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[Question] [ The whole 'prejudice against mutants with powers' thing has been done to death, most notably with X-men. However, I always felt that it was too over the top, the blind hate being excessive and no attempt was made to justify it. The point is sort of lost if the ones who are bigoted are so over the top villains that everyone can say "well, I'm not that evil, so guess I'm fine." If someone was trying to write a story that used prejudice, but not in an [anvilicious](http://tvtropes.org/pmwiki/pmwiki.php/Main/Anvilicious) manner, I'm wondering what are more reasonable way those who had anti-mutant prejudice would be like. What forms of prejudice would occur, and more importantly how would those who were prejudice justify them? My belief is that plenty will hate the unknown, but will try to cover their bigotry with all kinds of rationalizations. Most bigotry of today has these rationalizations, ones that are blatantly flawed and just excuses to hate; but still have some tiny kernel of truth that is simply misrepresented in insane ways to justify bigotry. Today people try claim come minority is 'stupid' because they have less education on average (ignoring that this is due to difficulty of someone from lower socioeconomic standing getting into, and paying for, colleges) or how illegal immigrants are destroying America by not paying taxes (which ignores the fact that illegal immigrants are a tiny fraction of our population and frankly there are not enough to have a significant impact on our economy no matter what their doing), or that all Muslims are terrorist or untrustworthy by pointing to the actions of a tiny group while ignoring that 99.95% of Muslims do not agree with or approve of the group. I'm looking for these sort of flaws rationalizations people would use to 'prove' their bigotry is justified. For example assume a world where people develop powers, usually around puberty. Some may look different (think Beast from x-men), others may look like normal humans, and those that look different may or may not gain any power (may in fact have only disadvantages from the changed form). Also presume that the government is reasonable enough to document special powers and register potential lethal powers. Few powers are much more lethal then having a gun, and many aren't lethal at all. People often use their powers as source of employment, people teleport themselves and another as human taxis, weak healing gifts used at hospitals to patch wounds etc. Powers are rare, but not unheard of. Also, what will be the thoughts of the err..subtly bigoted. Not the ones that put on white robes to burn effigies or stand outside of funerals with colorful signs about how God hates everyone, but the ones who are mostly decent folk and don't have a desire to hurt mutants, but still have some subtler distrust or unease about mutants. I already know pretty well the religious argument, and the "they're dangerous" argument; as these are the most common ones used in fiction. I'm more interested in the other arguments that might be made. What would an atheist use as a justification to distrust a group of mutants who are certified as not having 'weapons grade' powers? [Answer] So you're looking for the somewhat reasonable arguments for why people might resent people with powers? For that you'd still probably want to look to the real world. Many people resent smart people. They may benefit directly from their doctor knowing how to diagnose heart disease but they can also resent people for their knowledge, status and income. Lots of people complain about "Ivory Tower Intellectuals" and make up narratives about how they're disconnected from the real world or don't have real knowledge or understanding. They may believe that the smart people look down on them in their normality. "thinks he's so high and mighty". They might resent the status that the person gains from their ability. "Just because his daddy sent him to medschool he's making 6 figures while I'm stuck here". Your mutants are going to have unusual abilities and even if most aren't powerful most are going to be unusual meaning that a large portion of them are likely to be able to pull in a big income whether it's as emergency responders teleporting people to hospital, seeing glimpses of the future that can be used to make the occasional stock trade or similar. They may even be justified. Many of the people with extra abilities may actually look down on normal people. People who are unusual in some shared way are also going to naturally form their own groups at which point human ingroup-outgroup behavior kicks in and people start thinking in terms of us and them. <http://www.simplypsychology.org/robbers-cave.html> Some people are going to be put out of work by mutants, judges put out of work by mind reading mutants, steel workers put out of work by mutants resistant to heat etc. Some mutants are going to abuse their abilities in horrible ways and people are going to judge mutants by the actions of the few who hit the headlines like that one guy with mind control powers who collected his own harem of slaves or the mind-reader who used his power to con people. There's going to be arguments about your registry, there's going to be accidents where some teenager has a nightmare and burns a bording school to the ground and then there's going to be calls to ban people on that registry from living near vulnerable people even if 90% of the people on it are harmless. [Answer] Probably the first place superpowered individuals are going to have problems are at school, with other non-superpowered kids. Puberty is already a dangerous time for kids, but throw in random powers and these individuals are most certainly going to get bullied. At this point, there doesn't need to be a justification: teenagers are irrational. The interesting part is that a childhood of bullying is going to mean that a lot of these mutants are going to have things in common; they'll have a common culture of coping mechanisms, and the lucky ones will find a community of their peers to turn to. Unfortunately, what started as a comforting place where these children could escape the persecution of others becomes a box from which they can never escape. For the rest of their lives, many of these mutants will define themselves by this group, and surround themselves with other mutants. To them, it just feels right, but to the rest of the world it looks like the mutants think they're better than everyone else, or at least different. This presents a problem, as now pretty much anything the mutants do to help each other pushes them ever further from the rest of the world. They make a school to bring up mutants in a more accepting environment? "What's wrong with regular schools? Do they think they're better than us?" Some mutant gets shot by a scared cop, and his mutant friends hold a memorial? "Why do they have to make this a mutant issue?" Mutants live in an all-mutant neighborhood to avoid the dirty looks? "It's like they're not even trying to be a part of this community, so why should we treat them like equals?" From here, it's a feedback loop: the mutants have to band together to stave off an ever-more-threatening public, and the public takes every new step by the mutants as an insult. People may not think they're bigoted (they may have a 'mutant friend', maybe they like that one actor who's a mutant), but deep down they've already been indoctrinated into the crowd mentality. [Answer] Misunderstanding and mistrust of the 'other' are huge in human psyche. Many that have useful talents might be looked on as taking jobs away from others. If you have a small healing power you are more likely to be hired as a nurse or doctor over someone without it. Even if they are a better candidate on all other metrics. The teleporter can deliver goods and people much faster and easier than any other form of transport. These are just the regular low end powers. Now you add in some very powerful powers, reading minds, or worse changing thoughts, controlling actions. If 1 out of 10,000 with powers have something that can be dangerous or abused to harm or humiliate others, then in the eyes of many all will be grouped together. The ones with only physical changes will be the worst hit, since they are obviously 'one of them'. You add in economic downturns and people want to blame someone for their ills, mutants are an easy scapegoat, an easy line to make. Even easier than targeting Jews during WWII. [Answer] One theory I’ve heard from otherwise well educated people is the Great Replacement theory. Basically the idea is that some in-group (e.g. the supposed “native people” of a country) is being "replaced" by some other out-group (e.g. immigrants flooding into a country, and having more children than the “natives”), especially when the two groups have different ethnicities or faiths. The core idea is that, if the out-group’s population growth is higher than that of the in-group, they will eventually outnumber the in-group and impose their values and beliefs on the rest, thus “replacing” the in-group’s culture and identity with their own. In France, this idea is pushed a lot by the far right, notably by writer and far right militant Renaud Camus. The theory is that immigrants in France, and particularly Arab Muslim immigrants (for some reason white immigrants from neighboring countries aren’t as much of an issue), will “invade” the country of “native” white Catholic French people, and because they supposedly reproduce faster (which is false, 2nd and 3rd generation immigrants tend to have about the same average number of children as the general population), they will eventually outnumber the “native” French and impose their own culture and identity (sharia law, the Arab language, etc.). Despite all the evidence contradicting such theories, it’s still very popular among far right groups, and is a classical way to portray the dominant majority as somehow in danger or threatened. It is (apparently) a very compelling justification for racism, and in particular mass expulsion of immigrants and forceful assimilation of minorities by erasing their culture and forcing the “native” in-group culture upon them, so as to remove the perceived existential threat posed by foreign cultures to the in-group’s. This works especially well with super-mutants, because people like Magneto explicitly claim they intend to replace non-mutants, portraying mutants as the natural next step in the evolution of the human race. This is great kindle for anti-mutant pressure groups who then claim that the very existence of mutants is an existential threat to non-mutants, as they risk being “replaced”, marginalized, and even exterminated by mutants who see non-mutants as less than themselves. So in a world with mutants, I would imagine far-right intellectuals writing many books on the subject, organizing anti-mutant protests and seizing any opportunity to marginalize and assert control of mutants. One of their justifications would be the Great Replacement by mutants of non-mutants, the idea that if we let mutants be, they’ll eventually, necessarily, become so numerous or powerful that they’ll assert themselves as the norm and treat non-mutants as second-rank citizens. This will be portrayed as unavoidable, a natural way for cultures to evolve. Although the parallels are interesting, this doesn’t apply perfectly to super-mutants. Mutants don’t form a well-defined out-group, because they naturally emerge from the general population rather than emigrate from a foreign country. In fact, before any mutation manifests itself, these individuals are completely indistinguishable from non-mutants, which isn’t the case for children of immigrants (which are distinguishable by e.g. their skin tone, accent, and name). However, neither Arabs nor Muslims form a clear out-group either, since a lot of them have been born and raised within the country and their cultural identity has become a blend of both their heritage and their adopted country’s culture, blurring the lines. The idea that both cultures are fundamentally incompatible is itself an unsubstantiated and racist one. However, as a group becomes more isolated – in particular as a result of discrimination and prejudice against them – they become an out-group, and the racists can then conveniently push their Great Replacement theory to marginalize that out-group even further. Wiki: <https://en.wikipedia.org/wiki/The_Great_Replacement_conspiracy_theory> [Answer] > > What would an atheist use as a justification to distrust a group of mutants who are certified as not having 'weapons grade' powers? > > > Almost any useful power can be weaponized, and restrictions would be called for under the umbrella of Terrorism. With "useful" being defined as "can make a living from". Teleporters, for example, are extraordinarily dangerous. They can bypass security, stealing money, weapons, or intelligence. They can do the reverse to place untraceable bombs. They can kidnap high value targets, kill people by dropping them from great heights, etc. [Answer] If the government had any reason to initiate a conflict then they could spin the news and have the majority of citizens backing the conflict in two weeks. So lets say a corporation wants access to resources in a country high in mutants. The government will then claim that the mutants are terrorist and need invading, as the intelligence agencies secretly fund and support those terrorist organisations or get their own operatives to pose as terrorists and send provocative videos. In two weeks the country would be ready to invade and seize the resources. [Answer] # Envy "Jimmy has a superpower and I don't. Maybe if I make fun of him I will feel better about being a normal." We see this sort of thought process all the time in today's world, so it naturally follows that a similar phenomenon would happen in a world full of supers. It happens to the rich kids, the smart kids, and drives the "keeping up with the Jones's" syndrome. I personally have fallen prey to mistreating people out of envy on occasion, so I think this is relatable at a personal level. # The Perceived Threat of Power Imbalance For example, most people feel threatened by: * Their boss * Guns * Cops * Big scary dogs * Uber-muscular men at the gym * People much taller than them People tend to retaliate when they feel threatened, so it wouldn't be surprising for this to be directed at supers. # Religion A lot of anti-super bigotry would come from religion. Some people would assert that their God(s) created the normals to be limited and that supers are violating the natural order of things. Which is funny, because other religions would absolutely embrace it as a god-given gift. [Answer] Alot of good answers. Anti-Elitism seems to be popular. However the community rewards and preferences only certain types of competition. * You are smart and good and making money, we let you compete in business. * You are smart and good at combat, we don't let you compete in stealing all the things. The generally are directed towards a common good for the community; and sometimes about stacking the decks in your favor (knights disliked the crossbow because the could easily kill a knight, so tried to have them banned) * The super powers will up set the existing social order (ie every banker who makes money on the stock market, is replaced by one person who predicts the future of every business decision.) * The super powers encourage competition in way that doesn't aid the community as a whole. Ie they mind read people to extort them for money. [Answer] There have been a lot of good answers here so far, but I'd like to point out a few additional avenues that people haven't considered. Superhumans are a lot more dangerous than you think Nobody's perfect. Everyone has a bad day, lashes out in anger, does things like hit a wall or throw things across the room to vent. Even people who have great anger management often had to learn this skill. A lot of the arguments over mutants being "dangerous" in works like X-Men mostly involve cases of outright evil mutants using their powers for law-breaking purposes. The perennial argument is "what if someone with Kitty Pride's powers were evil and just decided to phase into a bank vault and take all the money. What people don't often seem to consider is that all mutants are potentially dangerous because everyone has moments of emotional vulnerability, and even a slight lapse in control can result in people dead. In real life an angry dispute that leads to a fistfight or a person kicking something in anger in a world with mutants ends with a massive explosion or somebody having a hole drilled in their body with lazer eyes. And what if you have a mutant that has some sort of mental disorder, like borderline personality disorder, schizophrenia, depression, or bipolar on top of their mutation which makes their moods unstable and often difficult to control? Hence, even if a mutant is perfectly friendly, law-abiding, and has absolutely no desire to hurt other people, they are still dangerous and not safe to be around. Of course this argument is kind of bull. Anyone can literally be a threat to anyone. A big person, if they snapped, could easily overpower most other people in a rage and harm or kill them. But that big person could be taken by surprise by a person they think is a friend and have their throat cut (the element of surprise buys you like, what, 5-10 seconds in a fight?), and they die like anyone else. Or someone could just straight up poison you when you aren't looking, history's go-to technique for people who lack physical strength (hence why poison was seen as a weapon of treachery in many cultures). Society just kind of...collectively ignores the threat the people around us pose because if we didn't society couldn't exist. The argument of mind control A counterargument might be that "well Superman is a nice guy and paragon of morality who would never even swat an insect". Well, in a setting with mind control, it doesn't really matter. See, the funny thing about hypnotism and mind altering substances in real life means that there are really only two ways to go about it: hypnotism only works because the subject subconsciously wants to do it or the victim's normal thought process is totally gone. There is no "the mind controlee is still there and subconsciously stops themself from doing anything too evil". You could brainwash Superman and command him to go on a rampage killing millions of civillians, and there is nothing anyone could do to stop you. If you have mind control in a society of superhumans the world is your gunrack and all the people around you are your guns. Indeed, this is exactly what happened in Injustice: Gods Among Us. The Joker dosed Superman with Scarecrow's fear toxin and caused him to hallucinate and kill Lois Lane and his unborn son, believing they were Doomsday. No amount of the power of love or a subconscious desire to not hurt his family could stop him. Or Professor X in the recent Logan movie. Due to a brain disease that he had no say in or control over, he had a seizure that caused him to lose control of his powers and ended up killing hundreds of people, including all of the X-Men against his will. Deny job opportunities Most bigotry in real life isn't lynch mobs and concentration camps. It's the casual, small things that add up until people are deprived of opportunities. One obvious way that mutants could be discriminated against is job opportunities. Think of it this way. You're a bank owner in the Marvel universe who is trying to figure out whether they should hire Wolverine as a bank guard. However, you also know that mutants in the Marvel Universe seem to be targeted by Sentinels seemingly every month. If you hire Wolverine, it's only a matter of time before the Sentinels show up at your bank looking to kill him, and you really don't want your bank to be levelled in the midst of a superhero fight. The insurance premiums will be nuts. Indeed, this kind of happened in Spider-Man, where supervillains kept attacking the Daily Bugle just because Spider-Man worked there (okay, he was a freelance photographer, but he worked for the Bugle in everything but name). But back to bank guard Wolverine. Wolverine, of course, has powers he can use to defend himself. But if he uses his powers on a potential miscreant things could get...messy, and said miscreant could turn around and sue you, Wolverine's employer, for gross negligence or cruel and unusual punishment. Gee, all of a sudden you don't want to hire a mutant like Wolverine. And that's how a lot of discrimination works. People individually make the decision to avoid you because of seemingly logical reasons like you're a potential liability, or they have stereotypes in mind that make you seem as not worth it. Eventually you get to the point where you've been ostracized because no one will give you a break and the people in the society you belong to all independently made the decision that you're not worth dealing with. "Oh, these people should definitely not be ostracized by the community and given a chance to be treated as individuals rather than threats or stereotypes," they'll say, "it's just I don't want to be the one to do it." Hatred from the elites Another thing to consider is that you don't need mutants to be a threat to people in order to be hated. Throughout history, people in power have always hated potential threats to their hegemony. The samurai hated the idea of guns, to the point that part of the reason the Shogunate closed off Japan from the world for 200 years is they didn't want the peasantry getting access to firearms. In medevial Europe the born-nobility hated how the bourgeoisie were gaining enough power to challenge them. Modern governments hate tech giants like Google because they have increasing power over them and due to their nature as multi-national corporations there have less and less power over them. Basically, the elites in society have always hated people with alternate sources of power that could challenge their supremacy and that the elites cannot dictate or control to make useful to them. Mutants are the ultimate expression of this. Their powers come from their bodies, not their wealth or their inventions, and you cannot take that power away from them or easily regulate it. Mutants represent a threat to the elite's status quo. You could have a situation where the presence of mutants is unambiguously good for the majority of human society, but the elites still hate them because they are eroding their power base. For example, you could have mutants that could produce unlimited clean energy like the Flash or the Human Torch are sometimes shown doing, and energy companies (both fossil fuel and renewable like solar or wind) would hate them because they are cutting into their bottom line. Or mutants who have the ability to cure viruses and heal the sick and are hated by pharmaceutical companies because curing the sick instead of palliating them means they can't sell as many drugs. In most societies, the elites also have a significant amount of control over the media. So if the elites hate mutants, all they have to do is use their influence over the media to run a smear campaign with anti-mutant propaganda and whip public sentiment into a frenzy to get mutants marginalized and hated by the common populace. Forced mutant draft [Motherland: Fort Salem](https://tvtropes.org/pmwiki/pmwiki.php/Series/MotherlandFortSalem) showed this aspect pretty well. Basically, in a world with mutants whatever country has the most powerful superhumans would be the one on top. It would be a Cold War-style arms race but with human beings instead of bombs. Therefore, governments would be pushed towards gathering up as many high-power superhumans as possible. There could be a mandatory draft for mutants, all mutants are forced to join the military and serve it until they die, no ifs, ands, or buts. Many countries might pass laws making it illegal for mutants to immigrate to other countries (you might think this is silly, but countries have passed laws making it illegal for minorities to leave the country in the past like the Huguenots in France or the perennial example of Nazi Germany). It doesn't matter if your local flying brick is a conscientious objecter, your government needs every mutant it can gets its hands on in order to maintain a military advantage over other countries. And if they let one superhuman slip through the cracks because they are a pacifist or don't want to be a tool of the government, they open the door to everyone else leaving as well, which leads them to become even harsher. [Answer] Prejudice: dislike, hostility, or unjust behaviour deriving from preconceived and unfounded opinions. Your world needs no prejudice to justify treating mutants differently. ]
[Question] [ Let's suppose that after seeing aliens get portrayed negatively in science fiction and wishing to end the discrimination, the ancient H'andh'wh'a'vians decide to destroy Earth and humanity. As they are a Tier-U-uber-civilization, they decide to just spawn a sphere of Uranium-235 in a circular equatorial orbit with a sea level altitude of 400 kilometers. The diameter of the sphere is 1000m. Apart from U-235, there are no other materials or impurities at T=0. You can assume that any atoms that would be displaced by the sphere are removed prior to its creation. * What happens? * Does the explosion occur immediately, or only at impact/atmospheric entry? * How long does it take for orbital decay to put the sphere out of orbit? * How bad is the explosion and what effects does it have? Is there any chance for survival? Is the Planet's orbit altered significantly? [Answer] Normally, only the innermost kilogram of uranium in an implosion-type bomb actually undergoes fission (and only 0.6 to about 5g of mass are ultimately converted to energy - the sources don't agree on this), because the explosion itself vaporizes and blows apart the rest and the fission cannot proceed further. This, by the way, was the main limit to the size of fission devices, that led Sakharov, Ulam et al. to design fusion devices. In this case, though, practically the whole mass of uranium undergoes fission within a millisecond, while the outer shell (while still exploding) acts as a tamper. Only a very thin layer will neither undergo fission nor provide inertial confinement. Immediately after, the enormous neutron flux will trigger fission in that thin layer too. At the same time, the neutron density will be enough to achieve a [very high burn](https://www.sciencedirect.com/science/article/abs/pii/S0029549303000347) everywhere inside the sphere. So, while [Little Boy had an efficiency of about 1.4%](https://nuclearweaponarchive.org/Nwfaq/Nfaq2.html), and we can expect a fission efficiency of 50% (same source) due to the size, the actual energy efficiency will be much higher because the reaction will proceed further. A rough (probably incorrect) estimate based on the hypothesis that all the byproducts will be made up of the lowest (most "burnt") isotopes from the Hiroshima explosion tells us that the per-mass energy release should be about twenty times higher. And the mass of the sphere is around 9,948,368,333,000 higher than the fissioned mass at Hiroshima; we can then estimate an energy release to the tune of three billion megatons. I wouldn't be surprised in the least if the radiation density at the center of the fireball allowed [photodisintegration](https://en.wikipedia.org/wiki/Photodisintegration) (photo-fission) and further increased the energy release (or maybe the reaction would find an equilibrium between photofission and nucleosynthesis, which is endothermic). There is no need to calculate the exact magnitude of the explosion: it would not be enough to vaporize the Earth, but the radiative shock would scorch the target hemisphere and supply enough secondary activation to thoroughly poison the whole atmosphere as well as the oceans, as if the primary onslaught weren't enough. The atmospheric blast reaches the other side of the planet after about sixteen hours - actually way less than that due to the speed of sound being higher in the high atmosphere - and increases constantly for at least eight hours; but the havoc it causes is probably nothing compared to the reentry of the incandescent, radioactive tephra from ground zero. Oh, the storm winds are radioactive too. Primary concussion should be more than enough to trigger most existent fault lines, and seismic waves travel faster than sound in air; so for those countries that did not see the blast aurora, the first hint something went very, very wrong (apart from communications gone awry and possibly a sudden ["sour, metallic taste in the mouth"](https://en.wikipedia.org/wiki/Louis_Slotin#Criticality_accident)) might be a series of catastrophic earthquakes and volcanic eruptions. Also, atmospheric pressure will finally stabilize to much lower value, possibly all the way to half of the former total, due to the gases being ionized and stripped off the Earth. In the worst scenario, oxygen partial pressure goes from 21% to about 11-12%, below the level sustaining current terrestrial life. I'm uncertain whether to count oxidation and burning - it might well be the case that there is not very much left to actually burn. If there is, then the oxygen goes still lower, and CO2 contents goes up. Plus, the firestorm triggers the grandfather of all nuclear winters. Photosynthesis stops on the whole surface, probably for several years. Plus the neutrino flux might supply enough inverse-beta decay to sterilize the whole planet, both hemispheres at once, or at least ensure death by cancer to all superior organisms. Deinococcus radiodurans might yet survive. Nothing else will. [Answer] T = 0.0000000000 seconds : The Sphere appears. T + 0.0000000001 seconds: The Sphere disappears. some...minor... light flash may be observed shortly thereafter, as the planet is vaporized. Supporting numbers: sphere: 1000m diameter. Radius 500m volume 5.24e8 m3 total content = 5.24e14 cm3 Uranium-235: Density 19.1 grams/cm3 Molar mass 235.0 Molar volume 12.3cm3 thus sphere = 42601626016260 moles (10.011 billion tonnes) With so much more than critical mass, we can assume 100.0% fission. (there may actually be enough neutron flux to facilitate trans-uranic nucleosynthesis, similar to what occurs inside a supernova) Energy released per mole of U235 fissioning: 1.954e10 J Energy released by whole sphere fissioning: 8.3e26 J Gravitational binding energy of planet Earth: 2.0e32 J The explosion is not nearly enough to actually blow up the planet, it merely toasts it gently to a white-hot (radioactive, due to the neutron flux) cinder. Ok, Maths fixed. The explosion is about 4 billion times bigger than the Tzar Bomba. Still not enough to disrupt the whole planet, barely enough (if it was all captured, which it definitely won't be!), to raise the whole planet's temperature by about 1 kelvin. But ample to turn the whole hemisphere under the sphere into a kilometers-deep blast zone, and rip off every trace of atmosphere on that side of the planet. [Answer] I'm going to guess at it. I can't do calculations, so this is kind of a broad brush sense of some effects that might happen. In no special order: * The sphere fissions. It fissions everywhere, the outside acting as others said, as a tamper even while detonating. * The fissioning process leads to inward and outward directed pressures. * The inward pressures, like in an H bomb, both tamper and contain, and for a small time create incredible pressure. Novel nuclear processes will probably arise. Photodisintegration was mentioned, that's