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I am wondering what would be the most likely cause of zombies. The movie [Night of the Living Dead](https://en.wikipedia.org/wiki/Night_of_the_Living_Dead) suggested that radiation may have been the cause for the zombies. But plenty of incidents on Earth have exposed people to varying degrees of radiation, and none of them have turned people into zombies.
Perhaps an infectious agent (such as a bacterium, virus, fungus, prion, or parasite) would be more likely to turn people into zombies. The novel [World War Z](https://en.wikipedia.org/wiki/World_War_Z) used a virus as the cause for the zombies, but I'm not aware of any virus on Earth that comes close to turning people into zombies.
Would a [prion](https://en.wikipedia.org/wiki/Prion) be the most likely cause of zombies? It seems all known prion diseases attack the brain. [Mad cow disease](https://en.wikipedia.org/wiki/Bovine_spongiform_encephalopathy), a prion disease, results in the following symptoms:
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Deteriorating behavioral and neurological signs, increase in aggression, reacting to noise, and becoming ataxic are all exhibited by zombies.
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Here’s the definitive paper: [The Etiology of Romero-Fulci Disease: The Case for Prions](http://iamanangelchaser.com/writings/fiction_science/the_case_for_prions.pdf)
In particular,
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> Besides the evident histological similarities, there are some striking parallels between the modes of transmission and symptomology of TSEs and those of Romero-Fulci disease. Here perhaps the most compelling example is kuru, an endogenous disorder unique to the Fore-speaking peoples of the eastern highlands of Papua New Guinea. Kuru, which means “trembling with fear” in the Fore tongue, reached epidemic proportions in Papua New Guinea prior to 1971, when the practice of ritual funerary endocannibalism responsible for its transmission was abolished by law. Traditionally among the Fore people the cooking and consumption of the corpse—particularly the brain—of a recently-deceased loved one was considered a gesture of respect for the departed and an integral part of the mourning process. Because kuru’s incubation period can be as long as three decades, some older Fore who participated in cannibalistic rites are still dying of the disease. However, no young person has exhibited symptoms of kuru since the practice of endocannibalism was discontinued (14). Although the incubation period of RFD is radically shorter, the similarities between it and kuru are difficult to ignore: Both are fatal neurodegenerative diseases transmitted orally by an act of cannibalism focused particularly upon the brain matter. Kuru is known to be caused by prions; it therefore seems not unreasonable to propose—especially in light of the striking histological similarities exhibited in Figure 1 and Figure 2—that the causal agent in RFD is also a prion, albeit of a hitherto unknown fast-acting variety.
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The main problem is that the speed of infection (or activation?) Is orders of magnitude more rapid than would be expected. The article speculates
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There may be a complex mixture of agents involved including other biological agents, poisons, and ionizing radiation. Prions are *involved* and behind the zombie effect, but not the sole cause. Even if prion conversion is the actual mechanism for the zombie state, other mechanisms are needed to disperse them through the tissue and catalize the needed changes.
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Here’s my remix: [Nanites](https://en.wikipedia.org/wiki/Nanorobotics#Nanomedicine) are invented to fix tissue. They are to the point of mostly working. But unexpected prion foldings act like a bug in the system, just as they do naturally: the nanites try to “fix” things using the misfold as the exemplar! Meanwhile the body is kept working by any means the nanites can manage without caring that the brain is messed up. Rather than a persistent vegitative state though the misfolding affects the nanites themselves, making them (further) malfunction and create a Romero-style zombie.
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Classical "Zombies" - undead being which feed on flesh, and can only be killed by destroying the brain - ***cannot exist***.
## Basic biology forbids this.
**Muscles**
When you die the normal processes which power your body end. Your heart stomps pumping blood. You stop breathing. Without blood distributing energy and oxygen to your muscles, they can't function. If they can't function, you can't move.
It doesn't matter if a Zombie eats brains, or anything else. If that food is not broken down, and the energy not transported to the muscles then you can't operate the body. The whole system needs to be functioning, not just convenient bits and pieces.
**The Brain**
Within minutes of the brain being deprived of oxygen our neural pathways begin to deteriorate. There is a very real risk that if you reanimate someone after they were deprived of oxygen for a long time they may suffer from severe and completely unforeseen brain injuries.
Maybe they will have lost their memories, maybe they will be "alive", but never wake up from the coma they're in, etc.
The brain also "runs the whole show" as far as operating the body goes. There is no way that a dead body could rise after months of undergoing decomposition. Even after days of decomposition. There would be nothing left to "think" about eating or anything else.
## More Likely
**Rabies**
A virus which makes people go crazy and attack others is not that far fetched. Watch the movie "28 days later" for a pretty chilling view of what could easily happen if the right animal activist breaks into the wrong lab.
These are not zombies, however, in that they will die of the same things we do: malnutrition, injury, poison, disease, viruses and bacteria - even the common cold could do them in.
A bullet to the chest would be just as effective as one to the brain (in the grand scheme of things).
They would still need to go to the bathroom, except they wouldn't remember how to take their trousers off, or how to wipe their asses. How long would it take for some ***severe*** and utterly nasty infections to set in?
**Nano-Plague**
If you're dead set on setting the undead loose on the world, then nanotechnology might level the playing field for you.
Nanobots wielding the bodies of dead humans and animals in order to fight their creators (us), could sound somewhat plausible in a sci-fi setting. I say this because you can claim that rather than having the body move under the power of its own muscles, nanobots would actually be facilitating the movement, not living cells.
All you'd have to do is explain why those nanobots did not simply choke the life from every human in the first place, or why they don't build robots to murder us all in our sleep, rather than shambling about in rotting corpses.
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There's a [fungus](https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis) that turns insects into zombies. I don't know how viable that is for larger animals, like us fleshy humans, but it does exist. I have a vague recollection that a TV show did this once for people as well (as Monster of the Week), but I can't think of what series.
I also happen to be reading EX-Heros right now and the vector in that book is a virus that as it turns out (spoiler!) was created on accident by a superhero with regenerative powers trying to resurrect his dead wife. So the virus being semi-magical having the described behaviour is *plausible within the setting.*
Edit:
Now that I think about it, *Invasion of the Body Snatchers* could be seen as zombie-like: the "infected" are actually aliens and will abduct people, make a copy of them (that's actually an alien) and reinsert them into the population. With the right behaviours and attributes, these aliens could be considered zombies.
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I read a book a while by Brandon Mull, and in the series *Beyonders*, they have a zombie plague. It is cause by little worms with hive minds. These worms knit together wounds, and somehow work together to move the body, like a second set of muscles. They feed off of the blood of their victims, and take their bodies.
I find this scenario the most realistic, otherwise, how would a zombie stay in one piece, or get anywhere at all? Why would it feed on flesh, like in the walking dead? The food is irrelevant to their survival, and they don't think or breathe, so their brain would be dead and they'd have no reason to go eat people. But man, do these nasty little worms crave blood.
I don't think prions are realistic, because once the body becomes significantly damaged, then you have brain death, which mains you cannot move. Besides, what purpose would prions have with eating people? Unless these prions somehow supplied the brain with oxygen, and made sure the body was not damaged, they wouldn't be very intimidating. Break its leg and it can only drag itself very slowly, or crawl.
I recommend using some kind of parasite, because then there is an actual purpose to the madness of their violence. Also, some people might have a smidgeon of reason, maybe enough to barely keep a hold on themselves, or enough to strategize how to catch people. This might make your zombie apocalypse more dangerous and interesting.
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> Would a prion be the most likely cause of zombies? It seems all known prion diseases attack the brain.
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That's true, but prions are backwards for zombie purposes. How do you get a prion disease? By eating infected brains. But why would you start eating the brains in the first place? The zombie story (ignoring science) is that a zombie bites you and infects you, then zombies eat brains. That's not how prions work.
Someone will likely point out that it is possible to get a prion disease without eating brains. The infectious agent can also show up in blood and other places. This is true, but its normal transmission method remains ingestion (as seen in your links). So the zombies would be created by food, not by zombie to human transmission.
Rabies is probably a much better basis. It transmits via bite and affects the brain. There is some speculation that rabid humans were the origin of the zombie stories.
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Just a quick input - the rabies virus has a similar effect to zombiism - victim becomes irrational, reverts to animal-like and extremely aggressive behavior, bites victims.
I think that the best counterargument to the virus idea is the fact that viruses must invade cells, one by one, and the cells must then produce more viruses. All this takes time - enough time for a victim to be quarantined before further transmission. Generally speaking, viruses are not sufficiently rapid acting to create a zombie pandemic.
It is for this reason that I would favor the prion as a hypothetical pathogen to create zombies. Of course, death would follow soon after (as is seen in BSE or other prionic diseases), but there would be a sufficient period of severe cognitive impairment and irrational behavior to allow transmission before the victim finally succumbs to the disease.
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I think prions may be one part of the way, but it's not enough. Prions themselves exist in our body and would be turned into to a so-called 'zombie virus' for an unknown reason. Therefore,there must be some mechanics that turn the prion in our body to dangerous one, such as some kind of virus or genetic mutation. Anyway, prions don't have high infection rate **but** the prion in our body may be detonated and turn us to zombie.
P.S Don't be afraid.Just avoid eating infected meat and you are 70% safe.
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[Wasps](https://www.scientificamerican.com/article/how-a-wasp-turns-cockroaches-into-zombies/). It's wasps you need to worry about. (Or some other means of injecting suitable neurotoxins into key areas of the brain.)
No, they aren't traditional undead beings fresh from the grave and roaming in search of brains to eat, but they are beings entirely under the motor control of another. Perhaps some mad scientist has figured out a way to achieve similar results with humans.
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I hope this isn't a stupid question ("just add air").
I would like my intrepid explorers to have drilled through the ice of Europa and into the water without creating a geyser (they plugged the hole behind them). This is assuming a [liquid subsurface ocean](https://en.wikipedia.org/wiki/Europa_%28moon%29#Subsurface_ocean).
Once under the ice, they encountered a very large, stable cavern of air between the water and ice. Their submersible 'surfaces, and when they look around they see water, and when they look up they see ice. It measures several kilometers wide and at least one km high to the ice. I am not married to those dimensions, though.
It doesn't necessarily need to be breatheable, but it should be enough that they can exit their vehicle with scuba-like gear (ie - breathing and warming/cooling apparatus). However, bonus if they surface and the pressure, temperature, and composition are suitable, however shortly.
*I really hope this isn't as straightforward as it seems.*
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It seems you can find everything you need in [Wikipedia](http://en.wikipedia.org/wiki/Europa_%28moon%29#Physical_characteristics):
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> **Plumes**
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> Europa may have periodically occurring plumes of water 200 km (120 mi) high, or more than 20 times the height of Mt. Everest. These plumes appear when Europa is at its farthest point from Jupiter, and are not seen when Europa is at its closest point to Jupiter, in agreement with tidal force modeling predictions. The tidal forces are about 1,000 times stronger than the Moon's effect on Earth. The only other moon in the Solar System exhibiting water vapor plumes is Enceladus. The estimated eruption rate at Europa is about 7000 kg/s compared to about 200 kg/s for the plumes of Enceladus.
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In other words, Europa may have cryovolcanoes/geysers. These cryovolcanoes would, presumably have the possibility of becoming extinct. When operational, a cryovolcano would draw whatever gases are dissolved in Europa's ocean (CO2, N2, CH4\*) to the surface, where they would come out of solution. It's therefore not only possible, but quite likely, that if there are extinct cryovolcanoes on Europa, they have gas pockets beneath them. It also gets round the issue of the thickness of the ice, which as a best estimate seems to be several miles, but could be much thinner under an extinct cryovolcano. Even an active one might do, 7000kg/s is not a particularly high flow rate, and according to the theory these cryovolcanoes are only active once per orbit (3.5 days.)
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\*Normally it is difficult for O2 to exist because it is so chemically reactive and tends to combine with other elements over a geological timescale. But Europa apparently has a mechanism for splitting H2O into H2 + O2 and ejecting the H2 into space:
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> Unlike the oxygen in Earth's atmosphere, Europa's is not of biological origin. The surface-bounded atmosphere forms through radiolysis, the dissociation of molecules through radiation. Solar ultraviolet radiation and charged particles (ions and electrons) from the Jovian magnetospheric environment collide with Europa's icy surface, splitting water into oxygen and hydrogen constituents..... Molecular hydrogen never reaches the surface, as it is light enough to escape Europa's surface gravity.
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Some of this may make it into the oceans:
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> Observations of the surface have revealed that some of the molecular oxygen produced by radiolysis is not ejected from the surface. Because the surface may interact with the subsurface ocean (considering the geological discussion above), this molecular oxygen may make its way to the ocean, where it could aid in biological processes.
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[Answer]
**Introduction**
You want beans with that?
I can think of two natural processes that might generate a very large bubble of gas under Europa's ice.
Air under arctic ice
and no, flatulence isn't one of them.
**Precipitation**
The first would be an ocean completely saturated with gases (you can pick your gases but some of them are not as suited to this as others) encountering conditions (lower pressure / higher temperature) which causes some of those gases to precipitate / out gas.
If the process needs to be abiotic, then the most likely composition of this gas would be the volcanic gases (*shown below*). But if you have a lively biosphere, then it could be something like $O\_2$ or other biological gases.
The bubble would be created when the water conditions suddenly changed. For instance, if the layer of ice above it suddenly thinned and the temperature increased (say due to ice crustal deformation).
**Out gassing**
The second would be volcanic fissures releasing gases beyond what the ocean can absorb (another case of a saturated liquid). On Earth the volcanic gases most likely to be encountered are:
$H\_2O$ Water
$CO\_2$ Carbon dioxide
$SO\_2$ Sulfur dioxide
$N\_2$ molecular Nitrogen
$Ar$ Argon
$He$ Helium
$Ne$ Neon
$CH\_4$ Methane
$CO$ Carbon Monoxide
$H\_2$ molecular Hydrogen
**The problem**
The problem is this condition is not stable. The gas is **MUCH** lighter than ice and will flow through any cracks to reach the surface. I wouldn't expect it to last long. Since I have no background in this subject I couldn't tell you how long is "not long".
It could fail by gradual (or sudden!) deflation, gradual reabsorption by the water, or most spectacularly by the sudden break-up of overlying ice.
I hope a temporary bubble is good enough for your purposes.
**Size**
Since the ice above this air has no support, there are mechanical limits to the amount of air in this space. Under great pressures (like a mile or more of overlying ice), ice tends to flow like plastic.
This is another reason I think the bubble would be a temporary feature. The larger the bubble the shorter the time it could exist.
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Not only are you dealing with a creating a pocket of air under the ice you have to deal with the pressures. Some say the Ice could be 62 miles deep. That is a lot of Ice over your head and putting a lot of pressure on the 'air' in the space. It would have to be at the same pressure as the water because if it was less, the water would push up into the cavity until they reached equilibrium.
Now can this happen? quite likely there are bubble trapped in the ice in different places through the planet. This could come from chemical reactions deep in side, but it is unlikely that it would be 'livable' and quite likely that it is highly toxic and/or caustic.
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**It actually may just be that simple.**
The concern is presumably one of structural integrity of the ice layer above and the ability for a gaseous atmosphere to form (and not precipitate immediately). I think there are not specific data on this, but it appears that a cave of the size you mention is feasible for the ice of Europa. Actually, I think the least plausible part of the layout is that there would be a liquid surface. There would very likely be a layer of ice on the water inside the cave. It might be broken through in many places from ice falling from the cave ceiling above, but I don't imagine it would stay liquid. The air inside is presumably warmer than the ice though, so it may help that it's slightly melting the surrounding cavern which, upon refreezing, would create an airtight seal. The stability is likely only in the thousands of years range though, the tidal forces from Jupiter will likely cause such a structure to eventually fail.
Think about the scale of things here. The small squared off section is way way bigger than the area you're asking for. If you were to add about a 100 million cubic meters of pressurized air to that space it would provide the bubble you're looking for.
**The Cave**
The Wikipedia article you linked states that the very cold surface temperature of Europa makes the surface ice "as hard as granite". Granite is a pretty tough stone. There are some [very large cave](https://en.wikipedia.org/wiki/S%C6%A1n_%C4%90o%C3%B2ng_Cave) systems on Earth which are made of limestone, which is about 50% stronger than granite. However, gravity on Europa is also 7.5 times less than on Earth, so larger structures would be able to form.
**The Air**
Europa has a weak [atmosphere of oxygen](https://en.wikipedia.org/?title=Europa_(moon)#Atmosphere). Though it's difficult to hypothesize a way for very much to get under the surface ice. A more feasible idea might be that the gas is a byproduct from organic life or a chemical process related to the hydrothermal vents. It would strain plausibility for it to be breathable.
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I suspect that due to the cold and huge depth of the water column, gasses dissolved in the oceans of Europa will stay dissolved, so cracks in the ice "crust" will fill with water rather than gasses. This may partially explain the cryovolcanoes observed on Europa; if the ice cracks open enough to expose the water to vacuum, the gasses will explosively come out of solution.
For your intrepid explorers, they might be able to use shockwaves or other means to try and trigger the release of dissolved gasses inside a crevasse under the ice, but will need to be very careful. The released gasses will temporarily displace the water and create the cavern you are looking for, but as noted on other posts the temporary cavern will not have breathable air, and the gasses will either be reabsorbed by the water or leak through the ice towards the surface. Calculating how long this will take depends on a multitude of factors, but the cavern will probably be "dry" for only few years at most before the gasses are absorbed, leak out or "geological" processes cause the ice crevasse to close up on its own.
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Tanks are better than (realistic) mechas. This is an unavoidable truth. However, whenever they appear in general fiction, mechas tend not to be overtly realistic. Still, plenty of the points argued for the benefit of using tanks are indisputable. They are lower to the ground, carry a bigger gun, and can probably move faster than a mecha if they 'floor it'.
So, in my setting, the aristocratic nobility of this world has overthrown the rebel forces using highly unrealistic mecha (think [Mazinger-Z](http://en.wikipedia.org/wiki/Mazinger_Z) and [Getter Robo](http://en.wikipedia.org/wiki/Getter_Robo) rather than Gundam). They then oppressed the masses, sending society back into their own 'romanticized' version of a feudal society, and destroying all modern machinery besides their own super-powered warmachines.
The question isn't really about those super robots, however. The peasantry and common folk have been given access by the nobility to small, more realistic robots, with which to fight their wars and do their heavy lifting. This question will be mostly about these tiny robots, specifically the ones used by the lower ranking soldiers.
A group of rebels, armed with 'Ancient Forbidden Knowledge', are trying to build tanks. What would be the best way to design these tanks to fight the common small mechas?
The capabilities of the small mecha:
1. They are mostly round and angled, to provide resistance to firearms (think sloped plate)
2. They have small stumpy legs, but are capable of moving surprisingly fast when they sprint, and jumping something like 15 meters or so (not taking into account any customisations).
3. The most common firearm they have is a 40mm autocannon that is shaped like and functions like a modern automatic rifle.
4. They carry swords. These are mostly decorative, but are still a heavy sharpened bar of steel.
The tech level for the rebels should be current era or at most 20 minutes into the future. They cannot afford to make mobile gun platforms that trade deaths with the nobility, because they are the ones who are outnumbered.
EDIT: Limitations: As suggested by a comment by @VilleNiemi, a few limitations will be placed on the rebels' tank building capability:
1. They are capable of producing certain industrial parts by stealing into nobility-owned factories at night, but not en masse, due to the risk of being detected.
2. They probably get most of their components by salvage or underground trade.
This means that things like Depleted Uranium Shells will be very rare and very very hard to get more of. The tanks can and should still be treaded though, as that is part of their strength in comparison to the mechas.
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To defeat small, agile mecha armoured with 40mm repeating cannon, we need what would effectively be a medium tank, not quite a main battle tank. Medium tanks have lighter armour, though the [composites](http://en.wikipedia.org/wiki/Composite_armour) used would still be capable of resisting repeated 40mm cannon hits from any aspect. With lighter armour, add a large gas-turbine engine to give the tank a good power to weight ratio and a high speed, capable of outrunning the mecha if not necessarily outjumping them. Ensure that the tracks are well protected by armour skirts.
As to armament, mount a heavy, large-calibre gun. The [120mm smoothbore cannon](http://en.wikipedia.org/wiki/Rheinmetall_120_mm_gun) used by US tanks, along with the computer-assisted aiming mechanism means that as long as the target is properly tracked prior to firing and the range is sufficiently low that the target cannot dodge effectively, the shot *will not miss*. A hit from a 120mm cannon round, loaded with a depleted uranium penetrator or even just a shaped charge explosive will instantly wreck any mecha designed to take on opponents armed with 40mm cannon, probably turning it into a collection of ballistic limbs. As long as the turret traverse and elevation mechanism has some heavy-duty power assistance, it should be able to track any mech at any reasonable range. A lighter, older 105mm or even 88mm cannon should still be able to wreak havoc on such a lightly armoured mecha, and would allow more shots.
Given the strength of composite armour, while not capable of withstanding a 120mm cannon shell, it would still be well up to the task of resisting multiple hits from 40mm shells and big sharpened crowbars. Also, given the acceleration and weight of the tank, at close range, the tank could be used as a battering ram, and running over a mecha would probably cause a mission kill, if not a total kill.
An alternative weapon system, if the tankers expect to face large numbers of mecha with relatively few tanks, would be the [GAU-8](http://en.wikipedia.org/wiki/GAU-8_Avenger) 30mm gatling system found in antitank aircraft. This weapon's high rate of fire would be ideal for mowing down massed charges by mecha, and while one hit may not incapacitate a mech, the multiple hits such a system would allow likely would.
The weakest point on such a tank would be the tracks and personnel hatches, though it would not be a difficult matter to armour and shape the hatches so that they would present minimal edges to be levered up by the mecha's swords, and could resist 40mm rounds quite well. With low armoured skirts, the tracks could be made to be a small target, and even when immobilised, a tank remains a difficult target to neutralise, unlike a mech.
To achieve some degree of stealth, a tank can be relatively easily waterproofed and hidden in any reasonably large body of water, with only a periscope showing above the surface. Given the ground impacts that mecha movement would cause, there would be relatively little need even for a periscope if the tank was equipped with seismographic equipment. Alternatives for stealth would be to cover the tank with the branches of dense shrubs for a forest setting, or hay in a rural setting.
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Basic warfare is to **have multiple kinds of units, with different capabilities, supporting each other.** Unless you have magic, big firepower weapon will inevitably will be heavy and less maneuverable than light weapon.
So best weapon against your mecha would be something like [BMP](http://en.wikipedia.org/wiki/BMP-3):
* light tank (with gun),
* which is amphibious (can cross lake which your mecha cannot). Can jump to water with no preparation,
* has laser-beam riding anti-tank (and anti-mecha) missiles,
* can hold 7 infantrymen, who can disembark, penetrate terrain which is hard for tank, and protect it, say by killing mecha by RPG
* very mobile - forest from young trees (or legs of mecha) will not stop it - sharp nose (see BMP-2 photo) will cut it with surprising efficiency, can go fast (up to 45 km/h off road, 70 km/h on road)
If you can have it, add [A-10 "Flying tank"](http://en.wikipedia.org/wiki/Fairchild_Republic_A-10_Thunderbolt_II) designed for close air support (not dog-fighting/interception, not bombing, but close support of infantry on battlefield, killing stuff like your mecha from air). Or [anti-tank Apache helicopter](http://science.howstuffworks.com/apache-helicopter.htm)
How you fight mechas?
Group of BMP will move into battle area, infantry will dismount. Mechas far away will be killed by BMP's cannon and/or guided missile. Anything closer will be handled by infantry, which has machine guns and another excellent anti-mecha weapon: [rocket-propelled grenade](http://en.wikipedia.org/wiki/Rocket-propelled_grenade) - which is cheap, easy to make and hide, fits perfectly to your scenario.
So BMP+7 infantry units has much greater firepower than mecha: cannon + 2 or 3 RPGs + 4 or 5 machine guns + personal grenades. Much cheaper to equip (especially if you have lots of manpower and limited manufacturing), and more modular: easier to replace damaged parts.
If you have extremely limited manufacturing, **you can scale down: 4x4 pickup truck**
Slightly up-armored civilian 4x4 pickup + your infantry with RPGs and machine guns. [Toyota Pickup Truck Is the War Chariot of the Third World](https://medium.com/war-is-boring/the-toyota-pickup-truck-is-the-war-chariot-of-the-third-world-ea4a121e948b). That would be [ideal against enemy army with overwhelming technological advantage](http://warontherocks.com/2014/02/the-pickup-truck-era-of-warfare/), as US army found very painfully in Iraq and Afghanistan. Truck is cheap, reliable, fuel efficient, and **6-8 infantry provide lots of firepower** (with RPG and anti-aircraft machine gun mounted on truck). And it has stealth capabilities: looks almost exactly like civilian truck, so it can hide in plain sight.
Read links above about [Toyota war](http://en.wikipedia.org/wiki/Toyota_War) - how Toyota truck provided mobility to Chad forces to successfully fight and destroy "superior" Libyan army armed by tanks.
To support slow mecha against your more mobile pickup truck chariots, enemy would need air superiority. And again, [MANPADS](http://en.wikipedia.org/wiki/Man-portable_air-defense_system) like [Stinger missile](http://en.wikipedia.org/wiki/FIM-92_Stinger) can be easily added to your arsenal. and be devastatingly effective against low and slow flying aircraft. Unless your enemy has A10, because A10 can absorb ridiculous amount of damage and fly another day.
Or, as kung-fu sensei says: **speed defines the master** - and can beat superior, but clumsier, firepower.
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Make a tank with a flat top, a bunch of vertical launching tubes and use fiber-optics guided missiles to take on the mechas. They will not even know what hit em.
Missiles like the brazilian FOG-MPM can hit targets 32km away, they are guided by a camera in the nose that relays imagens to the station via a fiber optic. Commands are sent upwards from the command station via the same fiber.
You can use those missiles to scout (spending then) for the sake of its camera, to shot low flying helicopters, to sink incomming speedboats at beach etc. A mecha is no harder target than those.
Something like a armored car with 8x8 traction and a flat top, a row/column of missiles in the middle area and driver plus weapons officer is all that it takes. Heck such a vehicle, added to a infantry battalion might take on even on modern, heavy armored tanks due to its top attack capability.
Using movement detection radars would pinpoint the quick and jumpy movement of a mecha. Infantry would provide screening at the front, allowing the armored vehicles to hide behind cover and launch missiles at will.
Even if the mecha is quick and moves by jumps and tries to dodge the incomming missile, a mecha is no more agile than an helicopter, yet helicopters can and will be shot down by such class of missiles.
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Take a lesson from Iraq: Command detonated explosively formed projectiles. Since you're talking a higher level of sophistication than most of our opponents had over there it will be much easier. Put a camera on the charge so it can see exactly what's in front of it, the operator only pushes the button when he sees a mech in it's sights.
It's extremely hard to defeat the plasma jet of an explosively formed projectile. Reactive armor works against man-portable missiles because their charges are very short range--the armor destroys the missile before the jet is fired. When you don't need to send it after it's target on a tail of fire you can build it bigger and longer ranged.
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Tanks have two advantages over mechs straight up. Cost and terrain
Tanks are far simpler to build thus cheaper to make. The Russian tanks were built three to one against the Germans. They cast the armour instead of forging it and only supplied each tank with three shells but there was much bigger army and the Germans got overwhelmed despite having the superior tank.
Tanks are also better at moving over poor terrain. A tank can churn through a muddy field or sandy beach or over loose rocky ground but a mech puts all it's weight on it's feet which is a much smaller surface area so will sink into the ground or roll it's ankle or trip like humans do on a loose surface.
That means a tank army can ambush the mechs and then flee across muddy fields to escape.
Just as a side note, rebels aren't likely to build tanks at all. Tanks (or mechs) are the domain of a standing army. Tanks are loud, noisy and hard to hide. Rebels would ambush mechs and vanish into the civilian population. Why build a tank when you can fill a car with explosives and take out several mechs? They could lure then into pit traps or attach limpet mines to the knees and then napalm them to burn out the pilots.
Rebels can do a lot of damage to a standing army without much tech at all.
[Answer]
Given the speed and jumping ability of the mecha...
I'd go for a heat-seeking missile, and shoot at them from range.
Why?
* A missile is still faster than a mech (this is an assumption, but a safe one),
* Distance means you can avoid being stomped on, or stabbed, entirely,
* Distance also gives you *some* safety against that 40mm gun,
* And it follows a target that tries to dodge.
The rebels are going to be employing guerilla warfare, so ambushes are the proverbial par-for-the-course. Don't expect a lot of honourable combat. Catch people(mecha) that are by themselves, or not paying attention. If there's any serious risk faced by the rebels, their most logical action is to slip quietly away.
If heat-seeking is beyond the rebels' capability, go for laser-guided.
[Answer]
Considering these tanks are to be built by scavenging and stealth, I would make some pretty extensive modifications to make it more reasonable to pull off. After all, designing, building, and then supplying modern armor is a *huge* task even if you're doing it with trained engineers in dedicated facilities.
But doing it in secret means you won't have access to advanced weaponry, most likely. Instead I'd pick a base chassis that resembles a giant bulldozer. Thick plating all around, and a massive extra pusher at the front, preferably with as little clearance as you can get away with. Then, you just try to run the mechs down. Since your front is just thick armor, there's not much their light weapons can do and no mech is going to outrun a threaded bulldozer.
At worst, you'd have to deal with highly mobile enemies, but if you're trying to run them down, they are already on the defensive, and their weapons aren't very effective. It's way cheaper and easier to build and even if it's not as powerful as a real tank it's much more reasonable to be pulled off in secret.
You can support such vehicles with light infantry weapons, as the shock power of a dozer would have enemy vehicles on the defensive enough that you wouldn't be in as much danger. Or you can mount them on/in the tank as you collect them. Since the Mechs are designed to combat each other, mounting their scavenged 40mm turrets on the dozer would probably be enough.
An additional advantage: if you are the rebels, you'll want to use the element of surprise as much as possible. Nothing screams "surprise!" like driving in straight through the wall.
[Answer]
would this be something you'd be looking for?
Its a vehicle from the direct to DVD anime called Appleseed, it seems like a good reference to your world:
GUNSLINGER TANK
A tank more suited to the urban jungle than to the badlands. It carries a variety of weapons to get the job done, but under adverse conditions its electronics and cooling systems have been known to malfunction. Depending on the terrain the Gunslinger can switch from tread to tire, to make maximum control of its environment.
Top Speed:60 mph
Crew:3
Range:230mi
Passengers:4
Cargo:4 tons
Type:IFV
Mass:20 tons
Special equipment:
Reactive armor, amphibious modification, fire extinguisher, environment control, military radio w/scrambler, anti-personnel grenades, visual and laser rangefinder, auto pilot and navigational system, image enhancement, thermograph, 4 IR smoke projectors, radar, motion detectors, spotlights and enhanced audio detectors.
Weapons systems:
30 mm Gatling in turret mount, 6 shot revolver style 75 mm cannon, in turret mount.
[Answer]
Is this group of rebels on equal footing with the government they're rebelling against? If not, why are they attempting to fight a conventional war, with unit vs. unit? The goal of a war isn't to destroy the other side's army, but to destroy the other side. The tanks should be very mobile - able to escape from a battle quickly - and powerful enough to attack the non-mech military targets. The rebel's goal with the tanks should be to provide mobility to avoid a fight, firepower to destroy a target, and protection for the retreat from battle.
[Answer]
You would need to make an electric tank:
If this civilization has the ability to create mechas, and the rebels have limited access to the production facilities, then they have the ability to steal some very high tech equipment.
The drive train would be an 8 wheel tracked system driven by 250 hp permanent magnet electric motors on each wheel.It would have 2000hp in total. These would be easy to get access to because normal motors would burn out much easier and be replaced so the mechas would need to use some sort of permanent magnet motor which is much more rugged and reliable with a longer service life. The vehicle would have a lower heat signature, it would make much less noise and the drive train would be less mechanically complex owing to the fact that the motors not only take up less space, but have fewer moving parts and reduce the need for a large engine block. The fact that there are multiple drive systems means the vehicle can move even if one or two of the wheels are hacked off. The motors would also be much lighter than a massive engine. The axles of the motors would have miniature electrical generators attached so that the vehicle can partially recharge as it moves. Due to the advanced pneumatics and hydraulics used in a mecha the ability to make a pneumatic suspension system would be there, unless they opt for a cheaper one similar to the one in the merkava.
Power would be stored underneath the floor of the tank (between the floor and the underbelly armor) in layers upon layers of paper thin graphene super capacitors. These would propbably be used in the mechas due to the need for a compact power storage solution. They can recharged in as much time as it takes to fill a gas tank and can be discharged very quickly in case of a lower hull breach. This negates the need for a huge tank (no pun intended) containing volatile fuel. On the motors to cool them down is a system of solid state thermoelectric panels that absorb most heat emitted and turn it to electricity, same with other heat producing components, these could be found on mechas also if they have a compact cooling system.
Since the ability to manufacture composite armors is not there I do have an alternative. The chassis of the tank itself would be made of steel, titanium, or high grade aluminum similar to that of the M109 paladin whichever is available.
Over top of the chassis would be plating of alternating layers of stainless steel composite metal foam, and steel RHA. stainless steel coposite metal foam is made by literally adding tiny hollow air filled metal spheres into molten stainless steel to create a foam, The material is extremely light and has a composition of 60-70% air. It can resist 800 degrees celsius of heat for over 30 minutes. It has high ballistic resistance, a single inch of this material can obliterate an incoming 7.62x45mm armor piercing round to dust with only a 8mm indentation in the backing. it also has a high resistance to radiation. The RHA will be there as extra reinforcement against kinetic projectiles. This lighter armor will allow you to place more armor without adding too much extra weight. The fact that the tank has no emissions reduces the need for vents in the back allowing the rear armor to be just as thick as the frontal. The bottom of the hull would be V-shaped to deflect mine blasts. The inside of the hull would be lined with kevlar or ballistic nylon to prevent shrapnel and spalling. The hull would also include a faraday cage of copper wire to protect against EMP. The tank would have armored skirts that are lower to the ground than normal. If you wanted to up armor the tank you could add porcelain panels over top to absorb impact. All viewports are made of nanocellulose, a plant derived polymer that is transparent, stronger than steel, and stiffer than kevlar.
The turret ring would be made of steel and driven by two electric motors using gears with pneumatic assistance. The ring itself would be coated in copper or a similar conductor to allow for power transfer between the turret and hull to allow for redundancy if the capacitor bank in the turret is rendered unusable. The turret is attached to the hull via magnetic seal to prevent it from popping off if lifted by a mecha.
The main gun would be a 90mm coilgun. Coilguns are very reliable and they do not contain many moving parts. It would be about the same velocity or slightly faster than a standard 90mm cannon similar to that mounted on the M36 jackson. They are quite easy to manufacture as to the fact that handheld versions capable of killing small game and unarmored humans along with even semi and full auto versions are made by hobbyists from household parts. The guns themselves are much more efficient than railguns and do not have the problems of barrel wear and dont generate as much waste heat. They have no muzzle flash or report, and have much lower recoil than conventional cannons. There is a recoil absorption spring located behind the gun. The weapon is much more accurate than normal weapons due to the fact that the magnetic field keeps the projectile in the center of the barrel at all times without it bouncing around like in a normal weapon. The barrel itself is smoothbore, and the rounds are fin stabilized. The gun itself can be gyroscopically stabilized allowing it to fire on the move by taking a gyroscopic stabilization system from a mecha. It would have a coaxial 40mm cannon also taken from a mecha. A ballistic computer and laser rangefinder can also be taken from a mecha. Parabolic microphones taken from a mecha are hardwired to the computer so that they can hear the trajectories of incoming rounds and within a few seconds triangulate the position of where they came from. It also has 1-60x variable zoom optic for the gunner's sight, along with a thermal camera and laser rangefinder taken from a mecha. The tank can also have multiple video cameras dispersed around the hull to allow for improved situational awareness by the crew. The gun's ammo would be cheap to manufacture because it consists of mostly ferromagnetic metal slugs, or other ammo types with ferromagnetic sabots. The ammunition would have no propellant so it wouldn't be volatile unless you are carrying HE or HEAT, and has no casing so it weighs less and you can carry more of it. If the coils of the gun are properly insulated it could be fired underwater.
There is a crew of four men, a commander, gunner, driver, and a loader. The gunner and loader are in the turret, along with the commander. The driver is seated in the front of the hull. The extra space in the hull can be used to carry troops if you add a rear door, or it can carry extra ammo, and can serve as an impromptu living area for the crew. If you do not want to have to recharge your tank you can mount whatever magical powersource the mechas are using. It will have a hydraulically operated retactable bulldozer to steamroll the mechas.
The tank will weigh in the 30 to 40 ton range. Its profile will be made slightly narrower than a normal tank to be able to traverse the narrow roads in this semi medieval setting.
this tank due to its quiet nature would be perfect for hit and run attacks against mechas from long range, even if a shell does not penetrate a mecha it will knock it over due to the high center of gravity, and could possibly deal with a noble. In a close battle this tank will have the distinct advantage that the small mechas won't be able to harm it unless they score a very lucky hit.
Even if the nobles show up to battle, they may have a tough time fighting this thing because they will probably be using samurai syle tactics which are obsolete compared to the combined arms employed by the rebels.
Cheers :) enjoy my design before the engineers come and overanalyze it with pitchforks and torches.
[Answer]
If the rebels have to build out of scraps, mount missiles on Jeeps, pickups or SUVs.
The vehicles are fast and relatively mobile and may be found or bashed together from multiple damaged vehicles.
Also, decent missiles may be easier to build than the precision parts needed for an artillery piece. Also, once the missiles are fired, your vehicle is much lighter for getting away.
[Answer]
Without access to dedicated facilities, it's going to be exceedingly hard to make a viable tank. The industrial facilities that you're describing probably aren't going to cut it - to make the protection of a modern armoured vehicle requires the use of some fairly high-tech armour (steel plate is going to be like butter against a 40mm cannon round) and the ability to properly join such materials together (WWI tanks had big problems with bullets 'splashing' between joins in the armour.
Then you need the drivetrain - effective armour against a 40mm is going to require something akin to a modern main-battle-tank, at 50-odd tonnes of mass. This will need components designed for such machinery - maybe available if there is re-purposable machinery for construction or agriculture.
Weaponry is either:
* easy - just steal it of of the enemy (but why not steal the whole vehicle?)
* incredibly difficult - forging large-calibre gun barrels is one of the toughest tests in metallurgy, and far out of reach of hastily-repurposed factory equipment.
Targeting is also a concern if you want the tank to be a match for a mech which can presumably move and shoot simultaneously - stabilising guns was a big challenge for earlier tanks and a huge advantage when it was cracked.
TL;DR - only a few countries on Earth currently make tanks (maybe a dozen or so) and they have free and easy access to their own factories, decades of experience operating the machines and the luxury of long R&D periods. Making tanks isn't easy!
Your best bet for a believable reason to have tank vs mech might be if the rebels had a much more unrestricted access to factories, just not necessarily ones making the mechs. An unsupervised heavy-machinery factory along with a plant that can make hardened steel might be your best bet, just need to find them a source of weapons.
[Answer]
Underground or underworld trading could be quite dangerous. (Think about the Hob from the Hunger Games). If these knights were found out, then the limitations they face could cost them their lives. Just something to think about. Plus, if they're outnumbered by the nobility, then they're frankly stuffed.
So, in conclusion, they're outnumbered and their tanks are unreliable. It would take a miracle for them to win. Just saying.
[Answer]
A 40mm cannon is not every impressive by tank standards; early WWII models were typically 37mm-50mm ( 2pdr to 6 pdr), with the odd 75 millimeter game-changer like the T-34.
Given that mechs necessarily have light armor, they will not be geared up to dealing with anything that takes serious armor-piercing ammo.
So a 1940-vintage T-34 design, but with improved visibility and a few other upgrades, should give you all you need. Shells from German light anti-tank guns of the time just bounced off the sloped, high-grade armor, the 76 mm gun will demolish and mech with ease, and you have plenty of mobility if you need to go after the. Also has lower ground pressure than a mech so better in mud and snow, probably also better at gradients.
Given *modern* tech though, you couldn't build a tank; you'd use a swarm of smart bombs, EFP-carrying drones or similar , or even an tank-hunting helicopter if you wanted to be more retro. They key is hitting them from well outside the range of their puny 40mm nonsense.
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[Question]
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**This question already has answers here**:
[Could a brown dwarf in our outer solar system remain undetected today?](/questions/146334/could-a-brown-dwarf-in-our-outer-solar-system-remain-undetected-today)
(2 answers)
Closed 1 year ago.
I have an idea to put another life-bearing planet in the solar system. You could have **a brown dwarf orbiting perpendicular to the solar ecliptic**. It's a brown dwarf so that it can send infrared radiation to its closest and tidally locked moon, and heat the lit side up beyond the melting point of water, allowing that body to support life even when it is very far from the sun.
The perpendicular orbit (caused by the thing being an extrasolar capture) is so that it's reasonable that this planet has not yet been discovered by the year 2022; we have mainly been looking along the ecliptic, and for the duration of modern human astronomy the planet has not yet intersected it. A perpendicular orbit would also not perturb the orbit of Neptune that much, leading us not to even suspect the existence of the brown dwarf. The James Webb telescope can be the one that finally discovers it.
That gives me a question. Brown dwarves emit radiation, so even if it is not located where you would expect to find planets, it's bound to show up in pictures of other things - unless it is far enough that the radiation would be too faint.
**What is the minimum realistic orbital distance for my brown dwarf to have gone undiscovered for so long?** Is there any way to estimate that? Can it still be well within the Oort Cloud, or would it have to be so far away that it's basically halfway to Alpha Centauri?
[Answer]
Any such object would not be orbiting the sun and remain undiscovered past the all-sky survey of [WISE](https://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer), in 2011. There was an earlier full sky infrared survey, [2MASS](https://en.wikipedia.org/wiki/2MASS), that discovered other brown dwarfs, in 2001. It is extremely unlike that both **full sky** surveys would fail to detect a brown dwarf in orbit around the sun, while detecting fainter objects at much further distances.
This telescope scanned the entire sky and was sensitive enough to detect an object of Jupiter's mass out to 1 light year, with 2-3 Jupiter's mass objects being detectable out to 10 light years. Keep in mind that in addition to being many times heavier than Jupiter, your brown dwarf is putting out a massive amount of energy in the infrared spectrum, enough to melt water on it's moon. For perspective that's over 200C warmer than Pluto.
A realistic lower bound on the range of an undetectable brown dwarf is around 10 light years away.
[Answer]
Let's say the distance is 95,000 AU, as proposed in the [Nemesis star hypothesis](https://en.wikipedia.org/wiki/Nemesis_(hypothetical_star)).
>
> Nemesis is a hypothetical red dwarf or brown dwarf, originally
> postulated in 1984 to be orbiting the Sun at a distance of about
> 95,000 AU (1.5 light-years)
>
>
>
At the moment, Nemesis hypothesis looks highly improbable, however, existence of a brown dwarf at that distance had not been ruled out.
[WISE survey](https://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer) could detect existence of Jupiter mass objects up to 1 light year (63,000 AU), so we can rule out any brown dwarfs closer than that.
[Answer]
**Oort cloud's symmetry.. brown dwarf must have a (far) wider orbit**
I'd like to add another reason this brown dwarf must be many light years away. Any such object *within* [the spherical Oort cloud](https://en.wikipedia.org/wiki/Oort_cloud) would have been detected. The Oort cloud is stretching from 0.03 to 3.2 light years. Within ca 1-2 light years, it would have been found, like the other answers point out.. Beyond that range, you'll run into a problem: the Oort cloud can be observed, its *shape* can be measured,
<https://www.researchgate.net/publication/312542625_On_the_present_shape_of_the_Oort_cloud_and_the_flux_of_new_comets>
it is near spherical (3d).. and therefore the distance must be *much larger*.. The orbit cannot cross the Oort cloud, without astronomers detecting deviations in the Oort cloud density. The Oort cloud is perfectly spherical, which indicates no heavy objects anywhere near, except the sun. To keep your brown dwarf away from the Oort cloud, you'd need an orbit far beyond it. I don't have the means to calculate this exactly, but I estimate your brown dwarf would need to be 10-30 light years away from the sun (see note below), assumed its orbit is circular. Elliptical is ok, but it cannot cross the spherical Oort cloud anywhere. The distance would bring your brown dwarf [in the vicinity of other stars](https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs), which will make it a "rogue star" rather than an "orbiting star"
**Notes on my distance estimation**
NOTE: as KeizerHarm put in the comments here, Proxima Centauri is nearer. Its distance is only 4.2 light years. Maybe there's a "sweet spot" between 3 and 4 ? I found another source that sais the Oort Cloud extends to about 1 light year, not 3.2
<https://www.quora.com/Is-the-Oort-cloud-influenced-by-Alpha-Centauri>
Maybe it's not known ? In any case, the orbit should stay away from the Oort Cloud, it excludes an extremely elliptical orbit. That would cross the Oort Cloud !
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[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
In SciFi Art we often see planets/moons/stars fill enormous amounts of the visible sky. I'm wondering what the theoretical limit for this is realistically, since there are maxima for the possible size of planets, for how close stable orbits can form, for how close you could orbit a given star, [Roche Limit](https://en.wikipedia.org/wiki/Roche_limit), etc...
--> Specifically, what is the **maximum size in degrees/arc seconds** at which a celestial body could appear in the sky for an observer on the surface? And what would that observed celestial body be? A very large moon? A twin-planet arrangement? Something else?
**Assumptions:**
* Let's assume that the observer stands on some celestial body (and they would like to survive).
* Body size/mass is such that it could be (made) habitable for humans.
* Proximity to the bodies star is such that the temperature can be manageable for humans given approx. current level of technology.
* The constellations of celestial bodies should be possible according to current science and *stable* at least in the short term.
>
> E.g. standing on a sizeable moon looking up at the planet does count. Looking up at an incoming rogue planet 10 meters before impact obviously doesn't, since that arrangement is neither stable nor survivable.
>
>
>
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Inspired by these questions...
* [What could be the largest geosynchronous moon?](https://worldbuilding.stackexchange.com/questions/199718/what-could-be-the-largest-geosynchronous-moon)
* [Could We See a Lagrange Giant in the Sky?](https://worldbuilding.stackexchange.com/questions/199590/could-we-see-a-lagrange-giant-in-the-sky)
[Answer]
First thing to remember is that when you're close to a spherical object, you can only see a portion of its surface ([the horizon](https://en.wikipedia.org/wiki/Horizon#Distance_to_the_horizon)). Therefore the anglular diamater of some body with radius $r$ viewed from a distance from the surface of $h$ will be $2\sin^{-1}\frac{r}{r + h}$.
(this also means that the maximum angular diameter of a celestial *object* (such as the galaxy you are in) for someone standing on some moon or planet is going to be greater than 180° unless that person has zero height, but that's not a useful answer to your question)
Clearly this tends to a maximum of 180° as $h$ tends to zero, so need to find the biggest thing you can and orbit it as low down as possible. The biggest object *currently* viewable by humans in something with a short-term stable orbit is the Earth, as viewed from the ISS. With an altitude of 408 km and an equatorial radius of 6378.1 km, the angular diameter of the Earth is 140°3'42.68'', and whilst the ISS is habitable you can't really stand on it as such, so it isn't quite an answer.
I'm not going to consider the Sun, as it is just a bit too hazardous.
The biggest thing that you could reasonably see in the Solar System from an ISS-like orbit would be Jupiter. You could imagine parking a suitable body just above Jupiter's [exobase](https://en.wikipedia.org/wiki/Exosphere#Lower_boundary). Earth's exobase doesn't generally fall below 500km, so by being just above it our theoretical moon will have a more stable orbit than the ISS. Jupiter's exobase is at [~2300km](https://arxiv.org/pdf/1312.1947.pdf). At this altitude, Jupiter will have an angular diameter of **151°18'52.44''**, bigger even that Earth as seen from the ISS.
The [Roche limit](https://en.wikipedia.org/wiki/Roche_limit) for a your moon is largely determined by densities and the size of the body it orbits: $l\_R = R\_J \sqrt[3]{\frac{2\rho\_J}{\rho\_m}}$ where $R\_J$ is Jupiter's radius, $\rho\_J$ is Jupiter's density and $\rho\_m$ is the required density of the moon. This means that anything that's more than twice the density of Jupiter will have a Roche limit that's *less* than Jupiter's own radius! Jupiter, being a gas giant has a pretty low density of ~1326km/m3. Jupiter's own icy moons [all have lower densities than this](https://en.wikipedia.org/wiki/Moons_of_Jupiter#List), but if your theoretical low-altitude moon were even as dense as the Moon (3346km/m3) it would not exceed the Roche limit!
It does not appear that anyone has considered any other lower limit on moon orbital radius other than the Roche limit, so my suggestion isn't currently known to be implausible ([Limits on the orbits and masses of moons around currently-known transiting exoplanets](https://www.aanda.org/articles/aa/full_html/2010/13/aa14955-10/aa14955-10.html)).
Note that this is now *right on the edge of plausibility*. Long term stability of the moon's orbit is dubious, and were Jupiter close enough to the Sun for the moon to be within the habitable zone the additional heat input from solar irradiance would warm the gas giant and inflate its atmosphere, and your low-altitude moon would likely be dragged down into the atmosphere in a relatively short period of time. Because the precise relationship between atmospheric height of a gas giant and surface temperature isn't trivial to pin down, this could be handwaved as having a less-massy giant than Jupiter which has expanded to the same size in the heat... this would of course affect things like orbital period, but as you've not asked about that in your question it does not need to affect the answer in the slightest.
It does however put a fairly reasonable upper bound on the apparent size of an object in the sky. It may be possible to fit in something a tiny bit bigger, but I'm having trouble finding a plausible brown dwarf/gas giant cutoff which has implications for radiative heating of your satellite. I'll update in future if I find something bigger, but for now Jupiter is a reasonable proxy for a very large non-fusing gas giant.
Here's a simple chart of angular diameter vs altitude. The orange circle marks [Metis](https://en.wikipedia.org/wiki/Metis_(moon)), which I believe has the biggest object in its sky of any known body in the solar system, and with its surface gravity of half a milligee you could conceivably stand on it. You'd have to attach a habitat to it in order to live there, though. At its perijove of 127974 km (equivalent to an altitude of 56482 km) Jupiter has an angular diameter of **67°55'27.29''**. This marks a good proxy for the best *achievable* view, and one likely to remain stable even when the parent planet inflates if bought closer to the Sun.
[](https://i.stack.imgur.com/CTM3P.png)
This issue of habitability is a separate one that has been covered in many, many other questions and answers here *passim ad nauseam* so I shall not be going into detail there. Suffice it to say, your atmosphere scraping moon *could* be habitable.
* It will be tidally locked, but reflected light and radiant heat from the has giant will keep the planet-side warm and light, and with a day length of a little over 3 hours there's little risk of the non-planet side getting cold at night, eliminating the usual problems with tidally locked worlds.
* It will be well within its parent's magnetosphere, so it does not need to generate one of its own to preserve its atmosphere.
* In the absense of gravitational influence from other large moons around the gas giant you can expect its orbit to be quite circular, which means it will not suffer from excessive tidal heating like Io, which has [orbital resonances](https://en.wikipedia.org/wiki/Io_(moon)#Orbit_and_rotation) with other Galilean moons which in turn drive its massive tidal heating and vulcanism.
* Without Io-like vulcanism, there's no [plasma torus](https://en.wikipedia.org/wiki/Gas_torus) around the gas giant, rendering space around it much less hostile than Jupiter.
All that needs to be done is to keep the exobase of the moon's atmosphere clear of the gas giant's exobase, to prevent any drag or atmosphere-stripping problems.
[](https://i.stack.imgur.com/uH4Vy.png)
Here's a [slightly different diagram](https://sites.google.com/a/upr.edu/planetary-habitability-laboratory-upra/library/notes/thesurfacepressureofearth-likeexoplanets) from the usual chart for [atmospheric escape](https://en.wikipedia.org/wiki/Atmospheric_escape), just for variety. You can see that [Mars](https://en.wikipedia.org/wiki/Mars) is right at the lower limit for the Mass required to retain an N2 atmosphere. It is also dense enough, at ~3900 kg/m3 to be safe from destruction by tidal forces. Unlike the real-life Mars, a Mars moon snuggled up to a gas giant is safe in its parent's protective magnetosphere and so should hang on to much more gas for much longer.
The [scale height](https://en.wikipedia.org/wiki/Scale_height) of a Martian atmosphere with an [Earthlike average atmospheric temperature](https://en.wikipedia.org/wiki/Atmosphere_of_Earth) of 287K is defined as $H = \frac{k\_BT}{mg}$ where $k\_B$ is Boltzmann's constant, $T$ is 287K, $m$ is the mass per molecule of the atmosphere (4.65x10-26 kg for N2) and $g$ is the surface acceleration due to gravity, which for Mars is ~3.7m/s2. $H$ is therefore ~22.9 km, not far off Jupiter's own. Earth's scale height is about 8.5 km, and its exobase is ~500 km. Given the same proportions, the Mars-moon's exobase would start at ~58.8 times its scale height, or ~1350 km. In practise you could get away with a lower surface pressure than Earth for a reduced exobase altitude, but this is an adequate start.
Your minimum altitude therefore becomes 2300 km (for the parent's exobase) + 3400 km (for the moon's radius) + 1350 km (for the moon's exobase) or ~7045 km for the barycenter, or merely 2300 km + 1350 km for the closest sub-Jovian point, giving still quite dramatic maximum Jovian angular diameter of **131°**.
[Answer]
Let's break it down by type of system, as planet-moon or planet-planet systems will have different constraints from star-planet systems.
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### Planet-moon/planet-planet system
Looking at planet-moon or binary planet systems, the answer to your question will always involve standing on a decent sized moon and looking up at the host planet. A moon by definition has the centre of mass (barycentre) of its orbit inside the host planet, thus one cannot make it arbitrarily heavy. If we want a stable system, we need to be at a certain minimum distance (the Roche limit) and thus if we want the largest angular size, for which we want the closest possible distance, we need to increase the size and thus mass of the object we are looking at. For the largest angular size we will look at the most extreme case of a system where the observer stands on a moon orbiting around a giant planet.
To make calculations a bit more simple and not leave it questionable whether the place is habitable, let's assume the observer is standing on an Earth-analogue.
The (rigid body) Roche limit gives the radius at which the gravitational pull of the second body equals that of the primary, thus providing the minimum distance at which a body can orbit before being torn apart by the tidal forces.
$$d=R\_2\left(2\frac{M\_1}{M\_2}\right)^{\frac13}$$
Setting $R\_2$ and $M\_2$ to Earths values shows that our minimum distance scales with the cube root of the mass of the primary. Of course the habitability of such a system becomes questionable because the gravity felt standing on the moon will be varying hugely depending on where you stand on it and could go to zero. Plus we haven't looked at the effect of tidal heating, which occurs when the tidal force of the host is strong enough to kind of knead the moon and thus warm it up by friction. You could of course use this to your advantage and let it counteract the fact that you are much farther removed from the star than Earth is.
The angular size is obtained from the radius of the primary and the distance with:
$$\delta=\arctan\left(\frac{R\_1}d\right)$$
Gas giants like Jupiter don't behave quite like your average rocky planet anymore in the sense that the radius doesn't increase very much with mass. The gas will compress and settle into hydrostatic equilibrium if more mass is added. If we look at the extreme end we get to the limit of brown dwarf stars. This is defined at a mass of $13 M\_{\text{Jupiter}}$, but the radius will not be very different from $1 R\_{\text{Jupiter}}$. To quote [Wikipedia](https://en.wikipedia.org/wiki/Brown_dwarf):
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> Brown dwarfs are all roughly the same radius as Jupiter. At the high end of their mass range (60–90 MJ), the volume of a brown dwarf is governed primarily by electron-degeneracy pressure,[26] as it is in white dwarfs; at the low end of the range (10 MJ), their volume is governed primarily by Coulomb pressure, as it is in planets. The net result is that the radii of brown dwarfs vary by only 10–15% over the range of possible masses.
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The larger radii that you might have read about of some exoplanets is due to their much hotter temperature, since these reside very close to their sun. They have their name 'hot Jupiter' for a reason. So I will not consider those and just take the size of Jupiter as our maximum planet size. We have seen that the minimum distance increases with mass, so taking a more massive planet is actually disadvantageous. Taking mass away beyond a certain point will decrease our radius again, so let's take $M\_{\text{Jupiter}}$ as our realistic extreme case.
Filling all of this into the relevant formulas gives an angular size of 374000 arc seconds or 104 degrees. But you will be orbiting at a distance of 8.6 Earth radii or just 0.78 Jupiter radii!
Let's say we double that orbital distance so that we feel a bit safer, we end up with a size of 65 degrees. You might still feel a bit lighter in some places on your moon though...
If that still feels too iffy in terms of realism, we can put ourselves at a distance of $6 R\_{\text{Jupiter}}$ (roughly how far Io orbits around Jupiter). Now Jupiter still only has an angular size of about 19 degrees (our moon is 0.5 degrees, so this is still quite big! :D).
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### Star-planet system
With stars we have to consider the extra constraint of flux received by a planet. The Stefan-Boltzmann law tells us that the flux emitted by a black body (=star to good approximation) scales with the temperature to the fourth. If we don't want to get too toasty, we better choose a star that is cold (for stellar standards). The total power emitted by a star is the flux times the emitting area. To calculate the flux at Earth (or at any distance) we simply divide this power by the total surface area of a sphere centered at the star and with the radius equal to the distance of the planet.
Red giants are the perfect candidate here: they can be as cool as 3000 Kelvin (on the surface) and are around 200 solar radii so at first thought that might maximize the angular size.
If we would take Earth as an example of a cozy amount of flux, we can combine these formulas to scale the flux to the new temperature and distance while dropping all constants:
$$P\propto A\_R\cdot T^4\propto R^2\cdot T^4\implies F=\frac P{A\_d}\propto\frac{R^2\cdot T^4}{d^2}$$
so if we set $F\_1 = F\_{\text{Earth}} = F\_2$: $$\frac{R\_1^2\cdot T\_1^4}{d\_1^2}=\frac{R\_2^2\cdot T\_2^4}{d\_2^2}$$
We solve for the new distance that our planet would be at to receive the same flux from a red giant: this puts us at about 54(!) times the distance Earth-Sun. Turns out a Red giant generates a lot more flux even though it is a lot cooler (which is why Earth would be incinerated when the Sun goes red giant). We simply use the formula for angular size again with 200 times the solar radius to arrive at an angular size of: 7122 arcsec or ~2 degrees. This is still better than our Sun at ~0.5 degrees!
What would have happened if we took a small cold star? If we take a quote from [Wikipedia](https://en.wikipedia.org/wiki/Red_dwarf) again:
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> The coolest red dwarfs near the Sun have a surface temperature of ~2,000 K and the smallest have radii of ~9% that of the Sun
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Using that in our equations yields a distance of merely 0.01 times the distance Earth-Sun and with angular size: 16000 arcsec or 4.4 degrees. We actually did better! Keep in mind that tidal locking might be a problem now though, due to the very close distance to the star, so again might affect habitability (not to speak of the violent flares that can occur in these types of stars).
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A closing remark:
It was a fun exercise to actually run the numbers on this, and even I hadn't realised that looking from Io, Jupiter looks quite that big! Angular size falls off really fast with distance as we saw. Distances in the universe are immense, and most celestial bodies do not actually reside very close to each other, or if they do, they are not very hospitable. This makes such beautiful big-planet-in-the-sky scenarios actually quite unlikely unfortunately.
[Answer]
Short Answer:
Many of those images might be designed to show astronomical objects though imaginary telephoto lenses. According to my reserches, the largest possible astronomical object as viewed from the surface of a habitable or potentially habitable world would have an angular diameter of 22.9183 degrees of arc, or about 82,505.88 arc seconds. Except that Part three of my aswer to: [How would the reflection of sunlight change the day / night cycle of a binary planet system?](https://worldbuilding.stackexchange.com/questions/200498/how-would-the-reflection-of-sunlight-change-the-day-night-cycle-of-a-binary-pl/200539#200516) Discusses another type of astronomical situation were two astronomical objects can have very large angular diameters in each other's skies. Possibly the largest angular diameters which are possible.
Long Answer in Six Parts:
I have often wondered about the subject.
Part One: Telephoto Lenses.
I note that humans have invented something called telephoto lenses for still and motion cameras.
Thus you should have often seen still photographs, or scens in movies & Tv shows where Earth's Moon appears to be vast and cover most of the sky. And Earth's Moon does cover most of the tiny angle of the sky which is visible in those scenes shot with telephoto lenses.
And we have all seen scenes in science fiction films where the moon appears to have an enormus angular diameter. LIke in *E.T.: The Extraterrestrial* where a bicycle flies across the face of the Moon that appears to be enormous. Those scenes in science fction movies aren't designed to show the Moon with a much greater angular diameter than it actually has, they are designed to show what the scene would look like photographed thorugh a telephoto lens that makes the moon look much larger.
And similarly many illustrations of alien worlds and movie and tv scenes show stars, or planets, or moons near the horizon that appear to have a vast angular diameter. In some cases the scenes may have been designed to show what someone would see without any magnification, in others they may have been designed to show what it would look like thorough a telphoto lens making the objects in the sky loook much larger, and in many cases nobody thought about whether the apparent angular diameter would be the actual angular diameter as seen with the naked eye.
Part Two: The Angular Size of Stars.
A small difference in the mass of main sequence stars will cause a much larger difference in their luminosities. A small increase in mass will cause a larger increase in luminosity. A small decrease in mass will cause a larger decrease in luminosity.
More massive stars also emit more light per unit of their sufraces. Less massive stars emit less light per unit of their surfaces.
So a planet that has the sem temperature as Earth orbiting a more massive and brighter star will have to orbit it farther than the distance at which the star it would have the same angular diameter as the Sun. A planet with the same temperature as Earth orbitng a less massive and less luminous star would have to orbit it closer than the distance at which the star would have the same angular diameter as the Sun.
Astronomers have calculated the sizes of the circumstellar habitable zones of main sequence stars of various spectral types. All one has to do is find the luminosity of the star comparared to that of the Sun and then multiply the inner and outer edges of the Sun's circumstellar habitable zone by that ratio.
Unfortunately, different calculations of the inner and outer edges of the Sun's circumstellar habitable zone vary greatly, as this list shows:
[https://en.wikipedia.org/wiki/Circumstellar\_habitable\_zone#Solar\_System\_estimates[1]](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates%5B1%5D)
A writer who wants to have several habitable planets orbiting the same star will have to see if he can fit them in within a habitable zone that seems reasonable and plausible to him. A writer who wants one and only one habitable planet in his star system can play it safe and calculate the Earth Equivalent Orbit for that star, an orbit where a planet would receive exactly as much radiation from its star as Earth receives from the Sun. Thus he would know that a planet in that orbit could be habitable.
The answer by user177107 to the queston:
[https://astronomy.stackexchange.com/questions/40746/how-would-the-characteristics-of-a-habitable-planet-change-with-stars-of-differe%5B2%5D[2]](https://astronomy.stackexchange.com/questions/40746/how-would-the-characteristics-of-a-habitable-planet-change-with-stars-of-differe%5B2%5D%5B2%5D)
Has a table listing main sequence stars of various spectral types.
For each spectral type of star the mass, radius (half of the diameter), luminosity, etc. is listed, as well as the distance a planet would have to orbit to received exactly as much radiation as the Earth receives from the Sun.
The smallest type of star listed is spectral type M8V, with a mass of about 0.082 the mass of the sun, and a diameter of about 0.111 of the Sun, and a planet in an Earth Equivalent Orbit would orbit it at a distance of 0.0207 of an Astronomical UNit (AU), the distance of Earth from the Sun.
Because the orbit of the Earth is elliptical, the angular diameter of the Sun as seen from earth varies between 31.6 and 32.7 arc minutes, or 1,896 to 1,962 arc seconds. Since there are 60 arc minutes in a degree of arc, we can simplify the calculation by assuming that the Sun has an average angular diameter of 0.5 degrees of arc, or about 1,800 arc seconds.
Since a planet in an Earth Equivalent Orbit around a M8V star would beonly 0.0207 as far as Earth is From the Sun, the angular diameter of the Sun would have to be multiplied by 1 divided by 0.0207, or by 48.309, to get an angular diameter of 24.1545 degrees, and then divided by 1 divided by 0.111, or 9.009, the ratio of the diameters of the two stars, to get an angular diameter of 2.681 degrees, or about 9,651.6 arc seconds,.
So a M8V star would look about 5.3 times as wide seen from a planet in an Earth equivalent orbit as the Sun looks from Earth. Which would be quite noticable for a human on the planet, but probably not too spectacular.
Of course, if the planet orbits a bit closer to its star than the Earth Equivalent Orbit, the star would appear to have a larger angular diameter.
According to the estimate by Kopparapu et al in 2013, the inner edge of the Sun's circumstellar habitable zone is 0.99 AU, or only 0.01 AU closer than the Sun's orbit. However, Zsom et al in 2013 estimated that the inner edge of the Sun's habitable zone could be ast 0.38 AU. Their estimate is probably for a planet with atmospheric condidtions suitable for some forms of Earth-like life and not for humans, who might, however, be able to live on such a planet with protective gear.
At such a distance around a M8V star, the star would appear to have an Angular diameter of about 7.055 degress or about 14.11 times teh angular diameter of the Sun as seen from Earth.
The closer a planet orbits to its star, the stronger the gravity and tides of the star will be upon the planet. Because the luminosity of low mass stars decreases faster than their mass, planets in the circumstellar habitable zones of low mass stars will experience intense gravity and tides, which will tend to slow down the rotation of those planets.
So as the stellar habitable zones around stars get smaller and smaller for less and less massive stars, eventually the inner edges of their cicumstellar habitable zones reach the distance at which a planet would swiftly become tidally locked to its star. With stars of even less mass, the Earth equivalent orbit will eachethe distance at which the planet will become tidally locked to the star. With stars of even less mass than that, the outer edges of their habitable zones will reach the distance at which a plaent become tidally locked and it will be impossible for any planet witin their habitable zones. to avoid being tidally locked.
Stephen H. Dole in *Habitable Planets for Man*, believed that a tidally locked planet would be unhabitable. He also calculatled that at 0.88 the mass of the Sun, the inner edge of the circumstellar habitable zone, or "ecosphere" as he called it, would reach the distance where a planet would be tidally locked, and at a stellar mass of 0.72 that of the Sun, the outer edge of the habitable zone would reach the distance at which a planet would be tidally locked.
[https://www.rand.org/content/dam/rand/pubs/commercial\_books/2007/RAND\_CB179-1.pdf[3]](https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf%5B3%5D)
Dole also noticed a potential escape clause, where a planet which became tidally locked to a large moon, or a companion planet, could avoid becoming tidally locked to it's star.
Dole estimated that could enable habitable palnets to exist n the habitable zones of stars down to a stellar mass of 0.35 of the Sun, before the sun would raise too high tides on the planet.
O.35 the mass of the Sun would be somewhere between a M5V and a M2V star; 0.72 the mass of the Sun is approximately a K1V star; and 0.88 the mass of eh Sun is approximately a G9V star.
But there have been calculations indicating that a tidally locked planet could be habitable if it had enough atmosphere and water to distribute heat from the day side to the night side. This is rather controversial.
Part Three: The Angular sizes of Brown Dwarfs.
Brown dwarfs are objects with masses greater than about 13 times that of Jupiter and up to about 75 to 80 times that of Jupiter. Brown dwarfs are intermediate in mass and conditins between planets and stars, and could be orbited by natural satellites, perhaps large enough for life.
Considering how dim brown dwarfs are, any theoeretical habitable moons or planets or whatever obiting them would have to orbit very close. Thus it is possible that A brown dwarf would appear several times as wide in the sky of a habitable world orbiting it as any star appers in the sky of its habitable planets. And possibly humans in space suits or lesser environmental protection could work on the surfaces of nonhabitable worlds with large brown dwarfs in the sky.
I am unable to clculate the maximum possible angular diameter of a brown dwarf as seen from a world which humans might want to land on.
Part four: Planets With Neighboring Orbits.
The star TRAPPIST-1 is a dim M8V class star, noted for having several potentially habitable planets orbiting in its circumstellar habitable zone.
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> The orbits of the TRAPPIST-1 planetary system are very flat and compact. All seven of TRAPPIST-1's planets orbit much closer than Mercury orbits the Sun. Except for b, they orbit farther than the Galilean satellites do around Jupiter,[43] but closer than most of the other moons of Jupiter. The distance between the orbits of b and c is only 1.6 times the distance between the Earth and the Moon. The planets should appear prominently in each other's skies, in some cases appearing several times larger than the Moon appears from Earth.[42] A year on the closest planet passes in only 1.5 Earth days, while the seventh planet's year passes in only 18.8 days.[40][37]
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[https://en.wikipedia.org/wiki/TRAPPIST-1#Planetary\_system[4]](https://en.wikipedia.org/wiki/TRAPPIST-1#Planetary_system%5B4%5D)
The potentially habitable palnets of TRAPPIST-1 are d, e, f. and g. They could be habitable, and maybe if not they could be terraformed to be habitable. Anyway, habitable or not, people should be able to walk around on them in spacesuits and possibly less evironmental protection.
The semi-major axis of the orbit of the Moon is about 384,399 kilometers, or about 0.002569 AU. At that distance Earth has an angular diameter of approximately 2 degrees of arc or 7,200 arc seconds.
At their nearest, TRAPPIST-1 f and TRAPPIST-1 g are about 0.00834 AU apart, which is about 3.246 times the distance between the Earth and the Moon. So if those planets had the same diameter as the Earth, they would appear to have an angular diameter of 0.616 degrees or 2,218.114 arc seconds. They are both larger than the Earth. The larger, TRAPPIST-1 g, has a diameter 1.129 that of the Earth, and so would have an angular diameter of 0.695 degrees or 2,504.251 arc seconds when seen from TRAPPIST-1 f at its closest.
The innermost potentially habitable planet, TRAPPIST-1 d, orbits only 0.00647 AU beyond the orbit of TRAPPIST-1 c, which is 2.5184 times the Earth-Moon distance, which would make TRAPPIST-1 c look up to 0.7941 degrees wide from TRAPPIST-1 d, except that TRAPPIST-1 c has 1.308 times the diameter of Earth. So TRAPPIST-1 c would have an angular diameter of about 1.0387 degrees of arc of 3,739.517 arc seconds when the two planets were closest.
The absolute maximum possible angular diameter of a planet seen from a habitable or potentially terraformable planet in a neighboring orbit should be at least that much.
The best is yet to come when I complete this answer.
Part four: The Ultimate retorgrade solar System.
The planetPlant blog has a section called the Ultimate solar system, with attempts to design imaginary solar systems with as many habitable planets as possible.
The post called "The Ultimate Retrograde Solar System" cites a paper demonstrating that more planetary orbits can fit inside the circumstellar habitable zone of a star if half of the planets orbit in a backwards or retrograde direction compared to the other planets.
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> It makes a big difference. You can fit about twice as many planets into a given stretch of orbital real estate. The requirement is simply that every other planet must orbit in the opposite direction. So, planets 1, 3, 5, and 7 orbit the star in a clockwise direction, and planets 2, 4, 6, and 8 orbit counter-clockwise.
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[https://planetplanet.net/2017/05/01/the-ultimate-retrograde-solar-system/[5]](https://planetplanet.net/2017/05/01/the-ultimate-retrograde-solar-system/%5B5%5D)
So depending on how close the TRAPPIST-1 system comes to being as closely packed as posssible, a retrograde TRAPPIST-1 system could have 7, 8, or 9 planets orbiting within the circumstelllar H habiable zone e if each palnet orbited in the opposite diretion to the planets in the next inner and outer orbits to it.
So possibly a retrograde solar system could have planets which can have an angular diameter of about 2 degrees of arch, or 7,200 arc seconds, when seen from potentially habitable planets in the circumstellar habitable zone.
But:
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Writers who use such a solar system will have to show that it must be artificial, created by a very advanced society.
Part Five: Giant Planets Seen from their Habitable Moons.
It should be obvious that a moon could orbit a large enough planet closely enough that the planet would almost fill an entire hemisphere of the sky of the moon. But unfortunately the question asks for the viewing to be from worlds shich are habitable or which could be terraformed to become habitable. Habitable moons are not very common.
It is possible that a planetary mass exomoon could orbit a giant exoplanet and be habitable. But such an exommon would have to meet the requirements for an exoplanet to be habitable, such has having a mass in the proper range. And the exomooon would also have to meet special requirements due to being a moon of a giant planet.
For example, there is the concept of a habitable edge, a minimum distance from a planet that a potentially habitable exomoon would have to be in order to avoid too much tidal heating from the planet. Too much tidal heating would cause the exomoon to suffer a runaway greenhouse effect and become lifeless.
Rene Heller and Jorge Zuluaga, in Magnetic Shelding of Exomoons Beyond the Planetary Habitable Edge" discuss a maximum possible distance of a habitable exomoon from its planet.
[https://arxiv.org/pdf/1309.0811.pdf[6]](https://arxiv.org/pdf/1309.0811.pdf%5B6%5D)
They discuss exomoons whch are large enough for life but significantly smaller than Earth, and which thus wouldn't have their own magnetic fields to shield them from high energy particles from space. Those moons would have to be within the magnetic fields of their planets and be shielded by those planetary magnetic shields.
They believe that there is no safe zone around Neptune sized planets. Their exomoons would orbit either within the habitable edge and suffer runaway greenhouse effects, or else orbit outside the protection of planetary magnetic fields.
But moons around Jupiter sized planets could be habitable in orbits at distances between 5 and 20 planetary radii, or 2.5 to 10 planetary diameters.
According to my rough calculations, an exomoon at the outer edge, or about 20 planetary radii, would see the planet as having an angular diameter of about 5.7295 degrees of arc, or 20,626.2 arc seconds.
And according to my rough calculations, an exomoon at the inner edge, or about 5 planetary radii, would see the planet as having an angular diameter of about 22.9183 degrees of arc, or about 82,505.88 arc seconds.
Part Six: A large Moon Seen from its Planet.
The planet Earth is habitable for humans at the present, and and has a lorge Moon, which at the present time orbits the Earth in an elliptical orbit with a semi-major axis of 384,399 kilometers.
At that distance the Moon has an angular diameter of 29.3 to 34.1 arc minutes, or 1,758 to2,046 arc seconds, depending on its current distance from Earth.
But this was not always the case. Earth only acquired enough oxygen in the atmosphere to be brethable for humans a few hundred million years ago, after existing for billions of years.
And the Moon was not always at its present distance from Earth.
According to present theory, the Moon formed after Earth collided with another planet, called Theia, over four and a half billion years ago. Most of the mass of the two planets merged, much of it was ejected into space and lost, and part of it formed a ring around Earth, which eventually formed the Moon. tidal interactions between the Earth and the Moon caused the Moon to gradually move to a higher and higher orbit over billions of years.
When the Moon formed out of the ring it was abourt 4 Earth radii or 15,000 to 20,000 miles from Earth. It would have appear 15 times as wide as it now appears, and it would have been glowing dull red from the hot lava it was made of. So the Moon would have had an angular diameter of about 7.5 degrees or about 27,000 arc seconds.
About four billion years ago, after 500 million years, the Moon would have moved to an orbit about 80,000 miles from Earth and would have had about three tiems its present angular diameter, and so about 1.5 degreees of arc or about 5,400 arc seconds.
[https://www.forbes.com/sites/quora/2018/07/11/what-did-the-moon-look-like-from-earth-4-billion-years-ago/?sh=1a465ddf1151[7]](https://www.forbes.com/sites/quora/2018/07/11/what-did-the-moon-look-like-from-earth-4-billion-years-ago/?sh=1a465ddf1151%5B7%5D)
And I presume that hypothetical aliens who found a similar system of a young planet with a young moon receeding from it could have decided to terraform theplanet to make it habitable at a point where the moon was a lot closer than 80,000 miles and had a much greater angular diameter than 1.5 degrees or 5,400arc seconds.
And I suppose that sometime the future humans could find such a young planet with a moon that appears very large in its sky, and decide to terraform that planet to make it habiable for humans.
Conclusion:
As I said in part one, many of those images of astronomical objects looking very large in the sky could be depicting how large those objects would look seen through a telephoto lens, instead of how large they would appear with the naked eye.
The greatest angular diameter of an astronomical object as seen from the surface of a habitable or terraformable astronomical object I could find would be a giant planet viewed from the surface of a large habitable or potentially habitable moon, with an angular diameter of up to 22.9183 degrees of arc, or about 82,505.88 arc seconds. Except that Part three of my aswer to: [How would the reflection of sunlight change the day / night cycle of a binary planet system?](https://worldbuilding.stackexchange.com/questions/200498/how-would-the-reflection-of-sunlight-change-the-day-night-cycle-of-a-binary-pl/200539#200516) discusses another type of astronomical situation were two astronomical objects can have very large angular diameters in each other's skies. Possibly the largest angular diameters which are possible.
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[Question]
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I want to have a powerful Mesoamerican civilisation by the 1100s; one that decides to sail east and discover Europe. [Earlier versions of the story had them contacted by Zheng He in the 1400s](https://worldbuilding.stackexchange.com/questions/173173/an-aztec-ship-sails-east-where-does-it-land), but I want to move the setting farther into the past and do something with the fabled Toltec society. So I need to provide them with the means to pull themselves up by their own bootstraps and become a country as powerful as the China of that time.
So how do I buff them, and make them able to traverse oceans? There are a handful of obvious picks: I am making the [American horse](https://en.wikipedia.org/wiki/Equus_scotti) survive and become a suitable draft animal. I am also going to move the Rio Grande south a bit, and provide a fertile plain ripe for agriculture and an even larger population (not that the Valley of Mexico was ever underpopulated to begin with, but it can help the advancement of a state in Anahuac to have a northern rival to eventually conquer).
But the biggie is seafaring. Early Europeans had the gentle Mediterranean to cross, and plenty of reason to cross it in order to trade with the countries on the other side. I think the Caribbean Sea and the Gulf of Mexico *can* function in much the same way, but I need a reason for my country to traverse it, and learn navigational skills from a thousand round trips to Cuba and the other islands.
What can I put on those islands to make them desirable to sail towards?
My idea: [guano](https://en.wikipedia.org/wiki/Guano)! That second fertile plain I added; if over-exhaustive agriculture can make it lose its fertility after time, accumulated bird poo can do wonders as a fertiliser, and my Mesoamericans would have to mine those guano islands in order to avoid starvation. More interestingly, there is a real string of islands going farther and farther east, until it stops with the Atlantic. So back to my original idea: that expedition that discovers Europe? It could have been a quest for more guano islands!
What I would like to know is how reasonable this scenario is; and particularly the agriculture and guano part. If it isn't; is there anything I can add to those islands, to make them a desirable destination, in order to have a seafaring Mesoamerican nation by the start of the 12th century?
Specifically, **out of scope** are:
* Getting a state as powerful as China in Mexico. I think that's a solvable problem; just alter the climate and geography until it's paradise on Earth.
* The trans-Atlantic expedition. Their path has been addressed in the linked question, and their specific motivations would be story-based.
**In scope** is:
* Having my powerful Nahuatl state possess seafaring technology. For that I surmise they need a motivation to routinely traverse the Gulf of Mexico, which the Aztecs historically did not. Getting them that motivation, or that technology through some other means, is what the question is about.
[Answer]
# They need a reason to go to sea and it needs to be a good one
You're starting to look in the right direction, they need the population to back anything up so they'd need to have solid agriculture, but they'd have to get to the islands to know they had guano and they'd have to understand what it was. Check that was known at the time. Really the first thing to check is the state of the coastal fisheries. If there's good fishing out there, they'd have a reason to put to sea on a regular basis.
Once they're actually at sea they'll discover the local islands, if there are people there then either trade or raiding will be a thing. If there aren't yet people there, there will be fairly soon once they've been discovered. Again it's just a matter of population pressures, you'll end up with Mesoamerican vikings.
However you have a problem for long distance ocean travel. Columbus knew the Earth was round, but his maths was bad and he thought it was smaller than everyone else knew it was. But even so, he had a good reason to set sail, trade. Columbus knew there were valuable goods on the other side of the world, he just had to find a better way to get to them and his fortune was made. The goods were coming over land, and he thought an ocean route was possible. Who are the Mesoamericans trading with to know that there's something out there worth sailing far out to sea to find? Up and down the coasts certainly, but not out into the great oceans.
An itinerant coastal trader going up into the far north might have found a way across to Russia and then on down to the spice islands. That gets them across the pacific, you could then sail straight home with a suitable ship. After that you'd need someone to make Columbus' mistake and think it was shorter to go the other way. They'd be experienced ocean travellers by the point they reached Europe, but they'd already have common trading partners in the Spice islands with the Europeans and hence the great "discovery of Europe" would simply be shortcutting the already existing "wool road" from Europe the long way round to America.
[Answer]
Firstly you are correct to suggest having beasts of burden as this would certainly make their civilisation much more productive and would be a prerequisite.
You might find [this](https://worldbuilding.stackexchange.com/questions/92391/could-the-romans-have-colonised-the-new-world) question of interest which asks the reverse question of the Romans.
The key points are that the Romans didn’t cross the Atlantic because they had no idea there would be anything to find except endless ocean, and even if there was land some where there would be little to gain by travelling to such a remote, dangerous and difficult to reach location. The same would be true of the Maya.
However whereas the Romans could have reached the Americas but would have found it very hard to return home, the Maya would find it very hard to get started, but easier to return. This is because the position of the winds and currents at the closest crossing point are against them. Also like the Romans the Maya were not great explorers like some other civilisations.
I propose a similar solution for the Maya crossing the Atlantic that I proposed for the Romans. The primary need is for a motive and the only one I can think of is religious. Changes would be needed to the basic religious underpinnings of their civilisation. This is not an easy thing to deal with and would change the character of the people, but is probably necessary.
I suggest that they are driven to the east to discover the source of the portal on Earth through which the sun god Kinich Ahau emerges from the underworld and transforms from a jaguar into the sun. The exact theological requirements would be a interesting project in its own right, but given the variegated nature of their beliefs and hundreds of gods it should be possible.
If this was a strong enough conviction they might well develop a much greater interest in the sea and in the oceans and currents. Their ships would get bigger to carry more supplies and they would discover all the islands of the Caribbean. They might even cross the Gulf of Mexico and reach Florida.
At some point an observant Maya would begin to pick up on the way the winds and currents flowed and realise how they varied with the time of the year and how they might be able to sail ever closer to the point on Earth that the sun rose from by first sailing north east\* then south and home in ever bigger loops.
Huge losses would be expected due to storms but some might eventually have made it and returning home would be easier for them than for the Romans. Losses might even have been considered as sacrifices to Kinich Ahau. What they would have made of the “New World” and it’s inhabitants is impossible to say. No doubt disappointment at not finding the portal.
\*They had no compass and this would have been a major problem, but they had considerable knowledge of astronomy and might have navigated by the stars like the pole star. Much later when Spanish arrived in the New World they found that the Aztecs were able to predict the movement of the planet Venus more accurately than they could.
[Answer]
**Iron from West Africa.**
You can find loads of speculation about ancient West African trade with the Olmecs and Mesoamerica. Here is an example.
<http://raceandhistory.com/historicalviews/ancientamerica.htm>
Theories about Mesoamerica get as wild as you want them - Egyptians, Israelties, Atlanteans, Australians, Aliens etc. But the West Africa one is a little less wild than most, and is good for your purposes. West Africans had iron from way back and iron would be a valuable to the ancient mesoamericans. If West Africans with ships showed up periodically with iron to trade the mesoamericans might decide to go over there themselves, if only to get better prices for their stuff. And if you augment the west African kingdoms of the period to become ocean-crossing traders I do not think anyone will take offense.
[Answer]
You have several rich resources that could drive seafaring:
* [Copper in Cuba](https://en.wikipedia.org/wiki/Cobre_mine,_Cuba)
* [Gold in Hispaniola](https://en.wikipedia.org/wiki/Hispaniola)
* Trade with the [Missippian Culture](https://en.wikipedia.org/wiki/Mississippian_culture)
* Importation of llamas as beasts of burden
* Trade for alpacas or alpaca-based textiles
* A fashion for exotic pet alligators, buffalo, vacunas, and/or rheas among the wealthy
] |
[Question]
[
A creature I am imagining is a small mammal about the size of a domestic cat which - through symbiotic bacteria which live in its fur - is covered its whole body over in blue-white bioluminescence, 24-7.
**Is there any reason why an animal would be bioluminescent all over its body rather than in just one part or a few parts?** The light can't be "turned off". If you need to know; the creature is terrestrial and lives in a forest environment which is, for whatever reason, permanently in relative darkness. It eats fruit, nuts and the like, is social, and not physically dangerous to aggressors (at least when alive, it can be poisonous if necessary).
Note that the method of light production, mentioned above, is also open to change if it needs to do so to fit your answer.
[Answer]
If it is caused by a bacteria, everywhere or nowhere would be the obvious choices for location. The bacteria could even be commensal where it doesn't help or hurt the creature. If the creature has hollow hair follicles for reasons(Doesn't matter really, hold over from arctic evolutionary phase, extra buoyancy, weight, biologically cheaper, etc...) then the bacteria could have evolved to fit inside the hair follicles, (free ride) and the rest is history.
One possible advantage to the creature in this is that the GITD bacteria fill the ecological niche and keep out other things. They live, fill space, photosynthesize and keep other things from growing, much like a good chunk of our gut bacteria serve to slow down C. diff.
There doesn't have to be an advantage though. It could just be something floating around that colonizes the young of the species and short of shaving they never really get rid of.
[Answer]
Bioluminescence in animals generally serves the purpose of sending some sort of message to other animals. These other animals could be members of other species and the messages serve purposes relating to predator and prey interactions or these messages could be intended for individuals of the same species and most often play a role in mating. Bioluminescence has evolved independently dozens of times for different purposes, but here are what I consider the two most likely uses:
**Aposematism** is the concept of using your conspicuous appearance to advertise that you are unwise to attack. If your animal is poisonous or otherwise dangerous to potential predators bioluminescence might play this role. Perhaps the bioluminescent bacteria themselves are unpalatable.
**Sexual selection** is responsible for the majority of visually striking animals in nature. In a process known as a Fisherian runaway preferred selection for a certain visual trait by potential mates leads to the evolution of displays that would otherwise be extremely maladaptive. The classic example of this is the tail of the peacock. Perhaps glowing doesn’t serve any real purpose besides making your animals attractive to the other sex.
[Answer]
Many bioluminescent creatures on Earth are semi- (or very-) transparent with the illuminating component inside the body where the chemistry is protected — where it can't be corrupted or washed off.
If you want something akin to "reality," consider making the fur semi-transparent and with the bioluminescent inside the fur for the same purpose.
It's somewhat unbelievable that a bioluminescent creature would glow noticeably in full daylight. But it is believable that the glow would create an under-color to the grayish, shimmer caused by the semi-transparent fur. Personally, I think this would not only look cool, but it would give the creature something a a chameleonesque camouflage during the day as the reflection of surrounding colors would combine with the creature.
At night the creature would look blurry due to the semi-transparent fur. Almost like a big wil-o-the-wisp.
Finally, it removes one aspect of the creature you might have been depending on: the fur, once shaved from the body of the creature, would stop glowing. This is because the hair is removed from the follicle (and the chemistry of the body). If you were counting on harvesting the glowing fur as an aspect of your book, this would be unfortunate. But it would make the creature very hard to prove exists since no glowing fur would ever make it back to the village.
**Conclusion**
IMO, you can believably have an all-body bioluminescent creature using the same mechanisms terrestrial bioluminescent use, just on a somewhat larger scale. Evolutionarily you'd have trouble justifying the creature, but do we care?
[Answer]
**It was genetically engineered to be that way.**
[](https://i.stack.imgur.com/tFrfJ.jpg)
<https://theweek.com/articles/464980/7-genetically-modified-animals-that-glow-dark>
Way back in 2000 an uniformly green glowing rabbit was made as an art project. Since then all kinds of other glowing animals have been made. They glow in various ways.
So too your animal. The linked animals themselves create glowing chemicals in their cells. But for yours, perhaps the symbiotic bacterial were engineered and the host then engineered to support them.
Why? Maybe an art project? An attractive pet? I have seen glow engineered fish for sale at PetSmart. Possibly to enable medical experiments?
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[Question]
[
Wild boars are well known for their large, bulky body, their aggressivity and their tusks.
They are animals from which a predator would gladly stay away if some easier prey is available. And, last but not least, they are omnivore.
How can a water dwelling creature (fish or water mammal) evolve to have the same features?
Clarification: the sea boar has to spend all of its life in water.
This is my contribution to the [Anatomically Correct](http://meta.worldbuilding.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798) series.
[Answer]
**Whales, nice hippos and mantees.**
* **Whales** and **hippopotamuses** are close relatives. Nice example of how life went from sea to land and then [back to sea](https://evolution.berkeley.edu/evolibrary/article/evograms_03). Hippos are agressive too and big, you may take some of it's extinct relatives or make one up, so it is more close to needed specs and looks.
* Make them more like relatives of elephants: **[manatees](https://en.wikipedia.org/wiki/Manatee)** or their ancestors **[sirenians](https://en.wikipedia.org/wiki/Sirenia)**, for more **herbivore specs**.
* Pigs are related to them too and could do the same: go back to sea! You just need to make up how boar and ancient whale or mantees mix would look like.
So 5-15 million years ago group of boar ancestors started to live in ancient mangrooves (brackish water) and adopted more aquatic lifestyle. Millions of years of evolution and now we have pig-like-whales or pig-like-mantees. They are aggressive omnivores and may have tusks.
---
**[Rodhocetus](https://en.wikipedia.org/wiki/Rodhocetus)**[](https://i.stack.imgur.com/uJlSA.jpg)
**[Dorudon](https://en.wikipedia.org/wiki/Dorudon)**
[](https://i.stack.imgur.com/4LFTe.png)
**Mantees and sirenians**
[](https://i.stack.imgur.com/RKjjl.png)
[Answer]
# Catfish, especially the [Channel Catfish](https://en.wikipedia.org/wiki/Channel_catfish) from the US
[](https://i.stack.imgur.com/liv86.jpg)
* **Large bulk body** - They are thick and weigh up to 50 lbs, which is pretty darn big for a freshwater fish. If Blue Catfish (~150 lbs and predatory) are the lions of the American freshwater environment, Channel Cat are the warthogs.
* **Aggressiveness** - They are a prized fighting fish (at least in [New Jersey](https://www.state.nj.us/dep/fgw/artchcat04.htm)):
>
> Its potential size (the current state record caught in Lake Hopatcong
> - 33 lbs. 3 oz.), propensity to hit a variety of natural baits and artificial lures, hard fighting ability, as well as its quality as
> table fare make this species very popular.
>
>
>
* **Tusks** - Catfish don't have tusks, but they have spines and stingers and are notoriously hard to hold for beginning anglers. Here is a [video of a guy](https://www.youtube.com/watch?v=NLdoSDgAJZ0) explaining how to not get stabbed by the spines. Smaller catfish, like the Bullhead have [poisonous spines](https://en.wikipedia.org/wiki/Brown_bullhead#Predation), to boot. If there were large predators, it would be reasonable that the larger catfish could be poisonous, too.
* **Omnivore** - Not all catfish are, but the [Channel Cat](https://americanexpedition.us/learn-about-wildlife/channel-catfish-facts-information-and-photos/) is.
>
> Channel catfish are omnivorous and feed mostly at night on snails,
> insects, crawfish, algae, and plants.
>
>
>
[Answer]
## [Southern elephant seal](https://en.wikipedia.org/wiki/Southern_elephant_seal)
* They are the largest extant marine mammal that is not a cetacean. Their bodies are massive and they use them to fight for territory and females.
* It's primarily the males that fight, but when they do, they do it right! They throw their massive bodies against each other and bite each others necks blody. The dominant males with the biggest harem has to stay in his territory constantly to defend it against competitors.
* Their diet consists primarily of meat, but they also consume algae.
>
> When at the subantarctic or Antarctic coasts, the seals can also consume molluscs, crustaceans, nothothens,[27] lanternfish,[27] krill, cephalopods[28] or even algae. ([source](https://en.wikipedia.org/wiki/Southern_elephant_seal#Feeding_and_diving))
>
>
>
* They have canine teeth rather than tusks, but it is conceivable that they could develop into tusks to aid in their fights during mating season.
* They currently do spend time on land to mate and give birth. Maybe they adapt to the global warming and rise of sea level by gradually spending less time on land and eventually giving birth in the water. That could make the fights of the males during mating season more boar-like because they cannot crush their opponent but have to charge them.
[Answer]
A few thoughts...
**Odobenocetops**
[](https://i.stack.imgur.com/JumCY.jpg)
*Odobenocetops* was a genus of Miocene Odontocete (toothed whale), related to dolphins, which was bulky in build, had tusks, and may well have been aggressive. They were carnivores (but certainly had their predators - they lived alongside such icons as Megalodon and Livyatan), but a couple million years of evolutionary modification could easily see them take on a more omnivorous diet, should one food supply drop.
Alternatively...
**Pelagic walruses**
[](https://i.stack.imgur.com/9CTmv.jpg)
Walruses have tusks, are bulky, and are aggressive. They are not, however, fully aquatic, or omnivores - however, both of those things can be changed. Walruses appeared in the middle Miocene epoch, about 15 million years ago, so that's about enough time for a transition from semi-aquatic to fully aquatic. Perhaps, individuals with better adaptations for swimming were selected for until this change occurred, and then the newfound greater range at sea allowed populations to migrate to warmer waters where there's at least some aquatic flora (seagrass plains, I'm thinking), and thus a transition to omnivory occurred.
Lastly, a third option.
**Actual suids**
[](https://i.stack.imgur.com/0p8Ny.jpg)
A population of pigs in the Bahamas, specifically on Pig Island, are world-famous for their swimming abilities. They're not native, and it's theorized that the island was meant as a food store for some crew of sailors and that they planned to eat the pigs. In any case, it's entirely possible that this could be the beginning of a new clade of marine mammals.
Perhaps have your sea boars be actual pigs (which are domesticated boars) which colonized the ocean - whales are an example of what aquatic artiodactyls would look like in reality, so you could go for a Cetacean-like body plan but have the boar-like features retained, or perhaps just evolved secondarily.
[Answer]
# This Sea-Boar is an Odontocete
Specifically, they could be a sort of digging whale, with an elongated upper jaw adapted to dig through sediment like a pig's nose. This would allow them to find burrowing animals and eat them. They could also supplement their diet with sea-grass, with the teeth of the lower jaw opposing a hard plate in the palate which acts like a cow's dental pad
This anatomy would leave plenty of teeth on the maxilla to adapt into tusks. From there, they could easily adapt to be a big, bulky fighter as the question asks for
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[Question]
[
I am trying to figure out the sex-determination of a *very* foreign form of reproduction.
A species has three sexes X, Y, and Z. X produces X gametes, Y produces Y gametes, Z produces Z gametes. They do not correspond to male or female, as any may impregnate or be impregnated. Only two parents of different sexes are needed to reproduce, because the only possible combinations of gamete fusion are X and Y, or X and Z, or Y and Z. The offspring may be any sex, including the one that neither of their parents are. Sex is determined genetically, not by environmental factors.
**How does the zygote determine whether to be X, Y or Z?**
(Based on this: <https://paperiapina.deviantart.com/gallery/31840163/Triaformica>)
[Answer]
Your 3 sex system lends itself perfectly to a **"scissors-rock-paper" system** of determining which sex is expressed using regular old dominance / recessiveness. Rock crushes scissors, scissors cuts paper, paper covers rock. So too as regards gene expression: X is dominant over Y, Y is dominant over Z and Z is dominant over X.
Thus XY = X sex. XZ = Z sex. YZ = Y sex. Because XX is nonviable in your system, parents of XY (X type) and XZ (Z type) could produce XZ, YZ, or XY offspring, the YZ offspring being Y sex and so unlike either parent.
The nonviable XX, YY and ZZ possibilities would mean 1 in 4 conceptions would end in miscarriage as is the case with humans when the 2 parents are heterozygotes for a recessive gene which is lethal as the homozygote.
[Answer]
These organisms should be diploid (2 sets of chromosomes like humans). Whenever 2 gametes approach each other to fuse there simply needs to be some element that prohibits the formation of a zygote if both gametes are of the same type.
This might be achieved if there were 3 different possible protein structures at one key point on each gamete. The properties of the proteins would have to be such that the x protein was attracted to a y or z protein but repelled by another x protein. The y protein was attracted to the x or z proteins but repelled by another y protein and the z protein was attracted to the x or y proteins but repelled by another z protein.
In this way x or y could fuse with z, y or z could fuse with x and x or z could fuse with y. But x could not fuse with x, y could not fuse with y and z could not fuse with z.
**Edit some more examples to clarify**
Proteins come in an almost infinite variety of configurations and shapes so imagine 6 proteins forming these shapes
1 Sphere
2 Cup
3 Cube
4 Square hole
5 Tetrahedron
6 Triangular indent
The X gamete has proteins 1 and 6
The Y gamete has proteins 2 and 3
The Z gamete has proteins 4 and 5
X-Y Sphere fits into cup, Y-Z cube fits into square hole, Z-X tetrahedron fits triangular indent no other combinations fit.
The system could easily be extended to four gametes by the addition of another six protein pairs. As an example
7 single prong
8 single prong indentation
9 double prong
10 double prong indentation
11 triple prong
12 triple prong indentation
Each protein would provide compatibility with one other gamete type so X is compatible with W,Y and Z etc
The X gamete has proteins 6, 7 and 10
The Y gamete has proteins 2, 8 and 11
The Z gamete has proteins 1, 4 and 9
The W gamete has proteins 3, 5 and 12
[Answer]
Here's another option:
There are three genes: The X gene, the Y gene, and the Z gene. And there are three sex chromosomes: The XY chromosome, the XZ chromosome and the YZ chromosome. Each sex chromosome has exactly the two genes found in its name. Just as with humans, each individual has two sex chromosomes, but the gametes have only one.
Now the following rules apply:
* Each individual must have all three of the genes.
* The one gene that appears twice determines the sex. For example, an individual that has an XY and an XZ chromosome is of sex X.
* Gametes of the same sex simply don't fuse, due to receptors on their gametes; that is, while 50% of same-sex fusions *would* give a working gene combination, this is irrelevant because the fusion simply doesn't take place.
So if e.g. an X (gene combination XY + XZ) and an Y (gene combination XY + YZ) get offspring, there are four possibilities:
1. XY + XY: The fertilized egg won't develop, as Z is missing. Since this happens before the egg even gets to the placenta, this will be indistinguishable from no fertilization happening in the first place.
2. XY + YZ: The child will have sex Y.
3. XZ + XY: The child will have sex X.
4. XZ + YZ: The child will have sex Z.
So independent of the sexes of the parents (as long as they are different), the children will have all three sexes with equal probability.
Note that while this has some similarity with Kyyshak's answer, it's not the same as it only needs standard chromosome pairs and does away with the dominant/recessive complexity by simply having the same-sex fertilization prevented by a different mechanism.
[Answer]
Some organisms use an XX, X0 mating system in which sex is determined by the presence or absence of a second sex chromosome. This system can be extended to provide a three sex system.
Suppose that (1) there are two sex chromosomes: X & Y; (2) non-disjunction regularly produces loss of one sex chromosome (as happens in, for example, *C. elegans*); and (3) the total absence of sex chromosomes (00) is non-viable.
Then we have five genotypes: XX, X0, YY, Y0 and XY. Let us further assume that XX and X0 produce the same phenotype, as do YY and Y0; whilst XY produces a co-dominant effect of a third phenotype. We than have three sexes: XX/X0 (X), YY/Y0 (Y), and XY (XY).
XX/X0 can produce X or 0 gametes, and mate with Y or XY. This can produce all three possibilities with genotypes XX, X0, Y0, or XY.
YY/Y0 can produce Y or 0 gametes, and mate with X or XY. This can produce all three possibilities with genotypes YY, Y0, X0, or XY.
XY can produce X, Y or 0 gametes, and mate with X or Y. This can produce all three possibilities with genotypes XX, X0, YY, Y0, or XY.
The probability of getting each of the sexes will vary with the exact genotype of the parents and the possibility of disjunction (producing a missing chromosome and thus an 0 from an X or Y) but all combinations can produce all three sexes.
[Answer]
Instead of assuming a Haploid/Diploid set, what if we instead had Diploid/Quadraploid? Thus an adult would have four gametes of three types (X, Y, Z) to make up the following sets:
XXyz = X Gender
xYYz = Y Gender
xyZZ = Z Gender
These quadraploid sets are actually a loop, with the last gamete also being connected to the first. They must be in alphabetical sequence to be viable, however a quadraploid of YZZX is the same as XYZZ, you've just started reading at a different point.
Each parent would contribute one of their dominant gametes (the one they have two of) in addition to one other. These Haploids are transferred as a unit and bonds with the Haploid from the other parent to create the full Quadraploid.
Using an XY mating pair, we thus get the following possibilities:
Xy + xY = XyxY (non-viable)
zX + xY = zXxY = XXyz (viable)
Xy + Yz = XyYz = xYYz (viable)
zX + Yz = zXYz = xyZZ (viable)
Thus the child will have equal chance of being any of the three genders, with a 1/4 chance of immediate miscarriage (likely undetectable at this early stage). In addition to requiring all three gametes, the dominant gametes must be different to maintain viability, thus eliminating all possibilities with a same-sex mating pair. Without this dominance requirement, a same-sex pair will have a 50% miscarriage chance, and will only be able to produce children of their own sex.
This is admittedly the biggest stretch in this answer, but as I have absolutely no biology knowledge, I'd find it very easy to Suspend Disbelief in this case.
[Answer]
If they reproduce sexually and their reproductive cells are haploids but they are isogamous (*Isogamy is a form of sexual reproduction that involves gametes of similar morphology (similar shape and size), differing in general only in allele expression in one or more mating-type regions.*)
Then:
x:XX
y:YY
z:XY
All combinations are valid.
[Answer]
In re-reading the question, and some of the answers, it does not exclude the possibility that all THREE sex gamete individuals are required in reproduction.
That is, two different gamete sexes, say X and Y, form the zygote, but it is embedded in the third host, Z, to develop to a viable fetus. It would seem that, by the criteria, any of the X, Y, or Z could be the host, and any two of the X, Y, or Z could be the two donors of genetic material, the only requirement is that the genetic material donors be of opposite gamete sex and the host be the third. Perhaps it is an immunity thing. A Z host will reject Z gametes through an immune process. However, it seems a Z host COULD carry a Z zygote. Thus, the offspring gamete sex would not normally be determined by the host, which did not donate any genetic gamete material, but it COULD be.
Interesting.
The act of copulation would be even more interesting.
[Answer]
Do your types have to be genetic? Lots of reptiles (the crocodilians and the turtles) determine the sex of their hatchlings by the temperature the eggs are incubated at: <https://en.wikipedia.org/wiki/Temperature-dependent_sex_determination>
Obviously, it's easier to manipulate temperature when the eggs are outside the body. But for internal gestation, give your aliens a womb which can tolerate bigger temperature fluctations (i.e. core body temperature fluctuation) than most mammals can tolerate. That way, the 'mating type' can be seasonal. In winter more X, in spring/autumn more Y, in summer more Z.
If their planet is like Earth, then in December northern hemisphere folks are birthing X babies and southern hemisphere folks are birthing Z babies. It gets more complicated in the tropics, where temperatures are more stable. But perhaps that might be a useful cultural difference - Country AAA in the tropics has a high proportion of Ys and has encourages Z and Xs to immigrate to their land. Or they make all the 'surplus' Ys join the army or the priesthood.
Alternatively female honey bees end up with a very different body form depending on whether they were fed royal jelly or not when they were bee larvae. So maybe the diet of the parent is important - and they may not even know it. If the parent prefers tea to coffee, they get more X and fewer Y and Z kids.
Genetics can be superimposed upon this to make things more complicated - so your W could still be a recessive, but only expressed if both genes (WW) and a low temperature/royal jelly are present. Perhaps the invention of central heating has doomed the Ws! :-)
[Answer]
To answer the title-question :They determine the sex by it's physical characteristics attributed to the given sex, like we do.
Regarding the genetic mechanism I would think that a combination of X and Y partners would only produce an X or Y offspring and not Z, given that neither carry Z.
Also having both organs necessary for impregnating and being impregnated might render pointless a partner.
[Answer]
As an alternative to my previous answer. The other option is the same way that yeast do it, although this requires a haploid organism or, at least, a haploid sex chromosome or for sex to be determined by an extra-chromosomal element such as mitochondria that is haploid.
In (some) yeast, mating type is determined by a switchable "cassette". All yeast carry the gene for both mating types (I'll call them + and -) but only one is in the active position. There are also flippases which during division, with low random probability, will "flip" out the current active cassette and replace it with the inactive one (and vice-versa), resulting in a change of mating type. There is no inherent reason that this process cannot have a third state resulting in three mating types (similar six way switches are known in some bacteria) or that the activity of these flippases cannot be upregulated to result in random assortment at every generation.
[Answer]
Here is my pick: The creatures are zwitters and the XYZ system is there to guarantee self-infertility.
