. If your foothold is not large enough to support an air field, then you might look at CH-47's (Chinook helicopters). With a carrying capacity of about 10,000 lbs, they can get a lot of supplies and even vehicles onto the continent. If you don't mind taking some help from the East, you could also employ the Mi-26, a soviet transport helicopter capable of lifting APC's, the heaviest that I could find record of being 29,000 lbs. The Mi-26 is powerful enough, it has even been used to recover downed CH-47's. Plus, it comes with an awesome NATO nickname, "Halo".
From the standpoint of cost, this is going to be incredibly expensive, and a bit of a logistical nightmare. To keep your army fed and supplied, you're going to be flying missions 24/7 regardless of weather conditions, visibility, etc. A good place to look for inspiration is the Berlin Airlift. Heck, the logistics alone could make for a good book.
For some options outside of a fleet of helicopters and planes, you could look at Raditz\_35's suggestion of cable cars. The questions with these type of fixed transport methods are: How well can you defend them? Does the continent move at all? Is there a land mass near enough to the continent that both ends of the cable can be secured? You would have to treat these transport lines like railroads in WW2. Incredibly vital, but also incredibly susceptible to aerial attack and sabotage.
Finally, you have stated that the continent is self-sufficient. Thus, it stands to reason that if the invading force were to capture the right portions of the land mass they could supplement whatever supplies they receive from home with captured supplies. Seize the means of production!
If you don't already have one, this is where a detailed map of the continent would come in handy. What are the major cities? Where are the primary deposits for various resources? Where are the military and air bases? You need these, so you can plan the assault and find the most reasonable staging area for it.
Keep in mind that even after the initial attack, with such a fanatical enemy force that fortified cliff face would represent a near impossible to clear obstacle with a vertical insurgency causing havoc for months if not years even after the initial defeat. So expect your transport vehicles to be under constant threat of attacks from the cliff side on their way up. You might look towards Vietnam, WW2 Japan, and the modern Afghanistan insurgency for some ideas on what a war through that honey-combed nest of a fort might end up looking like.
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They attack from bellow, the continent is floating and noone guards the bottom, so just dig tunnels, the navy can support the units that are trying to dig.
Worst case scenario, insert explosive charges into the plate of the continent and break it apart. There is no other material or contact with other solid material that would dampen the shock from the explosions, so the continent would get the full hit.
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Apps.
It's the 21st century. Build a market out of taking supplies to forces. For example, soldiers can order ammo and guns online. Wallmart will deliver with drones. Transport can be done with an aerial version of Uber.
If you convince the superpower to pay money for every ascended citizen kill and coordinate tactics and strategy through an app, people will flock in to the floating continent and get killing, and the will bring their own supplies. Since the coordination would be done through your app, you can make a profit by taking 20% of their cut.
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More posts from this thread are here:
[Metal-Feathered Macaw Viability Part 1: How Can It Fly?](https://worldbuilding.stackexchange.com/q/115491)
# Info
See [this previous question](https://worldbuilding.stackexchange.com/q/115491) to learn about the premise.
We now know, via [this amazing answer](https://worldbuilding.stackexchange.com/questions/115491/metal-feathered-macaw-viability-part-1-how-can-it-fly/115492#115492), that a steel-feathered macaw can pretty much fly on its own. But wouldn't it be cool if it could actually fly as fast or ***faster*** than a regular macaw?
Diet: (Macaws normally eat seeds, nuts, fruits, palm fruits, leaves, flowers, and stems, but I'm upping their fruit intake for this.) They do gather at clay licks. (A clay lick is a riverbank of clay heavily saturated with minerals; the macaws will literally "lick" the clay to get salt and minerals.)
They are active and fly through trees searching for nuts, fruit, and seeds, mainly. Unlike regular macaws, they migrate, not due to temperature changes but to massive pressure changes in their environment caused by natural phenomena. They migrate about 5000 miles to reach their "other home," riding a draft of warm, wet air that follows them from the pressure fluctuations. But they don't cruise higher than 2000 feet.
They have just three predators:
* Birds of prey with an unfortunate ability, considering that the macaws are made of metal: Birds of prey, of the eagle family, that conduct electricity to shoot lightning bolts. They have the natural speed/wing shape/etc of normal eagles, with the exception that (1) they shoot lightning and (2) their favorite food, ever, are metal-feathered macaws, since they get cooked and toasty inside their metal shells.
* Caimans that can shoot concussive (stunning) blasts to a distance of about 30 meters, traveling at a rate of 10 meters per second. These have evolved to walk on land for long distances at high speeds.
* And jaguars that can jump to about 10 meters up. (To defend my premise a little, the metal feathers help a little here, because the jaguar has to pin down the bird (Claws won't rip through metal feathers))
And most of them need to be able to evade them all (well, some macaws will fall prey to these predators, doubtless. And some jaguars might get surprised by a steel beak in the face.)
Assume 2 predators per square mile (for purposes of this question.) The predators are interchangably regular: 1/3 of all predators are caimans, 1/3 lightning-eagles, 1/3 will be jaguars.
I've seen two good diagrams on different wing shapes:
This one:
([Source](https://www.pinterest.com/pin/747738344355500881/))
and [this similar one](https://i.pinimg.com/originals/2a/56/80/2a5680f97a72de6796536075b9039b61.jpg), which has slightly more description but less shapes.
([Source](https://www.pinterest.co.uk/pin/534309943283614271/)).
But I'm not sure which wing shape is best for their life, or even if there might be some combination.
# Question
What would be the best wing shape for my macaw? One of these from the diagram, a different one, or an amalgamation of two or more wing types? Which ones, and what would they look like?
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Thank you to those in the [Sandbox](https://worldbuilding.meta.stackexchange.com/questions/6168/sandbox-for-proposed-questions) for helping me develop this question.
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[Answer]
## Elliptical Wings
I think that these would be best, after reviewing your information on the birds. The main reason why I think this is that it would be useful as a counter-predator method.
If a metal animal is fried with lightning, then it's toast - literally. Therefore, armour or size isn't going to help it. It needs a way to not get hit in the first place. And a great way of doing that is to be able to quickly dodge the lightning bolts.
Stunning blasts are also almost definitely going to be fatal. Since the blasts' range is limited, if it has the reflexes and speed to get out of range in 3 seconds, then it can survive.
Assuming that your jaguars are ambush predators, sudden bursts of speed are ideal. If a jaguar catches a perching macaw off-guard, it doesn't have the time to go down a runway. Fast reflexes are also best here.
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All of those skills can be accomplished with elliptical wings, which allow for high speed in short bursts, take-offs on short notice, and quick maneuvers.
The downside of this is that everyday flight will not be as graceful, with a lot of flapping, so long-distance travel is not an option. At first the diet threw me off, but there are birds - thrushes for example - that eat nuts and berries too and have elliptical wings.
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I hope this answers your question, and good luck with your worldbuilding.
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Previous parts here:
[Creating a scientifically semi-valid super-soldier, part 1: Skeleton](https://worldbuilding.stackexchange.com/questions/106292/creating-a-scientificly-semi-valid-super-soldier-part-1-skeleton)
[Creating a scientifically semi-valid super-soldier, part 2: nervous system](https://worldbuilding.stackexchange.com/questions/107365/creating-a-scientificly-semi-valid-super-soldier-part-2-nervous-system)
[Creating a scientifically semi-valid super-soldier, part 3: Physical shock resistance](https://worldbuilding.stackexchange.com/questions/107635/creating-a-scientificly-semi-valid-super-soldier-part-3-physical-shock-resista)
[Creating a scientifically semi-valid super-soldier, part 4: respiratory system](https://worldbuilding.stackexchange.com/questions/108558/creating-a-scientificly-semi-valid-super-soldier-part-4-respiratory-system)
And one thread that has some information that is helpful: [Is a double circulatory system useful?](https://worldbuilding.stackexchange.com/questions/45289/is-a-double-circulatory-system-useful)
In some sci-fi or fantasy, when they want you to know that some kind of creature means business they give them extra hearts. If you get an extra heart you have a spare one if the other one gets damaged, right? Often this goes along with some kind of super-coagulant that lets blood clot almost immediately, somehow without generating super-thromboses.
So the question is, how could you create an enhanced being that won't keel over if its heart is hit? This includes the circulatory system (might need a separate question later). The body should be able to build, maintain and repair this system.
I had two ideas on possible systems. The first is a lot like described in the "double circulatory system" thread linked above. Two hearts, each has a small circulatory system to one lung half (in case of an enhanced being with bird-lungs, two lung areas will be used). Then they pump it into the body. To preserve redundancy potential, the blood vessels each reach most of the body but each from the other end. So the right heart does the top of the arms for example before going to the bottom of the arms. If the right heart fails, the left heart will still supply enough blood to keep the top of the arms alive and slightly functional.
A big problem with such a system would be blood pressure. The blood vessels would need to be thinner because each heart pumps less blood per unit time and because they would take up too much space otherwise. This means that the blood quickly loses its velocity through your veins and needs to use your lymph system and muscle-pumps (normal contraction of the muscles pushes blood out and further).
Another option I thought off that could coincide with many systems, would be a peristalsis-capable blood system. This has two advantages. Even if the main heart stops the blood vessels would be able to pump the blood further, and in case of a blood vessel rupturing there is little need for high-strength coagulant if the blood vessel itself can squeeze shut and prevent further blood loss. The big drawback is, of course, the large amount of energy such a system would need.
So what would be good and solid options for a heart and circulatory system to work on an enhanced super-human or similar?
[Answer]
So this is going to sound weird, but: separate the coagulants from the actual blood. Imagine a secondary set of veins wrapped around the actual blood vessels, containing a powerful coagulant. Whenever a blood vessel is opened, the secondary system is opened up too, and immediately begins reacting with the air. It quickly produces a plug over the injury, locking it down until the super-soldier can get back to base and get fixed by a doctor with access to a counteragent for the coagulant. Basically, it's an entirely organic bandage that applies itself. It plugs up any leaks quickly, without risking the blood itself sticking, and needing the coagulant to react with air (or maybe a special chemical seal the soldier can apply) prevents the secondary system from clogging.
However, this comes with risks of necrosis, since the plugs will block blood transfer. To this, I suggest one of two solutions. The first one is regeneration; give up saving the limb, and just let the soldier grow a new one afterwards. Hardly ideal, but the plug prevents exsanguination, and it's probably the easiest option if you can make super-soldiers anyway. The second is oxygen storage; put the injured limb into a kind of hibernation where oxygen needs are reduced. Likely it won't be able to do much, but neither will a lost limb, and the oxygen storage means that you're unlikely to lose the limb if it can be reattached afterwards.
A final note: I realize I haven't put any thought into protecting the heart with this. This is because I'm not sure HOW to protect the heart in a way that makes any sense at all. Anything that destroys the heart is probably going to also take out at least one lung and a few ribs to boot, and at that point it's just damage mitigation. A secondary heart would still have to contend with a gaping hole in your chest where the first one was, and a lack of oxygen from a missing lung. However, it could be wise to figure out a way to save the head, especially if regeneration is possible. Perhaps a secondary heart (yes, I know what I said) in the skull, capable of sealing itself and the veins in the head off from the main circulatory system, plus some lung tissue located in the mouth or trachea. Basically, a miniature circulatory system that exists solely to preserve the brain - if intelligence survives the rest may be able to be rebuilt, if your world allows it. (If it doesnt, disregard this.)
[Answer]
It could have like small heart-like structures spread all around in body, and system of valves making movement of muscles and even moving unconscious soldier boosting blood, so soldier could be revived (from unconsciousnes of cours) even by not-knowing-anything guy that stepped on body laying on ground for maybe up to week. So there wouldn't be any trouble, because it would be e. g. loops and loops going finger, lungs, finger, lungs, finger, lungs, finger, lungs, finger, lungs, finger, lungs, and get to looping from lungs to other organ. Also bloood would be thick, because red blood cells would be more densily packed into bloodstream, and veins would be like 1 mm wide, not like 0.1 mm like in normal person's blood stream.
[Answer]
A possible reason and concept for a dual circulatory system, is that one bullet or sword-stab (or shrapnel-stab or whatever) has a small wound channel and would therefore only damage a small-diameter cylinder. If you had two hearts, one in the usual place and one (say) pelvic, and each one was fed by one lung - add 'crossover' and shutoff valves - then a single rifle bullet would probably not damage both hearts. Priority in a human should go to feeding the brain and heart and lung and enough muscle to pump the lung; losing half its oxygenating capability would cripple the soldier but make it recoverable and fixable.
To prevent blood loss, expand the concept of arterial muscles to many MANY more and on the veins and lymph-system as well, so that 'damage' causes valves to shut. You'll eventually lose the area due to ischemia, but not the entire organism. Perhaps make it a reflexive but brain-controllable action, so that when the soldier or medic can examine the wound, the valves could be cautiously opened. (add a medical chemical to relax the valves for the same thing if the soldier is unconscious or too pained to re-open the valves)
Come to think of it, this might NOT be worth doing if the super-soldier is a mass-produced expendable. But I assumed we're starting with humans, which are expensive in terms of time (and calories of food) to produce (and grow to a workable size/state).
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Inspired (loosely) by societies like the Gunditjmara and natives of the Pacific Northwest, I always have envisioned a system of aquaculture for one of my concultures, though agricultural studies are hardly my forte, so I figure I should make sure that my system is feasible, and that there are no glaring mistakes.
The society in question lives in a cool temperate climate; summer highs are in the low 60s Fahrenheit, winter lows drop into the 20s Fahrenheit, with low pressure systems from the west bringing rain year-round. It's roughly analogous to the southern tip of Chile.
Broadly speaking, the west is mountainous fjord country and the east transitions from higher land in the interior to a coastal plain. The eastern side is a bit more continental and much drier than the western climate, due to föhn winds as well as more persistent winter cold fronts.
My idea was that people on the northern part of the western coast would invent a form of aquaculture, maybe first by harvesting tide pools and littoral environments, and then by building small structures where they would grow products like kelp, mussels, sea slugs, and fish together in a kind of mini-ecosystem, resembling modern Integrated Multi Tropic level Aquaculture (IMTA).
This would be supplemented by learning to grow tubers and peas, as well as trading for livestock (llamas, maybe sheep) from herders in the highlands.
I know that neither my western nor eastern regions are the kind of subtropical river valley paradises where complex societies emerge the best, but I'm willing to have these people take some more time to have a food surplus and create a civilization in their own, cool temperate environment. I'd just like criticism on whether this is a feasible path and whether the eastern coast is actually a better place than the west for the emergence of a civilization (I always imagined a vibrant urban and maritime culture emerging along the west coast).
Thanks
[Answer]
This is possible.
Aquaculture has been done in early history by various groups.
The [Australian aboriginals](http://theconversation.com/the-detective-work-behind-the-budj-bim-eel-traps-world-heritage-bid-71800) in Gunditjmara country made fairly impressive flooded ditches that eels would swim into and become trapped. This was done possibly as early as 3500 years ago. While the terrain in your world may make such widespread irrigation unlikely, done on a smaller scale all along the coast to trap animals as the tide goes out would be easy.
In 475BCE, a [Chinese official](https://blog.nationalgeographic.org/2013/07/11/sustainable-ancient-aquaculture/) wrote a book about how to raise fish in specially prepared ponds. They also did something similar in Rome who also raised oysters away from the ocean, and apparently later on some castle moats were stocked with game fish.
The [Chinese aquaculture](http://www.fao.org/docrep/field/009/ag158e/AG158E02.htm) saw the carp go around Asia as a pet and food source. The migration of Chinese familiar with aquaculture also spread it to Southeast Asia, where they trapped and raised various fish that were native to that area.
While aquaculture never overcame land based agriculture or a semi-nomadic lifestyle, it was done. There is no reason it couldn't be the main source of food for your people. With the rivers and lakes full of freshwater fish that exist in that type of environment, it would be reasonable to see aquaculture move inland. This would encourage agriculture as the ditches and man made lagoons would create well watered mounds of soft dirt for legumes and root vegetables. At first they would be seen as a nice little side affect, and then large scale farming and aquaculture could happen together. This would be similar to how Chinese farmers encourage a fresh water eel to enter the flooded rice fields, only to harvest them later.
[Answer]
This idea is not only possible, but brilliant! The only limitation is your scenario: the most nutricious fish generally live in hotter areas. A better scenario, more suitable for aquaculture, is a tropical or subtropical wetland, with silty rivers in the proximities, next to the coast. I can't tell you exactly what kind of climate is the best (climatology puzzles me :P), but think something like southern China, or the Brazilian Pantanal, maybe even a mangrove.
Once the scenario is ready, you have a lot of interesting possibilities. For example, hagfish:
[](https://i.stack.imgur.com/yKXaY.png)
Hagfish may see weird, but they have an interesting ability: They produce a special kind of slime when threatned. This slime blocks the predator's gills, making it suffocate and forcing it to go away. It activates when in contact with water, but if you further stretch the formed fibers in water and later dry them, it gets a silky conscistence. So, your civilization maybe can learn how to use the fibers to make clothes with this exotic fabric and trade with your "hightland herders", all by just raising hagfish in their aquaponds (you can check this with further detail here:<https://www.bbc.com/news/magazine-21954779>) By further search, you can see that aquatic animals hae a lot of interesting proprieties never seen in land ones. So, free your imagination with this scenario.