one of those. Reactions will occur far longer and more completely than in A bombs which only typically detonate a small percentage of their uranium. The neutron flux can't escape without reacting, so even as a fission reaction it's far more complete - probably could be near total for much of it(?). (That doesnt mean total matter to energy, just very high or near total U235 fissioning, to be clear). The nuclear reaction byproducts also can't easily escape, except neutrinos. We know about neutrons and chain reactions, but expect other byproducts to be unable to escape as in a small A bomb, and they will contribute to increased or novel reactions too. * The outward pressure may or may not cause the outer surface to shatter into fine dust, before being absorbed into the huge fireball. Bear in mind a small sphere a few cm, can fission, so anything more than a few cm from the surface will be close enough to enough uranium to almost instantly do so. Not much will be close enough to the surface to be blasted apart as dust before fission is.possible. The question is, will the reaction be so violent and contained that almost all uranium engages in some nuclear process, or will a fair bit of it be left as-is but as almost atomic dust? In a way it doesn't matter, because even the uranium that fissions will ultimately result in final byproducts that fission less easily or not at all, so expect a huge cloud of all kinds of interesting atoms and elemental isotopes. Many highly toxic or reladioactive. I don't know what proportion of mass ultimately ends up as energy., or the nature and division of byproducts. That's crucial. But takes some supercomputer modelling on this scale. * We pan back a bit. The explosion sends heat, radiation, and general blast in all directions. Directly towards the atmosphere, away, and in retrograde orbit, among others. * The blast and heat hit first, directly below and for much of the hemisphere facing the explosion. I don't know exactly how that plays out because a lot depends what momentum the particles and energy have, and that I can't tell. Probably huge, even though individually, microscopically small. Bear in mind energy has momentum and a heating/expansion effect, and a kilometer sphere even after very high levels of matter to energy conversion has a hell of a lot of matter left in it. The dinosaur killing asteroid was much larger but much slower moving perhaps. I suspect momentum and pressure would be due to radiation and heating/expansion effects not due to solid debris at high speed. But then again nuclear blasts we know of, all happened in dense air that (like the WW2 Dambusters bombs) added resistance and great momentum to the blast. This is happening some 350-380 km from any dense air, so the shock wave though huge spreads out to a sphere almost 400 times as large as it began, and perhaps dissipates considerably, before it can even begin to add any significant air to its blast momentum. Even then its many km to the ground. * Either way, the atmosphere is not only impacted but heated and expanded, the heat is trapped, and everything simultaneously goes incandescent hot, and expands - and this adds hugely to the blast, which cirkces the world many many times. Turbulence, self interactions and storms are also colossal. I can't say how big earthquakes are. The heating effect magnifies momentum massively but how much of that translates into the ground or sea, I can't say. Assume big, for some value of "big". * The sphere was in orbit. So on average, its fireball and debris still has some orbital bias. It's a huge expanding nuclear sphere whose centre is still in a 400km orbit, which means it circles the earth at about 7.57 km/sec and completes an orbit every 92 minutes. Any atomic scale dust and matter trails in its path, both blasted into and settling into the upper then lower atmosphere, and gradually spreading out to be a shell or ring around the planet most likely. Outer atmosphere friction and interactions mean the "tail" grows and it develops a thick ring like style more than a simple expanding sphere. Interactions with the earths magnetic field also influence its distribution and how.it lands. I don't know how long the fireball is ongoing, but if its more than trivial, then the hemisphere it detonated above is not the only place its exploding above or radiating into, either. * Even when the reactions end, we need to consider the final temperature and distribution of the matter left. If we have dust at a million degrees circling and taking time to cool (I dont know what figures are sensible) or a superheated ring or huge growing cloud, we have further consequences of that, until it's cooled somewhat. * As a byproduct, the earths ozone layer and its van Allen belts, protecting it from the vicious solar climate and radiation, are both probably badly screwed, too. * Does the earth survive? Probably. No.idea how deep the changes go. The energy release and the amount that reaches earth heats and scours it, but I intuitively suspect isn't enough to unbind or fundamentally split it, maybe they don't go too deep at all comparatively??? After all, earth is 8000 km across, the closest solid surface is 400km away (although to an extent the atmosphere may act as if solid in the moment of explosion due to the forces unleashed), and eartjs volime is 8000^3 = 500 billion x the orbiting sphere's, and that's a hell of a lot to unbind even for a 1km sphere of pure fissioning nastiness... and most of earths mass is shielded by the ablation and the brunt of impact taken by the outer few km. ]
[Question] [ How could an Earth-like tidally locked planet with no Moon have a bright and livable night sky? The bluish night sky should look like this: [![Image of bluish night sky.](https://i.stack.imgur.com/IVbjO.jpg)](https://i.stack.imgur.com/IVbjO.jpg) But it should be 1% as bright as Earth's day sky and provide constant illumination to allow human-like creatures to see. It also should contain 1% UV illumination to allow plants to grow. Rules: * The illumination should not come from a star or any single bright source (a moon, ect.) * The light source will not cause any disturbances to human/plant life (ex. radiation) * The amount of light must be at least 80% constant and not fluctuating * The sky should not be constantly flashing with aurora-like phenomena * The planet must have a livable Earth-like temperature [Answer] If you don't want the light to come from a single source, presumably you need roughly uniform illumination across the night sky. One way to achieve that is with a [reflection nebula](https://en.wikipedia.org/wiki/Reflection_nebula), a cloud of dust surrounding a star. The nebula itself emits no light; instead, light from the star is scattered by dust grains within the nebula. If a planet orbits one of the stars within the nebula, some of that scattered light will reflect back onto the night sky of the planet, illuminating it. For your scenario, you might consider a nebula with multiple stars in it - the star you want the planet to orbit, as well as a collection of massive, luminous stars. If the wall of the nebula is dense enough, that light may be able to produce the strong emission you're looking for at night. Moreover, the light should be uniform, as you're looking for, without coming from a single source. I suspect that by tweaking the density and properties of the stars, you can achieve the exact properties you want. In particular, the ratio between the nebula luminosity and the luminosity of the stars illuminating it is, as per [Sobolev 1960](https://ui.adsabs.harvard.edu/abs/1960SvA.....4....1S/abstract), $$\frac{L\_N}{L\_\}=1-e^{-\alpha r}$$ with $r$ the nebula radius and $\alpha$ some absorption coefficient. By tweaking the number density and nebula radius, you can change this ratio as you want, which will in turn affect the brightness of the night sky. (As a side note, the light will tend to be quite blue, like the image you have above - short-wavelength light scatters more readily than long-wavelength light, biasing the color bluewards. This means you'll also get the UV light you desire.) [Answer] So I would like to point out that each of these things is an order of magnitude different in brightness. In this case, a little less than 1000X. Daylight -> Twilight -> Moonlight -> Starlight 75% of daylight would be considerably brighter than at sunset. Maybe a slightly overcast day. Also, another option other than a moon for reflected light might be a ring. Though rings aren't stable forever. Millions of years maybe. But it's time is limited. Here's an example of what the sky might look like if Earth had rings like Saturn. [![enter image description here](https://i.stack.imgur.com/7E7JT.png)](https://i.stack.imgur.com/7E7JT.png) You can imagine, that such a thing would probably reflect a lot of light. You'll notice, that if you get to about twilight levels, the stars start to disappear due to diffusion of light in the atmosphere. While it may be enough to see by, growing plants might be hard. Something that might make it easier for them is if they used a black pigment to maximize their light absorption. If they evolved to such an environment, they might have super efficient photosynthesis. Whether or not it's a realistic possibility to have plants able to grow in such low light, I'm not sure, but I think it would at least would make it seem more plausible. [Answer] In the first part of my answer I discuss whether a tidally locked planet can have life. In the other four parts I discuss various ways to get a bright night sky. Part One of Five: Habitability of a tidally locked planet. If you are asking about the permanent night of the eternally dark side of a tidally locked planet, then you have to worry about whether it will be warm enough for life or a frozen, lifeless, wasteland. One problem with having habitable planets orbiting dim stars, the majority of stars in the universe, is that the habitable zones of those stars will be so close to those stars that the planets will be tidally locked. A minor change in the mass of a star will cause a much larger change in its total luminosity. Thus reducing the mass of a star slightly will reduce the size of its habitable zone much more, and thus a planet in the habitable zone will experience much more intense gravity from its star. If the star is dim enough, the tidal forces from that star will tidally lock the planet so that one side will always face away from the star and the other side will always face the star. > > At the close orbital distances, which planets around red dwarf stars would have to maintain for liquid water to exist at their surfaces, tidal locking to the host star is likely. Tidal locking makes the planet rotate on its axis once every revolution around the star. As a result one side of the planet would eternally face the star and another side would perpetually face away, creating great extremes of temperature. > > > For many years, it was[citation needed] believed that life on such planets would be limited to a ring-like region known as the terminator, where the star would always appear on the horizon.[further explanation needed] It was also believed that efficient heat transfer between the sides of the planet necessitates atmospheric circulation of an atmosphere so thick as to disallow photosynthesis. Due to differential heating, it was argued, a tidally locked planet would experience fierce winds with permanent torrential rain at the point directly facing the local star,[21] the subsolar point. In the opinion of one author this makes complex life improbable.[22] Plant life would have to adapt to the constant gale, for example by anchoring securely into the soil and sprouting long flexible leaves that do not snap. Animals would rely on infrared vision, as signaling by calls or scents would be difficult over the din of the planet-wide gale. Underwater life would, however, be protected from fierce winds and flares, and vast blooms of black photosynthetic plankton and algae could support the sea life.[23] > > > > > In contrast to the previously bleak picture for life, 1997 studies by Robert Haberle and Manoj Joshi of NASA's Ames Research Center in California have shown that a planet's atmosphere (assuming it included greenhouse gases CO2 and H2O) need only be 100 millibar, or 10% of Earth's atmosphere, for the star's heat to be effectively carried to the night side, a figure well within the bounds of photosynthesis.[24] Research two years later by Martin Heath of Greenwich Community College has shown that seawater, too, could effectively circulate without freezing solid if the ocean basins were deep enough to allow free flow beneath the night side's ice cap. Additionally, a 2010 study concluded that Earth-like water worlds tidally locked to their stars would still have temperatures above 240 K (−33 °C) on the night side.[25] Climate models constructed in 2013 indicate that cloud formation on tidally locked planets would minimize the temperature difference between the day and the night side, greatly improving habitability prospects for red dwarf planets.[4] Further research, including a consideration of the amount of photosynthetically active radiation, has suggested that tidally locked planets in red dwarf systems might at least be habitable for higher plants.[26] > > > > > The existence of a permanent day side and night side is not the only potential setback for life around red dwarfs. Tidal heating experienced by planets in the habitable zone of red dwarfs less than 30% of the mass of the Sun may cause them to be "baked out" and become "tidal Venuses."[1](https://en.wikipedia.org/wiki/Habitability_of_red_dwarf_systems#Tidal_effects) Combined with the other impediments to red dwarf habitability,[3](https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets) this may make the probability of many red dwarfs hosting life as we know it very low compared to other star types.[2](https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems#Non-circumbinary_planet_(S-Type)) There may not even be enough water for habitable planets around many red dwarfs;[27] what little water found on these planets, in particular Earth-sized ones, may be located on the cold night side of the planet. In contrast to the predictions of earlier studies on tidal Venuses, though, this "trapped water" may help to stave off runaway greenhouse effects and improve the habitability of red dwarf systems.[28] > > > > > Moons of gas giants within a habitable zone could overcome this problem since they would become tidally locked to their primary and not their star, and thus would experience a day-night cycle. The same principle would apply to double planets, which would likely be tidally locked to each other. > > > > > Note however that how quickly tidal locking occurs can depend upon a planet's oceans and even atmosphere, and may mean that tidal locking fails to happen even after many gigayears. Additionally, tidal locking is not the only possible end state of tidal dampening. Mercury, for example, has had sufficient time to tidally lock, but is in a 3:2 spin orbit resonance.[29] > > > [https://en.wikipedia.org/wiki/Habitability\_of\_red\_dwarf\_systems#Tidal\_effects[1]](https://en.wikipedia.org/wiki/Habitability_of_red_dwarf_systems#Tidal_effects%5B1%5D) Thus some calculations suggest that a tidally locked would could have temperatures suitable for life on both the day side and the night side. Another problem with the habitability of a planet tidally locked to a dim star is that many dim stars are flare stars which emit giant flares from time to time. Being in the far side of a tidally locked planet might be safer than being on the near side. But if the flares are strong enough to strip away the entire atmosphere and hydrosphere of the planet, life would die on the far side as well. So we can assume that your tidally locked planet orbits a dim star which is not a violent flare star. Part Two: Illumination from companion star or stars. Possibly the dim star and the tidally locked planet are in a binary or multiple star system with one or more other stars. Presumably the tidally locked planet would orbit one dim star in what is called a non circumbinary or S-Type orbit And there would be one or more other stars several times as distant. > > In non circumbinary planets, if a planet's distance to its primary exceeds about one fifth of the closest approach of the other star, orbital stability is not guaranteed.[5] > > > [https://en.wikipedia.org/wiki/Habitability\_of\_binary\_star\_systems#Non-circumbinary\_planet\_(S-Type)[2]](https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems#Non-circumbinary_planet_(S-Type)%5B2%5D) So the other star in the system would have to have a closest approach that was at least five times the average distance between the planet and the star it was locked into. And the other star could be tens, or hundreds, or even thousands of times are far from the star the planet orbited. Depending on the mass, size, and luminosity of the companion star, and on its distance, The companion star might have a visible disc in the sky and appear like a sun, or it might appear as a tiny but brilliant dot of light in the sky. Depending on the mass, size, and luminosity of the companion star, and on its distance, The companion star might might give the planet a significant percentage of the illumination that the Sun gives to the Earth, or it might give no more illumination to the planet than a star does to the Earth. or might even be too dime to be visible from the planet. It would be quite easy to design a system where the companion star was as bright as the full moon on Earth, and thus provided enough light for people to perform their activities as well as in daylight. But many times brighter light would be necessary for plants on the day side to be able to grow. Anyway, the Op says: > > The illumination should not come from a star or any single bright source (a moon, ect.) > > > Which rules out light from a star, or from a planet, or from a moon of a planet. Part Three: Illumination from the center of a galaxy. The planet Earth orbits around the center of the galaxy about 26,000 light years from that center, and in the galactic disc of the galaxy. Other things besides stars orbit in the galactic disc, including clouds of gas and dust. And those clouds of dust block out the vast majority of the light from the galactic center - almost all of it. I once read that if it wasn't for those clouds of dust in the galactic disc the center of the Galaxy would seem several times as bright as the full moon and would be bright enough to read by. That would be bright enough for animals and people to be able to see well, though probably not bright enough for plants to grow. The light would appear to be coming from a glowing region of the sky since the individual stars would be too far away, and individually too dim, to be seen as separate stars, so a diffuse glow would be seen. The Sun is near the mathematical central plane of the galactic disc. If a star orbited about 500 or 1,000 light years "above" or "below" the central plane, it would be "above" or "below" most of the dust clouds and so would have a much clearer view of the central bulge of the galaxy and the light from tens of billions of stars. Or maybe the star in your story could orbit the galaxy out in the halo, a spherical region where globular star clusters and isolated stars orbit, and have an even more unobstructed view of the galactic center. If your fictional planet and star orbited half as far from the galactic center as the Sun and Earth do, the galactic center would be four times as bright as from Earth's distance. If your fictional planet and star orbited a third as far from the galactic center as the Sun and Earth do, the galactic center would be nine times as bright as from Earth's distance. If your fictional planet and star orbited a quarter as far from the galactic center as the Sun and Earth do, the galactic center would be sixteen times as bright as from Earth's distance. If your fictional planet and star orbited a fifth as far from the galactic center as the Sun and Earth do, the galactic center would be twenty five times as bright as from Earth's distance. But I don't know whether that would be enough light for plants to be able to grown by galaxy light. The tidally locked planet far side, away from the Star, would be facing more or less toward the galactic center only half of the planet's year. Thus that side would be dark, except for starlight, about half of the planet's year. The longer than darkness lasted, the more likely the plants would be to die during it. Fortunately, if a planet orbits close enough to its star to be tidally locked, the planet would be very close to its star and would have a very short year. Known exoplanets which are believed to be in the habitable zones of their stars and also so close they are probably tidally locked to their stars have years which are tens of Earth days long. Some have years less than 20 Earth days long, and thus if they had a good view of the galactic center or some other light source beyond their star system would alternately face face toward and away from that light sources for less then 10 days at a time. A few have years less than 10 Earth days long, meaning that they would alternately face toward and away from a light source outside their system for less than 5 Earth days at a time. The extreme known examples so far are Teegarden b, with a year 4.91 Earth days long, and thus potentially have alternating light and dark periods of 2.445 Earth days long, and TRAPPIST-1 d, having a year 4.05 Earth days long and thus potentially alternating facing toward and away from an external light source for periods of 2.025 Earth days. [https://en.wikipedia.org/wiki/List\_of\_potentially\_habitable\_exoplanets[3]](https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets%5B3%5D) Part Four: Illumination by nebula light. One of the other answers has suggested illumination by the light of a nebula surrounding the star and planet. Part Five: Illumination by a planet or a brown dwarf. This would be significantly different from what the OP suggests. Instead of being a tidally locked planet, it would be a tidally locked exomoon of a gas giant exoplanet planet or a brown Dwarf. A brown dwarf is an object intermediate in mass between a giant planet and a low mass star, massive enough to fuse deuterium but not massive enough to fuse hydrogen. The rough dividing line between massiveplanets and brown dwarfs is about 13 Jupiter masses, while the rough dividing line between massive brown dwarfs and low mass stars should be about 75 to 80 Jupiter masses. The giant planet or brown dwarf would be a rogue planet or brown dwarf, orbiting the center of the galaxy without any primary star. So your habitable world would be a hypothetical planet sized exomoon if it orbited the rogue giant planet and I don't know what if there is an official term for an object which orbits around a brown dwarf. I'm sure that the vast majority of exomoons, even planetary sized ones, of rogue planets without stars would be way too cold for life. But some would be heated up by tidal interactions with their planets and with other large exomoons that might be orbiting their planets. It is even considered possible that too much such tidal heating could make an exomoon too hot for life, and thus it seems possible that such tidal heating, when less extreme, could keep a planet sized exomoon warm enough for life, even deep in interstellar space light years from the nearest star. So an exomoon of a rogue giant planet could be warm enough for life, and have microsopic life forms. But how could it have enough light for plants to grow and to produce an oxygen atmosphere suitable for large animals?. The giant planet and the other moons of the giant planet would reflect starlight, and so there would be a dim light on the surface of the exomoon whenever and wherever one of them was above the horizon, making the surface a little bit brighter than starlight alone. But that doesn't seem bright enough for plants to grow. Possibly there will be many thunderstorms in the atmosphere of the gas giant planet. If there are enough thunderstorms at any one time, the combined light of millions and billions and trillions of lighting bolts at the same times might make the giant planet appear to be a huge ball the color of lightening in the sky of the exomoon. And if the sky of the exomoon is hazy enough, possibly the light from the lightening on the giant planet will be scattered all over the sky and appear to be coming from every direction at once, and the giant planet may not be clearly visible. And that light may be intense enough for plants to grow. Such an exomoon would be tidally locked to its primary, the giant rogue planet, and so one side would eternally face away from it and never get enough light to grow plants, and the other side would externally face the giant planet and perhaps get enough light for plants to grow. So presumably there would be plant life only on the side facing the giant planet. And things would be somewhat different if the primary of your world was a brown dwarf instead of a gas giant planet. The brown dwarf would have a little bit of fusion happening in its core, and would glow with light, but probably almost entirely infra red light and very little if any visible light. Thus the infrared light from the brown dwarf would help to heat up the orbiting world, along with any possible tidal heating. And possibly both the side that faced the brown dwarf and the side that faced away from the brown dwarf would be warm enough for life. And possibly the brown dwarf might possibly produce enough visible light from gazillions of thunderstorms for plants to be able to grow on the orbiting world. And possibly the atmospheric haze might scatter the light of the brown dwarf enough to to hide the brown dwarf from visibility. the brighter and more star like the brown dwarf got, the harder it would be for atmospheric haze to hide it. [Answer] # Compact dwarf galaxy 1. The planet orbits a red dwarf star in a tight orbit and is tidally locked to it. 2. The star is part of an [ultra-compact dwarf galaxy](https://en.wikipedia.org/wiki/Dwarf_galaxy#Ultra-compact_dwarfs) like [M60-UCD1](https://en.wikipedia.org/wiki/M60-UCD1) with over one hundred stars per cubic light-year, or even like [M85-HCC1](https://en.wikipedia.org/wiki/M85-HCC1) which is a million times more star-dense than the Sun's neighbourhood. 3. The star that the planet orbits is near the center of the dwarf galaxy, orbiting its supermassive black hole. 4. Atmospheric gases filter out most of the hazardous radiation. To be fair, I think it is very improbable that complex life would be able to arise in this setting since supernovas from nearby stars would cause havoc into life evolution and I doubt that this setting would last enough billions of years for that anyway. But hey, this is not a requirement of this question! Anyway, this is solvable if the creatures observing the skies are an advanced race of aliens colonizing the planet instead of indigenous life. Also, we don't know enough of in which settings complex life might emerge because we only know ourselves as an example and we might be very biased to that, so, it might be possible that some indigenous intelligent life arises somehow anyway. [Answer] Not possible. While you can devise arrangements that produce the requisite sky you can't make Earth-like temperatures as you are pouring too much energy into the world. You either need to reduce the light levels (day and* night would be ok, you can have your 75% ratio, just not of earth-normal light levels) or raise the temperature. [Answer] (1) Plants don't need UV light for growth. UV is outside the photosynthetic active radiation band (see [chlorophyll absorption spectrum](https://en.wikipedia.org/wiki/Chlorophyll#/media/File:Spectra_Chlorophyll_ab_oenin_(1).PNG)). (2) As pointed out in the comments, humans can see quite well in moonless nights, i.e. with starlight only. It takes about half an hour for the eye to fully adapt to darkness (unless you make the mistake of looking into some bright light or switching on your flashlight), and once fully adapted you can see not much worse than in moonlight. You may even find that some stars (Sirius, particularly) will appear bright enough to hurt your eyes. (3) On a tidally locked planet, there will be heat transport from the day side to the night side (see [these simulations of a tidally locked earth](http://climate-dynamics.org/videos/tidally-locked-earth/)). As you can see in the climate simulation, inside the continents the temperature will go down to about 30-40 deg Celsius below zero, while at the coasts it will stay around the freezing point of water (and there won't be large-scale freezing of the ocean on the night side). So even without an additional light source, in the coastal regions it would be essentially like in the arctic today (or even more favorable). People probably could live there the way the Inuit traditionally have survived in the arctic. The low light level of starlight would preclude farming, though. [Answer] If we're talking a tidally locked world, there is a belt around the planet that is perpetually twilight. It's not the whole planet, but that is a fair bit of real estate that never stops being twilight/dusk. There's also an interesting wrinkle you can add to this. This isn't a uniform brightness to the night sky, but there is actually a way to have a tidally-locked world's nightside be bright half the time, a wide binary system. Have the planet orbit one star, tidally locked to it, but that star is part of a binary star with a moderately wide orbit\* like Alpha Centauri. The secondary sun would rise and set over the course of the planet's orbit-day, providing a sort of night and day. Assuming it a relatively sun-like star, the illumination the secondary would provide would range from a couple hundred to several thousand times the brightness of a full moon when it was up, depending on exact distance. To put that into real-life values, the light would range from a well-lit living room to a bright office workstation. Not enough to feel warm or hurt climate, but more than enough to see by when the secondary sun was up. \The distance between the two stars is critical here. A very* rough rule of thumb is that a planet can orbit a member of a binary so long as its orbit is less than 1/5 the separation between the two stars. Too close and the orbit won't work. A tidally locked world will orbit pretty close though, especially around a red dwarf, so there is some leeway here. On the other hand, make the stars too far apart (like Zeta Reticuli) and the other sun won't be any brighter than a full moon. [Answer] Falling stars, all the time. The whole star system is intersecting with a cloud of small objects. Small meteors are burning up against the atmosphere pretty much all the time. Over time the planet's mass will increase, and so the star's. Air quality may also be affected. Just a raw idea. [Answer] <https://en.wikipedia.org/wiki/Gegenschein> Feel free to add more dust and/or artificial reflectors in the same (rather unstable, but pretty much manageable) orbit. ]