The phenotype `x` has genotype YZ and produces only X gametes (small and big ones); the phenotype `y` has genotype XZ and produces only Y gametes; and the phenotype `z` has genotype XY and produces only Z gametes. This works, because "by default" the creatures can produce all three types of gametes, but by inheritance each type is self-suppressing.
Now the fun part of world building: How do the creatures find suitable mates?
There are several possibilities
* They are promisk (at least as long as they have found a fertile, i.e. not incompatible, mate)
* They can smell the phenotype of each other and select a mate according to smell
* The different phenotypes are different visually (having different skin colours, skin patterns, or coloured signal spots, or some body modifications, e.g., only `x`'s wear horns)
* They may differ in their voices and the tunes they sing in mating songs
EDIT: I wrote up the answer before looking at the quoted deviant art site. From the depiction of the three types it is clear that they are indeed hermaphrodites (zwitters) and that differ in their phenotypes quite significantly. The only thing that I find implausible is having equal gametes while there is a pregnancy period: This would include the risk of getting pregnant with an embryo that has not genetic relationship to the "mother".
[Answer]
This question is basically a riddle/logic trap
**"There are 3 sexes: X Y & Z"**
**"There are only 3 viable offspring combinations: XY, XZ, YZ"**
The fundamental question is: **how do you determine the sex of those pairings?**
Even though the OP has invalidated my first answer by completely redesigning this question, **the question is still mechanically flawed and or a fabricated riddle/logic problem:**
In human reproduction gender in genetics is represented as: XX (female) and XY (male). With the male being able to contribute either an X or Y chromosome ultimately determining the offspring's gender. The problem with this scenario is it's starting off with 3 genders ambiguously defined as X Y and Z with the potentially misleading implication that the starting parents are XX YY and ZZ which by the OP's own rules is impossible as the only offspring combinations are XY XZ and YZ. The parents would have to have the same genetic logic as their children.
**This means that the 3 sexes aren't really X, Y & Z but are really XY, YZ, and ZX.** Such that: a XY parent and a XY parent can only have XY children or technically none by the OP's desire, a XY parent and a XZ parent can have all 3, XY and YZ parents can have all 3.
**So just like in human reproduction the X chromosome doesn't alone mean female or male, its the combination of both chromosomes that ultimately determine gender.**
---
**If however that is unsatisfactory;**
If X Y Z individually denote gender and there can only by hybrid representation of these combinations then that would mean gender must ultimately be determined by another method. Here are a few options:
1) another regulatory gene handles the determination acting as a proverbial coin flip between the two possible options making one chromosome's representation more pronounced. This isn't unheard of in genetics, it generally doesn't happen on this level or with gender but why not.
2) Pseudo environmental- RNA inherited by the hosting mother parent makes the determination. Would be an odd occurrence but also not impossible.
**NOTE:** A sex is nothing more than an organisms distinct template discrepancies between members, broadly covering physical and behavioral traits. This does not constrain itself exclusively to genetics with humans concocting "3rd genders". Even genetically there are cases where offspring aren't either XX or XY but are XXX. So in relation to this argument, definition of the pronunciation of a "sex/gender" is fairly subjective.
[Answer]
You are starting with a false assumption. You state that sex is determined genetically. It is not, not even in humans. The default sex in humans is female. To get a male, the default structures have to be modified and transformed. A long process of links and dependencies have to occur before the fetus becomes completely male. In the absence of any of these steps, the process reverts back to the default female.
Human sexuality is determined hormonaly, after the zygote starts developing. What is determined genetically is what hormones will be produced in utero in the first few hours, but these are not absolute. The default sex of humans is female. If after those first few hours, the process of masculinizing is not started, you get a female. Any interruptions in the process, you get feminization. There are many other factors besides the and Y chromosome that come into play. The sex of humans can theoretically entirely be determined in the complete absence of the X and Y chromosome. In fact' many researchers posit that the Y chromosome in humans may eventually completely disappear. It is pretty useless. It will be replaced by a standardized fully functional X chromosome. There are mammalian species in which this has happened. The sex of the offspring is determined by other genetic factors besides the Y chromosome.
In order for a genetic system to work, there needs to be a default setting. Nature seems to prefer the offspring-producing 'egg' sex as the default. That makes sense as a fail-safe mechanism. If all else fails, what is left will still be able to produce offspring. Genetic donor sexes are really not needed. They just provide extra genetic material for the sake of diversity. And genetic material can be provided by means other than sperm.
However many 'sexes' you have, somehow there has to be a process for one form to carry the offspring. Unless, of course, the 'egg' is simply deposited and abandoned, in the hopes that it is fertilized. The 'sex act' would not be between two members of the species, but would be something done over the egg. In which case, any gender can deposit the egg, and any gender can add genetic material to fertilize it. Gender becomes something other than sexual determination.
But if you stick to an exclusively gamete-determined sexual identification, you need to determine which gamete produces the genetic contributor, which gamete produces the offspring carrier, and, well, what IS the third one? Nature has a habit of making the third one 'neutral' (that is, incapable of egg OR sperm production).
So however you decide to do it, you will not end up with three 'reproducing sexual genders', you will end up with three different'functional genders' at a minimum, and maybe up to 6 combinations of X, Y, and Z. (Even more, if you specify that THREE gametes have to be donated. That is, viable offspring need a gamete from each of three different donors. So you need, for instance, XXY or XZY or ZZZ. This gives a possible 10 unique combinations. But now you have to decide which combinations are genetic donors, and which combinations are offspring carriers. There is perhaps no neutral, if it takes three gametes to produce a viable offspring). That is, it might result in functional genders of perhaps worker, leader, builder, reproducer and so forth. (Workers, for instance, might have more hands, leaders might have a bigger brain, and builders might have more legs). The only feasible purpose of having three form identifier gametes is to produce a different species functional forms for a different function.
Nature seems to prefer that, in such cases, one or more forms are infertile and incapable of reproducing. So your third 'gender' would probably be 'neutral'. You can definitely see the complications of this being left up to genetics, and not environmental, conditions. Species reproduction is now invested in only one of three identifications. If left only to the probability of mating, either that third is very prolific, or species numbers would decline.
So your answer is that you really need to re-think what your objective is in having three gametes.
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**Closed**. This question needs to be more [focused](/help/closed-questions). It is not currently accepting answers.
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Imagine a website where people can post questions, and receive just answers (no chit-chat). Anybody could ask a question, anybody could answer. Some questions would be fanciful, others relevant to current affairs, imaginary, or even scientific. Anything you can imagine could be asked. There would be little to no moderation.
Imagine the website then being used to "harvest" the answers by anyone who had access to the information published - and the people who participated with the best answers. Targeted individuals would then be privately contacted, or watched as the need may be, or even 'cultivated' into specific directions. Some could even be recruited to implement even better or related ideas.
Targeting inquisitive and bright minds would be tempting to corporations and businesses alike who learned of this website, perhaps government and technology industries or finance, or biology and science. Volunteering 'expertise' could even be perceived as dangerous for some, or as an opportunity by others.
So the question is, would this website be benign and beneficial or would it be something else?
[Answer]
Ideas are over valued, I have often heard from the specialists in the innovation industry. Often the ideas are something like: "Let's use machine learning to solve problem X." Machine learning is simply statistics optimized to data to find out most probable answer. There is a lot of math behind and the actual work. Think about Linus (Tornwalds) and his Linux. No-one would even know about it, if it weren't free. The true innovation was not the product, but how it was delivered. You can still argue whether it was worth the effort for Linus to do Linux. If the Linus had not coded Linux, no-one would care about him and his ideas.
Of course there is some value in ideas, but it is often the person that has the insight is the value. There is some abstract things about implementation behind the idea, that are seldom communicated.
I think that it depends whether it is benign and beneficial. Creating lots of good ideas only says that you have potential, while having bad ideas says that you have no idea what you are doing.
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The website is just a collection of ideas - either realistic or theoretical or fantastical one.
It's how you use the info that defines you. Don't forget, a knife is neither good or bad, it's just a tool. You can use it to slice bread or kill someone.
So, you ask a fantasy question about aliens wanting to spread a virus to the atmosphere to kill us all, and I provide a good answer on how to prevent this, or how to best accomplish this using a fantastic (non-existent) spread mechanism.
General Havok reads this and finds it to be a good option to weaponize (either offensively or defensibly).
James, the farmer, reads this and considers it a good approach to help him spread vaccines to his diseased crops.
Dr Evil finds this to be a good solution to spread his deadly virus.
An artist finds it to be a good approach, adding colors to the spreading mechanism and creating images out of colored clouds.
The possibilities are endless.
[Answer]
Someone could set up a website to harvest questions and answers. General information can be broken down into categories and would be beneficial, as the Stack Exchange network proves.
Several institutions already do something like this, including MI5, the UK security agency. They set an annual quiz that they publish and invite people to solve. If you can solve it, they offer you a job interview!
To use this for evil, you would run up against the problem of implementation. Ideas are a starting point, but you need to be able to implement them. Even having a prototype is not an answer. Prototypes usually start out working on a small scale, but might not scale-up.
Overall, the Internet provides a place to do this, where lots of people can benefit.
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The answer is Yes. Agencies, governments, next Bond villain can and probably are watching this board. And many others.
The proof is very simply: in World of Warcraft there was this "[disease](https://en.wikipedia.org/wiki/Corrupted_Blood_incident)" spread by animals. Epidemiologists used this opportunity to study how people act, how the "virus" is spread.
In the same time FBI put on "potential danger" people who well knew they are infected but spread the sickness, violated quarantine rules or used macros or hacks to further weaken the players and community for they own gain or just "for the LuLz".
What we are doing here is basically the same "The Pretender" was doing in the tv series.
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Humans got a one time ticket to the other side of the galaxy, traveling $2r$ in just a few days (where $r$ is the distance from earth to [the super massive black hole](https://en.wikipedia.org/wiki/Sagittarius_A*): 28,000 lightyears)
The stars we see are roughly 56,000 years old; now, that's not really that old compared to the grand scheme of things.
How plausible would it be for us to predict what stars would be there (considered the stars orbital period is roughly 225 million years, so that would give the stars movement a 0.08 degree movement.) Also predicting the age of the stars in terms of what star would be gone, and what new stars would have been born.
And could we, before we launch, make a map that would be usable from the other side of the galaxy?
**Answers and comments:**
The means of travel is of no interest to this question, the question is, can we as humans with the technology we have today and the knowledge about stars and with the predictions we can do (about star nebulae and star lifespan) make a usable map (You don't need to have EVERY star to make a map just a few "big enough" to be distinct - or am i wrong?)
Lets assume for all purposes whom ever gave us the means of travel will us nothing bad. (eg. place us inside a star), and lets also assume that it has been a one way communication, so no asking questions.
[Answer]
Quoting Wikipedia for a moment, we notice that
>
> The Milky Way contains between 200 and 400 billion stars (...). The exact figure depends on the number of very-low-mass stars, which are hard to detect, especially at distances of more than 300 ly (90 pc) from the Sun.
>
>
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So we're having trouble detecting "very-low-mass stars" (which might be as much as half of them) if they're more than 300 lightyears away - and the milky way's diameter (the distance we want to travel) is...
>
> usually considered to be about 100,000–120,000 light-years but may be 150,000–180,000 light-years
>
>
>
So, for at least 99.8% of the distance we won't be able to know whether there's a "low-mass star" (which is still, you know, a STAR. So "low-mass" is pretty relative) in the way. Pretty risky - though we might still want to take that risk, most of space is fairly empty after all and that kind of Opportunity won't come again very soon.
The other issue is predicting where the stars will be - it might be possible for us to compute the position of all KNOWN stars... but since we might be missing as much as half of them, the uncertainity there will be rather high.
"what stars would be gone, what new stars" - new stars would be hard to predict, but we can make some educated guesses at how long a star of a certain class has to live, and how old it was when the light reaching us right now was sent out. So that at least should be doable.
As I said, we should still definitely take the opportunity - but it'll be more like "setting out into (mostly) uncharted waters" than "this cluster of stars looks promising, set a course" ;)
/edit: My numbers are a bit off since they assume a trip through the entire diameter rather than just 2x the distance from the center, sorry about that. The general points stand though :)
[Answer]
We don't know a whole lot about the far side of the galaxy. We assume it's generally similar to the parts we can see, but we have little in the way of observations of it. The galactic bulge, with its messes of stars, clouds of gas and dust, and so on, blocks our view quite thoroughly.
So we can't specify where we want to go, because we don't know. Would the nice aliens care to trade our tickets for the long-distance flight in for a few shorter journeys? They'd be much more useful.
[Answer]
# For the parts we can see
**We think we could**. Astronomers and astrophysicists are pretty sure that star evolution is pretty well known and we can predict what will happen in billions of years. Just google for "what will happen to the sun" and you'll see. Given that, 56 thousands years seems trivial.
**On the other hand**, we amassed only few hundreds years of observations of scientific value, and few thousands indirect archeological tips. All that from only one point of view - Earth. So no one could actually see anything we think we know happening.
If such journey would be possible, astronomers and physicist from all over the world would insist that it's main concern would be to **verify**. And no one would be surprised, if map was pretty accurate. Every little inaccuracy would be treated like finding of great scientific value.
# For the parts we cannot see
No base for predictions.
[Answer]
As your question asks about what "stars" would be there the answer is that we could give you a rough estimate of the composition of the stars and their densities on average as well as a rough idea of the super structure of their galactic positioning (because it should be roughly the same as what we see on this side of the galaxy so we can estimate that there will be x% of stars we see with the y type of stars of z number of stars and towards some given region that will likely be more or less densely packed), but we would not be able to say there will be star x at coordinate y or a cluster here or there, because how could we? We're blocked from seeing stars easily within our galaxy after a certain distance towards the center of our galaxy via conventional methods of viewing stars...
However, given say 50 to 100 years we may have ways to get past these problems to see where and how dense stars are as far out as we can, using Gravitational(? this may be a wrong but close to correct term) waves which we can then use to create mathematical models of the galaxy which should be fairly accurate, and should be able to even predict a rough classing of those stars based on the mass of a star being correlated to it's class.
So presently the images that a4android is about the best you'd get for a prediction, but move up 50 to 100 years (maybe even sooner) and we might be able to predict and have models that are very highly accurate.
[Answer]
Astronomers seem to have already done a reasonable amount of mapping of the [galaxy](http://galaxymap.org/drupal/node/171). See [here](http://www.skyandtelescope.com/astronomy-news/mapping-the-milky-way/), [here](http://www.scientificamerican.com/article/a-stellar-discovery-on-the-milky-way-s-far-side/) and [here](https://in-the-sky.org/ngc3d.php). Admittedly locations on the far side will have moved. On average everything will have shifted 37.333 light years over the 56,000 year time difference between our observations and what is on the far side now. That's enough to make easy ball park corrections.
If humans did have a one-way ticket to the far side of the galaxy, *provided there was sufficient time before their departure*, it is very promising that good approximate maps could be made. This would probably be achieved by conducting extensive surveys, compiling existing information about the galaxy, and integrating this into useful galactic maps. Remember the use of maps would be supplemented by interstellar navigation.
Also, if it becomes too difficult we might be able to ask those who issued the one-way ticket to help us find our way around (assuming they're familiar with the galaxy's far side).
[Answer]
Ok, you want to travel the distance of 56,000 light years in a few days.
As you put the "reality check" tag on your question, I am going to say this now: this is not possible.
If you traveled at the speed of light itself (which AFAIK is impossible for anything with mass) it would take you 56,000 years to reach your destination (or 20,440,000 days). And you are proposing to travel there in a few days (lets say 5 days for arguments sake).
So you are proposing to travel at over 4 million times the speed of light.
Even if you had the most accurate maps of the galaxy ever produced, traveling at that speed would destroy you, your ship, the planet Earth and anything in the nearby vicinity. Possibly even the galaxy itself.
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However if you wanted to utilize some form of "Faster Than Light" (FTL) travel, then navigation becomes a different beast altogether. All methods of FTL travel are theoretical at best, but most of them involve jumping across space.
In this case navigating your way to a point 56,000 light years away is relatively easy. You find a point (or series of points) that is empty and then jump/warp/appear there.
All depends on the method of FTL travel you are employing.
EDIT:
You said that `Humans got a one time ticket to the other side of the galaxy`, which makes me think that this is something that affects the entire human race, and not one individual.
Who produced this ticket? And assuming the ticket is a metaphor, how did we encounter this opportunity to travel to the other side of the galaxy?
I can think of two possibilities. The first is that a more advanced race is giving us this opportunity and the second is a freak phenomena, similar to a wormhole or stargate appears within a reachable distance.
In either case the position of stars on the other side of the galaxy and whether we need to navigate around them is irrelevant.
In the first possibility it will be the advanced race that does the navigating for us, and undoubtedly they will have accurate maps of the other side of the galaxy. So we don't need the maps.
In the second possibility, we will get spat out randomly on the other side of the galaxy. Due to the interference caused by the super massive black hole in the center of the galaxy we have no way of finding out the position of stars on the other side. So the wormhole could put us within the close vicinity of a star, but more likely it will put us somewhere safe.
I think you need to provide us with more information on how you are getting to the other side of the galaxy in such a short time. This will then determine how navigation can be made and whether we can make maps of the other side of the galaxy.
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The [Unicorn](https://en.wikipedia.org/wiki/Unicorn) is a iconic symbol of fantasy, appearing in both mythology and modern novels. It is simply a horse with a single, spiral horn erecting from atop its head. How could a creature like this realistically evolve? How close to the stereotypical unicorn can I get using realistic anatomy?
A list of all of the Anatomically Correct questions can be found here
[Anatomically Correct Series](http://meta.worldbuilding.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798)
[Answer]
[This creature might have actually evolved, if its predecessor had not gone extinct already.](https://www.theguardian.com/science/2016/mar/29/siberian-unicorn-extinct-humans-fossil-kazakhstan)
Enter the Siberian Unicorn, which unfortunately looked a bit more like a mammoth with a horn than a horse.
[](https://i.stack.imgur.com/teH8d.jpg)
It's not unrealistic at all that this creature might've evolved into a (near) identical representation of our mythical unicorns. The biggest reason why we don't have Unicorns now is because the horn wasn't useful for horses when the horses were evolving. Had the horns been useful, for mating or whatnot, or even through careful breeding of the mutation by humans, we could easily have a unicorn on our hands today.
[Answer]
I wish we could have a new version of this question made, not just because this question is old, but because I think you can *absolutely* have a unicorn.
But it's not a horse
[](https://i.stack.imgur.com/ceOVA.png)
These things show up in several medieval bestiaries. At one point it was included in the Scottish coat of arms. but look at these depictions. Often depicted with a billy goat style beard and cloven (split) hooves.
[](https://i.stack.imgur.com/NFMhI.png)
Now why was it included in the Scottish coat of arms? Because it was said to be one of the only animals to be able to kill a lion. And lions happen to be the national animal of England. Nice little rivalry there. But that is odd, lions live so far away. They live in Africa!
Now, what lives in Africa where lions live, and potentially has horns and cloven hooves, and might even sport a billy goat style beard?
Antelopes!
[](https://i.stack.imgur.com/CB414.jpg)
Now, is it possible that there was ever a species that had horns that grew so closely together that they fused into one horn? Or if not a whole species, a disorder that might cause it to happen in certain individual antelopes? I think, ABSOLUTELY!
Could this animal through repeated depictions be later confused for a horned horse? Again, quite possible.
And I would be remiss if I didn't point out that there are said to be a few medieval accounts of people actually hunting for them, meaning they *may* have been real animals hunted to extinction at some point in the past. But I can't seem to find the article that actually listed those sources, so take that with a grain of salt. In absence of any actual historical sources to show you, I might just say that the *possibility* of it being real is there, and biologically speaking, there's no reason they couldn't have existed.
So, could they exist? Yes. But did they really ever exist? Well, that's a mystery we may never know for sure.
[Answer]
The simple answer is no, at least by what we imagine the unicorn as, which is a horse with a horn on it's head. First off, a horn is a very big nutritional sink. By that I mean the unicorn would have to find a way to take in enough calcium support the making of the horn. The unicorn's horse-like body with it's one stomach would not be able to gain enough calcium, making the unicorn have Osteoporosis, which would then make the unicorn too weak to function. Now if it was more of a cow or deer body, it would still have a bit osteoporosis but the unicorn would at least have multiple stomachs to get as much nutrients from it's food as it can. Watch this video to see what I mean. [Unicorn Design Flaws](https://youtu.be/6SHQoFgZYYI)
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I am wondering if alien race detecting our signal could actually understand such broadcast. But for my story, **I need the aliens being unable to understand what we are broadcasting.**
How can I achieve that?
Background about the aliens:
* They are sapient species and able of space flight
* They can use radio and are actively searching for life in the universe
* They have computers and overall, their technology level is higher than ours
* Later in the story they should make a voyage towards Earth, so it gives you even more detailed idea how intelligent and technology advanced they need to be
Background about signals from Earth:
* Our usual broadcasts: TV, Radio, maybe some satellite communication
Constraints:
* The aliens need to understand that such signal is not "noise" from background universe
* They also need to get the signal for long enough time to know where it is coming from. In other words:
* The aliens need to pinpoint at least our solar system as a source of such signal.
Yet, I need them to be unable to understand what is content of such signal. Am I able to make such constraints? How?
[Answer]
Like AndreiROM points out, recognizing that there *is* a signal, and understanding the *contents* of the signal, are two completely different things.
In fact, it's not even a given that the aliens would recognize some of our transmissions as deliberate transmissions. For an example of this, consider [ultra-wideband](https://en.wikipedia.org/wiki/Ultra-wideband) signalling: very little power, over a huge swath of radio spectrum, with the possibility even of each portion of the signal being below the ambient noise level! I believe some military radio systems work similarly as well, to make eavesdropping on and triangulating the transmitter more difficult. Without the code sequence, it's perfectly possible that you can't even tell there's a transmitter *there* at all, *let alone* figure out what is being transmitted.
Our modern communication systems use *incredibly* complex modulation schemes, in part to get us closer to the theoretical Holy Grail of the [Shannon-Hartley theorem](https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem). Even if the goals are the same, the odds that an alien civilization would arrive at *exactly the same* modulation schemes by chance appear sufficiently slim as to be nonexistent, and that's before we even consider the nature of the modulating signal (whatever is fed to the modulator stage, perhaps from a microphone or similar device; in technical parlace, the [baseband](https://en.wikipedia.org/wiki/Baseband) signal).
Hang on to your antennas, ladies gentlemen and xenomorphs, because over the next several paragraphs, I'll be taking you for a quick tour of the history of how radio has developed on Earth over the past 150 or so orbits of the third planet of the Solar System around its central star.
Radio started out simple, with trivial on/off keying (useful on its own for Morse code, but really not for a whole lot else), and then fairly quickly grew with [amplitude modulation](https://en.wikipedia.org/wiki/Amplitude_modulation) which (when viewed in the frequency domain) is a single higher-powered signal at a fixed frequency and two lower-powered signals corresponding to the modulating signal. (What enabled AM was figuring out how to generate a [continuous waveform](https://en.wikipedia.org/wiki/Continuous_wave); in the early days of radio, even that was a non-trivial achievement, and besides being a cornerstore for basically every modern radio and wired communications technology, its heritage lives on in how [radio amateurs today often refer to Morse code as "CW"](https://ham.stackexchange.com/tags/cw).) Those two are relatively easy to demodulate (if not necessarily to understand, but by then you are getting into areas like linguistics or transmission systems design), but we pretty much abandoned them a long time ago because they don't fit our current needs very well and we figured out how to do "better". In this context, "better" can mean things like "easier to understand for a layperson with an appropriate receiver", "higher data rate", "greater resilience to transmission errors" or "greater fidelity", with many combining elements of these; compare a noisy, cracking shortwave AM reception to the crystal-clear audio of a FM transmission with an appropriate [link budget](https://ham.stackexchange.com/q/352/29).
Some time after AM, we figured out how to do [frequency modulation](https://en.wikipedia.org/wiki/Frequency_modulation), which is basically just a single slab of RF power being shuffled around the radio spectrum. By that point, you can have two radios fully capable of FM on the same frequency and *yet* not able to communicate! (The transmitter and receiver need to agree on two signal parameters -- deviation and modulating bandwidth -- as these two directly affect the transmitted signal spectrum.)
And then there's [phase modulation](https://en.wikipedia.org/wiki/Phase_modulation), which can easily be every bit as complex as FM to decode, but also completely different. It's like FM in that it's generally constant power, but instead of changing the frequency, phase modulation is based on the idea of changing the *phase* of the signal to transmit data.
Not to mention that these days, *we don't use these in isolation!* No, we have invented beasts like [quadrature amplitude modulation](https://en.wikipedia.org/wiki/Quadrature_amplitude_modulation) (which gives you two different AM signals on a single carrier, each of which can be modulated with either digital or analog data).
Transmission modes can also themselves be layered, like [Matryoshka dolls](https://en.wikipedia.org/wiki/Matryoshka_doll). For example, you can have a FM signal being modulated by a phase modulated or perhaps more commonly an [audio frequency shift keyed (AFSK)](https://en.wikipedia.org/wiki/Frequency-shift_keying#Audio_FSK) signal which in turn represents some useful information.
And of course, the signal used to modulate the transmitter is generally not used directly. Many modern systems are digital, which by design places a modulation step between the useful (for example audio, video or data) signal and the radio transmitter. For example, DECT (which is commonly used for wireless phones; however, not cellular phones) uses [adaptive differential pulse-coded modulation](https://en.wikipedia.org/wiki/Adaptive_differential_pulse-code_modulation) to create the signal that is used to modulate the radio transmitter, and GSM (second generation mobile telephony) [uses what is known as code excited linear prediction coding](https://en.wikipedia.org/wiki/Speech_coding#Modern_speech_compression). Just the *names* of these should give you pause, and newer standards are even more complex. Add to this the fact that some radio systems are *encrypted* in (more or less successful) attempts to prevent eavesdropping. Compare this to good old AM, where the transmitter does little more than shift the baseband signal from the microphone into the radio frequency range!
Adding to the above, radio systems often use relatively directional antennas (at least in one plane, and for radio links, directionality in two planes is very often a desired property), so unless your aliens happen to be in the signal path, they might not know that there is a transmitter there at all.
With all of what goes on between you saying "hello" into the cellphone, and the signal reaching even the cellular network base station closest to you, let alone the remote handset, **it would be [more magic](http://www.catb.org/jargon/html/magic-story.html) if aliens were able to figure out anything more than that *someone just made a radio transmission*.** Which they would know because the transmitter transmitted several short bursts of radio signals, *if and only if* they happened to be listening to the right frequency.
In fact, that aliens would understand our signals is unlikely enough that [TV Tropes has a whole article on plug-and-play technology](http://tvtropes.org/pmwiki/pmwiki.php/Main/PlugNPlayTechnology) (quote behind spoiler tag because, well, *TV Tropes*):
>
> /.../ Without an agreement for everyone to follow fixed technical standards, computers would not be able to tell their precious 0's and 1's apart from each other in the datastream — compatibility is the exception, not the default. You can't open or shut your closet door by plugging a computer into it, or pick up FM stations on an AM radio. US-made TVs aren't built for the higher voltage levels of European electrical outlets (or the PAL broadcast encoding); you can't play Nintendo GameCube discs on your PS3, you can't run Mac OS executables on the Windows operating system, and the World Wide Web simply would not exist (at least not as we know it) without everyone communicating according to the HTTP technical standard. /.../
>
>
>
[Answer]
This is actually incredibly simple.
Our signals will and do differ significantly from the background noises of the universe - they have patterns. This is in fact the method that SETI is trying to use to differentiate between random "noise" and potential alien transmissions.
And we are constantly broadcasting these signals, so they can certainly use them to hone in on our solar system if they can "hear" us to begin with.
However knowing that the signals are non-random and interpreting them is something completely different. Even our technology needs to know how to interpret a certain signal before it can feed it to a user in a format we might understand.
Aliens would probably be completely lost until presented with a sample of our technology so that they might begin to understand what we are sending them. For example, on their world they may not use our style of visual communications (video signals) because their vision is in a completely different spectrum (IR for example). So they could be interpreting that video signal 100 thousand different ways, and it would still be gibberish to them.
Even if they managed to decipher an audio or video signal they would still need a Rosetta stone which would allow them to actually understand that message.
In person we could point to an object, repeat our word for it, and come to an understanding. However this interaction would be one sided, and they would probably have no idea what's going on until they made contact with us.
[Answer]
Actually, just don't bother worrying at all.
It is so hard to understand an alien signal that we, in fact, spent a *ton* of effort trying to make the Voyager probe plates readable by other species. Even after that effort, they find in a whiteroom test, even another group of engineers/scientists couldn't decypher the plates... and those were humans!
Decyphering signals is hard!
[Answer]
In Orson Scott Card's *Ender's Game*, the Formics never invented the concept of spoken or written communication. They were telepathic, and so it never occurred to them to use anything else to communicate, or to listen for other people communicating via radio. Presumably they did use the "radio" portions of the EM spectrum for astronomy just as we do, but they didn't have radios as we would call them.
[Answer]
First off, the aliens [aren't that far away](http://zidbits.com/2011/07/how-far-have-radio-signals-traveled-from-earth/), relatively speaking.
[](https://i.stack.imgur.com/gRy9y.jpg)
Most of our signals are pretty weak, especially compared to the radio output from our sun, and you'd have to be pretty close and listening very hard to hear them.
Your best bet is an event that actually happened in 1974, where an intentional, very strong broadcast was sent from the Arecibo observatory, and consisted of 1,679 binary digits and lasted three minutes.
If that signal somehow caught someone's attention, then the alien race is within 42 light years of Earth. That might be close enough to possibly pick up some of the strongest radio signals once you know where to look. As AndrieROM pointed out, once you have the signal, differences in biology and culture are going to have a big impact on being able to tell what the message actually says, making it much harder. Which does work out well for you.
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While there have been [numerous arguments](http://www.projectrho.com/public_html/rocket/spacewardetect.php#id--Strategic_Combat_Sensors--There_Ain%27t_No_Stealth_In_Space) about ways of actually pulling off stealth in space, what I'm interested in is the scenario in which you can't conceal your presence in the conventional sense of hiding emissions. If that is the case, what are some ways of concealment that could still be viable?
To be clear, while there are reasonable approaches given in places like [ToughSF](http://toughsf.blogspot.com/search?q=stealth), I'm interesting in just outright working within the limitations of the pessimistic scenario.
EDIT: It is fascinating that I just proved Nicoll's Law again "It is a truth universally acknowledged that any thread that begins by pointing out why stealth in space is impossible will rapidly turn into a thread focusing on schemes whereby stealth in space might be achieved."
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#### 1. Appear to be other than what you are.
You can hide in plain sight if the things looking for you do not recognize you when they see you. Use a disguise. Appear to be something that is expected or irrelevant. What that thing is will depend on what things besides yourself might occur in that space.
#### 2. Channel emissions away from potential viewers.
It is probably impossible to conceal all radiant emissions in space. It is possible though to emit only in the directions you choose. If you have an idea about where the things seeking you might be, you can emit emissions away from there and present them with an unemitting surface, cooled by rerouting emissions to the other side.
In a (relatively) crowded space of a solar system, seekers might note your emissions reflecting off of dust behind you, or an absence of solar wind in your shadow. Seekers would need to widen their scope of what they are looking for to perceive that shimmering dust could mean a hiding ship; this would be fine material for a story.
#### 3. Blind your seeker.
From this related question: [Is it possible to blind a spaceship/space warship?](https://worldbuilding.stackexchange.com/questions/184645/is-it-possible-to-blind-a-spaceship-space-warship/184647#184647)
If you can produce circumstances which blind your seeker, you will not be seen. If the seeker knows you have produced those circumstances they will be on alert even though blinded. If you can blind the seeker in a way that they attribute their blindness to something other than you (other actors, mechanical failure, natural phenomena) they may not be on alert.
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* Vary your trajectory randomly
The enemy knows in general where you are, but he doesn't know where you're *going* to be. He is millions of km away. By the time his attack gets near enough to harm you, you've changed course to be well out of the blast zone. [Aircraft did this in WW2](https://www.youtube.com/watch?v=ywzk73ahf00) to avoid flak.
* Send out bright decoys
The enemy knows in general where you are, but not which of those bright dots is you. That could be enough to foil a few of his attacks.
* At a crucial moment, pump liquid hydrogen to the surface of the hull and shut your motor off.
This will only work until the liquid hydrogen boils off, but it should mask your heat signature for a short time. Combine it with a course change so that your enemy doesn't know where you went.
The disguised course change may be more effective if you do it at the same time as you launch decoys.
* Don't use your motor in the first place
Just enter the system in a passive ballistic orbit so the ship is cold and dark. The enemy doesn't need to see you until you shoot your weapons. Of course, there will be a defender's advantage since he can already have many ships in passive orbits in his solar system.
* When your motor is off and you're cold, use mirrors for camouflage against sunlight
Now that your motor is off and you're no longer a bright spark, you look just like any small asteroid. But your enemy may be able to spot asteroids by the reflected sunlight. Use an angled mirror to direct reflected sunlight away from the enemy.
* Ride on the far side of a comet into the system
Unless the enemy is in the habit of blasting every comet he sees, the ice of the comet and the gas/dust cloud surrounding the comet will help hide you.
* Have an implausibly energy-efficient motor
The law of "no stealth in space" is a result of your motor's waste heat radiating in all directions. If your motor was 100% efficient there would be no waste heat and you could not be spotted by your waste heat, even if you're running a terawatt power plant.
* Pass behind a planet, then while behind the planet perform a random, intense course change, then shut your motor off/use the liquid hydrogen and mirrors
If you only perform course changes while hidden behind large objects, and are in cold, ballistic coasting mode at other times, the enemy is going to have a hard time locating you.
[Answer]
# BE LOUD
MAKE SOME NOISE, IN STYLE! THEIR SENSORS CANNOT DETECT IF YOU THEY ARE OVERWHELMED!
ARE THEY SCANNING THE SKY THROUGH INFRARED? LASER-PAINT THEIR TELESCOPES! RADIO? JAM ALL CHANNELS! VISIBLE LIGHT? X-RAYS? USE ENOUGH TO STERILIZE THEIR PUNY PLANET AAAAAAAAAAAAAAAA
**or use a decoy**
Find a loud guy that likes the sensorial overwhelm strategy and send him a bit ahead of yourself. No one will notice **you** for a while.
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If your story allows faster-than-light travel, or hyperspace travel:
FAST--if your ship is faster than what ever medium your enemy is using to track you, they can't track you. Radar wave travels in light speed, then if your ship is faster than light, the radar wave can never get to you. No radar wave reflecting back to the enemy's receiver means there won't be a blip on the enemy's scanner.
DIVE, DIVE--use the hyperspace itself to hide, like a submarine. If you can't hide in this universe, hide in somewhere else. Just like UX-01 in Space Battleship Yamato, they hide in the fault line between dimensions, so their emission dont travel into the dimension their enemy is in.
If your enemy needs to obey some sort of cosmos Geneva Convention and you don't. Consider hiding behind, below, or inside a civilian vessel. If the enemy is not careful, they would just assume this is a normal civilian transport. But if they do detect you, let's see whether Captain Goodguy would rather blow up a ship full of innocent civilian to destroy your ship than having your evil organization accomplishing your objective.
Similar trick can be used even if you are the good guy. The enemy might be detecting you, but they don't know who you are. Disguise your ship to be something else--for example, a space freighter, or a passenger vessel. Deliberately use unscrambled radio to create the illusion that you are just a civilian passing by. As long as you discard your disguise and raise your color before engaging your enemy, this is a legal trick and not a war crime. This has been done by an British vessel when exercising with a US carrier battlegroup, as well as the Q-ship during WWII.
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**An Agent in Place**
Have someone on the other side slow walk their data, or otherwise sabotage the search.
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Stealth does work in space, as further down it is a matter of good shaping and the right materials.
There are lots of military satellites out there whic hare difficult or impossible to find because the combination of low-observability and the bigness of space\*.
(\*space is *really* big).
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#### Many decoys
A cheap engine and a disguise on an asteroid and you have a fake space ship. Prepare a big fleet of them, break up a comet to project a lot of fragments towards the enemy, mix the fake space ships with the swarm of rocks and the enemy would be quite busy.
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"Stealth does not work in space" is inconsistent with basic logic. If stealth does not work in space then everybody knows position of enemy sensors and **what stops stronger side from destroying enemy sensors in some region and then just turning radiators** of their stealth ships toward that empty region?
You need stealth at least for launching sensors and it can be used for some other purposes.
Stealth in space is mostly about masking heat of you engines. Build giant ice spheres and tunnels in asteroids and launch your ships from there. And secret maps of those tunnels can be great plot driver.
Many ships can gather together and then run in different direction - it would be hard to get details of orbit of specific ship. They can use space tethers/magnet sails/cold hydrogen for slow maneuvers.
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In my story [Elves](https://worldbuilding.stackexchange.com/questions/167542/how-do-i-explain-the-long-life-spans-of-elves), Humans, and a bunch of other [fantasy races](https://worldbuilding.stackexchange.com/questions/168595/why-would-humans-be-the-dominant-species) live along side each other and i'm curious as to what evolutionary pressures would to a group of [divergent hominids](https://worldbuilding.stackexchange.com/questions/167799/whats-the-furthest-two-hominids-could-diverge-from-one-another-and-still-be-able) to evolve into Elves? some basic characteristics of my Elves are:
* are on average 158.4cm (5.2ft) tall and weigh 40kg (90lb)
* live on average between 250 and 270 years (addressed [here](https://worldbuilding.stackexchange.com/questions/167542/how-do-i-explain-the-long-life-spans-of-elves))
* have pointy ears
* are as intelligent as humans
* have an improved sense of hearing and eyesight
* are overall weaker than humans but do have a slightly stronger grip
* are faster and more agile
* have slightly worse endurance
* are more slender
* are less fertile
* can interbreed with humans
Note: magic does not exist in my story
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We have an example of this kind of divergence with Bonobos and Chimpanzees. They look almost identical, but have diverged enough to be considered different species. They are very similar but have different characteristics. This could be a basis of consideration when pondering how evolution would have created both species, even though we are talking about something pretty different.
So look at pressures that would create your desired characteristics.
Most of them could come from a single (and fantasy consistent) Biome. A Rain Forest.
Here is how it could work. The majority of the continent they develop on is covered in dense forests. Perhaps they came over a land bridge or something a long, long time ago back when they were an *Australopithicus*. They had not fully advanced into the naked pink Terminators *Homo sapiens* ended up being. Since they entered the vast forest, the pressures are there to maybe create an elf.
A big, lumbering ape isn't going to perform quite as well moving around in trees as well as a smaller ape. A heavy body cannot climb as high, and height is where relative safety is. This gives you a shorter stature and lower mass. A stronger grip is also advantageous for climbing.
Other characteristics could also be advantageous in a dense forest. The canopy is going to lower light levels quite a bit. That, over time, gives better night vision. Other animals with good camouflage means that excellent perception means you can eat and maybe avoid being eaten. Same with hearing. If you can't hear the snake coming up behind, you don't get to reproduce. Pointy ears that can move like a cats might result, but that could be a bit of a stretch.
Endurance could be sacrificed in favor of speed and agility. In a dense forest, you are probably better off as an ambush predator, as Gustavo's answer mentions.
So a dense rain forest gives you the pressures you need. Plus, they are elves. and elves go with trees like...well, you know
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Have them evolve from CATS!
They are ambush predators, so that checks:
* Better vision.
* Better hearing.
* Agile build but strong grip.
* Faster.
Remember cats get retractable claws since they need them sharp, vs dogs with endurance travel with exposed claws for better grip on the terrain.
Now Humans evolved to work on Endurance Hunting. While early hominids were fighting long drawn out battles, elves were brutal and short.
They get lighter bone structure and may need meat for shorter digestive tracks.
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That mostly sounds like adaptations towards climbing.
Slenderness, better eyesight, agility, poor endurance, and a strong grip are all adaptations common to climbing animals.
pointy ears is either sexual selection or for better directional hearing, and really depends on what you mean by pointy ears. there is quite a variety of elf ear designs, some purely cosmetic some functional.
The only thing that is tricky is lifespan, generally the only solution would be slower growth to maturity combined with some increased resistance to cancer to make it possible.
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I can't speak to all the other traits, but cosmetic traits like pointy ears are usually selected for as part of courtship rituals. Basically, one elf, who had above-average desirability due to other traits also happened to have pointy ears. His mate selects him due to these other positive traits. The positive traits, as well as the pointy ears get passed on to the off-spring. Over dozens of generations, pointy ears become a proxy for the other traits. Pointy ears don't actually confer any benefit themselves, but a pattern has been noticed that elves with pointier ears tend to be better in X, Y, or Z ways. They don't need to be consciously aware of this pattern either, it can be subconscious.
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I would actually go more of a mountainous evolutionary pathway. Pale skin is believed to be a result of nutritional deficiency that favors sunlight exposure in northern climates. Good hearing and eyesight, as well as good grip, fast and agile would let a mountain hunter pursue prey (think predatory goat). Scarcity of food favors low muscle mass and sheltering small numbers of offspring. That same food scarcity and cold temperatures favors slow metabolism, possibly even some sort of hibernation or even freezing in the winter and unthawing in the spring. Low fertility supports protecting your scarce young and females in craggy mountain fortresses and compensating for climate with technology (clothes, tools, etc.) Very polite because you don't want to kill any other scarce elves. Mountain hunting and castles suggest advanced ballistic weapons (bow, crossbows).
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What shape would the eggs of a species of oviparous humanoids be?
Eggs are common enough that you'd be hard-pressed to find someone who hasn't seen one. While birds' eggs are often thought of more frequently, a wide variety of eggs exist and are in use by various species around the world.
However, something worth noting is the shape eggs take on in relation to the parent species and environment. True spheres have no strengths or weaknesses because the pressure applied to one point is distributed evenly across the surface of the object. As anyone who's seen even the roundest eggs will tell you though, eggs are not true spheres. In fact, what most people think of as eggs are more oval in shape. This is believed to prevent them from rolling away--which would occur with truly spherical eggs--while also making it easier to get the eggs out of the body because of the tapered end at the top. However, this phenomenon is not often observed in species that nest in holes or other cavities, whose eggs tend to be more spherical, though this most likely has to do with decreased risk of rolling away in a closed area.
With that in mind, I am looking to determine the shape of the eggs that would come from a species with the following traits:
* Plantigrade, bipedal humanoids
* Hole-nesters
* Lays hard-shelled eggs, one per clutch
The reproductive method is thought to be something resembling a cloaca, but alternative methods are welcome. The color and size of these eggs are also not a required part of the question, but if you feel you can tackle those as well, have at it.
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### Elongated.
Here are some crocodile eggs:
[](https://i.stack.imgur.com/Jw0IG.jpg)
And some komodo dragon eggs:
[](https://i.stack.imgur.com/Gcn01.jpg)
That's because a humanoid being will have to lay these eggs much like a woman would give birth. A round, symmetrical shape would have to be small in order to get out of the mother. An elongated shape allows for more volume to be kept inside the mother's body while keeping the same width, which allows for larger eggs. That, in turn, allows for more yolk, which allows for larger babies being born. If the creature is humanoid and the babies are too small, they will be like humans going through premature birth, so you want those eggs to be as yolk-rich as possible.
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**Egg Shaped.**
Because that's what eggs are.
* **Plantigrade, bipedal humanoids**
* **Hole-nesters**
* **Lays hard-shelled eggs, one per clutch**
So other than walking on the soles of the feet (plantigrade), humanoid & clutch size, an Ostrich.
Other than hole nesting (which as you point out has implications for the egg not rolling away & the necessity (or rather the lack of any) of shapes that avoid that) your criteria have no implications for egg shape (well not much worth speaking of).
Typical clutch size can have some implications for the potential size of individual eggs, but not really for shape (if you only lay one egg you can put more resources in it).
It's not one of your criteria but the size of the birth canal (or whatever we call the bit an egg passes through) does have implications, you're laying one egg at a time so you'll want to put as much into that one egg as you can to allow for larger better developed offspring with the best chance of survival at hatching & an oval shape will allow a bigger egg to pass through the pelvic bones.
Other than that it will conform to the rounded oval structure of most eggs (simply because a sphere provides the most strength for the shell, & an oval is the closest you can get to that while allowing it to be longer than it's wide so you can have a bigger egg for the size of the pelvis).
The same as many other eggs it might be a little thinner at one end so it will roll in a circle instead of rolling away (just in case it is ever out of the nest hole).
The long & the short is that nature has had a long time to perfect the design & barring a very few outlying examples has chosen much the same design for almost every egg laying species eggs..
So it will be (really big surprise) egg shaped, meaning a slightly asymmetrical oval.
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**First** some basic considerations. The human has to stop using urea for excreting nitrogen It has to switch to uric acid otherwise the egg will be the size of an SUV to contain enough water. hard shelled eggs take up more space than the offspring in passing so females need much wider hips.
**Shape,** you have several shapes to work with for hard shelled eggs: ovoid/elliptical, elongate, spherical, or tear-drop. see examples in image.
A human fetus will fit best in a ovoid/elliptical egg or weakly teardrop egg with the least wasted space (and thus least unneeded egg width) so one of those is the most likely shape. Ostrich sized is not a bad ballpark if you go th egg laying marsupial route, based on human infant survivability.
[](https://i.stack.imgur.com/iPr0s.jpg)
**The kicker and why it will not work**.
However mammals produce well developed offspring which need more calories. Humans are particularly egregious and consume a tremendous amount of calories in the womb, around 84,000 calories (~300 calories per day average times 280 days). And becasue much of it is going to the brain much of it has to be protein and carbohydrates. Eggs have a calorie density of about 1.44 calories per gram so that is about a ~ 58 kg egg, to compare an ostrich egg weighs ~ 1 kg, that's a big egg, larger than the person laying it in many cases. Bigger proportionally than a kiwi egg, the largest proportional vertebrate egg (see image). So it is just impossible, mammals evolved to feed far more calories to their offspring than an egg can contain.
Even if you use a far more conservative estimate and half the size of the egg that is still far to large an object for anything like human anatomy to have room for. Your best bet is something like an egg laying marsupial with a pouch to feed, support, and protect an underdeveloped egg produced offspring which will be far less developed than human offspring, which are already rather helpless as placental newborns go.
[](https://i.stack.imgur.com/w4aoc.jpg)
Of course on an alien world with alien biology it might be possible you just need egg with a much higher caloric density and higher atmospheric oxygen to allow for larger eggs.
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The [Ahuizotl](https://en.wikipedia.org/wiki/Ahuizotl_(creature) "Ahuizotl Wikipedia") is a creature from Aztec mythology. It is aquatic, and appears similar to a small dog with grasping forepaws like a raccoon or monkey's, and a very long tail ending with an extra hand. It is capable of mimicking the cries of a human being, holding an adult human down in the water till the human drowns, and eating (and presumably digesting) human nails, eyes and teeth. How close could a world-builder realistically get to a creature with these attributes that could evolve naturally? In particular, what evolutionary pressures and niches could lead to evolving such traits?
A list of all of the Anatomically Correct questions can be found here
[Anatomically Correct Series](http://meta.worldbuilding.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798)
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Assuming we're talking about evolution from conventional Earth vertebrates rather than alien imports etc., and that it's native to the region of Mexico inhabited by the Aztec Empire:
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> It is aquatic, and appears similar to a small dog with grasping forepaws like a raccoon or monkey's,
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>
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This sounds like it might actually be a member of the raccoon family; their heads are rather dog-like already, and the approximate size is about right.
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> tail ending with an extra hand
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An actual, fully articulated hand (with all the normal bones, etc.) seems very unlikely - tetrapods (non-fish vertebrates) are pretty strongly constrained to no more than four limbs. However, there are two possibilities that could give the same effect:
* It has an ordinary prehensile tail like a spider monkey's or an opossum's, except that the tail tip is forked into apparently finger-like projections (either of the actual flesh or just the fur covering taking that form).
* It has only one pair of normal limbs, and the hind limbs are fused into an apparent "tail" ending with a "hand" - rather like a seal's flippers, except with grasping capability.
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> capable of mimicking the cries of a human being
>
>
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Assuming this just means crying sounds rather than articulate calls for help, that doesn't seem terribly difficult. It doesn't necessarily have to be learned mimicry (like a mockingbird), the call might just be similar-sounding.
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> holding an adult human down in the water till the human drowns
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The best bet would be it only hunting humans and similarly large prey around well-anchored or very heavy underwater logs, etc. it can cling to - if the ahuizotl isn't holding on to something, a human could walk off with it. The animal would have to be extremely strong and resilient to deal with the strain of holding on to a struggling human who's probably 6-8 times its mass, but it's probably less crazy than the hero shrew's apparent ability to survive a human *nearly 1,000 times its mass* standing on it!
<https://en.wikipedia.org/wiki/Hero_shrew>
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> eating (and presumably digesting) human nails, eyes and teeth.
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If it eats only this part of the person (not the flesh), that suggests that humans aren't its main prey (which would then suggest that the "crying" sound is probably evolved for some purpose other than luring humans - it might be simply coincidental, or mimicking the distress cry of some other animal).
Probably it is either looking for some specific nutrient (although teeth are largely calcium phosphate while nails are protein, so they wouldn't likely have the same nutrient) or it is not actually swallowing the nails and teeth, but carrying them in its mouth to decorate its nest/burrow/whatever?
The eyes might simply be opportunistic feeding on the softest parts of the body... maybe it also takes the tongue, etc.?
[Answer]
An aquatic creature like a small dog makes me immediately think of the [pinnipeds](https://en.wikipedia.org/wiki/Pinniped)- seals and walruses. They're a little big to be small-dog-like, the smallest seals being around a meter long, but that's nothing a little evolution can't handle. At least pinnipeds have fur, unlike [cetaceans](https://en.wikipedia.org/wiki/Cetacea). As an added bonus, they're in the dog-like half of the order [Carnivora](https://en.wikipedia.org/wiki/Carnivora) (as opposed to the cat-like half), although they're more closely related to bears, [weasels, and raccoons](https://en.wikipedia.org/wiki/Musteloidea) than dogs.
Seals have streamlined bodies and flippers, which is a step away from the ahuizotl's grasping forepaws. However, they could be an intermediate evolutionary step. Perhaps a population of raccoons found evolutionary pressure to take to the water and quickly evolved waterproof, seal-like fur, but have yet to lose their dextrous paws.
A very long tail is easy; many carnivorans already have those (although no existing pinnipeds seem to). An extra hand at the end of it is much harder. There's really no reason I can think of for such a thing to evolve. Some animals, such as New World monkeys, already have [prehensile tails](https://en.wikipedia.org/wiki/Prehensile_tail), with which they can grasp things by wrapping their tails around them. This works well enough, so there's little evolutionary pressure for any more sophisticated hand to evolve and quite a bit of pressure for it not to. Hands are darn complex, and vertebrate tails have exactly none of the support structure required to make them work. Perhaps the ahuizotl has a simple prehensile tail, and the "extra hand" bit is nothing more than a myth. I'll get back to this in a minute.
Mimicking human cries is easy enough. Just gotta have vocal chords that are the right shape. It's not likely that these things would evolve specifically to sound like humans, so we'll write this one off as a coincidence like how some hyena calls sound like human laughter.
Drowning adult humans is... hard. Unless they're already incapacitated. Or drunk. Or can't swim. I am reminded of the [evil carp of Dwarf Fortress](http://dwarffortresswiki.org/index.php/DF2014:Carp), which were famous for their ability to provoke unsuspecting dwarves into leaping into rivers to their doom. Most humans, however, aren't stupid enough to leap into a river at the sight of something in the water lashing out at them. Especially if they can't swim.
Anyway, this is where the prehensile tail comes back in. Maybe, instead of simply trying to drown humans, the ahuizotl simultaneously drowns *and strangles* its prey. The ahuizotl tricks unfortunate humans into falling into deep water, perhaps by grabbing at their feet and tripping them, then wraps its long, prehensile tail around the human's neck. The combination of suddenly being dumped into cold water and having a wet tail cinching down around your neck could well lead to panic and drowning in short order, especially if the victim can't swim. This could even contribute to the "extra hand" myth- to a terrified observer, this could well look like the ahuizotl was wrapping its hands around the victim's neck, much as one human would strangle another.
Selectively eating, digesting, and getting something out of human eyes, nails, and teeth is... weird. Maybe there's some nutrient in those parts that the ahuizotl can't get any other way. But nails are just [keratin](https://en.wikipedia.org/wiki/Keratin), a protein found in larger quantities and in a much more accessible form in skin. And teeth are darn near impervious to all kinds of things. Maybe they need to harvest the special photoreceptor proteins from human retinas for some reason. Or maybe human teeth just make good gizzard stones? A bit far-fetched, since I'm having these thing evolve from mammals with their own teeth, but I'm running out of ideas here.
Or maybe those parts just taste good and get eaten first, and every now and then somebody killed by one of these things gets pulled out of the river before the it gets a chance to eat anything else. This could lead people to believe that ahuizotls eat eyes, teeth, and nails, which could eventually morph into a myth that they *only* eat eyes, teeth, and nails.
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You are basically describing a giant river otter.
[](https://i.stack.imgur.com/xLATO.jpg)
[](https://i.stack.imgur.com/GuBf7.jpg)
They are big. They are smart. They play. Their faces are human enough to be creepy. They have long tails. They have grasping hands. Given that they eat entire fish, bones, fins scales and all they would have no problem with the hard bits of a human. As regards holding a person underwater these otters are big - 6 feet long and strong swimmers with claws and teeth to hold on. I think it sounds likely they could hold a person underwater.
The only thing they do not have is a hand at the end of their tail.
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I give you Drepanosaurus and megalancosaurus the weirdest damn reptiles I have ever seen. The whole group basically has a finger and claw at the end of its tail. We suspect it was for added grip while climbing, but honestly their tails are so weird it is little more than guesswork.
<http://www.reptileevolution.com/images/lepidosauromorpha/diadectidae/lepidosauriformes/drepanosaurus.jpg>
[](https://i.stack.imgur.com/lZvkm.jpg)
[](https://i.stack.imgur.com/Q0355.jpg)
[](https://i.stack.imgur.com/HZShq.png)
As for digesting nails, teeth, and hair crocodiles can do that, just by combining gastroliths and very strong stomach acid. Presumably your creatures eat everything else as well because the calories available in just those pieces are negligible.
Those weird forearms and huge claws give them the grip of an animal several times their size, although people are still trying to figure out why.
Their evolutionary history has had them getting bigger and bigger so it is not unreasonable for them to eventually get as big as you need.
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Ahuizotl could have evolved from a starfish. A mutation may have caused the starfish to lose its brachiolarial arms, causing them to be unable to stick to the sea-floor. This may allow them to evolve to crawl along the sea-floor as they develop. The brachiolaria might be better at survival, and so it may last longer, with the adult body then shrinking to avoid it weighing the larva down. To protect itself, it may gain tough, rubbery skin, and spines on its larval body. To further protect the body, they may produce bone-like structures throughout the larval body, which would not only defend against crushing, but would also make them more able to escape from predators. Some of the spines on the frontal limbs may be used to catch and pull apart prey. This may lead to these limbs fusing into a jaw beneath the head. Due to these limbs not being used for locomotion, the rear limbs may move forwards to allow them to turn their front more easily. They may also adapt some foot-spines into claws. A mutation may lead to them developing small, soft spines. These spines may be used to detect vibrations, and so might end up staying on the head as sensory organs. These sensors may split into different areas, and extend as triangular antennae, which would allow them to sense the direction of vibrations better. This vibration sensing may also lead to the development of some sort of ear cavity under the antenna. This may lead to the adult gut producing sounds to try and find mates. To increase the range of the calls, the sound producing organs might increase in size, leading to the tail extending into a long structure. These creatures may start to practise parental care, and build nests. To do this, they may become able to move their head more, and evolve a neck. They may also use the front 2 pairs of limbs to grab stuff, leading to them fusing into a chela, which may form into something resembling a raccoon's hand. They may also develop the adult arms into clinging digits to drag materials to the nest. Due to the increased effort put into mating, they may evolve display structures, such as dark skin and bright eyespots. They may also use the hard parts of animals as gifts, to prove hunting skill. They might move into shallower waters. They may become like crocodiles, but may also mimic the sounds of their prey to attract the prey. These creatures would likely have lots of food to eat, and could grow to large sizes. These changes would lead to a creature like the Ahuizotl
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The ahuizotl actually is a 4-foot long and ferocious opossum. You might ask ''But what about the hand on the tail?" As the ahuizotl wrapped it's tail around the victim, an onlooker might think that the opossum wrapping it's hand around the victim. As for the crying, it would be to lure more victims. It would carry the eyes, nails, and teeth in it's mouth so it could use them as decorations. It would then eat the carcass in it's lair. This would be an anatomically correct ahuizotl.
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It sounds like and raccoon that had an evolutionary need to take to the water to escape predators and/or hunt for food in which they would gain waterproof coat like some other mammals they might have evolved a Venom or poison that has a weakening effect on humans not enough to kill them but enough to make it to where they can drown the an adult human. they probably still have their hands to help around on land and the tail it probably came up from climbing and to hold on better. The hand at the end of the tail might be just fur that's much more puffed out then the rest of the tail giving get the look of extra hand at the end of the tail. The crying is just a distress call the animal probably just copied the that distress call and it just happened to sound like a human's that probably wasn't learned, at least not by the individual animals but its possible. Now with the eyes nails and teeth thing. The eyes were probably for food for it or its babies in which the babies might not be able to digest the other things in their later diet and the nails and teeth are probably either for his nest or specific mineral supplements.
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I think that the Ahuizotl could be the descendant of a giant river otter. Its head does resemble a dog’s to some degree, it has the grabby hands, it is aquatic, and it has a long tail. Ladies and gentlemen, the monster known as the Ahuizotl is no other…Than an otter!
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Trying to work out mechanics and visuals from one of two moons orbiting a gas giant. My idea is that the moons are tidally locked so they can never see each other's backsides, but this might be achieved by a different type of orbit. I just want these twin moons to maintain close proximity and they circle a gas giant and need to figure out how Moon A could hide the construction of a space station from its sister moon, Moon B.
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# Orbital Mechanics Perspective: Yes, This is Possible
I can say with a fair amount of confidence that this is possible from an orbital mechanics perspective. Two moons could orbit each other while orbiting a larger body. From a moon-formation perspective, I'm not sure if this is particularly possible or not.
If you fool around with some orbit simulators- [this one](https://phet.colorado.edu/sims/my-solar-system/my-solar-system_en.html) or [this one](http://www.stefanom.org/spc/), you could find a configuration that works. Don't worry about making a gas giant orbit around a sun, and then placing your two moons.
If you take the first simulator, change the number of bodies to 3, and make the mass of the third body 10, it can approximate the setup you want. (Alternatively: for body two, have a mass of 1 and a distance of 140; body 3 has a mass of 1 and distance of 145.)
[Tidal locking](https://en.wikipedia.org/wiki/Tidal_locking) in not hard to achieve- it just takes some time.
# Moon Formation Perspective: Also Possible
We have [some ideas](https://www.theatlantic.com/science/archive/2017/01/moon-formation-theories/504449/) about how moons are formed. Given some [theories of moon formation](http://blogstronomy.blogspot.com/2009/09/how-are-moons-formed-where-do-moons.html), this can happen, although it may not be very likely.
**A Note**: for most stories, the specifics of orbit are not as important, just that the configuration is possible.
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This scenario is possible, but it relies heavily on how far away the moons are from the gas giant. A statelite cannot be tidally locked to two different bodies, whichever one has the greatest tidal forces acting on it will be the tidal lock "winner". Its why Pluto and Charon can be locked while still orbiting the sun. Since the tidal forces of the gas giant will decrease as we increase the distance, with enough space this setup can work.
Its hard to say, but I think this setup could work on a system that's a similar distance Iapetus is from Saturn. Though this relies on a lot of factors such as the mass of the three bodies in question and whether any other moons throw this delicate setup off balance.
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# Yes, it's possible.
There is *no limit* to the number of sub-satellites a system can have. A sun can have a planet, a planet can have a moon, a moon can have its own satellite, and then that satellite can have its own sub-satellite, and so on.
It all has to do with the [Hill sphere](https://en.wikipedia.org/wiki/Hill_sphere) of the orbiting body, which describes the distance in which a satellite can exist in a stable orbit. Outside of the Hill sphere, the more massive body's influence is too great.
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What you describe is known as the [3 body problem](https://en.wikipedia.org/wiki/Three-body_problem). Stability in such a system is dreadfully difficult. The best bet you would have is with one of Euler's solutions, which require all 3 bodies to be co linear at every moment. Other than that, there's very few stable cases.
* If one body is of inconsequential mass (such as a spaceship in a system with a planet and the sun), there are stable solutions.
* A few dozen special cases have been discovered with special mass or orbit limitations.
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If you were to decide to live on a spaceship for the rest of your life, how would you farm?
* You have access to the necessary farming materials; Dirt, plants; etcetera.
* Ship is large enough to make room for farms, sufficient for ~20 people
(Whatever means of farming you can come up with, the spaceship is eligible for)
But what would the most effective way to farm on board this spaceship be?
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Farming in space is actually quite similar to farming on Earth, but with only a few differences.
In space, farming is usually done without the typical use of sunlight. I suppose you could use sunlight if you wanted to have a window to the sun in your farming room, but it would be much more likely that you would shine LEDs on the plants to deliver the appropriate amount of light. This constant light would enable plants to grow slightly more quickly than on Earth, where they have ~12 hours of darkness per day.
Plants also have a hard time growing in the correct direction in space because, on Earth, they use gravity to determine which direction is up and which direction is down. If you have a big enough spaceship, you could spin it to generate some gravity (you do not need one full g). Otherwise, you could do what they do on the ISS and place the seeds in "plant pillows" that encourage the plants to grow in the correct direction.
Once you solve those problems, now all you need are the standard things that plants need: soil, water, nutrients, etc.
EDIT: Upon doing some research in response to a comment, I have found that not all plants grow better in constant sunlight. Some plants need periods of darkness each day (the length of which varies from species to species) for optimal growth.
Sources: <https://www.nasa.gov/content/veggie-plant-growth-system-activated-on-international-space-station>
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**If you are living permanently on a spaceship, do you have gravity?**
There could be spin sections to provide a stable deck. At the large end, perhaps an [O'Neill cylinder](https://en.wikipedia.org/wiki/O%27Neill_cylinder). Many fictional settings have some sort of artificial gravity. Completely against physics as we know it.
**Soil or hydroponics?**
It is possible to grow plants without soil, like hydroponics or [aeroponics](https://en.wikipedia.org/wiki/Aeroponics). Using that saves mass, which will be important for space travel.
**Any livestock?**
A farm could include rabbit hutches, or [fish tanks](https://en.wikipedia.org/wiki/Aquaculture_of_salmonids). Or the spacers look for a balanced vegetarian diet.
**What about waste?**
A [closed ecological system](https://en.wikipedia.org/wiki/Closed_ecological_system) could provide air in addition to food, and take care of biological waste.
So the farm on the ship could be much like one on Earth, if you want it that way and if the designers have payload to waste. More likely, it will be an industrial-looking food production facilitiy.
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# A separate farming station
Whether connected as a separate cylinder from the living spaces or as a separate station nearby, you would want to build a place to do the farming. You would not really want to do it in the same place as the humans are living for various reasons.
Plants will not have the same temperature, gravity, atmosphere, and daylight requirements as the people. In particular, if you develop vegetable crops that can grow year round (like cabbages from the arctic circle that are accustomed to 24 hour days in the growing season), you will then want to keep these plants in full sun at optimal temperature (likely around 30 C) permanently. 30 C, and full 24-hour sunlight might not be the best conditions for people.
Since you would presumably develop low-gravity plant variants, your primary concern would be shaping a habitat so that it faced the sun (or got reflected sunlight) 24/7 to maximize growth per space. Space is your primary constraint; fertilizer and water are cheap compared to space stations. It is worth your effort to make optimal growing conditions to get 6 harvests per year to save space.
These conditions would probably not be great for animals, so the spacer would likely be a vegetarian. You would lean hard on beans and other pulses to meet protein requirements. Hope you like tofu!
Building vertically and trying aeroponics would probably not be useful. Since you are making your own station, you can design its geometry. Your geometry should involve the most area with applied sunlight possible, and that area should have gravity applied tangential to it, as on Earth. Plants will need some sort of gravity for their pressure based internal mechanics to work. Then you can grow Earth plants, slightly modified for space on this area. Aeroponics is great in theory, but there does not exist highly productive aeroponic breeds of corn, soybeans, lentils, potatoes, whatever else you want to eat. There do exist highly productive varieties of those plants for use in soil, so you should go with that.
So, in conclusion, develop a specialized farming station to grow your food at optimal conditions. This will give you the most food per area/volume while you are in space.
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I would go three ways:
* mainly grow mushrooms and fungi combined with some high fat plants. Fungi and mushrooms can be easily cultivated and need less care than many vegetables. As they need no light they can be grown densely packed with packets of soil out of which the fungi can grow into all directions.
* build biofilters for waste water that can double to grow edible algae. And other algae that can be used as fertilizer.
* breed insects that feed on (plant) waste and provide lots of protein
I did not specify the kind of high fat plants because I lack the expertise when it comes to what would work. But there are an abundance of plants that produce oil. Soy, Rapeseed, Helianthus for example.
Here is an called [Why Martian Settlers Will Eat Potatoes, Insects, Algae and Mushrooms](https://motherboard.vice.com/en_us/article/mars-food-space-potatoes-crops). It is about food that could feed settlers on mars. They suggest potatoes instead of oil-plants but the rest is more or less what I suggested.
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One of the oddest of cryptids is an octopus haunting the lakes of Oklahoma, a landlocked state. The reason this is odd is that although freshwater mollusks are common, Cephalopoda (the class consisting of nautiloids, ammonites, belemnites, octopus, squid and cuttlefish) is exclusively marine. The chemistry between fresh and salt water has so little compatibility that few animals manage to cross between both (among those few being salmon, bull sharks, saltwater crocodiles and ancient ambulocetids).
For a cephalopod to transition from salt to brackish/fresh requires certain changes in its physiology. Could such a change be possible, or is a freshwater octopus as likely as an elephant-sized terrasquid?
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Picture a lake directly connected to the Ocean or rather an inland sea. It has some flow of fresh water into it from rivers, but it's large and because of it's connection to the Ocean the salt content is about the same or probably a bit **lesser** as the Ocean.
Now picture a major geologic event that raises the elevation of the lake, and leaves a river outlet to the sea. Now you have a large salt water lake. Its outflow is larger than what is lost to evaporation, but combined the water lost to both is matched by rainfall and rivers flowing into the new lake.
Now, assume that the slow desalination as fresh water replaces the outgoing salt water will take some thousands of years to completely take place.
Such a slow rate of change could give opportunity for the generations of octopus to steadily become more tolerant of the less salty water until they are fresh water octopus.
Whether it *would* happen is another question.
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Cephalopods don't have a sodium pump in their gills in the way arthropods and fish do. Their "kidney"(nephridium) handles all osmotic balancing, which is fine in the ocean but makes it nearly impossible for a transition to freshwater. They will start taking on water and losing salt to the environment and lack a way to reclaim it easily. It is understood that freshwater clams and snails get around the problem by being very small and compact but even then they have some of the lowest body salinity levels in the animal kingdom. More research needs to be done.
There is speculation that the presence of a shell helps buffer snails and clams during their transition by acting as an osmotic barrier and, possibly, an ammonia sink.
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I am interested of a fictional future world where people can walk into a bar, order a drink with the flavors they want, and as that drink flows through their system, their DNA is modified.
An example of desired DNA modification is, let's say, the electric eel. More than four-fifths of the 2 meter long body of this fish consists of special battery-like cells that can collectively deliver a jolt of up to 600 volts. The interesting thing is that the eel can completely paralyze a nearby prey by releasing this stored energy as an intense volley of around 400 high-voltage pulses per second. (This information is from [this National Geographic article](http://phenomena.nationalgeographic.com/2014/12/04/electric-eels-can-remotely-control-their-preys-muscles/).)
In this fictional world, science has advanced sufficiently far to know which DNA code needs to be in place to allow humans to use their arms as the battery (the arms would replace the four-fifths of the eels body) and how to add the needed extra functionality into the nerve system, etc.
So the knowledge of DNA code and gene-phenotype interactions needs to advance to that level.
**What technological advances would need to be in place to make it possible for that civilization to produce drinks that can contain the DNA delivery vehicle?**
Does it require nanobots in the drink? Or can a virus be encapsulated so that it survives the stomach acids? How could the immune system be bypassed?
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**So you want be electric, son?
I gotta tell ya, it'll be a *whole* evening of cocktails, in a *very* shady bar.**
Here, put your finger here. It's gonna pinch just a bit. We need this blood drop to craft the brews, so they'll pass by your antibodies with ease.
1. First, you'll be drinking the **Beepiss Cocktail**. BPS stands for body positioning system. There is no need to make this drink glow an eerie blue color, but you can bet that all of them will be glowy and blue, just for effect. These are tiny transmitting bots whose purpose is to spread right around the body and create a body plan. We'll give it an hour to take full effect. Feel free to mix it up with some flavored vodka (you look like you'd drink your vodka flavored, don't you? I knew it!), cause the next part's gonna hurt.
2. The next one to go down is the **Bubble Tea**. This one's gonna be *nasty*. Those round jellies at the bottom will stick to your intestinal lining, and *dig through it*, spilling their powerful cargo into your body. Their contents are sesame to poppy seed sized little bots that will literally migrate through your body to BPS-specified locations and deliver their scaffolding and stem-cell cargo there. Over the next few days, these will build into the electric batteries and get those new neuron connections going, by BPS, all the way up to your brainstem. If it'll feel like you got ants running through your veins, it's because you will. Meanwhile, the now empty bubble tea jelly will use itself to patch all those tiny wholes in your intestinal lining. Don't worry too much, there's a fair bit of pain-killer in this brew.
3. Finally, you gotta gulp down the **Genejack Cocktail**, this is the big'un, and we're saving it for late in the evening. We asked the lab-techs to make it rainbow colored, but the head honcho there's a no-nonsense kind of lass, so this last one looks disappointingly like a glass of water. Don't be fooled, though. This is the most serious stuff. It's gotta take into account your, what is it, 25 years of misdeeds, epigenetic instructions, vagaries of intra-uterine development, not to mention the 20Mb of genecode that needs to be altered, trillions of times. Then there's the whatchamacallit, uh, the protein cascades of interactions, and the ton of ways they can gunk up your other existing cascades and kill'ya right dead. Deader than a door-knob, that is. Don't worry, these guys and gals are wicked smart. The resulting genecode package is nothing like the original eel's, I hear, but a whole brave new synthetic code. Oh, and before I forget: this'll leave a hell of a hangover: It'll be like a week of the worst flu you ever had, before it's all sorted out. Get yourself plenty of chicken soup and napkins.
Whazzat? Oh, controlling it. Yeah. We'll give you a little brochure and AR training kit. If you're any good, you should be able to stop shocking yourself in a few weeks, and really get the hang of it in about 6 months. Ok, give our cryptocoin-biometrics a nice good smile. Yeah, the payment just came through. Good luck, kid, see you back here in the evening.
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At a glance, your idea is very similar to the [tonics](http://bioshock.wikia.com/wiki/BioShock_Gene_Tonics) and [plasmids](http://bioshock.wikia.com/wiki/BioShock_Plasmids) from Bioshock.
First of all, [Lego Genetics](http://tvtropes.org/pmwiki/pmwiki.php/Main/LegoGenetics) does not work the way you would like to do, which is to say that you take the electric gene from an electric eel and then apply it to a rabbit to get an electric rabbit. So, the technical hurdle that would arise from trying to make a drink to apply genetic changes such as that would simply be that there is no one gene for a certain attribute, such as electric body. As such, it is not possible to get genes like that from nature.
Supposing your society has invented a specific gene which allows for these features to be bolted on to your human's genes, you would then need a way for it to work. In real life, genes very roughly work as genotypes and phenotype (no full citation, lazy to search it up right now).
Genotypes are, VERY roughly speaking, what people refer to as genes, they are the instructions to your body cells to build themselves the way they are built, VERY roughly speaking.
Phenotype are, VERY roughly speaking, the manifestations of genotypes, they are what you can see on a person, whether they have blond hair or black hair, blue eyes or green eyes, fire breath or laser eye beams.
The objective of your drink right now would be to graft external genotypes onto your human's genes and to be able to change what they were like and get powers. Unfortunately, suppose the drink could magically graft the the external genotypes onto each and every one of your body cell's genes, it would not then instantly manifest the new features. Your body cells will need to have died and then be replaced via cell division, and the new cells would have the new genes in them. However, the new cell is generally not the same as the old cell, and this normally tend to lead to cancer, very roughly speaking.
So, the potion would then need to also completely disintegrate your human's body and regenerate all the cells, to refresh your body's phenotypes. Then they would have the powers labeled on the drink.
However, that may lead to moral concerns that the person who drunk the potion is not the same person as before, but that is a whole other topic.
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It will almost certainly require nanobots, but not for the reason you're thinking of.
The biggest challenge you will face is that this new mechanism is not how new body parts grow. They grow smoothly, from a small group of cells, where everything is close together.
Your DNA needs to know *where* it should be upregulated. All of the scaffolding the body uses to put new muscles and body parts is long gone. Something running along a bicep might have been 4 cells long when you were in the womb, but now it's hundreds of thousands of cells long. Without knowing where in the body to put new structures, you run the risk of your new eel organs acting cancerous, spreading in random undesirable locations. DNA/viruses don't have very much to be selective on. Just proteins. Nanobots could at least interact with some external field while they attach to the right locations.
As for the neural system, we learn to control things quickly, but perfecting control takes a while. I wouldn't want to be anywhere near one of your eel guys for about 7 years (roughly the timescale it takes to rewire neurons to do what you want). I'd probably start by wiring up next to a muscle. For a while, you'd be constantly shocking, until you learned to stop flexing that muscle except when you want to shock something. Then you would alternate strengthening that muscle and practicing shocking. Trying to control both independently would eventually teach the brain to differentiate the muscle neurons from the nearby shocking neurons.
Learning to do this without months of physical therapy, if not years, could go very poorly.
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Perhaps future us 2.1 will have purpose-written geneomes rather than all the haphazard sloppy junk. It will featue the ability to load "apps" to modify its behavior while still under the control of the main operating system.
(Don't try 2.0 — wait for the first service pack before ordering your kid.)
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There have been many questions on this site about helmets with antlers, but I am going out and asking about antlers with helmets. Specifically, I am asking in the context of creatures that are basically human for the sake of the question, so think a human with deer antlers. That's it. Also, I do not want them to be forced to cut their antlers off or augment them in any similar manner, and I feel like stating that they just don't wear helmets or wait until their antlers shed is dodging the question. Now, let me go over the glaring issues that popped up when I first thought of this.
First off, antlers aren't made to have something pulled over them, it isn't hard to find videos of deer getting tree branches stuck on their antlers. I doubt these antlered humans could get shirts over their heads, much less a helmet.
Secondly, one could theoretically get rid of the top of the helmet and squeeze it over, but these are generally broad antlers, so it doesn't work except for individuals lacking antlers entirely, and for most individuals it would work better as a neckband than anything else at that rate.
And thirdly, any standard helmet I could think of could theoretically be placed on with some intense agony or perhaps a little flavor of magic, but good luck getting it off again.
Here's the criteria for the question.
* Must not augment or remove the antlers to work, which includes the ability to remove the helmet without harming the antlers on regular use
* Must be somewhat obtainable with medieval to early-industrial technology, so no plastics
* The helmet must provide genuine protection and be identifiable as a helmet to the point of not being mistaken as a headband
Also, the antlers do not have to be protected, just the head and face like a normal helmet, ideally without a gaping hole in the top if at all possible. In conclusion, **what helmet design would be applicable to antlered humans?**
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Make the two halfs of the helmet separable.
Just like human helmets have visors that can be pushed up yours could have pivot points that allow the helmet to be split in the middle. Two small holes at the top allow the antlers to stick out but the holes are also split so they can take the helmet off.
Another idea that I had was sort of a twist lock system.
If you look at the cutout for the face in the picture you can imagine having a similarly shaped cutout again at the top of the helmet. You then would have to slide the base of the antlers down the slit and then twist at the end to get the correct orientation of the helmet and also lock it in place somewhat.
I hope you can follow my descriptions. I'm not a native speaker so if anything is unclear please let me know and I'll try to explain more.
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You can make 3 bands:
* 1 covering the left side from the left ear up to the left antler,
* 1 covering the right side from the right ear up to the right antler,
* 1 going between the antlers, all with matching borders except in the area where you leave the passage for the antlers to go through.
The 3 bands will then be held together by quick release or straps, and might be pivoting around a common plate protecting the back of the head and the neck.
Or, as per Alexander's comment, you can do 2 bands - front one and rear one, with opening for antlers in between.
You can do this with leather or worked metal.
To wear it, one would pass the loose bands on the head and put them in position, then fasten them together. The contrary would go for removing it.
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Helmets could be made in a clamshell design, in two pieces with a hinge at the top, so that they have a front half and a back half. The helmet is opened, put over the face, then the back closed over the horns/antlers and the back of the head. The holes for the horns/antlers would be along the hinged seam. Once closed, the helmet could be latched to keep it closed.
This is the simplest possible design for a metal helmet for a being with large cranial appendages such as horns or antlers that don't themselves need to be protected, and would protect most of the head with the exception of the antlers themselves.
It is certainly within the bounds of possibility for medieval technology to manufacture such a helmet.
Inside such a clamshell metal helmet would be a padded cap that would serve to absorb impacts, much as in regular armour for humans who lack cranial appendages. That, too could have holes and slits allowing it to be easily slipped over horns or antlers, and it might lace up to provide a better fit and more complete protection.
I can't say that it would be terrible easy to don or doff such armour, but anyone who could afford such armour could no doubt afford a squire to help them with the process of arming for battle and disarming afterwards.
As technology progresses, laces could be substituted by velcro, and wearing such head protection would become easier to manage.
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Using only medieval technology, a helmet in three parts that interlock and buckle together.
Left side; Right side, Top side. Medieval metal smiths could custom fit very precise elements; all suits of armor were custom tailored to the wearer. So for this helmet; the Top piece fits between the antlers and partially around them; leaving little scalp exposed, and down the back of the head / neck far enough to protect it; perhaps change over to mail to preserve neck and head movement.
The side pieces complete the circle around each antler, and fit into the top piece; with tongue-and-groove edges. In steel, of course, this is what I found in wood:
[](https://i.stack.imgur.com/5uVec.png)
Both pieces are connected by "latch" buckles, I don't know when they were invented but they are easily plausible within the skill set of medieval metal workers. Make them as robust as needed for battle. Welded on, of course; not bolted.
[](https://i.stack.imgur.com/7qFjP.png)
You have a complete helmet with antlers sticking out.
If you want, once antlers are shed, you can fit (tongue and groove on the edge again) circular fill pieces to cover the antler holes; no new buckles necessary.
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# Slits and chain mail
Helmets are designed to deflect incoming blows. That is why slits on the sides that allow the antlers through will be enough. The slits can still allow stabbing weapons through, so to mitigate this further disadvantage you can add chain mail. This can easily be hung over the slits, leaving the antlers free.
But chain mail is malleable, allowing it to come in many shapes and sizes. It is in general the most heavyvand protective part of any armour. This is because each link can deflect a blow on it's round edges. The several layers help stop many blows and devide the energy. As all armour it certainly doesn't stop all weapons and still allows damage to the wearer. But the resilience and spread of energy of a hit makes it incredibly strong.
So I would suggest chain mail helmets. They certainly existed and their malleability makes them great for allowing antlers through as well as having the correct shape after it's rested on the head. If the helmet is created in pieces the layers allow full protection with only a few fixing points. This can decrease the time required to don the helmet while increasing the complexity as little as possible.
## Add the antlers for defence
If you have antlers you might be able to use them for further protection. You can put several layers of chain mail on the antlers, giving much more protection to the antlers and head. It will also reduce damage to the chain mail and the flex allows the energy of an attack to be distributed more gradually.
This does require a very strong neck though. The weight of chain mail is one of the biggest disadvantages of this armour. Together with leverage effects you need to be able to have a very strong physique for this to work.
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# Stay Peaceful during the Breeding Season
Antlers, unlike most anatomy, are rarely a permanent part of the animal. Hence, there is a simple solution to this problem, which would be to avoid any helmet-requiring activities until the antlers go
One major issue with this solution is that this doesn't leave much time, as antlers don't stay cast for long. I don't really feel there is much of a solution to this issue, as it is based on how long it take to grow and use the antlers, faculties which are already surprisingly fast
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I'm working with this alien race that looks and functions essentially like a mammal - skin, muscles, hair, internal bones, large size, etc. - but evolved from an insect or other bug. They're a large, about human sized, very territorial ambush predator species, and their planet is about Earth sized, filled with many unpredictable dangers such as predators and even carnivorous plants.
So far my only ideas as to how they'd acquire skin and an internal bone structure would be for their chitin to fuse together so they can become more flexible and chase faster, more agile prey, while their exoskeleton retreated to become an endoskeleton while still being made out of thick chitin, of course.
Mammalian traits that are not required: Live birth, warm bloodedness, and milk producing abilities.
**Is this possible? And if it is, why would my creature evolve like this?**
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## Yes, the scientific term for this is [convergent evolution](https://en.wikipedia.org/wiki/Convergent_evolution).
To be clear, we need a lot of different things in order to make this happen. We are talking about an extreme case of convergent evolution that probably takes hundreds of millions of years to happen.
In fact, a much shorter round-trip would be from mammal to ferocious insect-like mammal *instead*. Even just evolving into this insect/mammal monster directly from the dawn of time would be a shorter evolutionary trip, than the one we are talking about.
However according to the concepts of [evolution](https://en.wikipedia.org/wiki/Evolution), **and as a thought experiment**, moving from an insect to a mammal-like creature is **possible**.
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**Proof of concept: We need lots of different evolutionary pressures over a very long time**
Evolution gives us the steps to change an organism's [phenotype](https://en.wikipedia.org/wiki/Phenotype)/morphology into something else; we just need to manipulate what [traits](https://en.wikipedia.org/wiki/Phenotypic_trait) give a species [evolutionary fitness](https://en.wikipedia.org/wiki/Fitness_(biology)). In layman's terms, we need to influence what features are being passed down, so that we can control how the species changes over time.
We can do this by [altering the organism's environment](https://phys.org/news/2015-09-environment-rapid-evolution.html). This is very easy to do with artificial techniques like [selective breeding](https://en.wikipedia.org/wiki/Selective_breeding). However on an alien planet we either need a lot of luck to make everything line up the way we want, or play god and do it *manually*:
*If done manually, a super advanced civilization could theoretically make this happen in a lab. Or also planetwide with precision terraforming. However a lab would likely be hundreds of times faster, because we have more control. For example in a lab we could simply sterilize all the organisms that don't have the adaptations we want; thereby speeding things up.*
In our case we have an uphill battle to first remove certain traits, before adding new ones. We need to lose useful traits like [exoskeletons](https://www.calacademy.org/explore-science/exoskeleton-evolution), and gain seemingly useless traits like looking like a mammal. The only way that this can happen is through [shaping](https://en.wikipedia.org/wiki/Shaping_(psychology)). Shaping is the incremental change of a thing, and after enough time and enough incremental changes we finally arrive at our destination (looking like a mammal).
In our case we would first need to gradually create an internal skeleton for our insects, and then gradually soften their exoskeletons into skin. After that we need to (again) gradually change their physiology into the shape of mammals.
This process could very well take a billion years, even in an environment that we have explicitly crafted for this purpose. It would be faster in a lab, but this still going to take a **very long time**.
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**Other considerations:**
There is also one more very important thing to consider that I am sure you have not. Which is that **after going through all these processes, will the insect even be an insect anymore**? If it looks like a cow, moos like a cow, and acts like a cow. Well...it might not genetically be a cow... but it certainly isn't an insect anymore. Insects would just be a distant ancestor of your new species.
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**Conclusion:**
Yes it is possible, but it is not straightforward and the outcome might not be what you actually want.
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Extremely unlikely.
Let's take a step back and analyze your question.
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> Can an insect evolve to look and function like a mammal?
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What does it really mean? If an insect evolves into functioning like a mammal, that means it's *filling a niche* that was occupied by mammal-like creatures. So the real question is, what happened to those mammal-like creatures in your world? There are two possible scenarios:
## 1. All large land dwelling mammal-like creatures died out due to some catastrophe.
We know that this is entirely possible, from our own history. But, it's highly unlikely that there was an event that wiped out *all* land-dwelling creatures, unless it was a selective event by an intelligent race of aliens (or even a god-like power if you're in Fantasy territory). Assuming it's not, then it's highly unlikely that any single event can wipe out all such animals. And we know that what can happen if all of them are not wiped out; take a look around.
There's nothing really preventing you from going from an insect to developing internal bones and such, *but it's such a drastic change that it will take much longer for it to happen than the time it will take for smaller species to fill that niche*. Once they evolve to fill it (like on Earth where small ancestors of mammals took over from Dinosaurs), that nice is gone, and so is the evolutionary pressure (or incentive) for insects to turn into mammal-like creatures.
## 2. There never were land dwelling mammal-like creatures
Sure, insects were there long before the first fish jumped out of the water. But that's kind of the point too; it was easier for fish to walk on land and evolve into all the land animals we have today before insects actually filling that niche. Again, the point is time. It is such a fundamentally big change that for all practical purposes it's impossible, because well before that can happen other things can come in the way.
So, I'm afraid that your scenario isn't really possible.
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## It doesn't matter, you can have what you want anyway becasue you are talking about ALIENS they are not insects they are not mammals.
## You just need to layout what characteristics you want them to have and ask if THAT can evolve.
You don't need to turn earth life in another form of earth life. It adds nothing unless you really want them to evolve from earth life that somehow got transported to that other planet. Alien life is not going to have the same evolutionary baggage earth life has, It is not going ot find the same solutions to anatomical issues. Alien life will have a unique combination of characteristics. asking it this way shoehorns earth evolutionary baggage into it making it a much more difficult question for no benefit.
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So if I'm understanding your question correctly, you are asking whether or not a creature that originally had an exoskeleton can evolve to have an endoskeleton and other such features.
Short answer, possibly.
The reason such an evolutionary event did not take place on our world is that before such highly improbable evolutionary changes occurred, our amphibian ancestors started to walk on land and munch on the ancestors of insects. This caused a great deal of competition which relegated exoskeleton users to having no probability of evolving 'mammal' like traits.
In short, the insect like creatures of your world would need no competition to evolve in the first place. How this comes about can be for you to decide.
As for how they would function...well, I posted a similar question to yours here:[Can insects evolve their basic anatomy to grow in size?](https://worldbuilding.stackexchange.com/questions/159280/can-insects-evolve-their-basic-anatomy-to-grow-in-size) hope it helps. And Welcome to Worldbuilding!
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One drawback with exoskeleton is **molting** each time a stage in growth is completed. One thing for sure, the new exoskeleton must harden after the old one sloughs-off. In the mean time, the exoskeleton is too soft to carry the weight and is vulnerable to attack. For small insects, it is not such a big deal. For larger creatures, getting into the water is one way.
If you want a way to work around the problem, your bug's exoskeleton can be made-out of "plates" much like those of a tortoise shell: the plates can grow at their peripheries without the drawbacks of molting.
The second issue is lungs: Earth's bugs have tracheas, which are "air conduits" running from the "skin" all the way towards the center. Important junctions may increase in size into "sacks" which will serve as lungs. Inner tissues may become rougher to increase surface area and then become like gills or lungs. The imcreased surface area allows better gas exchange and allow the creature to grow larger and stronger.
Now, it is not easy to think how an exoskeleton may turn into an endoskeleton. I can imagine that a mutation may alter growth pattern to make the plates grow inward as well. If the part that grows inward connects a muscle, it may act as an endoskeleton. On the other hand, the exposed parts of the plates holn no role in skeletal support. They become incomplete and remain as **cartillage**. The cartillage is soft and flexible and acts as skin instead.
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**GMO SF Magic!**
Have your creatures be the descendants of bioengineered insects. Space travelers visited Earth in the distant past, admired the insect life, and collected specimens which they bred / engineered into servants or food animals or warriors, or all of that.
You could have an endoskeleton in the same way cephalopods have modified the molluscan shell into an internal pen.<https://en.wikipedia.org/wiki/Gladius_(cephalopod)>
Like the squids your creatures could have a soft body like a maggot around a firm internal structure derived from the exoskeleton.
If something seems unlikely to evolve that can be the engineered piece. If you want something to have evolved you can make that happen over the several million years since specimens of this species escaped their creators. Or overthrew their creators: the heartwarming story of the shoggoths!
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I'm sure arthropods could theoretically evolve to be mammalian via convergent evolution.
There are already some instances of that in our world!
-Tarantualas do look somewhat mammalian due to their fur.
-Bees make honey and wax from their bodies which is somewhat like milk.
-Crocodiles have a kind of semi-exoskeleton, so an endoskeleton could evolve in an invertebrate. (Yes, crocodiles aren't insects, but you get the point)
Perhaps via:
-an ice age to trigger more fur and warm-bloodedness
-larger size to encourage the growth of an endoskeleton
-colonial/child-bearing behavior
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The only obstacle to an insectoid creature becoming what the question needs is the skeleton
An insectoid could reduce or even lose its exoskeleton if it evolved to move through tight spaces like a rat or velvet worm. These creatures may become adapted to a new niche, and may evolve hard structures in the limb and body to allow better leverage
They will still likely shed their skin whole or in large chunks, as there may not be a pressure to shed the skin as small particles like mammals do
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**This Query is part of the Worldbuilding [Resources Article](https://worldbuilding.stackexchange.com/questions/143606/a-list-of-worldbuilding-resources).**
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I recently posted a worldbuilding question on this stackexchange about a magic system I am trying to develop, and realize now that it would be better posted in a place like a forum, where the conversation could range back and forth down the thread.
So my new question is: Is there a very active worldbuilding forum or other conversational venue appropriate for a thread on developing a magic system for a fictional modern world?
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There are many!
* **[CBB](https://cbbforum.com)** -- a discussion forum catering to invented languages & worlds
* **[Reddit Worldbuilding](https://www.reddit.com/r/worldbuilding/)** -- general worldbuilding forum
* **[Reddit Fantasy Worldbuilding](https://www.reddit.com/r/FantasyWorldbuilding/)** -- a narrow focus
* **[Reddit Fantasy Maps](https://www.reddit.com/r/FantasyMaps/)** -- fantasy cartography
* **[Reddit Fantasy Writers](https://www.reddit.com/r/fantasywriters/)** -- for writers
* **[ConWorlds](http://conworlds.fun/cwbb/index.php)** -- a general purpose worldbuilding discussion forum (defunct, posts still visible)
* **[GTX0](http://gtx0.com)** -- ConWorlds merged with Game Talk in 2019
* **[ZBB](http://www.verduria.org/)** -- another general purpose invented language & culture forum
Those are the main ones, and there are certainly other highly specialised forums as well.
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In addition to the other suggestions you can always try worldbuilding's chat on this very website: <http://chat.stackexchange.com/rooms/17213/the-factory-floor>
You're always welcome to discuss ideas and ask for suggestions there so long as you have the 20 rep needed to post.
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If you are interested in fantasy worldbuilding, Mythic Scribes is an excellent place:
<https://mythicscribes.com/community/>
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The general idea I'm looking to support here is that of a bird that produces a natural grease/oil that covers its feathers, similar to real-world waterfowl. Assume the purpose of this oil is to be lit on fire.
Is there any material that could theoretically occur naturally, either produced by the bird or produced by another organism and ingested by the bird, that could be used to grow fireproof feathers? I'd like to be able to rationalize this creature beyond "it's just magic, ok?"
Edit: If it's relevant, the world does allow for "guided" evolution. Without getting too much into it, there is a consciousness that can affect how DNA changes over time. It's more a fantasy world than a science fiction world, anyways, but it's always nice to use as little "it's just magic" as possible.
Edit the Second: Feel free to answer/comment any other thoughts that occur, even if they’re relevant to the bird in some way but not exactly the material of the feathers.
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**Calcium pyrophosphate.**
<https://en.wikipedia.org/wiki/Calcium_pyrophosphate>
[](https://i.stack.imgur.com/a0c5Y.png)
It does not burn, as you might guess from its structure - it is already almost completely oxidized. Calcium pyrophosphate occurs in healthy organisms in small quantities as a byproduct of metabolic activities. [calcium pyrophosphate deposition disease](https://en.wikipedia.org/wiki/Calcium_pyrophosphate_dihydrate_crystal_deposition_disease) is a type of "crystal arthritis" - large quantities of insoluble crystals accumulate in joints and tissues, causing a disease like gout called "pseudogout".
If humans can make calcium pyrophosphate crystals in quantity (albeit in diseased states), other vertebrates should be able to as well. Your firebird sheaths its feathers with calcium pyrophosphate. As the feather grows, the insoluble crystals are deposited on the feather, acting like an asbestos coating.
Also it would look shimmery and translucent and cool as stink.
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*Theoretically naturally* gives enough leeway to start considering [high-temperature greases](https://www.machinerylubrication.com/Read/340/high-temperature-grease). You'd need some pretty solid chemistry and abundant natural sources of base chemicals (or some pretty expansive hand-waving) to explain how the animal would form the grease and then extrude it, but the right viscosity could well mimic the water-resistant versions seen in real-world ducks.
This does not solve every problem though. Even if the feathers themselves can stand up to the temperatures the bird's body may not. Having feathers that are relatively undamaged might be cool, but less so if the bird still comes out like a flash-fried chicken.
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Dense greases would be an option; but it would make the bird rather heavy and probably not be good in the air... if it can even still get up in the air.
You could utilize those proteins differently and have them form tiny crystals on the outer facing areas of the feathers/body. Using an efficient system of energy transduction via the crystalline geometry; you could slow the incoming energy (fire) down to a less agitated state, which would turn the fire into light/energy... this could then be dispersed throughout the crystalline network and put off a glow of some sort; if you cared about getting rid of the energy. -- the bird could also utilize the crystalline system to ingest the overly agitated energy (fire, or other energies)... slowing it down enough to direct it through the body.. similar to what trees do. (Rereading this, you could also utilize that same absorbed energy, or the birds own energy to constantly emit energy through the crystals at a frequency that made the air surrounding itself very cold (slow) [if using the birds own energy, you need no transduction and just emission].)
Remembering that heat is created by fast moving particles and cold is slow moving... playing with that basic rule, you could make for many variations in this.
You could also bring in trace minerals.. and the ability to utilize metals in the feathers/body.. creating conductivity and allowing for the energy to go places throughout the body.. or even projected outwards into the environment. This may cause a weight issue...but probably not.
---- It also depends on how long you want this creature to endure fire. A light grease could make it fireproof for flying/swooping through fire... but staying there too long will make it go up in flames.
If I were you I'd get into condensers and crystalline stuff... that'd make it quite easy to convey and be very magical while still believable. You could also work with skin and heat transfering, heart/heat pumps... lots of stuff possible when you think of the process as "heat exchange" instead of "fireproof".
**-edit for specific phrasing to "answer" question-** A naturally occurring substance would be a self produced cellular protein which can be utilized in the construction of the feathers, hairs or skin of the bird. This protein would be crystalline in nature. -- being that the question is looking for a natural substance that "could occur", this is perfectly possible. Probably similar to what Will mentioned with pyrophosphates.
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Titanium is a relatively lightweight metal which has a high melting point. If your feathers had very thin braided strands of it, they could still be light and feel soft like feathers, but they'd be able to handle the heat for a pretty long time.
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Thanks to the orientation and position of the planet, *PommeDeTerra* has a habitable island with a temperate climate at it's south pole that looks a little like this:
[](https://i.stack.imgur.com/6sYhA.png)
This island is very similar to Europe with the same soil types, geographical formations, flora, and wildlife. The planet has no tilt on its rotation axis, so the sun never sets and seems to fly in circles along the horizon. (I'm not interested in the effects of this in this question.)
My humans have existed perfectly fine so far, and have reached a point where they now have seafaring ships and the invention of the compass. In Europe, this led to the cartography of most of Europe and the beginning of long-distance trade.
**How would living at a pole affect mapping and navigation?**
Navigation on land would be pretty much the same, since sign posts and roads would still work. Maps would look different, though.
Of course, North is now "out to sea" and South is now "To the centre" (making it very easy to find the capital city). Navigation based on the sun or stars will be useless, unless someone finds a clever way to combine a measurement of the time with the position of the sun.
International trading would involve heading away from the pole to areas where the sun rises and sets, making navigation based on the sun impossible at night. I suppose at this point people could switch to using a compass since they are away from the confusing polar regions, but I'm not sure how it would work.
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If you would rely on the sun for your direction, you will have to be able to track time accurately. If your time tracking is 10% off, you'll walk in a 10 day (poorly drawn) circle.
A compass would be quite useless around the poles, so they would likely not be invented: the inventor won't recognise their use.
So navigation would probably rely heavily on landmarks like mountain peaks or towers.
You can do the math to figure out your position relative to landmarks. [Land surveys](https://en.wikipedia.org/wiki/Surveying#History) would play a very important role in mapping. Angles and distances between different landmarks would be noted on the maps to assist with triangulation of your position.
Another important aid in navigation would be accurate time-keeping. Given the time and the position of the sun, you can figure out in which direction you're headed. To this end, portable clock technology would be much more advanced, and maps would denote absolute directions at specific points so you can calibrate your clock.
If you go out to sea, the only way to determine direction would be with clocks. It will probably take quite a while for people to figure out that other means of determining position and direction become available as they travel further from the pole. They will likely pick these up quite fast as they're already quite proficient taking accurate measurements of angles.
Another fun consequence: time and angle measurement would probably be equal: 3 hours would be expressed in the angle the sun travels along the horizon in 3 hours. A sensible design for a clock would be a single hand pointing towards the sun relative to an absolute direction. The markings around the edge denote both time and an absolute direction.
As they travel far enough and experience nights, navigating by stars would be identical to navigating by the sun. It would probably take them some time to figure out that the stars and sun move relative to eachother throughout the year.
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I can - and certainly am not alone - think of at least one fictious world with a similar setting :
[](https://i.stack.imgur.com/1eXXi.jpg)
*Discworld* is a collection of books written by Terry Pratchett telling the adventures and daily lives of characters who live - for the most part - on Discworld. Contrarily to your world, theirs is a disc, but there are some similarities that you can build upon.
Since their world is a rotating disc, their 2 cardinal directions aren't carthesian axis like our North-South/East-West (even though due to its spherical shape, our axis aren't perfectly carthesian...) but polar directions : closer-further to/the axis and clockwise or counterclockwise rotation around the axis.
Although your people live on a spherical planet, developing their civilization around the pole on such a wide landmass is likely to lead them to that kind of standard. Indeed, the ancients used astronomy heavily regarding all sorts of things, especially when it came to maps, periodic events and navigation/travel. They would get that the sky rotates around an axis that goes through a fixed point of their land pretty quickly, certainly way before the invention of writing. That point would be of very significant importance, maybe the center ( ;) ) of some major cult, as well as their maps.
If the pole is their point of reference, then all directions are related to it in some way and you end up with a discworld-like system. In fact, our pseudo carthesian system surely happens only because it was used mostly to travel along the Est-West axis and/or in places where the paralels are.. well... fairly paralel. That system being more and more distorted as you get closer to the poles until the point where your paralels all cross themselves, it would be unlikely that people who originate from that very same pole would develop it in the first place.
In my opionion, a map centered on the pole would make a lot of sense even today, so I guess it would be even more obvious to a civilization that considers it the default setting.
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I would suggest **redefining the cardinal directions** that your civilization uses. As with Earth, defining lines of longitude will [have to be done somewhat arbitrarily](https://en.wikipedia.org/wiki/Prime_meridian), so choose one direction and call that "North", or some other name to avoid confusion. The opposite direction becomes "South", and the perpendicular directions are "East" and "West".
Your *true* North and South would also provide valuable information, that is, distance from home. I would imagine people might use some simple notion like "Outward" and "Inward" to describe what we would refer to as latitude (e.g. "We have sailed 50 km *outward* from the Northeast coast.") Additionally, navigation by compass is very intuitive for inward/outward travel (If using the standard colors of a modern compass, your people would likely devise a saying like "Follow white, home in sight; follow red, new waters ahead"), but will be fairly useless for longitudinal travel.
Maps would most likely be roughly circular and pseudoantarctic-centric, as until the far side of the planet has been explored, the main continent serves as the center of this population's world. It may look approximately like the following map until your humans better understand the roundness of your planet and scale the continents more appropriately:
[](https://i.stack.imgur.com/hpF6p.png)
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If the planet has magnetic poles and one of them is on the continent, the magnetic inclinometer would probably be invented simultaneously with the compass. The inclination of the magnetic field, as measured by the inclinometer, would give a useful indication of the distance from the pole.
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Other answers have talked about concepts of north, south, east, west, outward, inward, etc. But there's the additional problem of finding your current longitude and latitude, which is something a compass cannot provide.
Your first method of figuring these out would be simple landmark navigation. Go north from Jumpoff Point to the Isle of Reckoning. From there, head north-northwest until you sea the Misty Lagoon over the horizon. Etc.
But we can use the sun and the stars to get much better positional data. At first, your people might have no concept of stars or star-mapping, because the ever present Sun in their sky might hide all the stars, depending on the atmospheric conditions present. However, if it's like Earth, we can still see a few stars on the horizon opposite the Sun at dusk and dawn. Likewise, your people would see the stars, and recognize that certain stars are visible at certain times of day.
**Summary.**
A simple sextant will give your mariners their current latitude by measuring the vertical angle of the Sun at noon (or some other object at its apex in the sky). Using accurate clocks can allow calculations at times other than noon.
Longitude is much more difficult, requiring precise time-keeping to measure. While the math itself is easy, we didn't develop properly precise clocks until the late 1700s.[1](https://en.wikipedia.org/wiki/History_of_longitude#Harrison.27s_proposal_.E2.80.94_marine_chronometer)
As such, landmark navigation will remain common for quite some time, particularly for longitude.
**Time of Day defined.**
For the sake of clarity, let's assume your people define the time of day according to which part of the horizon the Sun is at. So if the Sun is currently at 0°, it's 0:00, if the Sun is at 90°, it's 6:00, etc.
0° will likely be defined by some landmark. For example, the angle from the south pole to The Great Oak Forest might be 0°.
**Time of Year defined.**
Now, your people are going to realize that the stars visible at 0:00 will change over time. This will lead to the concept of a "star day", which is identical to our real-world notion of a year, without the seasonal variations. So maybe they define "January" as the month when the Gemini constellation is visible at 0:00, and "July" as the month when the Sagittarius constellation is visible at 0:00.
Originally, I thought there was a way to determine longitude from time of year, but I don't think that's accurate. Still, knowing which constellations are "equatorial constellations" allows your sailors to find the time of day even at night. Additionally, knowing the time of year can help keep local clocks accurate over long voyages.
**Long-distance Time-keeping.**
In order to find longitude, your sailors will need to know the current time relative to some known longitude. Generally, they'll probably compare local time to the time at the south pole, which we'll call "proper time".
With advanced satellites, they can use some kind of GPS, which would obviously also give them exact coordinates directly.
With basic radio technology, they can use radio stations to broadcast the current time. As the people expand their reach, then can have repeater stations set up so station A broadcasts every so often (say, every five minutes). Near the edge of A's broadcast radius, you have stations B, C, D, etc. around the ring. Each of them keeps a clock in sync with station A's broadcast, then broadcasts on a second frequency. Another ring of stations listens to the second frequency to sync their clocks and broadcasts on a third frequency. Etc.
With less advanced technology, your sailors will have to rely on simpler methods of time-keeping. Water-clocks, wound-spring clocks, etc. will all work to varying degrees of precision. Each port will be able to maintain an accurate clock, and the ships will re-sync their clocks accordingly.
I'm not sure what kind of accuracy they have, but numerous methods of determining time using other astronomical objects have been devised throughout the ages. Essentially, by accurately measuring various astronomical periods, such as the Moon's orbit around Earth, sailors can determine the current time by measuring relative motion of astronomical objects, such as comparing the Moon's position to the background constellations.[2](https://en.wikipedia.org/wiki/History_of_longitude#Proposed_methods_of_determining_time)
**Putting this together.**
From here, they can combine three pieces of angular information to know where they are on the globe.[3](http://astro.unl.edu/naap/motion1/tc_finding.html) [4](http://www.open.edu/openlearn/society/politics-policy-people/geography/diy-measuring-latitude-and-longitude)
First, they track the height of the Sun at noon. On the poles, the Sun will always be on the horizon. At the equator, the Sun will pass directly overhead (called the "zenith"). At any latitude in between, the Sun's height at noon will directly correspond with that latitude. From here, they can directly calculate their current latitude.
Second, they track the direction of the Sun's apparent motion. In the north hemisphere, the Sun appears to travel left-to-right. In the south hemisphere, it travels right-to-left. Combined with the above, this gives your people their exact latitude above or below the equator.
Third, they track the angular difference of an accurate clock between "proper" noon and local noon. This will be easier as they develop radio then satellite technologies, but can still be done with any kind of local clock. This angular difference gives the longitudinal difference between where they're at and some prime meridian.