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Ok
I have a moon, or cored out moon, that is a generation ship. I really do: I built it by mining out one of the rock/ice moons around my solar systems gas giants (not earth's solar system). Its diameter varies but it's roughly 1,390 km from pole to pole and 1,470 km at the equator. But it has this kind of bump there (see image), nice place for a particle accelerator actually now that I think of it.
This is the "surface" where no one lives. It's mostly rock tailing (mining leftovers) and some various volatile ices. This outer crust varies from 5 kilometers to 25 kilometers in thickness. But as the direction of travel is aligned with the poles (the thinnest section, bad design) will call the outer shell 5 km thick.
Beneath this there is a super strong structure of mostly carbon-nano "stuff", at least that's how one of the egg heads called it. This is only a few tens of meters thick. Further below this layer, there is the air, which is about 10 km thick then we come to the "actual surface" where everyone lives. Between the outer and inner surfaces, there are massive support "pillars", the one at the north pole is 130 km in diameter and is 5 km thick ( like a cylinder on a ball ) so this structure is directly in the line of travel.
As this is not your ordinary "moon" mega-structure but actually a ship, what you would call the exhaust of the engine is the 120 km hole in the "cylinder" I mentioned above, ( 130 km - 5 km - 5 km = 120 km ). There is one on the north and one on the south pole as obviously as we will need to slow down and we are not turning this thing around: we just switch from the south exhaust mode to the north exhaust mode.
This baby can get up to about 0.79315 c but has an average speed of about 0.5c. It's no "race" car so it takes a good amount of time to hit the top speed then we must slow down. The acceleration is only 0.0183 m/s^2 (if my math is correct) but it's capable of short bursts of much larger acceleration, and the lower acceleration can be kept constant for 650 years, and then again 650 years accelerating in the opposite direction. So a simple 50%/50% split on the trip.
Here is a 3d rendering of this beast (personal work).
[](https://i.stack.imgur.com/7GxSp.jpg)
The part between the "grey" outer shell and the "metallic purple" mineral storage is basically the "atmosphere" then on the right side you can see how the terrain is roughly laid out. Grey represents city bands, dark green is forest, the other green is farmland, and the almost non-script blue is waterways (between the 2 green shades). All laid out in bands along the latitude lines.
At the bottom, the "blue" section is a "water jacket" that is about 25 km thick about 1,070 km in inside diameter. The little "haha" turquoise balls, are baby ships about 100 km in diameter, just so you can get a sense of the scale of this beast (the death star was about 160k, just for comparison).
You can see secondary support pillars poking out at various angles ( little toothpick deals), not only do these help hold the roof up but they also regulate the weather, and generate some power, filter the air etc.. There are a few medium-sized ones, about 5 km and the smaller ones are just under 1.5 km.
Yup, it's big, really big.
If that doesn't convey that then consider this image (beside earth's moon)
[](https://i.stack.imgur.com/Y4W0B.jpg)
Basically, it's the size of Pluto (but it's not Pluto)...
**SO the question**
What are the effects of interstellar gas impacting on such a structure on the acceleration phase of the journey? And then when decelerating the "exhaust" of the "engine" will be in the direction of travel so that has to count for something. This exhaust is mostly light gasses, and radiation (various forms).
Basically, the north pole surface layer needs to survive for the entire trip, we can do some maintenance on it, how much I have no idea. But it would be nice to have some rough guess that way I could devote some resources to it.
The details of the engine are frankly "top secret" and you don't have that clearance level. As you may notice in the rendering there is quite a large empty space in the center that is where the engine goes. It's quite massive and produces about 0.98G of "gravity" on the surface which is 690 km from the center (radius)... "oh" but I have said enough.
I considered using a Bussard Ram for the outbound leg, this could help suck in some of the interstellar material. However, when decelerating this is not feasible as the exhaust gasses will be ejected from what I call the "north hole" (in the direction of travel) which would obviously block the Bussard Ram from working. So any insight on the effect the exhaust would have to push material out of the way would be good. As I said the exhaust is mainly light gasses. I did some rough work on calculating this (I could be way off on some of it):
* exhaust mass roughly `736,716.24 Kg\hr`
* exhaust thrust roughly `1.3938E+21 newtons`
* don't forget it's over a `120km` diameter nozzle.
* basically, it has a start mass of `6.7901E+22 Kg` and an end mass of `6.74257E+22 Kg` so a total mass loss of about `4.75307E+20 Kg`
* acceleration of `0.0183 m/s^2`
It was really difficult to work this all out. So I may have messed up some stuff, but this is what I came up with.
Thanks for any insight (if you can't tell this is pretty "next level").
AS a bonus any insights on how this relativistic speed would affect my trip would be nice, the total distance traveled is about 540 light years. With an estimated duration of 1302 years when at rest. Time dilation may or may not come into play in this situation, but some rough back of the napkin work suggest it should cut off a bit over 220 years for our citizens (are we there yet ). This would give me a moving frame time of about 1079 years.
My target population goal at the end of the trip is around 300 million registered citizens. I often wonder what effects the max speed will have on the perception of time. Does everything just slow down? I guess you wouldn't realize that time outside was passing faster.
I wonder too, with 10km of "air" and 1g of gravity, how much pressure I would need to keep the air from venting if the outer shell was breached. I doubt gravity alone will hold the atmosphere.
And the last thing, obviously I put a lot of work into this design. Please respect that.
**UPDATE**
My max speed calculation was off, I have a program I created to calculate some of this stuff. I had it set for constant acceleration, with no deceleration period. This affected the travel time by about 300yrs. I've updated the post for those "discrepancies". I really have tried to work most of this out, mathematically, so I can answer some pretty specific questions as to the physics of it. For example, the mass of the "water jacket" is about `9.198E+19 Kg`. That said, most of that "technical stuff" won't appear in the story body. I may include it in an appendix though, so I would like to make it as accurate as I can.
Thanks, Guys, I appreciate any feedback or creative criticism. My goal is to make this as plausible as I can, you won't hurt my feelings. Obviously, there is a point where I have to invent some technology to achieve this goal, but I would like to break as few physics constraints as possible.
[Answer]
The ship would experience something more like sandblasting than destruction of the outer surface. Here is a reference to the potential effects from a scientific mathematical analysis.
[THE INTERACTION OF RELATIVISTIC SPACECRAFTS WITH THE INTERSTELLAR MEDIUM](https://arxiv.org/pdf/1608.05284.pdf).
>
> For a spacecraft speed v = 0.2c, we find that dust bombardment can
> erode a surface layer of ∼ 0.5 mm thickness after the spacecraft has
> swept a column density of NH ∼ 3 × 1017 cm−2 , assuming the standard
> gas-to-dust ratio of the interstellar medium. Dust bombardment also
> damages the spacecraft surface by modifying the material structure
> through melting. We calculate the equilibrium surface temperature due
> to collisional heating by gas atoms as well as the temperature profile
> as a function of depth into the spacecraft. Our quantitative results
> suggest methods for damage control, and we highlight possibilities for
> shielding strategies and protection of the spacecraft.
>
>
>
Lots of formulas and graphs, and a thorough discussion. Even gives some ideas on shielding. Though the article recommends tungsten, graphite (heat transmission) or quartz. Dust and gas are manageable. Larger particles could be a problem, and at .89 cee, you do not get much reaction time. Recall the recent cigar-shaped visitor we just had from outside the solar system? Colliding with that just might split your spaceship open. There is some pretty BIG stuff out there.
As I understand it, your residents are living around the outside surface of the inner shell, and gravity is produced by the mass of the engine. If the inner shell were spun on the axis, and the residents lived on the INSIDE surface, they would have artificial gravity.
It would be interesting to see the calculations on a reaction mass drive, if the reaction mass available was the entire volume of the inner sphere being slowly consumed. However, I could foresee the necessity of somehow manipulating gravity and inertia (the Higgs boson?).
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You're talking about a top speed of approximately 269528409 m/s so every gram of matter that hits is going to cause about 36.3PJ worth of damage, that's 8.8 Megatons TNT equivalent, over half the size of the [Castle Bravo](https://en.wikipedia.org/wiki/Castle_Bravo) test blast at Bikini Atoll, per gram. To put it another way for every 1x1024 and hydrogen atoms, or their mass equivalent, that hit this generation ship it's going be subjected to a Castle Bravo level of damage (but less concentrated than a nuclear blast, unless it hits 1.7grams worth of micro-meteorite in which case it will be a single blast that looks almost exactly like Castle Bravo). The good news is that particle density in the interstellar medium is only around 1 atom per cubic centimeter, the bad news is that with an impact face of roughly 21.6 Billion square centimeters you'll collect that much hydrogen damage every 475 Million kilometers (3.1 AU) you travel, at top speed that's about half an hour of flight time. That should give you an idea of the amount of energy dissipation and mass ablation you're going to need to deal with. [This](http://nathangeffen.webfactional.com/spacetravel/spacetravel.php) is a link for a travel time calculator that deals with realistic effects that should help you get specific about the travel time.
Cute little ship by the way. Now assuming you have an internal biosphere roughly as productive as the American Midwest you can support about 2.5 billion people, based on the half a hectare per person agricultural requirement used by the FAO in 1993 and assuming that you need to cover part of that biosphere in built up areas (2.9 if all you do is farm it).
All these data points are for the original 0.89905c top speed I'm not redoing them.
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I'm really in doubt if a fusion thruster could be used inside a planet (populated places). As i saw in the TV show "The Expanse", their fusion engines are really, really hot, hotter than the surface of the Sun and they can't use it close to stations and on planets. So i ask: in a VTOL spaceship that uses fusion as a way of traveling, would its fusion thrusters and engines be prohibited from being used on a planet? Aside from the main engines that can be changed to atmospheric mode, what about its thrusters? Chemical reaction thrusters aren't efficient because it uses too much propellant. How do i solve this dilemma?
[](https://i.stack.imgur.com/1vrKl.jpg)
*How does the Tempest doesn't destroy everything with its million-degree thrusters??*
[Answer]
**Really hot is not as big a deal if it is really small.**
Consider the experimental [tokamak fusion reactors](https://en.wikipedia.org/wiki/Tokamak). They are real. They are hotter than one million degrees. They are sitting on the earth. How?
from <https://www.euro-fusion.org/faq/new-what-is-the-temperature-generated-in-a-tokamak-reactor-how-can-the-inner-wall-material-resist-that-temperature/>
>
> In order for fusion to occur in the very hot gas – or plasma – we
> create inside JET, the plasma must be heated to temperatures in excess
> of 150 million degrees Celsius. In order to achieve this, the plasma
> is actively held away from the walls of the tokamak container by using
> powerful magnetic fields.
>
>
> However, it does sometimes touch the walls: what material could
> withstand that temperature? The key here is that there is only a very
> small amount of plasma there( ~0.1 g). So although it is exceptionally
> hot, this is counteracted by the very small amount, compared with the
> wall, which is many hundreds of tonnes in mass. Therefore the wall can
> withstand impact without getting seriously damaged.
>
>
>
So too the thrusters of your ship. A really hot reactor like this could work like a ramjet in the atmosphere, ramming in atmospheric gas and spitting it out the back under pressure. The gas flow will keep things from heating up too much.
In fact a hot little fusion reactor seems to me to pose more trouble in space, where you do not have ready mass at hand for coolant, or to throw behind you for propulsion. But that was not your question.
[Answer]
The main reason fusion thrusters wouldn't be used in a planet's atmosphere is gravity. Will's answer already provides the key element. A fusion exhaust will be hot and will be small.
The small part is the real problem. The thrust will be small too. This means the acceleration will be very small too. Estimates are around a rate of one centimetre per second squared. This is barely enough to lift a spaceship off the surface of the Moon, let alone any of the planets of the solar system, and this would include the moons of the planets too.
Fusion propulsion systems blazing away like thermonuclear versions of chemical rockets are science-fiction. A fusion rocket will be essentially a high-energy stream of particles generating a low acceleration. Their main advantage is the long acceleration times that can propel a vehicle to high velocity.
Fusion thrusters won't used in the atmospheres of planets or even planets without atmospheres because the spaceships could neither land nor takeoff. While the jet from a fusion thruster would be effectively a deadly weapon and highly destructive that isn't the main reason for their non-use on a planet.
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In a large varied environment where strong winds are the norm and every few weeks or so a huge hurricane sweeps through, how would large land animals (horse- to elephant-sized) evolve to cope?
I understand palm trees to be well adapted to hurricanes; roots that anchor them into the ground, strong but flexible trunks and large leaves that yield rather than canopies that catch the wind.
Are there other examples of large plants with adaptations to hurricane weather?
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# Features of trees
* Many small shallow roots. The purpose of the roots in this case is to connect the tree with a very large mass of soil caught in the root ball. While other trees concentrate on sending a deep tap root in search of water, or wide spreading main roots in search of nutrients, a large mass of small roots limits the chance of a single fatal break while providing a big anchor for the tree.
* Columnar trunk construction. Most trees grow series of rings outwards as they age. However, a weakness of these rings is that repetitive side to side motion (caused by high winds) stresses the weak points at the ring boundaries. A ringed tree bend over 45 degrees will snap. Instead, hurricane resistance trees will grow as a series of tubes that extend vertically up and down the trunk. Each year the tree will add one or more new tubes. The tubes themselves are much more flexible; this is what allows a palm tree to bend over so far in the wind. Note that this system is unique to monocots as opposed to the ring forming dicots; most trees are dicots or magnoliids. while palm trees, bananas and bamboo are some of the few 'tree-like' things that are also monocots.
# Features of animals
* Size. There isn't really a good reason for animals to fear the high winds. Anything water buffalo to elephant size isn't really going to affected. Animals that large can have enough skin and fat to insulated them from heat loss (not that it is too cold during hurricanes, normally) and they are too large to blow away. Even a falling tree of moderate size isn't that much of a danger to an elephant. So hurricane lands will be relatively more hospitable for larger (buffalo, elephant) herbivores vs smaller (deer, pigs).
* Predation is affected. One thing to note is that hunting will be a lot different. I'm not sure if it would be easier or harder for a tiger (for example) to kill a water buffalo in a storm. On the one hand, it is a lot harder for a water buffalo to detect a stalking tiger in a hurricane. On the other hand, the tiger is exposed to significant environmental stress while hunting, and it might be better just to hang out in the den. I don't know how this one would go.
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I was reading [a question](https://worldbuilding.stackexchange.com/questions/84040/silica-aerogel-maze) and had a follow-up question with a story idea that I'd like to develop more fully.
The idea is a HUGE maze, thousands (or more) of square miles, that has small clearings created in it with magical happenings within them. It will have multiple biomes, but the main character is a "Cartographer" in that he makes maps for different paths through the maze to various communities that have developed in it.
The maze itself is composed of normal hedges with regenerative growing magic, and cannot be cut down or crossed on top of. The hedge will either grow in height or will continue to grow as it's being cut at a rate never allowing any gap at all to open. The setting is in the mid-1500's in terms of technology, and magic-tech fusion devices exist. There should be enough space in the maze to house at least 5 cities that can house 35000 people each, and numerous smaller cities/towns in smaller clearings. I want to stress that the maze **needs to take centuries to fully map**.
The gist of the story is that he finds a community, and falls in love with a fellow "cartographer", and loses her for years within the maze. I won't spoil the story and ending just in case, but I came on a bit of a scale question that I'm not sure I have the knowledge to answer.
**How big would this maze have to be to not only house actual villages with farms and such, but also that numerous people could feasibly make a living mapping the maze?**
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* Say a normal path through the maze is 3 metres wide. The hedges on each side are 1 metre wide. That means a square kilometre could have 250 kilometres of paths. I'm ignoring the possibility of cutting corners on the way through an interection.
* If supplies are not an issue, a wanderer might make 50 km a day. Five days to walk the paths of one square kilometre. 73 square kilometres per year, 7,300 square kilometres per century, 36,500 square kilometres for five centuries.
That would be a square roughly 190 km to a side, or a circle with roughly 220 km diameter. However, you should note some assumptions here ...
* I assumed that the wanderer never has to backtrack and walk the same path twice because it is a dead end.
* I assumed that the wanderer doesn't have to return to base to gather new supplies.
* I did not account for the mapping process, which will slow the wanderer.
* For that matter, he or she is immortal and doesn't take any vacations.
* On the other hand, the towns will have to be surrounded by fields and forests. This reduces the number of pathways in the maze.
* There is more than one cartographer.
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*Follow-up:* Combining the work of several cartographers is going to keep them busy for a *long* time. Just imagine: The first cartographer followed the path south-east from the village gate for 1,000 paces, then turned sharply west for 650 paces until he reached an intersection 100 paces in diameter. The second cartographer followed the path south-west from the village gate for 1,000 paces, then turned sharply east until he reached an intersection 100 paces in diameter. Were they on the same intersection?
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A pharmaceutical company begins drug trials of a pill that they believe can activate a previously understudied and widely unknown region of the brain. The trial begins and when the first participants take the pill, there's no obvious changes. The company decides they need to be subjected to intense physical and mental training in order to stimulate the body into processing the drug. Over the course of a couple weeks, one person discovers they can levitate objects with their mind. Then, a different participant starts to shoot fire from their hands. Other various powers emerge, ranging from typical powers, like flight, to truly unique ways to manipulate their bodies and the laws of nature.