[Question] [ I'm making a map for my friend - I drew a pretty neat cartographic grid with a proper map projection - and then he reminded me that his world is actually an inverted Earth with a glowing ball of concentrated magic in the middle. The sun is half black, so it creates day/night cycle by rotating. Now, the question is, because I'm a bit stuck - how could people with roughly Renaissance technology measure the size of the planet (so they could actually draw a cartographic grid)? In our world it's simple, just measure difference in the angle of sun rays between two position of known distance. But what for them? Maybe there are some ways to mitigate it with small changes to the setting? [Answer] This actually is pretty easy using the similar methods to what you mention. The "sun" is rotating, meaning that if you look up at night when the shaded side is toward you, you can see the inside of the sphere where it is still daylight. You can figure out how long it takes for the sun to rotate once. Lets say 24 hours just for fun. Then you figure out the distance between two points somewhere along the sphere where you can see them at night, and see how long it takes for the terminator line to pass between them. [Answer] # What light looks like from the surface The sun in your world is half-bright, half-dark. Assume that it is a perfect sphere with any radius greater than zero. Therefore, for any point on the surface, the percentage of the sun that is facing that point at any given time is $$\cos^2\phi\cos^22\theta + \frac{1}{2}\sin^2\phi.$$ Here are three plots of what that looks like at the equator: [![enter image description here](https://i.stack.imgur.com/iN2ob.png)](https://i.stack.imgur.com/iN2ob.png) At a point in the temperate zone at about 40 degrees latitude: [![enter image description here](https://i.stack.imgur.com/ldmci.png)](https://i.stack.imgur.com/ldmci.png) And at the poles: [![enter image description here](https://i.stack.imgur.com/wV9NV.png)](https://i.stack.imgur.com/wV9NV.png) # How to measure latitude between two points Without sunrise over a horizon or a pole star, it is much harder to measure latitude. The best you can do is to measure the brightness of the sun at various points in the day, and to compare with the trigonometeric properties of its brightness from the last section. The the best of my knowledge, there is no way to scientifically measure brightness until you have a photographic plate. That will not be available to people of Renaissance technology. However, you can at the very least dead-eye reckon brightness, so we will assume some sort of brightness metric. One potential way to measure brightness is that brightness is proportional to the 'bright' portion of the sphere of the sun that is visible to you from your location. If you look at the sun through a dark lens, you may be able to measure this, depending on how large the radius of the sun is. In this case, you can calculate latitude relative to the equator easily. Maximum brightness at latitude $\phi$ ($\max(B\_\phi)$) is $1 - 1/2\sin^2\phi$ times that at the equator ($\max(B\_{eq})$), solve backwards for $\phi$: $$\phi = \sin^{-1}\sqrt{2\left(1 - \frac{\max(B\_\phi)}{\max(B\_{eq})}\right)}.$$ It is possible that maximum brightness at the equator is a well known standard value in your scientific community, even for those who have never been there. You have to know, or at least be able to estimate, the maximum brightness to be able to calculate latitude. As an alternate measurement, not2 that equatorial max brightness is twice the constant brightness at the poles. You can re-work everything in terms of that value as $$\max(B\_{eq}) = 2B\_{pole}.$$ # Now there are two ways to measure radius Assuming the hollow world is a perfect sphere, there are two ways to measure the radius. you can compare latitude of two points to the distance between them, or you can compare the time it takes the terminator to travel between two points. ### The terminator line The terminator is important here, because with no stars in the background, the only way to ensure that two points are at exactly the same longitude is to visually signal when the terminator passes by the points. This can be done using one lighthouse to signal another point within visual range of that lighthouse. Since your world is hollow and thus concave from the point of view of someone on the surface, the line of sight of a lighthouse is actually very long, limited only by atmospheric attenuation of light (due to water vapor, or whatever). The terminator can be exactly identified by looking at the sun through a telescope with a dark lens. As soon as there is no bright patch visible, the terminator line has passed. ### Comparing latitude method The latitude way is take two points that you know are at the same longitude, and calculate their latitude using the above method and distance ($d$) between them, using what ever method. If the latitude delta is $\alpha$, then the polar radius of the hollow Earth is $$r\_{pole} = d/\alpha$$ in radians. ### Timing the terminator method To time the terminator, you will need to get two points at the same latitude (confirmed using the methods above), and measure the distance ($d$) between them and the time it takes the terminator to pass between them ($t$). You also need to know the length of the day $t\_{day}$. Then, the equatorial radius of the hollow Earth is $$r\_{eq} = 2\pi d\frac{ t\_{day}}{t}.$$ Note this only works if the points are less than $\pi$ radians apart on the surface, that is, in the same hemisphere. ### These numbers might not be the same! These two methods could give you different answers, polar and equatorial radius. If you have a perfect sphere, the two calculated radii should be the same, but if your planet is inscribed within an oblate spheroid with an equatorial bulge(like our Earth), or even a polar bulge, then the two numbers will not be the same. # Conclusion It is actually pretty difficult to time astronomical pheomena with only one available astronomical object. But, you can use the unique configuration of the sun's surface to do this. This does require some photometric skills more advanced than what was available in the Renaissance, which I'm not sure how to replicate with Renaissance technology, but I have faith that the Galileo's and Newton's of the world could figure it out. Also, there needs to be some sort of standard measurement of equatorial brightness to make these calculations, but given this number's importance in observational 'heliometry,' I would expect this number to be a well established topic in a Hollow Earth's scientific community. [Answer] Two points, a known distance apart, will have a straight line-of-sight between them that will not be parallel to the curving surface. Stand a pole at the centre between the two points. Where the sight line intersects the pole will give you the height (er - depth) of the arc. That will allow them to calculate the radius of their world. Even if they don't have the trig to calculate it, they can always just make a scale diagram and measure it. [![enter image description here](https://i.stack.imgur.com/YB4C6.png)](https://i.stack.imgur.com/YB4C6.png) [Answer] Providing long distance travel is practical, his could be done with pure geometry ( or more easily, assuming the natives had advanced to usable trigonometry). One could measure the distance between two points on the inner surface that are visible from the same location, then travel to one point and directly measure the distance to the other point -- or, lacking trigonometry, one could select two points that are sixty degrees apart (therefore forming an equilateral triangle between the two and your observation point), and know that the distance to either one is exactly one third of the circumference of the world. Angle bisection could be used, along with long distance signaling (with flashing mirrors, perhaps), to shorten the distance requiring measurement, at the cost of some loss of precision. If there's not access to the antipodes, one could measure a distance across water (perhaps by surveying around the shore of a large lake or inland sea), and directly measure how much the surface dips below the sight line; this would allow deriving the radius of the sphere directly via similar triangles (same method as is used to calculate horizon distance on the outside of the Earth). ]
[Question] [ This question considers the respiratory apparatus of [an aquatic (or amphibious) species descended from engineered humans](https://worldbuilding.stackexchange.com/questions/91897/why-might-it-be-desirable-to-engineer-aquatic-humans). The history of the species provides a relevant constraint. While the science in the setting is soft and the handwavery of fictional genetic engineering might be called upon to produce nigh arbitrary results, I would much prefer, if possible, to be able to claim “these structures that serve [some function] are actually homologous to [some other structure found in humans]!”, or “similar solutions are found in [some other species].” Given these conditions, what would be the reasonable changes to make to humans such that they would be able to breathe underwater? --- Relevant information come across during the search for an answer: I recall seeing objections to the practicality of gills (on the neck/beneath the jawline) citing the square-cube law, even though I am unable to locate the source text. I am also uncertain about the specifics of this claim (might it still be possible for, say, large external gills to provide enough surface area?) — I’d be grateful if anyone could verify this or point me to a source. Another issue with modified humans with authentic gills is that they would likely have to lack ears, tonsils, and the thymus, since those are developed from [the same structure that give rise to the branchial skeleton in fish](https://en.wikipedia.org/wiki/Pharyngeal_arch#Structure), and it is unclear what impacts this would have on the rest of their physiology. Some of the arguments presented above are also applicable to the option of having [both gills and lungs](https://en.wikipedia.org/wiki/Lungfish). Gills placed instead on the torso (to allow space for larger gills) is an often seen variation; and structures such as “gillungs”, as proposed in [this answer](https://worldbuilding.stackexchange.com/questions/44137/how-to-breathe-both-on-land-and-under-the-sea/44145#44145), seem to be regarded as feasible. However, these appear difficult to justify from a developmental point of view (to have lungs connected to openings on the side of the torso involves a change in topology, and there would likely be complications associated with punching through the chest cavity?) Finally, please note that this problem is not about how [whale-humans are likely to be more practical than merfolk with gills](https://worldbuilding.stackexchange.com/a/67076/42460): air-breathing aquatic humans exist separately in the same setting. [Answer] So, it's really hard to breathe water. The biggest problem is not where the gills are on your body but instead how gills might exist at all. The fundamental limit you'll run into when designing something like this, whether it's through biological engineering or something like [artificial gills](https://en.wikipedia.org/wiki/Artificial_gills_(human)) is that water only has so much oxygen in it- around 10 mg/L. Humans require a LOT more than this- mainly because we're not polikiothermic and use our metabolic heat to stay warm. We run through 10mg/L very rapidly, so we're going to have to keep oxygenated water flowing over our gills to survive. Essentially, there are three ways to solve this problem: 1. Make the humans really efficient metabolizers. You could reduce the human dependency on oxygen in two ways- one, by engineering a more efficient method of anaerobic metabolism, or two, by getting more energy from the small amount of oxygen you're getting from the water. Both of these are conceivable, but would be very hard- there's a powerful evolutionary advantage to be gained by getting the maximum energy out of your food, so nature's already optimized a lot in that avenue. 2. Increase the respiratory area Give. The. Mermaids. Wings! Rather than trying to push huge amounts of water through the mermaid body like fish do, make the gills external. As they flap their wings, gas exchange happens incredibly quickly through the thin membranes in their wings and they can extract oxygen from the water that way. This is a fairly common method for ocean organisms, especially the lovely [nudibranchs](https://en.wikipedia.org/wiki/Nudibranch), which are literally named after their external gills- nudi- naked, branch-lung. They're also beautiful: [![Nudibranch, from Wikipedia](https://i.stack.imgur.com/Lx67B.jpg)](https://i.stack.imgur.com/Lx67B.jpg) Those plumes on their back are their gills- no water filtering necessary! For mermaids, I'd imagine that their wings are thinner and flatter, more like the classic "faerie" wings. They wouldn't necessarily be used for swimming because they'd be quite delicate, but it's certainly possible to reinforce them with musculature that allows them to be useful for mobility as well. If you're hesitant about giving mermaids wings, you could also reuse the thin membranes already in place on the mermaid's tail. There, they'd have a similar mechanism and it might actually work better while swimming rapidly. However, they'd have to keep flicking their tails back and forth even when standing still, whereas with wings they could gently flick them back and forth while staying suspended in the water column. 3. Remove their dependency on oxygen altogether Not everything in the ocean needs oxygen. You could have the mermaids form symbiotic relationships with zooxanthellae (algae), like corals do, or have them endosymbiotically ingest chloroplasts- they'd have green skin but that might be totally okay. That would also limit them to the sunlight region of the ocean, however, and that might be a bigger problem. If you're prepared to do some more intense genetic engineering, you could make them entirely chemosynthetic- using elements like sulfur to obtain metabolic energy. They'd need to eat a lot more sulfur (as much oxygen as we consume daily) but for an advanced civilization that wouldn't be a problem. The general equation for chemosynthesis is $H\_2S + CO\_2$ -> $C\_6H\_{12}O\_2 + H\_2O+ S\_{(s)}$. [Answer] Use the lungs. from <http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/5903/SPUMS_V5N3_2.pdf?sequence=1> > > The entire chamber was pressurised with air and an anaesthetized dog > was lowered into a tub of oxygenated saline. The animal was kept cool > at about 32°C in order to reduce his oxygen requirement. While > submerged, the dog continued to breathe, and jets of water rising from > the surface showed clearly that he was pumping the solution in and out > of his lungs. At the end of the observations, the dog was lifted out > of the tub and his lungs were drained of water and re-inflated with > air. One of these dogs was later adopted as a mascot by the crew of > the Royal Netherlands Navy vessel HMS Cerberus. > > > This was some cool reading. I knew that animals (and humans) could breathe oxygenated perfluorinated liquids indefinitely. I did not know that before that there was research done with water. Issues with breathing water. 1: If osmotically much different from blood it damages the lung tissues. So these experimental animals (and people!) breathed saline solutions isotonic to blood. OK. 2: It is hard to get enough oxygen into the saline. They had to use high pressure hyperbaric chambers. I read an estimate of 160 atm to get enough O2 into saline to meet O2 requirements for a mammal. That is about 1 mile deep. 3: Surprisingly (to me) it was the gradual build up of carbon dioxide that killed the experimental animals. CO2 is not very soluble in water. We can blow off our CO2 by hyperventilating. > > Obviously then if we put all these factors together, we find that in > order to maintain his arterial carbon dioxide partial pressure within > tolerable levels - to prevent a sense of suffocation or even loss of > consciousness - a water- breathing diver would have to move a > substantially greater volume of water per minute in and out of his > lungs than the air-breathing diver moves air. > > > Apparently that does not work underwater. As an animal breathes harder, it reaches the limits of what the pliable airway structures can withstand. They collapse in (sort of like asthmatics have their airways collapse in when they try very hard to inhale - thus the wheezing) and so limit the water that can be moved back and forth. The merfolk will breathe like people breathe, moving water in and out of the lung. * These merfolk may be confined to depths where pressure is great enough that the dissolved O2 will meet their needs. Sort of like air breathing humans are confined to low altitudes, for the same reason. * The merfolk have saltier blood - isotonic to the seawater they are in. + The merfolks have big respiratory muscles - good for forcefully expanding the chest as well as forcefully contracting it - this latter piece is not especially strong for humans who are much better at inhaling. + Merfolk have comparatively rigid bronchi which withstand the higher pressures associated with more rapid inhalation and exhalation of water. [Answer] Lots of nice answers here! One problem which was pointed out is that humans, being warm-blooded, require much more oxygen than polikiotherms, because maintaining body temp requires a lot of metabolism, which in turn burns a lot of O2. This results in all kinds of special strategies to get enough "gillage". So... Why not make them polikiotherms (cold-blooded, for our purposes), like almost all fish? This reduces a lot of problems. First, less oxygen usage, meaning less extreme solutions for gills. Look at your friendly reef shark: [![gills gills gills](https://i.stack.imgur.com/B48r0.png)](https://i.stack.imgur.com/B48r0.png) Its gills are pretty reasonable in size. Second, being cold blooded means you don't need all that insulation. Most marine mammals have extensive blubber deposits to help them keep warm, and this doesn't really fit the mermaid image. Mermaids are expected to have a touch of avoirdupois, but tradition has it more fetchingly distributed and as much ... decorative as utile. Third, cold-blooded mermaids have less need for food, so they can spend less time foraging, and more time perched on rocks luring sailors to their doom. [Answer] The main problem you'll run into is that the human brain takes a lot of oxygen to run, and there isn't nearly as much oxygen in water as there is in air. So if these merfolk are to be able to breathe underwater without surfacing, they'll either need much more surface area on their gills than humans have in their lungs, or they'll need to pump a whole lot of water through their gills. According to the "gillung" answer you linked, freshwater has about 8 cm3/L of dissolved oxygen, while air has 210 cm3/L. That's a factor of 26.25 difference. So if you want merfolk with internal gills replacing their human lungs, they're going to need to pump over 26 times as much water through their lungs as humans pump air. That's going to be all kinds of impractical, even when they're not exercising. Adding slits between the ribs to expel water to keep it flowing one way through the gills will help, but they're still going to need to pump a huge amount of water in order to stay conscious. And pumping water like that will take a lot of energy, increasing demand for oxygen. Solution: [External gills](https://en.wikipedia.org/wiki/External_gills), and lots of them. According to that Wikipedia page, external gills on the creatures that have them (salamander, lungfish, and bichir larvae) typically take the form of 3-4 fernlike branching stalks coming out from either side of the creature's body, behind the head. I'm not exactly certain where that would correspond to on a human- maybe on the neck? You could probably get away with putting them on your merfolks' backs just as easily, which has the advantage of being closer to the pulmonary arteries/veins that they'll need to hook into. A system of external gills capable of keeping up with a pair of human lungs is going to have to be pretty huge, so these guys aren't going to be hydrodynamic. They'll also need to move around regularly in order to keep from using up all the oxygen in their immediate vicinity, and since they're genetically engineered from humans, may not have the instincts to do that subconsciously. So it might be better to have them live in rivers, so they won't have to worry about it. Alternatively, they could be engineered to be able to smell oxygen with their fluffy tentacle-like gills, which would be pretty cool in its own right. That's up to how far you want to take your genetic handwavery. Another alternative could be to do away with the forest of external gills and give them either fluid-flexible crablike gillungs or smaller external gills, and make them able to survive on the small amounts of oxygen that their gills would be able to provide. When they're resting or need to dive deep for whatever reason, they could go into a low-power mode, conserving oxygen and relying on their gills; but when they need to hunt, fight, or do math problems, they could surface for a breath of oxygen. [Answer] Or, you could simply do it like whales, which do breathe air, but have the ability to store vast amounts of oxygen internally, for extended stays under water. I believe the sperm whale has been known to submerge for over an hour, when they go to great depths to search for squid. A technique used by seals in arctic areas is to breathe out the air on the underside of the icepack in a big bubble, let the water refresh the O2 content, and breathe it back in. Perhaps a merperson could have a skin flap they could exhale and inhale a bubble of air into, for this purpose. With some air breathing aquatic reptiles, like turtles or alligators, their lower metabolism means they don't need to have as much oxygen on hand. But, that's a radical biological change, whereas adapting the merperson to be able to store far more O2 from air breathing would be a more likely change... as it has already happened when mammals returned to the oceans. Why would you want the merperson to breathe air instead of gills and water? Air transfers O2 far more efficiently, giving the creature greater strength reserves underwater. The largest non air breathing aquatic creature is the whale shark, at around 40 feet, and it is a very slow moving creature with a somewhat narrow range of habitats. Contrast that with the blue whale, about twice the size, that can move faster and venture into a much wider range of habitats, like the antarctic. [Answer] Fish pull water in through their mouths and push it out over their gills in order for the gills to be able extract the oxygen (or something to that effect). This would not work for humans since the amount of water they could pull in would be limited by the size of their mouths and possibly noses. I think the external gills ideas floated by @WilliamKumler and SomeoneElse37 would be the most practical solution. While wings would probably be aesthetically pleasing to look at (I do love the image that brings up in my mind), they might be less practical due to a smaller attached area versus their length and width (thinking of fairy/dragonfly wings here. @WilliamKimler, you might be picturing it differently). Gill tendrils (like those on the gorgeous nudibranchs), gill feathers (as sported on newts and salamanders) would be be the way to go, and considering that your engineered merperson would likely need to be in an area with some amount of water current, the tendrils can passively sway in said current, or even when the merperson is moving, but have limited motion in the event that the merperson is stationary in an area with limited water movement (like a cave, for example). Along similar lines, you can cover your merperson in fine hairlike tendrils, covering a larger area of their body surface. Or the tendrils can be engineered in some way to be derived from our human hair and can therefore be situated (mostly) on the head and tie in to the existing breathing system in some way. The limitation of the external gills would be that they would have to be kept wet, or perhaps be retractable in some way. Alternatively they could go to sleep or become inert when the merperson finds them-self on dry land or exude a slime or gel of some sort to protect themselves from drying out completely. Finally, speaking of noses, ears and other protruding bits and pieces, you would probably want to make those smaller or in some way bring then in closer to the body to improve streamlining. If you don't want to go with a mermaid-like tail, your merperson would need larger, finned hands with longer fingers, and flatter/larger feet. They might also need to be more muscular, as propelling yourself through water is harder to do than propelling yourself through air. [Answer] I would go with PEM electrolysis A gill like structure with the body ability to produce electrical current can be used to derive oxygen directly from the water molecules (H2O -> H + O2). This structure can pump the resulted gas directly in to lungs (even fairly human like lungs) and can be shunted of when outside water and exposed to free oxygen in the air. This has the benefit of not being dependent on the level of oxygen dissolved in the water and therefor allows survival in oxygen poor water like high depth or contaminates. This is a relatively energy inefficient process but is conceivable given the complex structures living cells can form even mimicking amphibian skin respiration (absorbing oxygen from the water via the skin). Also the existence of such organism (humanoid this case) can support symbiotic hydrogen based ecology with a possible micro re-claimers (H+O2 -> H2O) in areas with natural high oxygen content in the water (presumably near the surface). [Answer] Gills on the back would be my go to. Creating a structure that traverses or even changes the human chest cavity isn't unreasonable. There are currently gaps where muscle and flesh exist between the ribs. To simply say an oxygen exchanging membrane traverses the back ribs isn't to farfetched. Or simply cavities through the back ribs that bring water to the gill/lungs. The added advantage in simplicity is that because its located closer to the lungs you could reuse a lot of that organs structure. You could even likely keep both breathing methods, there are afterall creatures who can breath both air and water. As for other traits. just because you add gills does not necessitate the loss of ears and other organelles. Did you know whales still have their hind legs. As for making this more reasonable. I would increase the space between the ribs on the back (so a larger more pronounced chest) to allow a bigger gill slits. I would grow the lungs to be large and thin lining the back of the internal chest cavity, so you would have more functional respiratory surface area. The shape of the lungs is already conducive having 2 distinct halves with separation in the middle which would be needed to connect the central nervous system to the rest of the organs. If going with the cavity ribs notion then your only challenge is ensuring water circulation. Fortunately, we already have an organ that solves this called the diaphragm. Just modify the diaphragm to be drainable/floodable so it can operate in chosen environment. ]