Fourth, they can track various angles to or between astronomical objects, which may be helpful in more accurate time-keeping, but isn't directly helpful in determining position.
**A note about the Sun's angle near the pole.**
If you're extremely near the pole, and on or surrounded by land, it's possible the Sun will always be below the horizon, making it impossible to measure the Sun's angle at local noon. This would, in turn, make it impossible to know your precise latitude (and further, hard or impossible to know your precise longitude since you couldn't determine the exact proper time of local noon).
Note, however, that this is not likely to be a huge deal anyway. If you're on land, you can use landmarks to find your way pretty easily to begin with. It's really only when you're on the ocean that you'd have a really hard time finding your bearings. And on the ocean, the Sun will always be above the horizon at noon.
Regardless, I did some math. Let's say you're standing at sea level, and the horizon is covered by hills the height of Mt. Everest (about 5.5 miles in elevation). The angular height of the hills relative to the horizon is given by
$atan(\frac{5.498\text{ mi}}{X\text{ mi}})$
where X is the distance to the hills.
The latitude difference between you and the hills is given by
$\frac{X\text{ mi}}{24901\text{ mi (Earth circumference)}}\cdot 360°$.
Because the Sun's height at noon is equal to your latitude, we can set the above equations to equal each other and solve for X. This will give us the distance from the pole where Mt. Everest would prevent the Sun from rising.
I'm having trouble getting WolframAlpha to solve the equation directly, but my graphing calculator gives an answer of $X=\pm 147.578 mi$, which gives angles of 2.134° for both occluding height[5](http://www.wolframalpha.com/input/?i=atan(5.498+mi+%2F+147.578+mi+)+in+degrees) and latitude[6](http://www.wolframalpha.com/input/?i=(147.578+mi+%2F24901+mi)*360+degrees).
Because the viewer is 147 miles from the pole, and the giant mountains are 147 miles from the viewer, this means anyone within 295 miles of the pole will never see the Sun.
Realistically though, you're not going to have a horizon full of Mt. Everest-sized hills while at sea level. Which means the occluding distance will be much smaller. Doing the same math for an elevation of 1320 ft gives a 63-mile occlusion radius, and an elevation of 500 ft gives a 39-mile radius.
In general, the more bumpy the terrain, the more likely it is that you've got a huge cliff between you and the horizon. But it also means you don't have to walk as far out of your way to get a better view.
So even at distances much closer than 300 miles from the pole, there's a good chance you could use the Sun's position at noon to get your current latitude (and, with good time-keeping, your current longitude, since you know the proper time of local noon). By deliberately using a route that keeps you at higher elevations, you could maintain an accurate log of your position throughout most of your trip.
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Compass-like-devices would be quite useful.
1. As already mentioned in A. I. Breveleri's answer, by measuring magnetic inclination you get distance to magnetic pole even if sky is covered in clouds and you cannot see position of the stars and sun.
2. And what is more important, if magnetic and true pole do not coincide, then by knowing magnetic declination and latitude(which is easy to measure) you get longitude(which is hard to get) without high(relatively) technologies required for lunar distance longitude measurement or chronometers.
In real history magnetic declination method didn't work well because most travels occur far from pole and distance between magnetic and true pole is low so angle is small and it should be measured with high precision. But if you travel close to pole then you can get good results with low precision(angle would be big).
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In this world, there are two trans-human species that are emerging at the same time. They vehemently despise each other and conflict is fast approaching. I would like to make the struggle between the two trans-humans as hard-fought as possible. If I cannot realistically make the struggle close, and there is an obvious winner, I might just abandon the idea. Without further ado, the two trans-human factions are:
**The Bios**
They have decided to reject computer chip implants, but they may use tools, guns, ect. However, their primary characteristic is that they consider ANYTHING bio related fair game, so they take genetic engineering to the extreme. Some things to expect from them are:
* disease immunity/longevity
* accelerated gestation rates
* super-brains (larger-sized, multiple brains, enhanced neural
connections)
* giant muscles, overall size (potentially titanium or other strong material bones)
* genetically splicing in extrasensory senses (think sharks electrical pulse
detection, ect)
**The Cybers**
Conversely, these trans-humans do not genetically modify themselves, but instead embed computer chips and network cards into themselves and have many machine-like advantages like number crunching and network intelligence. They still have eyes, ears, and other vestiges of their former human selves, but these "monkey-meat" body parts act more like an input for the cyber-driven intelligence to get data from. Some things to expect from them are:
* fast reaction times (drones can react faster than fighter pilots even
at present given in aerial combat drills)
* computer aided everything (motor function, night vision, ect)
* quick skill learning (theoretically, just drag and drop skill sets into the
cyber brain)
* augmented physiology (an exo-skeleton suit integrated into their body
perhaps with gold/carbon fiber for anti-EMP, drills for fingers, ect)
**Assumptions**
* near future or at most 200 years in the future
* no morality comes into play
* advances in AI and genetic engineering could outpace each other
(whatever way makes for a better fight)
* conflict is inevitable
* pure bio vs pure cyber implies there are no hybrids
**Question (reiterated):**
Building off this basic premise as described above, but also subject to your own opinion on what additional advantages/disadvantages there might be with regards to the two factions, is this going to be a good match-up? If it is shaping up to be very anti-climactic and too predictable, I would also appreciate speculation as to how to level the playing field.
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The big issue here isn't that these advances are not possible, but since they are approaching singularity levels of technology, whichever faction is able to perfect their technology first is going to win. The Bios will either achieve their genetic engineering goals and be able to impose their will, or will not have achieved the ability to do so before the Cybers swoop down and impose their dominion upon the Earth.
This is pretty predictable because augmenting to such an extreme degree both implies a steadily and exponentially increasing advance in the knowledge base, but also an exponentially increasing set of skills, abilities and capabilities. If the mismatch becomes too great, then you will be faced with the situation of Imperial Japan just prior to the start of WWII, the United States outpaced Japan in every economic metric important at the time (for example, having 8-10X the annual steel production, a rather important metric if you plan to fight a naval war), so the side which can increase their capabilities more rapidly through first mover advantage will almost certainly win.
There are a few cheats you can impose as a writer. Perhaps the initial set of modifications provides a huge advantage, but unanticipated problems prevent version 2.0 mods from working properly, allowing the other side to implement their version 1.5.3 upgrades and catch up temporarily. Of course the losing side could also invoke the "Sampson Option" and bring the entire edifice of civilization crashing down by unleashing WMD (nuclear attacks are equally effective against both cyber and biological upgrades), in which case the survivors will be equally matched using sticks, sharp rocks and other advanced tools of post nuclear warfare......
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**Terrain**
The worse the terrain, the more the Bio will have the edge. Jungles, swamps etc. Cybers need more man-made infrastructure to perform optimally.
The big issue will be who controls space. Control of space gives a lot of options in terms of where you can suddenly attack. The Cybers will have the edge here.
What really matters in war: **Production**
Who can replace losses faster then the other team for longer? If both teams lose their armies in a battle but one team can build a replacement army in a week and the other team needs a month to spawn more troops, the war is already won. Vice versa too.
Adaption speeds and guerrilla tactics could really help decide the outcomes of battles but wars are won and lost on who can replace losses faster.
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Because these two technologies are distinct and you are free to advance one or the other however you’d like I don’t see why you can’t balance the two sides. One isn’t inherently better than the other at all technological levels. That said I do have some suggestions for you that I think might help flesh out your conflict.
If these two factions represent two nation states that are at war there are many other variables that matter more than the combat effectiveness of the individuals of each nation. First off, if we are in the near future is this a nuclear conflict? If it is then the flavor of transhuman probably doesn’t matter that much in the face of a nuclear holocaust. If for whatever reason it isn’t, then two other factors become more important, industrial capacity and manpower. Whichever nation can field the larger, better equipped army will most likely be victorious, regardless of individual combat prowess. For this reason I think it’s more important you consider the transhumans’ industrial capabilities rather than their combat capabilities. You could easily imagine that the Cybers have more efficient industry being capable of directly interfacing with machinery to control it. On the other hand the Bios could easily have a much larger combat effective population. Cloning, accelerated growth, and most importantly not needing to perform costly and expensive surgeries to implant their tech into workers or soldiers means their workers and soldiers could be plentiful and expendable. These factors will likely play a bigger role in the victor of the conflict then the reaction times or strength of the soldiers.
Along those line if you do feel the sides are unbalanced you can change the resources each side has access to to bring them back in line. Cybers too strong? Give them smaller borders, a smaller population, and fewer natural resources than the Bios. There are many ways to balance the conflict beyond the capabilities of the transhumans.
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Have you played Stellaris? They recently introduce a mechanism that provides for both of these (and psychic for a third option). Essentially you can build to a race that are robot containers for an intenlligence that originated from an organic source, a race that has opened their minds to psychic realms, or a society that has designer genetics for creating genetic offshoots for a specific task.
In the robot case, the advantages are a population that is good at everything, and the population is immotal (leaders have life spans, regular citizes don't but its assumed the population units represents more than one individual) and they can now live on any world habital world regardless of previous habitability. The trade off is that the empire creates conditions that could foster a galaxy wide computer virus that causes robot populations to rebel, they must delibertly create new populations, and there is no way to make specialized designs (this last one is getting fixed in the next update).
Conversely, genetics in Stellaris is represented by a series of traits each race can get, which give bonuses to different values. You can have at most five traits and each one costs a cetain amount of "Gene points" at game start you have two points and can get more by taking negative traits. All societies can research genetic techs to a basic degree which gives you more points and allows you to remove but never add negative traits and add but never remove positive traits and a few more points. Specializing gives you even more points and the ability to both add and remove any traits and ultimately to give you even better versions of some traits, especially those that affect production values.
In game, Genetics and Robots get along alright, its Robotics and Psychics that don't get along (they have requirements that are counter to each other and produce a negative opinion of each other).
To my mind, Genetics would be more fine tuning individuals to tasks where as robots would make good generalists. Remember, genetics realistically works if you can show that the trait exists in nature. Titanium bones are unrealistic as there are no organisms that can break down titanium materials that would be used in bone production. It's actually probably very toxic to consume titanium (however, carbon nanofibers are a bit belieavable as carbon is essential to life so creating a genetic instruction for a cell to produce nano-tube protiens is much more plausible. Still not likely for bone, but how about bulletproof skin as a trade off?).
Robotics offer a wider range of techonogical interfaces to do things not possible in nature and can be modular and quick to change and update software.
Ideally, the mindset of a biological ascendant is "we aren't perfect, but we can fix the parts that we don't like and be better". Robotics would be "Our bodies are our first tool and we need to improve the overall functionality and features offered by this tool" These are not in and of themselves incompatabile idealologies but adding values such as My body is a temple could complicate the matter. In addition, both sides could frame the more unfortunate implications of the noble philosphy. Bio-augmentation cuts close to eugenics ("They want to breed a master race that makes humans redundant") where as robotics has some authoritarian elements to it ("They say they are just patching vulnerable software, but what if they patch how you think or even take away your will to question them."). And of course, those can be spun a different wah. Bios can charge that they are pro-Individual ("We allow anyone to express their best parts and fix the parts they don't like. We can make your body the body you always were meant to have.") where as robots can say they are very tolerant (Our society is not racist. There are no black men or white men. We are all Tin Men.").
So the take away from all of this is... I should never be allowed to write propaganda.
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The most extreme victory tactic I could think gives a victory to **The Bios**. Engineer an immunity to a very advanced airborn patogen that their bodies can create and release to melt the tissue of anyone without it's immunity. However, to counter that the Cybers could just have some airtight form of armor to stop it from ever reaching their biological parts.
By focusing on their "purity", I believe you're damning **The Cybers** to defeat because, as long as they're matched in battle, **The Bios** can always resort to cloning to create more soldiers and replenish the population.
The only way I could see **The Cybers** win is if they worked similar to Doctor Who's Cybermen or Star Trek's Borg and began assimilating their opposition to bolster their ranks.
Apart from that, the truth is that they are as well matched as you desire them to be.
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I'd say you need to really pin down what abilities each side has, and where they're located, for a start, because right now, this question seems too vague to have a clear answer.
And to integrate my comment:
Are nanobots a thing? If so, I'd expect the Cybers to integrate them into their tech... And then use them as weapons or something...
Good weapons against things made of metal, would be [liquid mercury](https://en.wikipedia.org/wiki/Liquid_metal_embrittlement#Mercury_embrittlement), to weaken the metal? And it's also poisonous.
But, liquid mercury can be protected against with [anodizing](https://en.wikipedia.org/wiki/Anodizing) or a plastic coating... Although, such protections may be inadvisable with cyborg parts, perhaps.
In any case, mercury is still poisonous to the organic components, but there are methods to absorb it and render it harmless.
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When reading your post, i remember the RPG Cyberpunk, wich has more or less, among others, two nations that look like the ones you described.
Yes, I believe it works, because *bio engineering and nano technology pretty much aim at the same things*, and the buffs you gave to each team are ... pretty much the same. And that's also the problem :
**They are the same**.
Apart from how they got beefed up, they are the same. I don't think the story can work if you don't have more teams than that. If none of them really represents a threat to each other (they pretty much have the same strengths), i don't see why there would be such a conflict (maybe at first, but after a while, everyone would have settled down and dealt with it). If you decide to keep the conflict alive, I don't see how would any team win more than the other, since they all have the same bonuses :
* better reflexes
* more strength better
* learning better
* longevity/immune
system
I may edit my answer if you have more scenaristic arcs than what you gave us in mind, but if you didn't, as I said, I don't see why would they simply keep fighting.
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## The Gene-Editing Cyborgs will win
While you say that there won't be any hybrids, this would not be realistic. Looking at the wide variety of things humans have combined, these two technologies would be a no-brainer. Unless you can find a justification for the lack of hybrids, then they will inevitably arise, and inevitably win
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**Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers.
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I watched [a movie](https://en.wikipedia.org/wiki/Triangle_(2009_British_film)) that was inspired by the classic myth of [Sisyphus](https://en.wikipedia.org/wiki/Sisyphus). It’s a well-worn story element to have a character be cursed to repeat a task or relatively brief passage of events for eternity.
But how long would it really seem? Presuming your brain doesn’t reset as part of a time loop but rather you continue experiencing consciousness but are forced to keep trying the same thing, it would reach a limit at some point.
Supposing you can try variations always to the same goal, there will still be a finite number of different possibilities. You will forget exactly how many times you repeated each particular variation, and in any case repeating doesn’t lead to new memories once you’ve memorized it. So, doing it a million more time would not seem to be any longer than when you thought about it before, right?
Or there might be limits in the brain’s subjective memory capacity.
Using whatever mechanism you might consider, what would the *subjective* time span of eternal repetition be? Or, can you repudiate that and suppose that the mind changes in other ways, but I think that leads to a larger limit, not a lack of any limit.
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The brain is a strange and complex thing which we don't really understand. However it's suggested that the brain only lays down new memories for new experiences. Once something becomes repetitive your mind takes fewer samples and time passes without notice.
What this ultimately means is that Sisyphus' eternity blurs into one long day. Past the first few months the job ceases to be hard, just dull, but it doesn't matter because the brain doesn't remember it happening.
Ultimately, what difference is there between pushing a rock to the top of a hill and watching it roll down again and any other repetitive non-creative task any of us might do at work? At least he's out in the fresh air.
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## Repetitive tasks are way to meditate for westeners
This is rather addition to great [answer from Separatix](https://worldbuilding.stackexchange.com/a/67382/2071): Usual eastern meditation techniques require person to sit/lay down and "do nothing". Which is very unusual thing for most westeners.
However, when given repetitive, dull task (example clean huge area with broom), your mind becomes to "wander" after some time and subjective time tracking becomes loose.
So, for some, few hours can feel like "eternity", for some other few hours of repetitive task can feel like "few minutes"
## Make it dull, but not repetitive
For most westeners, being locked in meeting when someone repeats the obvious in most words possible is the new hell. Especially when you consciously have to follow the conversation, because you might be asked some question.
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You might suffer from [Commuters Amnesia](http://news.bbc.co.uk/2/hi/uk_news/4052861.stm) after a while.
If you're doing the same task over and over again, without the ability to have any control about it, like a commuter to and from work, your brain will switch into zombie mode, so that you will perform your task more or less automatically.
It may seem relaxing at first glance, but it produces more stress to the body than a jet pilot, as stated in the link and confirmed by personal experience of commuting 2 times 1 hour a day over nine years.
So, at the end of eternity, whenever that is, it may not have seemed so long to the person, because the brain was in hot-stand-by for most of the time.
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If life were discovered in the supposed ocean on Europa, it would be a popular destination for scientists and researchers. I am curious as to what life on Europa would be like, in terms of engineering and building a sustainable habitat.
First, to reach the ocean, is it more practical to melt down through the ice, or drill it? How hard would the ice be at 10km thick (in 1/9th of Earths gravity)
If melting/drilling a tunnel down to the ocean, would it be possible to passively leave this borehole open, or would the pressures cause the ice to flow together again? What kind of engineering would be required to keep the borehole open, assuming my colonists want an elevator to the surface... how would tunnels and rooms at the bottom of the ice behave, structurally?
If the ocean was reached, at about 10km depth, the water pressure would be close to 100bar with some rough calculations. Would it be practical to build habitats mounted on the underside of the ice, in the water, or would drilling rooms within the ice be easier?
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It is much more practical to melt through ice than to drill through it. The most likely way of doing this is to place either radiothermalgenerators or a reactor on the front of your craft.
It would not be possible to keep the borehole open after passing through without installing a thick steel tube the full width and length of the tunnel. This would still snap as soon as the ice moved though (which might happen every Europan day due to tidal forces). [correction: Europa is tidally locked and thus has no days.]
My rough calculations suggest 133 bar, which is more or less what you got. This is roughly 3x greater pressure than modern large submarines are able to survive, so your pipe would have to be roughly 3 times stronger than a Seawolf pressure hull. That is a heck of a lot of material to cart across the solar system, and any flaw in its entire 10km length would result in collapse.
If it was absolutely necessary for your story, I would probably build the tunnel from some modern version of Pykrete. <https://en.wikipedia.org/wiki/Pykrete> Perhaps using a carbon nanotube fiber rather than cellulose (and ideally manufacturing the CNT on site). You would probably do best to situate the tunnel at a point which experiences the least ice movement. (Presumably far from any fault zone.)
Ice at the bottom of the hole would presumably not be very strong as it is under enough pressure that it is very close to becoming liquid again. You should transition away from Pykrete before reaching the water layer, and use some other material.
This whole endeavor is pretty unrealistic with any technology we are likely to have in the next 100 years though. (IMHO) By the time humans have the technology to do something like physically surviving a trip to the Europan ocean, they will have long since developed many technologies which would undermine the plot of this story, like very advanced genetic engineering which make humanity unrecognizable to readers, super tough nanobots who would have already scouted the Europan oceans quite thoroughly, and super advanced sensors which would have scanned the Europan oceans in detail right through the 10km of ice.
Also, it's likely that if life were discovered on Europa (especially macroscopic life) the entire moon would be utterly and completely off limits to human explorers for fear of contamination.
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I just read JDługosz's answer and he makes a lot of good points that have made me rethink my answer.
Ok, the mass of the ice column that needs to be removed is M=density×height×π×r². Let's say the radius of the hole is 5 meters. Based on that I'm getting a mass of the column of 7.2E9 kg (neglecting the compressibility of ice). For the potential energy of raising those tailings to the surface I'm getting 11 MW years. (11 megawatts for 1 year). If your removal system is 50% efficient that would require a 22 MW (electrical) reactor, which is pretty serious hardware. At 35% efficiency, that would put out 64MW (thermal). Your boring machine is going to need more power to run the cutters, but I have no idea how to calculate this.
The energy needed to raise the temperature of the ice column to −50° C (which, from the phase diagram of water, appears to be the temperature needed to sublimate ice rapidly in a vacuum) is E = mass × specific heat × change in temperature. The specific heat of ice is roughly 2000 joules/kg°C. I'm getting a heat energy of 1.7E15 joules or 52 MW years (thermal).
The enthalpy of fusion of ice is 333KJ/KG. The enthalpy of vaporization of steam is 2257KJ/KG. I assume you just add these two together to get the enthalpy of sublimation? (I never did that in school.) That gives me a 1.86E16 joules to phase change the ice to steam or 589MW years, which is a really shockingly large number.
It also occurred to me after reading JDługosz's post that the sublimated ice would possibly recondense on the walls of the tunnel (although maybe not if the tunnel is in vacuum?) Regardless, the tunnel should probably be insulated in a melting scenario.
Regardless the vast majority of the energy need for the melting and vaporization plan goes into the boiling part of the phase change (rather than the melting part). This makes intuitive sense now that I think about it. Water quenching of hot things is crazily effective, and I once saw a TV show demonstrate that melting a hole through a glacier was way more efficient than drilling.
Based on these results, and taking into account the (probably) infeasibility of shoring up the tunnel, I would like to propose a new solution.
Covering the tunnel mouth with a lid to keep it pressurized to roughly 1 atmosphere. You still melt your way through the ice, but now you coat the interior of the ice tunnel with insulation rather than shoring. (Pykrete makes a great outer layer of insulation, but you would want something else on the inner layer.) Melted water stays liquid, meaning you don't have to spend energy boiling it off. This reduces the phase change energy requirements from 589MWY to 87MWY. Adding that to the temperature rise energy of 77MWY (you now need 0 degrees C, so this is a little higher than before) leaves you with 183MWY (thermal), which is still a heck of a lot of energy. I didn't even include the heat loss through the walls of the tunnel, but I think it's the least challenging part of the entire mission. Especially since the reactor needs no coolant radiators which, on a space ship in vacuum, would be enormous.
The weight of the water maintains more than enough pressure on the walls to keep them from collapsing. The reactor heat drills the hole without the need for thousands of tons of drilling equipment (and repair parts and machinery to let you install the repair parts) and ... billions (?) of tons of shoring.
Your explorers would need to live inside a super strong submarine which is 3 times stronger than a modern military submarine, but much less strong than the Alvin deep sea submersible. (The submarine would serve as an excellent space habitat by the way.) The reactor would need to be kept running permanently in order to prevent the column of water from refreezing, so you wouldn't just let it drop into the ocean once you broke through the ice. Probably the biggest challenge is now the mass of the insulation.
It would be really cool if there was a good way to manufacture cellulose (or other similarly performing polymer) from materials found on Europa. The ice on Europa is not 100% water. <http://people.virginia.edu/~rej/papers09/Carlson4019.pdf> Perhaps the ammonia and carbon dioxide ices can be used as feed stocks in a small factory to produce a hydrophilic polymer? The inner surface of the insulation might be a gel or a hydrate of some sort? You want something where most of the mass of the insulator is water, which is captured and held immobile.
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It is much more practical to drill (or tunnel or quarry) than it would be to melt the ice.
Consider: we have tunnel boring machines and other excavating techniques here. Do we melt the rock into lava and pump that? No, we just cary it away in chunks.
On a cold world, ice is a mineral. So think of it like rock.
To melt it, you have to raise [its temperature](https://en.wikipedia.org/wiki/Europa_(moon)#Subsurface_ocean) from a mean of −170°C up to 0 while the surrounding material is conducting the heat away, and then further add the amount of energy that would have raised the temperature of ice 80° before it budges again—the *heat of fusion*.
Then you *still* have not supplied the energy needed to lift the material out of the hole. And it has to be well insulated to be piped because it’s surrounded by cold.
(People in colder climates have to shift ice off roads and driveways. Do you ever melt it and drain the water? Or is it easier to just shift it while in solid form?)
Finally, the ice is ductile and under high pressure: the hole has to be kept open by adding a liner as you go (in the manner of tunnel boring machines) or filling it with a dense fluid (in the manner of oil/gas wells). Simply adding fiber to the ice to make a composite will not be anywhere near strong enough. A back of the envelope calculation indicates a pressure of 2 MPa (13% of the Earth weight of a column of ice 15 km tall). Note that on Earth the glaciers are fluid at the bottom under pressure, and rock is fluid in the pressure of the mantle. The top (ultracold) will have the consistency of granite and the bottom (ultra pressure and warm) like roofing tar.
The best way to tunnel will the same as how we treat hard rock here: apply pressure to shatter it, then sweep out the pieces. Think about oil drilling bits as your model. You have the further advantage in that ice is rather light weight, so you can arrange for it to float in the drilling fluid. That makes it easy to keep the chips away from the working face when digging straight down.
Maybe you won’t use teeth or pressure to crack off chips, but can use radiation (microwaves or lasers) to melt small spots and crack the working face into chips without using mechanical wearing tools. But, you don’t have to melt the *whole thing*!
For *much* more on ice mantles in general, see [this talk](http://www.seti.org/weeky-lecture/convection-ice-mantles-effects-texture-and-anisotropy) in the SETI weekly colloquium series. Europa in particular appears to have a “cold, static lid”.
# summary
The advantage of melting is the lack of complex moving machinery. But you’re not talking about getting a small probe through the ice without leaving a hole; you want to leave a (rather large) hole as a perminant access point. So you *do* need complex moving machines to lay the liner, and material must be evaculated.
Melting requires significant amounts of power, and must be intense enough to not be carried off by surrounding material.
I suspect that different techniques will be applicable at different depths, and you may include *cooling* the deeper part to stabilize the material!
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## First, to reach the ocean, is it more practical to melt down through the ice, or drill it?
The Russians drilled a hole 4 km down to Lake Vostok. They used a [drill](http://www.astrobio.net/topic/origins/extreme-life/breaking-through-the-ice-at-lake-vostok/). The technology they are using is prefectly capable of drilling a similar borehole on Europa.
## Would it be practical to build habitats mounted on the underside of the ice, in the water, or would drilling rooms within the ice be easier?
In [this](https://worldbuilding.stackexchange.com/questions/56606/building-materials-on-europa/56788#56788) question I calculated the water pressure at the base of a 20 km thick layer of ice at 237 atm. Since hydrostatic pressure scales linearly with depth, at 10 km thick, pressure would still be 118 atm, equivalent to 1250 m in our ocean. Modern submarine are rated to a pressure of about 500 m. Assuming that transportation cost of materials is a significant factor (i.e. moving all that structural alloy from another moon/asteroid, then down a 10–20 km shaft), it is probably not worth making a large permanant living structure that deep. Humans need a lot of air space at 1 atm to live comfortably, and that is very expensive to make available.
Also in that other post, I calculated radiation exposure. 10 m of ice is really all you need, so there isn't a lot of value in going too deep.
## If melting/drilling a tunnel down to the ocean, would it be possible to passively leave this borehole open, or would the pressures cause the ice to flow together again?
Ice has a viscocity. From this [textbook](http://www3.ul.ie/fowlera/courses/geo/chap10.pdf), the viscocity is about $2\times10^{13} \text{Pa}\cdot\text{s}$. This means that an internal pressure of $2\times10^{13} \text{Pa}$ will impart an expansion of 1m/s to an ice mass. 118 atm is about $1.2\times10^{7} \text{Pa}$, so the imparted speed of expansion will be $\frac{1.2\times10^{7}}{2\times10^{13}}= 6\times10^{-7}\text{m/s}$ which is about 5 cm per day.
The pressure of the ice on any structure made to hold the tunnel would be about 12 MPa. That pressure isn't excessive, but since ice is viscous you can't just put some support struts in there. The ice will ooze around it at 5cm a day. To put a cylinder in to maintain the size of the hole you need it to be.. well at least 10 km long. Too expensive.
The Russians drilling in Lake Vostok have similar problems here. Their hole is only 4 km, but since gravity on earth is higher, pressure is higher too, up to 350 atm at the bottom of the ice. They don't use a structure to maintain the hole, they simply melt all the ice that seeps in with a mixture of kerosene, freon, and antifreeze, and then pump it out.
This solution is a bit harder on Europa. Lake Vostok itself is about −3C, while the surface temps can be as low as −89C (coldest place on earth, incidentally). However, they don't drill in the winter so −20 to −50C is more like what the drill team sees at the surface. The surface temperature of Europa's surface is −160C, but the liquid ocean would be warmer than Vostok, based on the [phase diagram of water](https://www.google.com/imgres?imgurl=https://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Phase_diagram_of_water.svg/700px-Phase_diagram_of_water.svg.png&imgrefurl=https://en.wikipedia.org/wiki/Phase_diagram&h=591&w=700&tbnid=KZu7NDXMKfSPlM:&tbnh=160&tbnw=189&docid=gNswwOMUqqr4pM&usg=__NkBcJn1_gk-ndiZc_YTTgI10nWU=&sa=X&ved=0ahUKEwjehb3UjLbPAhWJez4KHX6bB5sQ9QEIIjAA) and anticipated pressure of 12 MPa.
## What kind of engineering would be required to keep the borehole open, assuming my colonists want an elevator to the surface.
After drilling is complete, the hole is kept open by pumping an anti-freeze solution around the edges of it to melt it. The anti-freeze interacts with the ice, lowering its lowering its freezing point below whatever temperature the ice is at. The rate of ice encroachment is relatively small, but since the shaft is big, the amount of ice to be removed is large. Assuming 2.5cm on average of ice encroach along the entire 10km length of the shaft, and with a 4m radius borehole, 12600 m$^3$ of ice must be removed every day, or 12 million tons of it. Fortunately, by melting the ice with anti-freeze and letting it flow to the bottom of the hole by force of gravity, the flow rate of 0.14 $\frac{\text{m}^3}{\text{s}}$ is not unrealistic. That would take 4 standard, [3" firehoses](http://www.qrfs.com/3-Single-Jacket-Mill-Hose-125-PSI), and is about 50% more than you can get out of a [single fire hydrant](http://www.southsaltlakecity.com/uploads/documents/%5E_Fire_Flow_Calculations.pdf).
The biggest engineering challenge is removing the ice that is collapsing in the top half of the ice sheet, where the temperatures are closer to −160C than zero. No anti-freeze is going to work at those temperatures; car anti-freeze freezes at -40C, and alcohol at -110C. The anti-freeze itself will freeze. Some sort of heating system will be needed. It would be much more effective, once the borehole is dug, to maintain it from the bottom, since that is the warmer side of the ice, and since gravity will pull melted ice down into the warmer regions without need for pumping; you only have to pump antifreeze and not melted ice too.
So you basically have to pump your heated anti-freeze solution from the base of the ice sheet to the top, and recover it at the bottom, separating the antifreeze out for reuse, and presumably dumping the water/ice into the ocean.
Pumping up is a big issue, due to [shutoff head limits](http://www.engineeringtoolbox.com/centrifugal-pumps-d_54.html) for centrifugal pumps. I deleted the math as extraneous since this post is already forever long, but, suffice to say, a centrifugal pump, which is good at high volume pumping, will not get the pressure you need. However, any good pressure washer can get the pressure you need (3000 psi = 204 atm) and they do this with positive displacement pumps. So you will need some enormous positive displacement pumps; flow rate has to be relatively high or your heated antifreeze will cool and freeze before it reaches the service. Not an impossible engineering challenge, since I have seen them. If you want 200 gpm of 3000 psi reciprocating positive displacement pumps, you will need about 400 kW of electrical power, based on the pumps I've seen.
So that brings us to generating both a.) enough heat to unfreeze a 10km hole and b.) enough power to run a 400 kW electrical load forever; for reference [this](http://www.generac.com/all-products/generators/business-standby-generators/commercial-series/100kw) is what a 100 kW diesel generator looks like and c.) doesn't take a ton of fuel. The solution with today's technology is a nuclear reactor. Fortunately, they already have them in submarines, so it's not too much to ask for to bulk up the pressure hull to handle higher pressure, and install one at the bottom of the ice to keep the hole open. Though, keep in mind, you can't assemble it 10 km under the ice, so the hole has to be big enough to get the thing down there in the first place. Also, you have to replace it every 10–15 years once it runs out of fuel.
## In conclusion
Most people would permanently live in habitats dug a few meters into the ice. This would give plenty of room for expansion by digging more warrens into the ice, without having to go into high pressure areas, and also keeping the colonists close to the outside world.
The hole would have to be significant. A submarine style pressure hull with reactor would have to be inserted into the hole. However, since the [smallest nuclear submarine](https://en.wikipedia.org/wiki/American_submarine_NR-1) had a pressure hull about 4 m in diameter, the size doesn't have to be unreasonably large. Maybe an 7 m hole and a 6 m pressure hull with nuclear reactor and ice melting equipment. This could be operated remotely, its not a threat to human life if the hole closes if there are no people below the hole. The worst you have to do is re-drill the hole.
In fact, I don't anticipate humans going down the hole at all, too dangerous. Just some construction-bots to install your ice-melter and some submarine-bots to explore. Maybe an [Alvin](https://www.whoi.edu/main/hov-alvin) for exploration, but you'd never want to try to dock and transfer people to the ice-melting hull at 12 Mpa.
[Answer]
when drilling/melting a hole in such a cold environment one important factor is time taken for the new ice layers to form. So the process should be as quickly as possible or we could figure out ways to prevent ice sheets from forming in a localized area.
>
> Ice forms When the water molecules move slowly because of low energy
> and it is easier for them to hook on to each other by sharing
> electrons. when salt is added salt molecules arrange themselves around
> the water molecules like little fences and keep the water molecules
> from hooking together. But if it gets cold enough, about 28.5 degrees
> Fahrenheit or -2 Celsius, ocean water will freeze too.
>
>
>
**source**: <http://quatr.us/chemistry/atoms/ice.htm>
So If we are able to build nano structures that can prevent water molecules from hooking easily while staying localized to that particular area and be degradable easily after sometime. Then we just have to put the nano material and wait without worrying of contaminating alien environment. There have been some research going in [this](http://www.livescience.com/8947-cool-tech-materials-prevent-ice-formation.html) area
[Answer]
There have been reports of cryo-volcanoes and water ice geysers coming from Europa, most likely caused by cracks in the ice due to tidal forces.
It seems that rather than trying to drill through the ice the simplest thing would be to wait for natural crevices or other openings to form and then move in through them. Even if not naturally wide enough they would provide a starting point to help the drilling and the flow of water would carry away drilled ice.
Of course this would be risky as if the crevice started to close the forces involved would be immense, but that is a hazard faced by any attempt to penetrate the crust. Most likely we would be sending through unmanned vehicles, in which case they could be made small and just inserted through the crevices and cryo volcanoes directly with no need to drill at all. Some sort of swarm system with members of the swarm stopping at intervals to act as communications relays would make sense.
[Answer]
One thing which the other answers overlooked is the need for getting below the ice as quickly as possible. The immense radiation fields around Jupiter make this imperative, since humans and unprotected electronic devices will receive a lethal dose of radiation in a relatively short period of time. High speed is essential.
Because the ice is going to be as hard as rock on the surface, due to direct exposure to space and heat energy rapidly radiating away, there are a few possibilities. This [technique](http://www.nextbigfuture.com/2015/07/drilling-10-times-faster-than-ever.html) uses high speed projectiles fired down a tube to strike the working face at speeds measured in kilometres per second. This sort of energy would shatter rock. In the case of ice, it would shatter the ice and possibly melt the walls of the tube, providing an impromptu smooth surface to lay down the actual tunnel walls (for insulation and to economize on materials, a foamed material made from silicate rocks imported from another Jovian moon should suffice).
[](https://i.stack.imgur.com/q9NM4.png)
*Ram Accelerator schematic*
Hammering the ice like this has a disadvantage in that there will be large areas of cracked ice radiating away from the tunnel exterior. This broken ice may eventually "flow" back together from static pressure and the action of the Jovian tides, but that is both long term and does not have the sort of quality control that engineered solutions havre.
As an alternative, if the spaceships and landers have fusion or nuclear drives, the power of the exhaust could be used to rapidly melts through the ice. The jet of plasma will rapidly melt through the ice, and one issue would be the venting of clouds of steam released by the process, or protecting the dismounted engine assembly while it cuts through the ice. Conceptually, the engine could be held in an articulating frame which grips the sides of the tunnel and can point the exhaust plume in the desired direction. After the ice has melted and the steam cleared, the frame can be "walked" by moving the supporting legs, while a "finishing machine" follows and lines the tunnel. This method also allows the device to carve larger chambers in the ice, once sufficient depth was reached for radiation protection. The frame can be swivelled so the exhaust plume moves in a cone or spiral shape to excavate larger areas under the ice.
[](https://i.stack.imgur.com/ccrGC.jpg)
*If a small plasma cutter can rapidly carve through steel, ice should not be an issue*
While there will also be a problem of cracks radiating away from the tunnel or opening, the heat energy should be able to create a relatively thick wall of fresh ice, providing support until the engineers can stabilize the area with "Rock bolts", injecting hot water like grout to fill and seal cracks (something like a giant Zamboni machine used to prepare ice surfaces at arenas), and liners installed.
To protect the tunnel from damage caused by heat leakage from the base, insulating the base from the intense cold and protecting the base from the inevitable movement of the ice, I believe the best solution there would be to have an inner liner with separation between the ice walls and the manned part of the base, like an insulated flask.
Several of these ideas could be used in conjunction with each other. The Ram accelerator could be used to drill pilot holes for the dismounted fusion engine to direct the exhaust plume. Extra holes could be drilled in parallel so when the main jet is used, steam can flow into the parallel tunnels through cracks in the ice and escape, protecting the driving platform from working in a steam bath. Even the meltwater could be pumped into forms and refrozen to create bricks of pure ice, free of trapped gasses and having no internal flaws or cracks. These ice bricks can then be used to create the initial liner of the tunnel, much like a barrel vault except completely circular.
Drilling is relatively well known technology. The difference here is you need to drill deeply and rapidly, in order to make livable structures in a reasonable time.
] |
[Question]
[
So I have a couple of stories I'm writing (I find it helps brainstorming better) and am wondering if magic can function quite literally as science.
In one of my stories, I have a character who currently attends a university for magic, but this character's world is nearly identical to our own except plus magic. Depending on the kind of genetic predisposition someone has, magic can be performed as general willpower- and intuition-based psychic powers (like telekinesis or pyrokinesis), channeling of a natural energy (akin to chi or chakra) based on skill, or incantations/spells and rituals based on learned knowledge.
If magic is regulated and already studied and experimented with, is it actually already a science? And if so, would I necessarily have to replace or remove traditional science with magic?
......
[Answer]
**Yes, and it did.**
Science is essentially just anything borne out of the [scientific method](http://chemistry.about.com/od/lecturenotesl3/a/sciencemethod.htm); however, good science typically adheres broadly to [scientific objectivity](http://plato.stanford.edu/entries/scientific-objectivity/) while following that method, which to put it tersely and not completely accurately, says the following:
* True claims are reproducible
* True claims are objective, not based on personal perspective or value judgements
* True claims are backed up by evidence
* True claims are internally consistent
Except for the first, these are not startling concepts. Reproducibility is as such the center of the entire scientific world. If you claim that water is flammable, then you are expected to provide not only your data, but your experimental procedure, so that we can be sure that not only are you being honest, but you didn't screw up the experiment or the calculations.
In fact, reproducibility is how science enforces the other three goals. If others can carry out the same experiment with the same results, those results are *objective*. The results then are solid *evidence*. For the experiment to be possible, it must be *internally consistent*.
So, how does this relate to your question? Because the scientific method was not always in use. Once upon a time, what we now call *chemistry* was *alchemy*. What we'd call *medicine* might have been known as *herbalism* or other names, depending on the region. Before modern science existed, people still worked within the fields we now identify with solid scientific names like chemistry, physics, and biology. They merely did not follow the scientific method. As soon as science came on the scene, the best parts of those fields we now often look down upon as pseudoscience actually became the foundations of modern scientific fields.
[](https://i.stack.imgur.com/Npbns.jpg)
Yet at the same time, while the scientific method might not have been in use, many involved had some idea of what constituted good practice. What sense would it make to claim you *had* converted lead into gold, if you could not show it? While such extravagant claims appear throughout history, the majority seem to not be taken seriously. The scientific method, while rigorously stated did not exist, is based on a degree of common sense which predated it.
If magic existed, it would be little different. If tomorrow magic suddenly existed in our world, then it would largely be considered absurd and unscientific - yet that is because of centuries of it being so. If it truly was happening, it would not take long for it to be seriously investigated, have the scientific method applied to it, and eventually end up being exploited to menial ends no differently than we exploit quantum physics to play Angry Birds.
Essentially, anything which exists can and eventually will be investigated scientifically. Magic is only in opposition to science in our world because it does not exist - at least by the standards I have laid down. As soon as you can make it reproducible, that changes. That answers the first question in that **yes, if you are already performing scientific experiments with it, magic becomes a field of science.**
As for your last question, the answer is a little more nuanced. As I said, magic would become another component of science as a whole. It would not replace it, just as quantum mechanics did not replace chemistry, even though it revolutionized physics. However, magic is, as a concept, incredibly broad and potentially powerful, and might have serious implications for other fields of science. If you can destroy entropy, the second law of thermodynamics ceases to hold. If you can teleport, relativity might break down. The exact nature of these implications depend on the exact nature of magic in your world, so I cannot answer them. I can say, though, **science as we know it would *adapt*, not be replaced**.
[Answer]
Of course it can work like science, **as long as it is predictable**, i.e. given an input, you will have known outputs.
Treating it like science ("you can study it and it makes sense") and engineering ("you can learn it, no innate shit") is actually a very good thing to do, since it "makes sense" and so **makes your world more believable**, as opposite to "just random stuff hihihi" like many low-care settings do.
You may **consider it an area of scientific study**, like there is biology, chemistry, etc. I have no clue why you suggest "replacing" science with magic, however, since it doesn't make much sense. It would be just another field of study, among many.
[Answer]
In this context [Clarke's third law](https://en.wikipedia.org/wiki/Clarke%27s_three_laws#Third_Law_and_variants) has to be mentioned:
>
> Any sufficiently advanced technology is indistinguishable from magic.
>
>
>
This seems to be the other way round but it still explains the same thing. An advanced technology seems like magic to some. Magic that can be explained can't be distinguished from technology. Where would be the main difference between (scientific) bioengineering and witchcraft with plants? They are both about the same subject. They probably both use the same methods. But even if the witch does things that are not explainable by science yet it can still be a subject of science. Neuroscience can't still explain everything that happens in the brain but we don't try to explain processes that we don't understand with magic.
So the law has been reversed for fictional universes:
>
> Any sufficiently analyzed magic is indistinguishable from science!
>
>
>
The one thing you have to avoid is to fall into the trap of creating [moron characters](http://tvtropes.org/pmwiki/pmwiki.php/Main/MedievalMorons) who believe everything they don't understand is magic:
>
> Any technology, no matter how primitive, is magic to those who don't understand it.
>
>
>
It may be magic, it may be technology (or science). But when shown such most people won't stand there with the mouths open.
[](https://i.stack.imgur.com/7DKJZ.jpg)
Normal people try (and tried) to explain it, to fit it into their world view, or just ignored things they don't understand. So, to answer the question, as magic can be and **is** a normal subject of science you don't need to remove or replace science. Stories that try to keep magic out of the science complex tend to be very unrealistic or exaggerated - and typically fail. Someone does something that others can't? It is random? Well, you *still* can and will try to explain it, the circumstances, the prepositions, the effects. There you go, science.
[Answer]
Yes, you can treat magic as a scientific discipline, but you have to do it well or it makes your writing look bad. Perhaps the best discussion of the topic I've seen comes from Brandon Sanderson, who is famous for creating stories with strongly rule-based magic systems and then analyzing what can be done with them. His thesis is stated as [Sanderson's First Law of Magics](http://brandonsanderson.com/sandersons-first-law/):
>
> An author’s ability to solve conflict with magic is DIRECTLY PROPORTIONAL to how well the reader understands said magic.
>
>
>
He says that generally speaking, there are two basic ways to deal with magic in your writing: give it strong rules that the reader (not just the characters!) can understand, in which case it can be used as a neutral storytelling tool, or keep it "mystical" and deliberately loosely-defined, at the cost of not being able to be helpful without looking like a deus ex machina. (Deus ex magia?)
He calls the first style "hard magic" and the second "soft magic", essentially a direct reference to "hard" and "soft" sci-fi, and points out that both styles can be quite successful, pointing to *The Lord of the Rings* as an exceptional example of soft magic. But because LOTR is soft magic, magic can't be used to resolve conflicts--though of course it can always make things worse for our protagonists. For example, when they have Gandalf hold off the Balrog with his magic, they end up losing his guidance for a major part of the story. (This is also why you can't "just have Gandalf fly everyone to the volcano on giant eagles;" it violates the convention and would ruin the story.)
In "hard magic", on the other hand, if the reader knows the rules and is able to follow along, then he doesn't feel like the author's pulling a fast one when the protagonist uses magic to solve a problem, because it makes sense that he can do that. He uses Spider-Man as an example, even though his powers aren't technically magic, because it's an example that will be (presumably) familiar to all readers: because the audience knows that he can shoot webs, sense danger, cling to walls, and has superhuman strength and agility, "therefore, we’re not surprised when Spider-man shoots a web in a bad guy’s face. We’ve established that he can do that, and it makes sense to us when he does it. It is narratively a Hard Magic system, rather than a Soft Magic system."
To give an idea of what not to do, one example (my example this time, not Sanderson's) of hard magic done badly is *The Sword of Truth*, in which the magic working by strict rules is basically an [informed attribute](http://tvtropes.org/pmwiki/pmwiki.php/Main/InformedAttribute): we're told, over and over and over in the story, that there are very strict, well-defined rules that magic works by, and several of the characters clearly have a very good understanding of those rules, but they are never explained to the audience, and so when, at the climax of several of the books, Richard resolves things by suddenly figuring out how to work some magical marvel, it ends up feeling like the author simply [extracted the resolution from his nether regions.](http://tvtropes.org/pmwiki/pmwiki.php/Main/AssPull)
[Answer]
Science is nothing more and nothing less than building models on a certain level of abstraction. You observe stuff in the past and try to predict how stuff will behave in the future. This is true for the natural sciences, but this is just as true for the human sciences or social sciences. Now, the important thing to realize is that building a model can **not** explain anything. Science is just building a black box which attempts to give tools how to control certain outcomes.
Either way, in regards to magic this means that:
1. **Yes**, it can be studied by a science
2. **No**, it needs not be predictable. As long as there is *any* relationship between what you do and what the result is science will try to model it, no matter how unpredictable and choatic it is. Take for example something like psychology, humans can be predictable in certain situations, but in general I wouldn't call human nature predictable. And the same goes for something like quantum physics: It's totally not predictable, but it definitely is modellable.
3. **No**, it can not be treated as a science, just like humans or machines are not a science themselves. Reality comes first and science is just trying to describe reality. To give an example: Gravity doesn't exist in any absolute sense of the word exist, it's just a name we have given in our physics model to a certain *imperfect*1 rule in our model. A science studying magic would create a simplified model of magic which will be (likely2) great for people learning magic. Concluding: You get both magic (the subject) and a science studying magic (magicology maybe?).
## Notes
1 Imperfect, because it's a simplification. For example, a statement like 'we drop this apple in a perfect vacuum and calculate how long it takes for the apple to move from A to B' sounds reasonable, but in reality a 'perfect vacuum' doesn't exist (neither in deep space, nor in a lab) and in any calculations we're more than likely to ignore the nihilistic quantum physical chances of stuff happening to the Apple which in theory could affect the velocity of the Apple. And that's fine, because all we care about is 'good enough' and 'usable', but understanding that all rules in an abstracted model are necessary imperfect can result in a far better treatment of the magical sciences.
2 Just likely, because for example if you wish to become better in interacting with humans you're better of just practicing it directly rather than studying psychology or sociology. Not to say there is no place for a scientist studying human interactions, but sometimes science can give us very valuable models at a macroscopic scale, but still only marginally help with controlling the subject of its study at a microscopic scale.
[Answer]
I've posted several times here on the theme of "real" magic in a universe that includes it. The difference from science would be the *teleological* nature of the laws.
[Science, Religion, Magic: Can they be maintained in equal and parallel opposition?](https://worldbuilding.stackexchange.com/questions/17404/science-religion-magic-can-they-be-maintained-in-equal-and-parallel-oppositio/17422?s=2|0.1603#17422)
>
> if physical law were teleological, an attempt to understand physics would be more like psycology or politics. It would have more in common with Madison Avenue than Mathematics.
>
>
>
[What might be dangers of connecting your own soul to a stronger soul?](https://worldbuilding.stackexchange.com/questions/13149/what-might-be-dangers-of-connecting-your-own-soul-to-a-stronger-soul/13653#13653)
>
> Underlying laws should be simple and "dumb". Making value judgements is not going to be fundamental.
>
>
> Quantum mechanics doesn't know about the boundaries of macroscopic objects. We can't describe some special rule for whales because an atom doesn't know where a whale ends and the water begins, or that a particular collection of atoms is a whale.
>
>
> So, rules need to apply to the smallest things, and know only about context in the same level being described. There are exceptions that are appoximations of emergent behavior: quasi-particles apply emergent behavoir of a large system back to primitive level quantum field theory.
>
>
> Magic, as commonly understood, would need to be driven by human brains, or the minds of gods that work like ours. Why would weather, for example, act in the manner of primate social behavior?
>
>
>
] |
[Question]
[
**The City itself**
Let's assume we have a city of the size of the [Peloponnese](http://en.wikipedia.org/wiki/Peloponnese) (round about 22'000 square kilometers) which is very dense populated (by medieval terms) and is isolated from the rest of the world (think of something like an ocean surrounding the island). The city wasn't 'planned', it just grew bigger and bigger so the city layout itself is a bit flawed (e.g. bad street layout). Let's for simplicity assume there is enough food for (nearly) everyone.
**The Population**
All citizens use the same common language, although many dialects do exist. Nevertheless it's a multi-ethnic population with different religions an different customs. Sometimes the tension between these different culture groups leads to nasty crimes but all in all the situation could be considered as stable. Wealth is distributed pretty bad (as usual) but there is no particular cultural group having a much greater share of wealth than the others.
**The Government**
Now that’s the questions. I'd like to have a central ruler sitting right in the middle of the city. Given the size of the city, a direct rule however is deemed to be impossible. Therefore, a greater deal of decentralization appears to be required.
**Ideas so far**
***Feudalism***
This is the first thing I had in mind: Have a single king with multiple vassals, which in return have multiple vassals themselves. You get a high decentralization with an acceptable control from the central government/ruler and you get a decent degree of stability. Feudalism also allows for some interesting storylines regarding counts, bloodlines and similar stuff. There are some fatal problems though...
* Feudalism was built on an agricultural society. The lower vassals had a large mass of peasants beneath them. Feeding people was hard so agricultural land was expensive.
* Feudalism needed a constant change in borders. The liege gave its vassals land in return for favors or good work which the vassals children inherited on death. Works fine until you got no more land to distribute. I'd like to dispose the idea of the civil war emerging every 100 years because the vassals get greedy for more land or the idea of extreme balkanization of the city until every citizen is a landlord himself.
***'Mayorism'***
This approach features more bureaucrats and fewer nobles. Each district has a mayor and a smaller council designated to govern the pile of land he's been assigned with. A mayor is not of noble blood but excels in administrative skills. Each mayor may rule until death, after which he is replaced by any other administrative professional from anywhere, or until another person has been assigned to do his job (because the former mayor was incompetent, corrupt or....). There are no elections for the mayor as we don't want the citizens to get a taste of democracy and get uppity against the crown-authority. Up to this point the system would prove pretty stable, but here are some problems:
* The king most likely has better things to do then to assign each of his thousands of mayors day to day anew. Like in feudalism he'd install multiple layers of administration, that in the end a group of let's say 10 people assign the jobs for him. This would then lead to a concentration of power in the hands of very few people which in return could get come to the conclusion a council of ten people is better than a single king.
* Bureaucracy was on the rise late 17th or early 18th century which is clearly not an option for a medieval based setting. Writers in ancient Egypt did a similar job and different empires had different people doing the same job too, but all of them used a more or less centralized approach. Using common people for administrative jobs became fancy after bourgeoisie was on the rise and enlightenment was more widely accepted.
*EDIT*
As there were many question regarding the city.
First of all, it’s a fantasy setting. The size is absurd, but that’s what it’s all about and that’s why it’s interesting in the first place. No some answers:
**Underground caverns/tunnels**
Get yourself some underground cave system with some tasty mushrooms and some solid building material to mine. If you’d go crazy you could use your poo to fertilize the mushrooms and build underground farms etc. but I’d rather like to keep the details out of here. Just dig down, eat mushroom and be happy. One could also dispose corps into catacombs. The risk of plagues a heavy disease is still high, but on the other hand side a city of that size probably won’t be a nice place in the first place.
Constant mining may also lead to parts of the city to collapse into the depths below, requiring the city to be constantly being renewed.
**Outer world**
The city is isolated because there is virtually nothing out there. Total wasteland, nuclear fallout, giant metal dome, isolated island – you know what I mean. Nobody wants to go outside, because there is nothing to go to.
**How to maintain order**
Having a high revolt risk and a high population density some nasty uprisings should be pretty common. But then again it’s not utopia. The ruler keeps an entire army to keep his citizens ‘happy’. In other words were maintaining order with shock and awe. No bad intention here from the ruler, but the alternative is anarchy which is probably a lot worse
**How to communicate**
This is a problem for sure. Even if you’d use a mounted express line as suggested (which is exactly what I was planning to do), getting through the crowds will prove rather difficult, even if the horsemen were ruthless and wouldn’t care about the citizens surrounding them. An alternative for must-receive-immediate messages are carrier pigeons. However getting a message delivered in a matter of hours shouldn’t be as important as getting the message in a reasonable time. Sending messages in the middle age took it’s time too. In fact, waiting for messages was most common for that time. Governors would need to be able to take care of themselves (and their realm) without getting orders constantly from the central government.
[Answer]
So I will write the dissenting answer here and simply say **it is not possible.** Ok it won't be that simple I have to explain...otherwise I would just comment.
Some of the problems have been listed in other answers so a nod to those folks.
**Issues**
* First and foremost the isolation aspect. A city that size would not be able to support building itself in the first place. The amount of wood, stone, clay and other building materials needed would destroy the habitat and the resources would disappear.
If we skip the building aspect there are still a whole host of problems.
* Food and water. Where does it all come from?!? Keep in mind that the water recapture and agricultural technology we have today is not available...and even today the largest metropolitan area in the world is only: [36,000,000](http://en.wikipedia.org/wiki/List_of_metropolitan_areas_by_population) If we accept @Royal Canadian Bandit's 790,000,000 person estimate that puts you at around **twenty-two** times larger.
* Waste and pollution. No powerplants, no electricity, no modern sewage removal, no running water. People in the medieval era were completely filthy from King to peasant by modern standards. If this city existed it would be rife with plague...and then where would the bodies go?!?
* Infrastructure, communication and transportation. The magical food arrives...how do you get it from the fields to the center of town? It would take days to get food to the center of the city not to mention there is no refrigeration so it would be rotten by the time it got to consumers in many cases. Communication would be virtually impossible, especially since you mention the city is not well laid out. IF there was a planned city with major thoroughfares then MAYBE you could effectively communicate but still...at horseback speeds you are still talking several days to traverse the city.
* Bureaucratic nightmare. How many city employees would you have to have to run this place, let alone maintain, build and expand. The response time of a government managing a city this size would be so very very very slow. It could take two weeks for a problem to traverse the city and layers of leadership to get to the supreme honcho man.
**Should it be done...**
If you simply must have this city, it demands magic, and not the kind where we have to discuss conservation of energy etc. The magic is necessary for a couple things.
* Raw materials...you need so many you need to be able to conjure them out of thin air essentially. Same goes for food and clean water.
* Communication. To make the bureaucracy, particularly the upper levels, effective without modern communications technology you would need to be able to scry on a massive scale.
* Sanitation...I don't feel I need to elaborate here..but I will... *waves wand "crappus vanishicus"*
Combining powerful magic and a Romanesqe system of layered management would be my only suggestion...but even then the initial level of disbelief is going to be tough to overcome from a user/reader perspective.
**The numbers.**
[It takes 1.2 acres per person](https://answers.yahoo.com/question/index?qid=1006050210699) to support modern American dietary standards. I think we can safely assume that your in your medieval setting that standard wont be met so I am going to drop that down to about .9 acres per person. (1/4th less).
**TL:DR** At 790,000,000 people and .9 acres per person that results in 711,000,000 acres which works out to 2,877,314.91 sq/km...which is kinda why I started out saying... it can't be done. That is over 100 times larger than your total landmass...
If we drop it down to 2/4ths and go with .6 acres you are still looking at a total needed landmass of 1,918,209.94 sq/km...just for farming.
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The form of government will depend heavily on the history and economy of your city.
Ancient Rome had an [estimated population density](http://www.highbeam.com/doc/1G1-20586744.html) of 36,000/km^2. Your city of 22,000 km^2 would then have a staggering population of roughly **792 million**. Roughly speaking, this is the equivalent of crowding double the population of the modern USA into the state of New Hampshire; or similarly, the whole European Union into Belgium.
Since you specify that it's "densely populated" by medieval standards, this is an absolutely huge city.
Some obvious considerations:
* How do people eat? You say "assume adequate food," but where does it come from? 700 million people won't be fed with rooftop gardens and fishing the nearby seas. Are there massive food imports, or is there some sort of magical solution? Where does the food arrive, and how is it distributed?
* In a broader sense, where do resources come from? The city needs raw materials such as fuel, wood, cloth, and metal.
* What about pollution and sewage? If it's a medieval city, the smoke from 700 million cookfires alone might make it uninhabitable. I won't even try to address the logistical challenge of handling the sewage from that number of people.
* How is order maintained? If the citizens decide to riot, a very large and destructive mob can form very quickly.
* What relations (if any) does the city have with the outside world? Is it open to trade and visitors, like Victorian London; or closed off to outsiders, like Tokugawa Japan?
It is possible to govern very large numbers of people without modern technology -- China in the 19th century managed it with a population of between 300 and 400 million. However, the unique challenges of such a dense population would require an *extremely* stable and well-organised government. Feudalism seems unlikely to do the job. Some sort of highly centralised bureaucracy, on the model of medieval China or the Tokugawa shogunate in Japan, seems more plausible.
The figure(s) at the top of this government might be selected in all kinds of ways: A hereditary emperor, council of aristocrats, prime minister promoted from within the bureaucracy, or some other way.
**To sum up:** It would be best to think about this city's government from the bottom up. Who distributes the food, maintains the infrastructure, puts out the fires, and quells the riots? Once you have answers to these questions, you can work upward to the Grand High Exalted Overlord.
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Since the city grew organically you could assume a mix of low level spontaneous organization and high level dictates of the king melding to work together.
So at the low level you would have individual neighbourhoods that choose some of their number to represent themselves and handle administrative duties. If there is a heavy prejudice against democracy these representatives can be chosen by the next step up, but there is no real benefit. In practice such administartors would either be people respected by local community or deal with the people respected by the community. So barring an ideological reason it is easier to simply let people choose a small group, let that group deal with the commoners and their problems, as well as communication with the higher levels of the hierarchy. These councilmen would be assisted by locals chosen by lot or some other fair method in performing their duties and be responsible for keeping the peace and upholding the laws.
For example see [the Roman vicus](http://en.wikipedia.org/wiki/Vicus). In general, if it worked for the Romans, it is probably close to as good as you will get.
Due to the insane size of your city, you'll need lots more layers above this local neighbourhood level, but if you take the neighbourhoods to be equivalent of the medieval village, which the Roman vicus kind of was, you can use feudalism for that. This would probably result in a patchwork map of vicus owned by different patrons, but that is how it was in Feudalism.
Romans actually had a system of clients and patrons similar to feudalism that could be adapted to this purpose. And probably would be a better model than the medieval feudalism based on equippind mounted military forces. Such forces would be of limited use in an isolated urban area. So the noble families would more likely be based on commercial relationships?
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It's called a bureaucracy. Ever hear of Byzantine used as an adjective? The Byzantine Empire is renowned for it's bureaucracy it grew to manage/rule it's empire. A City of that size could run very smoothly as long as the wheels were kept greased (and many palms).
Delegation and splitting of responsibilities are the only way it even has a chance. after a couple generations the king would be mostly a figurehead.
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A historical/biblical answer that might work...
During the 40 years in the wilderness Moses is leading well over a million people through the desert, and he's just about killing himself trying to deal with all their squabbles and problems. So some of his key people come to him and say, "Moses, this is not good. You are wearing yourself out dealing with all these petty problems when you should be focusing on the big stuff." So they set up a system kind of like our modern judicial system. Captains over thousands of families, and under those captains over hundreds of families, and under those captains over tens of families. If there is a problem it would go to the lowest level, and if the problem was difficult it would get bumped up the chain to that captain's captain. The most difficult problems would get to Moses, kind of like a supreme court. And it pleased the people.
In your case, your city could be divided into districts with a district manager. Each district is divided into neighborhoods with an overseer who is respected in the neighborhood. The overseer is charged with keeping peace in his area. If the people have problem they take it to him first. If he can't handle it, or if the people don't like his decision they can take it to the district manager.
The district manager is in tasked with keeping his overseers in line and honest, dealing with the bigger problems brought by overseers, and responding to complaints that people bring against overseers. He would want to know if an overseer is overstepping, but wouldn't have much patience for false complaints.
If a district manager comes up with a problem that he can't deal with, or if the people don't like his verdict they can go to the king, with the understanding that they better have a really good case, because the king's time is valuable.
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As your city is so vast it is like an empire within an empire. I think you look at how ancient empires maintained control. Intelligence and soft power would be used a lot. They often controlled the courier or primitive 'postal' network which doubled as spies. This city would obviously need some courier network. You have already mentioned that the army is essentially royal or imperial, and that is under the direct command of the ruler.
You would want to keep the army happy like dictators do, but also diffuse their power a bit so you would want to keep different generals in competition with each other over various sectors of the city.
Strong centralized empires and rulers who want to maintain tight control directly appoint officials. This bypasses nobility and insures you have direct line of authority. So you would want your ruler to directly appoint your own governors or various district leaders.
Since this is a city, then you would maintain centralized control, especially of critical infrastructure. This is typically expressed in different settings by the central government having tight control over food, water, electricity, and basic resources. This is also how dictators maintain control. Your ruler would have absolute control of the critical infrastructure of the city and could cut power as well as other needs. You may also have tight control of surveillance if that technology exists, but if not then you would use couriers as well as spies among the population. Agents who are handlers can handle multiple informants, and a whole network of informants can be created.
Your king should control trade and commerce. Minting coins and currency would be under the control of your king. That way the coinage would reach all sectors of the city. All other currency would be suppressed.
Gateways between districts of the city and control of passage would also be important. Your king's government would control trade, taxation, and passage between sectors of the city.
Your king and his spymaster among others would be skilled in learning the informal networks of power in the city. That is who are the more prominent citizens, merchants, neighborhood leaders, elders, and others in each neighborhood of the city. You would make sure that your government and governors kept close track of these informal leaders. You could even institute a type of millet system for various ethnic groups if there are particular areas of the city where they reside and if they demand to be governed by their law.
Sci-fi often depicts governance over small cramped domains in space. The series Battlestar Galactica shows what control and rebellion in a small tight space look like as early on the government is primarily governing a few cramped ships. Babylon 5 also depicts a government over a confined space. Control of critical infrastructure is often a theme.
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## Magic... Magic for everything!
Magic is the only thing that can make your city work.
### Food and other raw materials
First of all, get a lot of [replicators](https://www.wikiwand.com/en/Replicator_(Star_Trek)). They will be essential for producing all foodstuffs and materials needed for maintaining the city and her population. It would make sense to conjure only raw materials and do not allow duplication of manufactured goods. Replicators do not have to be machines.
A sensible solution would be creating a network of temples that have replicators. You can choose between a machine, divine help, or magic-wielding priests. I would go with the latter.
### Local governing
Organised religion is great for controlling masses. Especially, if it is also in charge of food and other materials. Make your king the head of the church and use church hierarchy as an additional brunch of bureaucracy and spy network at the same time.
Supplement your church with any other system of governing to create some balance. I would go with something similar to [scholar-officials](https://www.wikiwand.com/en/Scholar-official) of the [Imperial China](https://www.wikiwand.com/en/History_of_China#/Imperial_China). They would be perfect for maintaining cultural unity and common language. They would also take care of standards, local regulations, local disputes, etc. Mandatory rotations will prevent them from gaining too much power.
Keep churches, scholars, and local populations demilitarised. Make military service a privilege for noble born.
Organise all citizens into some kind of restricted societies. Medieval guilds are one of the possible options. Guilds would keep an eye on their members, take care of propagating standards, and maintain order within their ranks. Guilds are also great for *dīvide et īmpera* approach. If they try to become labour unions you can always bring some guns/cannons or just cut their supply of materials off.
### Communication
Magic will also solve the communication problem. You can opt for magical teleportation, or limit yourself to FTL magical communications via orbs, scrying bowls, mirrors, whatever suits your setting.
### Things to kill for and to die for
Obviously, in a world with replicators, the only things that will have a real value are magic and time.
You can keep the system more or less stable if only the ruling class can use magic. The easiest way to do it is to link magic with blood, i.e. only people born to two noble parents (to limit magical abilities of bastards) can initiate magic. You can also invent some kind of a ritual to 'activate' this blood bond/ability to prevent the unnecessary and inconvenient spread of magical abilities outside the circle of the Chosen people.
Time becomes even more valuable if only raw materials can be produced by magic.
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The answer is fairly simple: **give your ruler sole control of the magitech the city needs to survive.**
As other answers have pointed out, without some serious magic this city hasn't got an ice-cube's chance in hell of existing; a settlement of this size would require a colossal hinterland and super-advanced trade network to supply it with enough food and raw materials to sustain itself, which your question specifically states that it doesn't have. The question also states that there are nonetheless enough resources to go round, which presumably are supplied by an unspecified magical means. Given that you're already relying on this magic, when you fill in the details of how it works you may as well set some limits on its usage which ensure that it is under the king's control; **perhaps the royal dynasty pass down the knowledge of the resource-replenishing spell as a closely guarded family secret, or maybe there is one artefact/entity in their possession which enables the magic.** If this is the case then it will be possible to maintain a basic level of order in the city despite its size and complexity, because if the population try to overthrow the king he can just turn off the magic and starve them rapidly to death.
The king will still need a sizeable political apparatus to distribute the fruits of his magic and translate his colossal power into everyday policies, of course. I second the other answers which recommend a bureaucratic solution rather than a feudal one. There are in fact pre-Enlightenment models for how bureaucratic administrations could administer roughly comparable populations in the Chinese and Roman Empires. **Look up the Chinese 'ever-normal granary' system or the Roman 'cura annonae'** for some ideas about how state control of the food supply (in your case, generated by magic instead of agriculture) could be used as a tool to promote stability and control.
I actually think that your polity has reasonable prospects for success; it has no external enemies, no crippling internal faultlines, and I am a little confused as to why other answers cite 'communication problems' as a massive issue. Yes, you won't be able to pass messages from one side of the metropolis to the other as quickly as you could in a real-life tiny medieval city, but (even without any extra magic) it will still be much easier to maintain contact with all parts of the realm than it would have been in most medieval kingdoms and empires. **Concentrating the population makes communication and administration easier, not harder**; it wasn't concentrated on this scale in the real middle ages because it was logistically impossible, but as we've said, this problem has already been magically erased. Running any polity of this size will always involve a large degree of delegating and a certain amount of unavoidable chaos, but it can be done.
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## The Seven Sevens
As a lot of people have already pointed out, your city is absolutely enormous an virtually impossible to be physically maintained. That's not the question though. The question is how you govern a city that size. The answer is by stratifying the country into distinct social classes determined by your political station.
At the top, you have the God Emperor, King, President, whatever he's calling himself this generation.
He rules over everything because he's the king and everyone under him belongs to him.
Specifically, however, only seven men (or women, maybe it's not a patriarchy) report to him. These are your First Sevens.
Each First Seven has seven Second Sevens that report to them.
Each Second Seven has seven Third Sevens that report to them.
...
If you see where I'm going, then with a little math you'll see that there are 7^7 Seventh Sevens. In other terms, there are 823,543 of the lowest level lords. With a population of roughly 792 million people, that leaves roughly 961 peasants to be ruled by each lord. That's incredibly manageable on the lowest level, and the king only needs to get involved if things can't be handled on one of the seven lower levels of governance.
As far as keeping nobles from revolting, that's why there's seven of them at each level. At the highest level, any upstart Seven would have to secure the support of 3 other Sevens without arousing suspition of dissent. At the lower levels, the number of dissenters required to create a legitimate threat increases exponentially.
Truthfully, once any form of bureaucracy is well established, it's virtually impossible to unseat without a violent peasant uprising, and with each of the Seventh Sevens being responsible for no more than 1,000 souls, it's actually fairly unlikely that they will be particularly cruel to their people without being brow beaten by the other Sevens or murdered and quietly replaced without a fuss.
Hell, if you made the whole system a Democratic Republic where each of the Sevens is voted into power by the Sevens who they administer, then you've potentially got a system with better representation than most of the world today.
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I'm working on a story where the main character gains the abilities of a shapeshifter. In this case, defined as a human who can become any non-human animal, indistinguishable from the real thing, and retain his/her mental state.
Part of the story revolves around the character having to decide whether to share information about the ability with friends and family. Perhaps a situation where the ability must be explained or the character risks losing a love interest.
What are the possible larger outcomes if the secret leaks?
I've already considered the following:
* Scientists and doctors wanting to perform examinations to understand how the ability works.
* Government wanting to capture and keep the subject hidden, for study and possible exploitation.
* Religious organizations declaring varying stories ranging from the protagonist being god-like and revered, to evil and requiring destruction.
* The [HBO television series "True Blood"](http://en.wikipedia.org/wiki/True_Blood) hints that there might be groups of people who view shapeshifters as a threat and seek to kill them.
I'm interested in some plausible, realistic consequences of public knowledge of the existence of a *bona fide* shapeshifter.
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I think the most "natural" reaction from the US government if the information spread would be to put the shapeshifter in a laboratory and try to find out where the ability comes from. They will try to persuade him to go willingly and if it doesn't work, they will try to take him by force. That's where the storyline interferes with how the society sees him: Does he really want to help his country? Or maybe the country is the bad guy here and the shapshifter escaping the military becomes some sort of a lower classes hero? And what if he or she isn't a US citizen, but - let's say - an Iranian or Russian?
Also, if the ability to shapeshift is tested under scientific methodology then you have to think through where it really comes from - and it also can affect the way people will think of the shapeshifter. Let's say he's Indian and the ability seems to be magical. Then the hero will start to be perceived as a sort of a demigod in his fatherland. Someone who just has to help them, fight the corrupt government, right the wrongs, etc. And if he's just a regular American citizen... well, there are still lots of religious freaks who would think of him as an Antichrist.
And if the ability is scientific and reproducable, the governmet will try to use it to create supersoldiers or animal shapeshifting companions - imagine a dog, trained and obedient, who can shapeshift into a lion at a request. As good or better as a supersoldier and without any moral mumbojumbo about not killing people without good reason.
That could create political turmoil, as well as protests of organizations concerned with the government's rights to treat people like that.
On the other hand, there will be pressures to commercialize this. On the biological level shapeshifting might be useful in treating malfunctioning organs - after all, during the shapeshift the whole body changes, so maybe we will be able to use it to reshape and fix just some parts of the body. And even without this clear advantage to the society, I'm sure soon one of multimillionaires will want to be a shapeshifter too and willing to pay huge amount of money to get the technology in his veins.
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I third the paranoia/spying angle. I think it's an important angle but it's been already well addressed.
In the short term I think a big one is disbelief, lots and lots of it; and not unreasonably. If my sister showed up at my house right now, told me she could shapeshift, and did it I would *still* assume that it was an elaborate hoax. Shapeshifting violates so many laws of science that disbelief, even after seeing it once, is actually the logical response. I would insist my sister change into multiple shapes, while I was touching some part of her skin to feel the change, and swear up and down it wasn't a hoax before I would even begin to accept that it was true, and even then my next step would be to contemplate my own sanity and ask at least one other person to verify that they see my sister and she isn't imaginary while I look up schizophrenia. And that is coming from a reasonable person with first hand experience from someone he trusts.
Anyone that doesn't see the shapeshifters is going to believe they are fake. You can publish all kinds of videos, they will be claimed to be faked as well. Look how much people still disbelieve thing like the moon landing, which are completely possible and people don't claim violates physics, to imagine the response. There would likely be a whole culture clash over those that believe and those that don't believe these shapeshifters are real, and the majority will fall in the 'don't believe' category without absurdly strong evidence.
On a different front, I think that people misrepresent the 'want to study' concept. When someone with strange powers shows up they are always afraid of being 'studied' by being shoved into a cage and slowly dissected. The medical and scientific community would be amazed and fascinated by this, but not suddenly turn evil. We have an absurdly large number of rules we abide by in studies that won't change because something is a scientific curiosity. For that matter there is no reason to dissect someone. Even if your completely amoral and have no laws constraining you the fact is that dissecting someone isn't a very good study method. The studies would invariably spend years on preliminary non invasive and simple things with willing subjects. Unwilling subjects are very hard to study, you need their feedback. Frankly, study would be far more benign, and positive for humanity, then you imagine. Think shapeshifters as being payed very good money to shape shift into various rats inside an EKG one day, then to do some physical exercise as various animals to study the energy use. Maybe a 2 weeks study of caloric intake to see how various shapes handle calories and try to figure out where energy comes from. Good money for some non invasive and almost-fun tests.
Some other interesting angles, in brief:
* Worship or idolization, many gods WERE half animal in the past
* Re-imagining of animals and animal rights. suddenly there would be a lot more vegetarians, animal rights etc. If people can be animals this completely breaks and redefines the cultural divide we have between 'human' and 'animal'
* Rule 34...just...yeah you don't want to imagine the fetishes. I give it less then a week for someone to ask rather a shape shiftier can get an animal pregnant and what will develop if he does (along with a dozen other questions)
* Shapeshifting celebrities. Shapeshifting groupies, shapeshifting tell-all books etc etc
* Some paternity questions as to rather the shapeshifters are really someone's child. Maybe someone pointing out how well the mother gets along with Fido....
* Allegations of the government creating shapeshifters with everything from viruses and nanoteck to voodoo
* A race between governments to get the most shapeshifters on their payroll (for scientific reasons not military or espionage primarily! though of course espionage would happen too)
* People pointing out that a shapeshifter is a lethal weapon, able to turn into creature more dangerous then a gun at a moment. Some fear, some reanalyzing of self cary laws, more people carrying guns
* Bigotry. No shapeshifter will marry my daughter! That shapeshifter isn't a vegetarian, that's cannibalism! You're a shapeshifter; how can I trust you to not fly away (literally) with my money?
* Some people will suggest that shapeshifters can turn into other humans (even if they can't accusations will be made). This will lead to more distrust and uncertainty.
* The stock market will collapse. Seriously, fear and uncertainty hurts the market. this is so life changing that, if people believe it, it will start a collapse that will continue on itself. Look at the crash after 9/11, trust me shape shifters are scarier to accept then 9/11
And finally: realization that shapeshifting violates the law of conservation of mass, and thus thermodynamics. Use this to create perpetual energy, stop entropy and the heat death of the universe, completely redefine every scientific constraint known to man....what? you break physics a little you break it everywhere :)
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I'll just add one angle to your list that hasn't been done a lot in fiction: paranoia, with the possibility of widespread, culture-altering degrees of paranoia if this is a universe that has any significant number of animal shapeshifters rather than just the one.
On the most basic level, if I found out someone I knew well could turn into, say, a spider or a flea, I would have difficulty coping with this information. Philosophically, I'd be moving from a world where I feel reasonably secure that it's possible to keep some things private to one where Bob could be a spider on the ceiling watching me have sex without me knowing and with zero consequences. Ew.
Some people would take this knowledge better than others. Imagine, for example, Bob was a guy in your high school. Sooner or later, everyone's going to think of the spider-sex scenario and apply it to all of their secrets and all of the gross things humans prefer to do without an audience. In even that small group of people loosely connected to Bob, some people are going to have a pretty rosy view of humanity and think it's okay, some people will be realists and think about whether or not Bob has motivation to spy on them specifically out of all the people he might be spying on, and some will, in all likelihood, be inclined to paranoia anyway. Some people will try to put Bob out of their mind, and others will worry about the possibility of him watching every second of the day until they melt down.
All this would happen *even if* Bob was the best guy in the world and would never think of spying on anyone. Bob would be pretty lucky if nobody tried to murder him just to be able to believe in privacy again.
If anything, I might think someone in a very close relationship with your shapeshifter might take all this better, in the same way that you get used to compromising privacy when you're living with someone you for the most part like. People who know Bob peripherally would probably go the most crazy thinking about it, because they don't really know what Bob is thinking about them.
Lastly, inevitably, I would think at least *someone* would start developing religious thoughts about Bob, because frankly, if Bob could be watching you at any time, a sufficiently paranoid mind would start considering, as a matter of course, the possibility that Bob was watching any time they did anything shameful or gross, and from there it's a hop, skip, and a jump to the theological.
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>
> having to decide whether to share information about the ability with friends and family. Perhaps a situation where the ability must be explained or the character risks losing a love interest.
>
>
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The only time any of the negatives come into effect is when the love interest or the family or friends decide to rat out the shifter. Any number of secrets are held by families and friends from the government or society. Think of all the successful gays in the military back in the day. Then of course, the people who're ratting our your shifter would have to be believed (difficult to do). Might get the character on a watch-list, however.
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The ability to shift shapes into animal forms has some divine precidence. The Greek Gods used to do it all the time.
As for the social and cultural aspects of "coming out" as a shapeshifter, significant issues would include fear, envy and trust.
**Fear** A world-class karate champion who is single-shaped wouldn't stand a chance against an untrained shapeshifter who can become a grizzly bear.
**Envy** To fly like a bird, swim like a seal, run like a jaquar... who wouldn't be jealous.
**Trust** Keeping a human mind while looking like the family dog... the perfect spy! Who would trust anyone who could do that.
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This idea comes up quite frequently in science fiction, but there has not been a question about it yet on Worldbuilding.SE. **Is it possible that intelligent life was brought to Earth by an alien civilization?**
Would it be possible for these precursors to seed intelligent life here on Earth without leaving a trace, either archeologically or scientifically? Or put another way, how long ago would this have had to happen for us to not find evidence of it? By intelligent life, I mean that either the aliens directly created the intelligent life, or put in place a system designed to cause intelligent life to form.
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What you can do if you want no traces is to seed planet by microbes, and patiently wait few billion years as the complexity of the life increases. You come over every few dozen million years to see how life is doing and if it is evolving right.
If you get into some unexpected problems like gigantic dinosaurs ruling the planet so (supposedly smarter) mammals are surviving in small niches, you can orchestrate meteor bombardment to force rapid climatic changes, hard to survive for species overspecialized to be big and ugly. Smarter species will survive. Such bombardment leaves no traces of extra-terrestrial intelligence involvement.
Ice ages are another way to introduce changes, which give advantage to species better able to adapt. No traces on the planet if you can park your planet-shading spaceships somewhere away, like in Oort cloud (or different star system).
Why to do it? maybe for fun, or for PhD level terraforming degree? To see what other kinds of intelligence can evolve?
If you read about [forming the Moon](https://en.wikipedia.org/wiki/Giant_impact_hypothesis) by impacting old Earth, in just right time (for Earth life), with rock of just right size and just right material in just right angle, you may start wondering... :-)
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Seeding a planet with microbial life is easy. In fact, that's one of the standing theories for how life on Earth originated, a bit of space debris from some other life-bearing planet came near the Earth and some microbes migrated over and spread. We probably have the technology required to do so to other planets right now, though finding planets with appropriate conditions for their survival is harder. (Not to mention how absurdly long it would take for anything interesting to happen as a result.) Just put some hardy microbial life in a well-shielded, life-supported rocket and point it at a likely planet, more or less.
Planting **intelligent** life is much harder, at least if you don't want them to find out about it in short order. The problem here is the same problem faced by creationists in the real world; humans fit absolutely perfectly into the geological history. We know precisely where our species came from, where the species that our species came from came from and so on very nearly all the way to the base of the animal family tree. The only way aliens could have planted intelligent life is if they were capable of somehow falsifying our planet's entire geological record while also transporting every species the planet needs here or if they were capable of such fine and subtle genetic engineering that they could make humans fit in perfectly with the existing life with no telltale deviations. It would be easier to say that they came here, found the apes and "uplifted" some of them to sentience, though again you'd run into the problem of telltale deviations. It is believed that part of the reason humans have such large brains is because we possess a defective gene which, in other apes, causes the development of large and powerful jaw muscles and that lacking it gave our brains room to expand. The aliens could have been the instigators of that. That being said, the shear amount of observational data and computational power needed to determine the effect of that minor mutation would have been enormous.
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If you want to place intelligent life on a planet with an existing biosphere, perhaps the most feasible way would be to manipulate the evolution (or genome, for a more direct approach) of an existing species on that world. We know what animals we're related to, we've pieced together a family tree, and we know roughly when and where we've evolved. If we had come out of nowhere we'd have noticed a good while ago.
However, if they had picked a species of ape and manipulated it into us, depending on just how it was done, I'm not sure we could tell. There doesn't seem to be a terribly good reason for why putting apes on savanna would make them hugely intelligent. It looks like a freak occurrence. Intelligence on our level has not happened once before in the past several hundred million years the Earth has possessed complex life.
I don't intend to say that there's any reason to believe aliens were involved in our evolution in reality. There's nothing infeasible about our evolutionary history, and you can posit a lot of possible mechanisms for why we turned out the way we did. But my impression is it's probably a highly complex perfect storm of selection pressures, features specific to the species we evolved from, etc. We can suggest a great number of mechanisms by which it could have happened, but it's difficult to find out the actual truth so that we could point to a particular thing and say 'that's why we became intelligent'. As long as those factors are shrouded in mystery, it should be easy enough to justify alien influence for a story.
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To answer the question directly; I don't think it is possible "intelligence" was "brought" by anything; as an earlier answer details, the evidence is overwhelming that intelligence arose slowly over hundreds of millions of years. Our neurons are not functionally different than the million found in a fly or cockroach; we just have a hundred thousand times as many, far more complexly organized, and even then not very *much* differently than neurons in great apes. Mice and Corvids are "intelligent" and creative problem solvers.
A working definition of intelligence will help us: Not all scientists agree, but a pretty good working definition for AI researchers (including me) is that intelligence is the ability to form models based on observations that let us predict most likely states in the future or past. The more accurate and far reaching these predictions are, the greater the intelligence. Animals with less intelligence can be trapped by animals with greater intelligence; the fish doesn't realize what the hook shape will do in its mouth until it is too late; the human fashioning the hook shape does so with a model of how fish bite and behave, and a model of how the hook (like an arrow) can enter flesh easily in one direction but be difficult to pull out in the other.
In the "past" direction; we have forensics, or something like astronomy or geology: Intelligence, in the form of working models, lets us narrow down what must have happened, to either a singular event (e.g. a neutron star exploded) or at least a small set of possible explanations (e.g. Adam either killed himself or his wife murdered him and made it look like suicide).
Either way; consider it an ability to model interactions, predict the outcome of various interventions, etc. Then super-intelligent aliens may have **supervised** evolution and intentionally caused mutations they could predict would be key to developing future intelligence. That isn't "bringing" intelligence, more like "creating" it, or the conditions for it to arise.
The difference between causing seeds to be scattered on fertile ground, versus planting already sprouted seedlings.
To our knowledge there is some chaos theory that suggests **very** far reaching intelligence is not possible; there are too many confounding factors. So likely, if guided evolution is how we came to be sufficiently intelligent to create a civilization (however one might define that, but you know what I mean), then it could be "without a trace", because we have no idea where mutations come from. We think they are chance; but for a super-intelligent race, they may have chosen to mutate genes in ways that were specifically plausible but hadn't happened yet. Or they may have, opportunistically again, arranged certain "accidental deaths" to prune the tree into a shape they wanted.
I'd call that topiary: Some bushes sprout in many directions; but if you want the bush to look like a duck, you can choose to clip branching sprouts that won't fit into the overall pattern you see in your mind's eye. Darwin's *unnatural* selection model for livestock did exactly this: The mutations in the livestock were natural, but the human livestock managers terminated undesirable mutations, or at least did not let them mate, while desirable random mutations were mated extensively. Aliens supervising human evolution could have done something similar; with greater foresight into the ramifications of each mutation, both physically and socially.
[Answer]
Having trouble understanding your question. Define "intelligent life". Since the experts can't define what intelligence *is*, I'm doubting you'll have any greater success. (And I'm avoiding altogether the definition of "life"...) Intelligence isn't a "yes/no" property. Tool use dates back (in our genetic lineage) to somewhere between 2½ and 4 million years. So, sure, little green men could have come down and tinkered with our genes. Probably could still be doing it, although the vector(s) they'd be using would have to be more sophisticated. I don't understand why you think such interference/modification would necessarily leave traces? It wouldn't have to.
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[Question]
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Alright, we are in a medieval fantasy setting. In this setting, northern warriors (basically vikings or typical fantasy barbarians) have berserkers that use certain potions that make themselves stronger, called tonics. There are three main types.
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The first type fills the warrior with incredible rage and strength. Warriors under its effects feel no pain and may be injured, potentially fatally, and not notice or slow down at all until the effects wear off. The typical berserker rage. We will call this one the bear tonic.
Type two focuses the warrior and sharpens their reflexes. To the warrior, its as if time has slown down. They can react to arrows being fired the moment the archer releases the string and can see through any feint or trick in melee combat. The only limitation that a warrior has under this potion's effects is how fast the warrior can move normally. This is more like a focused berserker, one that can perceive pretty much anything around him. We will call this one the raven tonic.
The last one is what im having trouble with. While the bear tonic simply numbed the sensation of pain, it doesnt actually make the warrior's body actually resistant to damage. Injuries taken on that tonic are just as serious and deadly as without the tonic's effects. This last tonic does make it harder to be damaged. A warrior under this tonic's effect can take heavy blows and deadly slashes, and after the battle is done, they only seem to be minor bruises and cuts. Even slashes that are serious stop bleeding very quickly and fighters attacking those under its effect will find that their weapons seem to have more trouble getting their weapons to cut and stab deep, as if there is just more resistance when attempting to do so, like theyre attacking into a piece of wood rather than flesh. We will call this one the boar tonic.
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What im having trouble with is how the boar tonic actually does this. With the bear and raven tonic, these are effects that are (sort of) possible. Ive heard stories of people being able to lift vehicles off of trapped people in times of high stress, which would be similar to the bear tonics strengthening effect, and ive also heard of police officers being able to read the headstamps on the bottom of bullet casings as the casings fly past their eyes in intense shootouts, as if time has slowed down, like the raven tonic. These tonics are based of off effects that are at least believable.
But I dont know how anything could turn serious injuries into minor ones apart from dumb luck of people surviving accidents that they really should not have been able to. I thought that maybe it just creates an 'unconscious reflex' where warriors are dodging attacks in such a way that it turns serious injuries into more minor glancing blows and the warrior just isnt consciously processing that, but that sort of bleeds into the effects of the raven tonic, and id like for each of these tonics to be unique in their effects. So for the question:
**What does a potion that increases resistance to damage actually do to the body to make that resistance?** Is there a real bodily function that we have that helps us become more resistant to impacts and slashes before injury that this tonic can turn up to 11?
[Answer]
Alternative: Instead of reducing damage taken, it reduces the effect of damage taken. Namely by granting "fast healing". So normal bodily processes of healing and such, but they are supercharged. A sword will slash just as deep, but the wound will stop bleeding and start healing in mere moments and even start to scar over. The downside would be that any blow that would normally kill you instantly still does, you just won't die from bleeding out like you typically might. No "death by a thousand cuts" would be possible under the effects of this tonic.
This could be known as the Lizard Tonic (since lizards are known for their regeneration capability).
[Answer]
Increased/modified keratin production.
Keratin is the main structural protein that makes up your hair, nail, a rhino's horn etc. It's also present in the outer layer of your skin, making it more resistant to tears and cuts.
I could imagine a potion that would temporarily increase or in some other way change the user's production of keratin, making hair, nails and skin grow quicker and thicker for a limited period. There are plenty of examples of real world naturally sourced chemicals that will stimulate the production of proteins. Hormone therapy using estrogens taken from the urine of pregnant mares is an example that comes to mind. [Androgen supplements will affect you hair growth](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9788837/). A topical ointment, or maybe even a bath, could be an alternative to a potion that is ingested, as [transdermal delivery of hormones](https://en.wikipedia.org/wiki/Pharmacokinetics_of_estradiol#Transdermal_administration) is also a thing.
If you want to take things a little further, I'll just add that spider silk is a form of keratin.
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Something along the lines of giving the person scleroderma all over the body and perhaps on the vital organs for the duration of the tonic.
This hardens and thickens the skin which would mitigate against damage somewhat.
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Going to float three ideas here:
1. Lowering blood pressure by reducing blood flow to skin. In case of cuts you will bleed less. But the lowered pressure will have side effects that you absolutely don't want in a fight. You might be light-headed and have blurry vision.
2. That potion is just liquified butter. It doesn't have an immediate effect (other than making you sick, if you're not used to it). The idea is to become a human version of *foie gras* through prolonged use. Every extra layer of fat helps against damage. You need to develop subcutaneous rather than intraabdominal fat though, so you'd better train like a sumo wrestler.
3. That's not a quaffable potion. It's a non-newtoniam fluid (such as a corn stsrch solution) applied over the skin. It will reduce the impact of any weapon over the are you apply it over. A bottle will only cover an area such as the neck or buttocks. You would need a fill bathtub and bathe in it to cover the whole body, but then you would also be immobilized for a while.
[Answer]
**Boar tonic is blood coagulant and antibiotic**
According to [Battlefield\_medicine](https://en.wikipedia.org/wiki/Battlefield_medicine)
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> The most potentially survivable cause of death is hemorrhage from extremity bleeds, however more than 90% of 4596 combat mortalities post September 11, 2001 died of hemorrhage associated injuries.
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and according to [Medieval\_medicine\_of\_Western\_Europe](https://en.wikipedia.org/wiki/Medieval_medicine_of_Western_Europe#Battlefield_medicine)
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> As remains true on the modern battlefield, hemorrhaging and shock were the number one killers
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So to "increase resistance to damage" it would be most helpful to not let your soldiers bleed out. Here is an [article on blood coagulation](https://en.wikipedia.org/wiki/Coagulation). It lists calcium, phospholipids, vitamin K and many other coagulation factors. Anything increasing blood platelets would be usefull. As was already [pointed out](https://worldbuilding.stackexchange.com/a/248141/18798) low blood pressure also helps because of same reason.
Another issue after battle are wound infections so antibiotics would help with that. While in medieval times antibiotics were unknown, I believe it is not farfetched to use antibiotics. For example "[medieval remedy could be potential antibiotic](https://edition.cnn.com/2020/07/28/health/medieval-remedy-antibiotic-resistance-alternatives-scn-trnd/index.html)" and [Penicilin](https://en.wikipedia.org/wiki/Penicillin) is from mold and we use [molds for food production](https://en.wikipedia.org/wiki/Mold#Food_production) for a long time
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How about an effect that causes the drinkers musculature to react against intrusions, either bouncing blows away or receding away from blows.
It could also involve the affects from the second potion (focus, sharper reflexes, time slows down), but used purely defensively instead of offensively.
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Potion fills blood with special cells (or nano-machines) with connectors that grab neighboring cells, binding them together. Potion cells could disperse throughout the body but only bind cells in particular locations in response to fear or intense concentration.
I get that this would either require a LOT of these potion cells or they would have to move through the body incredibly fast in order to respond in time, but maybe this will give you a direction.
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The Great Wheel is a planar cosmology which defines how the planes, worlds, and realms of the multiverse are connected to one another. Throughout this multiverse, there are various gods that exist which have their own cult of worshippers and regularly interfere with humanity. Powerful barriers separate the higher realms from the mortal world, preventing these gods from controlling world events. This forces gods to enter a realm through more creative methods if it seeks to influence humanity and the flow of history. Daeva is an umbrella term used to represent a collection of divine entities that have since entered the mortal realm and have become human. There are three specific ways in which a deity can accomplish this:
1. A god can construct an avatar, an artificially created human body built to the specific instructions and needs to contain it's soul. A god can then possess this body and use it to navigate the human world in order to use its power. It can also place pieces of its soul into numerous avatars, potentially dividing its power among thousands of bodies, depending on its power level and might.
2. A god can use its own cult as a way to enter the world through a method known as Theosis, a transformation proces whoose aim is likeness to or union with a god. Through this ritual, a worshipper who has proven its faith and devotion can offer up its body as a landing pad for that god's soul to enter, becoming one with its deity. The resulting individual becomes a perfect union between god and human, becoming intertwined in mind, body, and soul down to its very DNA.
3. A god is born into the mortal realm as a human through a virgin birth, done through a millennia long eugenics program to create a physical body with the perfect set of genes to contain the god's soul. This entity is considered simultaneously divine and mortal, possessing two complete and distinct natures at once. This is referred to as a Hypostatic union, in which a deity contains the essence of both a god and a human, having both natures but being one individual.
The three forms of Daeva basically come down to a god in the body of a human, an entity resulting from the blending of a god and a human, and an entity that is both god and human. Nevertheless, they are all hybrid forms of the same two creatures, with the divinity becoming one with the mortal. The third type is hardest to justify, as it is modeled off the story of Jesus. In a world where multiple gods exist and are running around as human mortals, this method becomes redundant, requiring much more time and effort. It's also the hardest to explain, as its basically a mismatch of the other two with little in the way of separating it that makes it unique.
What would make the hypostatic union a more preferable method for a deity to enter the mortal realm as opposed to the others?
[Answer]
Let's compare-and-contrast the three modes by which a god may inhabit the mortal realm:
1. **Avatar**
Allows the god to manifest physically in the mortal realm, and gives the god direct control over the avatar. However, there is no real mortal component in the avatar, i.e. a mortal soul; it's just the physical construction materials plus the god's own soul. And the quality of the body depends on the god's ability to source the right materials and actually craft the thing.
2. **Apotheosis**
Allows the god to manifest physically in the mortal realm, and gives the god direct control over the body which *may or may not* be unconstested. Unlike the first method, apotheosis *does* combine both a mortal soul and a god's soul (which you imply is a useful thing). A significant drawback is that this option is only available to gods who (1) have a cult in the mortal realm, (2) have a cultist who is actually willing to surrender the rest of their existence to their god, and (3) that cultist is actually able to perform the ritual (which may require help from others, hard-to-get materials, and/or travel to hard-to-reach or denied areas). Also, the quality of the body and the mortal soul are outside the god's control: the god can elect to be choosy, but is ultimately constrained by the options that are presented to it. "You go to war in the mortal body of the zealot you have, not the mortal body of the zealot you want."
3. **Hypostatic union**
Allows the god to manifest physically in the mortal realm, and gives the god direct control over the body. Unlike apotheosis, there is no independent human personality that might compete with the god for control over the body. But like apotheosis, the union does contain both a mortal and godly soul. You don't specify what it takes for a god to seize upon a pregnancy, but presumably the mortal parents don't have to dedicate their lives to the pursuit of this goal the way a hopeful cultist must for apotheosis, and this method only requires a single mortal (i.e. no team of cultists, no ritual materials or prep). In some fiction, a god can just pick any woman, often without her knowledge or consent. Maybe the god can influence the development of the child *in utero*, but definitely controls the child's life from birth, and so can guarantee that the human body is ideally prepared for whatever work lies ahead.
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There's at least one more criterion that I'd think is relevant, but which you don't comment on: how does a god *extricate* themselves from one of these unions?
This could be a really important consideration. If one of these options effectively traps the god inside the body until the proper exit conditions are satisfied, and another option does not trap the god, that will matter. Imagine that apotheosis is such a deep intertwining that the god can't leave the body until the body dies *and is destroyed* according to some ritual. If that were the case, a god might find themselves trapped in a mortal body that's not in a good position to pursue the god's goals, and then stay trapped in the corpse for an arbitrarily long period of time until future cultists can find the body and perform the ritual. That could take a god out of the game for centuries. (But might make for a really neat story arc.) IIRC, the movie *Dogma* does something like this.
On that topic, I think this makes the most sense:
* gods can put "eject buttons" into their avatars that allow them to leave at a moment's notice
* apotheosis can be ended in reasonably short order with the help of the rest of the cult (e.g. with a few days' or week's notice -- however long it takes them to prepare for the separation ritual)
* hypostatic union ends when the body dies, which definitely trashes the body, but does not require any other special steps, i.e. suicide is the eject button
## Thus:
* the avatar is the most convenient & flexible but also gives the worst results
* apotheosis is the least convenient & flexible but *can* give truly excellent results
* hypostatic union has a mixed score as far as convenience, but guarantees truly excellent results
For visual learners like myself:
[](https://i.stack.imgur.com/gnZ49.png)
[Answer]
## The Hypostatic Union is the closest to the [*Condition Humaine*](https://en.wikipedia.org/wiki/Human_condition) a deity can get.
It is difficult to grasp human nature and its petty ways. Suffering through 'conception' (immaculate though it might be), gestation, and birth, will allow the deity to come closest to experiencing life as a human being — temporary and temporal, vulnerable, emotional, mortal, lethal.
Why would a deity want this in the first place? It is certainly not for all deities, but some
* are **genuinely fascinated by humans** and desire the extra edge only the Hypostatic Union can give them (e.g. a deity doing research on their anthropological thesis ['theosis'? Oh, right.]);
* want **to hone how or why they are being worshipped** (in order to become more powerful, perhaps?), and an understanding of what truly drives humans to revere their specific idols can dramatically improve the deity's results.
[Answer]
**Hypostatic Union Strikes The Best Balance Between Mortality and Divinity**
If I am understanding this correctly, an Avatar is having the god take a blank vessel and fill it with their power. In this situation, they are essentially purely a god but disguising themselves in a human meat puppet.
Even if this is easy to create, I feel like this would be rather uncomfortable for a god. Though the body might be set to all their specifications, it is not truly their body, but rather a skin suit that must be far more limiting than their true godly form (whatever that might look like).
You have to remember that humans and mortals are effectively ants compared to a god. This is more than simply a size difference, they are two vastly different creatures with vastly different brains. Imagine a person shoving a human brain inside of an insect's body. Even if they managed to get control over themselves, the sensation would be rather unpleasant. In the same way, a god suddenly jamming their consciousness into a fully formed human body is incredibly uncomfortable.
They are hit with a flood of emotions they would otherwise never be able to feel, including unpleasant ones such as pain or fear. Even sensations as simple as breathing would be utterly foreign to them and downright horrifying. All the vastly unpleasant aspects of the human body come rushing at the god at the same time, making them feel weak and powerless, much what would happen if a human suddenly woke up one day as an insignificant ant, seeing the entire world towering over them.
Apotheosis, on the other hand, is taking a fully developed human and shoving a godly consciousness and power into them. Even if the union is "perfect", the simple fact that a person's whole consciousness is being overwritten is horrifying to consider.
Some gods might object to apotheosis from an ethical standpoint, seeing it as taking over their follower's free will. A good god might find such a practice immoral, even if it is the follower's choice to undergo this transformation.
The biggest problem is that the follower is still in there somewhere. Unlike the Avatar, you can't even really pick and choose the exact characteristics that you want, the best you can do is find someone that is as close to you as physically and mentally possible.
What if even the follower you like the most, the one who seems perfect, has traits you do not like? One flaw that you cannot get over? Blending together your consciousnesses means that flaw is now your flaw as well, thus making you imperfect in that regard.
Asking a god to share headspace with a mortal is a lot like asking a person to share a brain with a rat. Even if the union works out nicely, these are two fundamentally different beings getting squished into one.
Hypostatic Union is the best of both worlds. It's not a meat suit like an Avatar, a puppet that you have to pilot around. The body that you've made is ultimately your body. I suppose the downside is that you cannot control what you look like unless there is a method of controlling it, but simply having a body that you can say is purely your own would be nice. It eliminates the problem of discomfort that I was talking about earlier. If you get an entire childhood to get used to the new body, you'll probably be so used to it that you'll forget ever wanting another.
That's another advantage. You get to have an actual childhood. If you make a fully-grown Avatar, you're skipping many stages of human development and going straight into adulthood, unless the form itself is starting as a child and can grow up. Even if there are no mental effects to skipping those stages, it gives the god more chance to feel like they are actually a human, making the experience more authentic.
You get to have parents, a family, and perhaps a job or a spouse. You get to experience all the pleasures of a mortal life from scratch. Where's the fun in that?
Avatars are best if you simply need a way to communicate with humans for a bit. For example, short-term interactions such as giving your followers a message. You're not there to be a human, you're there to be a god in a mortal shell.
Apotheosis is for when a follower has done a particularly good job. It is the ultimate reward for their loyalty. Results vary with the person.
The hypostatic union is for gods that don't just want to pretend they are human but ones that want to BE human.
Also, what if there are some places only gods are allowed to go to and only mortals are allowed to go to? Perhaps Avatars are still considered "Gods" and recipients of Apotheosis are still considered "Mortals", at least in certain places.
Dimension X is a place where only gods are allowed, but Apotheosis recipients can't visit because it still considers them human.
Dimension Y is a place where only humans can go (for example, some sort of afterlife) Avatars cannot visit because they are not human.
Gods who went through Hypostatic union would be a loophole to both of these rules because they are both god and human at the same time. If there are any rules like this in this universe, it is the perfect way to get around them.
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[Question]
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What is one factor or ability a creature needs to sustain infinite work? By work I mean physical activity, and to make it more specific **running**
I want a creature that can output work, or run until they literally collapse from sleep deprivation so the only thing stopping the creature from running is lack of sleep and obviously food... But eating while in motion is not the hardest thing ever. How does that creature need to evolve?
And it has to have a sleep pattern similar to that of a giraffe or whale, around 1 or 2 hours at most.
Running speed is 20 kilometers per hour, so slightly more than the average untrained human.
[Answer]
## **Basis in Life**
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> I want a creature that can output work, or run until they literally collapse from sleep deprivation so the only thing stopping the creature from running is lack of sleep and obviously food...
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I believe the animal you are looking for, is the [wolf](https://animalcorner.org/animals/wolves/).
[](https://i.stack.imgur.com/RcLmL.png)
Why is the Wolf a great archetype for an animal that has infinite stamina?
1. Efficiency: Wolves last for weeks without food, and are extremely efficient at digesting it:
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> Wolves have large stomachs and can devour 20 – 25 pounds of food at any one feeding time. However, wolves are able to survive without food for up to 2 weeks or even longer if prey is scarce. Their digestion is very efficient, with all but 5 percent of large meat feeds able to be digested.
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2. Persistence: Wolves are some of the most persistent hunters on the planet, unlike most other predators, they will continue to chase down prey until they succeed.
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3. Evolutionary Pressure: the wolf plays a part in the evolutionary cycle with the herbivores:
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We can take these features from a wolf and **enhance them**, to obtain our animal with infinite stamina.
## **1: Efficiency**
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To maintain a good running speed, for extreme periods of time, an efficient digestive system is needed. It would have to be able to digest while running, and digest it quickly to convert it into energy.
It would also need to be able to go for long periods of time without food when needed, so that the animal could continue to chase down prey. An addition to what wolves have would probably be a pouch of some sort, for storing more food. If the animal were intelligent, it could possibly weave pouches to attach to itself to store and preserve food. If not, this pouch could be biological, like what camels have.
## **2: Persistence**
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Wolves can hunt for a very long time, taking as long as needed to chase down and corner prey. Their spirit of the hunt, in this regard, is extremely useful.
This, however, doesn't quite mean that they can do it forever. Eventually, they will have to stop. To make your creature persist for as long as needed, however, we can turn towards **muscle memory**: even in humans, unconscious/subconsciousness and muscle memory alone are capable of doing some very extreme things. For example, a wrestler was able to continue wrestling for a full 9 minutes while still being [unconscious](https://411mania.com/wrestling/tommy-dreamer-bob-holly-unconscious-concussions/).
Your animal would have to possess an instinctive ability to run, even when their consciousness is not fully focused. They must develop their brains to a level where they can run even if they are completely unconscious.
They would also have to have a **special chemical composition** in their bodies. For this, we can turn towards one of the humans who possesses this trait, [Dean Karnazes](https://www.theguardian.com/lifeandstyle/the-running-blog/2013/aug/30/dean-karnazes-man-run-forever).
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But when they tested Dean, they found that his lactate threshold was almost superhuman.
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In this case, by combining muscle memory and an extremely high lactic acid threshold, your creature could run for as long as its willpower could hold out, until, as you said, they "run until they literally collapse from sleep deprivation".
## **3: Evolutionary Pressure**
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Not only are wolves highly selective in which prey they hunt down, wolves also spend a lot of time planning out an attack, usually focusing on weaker members. From this [source](https://www.livingwithwolves.org/how-wolves-hunt/):
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This would probably be the most important requirement. For a creature that can run forever to actually evolve, it would need an opponent. Something to compete with it, and give it evolutionary pressure. By hunting down only weaker animals, the evolutionary pressure will cause both the hunter and prey to become stronger and more specialized over time.
Through countless generations, your creature will weed out the weakest of its prey, allowing the prey to feel evolutionary pressure. The prey will evolve, to have better stamina and escape the creatures. To catch them, the creatures will also experience evolutionary pressure, to catch the prey so they can continue to live. The cycle will continue, on and on.