There's a lot I plan to hand wave about the powers from the drug (the brain is linking to a spiritual aura so not much to say on the science side), but I want the drug and the culture around the drug to feel realistic. A few notes about how I intended the drug to work:
* Taking additional pills beyond the recommended dosage doesn't increase the intensity of the powers
* Training is required for powers to emerge, plus a few days for your body to adjust to the pill in the first place
* You stop taking the drug, you lose the powers
How does the company hide their drug and keep the participants from spreading the word? I imagine this could not be a publically distributed drug, but what purposes could the drug be prescribed for? (Super soldiers seems obvious)
How would the black market handle a drug like this? Would it even warrant interest from the public due to the training needed?
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Sell it to the users as *something else* that's doing the lifting.
We, today, have a children's toy that allows you to lift up a ball with *literally your mind.* [In fact you can buy it off Amazon right now.](http://rads.stackoverflow.com/amzn/click/B003KISWNG) It works by having an electroencephalogram attached to your head. This is used to measure brain wave activity. If it sees you focusing, it turns on a fan and lifts a ball in a tube. It's also glitchy, but for $85 that's still pretty cool.
The point is, *we have technology that can read basic brain activity today, and we have it in the form of a toy.* It's not that much of a stretch to say that some super-secret corporate facility was working on a more advance program 5-10 years.
Of course *they're not*, this is just the cover story they're telling the subjects.
They'll go to great lengths to make a mock prop headset, and have the target objects to move hooked to pullies or pistons or some other mechanical device to lift target objects; there won't be any floating anything to become alarmed about. They'll spin the story to the subjects that the headset measures brain activity, and as verification objects in the test chamber can be moved around. They can say they're working on the code to handle the brain-to-movement transition, and need subjects to practice.
"Oh, that pill? That's just to make your brain easier to read for the headset. It's perfectly safe, simply helps for read outs. Don't worry about it. If you'll step right this way...?"
Every subject will be *closely* monitored to see that they don't try to do anything fishy, or play around outside the intended scope of the tests.
Unfortunately, the machine can cause dizziness, nausea, sweating (the scientists tell the subjects) so it's important to rest after use. Hopefully the pill has an effect time that is reasonably short (a few hours? Less?) and they can have the subjects sit in a dark room to sleep off the pill's effects--erm, I mean, the *headset's* (wink, wink) effects.
This is all a story that seems fantastic and interesting, and they can try to shut down any discussion with normal Non-Disclosure Agreements and general scary legal action. Worst case? One of the subjects spills the beans that your scientists are developing a cutting-edge electroencephalogram device, and specialized code to understand the brain signals. Since *literally* this technology (to some capacity) exists *today*... it should be an easy enough story to sell. Some people will still scream conspiracy theories, but like most conspiracy theorist, us normal folk will ignore them.
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So you set it up like a drug trial.
First phase is really small, maybe 10 people to get dosing figured out.
Maybe use some underprivileged people who would like a place to sleep and some money. If they talk after the effects wear off no one will pay much attention.
Wait for the powers to manifest and call in the Defense Department for a demonstration. Show it off and get their agreement to help with phase 2.
Phase 2 is a little larger test group of 100-200 to check for efficiency and safety, look for unwanted side effects. These would probably be volunteers from the armed forces. This is where you can really test stuff out without having to worry about security because DD would handle that.
Phase 3 is an even larger group of 1000-3000 to continue to look for side effects and safety concerns.
Black Market:
This is going to happen, but the fact that the effects wear off is a good thing, meaning that there will have to be a steady supply to be of much use, and having military security on hand is going to help.
Something like this would probably fall under some kind of code word level security where violation is Treason and very bad things will happen to people that violate it.
The biggest threat is going to be foreign powers trying to get a hold of it for the purpose of reverse engineering it for their own armies.
That's why trying to keep it all in house is probably a bad idea. If a nation state wants to break into your corporate headquarters to steal the formula corporate security may not be up to the job.
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1. Form a partnership with the military, They can supply a stead supply of participates in the study. And they will be under orders to keep their mouth shut so you there not likely to talk about it.
2.The black market should be a problem it not like you can just take the pill it takes training which would be much hard to sell on the black market.
Uses: Military uses is the most obvious, but the pill could also be used for intelligence. But am sure that they could have many practice uses as well but it might have to be declassify for that to happen.
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So I wanted to give the players a reason to eventually go to the moon. But this is a fantasy setting, so having the moon just be a big rock floating in space would just be so.... blasé. So I came up with a system where the moon is a giant battery storing up solar energy until it expends it on the night of the full moon to push back the forces of evil and keep them from entering our world for one more month. The moon's phases are pretty much a giant battery icon in the sky.
I've got a few plot points lined up where the bad guys do various things to mess with the cycle, culminating not just in visiting the moon to fix a leak, but going to the sun to... do something with sunspots that I haven't figured out yet. Whatever it is, the sunspots are a natural cycle that the bad guys have been preparing to exploit. The point is, everything lunar (and possibly solar as well) is a potential plot point.
Which brings me to the tides.
So far, what I've got is that there is a magical artifact (or possibly a pair of magical artifacts) under the sea that moves along a track to stay directly under the sun at day and the moon at night, alternately collecting and discharging energy to/from the sun/moon. While the artifact is under a region of the sea, the excess magical energy raises up that area of the sea, creating the tides. The first sign of something evil afoot is that there is a problem with the tides, probably that they are low or off-cycle, I haven't figure out what yet. And the way to fix it is to travel to the track under the sea and fix whatever is being done with the artifact.
The thing is, something feels off about this plan. Maybe it's the fact that I want the world to be a plane, I don't know. That seems to require a charge/discharge cycle instead of merely facilitating redirecting solar to the moon, which I would prefer because it would only require one artifact instead of a pair (though a pair might need repairs to be conducted at either high noon or midnight). Or maybe I feel like there's something better that I can't see right now. Whatever it is, I was wondering if anyone might have any ideas to help me polish this up a bit.
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You're treating the tides as just a side effect of what the machine/moon are doing. But what if you went in a different direction, and made the tides themselves the important thing? It's not unheard of for the deep, dark, and mysterious ocean to be the source of evil. In which case it could be the machine/moon's job to dredge up that evil periodically to where it can be thinned out and destroyed, hence the tides. In other words, tides could be caused by the artifact receiving energy from the moon instead of the other way around. Sailors might begin to associate high tide as a period of danger, but what they don't know is that the alternative would be worse. If the underwater artifact stops creating tides, then evil forces would be able to fester and grow until they can attack the entire world.
Why does your lunar battery need something to redirect energy from the sun? Why not just absorb it directly? Even though your world is a plane, there are still plenty of configurations where the moon could do so easily (assuming the sun still radiates spherically). Maybe it stays suspended above the world and is just invisible or hard to see during the day. Maybe its 'orbit' is several factors slower than the sun's: the sun races past the moon repeatedly, giving it plenty of time to absorb more energy. Although maybe the moon needs more energy than it can absorb in a month, which would make redirecting artifacts necessary.
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I would have thought the tides would be directly linked to the function of the moon.
Remember that while the tide is connected to the moon on Earth, it's not as simple as Full Moon = High tide. You need to provide two high tides and two low tides per day (more or less), with the biggest tides coinciding with the full moon and the new moon (spring tides), and the smallest tides being timed to the quarter moon (neap tides).
Now, your world is a plane, which is going to play all kinds of mischief, but from your description I get the feeling you'd like your world to mimic the behaviour of ours in at least some ways.
## Lunar Phases
First, the description of the moon expending all its energy on the night of the full moon, and the phases that follow being a giant 'battery status' icon, doesn't match the phases our own moon follows. The full moon is followed by the waning moon, taking two weeks for the full face of the moon to retreat into shadow to become a new moon. In your scenario, that would make the most sense if it takes two weeks for the moon to discharge and push back evil - rather than a single burst at the full moon, you could have a full-power push at full moon, then two weeks of steadily weakening pushback, then deactivation until it charges up again.
## Tides
So, we come back to the tides. We need two tides per day, a particularly strong high tide at the full moon, another at the new moon. We want whatever is causing the tide to be under the sea, so that the heroes can go there to fix it. So...
* There's a magic fortress on the sea bed that guards the portal of evil. Twice per day, patrols flood out of the fortress to search the whole seabed for any signs of evil, then return to the fortress. This causes the normal tides. During the full moon, the fortress itself swells, causing the spring tide. During the new moon, many more patrols emerge, using the last power of the moon cycle to prepare for the lean times ahead.
* The world is breathing. Twice per day, the world itself draws in breath and energy, which pulses throughout the world to keep evil at bay. When the moon is full, the earth takes a deeper breath than normal, providing more power to keep evil at bad. When the moon is new, the earth yawns, and begins to sleep, allowing evil to return. Beneath the sea, the veins of the earth are accessible, which allows your heroes to see the problem with the tides.
* There are two beasts under the sea, one evil and one good, and they strive with one another all the time. Their movement pushes the sea up and down as they fight. When good is weakest, evil tries to lift the sea off its back, causing a spring tide; the moon has to go to full power to push it back. Once the moon's glow is exhausted, at the new moon, evil tries again to lift the sea off its back, but good uses its remaining strength to pull evil back down.
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How about having the tides be a side effect of the magical tether that keeps the moon from flying away or falling down. In one respect this is another way of saying what actually happens in the real world, gravity holding the moon in place also causes the tides to happen, but if the world is flat (like a plane?) then obviously the whole gravity things isn't going to work the same way.
So instead you have a magical force that ties the moon to the world, moving it around from place to place, and this magical tether also pulls on the water and causes it to mound up. This force could even be repulsive instead of attractive like gravity, so it is actually pushing up on the moon to keep it up in the sky.
This could also be a way for your characters to get to the moon, by attaching to this tether with some artifact or whatever and climbing it or riding the repulsive force, and remove the need for rockets or anything like that.
The sun could be on a similar tether, which could have an interesting effect where the the repulsive force could be greatly magnified during an eclipse as the force holding up the sun and the force holding up the moon join together...
The question then would be would the moon be pushed further out? Would the sun all the sudden come crashing down as the moon blocks the force pushing on it? Maybe both? Maybe this is what the forces of evil are waiting for/trying to make happen...
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Species X is unique in several ways.
They were (the history lost to their people) genetically engineered originally, and appear as hairless humans of (intentionally) non-human looking skin of various grays, blues, and purples. They cannot reproduce, and depend on growing new members of their species artificially in a process similar to cloning (through combining multiple genetic bases in a way that leaves members being genetic copies nearly statistically impossible). Their species can be engineered to exaggerate some aspects at the costs of others; certain areas of the brain could be stimulated at the risk of mental deficiencies in others, or muscular growth could be set on the genetic level and sacrificing some other aspect. The most healthy (mentally and physically) members of their species tend to be the ones who are *not* guided genetically. Thus this allows them to somewhat create specialists, but not a 'master race.' Baseline they're roughly comparable to humans, but have shorter lifespans by a couple of decades. Growing a member of the species takes 2-3 years, and once the member emerges they do so with the reasoning, motor skills, and speech capabilities associated with early grade school, and are physically similar to humans in their early 20s. They lack reproductive organs, and do not look distinctly male or female.
The facilities that grow them have fallen into disrepair, and knowledge sharing about the growing process is almost non existent. The process of growing and modifying the genetics has devolved into superstition, and baring an academic revolution no meaningful advancement of the field will be seen. In fact, any attempts to make new facilities have ended in disaster, and this too has worked its way into their abstract superstition. Individuals have been flogged and hung who suggested tampering with the facilities to improve them.
Species X is also unique mentally from humans; they lack humanity's biological drive for tribalism and are biologically distrusting of others. They are very defensive (very wary of threats and find it difficult to form relations of trust), and readily separate and distance themselves. They do, however, biologically value recognition of others *more than humans*, and very much respond to a desire for a sense of power or authority.
Those who control the growing facilities control the power, but due to the nature of the species/culture, those who control the facilities aren't promised to remain in power long before an inevitable overthrow is attempted.
This mental biology would drive them to disperse, except the other species of *the galaxy are extremely racist towards them*, viewing them as a thieving, warlike culture (a reputation they have somewhat earned). Most organized groups of the galaxy are only a stone's throw away from endorsing their genocide.
To avoid extermination, they realize the need to band together, even if they are biologically repulsed by the idea. They need to come together and craft a government that:
* The facility owners can agree upon, and will support
* Will endure change of power of the facility owners
* Will endure the general lack of trust and strong sense of individualism of the species
* Will allow them to mass a military quickly if a threat arises
* Will resist internal forces that might attempt to tear it apart
* Will provide a unified movement to direct them in war
* Will show the external galaxy that they are a unified force
To clarify: the primary reason for the government is simple survival, not embetterment of the species, or trade, etc, although they would probably welcome that. Further, the government isn't attempting to achieve a moral highground; the growing facility owners are fine with forming a government under force if need be.
What government would support Species X, and best achieve these goals?
**Additional Information Per Request(s)**
There's around 100 facilities scattered around a single planet on the various continents of the planet. The facilities vary in size, with about a dozen or so being clearly the largest.
The current leadership of the facilities tend to have acquired their power through coercing others (including, but certainly not limited to violence) or making deals. Others might have used industries they lead, or simple wealth to provide leverage to make their way on top.
Power than is typically *maintained* since in <8 years those commanding the facility can begin to produce members of their species who are indoctrinated (as best as they can be) for loyalty. This isn't a guarantee by any means, however.
Lacking the draw of tribalism has significantly impacted their record keeping as they don't see the value of preserving the history of their ancestors. However as best as they know they escaped their masters 1000 - 3000 years ago (a period that, during which, they rediscovered a variety of technologies including spaceflight and later intersystem travel).
The facilities have undergone a process over those years similar to ship of Theseus; none of their parts are original, but they still serve (after a fashion) the original purpose. Slowly, crudely, they're repaired and parts are replaced to keep them functioning.
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It’s not a perfect fit, but I’m inclined to suggest a dictatorship.
Here are a few reasons I think this might work:
* **Lack of willingness to work together.** Most governments require some kind of voluntary desire or mutual need to work together. If that’s thrown out the window, then threat of force, death, torture, or other punishment has been shown to be very effective at keeping people in line.
* **Distrust of others.** This is practically baked into a dictatorship. Purges of top brass are common and the creature on top inherently needs some level of distrust to survive. Fear and a well-established chain of command can make successful coups less likely.
* **Genetic engineering can facilitate powerful, but less thoughtful armed forces.** With their form of reproduction, building an army both propagates the species and enables the iron-fisted ruler to emphasize combat prowess at the expense of thought-centers that might foment insurrection. This kind of manipulation could make a ruler a very powerful force.
* **Clear appearance of unified force.** With one man in command who answers only to himself, neighbors will know very clearly that he can carry through on threats. Strong control over internal reporting can hide potential weaknesses in the leadership structure or mask power struggles to the outside world.
This could even form somewhat naturally. If a particularly driven individual (driven by their interest in power / authority) were to gain control of a growing facility then they have the tool they need to engineer a physically strong force. With enough maneuvering, this one individual, slowly surrounding itself with “loyal” lieutenants (out of fear for their lives), could gain more and more facilities until they become very difficult to stop. If this is the case, facility owner agreement is no longer required — it’s forced.
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**Oligarchy** - each facility leader would be a member of the group of leaders (would they call it a board?)
If the facility gets a new leader, that leader takes this place on the board.
The larger facilities would have tie breaker powers.
Since there is a lack of trust, "meetings" would not be in person and there would have to be a physical, remotely verifiable security procedure to ensure each member on the board is who they say they are. Perhaps there is a place (a chair, a chamber, whatever) that only one person can reside inside each facility. The person physically located in that place is the leader of that facility.
There would be a voting system where some percentage of votes are required. At least 50% for the typical vote or at least 75% for important votes.
Each facility is required to send a percentage of their citizens to the military force in a time of war.
This rule is definitely tyrannical.
<https://en.wikipedia.org/wiki/Oligarchy>
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Something like the EU with a regularly rotating Presidency with terms measured in months, a highly federal system of administration, and lots of side deals between members might be a good model.
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A goddess decides to create a race of human-like creatures. Instead of leaving them to their own devices, she takes a parental approach and lives among them. She first creates a handful of them who eventually procreate and so-on and so-forth. She literally lives among them as a physical presence and looks like them, aside from being a little taller and, to their eyes, significantly more beautiful/perfect in appearance.
## Goddess' Traits
* Can see into the hearts and minds of her people but cannot physically see them if they are out of her field of vision (just as we humans cannot).
* If she wished to she could heal the sick, bring the dead to life, teleport across long distances and develop magnificent technologies for them, but she generally chooses not to. These miraculous powers are rarely exhibited, but likely often enough that each generation would have seen at least one.
* She provides guidance and wisdom, but otherwise does not intercede in the daily life of her people.
* However, she would intervene if it was necessary for the survival of the whole species (eg. natural disaster, plague).
* She values justice and fairness above all other things and functions as a judge for her people in disputes. (Though as the population grew she would likely be the "supreme court" to other judges.)
* She deeply loves her people, but does not wish to shield them against the regular hardships of everyday life.
* Could conjure anything she wishes from nothing.
* She is both invincible and immortal and so would be with her people forever.
* Being a goddess is also a 'learning process' for her - she may change her behaviour over time.
* In some instances she may deliver justice to people who commit crimes others are not aware of. For example, if she was aware of a particularly terrible murder that no one else knew about, she may take matters into her own hands.