[Question] [ OK, so you've got an empire in space. And that empire has a frontier. Now on Earth, we have many ways to defend a frontier. We can build border fences or even walls, we can build watch towers, and of course we can let people patrol; given that the border is just a line, patrolling is quite efficient. However, the space frontier is a whole 3-D surface, lacks the ground on which you could build fences or walls, and indeed would simply be too vast to completely cover it with a fence-like structure. Patrolling is of course possible, but should require very many ships simply because the border now is a whole surface. This doesn't seem too efficient, however, so one would hope that there are more efficient means. So what would efficient border control and defence look like in space? To set the scale, assume that the empire's space is approximately a sphere with a radius of 20 light years. Only sub-light speed is possible (signalling of course with light speed), but technology allows one to go arbitrarily close to light speed. No worm holes, hyperspace or other technology which would allow to "jump" across the border. [Answer] ## Mines, exploding space-mines everywhere! [Plagiarizing one of my earlier answers.](https://worldbuilding.stackexchange.com/questions/8565/which-space-based-weapon-technologies-are-going-to-thrive/8570#8570) Note that this answer assumes any and all alien/foreign forces are hostile and also a relatively high tech level for your empire. ### There's No Invisibility in Space While nobody can hear you scream in space, everybody can see you. To the hyperadvanced spacefaring civilizations, even a black-painted intertially-driven scout stands out as a sore thumb, since the defending civ has all the little objects in the system and their trajectories for the next million years calculated and recalculated over and over, so anything NEW, even a few stray photons bouncing off your invading ship from long-range radar sweeps would be ringing alarm bells. Moreover, if you're planning on doing anything in particular in the system you need to slow down. That takes reaction mass (assuming you don't have [reactionless drives](https://worldbuilding.stackexchange.com/questions/8550/energy-source-for-a-generation-ship/9053#9053)), so you might as well be announcing your arrival with giant flares. If you don't slow down, well, massive relativistic-speed objects also tend to stick out. If you've got space-warping technology, the warping you induce into space is also going to be easily detectable, since alcubierre warps don't just happen on their own. ### Where to defend You don't want to wait until the enemy gets into your star system. If they're within light-hours of Home, it's already game over. They can blast it with TerraWatt gamma lasers that go through your planet's crust like a bullet through warm butter, or perhaps launch dozens of relativistic kinetic accelerators at it, and believe me, those are a hassle to stop, and your bunkers aren't any good in a molten slag state. No. Your defenses for Earth should probably be far out in the Oort cloud at the very least, preferably a few light-years away from any world you're defending if you have the technology. ### How to defend You will defend in depth. You will have rings and layers, upon rings and layer. The first layer should be your centimeter-sized Remote Telemetry observation satellites. They will serve as an early warning system. Spaceships' heat signatures in space are very hard to disguise. Of course, a 1-meter probe will have an easier time slipping by than some massive colony ship or a warship armored to resist nuclear impacts. Besides optics, your detectors would use gravitational distortions, if far enough out from massive bodies. Since an object's propulsion jet is visible as well as its speed, you can easily tell the mass, so (accelerated) decoys would not work unless identical in mass to the spaceship you're trying to disguise. This confers an advantage to defense, since they don't need to break or accelerate. Your microsatellite sensor grid info could be sent narrowbeam at lightspeed (or darkspeed if you accept FTL and the mess it makes of causality) back to a defense outpost or used to activate some local defenses. While the micro-satellites are passive detectors, as your next detection layer every cubic AU or so you should have an active scanning station, a radar beacon blasting away into the enemy darkness. This will quickly paint a signature of any approaching target. This information will allow your sectoral defense AIs to order active denial actions, activating your first-line defenses. ### Good Old Kinetics Now what would these defenses be? There's an [extended discussion of classical kinetics/rockets/beams elsewhere](http://www.projectrho.com/public_html/rocket/spacewarship.php), and you can read that at your leisure. All good ideas. Probably the best in the class is a straight up directed multiple warhead relativistic impactor, essentially just accelerated mass coming your way really really fast, and spreading out into slivers as it does to cover a vast area. Even with randomized defensive maneuvers, these puppies make it hard to miss -- and [even 2 grams travelling a cool .99 c](http://www.wolframalpha.com/input/?i=kinetic%20Energy%20of%200.002%20kg%20moving%20at%20.99%20c%20) will leave you with $10^{15}J$ to deal with, or about 1 megaton of TNT equivalent. I'm guessing that will leave you with more than just a bad hairday. But you can do even better. ### Rift Weaponry My other suggestion is rifting. Imagine you have devices with the capacity to bend spacetime itself. Done carefully on a starship and with insane levels of precision, this might effectively shorten long journeys, and maybe provide effective FTL spacetime translation. But if all you care about is damage, than a set chaotic, highly unstructured rifts will play havoc with the delicate innards of a ship (such as humanoids or computers and their minds). Geometries bend at impossible angles, straight lines twist and intersect with each other, the ship's Combat Information Center and the million Kelvin engine room are suddenly superposed, leaving charred organic residue in the superpurified magnetic convection coils, past and present comingled as you see your mates both alive and and torn to shreds by the rift. Your defenisve minded civilization has littered space with billions upon billions of such "mines" that quietly store all this energy, like a set of corks in a dam. When activated by the early warning sensor grid, they unplug their carefully designed set of cone-covering spacetime rifts and let it rip the intruding ships apart over a wide area. ## Classical AI fleet Anybody that survives that flashy welcome that the first few dozen layers of kinetics and rift-mines have extended will then be greeted by your local spherical-octant mobile defenses: AI-directed firing platforms who were set on an intercept course as soon as the lightcone (darkcone?) of information reached them. These massive ships will have all the weaponry of your initial mines, dialed up to 11. Without squishy humans on board, these are capable of pulling 10,000 g accelerations with ease, so they will be on scene toute-suite. Without needing to be stealthy or discreete, these monsters will probably have an utterly obscene power output ... And just in case they don't suffice, somewhere a few light-days or weeks behind them is the actual Capital Fleet, which is the stuff that mothers in alien civilizations use to scare their disobedient little reptilian brats who won't go to bed. # Inner System In order to be able to field even such basic defenses as mentioned above, (i.e. nothing that would stop a determined Type II civ with a grudge), your civilization would need to be a high Type I, near Type II at least. Your system's industrial capacity must then be about $10^{26}$ watts, so generating $10^{11}$ (100 billion) kinetic impactors would take about 1 second of the civ's power output, while the rift devices might require more power, (but you'd need fewer of them). That said, a type II civ should be able to reach this basic level of militarization from scratch in about a year without any discernible impact on the inner-system standard of living. Your innermost defenses, if the visitors actually came for a real fight, will be powered by your Mercurian Solar Grid. While this is normally reserved for the purposes of research and investment banking AIs, in times of emergency the output can be directed into a beamed weapon of near unimaginable strength, with a continuous power output in the range of $10^{25}W$, that would be hitting with the energy of 100 dinosaur-killer asteroids each second. It would take a really determined enemy to get past this one. [Answer] This largely depends on your technology. Do we have warp drives? Wormholes? Or are we restricted to sub-FTL ships? Because your technology is going to drive your detection/mitigation strategies. In general though, it's just not possible. Most stories that involve effective space defense fall into the [2D-space](http://tvtropes.org/pmwiki/pmwiki.php/Main/TwoDSpace?from=Main.Two-DSpace) trope. And it does seem to make sense from that perspective. But the reality is that your border is 3-dimensional, which increases the difficulty of defense immensely. > > Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space. > > > Given the sheer size of space, it's not really practical to defend your frontier. You might be able to defend a planet or other fixed installation, but realistically if someone throws enough rocks at you at high enough velocities, you're not going to be able to stop it, and then your day is ruined. Depending on your relationship to enemies, you might be ok if everyone is avoiding those kind of attacks due to a [MAD](http://en.wikipedia.org/wiki/Mutual_assured_destruction) scenario, or because they want to take your planets and not just destroy them. You also need to decide what it is you're trying to detect. A death star approaching your border is orders of magnitude easier to spot than a smuggler who runs silent through your border region and isn't going toward anything tactically significant. Unfortunately in a realistic space war scenario that smuggler has a built-in [WMD](http://en.wikipedia.org/wiki/Weapon_of_mass_destruction), and once they're inside your border they can go wherever they want. So, here's what you can do: 1. Defend your important planets and installations against everything but MAD attacks. Make sure your enemies know that you have your own defenses in place, and if they take out your planets you'll respond in kind. Forget about smuggling entirely, it's not something you can stop. 2. Make sure your ship movements are randomized to some extent. A least-time optimal course is efficient, but predictable. In military terms, predictable is synonymous with dead. Space is big enough that you can aim for, say, 95% efficient and still have tons of room - that lets you almost entirely eliminate piracy or privateers. 3. Given the above restrictions, wars will likely be fought primarily with intelligence and special forces-type units. Concentrate on those. [Answer] The best defense is a good offense! You're likely looking at a system of early warning sensor arrays, some drone satellites that can launch interceptor missiles and the capability to make sure that anyone who fires at you won't enjoy the retaliation. I'd like to question the assumption that fences, walls, towers, patrols etc... are an adequate defense. Historically they've rarely worked for anything larger than a small town area. Even then very many walled castles have fallen to enemy invaders. [Answer] In short: you can't. Dan Smolinske's answer sums it up pretty well, but I did want to add a few things. First, there is no concept of a "border" in space. Your borders are the planets you control (also possibly things like asteroid fields or space stations as well). You can defend your planets and space stations, but trying to control a "border" of 3-dimensional space is impossible. In space, most military campaigns are going to center around planets. Furthermore, you can make the assumption that any life form must have evolved on a planet, and therefore will want to USE your planets as their own, so they aren't going to completely destroy them or risk rendering them unusable for themselves (unless they just want to kill all of your citizens). Unlike terrestrial battles, where every inch of ground (almost) can be useful in some way (farming, factories, etc.), in space, there are NO resources between planets. Therefore, planets, especially resource rich planets, will be highly valued and fought over. Therefore, you can setup your defenses to defend the planets, not necessarily worrying about the empty space between planets. Sure, you can setup long-range scanners (and at the speeds you are talking about, you will see them LONG before they reach you), and have patrols that can move to intercept threats, but the vast majority of your military will be dedicated to planet defense and protection. As an aside, your last paragraph makes it clear that an empire with no hyperspace/warp technology would be very at risk of raiders or similar, because even with signaling at light speed, it would take TWENTY YEARS for the signal to reach the other side of the territory... Most raids take a few HOURS at most. Without some kind of faster speed or heavy planet defense (shielding, etc.) I can't see how feasible it is to attempt to defend an empire that size, especially if you are relying on a centralized military/government. [Answer] Classic defense strategy is [defense in depth](http://en.wikipedia.org/wiki/Defence_in_depth). You do not expect that outer layer of your defense will be able to fight off attacker. All you want is to give you information where attacker is attacking, what is structure of enemy's forces, and give you time to prepare more focused defense. You want to focus your defense capabilities on attacker, not to spread them too thin and wide. You want to have overwhelming power, and all advantages, when engaging your opponent. Mines, AI probes, bases - all is just examples of defense in depth. After attack is detected, you need to start one or more of prepared defense strategies. And one of the defensive strategies could be a counter-attack, either hitting attacking forces from unexpected direction, cutting off supply/escape route, or attacking unexpected objective, like important base (or homeworld). As says [Sun Tzu](http://en.wikiquote.org/wiki/Sun_Tzu): victorious strategist only seeks battle after the victory has been won, whereas he who is destined to defeat first fights and afterwards looks for victory. Obviously this depends on weapons available, and difference in technology. Which might be huge, few thousands of years might make decisive difference, and then any question of fair fight is moot. One civilization either win decisively, or gets wiped out. Choose the planet you born on wisely! [Answer] I think the most likely would be to have a 'net' of sensor drones that report back. Both what it sees and what it doesn't. you could have outposts scattered around that the drones report to directly for faster response and it would allow a much smaller force to guard vast areas of space. Keeping the drones fairly simple. They relay what they detect and any changes in their area, they report to all the surrounding drones on a regular basis, if one doesn't report, then the rest send an 'alarm' to the nearest outpost. The outposts of course will be automatically doing a similar thing through the drones to 'nearby' outposts so if anything causes a disruption, someone will be notified. Of course if things like worm holes are able to be used and can 'skip' a net then there better be some way to detect their creation or all bets are off. ]
[Question] [ I am writing a short story about a fighter pilot on Venus, I was advised on my other post to break up the post into multiple others. What are viable methods to power a fixed-wing aircraft in the upper Venusian atmosphere as it exists right now (i.e. not terraformed)? Given that these aircraft would have to engage in combat maneuvers, the engines would have to be sufficiently powerful to allow for that. [Answer] Given there's no free oxygen in that atmosphere (that we know of), you're pretty well limited to non-combustion power sources (or rockets, but they have very poor duration due to having to haul both fuel and oxidizer). First, battery electric, either via propeller (strictly subsonic) or ducted fan (potentially at least transsonic). Energy storage is the bottleneck, but if you don't mind handwaving a major (physics breaking) advance in battery or supercapacitor energy density it might be plot-viable. Second is nuclear (fission or fusion), either nuclear powered propellers (see nuclear B-36 project history) or nuclear jet (itself divided into turbojet/turbofan and ramjet). Nuclear ramjet was demonstrate in southern Idaho in the 1960s, as I recall, and the engine worked -- and maybe Venus is the right place for this sort of thing (or maybe fusion as a heat source will be less prone to leave particles from the engine and core in its wake). [Answer] The fact you want to drive fighter jets basically rules out all sensible electrical power options. Without a ready source of atmospheric oxidiser, fuel cells have no particular benefit over batteries and batteries just don't have a high enough energy density to let you do any fancy high-speed manoevering. Maybe if you wanted WWI air combat ~~i spaaaaace~~ on Venus then batteries would work fine, but if you wanted anything more aggressive than that (even WW2-style) you need nuclear power. --- Nuclear jet engines are certainly possible. None have actually flown an aircraft, but [a working nuclear reactor has certainly been run on a (large) aircraft](https://en.wikipedia.org/wiki/Convair_X-6) by the US, and the USSR seems to have [run similar tests](https://en.wikipedia.org/wiki/Tupolev_Tu-95LAL). [![HTRE-3 nuclear turbojet, minus support and testing structure](https://i.stack.imgur.com/NGgfi.png)](https://i.stack.imgur.com/NGgfi.png) This is the [HTRE-3](https://en.wikipedia.org/wiki/File:HTRE-3.jpg) test nuclear turbojet, minus a support structure. It did run, and could power up on reactor heat alone. It is pretty hefty though, and would have fitted in a bomber-sized aircraft, not a fighter. It would be very difficult to miniaturize such an engine. Fission reactors are tricky to shrink, and there's a minimum mass of uranium required and a minimum mass of shielding so the rest of the aircraft (and the crew!) don't get cooked. Supersonic nuclear ramjets were also developed as part of [Project Pluto](https://en.wikipedia.org/wiki/Project_Pluto), with the Tory II-c model being actually run for several minutes. [![Tory II-c nuclear ramjet on test truck](https://i.stack.imgur.com/9wKoM.png)](https://i.stack.imgur.com/9wKoM.png) (image source: [Nuclear Powered Jet Engines: A Bad Idea that has Not Gone Away](http://www.safetyinengineering.com/FileUploads/Nuclear-powered%20jet%20engines_1631281313_2.pdf)) The problem with ramjets is that you need to get them up to speed somehow, so that the flow of air into the intake is sufficient to provide enough thrust to keep it flying. For going fast they'd certainly outperform a nuclear jet, but they won't run at lower speeds which probably harms their usefulness as in a fighter craft (as opposed to a missile). In either case the biggest problem is finding some fissiles. Venus probably has similar reserves of Uranium to Earth, but good luck digging that stuff up. You'd have to import it, but then you'd have to import almost everything so it isn't the end of the world. On the bright side, any catastrophic failures aren't going to be causing any environmental concerns, because you won't get much fallout above the clouds and no-one will be visiting the crash site in person. --- If your tech level can swing to compact fusion plants, that might be better. Fusion might scale down better than fission, and there are fusion reactions that reduce the amount of seriously problematic radiation such as [p+11B](https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron). Though often billed as "aneutronic", you'll still a small number of neutrons and some very nasty high-energy x-rays so you can't skip the radiation shielding. You can use a fusion-to-electricity setup to drive jets or propellers, or a simpler and probably much more efficient heat-exchange system that uses fusion energy to heat incoming air in the same way that the HTRE-3 design did. There are even more exotic possibilities such as using direct energy conversion of high-velocity fusion products to drive a megavolt-level electron beam which could be used to heat up incoming air like a "normal" nuclear jet, or use any other solid propellant for a quick high-thrust boost (up to and potentially including operating as an [SSTO](https://en.wikipedia.org/wiki/Single-stage-to-orbit) rocket for space operations). [Answer] Burn metal! That is also the title of the book. Insert power chord here. Venus is loaded with oxidizer if you are burning the right stuff. There are a number of scholarly papers looking at reduced metal as fuel and CO2 as the oxidizer. Metal is an awesome energy storage medium and fuel - stable, energy dense, easy to transport and abundant in the universe. Reduced metal does not burn easily outside on a cool spring day, but if you get metal hot it will rip oxygen away from lots of other elements including water, CO2 and other oxides. Consider the thermite reaction where normally staid and unflappable aluminum metal gets hot and bothered and grabs oxygen wherever it can get it, including from iron oxide. In your aircraft, the burning of metal fuel in CO2 will provide the heat and ambient CO2 the working fluid to drive a piston engine and a propeller. Your aircraft exhaust will be incandescent particles of metal oxide and glowing carbon soot. Background reading: [Combustion of aluminum particles in carbon dioxide](https://www.tandfonline.com/doi/abs/10.1080/00102200108952170) > > ...Because Martian atmosphere consists largely of CO2, a propulsion > system using metals as fuel and CO2 as oxidizer would enable one to > utilize Mars's resources very efficiently. > > > [Ignition and combustion of metals in a carbon dioxide stream](https://www.tandfonline.com/doi/abs/10.1080/00102200108952170) > > In the prospect of using metals as fuel of breathing combustion > engines in carbon dioxide rich planet atmospheres without oxygen such > as those of Mars and Venus, a fundamental study was performed > experimentally on the ignition and combustion of metals in an > impinging pure CO2 gas stream. Metals selected were lithium, > magnesium, boron and aluminum, because of their high heats of reaction > with CO2. > > > [Answer] # Electric propeller/ rocket combo with a lighter than air option: The lack of oxygen combined with the very dense atmosphere of Venus may provide a unique kind of approach to battles in the skies of you Venusian future. NASA has said solar-powered aircraft would be uniquely suited to the skies of Venus. But this doesn’t get you the high-speed fighters you’re imagining. Because of the challenges of surface mining, your planes will likely consist mostly of very light carbon materials (readily obtained from the atmosphere). Similarly, rocket fuel can be made from atmospheric components. And since the atmosphere is so dense, even breathable air is a lifting gas on Venus. I propose solar-powered cruising and battery recharging for your planes. Prop engines can provide faster maneuvering for sustained skirmishes, probably the same engines used for sustained slow flight. Rocket engines are carried to provide quick responses and sudden maneuvers, and inflatable solar panels allow your aircraft to stop mid-flight as lighter-than-air craft and sit, recharging batteries. If a rocket fuel (or potentially even a compressed gas) can be produced from electricity and the atmosphere mid-flight, the pace of your wars will look very different. * As the equivalent of war ships, you'll likely have vessels with more substantial means of propulsion (like nuclear reactors) but these vessels will be big, complicated, and valuable (read: Targets). * Civilian vessels will likely be comparatively slow and look like something more out of a steampunk/age of sail book. I'd guess lots of solar-powered, lighter-than-air ships to go with the lighter-than-air cities and factories. - I'm trying to find if there is any way to somehow get enough reactivity from the sulfuric acid to use it in place of an oxidizer. IF a way to make this work could be found, then sulfuric acid in the clouds MIGHT be able to substitute for oxygen. Unfortunately, I can't find a [better reference](https://www.reddit.com/r/space/comments/2ushss/h2so4_and_co_liquid_propellant_rockets_how_hard/) than this. Just thought I'd throw it out as a hypothetical. [Answer] ## This is as much an economic problem as it is a technical one Some technical options have been mentioned by the others. Chemical, electric, nuclear and fusion thermal and even more exotic options. I would add antimatter and beamed power to that list. Venus is rich in energy (solar and wind) and carbon but poor in most other resources. The rest has to be imported. Fissiles form Earth or Mars (most concentrated ore), volatiles and fusion fel from the outer solar system, antimatter from Mercury or the outer planets, metals from the inner planets, ... You get the picture. You could use local energy by using beamed energy, solar or even detachable windpower turbines which can get power from the lower atmosphere. These options can be combined with your best energy storage systems to power you in a fight. During the approach you hang on the cable. You might want to consider dynamic soaring as an option, if it works on Venus. You could use local deuterium for fusion, but it is a lackluster and technically difficult fuel. Mining fissiles on the ground sounds like a pain. Importing them is easier. Antimatter would probably be your best bet for great fighter performance. Concerning the environment it might be worth considering the tactical interplay of the space (you need rockets), high atmosphere (like Earth's atmosphere), low atmosphere (boyancy is trivial to use, lasers are less effective, missiles can cruse but are slow, as are fighters) (high visibility submarine combat could be a good analogy) and ground (which is, well the ground). The more varied the environment the fighter can operate in the better. You might want to check out the [Exacting Class Starfigter](http://www.projectrho.com/public_html/rocket/realdesignsfusion.php#exacting) from atomic rockets. It could probably operate in space as well as in an atmosphere. [Answer] First, with such a dense atmosphere a plane would not need wings, a lifting body design should be enough. Then, not only the composition of the air does not provide anything useful for a chemical reaction, but the high temperature would render any type of jet engine inefficient. So, the options would be a rocket propulsion or a propeller. But the dense atmosphere will make a lot of resistance and the rocket propulsion would have a limited range. The propeller driven plane will will be slow, but probably it will also lack manoeuvrability, an alternative that would fit in the dense atmosphere would be fins or paddles that will let it move more like a fish than a plane. Actually the most elegant solution would be [this one](https://www.youtube.com/watch?v=5_SWbwLNHew). For the power source the problem is the same, a nuclear generator will provide a lot of energy, but it would be inefficient. The same would be true for any combustion engine. The best way would be to have advanced batteries or a new type of super capacitor. The range might be more than what you might think. On Earth planes have to use a lot of energy to keep their height on Venus it is more akin to stay afloat, that would take less energy leaving it available for the forward motion, provided it is not too fast and it does not generate too much friction. [Answer] I believe that planes would use turbofan engines powered by some kind of non-cryogenic rocket fuel/oxidizer mix. The problem with rockets is that the fuel is also the reaction mass, which subjects you to the tyranny of the rocket equation. With a turbofan engine, the fuel just provides energy, and the ambient air is (most of) the reaction mass. Having to carry oxidizer would cut your range by as much as 3/4, which is a lot. But I don't think anything else in our current toolbox has close to the same power density. The design would have to be different than a jet engine since you don't want the ambient air to interfere with the combusting gases. Perhaps a gas turbine engine attached to a ducted fan by a gearbox. [Answer] If you're using a modern fighter jet, you'd need to carry your own oxygen, and have a device that injected that oxygen into the air stream as it entered the engines. You'd need an oxygen supply for the pilot, too, of course. Beyond that, I think you'd be just fine as long as you stayed above the clouds, in the appropriately pressurized part of the environment. In response to the comment that "this would be just a rocket": There are numerous difference between a jet and a rocket. For instance, jets have flight surfaces to provide lift, and they use the atmosphere as reaction mass, pushing it out behind it to increase the amount of thrust that can be achieved from a gallon of fuel. Jets at less than the speed of sound can also use incoming air to cool off the engines, whereas rockets have to cryogenically freeze their fuel and pump it through the bell at the bottom of the engine to keep the bell from melting off of it. I could also point out that most rockets are designed to turn on once, burn through all of their fuel, then detach and ditch. Jets are designed for a wide degree of throttling, and can even restart the engines while in flight (usually). The stoichiometric ratio of kerosene to oxygen is around 1:2.6, so you have to expect that a jet that carried its own oxygen would have about a quarter of the flight time of an air-breather. If we convert an F16 to this technology, it would be able to stay in the air for about an hour. With afterburners going, a NORMAL F-16 has a flight time in single digit minutes. If you're talking fighter planes, it's entirely a question of energy density. Normal aircraft can be lighter than air and solar powered, and run everything off of batteries. For fighter craft, you can't get even close to the energy density of chemical combustibles, even adding in oxidizers, without going nuclear, and then you've moved into the realm of hand-wavium, and there's no point in even doing math. ]
[Question] [ So this is an issue I have been thinking about for a while. Both in the fantasy world I'm making and in many examples of fantasy media magic users are able to bring in new amounts of physical matter into the world. For example ice wizards in Warcraft launch shards of ice out of thin air to attack enemies, a Final Fantasy mage creates a crystal shield, druids/plant mages make plants grow out of the ground or their hands, a nasty goblin warlock conjures acid out of his mouth, etc. Logically, wouldn't the world eventually fill up with new matter from mages using generic spells such as these until people literally run out of space to live? How could I avoid this issue while still having a magic system that allows the creation of new matter as depicted in fantasy media such as the examples I listed? Let's further assume that launching things off into space is not an option. Something I came up with is that my world has an ambient "mana field" (similar to how the real world earth has a magnetic field) that takes magically created objects and slowly converts them into ambient mana (effectively destroying them from a physical perspective). Are there other options for dealing with this issue? Or a way for me to improve my idea? I'm hoping for a solution that would be as inconspicuous as possible, ideally something that would take centuries to notice is happening on a large scale, and for most practical purposes is indistinguishable from a world without such a process. Also, I'm hoping for a solution that would still make it possible to keep magically created items around indefinitely, ideally through completely mundane means. I was thinking for example that my mana field would be linked to natural processes such as weathering and erosion, meaning that you could theoretically keep a magically created item around forever if you maintained it by keeping it clean and making sure it's not exposed to the elements for long periods of time without maintenance. One last thing, I couldn't seem to find any other examples of people asking this question or something similar, even in places like this dedicated to worldbuilding. Is it possible that maybe I'm overlooking something really obvious to most people that would render my dilemma a non-issue? Edit for clarification: I'm not asking about specific item summoning spells or "magic-item hoarders" or similar. I'm asking about an aspect of magic in general as seen in fantasy media such as books, games, etc. For example, in the game Skyrim there are spells such as ice bolt that launches a shard of ice created out of thin air, or say a generic fantasy druid that makes plants grow to enormous sizes. Logically, wouldn't the world eventually run out of space from mages using generic spells such as these? The solution I'm looking for is more something along the lines of some aspect of the world or a law of "physics"/magic. The best solution in the context of this question is something both effective and also importantly inconspicuous, as in as similar as possible to a world without this solution/magical law/etc, meaning that constantly creating "bags of holding" or pocket dimensions for storage probably don't fit. The "ambient mana-field" I came up with and listed as a solution is an example of what I meant. Does this make sense as a solution? Or are there better solutions (better here meaning more inconspicuous while still effectively solving the issue) or a way to improve it? Edit 2: Reading this <https://tvtropes.org/pmwiki/pmwiki.php/Main/ElementalBaggage> is part of what inspired the questions. I noticed a lot of you brought up conservation of mass. Once again I want to emphasize that I really appreciate everyone's help here, but I'm highly doubtful that conservation of mass could be at play in many of these cases. For example, the idea of using water vapor from the air to create ice, the issue is that there's only so much water vapor in a given area. In order to do the kind of feats someone like Iceman or a fairly typical fantasy ice mage does they would need to be drawing in water vapor from literally miles away, but they're almost always depicted as not being able to manipulate their element much further than a couple hundred yards away or so, if that. And that doesn't even get into cases where they're inside somewhere, like a building or dungeon, in which case they would need to draw in water vapor literally through the walls. Not to mention that this much matter being drawn in to one location logically would be easily visible. So if for example Iceman was drawing in water from the air for his power it would look like a huge cloud of mist (aka water vapor) suddenly gathering to him. Something like creating a block of ice would require enough water vapor to fill a large auditorium. Same thing applies to other examples like dust in the air for rocks or carbon for crystals etc. Edit 3: Just for clarity and emphasis, I'm specifically asking for something "inconspicuous" (as in as similar as possible to world without such a solution while still solving the problem) and more specifically if there is a way to improve my idea to make it more inconspicuous assuming it’s effective in the first place or if there’s a better (more "inconspicuous") solution. Such a solution would ideally allow someone to keep magically created matter around indefinitely through completely mundane means, such as in my example where the absorption back into mana is