## **Conclusion**
Starting with the wolf as an archetype, through many generations of natural selection, finally, the specimen that has the most efficient digestive system, mentality built for hunting down prey, a supernatural threshold towards muscle pain, and an environment and prey to showcase its infinite stamina to, will have been created.
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[Answer]
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> What is one factor or ability a creature needs to sustain infinite work?
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**Good cooling.**
Many furry animals need to stop and pant to cool themselves after hard physical activity. Your creature must be capable of dissipating heat effectively.
[Answer]
The first thing your species needs to conquer is sleep. Dolphins can sleep with only part of their brains, letting them remain semi-conscious 24/7. Your creature could do this too. For a few hours a day, half of its brain is asleep. It would be able to continue running during this time.
The next thing to conquer is speed. If this thing is running at 20k per hour, 24/7, it will be burning energy rapidly. 20 kph is faster than the highest trained humans can run for more than a few hours, but humans aren't optimized for running, and the fact that we **can** run that fast for hours shows that it's clearly possible. A quick internet search revealed that horses can run for up to 72 hours straight before they die. This creature will have to have an extremely well-made vasculature, heart, and lungs to ensure its muscles are thoroughly oxygenated.
The final obstacle to conquer is energy. This creature will be burning through energy quickly and constantly. It will probably have to eat every two or three hours and will have an extremely fast metabolism to keep energy levels high enough to continue moving. As you said, eating while running isn't that difficult as a human, so this creature will have no problem. How it gets food while moving has many possibilities.
There is no single factor that needs to be overcome for this thing to run indefinitely, but the above should cover the largest obstacles for a perpetual-running creature.
As to how it would have to evolve? It would need a selective pressure that punishes being still. Perhaps there are predators that pounce as soon as your speed drops below a threshold, or maybe it hunts herds of creatures that also continually move, so to stop is to lose your food source. There are a lot of ways you could create a selective pressure that rewards continually moving. In the ocean, there are many creatures that don't sleep as much as we do on land, probably because it's a lot more difficult to hide in the open ocean.
Hope that helps clear some things up.
[Answer]
Infinite endurance isn't that big a problem. After all, you already have it. You have several muscles in your body that work without pause for decades on end.
If you want your creature to run forever you need to use the same sort of muscles in the legs. However, you have some other problems:
1) As has been mentioned, heat. Humans fare very well compared to most creatures in this regard, but probably not well enough for infinite running. Your creature needs better cooling in some fashion.
2) Food. From looking at long distance hikers we can see that our digestive system maxes out at something over twice our base metabolism. You're going to have to beef up the digestive system to sustain the running.
[Answer]
# Your creature already exists
The most energy-efficient runners in the animal kindgom are kangaroos and wallabies. This is because of their springy legs. I found [this article from Stanford University about them](http://large.stanford.edu/courses/2016/ph240/cannistraro2/).
Check this excerpt (emphasis mine):
>
> When taking a closer look at the muscular-skeletal make-up of these hind legs, one will notice unique characteristics of both the tendons and muscles. A kangaroo has extremely long tendons in its back legs that undergo drastic length changes when the kangaroo is hoping. Acting like springs, the tendons stretch under the weight of the kangaroo, and, while elongated, contain elastic energy. The muscles in a kangaroo's legs are impressively strong and stiff, allowing them to handle the stretching of the tendons. One study conducted on the animals revealed that their tendons can store up to ten times as much energy as their muscles. All of this stored energy is released when the kangaroo pushes up and the tendon contracts again. **While the muscles in a kangaroos legs still work to help them hop, so much of the energy they use comes from the tendons. Unlike muscles, tendons do not fatigue and they do not require oxygen to work.**
>
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And further ahead:
>
> Since kangaroos garner so much of their hopping energy from the tendons in their legs, they consume oxygen at a significantly slower rate than other mammals of similar size. When studying the movement patterns of red kangaroos, one team of scientists determined that **as the kangaroos increased speed over flat ground their rate of oxygen consumption stayed nearly constant. In fact, the maximum measured rate of oxygen consumption of 3.0 mL kg-1 s-1 tops all animals with exception of a few vertebrate species**. A study done by the University of Wisconsin - Madison looked at oxygen consumption rate in three dogs that were trained to run on the treadmill. When looking at movement statics obtained from the two studies above, and comparing red kangaroos and dogs, it is clear kangaroos hold the advantage in efficiency statistics (...)
>
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> **While the oxygen consumption rates of the two animals are similar, the Kangaroo is moving at over four times the pace of the dogs**. Achieving the same oxygen consumption rate while moving at such a faster pace is truly an impressive feat for the kangaroo.
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This is not a proper article, but [a researcher once said this to phys.org](https://phys.org/news/2014-10-biomechanics-locomotion.html):
>
> **"In effect, it is impossible to tire out a kangaroo while it hops over level ground."**
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---
A few more thoughts.
You said:
>
> Running speed is 20 kilometers per hour, so slightly more than the average untrained human.
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According to [Wikipedia's article on fastest animals](https://en.wikipedia.org/wiki/Fastest_animals):
>
> **The comfortable hopping speed for a kangaroo is about 21–26 km/h (13–16 mph)**, but speeds of up to 71 km/h (44 mph) can be attained over short distances, while it can sustain a speed of 40 km/h (25 mph) for nearly 2 km (1.2 mi). **The faster a kangaroo hops, the less energy it consumes (up to its cruising speed)**.
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Also this:
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> And it has to have a sleep pattern similar to that of a giraffe or whale, around 1 or 2 hours at most.
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Some googling suggests that in the wild, Kangaroos spend 2 to 4 hours in deep sleep per day. As prey animals they must always be wary of predators, so most of the time they don't spend grazing (or mating, fighting etc.) they just rest lightly.
[Answer]
**Food requirements**
Putting some numbers to the calorie requirement for human equivalent:
* Human running: ~1000-1500 Cal/hr
* Fat ~9 cal/g; protein/sugar ~4cal/g
* Food requirement ~200-250g/hr -> 5-6 kg/day
* That much weight is probably going to slow them down by about ~10s/km\* => ~19km/hr which is not an insiginficant speed drop.
* Can they stash + grab food? (see ultramarathon aid stations)
\*Source: <https://runbundle.com/tools/weight-vs-pace-calculator>
Start weight = 75kg, distance=5km, pace = 3min/km
**Digesting**
This actually takes a lot of energy/time, if your bloodflow is going to muscles then you will likely struggle to digest food efficiently.
**Oxygen**
Any distance running is going to require buckets loads of oxygen as anaerobic respiration isn't sustainable for humans (If you can make this work then you might solve some other problems too!), so big lungs (which aren't compressed while in running position) with a strong diaphragm are a must.
**Sleeping and Cooling** are important too and dealt with in other answers
>
> Running speed is 20 kilometers per hour, so slightly more than the
> average untrained human.
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That's a lot more than an untrained human! That pace would be enough to earn you an Olympic starting place for Womens 5km or Mens Marathon.
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
La Rinconada, Peru is notable because it has an [effective oxygen concentration of only 11%](https://worldbuilding.stackexchange.com/a/146908/3097), leading to the need for special techniques just to keep a fire going, and preventing the use of combustion-based heat for smelting iron, as they simply can't get hot enough under the oxygen-starved conditions.
However, with today's technology, and a big enough power line and/or natural gas pipe running up the mountain, would it be possible to convert iron ore into crude metallic iron (it only needs to be good enough for an electric arc furnace to use) under these conditions?
[Answer]
# Yes, just increase pressure
Effective oxygen concentration is low because air pressure is low at high altitude. But oxygen is still ~20% of whatever air you have. The solution to the problem with starting fires is just to increase air pressure in the blast environment.
Given the scale of modern blast furnace operations, a 50% over-pressure in the smelting area is not unreasonable. After all, there are already powerful fans at work; the *blast* in blast furnace is a blast of hot air sent in through a [tuyere](https://en.wikipedia.org/wiki/Tuyere). The real changes would mostly be design of the facility to better restrict air flow out of the smelting area, so that the injected air results in a higher pressure region with a suitable oxygen concentration in contact with the molten iron.
[Answer]
How about using an induction furnace like Cody from [Cody'sLab](https://www.youtube.com/watch?v=DBBt7IhHOFQ) did. You wouldn't need any oxygen at all. It's also not restricted to such low quantities Cody used in his video. According to [wikipedia](https://en.wikipedia.org/wiki/Induction_furnace) induction furnaces can hold up to 100 tonnes and can even melt steel.
[Answer]
Sure, as long as you're willing to pay for bottled or piped gas of some kind, you can run a fuel-air system either using pure oxygen or just compressed air. There's lots of options but you really only need one; a propane burner supplied with compressed air will [apparently](https://en.wikipedia.org/wiki/Oxy-fuel_welding_and_cutting) burn at around 1980°C, [Iron smelters only need to get up to 1250°C](https://en.wikipedia.org/wiki/Smelting) to reliably reduce ore to metallic Iron, so such a system is more than sufficient. You'll still need to bring in a carbon source feed stock such as [Charcoal](https://en.wikipedia.org/wiki/Charcoal) or [Coke](https://en.wikipedia.org/wiki/Coke_(fuel)) to reduce the Iron oxides in the ore.
Short answer: You need to bring in Carbon feed stock as well as Iron ore and you need either piped or bottled gas and/or fuel to run a compressor but it's easily done with modern technology.
[Answer]
You can carry use molten oxide electrolysis to make steel just about anywhere.[](https://i.stack.imgur.com/pUZiu.png)
Even on the [Moon or Mars](https://isru.nasa.gov/Molten_Regolith_Electrolysis.html) where there isn't any oxygen at all.
] |
[Question]
[
>
> When the old mining town was founded, nobody did think of this ever growing into much more than a coal-mining town. The deposits of iron-ore, aside from the already developed peat bog to the north, driving the tools & weapons industries this city is now thriving from, have originally been estimated to be much smaller in size - and deemed not worthy of exploitation..
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Introductory course to the History & Sociology of the tri-region area, Ringstadt Militaric University.
---
This question is a spin-off to [this question about the topography in the below map](https://worldbuilding.stackexchange.com/questions/121834/ringstadt-how-sensible-is-my-topography). Please refer to it for general questions or observations about the map & area.
This spin-off is **about** understanding & determining the make up of the mountains to the north of the map. For future story-purposes the mountains/rock will have to fulfill certain properties, this is about finding out if my goals for them are possible or if I need to rethink this part.
---
*Desired Properties*:
For the purpose of developing an eventual city in this area, I was planning to have initial mines along the ridge from D2 to F3 (later expanding towards H4) producing coal from strata mostly parallel to adjacent ground-level.
Eventually I wanted expansion and further prospecting to reveal massive depots of iron and preferably some other ores/minerals as well (maybe copper?) in the deeper strata below the coal. Coal being carbonized organics, I imagined that the coal layer(s) could have been folded on top of the ore deposits by glacial movement or similar.
In order to get access to lower strata and deposits I imagined some eventual open-pit mining in the F2 area, the resulting waste-rock being used as building materials (if I can have sandstone, granite or other building rock there) and to raise embankments in the C2 to C5 area, creating a protected harbour.
For story & fanciness purposes I would love to have big tunnels leading into the mountains, and massive underground caverns that are left-overs from the mining process (so I can fill them with secret military installations, or simply storage, or what not).
[](https://i.stack.imgur.com/nYx1M.png)
```
Legend:
brown -> topological lines, 10 meters each
blue -line- -> streams, rivers
light-blue -solid- -> bodies of water
turquoise -> peat bog
olive -> reed marshes
Each grid-cell is 400m by 400m.
```
---
**Q**: Can the above described desired properties be *realistically* met by the rock and soil in this area Can my mountains be what I need them to?
A good answer should *at least* address the following topics:
* Can I have the resources I in the described area?
+ Can I have the upper layer of coal-seams?
+ Can I have the massive iron deposits?
+ Can I have the supplemental Copper (or other useful ore) deposit(s)?
* If this cannot work, why - what stands in the way of it?
In *addition* it would be amazing if answers that explain *why this cannot happen*, to include a section proposing alternative situations of resources that come close/to a similar result as what I am describing in the above prose.
* Please ignore the resources available in the peat-bog; I know there will be bog-iron and it will play a significant part in the *earlier* development of the region. Same goes for the clay and gravel available through the reed-marshes and river-deposits.
[Answer]
# So many minerals so close to a city is unlikely
### Your mining area is small
Limiting the mines to the area from D2->F3 is like a coal seam that is only 1-2 km long. That is short. Here is a [GIS mapping](https://eppcgis.ky.gov/minemapping/) of coal mining areas in Kentucky. The seams are hundreds of miles long.
[Scranton](https://en.wikipedia.org/wiki/Scranton,_Pennsylvania) was/is a big coal mining town in Eastern Pennsylvania. Scranton grew to over 100,000 at the peak of the coal mining boom. Combined with nearby Wilkes-Barre and other cities in the area, it formed a conurbanation of some 300,000 in the 1920s. These cities serviced coal towns from Forest City, PA to Bloomsburg, PA, some 110 km downriver. The two-county area ([Lackawanna](https://en.wikipedia.org/wiki/Lackawanna_County,_Pennsylvania#Demographics) and [Luzerne](https://en.wikipedia.org/wiki/Luzerne_County,_Pennsylvania#Demographics)) had some 700,000 people, so it was one of the most densely populated parts of the US at that time. Lots of people in a region = large city to support those people.
If you want a large mining town, it should probably be pulling from a large mining region. Some mines will be close by, but many more with be within a day or two's transport by horse or foot; or later, a few hours by train. A 'city' with only small nearby mines would be just a small encampment of a few hundred.
### Mines on top of each other are unlikely
I can't find any good examples of mines being just on top of each other like that. But I was able to find a variety of examples of such mines being in very close proximity. The rich bituminous coals are generally of an age [100-300 million years ago](https://en.wikipedia.org/wiki/Bituminous_coal#Bituminous_coal_by_geologic_period). Almost all high quality Iron ores are derive in one way or another from [banded iron formations](https://en.wikipedia.org/wiki/Banded_iron_formation). These formations are much, much older, in the 2 billion year range. They derive from the Great Oxygenation event, when the first atmospheric oxygen reacted with free iron to lay down great beds of iron oxide.
The gap in time between the two levels is what makes the idea of coal on top of iron so unlikely. If you had several hundred meters of coal-bearing strata, even if you just dumped that on top of a banded iron formation, that is still very deep for a early-modern mine. [Mines in Europe](https://en.wikipedia.org/wiki/Mining_in_the_Upper_Harz) were hitting 300 meters by 1700 and 600 meters by 1830; still these were exceptional. And this considering a ~300 mya formation directly on top of a ~2000 mya formation, with no intervening material, which I consider unlikely.
A second reason that this would not work is that you have large lakes nearby, so mine shaft drainage is going to be tough. Your mining hills only go up about 100 meters above lake level. Much deeper than lake level, and you will likely get very serious water intrusion. Mining below lake level at all will likely have to wait for the steam engine to pump water.
### A large mining area means many resources can be found together.
Jharkhand, in India, is a place with lots of mining resources in close proximity. It is the [leading](https://en.wikipedia.org/wiki/Jharkhand#Economy) iron and copper mining state of India, and third in coal. Meanwhile, much of India's coal reserves are just across the border in West Bengal and Odisha states.
You can see a big iron ore mining region near Gua, Jharkand, India on the [map here](https://www.google.com/maps/place/Gua+Iron+Ore+Mines,+Jharkhand+833213,+India/@22.1434796,85.3288054,26748m/data=!3m1!1e3!4m5!3m4!1s0x3a1fc72a10e8390d:0xdaf66a46afb1a575!8m2!3d22.2185736!4d85.3562565) (look for the open pit mines in the satellite view). Meanwhile, here is some [significant coal mining](https://www.google.com/maps/place/Global+Coal+And+Mining+Pvt.+Ltd.+Talcher/@20.9500388,85.0922498,26099m/data=!3m1!1e3!4m8!1m2!2m1!1stalcher+coal+mine!3m4!1s0x3a18b16196542a87:0x65ae90c0079f0992!8m2!3d20.9280814!4d85.1646353) in nearby Talcher, Odisha, India. Still these two mines are 140 km apart. But there are [copper mines near Jamshedupur](https://www.google.com/maps/search/copper+mine+jharkand/@22.5747552,86.3920152,23160m/data=!3m1!1e3) 110 km away from the coal mines, and also uranium, gold, bauxite and other things in the region.
# Conclusion
Your best bet is to have your mining town be the center of a larger mining region. Within the larger mining region, there are many regional centers of coal, iron, copper and more. Ringstadt is the central business city of the region, and the center for trans-shipment; after all it is a port town on the lake and what better way to move ore than by barge.
Also, it can eventually be the industrial center for the iron and steel industry. A good example is Cleveland, OH. This lake town isn't actually close to coal (which is in Pennsylvania and West Virginia, mostly) or iron, which is available in Minnesota and Michigan's Upper Peninsula. But it is the place between the two on the lake. Rail brought coal from the Pittsburgh area, and barges brought ore from Lake Superior; these met in Cleveland which became a big metals center. Gary, Indiana has as similar history.
[Answer]
>
> Can I have the resources I in the described area?
>
>
>
Yes, even though it requires an exceptional luck and combination of circumstances. Let's see a hypothetical geological history for your area:
[](https://i.stack.imgur.com/sZI2V.png)
Start with a sedimentary basin, tropical environment where you have lots of organic material which will eventually form coal. This is then overlain by other sediments (sand for example).
---
[](https://i.stack.imgur.com/oiBaC.png)
Now you have tectonic plate collison. An oceanic crust [subducts](https://en.wikipedia.org/wiki/Subduction) under your sedimentary rocks. Volcanic eruptions start in the [volcanic arc](https://en.wikipedia.org/wiki/Volcanic_arc) above it.
---
[](https://i.stack.imgur.com/Bhhy1.png)
This is where it gets really fun. You now have a [porphyry copper](https://en.wikipedia.org/wiki/Porphyry_copper_deposit) system, intruding into sedimentary rocks, which happen to have coal preexisting in them. So you have this volcano because of the subduction zone, and as it erupts it exsolves acidic hydrothermal fluids that carry dissolved copper into the limestone. The fluids are neutralised by the limestone, causing the formation of a copper [skarn](https://en.wikipedia.org/wiki/Skarn).
The magma itself also separates an immiscible iron oxide liquid. These are rare and are usually not as large as the BIFs mentioned in kingledion's answer, but they're big enough (for example Kiruna, Sweden or El Laco, Chile).
The rest of the fluids end up in hydrothermal springs and your lake making those sulfurous waters you wanted in your other question.
---
At first I thought this was a bit too much hand-wavy and unlikely to exist, but then I realised that a not-too-different example occurs close to home in Eastern Australia. There are many [sedimentary basins](https://en.wikipedia.org/wiki/Coal_in_Australia#/media/File:Australian_Energie_ressources_and_major_export_ports_map.svg) with coal in them, and these Permian in age. Later on, Triassic magmatic activity occurred [around the same places](https://en.wikipedia.org/wiki/Geology_of_Australia#/media/File:Ausgeolbasic.jpg), caused by subduction of the Pacific plate underneath Eastern Australia. So yea, feasible.
[Answer]
## Tl;dr: First, iron came from a Snowball Earth, then, copper came from volcanism, finally, coal came from peat forests
There was a lot of things I wanted to add to my answer in the first question, but I didn't have the time at the moment. Others have noted it was **possible but unlikely**, so now I will suggest a geology. (story narration in block quotes)
>
> Well, first, we go into biology. Our world wasn't always this hospitable. In fact, the air we breathe was nonexistent: composed of other chemicals. But a pioneering group of plants came: the algae. They lived on iron, producing oxygen from the air around them. The eroding mountains provided the iron. The iron then precipitated after the algae died, *ironically* because of all the oxygen they produced. Other areas of iron eroded. But our ores remained intact, sedimented down by the shallow sea we were a part of.
>
>
>
Real life example: [Mesabi Range](https://en.wikipedia.org/wiki/Mesabi_Range)
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> Next, near this sea, near this area of iron, a rift opened. The great rift, we call it, just to the west of us. This rift gave us potash for agriculture, sulfur for gunpowder, salt for food and money, bentonite for pottery, and gypsum for construction. A true windfall geologically, not even mentioning the copper, gold, and zinc deposited in the porphyric deposits.
>
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Real life (ish) example: [Afar Triangle](https://en.wikipedia.org/wiki/Afar_Triangle)
>
> Finally, the sea dried somewhat, and we were left with lush green forests. These days were warmer than today, allowing for a rainforest in this region. But then, the algae struck again. These plants, flourishing in the shallow lakes, combined with the forests on our land, caused a short, intense ice age, followed by a rapid heat-up after the ice age. The ferns and palms of our forests were too slow to adapt. And so they formed the coal seams now under your feet.
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Real life example: Most of the coal seams in America.
[Answer]
For copper your best bet in this setting is the hydrothermal ore [Malachite](https://en.wikipedia.org/wiki/Malachite), this is formed when copper rich water cools, depressurises, or is oxidised. You can have veins of it running through other rocks where water has historically moved along natural faults in the rocks.
Most massive iron formations are [banded iron](https://en.wikipedia.org/wiki/Banded_iron_formation), old ore bodies laid down in the ancient oceans during the oxidation of the atmosphere, these old formations could occur below/around a granitic intrusion being much older than any other rocks in the area. These deposits are relatively easy to work too as they're composed of the Iron oxide minerals [hematite](https://en.wikipedia.org/wiki/Hematite) and [magnetite](https://en.wikipedia.org/wiki/Magnetite) which can be directly reduced in a furnace without any of the preprocessing needed when using hydroxide and sulfurous ores.
Given the glaciated nature of the northern area I would expect most of the softer, and therefore mobile, strata like coal to have been scraped off the landscape and deposited on the plains as a sedimentary layer of broken coal mixed with gravel and some finer sediments. There is a layer of coal like this that, according to a petro-geologist who used to lecture some of my Earth Science classes, comes up in core samples in the [Taranaki Basin](https://en.wikipedia.org/wiki/Taranaki_Basin), it's composed of coal fragments eroded from onshore deposits during the last ice age and deposited on the continental shelf. The southern hills could have very thick coal measures per our discussion on their overall geology the other week; deeply buried granite, conglomerate aquifer, shale, limestone, coal, fireclay cap with topsoil over the lot.
[Answer]
Please understand i am not a geologist, so if i'm wrong on naything i say please correct me, i'm just doing research and looking into it as i go
Different resources appear at many different levels,
**Hiostorial examples:** in Cornwall, in the UK, there was numerous Tin mines, and those mines offered work for the towns around it, eventually tin got mined out or the veins were too deep to cheaply mine and the need for tin reduced and larger tin deposits were found on continental europe, this resulted in a large decline in mining in Cornwall. however a few centuries later they discovered that tin deposits tend to be close or above Copper deposits or and so mining in Cornwall started up again. but this time for Copper,
**Layering**
My understanding is that copper and tin are more common in hard rock (i think this is igneous rock) such as granite then in soft stone such as limestone which is sedimentary rock. however they are often found high up need the sedimentary rock level
most types of banded iron deposits appear in sedimentary rock. so Copper and iron being nearby would be unlikely for this reason, the same could be said for the Coal layer, as coal is again more often found in sedimentary rock formations.
However it is common to find sedimentary rock over igneous rock and the thickness or depth of the layer is entirely up to you as the writer. copper and tin would be found beneath the coal and iron levels. while i think its unlikely that a large deposit of coal would sit directly over a large deposit of iron, its possible that the large deposits actually sit close or nearby with some overlap.
the only thing i would advise you to look into is the size, looking up several other iron mines (open top) the entire mine itself can be miles long, or wide and can also get over a mile deep, then the infrastructure around it addes even more, so for you grid squares being 400m by 400m and you wanting a square or two to be the mine and city, you might need to scale up the mine a bit for example:
>
> The Kiruna mine in lapland has an ore body which is 4 kilometres long, 80 metres to 120 metres thick and reaching a depth of up to 2 kilometres. Since mining began at the site in 1898, the mine has produced over 950 million tonnes of ore.
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The entire mining site itself though including the mountains of waste material, access roads and equipment etc, is over 4km by 2km.
The other beautiful thing for you is most people don't know enough about mining or geology to know if its right or wrong, I'm a prime example of this at least until someone posts a question on the internet and i go off in search of answers
[Answer]
For such a large amount of resources to be together, my only explanation is a post apocalyptic scenario, with the former cars and buildings long ago eroded.
If a city such as Tokyo is allowed to be assaulted by Nature by ten thousand years, all the steel and alloys will transform to massive **IRON** & **Nickel/Aluminum/etc**.
The main issue is how to justify coal.
] |
[Question]
[
---
>
> **Thank you everyone.**
>
> This was certainly not a question with a simple solution, and was far more complicated than I could've imagined. All of you provided so many amazing, insightful responses, selecting an single answer has been extremely difficult. You illuminated and educated in so many areas, and you have my utmost gratitude and respect.
> *Worldbuilding* is an incredible community, and I'm genuinely honored to be a part of it.
>
>
>
---
# Request
Any suggestions for 4-5 items that could be collected for a fictional (yet convincing) immunization/inhibiting agent against an air-born, zombie virus.
# Scenario
5 years after a massive, zombie outbreak initially brought into the United States (before being identified within the country of origin).
Efforts to quarantine and irradiate the infected has proven ineffective since every individual is now a carrier, causing them "turn" when near death or ill.
The zombie infection changes dramatically when it mutates from the dormant state into the active version; assuming a nearly completely different virus altogether. Years were spent trying to cure the dormant version before discovering that it might be possible to immunize against the mutated version.
The CDC has finally identified a successful method of developing this immunization/inhibiting agent. Unfortunately, only a small group of them remain, desperately defending their position, using generator backups, and rapidly running low on resources. The military, who has been protecting them, is being reassigned but the researchers (being so close to their goal) refuse to leave.
The military advises that the area will be overrun regardless, but promise to supply a rescue chopper upon request. In a final act of hope, several soldiers volunteer to remain.
Now, it's a race to complete (and test) the vaccine using the limited equipment they have, and anything they can bring back from the surrounding area (pharmacies, hospitals, factories, etc.).
# Infection Traits
* The symptoms are that of the standard, *Walking Dead* style zombie: Aggressive, rabid-like, and mindless.
* Victims, once turned, may be partially alive, or fully dead. In this case it doesn't really matter, so either one can be assumed.
* The viral/microbial infection is spread though *direct contact* as well as being air-born.
* *Direct contact* refers to any transfer of bodily fluids (blood, mucus, sweat, etc.), causing the infected to decline rapidly (12-24 hours).
* The air-born strain remains dormant until the body's immune system is compromised (extreme illness or near death).
* When *turning*, victims experience high fever, increased heart-rate, and eventual blindness due to the fever (sight is restored once they've turned completely).
# Question: What components (medicines & equipment) could I use to plausibly immunize against zombism as described above?
* Components need to withstand reasonable scrutiny by anyone with a medical background.
* Medicinal components need to have a generic name (to avoid copyright infringement) and names that are *readable* are definitely preferred (*Melphalan* vs. *Talimogene Laherparepvec*).
* Components are not limited to medicinal ingredients, but can also
consist of anything else, such as equipment needed to prepare the immunization, tissue sample type, fungus, or anything that could reasonably contribute towards the immunization/inhibiting agent.
* All items must be gathered within a relatively close distance to the CDC. Roughly within this area: <https://goo.gl/maps/3Lk5KPZapiE2> (so locating immune survivors isn't possible).
# Example Components
* Anything related to immunization for rabies or any of the five, related viruses from Africa (since, in this universe, that's where it originates from): [obodhiang and kotonkan (African ephemeroviruses)](https://www.ncbi.nlm.nih.gov/pubmed/22305623), [Mokola](https://en.wikipedia.org/wiki/Mokola_virus), [Lagos bat virus](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3291461/), and the [Duvenhage virus](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3291369/).
* Anything related to immunization for afflictions with similar symptoms, like [encephalitis](https://en.wikipedia.org/wiki/Encephalitis), [cerebral malaria](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3056312/), [tetanus](https://en.wikipedia.org/wiki/Tetanus), etc.
* These are just examples -- any creative and plausible solutions are welcome.
**[Please visit my ArtStation portfolio to see my digital paintings depicting the fully-turned zombies.](https://www.artstation.com/dustinhalstead/albums/57912)**
[Answer]
Vaccine development in the real world is a resource intensive and time-consuming process. However, with the imminent threat of zombie attacks, there are many shortcuts that could be taken to speed up the process.
For the sake of making this as close to real life as possible, I'll draw comparisons to a couple of real-world vaccines against various viruses.
## Ebola vaccine
The direct-contact nature of the virus, plus some of the proposed symptoms, suggest parallels to Ebola. The **'Recombinant vesicular stomatitis virus–Zaire Ebola virus'** is an Ebola vaccine with 95-100% efficacy. It is made by combining the **vescicular stomatitis virus** with an Ebola **virus surface protein** (probably a protein that the virus uses to infect cells).
So for your zombie vaccine, let's presume that you want to isolate one of the zombie virus surface proteins, and combine this with a carrier protein to ensure optimal presentation by the host immune system, without causing any zombie symptoms. Most of the reagents needed for this work can probably be found in the labs at the CDC. You might need a working **PCR machine** for some of the DNA work - these would be found in most laboratories.
## Influenza vaccine
The current flu (influenza) vaccine involves an inactivated form of the virus, and can be produced in eggs. This is a low cost, but effective, means of producing the large quantities of virus needed for large-scale vaccine production.
I would suggest that this may be an appropriate way of producing your zombie vaccine, and would negate the need to do large-scale cell culture (which is very resource intensive). However, you need **eggs**. Lots of them. Surely someone has been keeping chickens in some of the nearby neighbourhoods.
## Purification of the vaccine
Having produced your vaccine in eggs, you then need to purify it to avoid any deadly reactions that would inevitably occur were you to inject raw egg into someone. To do this you're going to need some large-scale protein purification products. To do this, let's say you've determined you need to do a rough purification step using **Ammonium Sulfate Precipitation**. You'll need to find a whole lot of **Ammonium Sulfate**. Further purification might be done with **Ion Exchange Chromatography**, for which you will need a lot of **Ion Exchange Columns**. There should be some in the CDC, or in the nearby Emery University.
Final purification might be done with High Performance Liquid Chromatography, or **HPLC**. You're going to need to get some **HPLC Columns**, and possible a HPLC machine. Again, maybe one of the nearby universities or hospitals might have some?
Finally, for vaccine delivery, you'll need **clean needles and syringes**. Lots of them. Perhaps the nearby hospitals would have a large supply?
I've left a lot of things out of the equation here, and skimmed over the initial design of the vaccine. But I think the biggest issue is going to be large scale production, rather than the smaller scale work that would go towards initial development/creation of the vaccine. Maybe the scientists have done most of the initial development already anyway, and just need to produce enough product to be able to test it properly?
[Answer]
Classically, the key ingredient in a zombie-apocalypse cure (or vaccination) is an immune survivor; someone who has definitely been exposed, has subsequently been reduced to the triggering state of near death, and has later been restored to health without becoming a zombie. There is a strong (yet probably unsubstantiated) trope that for every possible disease, a small subset of potential hosts will possess a natural immunity and that any surviving doctor can somehow manufacture an effective medicine from the blood or DNA of a single immune person.
Since you are looking for the component**S** which would make up a cure, I would suggest enhancing this trope to state that no single immune person can provide a cure for the zombie plague. Your cure can only be found by collecting a number of unrelated immune people and comparing their DNA to each other and to the non-immune majority.
The cure is present somewhere within the 3 billion base-pairs of each immune person's DNA, but since the average diversity between any two people's DNA is at least 0.1%, finding which distinct gene sequence grants immunity from a single sample is statistically impossible. Your single candidate will differ from your singular (presumably non-immune) doctor's DNA by approximately 3 million pairs. Adding multiple doctors and other non-immune people will help cross off some pairs, but since the cure is probably hidden in a combination of otherwise unrelated gene sequences, the statistical contribution of the non-immune can only help so much. Eventually, you need multiple immune people to determine specifically which gene sequences are responsible.
So perhaps what your surviving CDC scientists have that none of the other research teams have, is a comparatively large group of genetically distinct (unrelated) immune people. They have a large enough immune-positive sample to find the responsible genes, so now all they need is the medical equipment, solvents and reagents to perform genetic comparisons.
So perhaps the quest for your CDC scientists and their remaining guards is to convey their immune peoples (or at least their blood/saliva samples) to the headquarters of [23andMe](https://www.23andme.com/) in Mountain View, California. There is sure to be plenty of the right kind of equipment and chemicals available in their zombie infested labs.
[Answer]
I'm taking a more low-level crack at this... I'll leave my other answer up in case anyone else finds it effective for their worldbuilding needs.
My knowledge of drug combination therapy is limited, so these components are more about the basic vaccine creation process:
**Suspending fluid** - The primary ingredient in most vaccines is usually water or saline. Pure, clean, distilled water can be found at most grocers when the water company is shut down. Dirty river water can be filtered and distilled by hand easily with the right tools. Filters are available primarily in department stores, but can also be created with sand, charcoal, and persistence.
**Active Ingredient** - The Antigen(s)/Immunogen(s) in question. Can be created from certain semi-effective plants which might be found in nearby wilderness, or reverse engineered from the virus itself.
**Antibiotics** - Used to prevent contamination during vaccine creation and storage. Examples: Penicillin, Cephalosporin, Carbapenem, and some other familiar -cillins and -sporins and -cyclenes. Probably only found in nearby drug or department stores.
**Stabilizers/Preservatives** - Employed to help the vaccine maintain its effectiveness after it leaves the lab. Examples: Gelatine, Sugar, Sorbitol, Lactose, MSG, Urea. Most can be found in any grocer's bakery aisle. Urea powder is sometimes sold as a topical cosmetic, and can also be found as a fertilizer in some hardware stores.
**Adjuvants** - Utilized to provoke the immune system to discover the vaccine, so it can learn to fight the actual infection. Examples: Alum (often sold as a spice over the counter), paraffin/mineral oil (sold at drug stores in pharmaceutical grade, though perhaps other mineral oil grades can be processed or reconcentrated in a laboratory or kitchen), Soybean saponins, Peanut oil.
**Sources:** [Oxford](http://vk.ovg.ox.ac.uk/vaccine-ingredients), [WHO](http://vaccine-safety-training.org/vaccine-components.html), [Wiki](https://en.wikipedia.org/wiki/Adjuvant)
[Answer]
## Murphy's Law
Drug discovery is an iterative process. I'm a assuming you have a cure, but that cure causes liver failure, renal bleeding, and permanent death. You just need one or two more iterations to fix it.
Drug discovery is also a collaborative process. This means you need to have internet access. Some of the software used for drug discovery rely on data pulled from various sources such as [PubChem](https://pubchem.ncbi.nlm.nih.gov/) and [PDB](https://www.rcsb.org/pdb/home/home.do).
To keep in line with your need to stay at the CDC facility, I'm going to add this logic:
The reason why the scientist want to stay at the CDC facility is because they have a unique-to-the-world piece of equipment that still works.
I used to work as a multi-hat IT person at a small pharmaceutical research company and have had many annoying little problems while there. Normally, they are easily solved. But, during a zombie Apocalypse, it could shutdown the CDC's research.
That is: anything that can go wrong will go wrong.
As such, I titled this answer as "Murphy's Law"
I've tried to described each item as if it was written on a "Chance" card from Monopoly. Also, I'm trying to keep the locations different.
Final Note - the company I worked at specialized in [small molecule compounds](https://en.wikipedia.org/wiki/Small_molecule). In this case, the compound will weaken the virus, prevent reproduction, and/or attach to the virus in such a way that white blood cells can do their job more efficiently. That is how this cure would work.
## Item 1 - Refuel
>
> The portable generator at `major news station` is down. You are using
> their satellite dishes to gain access to the internet. Go refuel the
> portable generator that is there.
>
>
>
## Item 2 - Pringles Cans
>
> A pack of zombies has taken out a section of your connection to the
> internet. Go through people's garbage to find some cardboard tubes
> lined with aluminum so that you can [increase the usable distance of
> your wireless access points](http://www.freeantennas.com/projects/template/).
>
>
>
## Item 3 - CR2032
>
> The last non-rechargeable electrical [pipetter](https://en.wikipedia.org/wiki/Pipette) ran out of juice.
> Run to the local convenience store to pickup some CR2032 batteries.
> Target/Walmart is known to have them too.
>
>
>
## Item 4 - Liquid Helium
>
> The liquid Helium in your superconductor-based [NMR](https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance) is running
> low. Go to `National Air & Gas` to pickup some more.
>
>
>
## Item 5 - Analytical Grade Solvents
>
> [LCMS](https://en.wikipedia.org/wiki/Liquid_chromatography%E2%80%93mass_spectrometry) equipment is out of Analytical Grade Solvents. Investigate
> the local University for some more.
>
>
>
## Item 6 - Specialized Circuit Board
>
> The [GPIB IEEE-488](https://en.wikipedia.org/wiki/IEEE-488) circuit board that the computer uses to control the
> analytical equipment has fried. You can cannibalize the one found at
> `nearby small pharmaceutical company`
>
>
>
Most equipment now-days use USB and standard network interfaces. Older equipment used the GPIB IEEE-488 interface.
## Item 7 - Snake-Away
>
> A snake was found in one of the mice cages and couldn't get out; it
> must have been something he ate. Run to the local hardware store to
> pickup some snake-away and material to repair the broken, due to lack
> of maintenance, emergency exit door.
>
>
>
Mice are used for testing in order to find the [lethal dose](https://en.wikipedia.org/wiki/Median_lethal_dose) of a compound. Additionally, they can be used to gauge how large of a dose you need in order to make the [drug effective](https://en.wikipedia.org/wiki/EC50). Taking 20 horse-pills 3 times a day for 20 days is not a valid cure.
## Item 8 - Digital Software License Keys
>
> The digital license keys for your main discovery software just expired
> and is now in the grace period. Break into \_\_\_\_\_\_ and generate a new
> key.
>
>
>
Drug discovery software is expensive. As such, they are protected by license management software. If the license was bought annually, the license key will need to be regenerated each year.
One option to generate a new key is to break into the HQ of the vendor and generate a key that lasts 100 years.
Another option is to generate a temporary key from the local sales rep's laptop. You'll need to take the laptop as these keys usually last only 1 month. One sales representative said their company stopped allowing sales reps to generate keys because they were giving away the software way too many times.
A third option: sometimes a [physical dongle](https://en.wikipedia.org/wiki/Software_protection_dongle) is used for single-seat/single-PC licenses. Today, the dongle is a USB stick. 1980's, companies like AutoCAD used Parallel Port dongles. Small company, maybe a consultant, would be the ones that have a dongle. However, you won't be able to use the full power of a super computer.
[Answer]
from OP: /Efforts to quarantine and irradiate the infected has proven ineffective since every individual is now a carrier, causing them "turn" when near death or ill./
1. As @pluckedkiwi points out in the comments, if everyone is a carrier it is too late for a vaccine. Sort of like everyone is carrying herpes. What you want to to prevent outbreaks of the herpes.
2. If the outbreak only happens when you die it is hard to get too enthusiastic about risking your life to find a way to prevent it, even for a scientist. The dying thing is a bummer. Turning into a zombie does not make it a whole lot worse. If I can avoid dying generally I am very enthusiastic about that. If I am around other people they can refer to #5 below as I am dying of taco poisoning. Quicker, too. If I am not around other people I can zombie around after I die, no harm done.
But these were not your questions. You want anti zombie virus medicine.
Your virus is an RNA virus related to rabies.
Ideas for treatment:
**1. Zombie virus, and a lot of it.**
from [Survival from Rabies Encephalitis](https://www.ncbi.nlm.nih.gov/pubmed/24582283)
>
> Insufficient rabies virus glycoprotein from low-titre inocula may also
> contribute to the delay (in immune reaction): an antibody response is
> not usually detected in infected humans before the second week of >illness, and often not until symptoms have appeared
>
>
>
If I am an asymptomatic carrier of zombie virus I conclude it is laying low in my body somehow, escaping immune surveillance. Some viruses (e.g. herpes) hide in cells and hibernate, escaping the immune system that way. Maybe for your virus it is because there is hardly any of it there, as is apparently sometimes the case for rabies. So: get a bunch of virus from zombies and inject me with it. I already have the freaking virus as OP states but I have no immune reaction. After I am injected, now my immune system will be aware of what it is and go to work building an antibody response. Later when the virus activates as I am dying of taco overdose, it will run afoul of the standing immune defenses my body made when I was healthy.
**2. Interleukin-2**
Same source as above:
>
> Previous reports that immune activation plays a role in the
> pathogenesis of furious rabies have not been substantiated:
> indeed, furious rabies is associated with minimal inflammation and a
> high viral load.
>
>
>
IL-2 is the T cell party drug. It makes T cells go wild. The result looks like overwhelming sepsis: fever, hypotension, organ failure etc. 1 in 10 people with advanced melanoma can have lasting remissions from IL-2. The wild activated T-cells somehow figure out in that state what they could not figure out before: melanoma is bad. So too with the zombie virus. It is somehow laying low, not recognized by the immune system. Immune stimulation might goad my immune system into action. As with #1 above, when I am dying my immune defenses will remain intact to some degree and suppress virus activation.
Interferon might be a less dramatic way to accomplish the same end. People routinely are treated with interferon-alpha for hepatitis C, an RNA virus. But it is not as exciting as IL-2.
**3 and 4: Amantadine and Ribavirin.**
[Treatment of rabies with induction of coma](http://www.nejm.org/doi/full/10.1056/NEJMoa050382)
The linked article describes the survival of a girl with rabies and how it was accomplished: throwing the kitchen sink at it.
>
> After the induction of coma and on the basis of discussions with
> scientists at the CDC, we instituted antiviral therapy. Studies in
> animals have shown little penetration of ribavirin into the central
> nervous system, and it has had little effect in animal models, but we
> administered the drug with the rationale that elevated protein levels
> in the cerebrospinal fluid indicated permeability of the blood–brain
> barrier and that ribavirin might protect against rabies myocarditis... >Amantadine... was added on the fourth hospital day because of its in >vitro activity against rabies virus.
>
>
>
Both these drugs have activity against RNA viruses. Amantadine is the original anti influenza drug (rimantadine or Tamiflu is its descendant) and it works thru some sort of action on the viral envelope. [Ribavirin](https://en.wikipedia.org/wiki/Ribavirin#Mechanisms_of_action) is used against hepatitis C and many other RNA viruses including those causing viral hemorrhagic fevers. It is a nucleoside analog and causes hypermutation in RNA viruses.
Both of these drugs are ok for long term outpatient use. I can take my "don't zombie when I die" pills when I brush my teeth and put on my rash lotion at night.
**5. Cyanide**
This one would not be for regular use, but to keep handy and take when it became clear that the taco was truly bad and I was done for. Cyanide is poisonous because it shuts down cellular metabolism. Viruses rely on cellular metabolism to reproduce. The cyanide pill will be the end of me and the end of my cells, and also the end of the virus.
[Answer]
I'm really focusing here on the "Components are not limited to medicinal ingredients, but can also consist of anything else" stipulation.
1. **Computers / Networking Equipment**
Assuming the internet has gone down (and really, why wouldn't it in a worldwide apocalypse scenario) the CDC would likely no longer have access to [The Cloud](https://computer.howstuffworks.com/cloud-computing/cloud-computing.htm) nor its power of [distributed processing](https://en.wikipedia.org/wiki/Distributed_computing). Therefore in order to calculate a cure in short order, they would have to build up their own store of available CPU cycles, which they would do by [networking together](https://en.wikipedia.org/wiki/Beowulf_cluster) more and more CPUs and GPUs. Locally. In their own building. On their own LAN. Which means they'd need computers. But they'd also need...
2. **Solar Panels / Gasoline / Wood**
While Georgia does have its fair share of [power stations](https://en.wikipedia.org/wiki/List_of_power_stations_in_Georgia_(U.S._state)), I'm not sure how many of them can be counted on to run indefinitely on autopilot when the world goes to pot. Meanwhile, the CDC needs power.
For every new computer on the network, our plucky survivors would need the ability to provide enough electricity to that computer in order to keep it running during the calculations. Solar panels may work well for this purpose. They're relatively rare, but can be spotted easily with a pair of binoculars from a tall building, and [can be serialized](http://www.alternative-energy-tutorials.com/energy-articles/connecting-solar-panels-together.html) fairly easily. As a downside, they might not be quite common enough within the intended radius, nor might they provide enough overall power for your situation...
Barring solar, gasoline is a somewhat common resource that could be used to power your standard gas-powered generator, but it would also run out as a resource fairly quickly. Honestly, the stuff [doesn't keep forever](http://www.fuel-testers.com/expiration_of_ethanol_gas.html). In a few months, whatever you siphon from any vehicle or station will become pretty much worthless. I know, most zombie movies and shows have that wrong. But if your timeline is short enough, gasoline might be your answer.
Your survivors might be crafty and resourceful enough to build [gasifiers](https://science.howstuffworks.com/environmental/green-tech/energy-production/gasification.htm). This is an old technology that is often employed during fuel shortages in order to turn wood into fuel for vehicles or to generate electricity. Wood is a fairly renewable and common resource, found in or near a lot of homes and forests. Chop quietly...
3. **Food / Water / Water Filters**
The survivors themselves should not be discounted as a crucial ingredient in preparing the cure. They're necessary for gathering all of these ingredients, after all, and they likely will be necessary for distributing the cure also. After some amount of time, the scientists certainly will have to attend to their own needs, and I'm pretty sure the Centers for Disease Control were more designed as just a set of research laboratories than any sort of long-term zombie shelters.
A constant source of fresh food and water will be necessary to keep these survivors whole and hale. The fridges and vending machines in the CDC kitchens are only so large. In maps of CDC Campuses I've found online, I don't necessarily see a garden or a greenhouse anywhere. Any water filters that may be installed will also only last so long, and that's assuming the water pressure doesn't dissipate completely when the power goes out. (People who currently work with, or have worked with the CDC, feel free to correct me if I'm wrong on any of this.)
4. **Viral Samples**
Some [viruses](https://en.wikipedia.org/wiki/Viral_evolution) and [bacteria](https://en.wikipedia.org/wiki/Antimicrobial_resistance) have demonstrated a pesky habit of adapting, mutating, or evolving to meet new situations; various sorts of mutations could make them unpredictable and difficult to fight. Assuming the zombie infection has made it around the world, there's likely some variety to the illness that needs to be accounted for... so zombies themselves (or at least, their vital fluids and tissue samples) may need to be harvested.
5. **Antibiotics / Antimalarials / Antiseptics / Antivirals / Antiparasitics**
Perhaps this is more what you were after, and I'd be remiss if I didn't include it:
Common [Antibiotics](https://en.wikipedia.org/wiki/Antibiotics) like penicillins, cephalosporins, and carbapenems; [Antimalarials](https://en.wikipedia.org/wiki/Antimalarial_medication) such as quinine, artesunate, and doxycycline; [Antiseptics](https://en.wikipedia.org/wiki/Antiseptic) such as ethanol, propanol, iodine, and hydrogen peroxide; or any of a slew of [Antivirals](https://en.wikipedia.org/wiki/Antiviral_drug), [Virucides](https://en.wikipedia.org/wiki/Virucide), and [Antiparasitics](https://en.wikipedia.org/wiki/Antiparasitic); each definitely would be important in specific situations wherein the method of transmission is primarily bacterial, malarial, topical, viral, or parasitic in nature...
But if this were indeed the case and these common drugs were largely effective, one might question why they weren't employed A LOT sooner to stem the tide of the outbreak. An obscure or complex [combination of these](https://en.wikipedia.org/wiki/Combination_therapy) might be necessary. If calculating a single new vaccine isn't what best suits your zombie apocalypse, calculating a combination of drugs and/or vaccines to quell the outbreak may be required.
[Answer]
You could pick any particular mechanism and build an explanation.
**Viral vaccination**
The word vaccination derives from latin for cow, since cowpox conferred immunity to smallpox. If your zombie virus mutated from some common (or rare) virus, then having previously been exposed to some (ebola, influenza, chickenpox, a specific rare variety of rabies) variant could confer immunity. Now, surviving ebola to gain immunity might be more risky than just staying indoors. Perhaps there are several techniques that make the initial disease more survivable, like regular transfusions or a specific medicine. So, your cure needs a mild strain of rabies, 10 units of blood, and 3 boxes of tamiflu to gain immunity over the course of a 2 week rabies infection.
**Latent viral infection**
You've described the airborne form as a latent infection, perhaps there is a treatment that will cure the latent infection, either a medicine or a course of treatment (it resides dormant in the liver, so exposure to methanol trigger stress in the liver that causes the virus to release into the blood, expecting a weakened host, but some medicine or blood chemistry destroys it or triggers the immune system to attack it).
**Bacteria**
Bacteria have more complexity than viruses, and numerous have several stages including dormant forms like TB, botulism, and anthrax. Again, pick a mechanism of infection or treatment and work backward to a plausible explanation. Bacteria have differing sensitivities to a wide variety of medicines, so you could need a drug cocktail or certain conditions combined with a drug (like temp or blood pH). Whatever you want to come up with.
Or the virus infects a specific bacteria preferentially, so it confers immunity to bacterial infection, or the bacterial infection causes the virus to be expressed and develop an immune response, or whatever.
Do you want the treatment to be some rare thing that needs to be collected? Or hard to do in the right order at the right time? Or to have an interesting discovery story?
] |
[Question]
[
A dragon has appeared on the streets of New York and is rampaging around attacking anything that moves- along with devouring the local wildlife (humans).
**Dragon Characteristics**
* Main body shares similar dimensions to a fire truck, with a serpentine neck of half that length and a tail of the same length as the body but slimmer.
* Four legs, sharp claws that can dig into concrete and steel. The legs are strong enough to move this dragon at up to 50 mph though it cannot maintain this speed for more than perhaps 10 minutes.
* No wings.
* It does not breathe fire so much as secrete a chemical in a special organ under high pressures. It can fire this liquid the length of a football field and it functions identically to Chlorine Trifluoride once it impacts anything beyond air. The dragon cannot be harmed by any aspect of this breath weapon.
* The dragon is more intelligent than dolphins/apes and is familiar with humans and their weapons. It knows military forces on-sight and prioritizes their deaths compared to civilians.
* The hide is capable of deflecting any bullets that are below the 0.50 caliber without issue, feeling only like an annoyance. 0.50 cal bullets will cause pain but will not pierce the hide without a sustained series of shots on the same area.
* The dragon can remain in combat for 24 hours before it will have to rest. Sometime around 20 hours it will attempt to burrow beneath the streets or possibly building rubble to make a den where it will attempt to get at least 5 hours of sleep before it's revitalized.
Note- The humans are not familiar with these characteristics until they experience them, for example, not knowing how durable the hide is until they presumably fire at it with different weapons.
With the above information in mind, and citizens frantically calling the local police about this issue, what is the best response with the following goals?
1. Minimizing civilians casualties and property damage
2. Stopping the dragon as soon as possible, death of dragon not required but not forbidden by any means
3. Obeying the chain of command (Proper procedure for calling SWAT, national guard, etc.)
4. Preventing mass panic
[Answer]
First we need to examine the dragon. It is a fast, armored, ground-based weapon capable of firing a projectile, and operates with a high degree of intelligence and autonomy. Does this sound familiar? **To me it sounds like a Tank**. Perhaps a bit hungrier and wigglier than the traditional models, but a Tank nonetheless.
With that out of the way, let's talk about how to engage it. As a few people have been discussing, the dragon is tough, but not invincible. Typical small arms fire is going to be useless, but .50 BMG seems to be at the lower edge of effectiveness, so we'll start there and work our way up.
There are also four conditions to consider alongside the effectiveness of the weaponry:
>
> 1. Minimizing civilians casualties and property damage
> 2. Stopping the dragon as soon as possible, death of dragon not required but not forbidden by any means
> 3. Obeying the chain of command (Proper procedure for calling SWAT, national guard, etc.)
> 4. Preventing mass panic
>
>
>
These restrictions limit exactly which weapons and tactics we can employ against the dragon. There are, of course, aircraft which would obliterate the dragon with little effort, and even ground-based weaponry that will suffice, but most of those options are culled by either consideration 1 or, surprisingly, consideration 3. Obviously we could just nuke the dragon, or carpet bomb it, or use any number of very, very destructive munitions, but you don't want civilian casualties or property damage so we can't do any of those things. Also, since this is a domestic emergency in New York, we are limited to the weaponry deployable by the **NYPD SWAT** teams, the **New York Army National Guard**, and the **New York Air National Guard**. Luckily, I think I have found some suitable weaponry accessible by each of the three branches.
The SWAT teams are going to be the first to respond to the "disturbance". Small arms obviously aren't going to work, and men on the ground are going to get roflstomped by the dragon, but as soon as they notice it has no wings it won't take long for them to deploy in **Helicopters**. A couple aircraft with sharpshooters armed with [.50 BMG](https://en.wikipedia.org/wiki/.50_BMG) weaponry might even be enough to put the dragon down all on their own, no National Guard involvement needed. You mention a vanilla .50 BMG will hurt the beast, but not penetrate its hide. Luckily for our intrepid SWAT team, the **.50 BMG AP** (Armor Piercing) or "Black Tip" cartridge is far scarier (I know from experience it can penetrate at least an inch of steel). There are also **.50 BMG API** (Armor-Piercing Incendiary) and **.50 BMG HEAPI** (High-Explosive Armor-Piercing Incendiary) rounds that can do even more damage, though they are probably harder to acquire.
The next step up on the escalation would be the New York Air National Guard scrambling from Hancock Field Air National Guard Base in Syracuse. To my surprise, the NY Air National Guard has only a single combat wing of aircraft and they are all [MQ-9 Reaper drones](https://en.wikipedia.org/wiki/General_Atomics_MQ-9_Reaper). At first I was a bit disappointed, but I think this is a blessing in disguise. Reapers are unmanned, so we won't lose any pilots, and they're smaller, slower, and arguably nimbler than traditional military fixed-wing aircraft which means they are better suited for engagements in an urban environment, plus they can still carry a wide variety of weaponry. They might not be A-10 Thunderbolts, but they *can* carry [Hellfire Missiles](https://en.wikipedia.org/wiki/AGM-114_Hellfire), which are specifically meant for use against armored targets. If the .50 BMG toting SWAT sharpshooters couldn't bring down the beastie, the **Reaper Drones armed with Hellfire Missiles** will probably do the trick.
Finally we have the New York Army National Guard (I can't say which specific regiment, since it seems the NY Army National Guard gets deployed overseas on a semi-regular basis). From a tactical perspective, if the Army National Guard is involved, then the SWAT teams have failed and the Air National Guard will be having a go. Unless the Army National Guard has any [FGM-148 Javelins](https://en.wikipedia.org/wiki/FGM-148_Javelin) (and I have found no evidence they do) then the ground troops will likely be little more than fodder for the dragon. The National Guard is, however, quite good at handling emergencies in general. Civilians will be panicking since that's what civilians do best during an emergency, and panicking people do not make good decisions (like stfu and gtfo, for example). **If the Army National Guard isn't helping in the fight then they can be managing people, getting them away from the dragon** as the Reaper Drones go to work, and handling the general evacuation of the area alongside the police and other emergency workers. It might not be glamorous, but I feel that in the spirit of your question, this job is probably the most important of them all.
So that's how I see things going down. Hope it helps.
[Answer]
After failed SWAT team intervention and more than a few failed sniper attempts, air support is requested. The National Guard responds to the call by deploying a small formation of Apache Helicopters. Using herding/suppression fire they drive the dragon to a less populated area, where they then strike it with a few sidewinder missiles.
Problem solved.
Reference: <https://en.m.wikipedia.org/wiki/AIM-9_Sidewinder>
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As I said [before](https://worldbuilding.stackexchange.com/questions/52555/how-do-you-beat-a-middle-sized-dragon/52581#52581), use poison, pathogens, or parasites.
At least that will *help*: if the dragon has a bad case of scale mites it might be easier to punch through with artilary. Since this is modern times, they might use weaponized diseases like anthrax or clouds of nerve gas.
Even without actual weaponized chemicals handy, just using commercial chlorine gas etc. would be easy.
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So this dragon is akin to Godzilla.
To minimize casualties, simply lead it away. Either by chasing it off with explosives or .50 cal rifle fire. Or entice it with prey. Alternatively evacuate the area. This will probably be the most likely response by authorities. The moment an unidentified threat starts killing civilians and destroying infrastructure you evacuate the area.
As for taking it down, tanks seem like a decent candidate. However it takes time to get those in range. So unless armor is near the dragon to begin with it's unlikely to be deployed.
The navy or airforce would have a better chance. Or in this case the CIA with drones. Regardless you want a highly mobile force with long range capabilities. Missiles are the easiest but also quite messy. Explosives create a lot of collatoral damage.
No the coolest effective way to take this thing down would be [railguns](https://www.youtube.com/watch?v=9PItPL7EZEc). Sure this comes with a couple of caveats. First it needs a direct line of sight so the attack has to be coastal. Second railguns aren't really deployed yet. It's future tech for the next decade. However it has no explosion and will tear through the dragon with relative ease. I mean it's a railgun, +1 for the cool factor.
[Answer]
**Taser drones.**
You could have taser drones with capacitors big enough to drop the dragon. Or you could have a drone carry a live wire from an adjacent building and drop it on the dragon.
If it has muscles it will be all over. If its armor works because it is metallic, even better. If it has hit a fire hydrant and is standing in a puddle, best of all.
It could stop a drone carrying a wire with a breath weapon but that is it. You could rig it so the whole drone is charged and if the dragon touches it, that completes the circuit. The drone itself will not be hurt by the wire en route because there is no path to ground as long as it is airborne. Have drones take off from (abundant in NYC) adjacent rooftops carrying wires and turn on the wires in flight.
If you sent 20 of these at once the dragon would be helpless. And: no stray bullets. No property damage. No expensive helicopters piloted by soldiers with families.
Best: you get the dragon alive. Question it at your leisure. Understand its motives. Exhibit it for profit? Have it fight other dragons that attack your city! How could keeping the dragon alive possibly go wrong?
Do you doubt that electricity will drop a large animal in its tracks? Doubt no more. <https://youtu.be/WKBC4bMKPnY?t=143>
Do you wonder what the Taser Drone theme song is? Wonder no more.
<https://youtu.be/yK0P1Bk8Cx4?t=27>
(as you sing along, change lyric to "taser drone")
If it is 1920 and drones are scarce, you could have guys on roofs throwing truck tires with attached wires at the dragon. Or charge it with an automobile with the wire mounted on the hood (the tires will insulate the auto). Or poke a wire up from an open manhole under the dragon. The theme song does not make as much sense with these methods.
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There are some excellent answers already. If the one from [MozerShmozer](https://worldbuilding.stackexchange.com/users/20048/mozershmozer) didn't kill the Dragon, this is your backup.
As noted, with the details given, it is only a matter of time when the Dragon goes down. To limit destruction of buildings and reduce collateral damage, I'll focus on ground units.
Luckily, NY has its own base: [Fort Hamilton](https://en.wikipedia.org/wiki/Fort_Hamilton#Units). But looking at the list of units there, only the `the North Atlantic Division Headquarters of the United States Army Corps of Engineers` might have a way to deal with the dragon. I am thinking explosives and anti tank mines. But this being the HQ I hope there are some senior NCO's who can deal damage.
[Fort Drum](https://en.wikipedia.org/wiki/Fort_Drum) has a nice collection of asskickers. Mountain troops, those guys should handle tall buildings as well. I cannot find their gear within 3 minutes of searching. But seeing they are well trained light infantrymen, I'll assume they have the gear needed to bring down a Dragon. Gear like: [AT4, LAW, TOW & Javelin.](https://en.wikipedia.org/wiki/List_of_equipment_of_the_United_States_Army)
Only question remains, how much time does the Dragon have? I'd say less then 6 hours. Maybe less then 1 hour if a group of troops is live fire training with things like the AT4 and a transport helicopter is ready to go.
Happy hunting!
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There are more than a couple of problems with your dragon. Consider the calories it would need to be extremely active for 20 hours. I'm having trouble imagining that any animal can project a stream of liquid 100 yards. Where does it store the mass for its "flame thrower" fuel? A 1 inch diameter stream of liquid the length of a (US) football field is nearly 50 gallons (400+ pounds). It would almost immediately be "out of ammo". It would certainly be more effective to "hawk" a more or less solid (mucus), and while its range would be limited by its aerodynamic resistance and initial velocity, a rheopectic liquid (solid under high shear, flows under low shear) might do the trick. Anyway, any modern High Explosive Anti Tank round would take. it. out. This could be delivered either via missile or shell. (I won't argue the implausibility of such a creature being impervious to 50 caliber (armor piercing rounds - and it *is* implausible). Another possibility is a flame thrower. If it's really burning that many calories per second, then it must have a real problem keeping cool enough to not boil. It wouldn't function at all well if the ambient temperature was a 300 - 400°C.
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> It knows military forces on-sight
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Using the fact It only knows forces 'on sight', try to attack his back, or a sneak attack.
Also, use electric mines. It would most likely be vulnerable to those attacks.
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The dragon is hungry or feel alone.
Give him a virgin and they use to sleep for a year more.
Then some say it do not exist any virgins, no from what we know they did die out with the dragons :)
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In the universe I am designing, an anthropomorphic species exists that can create fire at will. One normal human wants to trick others into thinking she is one of these creatures.
She wants to design a glove which produces little flames/sparks when it contacts human skin during hand-to-hand-combat, thereby demonstrating that she can create fire seemingly "at will." The fighting style is similar to MMA with fewer rules, which for this question means: a lot of skin is exposed, gloves are allowed, armor and other weapons are not allowed.
**Is it feasible to create a glove that e.g. is coated with a material that sparks little flames when coming into contact with human skin?**
Some points to keep in mind for creating this glove:
* The glove/flames should not hurt the wearer
* It is not important how big the flames are / if the flames damage the opponent (the psychological effect is enough)
* Technological level: I prefer ~15th century Europe, but you are free to choose whatever suits your idea
* It should be "reusable," so that you can hit the enemy multiple times with the "fire-glove" and produce flames/sparks each time
* The definition of "glove" for this question is ["a covering for the hand made with a separate sheath for each finger and for the thumb"](http://www.dictionary.com/browse/glove); I will not impose restrictions on weight/size/color/ … . This means you don’t have to restrict yourself to typical [MMA gloves](https://en.wikipedia.org/wiki/MMA_gloves).
* It is not important where exactly the flames are created. This means it doesn't matter if your idea for example only works at the tip of the fingernail or only in the palm of the hand. But some words on the preferred fighting-style when using your idea would be nice.
If you need any more background information about the universe that this glove is supposed to work in or about the creatures that this normal human wants to imitate please have a look at my other question ["The role of anthropomorphic foxes in a medieval army"](https://worldbuilding.stackexchange.com/questions/68131/the-role-of-anthropomorphic-foxes-in-a-medieval-army).
If you need to adjust the technological level, the attire of the combat, the damage of the glove or something else please feel free to do so.
**The goal is to create a glove that produces little flames/sparks on contact with human skin.**
[Answer]
There are several chemicals which could (for alchemically improbable values of "could") be produced with 15th-century technology (they called them *oil of vitriol* and *sal alcalinus fixus*, but still) which could erupt in flames when properly mixed.
What you would need then is a multilayered glove:
* an inner layer of supple leather, possibly water-soaked just in case.
* middle layers of gauze impregnated with combustible substance and accelerants.
* the outer layer is leather again, with small holes.
When you hit an opponent with enough force, the glove is locally squeezed, resulting in a bout of flame (the first two or three prototypes of the glove will probably sort of combust).
Adding specific chemicals can then change the colour of the flames.
Unfortunately, all reactions that come to mind tend to be too weak, leave a suspicious-looking and foul-smelling soot and smoke residue, or both. Also, the glove would quickly lose charge.
I had entertained the concept of piezoelectric crystals, but while such a glove would be possible with 15th-century technology, it still requires twentieth century *knowledge*. And of course, it is not *flame*.
Another possibility is mechanoluminescent crystals - see here for a [low-tech flashy ceremonial rattle](https://en.wikipedia.org/wiki/Ute_people) - but the light is weak, clearly not flame, and too clearly related to the hitting, not to any power of the wielder.
Then, probably not achievable with 15th-century tolerances but it *would* be flame, you could incorporate some [*slam rods*](https://en.wikipedia.org/wiki/Fire_piston) into the glove. Add iron filings to the tinder and get impressive flames.
Much more difficult to conceal, but extremely low tech is the hidden coal trick. There was this man, [Eunus - a Syrian slave if memory serves](https://en.wikipedia.org/wiki/First_Servile_War) - who used a nutshell with two small holes at opposite sides, filled with combustible materials and one small, oxygen-starved, slowly smoldering coal. One evening he would hide the nut in his cheek, purposely enter an altercation with someone, and at the proper moment he would move the nut against the palate with the tongue, and *blow*. The sudden burst of flames in the enemy's face was very impressive.
Using a semi-inflated air bladder hidden in the glove could help achieve a similar effect; I don't dare estimate the reliability in combat of such a cantrip, though. The coal might extinguish, or to the contrary, it might set the glove on fire.
For added reliability and control, the bladder could be somewhere else - e.g. on the upper arm. Contracting the upper arm would still get air flowing and fire blown out of hidden vents, but now hitting the adversary is not required, and it would not automatically (and visibly mechanically) result in fire spouts. *And* you could get a couple of spouts before combat, and before anything unforeseen happens to the mechanics.
[Answer]
Human skin does not have many properties which make it instantly "recognizable" to a device at 15th century tech level, but their are two noticeable features to it.
1. Moisture - There are multiple different substances which would produce flames on contact with moisture and therefore skin. However, these would NOT be reusable, and would have to be re coated with the substance fairly regularly. There is also a chance that a) the area of skin would not be moist enough to start the reaction, or b) the gloves would combust in contact with other moisture (bad). However, this added challenge with these particular gloves (i.e. limited uses per fight, have to strike in certain areas) might present a nice addition to your characters battle dynamic
2. Conductivity - The creation of flames using electrical conductivity would require a substance to be used as fuel which would be sparked and then lit, so we should really just stick to sparks here. There are numerous ways to create a spark on contact with a conductive material, but tech level must be taken into account, so a voltaic pile-style electrochemical cell would probably be your best bet. When these gloves come near a conductive substance (like a human) they could produce a cool tesla coil-esque spark that would hit the skin and give a mild electric shock. You would need to somehow integrate this cell into the glove, perhaps a cylinder on the back of the hand. Again, these gloves would be triggered by any conductive substance, but again, this could introduce an interesting plot element when it comes to the characters fighting.
Needless to say, the gloves would have to be both fireproof and an electrical insulator in contact with the skin, but there are are many ways of doing that and that should not be too much of a problem.
No matter how advanced these gloves are, however, nothing in the real world, at least with any non-modern tech level would be able to replicate this effect exactly, so it is probably more possible if you were to introduce a world mechanic, such as gloves made from elements of the bodies of these fire-creators, as this would be far more viable.
EDIT: Thinking about it, a souped up version of the kind of gunpowder caps used in cap guns would be very plausible, a small pressure activated explosive would be fine if it is not ESSENTIAL to be reusable, simply punching your assailant would be enough to detonate
[Answer]
**Materials**
Depending on how lethal you want the flames to be I would suggest one of the higher elements on Period 1 of the Periodic Table. Francium is an extremely unstable element that essentially explodes when it comes into contact with moisture. How ever for the safety and realism of the wearer I would suggest a small amount of Cesium.
**Design**
Alright so lets assume you go for a small amount of Cesium. You still need a very thick insulating lining that protects the wearer. The lining needs to be fireproof and very robust. The cesium should come in small discs on the tip of each finger and the base of the hand. If you cover the entire outside of the glove with cesium, it would remove the users entire hand.
**How to Use**
Simply grab the arm of your victim, the bodily moisture will react with the cesium. It will erupt in flames, leaving your prey with vicious burns.
The only downside is the cesium will need replacing each time. You might also want to take a damp cloth in case your victim isn't quite wet enough.
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What about building little flamethrowers into the glove, one on each finger? Run some flexible tubing (similar to vinyl, perhaps with treated animal skins) to the tips of the fingers, pump something flammable through it (if gasoline and butane are too advanced, you can use some substance like [Greek Fire](https://en.wikipedia.org/wiki/Greek_fire)), and have a flint sparker on the end of the tube, like a lighter. This way, it doesn't even need to be triggered by the enemy's touch, but truly on demand (and, if you wish, that can be every time they touch).
[Answer]
How important is it that skin itself be the trigger, rather than having a controllable trigger in the glove?
So, I have this lighter - unlike the wheel type ones, it has a simple press button on top to ignite the flame. Similar click lighting flint and steel mechanisms are a thing, and simple tubes will let the fuel be stored further away, the better to hide small mechanisms. One could certainly rewire such lighter mechanisms into a glove, to go off when certain parts of the glove are struck - and fuel stored in thin pouches on the back of the hand, or at the cuffs. Smack the glove in the right place, the button goes click, and you have a brief fire (brief because the mechanism stops supplying fuel when the pressure lets up). Smack and hold, and the fire stays up for a bit longer. Depending on placement, it might be possible to have the clickers spark only when striking, only when deliberately triggering (by hand pressure or finger placement) or some of each.
And that also got me thinking, about simple flint and steel - especially if you're looking for 15th century technology. I admit I'm not as sure about the historical development of lighters, but some flint, some steel, and a spring mechanism (which should be available at the time) could create a mechanism that sparked off when struck violently enough. You could leave it as is, if you have several - little sparks would fit the criteria (and leave scorch marks), though it might not be very flashy.
The trickier part, I think, would be turning that spark into flame... it needs fuel. Maybe some small gobs of pitch would work, if well positioned - if the flames can be shaken out by hand, the pitch will be good for several ignitions before it's all covered with soot or smeared about too much to ignite easily. But if the pitch doesn't go out easily, either it will be a one-shot trick (pitch keeps burning until eaten by the fire), or else the glove will catch on fire and scorch your character's hands. Perhaps some form of fat would be a better choice, I believe it takes a bit more to light, but it should light, and also go out more easily - and if a solid fat like lard is chosen, it might be easy to store (squash the stuff into cloth or leather tubes, as opposed to mucking about with liquid accelerator), and solid fat might only run out in drips and drabs as the hands and flames warm it up and let it ooze - much better for multiple use strikes.
A spring loaded mechanism would probably have to be loaded onto the palm or heel of the hand (flames with open palm strikes, but not so much fists), since it would take considerable force to force flint and steel together strongly enough for big sparks (slow pressure or weak force might make grinding noises, but probably not visible sparks). If slightly more advanced press button lighter-type systems are allowed, the buttons might be put between the fingers, so they only go off when deliberately pressing the sides of the fingers together, and not with normal lifting and gripping.
[Answer]
Maybe using small flints that make some spark, after that you can have some sections in the glove that will trigger with different types of hits, of course you will have a limited number of flames, but you can have a lot of little sparks.
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# Static electricity?
I'm surprised no-one has mentioned this. How about a glove, that when touches another's skin, generates a positive and negative charge. From there, either a gas or some type of highly flammable chemical would take care of the flame.
Your glove could be made out of any of the given materials:
* Leather
* Rabbit fur
* Cat fur
* Wool
* Silk
Naturally, after a single use, the charge and flammability wear out. You'd have to top up the flammable chemicals and, of course, recharge the glove.
There are a number of ways to recharge the glove. The most simple? Rubbing it against some type of plastic (Polyurethane). Perhaps that's where we run into a problem. The first polyurethanes were rendered in the 1930s. So you might want to research other alternatives, here's a [document](http://www.school-for-champions.com/science/static_materials.htm) that might answer that question for you.
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I'm thinking of some sort of point-blank nanoweapon, one in each of the fist.
My original idea was a small flamethrower on each knuckle, with a trigger also on the knuckle, so when someone punches another person, it burns the flesh. If it's handmade, say the base is a winter glove, if not use a shiny metal gauntlet. I'm a Sci-Fi person, so I'm going to be going into the advanced tech.
First of all, I thought of a small needle that punctures the skin then draws tissue, which triggers the mechanism. This would look like a thin ring with a needle on it and a wire leading down the arm. The whole thing would be hidden by a long sleeve. The actual weapon would do two things:
* open a valve which releases a vaporized sticky napalm, preferable early on in the fight or before it even starts.
* The second part is triggered by the needle, which is essentially the sparking of a lighter.
The result: A sly way to BURN YOUR ENEMIES TO DEATH!
[Answer]
Not being a Chemist thus not having knowledge for being able to cite specifics: but it could be conceivable that there is a substance the glove is constructed from/soaked with that reacts with sweat (or something in sweat, like salt).
It would probably only create a small flame, related to the amount of sweat in contact with the glove, limiting the duration thus allowing the glove to last an extended period of time. Depending on the reagent that causes the flame the user could have a hidden vial or bladder of the substance to 'create fire at will' outside of a fight.
A downside to this is that the fire gets worse as the combatants sweat more. This would make the user seem like they have little stamina or rely heavily on the ability to make fire in their combat style.
The only safety measures are the user couldn't touch themselves and the inside of the glove would have to be waterproof. (Or the fire 'producing' fabric is sewn on in certain patches, thus easier to replace and only the patches need to be isolated from the user's sweat.)
[Answer]
That is not possible in the real world, but you presumably have such a mechanism in your story’s universe. What you need to do is use the *same* mechanism.
The gloves are made from alien lether, or treated with extracts from the alien skin, or something like that.
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[Question]
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In [this answer](https://worldbuilding.stackexchange.com/questions/64649/when-creating-a-human-like-cyborg-what-hardware-and-software-are-critical-f/64654#64654) about how to design the ideal cyborg, I said:
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> ...
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> * **Use electric tissue to power the machines.** Cyborgs need some way to generate electricity when mechanical parts are involved. Rather than batteries, which can corrode and leak, generators, which are noisy, or charging, which isn't always an option, consider a polymer layer below the skin [that turns chemical energy into electricity](https://www.technologyreview.com/s/543781/plant-lamps-turn-dirt-and-vegetation-into-a-power-source/). Polymers solve everything.(™)
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I reasoned that while installing such a layer would be invasive and somewhat painful, it would work in all locations, and would not need to be refueled in the traditional way.
## The cyborg in question needs minimal power - to aid locomotion a bit, to maintain an artificial heart, and to maintain a series of pumps throughout the body.
### **Is this an efficient way to power a human cyborg?**
What alternative technology could do the job **better**, assuming charging / refueling cannot happen frequently?
[Answer]
## Radioactive Diamond Batteries
Diamond naturally generates electricity when exposed to radioactivity. So, [radioactive diamond batteries](http://www.forbes.com/sites/jamesconca/2016/12/09/radioactive-diamond-batteries-making-good-use-of-nuclear-waste/#747d3f36bac4) are made by [forming carbon-14 into diamond and encapsulating it in regular non-radioactive diamond](https://m.youtube.com/watch?v=b6ME88nMnYE).
These diamond batteries have a very specific purpose – low power and extremely long life. A standard twenty-gram non-rechargeable AA battery stores about 13,000 Joules and will run out of power in about 24 hours of continuous operation. One diamond with one gram of carbon-14 would produce 15 Joules per day, much less than an AA battery.
But the power output of the diamond battery is continuous and doesn’t stop. The radioactive diamond battery would still be putting out 50% power after 5,730 years, which is one half-life of carbon-14 or about as long as human civilization has existed. During this time, the diamond battery would have produced over 20 million Joules. And would produce another 10 million during the next 5,730 years.
These could be useful for pacemakers and other internal low power devices, since they do not have to be replaced via surgery.
## Thermoelectric Paint
Perhaps internal body parts could be coated with [thermoelectric paint](http://phys.org/news/2016-11-thermoelectric-enables-walls-electricity.html). That could absorb body heat and convert it to electricity.
## Piezoelectric Artificial Body Parts
While no one has made piezoelectric artificial muscle matrial yet to my knowedge, it seems like it could be an ideal innovation for cybernetics.
[Piezoelectric materials](https://en.wikipedia.org/wiki/Piezoelectricity) generate an electrical charge when deformed by mechanical stress. So, something like an [artificial muscle](https://www.google.com/search?q=artificial+muscles&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari) that is always flexing and contracting could be a great possibility for piezoelectricity. In addition, [bones, tendons and other natural body parts](https://en.wikipedia.org/wiki/Piezoelectricity#Bone) already are known to be naturally piezoelectric, so perhaps synthetic versions could be developed that produce even more electricity than normal.
[Answer]
[Artifical photosynthesis](https://en.wikipedia.org/wiki/Artificial_photosynthesis) has been making a lot of progress lately. Similar to your concept of a layer of skin which converts chemical energy to electricity, a possible better approach (depending, of course, on the lighting conditions of the host planet) would be to instead use a photosynthetic layer. That would make the cyborg very literally *green* as well as semi-transparent too. It has the bonus of running completely silent as well as requiring no daily dose of chemicals, aside from those found in your typical life-supporting atmosphere.
It's also worth mentioning that the most efficient kind of photosynthetic layer would appear deep black as it's absorbing *all* of the light that lands on it.
The structure of such a layer would likely be [nanograss](http://newatlas.com/nanograss-solar-cell/34080/) - a nanotechnology technique which helps maximise the available surface area, boosting the amount of sunlight it can capture.
One of my personal favourite real-world concept designs featuring this kind of layer is the [Nokia Morph](https://www.youtube.com/watch?v=IX-gTobCJHs&t=2m09s) - a concept phone which explores the ways in which nanotechnologies might be beneficial in the future.
**How much power could it generate?**
At the equator, the average sunlight received by the top of Earth's atmosphere is about 1.3kW/m^2, [according to NASA](http://earthobservatory.nasa.gov/Features/EnergyBalance/page3.php). On average, it's 340W/m^2. About 48% reaches the surface, giving us an average of about 163W per square meter, accounting for clouds etc.
Meanwhile, the average human male's body surface area is about 1.9 square meters - most of this is shaded, but that wouldn't necessarily be the case for a well designed cyborg which doesn't have any need for clothing. Humans also consume about 97W of power, on average. Keep in mind that a large portion of this is used for heating and digestion too, which the cyborg has little need for.
So, assuming our cyborg has a male build, is in Earth-like conditions and has human-like power requirements, as well as a nanograss power generation surface, it could easily have 4 square meters of power generating capacity; in the absolute best case scenario with 100% efficient panels, that means the best it can generate is 4 \* 163 = 652W, which is well above the 97W it needs, giving a possibly large enough margin for efficiency losses due to shade and non-ideal solar conversion efficiency.
[Answer]
The machine parts should be powered the same way as flesh, to take advantqge of the available distribution system.
It uses nano fuel cells to generate power from glucose and oxygen, extracted from blood.
See the details of the power supply for [respirocytes](https://en.wikipedia.org/wiki/Respirocyte) for in-depth details on how that would work.
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[Question]
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I recently came up with a lizard that had a sort of crystal-gem like attachment on its back. The problem was finding a way for such a thing to have evolved to have a largish crystal on its back.
The lizard is around 2 metres long, has a height of around 1 metre tall, probably carnivorous, could stand on 2 legs or 4 legs if it chooses to (there was a dinosaur that did this, I can't remember what it's called).
Now the crystal sail, it should be composed of [Euhedral crystals](https://en.wikipedia.org/wiki/Euhedral_and_anhedral) pillars that line its back to form a sort of 'sail'**(I'm not sure whether a singular large piece of crystal is better/less fragile or having multiple crystal pillars is better)**, the crystal itself shouldn't be very clear, I mean, we don't find very clear crystals naturally so it probably won't be clear on an animal. It's like the [Dimetrodon](https://en.wikipedia.org/wiki/Dimetrodon) or [Spinosaurus](https://en.wikipedia.org/wiki/Spinosaurus) 'sails' but one made of crystal. The sail peaks at 1 metre tall. **How would such a creature have evolved to have crystals growing out of its back?**
To clarify a bit, my conclusion has been that the crystals would 'grow' with the lizard during its lifetime due to the inherent problems of having eggs to fit young with a metre-long sail. This means that its diet would consist of meat, more meat and probably the occasional mineral that goes to building the 'sail'? <<< maybe?
The other problem I have is that crystal is usually quite heavy and brittle. Not all crystals of course but there might be more difficulty to have a less brittle crystal like diamond growing from its back. The heaviness part could be hand waved by 'strong' muscles and bones. The brittle part is worrying, I don't think a creature that breaks its sail every time it runs is gonna need it. (It's a good source of income for humans though.)
I haven't decided on a specific crystal yet, but if you need a specific one then go with either ruby, sapphire, obsidian or diamond. Or if none of these work then it's up to the experts.
If this creature couldn't possibly exist then I probably wasted the time you have spent reading this poorly written description.
I'm not sure if answers to this question require the function of a crystal sail but I'll get around to asking that question soon.
If you have no idea what a sail is then it's that really large extension on top of the creature you see down here; replace that with either a large crystal or multiple crystal pillars and voila. **Not to be confused with these [sails](https://en.wikipedia.org/wiki/Sail) you find on ships**
[](https://i.stack.imgur.com/jwr5O.jpg)
[Answer]
Your crystalline sail must exist for some purpose. It will be a heavy, unwieldy and cost a lot of energy to produce so it must provide some great fitness benefit to the organism. I have two potential solutions for you:
**Sexual selection**
Sexual selection can be invoked to explain all sorts of crazy things that seem wildly impractical at first. Especially things that look cool. The tail of a peacock is a classic example of sexual selection as are the fanciful colorations of most birds. Sexual selection is responsible for a large proportion of natural ornamentation. A large, shiny crystalline sail strikes me as something that might catch a potential mate’s eye. So the crystalline sail evolved simply due to mate preference, most likely females choosing males. Males that incorporated bright, colorful, shiny crystals into their sail were more attractive to females than their otherwise more fit competitors. This creates a positive feedback loop known as a [Fisherian runaway](https://en.wikipedia.org/wiki/Fisherian_runaway). It’s worth noting that the large sail of the [Dimetrodon](https://en.wikipedia.org/wiki/Dimetrodon#Sexual_selection) is theorized by many to be the result of just such a Fisherian runaway.
**Piezoelectricity**
While sexual selection is almost certainly the most plausible answer maybe you want your crystalline sail to *do* something beyond look pretty. Piezoelectricity is an electrical charge generated by certain materials in response to mechanical stress. Crystals are especially good at creating this electrical charge. A sail composed of piezoelectric-compatible crystals arranged properly could generate electrical charge from the mechanical energy of walking or wind acting to bend the sail. [Harvesting](https://en.wikipedia.org/wiki/Energy_harvesting#Piezoelectric) this piezoelectricity is actually possible and is an active area of research in the advancement of wearable technology. It’s perhaps implausible but not impossible to think that an organism might be able to make use of the electricity generated by the sail either to charge a capacitor for the purposes of attack or defense or directly convert that electrical energy into chemical energy such as ATP. So the sail acts as something of a passive electrical generator for any purpose you want to apply it to. As to how this actually came about evolutionarily, well, I did say sexual selection was the more plausible answer, but I think this one is more fun.
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I can see such a thing existing theoretically, but only because sugar is a type of crystal, such a creature would be very small, no larger than a mouse and would use its sail to store excess sugars, energy. These crystals would likely grow around long quills and theoretically speaking, a few quills could point up on their back.
[](https://i.stack.imgur.com/00zGO.png)
But let's say you want something... Bigger. Well if you're willing to bend on what the sail looks like, then we can reverse the scale.
Pangolins, turtles and ankylosaurus' all have heavy objects on their back and these are for defense. But what if your defense structure served a second purpose? Let's say we have a turtle, but this turtle starts growing excess sugar formations on its shell, over millions of years these could form the sail structure you desire.
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There is literally so much content to talk about regarding the purpose, structure, feasibility and effectiveness of this idea that isn't related solely to the evolution of such!! But I'll just focus on the crystal and development side; alright, here 'goes.
## **What crystal could be used to create this sail?**
As it turns out, the gemstones you've listed take on more the appearance of rock than crystal in their natural state, rather dull and usually suffocated by other minerals; they only get their inherent beauty from being cut and polished in specific ways, if they weren't, well, jewellery wouldn't be nearly as popular. They also will be unusable, these gem stones - sapphire and ruby and diamond - are all formed in extreme environments from being exposed to lots of heat and pressure, such amounts your creature wouldn't safely be able to create through natural biological processes.
So we look to alternate crystalline sources for inspiration, of which there are many; [Fluorite](http://geology.com/minerals/fluorite.shtml), [Calcite](http://geology.com/minerals/calcite.shtml), [Celestine](https://en.wikipedia.org/wiki/Celestine_(mineral)), [Barite](http://geology.com/minerals/barite.shtml), [Adamite](http://www.minerals.net/mineral/adamite.aspx), [Halite](http://geology.com/minerals/halite.shtml), [Colemanite](http://webmineral.com/data/Colemanite.shtml#.V_XjpyizdUQ), [Beryl structures](http://www.minerals.net/mineral/beryl.aspx), [Aragonite](http://www.minerals.net/mineral/aragonite.aspx), [Armalcolite](http://webmineral.com/data/Armalcolite.shtml#.V_Xk-yizdUQ), all these minerals form crystals that (provided the correct conditions) can grow very large indeed; they also have the advantage of being relatively easy to form under "normal" environmental conditions - such as on the back of your creature.
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> "I'm not sure whether a singular large piece of crystal is better/less fragile or having multiple crystal pillars is better"
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This is where some problems arise. Having a singular giant crystal on the back of your creature will not work, as it takes a great deal of time to build, per se, and will (if formed fast enough) be too thin and fragile to serve any purpose. This logically suggests that multitude of smaller pillars may work... not really. They would still take an eon to grow to the size needed, *from scratch*.
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But this got me thinking: as a child, who hasn't tried [growing crystal](http://www.instructables.com/id/How-to-grow-great-crystals/) in cups of water, using lots of string to give it more space to develop? This is effectively the system your creature will need to develop it's sail: some kind of large framework to grow the crystals on top of, giving it a larger surface area to bind to hence allowing it to grow faster from more locations. And what better material to use than a skeleton (calcium carbonate foam).
Coral is an ideal example of what I mean, able to expand outwards into the environment by building bone-like structures to grow upon; this gives them a very large surface area too, meaning lots of room for additional coral organisms to fix to, allowing it to grow to huge sizes.
Your creature will need to have a similar, coral-like structure protruding from its back (cartilage will do just fine) that forms the basic shape of your sail where crystals can grow. This leads us to the evolutionary part of your question:
## **How would it have evolved to grow crystals in this way?**
The animal your new creature has evolved from would have also had a sail, or fin-like protrusion from its back, that by all means could have acted in the same way a Dimetrodon or stegosauruses is suspected to have (for thermo-regulation purposes/ attracting a mate).
It would have had to have lived in/near an environment that was rich in the elements required to produce these crystals (they being iron, copper, silicon, fluorine - all abundantly available), for instance the land surrounding VOLCANIC PLAINS! They are the ideal environments, readily life-sustaining and rich in mineral-saturate lakes/pools that's sediment and water contain these required trace elements.
All it would have needed to do is move through these mineralised waters on a regular basis; when the water evaporates off it's skin (the majority being on it's sail) the crystal forming elements are left behind; they react with the oxygen in the air and form the foundations for further crystal growth.
As time progressed and a thicker layer of oxidised copper/iron/fluorine/ gathered, the sail became encased in a thin crystal-armour; this was good for protecting the sail, but inevitably led to it's overall destruction (deteriorating the skin, causing it to die and leaving only the bare bones behind, which quickly became coated in the same crystal).
As generations went on, young were born without their sail-skin, yet retained bones in the more flexible form of cartilage; as the creature grew these main cartilage spines split and branched inwards on one another like coral, creating a sort of mesh framework that resembled it's previous sail. As the creature moved through the lakes and exposed its sail to the crystal elements, they would oxidise on the framework and begin to grow, slowly but surely creating ever larger crystals that interwove with those in other area to cover the entire sails area in the minerals, hence effectively turning it into one giant crystal!
The colour it is will depend on the minerals used to form it but it's strength should be around 3-6 on Mohs Hardness Scale, making it pretty durable as well.
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You could go for a silicon based lifeform and quartz.
Either your lizard is silicon-based itself, or is living in a symbiotic/parasitic relationship with such a lifeform.
A silicon-based creature wouldn't be very complex, because of its unstable molecular structure, which would make a simpler additional symbiotic/parasitic creature or plant more likely.
When silicon reacts with oxygen it creates quartz (silicon dioxide), a very clear and strong crytsal that comes in a lot of different colours depending on additional minerals.
So maybe silicon-based, algal lifeforms are growing large quartz crystals on the back on your lizard - as a byproduct of their metabolism.
This silicon algae could eat silicon in form of sand/dust found on the skin of the lizard and would grow large and clear quartz formations while "exhaling" per se.
The lizard would profit from these hard and sharp crystals, they acting as protection and/or a weapon, and since this is good for survival it would be much likely a trait favored by evolution.
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If such a feature were to exist it would be based on a defence mechanism to avoid being scooped up by something from above or camouflage or be developed through sexual selection or a mixture of those. It's probably an evolutionary leftover from a top fin.
The crystal in question would probably be a silicone type considering the types of available crystals, the distribution of materials, and the way the crystals can be formed.
The size of these creatures would have to be rather small, because such a structure would make the creature top heavy and thus out of balance. This could be compensated for by a wider footprint, but only to a degree, because too wide and your sail becomes useless for defence.
The climate these creatures live in would have to be very consistent and moderate; the sail increases surface area / body mass ratio, so they would cool and warm more quickly. In deserts they would die of heat during the day, of cold during the night. In the north they die to cold regardless. They are probably cold-blooded. I'm thinking southern forests or jungles.
Their diet would consist of something that can be found on the ground by relatively small, not so very agile creatures. Think either vegetation or insects.
They would hide amongst ferns for camouflage during the night, and the colour of the crystal would match the colour of the ferns. During the day they would graze/hunt when it's warmer out and restock on body heat.
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Maybe the home planet's environment of these creatures has conditions that benefit such sails. I can think of a planet that has a very thin atmosphere (so wind isn't strong enough to blow this creature away), but is close to its sun and therefore is quite hot. The crystals could be porous and have chlorophyll inside them so the lizards can run photosynthesis.
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Every day the Sun is closer to be a Red giant, making the live of the initial home of the humanity practically uninhabitable. Humans are not there anymore. It's a protected territory, but the Sun gonna end with that and we need to do something.
**What humanity can do? There are a way to save the Earth, their flora and fauna from their own star? How much that solution gonna last?**
Humanity is dispersed around the Universe, has acces to a really advanced technology (you can be creative here, but respect the physics as much as you can) and all the resources from closer stellar systems.
It's a maximum priority to preserve our history. Humanity need you.
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Since this is tagged as `science-based`, here's a scientific paper on the subject of moving the Earth away from an increasingly powerful Sun:
D. G. Korycansky, Gregory Laughlin, Fred C. Adams. ["Astronomical engineering: a strategy for modifying planetary orbits."](http://arxiv.org/abs/astro-ph/0102126) Astrophysics & Space Science, Vol. 275, No. 4, pp. 349–366.
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> The basic mechanism uses gravitational assists to (in effect) transfer orbital energy from Jupiter to the Earth, and thereby enlarges the orbital radius of Earth. This transfer is accomplished by a suitable intermediate body, either a Kuiper Belt object or a main belt asteroid. The object first encounters Earth during an inward pass on its initial highly elliptical orbit of large (~ 300 AU) semimajor axis. The encounter transfers energy from the object to the Earth in standard gravity-assist fashion by passing close to the leading limb of the planet. The resulting outbound trajectory of the object must cross the orbit of Jupiter; with proper timing, the outbound object encounters Jupiter and picks up the energy it lost to Earth. With small corrections to the trajectory, or additional planetary encounters (e.g., with Saturn), the object can repeat this process over many encounters. **To maintain its present flux of solar energy, the Earth must experience roughly one encounter every 6000 years (for an object mass of 1022 g).** We develop the details of this scheme and discuss its ramifications.
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Other interesting quotes from the paper:
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> A great deal of energy must be expended to implement this migration
> scheme. However, the energy needed to move Earth is relatively
> modest compared to that needed for interstellar travel. ... The energy
> requirements and overall ease of implementation also compare favorably
> with various terraforming projects.
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>
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...
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> As for the Moon, reasoning by analogy with cases of stellar binaries
> and third-body encounters suggests that the Moon will tend to become
> unbound by encounters in which O passes inside the Moon’s orbit. (As
> well, there is the non-zero probability of collisions between O and the
> Moon, which must be avoided.) Again, detailed quantitative work needs
> to be done, but it seems that the Moon will be lost from Earth orbit
> during this process. On the other hand, a subset of encounters could be
> targeted to “herd” the Moon along with the Earth should that prove
> necessary.
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>
>
...
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> The fate of Mars in this scenario remains unresolved.
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...
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> An obvious drawback to this proposed scheme is that it is extremely
> risky and hence sufficient safeguards must be implemented. The collision
> of a 100-km diameter object with the Earth at cosmic velocity
> would sterilize the biosphere most effectively, at least to the level of
> bacteria. This danger cannot be overemphasized.
>
>
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# Move the planet
Ultimately, shielding or adapting to the increased heat will not be sufficient once the red giant phase gets underway. So skip half measures such as moving the planet, as described by [this question](https://worldbuilding.stackexchange.com/q/44910/885) and others.
# Fix the sun
One use of *star lifting* is [stellar husbandry](https://en.wikipedia.org/wiki/Star_lifting#Stellar_husbandry). More generally, take over from the natural process of the star’s lifecycle. Reduce mass or find a way to *stir up* the remaining material. Again, see [other questions](https://worldbuilding.stackexchange.com/questions/53526/is-it-possible-for-type-ii-civ-to-resuscitate-dying-star) asking this.
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Moving the Earth is the only way with plausible, known physics. (I am going to assume that for various reasons, Earth cannot simply be shunted through a wormhole to another star).
Much like spacecraft use momentum transfer to "slingshot" around Jupiter, you can also "slingshot" asteroids or comets around the Earth. If the orbital vectors are such that the comet or asteroid loses velocity, Earth will gain a corresponding amount of velocity. Given the vast disparity in masses, it will obviously take a lot of asteroids to do this. Realistically, you would attach a solar sail or similar device to the asteroid and use the solar energy to add velocity after the Earth crossing encounter and bring it into another Earth crossing orbit to exchange momentum again. XKCD describes the mechanics of the process [here](https://what-if.xkcd.com/146/)
Assuming super science, the Earth could also be moved by warping space and allowing the Earth to "fall into" the new depression in space-time. Given it takes an entire solar mass to generate the dent in space-time we orbit in, this would be an astro engineering problem requiring huge amounts of mass or energy to do.
Regardless of the method, the Earth needs to be moved gently. Even 5 billion years from now as the Sun is rapidly expanding into a red giant, suddenly imparting momentum to a planetary body would involve depositing huge amounts of energy and could cause earthquakes and other natural disasters. Slowly shifting the Earth out to perhaps the orbit of Neptune would probably provide protection when the sun is at its peak expansion, and then the same processes can be reversed to gradually move the Earth inwards to the newly formed white dwarf star which marks the remains of the Sun.
Of course, now you have to erect some sort of shield that will screen out the violent ultraviolet radiation the white dwarf will emit while bringing the Earth in to a much closer orbit in order to maintain the needed insolation for life.
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# Short answer? We cannot save Earth
Saving Earth from it? I don't think theres a possible way of doing that.
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> The reason that stars swell in size after exhausting their hydrogen cores is that the stars begin fusing helium, according to the University of Michigan. The helium releases more energy during fusion than the hydrogen releases during the process. The amount of energy produced by the helium is greater than that needed to stave off gravitational collapse, which causes the star to swell greatly in size.
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## Trying to slow down sun advance
Refuel the hydrogen core won't do nothing, even thought our sun still has a lot of it that would make nothing, let's not say that amount of hydrogen would be *a lot*.
**Reducing the size of the sun?** Well, I don't know if this is possible or not, if we can even have a machine that can do such task. Also humans can get near the sun, so we would need a machine to operate from distance or a machine controlled by robots that won't melt being near the sun.
Also, what would this machine do? If a machine like that is possible.
Of course I'm using the perspective view of a 21th century man, we really don't know what we may develop in the future. But in terms of what we know right know there's no possible way of slowing down or avoiding our star to devour us.
But, that would take time, around 1.75 billions years according to scientists, so...
## Traveling to another planet
If you want to save flora and fauna people has always come with the expectation that we can find another habitable planet where we can land our already know flora and fauna. But I always wonder if that would be possible due to the fact that would be like introducing a new specie to an environment, and that has not always had the best results, but it may be possible if the *new planet* has the condition the flora and fauna needs to survive.
## Moving Earth
Eventhought there are a [lot of post about moving the planet](https://worldbuilding.stackexchange.com/questions/44910/how-can-i-move-a-planet) we need a tremendus force to achieve that. We are not lifting a plane, we are moving a [dense rock that wieghts around 5,972 × 10^24 kg](https://en.wikipedia.org/wiki/Earth_mass). If we can achieve a source of energy capable of doing such task then we would need to figure out how to create a machine capable of moving earth.
**So, in my opinion**, we have around 1.75 billions years *(if we don't destroy ourselves before)* to figure a way out of this planet, because I think is the most viable method. Slowing the sun seems impossible and moving earth seems out of reach.
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An arxiv paper in astrophysics investigated that point:
<https://arxiv.org/abs/0801.4031>
Their idea is that the sun will lose some of its mass at the end of its life, about 1/3 in 8 billions years, causing the earth path to extend and giving us a "short" break. This mass loss would not save the Earth from being swallowed, except if:
* the Earth can be moved to a radius of 1.15 AU from the Sun
* the mass loss by the Sun can be increased
Anyway, interesting technologies ahead!
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A bit of elaboration about **fixing the sun** by star lifting
* actually you can preserve Sun and solar system indefinitely (until heat death of universe, or until it makes sense), given *Humanity is dispersed around the Universe* resources.
[wiki Sun,Life\_phases](https://en.wikipedia.org/wiki/Sun#Life_phases)
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> the Sun has so far converted around 100 times the mass of Earth into energy, about 0.03% of the total mass of the Sun.
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Which cause makes red giant from our star? Products of reaction, products of hydrogen fusion - which is Helium.
So one way is to remove this product from sun, it is about 1.1931e+17kg per year and replace it with Hydrogen from Jupiter as example. Jupiter mass should be enough for next 15 billion years. Sun produces more then enough energy for such operation, so energy of the process is not an issue.
speed of migration matter from Sun core is not a fast process , I guess, if it is like energy migration from core to upper layers of sun, but should work.
Just as notice, removing carbon also might affect speed of energy production, but eventually Helium fusion will dominate, so it is less efficient way in therms of indefinite prolongation, but more productive way in therms of getting useful materials from sun.
1.1931e+17kg of helium is something around 120km diameter sphere of liquid Helium. ($\text{125-145 }kg/m^3$ helium density in liquid form)
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Maybe not the answer you are looking for, but worth challenging. Human redundancy is our current answer to this issue...get off the planet and out of the star system before our sun dies so that any galactic calamity can only wipe out a portion of us.
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> What humanity can do? There are a way to save the Earth, their flora and fauna from their own star?
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Humanity can provide the same redundancy to the flora and fauna of earth...IE, get it off that planet and go find another 1 (or 2 or 2000) to put it on. But I somewhat have to question the why portion here...this event is several billion years in the future:
a) most of the life you are saving will be unrecognizable to todays standards. Much evolution takes place across this time scale
b) most of the earth will be unrecognizable to todays standards. This is billions of years and the world will heavily change. In 250 million years, it's likely that America will collide with Asia creating Pangaea Ultima. In another 200 million after that, they break up again forming continents, before reforming together once more. The globe will look completely alien. When you are talking such a large time frame, nothing is constant...why bother conserving anything but this changing nature?
This point in particular:
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> It's a maximum priority to preserve our history. Humanity need you.
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No it isn't. Preserving an unrecognizable rock that we may have developed once upon a few billion years ago is anything but maximum priority and I'm sure humanity needs you for many other things beyond resisting inevitable change.
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Are there bacteria or other types of lifeforms that feed on rocks and other ground minerals? And if there aren't, is it technically possible? It can eat other things but the majority of its diet should be rocks or ground minerals.
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[Look up lithotrophs](http://en.wikipedia.org/wiki/Lithotroph):
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> Lithotrophs are a diverse group of organisms using inorganic substrate
> (usually of mineral origin) to obtain reducing equivalents for use in
> biosynthesis (e.g., carbon dioxide fixation) or energy conservation
> (i.e., ATP production) via aerobic or anaerobic respiration." - Wikipedia
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>
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My understanding of inorganic substrate of mineral origin is that it uses rock and/or minerals as a source of food, however small those meals might be
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I should preface by stating I am a geobiochemist with a focus on ferrolithotophic bacteria, or bacteria that gain their energy from rocks and minerals that contain iron with ‘extra’ electrons. While it is colloquially stated that these organisms ‘eat’ rocks and minerals, they are only able to derive energy from this process, and must obtain carbon for biomass from additional sources, often carbon dioxide. In this way it is analogous to plants growing using sunlight, but in the stead of light, these organisms alter rocks.
Specifics and nerdiness aside, the answer is yes; it is possible. It is suspected the majority of organisms on Earth ‘eat’ rocks and minerals for a living, and this likely constitutes the majority of their energy intake. Bacteria (and Archaea) are commonly able to ‘eat’ minerals containing sulfur, iron, nitrogen, hydrogen of specific types. Less common examples have been found to ‘eat’ uranium, arsenic, and mercury. As an interesting aside, many of these minerals can be breathed as well. No known macroscopic organisms are known to do this (i.e. animals, lichen.. etc..)
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Let's say there's a humanoid species that are essencialy humans but tiny, around 13cm tall. As their vocal chords are smaller they would have high pitched voices, but could that effect be minimized in a biologically possible way?
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**Bullfrog says "NO WAY!"**
[](https://i.stack.imgur.com/XKRsk.jpg)
<https://www.youtube.com/watch?v=wbXItUDliuo>
Bullfrogs win mates with their low pitched masculine calls. This guy is likely less than 13 cm. I suspect (but do not know) that the trick is his resonant apparatus - that throat sac offers a larger surface than human vocal cords and consequently the ability to generate deep notes. Some frog sounds are considerably lower pitched than human voices.
Your small people could have large throat sacs that they inflate while singing the tenor and bass parts. It would be an intriguing look as well and one I am not sure I have run across.
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These humanoids could possess a disproportionate throat region to accommodate longer vocal chords that vibrate at a lower frequency. They may have a sort of throat pouch like many animals that require the ability to make booming calls.
Is it possible for them to have a voice that is as deep as regular humans? Probably not. 13cm is pretty small (the world's smallest living woman, Jyoti Amge, stands at 64cm). In theory, a 13cm human could have throat anatomy that accommodates longer vocal chords and disproportionately large lungs, but if these features were increasingly disproportionate it would start to interfere with other requirements of the body, but it could certainly be disproportionate enough to limit the squeakiness of their voices. I assume you only want their voices to be deep enough to not sound like chipmonks. You also have to ask why this would happen and that could be a feature of whatever story you are writing too.
Runaway sexual selection could, for example, end with one sex (for a mammal this would usually be the males but not universally) having disproportionately deep voices as an audible way to make themselves sound bigger and more dominant.
EDIT: What Willik said.
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They could have [syrinxes](https://en.wikipedia.org/wiki/Syrinx_(bird_anatomy)) in addition to larynges. This would permit them a much greater vocal range, and hence disproportionately low voices for their sizes. (Their voices would still be higher than a full-sized, anatomically-correct human's, though.)
To get an even lower range, they could have a structure that they vibrated directly, like a speaker. Human-sized muscles can't vibrate fast enough to get much beyond the very lower part of the human hearing range, but (wild speculation!!) perhaps smaller muscles could vibrate fast enough to give a range overlapping slightly with the syrinx range?
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The demigods are immortal individuals that protect our reality from eldritch abominations, such as Cthulu, Niggurath, etc, on a plane that exists between our world and theirs. These battles against these eldritch forces and their minions happen on a daily basis to prevent them from breaching our world.
A demigod is born with a divine spark in their soul, which matures as they age and blooms around puberty, when it reveals itself. At this point, they are taken from their families by the demigods and put through a process that turns then into true demigods in order to control their power. This process suppresses their memories as a human, in which they exist as a vague, half'forgotten dream.
In our world, we hear of and see our governmental forces doing things to protect their people, such as engaging with terrorists or enemy soldiers or crimminals. These confrontations are well-documented in media and public officials, so we know they happen. In contrast, battles of demigods against the darkness are not seen by the world's inhabitants, as they happen outside reality. They are also not meant for public consumption. Laying eyes on an eldritch abomination, even through filtered media like photos or video, is dangerous to the human psyche because of their otherworldly nature. Simply being too knowledgeable about their existence can invite them into the mind and twist an individual. Therefore, information is suppressed.