* She values life (but also the life cycle. ie. she doesn't prolong natural lifespans) and morals that are fairly consistent with our own.
* She is not omnipresent.
By our standards, whether the goddess is actually a god or not is debatable, but she does have power far beyond anything her people could comprehend or ever do themselves. From the first generation her people revere her as a god, though understandably there would be times in their history where they may not like her.
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> **My question is:** How would living with such a powerful being affect the development of a new society? How would such a society be different or similar to monotheistic religious societies on Earth?
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Look at the pope in the middle ages and times that by millions and you would understand the place the godess would play in society. The pope at the high point of his power was considered to be the mouthpiece of God on Earth, she is an actual goddess on earth. People from all around the earth would make pilgrimages to ask her for wisdom and justice.
Even if she didn't take politcal power, the populace would hanging on her every word, there would be philosophical and Theological debates over every small comment or slight gesture she made.
Kings would live in fear of her, if she didn't intervene often perhaps some of them might dare to defy her, but given how powerful she is that probably won't end well. Ever time there was a war both sides would send ambassadors to her with reasons for why she should help them defeat the other. Even if she only got involved in one for every thousand Wars it would still be worth it to at least try.
Should probably have some sort of priesthood that would serve as her servants and help take care of the thousands of pilgrims that would come to visit her every year.
Every time there was an outbreak of the plague or a natural disaster people would send for her, depending on how often she would get involved she could potentially prevent most serious threats to human life to such as disease, famine, drought and violent storms. This could lead to rise in population throughout the world.
Depending on her knowledge of the physical world ( and her willingness to share it) she could give humans the knowledge that could help them build Advanced machines.
Overtime some people might grow to resent the goddess either because they think she doesn't intervene often enough or that she intervenes too much or both, this group may try to kill or otherwise hinder the goddess, but since she is unkillable and extremely powerful I don't think they will be very successful, and will probably stay the minority with most people loving her or at least loving what she can do for them.
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I would say that eventually the society would be rid of her, especially if your society consists of humans like us.
Some members of the society would strive for greater power and control. They would see the goddess as a hindrance to that goal. So they would probably try to alleviate her influence. They might do this directly by trying to manipulate her or they would try to influence the society itself to reject her. They would probably find a way to manipulate her since they know what she values. And if the entire society were influenced to reject her, your goddess would either have to comply and leave the society alone or become a dictator to maintain her place in the society.
I guess you might want to consider not only how living with a powerful being will effect the development of a new society, but how living with a new society will effect the development of a powerful being.
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Given a "parallel" Earth-like world with 9 days to our own 7 days (ie, each day is around 18 hours, 40 minutes), what other differences would one expect/require to be otherwise "normal" and habitable?
Would such a world necessarily need to be of different diameter, mass, orbital distance, etc? Or could one assert that everything else is completely Earth-like?
One other exception I had in mind was having dual, larger moons with inherently more varied tidal patterns, as well, but I'm unsure if I'm overlooking something about how the length of a day might influence seasons, water cycles, or imply something like a greater or lesser year length or orbital distance.
PS. Safe to assume native species will have suitable adaptations, ie, not transplanted Earth life that would have to adapt.
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No differences at all. The length of day is based entirely on the rotational speed of the planet (well the orbit has a tiny effect as well but it's negligible in most earth-like scenarios). None of the other factors have any influence on it.
Seasons depend on axial tilt and length of year so again are not effected.
Multiple moons does change the tides, we've had some questions about that in the past. See here for example: [How would having multiple moons affect tides?](https://worldbuilding.stackexchange.com/questions/71/how-would-having-multiple-moons-affect-tides)
Rotation of the planet would have some effect there as it interacts with the tides, but it just makes them happen faster.
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As Tim stated, there aren't really going to be any catastrophic problems from spinning a bit faster - although you might want to consider that the Earth slows down slightly each year due to the friction of the Moon dragging the oceans around it. The effect of two moons will be somewhat more pronounced based on the amount of water moving around each day.
You tagged this weather, so to address weather specifics, you'll have a stronger [Coriolis effect](https://en.wikipedia.org/wiki/Coriolis_force) which will cause [wind bands to be more pronounced](https://en.wikipedia.org/wiki/Westerlies#Behavior). In particular, there will be less mixing of polar and tropical air, and much more pronounced climate bands at each latitude. Wind-related weather in general will be more severe, though I don't have any guess as to how much. Knock-on effects will make things like evaporation happen faster, but also more intense rains from the more powerful storms.
In general, everything will be stockier to deal with the more intense winds, which might be the most noticeable difference to a traveler, as wind speeds and storms will probably trend only toward the top of normal ranges.
Of course, you might be able to adjust the wind speeds to a normal range by increasing the atmospheric pressure by increasing the size of the planet...but that could get really complicated.
In general, just saying "it's windier" should be sufficient for weather.
As far as effects on people, there have been studies that vary the length of the day. I can't find any of the short-day studies, but [attempts to live according to Martian sols](http://www.theatlantic.com/technology/archive/2015/02/jet-lag-is-worse-on-mars/386033/) suggest that humans are pretty well wired for 24 hour days.
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If all the fresh water were at least 25% deuterium, would humans be able to survive?
Would there be significant other detrimental side effects to human physiology as a result?
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It depends.
Heavy water proves toxic to human cells [at levels ~20% of a human's body weight](https://www.ncbi.nlm.nih.gov/pubmed/10535697) (although other sources give 25%). At lower levels, however, it's harmless. Given that ~2/3 of a human's body weight is water, you'd have to have much higher ratios of D2O to H2O than you have in this scenario.
Even at levels from 15%-20% body weight, [heavy water may produce no adverse effects](http://www.concertpharma.com/wp-content/uploads/2014/12/IPT-0310.pdf). In this world, therefore, it seems like humans would be fine.
Raise heavy water levels, though, and things could get really bad. Death comes to mind at very high concentrations.
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This is a problem on Venus the solar wind unslowed by a decent magnetic field has blown a lot of the standard hydrogen away. Eucaryote Mitosis stops at about 20% heavy water so we would have to extract the heavy water before using the light water for agriculture or culinary purposes.
Considering a sizable chunk of our ecosystem including most of our food is eucaryotic there my be some discomfort.
conclusion: a tiny fraction of humanity survives in a very different world. Domed farms with sprinklers because the rain is too heavy. There would onlt be intentional macro-organisms like a moon base. Vastly smaller population and nobody living apart from the main groups. A silent landscape of dead trees and slimy water from the prokaryote explosion caused by all the resources freed up by the mass die off.
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It depends on the rate of uptake and retention of the heavy portion in the human body, if the human metabolism for some reason has a biochemical propensity to take up heavy water (DHO) preferential to standard H2O then an environment with concentrations much lower than the proposed 25% could be deadly since DHO can be toxic at high levels and it would be taken in at a higher rate. On the other hand if the bodily uptake of heavy water is *lower* than that for normal water much higher levels of heavy water would be required to poison someone.
Humans are about 70% water to get to lethal 20-25% of total body weight you need to saturate someone to between 30 and 35% of their total bodily water with heavy water to kill them and between 20 and 30% to start seeing ill effects. So assuming that heavy water is taken up in the same way as regular water and retained without prejudice then the environment described could be rather harmful but wouldn't be lethal. From my classwork on [forams](https://en.wikipedia.org/wiki/Foraminifera) I know that most living organisms actually retain H2O preferentially to DHO since it "fits" better into biochemical structures so you *probably* need slightly higher levels than the pure math above would indicate.
That doesn't however address three things 1. the fact that you are going to see at lot of super-heavy D2O with two deuterium because I don't know how toxic or otherwise that stuff is, 2. the fact that there *will* be an ongoing build up of Hydrogen-2 in living tissue with progressively deleterious effects and 3. the presence of tritium, radioactive Hydrogen-3, which may or may not be a factor but depending on the mechanism of accumulation high levels might be expected. Tritium is a beta emitter that decays to Helium-3, a process that really messes with life-systems that it is integrated into at the time. Tritium uptake is even lower than that for Deuterium but it's also going to be a progressive issue especially since the half-life is a relatively short 12.32 years well within the human span.
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## Some Details
Suppose an Earth-like world with the following changes:
* Atmosphere: 67% nitrogen, 31% oxygen, 2% other
* Average surface temperature: 16.7° C (62° F)
* Day/night cycle: 20 hours
* Gravity: 0.86 g
This world is inhabited by [genetically diverse creatures](https://worldbuilding.stackexchange.com/q/33040/6986) that are equipped with [sugar-laden cells](https://worldbuilding.stackexchange.com/q/33337/6986) to power seemingly supernatural abilities. In order to support the ever-increasing needs of these creatures throughout their evolution, the native flora has grown to harbor increasing amounts of starch in an attempt to acquire more attention from the sugar-dependent fauna.
Additionally, as the creatures became more genetically diverse, the flora required a means to adapt their own genetics to the variability of their consumers. To this end they developed a symbiotic zombie fungus that can take over one unfortunate species of minute flying creature. Like [*O. unilateralis*](https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis), this fungus has the ability to direct the actions of the host until its death. The target species is very similar to Earth's female mosquitoes: the creature feeds on the blood of its victims.
The fungus, however, interprets the consumed blood to extract DNA sequences. It then directs the host to fly to as many plants as it can, usually the generating species of flora, where it then releases spores the plant is capable of retrieving and realigning its DNA to match. This enables the plant to continue to be a producer for individual members of the victim's species. The genetic shift is mostly minor, so it can only expand the plant's ability to feed the native fauna.
## The Problem
Humans arrive at the planet with a desire to colonize it. After witnessing the abilities of the native fauna, they want to settle the planet without completely terraforming it. The zombie fungus defined above will allow the native flora to rapidly adapt to *H. sapiens*, but there is no such adaptability for the environmental concerns.
## The Questions
* Given the planetary details defined above, what precautions would
humans need to take upon first arriving on the planet?
* How long would it take for humans to adapt to the planetary
conditions to no longer require those precautions?
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Once the humans figure out that the zombie fungus will help make the planet more hospitable, they'd want to get the process started as quickly as possible.
They might not want to start the process with themselves though.
Biologically speaking, earth mice and other lab animals are close enough that a plant that is adapted to one of them will be edible to us.
This is why we use them as lab animals.
This is useful for a couple reasons:
1. **It acts like a buffer.** If there was something that could harm humans on the planet, it would be better if it happened to some animals first.
2. **We don't have to be annoyed with the bug bites.** Kind of speaks for itself.
One of the bigger dangers on an alien planet isn't the weather or large animals, it's the really really tiny things that would see humans as large bags of salty water and minerals.
Humans would want to quarantine themselves from the planet until those things could be found and studied to see what effects they would have on us.
**Edit:**
As to the environment, that gravity is a little lighter, but significantly so. People returning to earth after several years would be uncomfortable.
Earths average surface temperature is 15°C, so the planet would be a little warmer over all, but not excessively so, and there would be hot places and temperate places and really cold places, just like here.
It's a little more oxygen rich, but not enough to cause oxygen toxicity. It might just make it easier to work out, as your body wouldn't have to work as hard.
Found a few other [effects of higher oxygen](https://www.quora.com/What-would-happen-if-the-amount-of-oxygen-in-Earths-atmosphere-was-doubled-instantly). Mostly good, but there would be more free radicals, which is bad.
Things like fires might need a little more care.
The hardest part might be the day length, but 4 hours shorter is probably better than 4 hours longer. It would take a little time, but people would adapt to it eventually.
During the quarantine period you'd have plenty of time to model the weather and learn where a good place for a permanent base would be. There's a lot that goes into a decision like that, and you'd want to see the possible areas in all seasons to really get a feel for it.
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There have been a few times when oxygen levels were that high on Earth. That was the time in Carboniferous Era with *really* big insects. Higher oxygen allowed permeation deeper into the bugs.
But higher oxygen also means far more intense fires. One graph showed combustion rate initially linear with increasing O2 up to about 35-40%, then raising abruptly to a slope close to twice that.
Most metals will burn in a pure oxygen atmosphere.
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On Earth, the presence of tides due to the Sun and Moon influence certain currents and other movements of water. This in turn leads to different forms of erosion, which can transform a landscape.
I'm working on a moon that's tidally locked to a planet - pretty much identical to the Earth-Moon system, except that the moon is slightly more massive, and has an atmosphere, water, and life (thanks in part to a magnetic field).
How will the tidal locking - meaning a lack of tides - influence the geography of this moon? Will erosion rates be different? Will that land be shaped differently?
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I believe in this case [Sun Tides](http://hyperphysics.phy-astr.gsu.edu/hbase/tide.html) will become dominant.
>
> Even though the Sun is 391 times as far away from the Earth as the Moon, its force on the Earth is about 175 times as large. Yet its tidal effect is smaller than that of the Moon because tides are caused by the difference in gravity field across the Earth. The Earth's diameter is such a small fraction of the Sun-Earth distance that the gravity field changes by only a factor of 1.00017 across the Earth. The actual force differential across the Earth is 0.00017 x 174.5 = 0.03 times the Moon's force, compared to 0.068 difference across the Earth for the Moon's force. **The actual tidal influence then is then 44% of that of the Moon.**
>
>
>
So while tides will be much less than a non-tidally locked system, it's only by a factor of perhaps 2/3rds. That's enough to still leave significant tides, so I expect you won't see a significant difference in the factors you mention as important - geography, land shape, erosion.
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The tidal power effects are felt most greatly on larger bodies of water. Although waves are partly influenced by tides, most of their ferocity, and therefore costal erosion, is caused by winds so waves would remain largely unaffected by a tideless environment. Tides don't affect so much ferocity of waves but how far "inland" they travel.
The tides of Lake Superior vary by no more than two inches. On the other side of the spectrum tides on the Bay of Fundy can vary as much as 50 feet. So some parts that in a tidal planet would be wet part of the time would be left high and dry.
The greatest challenge to a tideless planet would not be erosion but the ecological challenges that a diminished churning of the oceans would present. There would be areas of high nutrient concentration bordering on toxic and dead areas almost completely devoid of nutrients.
Hope this helps.
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I don't think you'll get a magnetic field without faster rotation, and month-long sidereal day is not up to it.
Without tides from the primary you'll still have solar tides and tides from other moons (as with Pluto/Charon + 3 "regular" moons) and any libration if the orbit is not exactly circular and exactly over the equator.
You get erosion from rain on the mountains weathering the rocks, and wind blowing sand. It doesn't need coastal erosion only. I think the overall quantity of weathering will vary more due to the kinds of rocks and weather patters, so you can tune for proper feedback even without tides.
The overall plate tectonics, mantle convention, and geologic processes don't have any influence from monthly tides.
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I do not think tides have any considerable role in forming the landscape. An influence of storms and weather patterns in general is much stronger.
For example, consider Black Sea which had no visible tides for few last Mys. You cannot tell the difference from any other seashore in a similar climatic area.
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Ok, here is the deal... In my story, I am trying to create a small kingdom containing somewhere 1000-1500 people with a 30-70% female to male ratio & 10-90% children to adult ratio. It is an old fashioned medieval age era and also the kingdom is underground, beneath a very huge mountain (No, they are not dwarves).
The society is divided into various stratas consisting of people from different vocations including teachers, traders, hunters, craftsman, soldiers, etc but no farmers. They would also be maintaining animals, some as livestock like cows, goats, poultry, etc and some for war like horses or elephants. They have a source of water and their food is supplied via traders, so that is taken care of. Also, money is abundant.
So my questions are (in that order)
1. Is the scenario feasible ? Having the entire settlement underground including the animals and sustaining everyone.
2. What are the specifics I would need to take care of while setting it up, like the area it would cover, set up of the kingdom to accommodate the residents, the local shops, the animals, the nobility, if any ? Also, need to take into account the creation of perimeter defenses, though it would not be that huge.
3. Is the original estimate of 1000-1500 enough to maintain the kingdom or will I need to increase them ?
4. Since the kingdom will have a small army, it naturally follows that it would need barracks to house the soldiers, armory to store the weapons, blacksmiths to make the weapons, traders who trade in the specific metals used to make the weapons...it's kind of a snowball effect.. So what are some other similar things that would be required to sustain the kingdom ?
5. Any other general scenarios that I would need to take care of, considering that the kingdom is underground.
Any maps detailing the setup would also be welcome.
Note: was not exactly sure of which tags to apply, feel free to change them.
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**An underground kingdom of 1000-1500 people is plausible** with a long string of provisos. A medieval group with no native agriculture capacity is going to be completely dependent on trade for food stuffs for humans and animals alike. In order to maintain a food supply, your kingdom will need to make something incredibly valuable that a very close agriculture kingdom always needs and can't source from anywhere else. The logistics of moving that much food is difficult for medieval kingdoms and therefore expensive.
You'll have to be really careful with the 1:2.33 female:male ratio. Really careful. I'm also assuming that this is a mining town since money is plentiful but there's no farming.
[This question](https://worldbuilding.stackexchange.com/questions/25967/how-to-hide-an-underground-city) and [this question](https://worldbuilding.stackexchange.com/questions/23882/how-to-live-in-an-underground-city) may be useful to your query.
Keep in mind that 1000 to 1500 people is a tiny kingdom. [Dunbar's Number](https://en.wikipedia.org/wiki/Dunbar%27s_number) is only 150 so it's possible to know absolutely everyone in the kingdom in just two hops. Everyone knows everyone here.