tied to natural processes such as weathering, erosion, evaporation, decay, etc, meaning that you could theoretically keep a magically conjured object around indefinitely by maintaining it by doing things such as cleaning it, not leaving it exposed to the elements for long stretches of time without cleaning and maintenance, etc. essentially exactly the same way you would maintain a mundane object and keep it from breaking or eroding away, etc. In other words, how can I solve this issue while still leaving the world in as similar a state as possible to a world without such a solution? Edit 4: As I mentioned, I already came up with an idea of my own on how to deal with this issue, and I'm mainly hoping for feedback in regards to its viability (hence the reality-check tag) and if there's a way to improve it by making it even more inconspicuous. I'm not really hoping for people to come up with completely different solutions unless they better meet the criteria (effective and inconspicuous, as little difference from a world without the solution as possible) then the idea I already came up with, for example, as I mentioned is there perhaps something really obvious most people take for granted that I'm overlooking? Edit 5: Some people brought up the size of the earth and that it would hundreds of thousands of years for this to happen. The problem is that this still makes it an issue in fantasy. Timescales of tens or even hundreds of thousands of years are not at all unheard of in fantasy, some stories such as the Wheel of Time series (I'm not asking about the Wheel of Time, I'm just using this as a random example that hopefully some people are familiar with to better explain what I mean) even feature feature worlds that had been around for possibly eternity, with civilizations going through cycles of rising and collapsing. The fact that it would take a long time to happen doesn't solve the issue, because it would still happen at some point. This would particularly be an issue for my story because I am in fact planning on having long-lost civilizations from thousands or even millions of years ago in my story, with some of the oldest ones having a very "Lovecraftian" element to them. Edit 6: Great job guys! I'm loving the suggestions! One change I decided to implement was to change my "mana-field" idea into a "Matter Absorption Field" basically the same idea except that instead of converting magically created matter into mana it simply absorbs it into nothing (destroying it in other words). The reason for this is that as Vilx- mentioned, all that extra mana could cause problems. Edit 7: This is just a modified version of my solution made in response to the comments and suggestions here. I thought it would be better to just repost it instead of going back and changing the original statement, not to mention that having the previous version easily visible could be helpful in answering the question. Once again I would very much appreciate feedback in regards to its viability as well as how it could be improved to be as inconspicuous as possible. Or maybe you have an alternate, better solution that better meets the criteria of effectiveness and inconspicuousness. -My Idea: I have an idea of my own that I'm planning on using in a story I'm writing. It involves a "matter absorption field" (similar to how the real world earth has a magnetic field) that slowly absorbs magically created matter essentially into nothing. It would work through natural processes such as weathering, erosion, evaporation, decay, etc. Meaning that this would usually be too slow to notice at first and that theoretically you could keep a magically created object around indefinitely as long as you maintained it by keeping it clean, making sure it's not exposed to the elements for long periods of time without cleaning and maintenance, etc, basically exactly the way you would maintain something in the real world through perfectly mundane means. For instance you could keep a magically created sword around forever by maintaining it using exactly the same mundane methods you would use to maintain a normal sword, by cleaning it, making sure it doesn't rust, etc, no special enchantments needed. However if it gets abandoned in a field it would most likely rust and weather away and thus be absorbed by the "matter absorption field". This also means that you could still have magically created objects from thousands of years ago still be around because they were somehow well preserved, similarly to how in the real world we still have some things like swords and buildings from thousands of years ago long after most of their contemporaries rusted and eroded away. Also this means you could still have things like a mage creating a building from magically conjured stone, and not worry about it suddenly disappearing into nothing without warning, as long as they don't abandon it and occasionally maintain the building just like people in the real word do. Lastly you wouldn't need to worry about magically created food or water suddenly disappearing right out of someone's stomach, or worse their bloodstream or brain, and it would only be absorbed into the field when it leaves the person's body and starts evaporating, decaying, etc. Also, I think this solution could potentially work in pretty much any pre-existing setting and not change anything noticeable about the story or setting (this last part doesn’t matter much if at all and can be freely ignored, all that really matters is that my idea works for my setting, this is just a random observation on my part). Edit 8: I just realized that buildup of extra heat from the magical energy could be an issue as well, in which case absorption of extra ambient heat originating from magic energy use could be a feature of my field as well. Also I know that the name I thought of is very awkward, so I thought of changing the name to a “homeostasis field” as that is essentially what it does, helping maintain a certain set of conditions on the planet, i.e. the planets homeostasis. [Answer] ## Living things/constructs emit special magic fields Magic Fields are kind of like "laws" dictating how mana inside them acts. In most of the world, the ambient field is mostly neutral, tilting toward chaotic, which means that mana constructs are usually stable but deteriorates really slowly and inevitably (kind of like something with a long half-life). --- Living things (and maybe things like golems if you want) possess a different field from the rest of the world. Lets call them Bio-fields. Bio-fields: Magical matter that enters a living creature will be broken down by the bio-field, turning into mana. What happens afterwards will depend on you. The mana can then leak out into the outside world, be absorbed by the creature for their use, or give them mana poisoning. --- There also exist other kind of magic fields: Preserver-fields Preserver-fields are fields where the mana inside is hyper-stable. They can naturally form or be manually created. Most creator of magical items that want the item to last will encase the item in its own preserver-field that will prevent the item from naturally deteriorating. The field may or may not require it's own maintenance. Locations like dungeons may have their own fields that prevent the treasures contained within from disappearing. Masters of castles will probably also put their castles in these fields. --- Naturally, this means that if you want, you can have areas of unstable fields that will rapidly destroy magical items. --- Summary: Mana constructs like spell-water are subject to the whims of magic fields that they are in. Bio-fields mean that living things won't suffer the effects of nutrients suddenly disappearing but will instead evolve to know that some things can't be eaten to sate them. Preserver-fields will keep the items you want to stay around for a time. Otherwise, all magical things will slow disintegrate on the time-scale of decades to centuries or even longer depending on the ambient field as well as the natural stability of the object. [Answer] One can turn liquid water into vapor and vapor into liquid water. Your magic can turn nothing into things and also things into nothing. Why would you store something away, when you can materialize it on demand? The wise users of this magic would simply vanish the item after use, the sloppiest would neglect doing it, letting the most entrepreneurial to have a paid vanishing service for them. [Answer] Suppose you have a billion mages casting an ice blast every second. Every thousand seconds they'll fill a cubic kilometer of water. Oceans have [a mass of around a billion cubic kilometers.](https://en.wikipedia.org/wiki/Pacific_Ocean) So it'll take around a trillion seconds to make a notable difference, or around 30 millennia. If we use more realistic assumptions for an industrialized society- a hundred million mages who use an ice spell every thousand seconds, for a tenth of a cubic meter, then it'll take around 3 billion years to make a difference. One solution to add some drama and scale with events is have the world convert objects into mana in the background through weathering, as you said. When a mage casts a spell they're tapping into the plant mana, or ice mana, or whatever mana. Normally there's an equal balance of mages to keep the balance- water mages to desert mages, plant mages to city mages, enough to stop the ambient mana from being unbalanced. An excess of one type of powerful magic users can unbalance this, and they can crystallize a large amount of the natural magic into the world. This will increase the rate of natural erosion against that element, and weaken their own magic type, and encourage them to invade rival kingdoms to use their magic. [Answer] Your magic system is unbalanced It's important that your magic have both advantages and disadvantages. Allowing people to make something out of nothing, and allowing those created things to last "indefinitely," is massively unbalanced. You know this, or you wouldn't be asking your question. Curiously, you appear to be asking us for a way to keep your system unbalanced. From my perspective, that isn't valuable. But, before suggesting ways to have a more balanced magic system, let's see if I can come up with ways to keep the system rationally unbalanced. 1. Your magic is *whomping hard* to enact. Yes, what's created lasts forever... but it's so hard to create that there isn't much of it around. 2. Magic users, and magic consumers, must be *whomping careful* because if any two magical items happen to touch, they explode in a magnificent way! We're talking about shadows of you eating your Wheaties on the wall magnificent. People won't create a lot of items, nor own a lot of items, because they simply can't risk them ever touching. 3. You can create as many things as you like, *but they can't be bigger than a cup.* No houses, no carriages, certainly no towers... The world might eventually fill up, but it's likely it'll be hit by a meteor before it happens because it's only filling up with trinkets. Frankly, none of that is satisfying — It's better to have a balanced system The problem with forcing an unbalanced system to exist is that there's always a kind of odd limitation that keeps it from running amok. Honestly, why bother even uttering the word "mana" when it doesn't actually matter? In an unbalanced system, magic users are actually gods... which isn't all that fun in the long run. Think about it, if magic users can create money out of nothing, chickens out of nothing, cloth out of nothing, willy-nilly and without consequence, you have no poverty, right? No economy, either. No politics with any stability. In fact, all you might have is war because there's really nothing else to do. It's better to design a real list of limits and costs for your magic. This will create a more natural solution, one that will let you build all kinds of very human solutions that people can relate to. For example... * Just as $e=mc^2$, suggesting that mass and energy are interchangeable, you have $mana=mass\x^2$. There's only so much mana in your universe! Or, more specifically, there's only so much that can be accessed without problems. And the only way to get the mana needed to create something new is to eventually recycle some of that mana-embued mass. That variable "x" is important as a limiting factor. The bigger "x" is, the less stuff can be created without recycling. Mana isn't tied to the objects so much that it's tied to the magic users. So long as the magic user lives, the created objects survive. When the creating magic user dies, the protection of mana is lost (mana is returned to the universe) and the objects decay like normal things. * Nothing is actually created from nothing. Mass is removed from the environment to create the object. This can lead to fun things like sinkholes, earthquakes, tsunamis, and breached castle walls. In this way, there's never any more mass in your universe than what it started with. Just as you can't print an infinite supply of money without destroying the economy, you really can't have infinite creation without a consequence. Call this a [frame challenge](https://worldbuilding.meta.stackexchange.com/q/7097/40609). I've proposed a few ideas, but I think you'll have a more satisfying solution if you introduce real limitations. [Answer] Extra-dimensional (or hyperspace) storage Once you have conjured enough barely-used junk to fill your house, and the next house over, and then your whole block (elephants take a lot of room), and then your whole neighborhood... ...you start to notice that it takes too long to get to your friend's house, or down to the local pub. While you could conjure up a teleportation cabinet to save you the walk, it doesn't bring your belongings any closer (just your friends, and who needs those?) So instead, conjure a hyper-sphere and store your square-kilometers of elephant-cars and cookie-robots and game-mistresses and fart-castles and scorpion-tanks within it's infinite number of collapsed dimensions. Everything you made is still there, within easy reach wherever you go, but their mass and footprint are no longer associated with the Earth. It's like wishing them away, but they are still there and still yours. Just remember that you must still feed and water and properly care for your stored living pets! Stasis models cost extra. [Answer] I'm going to ignore the "storage" part of your question and focus on what I think is your main problem: a spell like Ice Shard leaves unintended ice in its wake after use, this will turn into water and suddenly theres half a liter of water extra on the world. The same for any and all other types of magic which use a created physical object as part of their spell. This does not seem to be a huge problem. The earth already loses and gains thousands of tons each year. It mostly loses hydrogen and helium as it escapes high in the atmosphere into space while the earth keeps collecting dust and particles in its path as it circles the solar system. This is a net gain of thousands of tons each year. This isn't a big problem for the earth, and I suspect that the addition of a few million mages casting spells at each other over the course of a year will have little impact on that total balance. We dont see masses of dust collect everywhere and I suspect that some spells like those that create water could help replenish the gas that leaves the earth. To significantly impact the earth and especially its gravity your mages would need to get REAL busy. Overpopulation would sooner be a problem than magic detritus covering the planet. Material dissipation: When it comes to material dissipation the idea of letting stuff desintegrate over time seems a nasty option. Imagine drinking magically conjured water and having it disappear from the molecular bonds it made within your body, chemical imbalances and weird chemical processes would mess you up, not to mention that losing a liter of the water in your blood or brain matter could kill or permanently incapacitate you. And thats just water, imagine all the other magical materials that could seep into the ecosystem and wreak havoc as it dissipates. You could just let natural processes take care of it, ignore it or introduce destructive spells. The spell desintegrate is usually depicted of turning an opponent to just a little dust, the lack of an explosion means that material needs to have vanished. Similar spells like implosion must also remove matter in order to work. A teleport spell could also completely remove a portion of the matter you teleport into (the air hopefully) etc. There is also the "just teleport everything" option. Rather than creating ice, you basically teleport particles of ice from all over the planet into the spell. There is a change in the energy budget of the planet due to this but use across the planet should cancel this out. [Answer] The question is most certainly an interesting one, and not one that I had thought about. ## The Rules Since the goal is to be able to create objects that persist without outside interference, but still can return to being magical energy at a future point in time, the rules set up here will aim to address that. I don't make any assumptions about spells other than those addressed in the question -- evocations and/or conjurations that create things. As a thought, the primary rules of the world are: 1. Things made of magic must return to magic 2. The spell that creates the object defines its existence 3. Once an object is created by magic, it is subject to natural laws 4. Only when an object, or a part of it, is unrecognizable from the whole does it return to magic While those four rules don't necessarily cover every situation, the idea is to create a starting point where the rules can apply to the majority and what doesn't fit can be dealt with after ### Rule 1 -- Return to the Source The first rule is bolded because it is the most important I think. The core point of the rule is that while the object created from magic is physical, when time or action has destroyed it will not remain as physical stuff and instead return to be magical power. This could be a plot point at a future point in the world -- destroying magically created objects in order to steal the magic that created it. ### Rule 2 -- Definition of Form The point here is that while a spell might appear to do something, how it creates the thing is just as important as what the thing it creates is. To use one example given: An ice lance is a chunk of ice yes, but how cold is that ice? Is there any considerations in the spell that might make it more or less resilient to melting or damage? At what point does the spell end and nature is allowed to take over on the ice lance? For your druid growing plants -- it's not just about how big the vine gets, but does it actually grow the roots and supporting systems to be able to handle its new size? All those fiddly details of the spell are important. Some objects may be specifically designed to only last a short time and return the object to magic when done. Or possibly designed to be released on command so as to not tie up large quantities of magic in a single object. ### Rule 3 -- Natural forces The gist here is that once magical energy is converted to a physical object and the spell has run its course, nature holds sway over it. The main reason for this rule is to prevent objects from immediately disappearing as per the request in your question. Yes, this also means that by this rule, certain spells will not have results present as long as others. If a spell created a kilogram of ice in the form of an impaling spike, then once the spell has run its course, the ice can only be acted on by nature -- notably magic cannot melt this magical ice on its own. In the case of the plants, once the growth spell has run its course, the plant matter created does not disappear, but the plan is now subject to trying to maintain its new size by natural means -- photosynthesis on the green parts, and drawing in nutrients through the roots. ### Rule 4 -- Self Cleanup Rule 4 provides the mechanism for returning magic to the world. By waiting for the broken bits of stuff to be basically unrecognizable from the original whole, it creates a subtler refuelling of magical energy from the conjured stuff then if it just vanished in a day or two. Consider ice again. Your ice lance, once the spell has run its course, will start to melt from ice to water. Eventually you get a puddle where your lance was. As the water evaporates, it does not evaporate into a vapour -- instead it vapourizes back into magic since the gas is both unrecognizable from the ice lance, and invisible to boot. For the druid plant growth example, as the plant decomposes, much of it does not break down into soil, but breaks down into the magic that created it. As a living plant before, it could be that as it tried to live at its new size, it was able to make new cells that weren't essentially products of magic. Certain conjured items may not break down so easily given their sturdier construction and possibly other magics woven into them. ### Application of the Rules I will fully admit that the rules are not perfect -- they likely leave themselves open for abuses and interesting side effects. Perhaps that might be the point of them once somebody can figure it out. For other things that are created, it is about applying whatever rules to the objects created in a logical manner. Well, as logical as magic can get anyways -- consistent might be the better term. [Answer] It's not really a problem. Quoting [wikipedia](https://en.m.wikipedia.org/wiki/Earth_mass): > > Earth's mass is variable, subject to both gain and loss due to the accretion of in-falling material, including micrometeorites and cosmic dust and the loss of hydrogen and helium gas, respectively. The combined effect is a net loss of material, estimated at 5.5×107 kg (5.4×104 long tons) per year. This amount is 10−17 of the total earth mass.[citation needed] The 5.5×107 kg annual net loss is essentially due to 100,000 tons lost due to atmospheric escape, and an average of 45,000 tons gained from in-falling dust and meteorites. This is well within the mass uncertainty of 0.01% (6×1020 kg), so the estimated value of Earth's mass is unaffected by this factor. > > > So the mass added via magic is probably not going to affect the total materially. If this gains industrial proportions though, it could become a kind of magical environmental pollution, which will just have to be dealt with just as we deal with CO2 emissions (ahem, ie., not). Note that some of your examples can be explained without additional mass, eg. a plant growing is just the normal process accellerated, ice shards can be from extracted atmospheric water vapour. [Answer] # Created objects need sustained magic inflow Or otherwise they vanish. So a wizard can sustain so many pure magical created objects, at same time. If they create more than they can sustain, old objects lose their magic influx and vanish. But pure margical object mass is a waste, anyway. Wise mages realize that normal matter and a little magic glue is way better effective way to make sobrenatural objects, with very little magic drainage, and by going matter+magic route they can sustain a vast superior arsenal, archive, gadgets, palaces. The powerfull mages prepare in advance: they put a lot of matter in dimensional pockets to easy and fast retrieval, be raw materials or prepared ingredients. The mage enters with a little magic, the world enters with mass, so the last is constant. Example: an ice spike machine gun. The wizard opens a bag of holding full of water, at the border solidifies and shoots ice spikes. After the splikes done the damage, the mage cut the solidify spell on old splikes, freeing MP to the next wave. [Answer] Perhaps these 2 approaches will be somewhat helpful. 1. Matter created by magic is unstable This is similar to your proposed idea: Mages convert mana into the matter, but it is not stable and after some time it reverts to mana state. The stable period may depend on the mage's power, specific spell, ambient conditions, mana availability, etc. This would be very consistent with magic depictions in games where physical manifestations of various spells disappear once the spell is fully activated or once the combat is finished. This approach makes the accumulation of magically created matter impossible, which solves your problem of running out of space. However, it also makes it necessary to explain how magical objects and materials can exist. Perhaps, some, especially strong and skilful, mages can somehow stabilise matter or can lock mana into specific objects/materials. Alternatively, magic objects need a constant supply of mana to support their form. This approach also requires additional explanations for conjured consumables or make them impossible. For example, it might be impossible to feed people with conjured food. Alternatively, if living organisms can sustain themselves with mana, conjured consumables are no longer a problem and are just another form of mana (however, this would be closer to Eastern fantasy). 2. The flashy effects of spells are illusory This is a fundamentally different approach and it does not involve matter manipulation. All magic is based on mind manipulation. Mages do not create any new matter. They make other people believe that they create matter. Illusions have real power in the world of magic and if a person believes they were hit by an ice projectile their body will manifest corresponding symptoms. This might seem very unrealistic. However, please consider [phantom pain](https://en.wikipedia.org/wiki/Phantom_pain), [false pregnancies](https://en.wikipedia.org/wiki/False_pregnancy), [somatic symptom disorders](https://en.wikipedia.org/wiki/Somatic_symptom_disorder), [psychosomatic disorders](https://en.wikipedia.org/wiki/Psychosomatic_medicine), and [hallucinations](https://en.wikipedia.org/wiki/Hallucination). All of these show that the state of mind can and does affect our perception and our bodies. So, it is not entirely impossible that magic affects minds and those affected minds create somatic symptoms. This approach also creates problems with magical objects and conjured consumables. Magical objects can be explained by faith and/or magical energy imbued within them. However, conjured consumables can only have a placebo effect. [Answer] Mana scavengers creatures Organic dead matter in out world never accumulates. This is because there are scavengers animals. Some of them are big animals, like vultures or hyenas, other are insects (like ants or dung beetles), and other are fungi/microbes. They eat this matter and bring it again in the circle of life. At the same time, the conjured-from-nothing matter is still made of mutated mana. This has created some evolutionary pressure on some of the most magic-sensitive creatures, both big and unicellular (dragons, pegasi, midichlorians...), which have evolved to assimilate these substances and revert them to pure mana. When wizards summon mana and convert it to matter, they need give it some energy in order to bring it from "mana dimension" (like lifting a rock against the gravity) to this world and make it change state. The mana-scavenging creatures, assimilating these substances, revert them to pure mana, which soon comes back to mana dimension, freeing energy in the process (like when the rock is released), which is harvested by the creature's organs or cells. [Answer] Creating matter or energy out of nothing simply breaks physics. There are plenty of magic systems which say it’s impossible for that reason. Instead, they say it’s only possible to move or convert matter which already exists. The energy for this conversion or transportation has to come from either the user, from the matter being converted or from other sources (i.e. the environment). [Answer] ## Dark Energy Expands Space The essence of your problem is entropy. It takes only one spell to make an ice shard or a baby rattlesnake (or a thousand), but to dispel the contents of an average mage's dresser drawer you need a different spell for every Tarot card, herb, body part and unidentifiable crawling abomination inside. It's just not practical. Fortunately (from an external perspective), neither mage towers nor their contents are impervious to harm. A simple Thermonuclear Fireball spell can send up all the contents as "dust", and let them settle as "earth" - not elemental earth, but the mundane variety known by farmers who can never guess quite what is eating their vegetables. Impurity rules the day. Now what happens as all this fine dust settles to earth over the ages? Well, the ground rises a little higher every day because of it. (Ignore all commentary by a certain well-known fellow [ignorant of magic](https://www.nypl.org/blog/2012/04/19/earthworms-darwins-last-manuscript), who failed to understand the spontaneous generation and degeneration of vermin) Now the nether realms are infamously filled with a dark energy from whence terrible things emerge; and as the ground rises, this dark energy inevitably pools beneath. The artifacts and creatures of the depths gradually turn more terrible, until they become part of the Underworld itself. Just so, the underworld experiences an unlimited expansion to accommodate the ranks of the dying, while the ordinary world appears to remain always the same. This compensation is not instant - if the wizards are especially prolific, they cover the earth in dust, and the power of dark energy weakens, and with it, their more prominent powers. Yet if they stop entirely, the dark energy continues gradually to rise, until every wayward child is at risk of summoning abominable creatures with a word. But always, the Underworld rises, ever hungry for the souls and works of all that live in the light. [Answer] I think you really should also think about the extra energy they create. In our universe, mass and energy is interchangeable and there's a fixed amount of it. You can't create it, you can't destroy it. Mess with that, and... well, probably nothing bad is going to happen on small scales like mere solar systems, but summon enough matter/energy for entire galaxies and things get weirder in the long run. Anyways, I like your magic field. But I think it could be a even bit more mundane and "scientific". See, the mana field could allow you to pull matter and energy out of the earth's core. There's plenty of both in there. After these things are summoned they obey the quite natural laws of the world - ice melts, plants rot, iron rusts, etc. All in all you don't get THAT much extra matter on the surface and it returns to the ground pretty soon anyway. In the long run, your planet may cool off a bit faster (since you're using up energy from the core, and teleporting/transmutating matter takes quite a bit of it), but the overall mass and energy don't change. The extra stuff will decay and go to the ground (as all things do), and in response, plate tectonics 'n shit will ensure that a bit more matter from the crust gets converted to the mantle, etc. The best bit is that this way you can still follow mass-energy conservation laws and entropy etc - so nothing gets seriously out of whack in the long run. Btw - this also adds an opportunity for more storytelling - as human understanding of this effect increases and they can manipulate the mana field even better, they could start using grand magic machines to summon matter/energy from the sun instead. Could be useful for spaceships and maybe make up for the core energy used with regular summoning. [Answer] I think I understand your question, so I'll give it a go. You want an inconspicuous system, so that means probably you wouldn't want to have your wizards "consume" water for their mana fields to later turn to ice shards or whatever (though it could add a layer of interest- an ice Mage is forced to be more connected to ice, a fire Mage to fire, etc.). The mana-field idea seems like a good one to me. I assume you want to more or less maintain conservation of matter, so you will probably want a way of drawing matter out of the world into the mana field (like erosion, as you mentioned). Someone with better science smarts can help me here, but you could say that in your world all chemical processes "shed" subatomic particles into the mana field which can be retrieved later and formed into ice, fire, or whatever else you want. This has the benefit of making people, stars, plants, and water - anything which has lots of chemical reactions going on - assume a more "mystical" air. It is also hard to notice on a short timescale and yet it solves the problem of too much matter in the world. Of course, you would have to work out the matter economics. How many reactions over how long a period do you need to make one shard of ice? What happens if all the mana gets used up? How do you access it in the first place? Another option, though more conspicuous, is to make your magically-summoned matter mimic its computer-game counterpart - make it act just like the real-world matter, but give it a life span after which it vanishes into nothing. You can still keep magically-created items with [insert magicsplain here], but by default they vanish. As a side note, if your wizards are using telekinesis to throw stuff around, they're also creating energy, possibly increasing the total amount of energy in the universe. Of course, Einstein et al showed us that matter and energy are kind of the same thing (see matter-anti-matter reactions for a concrete understanding of E=MC^2). Whatever your system ends up being, you can show your smarts by addressing how matter AND kinetic energy are drawn to/from the world or the mana cloud. Of course, since this is fantasy, we don't need to maintain conservation of energy or matter where magic is concerned, but it always feels neater to me when fantasy worlds still do this. Hope that gives your imagination something to chew on! Have a good one! [Answer] The stability of conjured objects existence could be tied to not only the physical form as you suggested (keep it clean/rust free/intact/protected from decay) but also the usage of said item by a being. To word that another way a conjured item will only continue to exist if it is used and is useful for the intended purpose decided at the time of conjuring. As an example a conjured robe left on a shelf and never used would eventually cease to be. On the flip side if a wizard is using that robe it would last as long as a equivalent robe made in a none magical way. (without intervention or magical repair) A damaged robe would remain until the point it's no longer usable for the intended use. Having a conjured item becoming worn out through normal usage or damaged just like a equivalent quality item made in non magical way would also assist with keeping conjured items unobtrusively distributed in the world. This way (if you so choose) will allow a unskilled user of magic to create a conjured a tool fit for his/her intended purpose but the slightest variation from the exact intended purpose will undo the item. On the other hand a much more experienced and powerful magic user could create a conjured item that will last much longer by imbuing the item with as many possible variations and contingency's of use imbued in to it if he/she is inclined to put in the effort/magic. The "contingency of use" could even have a physical attribute associated with it. Might make for some interesting visuals for conjured items where each extra use case becomes a tangible part of the items physical form. You can then decide at your leaser: 1. How strict that "useful for the intended purpose" is. 2. How long a unused (but still fit for purpose) item lasts. (dependent on magic users skill/effort used?) 3. If summoned items can even be used by anyone other then the one who conjured it. This could be tied in to the "intended purpose" qualifier, as in did the one who conjured the item intend the item to be use by others when it was created? [Answer] Classic: Magic effects are dispersed on the user death - the old trope that killing the mage will repair all damage caused by him. You also give mages ability to regain (some) magic by dispersing created objects they will be eager to do it, effectively cleaning up in the process. ]