These creatures crossing into our world is rare, with centuries or even millenia passing between incidents, which means the gods are doing their job. The problem is that since people don't really know much about what they are fighting, their necessity becomes questionable. At some point, people begin to question the demigods' true motives, seeing them as just child kidnappers who simply want to create more of themselves to further their own motives. At best, they are an out of date organization past it's glory days, creating soldiers against a threat that has long passed, similar to how people of westeros felt against the night's watch. This can lead to resistance among the public against them.
How can this perception be prevented?
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The demigods have many exciting stories about their lives and deeds. People tell and embellish these, setting them to music, devising plays depicting the actions. **All of this is true in our world for Christian saints.**
[](https://i.stack.imgur.com/avcnh.jpg)
source: <http://www.mysticsofthechurch.com/2013/12/the-battle-for-souls-mystic-saints-vs.html>
Depicted: Saint Wolfgang and the devil. I was looking for Saint Dominic and the Demon Ape (because I dig demon apes) but got this first. There are hundreds of saints in the [Catholic pantheon](https://timesofmalta.com/articles/view/a-pantheon-of-saints.663043). Each has an associated story about the events qualifying him or her as a saint and many have many stories. These are seriously exciting stories: monsters and angels, freaky visions, torture (garishly depicted in paintings!), suffering, triumph over huge adversity. Historically a church or neighborhood or town would have a patron saint or two that was special to them. And what are saints but demigods - superhumans with powers they use in the service of God to help humanity.
This is how it is for your demigods. The specifics of the actual horrors they face are not important, but a story about individual good guys fighting monsters will not weaken the minds of those who hear them. These stories bind society and religion together. It does not matter how closely these stories are related to things that actually have happened, as long as they are compelling stories.
It helps that your demigods actually show up from time to time to collect a teenager. They should not catch people by surprise when they do this. It is a big deal, this ceremony of ascent for the teen. Visiting demigods (each known by name and deed!) can lay on hands, bless buildings, lead prayers and marches, and other things of that sort.
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Once per year, the demigods will use chimneys to enter buildings and leave gifts.
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I love this question! There's a few ways you can handle this.
**Change nothing**
In real life, most religions persist despite the fact that there isn't too much evidence of a divine being in recent years. This is not a criticism of religion - I am somewhat religious as well - but this is a feature of humanity. It would be incorrect to say that everyone who considers themselves *insert religion here* perfectly believes it. In fact, I would argue that there aren't many people who are 100% faithful to a religion (if you could even quantify that sort of thing). But one thing we can agree upon is that religion does bring people together.
In your case, the magic is real - divine beings are born every now and then. Even if the eldritch forces do not breach our reality ever again (even though the battles are constantly taking place), if taking the occasional divine child does not exert too much stress on society and to have such a child is culturally accepted as an honor, this belief will persist. In fact, in this case these demigods could end up becoming worshipped by the people of our plane, and this would vary from place to place depending on what these kids were like growing up (I'm assuming they never come back).
Will there be resentment? From some, yes, but in our real world there also is, but this hasn't effectively killed many belief system - interestingly, some beliefs go out of fashion when impractical, regardless of whether there was any resentment towards the belief.
**Make it ceremonial**
I kind of hinted at this idea already, but make the act of having a baby demigod a mark of honor. I understand that this isn't obvious until later, but when such a person is found, make the demigod recruiters have a ceremony to properly induct this new recruit. In a way you can think of this like how in parts of Southeast Asia boys become monks for a part of their lives - or even all of it. It is not seen as a punishment - none of us would think so, and many of them become monks despite not being 'forced' into it.
The most important part of the ceremony: make everyone see it! If this ceremony is done in accordance to a primary or local religion, it holds fast better.
**Visitation rights + Retirement**
Make these demigods come back every now and then. Allow them visitation back to our own reality, and even retirement. I understand that this is not the *Jedi way*, but we know what happened to them. The *Sith* got it wrong too, by being overly passionate, so it would be best if these demigods got to go home and help out their families and communities. To make this more *real*, give many of these demigods some kind of PTSD. Give them bizarre scars too - nothing too graphic, but enough to prove that something is happening in the other realm. Even if they won't go mad like normal people, what kind of person can fight eldritch horrors and come back the same? What if they lost loved ones on the line of combat? Make sure they keep coming back and keep telling their stories.
Let the older warriors stay back and exist in society in constructive ways, like teachers, administrators, and more. Let them use their powers (if they have any left by then) for the good of humanity directly - not in combat. You can make retirement optional, but provide the option. As populations will grow, the number of divine children will grow, and the ratio of divine:normal humans will remain the same. If a significant number of these divine children come back and take up helpful roles in society (not as warlords or anything) maybe people will continue to respect them.
**Lie + Remove Exploding Teenagers**
You pointed out that these kids will explode if not transformed into proper demigods. Make this organization a community that helps these kids in need, or have them interpreted like the body-carriers in Black Death - a terrible but necessary job in society. Make everyone remember why these kids get removed, because even if everyone believes the demigods, the demigods are likely to still miss a child every now and again, causing explosions. Even if they don't believe, they would be pretty big on not having their village destroyed because some kid hit puberty. You can add a coming-of-age ceremony here, with those 'passing' it being the kids who don't show signs of exploding in the future.
These special kids will be hated by at least certain cultures, and could make some demigods unwilling to fight harder against the eldritch forces, as humanity had been cruel to them in their memory, adding additional complexity to different characters.
Keep in mind, all of these ideas will only keep interest in this effort for so long. There will always be people who think these guys are a remnant of the ancient times, even if they aren't baby-snatchers or anything. In fact, there will even be people who hope the eldritch forces eventually win. But don't make these beliefs uniform and a defining point for all of humanity. If you do pick any of these ideas, don't work with that for all humans and their communities. Europe is a pretty small continent, but even they have a variety of cultures living near one another. Make sure different cultures exist in the human world and make their treatment of these demigods differ in different ways.
I hope this helps.
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**The old ones (begin to) return.**
A potential demigod child is trained to fully control and harness the power within. This is for a very good reason.
The old ones require a conduit to enter this world, a vessel to inhabit - else if they enter they would possess no power - a human child or adult possessed by an old one could easily be locked up or disciplined by their parents - but an old-one in possession of a demigod, their power is multiplied many-fold. Reckless use of such a being's power could destroy civilization and render all the other gods to dust.
This can be seen to emerge at puberty, this is when the divine spark is sensed by the old ones, they sniff it out, feel it's presence and know that there is a chance for them to emerge. They create a breach within the child's mind, small at first, but enough to find a way to insinuate their wishes into the child's thoughts and actions.
The greater the child's power grows, the bigger the breach, allowing more and more influence - for the child's power to grow it must have an outlet, it must be released into this world in the form of extreme rage and violence, often accompanied by unexplained localised destruction. The old ones want out of their cold prison and into the world of light, heat and tasty flesh, and will the breach to grow.
I figure that people will notice at some point, hopefully before the stage of leveling quarters of the city or killing hundreds, and call-in the old demigods. As long as they succeed in getting there in time, calming or overpowering the semi-possessed one as necessary, then the people will see that an old one was close to being released and will call upon the demigods sooner next time.
Training then begins. This is to close the breach, to control the power within - the eternal battle for all people and demigods throughout history to keep the old ones at bay for all time..
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The demigods let some abominations into the mortal world from time to time, in a controlled manner, so that the mortals don't forget what they are up to. Whenever some mortal group starts questioning too much, an abomination appears near them, rampage for some time, and the demigods come and kill/banish/jail it.
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“Most witches don’t believe in gods. They know that the gods exist, of course. They even deal with them occasionally. But they don’t believe in them. They know them too well. It would be like believing in the postman.”
― Terry Pratchett, Witches Abroad
I think that sums it up pretty well. They're there. You deal with them. But you don't *believe* in them, as "faith" pretty much requires the **absence** of the being that is the object of said faith. If God popped in to borrow a cup of sugar, chatted about the weather, and then transformed a liter of water into wine, what're you supposed to do? (You check to see if it's any good before you serve it to company, of course!) But you don't have "faith" in it, because it just happened. "God" becomes "that stupid bugger from next door what never manages to have what 'e needs on hand when 'e needs it, an's always stoppin' by to *borrow* some. Well, there goes a cup o' sugar I shan't be seeing again soon, I shouldn't wonder!".
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I've just been transported into a world where I have god-like powers, they are near absolute as far as I can tell, at least I've yet to find their limits.
The guiding principle of my powers seems to be **"if I understand it, I can use it."**
I want to experiment and figure out the extent of them, but also figure out the physics of this universe to extend my powers (assume physics comparable to our own).
As a fresh graduate of college in a science discipline, I have a broad but not very deep understanding of chemistry, mechanical physics, relativity, quantum mechanics, etc.
What would be a well informed testing regiment? What are some of first experiments I should perform to form a solid basis? Optionally later, what shall be my magnum opus? The test that justifies all this time and effort, and what does its results tell me?
**META**: I am new to this community, I don't know if this questions fits within worldbuilding, if not where would be a better place for it? Or simply a more fitting variant for this community?
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Given the rule "If I can understand it then I can do it" - which I feel needs some expansion - then the obvious first goal should be to increase your methods of improving your understanding. Ultimately you're going to want to get as close to omniscience as you can reach, which will give you the maximum amount of possible actions.
From one of your comments:
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> If I used the aerospace knowledge that having more air pass under me than over me would create lift, I could fly.
>
>
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This implies that any effect that you know the mechanism of - generation of aerodynamic lift in this case - can be produced directly without having to mess about with the actual *mechanics* of lift. You understand how wings generate lift so you can generate lift *without in fact having wings.*
This seems to be contradicted a bit later in the same comment (regarding Gravity):
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> If I knew of spacetime warping, I then had the knowledge to affect gravity by affecting change in spacetime?
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>
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This implies that in order to alter the force of gravity you have to go all the way down to affecting the (to the best of our knowledge) fundamental cause of gravity. You can't magically generate gravity but you *can* bend spacetime to your whim.
Let's say you understand Newton's Law of Universal Gravitation. You know that there is a force called Gravity that acts between particles with mass, you understand the formulae and so on. But your understanding is based on a flawed model. Actually gravity is a fictitious force that is due to motion through curved spacetime. Or it might be a quantum field effect. Or the interaction of mass with some unknown field. Or any of a number of other things. How would you progress from your understanding of Newtonian Gravity to Relativity?
Unfortunately this is going to be a big problem. Before being exposed to Einstein there were very few people who ever even considered empty space to be a thing that could bend, let alone time being part of it. There are people today who don't believe that time is dimensional who think that Relativity is a handy model but isn't actually *true.* If you have to understand what is actually, *really* true about how the universe functions then you might never be able to do much without revelation.
But maybe it's enough to have *confidence* in your understanding. You've figured out that you can do magic, but your brain is trained in logic and reason and won't let you just accept the situation. It demands that there be reasons and limits and so on, because otherwise the universe can't *possibly* make sense. So when you try to lift a rock with your understanding of physics, using your understanding of warped spacetime for example, what you're actually doing is simply justifying your ability to make the rock move. Actually you're just moving the rock by force of will. If you didn't believe that you could because you don't understand enough about the physics then, sadly, the rock remains unmoved.
It would be kind of sad if you spent decades trying to understand things only to discover that you just have to want it to happen and it does, huh?
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This has a bit of a meta twist to it.
"If I understand it, I can use it" is pretty much the rallying cry of engineers. Once science is understood, it is applied by the engineers. As such, if you undertake many engineering tasks, you can build up confidence that you understand "If I can understand it, I can use it." Yay recursion!
Once that step is complete, you may wish to tackle understanding understanding. That's a monumentally challenging thing. Oddly enough, those who ascribe to "know thyself," have a strange tendency of arguing that anything they want to do is achievable. Food for thought.
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Fortunately, you've given us a very important clue when it comes to figuring out the limitations of your new universe - *it exist.* This lets us apply logic from the fine-tuning problem.
All laws of nature stem from applications of the prior laws, for instance atomic interactions laws can simply be said to be a natural extension of the laws that create them in the first place, i.e. the Strong Nuclear Force and the Weak Nuclear Force. Right now, we've boiled the forces of the universe down to four fundamental forces (gravity, electromagnetism, strong nuclear force, weak nuclear force), and they're theoretically all unified in one force, the single unifying force (which is known as the '[Unified Field Theory](https://en.wikipedia.org/wiki/Unified_field_theory)').
Now, for a universe to have different laws from out universe, it needs to have a different Unified Field Theory - at which point the universe falls apart. Everything in our universe only works because of how finely tuned the forces are. If gravity was a magnitude stronger or weaker, we wouldn't have stable stars. If nuclear interactions worked differently, elemental atoms couldn't form or interact, depending on the forces. Any change to the Unified Field Theory means that the fundamental laws of the Universe now *prohibit existence.* That means since your universe exists, it now follows all the rules you know and love.
Is there another possibility? Yes. Since proving negatives is impossible, it's possible that another configuring of the Unified Field Theory could produce a workable universe. But that would be near-incomprehensible. Literally, we're designed to operate in a universe that obeys our laws, and a universe that obeys entirely different laws wouldn't be able to interact with you well. And, even in the event that you somehow could, you'd have to start from scratch. So, either you understand everything, or you understand nothing and are stuck doing everything from ground zero up.
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First you need to verify the unaltered physics of your new home. Ideally, someone who *does not* have god-like powers should recreate Galileo's and Newton's experimental work (pendulums, centripetal force, etc.), while someone performs or researches the equivalent of Tycho Brahe's and Johannes Kepler's observational confirmation of orbital motion and a non-geocentric (or even non-heliocentric) universe.
While that work is going on, you could give someone a jump start on the knowledge to recreate Maxwell's electromagnetic equations, along with Franklin's, Faraday's, and eventually Stinmetz and Tesla's work with electricity and magnetism.
Starting from the knowledge base you describe, all of this should be accomplished (given a reasonable level of recruitment) in a matter of a few years.
The real trick will be biology -- unless you understand biology better than our society, you can't extend your own life to god-like immortality. Better get the smart folks on that one.
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[Harry Potter and the Methods of Rationality](http://www.hpmor.com/) is mostly about this. For example in chapter 28 Harry uses his scientific understanding for partial Transfiguration, deemed hitherto impossible:
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> "Fascinating," said Dumbledore. "It's exactly as he claimed. He simply
> Transfigured a part of the subject without Transfiguring the whole.
> You say it's really just a conceptual limitation, Harry?"
>
> "Yes," Harry said, "but a deep one, just knowing it had to be a
> conceptual limitation wasn't enough. I had to suppress the part of my
> mind that was making the error and think instead about the underlying
> reality that scientists figured out."
>
>
>
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Despite the wide variety of movement strategies employed by Earthling animals, up to an including [curling their bodies into circles and rolling](https://www.youtube.com/watch?v=vQtR6ZuUSLg), there is one mode of locomotion that is glaringly missing: nothing [slinkies](https://youtu.be/glkgyRsovRE?t=171)!
What I have in mind here is more a whole class of creatures than one specific creature, but to keep it from getting too broad, let's focus on the base case of a simple slinky worm:
The basic body plan is a simple muscular tube, externally symmetric, capable of stretching out or squishing down (like any soft worm) and capable of balancing upright on either end, such that it can move by flipping end over end like a slinky: with one "foot" planted, the other foot is lifted, flipped over the top, set down on the other side, and the process repeats.
So, how / why might such a thing evolve? As lemmas to that overarching question, where is its mouth / anus (does it run from one foot to the other, does it have a "head" in the middle of the body)? What kind of sensory organs does it have? Maybe eyes on stabilizing stalks in the middle, like a [squibbon](https://youtu.be/w0kzMmcTS8I?t=1398), or eyes ringing the feet? Aside from conforming the the basic end-over-end tube plan, anything goes.
A list of all Anatomically Correct questions can be found here: [Anatomically Correct series.](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798)
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You mean like an actual [hydra](https://en.wikipedia.org/wiki/Hydra_(genus))?
Their feeding strategy is "waiting until someone I can eat falls into my trap", just like weaving spiders, but with an array of tentacles instead of a web. Mind you, they are related to jellyfish, so victims are paralysed by its poison. Staying still is a plus because it saves them energy, so their suction cup "foot" works kinda like a root.
Being able to uproot and going somewhere else is nice if you haven't been able to catch prey for a while in some area. They evolved the ability to slink around probably because having proper feet or flippers would cost them more energy. Those would be dead weight when the hydra is in feeding mode.
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> As lemmas to that overarching question, where is its mouth / anus (...)?
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Ah, the most important part of the question. No animal is complete without an anus. You hear that, sponges?
You see, the hydra is such a miser when it comes to evolving that it said "why have two main body orifices? That's redundant and a profligacy!". So its mouth doubles as its anus. You might think that is not hygienic, but it sure is more efficient.
And here is a picture of the critter, credit at the upper left corner:
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My first thought was a very strange leech.
Suctioning mouth on one end, non-eating suction cup on the postior. Worms and leeches seem perfectly capable of constricting and lengthening themselves, and though the classic 'push and pull' of an inchworm may be more efficient, I can definitely say that it's possible to have a slinking leech.
Tentacles are always fun, but as per most creatures sensory organs are probably best situated near the head. Leeches have their anus dorsal to the sucker (ventral would also work, as long as it's not **in** the sucker). Similarly, eyes are dorsal to the mouth, though if our leach is bending end-over-end we may want a ring of eyes (tentacled or not) - no reason to have eyes on the posterier end that I can see. Given our tube design, respiration should either occur via diffusion through the skin (small slinky) or through lamprey-like orifaces along the body into lungs/gills (bigger slinky).
Should our slinky be semi-vertebrate, they would probably still need to be segmented to allow that worm-like length-ways squishing, and since they're flipping ventral and dorsal constantly maybe this vertebra should be central to the animal.
Fun features might include false eyes/other 'face' features on the posterior end to take advantage of the 'which side is the head?' confusion some animals take advantage of.
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**The Tentacle**
My suggestion is a [molluscoid](https://en.wikipedia.org/wiki/Mollusca) creature combining charasteristics of cephalopods (aka squids and the like) and gastropods (slugs and their cousins).
The slinky has a bilateral body symmetry that lacks an apparent head. On one end of the creature we have the mouth, with [teeth](https://en.wikipedia.org/wiki/Radula) organised in a circle perpendicular to the body's axis. Might have a molluscoid tongue there. Internal organs are dorsally concentrated and covered by a mantle, leaving in between the mantle cavity, where the anus and genitals open. The mantle is not hardened by calcium carbonate like in snails, except at the end opposite to the mouth, where it forms hook like extensions. The slinky's metabolism could in my mind follow that of slugs.
The entire creature is [tongue-like](https://en.wikipedia.org/wiki/Muscular_hydrostat), similar to a squids tentacle or a jacked slug. Its slinky like movement is accompanied by torsion, as it holds always the dorsal part of its body up. It could have protective plates on its back mantle, provided that they do not prevent movement. The slinky's movement would be intermittent, since it would prefer to grab its surface with its strong mouth. From that position it twist-bends to attach its end-hooks to the surface, then quickly twist-bends a second time to bite down again.
Lacking an apparent head, the slinky cannot have a neural system [as complicated as cephalopods](https://www.youtube.com/watch?v=kFvrAdyFUJ8), but it could have central ganglia with two main nerve cords. I don't manage to place believable eyes on my creature, but it would sense vibrations, touch, balance and different chemicals.
The only reason I came up with for this freak to evolve is a random mutation that caused an early marine mollusc's musculature to be organised more in a helix-shape. Better end-hooks gave an edge in natural selection, and the support of water permitted a less efficient way of movement to evolve. I see my creature roaming the bottom of shallow bays searching for algae. Its wild style of moving is certainly more noticeable to predators, but it could evolve into an elaborate mating dance, where only the most head-spinning pirouettes are guaranteed to win the bicameral hearts of females. Maybe in time, the slinky could evolve to live on land as well.
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Scientists recently discovered a propellantless drive capable of completely negating gravity with low energy inputs! Huzzah! Sadly the Earth is going to be destroyed soon by a rogue handwave. Looking at their possible escape candidates the scientists settle on Venus. They build flying cities and sit them at 50km up.
They're having a great time but some of them want to open a window. What is the fastest way for them to alter the atmosphere to be breathable?
Edit: We can assume our scientists have access to the technology above our current level but within 50 years of advancement so nothing too amazing (think asteroid mining and relatively quick interplanetary travel) and the infrastructure to produce any raw materials or tools needed within a reasonable time frame.
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# "Oxigenated" and breathable aren't the same thing.
Venus' atmosphere is mostly carbon dioxide. You can fixate the carbon to graphite with relative ease using the Bosch reaction and electrolysis of the resulting water, wherein the hydrogen gets reused as long as needed venting the excess oxygen.
This has only the effect of reducing the habitats' buoyancy and starting lots of interesting oxidizing reactions down on the surface (which by the way will be 50 km lower, not 500).
The problem is that to be *breathable* the CO2 concentration must be less than 5,000 parts per million (down from the current 975,000), while oxygen concentration must not exceed 60%. We don't have anything available to make up the remaining 40%.
Magically converting 60% of the atmosphere to oxygen would have people die of CO2 poisoning, and converting 100% of the atmosphere would have them die of oxygen toxicity.
Freeing enough nitrogen from the surface of Venus that its concentration at 50 km is breathable also looks like a losing proposition - it's mostly aluminum silicates. Also, I'm not sure we could work a viable solution for O2 and N2 partial pressures at that height.
So, the simplest alternative would be to either build *really large* habitats, or equip them with very good projectors and external displays.
As @Rekesoft noted, Venus *does* have nitrogen in its atmosphere, it's just not concentrated enough. To use this, we need to get rid of about 15/16ths of the overall CO2 atmosphere (and then some more, because of the predictable outgassing), leaving in place all the nitrogen. This should give us a 80% N2, 20% CO2 atmosphere, about four times as dense as Earth's; at a sufficient height, that ceases to be a problem (but now buoyancy *is*). Proceed with the conversion of CO2 to O2 and graphite, and you're left with a breathable atmosphere, as long as you don't go too near the surface.
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There isn't a really fast way to oxygenize a whole planet.
You could use plants but no plant would survive. So you could maybe place microorganisms. The organisms will take in the poisonous gases and release oxygen and a little nitrogen. The organisms could be genetically modified to reproduce in a crazy fast rate.
Researchers have discovered a possible new species of bacteria that survives by producing and 'breathing' its own oxygen. The finding suggests that some microbes could have thrived without oxygen-producing plants on the early Earth — and on other planets — by using their own oxygen to garner energy from methane (CH4).
M. oxyfera can survive in mud that is inhospitable to other forms of methane-consuming bacteria such as Methylobacter mesophilic .
[](https://i.stack.imgur.com/mGT55.png)
Here are some other examples of microorganisms you can use:
Cyanobacteria
[](https://i.stack.imgur.com/noos3.png)
Benthic Bacteria
[](https://i.stack.imgur.com/pxwWH.png)
Genetic modification will allow the organisms to survive
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## Cheat and open windows in a few weeks
The stated objective is to be able to open a window in the hull of a floating city at 50km altitude.
Part of the appeal of opening a window on earth is that outside often smells better, or at least different than what it smells like inside. Also, cross breezes churn up the air inside to cool things off. We assume that humans in these Venesian habitats will want some or all of these benefits.
## Cheating Approach
Changing the entire atmosphere of a planet is really expensive and really time consuming. Ultimately, humanity may want to do that but it won't be done any time soon.
So, if someone wants to open a window, wrap a big bubble around the living quarters. Fill the bubble with breathable atmosphere. Build in large fans to create winds and breezes. Add small chemical factories that generate aromatic compounds to seed the breezes with. Make these match Earth as much as possible.
Or, seed the outside of the habitat with trees, bushes and flowers. The load on life support goes down and the plants will make their own scents to make the breezes smell different.
Link the air circulators for the outside bubble to the regular habitat air system. This way, if someone opens their window they can get cross breezes through their apartment.
## Expensive Approach
Do the terraforming thing. Seed the clouds with the right bacteria to turn the atmosphere into something breathable. Finish the process in your grandchildren's lifetime.
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This will the large-scale application of completely gravity negating propellantless (CGNP) drives which, fortunately, only require low-energy inputs.
First, build all the floating cities you need to house the population of planet Earth. Second, build a two gigantic fleets of CGNP drive tanker spaceships. One fleet will scoop up the atmospher of the planet Venus, while the other scoops planet Earth's atmosphere. The two fleets transfer the atmosphere from one planet to the other.
Since Earth is about to be destroyed by a rogue handwave nobody will miss it if it now has Venus' atmosphere instead of its atmosphere.
Venus will have an oxygenated atmosphere. But before you start opening windows, disassemble the two gigantic fleets tanker spaceships and reconfigure them into a gigantic sunshade to allow Venus to cool down and remain cool enough for human habitation.
The floating cities can descend to the surface of Venus, once it's cooled down enough, since it's pretty barren it might be a good idea to bring some of Earth's oceans too, before that rogue handwave strikes. Nothing like prettifying your new planet when you move in.
When all that's done, you can open your windows.
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There is no fast way to make it breathable. For that you would need to make at the least a partial terraforming to happen.
At 50 km up in the Venus atmosphere your problems are:
* **Acid clouds**, people do not like to breath mix of acids and acidic oxides. So you would need to convert them in to salts, minerals or collect and send them somewhere.
* Atmosphere is 96.5% **carbon dioxide** so even if you convert some of it to oxygen to have 21% oxygen at your altitude and deal with acidic compounds. What would take you to move or convert around 30% of the atmosphere of the Venus.
That still would not do a thing as it still leaves you with a 65% carbon dioxide atmosphere, anything above 1% is not where you want to have a walk or 0.5% for a living.
But converting more just to oxygen is not an option too as high oxygen partial pressure is [toxic](https://en.wikipedia.org/wiki/Oxygen_toxicity) too.
So for extra we can: convert it to water, move to Mars or any other places, convert to minerals, biosphere. And that leaves you at converting 95-96% of the atmosphere. You as well can finish the change and live at the surface and not float ten-something kilometers above ground.
* **Temperature** outside is 75C. I would not find it a nice walk. As you make atmosphere smaller and deal with greenhouse compounds, temperature drops. But you will find hard to balance optimal temperature and breathable composition of the atmosphere
* Around 4 times as much of [**nitrogen**](https://en.wikipedia.org/wiki/Nitrogen_narcosis). Not a problem at altitude with a 1 bar pressure, but a problem at the surface. Deal with extra to live at the surface: removal, conversion to mineral, biosphere.
---
So you have options:
1. **I want to float in my cool cities** with breathable outside. That leaves out the need to deal with mostly only nitrogen. Altitude of your cities will drop to ten-something kilometers.
2. **Complete terraforming**. With extra 5% work deal with excess nitrogen.
May as well move Earths oceans or move hydrogen from the gas giants to produce new ones if the Earth ones are already gone in a boom. That will give you a lot of extra work, but people like water and seasides.
Good decision is move some of unneeded atmosphere to the Mars or just plainly terraform it too.
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I am writing about two characters that come to our world from their own mirror dimension. There is cultural exchange between the two, but not tourism-level.
The two characters are a royal witch and a vampire. When creating swears and slang, I want the characters each to have their own distinct feel, as they both come from different backgrounds.
However, I do not know how to develop swears without having them sound corny. I am looking for swears that pack a punch (sh\*t) without lacking significance or seriousness (leaping lizards!).
Another important thing to note would be that the dimension they come from is very open and fluid when it comes to sexuality, so sexually charged swears (f\*ck, Merlin’s balls) wouldn’t carry as much taboo as they would in this dimension.
Any tips? :)
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To begin with, there's a few kinds of curses. Invective like "Merlin's balls" or "Zounds" (which originated from the phrase "God's wounds," referencing the injuries sustained during the crucifixion of Jesus) are not precisely curses - instead, they're swearing BY something. Find something important in your culture, and let them swear by it to express emotion. The other two types of curses are more similar, and they're vulgarity and insults. Vulgarity revolves around what the culture finds taboo or, well, vulgar; in our culture, those are based around sexuality and our own waste, hence the words we use when swearing. Those are relatively tricky to come up with - you need to develop their culture and determine what is deemed too disgusting or taboo to talk about in polite company. Insults, conversely, are easy (especially after vulgarity) - just call the target someone who commits those vulgar actions. Alternately, come up with a person infamous for committing those actions or otherwise screwing up royally, and then derive some vaguely insulting word from their name.
A final note: the root words are important, but there's also the way you get to say them. Most common curses are short words of a single syllable, maybe two, and feature at least one hard consonant. They're something you can spit out in a single breath and feel coming out of your mouth. It's cathartic. When coming up with curses, particularly vulgarities, try to make them satisfying to say.
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**Religion**. There's tons of swears that call The/A god's name in vain, or even just parts of said deity. "Odon's Beard", "God's Body" (which morphed into "Odd's Bodkins"), "Go to Hell/ The Devil", etc. One of my favorites from Spartacus "Great Merciful Bloodstained Gods!"
Many curses and swears are connected to specific **unpleasant events**. In a sci-fi series I enjoy, one of the foulest swear words around is "whistle", referencing the sound of escaping air that a micrometeorite puncture would cause in a space suit. References to evil or incompetent leaders might serve well, as in Star Trek's "Herbert". King William the Large might be so universally despised that calling someone a "Bill's Boy" is on par with suggesting one of your parents was a farm animal.
While sexual taboos aren't as big a thing in your world, there will absolutely be rude terms for **bodily functions**. There will be a plethora of words for poo, pee, and the various reproductive fluids and equipment, varying from "patently adorable" ("Are you referring to number one, or cockee-doody?") to the kind of words that'll get you excommunicated.
Sometimes getting the etymology down isn't as big a deal as just **getting the sound right**. So many sci-fi curses sound sort of like "real" ones, like Smeg, Frak and Sprokk/Drokk (from the Legion of Superheroes comic). We never learn their origins, but we know immediately they're "sour language" (as my kid calls them) Single syllables, with a solid consonant in them, something that makes you feel better after your stub your toe.
There was a great episode of the cartoon **Recess** where the gang decides to create a new curse word, one they can use without getting in trouble. They settle on "whomps", as in "This really whomps". It's so successful, a school administrator hears it an tries to get it banned.
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There's also the Firefly solution where they implemented archaic swear words (Gorram subs for God Damn and Ruttin' subs for the F-bomb). You could also use inappropriate words that your culture wouldn't know. English is great for this in that it is often said that the United States and England are "two cultures separated by a common language)... and it's not just those two English Speakers. For example, saying "I will knock you up tomorrow morning," has a vastly different meaning to an American and a Brit (its the difference between impregnating you at 7 am and knocking on your door to wake you up). An 11 year old Rupert Gint saying "Bloody Hell" had different reactions depending on which side of the Pond you were (Americans would be more offended by an 11 year old saying "Hell" while British were more offended that it was "Bloody Hell".). And make sure you know your Aussie (and Kiwi) friend are well aware of your meaning when you "Root for your team" (Hint, see the above mentioned Ruttin' for what the Lands Down Under will hear.).
Another thing to do is to make up a harsh sounding term that "doesn't translate well". I would look at casual utterances in Klingon languages that Star Trek used that were often insults. The word pet'Q (and that's proper capitlization) means "dishonorable" and is quite an insult. There has been some fan theories that because Star Trek has "perfect translator devices", pet'Q's lack of translation into English could mean that it could carry a definition that is so unique to the language that the concept just does not translate to any English word reliably. While the closest equivalent would be dishonorable, it carries far more (insulting) meaning than dishonorable would in English.
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Swear words are cultural.
Figure out what is negative in their culture.
If in the vampire's culture everyone is a vampire then things that hurt or make vampires ineffective may serve as swear words, like sunlight or stake or calling someone toothless or something similar.
In your witch's culture, lacking magic might be a negative thing, or things that prevent people from doing magic.
Maybe there are insults in one's culture that would qualify as compliments in the other's.
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Good answers already, but a few extra points
**Use words with "k" in them**
As described [here](https://en.wikipedia.org/wiki/Inherently_funny_word), words with the letter "k" in them are inherently funnier and "bad-sounding" than other words, which is at least partly why modern comedians use the f-word so often and "frak" worked so well in BSG.
**Keep the word length short**
When a brick is dropped on your toe, someone will not say "Iogommorrahwoowootweak". Normally it will be a single syllable with a short consonant (although [Deadpool](https://en.wikipedia.org/wiki/Deadpool_(film)) breaks this rule by sometimes saying "Canada!").
**Keep the list of words short**
The original version of [Shadowrun](https://en.wikipedia.org/wiki/Shadowrun) had two primary swearwords - "frag" and "drek". Even if you have never had any exposure to Shadowrun or refused to read the glossary, if you read the sentence "Get fragging clear of that drek!" you would be able to work out the equivalence. At the other end of the scale, one of the most unpleasant reading experiences I had recently was a sci-fi novel where most of the pages had made up words with definitions in footnotes. Many of the words were used only once in the entire book and had no effect on the plot. The xkcd strip Renan quotes is humorous but serious advice.
Besides, if you work out the culture then you may not require made up words at all, just different emotional indices on existing words. While it is rather dated now, Ira Levin's book [This Perfect Day](https://en.wikipedia.org/wiki/This_Perfect_Day) described an overtly wonderful but actually corrupt future in which the population were required to have regular sexual relations and be cool with nudity, but any violence and/or strong negative emotions were forbidden and grounds for therapy. So the key swearwords were "hate" and "fight" or their noun forms, while the f-word was used casually to describe consensual acts of sex. When a character says something like "Fight! I hope something unpleasant happens to that little hater!" the reader does not require a translation.
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Well swear words can be anything you want them to be. Madeup words are fun to make and swear words can be anything you'd want.Think of your society and inner groups what do they find distasteful or rude to just that one society or inner group. Outsiders may not think this gesture is rude or they confuse the swear word for a positive or neutral word to them. This would be regardless of weather or not you intend to make up words.
You could also just combine English words together like metal clinker could mean the insulted is greedy and greed is not a worthy attribute in the society.
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I want to have an Earth-sized planet (with similar gravity) with an extremely low-density atmosphere (comparable to Mars) at most of its surface. Complex life, including an information-age civilization, lives in enormous sinkholes many kilometers across, some up to 100 km across. Due to the lower elevation, the air pressure and composition is comparable to Earth‘s. The sinkholes are flat on the bottom and have vertical-ish walls, so they’re shaped like carved-out cylinders. The planet has many such giant sinkholes, and they’re connected by underground rivers.
Is this realistic?
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For an average across the Earth the pressure is roughly 1000 millibars Mars on the other hand has about 6.0 mb, about 0.6% of Earth's (These are rough figures!)
Most of the Earth atmosphere's molecules are concentrated close to the earth's surface due to gravity. Because of this, air pressure decreases rapidly at first, then more slowly at higher levels.
Since more than half of the atmosphere's molecules are located below an altitude of 5.5 km, atmospheric pressure decreases roughly 50% (to around 500 mb) within the lowest 5.5 km. Above 5.5 km, the pressure continues to decrease, but at an increasingly slower rate (to about 1 mb at 50 km).
So if you truly wanted the Planet to have Earth Like atmospheres in Sinkholes, but Mars Like ones on the surface, then the sinkholes would need to be about 50km deep, however the problem arise from the extra mass from having the correct pressure and gravity at the bottom of the hole, the planet would be too heavy and need to be slightly bigger but also have a makeup similar to Swiss cheese and be full of these sinkholes, this then causes issues in terms of sunlight reaching the bottom of the holes to allow photosynthesis, even when they are 100km across
The next issues is the planet still having a molten core as that sort of makeup would almost act like a heat sink and dissipate heat very quickly, which means the core would cool, that would then remove the protective magnetic field from the planet and the solar wind would burn and drag the remaining atmosphere off
and limit the weather patterns of earth developing... making life unlikely (Although not impossible) to begin there.
**An Alternative**
Perhaps make the "surface" pressure slightly higher, enough that maybe it was at the 4-5km range, so ~50% of the atmosphere is lower than this, but it would allow some weather patterns to transit between sinkholes, as well as jet based flight between them to expand.
or make the planet similar to Earth and have it have no Jupiter to act as a comet catcher, so it has been impacted thousands of times by huge meteorites, this would cause large deep craters which could be similar to the sinkholes that you want? some of those meteorite craters could be flooded to create a sea others are dry and have a variety of life in them, maybe even the meteorites carried bacteria to this planet in the first place?
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Perhaps your sinkholes are **refugia**. My similar answer here.
[Potential ecology of a magic hot spring?](https://worldbuilding.stackexchange.com/questions/79660/potential-ecology-of-a-magic-hot-spring/79687#79687)
Refugia are sanctuary sites where creatures can survive and ride out widepread changes in conditions. One of my favorites are the tiny watering holes in the Sahara desert where Nile crocodiles live - these were stranded here as the world changed and the Sahara dried up. They are little and inbred but they survive.
Your world is losing atmosphere as its magnetic field weakens, allowing the solar wind to strip it away (much as is thought to have happened to Mars). The degenerate remnants of the world that was remain on the surface, sort of like Burrough's Barsoom. The giant sinkholes are where life clusters. Your intelligent life was once planetwide and the empty cities of their ancestors now are home only to the few life forms able to withstand surface conditions. The intelligent life has retreated to the sinkholes and subsurface refugia.
Sort of like the Elder Beings, in a way. Unfamiliar? You are in for a treat: <http://www.hplovecraft.com/writings/texts/fiction/mm.aspx>
My recommendation for your intelligent sinkhole dwellers - do not bring the shoggoths down there with you .
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This actually does seem like novel way to prevent out-gassing on a mars sized planet, especially with the underground rivers preventing stagnation and excessive evaporation. In my mind, these sinkholes would be amazingly lush, as they get feed a lot of nutrients from the rivers and would have rain-forest levels of precipitation. I would have a hard time believing a system like this would occur naturally or be build by whatever life forms that are native to the planet, however.
Maybe there could be an implication that the sinkholes were built by off-worlders as low maintenance habitations or prisons? This wouldn't have to be a plot point or anything. Just some mythology or an in-universe theory.
But yeah, I would totally buy into this being a plausible setting with a lot of potential, though your planet would likely have to have less mass than Earth for surface to have such thin atmosphere. Like, 8 m/s^2 acceleration from gravity verses Earth's 9.8 m/s^2. This might lead to lankier people and buildings, but I doubt that will be a dealbreaker.
Some questions I would love to see answered as a reader: When a civilization expands, do the more prosperous seize the sinkholes while the poor live in dark tunnels? Are their trade towns build in the underground rivers that have never seen the sun? When the industrial age occurred, did the people put the factories in the sinkhole or did they carve new tunnels for them, not wanting to waste super valuable land on buildings that would fill the sinkholes with toxic air? Which is easier for explorers; digging new tunnels or launching expeditions to the surface? I am really curious to see the consequences of this system of habitation.
Nice idea!
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Let's consider the planet as populated by humanoids similar to us. We need air to breathe so we will assume there is enough nitrogen and oxygen for us and carbon dioxide for the veggies. The big parameters to create your planet would be excess gravity and a really calm atmosphere. Those conditions could create stratification in the atmosphere which separates breathable air in a thinner layer than on Earth. Arguably there may be poisonous gases at the lowest elevations (<https://caves.org/pub/journal/PDF/v71/cave-71-01-100.pdf>). Maybe the fish in the rivers are like fish found in our deepest oceans or Sperm Whales that breathe CO2 and exhale oxygen and carbon nanotubes. Tomatoes would grow flat on the ground like a pie and we would have robot exo-skeletons and breathing regulators. The walls could be only a few thousand feet such as I have seen in the Dolomites, Yosemite or Upstate New York.
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First of all, **how deep your sinkholes need to be?**
Let's assume that atmospheric density at the "top surface" is 1/2 of that at the lowland. For Earth, this is **about 5500-6000 m** elevation difference. Also assuming that this planet's temperature is similar to Earth's, your "top surface" is going to be very inhospitable, but not instantly deadly. Most of it will be glaciers with no vegetation, and going between sinkholes (using top route) would be worse than traveling on Antarctic ice shield.
**What if your planet's gravity is lower** (or higher)? In this case, required elevation would be **inversely proportional to planet's gravity** (according to transformation of the [Barometric formula](https://en.wikipedia.org/wiki/Barometric_formula)). So, for Mars, we are looking at some 12 km difference.
All of these numbers are well within possible variability of planet's crust, so it is very plausible that large surface areas have too low atmosphere to support abundant life, while at low elevations conditions would be much more favorable.
Next question is, **how this terrain can be possible?**
This is much more difficult to answer. Normally we would expect to see large low elevations basins, not sinkhole pockmarks. Processes like plate tectonics or asteroid impacts can create deep rifts or craters, but they are not going to last long (like a million years), if air and water are present.
One possible theory is that this planet has many more small continental plates than Earth, and as a consequence, ocean basins are small, but very numerous. This will explain not only elevation differences, but the overall "isolated sinkholes" topology. In any case we should expect that at the bottom of every sinkhole will be a sea or saltwater lake. Biological diversity would be much higher than we see here on Earth.
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## How Earthlike?
Earth's atmosphere is about 80% nitrogen, which is more than is needed to support life. You could keep the density of oxygen consistent, lose 75% of the nitrogen, ending with around 50% O2, 50% N2, and 40% of the total atmospheric density of Earth. On Earth you need to get to 18 km to reach 0.1 bar, on this planet it would be around half of that.
The troposphere (where weather happens) would also lower, so weather would only exist in the lower areas.
## Earth Without Oceans
[Ocean Depth Viewer](http://portal.gplates.org/cesium/)
If you took away the oceans, you would end up with a series of large basins that are several km lower than continents, often with nearly vertical walls. Plus, ocean trenches would be several km deeper. If you need 7-10 km difference between livable and alien landscapes (the mid Atlantic trench is 8 km deep, Mt Everest is 8 km high, the Mariana trench is 11 km deep), a planet with large continents and small oceans, where the oceans were lost to some process, could be the formation story of the geography.
### Hydrology
Underground rivers might not be realistic. That term can refer to a river that flows through a cave or groundwater that flows through permeable soils, and both are driven by water flowing down hill due to gravity. Surface water only stays surface water for a few weeks before flowing to its terminus or infiltrating, and requires constant snow melt or rainfall to replenish it. Fast moving groundwater would also move downhill quickly. Normally surface and shallow graoundwater is recharged by evaporation from oceans and lakes, but if the water is leaving one depression and flowing downhill to another depression and the weather can't carry it back, then there won't be any water left in the uphill location after a short time.
If you want earth-like water cycles, you need lakes or oceans at the bottoms of the depressions where evaporation can occur. You could also have giant glaciers at the heights that steadily melt, and some sort of recharge mechanism that is either local to a depression, or huge winter storms that carry the moisture over the rims of the depressions to deposit it around the planet. But you'd probably need some ocean somewhere supply those storms.
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The best way to survive on an otherwise hostile planet is to build a space base with an enclosed ecosystem there. The best way to keep a planet's atmosphere from escaping into space is to enclose parts of the planet, or the entire planet, with a giant roof or roofs to keep the air in, and to keep repairing the roof(s).
But if you are going for a more natural way to have a partially habitable planet, I should point out that Earth is mostly uninhabitable for humans, though almost entirely habitable for various lifeforms. The oceans produce a lot of oxygen we breath, and water evaporated from the oceans is the source of the fresh water we drink to stay alive.
But if you are teleported to a random position on Earth, it will probably be a spot on the surface of the ocean, and you will probably drown. An d if you are teleported to a random position on land, there will be a significant chance you will die of thirst, starvation, or exposure to hostile temperatures.
I would suggest that for your planet, it might be good to calculate a mass and volume, and thus density, that gives it a somewhat higher surface gravity, so that the atmosphere is more compressed, and also a somewhat lower escape velocity so it looses atmosphere faster. And also make it with less of a magnetic field to protect the atmosphere from loss.
The highest known human town, La Rinconada in Peru, population 30,000, has an altitude of 5,100 meters or 16,728 feet.
This Wikipedia list: <https://en.wikipedia.org/wiki/List_of_highest_towns_by_country>[1](https://en.wikipedia.org/wiki/List_of_highest_towns_by_country)
Has nine countries with settlements over 4,000 meters (13,123.36 feet) elevation.
Thus there are tens or hundreds of thousands of humans today who have adapted to living above 4,000 meters permanently, although many people have difficulty with much lower altitudes. Thus if the pressure at sea level of your planet was the same as at 4,000 meters on Earth, native intelligent beings could easily have evolved to flourish at that pressure.
At 4,000 meters above sea level the air pressure is only 0.85 that at sea level.
>
> The atmospheric pressure on the Martian surface averages 600 pascals (0.087 psi; 6.0 mbar), about 0.6% of Earth's mean sea level pressure of 101.3 kilopascals (14.69 psi; 1.013 bar). It ranges from a low of 30 pascals (0.0044 psi; 0.30 mbar) on Olympus Mons's peak to over 1,155 pascals (0.1675 psi; 11.55 mbar) in the depths of Hellas Planitia.
>
>
>
<https://en.wikipedia.org/wiki/Atmosphere_of_Mars>[2](https://en.wikipedia.org/wiki/Atmosphere_of_Mars)
These pressures correspond roughly to pressures on Earth at altitudes of 30,125 meters or 98,350 feet to 57,150 meters or 187,500 feet - 30.125 to 57.18 kilometers or 18.626 to 35.511 miles.
Even if the air pressure inside your sinkholes is only the same as at 4 kilometers or even 5 kilometers on Earth, and even if the air pressure of Hellas Planita is defined as the Martian air pressure, that would still reduce the needed elevation difference by only 4 or five kilometers to 25 or 26 kilometers or 15.534 to 16.155 miles.
On Earth the difference between Mount Everest 8,848 meters, and the Challenger Deep, minus 11,034 meters, is 19.882 kilometers or 12.3541 miles.
Because the Earth is an oblate spheroid, the difference between the farthest point from the Earth's center, the peak of Mount Chimborazo, at 6,384.4 kilometers, and the closest point to the Earth's center, the bottom of the Litke Deep in the Arctic Ocean at 6,351.61 kilometers, is 32.79 kilometers or 20.1 miles. But the atmospheric density would tend to be equally oblate as the Earth's surface instead of spherical, i think.
Because rock on the sides of slopes a has a direction without presssure, it can collapse and slide down the slopes while rock inside a mountain has no place to go. Thus mountains and other elevation features tend to collapse and avoid reaching heights above the limits of their structural strengths.
Thus it seems very unlikely that a planet similar to Earth would have a much higher range of elevation, sufficient for the one lowest spot on the surface to have a breathable atmosphere and for the one highest spot on the surface to have an atmospheric pressure as low as the highest atmospheric pressure on Mars.
And of course it would be many times less likely for a planet to have the surface pressure of Mars, even the highest surface pressure of Mars, over the vast majority of its surface, and have several depressions deep enough to have breathable air at their bottoms. Stone just isn't strong enough for such depressions to avoid collapsing and filling in.
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Piggybacking on this question: [Can you simply scale up animals?](https://worldbuilding.stackexchange.com/questions/316/can-you-simply-scale-up-animals) how CAN we scale up living creatures to be giant sized? What would need to done to make truly giant animals (Dragons, Kong, Godzilla, etc.) possible? Land creatures, flying creatures, ocean creatures, included.
All the questions I've found pretty much say that it can't be done. Fine. But if we were to try to create said creature, what would we have to do?
As the previous question states its just not possible, I get that. So let's assume in this fictional universe there's some super science technology and that said technologies users are creating the creature from scratch or manipulating an existing creatures DNA to make the changes necessary. Don't just say "magic" though please.
For example: Bones and muscles made of denser but lighter material?
Multiple hearts to get the blood pumping?
Some cavity(s) in the body filled with a gas that makes the creature more buoyant?
Brain with extra organ(s) that can send out greater/faster commands to the body?
Even changes to the creatures environments are welcomed if necessary, though I'd rather focus on the creature itself.
EDIT: Some more details- Earth gravity and environment, and no more than 24m / 80ft tall.
EDIT: I wanted to add these pics to give a kind of scale to the size of creatures that have existed IRL. That really big Brachiosaur in both pics must give us some ideas.
[](https://i.stack.imgur.com/6ZQ4d.jpg)
[](https://i.stack.imgur.com/qDj2r.png)
<https://en.wikipedia.org/wiki/Argentinosaurus>
[](https://i.stack.imgur.com/7PQ8B.png)
EDIT: I believe my question is different from [Is there a maximum size an ocean bound creature could grow to?](https://worldbuilding.stackexchange.com/questions/317/is-there-a-maximum-size-an-ocean-bound-creature-could-grow-to) in that the previous question is more specific to ocean bound creatures and I'm hoping to get answers that apply to any and all creatures that would be giant sized. Thanks.
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The limits to the growth of an organism (most can be avoided by slowing down the metabolism and living in the water, but let's remain on dry land since it's more challenging) are - and I'm probably forgetting some:
* structural: the organism no longer can support its weight, no longer can expand its lungs.
+ solution: replace the bones and the relevant muscles with artificial materials and externally powered cybermyomers (you will need a power source).
* respiratory: the lung to body volume cannot increase past a certain point before the lungs become inefficient.
+ solution: you'd need to replace the lungs with a sort of continuous-flow turbine pipe (like the intestine, but *way* faster), solving also the problem of drying up; or equip the animal with externally powered oxygenators. Or you might supply it with independent "lung blisters" on the skin, which would also ensure redundancy.
* circulatory: the heart cannot move the required volume of blood. Even if it could, the pressure would burst any organic vessel. And anyway, the blood can't contain enough oxygen to saturate both the nearest and the farthest cells along arterial radii.
+ solution: you need multiple hearts, wider vessels, a much faster circulation, and multiple separated circulatory systems, possibly each connected to one of the "lung blisters" above. Also thicker vessels and a pressure-compensating mechanism (from the top to bottom of *Gypsy Danger* there would be around three atmospheres of blood pressure differential).
* sensorial/nervous: nerve signals don't travel fast enough.
+ solution: for a while, having multiple brain ganglia disseminated throughout the body will help. After that, you'll need to look into alternate solutions, like electric signals (not bioelectric ion waves) inside really insulated nerves - or artificial electric conductors. Possibly, a sort of organic optic fibers are possible by using very clear lymph in dedicated vessels, and retina-like, [luciferin](https://en.wikipedia.org/wiki/Luciferin)-rich ganglia as signal regenerators.
Then, such an organism would be too weak for itself. Simply banging into a tree or a rock would deliver enormous amounts of pressure, and therefore inflict untold amounts of damage.
Therefore, you also need to supply the organism with much tougher skin, or even armor (and somehow make that not interfere with air supply). You would have a segmented armor with the lungs beneath; the armor would continuously separate from the body for a suitable distance, with the scales sliding one against the other and leaving sufficient space for the air to flow inside. Then the armor would "deflate", forcing the air through the oxygen-absorbing channels immediately below, and you would end up with a wobbly, accordion-like rhino skin with "nostril"-like air ducts opening directly on it:
[](https://i.stack.imgur.com/sdohk.jpg)
Having "even" squares inflate while "odd" squares deflate, and then inverting the air direction, could solve some of the drying-up problem and optimize air flux.
And finally you get to *feeding* the beast...
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We believe all living beings on Earth came from simple, microscopical organisms. The largest animals we have seen on Earth are the blue whale in water and *Patagotitan* on land:
[](https://i.stack.imgur.com/BitDP.jpg)
You can make any animal just as big if you follow some guidelines:
* You will need lungs. Simple oxygen diffusion will probably not do. Look at the chest cavity of those beasts.
* Similarly, a very strong heart. The whale's can be as big as a Wolksvagen Beetle. As for the lizard, some scientists believe sauropods had evolved extra hearts along the neck. I don't think that hypothesis is popular these days, but you could think of that.
* The weight of the creature must be sustained by water, or by a skeletal system that is comparable to a suspension bridge.
* The creature will be fat, and will have to spend a considerable amount of its time eating. It would probably be a tree-eating herbivore or a filter feeder.
* The brain will be comparably small compared to the rest of the body. That, compared with the inertia the beast will have, leaves little room for agility.
* Its main defense against predators should be its sheer, obscene size.
* Since it has to grow a lot, it will probably take decades to go from newborn to adult. More decades than a human in the very least.
And these are what I can think off the top of my head right now. Look for what is common between these creatures and the largest land dwellers we have these days (such as hippos and elephants).
A giant predator can exist in water (see *Megalodon* and sperm whales), but probably not on land.
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**Giant photosynthetic jellyfish.**
[](https://i.stack.imgur.com/GqKhR.jpg)
<https://en.wikipedia.org/wiki/Cassiopea_andromeda#/media/File:Cassiopeia_andromeda_(Upside-down_jellyfish).jpg>
[Jellyfish Body Plans Provide Allometric Advantages beyond Low Carbon Content](http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0072683)
>
> The fundamental differences in the body plans of jellyfish and other
> pelagic taxa appear to have a large influence on metabolic rates.
> Unlike most metazoans, the bodies of jellyfish comprise thin layers of
> ectodermal and endodermal tissue that line the external and internal
> surfaces of their bodies. The bulk of the body consists of the
> mesoglea, a robust extracellular matrix that comprises water, collagen
> fibres and salts [20] although in ctenophores, some muscle cells are
> also located in the mesoglea. The mesoglea provides structural
> support and has elastic properties that enable it to function as a
> hydrostatic skeleton, but because it contains few (scyphozoans and
> ctenophores) or no cells (hydrozoans), its metabolic demand is small
> [20]. Thus on a wet-weight basis, rates of respiration of jellyfish
> are much slower than those of other pelagic taxa but when scaled to
> carbon content, rates of respiration are similar to other metazoans.
>
>
>
Jellyfish scale up cheaply as regards energetics and materials. A jellyfish which did not need to move its body but could make reduced carbon via photosynthetic symbionts could get even bigger. Larger body = more surface area for photosynthesis = more food. Medium sized "photosynthetic" animals like this are common. I suspect the reason they do not get larger is that rough conditions stress large fragile bodies more, and also predation. Sidestepping these two issues, I could not figure out any theoretical upper limits on the size of an organism like this which is mostly water.
An animal like this is an animal, but has converged on the life strategy of a plant. Ocean plants can get very, very big.
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You can also explore the possibility of increased gravity. Creatures from a world with a high gravity would be either become smaller or larger. See this Reddit (<https://www.reddit.com/r/worldbuilding/comments/4jpidj/how_does_stronger_gravity_affect_evolution/>)
It really depends on how you want the outcome to be. If the stronger/higher gravity was not sudden then life would evolve to fit the environment and that would include denser bones, probably larger lungs and multiple hearts to support the body, muscle density becomes higher and would make creatures larger.
I've read a few books I think it was Pip and Flynx by Alan Dean Foster (don't quote me on this) where one of his species was large and strong due to living in a higher gravity world.
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**Decrease the size of the planet**
On a smaller planet, you can have a bigger creature. Really, the largest problem with having a scaled up creature of any size is that it will get crushed under its own weight.
There are two problems with this:
* If the planet is smaller, why does it have an atmosphere dense enough to support life?
* The creatures wouldn't be able to survive on other planets.
Unfortunately, answering the first problem is more or less beyond me, short of having a heavy gas, or all life being water breathing (would the water need to be encased in some sort of shell to stop dissolved gas escaping?)
The second one limits the scope a little, too. It may be that large organisms will be able to survive fairly long in planets such as ours for relatively short periods.
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\*\*No There are limits. \*\*
One of the simplest is the larger you get the stronger the limbs need to be, no matter what you make them from there is a point when they cannot support their own weight.
Other limits include the square cube law and gas/nutrient distribution, circulatory fluid column height limits, neural connection lag, heat dissipation, ect.
**No they cannot just be scaled up**
Additionally animal anatomy changes in noticable and predictable ways as they increase in size, this is especially well studied in [dinosaurs](http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0158962), they cannot simply be scaled up. The square cube law lies at the heart of most of these changes and will hold true no matter what you make the organisms out of.
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Sometimes you just want to have a dragon, giant scorpion or a superhuman that has a bit more realism behind it than "it's strong, fast, can jump extreme distances despite it's weight and it's smart, deal with it". The original question(s) were far too broad for a single post, so I'm making a series of posts about things like skeleton, muscles, nerves, immune system and more to try and get an answer on how to build some of the best but still scientifically semi-realistic creatures. My personal question mostly aims at a humanoid super-soldier, but I expect that most of the idea's would be useable in other creatures as well.
For completeness, here's a list of things that I think such a soldier needs to adhere to:
* Uses biological components to function
* Can regenerate wounds without needing to be brought to a certain facility for repairs (but if available they would use it). Regeneration does not have to be 100% successful, as long as they can continue at a high % of their original functionality it's OK.
* Can survive on food when necessary.
* Has ways to reduce the effects of radiation, both cosmological and from weapons (like a robot that's holding a Paricle Beam in close quarters).
* Can survive short periods out in space, preferably in a damaged space
suit but naked if necessary.
* Has protection against extreme heat (lasers, Plasma, Particle Beams) and extreme cold (space, liquid nitrogen and other cold stuff weapons)
* When necessary, can still reproduce normally.
* Can survive breathing toxic air for extended periods of time (not
very good on the details of what "toxic" is right there)
* Has a resistance to small-arms fire, either through protection and/or being able to keep going regardless of damage
* Can withstand immense amounts of recoil forces.
The goal of this post is to come up with idea's for the skeleton, what materials it needs to be build of, what shape it would be and how easy it would be to repair and maintain.
My personal take on this part is as follows:
Materials: Graphene, Carbon Nanotubes (CNT's).
Graphene seems like a perfect fit for a skeleton. It's Carbon-based like most of the body's structure (that isn't water), it's incredibly strong but it's not extremely brittle and it's lightweight. Any alternative functions that normal bone would do and Graphene couldn't would be taken over by bony calcium deposits.
Repairs and checks on how the Graphene bone is currently doing can be done by systems already in existance: Currently the body uses electric potentials to check how much stress a bone receives and then uses that feedback to strengthen or weaken the bone locally, this same process could be used to check for damage to the Graphene structure and have repair cells be activated/attracted to such area's.
Another advantage pointed out by Nick: Graphene can conduct electricity extremely well. When using an exo-skeleton you can make the person highly resistant to electrical attacks as the exo-skeleton would conduct the electricity into the ground without the surrounding tissue receiving much of the punishment.
Disadvantages could be that Graphene is a single molecule thick to gain it's properties, so you would need to have many many layers of graphene that aren't attached to one another to build the bones out of. Another possible problem is that the cells wouldn't be able to create a full-scale graphene layer and would only be able to build small portions of Graphene that has to be connected without being a single large molecule. An alternative is to roll up the Graphene into CNT's and put those into another material, like normal bone. There's a perfect size for these rolled up nanotubes that gives the best strength properties, and there's room enough to insert another smaller CNT inside for extra strength.
One big advantage is that you can vary the amount of Graphene or CNT's to give different strengths, in case you don't want people running around with skeletons 5x stronger than steel using 3D Graphene (just found out it exists: <https://www.engadget.com/2017/01/09/mits-3d-graphene-is-ten-times-stronger-than-steel/>), or even 300 times stronger than steel(<http://theconversation.com/harder-than-diamond-stronger-than-steel-super-conductor-graphenes-unreal-5123>)
Shape:
For the shape I would use both an endo-skeleton combined with an exo-skeleton. With the weight issue's removed due to the skeletons strength and light weight, having an exo-skeleton won't make you collapse under your own weight. The addition of an endo-skeleton would help support the body especially in case the exo-skeleton is damaged and offer extra places for muscle attachments. The exo-skeleton would also serve as a perfect shield against incoming harm, with a single millimeter thick exo-skeleton possibly counting as 5 to 300 mm of steel.
To increase sensitivity, speed of repairs to damage and make it looking more like a humanoid rather than a humanoid crab, a layer of skin would still cover the exo-skeleton. This way damage on the outside of the exo-skeleton can be repaired more easily and the being has an easier time feeling his surroundings with a normal skin layer (don't worry we'll get to upgrading the skin to super-human status as well).
The biggest questions that remain for the Graphene for skeleton idea:
Isn't Graphene too flexible? Does it need a material beneath it or through it to provide strength?
Can the body acquire enough Carbon and energy to form Graphene in large enough quantities to repair and maintain the body?
[Answer]
So this is a big question but it seems like the heart of if is that you want something that is human but just better, so let’s try to break it down system by system.
**Skin:** Graphene, full stop. In fact you’ll find me answering that for a lot of these questions. More to the point, graphene is incredibly strong, very hard to pierce, and a hundred layers is still incredibly thin. It also has the bonus of being made of carbon. I’m not sure how feasible it is to have this grow naturally, but since you’re making these guys just 3D print layers of graphene to go just under their skin. This provides protection from small arms fire, knives, and pretty much anything that would penetrate the body. It would also help with electrical resistance. But graphene is a conductor (you say as you read this)!? Exactly! An insulator absorbs the energy from the electrical current, which then turns into heat and at high wattage this results in a melted insulator. A graphene layer, on the other hand, could conduct the current across the plates and into the ground, resulting in only minor surface damage to your super soldier.
**Respiratory and Circulatory:** These really need to be lumped together, because even though it is two different systems their functions overlap so much. Here is also where you’ll run into a few issues. First off super soldier means super oxygen requirements and super waste generation. This means that during intense activity blood pressure will have to reach levels much higher than those of a normal human in order to deliver oxygen to the muscles and take CO2 away. The lungs will have to be quite a bit larger, as will the heart. Yes I know, you thought about taking it away, but that will create more problems than it solves. Look at nature, active predators have at least one heart, and in the case of squid they have three, one main heart and one for each gill. So what you need here is a very large, very powerful heart that can pump blood at immense pressures through the body when needed. You’ll also need much more robust arteries. The vessel walls will need to be thicker and more muscular, and the exterior could be coated in very elastic fibers, like collagen, to help support the vessels. Nanobots are definitely your friend here, as you can have specialized versions that carry extra oxygen and CO2, activate stem cells, repair damage, and fight off foreign bodies. A side effect here is that your soldier will create much more heat than normal, so they will need lots of surface capillaries near the skin so they can cool themselves. Better bring plenty of water for those tropical environments.
**Muscles:** So it might not seem like it, but most of the time what limits a human’s muscle strength is the strength of the connective tissue like the tendons. So I think using some sort of spider silk type substance for tendons and ligaments is your best bet here. As for the muscles themselves, I think that they have a similar solution as the nerve cells, a literal silver lining. Silver is an excellent conductor of electricity, and if the conductive fibers of muscle cells, and parts of the nerve cells for that matter, had trace amounts of sliver that could increase their conductivity and result in less waste. In addition, more support from a stronger skeleton and connective tissue, more nerve enervation, a better blood supply, and genetics for good muscle growth would vastly increase the strength of your soldiers. Finally, your soldiers could be trained on using what I call muscle chains. It’s a concept in martial arts where you tense and relax muscles in certain places all over the body to increase your strength. This concept is what allows boxers to throw such devastating punches, and how Bruce Lee could kick holes in heavy bags.
**Nervous system:** So the silver lining that I mention previously could help with increase the conductivity of the nerve cells. However no matter how much you increase the electrical conduction, you have to remember that one nerve cell communicates with another via neurotransmitters, and these chemicals are vital to a human’s mental and emotional health. So you can’t get rid of them, because depressed, possibly suicidal super soldiers would be very bad. However, more nerves and more pathways, in both the central and peripheral nervous systems will increase intelligence, speed, and reaction time. One thing you may have overlooked, and this is pretty cool, is that you can make combat much faster and more efficient by essentially automating it. Again, this is something that happens in martial arts, and the term in English is “no mind.” What happens is you are able to move and react without any conscious thought about it, so your body will avoid getting hit, and for very experienced martial artists, hit back, without any conscious input. I can tell you from experience that someone who can do this is at a massive advantage against someone who can’t. So make combat reflexive. You’re spinal cord can send messages to your muscles for certain reflexive actions instead of your brain, so have it tell your super soldiers to dodge that punch and follow up with a boot to the face!
**Bones:** Graphene. There it is again. Roll it up into tubes, which is basically carbon nano-tubes, and have it support the bone structure. Notice I didn’t say replace! The bones serve about a bajillion functions in the human body, including storing and releasing vital nutrients like calcium, so you cannot replace the bones, but you can support them and thus vastly increase their strength. The nanobots will come in here as well, enabling the bones to automatically set if broken, and speed up the healing process. BEWARE! Every time you speed up any process in the body you will vastly increase the heat output so you need a way to deal with that or your super soldier will cook themselves.
**Digestive system and other organs:** When we do something physically exerting, our bodies already pull most of the resources away from our digestive system, so you can design your soldiers in such a way as to make their digestive systems more efficient, likely using those nanobots again, and as such the minimum oxygen requirements for those organs will be lower. You won’t be able to shrink them too much, as they are already pretty compact, unless you want your super soldiers to live on IV diets. Your other stuff like the reproductive organs won’t really require any changes as far as I can tell.
As some final notes. A human being can already survive in space for a surprising amount of time, much longer than most movies would have you believe. So with the graphite skin layer, extreme heat generation, and nanobot support, your soldiers could easily increase that time. Also remember that in order to power these changes you will need a much higher metabolism which means that the soldiers will need a very high calorie intake every day. Their bodies could be made to go into a type of hibernation so that they can survive for long periods of time without nutrients, but they won’t be doing much in that state. I would also say that these soldiers should be relatively normal size, 5’10” to 6’6” and keep their weight between 170 and 250 lbs. There is a reason why most humans fall into that size range, and that’s doubly important for your soldiers. Too small means they are easy to throw around, have limited leverage, loose heat too quickly, and have less mass to absorb impact. Too big and they lose agility, speed, and endurance, they’ll be prone to overheating, and they’re a much larger target. I would also recommend that they have a decent layer of subcutaneous fat under their skin, so they probably won’t have washboard abs. This layer of fat will absorb impact, provide extra protection from cuts, and most importantly, be a wonderful source of energy. Your soldiers will actually need a substantial amount of fat now that I think about it, as it is the best source of energy that the human body metabolizes. So their body fat percentage will need to be somewhere between 10 and 20 percent at least. If you want to look into some more exotic materials to upgrade your soldiers, I’d suggest looking into aggregated diamond nanorod, which is the hardest material I know of. However I don’t know enough about it to speculate how it could be used in this fashion, but maybe you could come up with something! I know I missed some stuff that you mentioned, such as the magnetic field thing, but I have a feeling that a natural magnetic field strong enough to deflect radiation could cause your soldier a lot more problems than it would prevent.
Also congratulations, you just made me post the longest answer I ever have and I did it from a phone! Great questions, and if I missed something important let me know and I’ll try to go back and squeeze an answer in here somehow!
[Answer]
**You want a cockroach.**
[](https://i.stack.imgur.com/gabSZ.jpg)
<https://www.weforum.org/agenda/2018/02/want-to-build-a-better-climbing-robot-copy-a-cockroach>
Yes, cockroaches are not humanoid, but you are in space now and need to step outside of your humanoidocentric world view. Roaches can do nearly everything you want.
**• Uses biological components to function**
Yes.
• **Can regenerate wounds without needing to be brought to a certain facility for repairs (but if available they would use it).**
Roaches can regenerate a leg. They regenerate their whole cuticle with each molt. They cannot regenerate a head but they can do without the head for a week or more. Punctures of the cuticle are problematic but if there were a field patch a comrade could apply (or the roaches wore self-sealing polymer armor) they would be good to go.
• **Can survive on food when necessary.**
Oh yes.
• **Has ways to reduce the effects of radiation, both cosmological and from weapons.**
[Roaches are extremely resistant to ionizing radiation](http://www.discovery.com/tv-shows/mythbusters/mythbusters-database/cockroaches-survive-nuclear-explosion/). A quick perusal of Youtube also shows that roaches do well against microwaves as well.
• **Can survive short periods out in space, preferably in a damaged space suit but naked if necessary.**
[Roaches can survive in a vacuum for surprisingly long](https://www.youtube.com/watch?v=wgO8JTZd6N4)
• **Has protection against extreme heat and extreme cold.**
No luck here – freezing will kill roaches and cooking will kill roaches.
• **When necessary, can still reproduce normally.**
Gladly.
• **Can survive breathing toxic air for extended periods of time.**
Roaches are resistant to poison and can keep going for some time even after being exposed to a lethal dose. I know this from experience.
**• Has a resistance to small-arms fire, either through protection and/or being able to keep going regardless of damage.**
Peforating the cuticle will eventually dry out the roach, but it will keep going until it does. Loss of the head will make it hard to steer but roach will keep going.
**• Can withstand immense amounts of recoil forces.**
The roach exposes itself to 30g when it jumps. The determining factor for acceleration tolerance by an insect is the durability of the exoskeleton. A roach can withstand 900 times its own weight before being crushed, so 900g would crush it.
You should use regular roaches, maybe with polymer armor. Not big ones and not humanoid ones. They are bred to home in on things which might be targets and attack once there. How they attack is up to you. I think I might use them as suicide bombers: when they come into contact with the enemy the tiny explosive glued to them detonates.
Your cannon fodder ships can be filled with hundreds of millions of suicide warrior roaches. It doesn't matter if they can repair themselves, or if thousands of them die because there are hundreds of millions of them. They do not know morale. They do not know their comrades are dying or that they are dying, or that they are your soldiers, or that they are soldiers. They do what they instinctively do.
Also: roaches can fly.
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[Question]
[
If there existed a planet that was made completely of liquid water, no solid matter at all, what would the core of such a planet be like? Let's assume that this planet has conditions similar to earth, so that it could support liquid water at its surface, with ice caps at the poles. But there's no matter of any kind except for liquid water, pure H2O. The surface is basically one big ocean. But what would happen if you dove down into that ocean? There would be no solid ocean floor in the traditional sense, but weird things would probably start to happen due to the pressure. Would the water be pressurized into ice? What abnormal properties might this core-ice have? How gradually would this happen? Would the core be hot or cold? If you could survive the extreme pressure, would it be possible to make it all the way to the core?
[Answer]
## For planets the approximate size of Earth You would find Ice VII, X, or XI. Possibly even liquid water existing as a supercritical fluid.
This is a surprisingly hard question, and depends on the radius and mass of the water planet in question. A water planet of Earthlike mass would definitely not have an Earthlike radius, and it's difficult to say exactly what its radius would be precisely because water is so damnably weird with so many different crystalline structures at different temperatures/pressures.
Have a look (and mind the logarithmic nature of the Y axis, and the moderate range of temperatures covered):
[](https://i.stack.imgur.com/z3CIg.png)
By [Cmglee](//commons.wikimedia.org/wiki/User:Cmglee "User:Cmglee") - Own work, CC BY-SA 3.0, [<https://commons.wikimedia.org/w/index.php?curid=14939155>](https://commons.wikimedia.org/w/index.php?curid=14939155)
Every labelled region on that diagram has different structural properties. As a point of reference, pressure at our planet's core is estimated to be in the neighborhood of 330–360 gigapascals. Since Earth is made of much denser stuff than water, we can probably take this a comfortable upper bound on an earth-radius water world's internal pressure. As you can see from the phase diagram, water at this pressure would be Ice X (assuming a moderate temperature, which is a poor assumption at a planet's core, but these are the data I could find), distinguished from Ice I–IX by its novel crystalline structure. In fact, Ice VII, X, and XI are the only ones one this diagram suggests could exist in a planet's core (which would, again, be very hot as well as under great pressure). The boundary between fluid and solid phases of water also goes to higher pressures as temperatures increase. In a particularly hot and small world, you could find plain old liquid water at the core, or more likely water existing as a supercritical fluid. [2](http://www1.lsbu.ac.uk/water/supercritical_water.html)
It is hypothesized that at even greater pressures, well above 1000 gigapascals, water would take on metallic properties. You'd need a truly massive water world for that to occur naturally at its core, however, perhaps approaching the limit of stellar fusion. Jupiter is thought to have internal pressures in excess of 3000 gigapascals, but Jupiter contains some materials significantly denser than experimentally verified phases of water, and is as you know, quite large. In addition, at least one theoretical prediction regarding the metallic phase of ice expects it to occur only at pressures in excess of 5000 gigapascals. (However, those endorsing more moderate theories placing it nearer 1000 gigapascal do indeed expect metallic ice to exist within Jupiter.) This site (<http://www1.lsbu.ac.uk/water/water_phase_diagram.html>) has extensive information on phases of water, including a more expansive phase-diagram that includes water as a supercritical fluid and the metallic phase of ice, though the latter is only theoretical.
As for the possibility of traversing the core, you can pretty much forget it. It's hard to imagine pulling together enough handwavium to help a human body survive pressures on the order of 100 megapascals or above. Even considering an autonomous drone core-explorer, it doesn't look good. For a solid core of exotic Ice VII, X, or XI, as you dig into it the supercritical fluid water above would immediately flow into any hole you dug and freeze into the depth-appropriate phase of ice, arresting your progress. (However, some exotic ices are metastable at temperatures and pressures other than those at which they are created, so if you have need of exotic ices, you might be able to mine them with a handwavium digger.) Even traversing the supercritical fluid would be an interesting engineering challenge, as supercritical fluids are, well, kinda weird. We actually use supercritical water as a means of rapidly oxidizing hazardous wastes [3](https://en.wikipedia.org/wiki/Supercritical_water_oxidation) that would otherwise persist effectively forever on the scale of our civilization, so good lucking carrying a sacrificial anode strong and large enough to offset that.
[Answer]
It is speculated that it would be [just ice and compressed water](https://en.wikipedia.org/wiki/Ocean_planet) (different from ice):
"Their abyssal depths would be so deep and dense that even at high temperatures the pressure would turn the water into ice. The immense pressures in the lower regions of these oceans could lead to the formation of a mantle of exotic forms of ice."
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[Question]
[
Assume you're in a world where you can increase your strength with magic and you can get a bow with enough resistance that you can shoot arrows at a supersonic speed.
How strong would the person need to be to wield it? How many pounds of force would they have to be able to apply?
Also, is there another way using not magic but physics to allow a bow to shoot supersonic arrows (beside having insane resistance and resilience)?
Lastly, does a supersonic arrow have any advantages over a supersonic bullet?
Edit: So, it seems that supersonic arrows aren't that great. Are there any range weapons what when combined with super strength would make it as good as a gun?
[Answer]
You're going to find a lot of [physics](http://www.meta-synthesis.com/archery/archery.html) gets in the way.
The most important detail will be that *arrows bend while being fired.* Because all of the propulsion is coming from the back of the arrow, the arrow is naturally unstable during firing. This is something archers are aware of at normal archery speeds. However, you will need to break the sound barrier while the arrow is still under power, so you'll need a lot of power in this unstable time.
Let's pretend your arrow is made of unobtanium, and is rigid enough. Let's also pretend your bow has a good enough "dry shot" velocity to accelerate anything to those speeds (which I think may be reasonable, with enough clever geometry). A reasonable mass arrow is around 200 grains (13 grams). In the interest of approximations, let's round down to 10grams, or 0.01kg to make the math easier. The draw length of an average bow might be around 0.75m. We can do the calculations to see how much energy an arrow has to have at the sound barrier: 340 m/s, and then use that to figure out how much force is needed to do that work over the draw length. E=1/2mv^2 = 578J. F=W/d = 770N. That's roughly 175 pounds of draw strength, to accelerate the arrow with no air friction or anything.
That's about triple the strength of a human right now. However it fails to take into account a lot of things, least of all being the inefficiency of the bow near the speed of sound (you're basically going to have to make the string into a bull whip).
However, that's just to get to the speed of sound. The drag of a projectile at supersonic speeds is quite high, about three times higher than you'd expect *for a well designed projectile.* Consider that a 9mm bullet is supersonic when it comes out of the barrel, but rapidly slows to subsonic. You would actually have to accelerate the arrow to a much higher speed to remain supersonic in flight. Trying to fire at mach 2 would require 4x the force.
All of that presumes access to an unobtanium shaft that can take the stress of launching, a carefully constructed bow with pulls quite stronger than any human can handle, and probably ignores a half a dozen limitations that appear in the transonic region that I am simply not accounting for.
The arrow shafts seem like the most difficult part to solve. Modern archers pay top dollar for ultra-exotic composite arrow shafts to minimize flex at human speeds. The material requirements for that arrow shaft supersonic may simply be outside the realm of known materials.
Want to shoot an arrow supersonic without these problems? Try a [sabot](https://upload.wikimedia.org/wikipedia/commons/b/ba/Obus_501556_fh000022.jpg). You can use them to basically put a sharp small object (like an arrow) into a gun. The sabot holds the shape as the explosives project the entire construct out of the barrel. Then the sabot falls away and lets the sharp thing fly.
[Answer]
Not really on answer, but you should give up on this idea. In all cases if your strength and the resistance of bow go up, it is better to add mass to the arrow than to make it supersonic. So a situation where someone would build a supersonic bow does not really exist. (With magic it could happen by accident, of course.)
This is because energy losses to drag and mechanical resistance will rise rapidly when the speed is increased. Traditional bows and arrows are meant for subsonic speeds so their base drag and resistance from the basic design is fairly high. If you accelerate it to supersonic, you'll get lots of wasted energy. Basically I am talking about the bowstring and the arms having large surface area and relatively bad aerodynamic shape. The ratio of the mass of arrow to the mass of the moving parts of the bow is also important.
Thus while it is actually fairly simple to calculate the force needed in ideal case, I didn't actually do the math because the actual force needed would be dominated by the mechanical and aerodynamic losses which would be difficult to even estimate without an actual bow with known design and materials.
Note that the same rapid increase of drag applies to the arrow afterwards as well. So for the same energy a subsonic arrow with more mass will fly farther and penetrate deeper on impact. In theory supersonic arrow would be more accurate, but in practice that would require the arrows to be precision manufactured from metal. Traditional arrow construction is not optimized for supersonic flight. Modern arrows might be more practical with more precise construction and higher quality materials.
A crossbow can be made very strong with pulleys or cranks to amplify strength. There is nothing stopping you from making it strong enough to propel the bolt supersonic. Except the fact that it would be even more inefficient than magical supersonic bow due to the added mechanics adding their own losses. And you can add the same mechanics to a bow if a crossbow is a no go. It just isn't particularly sensible, since the crossbow construction is more convenient for difficult to load cases.
A supersonic arrow (**designed** to be supersonic, not just normal arrow going fast) has better mass to drag and mass to front area ratios. Or said simply larger aspect ratio. Larger aspect ratio may result in higher range, better accuracy, and better armour penetration.
[Answer]
You've asked for ranged weapons which are alternatives to a bow and arrow where super-human strength would make the weapon more potent.
I would suggest the following:
* A [sling](https://en.wikipedia.org/wiki/Sling_(weapon))
* A [slingshot](https://en.wikipedia.org/wiki/Slingshot)
* A [woomera](https://en.wikipedia.org/wiki/Woomera_(spear-thrower)) or other [spear thrower](https://en.wikipedia.org/wiki/Spear-thrower)
Most of these may strike the same problems of material strength pointed out by other answers when extreme (supersonic) use is required.
[Answer]
It troubles me that everyone went to so much trouble to point out it's a terrible idea, but no one actually answered the question...
First off, is there a way to accomplish supersonic arrows in a non-supernatural way.. no.. but for different reasons than you think. Could we build a mechanical assist longbow? Sure. But when you think about what a bowstring moving at supersonic speeds would do to your face and arm, *shiver*
For this to even be feasible in reality, you'd need to invent some sort of magnetic launch mechanism because the string would mess you up pretty badly.
But in a supernatural setting?
Oh DEFINITELY!
First understand that strength adjusted bows have existed forever in Dungeons and Dragons. Second, to answer your question accurately would require some specifications..
For one.. You'd need a special bow, probably notched, so arrows can fly with minimal flexing.. it would also need to be enchanted to protect you from the bowstring and sonic crack in your face.
Second.. you need to decide what look you are going for.. are you shooting for the long long range sniper? Because now you have a range of about 6,000 feet.. or are you going for the barbarian who can shoot down castles and blast people out of a forest?
An arrow would need to be a mythological metal to survive.. so either something like a 20,000 grain (almost 3lbs) adamantine arrow.. or at the truly ridiculous end, a 27lbs ballista bolt. I'm going to assume you're going for the more "normal" adamantine arrows (which would be ridiculously expensive but almost invincible!)
Assuming a lot, I'd guess a heavy arrow (600 grain) made fully of adamantite would be about 15000 grain (about 2.25lbs, HEAVY! Note that adamantite, steel and dense ironwood have about the same density). Assuming a 75cm (29 inch) draw and an acceleration TO the speed of sound (thus minimum power) giving about 106,000 m/s/s of acceleration. Force equals mass (0.972kg) times acceleration (106666 m/s/s) gives 1,036,793 Newtons of force, or a draw strength of about 232,000 lbs, or a minimum strength of 7,000 in D&D 5e.
But fret not! There's magic afoot!
If you use a bow of FORCE then you would only need a STR score of about 21 to fire an arrow (assuming the arrow is normal at draw and until after release) at supersonic speeds and 6k range. Now THAT would be something to see no?
I hope that answered the question.
And now I really want a silenced sniper's bow of supersonic force.
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[Question]
[
This is going to require some explanation to set up, as I have been working on this world for a while.
The world is an isolated alternate dimension (no stars in the sky) that contains a bizarre feature called 'The Rift.' The true nature of The Rift is unknown, but it is a 2km diameter feature that most people describe as some sort of opaque pit (it looks different to everyone). The only thing that is absolutely known about The Rift is that it expels things from itself that seem to come from a myriad of different universes. There is no set in stone rules as to what comes out of the Rift; organic, inorganic, magical, scientific, or mundane. However, there are some general guidelines for what it spits out.
It generally expels 'whole' objects, so you don't end up with only half of a cat, and it doesn't tend to produce things that are pre-damaged. While larger things come out sometimes, roughly cow-sized and smaller is much more common. Yes, it also expels people. Although not always the case, it tends to expel useful things (so random rocks are uncommon). Everything that comes out of The Rift lands on the 50m wide, desolate 'Rim' that surrounds The Rift, and is undamaged by landing. It is believed that everything in the world can trace its ultimate origins back to The Rift.
The rate at which things are expelled from The Rift is inconsistent, but high enough that several hundred people can make a living salvaging along The Rim. Despite the comparative rarity of life in the multiverse compared to inorganic materials, living things (including sentients) are still fairly common. The town of Edge is the treaty-enforced hub for all Rift-based trade, and is a Plutocracy (ruled by the wealthy). Edge maintains a small amount of food production, but is primarily focused on Rift-salvage. It has no real industry to speak of. There are systems in place to allow for magical translation (so language barriers aren't a big deal). Slavery is legal in Edge, though technically, entering slavery *must* be voluntary.
Rapid-growth flora (has to be driven back daily) has restricted the development of the world, but trade is still common, especially from Edge to the rest of the world. For now, I'm going to ignore the cultural Charlie Foxtrot that results from the population of the world originating from all across the multiverse (at all tech levels), that may come up in a later question.
The general tech level across the world is wildly inconsistent, but there are a few cities capable of industrial-level production on a roughly modern level, and at least one at a futuristic level.
So my question is this:
The Rift is a potential source of pretty much anything, but cannot be counted on to be predictable. With access to a random (and unpredictable) grab-bag of stuff from all across the multiverse, what would the economy of Edge look like? What sorts of things would they need to import to remain stable? Would having such unpredictable exports be a strength for their economy, or would the lack of consistency be a weakness? Would the Plutocracy need to build a backstock of valuables to trade, in case The Rift goes through a bit of a dry spell, or would the fluctuating value of their trade goods roughly balance out, as long as they were smart with their money?
[Answer]
The rift is going to be the primary source of wealth on this world even if only occasionally a high-tech artifact or person with novel knowledge is produced.
After all: If a cell phone had dropped into the laps of 1940's era humanity it would have accelerated technology worldwide by a decade or more. The rift is going to have this happening regularly and sometimes artifacts which were thought to be junk will turn out to be advanced technology as their understanding advances.
You mention a treaty so the governments have come to some kind of agreement to allow them all access but they're going to have highly regimented systems around access to things produced by the rift.
Societies with more access are going to be more advanced and more wealthy. collecting artifacts isn't going to be a job for homeless drifters. every item that comes out is going to go through a production line style inspection to assess it for value no matter what it is. Every new person is going to be interrogated to see if they know anything of value and living things are going to be assessed for economic value.
Unpredictability will be a very small problem. If those given the right to assess items only rarely find items of value then a futures market will develop where they simply auction off the future rights to anything found between certain time periods in certain areas which will make their income utterly predictable. They'd need to import pretty much any mundane things but Edge will be a wealthy place with a rich smuggling market. (after all if something a little too good turns up in a time and zone that's been sold to futures traders people will want to steal it and smuggle it out). There will also be a rich trade in fakes.
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The Rift is going to be an incredible source of contention and conflict which is going to destabilize the economy, disincentivize all non-Rift-scavenging activities, flatline the rate of technological growth, and probably won't result in a plutocracy being able to maintain control of it without extreme secrecy, group loyalty, or liberal applications of Plotonium.
If, once a year, or even once a decade, century, or millenium, some kind of game-changing, balance-breaking item (or person with such knowledge) pops into existence, the hole it comes out of is going to be fought for and fought over--forever. It doesn't matter whether what comes out is a self-powered projected energy cannon, a machine gun, a lightsaber, an AI-controlled nanoassembling molecular factory, a cyborg supersoldier, a potion of immortality, a T-1000, a bioweapon-armed cruise missile, a Philosopher's Stone, an [Astra](http://en.wikipedia.org/wiki/Astra_(weapon)), a Wand of Teleportation, a personal forcefield, an Amulet of Mind-Control, a necromancer, or any of a thousand other things. All it would take is one massive force multiplier to tip huge amounts of power into the hands of whoever found it, and he or she would guard the source of that power jealously. Just as everyone else would covet it, band together, and try to take it from him.
Everybody has to sleep sometime (except for that guy who found a Potion of Everwakefulness), and even if your newly-found Unobtainium Sword of Force Multiplication allows you to fight 1000 soldiers and win, the 1001st member of the newly formed Stealing-Stuff Expeditionary Force is going to kill you and take it.
The Rift itself would be valued just as highly, and contested just as hotly. After all, it's where the next game-changer will come from.
Technological development—at least, non-Rift-powered, incremental tech development—would stall; what's the point of spending a lifetime honing your smithcraft and developing a slightly better steel alloy to make stronger swords or armor when a crate of monomolecular blades or an Avada Kedavra-caster might fall out of the Rift next week?
Economic activity is going to fare similarly. Who's going to want to waste their time stockpiling more grain than it takes to survive winter when they could spend that effort making sure they become the proud owner of the next infinite, food-generating cornucopia to pop into existence?
The Rift will be the source of your economy, and access to it will provide unmatchable economic power and wealth. Price is just a measure of how valued or desired something is, so what price can you put on a Heal-o-matic 5000 nanotech medical droid that provides functional immortality?
Which brings us to the power dynamics problem that the Rift will necessarily create. It's not enough to be a member of the Plutocracy that currently wields most of the previously Rift-emitted game-changers and ruthlessly defends salvage rights. They've got to have a system in place that makes certain they get the next one, too. Otherwise some lucky minimum-wage scavenger in their employ is going to find a [Ring of Gyges](http://en.wikipedia.org/wiki/Ring_of_Gyges), seduce their wives, murder them, and become king.
At the same time, 85% of what comes out of the Rift is going to be unmatched left socks (that's what happens to them!) and unskilled laborers. 1% is going to be plague rats, fatally radioactive spent nuclear fuel rods, psychotic stab-happy mass murderers. 0.01% is going to be adamantium armor, antigravity belts, and Jedi knights. You didn't usurp and kill off the previous Plutocracy to spend your life sorting through junk, hoping not to be killed by what you find, just to maintain your present position of power, did you?
Whether that system involves highly-paid, well-armed, loyal guards (all cousins and sons-in-law and best friends of yours) that patrol the rift, a religion you've set yourself up as the Pope of, or something even more interesting, possibly relying on something that came through the Rift itself like a Potion of Loyalty or metacognitive reprogramming module is up to you. But there has got to be a system.
The people that come out of the Rift present a different set of problems. Like most of the items that come out of the Rift, most of them are going to be useless to you, but they'll have their own wildly varying desires. A very small percentage are going to be benevolent nanotech experts who believe in freedom of information, and a similarly small percentage are going to be immortal liche sorcerers dead-set on world domination. Most of them are going to outright contradict any religion you set up to control access to the Rift. Some are going to start their own competing religions.
The ones with advanced scientific knowledge are actually going to be less useful than you'd think--and that's assuming physics in their originating universe works the same as it does on Riftworld. The reason is infrastructure. Just because you know every intimate detail about how to construct a planet-destroying superlaser, hyperspace stardrive, positronic brain, or nonlocality engine doesn't mean you can do it starting from a Medieval technology base. It's going to take a long time and a lot of effort to get from Iron Age smithing to a modern silicon chip fab plant to nanoformers even if you know exactly how. And you'll need a lot of help to do it.
The mages and wizards, assuming their magic works the same on Riftworld as it did back home, are probably going to be a bigger deal, at least until the cyborg who may as well be from 20000 years in the future manages to bootstrap some serious high tech. If they can teach their own magic systems to others, they will charge for it and become serious economic powers in their own rights. As will the ones who just bag it, claim to be gods, toss off a few miracles, and start their own religions.
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This scenario reminds me of the position of certain Melanesian societies when US airbases were set up on their Pacific islands during World War II. Suddenly there is an influx of new stuff, some of it valuable, some of it apparently meaningless, placed there according to a pattern the islanders did not understand. That analogy suggests that the Plutocracy is going to have to work very hard to maintain its existing economy, let alone benefit from the Rift. The things that arrive will be extremely disruptive to anyone's long term plans. Yes, as a whole the Plutocracy *should* certainly stockpile trade goods in case the Rift goes through a dry spell - but people as individuals are going to be demotivated to engage in any long term economic activity when it could happen at any moment that your carefully maintained stockpile becomes valueless due to the arrival of a new gizmo.
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You're forgetting that politics is going to have a huge influence, trumping even the economy. Assuming the people in this world think like us, most would be engulfed by a religion that everything that they know came from the rift. Religion in our world has a strong hold and we don't have some gigantic supernatural gateway shooting random objects from it. Imagine how many people would follow this religion with such a phenomenon in this world?
As such, you would see cathedrals or places of worship near the rift mostly, but also in other places in this world. Those with the most power would be those who head the religion, like say the pope, except that given that most people belong to this religion, he would be like the absolute king. The world would pivot around this religion, and most cities would try to show how devote they are to the religion, because this too is a form of power to those who wield it.
You would not see scavengers picking up what comes out but rather highly religious and sacred men and women raised from birth whose only purpose in life is to be the first to see the wonders coming out of the rift. A wall would be built around the rift keeping everyone else out. The area itself would be considered holy ground. To be such a person would be a position of priviledge. On that note, the poorer people would likely only be able to view these objects (or at least the more spectacular objects) from a distance. If normal everyday objects can shoot out of the rift like apples or fishing rods, these sacred men and women would likely destroy it, since it doesn't purvey the idea that only wondrous things leave the rift. In this sense, most common folk would likely be kept in the dark about this particular aspect, instead seeing only the more brilliant things that leave the rift which would commonly be put on display.
The wealthy and those in power would only have direct access to these objects, and only those which have ties in the religion. They in turn may sell to more common folk, but more likely that they'll use it for favors or a form of currency.
And to make things interesting, you could form several religions. One religion that says the rift *is* a god and another that thinks the rift is a gateway to a new world that they must go through. Obviously the idea of passing through the rift if you think the rift is a god is rather horrifying, so these two religions would be at complete ends with each other, and most people would clearly be on one side or the other (and perhaps a few which don't care, but practically nobody who is athiest and believes in neither). Wars would likely be fought to control the area near the rift.
If several civilizations are more advanced technologically, then they will clearly dominate control. Wars may still be fought, but it would always end in favor of the more technologically advanced civilization and whatever side they pick.
It would be interesting to know what happens if someone were to pass through the rift. Could make for an interesting story.
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My opinion would be that it's likely going to primarily serve people that pass for wealthy in your universe. Because the things are so varied, and presumably there will be many one of a kind things, the rich (and famous?) will often visit trying to get the next thing that will set them apart and show their status: exotic pets, alien art, surreal objects, weapons and items of exceeding craftsmanship, etc.
In addition, there would likely be a/several group of scientists/mages/intellectuals based at or very near to Edge. They'd want to be close so as to have the best chance of claiming anything particularly powerful or promising for technological advancement before it could be bought or spirited away.
Likely there is also a fairly successful black market where more dangerous "products" can be bought/sold, and presumably less than willing slaves as well.
The question of security would probably need to be addressed. I don't think you mentioned, in particular, any reason why dangerous creatures/people/items couldn't pass through and wreak serious havoc on the area/people near the Rift.
As far as imports, it seems to me that a government or plutocracy or whatever else could probably simply arrange to trade for anything it needs. They'd likely have treaties in place offering something along the wording lines of "goods to amount to a total of X {currency} for y amount of {food}", etc. This way, even if it is inconsistent, they might be trading one ultra valuable item one month, and a bulk of more generic goods the rest. Presumably, however, if most of its inhabitants are risking themselves near the Rift where things could be quite dangerous they probably import specialty tools found to be useful over the years by "veteran Rifters" (filler name, sorry). Anything from carts/wagons to move bulkier objects, to specialized kits for dealing with magic items, hazards that are possibly radioactive, or dangerous creatures/people.
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It will be a rich place. Blooming trade. A monopoly on out of this world stuff! As it just appears it is like free money. Everyone who can will have a stake in it, like the very very profitable oil trade in this universe.
This will also be a patched together place, utilizing everything not worth the effort to transport.
I can also see the immense junk-yards where scrap is recycled and the leftovers are gathering dust.
But to get to the main point, how do you determine what is a priceless artefact and what is junk, and how do you avoid damage while doing so?
I can see a pivotal **profession** emerge of detecting useful properties at several levels: First Picker, Secondary Picker, Two-bit Picker, Dead.
The best stuff will be divided among the ruling class and/or auctioned off regularly. Certified Rift products will be traded at a premium. Lesser, mundane stuff will be in regular shops and caravans. The stuff nobody can make sense of will enter the junk-yards.
Loads of gold-diggers will be sure their big break is around the corner any moment now. The older they get, the more limbs will be missing.
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The effects of the rift depend on the level of development. I'll break it down to sub-conditions.
Whether the society has developed organized education such as universities or the great Hellenistic or Islamic libraries. Basically corresponds to having a mature urbanized society with common literacy and an established upper class with idle time. Such system is required to effectively study whatever comes from the rift and collate and organize the data gained.
Your setting was said to be industrial, so at some safe distance from the rift there would be large universities that compete and collaborate in collecting and studying what comes from the rift. The steady flow of objects would imply some sort of stable arrangement regarding the collection of objects and people, probably with an illegal, profitable, and violent black market. There might be a single institution managing the collection of objects. Another to handle people. Third to handle potentially dangerous creatures. Objects could be distributed to other institutions based on quotas or auctions with specific organizations or people only eligible for objects of certain level of rarity or risk.
Whether private people can legally buy objects would depend on the rate of collection and social system. In a class based society, royalty and high nobility would certainly be able to buy objects or even get them by quota. They'd then probably loan interesting objects to researchers. Regardless there would be a black market available for the wealthy.
Whether there is mass production. Before industrialization the rift might be a significant source of items. With mass production the volume of items produced by the rift would be too low to have major direct economic effect.
Since the society would have industrialization, we can assume the latter. The main effect of the rift would be as a source of information, both directly in form of people and indirectly in the form of objects and creatures to study. This would be the core the rest of economy would be built around.
They would presumably have relatively high level of knowledge albeit possibly with large and weird gaps. It is reasonable to assume their available knowledge would be larger than their ability to understand and organize it. They might lack both the kinds of polymaths that used to be common before the 20th century and the kinds of specialized areas of study that characterize modern science. The effects are difficult to predict.
When you say that tech level varies that kind of implies that technology and economy are restricted by the available population, resources, and infrastructure. Basically they would know how to built more advance technology but do not have the industrial base needed.
Possible reasons are the world not supporting agriculture well enough to allow large population, the rift constantly introducing new disease which makes large populations vulnerable to epidemics or the world being poor in easily accessible metals. All three actually make sense for your setting. Fast growing local flora would make agriculture difficult, people and creatures coming from the rift would carry lots of germs with them and an isolated dimension might well have limited mineral wealth.
That fast growing flora would make for a good source of biogas, if collected and placed into a bioreactor. And the locals could have realistically heard of the concept. This also would also produce fertile soil for agriculture, so the agriculture would be highly productive, they just would have issues having large areas in production.
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# Techno-Military Dystopia
Only 80 years after its first colonization, all of the people of Edge spontaneously and mysteriously fell dead -- an event now known as *The First Cataclysm*, largely suspected to be some sort of rabidly infectious disease which failed to spread further in the world and instead exhausted itself by too-rapid expansion. There have been seven more cataclysms since, sometimes resolved by international cooperation, sometimes simply resolved by the phenomena working themselves out (e.g. advanced predators being unable to yield offspring).
In the wake of the Third Cataclysm, the nations of the world united in fighting off the beast and then joined together in a massive effort to wall off the Rift, with only a couple major gateways into the interstitial region. Of the different companies to survive in the interstices, three were tough enough to survive the Fifth Cataclysm. In the wake of the Sixth Cataclysm, two were sufficiently damaged that all three combined together into the Alliance. There are still remnants of the three-fold division in Alliance culture, much as there is still a division between England, Scotland, and Wales even though all three are part of one geopolitical entity on the island of Great Britain.
Together they isolate anything new that comes out of the Rift, and they potentially run many-century-long projects to analyze new technology that is not so risky as to be immediately destroyed.
The Alliance relates to the rest of the world as a high-tech manufacturer with no solid political ties; it is its own geopolitical entity with a technologically sophisticated military. Since technology is its central advantage over other cultures, it is as paranoid about spy infiltration and information leaving the Borderlands as, say, the CIA. Expect rigid hierarchies of authority, ubiquitous surveillance, and a complicated manufacturing economy where raw materials are imported and advanced items are exported, but the secrets of the manufacturing plants are guarded by automatic laser turrets.
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Distance in space battles is a crucial variable that affects the tactics and outcomes. With the following tech what is a reasonable distance for battles to be engaged:
Engines:
Fusion drives with max safe acceleration at 156 m/s2
Maneuver drives with max acceleration at 20 m/s2
Weapons:
Railguns with **velocity** of about 5000 m/s every 5 minutes or 7500 m/s every 4 minutes for the bigger ones.
Missiles with about 650 m/s2 acceleration and a 10 kilometer sphere kill zone.
PDCs not really a good weapon but like small Gauss guns firing 1000's of rounds at 2000 m/s
Fire control and sensors:
Able to track and lock most ships and missiles using radar and lasers. Jamming and chaff for countermeasures. Missiles are self homing with radar and heat tracking.
Numbers:
About 20-3 ships per side. Most will be corvette/destroyers with a small railgun and 30 missiles. About 4 of the ships will be cruiser with 2 medium railguns and 50 missiles. On or two will be battle ships with 2 heavy railguns and a hundred plus missiles. The PDCs are not really offensive weapons.
So with these parameters what are a realistic distances for space battles?
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You have to wrap your mind around the fact that space warfare is 6 dimensional. X, Y, Z positions and Vx, Vy, Vz velocities. The set of possible future positions of a spacecraft is an opening exponential horn. (Actually, something more complex than a horn.)
You want to set up a spreadsheet with the speed, distance and acceleration equations.
You need to decide how long the powered flight envelope is for your missiles. In Weber's Honorverse books, missiles at the start have an acceleration of about 8,000g and a burn out time of about 3 minutes. This gives them a range measured in millions of km. Later in the series missiles improve. In general the armaments race makes an interesting thread that runs through the series.
Weber doesn't use the free flight option much. But consider a weapon that was smart enough to be left behind, or to circle around the target. Or consider a missile that could be retrieved if it missed the target.
You need to decide how smart the missiles are. Do they have frequency shift radar so that jamming is harder? Tagged pulses so that each missile knows it's own radar return signals. A somewhat lighter version that comes in ahead of the pack as electronic jammers for the slower main bombardment. Do they have bomb pumped x-ray lasers to increase their kill radius.
Much depends on the electronic counter measures. E.g. When a rail gun throws a slug, is it coated with a radar absorbing coat? How far can the enemy detect the magnetic pulse from firing? How far can they detect the shell? Do rail guns throw explosive shells? What is their radius of effect? Same as missiles?
Missiles are easier to detect due to exhaust plume. Seeing one gives you an aiming point for tracking radar. But consider a missile that is restartable. It accelerates for 20 s, at 650m/s so it's now going at 13 km/s At this stage it throws an asymmetrical cloud of objects that have the same radar cross section. Suppose they are thrown sideways at 1 km/s. Now your target ship has to figure out which one is real. While the target's tracking computer is having fits, 2o seconds later the cluster of decoys is 40 km wide. In that same 20 seconds your missile has traveled another 260 km. Now only 2 seconds from the target, the missile restarts its engines and makes the final dash.
So missiles have a target envelope measured in hundreds of km given 20-30 seconds burn time.
The Vulcan Phalanx on the aircraft carriers throws shells at an incredible rate, and fire director radar tracks the outbound shells to refine the solution. It fires 90 rounds per second at velocity of 1.1 km/s so for a target 2 km away there are about 160 rounds in flight. It uses a 20 mm shell. This, I think, is the role of your rail gun. It targets incoming missiles and attempts to destroy them at a distance of about 20 km. If it could fire at, say 5 rounds per second using amount the same size shell that WWII anti-aircraft artilery used, but vary the muzzle velocity slightly so that a 4 second burst arrived on target at the same time. In addition the final aim would be modified so that the coverage included the space where the incoming missile could evade to, they would explode at the same time, creating a wall of shrapnel.
<https://en.wikipedia.org/wiki/Phalanx_CIWS>
Rail guns don't matter until you are very close. If the kill radius of the warhead is 10 km you don't want it blowing up any nearer than 20 km to yourself. So if you had an optimum engagement envelope for RG of 40 km that means that it has 8 seconds travel time. Target ship has to change it's path by 10 km in 8 seconds. That would require an 8 second 12G burn at right angles to the present course. Pushing it.
But if the cycle time of an RG is 5 minutes, then it becomes a game of tracking when the opponent last fired. 300 seconds at 5g (50m/sec2) is 1.5 kps. In that time 1/2 at2 = 25 \* 90,000 = 2400 km. Lots of time to get close enough
I don't think rail guns matter initially.
Are rail guns on turrets, like a modern battleship, or are they essentially fixed, like the bowchaser on a 1800's frigate.
Railguns may be better used as an anti-missile defence.
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Here's a quick break down with your values listed, without going into any deeper speculation or theory.
Assume two ships are pointed at each other and about to fire. How close can they be and still dodge an incoming shot?
If we assume the ships are cylinders with a 10 meters radius and are stationary with respect to one another, we can use the Distance equation of Distance = 1/2 \* Acceleration \* Time^2 + VelocityInitial \* Time. The ship need to be able to move 10 meters in any direction to dodge a shot, and can maneuver with 20m/s^2 of acceleration.
So that solves to Time = sqrt(2 \* Distance/Acceleration + 0) = sqrt(2 \* 10/20) = sqrt( 1) = 1 second.
You have 1 second to dodge an incoming shot with your maneuver thrusters.
That means that if the enemy is about to launch a projectile with 7,500 m/s velocity, you can be ~7,500 meters away and still have time to dodge. If you need an additional second to detect the round, plan and plot evasive maneuvers, and get moving, then you can engage at around ~15 kilometers.
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**Won't Know Until You Fly Them**
As has been previously mentioned, a ship of an arbitrary size (10 meter radius and cylindrical) would be able to dodge your weapons at about 7,500 meters provided it had 1 second of warning. But there are some problems with this (excellent) "perfect secnario" mathing out of your question.
1: It isn't a perfect universe. These things look simple, but as Clausewitz said, "In war simple things are hard" (Drink!) Are your ships flown by humans? Their reaction times might not be quick enough to dodge, and it only takes one mistake to have a Very Bad Day. Computers? Their sensors can be fooled by offensive jamming/decoys. Maybe you have algorithmic "jinking" programmed in. But then of course the enemy would try to figure out our patterns, and with computers there's always a pattern. To mitigate that maybe your "ideal" engagement range isn't as close as you would think. After all, if you can hit your enemy 99% of the time at 7,500 meters, your enemy can hit YOU 99% of the time at that range as well! For example, before WWI the Big Gun ships (meaning armored cruisers and larger) had trained to fight engagements at about 2/3 of their top speed (because top speed involved occasional explosions in engine rooms if you were unlucky and people thought captains wouldn't risk the extra speed with the chance of becoming dead in the water in a fight) and at rangers of about 10,000 yards, despite the guns themselves having much longer ranges. Well the war broke out and what do you know! Captains and Admirals went as fast as they could, and stayed at the maximum range of their weapons (up to 20,000 yards in some instances, 2x further than theorized!) because they didn't want to take losses! There are also some great instances where one squadron would keep the range at THEIR maximum (say, 16,000 yards) because even though they were more accurate at shorter range the enemy's guns only reached out to 14,000 yards, so why get shot back? Given two equally-equipped fleets, the engagement range is likely to be as-far-away-as-possible, with the more inexperienced fleet either trying to get in close (an aggressive commander, trying to get where he can shoot back even if takes more losses) or stay far away (a cautious commander, trying to minimize his own damage and hope to get lucky hits on the foe).