In terms of floor space, each person will need between [100 and 400 square feet](http://www.engineeringtoolbox.com/number-persons-buildings-d_118.html) so that's 100,000 sq/ft on the low end or 400,000 sq/ft on the generous end. Obviously this amount of space is easier to supply on the surface than underground but if the primary industry is mining then building large underground space isn't too hard. 400,000 sq/ft doesn't include offices, shops, stables, barracks, palaces, trade houses, mining facilities, foundaries, cisterns or food supplies. All these additional facilities can easily double or triple the floor area needed. For comparison, the largest structure by volume is the [Boeing Everett Factory](https://en.wikipedia.org/wiki/Boeing_Everett_Factory) at 4.3 million sq ft.
The amount of exposed surface structures can be very small since everything else is underground. Tunneling to attack this kingdom will be slow and easily detected. But, also keep in mind that your inhabitants are highly dependent on air from the surface (unless you use magic to make breathable air) so those air vents must be heavily defended. You'll also need to be able to handle flooding and cave-ins. Handling the tailings of excavated rock/dirt will need to be handled too since pilling it up next to the kingdom's entrance is both ugly and potentially dangerous.
Why do you need a standing army? Are they defending the mine from attack as the standing security forces or is the king just a warmonger? As you said, a standing army is expensive so it either needs to justify its existence in active defense duties or it is by the personal whim of the king. (If the latter, expect a lot of griping about taxes and conditions created by bored soldiers.)
[Answer]
**TL;DR: It's not a stable situation.**
### Overview
I am going to completely forgo any technical issues with actually constructing the underground kingdom; let's just assume that space, illumination, ventilation and such are taken care of without compromising defensibility.
Since we are talking about mediaeval technology however, the weak point is going to be food (both for the people and fodder for animals). There is a reason why wealth in the middle ages was measured not in coin, but in land; you can't eat gold, but you can grow food on land.
Generally anything between 90-99% of the population of a self-sufficient kingdom would have been employed in agriculture just to keep everyone else from starving, and even then famine was a semi-regular ocurrence.
So, your kingdom (and at a 1000 people, it's a tiny one) has a big problem - it's surrounded by at least ten times their number in farmers, and it needs to play nice with all of them to avoid a catastrophe. It won't have much of an army, either.
### Political implications
Obviously, even if the kingdom were completely impenetrable to siege or assault, all an attacker needs to do to utterly ruin it is to stop food supplies going in.
In the middle ages, this problem was generally solved in one of three ways:
First was that the city would be endowed with farmland (and the associated villages) as a part of its founding charter. This would effectively make the city self-sufficient and the farmlands part of its polity.
The second one was often used for mining towns; these would be owned by the Crown, which meant that cooperation of their food suppliers was guaranteed by the implicit threat of the overwhelming strength of the royal army.
The final one was a hallmark of ancient city states; they would just form an army, go on a campaign and conquer some farmlands to feed the city, repeating the process as needed as the city grows.
Obviously all three of them are incompatible with your premise of sovereignty of the city-kingdom not extending beyond the mountain it is under. If you consider its history, it would be pretty difficult to explain away how there never was any conflict between the city and the surrounding kingdoms, which would have ended either in the destruction of the city, or by conquest of the surrounding countryside.
**Solution:** Either give the kingdom some farmland (which will then have to be defended), or make it so that both the kingdom and its neighbours owe fealty to a powerful emperor-type figure which acts as a patron and by force of arms prevents outright warfare.
### Population and army
The rule of thumb is that in a mediaeval population, about 15% of the people are useful as soldiers. With the ratios you are presenting, it will be maybe twice that, so let's call it 500 soldiers. This is about the size of a battalion; if it comes to blows with the neighbours, you can expect them to field about nine times that (assuming a ratio of 95%, ie. a population of 30k). Since your city is already screwed if it comes down to a siege, you need to meet them in the field; which in turn means you need some ace up your sleeve that you can reuse and the neighbours can't replicate.
Otherwise the composition can be basically whatever you want it to be, since you did away with farmers; I'd expect about one noble family, or a couple of patrician families that are also traders or some such; majority of the "lower" and "lower-middle" class occupied with mining and associated crafts (if mining is the primary economic activity) and the rest of the middle class doing the teaching, trading and high added value crafts.
The population is altogether pretty small, though; don't expect to be seriously developing more than one industry.
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I doubt it, medieval societies simply don't have the tech for it.
The first and most obvious challenge is the lack of light. Humans need sunlight for vitamin D production, as well as for mental health reasons.
Torches can be use but the smoke will be very unhealthy.
Maintaining the mine with medieval tech, preventing caveings, making sure that the mine is properly ventilated, etc, will be virtually impossible.
Finally, not having any food production makes the kingdom extremely vulnerable. How long before the neighbouring kingdoms decide to starve them out and take the extremely profitable mine?
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The village background:
* It is located at an elevation of 2,119 m (about 6,952 feet) above sea level with a population of about 1,800.
* It has a continental climate with Oceanic influence. Summers are
moderately hot and winters are very cold and long.
* Night temperatures tend to be below freezing point for half of the
year months.
* Summer usually starts in June and ends in late September.
* The average annual precipitations are above 400 mm (about 16 inches) but can reach up occasionally to 800 mm (about 31 inches).
* Rainfall is distributed evenly throughout the year, although summer
tends to have lower precipitations than average.
The main problems to solve:
* How to get clean water for the people living there at a low cost?
* How to teach the people (illiterate people) to get their own water
without travelling great lengths to get it?
* How to get heat with low costs?
* How to teach them to self-produce and self-sustain the heat?
If possible, I'd like to know about low cost technologies that would help in making the tasks mentioned above easier.
I'd also like to know about the ways in which we can use the characteristics of the field to our advantage and make local products that contribute to the final goal of founding a self-sufficient village in terms of heat and water.
[Answer]
Since there is a small but reasonable amount of precipitation, the water issue is probably best solved by building cachement basins to store rain and meltwater for future use. This can be as unsophisticated as rain barrels by every house (and that would be a good start) to small dams and ponds dug in along stream beds.
For non potable water use (washing, irrigation), it might be sufficient to simply let the water settle, or in extreme cases, filter it through a bed of fine sand to trap particulate matter.
Heating water and purifying it for drinking and cooking can be done through solar heating. Depending on the sorts of materials available, the village can construct various types of solar heaters and concentrators, but a parabolic dish which can flash the water to steam during the day makes the most sense, the steam can be tapped for heat, and condensed for relatively pure water. Simpler systems can be built, including rather simple systems involving a fresnel lens propped up by 2X4's over a clear plastic bag of water (good for hot water, not so much for purification by heat). One issue with solar heating is the heat source goes away at night and in bad weather. Storing barrels of hot water indoors (think of a hot water tank) provides a way to retain some heat during the night, but is ultimately limited (very large tanks can contain a lot of hot water, but are expensive and take a long time to "charge up" with heat).
With limited resources, there are only a limited number of options these people can take, but small scale projects like this can go a long way towards making a difference.
[Answer]
I'm more knowledgeable of climates that sustainability. There are not many places with the characteristics you pointed out. Morocco is not cold enough unless you consider -5 as very cold. The mountains of Central Asia (the Tien Shan range) is the most likely place with these characteristics. There is no dry season, unlike in Afghanistan, Iran, Morocco, etc.
**Kyrgyzstan**
is a poor country with a lot of mountainous areas. Some pat of it have a steady amount of low to moderate precipitations over the year. At 2100m of altitude, they are likely to have even higher mountains not far. That means they can use the water falling in these higher places. They can build dams and reservoirs to use as water supply and to power hydroelectric power-plants so they can heat their homes (among other things). It doesn't need to be gigantic like the Three-Gorge Dam in China, power-plants can be small and efficient.
The call it small or micro hydro power. It is much cheaper that other types of energy but it still cost some money.
**Sources:**
<http://www.eurasia.undp.org/content/rbec/en/home/ourwork/environmentandenergy/successstories/kyrgyzstan--setting-ground-rules-for-investment-in-hydropower.html>
<http://practicalaction.org/micro-hydro-power>
Another solution would be geothermal energy. The main problem is the initial cost is apparently very high but it's one of the most efficient form of renewable energy. Overall it might be better on the long term. But the initial cost is prohibitive.
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**Heat**
Burn wood, straw, conifer needles, grease, and/or dung for heat.
**Stoves**
Use stoves made of metal or brick. Get the air for the stoves from outside, and emit the exhaust to the outside. This minimizes the need for drafts, and mitigates indoor air quality problems.
**Buildings**
Air-seal the walls, except as needed to provide needed ventilation.
Heavily insulate the walls, perhaps using straw or conifer needles.
Either use bricks to make firewalls, or keep the buildings separate enough to avoid risking much of the village burning in a single fire or forest fire.
Have a local brickworks. In a very poor society, this might make adobe bricks. A somewhat richer society might make burnt bricks out of clay. An even richer society might be able to make cement and concrete. (An ore-smelter/foundry/smithy would be a major bonus.)
**Water**
Use gutters and cisterns to trap precipitation that falls on the building roofs.
Divert stream(s) into small reservoirs. Use short earthen-dams, with the water-flow region lined with concrete, brick, or stone. If possible, have the water storage not be in the same immediate basin as the village. The water will be purer if it is not taken from downstream from the village. The damage from dambreaks will be less if the water is not stored upstream from the village. The cost of transporting water from the storage to the village will be less if the storage is not lower than the village. Use gravity-fed canals or viaducts (preferably lined with concrete, brick, or stone) to transport the water.
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First, they need a starter kit air-dropped in, with
* communications equipment (satellite internet, laptop, charger TBD)
* some practical books about heating and water technologies
* some durable tools (TBD)
* a few water bottles and hand warmers
* a project manager trained in sustainability and appropriate technologies
Next, the project manager should conduct a site assessment to determine what energy resources are available, including biomass, solar, wind, and hydro. A geothermal heat assessment would be challenging but potentially highly rewarding, especially if the mountains lie near an active fault region. She should also interview the local residents to understand how they have survived, presumably with some source of heat or shelter, for such a long time. If they get by but would like to trade their resources for more bottles and hand warmers, then the project manager should phone home and determine the exchange rates, and whether tourism and trade by helicopter is mutually satisfactory.
Presuming the local residents started reading online about imperialism and prefer a sustainable alternative to dependency on imports, the project manager should find a partner university to perform a study on feasibility of different technologies for providing heat and water. They will find that a range of technologies exist, but many will be challenging to maintain on-site.
For heating, some technologies are:
* Insulation (ie, renovate construction with earthen or imported material)
* Biomass gathered on-site
* Imported fuel (pellet, cooking oil, or natural gas) and stovetops
* Solar thermal collectors (CPC + tube, or Scheffler dish)
The university partner can help identify organizations that supply either these products for sale, or instruction in their construction, or charitable fundraising and products as gifts. A student organization may be able to raise funds. The best option will depend on the site assessment.
For water, some technologies are:
* Dams and reservoirs, since the annual rainfall is high
* Aqueducts
* Atmospheric water generator
* Pumped well groundwater
Finally, the project manager should consult with the local education authorities to determine if a student exchange program is acceptable. Returning students could then replace the project manager and establish connections in case further outside assistance is required.
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Well heat would be simple if we had resources to use geothermal energy for heating. It also depends if it is easily reachable. I suppose someone would have to put some money in it, but there should be profit in it. So perhaps building a geothermal power plant and hiring locals to tend it would create enough income for some party to have interest in it and leave enough energy for locals to use.
As for water I have no other idea then Thucydidles had.
[Answer]
Water:
Building reservoirs to catch rain and melt-water running down the mountains is certainly the cheapest, most practical and self-sufficient way of meeting the village's needs. It can be used as-is for washing and irrigation. It may not be so suitable for drinking, unless distilled or otherwise treated or purified... all of which is expensive. Fortunately, in a climate and terrain like this, mountain springs are a strong possibility. Springwater is reliably clean and drinkable, and it could be piped directly to the village to supply it year round. During the winter, melted snow is a clean (though somewhat energy-intensive) alternative.
Heat:
Start by building large, round, straw-bale houses. Large and round, because that minimizes the surface to volume ratio, which optimizes construction cost and energy efficiency. Straw bale, because:
1. It's affordable and accessible, using materials that the villagers can grow and gather for themselves (wood, straw, and clay, mostly).
2. It's a great insulator, which further optimizes energy efficiency.
The skills for building a straw-bale house are something anyone can learn. With a few good teachers, the villagers will be putting up houses in no time.
To actually heat these buildings, I recommend [rocket mass heaters](https://en.wikipedia.org/wiki/Rocket_mass_heater). These have many of same advantages as straw-bale houses: they're energy efficient, use local materials, and are simple to build. If wood is scarce on these mountaintops, and dung is more plentiful, they can burn that as well. Really the ideal heating system for an isolated mountain village.
Finally, there's an old trick the Swiss used to use in their alpine houses. Do these villagers keep animals? Cows, sheep, goats, pigs, horses, and chickens all produce substantial amounds of body heat. The Swiss way was to house these animals underneath their own dwellings during the winter, in a kind of walk-in basement dug into the hillside. This provided them with an effective (though possibly somewhat smelly) form of in-floor heating.
With these techniques, I think the village could be very comfortable, and highly self-sufficient.
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What is the smallest set of different crops a (vegan) human population could grow to sustain itself?
We'll assume they have an ideal environment, where anything and everything can grow and the technology to grow aquatic plants.
It can be anything from baobab fruits to micro-algaes.
My first list contains soy beans, spirulina, barley, cabbage, bananas, and a few others. It keeps getting longer but I'd like to keep it as short as possible.
[Answer]
I should note that having the minimum required is a bad idea. If one disease or disaster wipes out a particular plant then you are in serious trouble.
Really you want at least 2 plant species providing for each requirement, which will also help make the diet more varied and interesting.
You should not overlook the humble potatoes:
<https://en.wikipedia.org/wiki/Potato#Nutrition>
Other good choices include:
**Barley**. From your list above this is an excellent choice.
**Beans**. Black, Red and Soy beans are all excellent sources of calcium and iron. They can also be dried for long term storage.
**Berries**. Pretty much all non-poisonous berries are packed full of goodness.
**Cantaloupe**. An excellent source of vitamins A and C and potassium. It's a slightly upgraded banana which would also be a good choice.
**Kale**. Particularly rich in vitamins, minerals and fiber. Other cabbage varieties are also strong contenders.
You should look at some of the research that's been done on subsistence diets and on space exploration. Space Exploration is considering genetically engineering the crops though.
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The agriculture of the Iroquois and other northeastern (American) Indians was based on the "Three Sisters": corn (maize to British/Europeans), beans, and squash. Of course they had other plants, cultivated and wild-gathered, as well as meat from hunting. I don't know whether the three alone would provide a complete diet, but it's a starting place, and has the benefit of tradition.
And of course the Irish survived mainly on potatos for quite some time, but this (<https://en.wikipedia.org/wiki/Great_Famine_(Ireland)> ) is a good example of why you wouldn't want to be dependent on a small set of plants.
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My story setting's group of AIs and brain-uploaded humans wants to colonize space. They have an advantage over us, meat humans, because they don't need conventional life support (air, water, sewage treatment, food...) and are as durable as a computer can be made. Mentally they're happy with a VR environment within their computers, which is big and varied. They can slow their time perception and hang out in VR, or speed it up to operate robots. They're at least as smart as us.
Trouble is, to build a base beyond Earth, they need to build more computers and robots. **How can they build computer/robotics hardware given local resources?** If I give them a fusion reactor they might mine the Moon for fuel, but on Mars it looks like they'll need to bring fuel or rely on solar panels. As for materials, I see lunar dust contains iron and silicon, but I'm also aware that chip fabrication is very tricky business you don't knock together in a frontier garage. Similar idea on Mars: all the iron oxide and carbon dioxide you could want, if you've got an energy source, and it looks like soil samples include silicon and aluminum. But is it at all practical to start building circuitry and robot parts there, or do you have to ship all that stuff from Earth?
It makes a big difference for an AI-driven base, because the "people" are physically nothing but computer hardware. If the only thing they can accomplish for themselves is digging out radiation-proof caves for their server rooms or something, they'll remain highly dependent on Earth.
So far I'm picturing some kind of low-quality computers being built with an organic circuitry tech that relies on carbon (nano-tubes? graphene?) and hoping to turn that into a solar panel that has computation ability for an expanding Mars-surface network. Less computation per area than an Earth chip, but buildable with local materials and just plain cool.
Specifics I'm looking for are what we could build today or in the near future, on the Moon or Mars, assuming great AI and availability of a spacecraft and a fission or optional fusion reactor, with an eye toward not shipping all the computer stuff from Earth.
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That's gonna be a tough cookie. Microchip fabrication plants are among the cleanest, highest technology processes we have. Each individual plant costs somewhere in the neighborhood of 3-5 billion dollars, and the costs seem to increase (almost double) with each new generation of chips, i.e 32 nm chips that were cutting edge in 2010 were almost twice as cheap to build a fab for as the 14 nm chips that are currently the rage, and the 10 nm chips look to make them seem like a bargain by comparison.
Moreover, the supply chain for this sort of high technology process involves literally tens of millions of people, from mines in Congo down to design labs in Taiwan. It seems rather implausible that landing with a nuclear reactor and a large scoop will be enough to start building advanced chips, although perhaps primitive fab versions in the micron range (1000 nm - 1980s technology levels) might just be achievable with a strong miniaturization effort. It might take years or even decades to build the requisite industrial base for up-to-date fabs.