[Question] [ I would like to have a city sitting on top of a large iron deposit that will be mined by the inhabitants of the city. Is that feasible for them? Won't the city collapse under the mines? Are there some other issues I should be aware of? [Answer] There are cities with extensive mining operations below them. The most famous is probably Paris. <https://www.nationalgeographic.com/magazine/2011/02/paris-catacombs/> > > Under Paris there are spaces of all kinds: canals and reservoirs, > crypts and bank vaults, wine cellars transformed into nightclubs and > galleries. Most surprising of all are the carrières—the old limestone > quarries that fan out in a deep and intricate web under many > neighborhoods, mostly in the southern part of the metropolis... Into > the 19th century those caverns and tunnels were mined for building > stone. > > > You can tour the Paris catacombs full of bones, but the tunnels were there before they put the bones there. And there are apparently many more tunnels than are occupied by bones. Kansas City also has extensive limestone quarries beneath it, although of course more recent (and less chaotic) than the ones in Paris. I found reference to the [Kiruna Mine](https://en.wikipedia.org/wiki/Kiruna_Mine) which is a mine underneath a city of 24,000. Wikipedia states that subsidence related to the mine has affected some parts of the city. [Answer] If iron is that valuable, sure. Detroit, Michigan is built on top of some pretty extensive salt mines. The first image shows the vertical extent of the salt mines: [![enter image description here](https://i.stack.imgur.com/YmcDo.jpg)](https://i.stack.imgur.com/YmcDo.jpg) The second picture shows the horizontal extent of the mines: [![enter image description here](https://i.stack.imgur.com/uHE8V.jpg)](https://i.stack.imgur.com/uHE8V.jpg) All that you really need for a city to live on top of the mine is to have the mine deep enough and/or have enough structure left around the mine so it doesn't collapse (you want that anyway). Edit with Image to show actual vertical scale: [![enter image description here](https://i.stack.imgur.com/kKGxM.jpg)](https://i.stack.imgur.com/kKGxM.jpg) [Answer] It's possible, but you almost certainly need steam engines (or some kind of magical steam engine analog). A good real life analog would be Butte, Montana. Butte had a number of mines, primarily owned and operated by the Anaconda mining company. Wikipedia tells me that from 1880 to 2015, [15 million metric tons of ore were extracted from underneath the town](https://en.wikipedia.org/wiki/Butte,_Montana#Anaconda_Copper_and_civil_unrest). Most of the mines were producing copper ore. It is said of Butte that it's "A mile high and a mile deep" -- the city sits a mile above sea level, and the deepest mines reach a mile down. At its peak, the town had a population of about 40,000. There was quite a bit of labor unrest; Butte was the site of the longest strike in US history, the worst hard rock mining disaster, and was the birthplace of one of the most active and radical labor unions, the Western Federation of Miners. Something to consider is that large-scale mining is very resource intensive, and requires trade with outside regions. The energy to run the mines and the food to feed the miners probably needs to be imported, and then once the ore is produced, it needs to be shipped off to somewhere that wants ore in the quantities that its being produced in. The mines will probably be pretty deep if the mining is not going to totally destroy the integrity of the surface. This means hard rock mining, probably for something with an industrial value like copper. Hard rock mining is really slow. Before dynamite, a couple of guys would pound an iron rod into the rock face until a bit cracked off. Progress could be as slow as [0.2 inches a day](https://www.forbes.com/sites/davidbressan/2016/10/31/how-dynamite-revolutionized-tunnel-excavations/#2bdff7df2abc). Blasting speeds things up immensely, but is dangerous. Pneumatic drills come later, and also speed things up quite a bit. The deeper the mine goes, the harder and more costly it becomes to keep them running. Once a mine shaft crosses below the water table, it becomes necessary to run pumps around the clock the prevent the mines from filling up with water. Furthermore, fans must be run to circulate fresh, breathable air from the surface down into the shafts where the miners are working. Elevators must be run to move miners down into the mines and to move ore back out. All of this gets harder and harder the further down you go. The costs are fixed costs, so the mines will run 24/7. Keeping the mines running requires a lot of resources. You need to power the fans, the pumps, and the elevators, and you need to power them all of the time. And you need wood to build supports for the mine -- a lot of wood. In the case of Butte, the need for wood was so great that they were importing mahogany from South America for the supports. Even just producing enough energy requires steam power or its magical equivalent, and either way the fuel must be imported. All of the ore produced must then be processed and shipped out. In the case of Butte, the Anaconda Company built an entire other city nearby to smelt the ore. This too is a big operation, requiring lots of fuel and water, and it absolutely wrecks the environment. Transporting the ore out then requires still more energy. Industrial mining is only possible because locomotives make it cheap to move tons and tons of materials around -- if the mines are producing thousands or tens of tons of ore a day, they need a way to transport that over long distances to whatever market needs all this ore. [Answer] You are describing exactly the situation of Kiruna, in Northern Sweden. It is not one of the biggest deposits, but it is still relevant because the ore is magnetite, which is cheaper to purify than from other sites. The mineral is in a downwards slope, going under the city. [![enter image description here](https://i.stack.imgur.com/Izk1R.jpg)](https://i.stack.imgur.com/Izk1R.jpg) [Source](https://www.nyteknik.se/industri/kirunagruvan-pa-nytt-djup-6396217) The text is in Swedish, but the mineral is the "metallic" looking diagonal. The cracks coming up from the excavated part are caused by rock collapsing. The white channels are the tunnels used to access the ore, and the red are the future tunnels. They have now started to dig deep enough that the city itself will be affected, so the whole city is being moved, building by building. The current evacuated area will still be safe to walk on, but not to build anything bigger than a shed, since the ground will suffer displacements. So, answering your question, you cannot really mine ore from under a city and expect everything on top to stay put, unless you seriously restrict the amount of material that they can extract from each location. It may work if the buildings are small, so they can deal with soil displacements. You can look at Japanese architecture of the epoch corresponding to your technological level: they are very good at building things that can withstand moving ground. Or you could side-step it and place the city on the other side of the ore. This places the entry of the mine on the safe side (inside of town), and only the fields are affected by ground displacements, which is not a problem. [Answer] For a real world example of what can go wrong with a mine collapse, look at the case of the Retsof salt mine: When a 500 foot square section of one of the mine chambers collapsed, it drained the aquifer for many miles around, causing water shortages in the surrounding area for nearly a decade. See <https://pubs.usgs.gov/circ/circ1182/pdf/14Retsof.pdf> and <https://www.washingtonpost.com/archive/politics/1994/05/15/salt-mine-collapse-shakes-residents-of-genesee-valley/9d0fe3fc-9e1b-4135-ac89-ee0f38520ecd/?noredirect=on&utm_term=.57131a3aa889> for more information [Answer] Undermining was used in sieges for many centuries. <https://en.wikipedia.org/wiki/Tunnel_warfare>[1](https://en.wikipedia.org/wiki/Tunnel_warfare) A number of buildings have been damaged by commercial mining too close to them. Hamilton Palace was demolished in 1927 partially because of damage from nearby coal mining. <https://en.wikipedia.org/wiki/Hamilton_Palace>[2](https://en.wikipedia.org/wiki/Hamilton_Palace) The Borough of Centralia, Pennsylvania, had a population of 1,000 in 1980 but now has only 13 residents due to a a fire burning in the coal mines under the town since 1962. <https://en.wikipedia.org/wiki/Centralia,_Pennsylvania>[3](https://en.wikipedia.org/wiki/Centralia,_Pennsylvania) So it is certainly possible for a settlement to be undermined by careless mining beneath it and that is something that the residents of your city would need to guard against. ]
[Question] [ On my world a jellyfish type of animal exists, it's an aquatic animal of course and extremely dangerous as it consumes anything organic it touches. It's thin and wide, like a fleshy transparent blanket, not fast at all depending on the currents to go from one spot to another, mostly it just floats about. The most "solid" parts of it are the millions of tiny, pin-tip like, protuberances which secret a digestive liquid when it catches a prey. One of my characters is a mariner and on their boat they have a primitive radar system. would the radar be able to detect the animal? [Answer] No radar underwater. Radar uses a frequency which is essentially microwaves. The original microwaves were called radar ranges. Water soaks up microwave energy very well, which is why you can cook with them. Radar is not useful underwater. <http://www.physlink.com/education/askexperts/ae456.cfm> Submarines use sonar, which is sound waves. An interface between something which was slightly different from water and water might reflect some sound waves and so be detectable. It would not be like detecting a submarine, or even a fish. I think it can be done. from <http://www.umces.edu/cbl/story/2015/oct/13/tallying-sting> [![sonar jellyfish](https://i.stack.imgur.com/UFg0R.jpg)](https://i.stack.imgur.com/UFg0R.jpg) [Answer] During World War 2, both SONAR and RADAR where deployed against submarines, both from planes and surface vessels. Anti-submarine warfare planes, until they built radar arrays small enough to fit on those planes, where basically large spotter planes, often seaplanes, with a high flight time. They looked for the submarines using their good ol' Mk I Eyeball and binoculars. This was the same for surface ships (they too were retrofitted with radar in the later years of WW2). When they employed Radar against submarines, it was to detect them when they were surfaced, or later in the war as they were snorkeling, as submarines were basically just ships that could dive for a finite amount of time, and had to resurface when their batteries were depleted. So usually, submarines would surface at night or during bad weather, since spotters would never find them. Radar did help with this, as radar could pinpoint their location pretty good. However, this did not work when the vessel had been submerged. Even if Radar waves were to hit the water surface orthogonally to minimize the huge reflection/scattering effects caused by the water surface, radar will only penetrate a couple of meters, and even if it reflects off the submarine hull then, on the way back through the waters surface it will also reflect and scatter off of that surface. The remaining radiation wouldn't be sufficient to detect anything, as it would be much less than the reflections off the waters surface. This is also the same with radio. It's why civilian submarines are usually connected to a surface ship by cable to communicate. So, the alternative to detect these vessels were, at first, hydrophones (basically microphones for the use in water). Sound waves travel much faster under water than they do in air too. However, this method had also multiple drawbacks. First, you'd have to be quiet enough to actually hear the target over your own engine noise, and second, the target must be loud enough for you to be able to discern it from the background. Thirdly, water has thermal layers that reflect sound waves in the same way as water surfaces do with radiation. It got partly remedied by using an active ping, the predecessor of the sonar, ASDIC. The thing is, both ASDIC/SONAR and RADAR depend on the property of the target to be reflective in a way you can pick up the reflection at your vessel (or deployed buoy or whatever). You will not see anything when the waves get absorbed. You will not see anything if the reflection of sound/radar is not going back to you. If it is reflected away from you, you wont see it. Now, since its waves we are talking about, there is little chance there is literally zero getting back to you, the problem is that what is coming back has to be discernible from all the other reflections you pick up. Now jellyfish tend to be 99% water... I am pretty sure you won't see that on a rather primitive sonar system, as the wave will probably propagate through the jellyfish. I recon this would be the same with radar, even if you were able to penetrate the waters surface and/or reach more than a couple of meters range. TL;DR: No, not with mid 20th century technology. [Answer] Perhaps. If this creature is a large mat on the surface, it could alter ocean waves enough for it to be detected by radar. It'd have to be pretty large, probably dozens of meters wide, to be detected by a primitive radar set. There are radar like alternatives to sonar, primarily using lasers or LEDs. You may also be able to detect them via passive hydrophones, if they mute background sea noise or if they emit sound (digesting prey perhaps?). Obviously sophisticated computer processing is required for these alternatives as they are much more advanced and have to filter tiny changes from background. Seems possible to train something like a dolphin or seal to patrol around a boat and alert humans if one of these things is present. Maybe train birds to drop down on them in a, unknown to the bird, suicide dive. If you are low tech, that is your best bet (other than learning to read the currents and detect these creatures by the absence of whatever it is they eat). Ultimately you could trawl the area with nets and scoop them up. [Answer] Unfortunately the creature's jellyflesh is invisible to sonar/radar. Fortunately the same is untrue for the large collection of prey suspended inside and slowly being digested. So a creature that recently encountered and devoured half a schoal of fish pops up on the screen looking like half a shoal of fish. ]
[Question] [ While rewatching the first episode of Stargate SG-1, I realized again, that it might not be a good idea to put your secret portal to other planets right under your central air command bunker. The Problem An attack through the stargate could not only give the invading aliens a defendable beachhead. It would also destroy the current command structure and could thus slow the response time of our air force, when a full-time invasion hits. But where would we put such a teleportation device, to explore the galaxy? Constraints Assuming the device would work similarly to the TV-Series, so it would need a lot of energy, and we have no other alien technology, other then the stargate itself. So we would need some kind of infrastructure, where people working on the project could live and where research is done. The stargate is secretly owned by the US, without the knowledge of any other county. I'm seeing three possible threats at the moment which should be addressed: * An alien Invasion by the Goa'uld, trying to come through the wormhole. * A malfunctioning alien device, that will affect the surrounding area. (e.g. a nuclear explosion or a [time dilation](http://stargate.wikia.com/wiki/A_Matter_of_Time)) * A disease, affecting people. (Similar to [Sight Unseen](http://stargate.wikia.com/wiki/Sight_Unseen)) [Answer] Cheyenne Mountain is actually a good location. 1. It's bundled with a big non-secret military base. Meaning there's a good reason to have tons of soldiers hanging around, tons of money in the budget and tons of power being used, and there's a good reason to have extremely limited access and an extensive array of defenses and countermeasures. 2. It hosts a former missile silo (in the show at least), which means you can fit the gate through it. Fun fact, Stargates can't be dissambled. Unless yours can, you'll need pretty big doors. 3. There isn't any big population center near by (at least none that is mentioned in the show), so they can close the area fairly easily without causing too much hubbub. Presumably, military personel lives either in the base or nearby, which would make the area a bit easier to control. 4. It's in a mountain, so if all hell breaks lose, you can just blow it up. You can presumably pass that as an earthquake, and it would still probably look like a mountain. Also being a mountain, it's pretty hard to destroy from the outside. 5. It's underground, so any invader would have to fight their way up, which would be a rather tall order if you are only using force. Underground is also a good defense against satellite imagery. Admittedly, for point 3, acceptable distance to and size of population center may vary. In the show, they mention at least once they have closed the surrounding area due to "chemical leak". I don't remember they ever mention including Colorado Springs in a quarantine zone. To be fair, I've watched the show a lot, I never catch they had a 450k city sitting 15km away. --- Area 51 would be a good candidate as well. Reason #4 maybe wouldn't hold as much, but to counterbalance that, the base has a perfect cover. If anyone were to say "Area 51 is home to a super secret military project that explores other planets and fights aliens", that'd sound like a conspiracy theory from the 1950s. It's probably why they stacked their alien artifacts there in the first place, because reasonable people won't lend any credit to Area 51 conspiracy theories. --- Extrapolationg from these examples: * Anywhere with an actual, non-secret military base. That is to say, anywhere where you would expect large military presence, large budget, large power consumption and restricted access. * Anywhere that you can hide easily. Which is to say pretty much everywhere you can dig and build a thing underground. Underground provides cover from satellites and can hide some amount of explosion, as opposed to something above ground which will very noticeably disappear when it explodes. * Anywhere far from big population centers. You don't want too many pesky civilians around. * Anywhere with at least one big door. Because the Stargate is big and will have to fit through that. [Answer] Create a cover story for something that needs a lot of the same resources: huge amounts of underground excavation, many miles of superconductive magnets and infrastructure for same, computing resources, etc. That sounds like a collider, but on an unprecidented scale: a superconductive super collider! You also choose a site good for underground chamber making and free from seismic activity, just as for building a collider. People see the published (cover) specs, and see how much chalk and shale is coming up, and assume that you are making a huge circle tunnel, but a large chamber with several small tunnels have the same volume of digging. Be sure to design in an access hatch by which a [huge wheel-shaped instrument](https://en.wikipedia.org/wiki/ATLAS_experiment#) can be lowered later. [![detector down shaft](https://i.stack.imgur.com/PrecN.jpg)](https://i.stack.imgur.com/PrecN.jpg) [source](http://www.universetoday.com/13005/final-detector-in-place-at-the-large-hadron-collider/) Then, when money is spent and the needed work is done, you cancel the project. You skip hooking up the huge power feed to the huge intake you built, never running power lines into the area, so people assume the site really is dead—nobody knows about the off-the-grid [Naquadah](https://en.wikipedia.org/wiki/Technology_in_Stargate#Naqahdah) reactor. The newly discovered [high-temperature superconductor](https://en.wikipedia.org/wiki/High-temperature_superconductivity#Crystal_structures_of_high-temperature_ceramic_superconductors) material — this “invention” had to be leaked to general scientific community in order to provide for industrial quantities to be manufactured — turned out to be fatally flawed for the supercollider usage, as it is not only brittle but can't handle the stress of the magnetic field it was made for. This fiasco was the very excuse for cancelling the project with such high sunk costs, and everyone in the scientific community can see for themselves that it is true and repeatable: they crumble like dry soda crackers, and only handle a fraction of the magnetic strength predicted in theory and extrapolated from small samples. But, it is all a ruse. The use case is actually different from what the public thinks, and a stabilizing coating was kept secret and not revealed with the material proper. The 80 killometers of superconductor is safely stashed in the hole, refit to its real purpose. So, I conclude that the place to put the stargate command is [near Waxahachie Texas](https://en.wikipedia.org/wiki/Superconducting_Super_Collider). Finally, as a disinformation campaign to camouflage and repudiate leaks, [create a TV show with the same rough premise](https://en.wikipedia.org/wiki/Wormhole_X-Treme!), but campy and differing in actual detail, including the use of a high-profile location for the command center. --- # addendum > > it would need a lot of energy, and we have no other alien technology, other then the stargate itself. > > > The original plan was to use a reactor from an aircraft carrier, with additional cover stories about “loosing” one. But small Naquadah generators were discovered on early missions and easily scaled up. > > [cover for] An alien Invasion by the Goa'uld > > > [People already run around in strange costumes](https://en.wikipedia.org/wiki/Scarborough_Renaissance_Festival), and this started in 1981. This was just 2 years before the SSC project was publicly endorsed, about the time it was first planned as a cover. In fact, it was itself a cover story for a camp of relocated offworlders living with medeval technology. The newspaper was told “oh, they're re-enactors (or larping)” and everyone decided to join in. The large movement of people through the normally rual area was an initial lure to do more project-related activities there. [Answer] Somewhere not too obviously suspicious and it should be logistically feasible while having a place where massive energy usage doesn't draw unnecessary attention. It should also be a place where regular people don't find it abnormal that a section of the facility has restricted access. Also, the cover should be large enough so that a lot of human traffic is deemed normal. A 100+ people leaving a local bakery on a daily basis is going to be suspicious. I'd still put it in a military grade bunker deep below maybe ... * A large powerplant * A steel mill (or any other large production site) * Some university's high tech research center [Answer] Given the number of long shot survival scenario's that resulted during the TV show, and accepting that even though lots of alien technology was acquired, none of it ever got out to the public where it could do real good, there is only one valid conclusion... The Ancient Egyptians had the right idea! Bury it. However, we have now better options than a big cover stone. We can sink it into a vat of concrete or molten steal. ...or since the OP has asked for a specific location... We could set it up in the lowest level of a nuclear waste storage facility. That way, when the Goa'uld send in their troops, we don't have to fight them. We just let them cook in the radiation for a while, then send in a properly shielded team to recover their high tech weapons and armor. --- Edit After Change of Heart --- I originally wrote this with a tongue-in-cheek attitude, imagining a reboot of the Stargate franchise where the characters came to this conclusion, causing the long-running multi-thread storyline to reboot into a single episode, half hour short with no hope of a sequel. But the more I think about it, a nuclear waste disposal site isn't a horrible choice. Operate the Stargate as in the series, but keep it housed in a properly shielded, lead-lined chamber within the basement of a disposal site. Then, should the enemy ever establish a stronghold, you can press a button which slides the shielding out of the way and cook the invaders. [Answer] Area 51 :) You need a place that: Won't raise too much suspicion. Would need to be underground, otherwise it's visible from space (Russian/Chinese/North Korean Satellites) Would need to be defendable, and self destructible. As such a military base somewhere in the desert would work. I see most people talk about high people traffic, but we have no idea what happens inside a military base, so as such, having say 20 teams of 4 people embarking on missions + 100 more for backend operations doesn't seem too much. And as long as you have them mostly on base, there's not much traffic going in/out of it. [Answer] Since it is very likely that you will have to nuke the structure at some point, I would place it in an a-bomb testing area. As the Bikini Atoll seems to be too far away from the US mainland, I would suggest the Nevada Test Site <https://goo.gl/maps/pKn879JW8iJ2> which is very close to Area 51. That way you could use a restricted area that can easily be connected to existing infrastructure and when you have to nuke it, you could say it was another test or part of an old bomb which didn't detonate. [Answer] Thinking from the alien invasion point of view, I'd want to put it somewhere that's a long way from civilisation and is surrounded by open, barren terrain. Some options would be: * The desert - some people have already suggested Area 51, but how about on a bombing range? Lots of reasons for people to come and go, lots to stop people from wanting to go there - and if it all goes badly wrong, a plausible reason for a B52 to be scattering JDAMs around as though they're going out of fashion * The sea - how about an oil platform or similar? The [Sea-based X Band Radar](https://en.wikipedia.org/wiki/Sea-based_X-band_Radar) would be a good example; perhaps it really is the real location of the Stargate [Citation needed]. You could even use submarines to get too and from it. ]