2: Armor. Sure you might be hit by a railgun or missile from a destroyer, but does your Battleship actually care about that? If it does, why have a battleship at all? The speed vs armor equations on all your vessels will dictate different preferred engagement ranges. If they can shrug off multiple missile hits, they won't mind getting into ranges where they'll get hit but can deliver devastating strikes themselves. If they can't survive even a single hit, they'll keep as far away as possible to maximize their own survival.
3: Armaments. Does your battleship carry bigger missiles than your destroyers? Or just more? Does it have enough launchers to overwhelm point defense of smaller ships at range, thereby preferring a "stand off" attack compared to the smaller ships who MUST launch closer to get their warheads through enemy countermeasures? Or just more missiles, allowing it to sustain engagements for a longer period? Does one fleet have different doctrinal approaches? For example, if one fleet decides that economy of force is paramount it might order destroyers to make individual close-in runs, relying on their greater maneuverability to make 1 shot/1 kill attacks while avoiding enemy fire. Whereas another fleet similarly equipped might decide that a ship's main job is to not blow up, and have their destroyers attack at maximum range, launching coordinated strikes which cost a lot of missiles for the same amount of hits as a more daring close-in attack.
4: Countermeasures. How good are they really? Does 1 chaff launch guarantee all missiles within X seconds of impact miss? Or does it always spoof one missile into missing but is overwhelmed by multiple launches? Do ships carry more chaff than they do missiles? Is it only 50% effective? 20%? 90? All that will dictate engagement ranges as well. If I know I have 60 loads of chaff and they will 99% stop 1 missile per launch, I feel pretty good getting close to a 30-missile destroyer to make sure my own missiles work. Or maybe forgo missiles entirely with my big immune-to-destroyer-railguns battleship and blow that destroyer away with myrailguns. Chaff only 20% effective? That's a hope, not a strategy, and I maintain a long range and launch chaff as an addition to dodging, not a replacement.
I'm not trying to rain on your parade by saying all this, I'm just pointing out that a realistic engagement range has a LOT more variables than just doing math on how quickly something can turn or accelerate.
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**Really close.**
You don't have offensive lasers. All your weapons are subluminal. You do have lasers and radar & presumably other EMR sensory techniquies. That means you can detect incoming projectiles at a distance and negate or deflect them with your own projectiles. You wont need to dodge. Those defenses are outgrowths of older defenses against meteroids and so they are mature and effective. It is hard to get past. The question is how fast you can detect incoming and fire a defensive railgun round.
The offensive solution is to get close enough that there is no time for detection / deflection of a projectile. At such distances, boarding operations also become realistic.
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Missiles with a 10km zone kill capability are going to keep ranges out at at least the 10km (and probably a lot more since you want to be out of the damage range not just the killzone), until everyone's magazines run dry because you can't engage with them at ranges smaller than that 10kms without them killing the ships that launch them. If those missiles can effectively loiter, shut down and hang around the battlefield undetected until a good target becomes available, then closing combat range after they're all fired becomes suicidal unless and until you can positively account for all the self-guided munitions launched by the opposition, and maybe yours too depending how smart they are.
With the railguns being linear accelerators the most logical ship design is a long cylinder with a heavy armour belt forward ringed with maneuvering thrusters. Main engines aft with lateral fire missile batteries around them. Head-to-head even at very low ranges such ships may not get a hit but a LOT depends on sensory data and minimum tolerances.
For example is your sensory system good enough to tell you your opponent is charging the capacitors for their main guns or do you have good enough [Van Eck phreaking](https://en.wikipedia.org/wiki/Van_Eck_phreaking) to know where a shot is aimed *and* when it will be fired?
In terms of tolerances the minimum vector change you ship and it's weapons can traverse, because there will be one, massively effects weapon accuracy tolerances and also firing windows. You may think your weapons are on point when you're .01° off which isn't a lot when the muzzle is touching the target but it is over two and half metres at 1km.
A couple of ships with poor sensory systems and high minimum tolerances facing off nose to nose at 100m with 1° offset fire rounds with a 1m diameter more-or-less simultaneously, the two rounds glance off each other producing a cloud of plasma and shrapnel but neither scoring a direct hit on target, and that is without either ship trying to dodge.
So the answer is railgun engagement range will be as close as possible, with a lot of maneuvering going in to trying to gain high cross-section firing intercepts, [crossing the T](https://en.wikipedia.org/wiki/Crossing_the_T) comes back into it's own for example. Railguns will only be used AFTER everyone has run out of missiles and the battle groups have either left their range from launch area or positively eliminated the threat. The optimal ranges for firing passing will depend on the exact cross-sectional size of vessels and the firing cones of the railguns being used.
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It is my belief that any space ships trying to battle one another are going to a close distance. Any further away than a single light second, you run into complications that make any form of combat impossible, especially with slower than light weaponry.
Let's say you fire a missile at an enemy ship, from ten light minutes away, that enemy ship sees that you fired a missile ten minutes ago and because that missile is way slower than light, the enemy ship still has plenty of time to coarse correct to dodge it. So unless you are within one light second, any fight will look like Neo dodging gunfire from the Matrix, especially if your fastest projectile can only go 0.000025 of light speed.
Railguns are pretty much the best long rang space weapon because of how fast they can go, the only way you can do better is with lasers. So the only way I can see long-range engagements would be like a sniper picking enemy ships off, and if you have stealth tech for your projectiles, that might work. But if your fastest projectile still takes over an hour to hit the target within one light second, your only hope is to get in close, empty the clip and run.
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There's nowhere near enough information here to answer the question. To address it we should look to videogames--specifically, the concept of damage per second, often called DPS. I have never played such a game where range is an appreciable factor, but in this scenario it is.
For each possible range (you'll have to pick some interval to calculate it at) put the fleets that distance apart. Figure each shot is one point of damage, multiplied by the chance that it actually is aimed well enough and multiplied by the chance the enemy fails to evade/intercept the shot. Do the same calculation for the enemy. Now compute the ratio of your damage to their damage--your ideal engagement range is the range where this ratio is highest.
Note that if you outrange the enemy this ratio is infinite at all ranges beyond their maximum range. (Yes, there can be maximum ranges on weapons. Consider the previously-mentioned *Honorverse*. Missile performance vastly exceeds ship performance, evasion is not possible and nobody meaningfully tries. However, once a missile's booster burns out it's ballistic--it has no performance at all. Move beyond it's standoff range and it's harmless, or simply orient your ship properly and it can't attack (Honorverse ships have completely invulnerable top and bottom shields.) Hence everyone wiggles around enough to keep the enemy from trying ballistic attacks.)
To make matters more complex you have to add velocity to the picture. Just because you're at your ideal range **now** doesn't mean you can stay at that range. (Once again, thinking of the *Honorverse* novels, there are multiple battles earlier in the series where one side comes barrelling in because they know they're inferior at missiles but superior at lasers--they'll take losses while closing but laser battles are decisive. Then later in the series there are a few fights where someone thinks they can do this and learns the hard way how utterly obsolete their ships are.)
Then to make matters even harder you might have a situation where having different ships at different ranges might be superior. This is only viable if intercepting inbounds is not a big part of the battle so the more forward ships don't need the defense cover of the ships that don't get as close.
Also, how much ammunition do you carry? Do you have to conserve ammunition during the battle, only firing high probability shots, or can you simply open fire as soon as you can get hits? The former case makes the damage calculations even harder.
Is ganging up a viable strategy? Those little, maneuverable ships are good at getting out the way of that 10km lethal range on the missiles--but what if you fire 6 of them, each set to pass 10km from the target, spaced every 60 degrees around it. Oops, now you have move nearly 20km to get out of the lethal range. If defense comes from interception how good are ships at intercepting inbounds aimed at another ship? (I'm thinking of playing *Harpoon* long ago--if you could punch out a fleet's airborne radar you could then pick off the outer ships layer by layer with very little defensive fire as each ship was now on it's own and got at best only one round of defensive fire.)
You're going to need a lot of computer power to simulate all these options and without that you don't have an answer.
[Answer]
What you should consider is the amount of fuel a missile carries, and it's powered flight time. As many before have pointed out, an unpowered missile can be easily shot down by railgun fire. But with a 10 km kill radius, the missiles could explode outside PDC range and still be effective.
Though they have to be able to maneuver to avoid being shot down, so they need to have fuel until they detonate.
You could also use missles as counter missles. With a 10k kill radius, that would be quite effective.
You could potentially accelerate missiles with electromagnetic launch tubes, so the firing is not as easy to detect and have them fly unpowered in a wide pattern, until they are closer to the enemy. Then they all ignite their drives simultaneously, striking from different angles, trying to overwhelm the enemies' missile defenses. You could even lay a spread of missiles as a minefield.
I imagine, a battle would be started at extreme range. Depending on your missile range, hundreds or even thousand of kilometers. Each side will fire missiles and counter missiles, as fast as possible, trying to overwhelm the other sides' missile defense. Then if they either run out of missiles, and still want to engage, or if the range drops below 10km, it will become a railgun slugfest.
] |
[Question]
[
I know that when some rivers (such as the Nile) flow out to sea, they break up into several smaller channels. But I was wondering about the necessary features of the land and water for it to occur.
[Answer]
The reason why some rivers form a delta (Nile, Ganges, Mississippi, etc.) and some other form an estuary (Thames, Seine, etc.) is in the balance between sedimentary deposit from the river flow and sediment removal from the sea waters.
When this balance is positive (the river deposits faster than the sea can remove) a delta is formed, while when the sea removes faster than the river can deposit an estuary is formed.
On the sea side this is influenced mostly by tides and currents, while on the river side this is influenced by all the factor regulating the amount of transported sediments.
I.e. Nile has a delta, but since Aswan dam has been built, the amount of sediments transported to the sea has greatly decreased: in return this has resulted in the delta starting to be eroded by the Mediterranean sea.
[Answer]
If you mean geographical requirements, then all you need is,
1. A body of water (preferably salty)
2. Some land (the soily or sandy type) that is lower or just above sea level (optional)
3. A river (the fresh kind)
If you put these together, and the river is depositing sediment from its bed faster than the ocean/sea can take it away, then boom, you got yourself one heckuva river delta. Now, if your factors do not overlap correctly, then you may end up with an estuary instead. that, you do not want.
] |
[Question]
[
I'd like to know if such a material would be, at least, theoretically possible nowadays, if we somehow were to be able to have enough material of whichever one we wished for and the theoretical knowledge to do it.
The suit should be able to, at least partially, reduce the inflicted damage from attacks from blunt objects, physical attacks, bullets shot from a distance where a bulletproof vest would be able to support a bullet with an standard caliber, and so on.
Maybe it would be possible to combine such a suit with something like [graphene](https://phys.org/news/2013-05-defects-graphene-strongest-material-world.html), that would maybe offer that protection without losing the spandex like aspect.
PD: Yes, this question is inspired by the Power Rangers series.
[Answer]
Spidersilk protein taken from genetically engineered goat's milk. GAH, that doesn't sound real. [But it is](https://www.youtube.com/watch?v=Q6S4fMOxuyE)! It's still in development but has the possibility of skin tight. The demo shows "bullet proof human skin" Like actual human skin mixed with the spider silk. However, there are problems. The skin remains intact, but the human within would be, to quote "soup."
From what I can see, no material with the characteristics you want actually exists. Further, bludgeoning, stabbing and shooting are very different mechanically. This means that stab-proof vests are designed differently than bullet-proof vests, as are things that are meant to protect from blunt hits. When you're trying to protect from all three, it gets bulky as heck, because there have to be layers.
>
> Many are under the impression that a bullet proof vest is suitable for
> protection against knives and other similar weapons. However, the way
> a bullet impacts on body armor is very different to the impact of
> edged and spiked weapons. This is why edged blade proof vests are
> separate to bullet proof vests, but there is also spike protection to
> consider. Many use the words stab, spike and edged blade
> interchangeably, referring to any armor that protects against
> something other than ballistics. The preferred terms are edged blade
> and spike, which are different threats respectively. Nevertheless,
> many will refer to spike protection as stab protection, and vice
> versa.
>
>
> Just as ballistic protection will not protect against edged weapons,
> so too will edged blade protection not protect against spiked weapons.
> An edged blade, like a knife, cuts through the protective fabric
> instead of getting trapped within the fibers like a bullet does. While
> stab proof vests still utilise Kevlar or similar materials like a
> bullet resistant vest, they also require added materials like
> chainmail or laminate to stop edged weapons from cutting the
> protective fibers. [SOURCE](https://www.safeguardarmor.com/articles/types-of-body-armor/)
>
>
>
Graphene is great, as is spidersilk, but just because you can't break through a material doesn't mean that the kinetic force doesn't harm what's within. And graphene isn't stable enough to create any material large enough to really protect anyone.
So the answer to: is there a way to create a spandex skin-tight suit (no padding or plates at ALL) with all the protections you require-- is sadly no. You're asking for something far beyond the capabilities of science as it currently stands.
[Answer]
Yes, with the qualifier that it only looks like a spandex suit.
The suit would have an outer layer that is basically reinforced pseudo-spandex. Weave some sort damage resistant fiber around highly elastic fiber and surface everything with brightly colored and reflective dye.
The elastic fiber makes it act like spandex, the other fiber gives it damage resistance and the brightly colored dye makes the surface look smoother than it is by hiding shadows caused by unevenness. This is also convenient since it is an excuse to have suits with bright colors. The suits might even come with small LED system to boost the effect.
Under the spandex looking layer would be the actual armor. Structurally it would be plate mail composed of interlocking plates of varying size. Plates would be connected with actual hinges that would let them move fairly freely within the limits needed for normal movement. Small springs would maintain tight fit without compromising flexibility.
With the tight fit and interlocking plates the outer layer should be sufficient to hide the relatively small gaps between the plates. And as long as movements stay within what the armor is designed to handle there would be no visible extra rigidity or looseness. And it is not really not an issue that the suit is more rigid than your body if somebody tries to break your limbs or neck.
There are several alternatives for the materials. Steel or reinforced plastic gives adequate protection for your needs and machining steel or 3D printing the plastic can be done by computer controlled machines which simplifies making the custom fitted plates this type of armor requires.
I'd probably use plates made of two steel plates with rubber in between in manner similar to [non-explosive reactive armor](https://en.wikipedia.org/wiki/Reactive_armour#Non-explosive_and_non-energetic_reactive_armour). This wouldn't really give resistance to shaped charges or anything but the movement of the outer steel layer would absorb some of the energy without breaking anything and it should be possible to make the joints between plates lock when the outer plate moves spreading the impact to neighbouring plates.
Under this would want some sort of well breathing padding to make wearing the suit bearable and further absorb any impacts.
This should give you a bullet proof armor that looks like spandex suit. It would also make you look really bulky and probably weigh a lot. It wouldn't really impact your movement since the extra weigh would be well balanced and tightly fitted to your body but you probably would not look like somebody who'd be expected to want to show off their body with a spandex suit. It might get embarrassing if people get the idea that you are some sort of a role model because you defy the "thin is beautiful" ideology.
I am only mentioning the looks issue since it is kind of important to the genre. But the amount of thickness obviously corresponds to the amount of armour protection and the plates can be shaped to exaggerate your musculature so it might be fine?
[Answer]
In fact a dilatant-impregnated material would help decrease blunt-force trauma injuries by distributing force across wider area, assuming such blunt force were applied rapidly. It would also protect against rapid stabbing attacks via the same mechanics, however slow stabbing would be unaffected by the dilatant - that's why you'd be looking for a three-ply Kevlar suit: dry Kevlar vertical layer 1; dilatant-impregnated diagonal (45° left) Kevlar layer 2; dry Kevlar horizontal layer 3.
[dilatante materials & body armour](https://en.wikipedia.org/wiki/Dilatant#Body_armor)
[Answer]
Yes I believe its feasible. What I am imagining is a smart fabric. Imagine a fabric that has been engineered to stiffen when its being compressed. For instance, in its normal state, it is loose (on the molecular scale, not in the sense that its loose fitting) but as soon as you apply some type of significant force it compiles itself. Similar to how an Electroactive polymer responds to electricity, you're material could respond to any force, not just an electric pulse but any force exceeding some predetermined threshold. There are many materials already in existence that will change their shape or even their molecular structure when reacting to force, thermostats for instance, change their shape depending on temperature. This technology is actually not as far off as you might think, their are people working on it even now.
[Answer]
**Non-Newtonian fluids**
If the suit was graphene based and contained a special [non-newtonian fluid](https://en.wikipedia.org/wiki/Non-Newtonian_fluid), the suit could act like spandex but when hit at high speed, harden to something like plate armour spreading out the force evenly over a larger area.
See [liquid armour](https://en.wikipedia.org/wiki/Liquid_Armor)
] |
[Question]
[
A ground based army wishes to be able to defend against orbital strikes by unguided hypervelocity projectiles. Handling orbital laser platforms and guided orbital projectiles is out of scope for this design. Since the best defense against these kinds of attacks is to not be where the projectile impacts, the early warning system is supposed to facilitate getting out of the way.
The design intent is to develop an early warning system that will allow ground troops to function as autonomously as possible. Army doctrine is to not rely on the Space Navy anymore than absolutely required. Having a constellation of satellites would solve this problem but is unacceptable to Army High Command. High Command wishes to have fallback early detection services should the Navy decide they need to be elsewhere.
## Early Warning System Requirements
* Self-contained
* Able to run off 100KW power source
* Mobile (static early warning measures are huge targets)
* Carry enough processing power to make the signals gathered into something useful.
* Only for use on Earth-like planets.
* This system can be tied into the global battle information network but should be able to function without this connection/functionality.
## World Constraints
* No FTL travel or comms
* Laws of orbital mechanics are no different than real life
* There are space fleets in orbit.
* Troops are delivered and retrieved from the surface by large shuttles.
* Tracked and wheeled vehicles only. Legged vehicles have been shown to be less effective and harder to maintain.
* All infantry is mechanized. Every infantryman has a truck, tank or APC that they can use. Troops are trained then drilled frequently to facilitate rapid egress from an area.
**Is ground based detection of hypervelocity projectiles from space possible? Can the detection method be mounted on mobile platform? Is radar good enough or are there other/better approaches?**
[Answer]
>
> Is ground based detection of hypervelocity projectiles from space possible?
>
>
>
No. If you are detecting potential projectiles from ground stations only, without being able to trace their trajectories in space, you won't be able to differentiate a missile from a meteorite until it is too late.
A hypervelocity projectile may have the same mass and profile as a meteorite, but with an ablator to keep it from disintegrating in the atmosphere.
All an enemy needs to do to fool your system is throwing a lot of rocks against the planet in different locations. The amount of false positives this will trigger on the systems should be enough to render it useless - you will either be constantly and pointlessly moving your forces around, or you will stop trusting the system.
Once a projectile has gone deep enough into the atmosphere that it won't be burning anymore (about 70 kilometers away from sea level), it can discard ablators, turn on thrusters and hit the ground in a matter of seconds. I did a quick research on the world's fastest missiles nowadays... I don't know if this is the fastets one, but The Indian Armed Forces's [Shaurya](https://en.wikipedia.org/wiki/Shaurya_(missile)) are able to reach Mach 7.5, even on low altitudes. **They could clear the distance between ablator discarding altitude and sea level in less than twenty-nine seconds**. If the payload is a nuke, you will never get far enough from the blast. Food for thought: in the future, missiles may become even faster.
>
> Can the detection method be mounted on mobile platform?
>
>
>
With our current technology, we use things like these to search for NEO's (near Earth objects):
[](https://i.stack.imgur.com/6qOGF.jpg)
Source: <https://www.nasa.gov/feature/nasa-office-to-coordinate-asteroid-detection-hazard-mitigation>
And it can only detect a portion of of the sky at a time. In order to replicate that with mobile bases, you would need a very large array of mobile antennas covering about the same area, and working as a network. And you will only be looking at a very narrow piece of the sky. Not efficient enough for your needs.
>
> Is radar good enough or are there other/better approaches?
>
>
>
Radar is the method favored nowadays for [Ground-Based Midcourse Defense (GMD)](https://en.wikipedia.org/wiki/Ground-Based_Midcourse_Defense), so at least here you're good.
[Answer]
## Sensors
**IR and Radar:**
A projectile entering atmosphere is going to generate a lot of heat. Thus, infrared imaging is how you first find your target. Then a powerful radar lights up the target to get a more accurate trajectory.
## Platforms
**Air or Ground:**
You're going to mount these sensors on different platforms depending on your specific conditions. Airborne drones would be nice - there's less atmosphere getting in the way between you and your targets. Also, there's some distance between you and your radar in case someone detects it's activation and fires on it. But if you don't have air superiority, a ground based asset may be more survivable / defensible.
## Actions
**Shoot it Down:**
Getting out of dodge probably isn't a good strategy - the time from detection to impact will be low. Instead, think of birdshot. Put a lot of flak in the air, and the hyper-velocity round will make contact with some of it. At those speeds, any change in flight profile is going to result in a miss. A hit that's direct enough to induce tumbling is going to bleed off a huge amount of energy all by itself.
## Putting it Together
This may all happen fast enough that person cannot be in the loop. It's a system that you turn on, and **it alerts you as it's shooting down the target**.
[Answer]
A rod from god drops at a bit less than orbital speed (because it is "braked" out of orbit, in which it had, by definition, orbital speed). By m\*v² we know that is a lot of energy, and we shudder in awe. But. The atmosphere will make sure, for any reasonably small object, that it hits ground with terminal velocity. For a heavy rod 10 meters long that may be Mach 10, but 3km/s is still much less than orbital velocity. This does not improve for rods that are somehow "shot" down, i.e. accelerated into an more eccentric orbit that intersects the atmosphere - that would just mean more energy to bleed. It is this atmospheric braking that essentially confines the rods to being sleek masses of tungsten - most other materials are either not dense enough (the rod needs to be sleek yet heavy), or not heat resistant enough (remember the awe-inspiring amount of energy fresh out of orbit? 80% or more of that will need to go away...). So you can be pretty sure there are no fins or guiding mechanisms on that thing. The trajectory will thus be a parabola. Know three points on a parabola, and you know the parabola. Of course there are winds and non-uniform air-densities and bla bla, but the travel time from intersect with atmosphere to ground will be on the order of 60 seconds, so not much time to interfere. All the shed energy is discarded in those 60 seconds, which means a huge value for energy/time, which is **Power** So there should be no real obstacle in detecting it. Allow for 2 seconds to discern from micro-meteorite. Blare alarm. Allow ten seconds for every soldier to lash themselves to the nearest truck by means of a specially designed leash. Everyone else just ducks and covers. The trucks have a (probably electric) sprint capability, and a guidance system that allows for "be quick or be dead" kind of path-choosing (better not be in front of one...) the trucks now accelerate away from impact, and eight seconds later they are at 100km/h, meaning they have covered about 100 meters. Every second more (and there should be about 40) will gain another 25 meters. Is that enough?
Wikipedia has a 10 ton rod at about 10 ton TNT impact energy. That is a lot, until you realize it's not a bomb, its a tungsten rod travelling really fast. No air burst, not even ground burst. It's going to penetrate. It's a bunker-buster. You'd probably not like to be around (and even more probably not like to be around in a truck careening at 100km/h), but it's a lot less dangerous for ground troops than it is for bunkers. Assuming the impact-forecast was correct +-100m, and everybody was scattering radially from that point, the most out-of-luck crew will be 1000 meters from impact - it will suffice. It's not high-explosive, and it's not shedding that energy into the air or structures - it's shedding into the ground.
About detection: you'll have to detect a glaring object, from a few hundred kilometers away, there should be no problem. You need a splash-down forecast 12 seconds into the atmosphere (Think, blare, lash), which should be enough for a rough estimate **if** you have your detection gear lateral from the flight-path. This means the detection gear travelling with your troops is actually protecting the people a few hundred km away, and theirs is protecting you. Good for morale... If your detection gear needs to be with the troops it's protecting, i.e. near ground zero, the best it will be able to do is predict a very long impact-ellipse, which can help to flee the area perpendicularly.
Note that it is impossible to discern between a tungsten rod with, say steel, weak spots, and a usual rod from god. So the enemy now has a means of clearing a km²-sized area by sending a fake rod that breaks up and fireballs harmlessly 10km above target, while their ground troops move into the area unopposed.... Perhaps better to adopt a general duck and cover strategy, maybe splurge on some inflatable cocoons to mitigate the shock wave.
[Answer]
Not really much point, signal return time is not your friend, orbital observation platforms, AKA your troop ships, are better as they can see rounds launching in something like realtime. They also carry enough computing power, it's call an orbital navigation bridge station or their own planetary bombardment systems, to work out their point and time of arrival fast and accurate. Since they're closer to the launch platform they can relay good targeting data to the troops on the ground quicker than the round trip time of any lightspeed ping from ground to orbit and back. Also orbital assets are able to see rounds launching from positions that are "over the horizon" from ground positions.
If the army really wants an independent system they can build one but it's going be less effective, possibly terminally so. Radar or microwave are going to be your most practical lightspeed radiations to resolve incoming rounds but they're also prone to severe pollution in the form of unit communication networks, cell towers, radio stations, etc... and from the ground an orbital round coming straight at you is a very small reflective object too. In short your first warning at ground level is probably going to be when it punches through the cloud layer.
Do note that most orbital bombardment weapons have damage outputs measured in, at minimum, [kilotons](https://en.wikipedia.org/wiki/TNT_equivalent). As such even mechanised troops are in trouble, as in completely done for, if they're at or close to ground zero.
[Answer]
I assume that the people doing the orbital bombardment dont have the option to suckerpunch (get in and only be detected after launching the attack). So perhaps you could use sinple observatories that litterally look at the ships in orbit. They check their bearing and where their weapons are aimed at, those rods from God/nuke weapon mounts shouldnt be too hard to spot.
Taking from someone elses post recently: <http://tvtropes.org/pmwiki/pmwiki.php/UsefulNotes/Airships>
Using some high-altitude Airships with a large visual range of the space including the sides of the planet and placing observation equipment on them might do the Job. Its relatively cheap, you dont need radar only a direct line of sight and low dust particles for vision and the visual goes at lightspeed so you have one of the fastest mechanics to determine the ships weapon positions. Bonus for having more than 3 Airships with a line of sight so you can without a doubt triangulate the weapons direction and notify troops BEFORE the shot is fired. Although to prevent fake shots the first notification is more of a "get ready you might need to run".
[Answer]
I am going to make some assumptions. The fact that there are ground forces means that they are fighting other ground forces. This means that the enemy will avoid using orbital bombardment methods with extremely high yields. The higher the yield, the more of an early warning you need. This means small [impactors](https://en.wikipedia.org/wiki/Impact_event).
I am also going to assume that these projectiles are mostly unpowered and unshielded. A clever enemy could make a very deadly orbital strike weapon, resistant to standard detection techniques and the ability to course correct. However, you have to ask yourself if it would be cost effective. The price of a single advanced warhead could pay to fling dozens if not more small "dumb" rocks to the surface.
I do think there is one method that may work, but first I want to dismiss some of the methods that could possibly work.
**Visual Detection**
A series of cameras on your vehicles pointed skyward would be able to spot the heat of an incoming orbital attack hitting the atmosphere. Decent enough computer systems could calculate the impact point.
The period of time it will be visible can very quite a lot based on the speed and angle of entry. However, on Earth like planets, the atmosphere will be about 60 miles thick. At speeds of around Mach 1, it would take only about 6 minutes if directly incident (what is going to happen to its speed will depend a lot on the aerodynamics, ect, though it will likely slow down). Likely our projectiles will initially be going much faster. Geostationary orbit is close to Mach 4 for example. The Russian meteor a few years back was going close to mach 100.
So a warning time of about a minute might be possible in some situations. That doesn't really seem like enough time to me.
Outside of the Earth's atmosphere they will likely be to dim to detect with small mobile optics.
**NEAR IR**
One way that we track NEO (Near Earth Objects) is Near IR. Things in space will absorb heat from the sun. They then will reradiate that heat.
You may wish to read up on [WISE](https://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer) and [NEOCAM](https://neocam.ipac.caltech.edu/page/whyinfrared). WISE is an orbital satellite with a 40cm diameter lens (about 1 and a third feet). However, there is no reason you couldn't have similar detection on the surface of the Earth. You will need to kick up the sensitivity a lot, but adaptive optics have gotten a lot better.
Based on its field of view, if something similar was mounted on a surface based vehicle it would be able to image the entire hemisphere it was in with about 2,000 images (If I did my math right, 47 arcminute FoV). At 11 seconds an image that is 6 hours to image a hemisphere . Way TO SLOW. You are really likely to miss a threat.
However, if a group of soldiers had 3-4 vehicles, with an array of like 3 of these on top and they were all working in unison? 30 minutes to image a hemisphere.
This detection technique can be used to track things as far out to the keiper belt (they are to cold past there). Not atmospheric interference would greatly reduce the range.
The problem becomes one of resolution. An object about 15m in diameter (the Russian impactor) would need to only be about 2km away to be seen (far too late). In practice it can only practically detect things 150m or larger in diameter.
NEOCam is a new satellite that has been designed that is only slightly larger and uses much more modern technology (though same basic idea) It has a much better resolution, designed to detect things down to 30m. Hypothetically, it could spot a 15m impactor about at about a third the distance to the moon based on its resolution. NEOCam also has a much wider field of view (almost ten times), but I believe takes pictures much slower.
We can assume the future will see continued development on this front.
There is a lot of story potential with this type of detection. They require cooling (WISE requires Significant cooling). A detachment unable to resupply would risk running out of cooling. The ability of a detachment's ability to detect would also decrease if they lost vehicles, degrading their knowledge over time. Without communication to forces in the other hemisphere, they would also be blind to half of space. An impactor could be hiding just around the corner.
During the day impactors would be more visible (they would be heated more), but there would be a blind spot where the sun is.
**RADAR**
You can check out [This link](https://copradar.com/rdrrange/) if you want to do the radar calculations yourself. However, with a power source of only 100kw as stipulated in your question, the system would be able to detect a small 15m impactor at about 50km away. You would honestly need a terrible amount of power to detect an orbital impactor at a useful distance with the type of radar that would be mobile. So radar is out.
**LASER**
This one is a bit more out there, if you don't want people calling you on getting any of the engineering wrong. Here you can read about using [magnetic fields](https://phys.org/news/2013-04-space-scientists-elusive-collisions.html) to detect asteroid collisions. Here you can read about using lasers to measure magnetic fields. [enter link description here](https://vcresearch.berkeley.edu/news/ground-based-lasers-vie-satellites-map-earths-magnetic-field).
It may be theoretically possible to have some sort of LIDAR array looking for magnetic perturbations caused by these impactors. A system like this would have similar limitations as the IR solution.
[Answer]
# I'm going to challenge the basic premise on the grounds that you've already lost the war.
Air superiority is key, if you control the airspace you can control the ground. If you ground troops are worrying about rods from god, you've lost air superiority and probably lost the war. Your air/space superiority forces should be handling this by keeping the appropriate orbits clear of vessels capable of launching such weapons.
# Don't track the projectiles, track the launchers.
The launchers are going to be large, slow moving and fairly obvious. There's no point trying to track a bullet, even one fired from such a range that you've got 5mins or so to impact. By the time you've detected the launch, located the projectile and identified the course, determined and communicated a safe direction for the troops to move in, it's probably too late to get out of the impact zone, especially if they've fired a spread centred on your location.
Let the flyboys handle the flying stuff, the grunts should be worrying only about what's on (or near) the ground.
[Answer]
Noting the recent event of the falling Chinese Tiangong space station, and the inability for anyone to calculate where it would fall due to the unpredictability of the station passing through the atmosphere, it would be virtually impossible to determine with precision (enough precision to move your troops in time) where a projectile might land even if detected with a good fix on position and velocity.
[](https://i.stack.imgur.com/mGT6N.jpg)
The detection can of course be performed by radar, or even optical observation, but the difficulty lies in calculation, and doing so in time to establish a course of action.
I should add it would be unlikely for your troops to survive a near hit even if mechanised, the scope of an attack would simply be to soon and too large by the time you know where to move to.
[Answer]
The most likely type of unguided orbital strike would be a [Thor type railgun](https://taskandpurpose.com/kinetic-bombardment-kep-weaponry/) strike from an orbiting weapons platform.
A sensitive magnetic sensor could, in theory, pickup the charging of the weapon in space using triangulation and give a warning that it's about to be fired.
It won't tell you what the target is but would make a useful warning to scatter and spread out.
By detecting the charge up, you might have a couple of minutes warning as opposed to seconds if you wait for the weapon to fire.
[Answer]
You cannot see a bullet coming at you. But you can see a guy with a rifle getting set up, and seek cover.
So too with projectiles dropped from orbit. There must be something in orbit to drop them. You will be able to see the something in orbit when it comes over the horizon.
There already exist automated systems for tracking objects in the air and in orbit.
From <http://www.optictracker.com/What_is_it.html>
>
> OpticTracker:
>
> Pre-guiding for Satellites, Comets, and More!
>
>
> You may know exactly where all the interesting celestial objects are,
> but how about a satellite, a comet or your drone? OpticTracker can use
> a variety of information to point the telescope to where your target
> should be, helping you establish a visual lock.
>
>
> OpticTracker can download satellite orbit data and report to you the
> exact time they will pass over head. You can follow it rising up from
> the horizon. When it becomes visible, OpticTracker will get the visual
> lock.
>
>
> OpticTracker can also read comet and dwarf planet orbit elements. Use
> them to pre-guild your telescope, turn on the built in stacking
> feature, and see if your telescope is powerful enough to pick up the
> image.
>
>
> One more thing, for advanced users, you can feed target GPS locations
> into OpticTracker’s REST API, and all those targets become
> pre-guide-able.
>
>
>
Your system will be a telescope and a computer that you will set up. It has a database with known satellites. If some of these are known orbital platforms it can warn you when one comes over. If something new shows up it can warn you there is something new and you can take a look at it. If it looks like an orbital weapons platform, take cover. Once it is out of range you can come out.
I should add in this context that the best defense is a good offense. An orbiting platform is a sitting duck. You can predict when and where it will show up. You might even be able to light it up with a laser from the ground. Send a moderately large missile up along that laser.
] |
[Question]
[
Let's say I'm a secretive organization who's recently come into possession of two individuals of the genus, Giraffatitan (a sauropod similar to the more famous Brachiosaurus for those unfamiliar with it). Most other creatures that this organization comes into possession of aren't theoretically hard to find space for, but a 70 foot long, 40 ton animal is another matter from anything they've had to manage thus far.
This poses a problem, as, to remain in a generally healthy state, these massive animals need a lot of room to search for half a ton of vegetation per day. Keeping the animals indoors is theoretically possible, but pretty much impractical when compared to allowing them to be "free range", so to speak. The issue here, if this secretive organization wants most of its actions to remain hidden is that there aren't a lot of places that both provide a lot of space and are away from the public eye that are simultaneously on land and generally suitable to being Giraffatitan living space.
My question is this: Where on Earth could you let these two animals roam and feed themselves, tracking and managing their movements, without the public getting too suspicious? I've thought about somewhere in Central Africa or perhaps the fringes of the Amazon rainforest, but I'd like to hear other ideas on the matter. Here's an organized little list of the general requirements of the location.
* This place needs to be large enough for two very large animals to move around and do what they do.
* It needs to contain enough plant matter for them to survive.
* It needs to be suitably far enough from civilization that any potential prying eyes could be averted and/or covered up.
[Answer]
Find a convenient [Tepui](https://en.wikipedia.org/wiki/Tepui). There are many of them, some of them quite large, more than enough to provide for your dinosaurs for a long time - you can move them between tepuis to prevent damages to the vegetation to be noticeable from the air, although as ACAC has pointed out, moving these large beasts unnoticed is not going to be easy.
They are in the middle of the jungle, and most of them are inaccesible from below, so there's nobody there, nearly nobody around and nobody can get in nor the dinosaurs can get out. There aren't cameras, drones or aircraft that you have to worry about - the only planes that fly over them fly too high to notice anything.
[Answer]
I kinda hate to say it in some was, but it might be impossible, in this day and age. Consider the following:
Firstly, we must understand what *Giraffatitan* needs in its environment to be healthy and stable. Looking up on Wikipedia gives us:
>
> [*Giraffatitan’s*] ecosystem consisted of three types of environment: shallow, lagoon-like marine environments, tidal flats and low coastal environments, and vegetated inland environments. [The climate] was subtropical to tropical with seasonal rains and pronounced dry periods.
>
>
>
So this translates to a near-coastal swamp, perhaps partially brackish with mangrove-analogues, and dense forest cover. That being said, I can’t think of any natural location which could 100% match this setup, *as well* as give enough room for our sauropods to live. Odds are, you’d have to terraform/later the landscape to suit them, which would be very noticed.
The closest natural matches are the mouths of the Congo and Amazon Rivers, but the problem is both of those locations are still travelled enough by humans that people would notice a couple sauropods in the area.
This leads us to problem number two: **Google Maps**. Satellites will notice these areas, and will also likely spot any dinosaurs living in there. Frankly, unless you’re willing to spend money to make an underground swamp habitat, you’re not hiding these sauropods. Humans have eyes everywhere.
Now, if you wanted to hide something smaller, say, a *Hypsilophodon*? That might work...
[](https://i.stack.imgur.com/yHIoF.jpg)
[Answer]
Here's a possible inspiration for a possible solution: [Musha Cay and the Islands of Copperfield Bay](https://earth.app.goo.gl/uXCzz).
This is a set of 11 islands privately owned by David Copperfield, that house a resort. together they are about 700 acres of land. And I think that a similar place would be perfect for your needs (and there actually are lots of places on earth that can house similar conditions). Let's take a look at a set islands like that one, and see how feasible they are as a solution:
### Can the creatures even live there?
Given the details in your question, yes. You probably want to make sure plenty of vegetation is planted constantly to account for what they eat, but there's plenty of space. also, if you pick a group of islands close to Musha Cay, the island will probably have lots of natural vegetation.
Bottom line - Monitoring the health of the island and your dinos is a good idea, but the islands can house the dinos.
### Can you keep that secret?
**Note**: I'm assuming your group has the means for all this (it's a secret dino-collecting group after all...).
So this is what I think is the really interesting part. There are a lot of places with forests out there, but the resort island model has an advantage of helping you with secrecy.
What your organization can do, is acquire a set of islands similar to Musha Cay (because we want it to have vegetation and to be attractive). Then build a high class resort on it.
Next step - get some celebrities to vacation on your island. What you then do, is claim that they have been filmed during their stay. Using that as an excuse, you ask the country that sold you the island to outlaw drones in the area, and in similar fashion you ask Google (and other companies that take sat-images) not to take pics there.
The people you interact with think you're just trying to please some diva celebrity, and not that you're hiding a dinosaur, so they aren't likely to look to much into it.
What you achieved is a state where you have an inconspicuous reason to ask for privacy in your islands, which is great.
### But will this actually work? Is it enough?
Well, if you manage to convince the local gov. to close ban aircrafts near you island, you are now the only one that can take a (high-res, non satellite) picture of the entire place. Take a few before moving in the dinos, and post them publicly. Spread them on a website where you claim to book the resort, and set up a phony business around them. In real life, not many questions are asked about Copperfield's islands, and most attention it get's is because of the owner. This means an island resort owned by "Pacific Resort Inc." is likely to not generate to much unwanted interest. Even if it does, you control all public photos of it, and none will show evidence of your dinos' existence.
As a bonus, you can have a remote section of them actually rented now-and-then. a nice stream of money to lower costs, and more importantly - a better cover.
**A(n unfortunate) piece of reality** - It is going to be hard (and nearly impossible) to actually stop all sat-images of the island. In the context of a fictional world, I'd say best option is for the group to have agents in companies and governments that have satellites, and have them blur the island or corrupt the photos in a different way.
[Answer]
Assuming they don't mind bumping into a few trees (and crushing some), a good bet to finding sauropods would be the temperate rain forests of Washington state.
The reasons being that there are a lot of sparse regions of vegitation intertwined with the heavy vegitation. Up here, the girafatitan would have plenty to eat a the forests here cover hundreds of miles of deciduous and coniferous trees alike. The last reason is most of these regions are not visible to public eyes, meaning they are not likely to be found.
If they *do* mind bumping into trees, then I'd say the prairie in much of the center of the U.S. - there is an absolute ton of tall grass for them to munch on, with extremely wide, open, and flat space. It also is mostly out of view of humans.
[Answer]
Aerium Hanger, also knows as [Tropical Islands Resort](https://en.wikipedia.org/wiki/Tropical_Islands_Resort) is an enormous ex-airship hanger turned holiday park, with an internal volume of 5.5 million m³. It is not unreasonable to build something like this in a classic Area 51 location, terraform the inside to match your Giraffatitans' needs and put them inside. You will have to ship in a literal ton of food each day, but it avoids the risk caused by aircraft and satellite photography.
Of course, people will wonder what's inside the huge building, but you just need to circulate rumours about it being a UFO storage facility and you'll be fine.
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[Question]
[
What I'm talking about is a gun that shoots red laser beams at the speed of light in pulses in an equivalent of semiautomatic fire, delivering electromagnetic damage to an enemy that melts through his armor and slices through body parts while making a pew pew sound of some type? Something that makes cauterized holes and slices through the target, plus or minus lighting nearby tissue/clothes on fire.
Think blaster from Star Wars, if the beam traveled at the speed of light and not a crossbow bolt, but otherwise behaving as a blaster does in all other respects. Is this possible, unlikely or not?
[Answer]
Man portable laser weapons and sidearms are not going happen soon at our current level of technology, mostly because the energy density of portable power sources is too low, and the heat rejection issues of lasers (especially visible light lasers) is pretty high (something like 20% of the input energy is converted to laser light). Even Free Electron Lasers with a theoretical "wall plug" efficiency of 65% would have issues, especially since an electron beam moving at close to the speed of light would be a source of pretty intense radiation.
There is a reason laser weapons are currently designed for use on ships, aircraft and large ground vehicles. More on the mechanics of laser weapons on the [Atomic Rockets](http://www.projectrho.com/public_html/rocket/sidearmenergy.php) page.
As for sound effects, a pulse laser (which is what you are describing) would actually sound much like a current semiautomatic rifle or machine gun. Ne "pew pew" but rather "crack-crack-crack".
The reasons is the same as the clap of thunder accompanying a lightning bolt. The energetic laser beam causes the air to rapidly expand and clear the laser channel. Once the laser beam stops, air rushes back into the vacant space, creating a miniature clap of thunder. Since the laser pulse is moving at the speed of light, there is still a finite space the beam fills as the laser pulses, so there will be a gap for air to smash back into.
As for the mechanisms of damage from a laser weapon, [Atomic Rockets](http://www.projectrho.com/public_html/rocket/spacegunconvent.php) has pages devoted to that as well (although the general thrust of that section is massive megawatt+ weapons for spaceships). The principles are the same, however, and by filling in the appropriate numbers, you can calculate the potential damage your laser weapon can cause, range and other important information.
Now the theoretical workaround for a man portable laser weapon is going to sound strange; use chemical energy stored in disposable cartridges. Each cartridge is pushed into a chamber where the energy is rapidly released. The hot gasses pass through a MHD generator, and the electrical energy is converted into laser energy while the empty cartridge is ejected and a fresh one inserted.
[](https://i.stack.imgur.com/4g9HK.jpg)
[](https://i.stack.imgur.com/ek8Vx.gif)
Of course, you could make things simple and just have the chemical energy drive a projectile directly...
[](https://i.stack.imgur.com/ounsV.jpg)
[Answer]
Pew-Pew sound would definitely not come from the laser beam itself - light doesn't make any discernible sound. I could see you making it an artifact of the power rapidly charging and discharging, though it's not necessary for the device to function. Typically solid state electronics are pretty silent.
As mentioned in a comment, light moves way too fast for you to see. Assuming you could shove that much electrical power in a blaster-sized package (not possible with modern technology), you might have something slightly close. Some differences includes that there would be no recoil to the shot, and no explosive impact - it would burn the target, and not much else. Also, even the most powerful modern lasers take time to put a hole in a target - a sustained beam, not a gun-like shot in a single instant.
[Answer]
I know that this type of weapon is not a laser, and probably not exactly what you think, but there is a theoretical weapon explained in this [video](https://www.youtube.com/watch?v=1po2ut5zi0Y) called Plasma Railgun. Basically, it shoots plasma "bubbles" with electromagnetic fields that can reach speeds of 200 km/s and higher temperatures than the sun.
It could be visible for the eye (200 km/s is REALLY fast), but it's not a laser, I don't know if make Pew Pew sounds, but I really hope this helps you.
[Answer]
Closest existing thing I can think of to your answer is a magnetron gun... You mentioned electromagnetic and laser as the same thing. They are not at all. You should touch up on some scientific articles regarding this, it's quite interesting. Even in a magnetron gun you can not see the radio waves going through the air (it is a HERF, high energy radio frequency), unless you covered it in flammable gas... :/. Also pew pew sounds don't really exist in this kind of thing unless you are slowly deflating a balloon with it. :)
[Answer]
**Visible component**
Several people have commented that light travels too fast to see it travelling in bursts.
Here's how you can overcome that and produce any apparent speed from zero to C. The gun fires pulses of say a metre in length in *very rapid succession*. Thus the pulses overlay each other. There is a critical level of overlay that causes the air to ionise. It is the maximally overlaid portion that travels at visible speeds. (I'll add the maths here when I have time).
The main problem is that you want red. Air fluoresces in what is called electric blue. <https://en.wikipedia.org/wiki/Ionized-air_glow>
You could use overlaid bursts of a red laser without having to cause ionisation. The apparent slow movement of the beam would be caused by an animation effect of rapidly repeating pulses combined with persistence of vision. However there would have to be sufficient dust in the air for it to be visible from the side. Maybe the gun could project a cloud of powder or smoke for some unfathomable reason. Maybe the anti-hero has bad dandruff.
**Pew pew component**
This is pretty easy. You amplitude modulate the pulses. As they pass the listener and the air is distorted you get the characteristic Doppler effect. Only an observer at the side would notice the pitch change. For the shooter and the victim the pitch would be constant but the volume would still vary.
**Mach diamonds**
This is another possibility that doesn't use lasers. I'll have to flesh this out later.
Mach diamonds video
<https://youtu.be/kEw2msVaVy0?t=7>
[Answer]
# Hello From the Future!
(This answer purely deals with seeing and hearing a beam, and assumes power supply questions and the like are non-issues.)
I don't know why WBSE showed linked me to this question again after so many years, but under the right conditions lasers may indeed make sounds frequently associated with sci-fi depictions of them. Naturally, a shorter dwell time on a given surface would create a shorter sound than the following sources.
[This video](https://www.youtube.com/watch?v=1DfSWFbEHUo) of laser rust removal gives an excellent example of the variety of tones lasers may make when interacting with certain surfaces. Thus the device producing the beam itself is fairly silent, but the sound is produced by the beam interacting with its target. As a bonus, [this video](https://www.youtube.com/watch?v=QrreM0TAWk8) shows how a beam may be clearly visible when moving through a cloud of the very material it vaporized. A dusty or hazy environment would increase visibility significantly.
I can't be certain, but the latter video appears to have audio filtering applied to highlight certain tones. In the same way, one's chances of hearing this noise would be (perhaps accidentally) improved for anyone wearing certain [electronic hearing protection](https://www.3m.com/3M/en_US/p/c/ppe/communications/over-ear-headsets/i/safety/personal-safety/) that implements the audio equivalent of a [high pass filter](https://en.wikipedia.org/wiki/High-pass_filter). Such hearing protection is common in military, industrial, and aviation contexts.
A laser won't *always* be visible and make pew-pew-zap noises, but it is certainly plausible under the right conditions.
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[Question]
[
It's common knowledge that one of the things that makes stealth aircraft so stealthy is that the body is covered in a skin of special material that interferes with radar. Would it be theoretically possible (for a more-or-less reality-based superhero concept) to create a "stealth car" based on the same principle, that won't register on a cop's radar gun?
[Answer]
The radar guns used for speed measurement are an extremely primitive form of radar called continuous-wave radar that just compares the frequency of a transmitted and a received signal to determine (based on Doppler's formula) what the target's speed is. Whereas the air radar you were referring to is a highly sophisticated pulse-based form of radar that uses advanced processing to reconstruct both distance, speed and azimuth/elevation information about the target. So the radar gun definitely would be trivial to jam through actively emitting a signal in its operating frequency.
With the right materials, you could also build a car that has such a small radar cross-section that it simply doesn't pick up on the gun. Because the reflected power decreases with distance to the 4th power, this would be hard to do. However, you wouldn't need to make it perfectly invisible, but just so small in terms of radar cross-section that other vehicle or the ground have a stronger reflected signals.
Therefore, my conclusion: Yes, you can build such a car. My understanding is it would even be legal under FCC regulations, since you're not emitting anything to jam. However, the difficult choices in materials and the design sacrifices you would have to make in other areas (no sharply curved surfaces, shrouding of the exhaust, etc) would not make it worthwhile.
[Answer]
## Let the arms race begin!
Let's start by saying yes, it is theoretically possible but no, it's not practically possible. Being stealthy in the air is very hard to do. Being stealthy on the ground against [current radar/lidar speed guns](http://www.stealthveil.com/guides/radar-jammers) is tricky at best.
## Passive Measures
If one designed a car to bounce radar and IR energy somewhere other than back towards the radar gun, then it would be difficult or impossible for the radar gun to get a good enough measurement. If this technique worked, the radar gun would think it is pointing at empty sky.
Passive measures will deal primarily with the shape of the car. Highly angular surfaces that reflect the radar away from the gun should be effective. Basically, you'll get a car that looks like the USAF F-117.
[](https://i.stack.imgur.com/EUZGx.jpg)
If you have the compute power, you can work out radar sneaky *curved* surfaces which will get you airplanes that look like the USAF B-2.
[](https://i.stack.imgur.com/pbt9o.jpg)
You'll need a specially shaped car, with radar/IR absorbent paint. Also, ensure that *all* of the bits on your car will contribute to sneakiness. Having a giant cooling fan hidden in your front grill could make you stand out like a lighthouse, even if the rest of the car is very sneaky. Side view mirrors could also ruin the sneakiness. You'll have to be very careful with the shape and reflectivity of *all* car parts....like the shape of your wheel rims (if radar goes through rubber).
The plus side to passive measures is that it's not illegal to make a weird shaped car. If you go with curved surfaces, no one will probably even notice. If you go angular surfaces (a la F-117), you'll have a very distinctive car....that may look something like this:
[](https://i.stack.imgur.com/IQGaE.jpg)
...except without two giant radar reflectors on the front in the form of wheel rims or the extra fiddly bits to form nice big radar reflectors. Remember that the [corner reflector](https://en.wikipedia.org/wiki/Corner_reflector) is one of the most efficient radar reflectors there is, so avoid that shape in your car if at all possible.
In short, yes, you can make a passively radar/lidar sneaky car, it's just crazy hard and very expensive.
## Active Measures
In the Vietnam war, with the advent of surface-to-air missiles, an arms race began between radar operators and the aircraft flying against them. The aircraft would get a new jammer that would decrease the effectiveness of the radar, so the next generation radar would hone in on those jamming signals. Then the jammers would get a little bit more clever in how they jam to defeat the radar's new detection ability....you can see where this is going. The race continues to this day.
So, ignoring that active radar jamming is illegal, and laser jamming sometimes illegal, your active jamming measures must compete against the radar/lidar guns themselves. If lidar guns develop that can detect active jamming attempts, your jammer will need to account for that. If they send out lidar pulses in carefully coded bursts to ensure that the laser light coming back came to the gun came from that gun, you'll need to account for that too. Conceivably, radar/lidar guns could start to use quantum cryptography on the light they send out...let's hope it doesn't get to that point.
## Complicating Factors
If this car is just avoiding speeding tickets, it's likely not worth it. Let's assume a perfect stealth car, invisible to lidar and radar. When you blow past a police officer, they will see you go past. Even if they don't know exactly how fast you were going, they will know that you were going faster than you should have which is enough for him to give chase. Stealth airplanes are designed to work beyond visual range where radar is the only way to detect an airplane. A stealth car inherently works within visual range so mitigating radar and lidar doesn't make as much sense.
## How much is it worth to you?
What kind of threat are you attempting to counter with this car? You could easily spend many millions of dollars in passive and active countermeasures. If this is just to avoid getting a speeding ticket then your cost-benefit ratio is completely bonkers. If this is for a super-secret billion dollar delivery then sure, it's worth it.
[Answer]
In short attempting to do that would be rather impractical.
The stealth aircraft reduce their radar cross section primarily in two ways: shape that reflects the radar waves away from their origin and radar absorbent materials. Those measures aren't perfect but they reduce the target's visibility to radars, which makes it a lot harder to acquire and maintain lock on it, which is primarily useful for avoiding stationary SAM sites. However if the airplane passes too close or is poorly oriented it can still be locked on and shot down. Which is why it is not a very practical solution for a car, as the car will be radared from very close range where even minor imperfection can give sufficient return, and the cop radar doesn't need to maintain lock for 30 seconds to tell speed.
Conclusion: you'd be much better off jamming or spoofing it (which is actually not that difficult in real life), rather then bother with stealth.
[Answer]
Since you can be tracked by visual means (as mentioned in other answers), you really need to think about a different means of avoiding detection: metamaterials.
Metamaterials are engineered substances which can refract light or other energy in directions that the engineer desires, rather than the direction that happens naturally (much like a pencil in a glass of water):
[](https://i.stack.imgur.com/oDCPL.jpg)
Since refraction depends on the wavelength of the incoming energy, metamaterials designed to refract light will be different from metamaterials designed to refract radar. Metamaterials can be designed to cloak submarines from sonar, and even theoretically refract shockwaves from earthquakes around buildings (on that scale they would look like an irregularly spaced group of pilings driven into the ground around a building).
With proper design, metamaterials could refract light around an object in such a fashion that the observer isn't even aware of the object, there will be no "hole" in their line of sight.
The downside of metamaterials is that they are tightly tailored to the wavelength of the energy being refracted. A sonar cloaked submarine will still be visible to the naked eye and radar on the surface, unless there are several layers of metamaterials overlain on each other. How they would interact is an interesting question, and to my knowledge, no one has done research on this to date. As well, most metamaterials utilize a technique called an "optical lattice", so the tiny spacing in the lattice are vulnerable to damage or being filled with dirt. This means unless there is very careful maintenance and driving, the benefits of having a metamaterial coating will be negated quickly
[](https://i.stack.imgur.com/JtuyQ.jpg)
Optical lattice
The irony is in order to best preserve your metamaterial coating you should drive according to the rules of the road, avoid speeding or otherwise putting additional stressors on your car that could damage or degrade the coating.....
[Answer]
I remember reading an article about this in Car & Driver about 1990. They said the best production car for this was a dark blue Ford Probe with no front license plate and the headlights down. They sighted minimal vertical surfaces on the front and a dark color.
Now that was for laser detection because that was the new thing. And the car was not invisible, but the detection range was reduced to 400' instead of a standard 800', enough time to visibly notice the officer.
[Answer]
The project car of a Camaro website used radar absorbent material (RAM) to make it stealth. Metal fenders and hood were replaced with fiberglass units with RAM beneath it. Lots of details are covered:
<http://www.camarotech.com/rcs.html>
It is all based on passive absorption of microwaves.
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
It's been 21 years Ms. Frizzle has been doing her best to educate the masses. Even with all the knowledge available provided on the internet, not only do people not take advantage, they choose to remain ignorant of as much as possible, preferring sound bites that have nothing to do with facts. She has had enough. She plans to teach one last lesson to her students and everyone else. It's one everyone WILL learn (for however little time it takes).
She blames the US as the center of ignorance movement and as such wants to wipe out everyone there. What she has is a special [magical schoolbus](https://en.wikipedia.org/wiki/The_Magic_School_Bus_(TV_series)) that can swim through oceans and fly into space, 10 elementary students and her commitment to see this through. How fast does she have to be traveling in the bus and where in the US does she need to target in order to be able to wipe out %95-99+ of all people in the continental US? I'm guessing the aim would be somewhere in Kansas or maybe Colorado.
This is a hard science question.
[Answer]
So...what this question is asking is this. At what velocity does a schoolbus need to go in order to, on impact, cause an extinction event that takes out the US. So, ultimately, this is a projectile physics question.
Note: I am assuming she wants them killed quickly, rather than letting them die out in a nuclear winter, which humanity might be able to pull together to survive. Unfortunately, nuclear winter is the fate of the rest of the planet, given the energy levels we are talking about here.
We can assume angle of incidence at 90 degrees to the surface, as that will deliver the most energy directly into the ground. We can assume the mass of the school bus to be roughly 10,000 kg (based on Median GVWR of school buses). The Magic School bus has shown to be indestructible (it's magic), so we can ignore the chances of it breaking up on re-entry.
So, we have a projectile massing 10,000 kg, and we want to slam it into the ground hard enough to destroy the Continental US. (I'm assuming we are ignoring Alaska and Hawaii, so we don't have to destroy an entire hemisphere.)
Our target is a spot 2 miles northwest of Lebanon, Kansas...the geographic center of the continental United States. Our blast has to be powerful enough to kill someone at around 2,000 km away, given the width of the US.
Of course, we have a bit of a problem. We don't have a lot of reference for the amount of splash damage caused by hypervelocity impacts. And, unfortunately, I'm having a hard time getting any impact simulators to properly model such high speeds (the best one died when I got too close to relativistic speeds). So, I had to get creative and try to figure out how much energy it would take to create the impact needed. This is the tool I ended up using to simulate the amount of energy delivered to the center of the US to get the desired effects. <http://www.purdue.edu/impactearth/> It's built by Purdue University, so I give it a fair degree of credibility. The ultimate simulation I settled on in order to obliterate the occupants of an area the size of the US was a 15km impactor, at 72 km/s, with the density of iron. And calculated effects at 2,000km away.
The results are the ability to kill pretty much everyone with the thermal blast and air pressure wave from the impactor...and it will teach the people distant from the impact point quite a bit about how impacts work. So that their deaths may be educational.
The energy delivered by this impact is $4.48e^{9} MegaTons$ which is an order of magnitude greater than the impact which caused the Chicxulub crater. In order to show the lethality, lets look at what that tool says life would be like at the 2,000 km mark.
Impact. We see a flare of light that appears 25 times larger than the sun in less than a second.
I+7.38 seconds: Thermal Radiation peaks. If it is flammable, it ignites. Trees, grass, wooden buildings, clothing, hair, etc. Humans do not ignite, but instead suffer 3rd degree burns across most of the body. People inside solid non-flammable structures with thick walls are still somewhat safe.
I+6.67 minutes: The ground tremors arrive. At this range, they are pretty minor and only crack plaster...alarming, but not of note, given that the world is currently on fire.
I+12.7 minutes: Ejecta starts to rain down on the area...it's mostly dust. Again, the world is on fire, this is largely ignored.
I+1.68 hours: The pressure wave finally arrives. Winds gust up to 489m/s (1,090 mph). Air Pressure spikes to over four and a half times normal atmospheric pressure. The sound wave is part of this, at 113 DB. This blast is sufficiently powerful to obliterate 90 percent of all trees (turning them into projectiles), distort skyscrapers to the point of impending collapse, and simply flatten houses.
The time delay before the pressure blast arrives would allow that anyone who survived the initial damage may have wandered out of safety by the time the blast wave arrives (and hurls them at things at absurd speeds).
The only people who would survive this are those in underground bunkers.
So, that brings us to the next question. How fast to we have to toss a 10,000kg bus in order to deliver this much energy?
Convert MegaTon value to Joules
$$
1 Megaton = 4.184\*10^{15}
$$
$$
4.48\*10^9 Megatons = 1.87\*10^{25} Joules
$$
Calculate based on Kinetic energy...
$$
E=\frac{1}{2}\*m\*v^2
$$
$$
1.87\*10^{25} = \frac{1}{2}\*10,000\*v^2
$$
Solve for Velocity...
$$
68,454,948,688.9m/s
$$
Well crap. That's higher than the speed of light. Which means we are getting into relativity instead of achieving that speed. Time to break out relativistic Kinetic Energy Equations.
$$
E=\frac{mc^2}{\sqrt{(1−\frac{v^2}{c^2})}}
$$
Plug in values
$$
1.87\*10^{25}=\frac{10,000 \* 299,792,458^2}{\sqrt{(1−\frac{v^2}{c^2})}}
$$
And we solve for v.
$$
\sqrt{(1−\frac{v^2}{c^2})} = .0000480618
$$
$$
1−\frac{v^2}{c^2} = 2.3099\*10^{-9}
$$
$$
\frac{v}{c} = 0.9999999988450
$$
$$
v = 0.9999999988450c
$$
So, there you have it. In order for a school bus to deliver $4.48\*10^9 Megatons$ worth of energy, right at the heart of the nation, you need to be moving at $0.9999999988450c$
At this point, the magic school bus is basically a particle beam. But, as it is indestructible, it should manage such an impact no problem.
The long term ramifications of this impact are best defined as 'global extinction.' Miss Frizzle just slapped the reset button on Earth...most terrestrial life is history from the climate impacts this will have. Humanity may survive...but the outlook is certainly bleak.
NOTE: I am making some assumptions regarding Joules of Impact relative to level of destruction, I know. But I had to simplify this somewhere...
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[Question]
[
Concerning long term effects of zero gravity on humans living in space compared with those living on super earths with 1.5x to 2x G, how could the gravity differences cause reproductive failure among the two groups? What biologic traits might be selected for (or against) that would start to cause infertility between humans living in zero gravity, and those living on planets with more gravity than earth?
[Answer]
What you're referring to is known as speciation. In the context of two planets between which there is minimal gene flow, this is probably going to be allopatric speciation. Speciation is the process of a single species breaking into multiple species, which are generally defined as populations which cannot create viable offspring when breeding with one another.
[Allopatric speciation](http://en.wikipedia.org/wiki/Allopatric_speciation) is speciation that occurs due to geographic separation. This is seen on earth when something like a river valley separates a population of animals into two populations that can no longer reach each other. Chimpanzees and bonobos are one possible example. They do not differ significantly in terms of their environment, but their separation on either side of the Congo river has led to the formation of two different species.
In order for allopatric speciation to occur, there do not need to be any specific population pressures that force evolution of the two groups. Rather, it has been hypothesized that genetic drift is sufficient to cause the two groups to become reproductively incompatible given sufficient time.
A long period of separation is the critical factor, here. Over shorter periods of time, the two populations are likely to remain capable of producing healthy children, even if population pressures have changed the physiological traits of one of the populations. Corgis and German Shepards, for example, can still breed, despite the fact that they've evolved (with human help) to thrive in very different roles.
[Answer]
The first obstacle would be the ability to physically mate with each other. Modern astronauts face fairly serious muscle loss and atrophy after weeks in space, so humans *living* in space would be that much weaker. I'm doubtful that they would even survive visiting the 2G planet, let alone build the necessary blood pressure to perform the act.
The 'super-earth' humans would also have problems, if they were to meet the others in space. Not surprisingly, there has been quite a bit of speculation (and very little actual testing) about zero-G sex, and the consensus seems to be that it's very difficult. Basically, without gravity there is nothing to keep the participants together. One thrust and you're tumbling across the room. There is also apparently a blood flow issue, in which the human body, adapted for Earth's gravity, has trouble sustaining physical arousal. It would presumably be even harder (or ...not) for people adapted to higher gravity.
This also leads to a physical adaptation that could cause speciation, as natural selection would lead to the space-people to be better able to copulate in zero-G, which could eventually lead to substantial changes in the reproductive organs.
[Answer]
It could be that our reproductive system doesn't work too well in zero gravity. That would impose a strong selection pressure to adapt the reproductive system to zero gravity, which then in turn might it incompatible with those living in a gravitational field.
The inability of cross-breeding would on one hand be a physical incompatibility, but the divergent evolution might also create a genetic incompatibility (for example, if the genes for the different reproductive organs are incompatible with each other).
In any case, something like this can only happen if the groups are not cross-breeding for a sufficiently long time (which may be reinforced by other adaptations to the respective environment which might make it impossible for the space dwellers people to even visit the planet surface, and at least inconvenient for planet dwellers to be in space).
[Answer]
If we imagine the adaptations for the different lifestyles are based on genetic engineering ( which seems quite logical in a interplanetary civilisation ) then we could expect rapid changes which may be sufficient to cause effective speciation. Not being a biologist I don't know exactly where you reach the point that offspring are infertile, but if peoples are engineering themselves in the interests of fitting better in specific environments then they are likely to hit that boundary sooner or later.
Also people who engineer themselves to be able to live in space might take things to a much greater extent than one might expect, like the Ousters in Dan Simmons' Hyperion novels - the lack of gravity meaning that our limbs designed for ground travel might be significantly changed or discarded to make it easier to get around.
There could be an interesting debate among colonists at the speciation point, where you have a political question of whether they want to become a new species or not and that becomes a decision for all the colonists of the new world. A speciation referendum is a great starting point for interesting stories.
[Answer]
A scenario that might lead to this case might be genetic engineering followed by a loss of the technology.
The rationale is if you took a group of colonists and dropped them on a 2G world, they wouldn't survive. Our circulatory system, bones, and joints couldn't handle it. Our bodies would break. The fittest might survive for a while, but eventually the high gravity would kill everyone.
So to survive on the planet you'd probably need one of these:
* Anti-Gravity technology to lower the gravity around the colony
* Other advanced technology, perhaps mechanical exoskeletons and implanted devices that support the heart and lungs.
* Genetic engineering, to modify the human body to make it more sturdy and to re-enforce the circulatory system. Perhaps supplemental organic hearts.
If you have the first or second, then infertility between the two branches of humanity wouldn't be an issue because there'd be no evolutionary pressure for humans to change. At least not for hundreds of thousands or millions of years.
If you have the 3rd, interbreeding would still be possible because of the high level of attainment in genetic engineering. They could just alter the genes as necessary.
So you'd have to have the genetic engineering that would make interbreeding impossible... but then lose that technology to prevent further engineering to make it possible.
On the flip side, the zero-G humans really have no reason to ever need to be zero-G humans. Rotating a space habitat can create 'artificial' gravity. And there's plenty of places in the universe where, even if at low G, there's enough gravity to prevent major health problems.
[Answer]
Another aspect that no one has touched on is radiation: You will be exposed to radiation that people on Earth aren’t.
We can assume shielding and whatnot, and so you’ll still be able to live mostly cancer-free and make babies, but you will see mutations that Earth-people will simply not have.
Like others, keeping the population separate, having properties naturally selected for based on environmental changes, and difference in goals for genetic engineering will drive these changes. But the continuous difference in amount and composition of the radiation these space-people will endure will be the driving force behind the actual genome shuffling required to make Homo *Aéronomie* and Homo Sapiens incompatible.
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[Question]
[
[This question](https://worldbuilding.stackexchange.com/questions/3188/what-should-three-men-and-three-women-do-if-everyone-else-is-dead) discusses the various steps a very small gene pool could take to avoid inbreeding however most of the answers agree that it's very unlikely that a group of 6 individuals could avoid all genetic issues.
I'm interested in exactly what those issues are.
It's my understanding that most issues arising from inbreeding are as a result of family containing similar sets of DNA. We all have recessive problems in our genome, this only becomes an issue when our partners' DNA also has the same recessive issues (because two recessive defects don't have the dominant one to correct them). Inbreeding is an issue because brothers and sisters have very similar DNA and the probability of both of them having the recessive genes is far more likely than a random person.
Assuming my understanding is correct why would a group of six unrelated people have this issue? Assuming that they all have different recessive problems their children would have a chance of inheriting the same ones however they are also almost guaranteed to have the correct dominant genes from their parents!
Given that a massive proportion of genetic issues will no longer exist (because the only ones going forward will be those present in those early progenitors) why are the probabilities any higher when starting with a smaller base?
Exactly what symptoms would a colony see if it had too few founding members?
[Answer]
So we’ve got the basics down. We all carry mutations in genes that are harmless by themselves, but if you get two broken copies of the same gene bad things happen. The answer to your question has to do with probabilities.
Let’s say you have two populations. In the first there are 100 genes with recessive lethal mutations, each at 1% frequency in the gene pool. This means that on average there are 2 recessive mutations per individual (because each individual has 2 copies of 100 genes with a 1% rate of being mutant). The probability of an individual receiving 2 copies of a single recessive mutation assuming completely random shuffling is 100 \* 0.01^2 (one hundred chances of getting two copies), or 1%.
Now let’s look at a population with only 10 recessive lethal mutations, but that are now at a frequency of 10% in the population. On average there are still only 2 recessive mutations per individual, but now if we calculate the chances of a person being born with two of the same mutation we get 10 \* 0.1^2 which is 10%.
The two populations have the same total number of recessive lethal mutations, but problems arise more frequently in the second population. So while a populations bottleneck will remove the vast majority of genetic issues, the ones that remain will run rampant in the remaining population.
To further illustrate how this represents a population bottleneck, imagine if you take 5 individuals from population 1 and use them to found a new population. Each of these individuals brought 2 different mutations from the original pool for a total of 10, and in the starting population there is 1 mutant copy out of 10 total (5 people, each have 2) so each mutation is at a 10% frequency. Now we have population 2.
To move away from the hypothetical and address your situation directly. It is estimated that the average person carries ~5 recessive lethal mutations. With a founder population of 6, that means you can expect ~30 total recessive lethal mutations. Each of these would exist in your population at a frequency of 1/12 or 8.3%. The first few generations would not show any issues as you are still breeding completely unrelated individuals, but once the bloodlines are sufficiently mixed each child will have a 1-(1-1/12^2)^30 ~= 19% chance of inheriting two recessive alleles and dying from a genetic defect. This chance will gradually decline over time as the children that die won't pass on those mutant alleles so the bad genes will slowly be purged from the population. Essentially for many generations the birth rate will be fairly low, but will slowly recover.
It's also important to keep in mind that the above only covers recessive lethal mutations. Plenty of recessive mutations are non-lethal and would also be frequently seen in the offspring of this population. Expect a lot of deformities and other weird stuff.
Edit: A recently published paper (<http://www.genetics.org/content/199/4/1243.full>) has estimated that the average person only carries around 1 or 2 recessive lethal mutations. If this is true then a founder population of 6 that each brought a single mutation would only create a population with 1-(1-1/12^2)^6 ~= 4% recessive lethal mutations.
[Answer]
One particular illness which was common in European nobility exactly because of inbreeding is haemophilia. Note that there were many more than six nobles, and yet you had a direct effect.
To see the problem in its purest form, take the most extreme case: Just one man, and one woman. And now assume one of them, let's say the man, has a recessive genetic defect. He's healthy (because he has a dominant healthy gene to compensate), and of course the woman is healthy because they don't have the defect.
Now they have children. All of their children have a healthy gene from the mother, therefore not a single of them is ill. However half of them will have the defective gene.
Now their children again have children. Now it gets a bit more complicated.
There's a chance of 1/4 that both don't have the gene. In which case neither will their children.
Moreover there's a chance of 1/2 that one of them has the gene. Again, all of their children will be healthy (because each one got a healthy gene from the other parent), but half of them will carry that gene.
Remains the 1/4 chance that both carry the defective gene. Then only 1/4 of their children will not carry it, 1/2 of them will carry one copy (and thus still be healthy), and 1/4 will have two copies of the defective gene, and therefore will be ill.
So together we have that 9/16 of the grandchildren will not have the gene, 3/8 will carry the gene but not be ill, and 1/16 of the grandchildren will have the illness.
Now take Mike Nichols' number that each human has on average about 5 defective recessive genes. That is, the original parents will together have 10 such genes. Assuming each of those genes is inherited independently, the change that a grandchild is healthy is $(15/16)^{10} \approx 52\%$. In other words, about half of the grandchildren will have some inheritable illness.
Now with three pairs, clearly the probability of getting two defective copies of one gene will go down, however you will still want to actively minimize it by ensuring that people who mate are as genetically different as possible.
[Answer]
Not sure if you can pick out specific defects in general...more of an amplification of shared defects. Think of a coin flip...if you flip it 10'000 times, there is relatively low chances of getting 10'000 heads for results. Flipping the coin 6 times however, and you have a 3% chance of all the same result. Do this 6 person coinflip for each recessive gene and you are going to have a few of these results where all 6 members are carriers of some defect (admittadely it isn't all 50/50 coinflips...but rolling dice 6 times will also have a probability of all 6's)
Hemochromatosis is a good example. It's a two part gene, one from each parent. If both genes are positive, then you have Hemochromatosis and do not process iron correctly. If you have a single positive, then you are a carrier that has a 50/50 chance of passing it to a child, but the one negative gene prevents you from having any effects yourself.
There are a lot of genetic disorders out there that operate on this scale. If there is a common defect amoungst them (flip the coin 6 times) and this defect will amplify through the population. Hemochromatosis has a 5 in 1000 positive in the Caucasian population and a 10% chance of being a carrier. Not likely, but there is such a number of these defects that are possible that odds are one of these disorders are going to be common between them (or at very least, be carries of the same disorder).
[Answer]
In addition to the active problems of lethal or (in many ways worse) deleterious recessive genes, you also have the problem of limited genetic diversity in other genes, leading to long term brittleness of the population.
Immunodiversity was mentioned above, but there are other examples, mostly dealing with flexibility in adapting to change. See <http://en.wikipedia.org/wiki/Genetic_Diversity> for more info.
Pity the world with only 6 basic types of human intelligence...
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[Question]
[
Normal seashores are curved.
On a planet with earthlike features, the seashores are entirely straight. For example, [](https://i.stack.imgur.com/7FA2F.png)
.
Long paths of straightness extend for many miles at a time. Note that these seashores aren’t hexagonal or ordered, they’re random.
What geographic processes could result in such bizarre seashores? And not only a few of them, an entire planet of them?
[Answer]
There are perhaps 2 methods that can achieve what you are looking for depending on the scale of your jagged edges.
## Sedimentary layer shifting, collapse and erosion
It is conceivable that a sedimentary area has over time become eroded and the layer angle shifted to produce straight edges over dozens of metres. This is evident at Mistaken Point, Canada. As the strata layers have different properties and formed over different eras of time, the layers are straight. As time progresses, they shift and erode, exposing the layers to water forming straight edges.
[](https://i.stack.imgur.com/tcqzq.jpg)
[](https://i.stack.imgur.com/JXFwK.jpg)
## Earthquake faults
Like at the Pupatea Fault, New Zealand, where a magnitude 7.8 quake caused a seismic shift and exposed along the shore a roughly km long straight edge. This is rare and relies on a geologically consistent layer to form, but nonetheless creates a permanent face in the rock which could be, over time, a jagged straight shoreline.
[](https://i.stack.imgur.com/Nh7Rt.jpg)
[Answer]
**Artificial.**
[](https://i.stack.imgur.com/vQLaF.png)
Depicted: [Emmeloord](https://en.wikipedia.org/wiki/Emmeloord) which is built on a polder - lands taken from the sea. The resulting engineered shorelines are straight because of the convenience of building in straight lines.
The Dutch are famous for this and these are the long straight lines requested from the OP. But the Dutch do not have a monopoly on this. Here are similar obviously artificial shoreline from Tokyo. Some of these are reclaimed lands and some were made to facilitate human use.
[](https://i.stack.imgur.com/OrPAu.png)
These artificial straight line shores are not some sort of fractal. To my eye they seem pretty random. It is not such a stretch to think that a planet inhabited by intelligences not unlike us might similarly engineer their shorelines.
They will not stay straight without maintenance. If they are not maintained the water will wear them into nonlinear shapes again. Unless the water also disappears. I found this city on what used to be the shore of the Aral sea.
[](https://i.stack.imgur.com/k7lPL.jpg)
[Answer]
I am going to suggest an earthquake faulting action with basically a stone sea-short. This ought to be able to give long fairly straight sections. You had an entire region above the waterline then the quake hit and some large pieces simply sank beneath the waves.
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[Question]
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A long time ago [homo floresiensis](https://en.wikipedia.org/wiki/Homo_floresiensis) split off into two main groups Goblins and Halflings. Now Goblins are an odd little bunch (here's a rough mock up of what a [goblin](https://i.stack.imgur.com/vHimf.jpg) might look like) and I was wondering what evolutionary pressures would lead to Goblins? some basic characteristics of goblins are:
* are as intelligent as humans (don't have any behavioral differences compared to humans)
* are 112.7cm (3.7ft) tall
* have large noses
* have big pointy ears
* have an improved sense of hearing and smell but do have slightly worse eyesight
* have green skin due to a symbiotic relationship with a type of moss or algae
* have life spans similar to humans though they do reach sexual maturity a bit faster than humans
Note: magic does not exist in my story.
[Answer]
**Island Dwarfism**
Like Homo Florensis, which you stated to be an ancestor in your question, living on an island in which food is relatively limited has selected smaller body size for your goblin population.
**Extremely Dense Jungle**
The underbrush of the jungle is thick, visibility is reduced due to foliage and it’s somewhat dark due to the shade.
Their small size is an advantage in the dense underbrush, as they can scamper quickly and quietly through it.
Because visibility is lacking, they rely on smell to find edible plants and grubs, and hearing to detect stalking predators and slightly larger prey like rodents. Their eyesight is weaker due to more of their brain being dedicated to smell and hearing, and it’s simply not as useful.
Their green skin has been selected for due to its camouflaging effect in the dark green jungle, as they are prey in this dark forest.
**Intelligence**
It’s hard to be small and weak, but even the strongest predator will fall to arrows and spears. Like humans, intelligence has been continually selected for.
In short, an equatorial island covered in dense rainforest would be the most likely conditions
[Answer]
1. are as intelligent as humans -> Covered in part 5
2. **are 112.7cm (3.7ft) tall** -> from your own [link](https://en.wikipedia.org/wiki/Homo_floresiensis), that is the size of homo floresiensis, so what you really need to do is make sure that the goblins don't evolve to increase in size over time. The typical way to do this is be on [an island without large predators, but also throw in some scarcity of resources](https://www.sapiens.org/column/animalia/island-dwarfism/). If you had a warm climate, this would also ensure that the Goblins wouldn't need a large body size to regulate heat.
3. **have large noses** -> You could get this by increasing the heat of the location of goblins. Part of the feature of a nose is [regulating heat/moisture](https://www.livescience.com/58297-nose-shape-climate-evolution.html) of air coming into the lungs. Typically though you have a trade off. It is either long/narrow nose (cold climate) or wide and short nose (hot climate). If you had a hot climate and sexually selected for nose length, seems like a likely outcome.
4. **have big pointy ears** -> [This answer](https://worldbuilding.stackexchange.com/questions/91957/what-would-be-the-possible-benefits-of-pointed-ears) highlights the benefit of a pointy ear which "may be useful to them in triangulating sound sources; perhaps higher or lower frequency sounds than in the human range". The solution for this one could be there is a certain animal/critter/plant that is highly nutritious/functions as a drug/etc, that emits a sound in such a high frequency that only pointy ears would be able to hear. The Goblins would be evolved to hear that animal or plant make the noise and have some pointy ears for it.
5. **have an improved sense of hearing and smell but do have slightly worse eyesight**-> improved hearing is covered in point 4 by the pointy ears (hearing additional frequencies is improved hearing in my book). It is suggested [here](https://phys.org/news/2011-12-good-evolutionary-advantage-neanderthals.html) that the sense of smell is "processed in the same brain regions responsible for processing emotion, motivation, fear, memory, pleasure and attraction" indicating that human and goblin cognitive abilities are loosely tied to smell. You could also make the majority of Goblin food be stationary, but hidden (like worms underneath the earth). This way Goblin food is found more by scent than by vision making the trait of smelling more selected for instead of vision for survival. Coupled with the fact that there are no large or super dangerous predators on Goblin island, there is no need for keen vision.
6. **have green skin (possibly due to a symbiotic relationship with a type of moss or algae)** -> The only animals I know of that are green like bugs, frogs, snakes, iguanas, are usually animals that don't move much and blend in with the environment to wait lurk for prey. Which would seem to conflict with the whole intelligent creatures that have a society vibe. Also conflicts with the size nerfs (as the lack of large predators will keep the size of population down by neglecting to select for size).
7. **have life spans similar to humans though they do reach sexual
maturity a bit faster than humans** -> There is some debate as to why some species live as long as they do with quite a number of [theories](https://jeb.biologists.org/content/208/9/1717). The only thing I can think of would be to have the metabolism and development of a Goblin baby to be incredibly high and then drop off dramatically when reaching adulthood. This way, they could age quickly to mature and then go on to live about as long as a human.
A large island, warm climate, scarce resources, natural Goblin food is either in the earth itself (worms/grubs) or hidden in some other way and has distinct odor, no large predators,
[Answer]
Consider goblins in the traditional role of dragon fodder and servants. Since I looked at orcs and mentioned they wouldn't be good laborers, perhaps goblins developed closely with orcs to fill the need for labor. If proto-goblin/halflings were enslaved by orcs, prolonged servitude under an aggressive and physically more powerful species would lead to a selection of individuals who were efficient at tasks but not physically large, powerful, or who even felt safe looking up at their masters. Eyesight might suffer if there were no advantage. Hearing would be important to anticipate tasks and avoid brutal punishments. A good sense of smell is important to separate safe from unsafe food when all you get are scraps. Green skin might be useful in any natural setting where the goblin would need to avoid being noticed or even a distinguishing characteristic to make orcs feel superior (depending on orc coloration). Sexual maturity could result from long-term pressure for goblins to give birth early to new slaves. Think old south. Pointy ears and long noses have as many possible reasons as there are ethnicities.
[Answer]
As stated by others, island dwarfism or selective breeding could explain the Goblin's size not growing past that of an ordinary *Homo Florensis*.
Their big noses and ears could easily be explained by living in a dark area;
Nixoncranium mentioned dense jungle underbrush. I would like to add *caves*, though, because small size would be an advantage when chasing prey through small tunnels and eyesight would be practically useless there.
While eyesight would be pretty useless in caves, hearing and scent would be *incredibly* useful; as evidenced by the Crawlers in *The Descent*, who navigate almost solely by those senses.
Their poor eyesight can also be explained by this quote about bat's sight from usgs.gov: "No, bats are not blind. Bats have small eyes with very sensitive vision, which helps them see in conditions we might consider pitch black. They don’t have the sharp and colorful vision humans have, but they don’t need that. Think of bat vision as similar to a dark-adapted Mr. Magoo (a cartoon character with very poor vision)."
Finally, caves are relatively scarce in resources, so the goblins will likely go foraging. This makes sight useful and therefore ensures it will be retained; but since sharper eyesight isn't an advantage in light-poor caves, it will remain poor throughout generations.
Green skin could be explained by:
1. Fungal layer-Caves come with fungi, it's quite plausible that the goblins, due to an unsanitary lifestyle, are coated in their very own layer of fungus.
2. Vestigial trait-Perhaps one of the Goblin's ancestors ended up with green skin and the Goblins kept it; it didn't hurt anything, so it stayed (like the vestigial claws on pythons).
3. Camouflage-When Goblins go out to forage the forests around their caves (I assume there are forests around their caves) green skin helps them blend in. This mutation arose out of nowhere generations ago, and since it kept the goblins who possessed it *alive* (as opposed to pale goblins, who stick out like sore thumbs except on, say, snowy mountaintops.)
4. Pigment Retainment-Perhaps the Goblins eat an awful lot of plants and green fungi. Regular humans can turn orange by eating an awful lot of carrots; a similar phenomenon could make Goblins green.
Their quick transition to adulthood could be explained by a harsh environment that makes lifespans relatively short for the vast majority; look at humans in the Dark Ages, which rarely lived to forty, or even thirty-two. The Goblins that reached sexual maturity faster were the ones who had offspring before natural selection got them, so that trait was found in all the survivors.
Later on, the Goblin's growing intelligence increased their safety and quality of life (and therefore their lifespans), and the Goblins who lived longer had more offspring, therefore outcompetiting their shorter-lived relatives. Finally, longer lifespans didn't cause a resurgence in slower-maturing Goblins since that trait had been (quite literally) killed out of the gene pool.
[Answer]
Imprisonment, torture would be the most effective way. Also being kept in harsh environment they are not naturally suited to would help as well. Being kept in very small spaces would prevent growth.
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[Question]
[
I am writing a short story about an overworked planet whose civilization has achieved space elevators and orbital rings.
The planet, which is earth-sized, has three complete orbital rings in stable orbit, each one 200 meters in width, which is about an eighth of a mile.
The rings are used for heavy construction and other industrial uses.
Where do you have to put the rings relative to each other for them not to have any issues or break, and should the rings be fixed onto the ground or allowed to orbit freely?
[Answer]
>
> I am writing a short story about an overworked planet whose civilization has achieved space elevators and orbital rings.
>
>
>
Note that there is no known material strong enough to build a space elevator. People will talk about carbon nanotubes, but even with the best manufacturing capabilities imaginable small imperfections in the material will reduce its breaking length to a point too short for elevators. With orbital rings you picked the best launch assist megastructure there is, since the ring is unchangeable regarding scalability, general utility, throughput and possible take of velocity.
>
> The planet, which is earth-sized, has three complete orbital rings in stable orbit, each one 200 meters in width, which is about an eighth of a mile.
>
>
>
Sounds perfectly reasonable dimension wise. Note that orbital rings have tremendous energy requirements to be started up, a skeleton ring will need half our annual energy production to get going as noted is [this paper, which will give you more information on orbital rings](https://jenda.hrach.eu/f2/Low%20cost%20design%20of%20an%20orbital%20ring%20-%202017-1.pdf), but the civilisations building them should have mastered fusion or off world solar or at least mass fission, so it will be fine.
>
> The sole purpose of the rings is to allow spaceships to enter orbit.
>
>
>
As Algebraist already noted is his answer, rings can be used for so much more. Definitely check out the Isaac Arthur video he linked, the guy is amazing. Concerning other things to do with the ring: hyper fast on planet transport, shellworlds, supermundane planets or megaearths, chandelier (hanging) cities (or gardens), colonising ice giants, gas giants and even suns and much more.
>
> Where do you have to put the rings relative to each other for them not to have any issues or break, and should the rings be fixed onto the ground or allowed to orbit freely?
>
>
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The simple answers are wherever and whatever you like. As long as the rotor sits in an orbital path around the planet and two rings rotors do not intersect everything is possible. Maybe having one equatorial ring for transfer to the planets habitat swarm and moon, one aligned with the systems plain of the ecliptic for interplanetary launches and one polar ring for power beaming receivers (Atlas towers will do the same) on the poles and more exotic launch trajectories is an optimal three ring setup.
I would suggest anchoring them to the ground, because one would lose so much of the rings utility if they were free floating. The only times you want to use free floating rings are when you are colonizing objects with no solid surfaces like ice-giants, gas-giants and suns.
[Answer]
There is only one orbit for a space-ring consistent with space-elevators - that is an equatorial orbit at an altitude above the earth's surface of approximately 35,800 km. At that altitude the ring will be in geo-stationary orbit - i.e. the ring will rotate at the same angular velocity as the earth-s surface so tethers stretching from the earths surface to the ring (i.e. space elevators) will not stretch or bend (significantly).
If you don't want to connect your space elevators directly to the ring (i.e. you have both, but they are independent from each other) then in principle you can have the ring in any orbit. That is to say at any altitude (outside the atmosphere) and at any orientation to the earth's rotational axis. So they could be equatorial, trans-polar, or at any angle you propose.
I say in principle, as:
* any orbital ring will be in an unstable equilibrium, so would need continual correction to remain in one piece;
* no materials are known to exist that could be used to construct such a ring;
And in regards to your comment
>
> The sole purpose of the rings is to allow spaceships to enter orbit.
>
>
>
A single space-elevator-tethered-geostationary space-ring has obvious benefits for getting materials into space in an energy-efficient manner (if you ignore the enormous sunk energy cost of building it in the first place). But I can see no energy, resource, or logistics benefit in multiple rings, so it is unlikely that this would be their "sole purpose".
[Answer]
Once you have a single orbital ring, your best bet is to make it wider and thicker. The places you bean stalks (space elevators) have extensions anyway for the counter weight to balance the weight of the stalk. Usually this is a small asteroid at around 100K from the earth.
For in system flights by matching speed with one of these exterior spoke (cable to a docking engine) you can save substantial amounts of fuel. Repeated encounters have to balance momentum in the long run.
See Arthur C. Clarke "The Fountains of Paradise" Charles Sheffield "The Web Between the Worlds.
[Answer]
# Any way you want.
*It depends on the energy you have available.*
To not tether them requires that you have thrusters of some kind to enable them to [maintain position](https://en.wikipedia.org/wiki/Orbital_ring) (ie. not crash into the planet).
The most energy efficient way to orient them would seem to be in line with the [ecliptic plane](https://en.wikipedia.org/wiki/Ecliptic), because this will require little energy to maintain.
Another possibility is that one could be as stated above requiring low energy to maintain, another could be in an orbit (since there are three) at 60 degrees to the first, another at 120 degrees. This arrangement would potentially require no energy to sustain it's orientation either. The reason why would be [gyroscopic stability](https://en.wikipedia.org/wiki/Gyroscope), It would mean that your planet would revolve beneath these layers, and the layers would stay on their own planes, relative to the stars (ie. not relative to the planet or sun). This would mean that the latter two rings would [precess](https://en.wikipedia.org/wiki/Precession) around the planet once a year, but since the planet rotates once a day, it would allow you to select which ring at which time you need to land on to be closest to any destination on the surface of the planet.
However: You can have them in any orientation you wish if you have the energy to counter the forces that would prevent their precession (Which would be quite prodigious BTW).
Ultimately, the whole thing would be a trade-off between the energy required to keep them from crashing into the planet versus the energy (if tethered) to stop them from deforming because of gravitational forces caused by the planet's rotational axis being not [tidally-locked](https://en.wikipedia.org/wiki/Tidal_locking) to the sun, not to mention the moon's pull on their bodies. It depends on the materials, the flexibility and the energy available to make them behave.
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Using the orbital ring itself for habitation is a poor use of its potential on a utility/unit mass basis.
To keep building up an orbital ring, you need to spin up the rotor even faster, or add mass to the rotor. Both are non-trivial requirements.
A more elegant solution would be to have a band or orbital habitats, connected together by physical supports but traveling at orbital velocity, with each habitat spinning to generate artificial gravity on the inside.
People planetside can hop on the elevators (they're not true space elevators, they don't bring you up to orbital velocity at the end), transfer to a maglev carriage on the orbital ring that accelerates them to match orbital speed with the habitat ring, then disembark unto whatever habitat they want to travel to.
You might even have a second maglev system for inter-habitat travel, which does not require the enormous rotor of the orbital ring.
Isaac Arthur did a good video on Orbital rings on YouTube: <https://www.youtube.com/watch?v=LMbI6sk-62E>
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If we were gonna develop a colony on mars would it be possible to explore geothermal energy and would it be viable?
(Assuming we could transport the required equipment)
**Edit:**
Recently I found this video, where Elon Musk actually mentions geothermal. Could he have some knowledge we don't know about?
[Elon Musk of SpaceX Introduces the Interplanetary Transport System](https://youtu.be/2rV35LZW8jM?t=1h8m40s "Elon Musk of SpaceX Introduces the Interplanetary Transport System")
[Answer]
Mars has lost most of its atmosphere due to the lack of a magnetic field, protecting it from the stripping action of solar wind.
A magnetic field is thought to be generated by a high temperature core; therefore it is plausible to assume Mars has a low temperature core.
Since the core will be always warmer than the mantel and the crust. Also the lack of observed recent volcanic activity supports the conclusion that the martian crust is cold. So it's highly unlikely that we can harvest high temperatures from the first few hundreds meters of the crust.
However we could still use the crust as thermostat for application like cooling down or preheating process fluids. I think this still count as geothermal energy.
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Looking online, we have [this](http://www.lpi.usra.edu/meetings/geomars2001/pdf/7044.pdf). Take home point is that whilst we have a temperature gradient of 30-35K / km on Earth, Mars may have a gradient of 6 - 10K / km. That makes geothermal energy very hard to do.
But it's worse than that. On Earth, you extract Geothermal energy by pumping water through rock formations that are already saturated with liquid water. The same paper shows that this won't be the case in the upper few km of the Martian crust. So extracting what warmth there is there would be harder.
As L.Dutch said, you could use the crust as a constant-temperature source for ground source heating/cooling, but actual geothermal energy is probably out of the question.
[Answer]
There might be large natural nuclear reactors on Mars.
From <https://www.hou.usra.edu/meetings/lpsc2015/pdf/2660.pdf>
>
> Previously, it had been hypothesized that Mars had been the location
> of large natural nuclear reactors[1,2], as are known to have occurred
> on Earth [3] This hypothesis was prompted by evidence of a large
> nuclear energy release in Mars past, and was considered the simplest
> hypothesis to explain the available data.
>
>
>
[Natural nuclear reactors](https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor) are concentrations of radioactive isotopes at concentrations high enough to undergo spontaneous fission. Some people think this happened or happens on Mars.
Those would be toasty warm and certainly suitable for producing geothermal energy. I would think they might be evident if someone made a heat map of Mars.
ADDENDUM: To be clear - I think building a colony atop a nuclear explosion is a poor idea. But if there are concentrations of fissile materials such that spontaneous fission happens in some of them, lesser concentrations should still have enough decay going on to produce substantial heat. Maybe steer clear of the really hot ones...
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One more detail, Earth's crust is much more active than Mars' because we have a (huge) Moon. The thermal energy that keeps the core liquid and generating Earth's magnetosphere comes from Earth's spin relative to the Moon. Moon's gravity field creates resistance on Earth spin -- called tidal force -- slowly halting it, so that eventually it will be tidal locked to the Moon (as Moon is locked to Earth, and Mercury is locked to the Sun). The heat that maintains our liquid core comes from the friction of this halting. So we have our thick atmosphere thanks to the magnetosphere, that we have thanks to the Moon.
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The premise: Radio-capable civilisations were detected on Venus and Mars in the late 1940s. At first by picking up accidental transmissions like radar pulses, then later with deliberate signals beamed to each world. Relations were reasonably cordial between the three planets, with regular data packets sent back and forth with cultural details and scientific collaborations. All was hunky-dory.
Then Mars had a nuclear war that wiped out most of their inhabitants, while Venus fell into religious in-fighting.
**The question: Given roughly 1970s technology, and assuming that we were paying some attention but probably not studying it intensively at the time, how much detail could Earth observe about exactly what had happened on Mars?** Would we be able to see individual detonations, or would the world just go silent? How much would it vary whether the planet was in opposition or conjunction?
[Answer]
# We would absolutely be studying them intensively at the time
This argument is just from human nature. Given that the Cold War was well underway in the late 40s, and a space race was about to begin, I can't imagine any other outcome from discovery of other civilizations in the Solar System then large-scale jockeying for diplomatic and scientific alliances between the West and the Soviet Bloc.
Given that, it is almost assured that both sides of the Earth divide would be heavily invested in looking at what was happening on Mars.
# There was plenty of excellent detection equipment available.
The [Arecibo Observatory](https://en.wikipedia.org/wiki/Arecibo_Observatory) was complete in 1963. The [Deep Space Network](https://en.wikipedia.org/wiki/History_of_the_Deep_Space_Network) started in 1958, and by the late 70s there was nearly full planet coverage in L- and S- band (on the border between radio and microwave). Optical range telescopes had already been numerous for centuries.
There were also plenty of in-space [satellite telescopes](https://en.wikipedia.org/wiki/List_of_space_telescopes) by the 1970s. [Cos-B](https://en.wikipedia.org/wiki/Cos-B) was a European gamma telescope launched in 1975; there were two [HEAO](https://en.wikipedia.org/wiki/High_Energy_Astronomy_Observatory_1) x-ray telescopes launched in 1977 and 1979; several UV telescopes including the Soviet Union's [Orion](https://en.wikipedia.org/wiki/Orion_%28space_telescope%29) series launched in 1971 and 1973; etc.
# A nuclear blast is easily observed from the distance of Mars
Let us assume that a 1 MT weapon yields 1% of its output energy as prompt gammas, using rough estimates from [Wikipedia](https://en.wikipedia.org/wiki/Nuclear_electromagnetic_pulse#Weapon_yield). That means 4.18e13 J is released just as prompt gamma energy. Given that Mars is 225 million km away from Earth, projecting that energy onto a sphere of that distance gives an energy concentration of 6.6e-11 J per m$^2$. Translating that into ergs / cm$^2$ gives 6.6e-8 ergs. While that isn't a lot, that is equivalent to the lower end of [observed](https://en.wikipedia.org/wiki/File:BATSE_2704.jpg) gamma ray bursts.
This is just back of the napkin math, but the power of a nuclear weapons indicates that the gamma burst at least should be clearly visible from Earth, and there were satellites in orbit such as the [Vela series](https://en.wikipedia.org/wiki/Vela_%28satellite%29) starting in 1963 that could detect such a burst.
# Conclusion
It is very likely that because of the attention we would be paying to this nearby Martian civilization, and because of the high energy gamma burst, the space agencies of Earth would know almost immediately if nuclear weapons were used on Mars.
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35% of the energy of a nuclear explosion is [released as electromagnetic radiation](https://en.wikipedia.org/wiki/Effects_of_nuclear_explosions#Thermal_radiation) to which Mars's atmosphere is mostly transparent.
Gamma-Ray Astronomy has been available since the [1960s](https://en.wikipedia.org/wiki/Gamma-ray_astronomy#Detector_technology) but depending on the [distance between Earth and Mars](http://mars.nasa.gov/allaboutmars/nightsky/mars-close-approach/) and when exactly your Martian war started and ended, Earth might not have seen anything at all (both on opposite sides of the sun), or Earth might have seen [individual explosions](https://en.wikipedia.org/wiki/Tsar_Bomba).
So if you fail to mention the season and the exact year you're in, you could go either way...
Or even write 2 novelettes in one book and have one front page be the mirror image of the other one and explore both story lines... **:-)**
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A while back I decided to [create a zombie virus to wipe out most of the human race](https://worldbuilding.stackexchange.com/q/34527/9498). That was fun and all, but now I'm faced with another problem - setting up a society.
I originally wiped out nearly all humans in order to create a better society, ridding the world of war and inequality.
Here's what's happened:
* Only a handful of humans (around 100,000) are left.
* Some things have been destroyed in the "fight", such as a few cities. However, it's not major zombie-apocalypse-movie destruction like the Eiffel Tower breaking.
* No technology has been lost (Except for maybe the most cutting-edge stuff being developed in labs at the time of the attack.)
* Farms and factories are still around, but currently there's no-one to operate them (computers still carry on as if nothing happened.)
* All the zombies have been wiped out, taking most of the human race with them. There is no more virus, and no more humans can be infected.
* As long as I can find a connected computer (which isn't very hard), I can use the Internet.
* I am in a group of around 100 people, found after wandering for a few days.
Now I need to set up a society and repopulate the Earth. Is it still possible? And if so, can I make it peaceful and equal?
[Answer]
There's several issues which should be addressed before you can establish a new world order:
**Laying the Foundation**
As Cyrus suggested, I would propose that you set up a group of people to kick start the re-population process ***before*** you unleash the virus. This way they will already look to you as their leader, and share your goals and ideals.
For example, you could gather a few hundred (or thousand) like minded individuals to come live on a remote farm. You can arm and organize them in order to protect and operate your facility - labs, fields, processing plants, etc. (the infrastructure doesn't have to be major, just enough to keep your group alive and at a decent tech level).
As survivors trickle in your group can indoctrinate and integrate them into your ranks.
As more and more people arrive you can start taking over the abandoned structures of nearby towns, and slowly expand.
Your group will have to be powerful enough to hold on to what they have, as well as impose their views on other groups they encounter.
If, for example, you run into a surviving military unit which claims that you should subject yourself to their authority, you must be able to convince them to join you, or fight them off.
If you run into a group of citizens led by a political figure who is trying to hold true to the Constitution/old government structure that might not fit with your ideology and objectives. You have to be ready to convince these people to join you, or take them out so that your ideology will prevail.
What this ultimately means is that you need a very dedicated group of people to act as the core of your community. A group of people who will borderline worship you, look to you as their leader, and follow your orders no matter what. It's far more difficult to establish this in the post apocalypse world than if you lay the foundations before hand (establish self sufficient facilities, recruit people to your cause, purchase arms, ammunition, seeds, provisions, etc.)
**State of the World**
A lot more technology will have been lost than what you're assuming (unless, of course, you also took major steps to preserve it). Keep in mind that you've killed off almost ***7 billion*** human beings.
The world you'll be inhabiting is one forever changed. In the US alone you'll have 300 million bodies littering the landscape. This will cause pests, predators, and disease to run rampant. Animals which before were no threat to man will now multiply and get used to feasting on human flesh. This is a very dangerous setting for your followers.
Without human supervision a lot of infrastructure will have been destroyed as well. Power plants left untended will have suffered severe failures, fires, or elemental damage. Data routing centers will have similarly shut down due to loss of power, or other damage. This means that no, you ***won't*** simply be able to access the internet from any powered terminal.
Infrastructure will have been destroyed in humanity's fight against the zombies. Fires left unchecked will have burned down entire towns, and might still be raging in large cities more than several months after first being started, engulfing skyscrapers, and residential neighborhoods alike - the pollution would further harm survivors.
It won't be as easy as simply walking out of your bunker and claiming the world.
**Loss of Technology**
The sad fact is that the average human being is no smarter than people were 500 years ago. Sure, we're a little more educated, and have developed a different skill set than our farming ancestors, but it's still only that: a limited skill set.
What am I talking about and why is it important? People may know how to use a cellphone, or drive a car rather than plant and till a field, however very few of us understand the underlying principles or those technologies.
Good examples are cars, computers, and cell phones - something we take for granted on a daily basis.
Most of us know how to operate a motor vehicle, yet few of us have any idea how to perform more than minor maintenance, if that. If a car breaks down you need the help of an expert - a mechanic. The mechanic is, to us, a bit like what a blacksmith was to villages of old. He's an expert that can help you get your horse/cart/tool back in working order. However, while a mechanic may be able to take an engine apart and figure out what's wrong with it, he can't manufacture the complex parts needed to repair it. Specialized manufacturing capabilities and engineering knowledge is necessary for that. Experts in those fields don't grow on trees, and neither does the technology itself.
Computers are ubiquitous in our world. However, very few of us can take one apart and rebuild it. Even then, how many people truly understand how a motherboard, and RAM chip works? How many of us could build one from scratch? With what tools? You get my point. Cell phones are the exact same.
It was estimated, in a report I read a few years ago, that if you were to kill the top 10 000 or so technical experts in the world you would stop human technological advancement in its tracks, possibly for decades, and set civilization back, technologically. Why? Because only a very small number of experts *truly* understand the underlying principles behind a lot of these technologies. A lot of us might have some theoretical knowledge, or understand, in broad terms how a piece of technology operates, but only that handful of people would be able to sit down and design/build that piece of tech you take for granted.
And guess what. You've killed them all. This means that your group of survivors might scavenge technology from stores, warehouses, etc., but no human being will be advancing science again any time soon. You've successfully crippled the human race for ***generations***.
**Ideological Inconsistencies**
In your title you claim that you want a more *peaceful and equal society*, however you're starting off my killing *7 billion people*. ***That right there is a red flag.***
Once society has completely crumpled you will step out into the battle scarred, corpse covered world, and find that chaos and violence rule the planet.
Groups of survivors will be living hand-to-mouth, scavenging the left overs from humanity's golden age. They will fight one another for the scraps of food, technology, ammunition, and fuel which they've collected. Bandit groups will roam the country - they will need to be dealt with, which undermines the idea of a peaceful society right off the bat.
Furthermore, in the absence of human beings predators will have bred and become far more confident. Wild animals will pose a pretty serious threat to people from now on. Your followers will need to defend themselves, which breeds a mindset of being ready to kill and be killed, not peace.
Last but not least, you've effectively plunged the world into a **Dark Age**. This is **not** a state of being which encourages equality between the sexes. Arguably, it's the industrial revolution which truly allowed women to emancipate themselves.
In a farming society which doesn't have the fuel or technology to sustain a modern farm women will ultimately revert to secondary roles. I'm not trying to be sexist, or misogynistic - it's simply the truth, however unpleasant. A woman cannot physically work the field the same way a man can, however your community will starve to death unless those fields are planted, tilled, and harvested.
This means that men will be required to perform the heavy lifting, while women will revert to the role of house wives: cooking meals for the men, raising the children, etc.
Some technological left-overs will allow them to perform other tasks. Modern firearms, for example, will allow a woman to just as effectively defend a fixed position as a man.
However it will become a lot more difficult to maintain equality when your society will slip back into classic gender roles (which are what allowed humanity to eventually reach this level of technological prowess - this was a "good thing" in the past, but simply not justifiable in our modern society).
Even if your community somehow manages to retain the mentality and technology which allow women the same rights, privileges, and opportunities as a man (due to your brilliant leadership, of course), that will *certainly not be the case* in most of the rest of the world. Women will have a tough going of it in this post-apocalyptic scenario.
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If you want to make it peaceful and equal, I would suggest having the virus strongly biased towards aggressive people. I am tempted to suggest "testosterone", but that would also target men.
Alternatively, make people somewhat "blissed out" by the cure. This is harder, because you say the virus is gone, so there's no real reason to keep up taking whatever the cure is. Addiction? Maybe the virus is dormant?