Unless you have nanofabrication, with nanoreplicators and the whole technomagic that implies. At which point, why bother landing on a planet? Just turn the nearest asteroid into computronium. No worries about dust or gravity wells.
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Focused Electron Beam printing: the basic premise work as followed: at a high enough energy, electron beam produces secondary electrons that woud trigger a free radical chain reaction, and with the right mix of silianes and semiconductor compounds, oxygen and carbon dioide, and possibly things like vaporized copper chloride and hydrogen gas, on a piece of flat glass, can deposit up field effect transistors-- at resolution at least as good as an electron microscope that can photograph and view the same transistors.
this sort of technology maybe is not garage-scale, but it is small and simple enough to be shipped by a spaceship, or being constructed by a 3d printer/cnc mill, and this is how a prototype-fab for testing transistor and chip technology can be shrunk to the size of a small lab.
As a matter of fact, this is how prototype chips are made before large scale production begins(at a proper fabrication facility).
magnetic coils and capacitor plates does not need to be precise or flat, and that leaves just a flat substrate that you can make with trivial processes(cleaving a piece of silicon, or a piece of mica, and some adjustments.)
the only downside is the fact that the technology is slow, producing only small amount of chips per process, but it can be avoided by building more devices (from your original device) and expanding with such devices. build a proper fab once you have expanded to a sufficient size and gathered sufficient resources.
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I stole this from [another answer of mine](https://worldbuilding.stackexchange.com/a/14448/3202) regarding turning the moon into a giant computer:
**Begin Construction**
Using a universal fabricator (not too advanced, like 3D printing with metal), or possibly just including them from the start, they can create some [Von Neumann universal constructors](https://en.wikipedia.org/wiki/Von_Neumann_universal_constructor) (or other self-replicating robots/nanobots) and begin to construct a subsurface computronium. This would most certainly be done by building complete cells which, as construction continues, would be linked in parallel. Ideally most of the mass in the area of construction would be used in construction, meaning there won't be any massive shifts (ha, get it) in moon density. The completion time of this process and the resulting computing power are nigh impossible to predict. Most likely, just due to available power (energy per unit time), it would take several years to complete. The computing power would be incredible.
**Solar, Geothermal, and Nuclear Power**
The process and resulting computronium can be powered by solar cells and, once deep enough, geothermal. Yes, [the moon has a molten core](https://en.wikipedia.org/wiki/Internal_structure_of_the_Moon#Core). Large solar arrays can be placed on the dark side of the moon. It is, of course, not really dark, just unobserved. The nuclear power comes [from the radioactive elements](http://blogs.discovermagazine.com/badastronomy/2009/06/29/uranium-found-on-the-moon/) that would eventually be mined during construction.
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The ***Gerontocracy of the Favored*** has ruled essentially the entirety of the Known World for countless generations.
The Old Favored might be men, might be machines, or some strange combination thereof. It is unclear, and none can venture into their High Towers and ascend their [Yelevators](https://en.wikipedia.org/wiki/Space_elevator) to their shining homes in the [Low Heavens](https://en.wikipedia.org/wiki/Low_Earth_orbit).
The Voices and the Will of the Old carry out the Gerontocrats' justice among the common folk, and while the pious and superstitious lot call them [Angels](https://en.wikipedia.org/wiki/Angel#Etymology), the wise among us remember these to be soulless Messenger machines.
Having carved out a niche for myself in the Badlands far from their towers, I have now delved into the histories and tasked wise men to study the mysteries of Physik, in the hopes of finding a plausible path by which the **Art of the Favored** works. So that I myself can ascend to their ranks, or otherwise bring out my strength against them in their discovered weakness and thus overthrow them and cast them down once and for all.
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It is unclear whether there really is such a thing as Luck, independent of human observers, so it might be that is not luck, but the flickering realm of Quantum possibilities that this technology impacts. Regardless, **it is generally agreed that the Old Favored derive their power and health from making each of their subjects marginally more unlucky and less healthy**.
I welcome ideas for building a more robust backstory to **Luck Mining**. How would such technology work? The way I'm thinking about it currently would be somewhat akin to the Improbability Drive of Hitchhiker fame and, more to the point, to the [system broadly described here](https://worldbuilding.stackexchange.com/questions/13285/magic-as-luck-control).
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From the clues in the backstory, it seems the *Gerontocracy of the Favored* is based on some sort of technological version of magic, altering probability.
This would be very difficult to explain without a lot of handwavium (hands moving at almost *c*), and also depends a bit on which version of the quantum universe you believe in.
In the "Many Worlds" interpretation, every event is played out, so in "otherwhen" a version of you is not drinking the warm drink you have in your hand right now (or alternatively, you don't have the drink, but one of the infinite number of your counterparts in otherwhen does...). In other words, for every decision you make or don't make, every possible outcome happens. The *Gerontocracy of the Favored* have therefore discovered a way to manipulate or otherwise access the "many worlds" and direct themselves along the pathways that mostly favour themselves. This will be difficult even with Clarke tech level magic, since not only do you have to anticipate and determine future outcomes for an almost infinite number of possibilities, but you have to do so in such a way that the average outcome is more favourable to a group of individuals, which is exponentially more difficult.
If manipulating quantum reality is a bit too much (this would be pretty much a post singularity landscape, and your hero would be wandering around essentially as an extra in *someone else's* dream), then you could simplify things a bit by postulating a cluster of AI's which could take input from a vast number of sensors and using game theory, probability tables and other statistical methods, advise the *Gerontocracy of the Favored* of what paths lead to the best possible outcomes. Once again, this runs into the problem of averaging out the outcomes over a group; outcome A may favour me over you, outcome B may favourite you over me but outcome C, while not optimum for either of us, is better than other outcomes for both of us. This is a variation of some forms of game theory.
The problem with either form of "magic" is twofold.
The fundamental problem is known as the "[Local Knowledge Problem](https://fee.org/articles/hayek-the-knowledge-problem/)", and was postulated by economist F.A. Hayek. Hayek observed that information is subtle and diffused in any system (this applies to markets, climate, ecosystems or other complex, adaptive systems) and local actors can observe and act upon this information far faster than any centralized system. By the time the information makes it up the chain, is observed, a decision made and the order to action given and passed down the chain, the conditions will have changed (either a little or a lot), leading to cumulative errors building up in a positive feedback loop. This is why market economies with local actors with free agency will always outperform centralized command economies. Your *Gerontocracy of the Favored* might actually be a craptacular USSR written on a global scale, and while the *Gerontocracy* is better off than the ordinary people (much like the Soviet era Nomenklatura), compared to us from the far distant past they are not well off at all.
The second and probably more immediate issue lies in game theory. So long as the *Gerontocracy of the Favored* can hang together with common goals and are willing to accept individually sub optimal outcomes to preserve their overall ranking, they can be ahead of the others. Human nature (and possibly post human nature) being what it is, the various members making up the *Gerontocracy of the Favored* will probably end up seeking ways to optimize their own individual outcomes, leading to covert and even overt efforts to oust other members and seize resources for their own use. By the time your story starts, there may be only one member of the *Gerontocracy of the Favored* left "standing" as it were; the sole and absolute ruler of Earth.
As Dirty Harry would say in these circumstances: "Do you feel lucky?"
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I recall several stories that employ relevant concepts.
Greg Egan has a novel in which a butterfly evolves future-feedback physics and then evolves rapidly without trial and error, always getting just the right solution.
James P Hogan has a novel where a planet has flowers that impart a sense of what's the right decision for long-term benefit.
I recall a short story in a magazine in which a decice is invented that is worn as a pendant around the neck, and feels ahead into the future to the organism's lifespan, and signals with a shock to the neck that something bad will happen. It worked to avoid a car crash, and a vague signal with no explaination was explored by making different plans until the signal abated (it was a house fire). It had some tech explaination in the text, not just a magic amulet.
A other Egan novel had a way to supress the wave collapse and allow multiple histories to exist, and it could be used to get the right random/lucky outcome. You ought to read *Quaranteen* for these ideas on harnessing the *many worlds*.
Another idea is that a network of nanobot sensors etc. and high powered computers can compute through *chaos* and, e.g. make a hurricane by getting the right butterfly to flap its wings on cue. Seeing the future more directly would amont to the same thing.
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The problem with 'Luck' is that it is a human concept applied to the quantum workings of the universe, which itself does not care if one macroscopic system is favoured by the vagaries of chance while another is harmed by the vagaries of chance, or is also favoured, or has no net benefit or loss from its point of view.
Put more simply: Our universe simply doesn't care how many people get lucky or unlucky.
This leaves us with two possibilities:
1. The universe described in the question is *different* to our own, and is quite probably (though not definitely) an anthropically-oriented simulation, (possibly matrix-like in which sentient beings are beings out-of-universe who are plugged into the simulation, though it does not necessarily follow that they *must* be plug-ins, and are not entirely simulated themselves), in which subjective luck is a limited resource,
or:
2. The creators of the technology that 'transfers' 'luck' (i.e. net benefit or harm to living beings) deliberately included an unnecessary component that negatively affects non-target beings at the same time as it positively affects target beings, according to the net gain or loss inferred on targets and non-targets, based on the subjective appraisal of said gain/loss by all beings within its area of effect.
In the case of option 1, this could be an experiment on the effects of an anthropically-oriented universe as opposed to our impersonal universe.
In the case of option 2, the creators of the luck transference technology/magic must either had the mistaken assumption that luck is a universally-limited resource rather than mere localised quantum variations that could be influenced without affecting other localities, or they must have - with malice aforethought - set out to ensure that the device they created had no *net* subjective benefit or harm to the beings in its area of influence.
The reason for this may be simple malice, or there may be a more subtle, probably legally-oriented reason. For example: the government in the time and place that the device(s) was(were) created may have had some arcane legal requirement that equated imposition of health benefits with financial gain, and that in order to avoid that government's tax laws that would have seen the device's owners taxed according to the net benefit it bestowed, chose to have it impose no *net* benefit, by causing low-level harm to a large number of non-targets commensurate with the benefit gained by the low numbers of target individuals.
As to how it works - that depends on the two cases above.
In Case 1, the simulation/different universe: The luckiness or unluckiness of an individual is determined by the generation of a random number in the simulation engine. Luck transference *to* an individual or group may occur by having a subroutine pick better values out of a buffer of truly random data that is otherwise streamed sequentially as randomness is required, leaving the less-lucky values for everyone else.
In Case 2, our own universe or a reasonable facsimile: The world may be seeded with nanites that are able to change living beings and influence otherwise random outcomes for better or worse relative to the living beings between them. Due to the requirement that the entire system confer no net gain or loss as subjectively assessed by those living beings, they would be networked, forming a distributed intelligence, reading peoples' minds and imposing 'luckiness' or 'unluckiness' according to their/its target criteria, the entire system designed to produce no *net* gain or loss except over short, non-reportable periods.
How? The nanites might read an individual's intent, and assess the likelihood that the actions they were performing would lead to a subjectively positive or negative outcome, and if necessary alter those actions by something as simple as adding or subtracting a few nerve impulses here and there so that an individual's actions were unexpectedly successful or otherwise, or someone had (or didn't have) a particular worthwhile thought or idea, or they might correct or create a genetic or immunological deficiency that would lead to cancer or disease immunity.
Either way, luck *transference* can probably be put down to someone quite a while ago making the informed decision to make a lot of people's lives more miserable than necessary.
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Here are some ideas, in ascending order of technomagic:
**Working the Mines of the Favored**
The Old Machines hate gravity enough to choose to live in LEO (Low Earth Orbit), yet the Earth is one of the main supply sources for Uranium and Thorium (fusion has sadly remained uneconomical, at least at the vision-sensor-gouging rates the masters of the Gas Giants have been charging the past few millenia). So the Earth is an open mining pit for radioactive nucleides, with all the radiation sickness that implies.
**Keeping Prols for Spare Parts**
The Earth-bound population consists of genetic clones of the Master copies in orbit and are treated in much the same way people today interact with a supply closet, with the occasional 'angelic' grabbing claw dragging an unfortunate (and relatively healthy) victim to their sad fate, leaving behind an occasionally renewed population of mostly defectives and rejects.
**Reality Engineering**
The technology of the favored includes limited prescience regarding their subjects (possibly due to detailed quantum simulations of reality ran by Oracles in LEO) allowing their robotic servant unprecedented control over the most intimate and relevant details of the lives of their subjects, which enables the favored to intervene at critical juncture points to prevent credible opposition within their rule-domain to even become a possibility.
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Well, I'm think the answer is in your question.
Since "Angels" was known as soulless Messenger machines we can asume the global information network. And it is known "information is power". It's not pointed to favored have individual high luck, so I'm guess it's a question of priority, e.g. One man developed a prototype of some great new device. As soon as he's not the only one who know about device the information leaked to the Favored. Now it's nothing but a deal of sequence of coinsedences. Man should deliver the prototype to some company, while on the way, lost his key from home (no one saw a boy who stoled it), was hitted by the car (no one hurt but prototype was destroyed), and the meeting was canceled (company got bad news from market). When returned home, Man see it in fire. Bad luck, bad luck.
Now, how it was from the point of view of Favored:
```
New information aquired about some new device.
New information acquired about the meeting.
New project started.
Possible route of target builded.
New task for local thieves sent.
Target progress on route - 10%. Deviation - 0,1%
New report from agent (Thief): Task completed.
Deviation process on market stocks started.
Road traffic simulation started.
Road traffic simulation finished.
Spam message sent to <"car driver">
Target progress on route - 70%. Deviation - 5,4%
Target and <"car driver"> encounter - in progress
Target and <"car driver"> encounter - complete
Protype destroyed.
New report from agent (Special): Documents received. Fire accident in progress.
Target company market status: unstable.
Deviation process on market stocks finished.
All project tasks completed.
Project completed.
New research iniciated.
```
At the end Favored got new technology. Good luck for them. So, it's not the question of Luck Mining, but Information Mining.
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Using some handwaves, you could do this with advanced probability computing.
For instance, if one of the immutable laws of the universe is that there is a finite amount of "Luck" available at any time, and that "luck" can be altered by doing the math, then you have luck "mining" by simply having that technology only available to the elite. Additional immutable laws could come into play by having luck attract luck (and vice versa) so that the lucky get luckier and the unlucky get unluckier.
For example, you have two people playing roulette - one of the technocrats and one of the proles. Our prole has no access to this probability calculating technology, wheras our technocrat does. Our technocrat can use his computing advantage to calculate what numbers to play based on every single variable - from the way the roulette operator rolls the ball to the temperature of the room. this gives him a significant advantage. The laws of the universe as handwaved above would then increase this advantage for each prior "lucky" moment.
Combine this with the huge advantage of information such connectivity could bring and you have a powerful "lucky", well informed elite and an unlucky lower class with an information disadvantage.
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Just to throw in the mundane answer:
"The more I practice, the luckier I get"
Luck is a concept which measures what has already happened rather than what causes it to happen - i.e. you were lucky because something good happened by chance, not something good happened because you were lucky.
So that being said, the only way to "increase" your luck, really, is to increase the probability of something favourable happening. And this is usually done through hard work, experience, practice, research, networking, superior or insider knowledge, etc.
e.g. you're likely to win a bet on a boxing match if you happen to know one of the fighters went on an all-night drinking session the night before and hurt his wrist, than you are by pure guesswork. Those people who are always in the right place at the right time when an opportunity presents itself? Quite often this is because they've gotten their name out there, made friends, done favours for others, put themselves in the minds of the people presenting the opportunity, etc.
So those "angels" who appear to have superior luck? They actually have superior knowledge, social skills, mastery of elements that appear to be chance (e.g. they have advanced long-term weather-forecasting and farming techniques so their crops always thrive)- but they don't reveal these skills, and make it appear like pure luck.
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Try to get out this dimension by meditation, then you will be multidimensional being, as that you can know and do whatever you wish in multidimensional universe or multiverse. Then you can see all possible life's and achieve your goal. Easy :)
Mathematically, you will be live unlimited parallel lives with different outcome or end.
But you will know all that in this one presence, so like there can be only one, who is wake is like who is live others are like sleepers. Can't achieve what you wish to do.
Sentence Jhvh Jehovah men's that brate mudri.
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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.
Would a spoked, rotating torus work as a method of colonizing space? If so, how feasible would it be? As in, what would be the cost, where would we get the materials for it, how fast does it have to rotate to simulate earth gravity, etc.
I'm actually thinking of a design somewhat like a wagon wheel. The outer ring is where everything happens, and the inner ring is where ships dock and such.
The questions, to be specific, are
* How fast would one have to rotate to offset the slight gravitation from its own mass and simulate Earth gravity?
* Where would be the best place to put one of these?
* What is the best size for one of these?
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The spoked wheel is the classical design for space stations and colonies. It was introduced as far back as the 1930's (if not before), popularized by Von Braun in the 1950's, appeared in the movie "2001, A Space Odyssey" and reappeared as the "Stanford Torus" in the 1970's when Gerald K O'Neill popularized the idea of space colonization.
To calculate the force felt by the colonists by a rotating colony (or any rotating structure, for that matter), use the following equation:
$a = \omega^2 r$
where $\omega$ is the angular velocity of the station (rad/s) and $r$ is the radius of the station. Acceleration, a is measured in $m/s^2$.