[Question] [ I am writing the lore for a currently in-development open-world freediving adventure game and am stuck with trying to keep some things scientifically founded. Overall the game style is closer to realistic than to stylized or cartoony (it's a 2.5D game to make this feasible in a small studio) and the lore should fit this atmosphere. The Setting The time period would be a couple of decades into the future. Mankind has made universal progress, including some artificial, biological enhancements to themselves, but with 10 billion people they do not keep the oceans clean by any means. Warming and souring of the ocean has also drastically influenced its food chains. Base of the game lore is a number of similar species of sirens coming out of hiding from the depths of the ocean as that got further polluted by humans. While not willing to communicate with anyone at the surface, they seek to reclaim the sea and forbid humans from traversing across the surface, let alone diving deep. The Sirens abilities/technology They are a sapient species with a generally inferior level of technology and possibly magic (albeit in terms of magic I'm mainly thinking of body-enhancing "natural" compounds which the player can later use as well). Their main perk is agility and eyesight/echolocation underwater, making even just rapier-style cutting weapons rather efficient. Using the thousands of water mines humans have deployed over the decades as well as natural resources, they can craft sufficient explosives or corrosives to sink ships and submarines especially after learning of weak points. Furthermore sea life is clearly on their side (or they breed and train it), allowing them to deploy areas of fish and jellies for alarm/scouts + passive defense and sharks as deadly guards (not as offensive attackers since RL sharks already suffer enough under their reputation as bloodthirsty killers :( ). The Lore vs Gameplay Problem Yet with that background of not making the Sirens absolutely overpowered, organized teams of Navy Seals or similar equipped with scuba/rebreathers would have easy game defending themselves and counter attack at least in the Epipelagic Zone (above 200m). Specially designed agile submarines with omnidirectional defense capability (instead of just stealth like today) could go even deeper. What I am aiming for the game though is that less organized and peaceful freedivers (biologically enhanced to be mostly proof against diver sickness and pressure) are the ones who will manage to discover secrets regarding where the sirens come from, what they truly want and eventually lead to some form of resolution. The gameplay shall be in the direction of Subnautica: Always having to take your air into account and you are able to make air pockets with slow air-generators to secure progress. Best solution to achieve this would be to make any form of high pressurized air supply (as gear or in submarines) mostly unusable. How to explain that without taking the game fully into magic territory is my problem. It always irked me in Subnautica why you don't have proper scuba tanks. Sure the "on board" compressor on your suit might be technologically limited, but you'd still bring a regular tank at very least for emergencies which can be refilled at a full size compressor at a base. I'd like a more proper solution with potential for gameplay elements (like providing POIs). My Thoughts/Ideas One thing that crossed my mind would be the sirens possessing a type of crystals or technology that emits a radiation which mainly affects pressurized oxygen, similar to how supposedly microwaves only heat up water. But turns out that on its own, is a myth - it's not how household microwaves actually work. Further notes * The land dwellers do need to send humans when they see the situation as a war (which they will, because transporting goods across the sea is as important as today). The issue of wireless transmission being very limited underwater has not been solved, making drones easy targets due to their cable and AI has not progressed further enough to truly replace humans for underwater missions (small AI drones will be partners for the protagonist though). * It does not necessarily need to be an absolute exclusion of scuba gear for everyone. The freedivers will just have a higher chance to not immediately incite aggression by the Sirens as at least some (probably one of the species) will recognize that humans who dedicate themselves enough to dive without gear do actually care about the well-being of the ocean and could be friends like dolphins are. * I am okay with toning down human ingenuity. Like surely one could probably think of drone-swarms that maintain a short-range network via ultrasound to be controlled from the surface without cables and if pressured O2 is really the weakpoint of scuba gear, there are chemical and electrical ways of generating O2. The game isn't at all about military tech however. Yet I would like to prevent the player from getting the obvious feeling "all this would be so much easier with scuba tanks and some spear guns; no human would risk doing this freediving". Am happy about any suggestions! Huge thanks! [Answer] There are a number of qualities that make free diving preferable over scuba for tasks that can be accomplished in the small number of minutes a free diver can remain submerged. First, free diving is, well, free. There were still places at least into the 1970s where free divers harvested pearls in water up to 30 meters or deeper, without fins or full-face masks, using simple stones for ballast (the rock drags you down, you let go when you're ready to go back up) and eyes-only goggles with pressure compensating squeeze bulbs attached (to prevent the goggle pushing into the eye socket), plus nose clips so breath need not be wasted to prevent water invasion. Given a free diver can train to stay down for more than five minutes, and using ballast can descend more than fifty meters in a minute and still have time to work and surface, diving with either snorkle, mask, and fins or even without that much assistance is very practical for tasks that can be divided into time segments and for which the same workers will stay on the job for years at a time. Additionally, free diving has fewer hazards related to pressure than SCUBA -- one need not exhale continuously during ascent, is at far less risk for decompression effects and will not encounter oxygen toxicity or nitrogen narcosis. And the limited equipment used (if any) is inexpensive compared to tanks, regulators, and high pressure compressors or paying for tank fills. [Answer] ## Stealth Man-made materials like metals, plastics, and ceramics have very distinct qualities that allows Sirens to immediately identify submarines and scuba gear from miles away. It's so distinct if you were to try to use subs or scuba gear, you would immediately be swarmed by thousands, or maybe even millions of Sirens and thier aquatic allies. However, a human is made up of more or less the same stuff as sea-lions and dolphins; so, unless they get really close to a free diver, they can't actually tell that they are dealing with a human. This lets free divers pass mostly undetected through the water attracting no more than the occasional curious observer. Also, if getting out to sea is important, perhaps these free divers could use small wooden boats like canoes so that they just look like driftwood. [Answer] There are several major issues with deep diving: [narcosis](https://en.wikipedia.org/wiki/Nitrogen_narcosis), [acute oxygen toxicity](https://en.wikipedia.org/wiki/Oxygen_toxicity) and [decompression sickness](https://en.wikipedia.org/wiki/Decompression_sickness). The specific details of each aren't necessarily important here, only to note that they are all caused by breathing high pressure air. Diving mammals don't actually need to breathe high pressure air... indeed, the deepest diving mammals breathe out before going down, to allow their air spaces to collapse flat. This subject has been covered in more detail elsewhere (here's one of my answers to [Are Air-Breathing Merfolk Viable?](https://worldbuilding.stackexchange.com/a/165725/62341) to get you started). Your bioengineered free divers can do long deep dives thanks to various blood and muscle modifications, and are much less vulnerable to various problems that people diving with scuba gear or rebreathers would be (but not necessarily immune... see [taravana](https://en.wikipedia.org/wiki/Taravana) and the [many kinds of freediver blackout](https://en.wikipedia.org/wiki/Freediving_blackout), etc). > > Best solution to achieve this would be to make any form of high pressurized air supply (as gear or in submarines) mostly unusable > > > Submarines don't actually use high pressure air, because that's a hazardous environment for humans and technology. They have very sturdy pressure hulls that can keep the water out and maintain regular air pressure in the habitation sections. Remotely operated or autonomous underwater vehicles neededn't have any air in them at all. You'll need a different excuse for those, unfortunately. You'll also have to think of a reason why depth charging a hostile underwater intelligence (up to and including the use of nuclear weapons) is not considered. This might be as simple as highly effective weapons built using electroceptive animals, perhaps as suicide attackers, that are attuned to the strong fields of electric motors, but not mere muscles and nervous systems so as to avoid attacking sea life by accident? [Answer] # Anti-tech organisms: Your Sirens have evolved organisms to combat humans - not human organisms, but the technology they possess. Plastic-eating bacteria thrives in the polluted ocean, and any plastics or rubber rapidly degrade. Metal-sniffing explosive sharks patrol the waters, ready to ram any ship or human artifact. Planktonic jellyfish have been been evolved to adhere to glass, metals, and plastics, rapidly blinding anyone with a mask. Then the jellyfish send a chemical signal to attract predators and other things made to degrade human tech. The sirens quite rightly assume that humans are hamstrung without their precious gadgets, but weren't counting on humans actually improving their species. So they haven't developed things that directly attack humans. They must rely on good old-fashioned weapons to kill denuded humans, instead. [Answer] #### Divers can perceive like the fishes through the skin It is dark deep down and often a little bit of silt raised by the stormy sea can drastically reduce the visibility even close to the surface. The divers through the skin can feel the small vibrations in the water. They can perceive anything even small fishes approaching without looking in that direction or seeing it through the muddle. The drawback is that they have to abandon the safety of the wetsuit. But actually by abandoning the wetsuit they also gain some agility. #### The bubbles disguise their position The bubbles coming out of the regulator are noisy. Not only they reveal the position of the diver, but they also identify them as a stranger. The rebreather that does not leave a bubble trail behind is not fit for deep dives because it would not be possible to regulate the internal pressure, or at least you would need a compressor that would suck out exhaled air and store it in another pressure tank. #### Storing oxygen in the muscles is better As others pointed out when you rely only on the oxygen transported by the blood when you dive has some problems. When the pressure increases and nitrogen and carbon dioxide dissolve better in the blood a lot of new dangers appear, like narcosis or decompression sickness. Storing oxygen in the muscles like other deep diving mammals do is way better. [Answer] The sirens are hopeless against real organized action. Various types of underwater munitions can be designed that destroy and debilitate them, nuclear submarines will completely overpower any resistance. Consider how much money and effort countries spend to keep marine life from dying. They can wipe the sirens out easily, especially in shallow places where free diving is an option. The sirens must be a small enough threat that nobody with real equipment wants to bother dealing with them. There are several ways to expand this space: * SCUBA is highly regulated. Why don't modern humans buy a lot of guns to defend themselves, take steroids to be stronger and take amphetamines to be smarter? The government doesn't like it. Just say that in your world, some stupid moral panic has led to a situation where only the very-wealthy or well-connected are able to acquire SCUBA gear, and everyone else is stuck diving. Or perhaps there is a sea war going on between human powers and all SCUBA is reserved for use by the military. * The targets are poor. Full SCUBA gear is expensive, and there's a lot of costly maintenance you need to do. It's not as bad as, say, owning a plane. But it's prohibitive for a working class person, especially in developing countries. * Conflict with sirens is over-regulated or illegal. Therefore ordinary people don't want to deal with the lawsuit that follows. People who are already criminals with no standing in society don't care, as they have little to lose. Perhaps they are actually poachers. These people cannot afford or are not permitted to acquire SCUBA gear. Or being caught with SCUBA gear would incriminate them. * Because of sirens, demand for SCUBA gear is high in wealthy countries and they cost a lot more than in our world. This is more convincing as a temporary thing, as eventually you would expect supply to catch up and drive prices down. * The sirens are ancestral enemies and for religious or cultural reasons, the divers consider it dishonorable to not face them unaided. Maybe there are even laws preventing "unsportsmanlike" methods of fighting them. This is a situation similar to hunting in many places, where you need a license, training and only some methods are permitted. People do it for sport, not out of necessity. * The sirens are irrational. They use some kind of weapon that specifically targets SCUBA. They fail to display the same ingenuity in developing weapons against freedivers (because that would make them overpowered). I dunno, maybe a magic fish that goes and cuts the SCUBA hose, but for some reason it just won't slice the carotid artery. Maybe a giant magnet that pulls all the SCUBA tank in (although the player would wonder why they don't make polymer tanks). Or maybe they're a degraded civilization that no longer remembers how to make future-tech artifacts, and their ancestors so happened to leave them only anti-SCUBA devices and nothing anti-freediver (or anti-nuclear sub). * The sirens live in some kind of narrow cave complex with tunnels just wide enough for a siren to squeeze through, and sirens are similar size to humans. Thus a human with a SCUBA tank cannot fit into many of these tunnels. Note that you have to be careful here because you could just tow the tank behind you - so you should combine this with one of the other options (eg. divers are too poor to buy the less common towable tank). This does go with the idea of exploiting air pockets. Also, since when does Subnautica not have SCUBA tanks? Obviously they are more advanced given that it's a far-future world with colony starships, and I assume decompression sickness is omitted to keep gameplay simple, but <https://subnautica.fandom.com/wiki/Ultra_High_Capacity_Tank_(Subnautica)> sure looks like a SCUBA tank to me. [Answer] You could just make the freedivers too poor to acquire the diving equipment that exists. Though you would need some way to how they became biologically enhanced without being able to pay for it. This could be perhaps be explained away as simply being hereditary once applied so they could be enhanced due to the circumstances of their birth without ever having paid for it. [Answer] Perhaps it could simply chase them away: * Scuba gear makes humans look like monsters, so the sirens wont go near anyone wearing it. You'll never even see them. * The military have secretly been attacking the sirens for years, so the Sirens hide from anyone wearing it. * The sound (or bubbles) of scuba gear is frightening because it disrupts the Sirens echolocation. None of this completely removes subs/scuba divers, so the gameplay may have to rotate around a group of people who learn to co-operate with the Sirens, and take on the techno-industrial empire/military etc... Kinda cliche, and not quite what you had planned, but it means your enemies near the end can be the human military! Or perhaps these ideas means that a special ops team operating without scuba gear can be much more sneaky and successful that regular frogmen... ]
[Question] [ Closed. This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49). Closed 4 years ago. [Improve this question](/posts/151853/edit) > > tl/dr: The zombies are coming. The first will "show up" in two weeks. I > have about $3000 to prepare and my plan is to hide in my home for as > long as possible. I need to secure my house, buy food and supplies, and make any necessary upgrades. I figure that ability to buy food/water will be my biggest limiting factor. What can I do on my budget to maximize the time my wife and I can hide out, and how long until I have to start scavenging? My goal is to hide for a few months, after which all the zombies will hopefully be dead. > > > The zombies are coming. Only I know it. Trying to convince anyone else will be a fools errand, and will waste the two weeks I have to prepare. These will be "28 days later" style zombies - fast and very dangerous, but they need to eat and will start dying on their own if I wait long enough. That's my goal: to wait them out. I certainly don't want to risk a fight with any of them. Here are the details: 1. I live in a typical suburban neighborhood in a medium-sized US city. There are roughly 500,000 soon-to-be zombies in the city around me. 2. My house is average - 3 bedrooms, 1000 square feet (100 m2), one car garage, and a fenced in backyard 3. Walls are plenty strong, windows and doors are not and must be secured. 4. The fence is a standard 6-foot (2 m) privacy fence and in good shape. It should be secure, as long as I don't attract an entire horde of the undead 5. The backyard gives about 0.25 acres (1000 $m^{2}$) of arable land. It is currently all grass. I can't decide if it is an asset or a liability. 6. My wife will be with me. She certainly isn't going to believe me, but I can convince her to not leave me for two weeks. She isn't going to help me prepare, but once the zombies show up she'll obviously be on my page. 7. Power and water will obviously be turning off soon after it starts. More importantly though, my toilets will stop working. That's going to be a large problem that I'm not sure how to deal with. 8. My finances are crappy and my mortgage just came out of my bank account. My next paycheck won't show up until Z-Day, so it's useless. I'm going to drain my checking and max out my credit card, but that will only get me about $2000. I can pawn some stuff for another grand. That's all the money I have to prepare. 9. After a couple weeks the zombie population will reach peak numbers, and start to decline. They'll be around for a while though as they pick out all the other survivors that don't hide as well as me. After 2 weeks of population explosion their numbers will start to half once every ~3 weeks. I'm hoping to stay in hiding for at least 12 weeks. 10. I want to avoid excessive rationing. The longer I stay in hiding, the safer it will be when I emerge, but if I've been on a starvation diet for a couple weeks and happen to run into a zombie, I'll definitely be a dead man. 11. Since this will hit quickly, I expect there to be plenty of room for scavenging once I emerge. As a result the goal is literally just to hide for as long as possible. If I can stay in hiding for a few months I should be okay after that. What's the best way to use my resources, and how long will I be able to stay in hiding? Will I be able to stay in hiding for ~4 months? [Answer] You have several concerns and the limiting factor here is money. We'll have to assume you're a handy person and can do your own installations. ## 1. Security. You want to buy a [security screen door](https://www.grainger.com/product/19N880) for each exterior door of the house (or at least one for the front and one for the rear and you can seal off side doors). These will run you about $300 each, but you can sometimes find them used, especially if you don't care if they are an exact fit (as long as no zombie hands can reach through, you're okay) and aesthetics. [![enter image description here](https://i.stack.imgur.com/ikpfS.png)](https://i.stack.imgur.com/ikpfS.png) Window bars aren't that expensive, but they will add up fast, depending on how many windows you have. [This 3x4 foot one](https://www.lowes.com/pd/Gatehouse-36-in-x-48-in-Black-Magnum-Window-Security-Bar/50015600) is $34. Again, they're often available used and do check your local junkyard or recycling place. Exact fit is not important. [![enter image description here](https://i.stack.imgur.com/cQT2r.png)](https://i.stack.imgur.com/cQT2r.png) Your fence is going to be the more expensive issue. It's in good shape but privacy fences are easy to climb and to break through. It depends a lot on how resourceful, agile, and desperate the zombies are. Can they get and use ladders? Move large objects to the edge of your fence and use them to get over? Can they just stand on top of each other? They may not bother someone with a fence in the beginning, but as they start to die off and their lack of food makes them more desperate, they are likely to take more extreme measures to feed. Securing the entire backyard is not possible on your budget (and timeline). Instead, put your resources into creating a cage out of chain link fencing (or similar fencing used in zoos and kennels) around your back porch/patio area only. Don't forget to fence in the roof of this extension. [![enter image description here](https://i.stack.imgur.com/jg1PE.jpg)](https://i.stack.imgur.com/jg1PE.jpg) This will protect your washing water that doesn't fit in the house, other large supplies, and your cooking area (and your toilet area if it's needed). Note that your security is to 1) keep out zombies, and 2) keep out other humans. ## 2. Food. This is easy. Go to [Grocery Outlet](https://groceryoutlet.com/) or some other discount place and get lots of shelf stable food that doesn't need cooking. Cans of beef stew, tunafish, etc. Things that are cheap and high in protein and calories. Consider also [restaurant supply places](https://www.restaurantdepot.com/). The prices are super cheap for a lot of things and most of them let you shop once without a membership (at my local one, membership is free but you have to have a business tax ID or other proof of a business, which does not have to be a restaurant). Make sure you don't buy anything that is perishable after being opened if you can't finish it before it goes off. Buy bags of beans and rice and dried peas and lentils. Fresh vegetables that easily keep a couple months without refrigeration: carrots, potatoes, onions. Dried fruit, jam, etc. Give yourself a variety. Stock up on cooking oil and herbs/spices. Make sure there is plenty of salt. You don't want to starve and you don't want to be tempted to leave the house. Buying in bulk is fairly cheap and there are places that sell stuff cheap because the labels got damaged or the manufacturer changed the packaging design. ## 3. Cooking. Camping stoves are cheap (a [heavy-duty single burner one](https://www.webstaurantstore.com/backyard-pro-square-single-burner-outdoor-patio-stove-range/554BPSQ16.html) that connects to large propane tanks is about $38), these are available used or sometimes in thrift stores (test them!), and run on propane. An [empty 40lb tank](https://rads.stackoverflow.com/amzn/click/com/B00005OU9D) runs about less than 100 bucks and holds just over 9 gallons of propane. Fill it up for 18-36 bucks. Buy several tanks. The above stove with the above tank will last for about 15 hours of cooking. But that stove is very strong (55,000 BTU) and is suitable for boiling large pots of water, making pots of beans, etc. Have a smaller camping stove as well for tasks like heating up small amounts of water and food ([this double burner one](https://rads.stackoverflow.com/amzn/click/com/B00005OU9D) runs $43). These only use more like 10,000 BTU per burner. So your tank will last for about 135 hours. If you already own a charcoal grill, you can use that too, but the smell will broadcast your location (especially to hungry and desperate humans) and it must be used in the backyard, which may not be possible after a while. Buy a big aluminum pot for boiling water and etc. Thrift stores and garage sales will have these plus camping stoves for cheap. ## 4. Water. Drinking water will be okay after a few weeks in opened containers, but buy purifying drops just in case. If your water is chlorinated, it should be okay to put tap water into old water bottles and close them. You can also buy sealed bottled water, but it tends to run about $1/gallon. For handwashing water, use tap water to fill up large empty drinking water containers with spigots. Enlarge the vent hole on top until you can get a funnel in there. I do this for camping and it works great for hands and dishes. [![enter image description here](https://i.stack.imgur.com/eSici.png)](https://i.stack.imgur.com/eSici.png) The standard is one gallon per person per day. Two people for 4 months is 240 gallons. About half of that should be sealed drinking water. The rest can be potable tap water in clean closed containers. ## 5. Sanitation. Find used wading pools that do not have any leaks and fill them all in your yard with the hose. This is your water for bathing, cleaning, dishes, and sanitation. You can do a final rinse of dishes and stuff with drinking water if needed. Have buckets of various sizes. Your toilets will still function!! The only thing that will be missing is the incoming water to fill the tank. And it might not even be turned off. If it is, know that all you need to flush your toilet is 2 gallons of water quickly poured into the bowl. You can fill the tank itself but just pouring into the bowl is probably more efficient. Test this out before the zombies come because you want to know which works better for each of your actual toilets (they're all a bit different). As a backup, get two chamber pots (so you and your wife don't have to share). And dig a hole in the backyard and cover with plywood. You can have a squat toilet or just use the chamber pots and empty them. Have a smaller hole nearer the house (in your outdoor security area) if you can no longer use the backyard. Make sure some of the washing water is reachable (fill your bathtub and also containers in the house). You can stay clean enough with bowls and washcloths but also consider a solar shower. They run about $20. Buy a case of two of toilet paper at Costco. Have plenty of dish soap, hand soap, etc. Cheap clean towels. A clothesline outdoors and one indoors. Stoppers for your sinks to use them for washing (the drains will still function). Don't get behind on laundry before the start of this mess. Keep dishes washed and don't let them pile up. # 6. Conclusions. Yes, you can have enough food, water, and sanitation with your budget and setup to last you 4 months. The issue you might not have the money (or prep time) for is security. But if you plan that you may lose access to your backyard and just secure the doors and windows of the house itself, you should be okay. Ideally you should have a back patio area secured as well. You don't have the money (or time) to secure your entire backyard but you should have access to it for a short time at least. It is best to do your cooking and toilet needs (if the house toilets stop draining) outdoors and water storage is better outdoors as well due to space. But you can do it all inside if you have to. [Answer] Water and Food: These are easy. Spend \$60 on a Costco membership and you can get a pallet of spring water for \$360. That's enough water for you and your wife for 8 months if you use it for nothing but drinking. Then stock up on non-perishable foods that don't need to be cooked. Beans, canned fish (in oil for extra calories), nut butters, crackers, and protein bars should be your staples; high calorie and nutrition density for low cost. Let's say you spend \$1000 on food, we can round your food and water bill to $1400. Fortification: Both Lowes and The Home Depot have an in-store credit cards. Assuming that your credit is decent, you should be able to open one at each store and max it out in the same day. By the time the first bill comes due, civilization will have long since collapsed. So, I'm giving you a bonus budget of \$2000 for construction supplies. I'm assuming your home is two stories plus a basement and attached garage. Your Lowes mad money should be enough to board up all the windows and doors on the ground floor and basement. Board up most of the windows on the second story as well, but leave one openable. Store a ladder near this window. You can lower it when you need to access the outdoors and raise it when the Z's are nearby. This is your only ingress and egress. On the ground level, have one board at eye-level on each door that can easily be removed and replaced from the inside. This is your Zombie-Killing Hole. If Z's start knocking on your door, open the ZKH and stab them in the brain with a long-handled melee weapon to silently kill them without attracting the horde; you don't want the first one to attract others after all. I recommend [this harpoon](https://rads.stackoverflow.com/amzn/click/com/B06XYV5NB8) from Amazon for \$150. You wouldn't throw it, just stab with it, although the retrieval rope will be useful if you make a non-lethal hit and a Z starts to retreat with your weapon embedded. To have a few spares, spend \$450. Waste removal: Convert your garage into a [ventilated improved pit latrine](https://www.open.edu/openlearncreate/mod/oucontent/view.php?id=207&printable=1). This will be your most complex construction job, but you should be able to complete it in a week and it will last 6-9 months without needing to be emptied. You'll need to rent a concrete cutter and possibly a mini-excavator from one of the hardware stores, and you'll need some pipe, mesh, and concrete, but you can put all of this on your in-store credit cards (see above section). So, the overall cost of this is \$0. Sanitation: Forget about showering. The less water you use, the longer you can stay holed up. On Amazon, you can get 5 gallons of sanitizer for \$100. Use this as needed to wipe down the smelly bits. You'll also need to drop about \$30 on enough toilet paper for 4 months and another \$30 on sanitary products for the missus, assuming she is pre-menopausal. (Get pads, not tampons, as this will lower the risk of an extremely inconvenient infection, given that cleanliness will be low). So your sanitation budget is $160. Heat/Comfort: You haven't given us the location of this disaster, but assume that in 4 months you will see some cold weather. Pick the smallest room on the second floor (NOT the room with the egress) and line it with insulation using your hardware store money. REI has an in-store credit card. Open that and max it out on a heater and all the propane you can get. This will only be enough to run the heater for 120 hours, so you will have to use it sparingly. If you expect a lot of cold nights, you can spend some real money on propane, but I'm going to assume that you will ration it instead. With the added insulation and every blanket you own in one room, you should be able to get through some cold nights with minimal added heating. \$0 spent. Entertainment/Communication: The first few weeks will be a flurry of activity, but after that it's gonna get BORING and you and your wife will start to turn on each other. A Kindle costs \$89, but you can sign up for 5 payments of \$18. Of course, you'll only ever make the first payment, so you can get 2 Kindles for \$36. Get a solar power bank for \$39 to keep them powered once the grid goes down. Then load both Kindles with all the public domain books you can; they're all free to download. Drop another \$50 on some [rechargeable lamps](https://rads.stackoverflow.com/amzn/click/com/B01K9HL200); it's gonna be dark with all the windows boarded up. Also spend \$25 on a set of rechargeable walkie-talkies. This way you can communicate from different parts of the house and alert each other of danger without shouting and attracting Z's. They will be especially useful once you start scavenging. Total: $150. All told, this accounts for \$2160. That means you have some wiggle room to go over budget at the hardware stores or REI. Or, you can get more food and paper goods and plan for an even longer hibernation. NB: You may be skeptical of all the extra credit I've given here. As evidence of my credibility, I will offer this anecdote: My identity was stolen several years ago and the thieves opened 11 in-store credit cards in 2 days and maxed them all out. I didn't find out until a month later when the first bill arrived - no red flags had been raised by the excess activity. The credit reporting system is not agile enough to stop this sort of thing from happening. I therefore believe our protagonist should be able to lean heavily on credit provided he has no reason to care about the consequences. [Answer] 1. Pay some punk kid to break your windows a couple of times in the night. Convince your wife that the only way to deal with this is to get steel grills over windows and doors. 