You would definitely want the virus to take out the army (which should be easy - they are on the front lines), especially those making the decisions (less easy - they're likely to have access to bunkers).
Perhaps taking marijuana would offer protection from the virus, so the remaining people have a high marijuana use?
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Problem #1: 100,000 people on the face of the planet. How do you collect all the survivors? How do you communicate with them? How do you run needed infrastructure for anything?
The power grid will fail and the internet exists across the entire planet, Google servers however, may have a huge portion of it copied. Still need to keep some power plants running just to keep up local power supply. Your average coal plant has enough coal for power generation from 24hrs to about 3 weeks. Granted they are powering huge areas and this can be reduced, still you are limited in time.
You need power to run the sewer and water. Books are your best source of information that will survive. Survival will be difficult. Granted there might be enough canned and dried food to last a few years but food production will need to be high on the list of things to do.
How do you collect enough people to start your new society? To fly around the country you'd need a plane, fuel pilots license and knowing which airfields have enough fuel to fill you back up. Then you need to find people and convince them that you have a better solution than staying where they are.
Overall, you would have much more success if you started planning this and recruiting your cult following before you release the plague. If you have a vaccine that protects them you can go a long way to convincing them that you are a worthy leader.
So if you wait to see who survives you will not likely be able to have much influence on the survivors. They will likely tend to be independent people distrustful of others. Might just brain you if you try any funny business. But if you have plans at the start. Know where you want to hold up, plans on how to survive and live afterward, then the other survivors would be inconsequential to your plans of world domination and personality cult.
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First, let us define what's peaceful. Fortunately for us, efforts have been made to give a *peace index* to countries on Earth. This is the **[Global Peace Index](http://www.visionofhumanity.org/#/page/indexes/global-peace-index)**, at Vision Of Humanity.
>
>
> >
> > The GPI is a composite index that measures peace based on 23 qualitative and quantitative indicators...
> > The 23 GPI indicators can be classified under three broad themes: ongoing domestic and international conflict, societal safety and security and militarisation.1
> >
> >
> >
>
>
>
Now that we have an empirical metric by which we can follow, if we want to be peaceful all we have to do is find which country has the lowest score (the closer to 0, the better.)
The top three most peaceful countries in 2015 were Iceland, Denmark, and Austria. These are the role models that we should follow. According to United Nations Office on Drugs and Crime, Iceland has on an average an annual intentional homicide rate of... one. Just one person.
The reasons behind Iceland's peaceful nature have been deemed to originate in Iceland's lack of immense class divides - it's pretty evenly divided among all of its citizenry. There's also a distinct lack of hard drugs - according to a UNODC report in 2012, cocaine, ecstasy, and amphetamines had a usage rate of less than 1% by 15-64 year olds.
With a clean slate, you have a lot of time to figure out what causes strife. The problem is that you have to collect the survivors, and convince them that peace, logic, reason, kindness, and lack of classism is a *favourable* thing, and convince them that your landmass of peace is going to fare better for them than whatever place they decided to hole up in.
Maybe you're lucky, though. Maybe the survivors will find that they can't survive without cooperating with each other, and over time, their lack of cooperation will be their downfall and the problem population that you are trying to convince kill themselves off. Not your problem anymore.
Assuming you can gather up a lot of people in one place, you can start by... divulging the same information I just posted above. If you can talk to a leader or if you are a leader, you can gather up as many people in your location as possible through a strategic recovery or call (radio, internet, whatever is left over) and have talks of peace and how to maintain it.
You're going to have confrontation, though. And you only have one option - convince them, or take them out so your ideas are the ones that survive.
Or who knows - maybe you'll be lucky and the only survivors will be Jainists.
1 For a larger list of all of the indicators, you can find that [here](https://en.wikipedia.org/wiki/Global_Peace_Index#Methodology).
[Answer]
Public utilities (power, water/waste, communications (cell/internet) will fail relatively quickly. These all need constant maintenance and something so small as a circuit breaker tripping at a major distribution point can wipe out the grid for an entire county (been there, seen that).
Assumptions:
* the virus has exhausted itself
* I am in my *current* location (general environs of Southern California) (i.e.: shelter is not a priority)
Priorities:
* Organization and delegation of responsibility (my take on standard Army org).
1. G-1 Personnel and recruitment
2. G-2 Intelligence and Communications
3. G-3 Planning, Ops and Training
4. G-4 Logistics
* G-4 Acquire transportation and stake out fuel depots. We can probably pump gas until the grid goes down. Finding a fuel truck is high priority, it can pump it's own fuel, can transport it, and hold a lot. It can maybe even pump fuel out of the tanks at gas stations after the grid goes down.
* G-4 Find gun and sporting good stores. Get weapons and ammo, get water purifiers and containers. Try hardware stores for rain water collection cisterns. You will need the weapons and ammo to defend yourself, enforce your rule, or just keep them out of other peoples hands.
* G-2 Hit up Ham Radio Outlet, get radios (portable and base stations). Also look for houses with both solar panels and radio masts. These can be long lasting comm centers.
* G-3 Hit up libraries, bookstores and homes for books. Everything is needed but look for the Foxfire series and books that explain how to live off the grid.
* G-1 Start a big fire on a hilltop somewhere. Use a tarp or blanket to interrupt the smoke stream (the smoke will be seen for a long distance, interrupting indicates it is under intelligent control and not just an accidental fire).
* G-3 Start disposing of the bodies.
Longer term projects:
* G-1 Develop specialists
* G-2 Get a pilot from G-1 and start searching for other groups
* G-3 Start a school system
* G-4 Start a farm
[Answer]
Peaceful society will be farther away, for few reasons:
* military training camps will be the most likely groups of people who are **trained, ready, and have tools and independent infrastructure** to fight off zombies and preserve the technologies they need to survive.
* other groups of survivors will naturally try to get under the protection of such military groups. Cities will be useless, because infrastructure will fail without constant maintenance. Cities will be targets to occasional raids to get materials to bring back to camp.
* you grossly underestimate the fragility of the infrastructure. Without constant maintenance work, it will fell apart, factories will burn by accidental fires. Power plants will stop producing electricity, and internet servers will be bricked. After [Northeast blackout of 2003](https://en.wikipedia.org/wiki/Northeast_blackout_of_2003), it took from 2 days up to a week to restore power to some remote areas, while thousands of specialist were available to fix the problems. Your scenario has nothing like that. **There is NO electricity or internet** (except maybe small local sources on camps).
* 100K survivors, spread in groups of few hundreds over planet, will have little means (or reasons) to communicate, and will have hard time to produce enough food to support themselves and necessary scientists. Technology (and medicine) will quickly revert to pre-industrial.
* Survivors would have no reason to be nice and share knowledge or resources between groups. Your primary allegiance would be towards your tribe. If next tribe takes over your resources, they may pick some survivors, if they can benefit the tribe - and banish the rest to the wilderness.
Next steps:
* get to some library and find a book (no electricity required) about how to make steam engine.
* find a skilled carpenter who can make crossbows for your team, so you can defend yourself after you run out of bullets
* whichever tribe figures out first how to make gunpowder will rule the planet.
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[Question]
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Experience shows me that some people dislike when a given world has monolithic species. By this I mean the planet has one culture, language, empire or purpose that unifies all of its member. Most that dislike this idea claim it is not realistic, judging from humanity and Earth.
Since it's not obvious, I ask: *What leads to monolithic races, and what would lead to diverse ones?*
[Answer]
Not to rip off an old guy in a robe but...
>
> Luke, you're going to find that many of the truths we cling to depend greatly on our own point of view.
>
>
>
**We as humans view humans as very diverse**. We vary wildly in terms culture, society, intelligence, color, gender, language, architecture, literature, weapons...I could go on but you see my point.
All that said **there are certain things that unite us.** We are all bi-pedal, we breathe the same air, heck, we share something like [99.5% identical DNA](https://en.wikipedia.org/wiki/Human_genetic_variation).
Now if we look back at our own history how did (as an overused example) Europeans treat the indigenous cultures they met? They were treated as "them" and the Europeans as "us". If you go back even further you could get to the point where people a day's walk from one another would have viewed each other as "not us" and when you view people in such a way **it is very simple to utilize a working assumption that they are all the same.**
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Why the brief overly simplified history lesson? Well now let's imagine that we are in the far future, or maybe next week...either way. We find out that there are aliens out there in the universe, and like us they all have the same form (not appearance, but general shape and structure).
Would we not view their planet as a whole? It is a matter of how much you know and how much you experience of a different group how well you are able to see and understand the differences within the group.
I personally (though I know better) have tendencies to view certain foreign nations as a monolithic whole. I know its wrong but its a shortcut we humans developed to put the world in simple easy to navigate lanes.
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The short version is I would suggest that **we are both diverse and monolithic** simultaneously based on our level of familiarity. Variation is good in genetics, so there will always be differences, but that doesn't mean we aren't a whole lot like everyone else on the planet...whether we want to admit it or not.
One exception, or special case I can think of would be the case of a sentient species that shares a mental link/hive mind. In this case you could well see a far more truly monolithic society.
[Answer]
People may be of the ***same race***, but have ***different cultures***.
They may be of ***varying races***, yet ***share a culture***, and thus be as brothers.
Even two different species may cohabit as long as they share an understanding, or a culture.
The deciding factor is typically ***culture***.
The more spread out a race is the more chances that culture will fragment, or change.
It will depend on the culture itself, and on the leadership of those people, whether this will be catastrophic or not.
Take the United States: immigrants would assimilate into the American way of life. They might speak with slightly different accents, and crave different foods (cultural fragmentation), but overall, they were all still American, and would fight for their country/help their countrymen.
Now look at Europe and the middle eastern migrants: millions of people roam across the continent with no regard for borders, or laws. They demand special treatment, aid, food, benefits, yet fail to learn the language of the land, and don't even attempt to integrate.
How a race/culture holds together (or not) will depend on their own customs and their leaders.
[Answer]
I'm first going to ignore the more difficult problem: culture. Let's first concentrate on the slightly simpler problem that we know (or at least are fairly sure of) the answer to: race. Specifically, the biological definition of race: haplotypes and haplogroups.
First let me give some simplified definitions of these words in case you are not familiar with them (though I recommend googling them if you find this topic interesting):
* A haplotype is a set of genetic differences that are usually inherited together. For example, the genes that give someone blond hair will usually be inherited together with genes that give them pale skin. It should be noted that there will always be exceptions in a population but there will also always be a general pattern.
* A haplogroup is a population of individuals that share common or similar haplotypes.
When talking about humans, we link haplogroups to races. It should be noted that they are not strictly equivalent. Each traditional "race" is usually made up of several haplogroups. For example, this is the haplogroup distribution of the Turkish people:
[](https://daftareyaddasht.files.wordpress.com/2015/06/turkey_y_chromosomein_20_haplogroups.png)
So each race is made up of many haplogroups. You can think of haplogroups as "genetic race" or ancestor race. Each race we recognise today is made up of many ancestor races instead of just one.
When talking about animals, we link haplogroups to breeds. Just like humans, each breed is made up of several haplogroups. Also just like human races, a breed is not a species. Different breeds of a species are still a member of that species.
Now that we have established an equivalence between breeds and races, let's talk about the simpler case: animal breeds.
Some species of animals come in a wide variety of breeds. The most obvious example is probably dogs. Some may not realise it but all dogs are of the same species: *Canis lupus familiaris*.
Some species of animals on the other hand come in only a single breed. One example is the mallard. Excluding crossbreeding with other species, there is only one breed of mallards.
Most animals are somewhere in between. Most species come in three or four breeds scattered geographically.
So, what determines the number of breeds a species has? For dogs it's obvious: we created them deliberately (basically inbreeding). For mallards (and most migratory birds) the reason that there's only one breed is that the species is highly mobile (they're migratory after all) and all members of the species have the same opportunity to mate with any other member. This results in a homogenous species. For most animals the number of breeds correlates strongly with the number of herds/pride/gang/groups there are and how isolated they are from each other. The main reason breeds exist is because not everyone in the mallard species can mate freely with anyone else. Matings mostly occur in the same neighbourhood and very rarely between two populations. So basically inbreeding.
Now, the exact same reason determines how races developed in humans. Since humans are scattered everywhere on the surface of the planet and travel is expensive it is more likely for people who live in the same area to start a family and very unlikely for people who live far apart to do so.
Having stated that, of course it's obvious! I didn't even need to explain about genetics and all the examples with animals. But it's important to correctly identify the real factors involved rather than just stating the obvious.
So the factor that determines how diverse or monolithic a species is is simply isolation. Make travel cheap and easy and you end up with a species that only have a single race. Make travel expensive or restrictive and you end up with diverse races. Make society accepting and inclusive and you eventually end up with a single race. Make society racist or biased (no matter how subtle) and you end up with diverse races.
Culture works sort of the same way. Culture is our shared experience of what a society is. Thus when we isolate a group of people (or they isolate themselves) they tend to develop their own in-jokes, their own sense of right and wrong, their own sense of style etc. Culture is also different in that it can spread through the media.
[Answer]
**It depends on the technology level of the world.**
If you live in a world where the majority of the populace will never travel more than 50km from their place of birth, it doesn't make sense for people who live on different continents to speak the same language. Languages evolve and change over time, and without steady contact, different regions will evolve different dialects, and then different languages, fairly quickly.
On the other hand, if you live in a world in which everyone is exposed to the same media, and in which teleportation technology makes distance between individuals irrelevant, it make more sense that everyone would be part of the same culture. Dominant languages will become more dominant if most people interact with someone who speaks them on a regular basis. Cultural exchange also happens much quicker.
Consider our modern world, in which India is moving towards English as its common language and lots of people celebrate Christmas. Without rapid transportation and communication, that would have never happened. If technology continues to develop and make communication and transportation even easier, I can see cultures like the Indian and American cultures in the modern day moving towards a point where modern humans would consider them to be broadly the same culture.
However, even in a tightly linked world, there are likely to be different *sub-cultures* within a larger, unified culture. For example, in the US, even though most Americans live similar lives and celebrate similar traditions in similar ways, a subculture of gamers and a subculture of football fans exist and are distinctly different. They speak the same language, but have broadly differing jargon and slang which they use to communicate. They live large parts of their lives in very different ways, and form into distinct communities that celebrate different events. While there is some crossover and overlap between the two subcultures, they are nonetheless very distinct from one another. It's likely that any world, no matter how unified would have a wide variety of such subcultures based on people's differing interests.
[Answer]
What has made the visible differences in Human beings is populations being relatively isolated from each other, and in living different environments with different selection pressures.
So if I were to postulate an entire species that for an extended period of generations had
* Total communications
* Little or no travel barriers
* No cultural inhibitions on mating selection for "racial" qualities.
Then you may well have a wide range of genes exhibited in that species, but no self-reinforcing homogeneous groups that one could call a "race".
If you instead don't have one or more of those factors, the two gene pools will eventually start to diverge over many generations.
So if you had a species that had instant communications and travel over its entire range (eg: One planet, with better than modern travel and universal global network and media access, or perhaps multiple planets with some kind of teleportation), then it might be feasible for there to be no discernible "races".
[Answer]
The first thing that comes to mind in the situation of a remote colony is the "founder effect". The common example of this is "the Island of Red-bearded Men". If a remote outpost is established with 20 married couples such that the 20 male founders all have red beards, then even though they were not directly related the subsequent generations will all have this as a prevalent trait.
You can expect an isolated colony to have low diversity within its population and vary greatly between such colonies.
But you said a "world". Does the world have multiple distinct populations? Is the total population large or small?
The answer isn't a simple single result, but for realism would depend on the details of the world in question.
Now, what we call races are, biologically, superficial constellations of externally visible traits. What set of features constitutes a "race" depends on what the population differences happen to turn out to be, and what people notice. For example, in the culture I'm familiar with we don't consider eye color to be significant. But you can well imagine that it could become the visible distinction between two valleys' populations, and they compete for resources after a period of isolation.
For a fictional setting, you might pick combinations of features that are different from present day "races", especially to point out awareness of that: in a famous Star Trek episode it wasn't until the closing line that they said what the difference was between the hostile groups, and this baffled the outsiders and the original audience.
] |
[Question]
[
Imagine a powerful being of your choice casting this spell on Earth:
1. Earth can hold only 8 billion people
2. If a child is being born and this child breaks the 8 billion rule, this happens:
3. Wait 30 minutes. If someone else dies in this time, then everything is OK
4. If not, take every human older than 32 minutes, and randomly kill one
If step 4 happens, such a person always dies by a sudden heart attack. If they cannot have a heart attack, they simply stop breathing. If they cannot stop breathing, their brain will simply stop working.
Example:
```
22:00:00.000 UTC: Earth population: 8.000.000.000 people, waiting...
22:00:00.015 UTC: Live child (A) is being born in Pakistan
22:15:00.389 UTC: Live child (B) is being born in USA
22:25:13.618 UTC: Someone in Mongolia dies of age. Child A is resolved, Child B still pending
22:32:00.015 UTC: Treshold for Child A, it can be given to random pool
22:45:00.389 UTC: Child B is still unresolved, start random search...
22:45:00.390 UTC: A hunter in Siberia gets heart attack and dies
22:45:00.391 UTC: Earth population: 8.000.000.000 people, waiting...
22:50:05.850 UTC: Plane crashes in China. 190 people dead. Next 190 children can be born without killing anyone extra
```
For the scope of this question:
Alive == Brain activity.
Dead == no brain activity.
So if someone manages to survive a heart attack AND lung failure, their brain will simply shut off. So, you can keep their body "alive", but take for granted that such a person will never wake up (and they are taken out from the Earth random pool, because they are dead).
**The question:** Will humanity ever find out that such a rule is in place?
It is estimated, that we will hit 8 billion people milestone by the year [2026](https://en.wikipedia.org/wiki/World_population_milestones#The_Day_of_Eight_Billion).
I know it is safe to assume that in (say) the next 10 year, people will somewhat realise that something weird goes on. But will they be able to pick this magical link?
And what would help them to do so? Do I have to create an alternate Earth, where there is more magic than just this one?
[Answer]
Something will send up a flag, if the population count appears to stall at 8,000,000,000. At first I thought it will likely take a few years past the mark to notice that overall population isn't increasing and maybe one or two more to narrow down a close number. However...
Looked it up it appears that the average death per day is 7.89/1000 people, the average births/day is around 20/1000. So there are over twice as many births as deaths/1000 people on the planet. Using these numbers once we hit 8,000,000,000 people the death rate will automatically more than double. That will be a huge flag for statisticians. And when the birth rate and death rate remain steady and equal (unless a large war or other event INCREASES the death rate) it will be pretty obvious that SOMETHING is going on artificially limiting the population.
The scary thing is that once the pattern is noticed, wars and genocide might be waged in order to 'choose' who will die, not us, but THEM!
EDT:
One last thing, if we discovered that being off Earth negates the 'spell', meaning it doesn't matter how many people are living on the moon, then we will start working hard at getting off this ball and colonizing the solar system.
[Answer]
The first sign that something fishy is going on probably will not be the stable population but rather the sudden, sharp, unexplainable increase in healthy people getting un-curable heart attacks for no apparent reason.
Since medical statistics are kept by all civilized countries, which normally also have the highest chance of saving people (especially young ones) from heart attack, you would probably notice something fishy going on really fast.
Once you compare statistics and do calculations, it should not be very hard (especially after a few months/years) to reach the conclusion that the number of random heart attacks correlates strongly with population in each country, which in turn leads to the conclusion that it's a global thing.
From there, you can count backwards to when it started to happen all of a sudden using existing statistics, and then link it pretty easily to the birthrate and come to the conclusion that it must be related to people being born vs people dying.
Personally I'll give it half a year before we figure it out, but much longer before we believe it and even longer before we can convince other people that something magical is happening.
] |
[Question]
[
If you see this type of road and you are Czech, you are going to say, that is made from cats heads:
([Image source](http://commons.wikimedia.org/wiki/File:Vrtbovsk%C3%A1_zahrada,_obl%C3%A1zky_dl%C3%A1%C5%BEd%C4%9Bn%C3%A1_cesta.JPG))
Imagine I am [Joe the Average, who was sent to medieval Europe](https://worldbuilding.stackexchange.com/questions/13030/what-could-an-average-modern-human-achieve-in-medieval-times) (by accident)
Not only I managed to survive, but also I managed to gather group of people to help me survive. These people believe that I am black mage possessing infinite magic powers (thanks to lighter forgotten in my pocket)
I would like to support this kind of thinking also in other medieval people. And because I did read far too many bad fantasy novels, there is idea in my head: What if I built myself **bone castle from actual bones**? And what if the road to such castle would be made from actual skulls?
Is it possible?
This question has one big handwave and assumption: Everyone is willing and wanting to help me. I know that it would not happen for real, but please accept this assumption and focus only on one aspect of the whole story: Building material.
**Rules:**
* I want to build building using only bones and skulls
* Such building should provide enough room for at least 10 people
* I am building it in "generic medieval Europe" (say around year 1400)
* Which means that such building should withstand all four seasons
* I do not want to kill people, so all the bones will be animal bones. Any animal which was living around year 1400 in Europe is allowed.
* And I would like to use bones and skulls as much as possible
Given the premise that everyone is willing to help me - am I able to pull it off? Will such "castle" be livable?
[Answer]
You say it wouldn't happen for real, so I'm guessing you are not familiar with the amazing Sedlec Ossuary, which is decorated entirely with human bones. Turns out in the middle ages, life was so cheap they didn't know what to do with all their human bones anymore. (Most of the bones used here are from plague and war victims.)
So it might not be as intimidating to medieval people as you think it will be.
That said; making the outside of your building from bones is a terrible idea. Bones are brittle, and they suffer from decay. Such a building would not be able to reach any kind of height before the bones would start collapsing under its own pressure. Besides, it would not keep the bone shape anyway if you want to make closed walls, and you do because otherwise the wind will cut straight through it.
Your best bet is to use the bones for decoration, but even then, the actual people of the middle ages have you beat because they already do that if they have the bones to spare.
[Answer]
Your road would be fairly easy, you can use most any thing as aggregate or cobble*stone*, worst case scenario the skulls eventually break up and form a looser gravel road...
Structures on the other hand will be more difficult, bone has pretty good compressive strength, but poor shear strength; a good deal of both is lost when the bone is no longer living.
It looks like building primitive structures with bone has been done though:
<http://donsmaps.com/mammothcamp.html>
It looks like the main problem you'll likely run into is weather proofing. Most primitive bone structures would have been covered in hides and furs to keep them warm and dry. But that would make your elaborate bone structure look like any other medieval tent and thus would defeat the purpose.
If you're open to incorporating other building materials you could, more or less, use bone as a building block and mortar them together, but your structure would end up being mostly mortar.
[Erik mentioned](https://worldbuilding.stackexchange.com/a/15014/7351) that medieval people were already using human bone for decorative purposes, so I doubt that a structure made from animal bone would have the intended effect. You would likely be seen as primitive rather than scary.
If I really wanted to scare medieval locals, I would tap their fears of witchcraft and damnation with [modern body modification](http://en.wikipedia.org/wiki/Body_modification). Extreme [piercing](http://en.wikipedia.org/wiki/Body_piercing), [tattooing](http://en.wikipedia.org/wiki/Tattoo), and [suspension](http://en.wikipedia.org/wiki/Suspension_%28body_modification%29) would go a long way to ensuring that you were feared and viewed as a "black mage".
[Answer]
Eskimos used [whale bones](http://digitalcollections.lib.washington.edu/cdm/ref/collection/alaskawcanada/id/1303) for Construction purposes. Both for making homes (the supports) and their kayaks, a large reason of course is because they don't have other building material handy, (meaning trees). At least in the places they are using these materials.
[Answer]
Build the structure form Adobe and then seal the bones into to the stucco on the outside of the walls for a suitable sepulchral effect. Otherwise, bone breaks down too fast to be helpful.
Now for something super scary, my favorite technique this week, Catalan vaulting, can be used to create a Skull shaped structure that would be very strong and enduring. It doesn't have to follow the same rules as a traditional vaulted structure. It can also follow a free form shape.
[Answer]
You could build a castle with a building shaped like a skull, as in John Dixon Car's mystery novel *Castle Skull*.
The gateways to your castle could be sculpted to look like the mouths of monsters and you could have the gatewway to Hell inscription of Dante's *Inferno* inscribed: "Abandon all hope, ye who enter here".
] |
[Question]
[
Is it possible to have a planet that is both bigger than Earth and weaker in terms of gravity? I've got an idea about it being less dense, but I don't know what to do about its magnetic field. I need to know this because I desperately want to write a short story involving human-powered flight with artificial wings. To clarify, what would the requirements be to have a planet larger than Earth, with weaker gravity, and a magnetic field strong enough so that people don't need extra protection from solar radiation?
[Answer]
Bigger planets don't always have greater masses. Remember, mass and volume are related by
$$M=\rho \frac{4}{3} \pi R^3$$
where $\rho$ is density. Make $\rho$ small enough and the gravity and be as weak as you like. So the answer to the title question is a firm "yes." I did some playing around with this based on mass-radius relations by [Seager et al. 2008](https://arxiv.org/pdf/0707.2895v1.pdf) and created a modified plot of mass and radius based on several different compositions:
[](https://i.stack.imgur.com/ECICX.png)
The blue shaded region is the allowed subset of parameter space with planets satisfying $R>R\_{\oplus}$ that have surface gravities less than Earth's - the properties you want. Very few terrestrial planets occupy this area, and few are primarily silicates, like Earth. Your planet is likely to have significant quantities of water and may be an ocean world.
>
> with weaker gravity, and a magnetic field strong enough so that people don't need extra protection from sun radiation?
>
>
>
This is trickier. According to the [dynamo theory](https://en.wikipedia.org/wiki/Dynamo_theory), the magnetic field is governed by the induction equation
$$\frac{\partial \mathbf{B}}{\partial t}=\eta\nabla^2\mathbf{B}+\nabla \times (\mathbf{u} \times \mathbf{B})$$
where $\mathbf{B}$ is the magnetic field, $\mathbf{u}$ is velocity, $t$ is time and $\eta=1/\sigma\mu$, where $\sigma$ is the electrical conductivity and $\mu$ is the permeability. Note that nowhere in there is a term involving the radius of the core. In the nonlinear theory, density does come into it. But that's the density of the material in the *core*. The planet could have a large mantle that contributes significantly to its radius. So the magnetic field can be any (reasonable) strength you want; it might not be impacted by planetary radius.
The tricky thing is that while the magnetic field protects us from the solar wind, we also have to worry about UV radiation. That's why the ozone layer is our saving grace, so to speak, and why its depletion by chlorofluorocarbons is such a big deal. I bring this up because a planet with certain characteristics (i.e. much bigger and yet less massive) will have a weaker gravitational pull on its atmosphere (with the strength depending on radius and mass).
Lighter gases escape easier from a given planet than do heavy gases. That's why the Earth lost any primordial hydrogen and helium envelope it might have had. Make this planet too big and you risk losing ozone. Sure, the planet would have to be pretty big (while staying at the same mass), but it could happen. A stronger magnetic field *might* solve this, but its contributions might not be too great.
[Answer]
A strong magnetic field comes with a heavy iron core, so a significantly lower density than Earth is probably out.
Fortunately, a magnetic field isn't the only way to get protection from radiation. A thicker atmosphere will block a lot, with the added bonus of making it easier to fly.
You also have the option of accepting a certain amount of radiation, especially if you limit the time spent outside. Sleep underground, and you can handle twice as much radiation when you are out flying around.
The low gravity and solar wind exposure may make it hard for the planet to hold on to an atmosphere, but that would happen over millions of years. Native life may not have time to evolve, but it wouldn't be a problem for humans visiting or for life introduced from elsewhere.
[Answer]
If you want terrestrial planet I strongly suggest to take a look at this video [The Trouble with Terrestrials](https://www.youtube.com/watch?v=bUPypOgNs_A) that explain what are the bound of the terrestrial planet it is based on this [paper](https://arxiv.org/abs/0707.2895) check chart on page 19 on what are your choices regarding planet size and composition.
[Answer]
Uranus has a gravity of 8.69 m/s2 at the surface, compared to Earth's 9.81, and if I recall correctly it is somewhat larger than Earth. (I just happened to see your question and looked this up - you didn't technically rule out that the planet is a gas giant, though it's probably not what you had in mind.)
[Answer]
Yes, it can be possible, and I can give you a solid example that exists in real life, and that too, in our solar system.[](https://i.stack.imgur.com/jSE32.png)
Ladies and gentlemen, I would like you to meet Uranus. (no pun intended)
Uranus is about 4 times wider than the Earth, and is 14x the mass. Yet, Uranus has the same gravity as Venus, a meagre 8.87 m/s2. Uranus has about 10% lower gravity than Earth's.
The reason for this is density.
Take a look at Saturn for example. It has nearly a third of the mass of Jupiter (95 earths) and yet its gravity is about 10.44 m/s2. This is because Saturn is less dense than water, and is so voluminous, that its **surface** gravity is really low. Saturn's surface, or atleast the altitude above Saturn's centre, where the pressure is roughly similar to Earth's atmosphere, is really far away from the center.
Uranus, similarly, despite having 14x the mass and 4x wider than Earth, has only $\frac{1}{4}$th of Earth's density, (1.27 g/cm2 vs 5.51 g/cm2. This means that Uranus is pretty voluminous, and its **surface** is really far from its interior. Despite this, Uranus has a **(lopsided)** magnetic field. Uranus's magnetic field, which is stronger than Earth's.
So the answer is:-
**It is possible to have a planet that is both bigger than Earth and weaker in terms of gravity.**
[Answer]
Just a bit belated on the answer, but assuming that human-powered winged flight is your primary goal, and not the planet's size or gravity, then a thicker atmosphere may be the way to go. It's been speculated that the atmosphere on [Titan](https://en.wikipedia.org/wiki/Colonization_of_Titan#Flight) could easily sustain human-powered flight.
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
All the recent talk on Worldbuilding about the vast energies available to higher-level Kardashev civilizations, the need for 50,000 year message-systems, and so on, got me thinking. With enough energy, wonderful things might become possible in space travel.
The galaxy is 100,000 light years across. Humans live about a century under optimal conditions. The speed of light cannot be exceeded. How do I get a live human from point A to point B 40,000 light years away? Seems an insurmountable problem, no?
Before I get accused of duplicating a previous question on faster-than-light travel, let me clarify: at no point would the ship move faster than the speed of light from the perspective of observers on Earth, nor would this ship use Alcubierre-style drives to warp space.
What I'm talking about are time and space distortions caused by relativistic spaceflight.
**Not only does time pass more slowly for the ship-board explorer from the perspective of observers at home, but as she accelerates, distances in the direction parallel to the direction of movement appear to shrink.** At some point (I think around 70%c from Earth's perspective), distance shrink will make the explorer estimate that she is going at 100%c if she where to assume that distances measured at Earth where correct. At the same time an person on earth would observe the explorer as aging less than one year for every light year she travels.
Recall that the formulas below must be true both from the perspective of a fixed observer and from the perspective of the explorer:
$L=L\_0 \sqrt{1-\frac{v^2}{c^2}}$
$t=\frac{t\_0}{\sqrt{1-(v/c)^2}}$
The energy requirements to accelerate a ship to this speed would be immense, of course, but a Type II civilization, having $10^{26}$ watts (joules/sec) at its disposal, should have no trouble with this at all.
**Would it indeed be possible to travel across the Milky Way in a single lifetime, if you were willing to forsake friends and family?**
**How would the monstrous time-lag at the homeworld affect a society's willingness to send out explorers?**
**Where would such expeditions go? What would be a worthwhile destination?**
[Answer]
***New answer for the added questions***
**Would it indeed be possible to travel across the Milky Way in a single lifetime, if you were willing to forsake friends and family?**
This is straight forward math. We know that the speed needed will be quite close to 1c.
So we need the length we are traveling to be one that light will cross in a single lifetime. The milky way is about 100000 light years across, we want it to be about 50 light years across.
$$L=L\_0 \sqrt{1-\frac{v^2}{c^2}}$$
$$L/L\_0=50/100000=1/2 000=\sqrt{1-\frac{v^2}{c^2}}$$
$$1-\frac{v^2}{c^2}=\frac{1}{4000000}$$
$$\frac{v^2}{c^2}=\frac{3999999}{4000000}$$
$$v=c\times\sqrt{\frac{3999999}{4000000}}=(1-1.25\*10^{-7})c$$
This requires $1.8\*10^{20} J/kg$ and as such would be a huge, but arguably possible, undertaking for a type II civilization.
**How would the monstrous time-lag at the homeworld affect a society's willingness to send out explorers?**
It would mean that sending explorers would be of limited use. You send explorers to learn about the world (or universe in this case). So you require that they somehow send information back. This means that for sending explorers the time span on Earth is what is important, which means about 4 years to nearest star, plus 4 years to send information back. This is doable, the Rosetta mission took 10 years - however that also gathered some interesting data on the way. Assuming a limit of 20 years for how long we are prepared to wait for data means that we can only explore stars within 10ly. We know of 12 stars or stellar remnants in that sphere. More might be discovered, but it will be a fairly small set anyway. Interesting targets could be the stellar remnant Sirius B (to gather data on a stellar remnant), Barnard's Star (to gather data on a very old star) and the Sirius binary system (to gather data on a pair of very young stars). The Alpha Centauri system is also interesting, since it's the closest stars and because it's the only target within the 10ly sphere where earth like planets could exist. If a potentially Earth like planet did exist around Alpha Centauri A or B, then that would immediately jump it to the top of the list. (the current Earth-mass exoplanet has not been confirmed).
**Where would such expeditions go? What would be a worthwhile destination?**
Other than for science as described above there are no destinations that are worthwhile for people remaining on Earth.
Because of the long waiting time for people back on Earth there can be no destination that would be worthwhile for an investor on Earth. The combination of an enormous investment to send the expedition and a 10 through 1000+ year wait for a return would mean that the return on investment would be negligible.
That means that any expedition would need to have value for the people making the expedition. - Settling is the only reason I could imagine as potentially worthwhile. So a target would be a star system with a planet that is confirmed to be terraformable. - No such target exists today, but we are getting better at detecting planets.
[Answer]
Here are my R calculation results. The first two columns are fractions (and multiples!!!) of $c$.
```
Effect.Veloc.Astronaut Starship.veloc.stationary Joules.100000.kg.ship
0.01 0.01 4.50E+17
0.1 0.0995 4.50E+19
0.2 0.196 1.80E+20
0.5 0.447 1.10E+21
1 0.707 3.70E+21
2 0.894 1.10E+22
5 0.981 3.70E+22
10 0.995 8.10E+22
20 0.9988 1.70E+23
50 0.9998 4.40E+23
100 0.99995 8.90E+23
1000 0.9999995 9.00E+24
10000 0.999999995 9.00E+25
100000 0.99999999995 9.00E+26
```
As you can see, humankind's energy output for *a year* early 21st century would barely suffice to accelerate a 100 ton craft to 0.2 c.
*Source: Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization*, 1975, R. Freitas
5e20 Joules are about 1.5e13 watts. A mature type I Kardashev (so by the chart above humanity cca 2300) could get 1e17 watts, so output of 3e24 Joules. Even for a type I, relativistic interstellar travel is difficult.
A type II, about 900 years at 3% growth rates after Type I is reached, have 10e26 watts to play with, or 3e33 J, so launching a small ship at relativistic speeds would take no more than a few seconds' worth of the civilization's power output, similar to a Saturn V launch for 20th century mankind.
That does still leave a few major difficulties.
1. Energy density of fuel.
2. Deceleration.
3. Shielding.
(1) Can be alleviated somewhat by beaming power to the ship.
(2) Remains open, and I have no idea how to get enough reaction mass to decelerate on board. Perhaps a payload consisting of a miniaturized AI with self-replicating machinery (a few grams), or a Bussard Ramjet could work as well.
(3) A lot of ablation mass will be needed since each dust particle in the way will strike my ship like a shaped charge. Perhaps a powerful laser to clear the path?
**As to where I'd go, I would probably go to the nearest Earth-like world, see what or who is there. On the other hand, I'm not sure I would want to lose all those Earth centuries it would take...**
*PS: I know it's generally bad form to give an answer to your own question, and all this might hinge on some miscalculation, but I got too excited about the effective FTL drive!*
[Answer]
Your conclusion, that an explorer can travel a distance that in our reference frame is 4 ly, in a time span that he can messure as less than 4 years, is correct.
However;
"Not only does time pass more slowly for the ship-board explorer, but as she accelerates, distances in the direction parallel to the direction of movement appear to shrink."
This is not quite accurate.
Only length contraction will be visible to the traveller.
Both length contraction and time contraction is visible for an observer moving with zero speed relative to an inertial frame observing objects having a nonzero speed relative to that frame.
So for an observer on earth observing the explorer you would not see length contraction. - Because the sun and target star is not moving at relativistic speed relative to your reference frame.
While for the explorer, he will not see time dilation. - His speed is zero in his reference frame. However he will see length contraction, because the stars have relativistic speeds in comparison with his reference frame.
So the two effects will be visible to different observers. The observer on earth will see the clock of the explorer running slower while the length between the two stars remain constant, while the explorer will observer the length between the two stars as shorter - while of course seeing his clock as running at regular speed.
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Additional to the other answers pointing out the huge amount of energy needed to achieve significant time dilation.
If the civilisation had achieved really long term stability it could send out self-replicating robot probes. On arrival in nearby solar systems they would construct a high tech infrastructure including interstellar radio transmitters and matter assembly systems. They'd also send out more probes. So the technological infrastructure would expand on a spherical wavefront across the galaxy at a small fraction of the speed of light.
A number of millions of years later every solar system in the galaxy would be connected.
To travel you would upload your mind and transmit it, along with a body plan. At the other end a body would be built and your mind installed into it. Effectively you would travel at the speed of light plus a constant upload/download time. There would of course be no way to go home.
Fermi paradox: where are they?
My usual answer to the strong anthropic principle is to dispute the premise. This universe is not perfect for human life. It is better for entities with lifespans millions of times longer than ours, or those that are not programmed to die at all. Perhaps we are an evolutionary stepping stone on the way to a much slower form of advanced life, that we'd not recognise as alive if we saw it?
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It seems like you could do it without even getting close to the speed of light if you could bend space.
The whole "Imagine the universe is a 12 dimensional piece of paper. Fold it in half so that the place you are and the place you want to be are touching. Now punch a hole through the paper so you can travel directly from where you are to where you want to be."
Can space be bent like that? Some people think wormholes work that way, like if space time is all crumpled up. IF that is the case, then you wouldn't have to bend space, just find the place where the crumpling has already brought the two pieces of reality next to each other, and then use a punch drive to move across.
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Suppose a civilization from the past was suddenly given access to a huge database of information from modern times. How fast might such a civilization develop, compared to how they otherwise would without access to such information?
Or, to make that a bit more concrete, let's say we gave the nation of England during the late renessance period (16-17th century or so) access to [the entire contents of modern-day Wikipedia printed on paper](http://www.theguardian.com/books/2014/feb/20/wikipedia-1000-volume-print-edition-crowdfunding). How long would it be before they developed an industrialized society? Would it be feasible for them to develop nuclear weapons or a space program anytime within the following century or so?
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There is actually an anthology about this by Eric Flint the first of the novel series is titled "1632."
It's is about an entire West Virginia town in the year 2000 transported to Germany in 1632.
Technology-wise. They could not just leapfrog technology 1632 to 2000 technology. As you might have already guessed there is a lot of "background" technology behind-the-scenes of our current technology or as they say in the novels they needed to make the tools that make the tools that make a product.
The anthology is the collective work of more than 300 persons (engineers and historian included). And they have a massive discussion board (started in 1999 and still going strong till now) about what technologies they can and cannot introduce complete with timeframes, where to locate specific resources, how to make alliances with towns that contain those resources etc.
<http://1632.org/1632tech/> is one of the sites devoted to the series (has link to their discussion board).
Short version **(and by no means comprehensive)**
The people of your time 17th century would first have to select what technology they can possibly re-create using their current base of technology.
Just to give some examples of what they were able to re-create in 1632 (also take note: in the novel 1632 they actually had people from year 2000 making informed decisions on what will be possible)
* Crude mechanical sewing machines
* Crude typewriters
* Rifling will be of great interest (but will only be possible with precision tools - so it will be a tool to make the tool problem)
* Also in the 17th century they had no factories and manufacture was done by guilds so it will also be an organizational logistics problem. Resistance to change scenario plus the fact that people who are best qualified to make the changes already belong to guilds.
* Medicine will be get a boost (but only in terms of knowledge-base) and you will definitely have a lot of resistance from doctors) no doctor will really want to admit they would have to re-study and re-learn everything again. Human nature laziness and resistance to change.
* Apothecary/ pharmacy definitely possible in months with the plant knowledge-base
* Penicillin not immediately possible but Chloramphenicol possible dependent on how fast your people can absorb the knowledge
* Ocean navigation should get a boost with better star charts. But captains are people too so you have to present a complete solution before they throw away their old methods.
* Wide-scale electrical distribution they estimate a decade (tools to make the tools problem and money problems) it will create a sort of polarization (forgive the pun) between groups of conservatives and progressives.
* On the bright side guilds can manually create limited lengths of copper wire and demonstrate the possibility of electricity (more like table-top demonstration) is possible.
* Potato chips, ice cream etc. very doable in the immediate months :)
* Who controls the flow of technical information, and why control the information (equality of the sexes, free education for all will be radical)
* Butterfly effect also discussed. Predestination. (even if people understand butterfly effect they are far more likely to believe that "x" person will stage a coup in the next few years and take steps to prevent it from happening)
Space Program? They would have to justify the need for it, and it will become a money problem. Money for the entire research program including training and education for all the people in the background supporting sciences. Money that conservatives will argue could be spent on other advances. The budget for a first-baby-steps Space program will have to compete with more immediate earthly concerns.
If you are really interested in a first-baby-steps money for a space program - try to join the the 1632 discussion board (to get a feel of the type of resource allocation opposition you will encounter). Advocate for them spending money on **early** research into space (I think they are on the first half-decade tech advances after 1632). You will most likely encounter opposition from the conservatives saying that money will be better spent on something else.
I still remember the ironclads discussion, soooo many flames I thought everybody's modem had overheated (it really felt like you were in congress asking for a budget) :)
Just the tip of the iceberg.
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I think you'd be surprised as to how slowly they would progress. Textual information is one thing, but the ability to actually apply it can take years. Consider things like "we don't know how to send an Apollo spaceraft to the moon." We have all the blueprints, and we have even more technology than ever. But there are things missing that we simply don't understand anymore. The information is incomplete.
**What such a document would do is tell people where to look to find things. What it would not tell you is how to make them useful once you find them.**
The easiest things would be discoveries. Structure of the atom, chemical equations, these things would be easy. The hard thing would be processes. Things like refining metals requires a certain skill that can't just be written down. Even with the full 1000 page spec for Ethernet, it's still extremely hard to make without 99.99% or higher purity copper wires, and achieving that purity is not easy.
**More interesting to me would be a document that focuses on discoveries that are known to cause cultures to be curious... to find answers, rather than just read them.** Consider "Diamond Age; Or, A Young Lady's Illustrated Primer" by Neil Stephenson for an example of trying to raise curiosity while teaching.
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This and similar questions keeps popping again and again. Seems that people keep underestimating complexity and inter-dependence of our current industrial society.
Building advanced technology would be extremely hard because you need advanced machinery serviced by skilled and trained staff. Most of information needed to build such tools is not in wikipedia, and would not be even understood by medieval researchers - for them such writings would be like magic, with no way to confirm it.
What would be better would be custom books describing just next layer up in current language. Steam engines instead of jets. Standardization of apprentice training and tools instead of automation.
It will still take few centuries to develop space flight - maybe half the time, but certainly not within 100 years.
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It's a commonly known fact that whale song travels huge distances. In fact apparently before the oceans were so noisy they could communicate over 10,000km!
However, whales are very big! They can create very loud noises, far louder than any being of 2 metres. In addition whalesong is typically around 10-40hz and is lower than a human is capable of producing. I'm unsure if this has bandwidth implications.
Assuming:
* A creature of about two meters in length
* Wanting to hold a normal conversation spoken (in their own language but basically humanlike speech)
* Assuming they can't open their mouths throat type sounds are permitted/encouraged
* The creature must also be able to communicate with humans (speak a human language as a second language)
What is a reasonable range they could "shout" to their friends underwater? 100 metres? 400? A mile!?
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**TL;DR:** Normal conversation at 1 km depth would travel about 2 kilometers in water. The loudest scream a human could produce would travel about 3.14 km.
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There are many factors that make it difficult to calculate how far sound travels, the biggest being pressure and temperature. The lower the temperature, the less far sound travels, the higher the pressure the farther it goes.
Calculation of the distance sound goes is difficult because not all the variables are known. But the principle behind sound losing volume over distance is called [absorption](http://oceanexplorer.noaa.gov/explorations/sound01/background/acoustics/acoustics.html). The sound also loses energy as it spreads out. The total energy loss of these two factors is called Transmission loss. Depending on the chemicals in the water, different amounts of sound are lost over different distances.
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To do some math trying to get average values. The unit for sound energy is dB. Normal conversation has a power of [60 dB](http://resource.npl.co.uk/acoustics/techguides/seaabsorption/physics.html). In water, sound is stronger, so we add 62 to all values for sound in the unit dB. This means that normal conversation under water has the effective strength of about 122 dB. Normal voice frequency varies, but a typical frequency would be around [170 Hz](https://en.wikipedia.org/wiki/Voice_frequency). At about that frequency in most oceans, the absorption rate is about [0.06 dB/km](http://resource.npl.co.uk/acoustics/techguides/seaabsorption/physics.html). So we can see that the absorption rate is negligible (Though it will be included in the below calculations). But this does mean that frequencies have a small effect on the distance sound travels.
Now, sound also loses energy as it spreads out. Sounds spreads out in two different ways, spherically, and cylindrical. When the water is deep enough, it spreads out spherically, but when the water is more shallow, it spreads out cylindrically. This happens because the sound bounces off the surface of the water and the bottom of the ocean. So while some energy is lost when the sound bounces, more energy is lost when it travels out fully in a sphere. So sound travels approximately twice as far when using the cylinderical form. Sound spreads out in a cylinder when the sound does not fade before it reaches the top of the water (so it bounces off the surface) The amount by which the sounds distance dilutes over a given distance can be calculated. The formula for the loss here is [TL = 20 Log(R)](http://fas.org/man/dod-101/navy/docs/es310/SNR_PROP/snr_prop.htm). TL stands for Transmission Loss, and R stands for range/radius of the sphere. Because dB is logarithmic scale, we can directly transfer this into dB units. So at 1 km, this comes out to 60 dB, which perfectly matches the volume of human conversation.
So the total Transmission Loss is 60 dB/km + the absorption rate, which is 0.06 dB/km, which comes out to 60.06 dB/km
Generally, the threshold of human hearing is 0 dB. So using the data calculated above, the sound of normal human conversation (if it could somehow be communicated at the same strength underwater), would travel about 2.03 km.
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Wikipedia says that the loudest recorded scream was [129 dB](https://en.wikipedia.org/wiki/Screaming#Audio_level), which is 191 dB in water. So using the above calculations, at 1 km depth, a scream would travel about 3.18 km. Note, that is high enough volume to hurt human ears, so the underwater creatures should be able to handle louder volumes, or they should speak quieter.
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There is one [phenomenon](http://oceanservice.noaa.gov/facts/sound.html) that lets sound travel for much longer distances. This has been especially noticed from the noises whales make and it allows them to communicate over very large distances. When sound travels through water it slows down, causing it to refract downward. The water below keeps getting cooler, so the sound keeps slowing down and refracting. At a certain point, the water stops getting colder, but the pressure continues to increase. When pressure gets higher, sound speeds up. This causes the sound to refract upward. It then refracts back down as it gets back into areas where the water temperature slows. This refracting up and down allows the sound to travel a very long distance without losing much energy.
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**Summary**
So there are a lot of factors that affect the distance sound travels, the biggest being pressure. At the standard pressure used by scientists the sound of normal human conversation would travel about 2km. But at certain depths, sound actually travels for a very long distance. This phenomenon is what allows whales to communicate over thousands of km. To a lesser extent it could work for human voices too, if not over crowded.
And finally I would like to say that this data is not fool-proof. There is no easy way to calculate exact values, so these values are not exact.
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**References and Notes:**
There are some very good graphs showing absorption rates on this [website](http://oceanexplorer.noaa.gov/explorations/sound01/background/acoustics/acoustics.html). I got sound values and conversion rates from air dB to water dB from [this site](http://oceanexplorer.noaa.gov/explorations/sound01/background/acoustics/acoustics.html). Unfortunately, copyright prevents me from re-posting them here. For information on the full math I did to get the base TL for spreading out, see [this site](http://fas.org/man/dod-101/navy/docs/es310/SNR_PROP/snr_prop.htm). Voice frequency information came from [Wikipedia](https://en.wikipedia.org/wiki/Voice_frequency), as did [scream information](https://en.wikipedia.org/wiki/Screaming#Audio_level). Thanks to Irigi for pointing out some mistakes in my first drafts.
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Might be way off with this, but what the hey.
I don't think you'll get very 'human like' speech out of a race that developed language under water. Humans fit into a weird category where our hearing 'system' evolved from aquatic creatures (same deal with our sight), quite likely from early fish...however our language itself developed in more modern times when mammals freely roamed the land. So our vocals became directly tied to the medium (air) in which we spoke through and not the water our hearing stems from.
A species that remained underwater would not have that 'vocals tied to air' attribute to them and would quite likely develop speech directly tied to the water as a medium. Are you aware of 'tonal' languages? It's a foreign concept for a native English speaker (except for a few rare examples...an upwards inflection at the end of a sentence will denote a possible question for example), but to people used to detecting it, these tones mean as much as the letters. Mandarin contains the 'ma' case (it's the reverse of the rice/lice difficulties they have)...the word 'ma' has 4 different meanings... “mother”, “to scold”, “horse”, “hemp”. The difference between these 4 terms is entirely tonal..a falling tone vs a rising tone vs a high tone is the difference in these words (the end result here is english speakers saying they are off to feed their mother hay and kiss the horse goodnight).
In the case of an underwater species, there are several sounds in English that would be pretty much useless. Mouth out the 'p' sound and then the 'f' sound...both these sounds are a puff of air with lips touching for p and not touching for f (Indonesian languages lack this distinction). Same goes with the r vs l (say earl fuller to get the differences in tongue position there)...th vs d is simply a tongue flick off the top of the roof of your mouth vs the back of your teeth (a tongue motion the french lack resulting in them saying dis and den. English lack the French OE sound, which is kinda like saying oooo while your mouth is in the smiling eee shape).
This limitation on 'mouthed' sounds not being effective underwater would do much to limit the language in terms of sounds that could be effectively communicated. This gives the tonal nature of an underwater language that much more feasible as a fill in for letters that they can't quite do in an underwater sense (would also produce languages that sounded a little more like a whales song than a human language...almost a whistling language where the changing pitch of a letter means as much to the meaning of the word they are saying as the word itself).
This is a very long way of saying that the English language underwater only has an effective range of a good 5-10 feet before things start to get lost, and the majority of the sounds we are dependent on in determination of words are near impossible to effectively communicate. An aquatic species that developed on it's own would much more likely have a 'song' language of their own that could have a communication range of well over a few KM had the intentionally made a sound for long distance travel (IE a shout)
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In general low frequencies travel further but carry less information in a given time span. As a result you have a trade-off between those two competing requirements. In addition low frequency noise generally needs the creature making the noise to be larger (although there are ways around that to a certain extent with specially adapted organs).
Water transmits sound much more effectively than air. In air the speed of sound is 342 m/s, in water it is 1,484 m/s. In terms of loss of volume there is very little absorption of low frequency sound (one reason it carries so long) but it is still spreading out and getting quieter as it does so. The water-air barrier acts as an almost perfect reflector so that does tend to reduce some of the loss but can create echoes and similar confusions.
This wikipedia article may be helpful for you, it covers the subject of [Underwater Acoustics](http://en.wikipedia.org/wiki/Underwater_acoustics). In particular there are several sections on the propagation of sound underwater.
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Dolphin echolocation works [at a max range of about 200m](http://seaworld.org/en/animal-info/animal-infobooks/bottlenose-dolphins/communication-and-echolocation/). That is at a slightly higher frequency though(40 to 130 kHz). Also that is 200m round trip so 400m one way, and accurate enough to target something the size of a couple of inches. For general singing or shouting I think something in the neighborhood of 1km sounds reasonable.
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Absorption of sound is actually a very minimal thing. The bigger issue is range losses. Sound power drops off by range^2 as it propagates outwards, and that limits most sound. The low frequencies of whale communications DO help (frequency does matter), but the more important factor for whale communication is that they are leveraging the Deep Sea Channel, which abuses pressure gradients to create a "wave guide" that keeps the sound from going up or down. This decreases those propagation costs to merely range rather than range^2.
A bigger limitation is your requirement that they hold a "normal" conversation. Any acoustic environment can be modeled as a noisy communication channel, where "signal to noise ratio" matters. Even whales have limited communication in areas where the sound of the surf is too noisy. As well, the higher the information content, the higher quality the channel has to be.
Consider making communication more directional. If you think about it, a "shout" across the ocean is heard by all. If there's thousands and thousands of creatures all "shouting" at once, they'll drown each other out.
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It might be plausible that an undersea creature with a fully optimized low frequency, long distance, like to like, communication system as a whale, might evolve a completely separate surface communication system. Perhaps a dolphin like blowhole that served some symbiotic purpose like calling birds to clear an obstructed hole, or was used like a game call to lure land animals close to the waters edge to be devoured. The low frequency system could be non vocal, triggered by whole body shuddering. The higher frequency air communication system while initially evolved as biomimicry, could further be naturally or artificially selected as sick animals that made sounds humans understood were more likely to be given antibiotics, or other treatment.
Artificial selection is when humans choose to breed animals with specific traits that are pleasing to them, despite being potentially damaging to the animal. ie. fainting goats, dogs with snouts so short they cannot breathe properly, great danes and St. Bernards so big they have heart trouble. It seems such a process might need to play a large role here.
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Whether solid or a swarm, a problem that occurs to me long-term in building a dyson structure are damaging flares and magnetic storms from the host star. It seems like the absolute best option would be to build a structure around a fresh white dwarf, which is unlikely to be terribly turbulent, but it should still radiate useful heat for millions of years. Assuming you can find - and travel to a white dwarf with nearby materials for the construction. Is there a better stellar object to build your dyson structure around?
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**your home star**
For the first Dyson sphere of a species you will always find it around its home star. The star it has evolved around. It dous not need to be complete. But significant buildup of the starting solar system will occur before damage to the sphere becomes too problematic triggering a large exodus. This may or may not occur and is largely dependant on your culture rather than star-type.
Later on after building multiple spheres a species may come to find that certain stars more suitable for large populations. Most likely those that offer the easiest and best of travel options available in the galaxy (Kinda like where large cities form nowadays.). This depends a lot on how one is to be travelling. And may not reflect the places with the least amount of maintenance required.
"edit"
If you are looking for the very best in the very long term then you are looking at a spinning black hole. Those are the most efficient in the conversion of matter to energy. And your civilisation will be constantly feeding the black hole with random excess matter.
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**Avoid fast spinners**
I think it will always be a dwarf, but be careful with white dwarfs. They look like a spike of light hurting your eyes. And white dwarfs are very active stars. They [can spin fast](https://www.space.com/fastest-spinning-white-dwarf-vampire.html), that is have a huge magnetic field, which may result in electric currents in your Dyson sphere, that could be inconvenient for people living there.
**Managing the energy**
A red or brown dwarf may be more appropriate.. you don't want too much energy inside a closed Dyson sphere. As opposed to a normal solar system, the energy will stay inside. Heat will have to be *removed* through the hull in some way.
**Pick your size, then pick your star**
Suppose the Dyson sphere would be relatively small, say Venus, or Mercury orbit size. Pick a suitable heater: a brown dwarf (nearly extinguished star) can maintain the melting temperature of iron, for tens of millions of years. If you want a big Dyson, spanning e.g. Earth's orbit, maybe you'd prefer a red, or yellow dwarf ? So the answer to this question would also depend on the size you want to build.
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Here is the fun thing about a Dyson Shell, sphere or swarm but swarms are better, it can be used, during production and later to control and/or alter the star it is built around. A Dyson Shell is, if built for it, capable of creating vast, extremely powerful, and finely tuned, magnetic fields. Those can be used to capture and funnel interstellar hydrogen, turning the star system into essentially a giant [Bussard](https://en.wikipedia.org/wiki/Bussard_ramjet) reactor, (not necessarily a jet just a huge fusion plant, or a jet that moves the star system) increasing the size and temperature of the primary, and/or they can be used in [star lifting](https://en.wikipedia.org/wiki/Star_lifting) operations to *remove* material from the star to reduce it's output. You probably want to maintain your Dyson star at roughly the same spectrum as your original home star, you and every other form of life-as-you-know-it has evolved for that level of output after all. The output will be slightly different if you're using a swarm or a double layer Dyson Sphere that has an atmosphere seal layer inside, rather than using gravity generators or spin, due to the refraction/absorption of the windows or the atmosphere seal.
But that's on the day you move in; you may want to start your building project at a much larger star though and star lift most of the material for the shell directly from the host star. This lets you tune the star to your needs and you're not completely reliant on planetary material for construction.
Assuming you're aim is longevity and that you don't care to do the engineering, or wisely don't trust your civilisation survive and maintain control, and are willing to put up with the complications of shifting your ecosystem to a different spectrum then you want a large-ish, older, stable, red dwarf like [Barnard](https://en.wikipedia.org/wiki/Barnard%27s_Star) (in fact something a little larger and even older would be even better because it would be more stable still). Regardless of stellar class a flare, let alone a [CME](https://en.wikipedia.org/wiki/Coronal_mass_ejection), hitting a Dyson Shell will be a catastrophe of vast proportions, it is slightly worse on a red dwarf because of the closer proximity of the [goldilocks zone](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone) but only slightly because the flares have much lower absolute initial magnitude and dissipate at the same rate. In return for accepting slightly worse flare damage you're trading a few billion years for 10s of trillions of years of habitability.
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Here is an out of the box idea...
Use a gas giant as a fuel and gravity source but handle the fusion through the same advanced technology with which you are building the sphere. This technique cuts down on the amount of material needed to build sphere and since you will be in control of the radiation output, flares and aberrant magnetic fields shouldn't be a major problem.
You will also avoid the disappearing star problem...
The creation of a Dyson sphere announces itself across the galaxy by the disappearance of a star from the skies of every civilization which is advanced enough to be tracking the contents of theirs skies. For those civilizations close enough and advanced enough to investigate, that disappearance is a mystery worth looking into. If the investigating civilization also happens to be imperialistic, xenophobic or just plain evil, their curiosity could have extremely negative consequences for your sphere builders.
By building your sphere around a humble little gas giant, and keeping its size down to the approximate diameter of the original planetary atmosphere, you are much more likely to stay unnoticed by any hostile star empires which might be watching.
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The People's Dominion of North Kadana is an arctic isolationist dictatorship, with lots of territory but it is all barren frozen tundra. Their plan: heat up the world by a few degrees, making their permafrost melt and turn into arable land, so that their nation becomes more productive whilst their southerly neighbours are hit with flooding, desertification and tornadoes (don't tell the Supreme Leader that molten permafrost will not be fertile for generations due to the lack of topsoil, he is wiser than all of us and surely knows better).
The Supreme Leader has faith that his line will stay in charge for at least three generations, so we have a hundred years to play with. To make it simple, assume constant 2020's tech throughout that period. Can a single, highly motivated nation warm up the Earth by three degrees Celsius ([a conservative estimate for the required temperature increase to melt Greenland](https://www.sciencedaily.com/releases/2012/03/120312003232.htm)) in that time period?
Assume a generally climate-apathetic global community, that is already warming up the planet a bit by themselves (they would heat it up by one degree Celsius, Kadana wants three more). It shouldn't be too hard to imagine. However, if Kadana is highly visibly wrecking the planet, the other countries may very well seize the opportunity to make it a scapegoat, and possibly even go to war.
So there must be an element of subterfuge to the operation, with reasonable excuses for everything they do that draws the attention of foreign nations. That means, building some polluting factories is okay (economic development), exploding stuff on their own territory is okay (military tests), but releasing vast quantities of artificial greenhouse gases is less feasible. Such a gas can be detected, and traced back to its point of origin, ratting them out. It's fine if many people suspect Kadana has a hand in the global warming, but there should be reasonable alternative explanations.
Other factoids:
* Kadana has about fifty million people, most of whom have poor living circumstances, but the military is well-funded and warming up the planet is the primary military goal. Assume an annual budget of around 5 billion USD for this operation, plus a virtually unlimited domestic supply of unskilled labour.
* There are many foreign military bases around Kadana, and even trade with its closest ally is kept in check. So another factor is minimising the amount physical material that needs to leave the country. That also applies to sending stuff into space.
* Kadana has some allies on the world stage, who may be amenable to hosting mysterious factories, but none of them wish to heat up the planet. They too must be kept in the dark. However, don't worry about Kadanan defectors; few would believe this ridiculous plan without hard evidence.
**What is the best way Kadana could heat up the planet?**
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as user535733 mentions:
Those deep [ocean methane clathrates](https://en.wikipedia.org/wiki/Methane_clathrate#Oceanic)...
Invest in a new "GREEN" power company, that uses the [thermal potential of deep ocean water to generate power](https://en.wikipedia.org/wiki/Ocean_thermal_energy_conversion). It's real. Not very cost effective, and maintenance is a pain, but it is real. and... one of the effects is to drastically increase deep-ocean (including ocean floor) temperatures.
The methane clathrates are very sensitive to local temperature changes. Boosting the local temperature of the seawater by even just 3C is enough to trigger a phase change in the methane ice, releasing the gas. Which, incidentally, stirs up the ocean currents more, leading to more water mixing, and more release. These events can form chain-reactions of quite monumental scope.
And, as it happens to be, some of the very best locations for OTEC power generation are located right next to some of the world's largest methane clathrate deposits! Just look at that motherlode a bit SSE of Okinawa, Japan.
Potential temperature differential for OTEC power
[](https://i.stack.imgur.com/6Kpfs.png)
Known locations of large methane clathrate deposits.
[](https://i.stack.imgur.com/t14L1.png)
Best of all, your country can (almost) honestly say "NOO! We are the GOOD GUYS!! See, we are working on zero-carbon power generation, for *all humanity*" hehehe-snerk!
[](https://i.stack.imgur.com/eCsuz.jpg)
(Picture of premier-president Lord Admiral-General Haffaz Ajamhinadad Osama Hussein Aladeen, Supreme Leader of the Republic of Wadiya.)
((Do not take seriously!))
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Dump methane into the atmosphere. Lots of it.
Dig a lot of "water" wells that "happen" to tap methane pockets.
Have your Naval Engineers find ways to release [methane trapped in undersea clathrates](https://en.wikipedia.org/wiki/Methane_clathrate). Then you can have your submarines nefariously release methane belonging to other countries.
Encourage agricultural and waste management practices for plausible reasons...that happen to encourage anaerobic methane production. Rice paddies and cows can make a lot of methane.
Your shills and toadies and apologists outside the country should engage in a campaign of misdirection, focusing world attention on secondary effects and less-impactful causes so you can dump as much methane as possible for as long as possible. They should also try to encourage other nations to adopt your "smart" or "sustainable" or whatever-buzzword-works agricultural practices.
If attention is drawn to your releases, time them to coincide with seasonal changes and storms to confuse the source and add deniability...or not. You're a sovereign country, your serfs will fight to the death to preserve their way of life, and you got a few nukes stashed away. Who's the punk now?
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In recent years, North Kadana has begun investing heavily in a few key industries:
* magnesium refining
* insulated glass
* high voltage electronics manufacturing
* if possible, semiconductor manufacturing (probably not, that is likely beyond the economic capabilities of such a poor arctic dictatorship)
All of these industries have on thing in common: they all use [sulfur hexaflouride (sf6)](https://en.wikipedia.org/wiki/Sulfur_hexafluoride), a greenhouse gas 23,900 times more potent than CO2. The current annual output of sf6 is [8,100 tons, equivalent to 100 million cars](https://energypost.eu/grid-switchgear-uses-sf6-the-worlds-most-potent-greenhouse-gas-how-do-we-regulate-it/#:%7E:text=Sulphur%20Hexafluoride%20(SF6)%20is%20described,grow%20by%2075%25%20by%202030.). North Kadana's goal is to bump up those numbers as much as possible. The equivalent amount of sf6 would be around 1.8 million tons of sf6 to match the entire global anthropogenic output of CO2 (43 billion tons). This is probably possible to achieve.
So we have a technical method, but the remaining challenge is disperse it without anybody knowing it was you. You need three things:
1. A method to release it without it being traced back to you
2. A scapegoat to take the blame
3. An alibi
For #1, user535733 had the right idea with submarines. Your nationalized SF6 plant safely stores the gas underground...right next to your secret submarine tunnel. Load the gas onboard, send the subs into the ocean undetected, and now they can go anywhere in the world without outside powers snooping.
For #2, you need another country to blame for this. Find a region of the sea with lots of competing interests and people to blame -- the Persian Gulf, the South China Sea, etc. This is where you will release your gas, slowly, from the submarines. When satellites and climate watchdogs notice these crazy new SF6 spikes around these ocean hotspots, watch as the competing nations begin trying to pin this on each other. It doesn't matter who exactly takes the fall, as long as there is doubt.
For #3, you need to fabricate a reason why SF6 is showing up in huge spikes in the atmosphere now. Otherwise, it's possible a global crackdown on the gas's use and production might set its sights on your nation. This is the hardest step, but the best way I can think of is to use a concerted misinformation campaign. Spread conspiracy theories, fake news, and fan the flames of confusion in major countries, based on whichever theories the players in #2 come up with. Meanwhile, join as many climate-activism treaties and conferences as possible as a nation. Set and fulfill goals on decarbonization, invest in green energy sources, and you will hopefully avoid detection by other nations who don't see you as a major player in climate change.
] |
[Question]
[
What **existing material** (e.g. 410 steel, *no unobtanium*) and **what thickness** should the ribcage of a creature (of humanoid size and shape, let's say it's a genetically-engineered human) have, **to survive the bite of a Tyrannosaurus Rex?**
The bite's strength can be up to **430,000 pounds per square inch** in certain areas.
*Deformation and breaking are allowed*, but it has to hold enough to keep the organs inside from being turned into goo and killing the unlucky individual.
*I know that the poor guy is probably dead even with his ribcage having resisted the bite, but I'm interested specifically in the ribcage and the organs inside. Death by bleeding and other non-ribcage damage can be ignored. Please do not try this at home. (... please do not even have a T-Rex at home)*
[Answer]
# Pressure at a point is not important
You mention that the bite strength is 430,000 psi. That isn't a bite strength, that is a bite pressure felt at a tooth tip. Two things are relevant here. First, that that amount of pressure will dent just about anything. Second, that amount of pressure will surely dent tooth enamel before it will dent a hard modern steel. So, the pressure you quoted will be doing more damage to the T. Rex's teeth than to any metal structure that I'm about to discuss.
However, a T. Rex can still damage a steel cage, due to its bite strength. But the true measure of its bite strength is in units of force. The [Smithsonian Mag](https://www.smithsonianmag.com/science-nature/the-tyrannosaurus-rexs-dangerous-and-deadly-bite-37252918/) gives T. Rex's bite strength at 12,800 lbs, or 57 kN.
# How to see if an item is damaged
This can do a lot of damage. On page 12 [here](http://www-mdp.eng.cam.ac.uk/web/library/enginfo/cueddatabooks/materials.pdf), there is a list of materials and their yield stresses in MPa. The pressure rating is calculated by dividing the bite strength by the cross section of the material being bitten. If T. Rex bites a standard brick (yield stress 50 MPa), the brick's width and height are 0.089 x 0.064 meters, or 0.0057 m$^2$. Divide the bite strength by this cross section and you get 10 MPa. So a T. Rex can't crush a brick outright, probably.
However, this is only crushing. There are various other way to destroy a brick. The same table shows a brick's tensile strength as 7 MPa. The same force applied in tension could pull a brick apart. A T. Rex can't quite do that motion, but it can apply a shear stress to the brick, and probably would since its teeth are lined up to shear; i.e. the teeth don't touch point to point. So if the T.Rex bit a brick, the local stresses between teeth would create powerful shear forces and overwhelm the brick.
# What can survive a T. Rex bite?
[ASTM A656](http://www.matweb.com/search/DataSheet.aspx?MatGUID=05067f61c34b4a7c9c1a67442ad1ccc3) is a high strength, low alloy steel commonly used as the structural component in truck frames. It has a tensile strength of 550 MPa. If we want the T.Rex's bite to reach no more than 50% of the yield strength, to ensure that we stay safe, then we need a cross section of $\frac{57 \text{ kN}}{550 \text{ MPa}\cdot 0.5} = 0.0002 \text{ m}^2.$ This works out to a piece of steel about 1 cm in radius; or about a 11/16" [steel rod](https://www.fastenal.com/products/raw-materials/bar-stock/round-bar-stock;jsessionid=EZJ3s1nC0TaWvXoziiz-vhDu.443d7b2e-1555-3602-a586-c0d73327934b?r=~%7Ccategoryl1:%22600930%20Raw%20Materials%22%7C~%20~%7Ccategoryl2:%22600932%20Bar%20Stock%22%7C~%20~%7Ccategoryl3:%22600937%20Round%20Bar%20Stock%22%7C~%20~%7Csattr01:%5E11/16%22$%7C~) (these things are measured in inches of diameter).
# T. Rex isn't so strong compared to a car
T. Rex's skull is about 1.5 meters long. Lets say his range of bite is 1 meter. Work, or energy, is force times distance, so a 57 kN bite over 1 meter is 57 kJ.
A car with mass 1000 kg moving at 35 mph is going about 15 m/s. Using the kinetic energy equation, this is about 113 kJ; or just over twice the energy of a T. Rex bite. An F-150 truck is more like 2200 kg; at highway speeds it is at 30 m/s. This works out to 1000 kJ; 20 times the work or energy a T. Rex is putting out.
So you can see that the stress a car bumper faces in a crash is going to be much higher than anything a T. Rex can do. If you look at the structural components of your car's bumper, there really aren't any solid metal components over 2 cm in diameter, other than the car's frame. Having been in a few accidents, a few car to car impacts at low speeds (> 20 mph) won't really bend the frame, at least not much. Since these slower impacts are roughly equal to a T. Rex's bit, this passes the smell test as reasonable.
# Conclusion
A 1 cm radius steel rod made of the same material as a car frame should resist a T. Rex bite pretty well. Overall, given the energy comparison in a T. Rex bit and a car crash, the materials and design of your car bumper should be up to the task of anti-T. Rex armoring.
[Answer]
[Ankylosaurus](https://infogalactic.com/info/Ankylosaurus) was the contemporary of T-Rex, and was armoured to protect itself from just this sort of thing. The protection consisted of closely spaced bony growths on the skin, apparently connected to the bone and musculature below with strong connective tissue (so an attacking dinosaur could not simply rip the protection off). This was supplemented by being low to the ground and presenting a large, convex surface overall, which would probably make getting a good bite difficult for T-Tex (especially when the target is moving and swinging a tail club to defend itself).
[](https://i.stack.imgur.com/3MZzw.png)
*Modern reconstruction of an Ankylosaurus*
[Turtles](https://infogalactic.com/info/Turtle) are another ancient species (actually predating T-Rex), but have evolved a similar solution. In the case of turtles, the ribs themselves have evolved to fuse together to form the [protective shell](https://infogalactic.com/info/Turtle_shell). While so far as known, turtles, tortoises or terrapins were not hunted by T-Rex, giant crocodiles and other large predatory dinosaurs and sea creatures existed that *did* prey on turtles, so evolving a hard shell was obviously advantageous to the ancestors of modern turtles.
[](https://i.stack.imgur.com/sPAnd.jpg)
*Example of a turtle's shell*
If turtles or their relatives were being targeted by Tyranosaurs, then they would quickly evolve proper defences to prevent themselves from being eaten (too often), such as larger, flatter shells to provide less traction for a bite, heavier shell construction or even modifying the rib bone which make the shells to create a sort of framework. If we imagine the cross sections of the ribs evolving into a "T" configuration, the armoured upper portion still provides the protection, but the projection parts below can attache differently to muscle and connective tissue to distribute pressure better, and these lower parts of the ribs may eventually evolve to fit together to create a pattern like the interior of a vaulted ceiling in order to provide more mechanical support against high pressure loadings:
[](https://i.stack.imgur.com/b7bor.jpg)
*A vaulted ceiling. The internal structure of a T-Rex proof turtle shell might resemble this*
The disadvantages of these protective measures is they are heavy and inflexible. They require a lot of energy from the creature carrying them, and make it harder to compete against other creatures in the ecosystem exploiting the same niches. Some creatures will be large and aggressive (like [Triceratops](https://infogalactic.com/info/Triceratops)), while others may be moving in vast herds for protection, and rely on speed (like [Hadrosaurids](https://infogalactic.com/info/Hadrosaurid)). Slow moving, lumbering creatures will be at a disadvantage in such an environment, and indeed Ankylosaurus seems to have been a fairly rare creature based on the number of recovered skeletal remains.
] |
[Question]
[
So, this question has been asked before, but I would like to make a few stipulations regarding the specifics of my question.
Firstly, the aluminium in question is fabricated in modern times, and access to aluminium alloys and forges to produce them are available. Secondly, rather than use the aluminium to make true plate armor, I would want to use it to make a jacket of plates or a brigandine. The armor need not be bullet-resistant, but is instead generally used to prevent harm from melee weapons and creatures, i.e. bites, claws, etc.
Is this viable? And if not, what materials, alloys, or armor designs would be better?
Thanks in advance.
P.S. The reason for aluminium being chosen was initially justified by the story taking place in Iceland. Iceland does not naturally have aluminium deposits, but hundreds of thousands of tons of aluminium ore are shipped to Iceland annually for smelting, as Iceland's geothermal energy allows for the generally costly processing to be quite inexpensive even after the transportation costs. Thus, in the apocalyptic scenario of the story Iceland is cut off from the world, but hundreds of thousands of tons of unrefined aluminium, and the means to refine it, are left behind. I've considered steel and other more conventional armor materials, but harvesting it would require tearing down their own buildings and vehicles in order to obtain it.
[Answer]
The society for creative anachronism (SCA) started out as a society of fantasy fiction lovers, and evolved into a serious medieval reenactment society. Mix lots of beer, gossip, and family fun with serious practical study of the methods and madness of the middle ages (and beer).
Many chapters have an armory shop where members can build their own equipment for use in battles and duels. Leadership of a kingdom is decided by combat intournament. Most events include battles.
Modern SCA plate armor is largely fabricated from surplus and scrap aluminum street signage. When well constructed, it is of comparable or better protective quality than middle ages iron or steel plating. The SCA rattan weaponry is about 50% heavier than period weaponry, so you actually feel more impact when you get hit than you would with period weapons.
Source - I made some of my own armor when I played in the sca.
[Answer]
Aluminum is a great material for body armor, but not as a metal or alloy. Alumina is aluminum oxide and it can be made into a ceramic. Alumina ceramic makes excellent body armor as well as many other things.
[](https://i.stack.imgur.com/S391z.jpg)
<https://www.youtube.com/watch?v=1HRGpQ6-rz8>
<https://global.kyocera.com/prdct/fc/list/material/alumina/alumina.html>
>
> Al2O3 Alumina (Aluminum Oxide, Al2O3)
> Alumina is the most well-known and most commonly used fine ceramic
> material. It has the same sintered crystal body as sapphire and ruby.
> It has been used for decades in electrical components for its high
> electrical insulation, and is widely used in mechanical parts for its
> high strength, and corrosion- and wear-resistance.
>
>
>
<http://www.bulldogdirect.com/alumina-ceramic-armor/>
>
> Alumina ceramic armor, working in conjunction with an appropriate
> backing system, can defeat various threats including armor-piercing
> rounds and IEDs. Typical ceramic composite armor systems, at
> approximately half the weight, outperform similar steel-based systems.
> These systems are frequently used in body armor, vehicle armor, and
> aircraft armor.
>
>
> How it works: Conventional steel armor plate defeats an incoming
> projectile by reducing its kinetic energy through ductile deformation.
> In a ceramic composite based armor system, a different process is
> employed. First, the strike face surface causes significant
> deformation to the projectile, increasing its cross section. Its
> kinetic energy is reduced as the bullet is fragmentized on shattering
> the tile’s hard surface. The residual energy of the smaller fragments
> is absorbed by plastic or elastic deformation within the backing of
> the armor tile.
>
>
>
Alumina ceramics are one of those topics where the huge number of (very informative) manufacturer sites are better than what wikipedia offers. For example, I learned the word "fragmentized". Alumina ceramic armor is not some MadMax adhoc thing - these armors are modern serious competitors against steel plate and a foray into youtube finds considerable passion for and against ceramic vs steel plate armor.
] |
[Question]
[
How would you modify a one-handed projectile weapon (preferably a crossbow) to make it trail a long, light string?
**Technology Level:** Similar to the mid 1800's, but without the discovery of gunpowder or development of modern firearms.
**Physics:** I'm trying to keep the basic physics of this world as similar to reality as possible, although "magic" will provide a bit of wiggle room here. I'm okay with it not being hyper-realistic, as long as your average college-educated non-expert wouldn't find it ludicrous.
**Some Background Info (why I need this):**
In this world, certain supernatural abilities are touch-conductive, meaning that they follow rules similar to electrical circuits. Like in electricity, certain materials are more or less conductive to magic.
One guy has figured out that a good way to use his healing abilities over a distance is to just shoot his accomplice with a sharp non-lethal projectile that trails a superconducting string. (Sure, his friend will probably be a little annoyed at first that he has a bolt in his ass, but probably less annoyed after he realizes his internal bleeding is gone.)
The problem is that I'm struggling a bit to understand how crossbows work, and mainly how bolts differ aerodynamically from arrows. I've found that conventional archers can attach [string trackers](http://www.3riversarchery.com/leather-string-tracker.html) to their arrows, sacrificing some degree of accuracy. However I'm having trouble finding an analogous setup for a crossbow. Is this because the bolt is so much smaller/shorter range than an arrow?
I think that the ideal weapon would have as many of the following characteristics as possible:
* It's capable of being shot one-handed after loaded
* It's as compact as possible so as to draw less attention
* It needs to be able to hit someone 30 yards away (or double that with some extra propulsion from magic\*)
* The string needs to be detachable in some way so someone yanking on it from the other end can't play tug-of-war with his weapon
I'm also a little concerned about the projectile itself--namely, how to make sure you don't immediately kill the guy you're trying to heal. At first I thought of putting a stopping mechanism\*\* on it to keep it from going all the way in. However, when I started drawing a diagram to include such a feature, I realized it would probably not work from an aerodynamic point of view.
[](https://i.stack.imgur.com/zq40c.jpg)
Instead, could I just make it too short and too light to pierce anything vital? (Hitting someone's eye or even their artery is probably ok.) If not, I guess that's just a risk he's going to have to take!
Thanks for all your help! I have the feeling that the answers are out there somewhere but I'm just missing the vocabulary needed to find them.
\*You might wonder why he doesn't just use magic alone to propel his projectile and skip the weapon. As it turns out, this kind of magic is a bit too clumsy and inaccurate to pull this off reliably. It's good at providing strong directional power in certain cases, but the experience would be a bit like trying to shoot an arrow by hitting it with a car.
\*\*What's the word for this?
[Answer]
You should check out some of the tools used by aborists to launch lines,, some of these definitely seem capable of launching a fair distance. Some links:
Someone using a crossbow, seems to get a large distance, looks like more than 15 yards.
<https://m.youtube.com/watch?v=qz8jG1p63NA>
This guy using a throwbag:
<https://m.youtube.com/watch?v=7v9f6isVx3E>
Some people on this:
<http://www.arboristsite.com/community/threads/best-size-for-throw-weight.33808/>
have thrown these about 30 yards nearly straight up ,and I assume this distance would be similar if not greater horizontally , but I don't know about accuracy.
This person using a small slingshot.
<https://treefool.com/2014/04/07/diy-cheap-throw-line-slingshot-vid/>
If you're not averse to using one of these(they are twohanded), but very small.
You could investigate something with an atlatl.
I don't suppose a flying disk or boomerang would work.
To be honest however, I think you'd be best off with a crossbow, readers would already be familiar with it and I think the danger of your main character misplacing a shot and injuring his friend would add tension and this would be exciting. To stop his friend from being hurt, maybe said friend could wear some leather armour/a helmet?
[Answer]
As far as the stringy thing goes, you can have the missile have a hollow in the tail with several yards of fine thread coiled in. This minimizes the drag on the missile as well as the friction on the thread. The thread can then be attached to a ring or carabiner on the crossbow, allowing for easy detachment.
Attaching wires to flying weapons is [doable](https://en.wikipedia.org/wiki/Wire-guided_missile), and if the distance involved is less than a hundred yards, there should be no accuracy problems even with your average crossbow:
```
<--- to crossbow string
==============================================
-------\ |\ |... coils of thread | WOODEN --> to point
\| \| | SHAFT
==============================================
```
You can use a bamboo or cane for the shaft, and coil the wire inside.
The nonpenetrating requirement can also be solved in a way, but requires careful construction.
When the arrow hits, the forces in play are the resistance of the victim's flesh and the kinetic energy of the incoming shaft. The part of the shaft that penetrates has very low speed and exerts a backward force on the incoming shaft.
You want an arrow made up like this
```
================>><##########>
```
once the first segment ### has entered the target for about half its length, the backward force is enough to break the arrow at `>><` - the left part of the shaft will shatter and splinter, and hopefully it won't inflict too much damage. Or it could drive *into* the right part which is partly inside the body, enlarging it and making its further penetration impossible:
```
-------\
================>> >>#####>
-------/
```
You can do this by having a solid left-part of the shaft, and a right part made up of several splinters welded together to the right, and held together all around the left shaft by the equivalent of a breakable elastic band that's just enough to hold under the stress of departure from the crossbow. When it hits, the right part penetrates and slows down, the middle part collapses and acts as a shock absorber, and in so doing it pancakes increasing in width, so that further penetration is avoided.
All this must not split the thread connected to the rightmost conductive head, of course.
One other option, probably simpler, is to have a point made of soft wax, with a needle inside. The wax is shaped aerodynamically, and on impact the blunt body of the arrow doesn't penetrate (it might well leave a nasty bruise), the needle does (up to a controlled depth). The wax point can be quite large and offer aerodynamic penetration to a large "shoe" to ensure lack of penetration:
```
|WWWW
=============#|WWWWWWWW
#|---------->
=============#|WWWWWWWW
|WWWW
```
[Answer]
The biggest problem here is the definition of "non-lethal" in an age before proper medicine. Any wound is potentially lethal, maybe not immediately, but in the long term. You're dealing with a magical healing here so there's more flexibility, but you're still doing a lot of damage on the way. The chances are your victory here is pyrrhic and you're going to have to get some hands on healing in short order to deal with that puncture wound.
Then there's the range consideration. Any projectile weapon with intent to puncture is going to have a set of ranges: lethal, possibly non-lethal, and useless. The last thing you want to do is punch a hole clean through him because he's a bit too close.
The gunpowder question: Without gunpowder combatants would still be armoured. This is a problem. To penetrate armour the power on such a device would be lethal to an unarmoured target until close to the normal useless range. Again, get your range and armour balance wrong and you're punching a hole straight through him.
[Answer]
In the 1970s or 80s I read an article claiming that until recently crossbows were very inaccurate. This was in a discussion of siege warfare & castle defense. I now doubt that information, since compound xbows have been around for many thousands of years. Currently, xbows are as accurate as pistols at modest (30-40 yard) ranges. Scopes are necessary. There is no, I repeat, no safe way to shoot a xbow at someone. You risk maiming or killing them. As you seem to know, bows are used to hunt both fish and birds with strings attached see, for example Wikipedia Bowfishing. I'd guess the accuracy of such projectiles is miserable at any distance more than a few yards. Increasing muzzle velocity (or whatever it's called for a bolt) should increase distance, but will also reduce accuracy while at the same time making injury more likely. Tasers have maximum range of 35 ft and use compressed gas. Serious injuries are rare...at least, so says the law enforcement agencies that use them. Last idea, have you considered a stream of water? I guess getting a continuous 30 ft stream is unlikely...
[Answer]
A crossbow imparts the same momentum no matter what. You cannot pull your punch based on range.
So unless you change these to Nerf style suction cup darts, you have a high risk of *punching into / through* your target. For a healing bolt, you're going to have to heal the bolt-strike and whatever you intended to heal at the same time.
With a standard bow, you can reduce the force for close-up vs long range shots. And that's a plus. But you still have a high risk here.
You might try to make a thing more like real-world taser systems that use tiny barbs and wires. Those are small enough to be non-lethal.
[Answer]
Anything functional at long range that can carry a line could actually be lethal. Is it really necessary to actually hit the person or just land it near enough that they can grab it? I wouldn't aim a crossbow at a friend, especially if I am going to have to heal them.
If you want a non-lethal projectile think of something like a yo-yo or a blowgun. However, the range may be much shorter than you would like. However, one should consider whether a healer is really also likely to be a master marksman at long range. Also, if your healer is at an extreme distance from his allies doesn't that make him a prime target in many cases? A shorter range weapon may be appropriate since he would still be able to heal from cover or hiding. However, he would still need to be pretty close.
[Answer]
As far as your stopping mechanism goes, two things can be done to help prevent deep penetration of the projectile. First of all, taser darts are made small and light to reduce their inertia, allowing them to be stopped easily when they hit something. The two drawbacks to this are that the light projectiles can be influenced by air currents and the drag of the tether and become inaccurate at longer ranges, and the reduced penetration prevents them from getting through thick clothing such as leather.
The other method to prevent deep penetration is seen on a boar spear. This spear has two blunt "wings" behind the blade to stop it from going straight through the target. Changing your disk to bars could solve your aerodynamics problem.
] |
[Question]
[
I'm imagining if we can live on a very special white dwarf which has very special characteristics:
1. It has cooled down to a very low temperature
2. Its rotational speed on the equator can almost cancel out the gravity (ie: the gravity is almost same as on Earth)
3. Accretion occurs so that rocks accumulate on the equator of the white dwarf, and a ring shaped crust is formed, also there is water and ice from comets on the ring rock
4. It has a star around the White dwarf which is in the habitable zone, just like the Earth around the sun
Can that type of white dwarf exist? Can we live on this type of white dwarf (either in short term or long term)?
[Answer]
David Goldstein provides an answer on how fast the earth has to rotate to nullify Earth's gravity on the equator and the answer is [a period of 5066 seconds or roughly 1 hour and 14 minutes](https://www.quora.com/How-fast-should-the-earth-rotate-to-nullify-the-effect-of-gravity?share=1)
Bruce McLure describes the binary star system that you have in mind: [the star Sirus and its white dwarf companion, Sirius B ("The Pup").](http://www.idialstars.com/pup.htm) In [**"Your Weight On A White Dwarf"**, McClure computes how much a human being would weigh on white dwarf](http://www.idialstars.com/wowd.htm):
>
> “Since the Sun is about 333,000 times more massive than Earth, that
> means you'd weigh 333,000 times more on a white dwarf having the Sun's
> mass but the Earth's size.”
>
>
>
Let's use McClure's number (333,000) and plug it in Goldstein's computation by dividing 5066 with 333,000 and [the necessary rotational time that you need would be 15.21 milliseconds](https://www.wolframalpha.com/input/?i=5066%2F333000%20seconds).
Mark Barton on the same thread as Goldstein points out that [the Earth is already out of shape 1 parts in 300 because of the centrifugal force of its rotation](https://www.quora.com/How-fast-should-the-earth-rotate-to-nullify-the-effect-of-gravity/answer/Mark-Barton-1?share=1). The "little rock" that you imagine as habitation would probably be like a very flattened disc (I'm imagining like Saturn's rings).
Assuming that in your world-building, humans have achieved some technology to endure these kinds of massive gravitational influences, the possibility of habitation would be on the same scale as the possibility of having human habitation on one of Saturn's rings. As a4android points out in the comments, if the equator is earth-sized, the rotational velocity will be faster-than-light. You probably need an equator length that accommodates Chandrasekhar's limit of of 1.4 solar masses so that the rotational time is slower-than-light.
[Answer]
As explained above, there are at least two problems with the scenario.
1. White dwarfs, since they have a very small surface area, cool down slowly (and the cooling itself decelerates over time). The inner part of the star stays very hot for a long time and radiates slowly through the crust. It's not clear how much time it might take for the crust of a white dwarf to cool down to Earth-like temperatures, but it must be *a lot* (in the order of trillions of years).
2. The rotational speed needed to counteract the equatorial gravity of a white dwarf is immense, as you're assuming an object with roughly the same equatorial circumference as Earth but about the mass of our Sun. The only big solid bodies that rotate that fast are neutron stars, and they are much more compact than white dwarfs. Also, it's unclear how an Earth-size object could naturally gain such angular momentum. Neutron stars do because they shrink a lot in size.
You could circumvent problem number 1 by proposing that the story takes place in the very distant future. The main star your white dwarf would be companion of, therefore, won't be one of today's stars and might be among the last. The [Stelliferous Era](https://en.wikipedia.org/wiki/Future_of_an_expanding_universe#Stelliferous_Era) is supposed to last until 100 trillion years after the Big Bang.
I don't see how you could go around problem number 2 without very serious astroengineering.
[Answer]
Condition 2 and 3 are conflicting: if the rotation almost cancels the gravity at the equator, it means it is really easy for anything to escape. So no significant accretion can take place, since as soon as a significant boulder will stand up its top will be launched on the tangent into outer space.
[Answer]
I believe, such object is not possible for our universe. Right now the coldest possible WD has 3,9 kK (3,900 K) in the photosphere. It's really hot place to live. The rotation speed for an object with radius of WD to compensate the gravity to 0,5-1,5 g should be very high, I don't know, how stable WD are, but pretty sure it will be destroyed at that speed. And if it was binary stellar system, with one star evolved to WD, it should lost its stability, so, again, not a very good place to live.
[Answer]
Such a white dwarf cannot exist.
The reason is simple, and does not require any calculations or deep understanding of physics.
White dwarfs are incredibly dense, orders of magnitude denser than ordinary "molecular" matter, which means that the Coulomb force whose outward pressure keeps the latter within its characteristic range of densities must be completely overwhelmed by inward pressure (resulting from gravity) in the former.
In other words, close to the white dwarf's surface, the gravitational field must still be strong enough to keep it as dense as a white dwarf. Edit: *The faster the star is rotating, the stronger the gravitational field must be in order to compensate.* Such a gravitational field would also compress a human to the density of a white dwarf (edit: assuming that the human was trying to stand on a surface attached to the white dwarf. Staying safe in a fairly close orbit might be feasible).
The same reasoning shows that one cannot stay alive close to (edit: and stationary relative to) the surface of a neutron star or other exotic star made of incredibly dense matter, which includes stellar-mass black holes, but notably does *not* include the supermassive black holes which exist at the centres of most galaxies, and which are far *less* dense than these other objects (at least, if one counts their size as being given by the extent of their event horizon).
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If it were spinning fast enough to cancel most of the gravity, the material would puff back out again into normal atoms. That would apply all the way down, since the pressure would be releived from the core material. So it would no longer be a white (or black) dwarf at all. An object as you describe is simply not possible.
If you want to cancel the gravity, the *ship* could be in orbit just a few feet above the surface of the dead star.
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One of the many problems with making really, really big creatures is that their bones are, eventually, incapable of supporting their own weight. Eventually, they get to be all leg and no body. This is *especially* a problem when trying to make something that's humanoid but larger than normal, because you have to make the legs elephantine in order for them to support the weight of everything else. The [square-cube law](https://en.wikipedia.org/wiki/Square%E2%80%93cube_law) is generally a pain in the rear when doing such things.
Now, the obvious solution to this is to make better bones/supportive structures - ones that can withstand more compressive force per unit of bone mass, meaning that you can use less of them, meaning that you don't need to make disproportionately-wide limbs to counteract a creature's mass.
I considered using the [goethite](https://en.wikipedia.org/wiki/Goethite) nanofiber/protein mixture that limpet teeth use, [which has a tensile strength of 3-6.5 gigapascals](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4387522/), but I don't think that that [*tensile* strength](https://en.wikipedia.org/wiki/Ultimate_tensile_strength) translates into the [*compressive* strength](https://en.wikipedia.org/wiki/Compressive_strength) required to make an effective bone, since tensile strength is a measure of how durable a substance is when being *pulled on*, whereas compressive strength is a measure of how durable a substance is when being *squeezed*.
**So: what are some biological substances stronger than bone?**
**Quality answers to this question will cite a substance that falls into the following four categories:**
* Either capable of being processed by Earthly biology, or capable of being built out of metabolizable sub-components of itself by Earthly biology. No noble gases or non-reactive substances, here, please, although I wonder how they'd ever be a suitable answer to this. Note that those limpet teeth I previously mentioned *are* made of such a metabolizable substance, in that the limpet turns iron into [ferrihydrite](https://en.wikipedia.org/wiki/Ferrihydrite), which is then [nucleated](https://en.wikipedia.org/wiki/Nucleation) and turned into goethite crystals (i.e. those nanofibers I mentioned earlier).
* Stronger than bone in terms of compressive strength. [Bone has a compressive strength of 170 megapascals](https://en.wikipedia.org/wiki/Bone#:%7E:text=Because%20of%20the%20way%20that,stress%20strength%20(51.6%20MPa).). I want more. I can worry about shear loads later, or counteract them by wrapping the compressive core of the bone (i.e. what carries the weight) in biologically-grown limpet-tooth [spaced armor](https://en.wikipedia.org/wiki/Spaced_armour) with [bone marrow](https://en.wikipedia.org/wiki/Bone_marrow) in-between as a shock absorber.
* Not water or muscle. I do not want [hydrostatic skeletons](https://en.wikipedia.org/wiki/Hydrostatic_skeleton) or [muscular hydrostats](https://en.wikipedia.org/wiki/Muscular_hydrostat).
* Has to be possible on Earth. No frozen hydrocarbons. Especially no neutronium. No, not even a little. Bad Stack Exchange. Bad. Drop. Drop the neutronium. Good boy.
Note that I am not interested in determining what evolutionary pressures might lead to the adoption of such a material as a supportive structure; we're talking mad science and the limits of what's possible here, not boring old evolution. I am also not interested in how this might affect the biology of the creature it's attached to - i.e. things like blood flow issues or increased nutritional needs. All I am interested in is whether there are biomaterials with better compressive strength than bone.
Tagged "science-based" because I want this to be an actual material, and not [handwavium](https://tvtropes.org/pmwiki/pmwiki.php/Main/AppliedPhlebotinum), but not "hard-science", because whatever this is has probably never actually been used in a supportive structure in real life.
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**Silica** - networks of silicon and oxygen with the general formula SiO2.
Diatoms make their shells out of it. Plants incorporate it into their cell walls. Sponges make their spicule skeletons out of it.
You just need to scale it up. Rather than building microscopic shells or a composite matrix of tiny spicules and collagen / cellulose, just keep depositing larger and larger layers of straight silica.
The easiest form to deposit bulk silica in would probably be opal (hydrated amorphous silica), which would look awesome, but isn't super strong--worse than regular bone. But if you can get the organism to exclude water and just produce macroscopic solid chunks of pure silica, you're looking at a compressive strength of around 1100 MPa.
And if you wanna go a little further out there... **Sapphire**
Sapphire is aluminum oxide, Al2O3. It has a compressive strength of 2 *giga*pascals, so even if you accept some losses in incorporating it into a biological composite, you're still starting out way ahead of natural bone. Aluminum is not currently know to play any significant role in biology, but it is bio*available* in ion form (e.g., as aluminum citrate) and accumulates in the biosphere, so it should be available in normal food supplies--and if biology can handle laying down oxidized iron crystals, I'm sure something can be worked out for depositing oxidized aluminum!
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# Abalone-chitin composites (and dinosaur engineering):
Without making the individual materials, it's hard to promise that the resulting substances will be super-materials. But research into [artificial bone graft materials](https://en.wikipedia.org/wiki/Artificial_bone) suggests a likely composite. Hydroxyapatite tends to be brittle, so more flexible materials are being researched. Another excellent article on biomaterial ceramics like bone and nacre can be found [HERE](https://ceramics.org/wp-content/uploads/2014/05/McKittrick-article.pdf).
* [NACRE](https://en.wikipedia.org/wiki/Nacre), also known as mother-of pearl, has great composite strength. [Artificial nacre](https://pubmed.ncbi.nlm.nih.gov/24635413/) is being developed as a material due to these properties. It has an extremely high [Young's modulus](https://en.wikipedia.org/wiki/Young%27s_modulus), which is a general evaluation of strength, and has a compressive strength of [300-500 MPa](https://pubmed.ncbi.nlm.nih.gov/19627773/). It is composed of small plates, bricks, hexagons or disks of [aragonite](https://en.wikipedia.org/wiki/Aragonite) that are then separated by elastic biopolymers. In a study of [nacre versus whale bone](https://www.jstor.org/stable/3067740), nacre outperformed bone in studies of toughness, with bone being weaker and more brittle.
* Your material will need a viscoelastic layer between the plates (platelets) of aragonite, composed of a polysaccharide-type material. I would suggest a silk or [chitin](https://en.wikipedia.org/wiki/Chitin) material, since it already has a long history of being used for this function, and chitin can surround and fill in where the nacre stacks don't.
Unlike more exotic materials like graphene, these are biologically produced with current biology and don't require your organisms to reinvent the wheel (biologically speaking).
* **Design from Dinos**: I suspect (but I'm not a bio-engineer) that the square-cube law will hit your giants in the [joints](https://www.insidescience.org/news/giant-dinosaurs-stood-tall-squishy-joints) before this material would fail. Pressure on joints is already a constraint on humans, and a regenerative and arthritis-resistant joint design will be important to your answer's long-term success. You may also want to look to [dinosaur bone structure](https://www.sciencedaily.com/releases/2020/08/200820143232.htm) to understand how the construction of bone in dinosaurs may have contributed to their ability to support greater weight.
[](https://i.stack.imgur.com/NWHWQ.png)
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A quick Wikipedia search returns [a list](https://en.wikipedia.org/wiki/Mechanical_properties_of_biomaterials) of biomaterials with related compressive strength.
Cortical bone has a reported compressive strength of 100-230 MPa, while [Hydroxyapatites](https://en.wikipedia.org/wiki/Hydroxyapatite) is listed at 500-1000 Mpa.
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> Hydroxyapatite, also called hydroxylapatite (HA), is a naturally occurring mineral form of calcium apatite [...] Up to 50% by volume and 70% by weight of human bone is a modified form of hydroxyapatite, known as bone mineral. Carbonated calcium-deficient hydroxyapatite is the main mineral of which dental enamel and dentin are composed. [...] Hydroxyapatite is present in bone and teeth; bone is made primarily of HA crystals interspersed in a collagen matrix—65 to 70% of the mass of bone is HA. Similarly HA is 70 to 80% of the mass of dentin and enamel in teeth. In enamel, the matrix for HA is formed by amelogenins and enamelins instead of collagen.
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Wrapping up, it looks like nature has done already a good job at tuning the bone overall performance.
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**Stone.**
<https://commons.wikimedia.org/wiki/File:Acropolis_-_column_of_the_Propylaea.jpg>
[](https://i.stack.imgur.com/ujaOcm.jpg)
<https://pubs.naturalstoneinstitute.org/pub/2c4ec57c-aef5-8a85-16e0-106c5cada13c#>:
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> A higher compressive strength indicates that the stone can withstand a
> higher crushing load. The required values range from 1,800 psi (12.45
> MPa) for marble to 19,000 psi (131 MPa) for granite.
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Your animals would of course not make stones, but would find suitable stones and put them in their bodies. Other animals use environmental objects chosen for hardness - hermit crabs come to mind, using found shells (or anything else of suitable size and shape) as carapaces.
Your creatures will find stones and incorporate them as weight bearing elements. I envision them stacked like the above column, much as our own vertebral column is stacked. Stones will be held in place by tendons and ligaments just as our bones are. They could be endoskeletons or exoskeletons.
The stone - stone interface will naturally wear into shape as the animal moves, forming interfaces the one to the next. A consequence of this is that previously used stones from dead giants will already have wear on them and so would work better as skeletal elements than fresh stones with only abiogenic wear.
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I like the idea of technologically sophisticated aliens bringing presents to these giants: ceramic coated metal skeletal elements. Now the giants can get really big!
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I have a planet covered with a large shallow ocean, which extends over most of its surface. I want to turn this planet into a great desert, specifically a salty desert (the salts of this desert are a mixture of several chlorides, not just NaCl, there is also NH4Cl, MgCl2, CaCl2, etc.). On Earth there are small salty deserts ([salt flats](https://en.wikipedia.org/wiki/Salt_pan_(geology))), which form when a lake evaporates and leaves behind all the salts that were dissolved in it. I wanted to do something similar to form the salty desert of my planet, but the question is, where will all the water go?
The surface, which is completely covered by large amounts of salts, must be depleted of water, since it would dissolve the salts in one way or another (with rain, for example), which I do not want. What mechanism could I use to remove all the water without affecting the salts?
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Keep in mind that I don't want to eliminate the atmosphere (as happened with Mars) or add greenhouse gases to increase the average temperature of the planet and keep the water always evaporated in the atmosphere. Freezing the water and depositing it on the surface is not an option either. Sending the water underground is a good idea, but you should find a way not to send the salts too. It would also be possible to add some compound that reacts with water and depletes it. Things like that.
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Answer is very simple: **Glacial Period**.
Most of the water would be captured in polar glacials, while at the equator, it would be a very dry, extremely hot at daytime, desert.
There was such a situation on Earth during the (last) glacial period (our oceans are too deep to dry out, but some water bodies did).
**Edit:** There would still be rivers flowing from glacials which will bring minerals with them. If there are vast shallow basins, where this river will flow, they will form vast salt deserts in mid and low-mid latitudes, exactly as you want it.
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Earth has a lot of water because it is made from the remains of old stars that spit out tons of Oxygen and Hydrogen. If your planet is in a star cluster where none of the right stars have ever exploded for there to be much Oxygen, there would not be water in it's makeup.
So at first, your planet is just a boring, dry as a bone world. Then one day it collides with a massive comet from a distant star cluster where water is plentiful. It explodes leaving a shallow ocean over parts of the planet and introduces large amounts of CO2 into the atmosphere. The carbonic acid needed to dissolve the salts forms as the rain water falls through that CO2.
*This brings up one minor issue with your planet which is that ocean salts come from acid rain hitting land. Your world can not be completely covered in salty deserts, but they could cover a large % of the world.*
On Earth, the water that slowly sinks into the ground is being spit back out just as fast by volcanoes, but on this world volcanoes don't spit out water because there is none in the mantle. This means that after some time frame, the water left behind by the comet would mostly dissipate into the ground. There would still be water on the planet, but by the time it is done defusing evenly into the planet's interior, surface water will be just as scarce as any desert.
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One option would be to have an huge geological formation that formed a completely closed bowl with mountains on all sides a little like the ring of fire but on a smaller scale perhaps a few hundred - a thousand miles across. This could be in a remote but wet area.
Over time this area would fill up with rain water to form a very deep wide inland sea and the rest of the planets shallow oceans would be depleted of water.
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I don't think that you can get rid of the water without getting rid of the atmosphere. You just need a mechanism to replace the atmosphere.
Hit it with a big enough rock.
Theoretically Earth was an ocean world before it was hit by a rogue planet about the size of Mars. A lot of the lighter stuff was blown out at or above escape velocity. So that blew off most of our ocean (or all of it and it was then repopulated via comets). If the strike happens after most of the planetary afterbirth has been swept up or kicked out by other planets, you would end up with a dry world. Out gassing from volcanoes may be enough to restore an atmosphere (or just one or two comets after the big hit).
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Does the entire surface of the planet need to be desert, or just most of it?
If your world with a shallow ocean experienced some form of massive, sudden continental shift that then formed one very deep ocean, in theory all of the water could over time evaporate from the shallow ocean and rain over the deep one. Of course there'd be some redistribution, but if you enclose your deep ocean inside a rim large mountains, it could cause a sufficiently contained localised climate that would keep most of the water there. And if that ocean formed in one of the colder regions of your planet, there would be far less evaporation there than on the rest of the world.
Even with all of that, it would still rain from time to time on the rest of the planet. I think it would be impossible for this to keep rain away forever. But it could create massive expanses of salt deserts that experience rainfall less than once a year, and probably less than once a decade if you force the system enough.
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Electrolysis
The water gets broken down into hydrogen and oxygen by lots of lightning strikes. The hydrogen escapes the planet's gravity. Salt water actually aids in the process -- most hydrogen gas generated on earth by electrolysis is a byproduct of producing chlorine.
It requires A LOT of lightning strikes, of course.
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# Turn your large shallow ocean into one small, very deep one. And cover it in ice.
To make a world mostly dry, and the surface into a lot of desert, you just need to reduce the surface area of exposed water. The less surface is exposed to air, the less evaporation, the less rainfall.