The Stanford Torus is 1790m in diameter and rotates once a minute to simulate a 1 *g* environment
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On Earth:
$$ a\_G = 9.81\text{ ms}^{-1} $$
That's acceleration due to gravity. On a spinning torus, you simulate gravity by living on the outer edge and using centrifugal force, for which the formula is
$$ a = \omega^2r $$
where, as Thucydides says, $\omega$ is the angular velocity and $r$ is the radius.
The comments have it right: about a 2km radius is the sweet spot balancing material limitations and having a decent size station, so to simulate gravity $\omega$ must be $0.070 \text{ rad/s}$.
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A fictional rotating station much larger than the Earth diameter is described by Larry Niven in *Ringworld*. He invents a fictional material with extraordinary strength. Not hard science, unfortunately ...
Slightly smaller are the orbitals in Iain M. Banks' Culture series. Again fantastical science is used.
A hard design in 1976 was the [O'Neill Cylinder](http://en.wikipedia.org/wiki/O%27Neill_cylinder). Compared to your cylinder, it is longer and has an air-filled center. Also consider the [Centrifuge Accommodations Module](http://en.wikipedia.org/wiki/Centrifuge_Accommodations_Module) -- much smaller, but also much closer to reality. Those two don't look like spoked wheels, but the principle is the same.
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A ***LOT*** of thought has gone into the question of how to build space stations and use rotation to provide simulated gravity.
Space Station built from Shuttle External Tanks
I don't see anything wrong with prior answers but thought I'd add my $0.02.
**Minimum size constraint**
It turns out that any rotation speeds >= 3 rpm makes people motion sick. For design purposes, designers felt a maximum rotation speed of 2 rpm would ensure very few people would suffer motion sickness. Scientists felt that most people could acclimate to a rotation of 10 rpm but I think I'd reserve such a design to mission specific applications (e.g. a small military ship crew).
So the minimum size of your cylinder is constrained by human physiology.
**Maximum size constraint**
As many others have pointed out, the maximum size of the station is constrained by the tensile strength of the construction materials.
I don't feel like doing the math and others have commented on it so just use their numbers.
**More information**
The most excellent **Atomic Rockets** web site has a vast store of useful information for world builders. Even better, it has a whole (& very large) page devoted to [Space Stations](http://www.projectrho.com/public_html/rocket/spacestations.php).
For people looking for math, numbers, and other reference materials - including actual design studies for rotating stations (as well as other issues that might arise), run to the web site and be prepared to spend a couple of weeks reading.
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As for location, it depends on your story setting.
The International Space Station (ISS) is orbiting around 400 km above Earth. This is about the optimum with the technology we have today. Go too low and atmospheric drag will slow down the space station causing it to lose altitude and eventually re-enter in a giant fireball. To prevent this from happening, the ISS occasionally gets its altitude boosted by visiting Soyuz crew capsules. Go too high, and it becomes more expensive to reach the station.
If the station altitude is higher than 1000 km, then some sort of radiation shielding will need to be considered. The [Van Allen belts](http://en.wikipedia.org/wiki/Van_Allen_radiation_belt) are high radiation regions between 1000 km and 60,000 km. Satellites passing through this region need shielding to protect their electronics. People probably need more shielding if they are going to be living here.
Other places to consider would be the [Lagrangian points](http://en.wikipedia.org/wiki/Lagrangian_point#L1). These are stable points in Earth's orbit around the sun. Colonies placed at these points would require minimal station-keeping. They would, however, be pretty hard to reach with current tech.
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I'm trying to write hack-ish (As in, I'm a hack) science fiction that is realistic except where it is inconvenient to me. That being said, animals are not an area I want to handwave. I want the animals on a planet humans colonize to fall under different categories than those of Earth. I've got some stuff "down pat", but I've hit a roadblock in trying to come up with some alternative skin coatings. On Earth, we have things like
* Scales
* Fur
* Bare Skin
* Feathers
And
* Exoskeletons
I ask you; What sort of skin/coating might an animal from a planet with 20% lower gravity and higher air pressure at sea level evolve?
Right now, I'm thinking that some animals might take indigestible components of their food and force them to go through a "Deconstruction system" where they are processed into a form that can be excreted as a paste over the body that hardens to provide protection and insulation based on what they've eaten. Is this viable?
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Always consider the purpose and desired behaviors of an organ when trying to determine how it will look.
Every skin material is "chosen" because it fits a role. Scales are great because they are rather impervious (which is a big deal if you are in an environment where dodging blows is difficult, or where forces like sandstorms reign supreme). Exoskeletons do this to an extreme, though they pay a price in terms of growing pains. Bare skin, on the other hand, focuses on maximum flexibility and pliability.
Generally speaking, if you look at skins of animals on Earth, gravity and air pressure have little to nothing to do with choices. The skin supports very little of the body, so the effects of gravity are minimal (other than the feet. The skin of the feet can be interesting). Air pressure has almost no effect at all until you get down into the single-digit torr range (vacuums) where the ability to create a pressure tight seal becomes useful.
As for your deconstruction system, it seems valid to me. Elephants do the same thing with mud. The only concern I might have is the health concerns of spreading processed waste (and the energy it takes to process it).
It actually strikes me as what I think of as a "falling off the bicycle" point for evolution. Realistically speaking, its much cheaper to maintain a skin compound that is emitted from the skin, rather than manually applied, especially when you think about the need for adults to spread matter on the children before they learn to do it themselves. In famine cycles, you'd have a double-whammy of no food and more damage from the outside environment. However, this sort of strange thing does seem to happen from time to time. Every now and then evolution picks something really wonky and runs with it. I recently ran across a species of bird where the males announce their stature to the females by blowing up a large inflatable red sack under their beak. The sac is nearly as large as the bird, when fully inflated, and takes 20 minutes for the male to inflate. This is totally absurd, and yet has proven to be the most effective way to pass his genes from generation to generation.
If I saw a species with such a waste-matter insulation, I would expect to see them on the bleeding edge of what their genome could do for the scenario. It clearly chose a strange solution to the problem, one which is not genetically very sound... but genetics is not proud, it simply goes for what works.
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I'd agree with @cort that the conditions you mention would not have a dramatic effect on the type of outer coating of an animal - so it wouldn't differ much from Earth where (as you point out) there are several choices.
Perhaps the excretions could be from specific points on the skin which add to the base of the previous excretions and lengthen them, resulting in... hair! But if you want to toughen up the creature, they could be strong and thick like quills. Or to shield their skin they could be fluffy and downy. And feathers (while not the same as hair) are just a special adaptation of the same idea.
What would be more important to your creatures would be adapting to their environment - sea creatures don't have fur or feathers. There are some evolutionary compromises (penguins, fur seals, polar bears) but these animals spend most of their time out of the water. So, perhaps you have to design your creature(s) to match the way they live, and invent some useful details if you want them to be "interesting". For example, if it may be predated upon in an aquatic environment, perhaps it has an outer layer of slime which allows it to slip out of the grasp of predators. Or to take that one step further, a whole outer layer of skin which it can shed. Or pouches of foul goo covering them which deter predators.
But animals here on earth have already developed almost every variation I can think of.
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Following this [question](https://worldbuilding.stackexchange.com/questions/12552/cosmic-background-radiation-in-the-past), I had additional question of habitability.
Assuming that life could exist on planet formed roughly twelve billion years ago, allowing complex life to exist as of seven billion years ago, what would be the most plausible explanation of how they survived from:
>
> Given the much, much higher gas densities of the era, I'd be **far, far more worried about getting blasted apart by the numerous supernovas popping all over the place**, and black hole radiation blasts from the super-massive central black hole and actively feeding nearby black holes. Each of these might be sufficient on its own to sterilize areas ranging from dozens of light years for a supernova to perhaps a whole galaxy for the central super-massive. Plus rare events like a triple neutron star collision, etc. - *Serban Tanasa's [answer](https://worldbuilding.stackexchange.com/questions/12552/cosmic-background-radiation-in-the-past/12555#12555)*
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To keep the question in narrow term,
1. How does the star system (that hosts the planet) survive or protect its planets of those dangerous radiation sources?
2. If the above condition is impossible to meet, how could a planet protects its life from such radiation?
2.1 Is it possible for life to evolve underground during the early era, and later (at seven billion years ago) populate the surface?
2.2 Is life in an ocean environment similarly affected by the radiation? Or could they survive?
3. And finally, if all of the above requirements were impossible, could life itself have evolved in a way that that could resist radiation?
Answers do not have to cover all of the questions above, you should just move to next questions if previous question(s) were deemed impossible.
I'm expecting that the evolution of life on that planet follows similar path as of earthen life, like:
1. RNA life at first,
2. Cellular life,
3. There would be a [Great Oxygenation Period](https://en.wikipedia.org/wiki/Great_Oxygenation_Event) to fill the atmosphere with oxygen,
4. And complex life evolved a a later time (similar to Earth's [Cambrian](https://en.wikipedia.org/wiki/Cambrian) period)
Of course it doesn't have to be on that sequence, and the answer could be more flexible.
[Answer]
Couple ways it could work:
**Magnetic fields**
The planet could have a really strong magnetic field. Earths magnetic field protects us from a nuclear furnace that's relatively close by.
Likewise, the sun has a magnetic field which would offer some protection.
**Water**
[Some theories](http://www.space.com/7779-water-shield-seeded-earths-oceans.html) say that early earth was protected from radiation by a shield of water. Being deep underwater for the first billion years or so would also help. Maybe forming around nutrient rich underwater volcanos.
**Nebula/Molecular clouds**
Gasses could absorb some radiation. A stellar nursery is a molecular cloud where stars are forming, possibly with a planet.
**Boring neighborhood**
By shear chance the star forms in the most boring part of the galaxy, where nothing much is happening. Considering how many things have to not go wrong for evolution be possible, it seems like a miracle that our world isn't a lifeless rock.
[Answer]
My initial answer suggests nothing more than a *statistical likelihood*. In [a young universe supernovas were a lot more frequent](http://crd.lbl.gov/news-and-publications/news/2011/distant-supernovae-reveal-10-billion-year-old-secret/). That makes it more likely that any particular world would be close enough to a supernova to risk being sterilized.
It does not mean that all worlds in all galaxies were all constantly sterilized. Perhaps a few (or a lot) escaped unscathed.
Earth life evolved in the oceans, as far as we can tell, the ground we call home was colonized far later. Water does provide significant shielding against radiation. However, it does not provide complete protection. Gamma radiation from supernovas has been proposed as the cause of the end Ordovician extinction, which resulted in the death of nearly 60% of the oceanic life on Earth.
Moreover, once established, life can adapt. There are microorganisms on Earth with amazing resistance to radiation, such as Deinococcus radiodurans, which can survive not only radiation but also cold, dehydration, vacuum, and acid.
As a final real-world consideration, one interpretation of the [Fermi Paradox](http://en.wikipedia.org/wiki/Fermi_paradox) is that conditions were adverse to intelligent life until the recent past, so that we are alone as sentient beings in the galaxy. It is not the sole interpretation, of course.
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There *are* stars in the intergalactic space, if sparse, and we know of no reason for them not to have planets. Of course that means extreme isolation from other systems, no dreams of "flights to Proxima Centauri". Very little hope for interstellar escape when their star goes red giant. But they would be safe from all dangerous neighbors like supernovae and black holes.
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[Question]
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This question is inspired by book [The Day of the triffids](http://en.wikipedia.org/wiki/The_Day_of_the_Triffids) and [this question](https://worldbuilding.stackexchange.com/questions/11170/what-could-kill-all-vegetation-in-an-area-and-then-stop-it-from-growing-back)
Russia and USA have never been really "friends", lets admit it. So we will not be surprised, that one of them (pick your side) secretly developed "The triffids" - plants which can move, produce loads of seeds and such seeds can be spread in the wind.
And yes, these plants seem to be intelligent and use poisonous spit to paralyze their prey (which causes humans to go blind)
During one military training, where the seeds were loaded, something went wrong and triffid seeds were released in stratosphere. So these plants were successfully released to the whole Earth.
The sad news: **Humans did not make it. They all died, Jim.** (Or, if you cannot accept it, try to accept the fact, that humans very few survived and are so busy fighting off the triffids that they cannot come up with a plan into getting rid of the plants)
Moving on into the future, thousands and thousands of years, even eons, if needed.
It is safe to assume, that some animals did survive the triffids. Now:
1. Can I assume that some animals would develop into fighting the triffids?
2. Is it plausible to assume, that the "deadly" weapon against the triffids would be salt? They are still plants...
3. What threats could such animal have to use salt as weapon against the plants?
[Answer]
There's an abundance of a certain plant - surely a herbivorous species will enjoy the new source of food, developing immunity to the poison. They can be insects or small rodents, or pretty much anything that could avoid the plant attacks relatively efficiently.
Salt is unlikely to be plausible, because in most world regions it's a very precious mineral in the nature, and in large concentrations it's deadly to most life. Animals wander long distances to reach places where a salt vein is exposed, licking the mineral to resupply the ions in their bodies.
Still, there are regions where salt is abundant. Specifically, all sea shores, salt lakes and... cities in winter areas, where roads were salted in winter - the contamination will last for centuries.
Now, our animal species developed a poisonous bite - injecting saline into the victim. While it would be hardly harmful to most species, it changes the vulnerable electrolytic balance of triffids (we can assume it's vulnerable, because why not? Snails are extremely vulnerable to that, even minimal amount of salt is lethal to them). The side effect is leaking 'ichor' from the wound, which the animal drinks, both feeding and recovering some of the lost salt.
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I have got a fictional universe, where a humanoid lifeform evolved on earth not from apes, but from bears. The humanoid bears are like humans; they walk on their legs only, wear clothing, have various languages and civilizations; the only thing is that they still have snouts like bears have and still have fur on their whole bodies.
What could be a good PoD or event which would prevent Apes from becoming Humans and would instead let Bears become humanoids?
[Answer]
In order for bears to become humanoid tool users, they'd need to evolve a few things first:
* Tool use
* Dexterous hands
* Abstract spoken communication
* Group living
* Bipedal stance
Notably, all of these but the last one are found in non-human primates, though the adaptations towards abstract communication and tool use in something like a chimpanzee aren't evolved to anywhere near the degree they are in humans. Bears, on the other hand, have none of these things. As it currently stands, apes are closer to evolving into bear-like humanoids than bears are.
We do, however, see at least one of these adaptations in one specific kind of bear: pandas, which have thumbs. Sort of.
In order to better grasp bamboo, pandas have evolved thumb-like spur on the side of their wrist which they can oppose the rest of their fingers against to grasp shoots of bamboo. This is the sort of an adaptation that could one day lead to a dexterous hand. Some pandas could, for example, begin to use bamboo shoots as tools to knock nests, low hanging fruit, and bee hives out of trees. If they lived in a place that had lots of these sorts of things for food, and in which bamboo was becoming more scarce, using bamboo shoots as tools could be a natural way to increase the amount of protein in their diets.
Next, if our mutant panda environment was relatively rich in food, our pandas might begin to see more benefit in hanging around as a group instead of going solo. Since they wouldn't need a large gut for digesting lots of cellulose they'd also begin to get slimmer, at which point bipedalism might allow them to reach more food and better manipulate the sticks they're using to access their food. At some point, they might begin to try throwing their sticks to get things that are out of reach.
All of this would take a long time, as well as some ideal conditions. Pandas are far from stick-wielding bipedal fruit-knockers, but it's possible they could evolve to be as such. All of this would put them in a position where they could develop into something we regard as a sentient species, though.
They would, however, have some distinct differences from humans. For one, they would probably be terrible runners. Pandas, as it currently stands, are pretty slow, and the evolution towards bipedalism we're looking at is not an evolution for bipedal *hunting*. If they did hunt, it would probably be by throwing things.
Our panda-people would have much stronger arms, even proportional to their size. Their main means of getting food, at least early in their evolution, is to whack things in trees with sticks. The bigger their muscles are, the bigger the sticks they can use.
Lastly, they probably wouldn't wear clothes. Pandas are quite furry, so clothing wouldn't be necessary in most environments.
**Why wouldn't ground dwelling carnivorous running bears become humanoid**
Most animals in history have evolved without humans and never become humanoid, because evolving some or all of the traits that define a creature as 'humanoid' is not evolutionarily viable.
By evolutionarily viable, I mean that every step of evolution (generally) leads towards a form which is better evolved for survival. Apes, for example, developed progressively more dexterous hands because at each point during their evolution, increased dexterity lead to improved ability to climb trees. Eventually, these dexterous hands allowed chimpanzees and early hominids to begin creating and manipulating tools, but they were only evolved in the first place because every step along the way improved their ability to climb trees.
For ground-dwelling bears, the primary purpose of feet is for walking, and the primary purpose of front legs is for supporting body weight. Hands, unfortunately, aren't terribly good for walking on the ground on. This is why we humans have stubby little toes. In order for paws to develop into hands, grasping must be more important than walking. Pack dwelling bears that ran after food on the ground would develop hand-wise in the opposite direction, with fingers becoming progressively shorter and stouter.