If you want to make the drought even worse, put this new, deep ocean on one of the poles. So what surface water is exposed, is not water but ice.
All that is required for this sequence is some nicely accurate Geological shuffling, possibly a new tectonic plate movement away from the polar region?
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If for some reason you have a lot of alkali metals or alkaline earth metals (maybe underground deposits that at some moment get in contact with the water), water will react with them to form a hydroxide and H2, which in turn can escape from the planet. You will need a lot of them, though.
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Simple: You fire solar flares at it and weaken its magnetic field. That works. Just ask Mars.
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# The Dune Way:
Import Shai Hulud. Wait 200 years. Your planet turned into Dune II. Wait, that's already a book: *Heretic of Dune*.
# The Space-travel way:
Your ships use water in their drives. They fill up on water, then blast that out of the engines as "reaction mass" when they fly. A lot will be used in interplanetary travel. Slowly, the planet will end up dry. There was a story about that, which I fail to remember, where Mars, to try to evade Earth's raising water tax, sent a ship to haul an ice asteroid in. Your planet? Was sucked dry instead.
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**The water permanently drains into the mantle**
Earth's mantle contains at least as much water as all of Earth's oceans, dissolved in various minerals. On your planet, make the crust very porous, and the ocean water will sink into the mantle at a high rate. If the mantle is able to retain all of it, then most of the water will be lost off of the surface and be trapped deep underground. In other words, the water table will start tens of thousands of meters under the surface. This will result in a planet-wide desert. Make sure your planet is not too geologically active, because vapor water might re-enter the surface water-cycle from volcanoes.
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Initially Earth was very close to a water world.
From about [4 billion to 2.5 billion years ago](https://en.wikipedia.org/wiki/Archean) The early Earth was a lot more tectonically active than today, due to the combination of the energies of accretion, radioactive decay, and the formation of the metallic core. It was during this time that the Earth's crust cooled enough to be called solid, although again, there was quite a bit of tectonic activity.
This activity generated structures called [cratons](https://en.wikipedia.org/wiki/Craton), which are the oldest rocks on earth, about 5-7% of the total crust. Cratons are like daggers of rock that reach deep into the mantle. The Canadian Shield is one example. These structures are also the place where diamonds can form, deep enough for the pressure to create them, and then they work their way up to us in a few places, such as the Kaapvaal Craton in South Africa.
Even at this stage there was evidence for deep oceans on Earth. Volcanic eruptions under water generate distinctive shapes known as pillow lavas. More to the point, these oceans had sky high iron content, not surprisingly. What they also had was some kind of photosynthesizing cyanobacteria, which is how the distinctive [banded iron formations](https://en.wikipedia.org/wiki/Banded_iron_formation) are created.
Now, there is a trick one can do, given tectonic activity, and moving plates. The plates will move around the planet, dragging the cratons with them. Cratons, for all their durability, are a fair bit lighter than the basalts that are erupted under the sea to create the sea floor. These eruptions happen along the fault lines that make up the oceanic ridges, pushing basalts outward.
As these basalts cool, they become denser and eventually slide under the cratonic plates, and sink towards the mantle, along with seawater, which makes the rock thinner.
These are the [subduction zones](https://en.wikipedia.org/wiki/Subduction). Alaska, California, Japan, Indonesia, the Andes, the Rockies, the Ring of Fire is where this process happens.
This thinner rock is heated and forced up to the surface. Some of it is molten, and gets erupted into igneous crust, like we see in Scotland, and the Black Mountains in England, when it passes over a hot spot, or mantle plume. Compared to the plates, this rock and water mix is frothy, and light.
This process is how continental crust is created, more or less, over geologic time. Fresh rock from the oceanic ridges, pushed outwards, cooling as it goes, until it is heavy enough to sink back to the mantle, except that the water makes the rock thin enough to be erupted via surface vulcanism, the lava flows become new land. This new land gets smashed into other new land at the subduction zones, or pulled apart which allows for more vulcanism, and more new land.
Now, Earth possibly went through something called the [Late Heavy Bombardment](https://en.wikipedia.org/wiki/Late_Heavy_Bombardment) which would have brought a great deal of water bound in the rocks themselves. However, your planet may not have gone through this. YMMV.
Over time the continents will become bigger and bigger, and drift will eventually create a super [Pangea](https://en.wikipedia.org/wiki/Pangaea) type continent.
This structure will last for millions of years. There will be heavy rainfall near the shores, and a vast, world sized desert in the rain shadow created by the uplifting of the crust to create the continent. The salts you require will be all over the interior of the continent, which will be vast, but most of it would have been sea floor a few million years ago. There'll be your salt, as well as limestone, everything you might want, but almost no water.
The oceans and coasts will generate enough oxygen to create an ozone layer, so your desert can be utterly dry, like the Atacama, or the Gobi, and yet not sleeted with killing UV so life can exist.
I think that covers most of the requirements?
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If a character in my book series gets petrified by magic, how would the process feel physically? Here are some things to note when answering this:
-The character has similar physiology to that of a human
-The petrification process takes approximately 5 seconds to complete
-The character loses consciousness as soon as they are 100% petrified
-The petrification is undone later via magic
-The character is not simply being frozen in place but is literally being turned to stone
-The petrification happens as a result of magic
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Similar to some kinds of convulsion, everyone put under petrification would let go a loud and horrible scream as all the air is forced outside his body due to intense contraction of muscles or them becoming stone.
The sensation of heaviness of limbs, upper and lower, could be similar to the ones experienced by diabetic people who suffer from peripheral neuropathy. First the sensation of wearing thick gloves and socks, then, as the condition furthers, the lack of feeling with the remaining heaviness.
As the diaphragms gets immobilized, accessory muscle of the chest start to try and balance the inspiration. Visible muscle of the neck and thorax contract painfully until they too get petrified.
Shortness of breath takes place until you just stop breathing, you gasp uncontrollably seconds before you cease any pulmonary activity.
Your muscles may tear, as you're desperate to do something, anything, and keep fighting and moving. Newly transformed fibers might get shredded by soon to be stone muscles that are still functioning.
Your ear's drums just stop moving so you loose your hearing just before losing consciousness, being thrown to a world without any sound.
As your eyes become petrified you feel that scratch and the urge to close your eyelids, but you just can't.
Before you know it, you're out and everything stops. There might be pain involved or not, that's up to you, but clearly desperation would be a part of it. As you get depetrified, you come back to the last thought you had, feeling pain, out of breath and everything. You may not have any damage to you physical body, but your mind might be psychologically damaged and the fear lingers on as you try to understand what just happened.
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This answer will focus on the sensation of petrification. After all, the question asks what would petrification feel like.
If petrification only takes five seconds and the petrified person loses consciousness after the conversion into stone. Frankly five seconds isn't much time to respond or react to the process. It would be like undergoing paralysis, being turned into stone make any movement difficult, with rapidly impaired circulation of the blood accompanied by loss of sensation. Large sections of the person's nervous system would be turned to stone. This means any neural signalling would be shut down within seconds.
This makes it very likely the person being petrified will undergo a numbing sensation to their whole body to the extent of a total loss of awareness of their body. Five seconds after its commencement, they will have lost consciousness.
In conclusion, being petrified will feel like fainting or blacking out. There won't be amount time for the failure of their physiological functions to cause any discomfort or pain, becoming immobilized within a very short time (less than five seconds), and followed by a complete loss of consciousness.
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To round off the little series started by [this](https://worldbuilding.stackexchange.com/questions/123534/what-would-a-medieval-war-against-an-aquatic-race-look-like) and [this](https://worldbuilding.stackexchange.com/questions/123598/what-would-a-medieval-war-against-an-air-borne-race-look-like), I figured that I should add this question.
The setting: there is a race of underground people living beneath a human kingdom.
To avoid the connotations that come with ‘dwarf’, lets refer to these people as ‘molemen’ instead.
These molemen are short, stout, nearly blind, and are excellent burrowers and miners. They have evolved in an ecosystem that is completely removed the sun, their culture has no concept of the world above. They live in a vast network of deep tunnels and in extremely close-knit communities, and they have a very well-structured society.
These molemen farm lichen and mushrooms, they tender rats as livestock, and they gather roots. They harness heat from deep volcanic vents, and they draw water from underground aquifers. They are extremely proficient in tool-making and metallurgy - much more advanced than their counterparts on the surface. However, their numbers are smaller and their society is very rigid. Food is constantly limited, so the molemen live frugally.
The molemen have developed gunpowder, while the humans have not. They haven’t yet invented the musket, but the molemen are using [fire lances](https://en.m.wikipedia.org/wiki/Fire_lance) similar to early China, as well as explosives used in mining.
For centuries, neither moleman nor human have had any knowledge of the other. The molemen shun the surface and tell horror stories about a ‘big ball of fire’ that hangs in an abyss. The humans have occasionally seen evidence of molemen (their sewage and waste expelled to the surface, for example) but have assumed that it's just some freak natural occurrence.
But then, this all changes. One of the molemen’s main tunnels is overmined and becomes structurally unstable. Above, the human’s capital city grows too large and heavy. After a series of earthquakes and tremors, the ground collapses - swallowing half the city into a pothole two hundred foot deep.
The two species are revealed to each other, and both their reactions are “Holy shit, there’s a bunch of monsters living down/up there!”
After this unpleasant first contact, conflict arises. Despite their aversion towards light, the molemen are drawn to the surface for its abundant food and supplies. The humans are drawn underground by rich veins of metal and gold.
War is declared, and the human king is very eager to crush these strange underground people.
But how?
As his advisors warn, the molemen’s tunnels are labyrinthine and they have no idea how far they stretch. It is very likely that there are tunnels beneath other cities and castles too, and there is a very serious risk of their infrastructure being undermined and collapsed from below.
Any regiments of soldiers sent below ground into the opening are at a severe disadvantage, being blind and lost. The molemen can easily ambush the soldiers in their tunnels, or collapse the tunnel and leave the soldiers trapped. The molemen have the superior weaponry, knowledge of the tunnels, and their underground defences are absolute.
Nobody knows how deep the tunnels go, but it is suspected to be hundreds of feet. The molemen are by the far better miners, and they are also fond of burying caches of gunpowder as explosive traps.
Even worse, the molemen can pop up from their tunnels anywhere, at any time, and there is no means of tracking their movements from the surface. The sun hurts their weak eyes, so the molemen often attack the surface at night.
The humans fear the molemen will collapse and overrun their nation from below.
They require a military strategy to both defend themselves and counter-attack, but how?
For answers, assume that this is a low-fantasy setting. Solutions that rely on magic are possible, but discouraged.
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**you don't need to fight them at all**
**turn them into the next Atlantis**
if the humans city is near a river/sea (i would hope that it is) make the humans dig a trench over to that big gaping hole that just opened up, then just let the water do the work for you. The mole-men nation will all drown before they had a chance to fight back
To quote Pennywise
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> They all float down here.
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**Smoke them out**
Another way without sending any men down there is to set fires in every tunnel entrance. The smoke will suffocate any mole-men near, making it easier to clear entire burrows in one go. Or drive the mole men to come to you where you surface dwellers will make quick work of them. Adding toxins to the fire will aid you in the killings
**Poisoning their water supply**
Even being a subterranean race they will have a water source somewhere. Poison the water and soon the mole-men will know why they fear the surface world. Even if all the water is underground there are ways to poison it, send a few brave men to the water, dig till you get to it ect.
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We can eradicate the moles the same way that we have been eradicating other species for millenia - by destroying their ecossystems.
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* It is unrealistic for them to feed on lichen. Lichen is a symbioses between a fungus and photosynthetizing bacteria. That requires sun.
* Shrooms depend on organic matter to decompose. Once it becomes the sole food source for them, they will be feeding their dead to it.
* Roots - now this is where it's at. You can cause a lot of damage by finding out the plants from which the molemen gather roots, and watering those plants with lead or arsenic. Or you can just burn the upper portion of the plants to the ground - after all, the photosynthetizing that makes the roots so nutritious happens on the sun-exposed side.
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> The humans have occasionally seen evidence of molemen (their sewage and waste expelled to the surface, for example) but have assumed that it's just some freak natural occurrence.
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I used to play and old PC game called Sim Ant, from the same minds behind Sim City. You control a nest of black ants and you have to destroy a nest of red ants. The game usually involves a lot of strategy regarding food acquisition, breeding a large amount of workers and soldiers, cornering the enemy and doing tunnel warfare to kill their queen.
But I discovered that you can cheat your way to victory quite fast by sealing the enemy's tunnels.
We are already poisoning the moles' food supply from above. Next, seal their waste and sewage tunnels. The smell inside should become unbearable to them.
---
Now, they can pop up from anywhere. But they can't farm anywhere, because they fear the very source of energy for practically every ecossystem on Earth. When they are feeding their dead to their shrooms, they will attack humanity to steal food. What we do then is guard our granaries. Use underground traps - let them dig through a cesspit or tar if they want to come from below. Otherwise they have to come marching, and that's warfare that we are used to.
---
When they are so poisoned, starved and covered in waste that they can't go on anymore, they will either give up or move somewhere else. We win.
[Answer]
**1) Force disorganization**
Find an entrance tunnel of theirs and dump some toxic gas (smoke works), preferably denser than air. The gas sinks into their deepest tunnels. This force the moles to rearrange, as their most valuable resources will most likely be down there, including their children. Continue doing this, until a significant portion of their tunnels is filled with the gas. Smoke also works for this purpose.
Alternatively, if there is a large body of water nearby, make a connection from their tunnels to it. This may require the deaths of a few workers, but it will surely force the molemen out of their deepest tunnels. The body of water just needs to be close to one of their waste tunnels, because there must be other tunnels near there.
**2) Attack**
The molemen are disorganized. A significant portion of their manpower is devoted to making their tunnels less accessible to the human chemicals. Send men with a light source to charge through the tunnels. The news of the flood will have reached all the soldiers, making them panic, and more likely to flee. A couple groups of your soldiers might die from the moles, but you should make most flee.
To create even more confusion, in the previous step, pour oil into the tunnels of the molemen to make them think that the fireball in the abyss is spending into their tunnels.
Your soldiers will follow the molemen through the tunnels, hopefully leading them into a "city" of tunnels. Your soldiers should then massacre all of the mole men they find. Follow the molemen that are fleeing to the next city. Repeat.
[Answer]
**Use the natives against the natives.**
>
> When asked by George Marshall in 1942 how the Army should train for
> pivoting from the war in Europe to the Pacific, the commander of the
> Marines on Guadalcanal answered “go back to the tactics of the French
> and Indian days . . . study their tactics and fit in our modern
> weapons, and you have a solution.”
> <https://www.hoover.org/research/lessons-indian-wars>
>
>
>
Fighting strange natives on their home turf is a risky endeavor. But maybe these warlike natives like to fight each other? Co-opt one group of natives with your resources and wealth and then let them teach you how to fight their own kind. This is what the Americans did with the Indians during the settling of North America.
So too with these molemen. Fighting them all in the tunnels is a losing proposition. The king will need to learn their ways and then back one faction. Toplander food alone will give that moleman faction an advantage. If the molemen do not have liquor, see how they like that too. Then have your allied molemen help you wipe out the rest or drive them deeper underground, giving you access to the mines.
---
**Let the germs do the work.**
Move quickly in the above endeavor. The molemen might not have been exposed to surface world diseases and you might find your allies getting sick. Disease actually did much of the heavy lifting softening up the Amerinds for conquest. It would be good to learn your way around down there before they all die. Note: disease can be a two edged sword. The Europeans had smallpox and measles to share but the Amerinds handed off the Great Pox syphilis. The molemen might have diseases of their own your toplanders have never seen.
[Answer]
Moles rely in their highly developed hearing for probing their surrounding environment. It's highly likely that also your molemen will do the same.
Therefore your only hope for limiting them is to create loud noises underground. Lacking explosives, you have to rely on mechanical means: a series of trip hammers constantly hitting poles in the ground would create a loud underground environment, ensuring a molemen free zone.
This could ensure some protection to location like mines, wells or deep cellars. I don't think the molemen are a real threat for cities and buildings: since you mention they are afraid of the outer environment, they will probably refrain from being accidentally exposed to it.
You might even try using molemen-proof poles (if existing) to create a sort of underground maze to hamper their movement.
But that apart I don't think you have real means of attacking them.
] |
[Question]
[
My [question on refueling around stars](https://worldbuilding.stackexchange.com/questions/79376/refueling-from-stars) got me thinking about the [transit method of detecting planets](https://exoplanets.nasa.gov/interactable/11/) and how it could be used to detect a ship whilst it is refueling (either by accident or on purpose).
Now I know whether they can detect the ship depends on the size of the ship and the distance it is from the sun. I'm not particularly fixed to these figures but it leaves the question too broad without it so lets say my ship looks like a cylinder $20$ kilometers long and with a radius of $5$ kilometers.
I want the ship to be detected and then, to avoid detection again, one of the scientists on board comes up with the [neat solution Xen2050 proposed](https://worldbuilding.stackexchange.com/a/79513/36817) so the ship can hide next to a planet.
**So my question is whether it is realistic to assume a civilisation with similar tech levels to us could detect a ship like this within their galaxy.**
* If not then what are the limiting factors?
* Obviously this is distance dependent...we would notice it orbiting our own sun (I imagine) but would we notice it around a star 1 ly away? Is it possible if it is the other end of the galaxy?
[Answer]
**No**
An object that size simply would not block out enough light to be detectable. If we assume a [sun-sized](https://en.wikipedia.org/wiki/Sun) star then the surface area of its disk is $1.5\times10^{12} \text{ km}^2$ and your ship at its largest apparent surface area is $200\text{ km}^2$. Which means it would block $1.3\times10^{-8}$ percent of the light, which is well inside the noise coming from a star's brightness measurement. [Here](http://www.nature.com/nature/journal/v494/n7438/fig_tab/nature11914_F1.html) is an example of what a light curve from [Kepler](https://en.wikipedia.org/wiki/Kepler_(spacecraft)) would look like anything not planet sized would be undetectable.
Here are some examples of a light curve from the link. Three different transitioning planets are shown here. Notice how the measurement jumps around from environmental noise.
[](https://i.stack.imgur.com/nee7C.jpg)
[Answer]
**TL;DR:** It seems like your craft will produce brightness changes many orders of magnitude too low to be detected by a civilization with technology comparable to ours at the present day. Even in a couple of decades, I don't think our telescopes will have improved enough. In particular, variations in the star's intrinsic brightness will drown out any signal of an exoplanet.
# Transit simulation
I simulated the transit of your spaceship in front of a Sun-like star. Besides the dimensions of your ship, I made the following assumptions:
* A roughly circular orbit, with semi-major axis $a=0.1\text{ AU}$.
* A [limb darkening](https://en.wikipedia.org/wiki/Limb_darkening) coefficient of $u=0.6$, and a linear limb-darkening law.
* The star is Sun-like in terms of mass, luminosity, and radius.
Mathematically, I used a limb darkening law of the form
$$I(r)=I\_0\left(1 - u\left(1-\sqrt{\frac{R\_\*^2 - r^2}{R\_\*^2}}\right)\right)$$
where $I$ is the power per unit area on the star. I calculated the proportionality constant $I\_0$ such that the star's luminosity before the transit was equal to $L\_{\odot}$. For each time $t$ during the transit (with 500 timesteps), I created a 50-by-100 grid representing the outline of the ship, and integrated $I(r)$ across that grid, then subtracted this from $I\_0$.
Here's the resulting light curve I simulated:
[](https://i.stack.imgur.com/NrCwi.png)
A quantity of interest is $\Delta F/F$, the fractional change in flux at a point during the transit. I found the maximum value of $\Delta F/F$ to be $4.14\times10^{-9}$ - higher than [Joe Kissling's answer](https://worldbuilding.stackexchange.com/a/79545/627) of $1.3\times10^{-10}$. The reason for this, I think, is that Joe used the average intensity of the Sun; taking limb darkening into account means that the center of the solar disk is brighter than average, meaning more light is blocked at the peak of the transit, and less light is blocked at the beginning and end.
# Lost in the noise
There are two factors that determine whether or not a given value of $\Delta F/F$ can be measured by a telescope. The first consideration is that a star's luminosity can vary on timescales of hours or days. Even a non-variable star like the Sun may experience changes of $\sim10^{-5}$ - orders of magnitude larger than our value. Sunspots, for instance, can be contributors. Here, stellar variability is going to wash out our transit.
The second issue is that a telescope's sensitivity is limited. Hubble and Kepler can detect transits of $\Delta F/F\sim10^{-4}$ (I'm trying to find a good citation; [the original link I used](https://www.ethz.ch/content/dam/ethz/special-interest/phys/particle-physics/star-n-planet-formation-dam/documents/Courses/ExtrasolarPlanetsFS2016/exop2016_chapter3_part2.pdf) seems to be broken) - impressive, but not good enough for our purposes. For comparison, a hot Jupiter orbiting a Sun-like star may produce $\Delta F/F\sim10^{-2}$, and an Earth-like planet orbiting a Sun-like star may produce $\Delta F/F\sim10^{-6}$.
In short, even at the peak of the transit, the change in flux is going to be several orders of magnitude too low for current (or even near future) telescopes to detect, and it will likely be lost in regular fluctuations in the star's luminosity.
[Answer]
It's not completely clear why something that happened 1 yr, or 100,000 years ago matters. From a distance of 1 ly, it takes 1 year for the light to reach us. A cylinder of the dimensions of 20 x 10 km would occlude < 1.5E-8 % of the Sun's light, and if it's orbit was oriented randomly with respect to our line of sight would have 0.5% of actually transiting across our line of sight. I'm not very familiar with astronomical statistics, but for general gaussian noise, the signal to noise ratio improves with √n where n is the number of samples. So, while I'm too lazy to compute the orbital velocity of your ship (at whatever distance from the star) after 100,000,000 transists (assuming we've been observing them all, and if we have, WHY???!!) the s/n will have improved by a factor of 10,000. So, say that the transit is in our line-of-sight (is in the 0.5% of all possible orbits), then it would be the equivalent of improving the light occlusion by 10,000X - meaning instead of 0.000000015 it would be 0.00015%. I think that is detectable, but I'm just basing that on what I think p.p.m means on the graphs I've seen. (I think it means parts per million of the average light intensity). Finally, most of the small exo-planets have been between 10 and 2000 light years from Earth. Our Galaxy is a very dusty place. We can see thing only quite close to us unless they are unusually bright. The rest is lost in the dust. But who cares about seeing whether your spaceship stopped to fill its tanks 3000 or 300,000 years ago?
] |
[Question]
[
I've watched and read many SF stories which included nanites as a wonder weapon that can do pretty much anything. One such series is the [Star Marine series](https://en.wikipedia.org/wiki/Legacy_Trilogy) by Ian Douglas.
Those books frequently quote the nano disassemblers as able to chew through a meter or more of exotic materials in several minutes.
I've always thought this was far too optimistic performance for nano-machinery.
I would agree with the theoretical capabilities of these devices (manipulate materials at the molecular level, transport materials from one location to another, etc.). However, manipulating materials at this scale does not circumvent the laws of thermodynamics or geometry.
From a thermodynamics perspective, they require a means of transporting instructions into the nano machines, *usable* energy into the system, transporting waste heat out of the system, and transporting materials out (for disassembly) or in (for assembly).
One great advantage of nano machinery is its potential ability to multiply capabilities. However, geometry restricts them to acting on an expanding spherical surface or a constant area surface (e.g. burrowing a tunnel).
Nano machines do not move quickly in relation to the macroscopic world. [The world's first nano-machine race](https://www.scientificamerican.com/article/drivers-gear-up-for-worlds-first-nanocar-race/) is expecting the machines to move 0.3 nm (0.000000003 meters) per each propulsive impulse and **complete the 100 nm course in 36 hours.**
What are realistic numbers for nano-machine performance?
1. How fast can they move?
2. How fast could they chew through a surface?
3. How fast could that build a macroscopic machine?
[Answer]
Forgive me if this carries on a bit. I tried to be comprehensive and remain brief. Comprehensive won out in the end.
I'll define a nanomachine as an artificial mechanical construct to the scale of a nanometer (10−9 m). I would assume anything measured under 100 nm could be considered "to the scale" of a nanometer. I'll use a 10 nm3 block as a general size for one of these nanomachines.
This size brings problems with mobility, precision movement, available construction materials, and versatility among other issues. I hope to cover those somewhat thoroughly in the answer.
Also, there are a wide variety of potential uses for these machines, so for simplicities sake I will assume you are dissolving bad guys and their stuff with these little destructo bots or building yourself something awesome with them.
## Let's hit the first topic: **How Fast Can They Move?**
Often nanobots are introduced into an already existing system (usually aqueous) and serve a specific purpose within that system. I think comparing them to catalysts, or cells is a pretty good way to look at it. With that being said, almost nothing of this size moves on it's own in nature. The only self-propelling elements at this level that readily come to mind are viruses and bacteria.
The fastest speed I can find for bacterial movement is [200 microns/second](http://hypertextbook.com/facts/2000/ElaineKung.shtml) (a micron is 10−6 m). For something 10 nm in size that is an incredible rate, though not a lot of overall distance. If your machines were to move on their own I arbitrarily think up to doubling this could still be considered believable. I submit a max **self-propelling speed** of **~400 microns/second**.
However, systems themselves can move *much* faster. For example, the highest blood flow rate in the human body reaches ~180 cm/s. If you were to transport nanomachines in a similar way (expelling an aqueous solution through pressured valves) you would not have to bother with aiding their movement. This leads to the maximum speed that a thin aqueous solution (like an alcohol) could move. However, a reaction between the nanomachine and whatever it is eating needs to happen. I would again apply my arbitrary double rule to the blood flow rate since countless reactions happen while blood is moving. **System propelled speed** of **~400 cm per second**. That gets you magnitudes greater in nanomachine speed.
Really, depending on the activity the machines are serving this could vary greatly. In essence, if you propel them, they are limited on the speed of the action they perform. Seeing as some chemical reactions are basically instantaneous (photo decomposition) while other physical reactions can take millenea (forming diamond), your variety is *huge*. I'll address this later though.
## Now we move on to the next topic: **How fast can they chew through something?**
This is also pretty variable. There are so many surfaces they can chew through, from weak fleshy membranes which even mild chemicals destroy instantly, to a [slab of tungsten](https://what-if.xkcd.com/89/) that could possibly survive hitting the surface of the sun (for an instant). I'll keep any calculations vague to accommodate this.
I'll settle on magnesium metal since it is somewhat similar to aluminum (one of the most commonly used metals in modern manufacturing) and I found data for it without needing a lot of research. If you react magnesium (also aluminum) with Hydrochloric acid (HCl) it quickly dissolves. I found [this](http://www.scholaradvisor.com/essay-examples/reaction-of-magnesium-and-hydrochloric-acid/) data from an experiment measuring the rate of dissolution for magnesium in HCl. Powdered samples dissolved within 30 seconds when submerged in 3 molar HCl. It is possible to get higher molar acid, with a [max around 12M](https://chemistry.stackexchange.com/questions/27748/what-is-the-maximum-molarity-of-aqueous-hcl). It appears that even with the strongest acid the max speed of dissolution floats around 15 seconds. These samples could be equivalent to maybe 1cm^3 of solid metal. Because solid metal has less surface area I'll use my magic doubler and give a value of 1 cm of metal surface dissolved every 30 seconds. Assuming we would only use nanomachines if they were more efficient than this acid, I'll double efficacy, leaving **1cm of metal dissolved per 15 seconds**.
## Now for your last question: **How fast could they build a macroscopic machine?** (if I got that right)
This is where I think nanomachines are a bit over-hyped. There are a couple of issues that we run into.
1. Where do the machines get the materials to build with?
2. How do these machines transport these materials?
3. How do you give detailed instructions to the machines?
With these questions in mind, I am giving a lazy answer: *Don't use nanomachines for manufacturing*
Right now we have so much available that is rapid, precise, and simple. Robots already pump out parts, devices, and machines at incredible rates. These parts are often on a macro scale, and when they are not, the process is still incredibly efficient. I mean, we have 3D printers that use lasers and gel to create anything that you can draft accurate to microns. It is fast and cheap and easy. I don't imagine that throwing nanomachines into the mix would make any aspect of manufacturing measurably better. The energy used to move materials with nano-machines and to give instructions to them seems too great to be of benefit.
Their use in creating drugs and chemicals is already pretty amazing. They can clean materials or products, treat materials for specific uses, and do a host of other things, but as far as building larger machines themselves goes, it does not seem too useful (please list any good uses you can think of in a comment).
Maybe a better idea would be like the nanobots found in *Big Hero 6*. Instead of building a macromachine, perhaps these nanomachines could combine their efforts and function as a macromachine collectively.
Altogether my answer comes to this:
* **Self Propelled Speed: ~400 microns / second**
* **System Propelled Speed: ~400 cm / second**
* **Speed to eat metal: ~1cm / 15 seconds**
* **Speed to build a macromachine: Not useful to build macromachines**
This is all very general, and depending on specifics could vary quite a bit. I hope that helps.
[Answer]
I think the key is to span scales. A multi-cellular organism like a whale is not a simple collection of cells like a biofilm or even a sponge. It has a circulation system where materials are pumped at speeds many orders of magnitude faster than the numbers you lament about, and the vescles and pump are *made from* those same cells. There are large scale systems made from organs, which are made from tissues, which are made from eucaryote cells. Continuing down, those complex cells are made from organelles and internal resource distribution systems, made from nano tissues (to come up with a term) which are masses of individual nanomachines.
So you don’t apply a mass of primitive procaryote-scale nanobots at a meter-scale task. You organize them into a series of successive systems at ever larger scales. Each system operates at a scale about the same as its own size, and is made from systems at the next scale down.
Look at the task of making a meter diameter tunnel of some length through rock. Consider the difference between a *drill* and a *hole saw*. You don’t need to rip apart the entire bulk of rock at a molecular level. You break it up into small chunks and then move those chunks. This might be done like a fungi growing, with the working face attacking the rock with “enzymes” or other nano-scale tools to rip the atoms apart. Power, raw materials, and cooling is transported using a circulation system — blood or sap in pipes moving at high speed, not the same speed as nano-transport *within* a nanobot.
Clearing the debris can be done the same way a mole rat does it, by building up mechanical systems at the proper scale to lift and push them. So you build up tissues and then muscles (or whatever — hydrolics, belts and gears).
[Answer]
* I think If you want to go with disassembly, choose your regular
fluor-antimonic acid. (the nanites can control, where it flows)
* The real problem is transporting. I can only speak about how my story
got around this: magnetic nanites, carried around by superconductors
([based on this](https://worldbuilding.stackexchange.com/a/12527/32097)).
* For building, I think it would be good if you use this strategy:
nanites get a small task assigned to them, they execute it and build
a block of the structure you want, these blocks get placed together,
into bigger ones and the bigger ones into more bigger ones, the
process will repeat itself.
* Communication and data storage: go with natural stuff (DNA, hormones,
nerves, etc..), choose the toughest creature as your base for
nanites, our [tardigrade overlords](https://en.wikipedia.org/wiki/Main_Page), the ones who won the
evolution.
And keep in mind:
>
> Nanite's strength lies in their ability to cut the great work into
> their smaller, personal tasks. You don't just grow sphere with
> a constant speed, you cut it into two, then reunite them, once they
> grew enough.
>
>
>
Quotemine This! -*Redacted Redacted*
And for the aforementioned reason, I can't really answer your question, as there are lots of ways, in wich building times can be gradually decreased, but I'm gonna give you a link, about an ancient nano-factory, that is capable of reproducing itself, has some lower efficiency solar panels and has overtaken the planet by now. [Here](https://en.wikipedia.org/wiki/Poaceae) it is.
] |
[Question]
[
I have been daydreaming about this scenario a lot. There are many similar questions here about time travellers being thrown to the middle ages, but they usually can't prepare and can't bring anything from the modern times.
Let's set some constraints:
* Time traveler can only travel once from today to 14th century
* He can choose any location in the world to land
* He has a one year in the modern time to prepare
* He can bring one vehicle from the modern times full of modern things
He has a goal to **accelerate technological and social progress of humanity as quickly as possible**.
I'm wondering about:
* Which location to choose to establish base?
* How to prepare in the modern times for one year? What to focus on?
* Which vehicle to choose? (Tank, helicopter, truck, boat, ...?)
* What to bring in the vehicle? (off-line Wikipedia, antibiotics, guns, ...?)
* How to make a good first impression?
* How to hire locals into his services?
* How to deal with the church and religion? How to avoid total rejection of the people, because it's all 'work of the devil'?
* How to educate locals efficiently and give responsibilities to them to scale quickly?
* How to rule and form the society? Is it even possible without dictatorship and frequent demonstrations of power and violence?
*Is there some fiction which explores this scenario? So far I found only fiction where people are stranded in the past without any preparation or modern items*
[Answer]
I'd think the trick is, you have to bring technology that's more advanced than what the people of that time have, or what's the point?, but it can't be so far ahead that you have to build the infrastructure from scratch.
Like say you went to AD 1400 with cell phones. Of course the people there have no knowledge of electronics, or radio, or plastic, or even of electric lights. Even if you could explain to them how a cell phone works and make them understand, you have to not only teach them how to make cell phones per se, but how to make electrical wire, plastics, etc up to integrated circuit chips.
Unless you're bringing back a team of experts, you have to know all the pieces that go into whatever technology you're bringing back. Even with a year to prepare, that could be a tall order. Any given technology often builds on many other technologies. For example, I write software for a living. I like to think I'm a smart guy. If I had a little time to study and prepare, I could probably go back in time to 1920 or 1930 and teach people how to build simple computers, because most of the infrastructure is already there. But 1400? Where to start? I'd have to teach them how to make electrical wire. How do you do that? How do you make plastic? I know that integrated circuits are made from silicon and germanium. Silicon comes from sand. How do you turn sand into usable silicon? Where do you even find germanium? What does germanium ore look like? I haven't the vaguest idea. I could look all these things up, but there's a LOT to learn. I'd have to know about mining, metal smelting, electrical engineering, electronics engineering, physics, chemistry ... the list goes on and on.
On top of that, you have to have leadership and management skills. Like you ask about "how to hire locals". Lots of people with a great idea or great technical skills have tried to start a business and gone bankrupt because they don't know anything about management. Motivating people and getting them to follow you is a skill in itself. This is not something that can be learned in a 10 minute session.
You ask "how to rule and form society". Yeah, good question. Just because you have technology that they don't doesn't mean that people will want to follow you. When Europeans went to Africa in the 1800s, they had lots of technology that the locals didn't. Did the locals immediately hail these Europeans as their new leaders and make them king? That was a popular theme in fiction -- European goes to Afghanistan tribesman, shows some modern (19th century) technology, and they immediately make him their king, if not their god. In real life, I'm not sure that that ever happened. The Europeans often used their superior technology to subdue the locals by force. But that took an army. One man with a machine gun might be able to subdue a few dozen people with swords, but not a nation. If he's obnoxious enough, sooner or later they'll overwhelm him by shear numbers and kill him. And with just one man ... you have to sleep sometime.
And would they be wise to make you their king? So you understand technologies that they don't. Does this mean that you know anything about how to run a country? What sort of tax structure should your government have? What economic policies? How do you negotiate trade deals with other nations? How do you lead an army?
You seem to be assuming that because your time traveler is from the future, he is not only an expert on technology, but also on politics, economics, management, finance, military affairs, and every other conceivable subject. Just being from the future wouldn't necessarily make him better at ... any of these things. And while he could study and prepare, no one is going to learn to be a great engineer AND a great politician AND a great business manager AND a great economist AND ... AND .. AND ... Certainly not with one year of study. Most people spend their lives studying just one field and never rise above mediocre.
I'd think a realistic goal would be to try to jump the people forward a century or so. The printing press was invented in 1439. So learn how to build one and then take this knowledge to 1300 or so. That would probably be doable. And be content to be an engineer, don't try to make yourself king and god at the same time.
By the way, I doubt the problem would be how to fight the church, but rather how to get the church on your side. In the Middle Ages, the church was the people who ran the schools and sponsored scientific research. Monasteries were centers of learning. Many great scientists were priests or monks, from Gregor Mendel to Copernicus. Yes, yes, the Catholic church persecuted Galileo. But Galileo started out with the support of the church. He had new ideas and of course people questioned him, but it was all a polite, scholarly debate until Galileo started insulting powerful people for not instantly accepting his theories. Anyway, a monk or priest would probably be the first person of the time to embrace new science and technology.
*Update: Let's be more positive*
So how could you realistically go about it?
**How to prepare**
Step one: Come up with a plan for what technology you can realistically introduce. Just bringing a truckload of 21st century gadgets to the past would be mostly useless. The people won't be able to reproduce them because they don't have the infrastructure. Many wouldn't work in any practical sense. A cell phone is useless without a network of cell phone towers. A sports car is useless without paved roads. Etc.
Figuring out what you could realistically bring back would be an exercise all on its own. I'd pick two or three key inventions. Most 21st century technology would probably be impractical; more likely bring back some 19th century or earlier technology. Introduce the printing press 100 years earlier than it was really invented. The steal plow revolutionized agriculture. Maybe something medical or chemical? Could you bring back electricity? If you could teach people in the middle ages to build electrical circuits, that would jump start all sorts of technology.
Of course you would have to thoroughly research whatever technology you are trying to bring back. There is, of course, a huge difference between being able to drive a car, being able to repair one, and being able to build one from scratch. If this is a one-way trip, you don't want to get there and suddenly find yourself saying, Oh, wait, there's one thing I forgot to read up on ...
Research the infrastructure available in the time and place you're going to. You don't want to get there and find out that, while you need, say, aluminum for this device, the people there have never heard of aluminum and have no idea how to produce it. Make sure that you can get everything you need. You may need to research not only how to build this machine, but how to find metal ores that you need, and mine them, and refine them. Or how to synthesize particular chemical compounds, etc.
I'd practice actually building the thing using only materials that will be available at the destination.
Learn the language of the place you're going.
That's a lot to do in a year. 'Hope you're industrious.
**What sort of vehicle**
Well, I'd rule out any vehicle that requires paved roads or runways. Possibly an all-terrain vehicle of some sort. I'd think a boat would be most practical. Sure, you're stuck on the rivers, but that's probably more versatile than being stuck on roads or open terrain.
Whatever vehicle you bring, consider how you're going to get fuel for it. Unless your plan includes teaching the people how to find petroleum reserves and build oil refineries, any modern engine will be limited to the fuel that you bring with you. I'd look into what sort of fuel people of the time use, Kerosene? Some unrefined oil? Maybe find or build an engine that runs on that. Or, maybe an electric motor and run on solar power. The solar panels will break or wear out eventually, and will almost surely be impossible to replace, but it could keep you going for a while.
Is there a limit on the size of the vehicle? If not, perhaps the bigger the better, because then you can bring back huge quantities of stuff, even if you can't move it once you get there. Someone on here mentioned a nuclear-powered aircraft carrier. Or a freight train.
**What to bring?**
Books fully describing whatever technology you're trying to bring back of course. I'd lean toward printed books despite the size and weight. Sure, a computer with a terabyte hard drive could hold way more information than you could fit in books in a big truck, but what do you do when the batteries die? Or the computer breaks? Will you have the means to repair it?
Presumably you need basic supplies to keep you alive until you can establish yourself: food, clothes, medicine. I'd bring at least some weapons so I could defend myself if things went bad. Tools you will need to build whatever technology you're trying to bring back. Especially, tools to make the tools you will need.
**Make a good impression**
Hmm, well of course step one is to learn the language, and learn the customs of the place. Don't go urinating on their sacred shrine and so forth.
Don't suppose that people will flock to you because you have scientific knowledge they don't. At first they won't even know if what you're saying is true. I mean, if you tell them, "I know how to build a machine that flies through the air" or whatever, why should they believe you unless and until you've demonstrated it? Just like if someone came along today and said that he knew how to build spaceships that can travel faster than light, would you just believe him? Probably not.
I suspect the best approach would be to start with modest claims, i.e. things that don't sound unbelievable and that you can actually do on the spot with things you have brought, or that you can build fairly quickly.
Do I even need to say: Don't tell them that they're all ignorant fools and you have come to bring the light of wisdom and knowledge to them, and they should all fall at your feet. Don't ridicule their culture, their government, their religion, etc.
**Hire locals**
I think that's pretty straightforward: have something to pay them with. Bring back some gold or silver to get started. Maybe you could bring back hand tools, pots and pans, or things of that sort that people would be willing to barter their services in exchange for. If you're bringing back a technology of value, you should be able to find a way to make a profitable business out of it, or to get the patronage of wealthy people. Oh, figuring that out should be part of the plan you make before you leave.
**Deal with the church**
Contrary to popular modern mythology, the church in the Middle Ages was a major -- probably THE major -- supporter of scientific research. Yes, Galileo clashed with the church. Can you think of another example? People did not go around saying that every new discovery was "of the devil". I am not aware of any case in real life of a scientist or inventor being accused of being a witch by church authorities. Many, many scientists of the time were priests or monks, or taught in universities that were run by the church. The church is more likely to be your friend than your enemy.
Of course if you go around saying the church is teaching a bunch of superstitious nonsense and that church leaders are all ignorant fools, you're going to get into trouble. Insulting powerful people in any place or time is not generally a strategy for success.
[Answer]
So... before we go changing the past, let's get the basics done... **SURVIVAL**!
The rules of survival
* Shelter
* Water
* Fire
* Food
* Company
**Shelter**
Here you're ok, you have the vehicle that you are travelling in so you're covered initially. Add insulation if you're going somewhere cold.
**Water**
Getting a water source is going to be your next priority, you want to be upstream from any settlements to avoid contamination (filthy peasants) but not too close as rivers move over time.
**Fire**
I think the best way here is to take some gas for your first year, get out and chop some trees as soon as you get there. Green wood need 12 months of seasoning for the best use.
**Company**
You need to learn the lingo, ideally a language that hasn't changed over time. Maybe [icelandic](https://answers.yahoo.com/question/index?qid=20081114200702AAhk4pl) although it is a very difficult language to learn
After this your other questions start to answer themselves
**Which location to choose to establish base?**
The base needs to be where you can access people with a language that hasn't changed. It also wants to be close to water but not on the banks of a river.
**How to prepare in the modern times for one year? What to focus on?**
This is good, get your survival gear on, try it out, if you can't get stuff to work in modern times you ditch it. Get on YouTube and download as many tutorials as you can,
**Which vehicle to choose? (Tank, helicopter, truck, boat, ...?)**
1. Tank - lots of fuel, lots of noise, reduced storage
2. Helicopter - you can't land anywhere that isn't flat plus you need to continually maintain it
3. Truck - maybe, takes less maintenance and fuel
4. Boat - this is a great idea, although you are limiting yourself to waterways, which may not be a problem
**How to make a good first impression?**
Smile! but in seriousness this will take an awful lot of work, hide technology and other things initially and offer good services to people (maybe treating illnesses?) at a good price. Once you have a connection with a place it makes things much easier
**How to hire locals into his services?**
It depends what you want and where you are, for this action I would have them only do normal work initially and hire kids with less superstition for technical jobs and learning technology
**How to deal with the church and religion? How to avoid total rejection of the people, because it's all 'work of the devil'?**
Go to a place well away from the rule of the church! Out in the hinterlands the church has much less power. Avoid major cities, towns and thoroughfares.
**How to educate locals efficiently and give responsibilities to them to scale quickly?**
Kids, use the kids, take them on as apprentices and train them up in new skills and education. Start simply and then work upwards, teach letters, language, concepts, science. Don't denounce the church and be able to pay people.
**How to rule and form the society? Is it even possible without dictatorship and frequent demonstrations of power and violence?**
Society will form around you, the more you affect people, the more that society will change. However this is more than a lifetime's work.
In terms of structure, I would suggest taking over an isolated monastery and form a new brotherhood.
You will need to have people to carry on your legacy through the years.
**What to bring in the vehicle? (off-line Wikipedia, antibiotics, guns, ...?)**
So, first things
* Survival gear as discussed before
* food for a year, medieval food will make you sick
* all the first aid gear you can grab, plus all the dietary supplements you can as well
* limited, tough electronic gear. ideally military, with solar panels for recharging. Download as much youtube as you can, also the entirety of wikipedia. Have redundancies, don't use them until you need them.
* clothing, super simple undergarments that you can wear underneath time appropriate clothes
* Tools - this is a whole section, blacksmith tools, glassworking tools, farming tools, axes, bows, needles, cook gear
[Answer]
Well the 14th century is full of crisis :
**The Black Death** that wiped half of the population.
<https://en.wikipedia.org/wiki/Black_Death>
**The Great Famine of 1315-17**
<https://en.wikipedia.org/wiki/Great_Famine_of_1315%E2%80%9317>
So if he brings medications and antibiotiques, he will be idolized by them.
[Answer]
I think the existing answers have some great points in terms of practicality. However, I think they are all choosing the wrong PLACE to go.
Europe was a backward den of superstition and mayhem in the Middle Ages.
You would be much better off going to Byzantium (although it was in decline by 1400), Northern China, or Northern India.
I think India would be the best bet, for one overwhelming reason - it is not only possible, but actually easy, to learn Sanskrit in the modern era.
Do your research, and select an up-and-coming local ruler who was known by history to be open-minded and progressive. Remember, India was a lot less socially conservative back then than it is now - especially in the Tantric areas.
The game-changer militarily at this time was the advent of cannons, making fortified cities easy to breach and conquer. Cannons were invented in China, but only spread slowly and patchily westward. Any method for improving their manufacture (early ones were inaccurate, and prone to exploding) would give any kingdom/empire a winning edge militarily.
To make the biggest difference to history, choose someone near modern-day Punjab. There was a Sikh state there which held out against the Muslim invasion and kept the seeds of Hinduism alive when the rest of the subcontinent was over-run. Create a strong Hindu ally nearby to the Sikh empire, and the modern-day nuclear posturing between India and Pakistan could be completely eliminated ...
[Answer]
Bringing things is of course a nice idea but you need to be able to sustain yourself and bring a new culture to the area. In order to do this you need to teach yourself one skill that you can bring to the culture. I would take the one year to learn as much about medicine as I could. This is the one area that will directly improve people's lives more than any other (and get you the respect and trust of the people which is key to becoming a leader). You should also study up on how to generate electricity and use it for refrigeration for food preservation. These "inventions" will bring the most advancement bang for the buck and are relatively easy to do in medieval times (wires and magnets are easy to acquire and make). You can bring some laptops with info (i.e. loaded with wikipedia, youtube, etc.) but if you're not practiced with it most of it will be useless (other than predictive power that might garner you some followers but also make you a target for assassination). There is virtually no manufacturing that could create advanced tools so you would need to teach people how to do basic things that they could then build on, i.e. you teach them from your font of knowledge (wikipedia). As was said earlier teach the young and in two generations you will have a very advanced society (relative to what is there). Teach them democracy and how individual achievement can be for the greater good so that when you're gone all the newly educated adults will be able to govern themselves and perpetuate your teachings.
[Answer]
I'd suggest reading "Lest Darkness Fall", the main character is from the 1930/40's and experiences a time slip, ending up back in Rome in the year 535 AD. He brings nothing with him, except a decent knowledge of how things work. He's an archaeologist, so he knows history and culture but the "inventions" he creates don't use any more knowledge than an average educated person would have had at the time.
<https://en.wikipedia.org/wiki/Lest_Darkness_Fall>
As others had mentioned there are few things one could take back into time and either have them continue to work or be able to explain them to a person of that period. An exception would be a lighter or matches, which should last a fairly good amount of time before used up and is self contained. However a cell phone wouldn't work back then; there is no cell towers and it's unlike a person from 100s of years ago would understand how useful a computer can be; even if it was explained.
It also would be almost impossible to create most items and technology we are used to. It's one thing to carve furniture out of wood but to create a cell phone or a television set or a computer requires electronics, silicon, plastic and metal as well as way to charge or supply electricity, broadcast communications, etc. Even if a person was able to travel back in time, it would take more than a life time and many people just to develop the technology to refine or create those things.
In "Lest Darkness Fall", the main character accepts his time slip situation quickly and gets to developing some small inventions which don't depend on anything to come before it. As he progresses, he starts developing communication and building on one invention after another. Eventually he starts inserting ideas into the society, which changes things for the better.
[Answer]
I like time travel stories but there's always the "paradox" issue that I've never heard any good explanation (and of course since time travel appears impossible, there really isn't an answer.)
As all time travel stories will tell, going back in time can have devastating consequences for the future (our present.) But changing the timeline may not really matter (particularly if it can improve it) but for one issue. What happens if our time traveller in the past changes a circumstance that erased a direct ancestor from history meaning that in the new reality the time traveller was never born.
So there's the obvious paradox. a) You found out how to go back and change time, b) You accidentally erased your future self so you never existed, c) Therefore you never went back in time and did not erase yourself, d) Therefore you did go back ... see where this is going? A vicious circle of impossibility.
There was a 1980 movie "Somewhere in Time" that stuck a similar circular thought in my head I could never let go of. The lead character was given an old piece of jewellery ... a watch I think ... from an elderly person. He managed to go back in time and met this person as a young lady and we learn that he had given her this watch in the past brought from the future that she had passed to him in the future brought from the past. My unanswered question when I saw the movie was ... Who manufactured the watch?
Another movie, name long forgotten, had a character who went back into the old Wild West, fell in love with a women, had an affair, and then was rescued back to the present. The lady had a child which turned out to be either his mother/father or grandmother/grandfather I think (don't remember which) ... another paradox circle. If he hadn't gone back, he would never have been born.
Just something to think about in time travel scenarios.
] |
[Question]
[
Many half-human mythological creatures follow a few common anatomical schemes.
* Some consist of an animal with a human face, such as the sphinx, naga
and manticore.
* Some consist of a human anterior and animal posterior, such as the
satyr, faun, ipotane and mermaid.
* Some consist of an animal whose head has been replaced with a human
torso, such as the centaur.
Using latin as the source language a la Linnaean taxonomy, what would be a logical terminology for unambiguously distinguishing between these body types?
EDIT: The answers I've been getting have been really great. I was inspired to do some more research and discovered some Latin, Greek and "New Latin" vocabulary as an alternative to linguistically correct terms.
* *Semifer* and *Semihomo*, Latin synonyms for half-beast half-human
hybrids.
* *Theropod*, or "beast-footed", referring to theropod dinosaurs, but could easily be repurposed to distinguish satyrs, fauns, ipotanes, mermaids, cilophytes, etc. In these hybrids the body sections are joined at the pelvis.
* *Therocephalian*, "beast-headed", referring to a suborder of eutheriodont therapsids, but could easily be repurposed to
distinguish animal-headed Egyptian and Vedic deities, minotaurs,
werewolves, reverse mermaids, etc. In these hybrids the head is
animal and the body is humanoid.
* *Anthro(po)cephalus*, "human-headed", used for a variety of species names, but could easily be repurposed to distinguish sphinxes, naga,
shedu, lamasu, etc. In these hybrids the head is human and the body
is animal.
* *Cephalothorax inversus*, of my own coinage, could refer to centaurs, khepri, etc. The phrase works by analogy: where a cephalothorax is a
torso with a head and face in the chest, the inversion is a torso
sprouting from where the head and face would be. In these hybrids the
head of one parent is replaced with the torso of the other; unlike
the theropods the join is between pelvis and clavicle.
[Answer]
Upper part humans or Semisohominum - from Semisos meaning half and Hominum meaning human. This includes the species of;
* Centeroids or Semisohominum Equus which includes the subspecies; Centaur or [Semisohominum Equus Caballus](https://en.wikipedia.org/wiki/Centaur) and Onocentaur or [Semisohominum Equus Asinus](https://en.wikipedia.org/wiki/Onocentaur)
* Faunus or [Semisohominum Capra](https://en.wikipedia.org/wiki/Faun)
* Harpys or [Semisohominum Aves Aegypius](https://en.wikipedia.org/wiki/Harpy)
* Merfolk or [Semisohominum Craniata](https://en.wikipedia.org/wiki/Mermaid)
* Naga or [Semisohominum Serpentes](https://en.wikipedia.org/wiki/N%C4%81ga)
Human-headed or Maximobestia - from Maxime meaning mostlyand Bestia meaning animal. This includes the species of;
* Seamen or [Maximobestia Craniata](https://en.wikipedia.org/wiki/Atargatis)
* Manticore or [Maximobestia Leo](https://en.wikipedia.org/wiki/Manticore)
* Dogfolk or [Maximobestia Canis](https://en.wikipedia.org/wiki/Penghou)
* Sirpents or [Maximobestia Serpentes](https://en.wikipedia.org/wiki/Zhulong_(mythology))
Human with animal head or Maximohominum - from Maxime meaning mostly and Hominum meaning human. This includes the species of;
* Doghead or [Maximohominum Familiarus](https://en.wikipedia.org/wiki/Cynocephaly)
* Minotaur or [Maximohominum taurus](https://en.wikipedia.org/wiki/Minotaur)
Human with some animal parts or Bestiahominum - from Bestia meaning animal and Hominum meaning human. This includes the species of;
* Adlet or [Bestiahominum Cruris](https://en.wikipedia.org/wiki/Adlet)
* Angeloids or Bestiahominum Penna which includes the subspeices; Angel or
[Bestiahominum Penna Columbidae](https://en.wikipedia.org/wiki/Angel) and Fairy or [Bestiahominum
Penna Cimex](https://en.wikipedia.org/wiki/Fairy)
* Oni or [Bestiahominum Cornu](https://en.wikipedia.org/wiki/Oni)
* Gorgon or [Bestiahominum Anguis](https://en.wikipedia.org/wiki/Gorgon)
* Kemonomimi or [Bestiahominum Pars](https://en.wikipedia.org/wiki/Kemonomimi)
[Answer]
As a native speaker of a romance language, I'll vouch for [Semi](https://en.wiktionary.org/wiki/semi-)-[humanus](https://en.wiktionary.org/wiki/humanus) as an umbrella term for all those body types.
If you want to make that into a phylum or some other taxonomical level, contract it by dropping the -, making it Semihumanus.
If you allow for a mix with greek, Semi[antropos](https://en.m.wiktionary.org/wiki/antropo) will also do.
Now, for each body type:
Human head, animal body: Humanocaput (from "humanus" and ["caput"](https://en.wiktionary.org/wiki/caput) which means "head" or "top"). Again, if you allow for some greek mixing, you can have ["ops"](https://en.wiktionary.org/wiki/%E1%BD%A4%CF%88) ("face") instead of "caput": Humanops.
Half human, half animal body: Animumanus ("animal" is originally a latin word) (can also switch this one with Semihumanus).
Human body, animal head: Animocaput (or Animops if you allow for some greek).
Append a name having to do with each animal for a complete species name. For example, the Minotaur can be Animocaput [taurus](https://en.wiktionary.org/wiki/taurus).
] |
[Question]
[
People can, through sign language, express anything that can be expressed through spoken language so far as I know. So gestures *can* be fully expressive (there's enough "gesture-space" to build a language). Sign language, though, is derived *from* that spoken language, because it was developed to allow the hearing-impaired to converse with speakers. Sign language uses gestures mainly at the "word" level and the occasional phrase, though finger-spelling allow allows a signer to convey letters.
What would a gesture-based language look like if it developed organically in a civilization of people who do not speak and hear? For the sake of this question, assume that -- as with speech -- the gesture language develops well in advance of a written form (if a written form even develops at all): we have a civilization of people with no written or spoken language but they use gestures to communicate with each other.
Would the building blocks of the language still be words and grammar, or should we expect to see something very different develop (a la the analogy-based language of [Darmok](https://en.wikipedia.org/wiki/Darmok), though that specific example isn't feasible so please don't focus on that)?
[Answer]
**It would look similar to sign language.**
We see this where there is an absence of a common spoken language between people. Gestures mimicking actions are far more intuitive likely the reason people with spoken language barriers resort to pantomiming or pseudo-signing to communicate. If you've ever communicated with someone who did not speak the same language as you, how would you ask them for something to eat? Probably the same way people who sign do:
[](https://i.stack.imgur.com/NQx9I.jpg)
American Sign Language (ASL) is very visual and conceptual. ASL doesn't really try to mimic spoken language. It's actually likely to be understood by people regardless of their spoken language (if any) because it relies instead upon concepts and visualizations that don't require you to know what word is being used.
For instance the sign for 'year' is one fist orbiting the other one time.
[](https://i.stack.imgur.com/i2MCB.gif)
The sign for 'teach' is the action of transferring knowledge from the mind and giving it to another (with the addition of person sign to specify a teacher; a person who teaches):
[](https://i.stack.imgur.com/gxWmk.jpg)
How to learn? Pick up that knowledge and put it in your own head (but maybe get some new glasses):
[](https://i.stack.imgur.com/G8ins.jpg)
---
**Getting more complicated:**
Advanced concepts can also be described. ASL is a living language, so it's constantly growing to include more advanced concepts. [This article](https://www.newscientist.com/article/dn21967-obscure-physics-words-get-sign-language-equivalents/) describes some expansions in physics:
>
> The glossary builds on existing signs used by the deaf community and on “the visual or metaphorical relationship to what the things are like in real life”, explains O’Neill.
>
>
> The signs also build on one another to help convey the scientific
> relationships between the terms. The sign for mass, for example, is a
> fist which is then used as a basis for the sign for density (a hand
> around the fist) and weight (the hand and fist moving downwards).
>
>
>
[Answer]
About 15yrs back I read an article comparing multiple forms of sign languages, including some that were truly natural languages. (in the sense that they were created by people trying to speak and not based on encoding another language nor created as some arbitrary project. Some of these involved feral children.)
They had some trends. Some of them were familiar. Pointing at things or relative stuff figured in prominently. Pantomime plays a part in pretty much all of these, as I recall, but often abbreviated as with something like ASL. (Which is, by the linguistic terms *I* learned, a living language but synthetic.) The grammar rules can literally be anything that any language could have. Those vary a ton.
Look up support and criticism of "Universal Grammar" to find the discussion of the question I think you may be trying to ask. Wiki P. is a good place to begin. <https://en.wikipedia.org/wiki/Universal_grammar> It's one of Chomsky's passions.
[Answer]
Sign language is in itself an analogy; it's an analogy of actions. It maps what humans *do* to a sign representing that action closely enough to be understood; this is then standardised with the introduction of a formal sign language.
The relationship between sign and natural language is vague enough that you can safely discount it when trying to create a sign language. As the first point here says, sign language is about actions. Sign language seems too close to our natural languages to be useful without a natural language because you automatically associate the actions in sign language with the action you'd take, and then the word for that action. If such a species doesn't have natural languages and therefore words, they'd just associate the action in sign language with the action they'd take, and not go on to associate the word. In a sense, for this species, actions would be the form of communication.
A sign language of another civilisation would, therefore, be formed similarly to our sign languages. How does this civilisation act in certain scenarios? What do they do? Take those actions - such as eating - and form a sign for them. There are a number of other questions around the site about forming a language; you can also use the advice in those to record your language and use it again later.
[Answer]
# Nicaraguan Sign Language
In Nicaragua, before the 1970s, there was no Deaf community, and most pre-lingually Deaf people never developed much proficiency in any language.
In 1977, a Nicaraguan center for special education put together a program that brought together 50 Deaf children for education, and by the 1980s, numerous schools for the Deaf existed in Nicaragua.
Note that although these children were now attending schools for the Deaf, they were not being taught sign language. Instead, Nicaraguan schools for the Deaf focused on oralist teaching strategies, emphasizing lipreading and making use of residual hearing. These strategies have a poor success rate without cochlear implants, and most orally-taught Deaf children either switch to sign languages, experience serious language delays, or both.
However, what these schools did do was bring Deaf children together. Deaf children who are not exposed to sign language education naturally tend to invent simple signed communication systems, known as "home signs", to communicate with familiar individuals. However, in these schools for the Deaf, these children started learning and using *each others'* home signs. And each new year saw more young children joining the student body and imitating and improving on the older childrens' signed communication, until a proper sign language formed.
This sign language is one of a few examples of a sign language invented entirely by Deaf children, and therefore a good example of what a sign language designed in the absence of spoken language fluency would look like. It's not a perfect example because many of those children did know *some* spoken language, but few of them were truly fluent, especially at the time they were making their biggest mark in Nicaraguan Sign Language (which, as stated above, was primarily driven by innovations among the youngest children).
] |
[Question]
[
In every fantasy setting, dragons are famous for their massive hoards of treasure. But the economic consequences of money suddenly disappearing from circulation are never really addressed. Smaug, for instance, took all the treasure of a small-but-wealthy nation. This would surely have farther-reaching repercussions than the nearby city of Dale going broke.
(This isn't necessarily just about dragons, or a fantasy setting.)
My question has two parts:
1. What would the effects on the global economy be if a large amount of wealth were suddenly and completely inaccessible? How would this be different if the wealth were accumulated slowly instead of all at once?
2. What would happen when the dragon is slain and all that wealth is suddenly in circulation again?
[Answer]
An interesting real life example of this is the influx of silver from the New World during the 1500's. While this initially helped the Spanish Empire by allowing them to hire mercenary soldiers and pay for a plethora of projects ranging from diplomatic to artistic, the end result was an inflationary spiral which swept the European world from West to East.
An interesting example is the changes in war galleys. Galleys were rowed by free crews in the 1400's, and the Venetians, in particular, used their free rowers as extra manpower when they rammed or grappled an Ottoman ship to board it.
As the 1500's progressed, the cost of hiring rowing crews began to rise due to inflation, and first the Spanish, and eventually all the others (moving from West to East) were forced to replace free rowers with condemmed criminals or slaves. During the battle of Lepanto, Spanish galleys were generally larger, slower and heavier since they had to be sized to carry a contingent of soldiers in addition to everyone else in order to carry out boarding actions. The Venetians had managed to continue using free crews as oarsmen, and their ships were able to carry out complex evolutions including backing water in line (with almost 50 ships!) to prevent the Ottomans from outflanking the line. Slave powered galleys would not be able to do this since the crews were neither skilled or motivated to do so.
So a sudden influx of Dragon's gold could have some very unexpected consequences as inflation distorts the economy (and especially the cost of labour). Some detailed world building and modelling would be needed to see exactly what the consequences would be.
[Answer]
In economics, the sudden change in the supply of a good is known as a [supply shock.](http://en.wikipedia.org/wiki/Supply_shock) If the treasure the dragon has stolen is in active circulation, we can expect the change in the supply of treasure to affect the price of treasure in the following ways:
If the dragon steals all of the treasure, this will lead to a *negative* supply shock, with the quantity of money available suddenly decreasing. This will lead to a sudden increase in the 'price' of money, effectively causing rapid deflation of the prices of all goods in the affected area. This will also reduce the purchasing power of the nation as a whole, which will be a major problem if the nation is largely an import economy. Deflation will also reduce the costs of operating in the area, which could attract more businesses.
When the money re-enters the economy, the opposite will happen, with inflation due to the increased monetary supply making local costs higher. If the repatriated treasure remains in the hands of the wealthy, this could lead to increased economic disparity and a reduction in the buying power of the lower class.
If the treasure is not in circulation, perhaps being stored in a bank to back a paper currency, the same thing will happen if the currency is left pegged to treasure. However, in this case, the government has the option of switching to a fiat currency, in which case the 'supply' of money could remain effectively the same, at least locally. Foreign markets may be less willing to accept a fiat currency, though if draconic raids are a common occurrence, they may also welcome the opportunity to trade for a currency with a more stable value.
[Answer]
In my earlier answer, I speculated as to how a large quantity of treasure wound up in a dragon's lair. The dragon doesn't just rob everyone and every institution in a provence in a short period of time, right? One anwer is that someone put it there in a large organized effort, and that has a profound meaning as to the question.
Another way is that it was gathered slowly over time. That makes the question vacuous, as it did not vanish all at once.
The talk about soldiers and rowers made me think of another answer. It wasn't taken from circulation but is a fresh resource. Soldiers were famously paid in *salt*, and that is the basis of the word *salary*. What if the dragon lives in an exposed salt dome? Maybe dragons seek them out and excavate them, so the cave isn't filled with treasure but carved into it: a salt mine. That is why dragons are associated with caves of treasure.
As a plot device that would be quite a twist for someone to finally discover, after salt is no longer valuable in his society, or the legends have crossed into a region that *supplies* salt and it's common place there.
---
The dragons find a salt cave to be great shelter from preditors because nothing else can live there. The need to eat salt to produce metalic sodium via enzimatic pathways, which is what makes them spit fire. A venom gland produces alkili metal nanoparticles surrounded by an oily membrane, suspended like milk. That is mixed with modified saliva which contains an enzime that destroys the membrane, so he shoots boiling steam that's also extremely caustic to flesh and releases hydrogen and methane gas which burns too!
Enzymes also concentrate all sorts of metals from the dragon's diet. Some are essential for catylists. Others are poop. Local ores of copper, gold, or silver cause concentrations to build in in the lair as a side effect of the dragon's need for platnum and and rare earths, and the eating of ore-bearing rocks to obtain it.
Metals are concentrated by symbiotic bacteria— decendent from the kind that helped make geological veins of metal— in a modified auxilary stomach chamber.
So even without the association with salt, you could have a lair build up concentrations of precious metal flakes over a long history of occupation.
[Answer]
Maybe the people still consider the gold to be owned by them. It's just well guarded, and they don't carry it around with them to trade: they just use numbers in accounts or printed certificates.
It's like Fort Knox. It's *there*, it's never touched.
The hoard could be a Ft. Knox repository from a fallen civilization. The stuff was never taken out of circulation except when the people recognizing the currency and banking authority got Pompeii'ed, and everyone assumed their banks were buried too, until the real safe is found, with the biological security system still armed and no access tokens in existence.
] |
[Question]
[
A long time ago in a galaxy called the Milky Way.....
An alien race had its planet thrown out of its solar system. It is now a rogue planet. They survived for thousands of generations in underground artificial environments. Then they achieve FTL and begin colonizing solar systems. A thousand years later the population of their planet is mainly too stubborn to leave since their race began there.
Since the government resides on their home planet and it does not intend on leaving (I know the following scenario is unlikely, but bear with me) they have decided to commission a hydrogen fusion project. This will build a miniature star orbiting their world via artificial means. I am not sure how big this star could be (or rather, how small?) and want it to supply the entire world with sunlight in a 26 hour cycle.
How can I go about doing this and how large would the 'star' have to be? Since we are dealing with a highly advanced civ, they can compress matter until it begins to fuse. The biggest problem I can foresee is supplying it with fuel.
You can use any technology level you want and are free to use the handwavium that such an impractical situation deserves. However, I do want answers to be descriptive and go into detail.
[Answer]
As mentioned in other answers, other than using super-tech, keeping a tiny star operating with out massive gravity is a problem. Fuel is another.
I would suggest going more artificial and less pet-star. Normal stars, operate naturally due to gravity, and they hold together a solar system with that gravity.
Your Race/Government has no need for an actual star, just the star like effects on a single rouge planet. So just construct a moon like object, orbiting the planet. The '''Moon''' emits energy as light/heat only directed at the planet. Put the '''Moon''' in a lower than stable orbit to point that will counter the solar sail effect from the energy emission.
The orbital body only needs to generate a more-reasonable amount of power than it would take to keep a micro sun going. It also require orders of magnitude less fuel to operate.
As for size, that would mostly depend on the energy density available to the civ, sized to the power generation scale of the planet's solar needs. I assume earth's moon as a generic size guess. The Orbital period is set to whatever the civ considers a day. The Orbital height would be set to make the stable Orbit (with emissions) at the speed/period/average-mass. Then the moon/emitter is sized to be the same relative size as their original sun as seen from the planet, based off the Orbital height. The emitter can be bigger or smaller than the main body of the '''Moon''', as it will be so relatively bright the rest of the orbital body will be not observable from the planet.
This is also a safer option to the planet, as it a less massive, and less energetic solution. It's less likely to end the planet, if something minor to major goes wrong.
The biggest downside is that it isn't as much of a show piece as micro-sun would be to other races, but you didn't mention other races as a design point.
---
[Answer]
I'm not an expert on this but I hope I'm not telling complete BS.
So I think one problem with making a miniature star that actually orbits a planet is, as you stated, not getting it going, but keeping it going. Because for hydrogen to fuse inside a star's core the star's own gravity has to push the hydrogen cores close enough together to undergo fusion. So the star has to be big, very big.
As per wikipedia:
>
> "Jupiter's upper atmosphere is composed of about 88–92%" and the
> interior contains denser materials, such that the distribution is
> roughly 71% hydrogen."
>
>
>
And jupiter is already very big. So, basically you'd need something bigger than jupiter with an even higher hydrogen composition to actually create a star.
At that point you'd have to be orbiting the actual star. Because it has a greater gravity than your actual planet, and you will eventually crash in to it because its orbital velocity relative to the earth is lower than the stars own orbital velocity. If you know what I mean. (correct me if I'm wrong)
Say it would be possible to have an object with greater mass than your planet to orbit your planet. And you don't want something that's almost as big as an actual sun to orbit your planet. And your civilization's tech is good to make REALLY dense materials I would opt for a neutron star. According to [this](http://abyss.uoregon.edu/~js/ast122/lectures/lec19.html) website:
>
> "If the mass of a normal star were squeezed into a small enough
> volume, the protons and electrons would be forced to combine to form
> neutrons. For example, a star of 0.7 solar masses would produce a
> neutron star that was only 10 km in radius. Even if this object had a
> surface temperature of 50,000 K, it has such as small radius that its
> total luminosity would be a million times fainter than the Sun."
>
>
>
A million times fainter, but at a much lower distance is still A LOT of light.
But with an object the mass of the sun orbiting your planet, you'd have to deal with **HUGE** tides.
You could (and this is pure fantasy) also choose for creating some sort of very high point mass (maybe a very small neutron star). So this way you have a lot of gravity in a very concentrated place. This can be used to keep the hydrogen in place and compress around the point mass, and close enough to keep fusing. But I have no idea how you would indeed fuel something like this.
Hope this gives you some ideas.
[Answer]
If they have FTL travel, it must offer some advanced physics to exploit. For example, open a wormhole with the other end inside a suitable star. Less dramatic: near a star, with the other end directed at the planet.
Control over bending space, even if not able to change topology, create an artificial gravity well to make a star that works like a normal one but doesn't need so much mass to self-gravitate.
How much light do they *need*? If they are adapted to living underground on a cold world, they might not want to melt their bedrock (H2O goes from a granite-like mineral to being an ocean) and disrupt everything.
So they may want to be showy, and produce what for them is a lot of light, but not much warmth. The energy requirements would be orders of magnitude lower than duplicating our insolation.
[Answer]
I would create an artifical black hole whose hawking radiation power matched sun emission and the time it stays shining big enough to be economically viable. Unfortunatelly my math is not enough to calculate how much mass you'd need to do so.
[Answer]
Like others, I think [wave hands] gravity tech. will do. But you want details.
Put the machinery inside a spherical, one-way radiator. There is no gravity inside, so the machinery isn't crushed by its own weight. (It *is* inaccessible. This star contains no user-serviceable parts.) Also provide antigrav. bracing inside the radiator so it isn't crushed by the effective weight of the fuel above. (Maybe it *is* two-way: tractor outside, pressor inside. Maybe they know tricky ways to make gravitons spin, or something, so the two effects nearly balance and the net energy input is small *for a star*.)
The machine uses monstrous amounts of energy which *just happen* to be the amount of thermal radiation heading inward, so it stays cool. I suppose the radiator was sized to make this happen. No, I don't know how they achieve 100% conversion.
Sizing. Orbital period determines the altitude. Temperature of the photosphere determines the spectrum, which they will want to specify. I think temperature also determines the output per unit surface which, together with the desired level of insolation and the altitude, should tell you the necessary size of the photosphere. I have no idea what the math looks like for any of this.
Is it practical? What is the strength of tidal forces from an object with that surface gravity at that distance? How often do they have to drop another gigaton of H2 on it to keep it fueled? (How big *is* its fuel supply anyway? Where do they get it?) What are the safety margins you need in order to avoid roasting the planet due to a control hiccup? How much gamma and particle radiation does it deliver to the planet's surface?
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
This is supposed to be a test of the [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") tag. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Speculative or unreferenced answers, as well as those not supported by strong scientific theory, are not welcome. Long, comprehensive answers are desirable, but length and quality aren't always correlated.
---
A young B-type star (with a mass of about 10 M$\_{\odot}$) is surrounded by a debris disk extending from about 2 AU to 1000 AU away. The disk has a mass of about 300 Earth masses - enough to form quite a lot of planetesimals. There is also an outer cloud of icy, comet-like bodies extending from 750 AU to 5,000 AU away.
The star stands out from other Sun-like stars, though, because recently a strong stellar wind has developed, which comes with a mass loss rate of about 1.0 $\times$ 10-6 M$\_{\odot}$ per year. The stellar wind may die down eventually, but for now it's having quite a strong effect on the star and its disk. It is thought that much of the inner debris disk will be blown away very quickly.
A nearby red dwarf of about 0.76 M$\_{\odot}$ (not a flare star, fortunately) is passing through. At its nearest point, it comes extremely close - an astounding 1500 AU away from the B-type star!
There will absolutely be some accretion by the red dwarf. But how much? An advanced civilization (Type II on the Kardashev scale) is watching closely. They're considering the red dwarf as a sort of "rest station". If planetesimals form, they could be mined for raw materials, and any icy bodies could be an excellent source of water - which can be turned into hydrogen and helium.
How can they figure out just how much dust from the debris disk and icy bodies will be captured by the red dwarf? Can they then predict if planetesimals are likely to form (though subsequent planetary formation isn't necessary)?
That bit could be construed as pure science, which it may be. But there's another, much more important question that's absolutely related to world building: Can the Type II civilization do anything to influence accretion?
This is what I'd like answers to focus on.
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I've done some reading, and the situation is plausible. Accretion rates can be computed, and whilst encounters between stars this close are extremely rare, they're still possible. I didn't list density parameters, but those can be found rather easily in the scientific literature. Taking all this into account, I'm looking for answers based in [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'").
[Answer]
Perhaps your best source here is the recent [Ribas, Bouy, and Merín 2015](http://arxiv.org/abs/1502.00631) paper, distinguishing between primitive and processed disks by the mass of the stellar object.
The take home point seems to be that larger stars tend to process or blow away their disks relatively quickly.
The actual N-body dynamics you describe (two stars and a granular disk) are far too complex to be easily treated here, but [this is the closest I could find](https://archive.org/stream/arxiv-astro-ph0504590/astro-ph0504590_djvu.txt).
>
> Recent simulations of the ONC cluster indicate that at least 20% of the stars undergo encounters closer than 300AU during the first 3Myrs of the cluster development (Olczak et al. in prep.).
>
>
> Naturally such encounters will influence the mass and angular momentum distribution in the disc. The total mass of - and the mass distribution within - the disc after an encounter are important, as this directly influences the likelihood of the formation of planetary systems.
>
>
> The change of the angular momentum distribution due to an encounter is of relevance since it is still unclear how the disc loses enough angular momentum that accretion of matter onto the star is possible. Although it is unlikely that encounters are the dominant source of angular momentum loss, their contribution is probably not negligible.
>
>
>
The main discussed effect is in a disk-disk context and has to do with changes in the angular momentum of the star-transferred mass that does not fall into the capturing star, and its impact on planetary formation. If you're interested in the topic, the entire paper is definitely worth a read, as is the bibliography (esp Pfalzner).
Speculation about the abilities of a Type II Civ is not a clear-cut case of [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'"), although we can definitely impose lower and upper bounds on their ability to modify a stellar environment based on their relative energy budget.
A Type I civilization has a low budget of ($10^{15}$ watts), while a typical type II could spend $10^{26}$ watts, whereas a Type III culture at its peak would command the power of a hundred billion suns -- upwards of $10^{37}$ watts. The best discussion on this remains the Freitas book [Xenology](http://www.xenology.info/Xeno.htm).
From the perspective of a mature Type II civ, stars are merely piles of valuable resources that have unfortunately caught fire and sunk into the fabric of spacetime. Protoplanetary disks have 2 advantages: a distinct lack of deep gravity wells and the fact that they are not on fire. Again, this is speculative, but given that their energy budgets place overcoming the binding energy of planetisimals easily within their reach, they would look to a low-gravity protoplanetary disk in a way similar to how a 6-year old would look to Halloween: lots of delicious candy just lying around for the plucking.
[Answer]
I decided to start working on my own answer after I asked the question, so here's the result of a few days' work.
An excellent (and very recent) paper regarding accretion is [Debnath (2015)](http://arxiv-web3.library.cornell.edu/pdf/1503.01645.pdf), which can be applicable at least for material gathered onto the surface of the red dwarf.
Debnath assumes a static1, spherically symmetric metric:
$$ds^2=-A(r)dt^2+\frac{1}{B(r)}dr^2+r^2(d \theta^2+ \sin \theta d \phi^2) \tag{1}$$
which uses the (-,+,+,+) sign convention. For now, we can leave $A$ and $B$ undetermined functions of $r$. We have to treat the surrounding matter as a perfect fluid, with a stress-energy tensor of
$$T\_{\mu \nu}=(\rho+p)u\_{\mu}u\_{\nu}+pg\_{\mu \nu} \tag{2}$$
with $\rho$ and $p$ being the density and pressure, respectively.2 $u\_{\alpha}$ is the four-vector, with the condition that $u\_{\alpha}u^{\alpha}=-1$. For this fluid, though,
$$u^{\alpha}=(u^0,u^1,0,0)$$
We can then re-write the earlier condition as
$$g\_{00}u^0u^0+g\_{11}u^1u^1=-1$$
Substituting in that $g\_{00}=g\_{tt}=A(t)$ and $g\_{11}=g\_{rr}=\frac{1}{B(t)}$, as well as assuming (for simplicity) that $u^1=u$, we get
$$\left(u^0\right)^2=\frac{\left(u^1\right)^2+B}{AB} \to u\_0=g\_{00}u^0=\sqrt{\frac{A(u^2+B)}{B}}$$
We can also calculate $\sqrt{-g}=\sqrt{\frac{A}{B}}r^2 \sin \theta$.
The law of conservation of energy states that $u{\_\mu}T\_{; \nu}^{\mu \nu}=0$.3 Putting this together with $(2)$ gives
$$u^{\mu} \rho\_{, \mu}+(\rho+p)u\_{; \mu}^{\mu}=0$$
Doing it out, we find that
$$C=-ur^2M^{-2}\sqrt{\frac{A}{B}} \exp \left[\int\_{\rho\_{\infty}}^{\rho\_R} \frac{1}{\rho + p(\rho)} d \rho\right] \tag{3}$$
where $\rho\_R$ is the density at the radius of the red dwarf and $C$ is a constant (which will be used later).
The rate of change of mass of the black hole, $\dot{M}$ (the negative rate of change of the mass of the fluid) is expressed as4
$$\dot{M}=\int T\_0^1dS \tag{4}$$
where
$$dS=\sqrt{-g}d \theta d \phi$$
From $(2)$, we get
$$\dot{M}=4 \pi CM^2(\rho + p) \tag{5}$$
[Abramowicz & Fragile (2013)](http://arxiv.org/pdf/1104.5499v3.pdf) give a slightly different expression in place of $(4)$ (Equation 125):
$$\dot{M} = \int \sqrt{-g} \rho u^r d \theta d \phi \tag{6}$$
and use $(5)$ for the energy flux. Both expressions are applied to jets on black hole accretion disks.
Working off of Debnath, the total mass transferred to the red dwarf's surface is
$$M=\int\_{t\_0}^{t\_f} \left[\int \sqrt{-g} \rho u^r d \theta d \phi \right] dt \tag{7}$$
where $t\_0$ and $t\_f$ are the initial and final times during which the red dwarf accretes material.
I haven't quite figured out the full Roche lobe calculations just yet, but I was able to find some of the major equations. [Paczynski (1971)](http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1971ARA%26A...9..183P&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf) mentions that the radius of the Roche lobe of the red dwarf is
$$r\_1=\left[\frac{2}{3^{4/3}} \left(\frac{M\_1}{M\_1+M\_2} \right)^{1/3} \right]A \tag{8}$$
where $M\_1$ is the mass of the red dwarf and $M\_2$ is the mass of the B-type star, and $A$ is the distance between them.
The issue is that this is typically applied in binary systems, while, presumably, the red dwarf is traveling at a speed greater than the B-type star's escape velocity. It is, therefore, not orbiting it. So I'm not sure if the formula is valid.
Let's say that the civilization places a planet-sized object into the disk, inserting it at an orbital velocity $V\_0$. It would then undergo Bondi accretion, as shown in [Bondi (1951)](http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1952MNRAS.112..195B&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf).5 In that paper, he goes from the expressions derived by Hoyle & Littleton and Bondi & Hoyle to get the accretion rate of
$$\dot{M} = 2 \pi (GM)^2 (v^2 + c\_s^2)^{-3/2} \rho \tag{9}$$
where $v$ is relative to the fluid. Taking the limit as $v \to 0$ gives the approximation shown on [Wikipedia](https://en.wikipedia.org/wiki/Bondi_accretion), although it differs by a factor of 2.
We can't just use this, though, because there are other things to consider. First, all the gas and dust in the disk is orbiting at the same rate as this object, so $V\_0 \neq v$. Second, the conditions change. For each orbit the object makes, the density of the matter in the path through the disk changes, because it has been swept up. Finally, the object may be severely affected by Stokes drag.
The density issue can be dealt with by simply assigning the object a number of orbits $n$ at time $t$, and saying that during each orbit, it accretes $x$ percent of the gas and dust in its way. Once this is known, an expression can be derived for the accretion during each orbit.
The Stokes drag is slightly more interesting. As shown in a derivation by [Gavnholt et. al. (2004)](http://web-files.ait.dtu.dk/bruus/TMF/publications/3week/Jun2004FlowSphere.pdf), the formula is
$$D=6 \pi \mu U a \left(1+\frac{3Re}{8} \right) \tag{10}$$
where $U=v$, $a$ is the object's radius, $\mu$ is the viscosity and $Re$ is the Reynolds number. This means that
$$\frac{dv}{dt} \propto v$$
Knowing that, and placing the object in a circular orbit such that
$$F\_g=F\_c \to G\frac{M\_sm\_o}{r^2}=\frac{mv^2}{r}$$
where $M\_s$ is the mass of the B-type star, $m\_o$ is the mass of the object and $r$ is the distance between them. we can write $v$ as a function of time and then solve for $r$ as a function of $v$, eventually witnessing orbital decay. Also, if $\rho$ is a function of $r$, we can further complicate everything. This also goes for the accretion experienced by the red dwarf.
I feel bad about not doing any actual calculations (i.e. with actual numbers), so I'll discuss a special case here: A dust disk surrounding a spherically symmetric body.
In a dust solution, $p=0$, so our generic equation of state $p=p(\rho)$ goes to 0. Imposing spherically symmetry means that $A=B$. Accounting for all this turns $(3)$ into
$$C=-r^2uM^{-2}\sqrt{\frac{1}{1}} \exp \left[ \int\_{\rho\_{\infty}}^{\rho\_R} \frac{1}{\rho + 0} d \rho \right]$$
$$=-r^2uM^{-2} \exp \left[ \ln \frac{\rho\_R}{\rho\_{\infty}} \right]$$
$$=-r^2uM^{-2} \frac{\rho\_R}{\rho\_{\infty}} $$
Plugging this into $(5)$ gives us
$$\dot{M}=-4 \pi r^2u \frac{\rho\_R}{\rho\_{\infty}} \rho$$
Just take a given $\rho$, pick a velocity, and solve for $\dot{M}$.
I still haven't put in any numbers, but it's at the point where you don't have to do much to find the result.
Accretion by planetary-mass objects in debris disk has been observed, such as in Epsilon Eridani's debris disk ([Greaves et. al. (2005)](http://iopscience.iop.org/1538-4357/619/2/L187/pdf/1538-4357_619_2_L187.pdf); explored also by [Backman et. al. (2008)](http://arxiv.org/pdf/0810.4564v1.pdf)). A good overview of the process is given by [Janson et. al. (2013)](http://arxiv.org/pdf/1306.0581v1.pdf), while it was simulated by [Stark & Kuchner (2009)](http://arxiv.org/pdf/0909.2227v1.pdf) and [Nesvold & Kuchner (2014)](http://arxiv.org/pdf/1410.7784v1.pdf). The only issue now is to establish whether or not a Type II civilization could build such an object.
---
**Footnotes**
1This means we have to neglect rotation, which could be a problem.
2Were we to assume vanishing pressure, as in a true dust solution, things could get simpler (and, perhaps, more interesting). For now, though, we'll treat it as a perfect fluid, and treat it as homogenous.
3I'm using the convention in which a comma indicates a partial derivative and a semicolon indicates a covariant derivative.
4Raising and lowering indices via the metric tensor.
5In "thin disk" scenarios, the red dwarf might not undergo spherical accretion.
**References**
Abramowicz, M. A. and Fragile, P. C. ["Foundations of Black Hole Accretion Disk Theory"](http://arxiv.org/pdf/1104.5499v3.pdf) (2013)
Backman, D. et. al. ["Epsilon Eridani’s Planetary Debris Disk:
Structure and Dynamics based on
Spitzer and CSO Observations"](http://arxiv.org/pdf/0810.4564v1.pdf) (2008)
Bondi, H. ["On Spherically Symmetric Accretion"](http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1952MNRAS.112..195B&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf) (1951)
Debnath, U. ["Accretion and Evaporation of Modified Hayward Black Hole"](http://arxiv-web3.library.cornell.edu/pdf/1503.01645.pdf) (2015)
Gavnholt, J. et. al. ["Calculations of the Flow
Around a Sphere in a Fluid"](http://web-files.ait.dtu.dk/bruus/TMF/publications/3week/Jun2004FlowSphere.pdf) (2004)
Janson, M. et. al. ["The SEEDS Direct Imaging Survey for Planets and Scattered Dust Emission
in Debris Disk Systems"](http://arxiv.org/pdf/1306.0581v1.pdf) (2013)
Nesvold, E. R. and Kuchner, M. J. ["Gap Clearing by Planets in a Collisional Debris Disk"](http://arxiv.org/pdf/1410.7784v1.pdf) (2014)
Paczynski, B. ["Evolutionary Processes in Close Binary Systems"](http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1971ARA%26A...9..183P&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf) (1971)
Stark, C. C. and Kuchner, M. J. ["A New Algorithm for Self-Consistent 3-D Modeling of Collisions
in Dusty Debris Disks"](http://arxiv.org/pdf/0909.2227v1.pdf) (2009)
] |
[Question]
[
I am trying to figure out how plausible it would be for people without electricity or steam power technology to use the sun to smelt and forge iron and steel. The people developing this solar furnace have limited fuel options for combustion.
The mid 20th century [Odeillo solar furnace](https://en.wikipedia.org/wiki/Odeillo_solar_furnace) is 54 meters high and can obtain a temperature of 2,500 °C (4,530 °F). This is perhaps overkill, because iron ore smelts at 1800°C (3270°F), though I do not know how large an area is heated by the Odeillo furnace so perhaps something even bigger (and more diffusely directed) would be needed to be useful. [Here](https://youtu.be/8tt7RG3UR4c?t=87) is a video of Odeillo melting a hole in steel in just a few seconds.
The ability to make mirrors that reflect and concentrate sunlight is ancient. Even if Archimedes' "[burning glass](https://en.wikipedia.org/wiki/Burning_glass)" never existed, the fact that this idea is so old suggests that the technology to focus sunlight has been around for awhile.
This solar furnace need not produce industrial quantities of steel. Instead, consider this a very high fixed cost, low operating cost alternative to a clay bloomery.
**Question**
Could the ancient Greeks, or else 15th century Europeans or Chinese, smelt iron with concentrated sunlight? If yes, how big would the mirror array have to be to smelt a football sized bloom?
Assume favorable weather conditions.
[Answer]
As you point out the concept that solar could be concentrated was well known for a long time, so there is some potential to explore an alternative time line where it could have been developed.
The [Nimrud](https://en.wikipedia.org/wiki/Nimrud_lens) lens was a 8th century BC polished piece of rock crystal archeologists found in Assyria that some think may have been used to start fires. Even more intriguing is in The Epic of Ishtar and Izdubar, Column IV, Coronation of Izdubar, written about 2,000 BC. 10th stanza. That reads:
>
> The King then rises, takes the sacred glass,
> And holds it in the sun before the mass
> Of waiting fuel on the altar piled.
> The centring rays—the fuel glowing gild
> With a round spot of fire and quickly spring
> Above the altar curling, while they sing!
>
>
>
So perhaps there are several motivations for concentrating sunlight, besides the Archimedes example.
Visby lenses made of polished rock crystal have been found in 11th and 12th century Viking graves and are of very high quality.
>
> In [Europe](https://www.researchgate.net/publication/346503550_Brief_on_Solar_Concentrators_Differences_and_Applications) (1515), Leonardo da Vinci proposed the idea of designing a Compact Linear Fresnel Reflector (CLFR), but according to what has been reported in the literature, his study of this system remained only an idea on paper and was not supported by experimental work [31], as he said that this system is valid for many industrial uses [32].
>
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More specifically for smelting metals this was investigated by Lavoisier in 1774 with temperatures achieved of 1750 C. The larger concentrating lens was 52 inches in diameter, made of two convex sheets of class filled with white wine. It was capable of melting steel and even platinum. Ben Franklin made high temperature experiments with smaller lenses.
[](https://i.stack.imgur.com/lm0F5.png)
Making mirrors or lenses for that matter, since the emphasis is on concentrating sunlight, the image quality doesn't need to be that good. However it is something of a problem to keep the light focused on one spot due to the apparent motion of the sun.
So you have a choice of moving the item being heated or adjusting the lens or mirror.
Polishing metals is one way to make mirrors, there are alternative routes that one could take cleaving crystals or fracturing obsidian or using flat sheets of mica to have very flat or smooth surfaces. That is all in reach of 15th century technology.
But it the mirrors are small, then the issue is positioning lots of small so the reflect the sun. You could have lots of small pieces that could be positioned in the side of a hill focusing onto a furnace area.
Silvering the mirrors can be another issue, but there were some silvering and gilding techniques in 10th century Persian alchemy texts, and different glass mirrors made with tin and mercury in the 15th century, and other small glass mirrors made in Ptolemaic Egypt ~ 300 BC backed with lead, tin or antimony. Since you want to reflect the IR as well as the visible gold will be reasonably good and can be beaten very flat. Gold also doesn't corrode and would withstand the elements.
As for how big to make the concentrator, that depends. But back of the envelope you get about 1 KW per square meter of sunlight energy deposited. The latent heat of iron slag is about 209 kJ/Kg (Cast iron about 123 kJ/Kg) so depending on what want to melt, it would depend. Probably more importantly you need to have very good insulation and not conduct the heat away. 1 kw is 3600 kJ/hour. A football is about 5575 cm3. The density of iron is about 7.8 g/cm3. So the mass is 43.5 kg.
So best case is with perfect 1 meter square mirror, no heat loss, 200 kJ/kG and 50kg of material to heat up, you would need about 2.8 hrs melt the iron, assuming all the energy is absorbed... or say 3 meters of mirrors to melt the iron in 1 hr, or 12 square meters to melt in 15 minutes.
If you lost 50% of the heat due to conduction... then 24 square meters.
If the mirrors for some reason only 50 % efficient... then 48 square meters. Then if only 50% of the energy is pointed to the furnace... then 100 square meters of mirrors.
So potentially something 10m x 10m could probably get your football sized material really hot.
By the way the nice thing about solar furnace is that the heating rate can be really, really fast, especially it the object being heated is small and thermally isolated.
So in the 15th century, you could build an amphitheater like structure into the south side of a mountain or a hillside, postion your mirrors with a common focus and you could probably get a few thousand square meters of mirrors. Or if you had 100 mirror have maybe 100 people help keep the mirrors adjusted. Paying attention to eye safety etc.
Or you could have a number smaller setups to melt smaller amounts.
In the late 19th century there were attempts to use solar for steam engines etc., but really they couldn't economically beat coal.
Other solar heating trivia... include the recent melting of a Jaguar car in London by a shiny skyscraper.
The science fiction author Arthur C. Clark also wrote the story " A Slight Case of Sunstroke" where the fans in a football stadium in South America vaporize a corrupt referee by using their shiny programs to focus the sunlight on the referee.
[Answer]
## Maybe, if they had the idea of Fresnel lenses
When Bottger and Tschirnhaus made porcelain, they used solar furnaces because European furnaces were not up to the task.
100 years earlier, lenses simply wouldn't have been big enough; they're hard to make and horrendously expensive. Lens making advanced enormously during the 17th and early 18th centuries.
However, in the 19th century, they figured out a way to make giant lenses for a fraction of the cost. By breaking the lens into separate arcs, you save a tonne of glass and hard work. Those are Fresnel lenses. They could have been made centuries earlier, had anyone had the idea.
Your people would probably be better off copying the enormous Chinese pottery furnaces, which were dug into excavated hillsides and reached temperatures easily hot enough to make steel; in the 1500s, they made porcelain items in batch sizes only matched by the Europeans on the 19th century....but solar furnaces would be waaay cooler.
[Answer]
I think you are missing a key point in the whole process of smelting iron ores to get iron, that is that the carbon burned in the process does two things at the same time:
* provides the heat to increase the temperature
* provides the atomic species which, at the temperatures reached in the furnace, shift the oxygen from being bound to the iron atom, leaving it alone and capable of forming metallic iron
Now, while as you state a solar furnace can reach way beyond the melting point of iron, even by eating up iron oxide to that point you have nothing to remove the oxygen from the melted mass.
Therefore by only having solar mirrors to concentrate solar energy one won't be able to go from iron ores to iron.
[Answer]
Good answers already, and every adds some points to consider, so will I add it too.
@UVphotons' answer is good, but one thing to consider is - forget about 50% efficiency in the case, as there should be no obstructions for light between mirrors and material heated, so thermal insulation in the case can't be done for the side where light enters, and hot material will actively emit energy as old light bulbs did, so as air will cary a lot of it, so as heat transwer in the material itself does not make things better.
At the same time as there is a problem to insulate stuff, there is a problem to protect it from interaction with oxygen, and while the problem can be tackled with some shield gas flows, as it is done in welding torches it requires understanding and practice in few fields - get that shielding gas requires undertanding it is a solution(so chemistry understanding is required, some basics), cryogenics (physics of gases, rectification columns, mechanics to do all the cryogenic stuff, pipes, insulators, etc) which is quite heavy area for not prepared folks even when there are good simple to make solutions for the problem it requires afterthougth knowledge.
* it possibly to adress two of those problems, insulating and oxidising by introducing some heat carrier - some gas and idk saphire(transparent heating area with high melting point, trough which the heat carrier is blown trough to be heated and then to the ore)
So blumeries aren't that bad for what they do - combining few physical chemical processes in one simple and easy to make setup which a quite straigth forward continuation of processes people used at the time.
And compare it to all kinds of problems which required to be solved, where complexity jumps rigth to 1900's technologies in one setup.
@L. Dutch correctly pointed out that one of the functions of coal there is to reduce oxides to metall, and do the same with solar furnance is not impossible but it requires those top temperatures which you mentiont about modern setups, and just right now without further research I even can't tell may it work in practice, is it enough(seems so, and physics of processes hints it may he possible but specifics are important here - do evaporation points and such are right for it)
And considering that coal is available when wood or plant matter is available by coal pits burning it and it is a renewable resource in many places, not all but most places.
It may make more sense to use solar to purify Iron - main problem of blumery is that Irons does not liquify there in this process(no crusible form it all), and slag goes not float up, does not separate well from the reduced metall, but if you liquify this blumery product with another method (like solar furnance) then such separation may happen.
So in your potencial scenario they are not limited by coal or blumery iron but it then goes to second stage of producing sun iron. In a simple setup one probably will burn back plenty of that blumery iron, but one may get slag free beads of iron, and that iron oxide can be reduced again, and even produce better blumery iron(not necessarly) as it easier to separate iron rust from other stuff as a dust thing. Maybe in a more convoluted way, in reality, ability to melt sticks of blumery iron which just need to drip down in some water bucket(or oil or whatever) may be a process to refine blumery iron.
Historically plenty of eforts were put in this process of refining blumery iron, and only a smal portion of it (best portions) were used for sword making in Japan, when batches were few ton in size, and other time consuming methods like letting it oxydise in earth, moist, water for a decade or more were used.
So people did try all kinds of methods, and solar concentration does not necessarly look that complex and effort hungry and time consuming compared to what people actually did in history to achieve more pure iron.
So I propose instead of melting football balls of ore at once - make candle sticks out of blumery material, and heat a limited spot(its tip), few cm area and let it drip as wax and just supply (horizontaly) shift that blumery candle in the spot. Let it drip in some coolant - fat oil water, then crush the stuff, collect beeds of iron, and then regular heating and smashing the stuff together.
Limiting the area of heating it also possible to create some oxygen free environment a small chamber where it will just burn out, so as slag may protect stuff to some extend(secondary schielding not so important), have some transparent window to the chamber(which may be secondary lens as well (or window and a lens is probably better, or flat window+water(coolant)+lens sandwiche - so you can replace flat window easier clean it easier etc)), no need to supply reducing agent etc.
* maybe it can be used this way as well to substitute blumery process, candles are pressed sticks of ore and reducing agent(coal dust) and some binding agent(clay)
In this setting it can be a reasonable way(compared to actual efforts which had place in history) and maybe a viable way, which improoves things as quality and even quantity of better iron.
There may be other ways, but it my 2 cent for the case.
[Answer]
The problem with the question is that while as a single problem the solar furnace is something that can be implemented in a pre-industrial society. There are however, several other related problems to solve simultaneously for a society to start producing iron from a solar furnace.
Problems to solve:
* The overall lens and or mirror system.
* Keeping the system focused/aimed at a target.
* Determining crucible tech to contain the ore and other reactants.
* Determining reasonable chemistry to use depending on source ore.
* Reasonable temperature control.
### Solar furnace
Mirrors have been made in antiquity. Focusing onto a point was a known idea. Other answers address this.
### Maintaining focus
This will either require a bunch of people to assist or a mechanical system. Very solvable, but increases overall complexity.
### Needs a crucible:
To go from iron ore to iron you need a reducing atmosphere.
Simply putting a lump of iron oxide at the center of a solar furnace will have about the same odds of getting iron as extracting hydrogen from water placed at the focal point.
Might be obvious but it is not mentioned in the question. A crucible would essentially a pottery container, but its additional mass to heat up. Thus increasing time and thus expense over "Just need to heat ore.".
### Chemistry to smelt.
Ie what else needs to go into to the iron ore batter before putting in the solar furnace for baking. Probably already known from other traditional processes. But might have to be adjusted for a solar furnace that has less carbon then a charcoal fire.
### Temperature Control.
This is a tricky problem. Other traditional processes relied on experience. For a solar furnace with less thermal mass involved it will be easier to over or under heat the crucible. Which will affect properties of the final result.
### Conclusion
There are all problems that can and could have been solved in a pre-undustrial society. It has the big negative in terms of it is a novel approach and several problems are needed to be solved together. Not a good combination for adoption of new tech. Never mind pre-industrial tradesmen and guilds tended to be secretive.
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[Question]
[
I am working on a sci-fi story and need a way to clone a person, body and mind. I also want it to be done without "far future technology" where anything goes. I want it to be simple and crude, but also believable. And I might have found it...
Background:
It's the near future. A interstellar spacecraft is sent to colonise a new solar system, a great feat, done on a budget.
A generation ship is unfeasible so instead they send a small craft with the ability to recreate the crew upon arrival (or whenever maintenance is needed).
So, this is how it is done:
Upon birth a sensory device is implanted in the brain of some babies. This device is connected to all of the nerves leading into the brain, it reads and registers all of these nerves firing. This means all of the signals sent to the child's brain is logged. (At the time this was marketed as a "backup", sold to overprotective parents.)
All of the data is stored in a harddrive somewhere. The children grow up and are around the age of 25 when this project asks for volunteers, some of them volunteer.
When the cloning initiates a cell is placed in a artificial womb and grows into a fetus (simple enough). As the fetus develops a system of wires is inserted into their brain and locked on to the same nerves as earlier.
When they are due for birth the system kicks on and starts stimulating the same nerves that registered stimuli in the original, to create a false input for the brain.
The child stays in the womb and is being feed the experiences the original lived, all in real time. The womb also function as a sensory deprivation tank, to prevent any real input.
When all the data have been transferred (the clone is around 25 years old at this time) the clone is born for real. He or she are now free of artificial input, a perfect copy of the original crewman, and can go on to confidently fix the leaking cooling system. (Sorry still 800 years to destination, maybe next time)
From the clones point of view they are growing up on earth, learns and loves, volunteer, hand over their "backup" harddrive and BAM... suddenly they are covered in goo, lightyears away from earth and hundreds of years in the future.
So the question is: How believable is it that this mind cloning method could work?
[Answer]
**Summary:** The problem with replicating a mature brain by replaying its past experiences is that if there are ever any differences between the brain state of the clone and the brain state of the original, the clone will be unable to learn by interacting with the world, as the illusion of true feedback will be irrevocably broken.
This inability to learn will not just cause a different version of a person, but, depending on the stage of child development at which it occurs, will break the clone to the point where their brain is barely human.
Because of the butterfly effect, divergence in clone brain state could occur from even the smallest unaccounted-for differences.
Ensuring that the clone's brain state is identical would require eliminating random, thermodynamic differences in the developing brain, ensuring that the brain state was identical after fetal development, and simulating brain injuries like concussions.
---
An unspoken assumption of replicating a mature brain by replaying its past sensory experiences is that the brain will develop the same way every time.
However, this isn't the case — even with a cloned cell, your proposed artificial womb means the environment of fetal development will be different.
Let's look at the consequences of this.
If you've ever watched a baby, you'll notice that many of their movements are somewhat random-looking.
This is because they are just kind of trying everything out to determine their place in reality.
"I feel angry, and then move my hand, and then feel my hand move, and then it hits the floor, and it hurts!" Discoveries like these are critical to child development as the child learns to adjust its behaviors to avoid negative feedback.
If the cloned fetus is even a little different from the original one, the clone won't be able to associate intentions to actions to feedback — it will just feel painful feedback and have no mechanism for adjusting itself.
It will spend its life trapped in a kind of hell in which it is an unwilling voyeur, a forced non-participant, in someone else's life, like an awful variant of [locked-in syndrome](https://en.wikipedia.org/wiki/Locked-in_syndrome).
The clone may never learn to speak, to walk, or even to breathe, and when it wakes up covered in goo in a spaceship far away, it will be something less than human.
It's not just the fetal environment that you'd have to make sure is identical — if anything causes the brain of the clone to at any point become different from the brain of the original in any way ([even a small way](https://en.wikipedia.org/wiki/Butterfly_effect)) the intentions and attempted motor actions of the clone won't be able to affect its world, and its development will stall as it is relegated to live the rest of its 25 years in someone else's body.
Differences that can cause the brain development of the clone to fall off its very narrow track include anything which would cause the physical conditions of the brain of the clone to differ from that of the original: things like minuscule temperature variations, blood flow to the brain, and things like concussions — how would you simulate a concussion in the clone?
[Answer]
There is a lot of hand-waving involved, but because virtually no one seems to know that, there's not a big problem for the writer.
Our minds are more than just the nerves. They are the culmination of the exact pathways they have, the amount these pathways are used, the chemical composition at the time and the many many feedbackloops that constitute the entirety of the nervous system. Your sensors need to log not just the individual signals but also map every neuron and every chemical inside the entire nervous system.
So lets say your deprivation tank clone broke her harm at the age of 12. If your tank does not break it and break it exactly, the chemicals in the brain are different and you get a different result. If your tank does not offer the resistances to movement and nutrients in the exact same way, your clone will have a different muscle tone and chemical imbalance. This will cause a disassociation: at first the clone will have microscopic deviances in its decisionmaking compared to the original to the same input. But as the years go by the decisions the clone would make to the same input changes. Where the original stepped left the clone stepped right for example, and the simulation shows something else. This will instantly jar the clone out of the simulation, he'll try to figure out what is going on while the simulation keeps going, throwing input at the clone of movements and experiences the clone no longer initiates. If the clone then has to live another few years experiencing someone else's memories while incapable of changing the outcome...
As an alternative: you are trying to achieve persona copying which is a ludicrously difficult if not impossible idea. Instead you should be looking at persona approximation. For example instead of cloning you use 3D printing. It is not impossible to assume we will be able to 3D print more advanced tissues in the future, and 3D printing entire bodies should not be a too big leap once you are able to grow and print any tissue.
You 3D print just the complete baby nervous system along with the rudimentary organs and pulmonary-vascular system to support it, but nothing else. This is printed inside the cultivation sacks of your clones using the DNA of the donor. This cuts down on the amount of resources you need to keep it alive and functioning and gives your machines direct access to the nerves where you need it. Now instead of perfectly recreating the life of the donor you let the computer try to approximate it. So if the clone decides to go left or right somewhere the computer will try to steer events to ensure the clone's life is pretty much the same as the donor. A life-altering event may take place in a different location because the clone decided differently, but it did take place in order to approximate the memories and personality of the donor.
Once the clone reaches maturity it will be put in a medical coma, after which the rest of its body is 3D printed. This way you can even set the muscle tone and body structure to the requirements of the planet, although you should not deviate the body proportions and weight much to ensure the brain's control over it does not suffer. Now you have a clone with as close as possible personality.
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