Bipedalism follows a similar trend. While paleontologists are still divided as to exactly *why* humans became bipedal, it certainly wasn't to help a ground-running predator catch food. The transition, at least initially, would have led to slower creatures than those which ran on all fours. If running quickly were important, natural selection would have selected for the quadrupedal creatures. [Modern theories](http://en.wikipedia.org/wiki/Bipedalism#Evolution_of_human_bipedalism) posit things like the ability to carry food or the ability to pick things off of low branches as being the reason for developing bipedalism. For bears to become bipeds, something similar must happen with them. It must be more beneficial for them to stand on their back paws while using their front paws for something else than it is for them to run on all fours.
[Answer]
You would need to go back a long way, probably about 4-5 million years.
There is little debate that animals in the genus Pan, made up of one species with four subspecies of common chimpanzees (Pan troglodytes of the Western, Nigeria-Cameroon, Central and Eastern varieties, in geographic order, with a substantial gap between Western chimpanzees and the continuum of the other three subspecies, with some zoologists preferring to split Eastern chimpanzees into separate Northern and Southern subspecies rather than lumping them into a single subspecies), and one species of bonobos (Pan paniscus) aka pygmy chimpanzees, are more closely related to modern humans than any other species of animals that still exist today. Common chimpanzees have 23 chromosomes, bonobos have 24 chromosomes and modern humans have 26 chromosomes, but the chromosome divisions are such that particular genes in modern humans usually have corresponding genes, sometimes on a different chromosome, in chimpanzees and bonobos.
There are roughly 170,000-300,000 common chimpanzees and 30,000-50,000 bonobos alive today. The 30,000-50,000 population of each of the chimpanzee populations today is probably a pretty reasonable estimate of the total population of species ancestral to modern humans while they were confined to Africa.
Lots of disasters and misfortunes (volcanos, floods, wildfires, disease outbreaks, droughts) can send a relatively geographically compact population of that size into a tailspin. Indeed, several species of hominins ancestral to us did go extinct over the last several million years.
The divergence between other great apes like chimpanzees and bonobos on one hand and hominins on the other is on the order of 4 to 7 million years ago, with more recent data favoring the older date which is when the earliest hominin fossils are dated. There are several possibly ancestral and possibly sister hominin species in this tie period in Africa.
The six million year old *Orrorin* is arguably more human-like than *Australopithecus* (e.g. Lucy) despite being about 3 million years earlier. *Sahelanthropus tchadensis,* which is about 7 million years old, has been classified variously as a common chimpanzee-human ancestor, as part of the genus *Ardipithecus* (which is about 4.4 million years old), and as the ancestor not of humans but of gorillas.
[](https://i.stack.imgur.com/czZn6.jpg)
*An artist's depiction of Ardipithecus.*
The oldest member of the genus *Homo* is *Homo Habilis* (an artist's depiction of which is below) dates to about 2.33 million years ago.
[](https://i.stack.imgur.com/hooUp.jpg)
The first hominin species to leave Africa was *Homo Erectus* [ca. 1.9 million years ago](http://johnhawks.net/weblog/reviews/archaeology/lower/early-pleistocene-china-paleomag-2013.html) in a single migration wave. *Homo Erectus* is the hominin species that in terms of technological developments we associate with comic book "cave men", using stone tools and fire and clubbing big game and living in natural caves, but any clothing used was probably pretty primitive because their range extended much less further north than Neanderthals and modern humans who came along later and are derived from a common ancestor well after *[Homo Erectus](http://johnhawks.net/weblog/reviews/archaeology/lower/early-pleistocene-china-paleomag-2013.html).*
The effective population size of the *Homo Erectus* out of Africa migration wave was probably pretty modest and all manner of misadventures could have prevented them from making it out of Africa. One or two encounters with giant crocs in the Nile or sharks while trying to cross the Gate of Tears if they took that route, could probably have done them in if they weren't lucky.
But, once *Homo Erectus* was out of Africa the window of opportunity for bipedal bear evolution pretty much closed because that ecological niche was now filled.
(Honestly, a scenario with an "inferior" *Homo erectus* or *Ardipithecus* species that didn't leave Africa, and a bipedal bear species that only entered Africa ca. 50,000 years ago, might be even more interesting than one in which there is no evolution for hominins at all beyond chimpanzees, or in which later hominin species go extinct.)
Your divergence date pretty much needs to be prior to *Homo Erectus*, or at least prior to *Homo Erectus* leaving Africa, as it becomes increasingly hard for *Homo Erectus* to go extinct at that point (although competition with humanoid bears could conceivably wipe them out), and as it probably takes at least 2-3 million years for bears to evolve from being bears to humanoid bears. Really though, the bears we have today are closer to *Ardipithecus* in terms of their level of humanoidness relative to the bipedal bears you imagine, so a divergence date more like 4-5 million years ago would probably be closer to the mark.
During the Upper Paleolithic era (ca. 40,000 to 10,000 years ago), before farming and herding were invented, [bear migrations and modern human migrations pretty closely coincided](http://eurogenes.blogspot.com/2016/05/parallel-migrations-in-brown-bears-and.html), so modern human prehistory can be a pretty reliable benchmark for prehistoric bipedal bear migrations. (The earliest archaeological evidence for modern humans out of Africa is about 130,000 years ago, but genetic evidence suggests that all non-Africans today have a common ancestor ca. 75,000 to 50,000 years ago).
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> We address several unresolved issues regarding the Late Pleistocene
> demography of brown bears: (a) the putative locations of refugia; (b)
> the direction of migrations across Eurasia and into North America; and
> (c) parallels with other mammals, including humans. We present results
> based on more than 200 complete mitochondrial genome sequences from
> Eurasian and North-American brown bears. Bayesian phylogenetic
> analysis revealed that most individuals belong to a very large
> Holarctic clade. The MRCA of this clade lived ca 40 thousand years
> ago, most likely in the Altai-Sayan area, a known Late Pleistocene
> refugium in Asia. We propose several migration scenarios for bears and
> suggest that brown bears and humans underwent a series of parallel
> migrations in Eurasia and to North America during the Late
> Pleistocene. Moreover, both species exhibited a demographic standstill
> in Beringia before colonizing North America. Synchrony in the timing
> of past migrations and standstill implies that the ecology of large
> mammals includes key limiting factors that can enhance our
> understanding of ancient human movements and on large carnivore
> conservation.
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[Question]
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What ethical/legal implications would there be if we invented a technology to make it possible to communicate intelligibly with some (or all) animals?
The constraints on this technology would make it such that it is easier to communicate with animals that have brains more similar to human brains -- but the result is that the animal's desires, needs, fears, goals, emotions, etc. are fed out of the machine in plain English, to the extent that such things can be inferred from the animal's behavior / brain activity. Similarly, humans can speak into the device and it gets translated into whatever signals (brain, chemical, sound, or otherwise) that the animal can comprehend, to the extent that the animal can comprehend them.
Is such a thing even possible in principle?
[Answer]
### Which animals would this work with?
The animals that this idea would work with would be those which have a language capable of expressing abstract thought. To my knowledge, this would probably encompass only humans, maybe some other higher primates, and cetaceans.
The ethical implication of being able to communicate on like terms with a whale, chimpanzee, or dolphin would be that we would not be able to mistreat and hunt them in the same way that we do now. It's also likely that they'd be able to greatly enhance our view of the ocean by giving us the perspective of an ocean creature. If we accepted them into our society, there would also be greater ethical implications of dumping waste into the waterways, since this would all end up in the homes of the cetaceans.
Another huge implication of this would be that it would allow all humans to speak with and understand all other humans on earth. We are animals, after all, so this would serve as a perfect universal translator.
### Communicating with other non-human animals
I don't think it's possible to have a device that would allow you to communicate to most other animals in the same way as you communicate to another person.
My reasoning is that most animals don't have the brain capacity to comprehend abstract thought. They've got the mental capacity to understand communication in the manner which they have evolved to do so, and no method of transmitting a signal to them is going to change the way they understand things or put together thoughts.
A dog whining won't translate into something like 'I want that bone on the counter,' for example, because that's not what they mean when they whine. It will translate into 'I want something,' because that's the specificity with which they have evolved to communicate. They rely on other context and body language to get the precise details across, which works fine almost all the time. Perhaps you *could* design a device that would tell a person what a dog wants, but it wouldn't tell them much of anything that they wouldn't be able to understand if they spent a lot of time around dogs and learned to read their body language.
[Answer]
**In principle,** is possible read the basical needs/ feelings of the animal like you said, but, of course, with not a actual tecnology.
we are in that way: swedish cientists already invented a device with EEG sensors in dogs and they discover can really feel love like humans. so, with a little more decades your story will be plausible.
**The ethical/legal implications,** if the animals are not abused, problably would be ok and the rights of animals will not interfere too much (at the beginning it is possible they will interfere).
For people in general will be strange because many humans will realize how your dog loves him, as the mouse is afraid of him, as the bird ignores him, so ... we can see the side of the animals :).
Even animals could create a riot, but only the most likely to intelligence as dogs, monkeys, dolphins ... but the revolt will not be attack humans, will probably run away from humans, but just if humans are really bad to the animals.
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The thing is, we don't know how "intelligent" whales and monkeys and whatnot are because we don't really know what we mean by "intelligent" or "sentient". But for all we know, cetaceans for example might be highly intelligent and just not care about the same things we do. Maybe we can't grasp their form of intelligence and they can't grasp ours.
Who's to say that mathematical logic is intelligence? We don't even know if they ay with abstract concepts (or what are their abstract concepts), if they have a conscious conception of happiness...
If this actually is the case, then we are so different that we aren't even able to see the other species as intelligent. In this case, "communicating intelligibly" isn't even on the table.
[Answer]
The exact method of translating would be the issue - most (or probably all, at least as far as I know) animals don't have a spoken language like we do and rely more on body language combined with scents and noises. There are a few animal species that we can communicate with - dogs and other domesticated animals can learn and respond to basic words. Great apes can be taught to communicate with humans through symbol books and sign language.
Presumably the "translation" you receive would have varying levels of refinement. In all likelihood you would receive mainly emotion words: hungry, scared, happy, ect. That's not the say that animals aren't capable of more complex emotions - for instance, elephants have been known to touch the bones of their dead in a way that may be their version of grieving. Mammals such as dogs are certainly capable of feeling love.
One thing I've seen in the other answers and comments is the idea that animals aren't capable of abstract thought. This is not entirely true. There are a few important measures of intelligence that involve some form of abstract thought which animals pass - recognizing yourself in a mirror is one. Elephants, dolphins and great apes can do so, so they'd likely be the species most effected by your machine. Creating tools is another (both dolphins and chimpanzees do so).
A note on dogs - While intelligence levels vary, they are not at the level of the above animals or humans. What dogs are really good at is communicating with humans. As an evolutionary tactic, they basically outsourced their brains to humans. So while they may be communicating to you very clearly what they feel and be able to respond to you, it's more a sign of how close they are to humans than how intelligent they are. That being said, there's occasional dog who's been breed to think independently (border collies are an example) that will be unusually intelligent.
For the species effected, I think it varies how much will change. Laws may be enacted to protect these species, although some already are protected in some way. I doubt that their lives would be considered equal to humans, but they would probably receive special protection. Elephants would still be killed by poachers. Given all the terrible things humans do to each other, people probably wouldn't stop hurting intelligent animals.
One thing that might change is using them as test animals in labs (effects mainly great apes). This may be banned or may become more tightly regulated.
On the whole, I doubt much would change. Humans still don't always treat humans who are different from them well, and I doubt that they'd treat animals much better. Besides, we already have a fairly good grasp of animal intelligence levels, that this wouldn't be to new. Possibly there would be more public support for animal protection? Or maybe people will doubt the data of your machine.
How widespread your translating technology is will also be important.
[Answer]
In order to talk to animals which don't already possess some kind of capacity for natural language processing, it would then be necessary to (magically) induce this capacity. This would essentially be rendering the animal sentient.
A good example comes from the [Harry Potter fanfic "Methods of Rationality"](http://hpmor.com/chapter/48), where the protagonist's ability to speak to snakes is interpreted as such.
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> The problem was that Draco had also asserted that Parselmouths could send snakes on extended complex missions. And if that was true, then Parselmouths had to make snakes persistently intelligent by talking to them.
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> And when Harry had offered that hypothesis, Draco had claimed that he could remember a story - Harry hoped to Cthulhu that this one story was just a fairy tale, it had that ring to it, but there was a story - about Salazar Slytherin sending a brave young viper on a mission to gather information from other snakes.
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> If any snake a Parselmouth had talked to, could make other snakes self-aware by talking to them, then...
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Another example would be [Tamora Pierce's character Veralidaine Sarrasri](http://tamorapierce.wikia.com/wiki/Veralidaine_Sarrasri#Magical_Abilities), who has the capability to make animals sentient by talking to them for extended periods of time.
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> Daine's uniquely strong Wild Magic enables her to communicate with all vertebrate animals, and speak mentally with those immortals who do not have voices of their own. She can even control animals and force them to do her bidding, though she doesn't like to use this power, for fear of abusing it.
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> Wild magic allows Daine to heal animals, though, like all her magical abilities, this can sometimes occur out of her control.
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> Any animal who comes into prolonged contact with Daine, notably her faithful horse Cloud, gains intelligence beyond the norm for their species and begins to act more human.
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If the magic was recursive (therefore allowing animals to speak to other animals), this would allow this sentience to uncontrollably spread by conversations. This would result in huge ethical implications, since the personhood of all these newly-sentient animals would be at stake.
[Answer]
There are two approaches to this. Most here are interpreting this using assuming the most scientifically sound version, that animals can only communicate up to their level of sapience, but most tv/literature instead shows human-level speech from animals instead. This is a very important distinction. Humans effectively provide moral weight to level of sapience. Killing a human or anything with human level sapience is unforgivable, killing a monkey or high order sapient mammal is the worst of animal quality, killing a chicken is acceptable, but only for a good reason, and killing an insect is done just because. The more sapient a creature is the more it is presumed to deserve human-level protection of law and culture.
**Animals capable of Human level communication**
This is scientifically improbable, to say the least, but this is how animal speech is usually implemented in most literature I see. If you went with this approach it would completely revolutionize how we treat all animals. I hope you like being a vegetarian, because killing and eating something you were just debating philosophy with is *not* going to happen. There would be a huge fight, but animals all over the world would receive far closer to human level protections. Pets would still exist, probably even occur more often, and some mostly-human use of animals, like riding of horses, may still exist; but only as a job the horse chooses to be employed at for pay in oats.
**Animals still limited to personal sapience**
This is far more realistic, though still hard to implement. Interpreting would be far easier side to do, but you wouldn't get nuanced sentences from most creatures. Look at your average dog, an experienced dog trainer can read quite a bit in body language, they are a very communicative species, However, they don't use verbs and adjectives and complex syntax. Your translator may say "defending home, uncertain if your threat" or "afraid and submitting" or something along those lines, explaining the meaning of their body language, but there will not be any real nuance beyond that, because that is as far as their minds are capable of parsing and thus expressing.
Talking back to the animal is far harder. Dog communication is mostly body language, a machine can't really communicate body language. Other creatures may throw in pheromones, or sound above or below what is audible to humans, trying to build a machine capable of doing any of those is quite difficult. It would almost be more plausible to assume some chip was implanted in the animal's brain that short circuited the process and jumped right to sending the concepts to their mind (still doesn't make sense, but the issues with this approach are easier to hand wave away by saying "we just learned allot more about the brain then we know now".
In terms of how it would change us, not too much for most animals. It may make pet owners better pet owners, many owners do not know how to interpret their own animals communications. Some may see an animal groveling in fear and think it's a cute thing they are doing to entertain their owner, without knowing the real meaning. Way too many allow small dogs to be rather aggressive and dominate because they think it's cute as well. A better understanding of what their pets are actually 'saying' could make them better owners, and perhaps lead to more pet owners. It would also make any industry that requires communication with animals easier, like breeding or riding horses.
Morally I don't think our views will be challenged by *most* creatures. However, there are a certain group of highly sapient animals that we constantly are setting harder and harder challenges to meet the definition of sapience because we want to believe humans are completely unique. These animals include many apes, octopus, dolphins, and any number of other 'smart' animals you have heard of.
these creatures still wouldn't be capable of full human-level communication. It's been shown they can't comprehend some concepts, such as the symbolic use of images (a scale model can represent a larger object etc). However, they will prove to have pretty extensive communication ability, we have already taught many apes to communicate rather well with sign language or symbol-boards.
This will of course prove a boon in researching these creatures, but the more interesting question is how humans will respond to the questions about their sapience and thus how deserving they are of protection. A believe a higher degree of animal rights activist would show up and argue for protective status of theses creatures, great ape personhood is already a movement now, though one that is mostly ignored.
However, there will still be plenty who will not agree to with this. They will point out the obvious limits to what these creatures can do to communicate. They will argue that the device you are using are putting 'words in their mouth' and is not an accurate translation, giving the appearance of more sapience then exists. They will argue that even if these creatures can communicate at something above toddler-level language they still lack creativity or innovation etc. In all honesty the majority of humans will just not notice one way or another, there are no apes local to them so they see it as academic and don't really care.
I imagine this would lead to some interesting philosophical debates and attempts to better define what gives one the right to legal protection. However, how extensive these debates actually became I'm not certain, as I aid the majority of the 1st world nations are far removed from most of these creatures, and in all honesty only 1st world nations will be able to afford expensive communication devices and philosophical debates on personhood, when your a subsistance farmer all you care about is keeping animals away from your crops you grow, and possible supplementing your food with some bush meat.
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