2. Stock up on food and water. 3. Buy a camp stove and plenty of fuel. That's pretty much all you have to do in practice. Your limiting factor is entirely about how much food, water, and fuel you can lay down without your wife losing her rag. Though you'll only have to put up with the silent treatment for a couple of weeks. [Answer] # Safe Space You'll want to compact your living space into a manageable and small restricted area. I'd recommend your garage, an upstairs area/attic or basement. If you wife is not to keen on zombie-renovations, I'd select an area away from her daily activities, i.e. if she paints in the garage, secure the attic! As running water is not guaranteed, an area with a toilet is not required. This will become your new home for the next 12 weeks and you will need to cut your way out after it is all over. You will want to go down to your local hardware supply store and buy steel reinforcement mesh, wood planks, brackets and attachments (i.e. nails, screws, caulk and bonus points for welding machinery). If you are dealing with windows, it will also be good to obscure vision with tarpaulin to limit light and the number of curious zombies. With this, you will reinforce your chosen room to the point where even a human would need special equipment to enter. Here are some examples: * If you are in your attic, you may not even need this if there is a retractable ladder, just nail this closed and place a heavy piece of furniture over the access point. * If you are in a 1st floor room or garage, you may want to weld/caulk roller doors closed and attach the steel mesh across windows and doors. Cover all windows with tarpaulin. * Any weak points should be reinforced with the wood planks. Also use these for seating if you do not have any. Once your room is secure, you will want to divvy it out to 3 sections: * Sleeping quarters in one corner will include your bedding and clothing storage. * Kitchen area will include your food storage and equipment (can opener, spoons, bowls and cups). * Bathroom area will include large plastic bags in which you will do your business (and if possible, eject from the area entirely). Keep this area as far from the kitchen area as possible; put up tarpaulin as walling. # Supplies As you are in now trapped in a zombie-proof room, you will have to eat, sleep, p\\\* and s\\\* in a confined area. This could get very uncomfortable if the correct supplies are not procured: ## Water You will want around 2L of water per human per day. You and your wife? That's 170L of water for 12 weeks but you will want around double that if you want sponge-baths and a nice safety margin. Consider getting purification tablets as they are cheap and may be useful once you leave the confines of your safety box. ## Food Canned food is your new best friend! Canned beans, meats (i.e. beef, sardines, tuna), veges and fruits are all very cheap and will last a lot longer than 12 weeks. If you do not expect to be able to generate food easily after the 12 weeks, it would be wise to buy enough canned food to last at least a year. Along with this, you will want to bring a selection of seeds to start planting after the ordeal is over, bonus points for farm-able animals (chicken and rabbit comes to mind due to size). ## Toiletries Toilet paper, sponges, large plastic bags, disinfectant and cleaning supplies. Self explanatory! ## Weapons When you do eventually make it out, you will want some protection against any straggling zombies. Cheap options are pitchforks due to their excellent range and molotovs for their crowd-control. If you have the funds, a semi-auto shotgun with buck-shot will go a long way. Heavy leather/bike protection clothing from a second hand store will protect you from zombie bites and is very cheap for the safety gained. [Answer] This isn't a full answer. Just a little zombie-prepper advice which might augment other peoples answers... If your house is in a hurricane-zone then it probably has hurricane shutters or plywood that is ready to shield all its doors and windows. Tell your neighbors you are going out of town for a while and put them up "for security". If your house is in a tornado zone then hopefully you have a fortified basement or shelter. If your house has no inherent defenses, scope out the neighborhood for the best alternative. Publicly accessible buildings like offices and schools often have easily defend-able basements or storerooms. Package all of your supplies for easy transport and bring some locks and chains to fortify your hiding place once it is yours. [Answer] $3,000 is plenty of money to purchase concrete. If you have a basement, you could start by hand-pouring a simple "safe room". Any leftover funds could be used to buy non-perishable food. Surviving for 4 months in a bunker will not be fun, but is doable. ]
[Question] [ Monster Slayer Stan, we are in dire need of your help! The caves in our nearby mountain are filling up with a [dense but non-toxic gas](https://en.wikipedia.org/wiki/Argon) that is protecting a monster's nest. The monsters are weak but are hiding deep in the caves. We need you to go in and destroy their nest. In [another world building answer it states that people who breathe in argon have a risk of asphyxiation](https://worldbuilding.stackexchange.com/questions/76132/how-long-could-humans-survive-in-a-primarily-nitrogen-argon-atmosphere/76163#76163). With that in mind, how soon would Stan notice the environment was 95% argon? After breathing in that much argon and escaping, how long until Stan can breathe properly again? [Answer] Stan will not notice he is suffocating. He will pass out and die. Our need to breathe is triggered by accumulation of CO2. High levels of CO2, even with adequate oxygen, will provoke the sensation of shortness of breath and suffocation. In contrast (for normal healthy people like Stan), if there is not high CO2 you feel no particular need to breathe from progressively lower levels of O2. When your O2 gets low enough you just pass out. This is called shallow water blackout. <https://en.wikipedia.org/wiki/Freediving_blackout> > > Shallow water blackout which occurs when all phases of the dive have taken place in > shallow water (i.e., where depressurisation is not a significant > factor) and typically involves dynamic apnea distance swimmers, > usually in a swimming pool. The mechanism for this type of shallow > water blackout is hypoxia expedited by hypocapnia caused by voluntary > hyperventilation before the dive. Blackouts which occur in swimming > pools are probably driven only by excessive hyperventilation, with no > significant influence of pressure change. This can also be > described as constant pressure blackout or isobaric blackout. > > > This happened to me once from breathing helium to make my voice high. I blew out my air and breathed a lungful of helium and talked squeaky. When it was gone I took another breath of helium. Then I came to under a table. In this circumstance, Stan has argon instead of helium. Argon does fine clearing CO2 out of the lungs and so he will not notice anything wrong. It is a pretty good defense for those monsters. [Answer] With 95% argon (oxygen can be 5% or can be 0%), Stan would likely lose consciousness within a minute - without feeling any suffocation alarms. If he is somehow brought into the normal atmosphere, it will take him a few minutes to get back no normal, assuming there was no permanent damage to his nervous system. [Inert gas asphyxiation](https://en.wikipedia.org/wiki/Inert_gas_asphyxiation) is a more sneaky killer than typical (smog or excessive carbon dioxide) asphyxiation because a person does not feel much until losing consciousness. ]
[Question] [ This question is connected to: [Fire Resistant Fauna](https://worldbuilding.stackexchange.com/questions/11180/fire-resistant-fauna) I've been pondering a short story concept where a scientific expedition discovered a planet with a huge amount of both free hydrogen and oxygen in the atmosphere. This is caused by an unobtanium crystal widespread on the surface of the planet which acts as a catalyst, splitting water into hydrogen and oxygen and absorbing heat and sunlight to do so. (That heat then gets released back into the environment when the gases burn). The resulting atmosphere is highly flammable and as a result flash-fires are a common occurrence. These involve a burst of heat and flame and even mild explosions but are also over very quickly. Very fast-moving flame fronts sweep through the atmosphere, averaging at least one a day, but passing in a matter of moments. Water falls out of the sky in the aftermath of the flash fire and is then split back into oxygen and hydrogen once more by the unobtanium crystals. Assuming plant life has evolved to survive in these conditions what adaptions could they make to survive? On earth plants tend to either have seeds that survive or allow leaves to burn away and then sprout again. Neither tactic would be effective against near-daily fires though. [Answer] If the flashfire moves very fast, it probably will lack the ability to truly ignite anything. Depending on the heat, anyway. We had an experiment in chemistry class where a balloon full of hydrogen was ignited. Even at short range, it didn't ignite anything and could be safely done against the ceiling tiles and with peope in the room. Most likely, the flora would not adapt to be fire resistant at all; it would evolve to be heat-blast resistant. Normally I'd say a thin layer of water would suffice, but since the unobtanium crystals would drain it, it'd probably be some other coolant-like substance that can absorb the incoming heat. The best kind of plants might even use the captured heat for some kind of process. The most logical thing would be to use the captured energy to unfurl the plant's leaves to catch the falling rain. That would make most of the flora be dormant for much of the day, but when the flashfire comes, they all open up their leaves to catch the falling water. Which would probably be used in part to create a new layer of coolant-material. (Honestly I think the plant life should be more scared of the unobtanium crystals that will tear the water inside of them apart over the blast of heat) [Answer] In a flash burn, assuming that the heat isn't super intense most of the plants (and animals) would have some kind of heat reflective coating. Most of the IR band would be reflected. Humans can take some pretty large fire balls without burning up, just loosing hair and low burns. If it's a short lived burn then the protection doesn't need to be that much. I think going with dessert flora might be a place to start. Cactus have spines ,partly to keep away hungry animals but also the help shade themselves while at the same time have a small surface area to lose water and be subjected to the heat of the sun. So I think a lot of plants would have a lot of spines. I would also guess that plants with leaves would be much thicker, more like leather to be more heat resistant for short periods of time. Last some plants will have reactions like the Venus Fly trap, only faster, where they close up at the first hint of a fire storm, kind of like anemones. [Answer] There are fire resistant plants on Earth that you can model it after. Redwoods are pretty hard to burn. I recall seeing a video of a guy holding a blowtorch to a piece of redwood, and it not catching. I haven't found the video yet. <https://www.youtube.com/watch?v=BIWc8jntIl0> has a little information on redwoods. Also: Fire Resistance The high level of tannic acid in the wood and bark in combination with the thickness of the bark (6-12") help to provide a resistance to natural and man-made fires. The growth layer, protected by the thick bark, allow a healing process to occur after damage. If you want to go with an otherworldly answer, why do your plants have to be carbon based? Silicon based plants would be more fire resistant. Maybe plants that are carbon based but grow a hardened shell. Diamond is carbon, and you have to get it pretty hot before it'll burn. How about some kind of slime coating that the plants excrete that acts line a natural fire suppressant. It really wouldn't take much protection to stop something from burning during a flash flareup like you describe. If you take a normal sheet of paper, you can hold a match to the center for a few seconds with just a little darkening, but if you hold it to the edge of the paper it'll light right up. So maybe plants that don't have normal leaves where edges can catch easily. Leaves could be thicker and rounded to avoid catching easily. It seems like high pressure blast waves would be the biggest threat. <http://io9.com/hydrogen-explosion-vs-oxygen-explosion-which-one-wi-1529540558> Is a pretty cool video about burning hydrogen and oxygen versus burning either by itself. Your plants would most likely be ground hugging or at least very elastic to lessen the chance of being ripped apart by over pressure. <https://www.youtube.com/watch?v=G46oncRAaTQ> [Answer] The premise is a bit flawed to begin with. Firstly, the hydrogen concentration will have to get above about 0.04 atmospheres (assuming roughly Earth-normal oxygen concentrations); above that it will burn spontaneously. That's not a big problem. What is a big problem is that the combustion will be explosive. If ignition is rare, your plants (and animals) will be torn to pieces by pressure, not heat. To get an idea of how bad this is, we can take the result that we release about 32 kJ of energy per gram of water created ([see here](https://physics.stackexchange.com/questions/131168) and reverse the process). If the water would have started at 20C, it takes less that 3 kJ to get it to steam, leaving an extra 29 kJ to heat the steam to a toasty 15,000C if you could get it to stay put. Which you can't. From the Ideal Gas Law, pV = nRT and T just went up by 50x while n went down by 2/3 (2H2 + O2 = 2H2O), so your pressure and/or volume must go up by about 30x. Even with a dilute mixture like 4%, this more than doubles atmospheric pressure in a matter of a fraction of a second. So I'm afraid your plants will get blown to bits. If we ignore that, then any plant without thin leaves will avoid catching fire. Cacti, moss, succulents, tree trunks, etc., all fail to catch fire easily because of their high moisture content or thickness of their stems. (Tree trunks do not burn easily because you need a high surface area to let off enough gases to combine with oxygen; until your wood is really, really hot (e.g. in a fireplace for a long time), not enough gas gets out to sustain combustion.) If evolution has been going on for a long time, I'd suppose that most plants would have a clear mucous covering to absorb the flash of heat from the fire. If thick enough, it might even help absorb the mechanical damage of the explosions. [Answer] Lichen and other [Resurrection plants](http://en.wikipedia.org/wiki/Resurrection_plant) are probably the best suited to such an environment, specifically the lack of available water and resistance to flash-fires. It's likely that other plants would evolve alongside or parasitising the resurrection plants, perhaps plants coated in lichen, rocks filled with colonies of lichen, patches of moss that release CO2 when the humidity dips below x%, etc. Though as Erik said, the greater threat would be from unobtanium crystals in sand and dust falling on the plants and destroying their tissues. [Answer] Both your flora and fauna will have to be based on some very exotic biology, because it could not contain any water. Basic chemistry of life would have to be very different, so not sure how you can even define plants. Plants (defined as life form using solar energy) are not necessary at your planet, because crystals of unobtainium make the work plants do on Earth (capture sun energy to and provide sustenance to other life forms). On such planet, with plentiful free energy from oxidization of hydrogen, there would be very little advantage for slow sedentary lifestyle of plants. ]
[Question] [ > > Pacing back and forth in the war room, vice president Biden carefully considered his options. The fate of the world was in his balance. Sweat condensed on his brow, and time was running short. He clenched his fist around the handle of the stone, ran forward, and cast it across the ice. > > > "Sweep, Barack! Sweep like the wind! All our lives depend on it!" > > > While perhaps the American president and vice president wouldn't have been elected if the fate of the world was placed on a curling match, the match itself would likely contain less bloodshed than a war between hundreds of thousands of men and women armed with assault rifles and bombs. Animals and teen comedies have come to this conclusion as well. Bighorn sheep ram heads instead of murdering for the right to mate, and we've been told time and time again that high school wars should be fought in full padding on the football field. Could this same principle be applied to countries? The challenge I see is that many countries wouldn't want to abide by the rulebook, and if Putin flips the table and pulls a gun after Poroshenko beats him in the chess match for Crimea, we're back at square A1. (By which I mean the square that contains war, not Putin's rook.) Could a system be created in which countries settled their differences over a chess board or a tennis court instead of a battle field? What would such a system look like? [Answer] Personally, I can think of two ways they could happen, but it would take a long time to get to the point of two 'champions' competing. To begin we already have the Olympics and while that isn't really a decision maker, it is used by many to be a 'proving' ground, each country testing their best against each other. However, to actually have national decisions changed buy such, I think wars would have to get closer and closer to games. I can see this happening. First as life saving techniques increase and we get a near god-like life saving tech for all but the most serious wounds, real war might start to resemble Call of duty. Then as tech also increases and we begin to use robots it will start to look more like robot wars. With fewer and fewer actual humans on the battle front and fewer of them suffering permanent life ending or life altering wounds. It will look more and more like a video game. Eventually loss of life will be rare enough (at least for advanced Western societies) that it will be much closer to a game than a 'modern' war. I think as long as things 'evolve' along lines like this that it will have a chance to come about. Being a social convention that makes sense to everyone and all abide because it is the 'right' thing to do, it could work and be binding. Some random body just forcing the decisions on countries to abide by the winner of a game just won't work. Unless we start to believe in 'trial by combat' again. As in Celestial favor grants the win. [Answer] It cannot. Sports are guided by rules and referees, to be a fair competition. War is not fair by design, and you want to get any unfair advantage over the other guys, to kill as many of them as needed to assure your own victory. As the saying goes: point of war is not to die for your country, but to make the other guy die for his. To make such sport-like competition be a valid replacement of war, you would have such war-like conflicts to be repeatable, survivable by most of participants, and guided by honor code. So for instance american indians were honor-bound to die gracefully. And again, rules would be used if conflict is survivable by most participants. If none of your peers who could judge your behavior can survive, having your options be limited by rules does not give you any advantage (unless you strongly believe in payoff in afterlife). [Anti-Personnel Mine Ban Convention](http://en.wikipedia.org/wiki/Ottawa_Treaty) is not signed by 35 countries including USA, China and Russia, because it would limit military options in a conflict. Even [Geneva Conventions](http://en.wikipedia.org/wiki/Geneva_Conventions) (written after the war by victorious alliance obviously without consulting losing side), and still include controversies, like legality of "unlawful enemy combatants" being indefinitely detained. [Answer] You mean something League of Legends like? I'm neither a furtune teller nor an expert politologist, so everything I can give is a bunch of thoughts, more or less sensible... and the first one is that what you mean is a very interesting idea, and I'd love to see it deeply worked out. The first question seems to be like: how could this be enforced, and how could this develop? And I still think this system could develop, however under certain conditions. ## 1. How could this develop? Quite obviously, there should be either a major power enforcing it (like a superpower state, for example the US, or maybe a more powerful version of the United Nations, or maybe even a world government?) or simply waging a war should be a suicidal decision (since everyone hates war so much that waging it means you suddenly get completely isolated with literally everyone against yourself). The problem is that in the second scenario waging traditional wars would probably be substituted by economic wars (for example buying out other country's businnes, or laying down embargos, or what China now does to the Western world) or cyber wars (the NSA and the likes...) The tournaments option still wouldn't make sense. Granted, countries would be forced not to wage wars, but they yet wouldn't be forced to actually give out that Crimea to Putin for loosing a tennis match... Now we go to the second option. A powerful entity enforcing it. This would of course require an explanation how could such an entity (a country, the U.N., a world government) reach such a power, but that's a whole different story. The important part is: why would such an entity enforce that system? ## 2. Why would a super power enforce this system? * For moral reasons - "Stop bloodshed!" * As a way to channel aggressive desires of ambitious individuals (or somebody's frustration, or something...) that could otherwise challenge world peace or that powerful entity's domination * For fun, like the Roman Colloseum ## 3. Problems Of course the first problem is that if such an entity reaches such a power that it can enforce this system (and enforce every country to pay for loosing matches), why won't it simply rule the whole world with an iron fist of tyranny? There's no need for Colosseums in the 1984 world! These days massive invigilation of everyone starts to be possible, and this addinotialy bonuses all wanna-be tyrants. Given the NSA thingy it no longer seems absurd for a soft-totalitarian regime to evolve in Europe or the USA. So this ruling entity should either - be ruled by a man or group moral enough not to go in this direction AND strong enough to ward off any cabals, lobbys etc; or - limited by a strict constitution and strong democratic structures; or - strong enough not to be easily overthrown, but still weak enough to have to thing twice before opressing everybody on Earth. And then. Would it really enforce peace? Yes, countries woulnd't be able to wage traditional wars... BUT what about riots? People would not necessarily be content with sudden changes of their nationality, so social unrest could develop in disputed lands. ## 4. Moral issues Would it really have to be just a tennis match? Consider the following scenario: a super mercenary guild emerges. Most armies of the world belong of this guild, so it is the guild who enforces the system. Wouldn't it probably boil down to bloody battles, just controlled enough not to escalate out of the arena? Such a system would, of course, be plain immoral. And then. Imperialism would still be Imperialism, even in the Football match scenario. Countries would be probably obligated to accept challenges. So nothing changes - the stronger takes the weaker's property. The system is possible I think, you just have to have a super power that enforces it. I've mentioned problems, but these are only problems IMHO, not blockers. Sorry for the messy nature of this post, but I've been in a hurry. I'll clean it up and expand it tomorrow. [Answer] Native Americans would do just this (sometimes). Rival tribes would gather for days at a time and and play lacrosse to to decide which tribe would get a the land they were fighting over (as an example). I personally don't think this would ever become popular because I think humans as a species love violence. Sorry, it is what it is... [Answer] The only way this would work is if there were enough other people willing to oversee and enforce the rules to keep it safe. For example the Geneva convention works because most countries have signed up to it, and they are willing to help enforce it by taking action against people who break it. So if you had a situation with enough smaller countries that all sign a treaty agreeing to settle their disputes this way then it might work. If a country lost the game and then refused to honor their side of the bargain then all the other countries in the world would immediately start punitive sanctions and maybe escalate towards genuine conflict. The problem though is keeping people honest, getting everyone to sign up to it in the first place, and making sure that no single country grows strong enough (or convinces enough friends) to say "screw you guys, I'm doing it the old fashioned way". [Answer] ## Rule Keeper While there is clearly a need to enforce both the rules and the admissions of the victor, having a superpower be the authority just poses all sorts of problems. One potential solution is a more technological system. Instead of having something about war keep people in their place, have a punishment to cheating be built in. Maybe after every conflict, if the loser hasn't met some pre-determined conditions, the computer automatically detonates a bomb in their capital, or reduces food supply, or some punishment. If the computer in charge is sufficiently safe, you have an absolutely neutral judge, strictly bound by logic. Of course, setting this up in the first place would be the biggest challenge. Each nation would have to willing plant harmful measures, ensure that the other nations also followed through, and ensure that the computer is actually fair and secure. ## War needs a cost However, war should still have a high cost to a country. If not in life, then in something else, otherwise whichever country was the best at some arbitrary game would essentially rule the world. If you have the best chess player, and all conflicts are decided by chess, then you can request anything from anyone, any simply declare war, beat them and force them to acquiesce. Instead, add an economic cost. Say, every move in the chess game costs a billion dollars. Then, if it's extremely important, you can still wage war, but it's not something to be taken on trivially, and something you can't often repeat. Since economic power is usually the most important factor in a war anyways, this won't horribly shake up the modern geo-political landscape. [Answer] The way I see it, turning wars into games might be possible only in two situations (which are rather similar if you think about it): 1) The world is divided by an overwhelmingly huge superpower and a bunch of lesser countries small and weak enough to pose no threat to the superpower. Since these lesser countries can't put aside their differences, and since superpower doesn't want any bloodshed, they agree to some kind of war sport with superpower acting as a referee. 2) The world is the way our world is, but these crazy conspiracy theories are actually true and all governments are controlled by ~~crab~~ lizard people/masons/these creatures from "They Live"/etc. This controlling superpower doesn't want it's cattle/slaves/lesser pet creatures/(whatever they think of us) to go to waste, hence the global "make sport, not war" program promoted by all governments. [Answer] The population has to be so invested in the game that the practical disputes they're fighting for take second place. The disappointment of the game being cancelled has to be greater than the pain felt from the other side winning the war. Then and only then can war be replaced by sports. Additional conditions that make this viable: * Countries set up an effective enforcement mechanism beforehand. * Some larger power encourages it. * It's understood that there will be a rematch in the future. * Populistic governments use the bread and circuses as a distraction. * Profitable industries surrounding the games lobby for their continuation. How could this get started? One option is that politicians choose to settle some minor international dispute through a game as a novelty, and this proves unexpectedly popular, escalating into a way to resolve ever larger conflicts. [Answer] It can't If someone lost at sport, they're just as likely to resort to war instead with a surprise attack. The only way it could work is some overarching power enforcing the rules to prevent bad sportsmanship. [Answer] ## It won't At its root, "war" is when two countries are unable to reach a mutually satisfactory agreement on a dispute, and the dispute is of such importance that one or both can't let the matter lie, causing them to attempt to force a unilaterally satisfactory "agreement" through force of arms. Unfortunately, this means that neither side is going to be willing to resolve it through a fair contest, since that represents an unacceptable risk of loss. Both want to maximize their chance of winning. Thus, unless someone forces it on them, they aren't going to accept the outcome of such a contest. While there have been various attempts to regulate war over the years (most notably the Geneva Checklist Suggestions Convention), they aren't very well enforced. Uninvolved countries don't want to deal with the public relations fallout that comes from getting your own people killed in someone else's war. As a result, they mostly function as a way for the victor to express its anger against the defeated. Insofar as the laws of war are followed nowadays, it's mostly on the basis of Mutually Assured Destruction ("if you use napalm, I'll use napalm, and now it's [stuck](https://www.youtube.com/watch?v=iYPEo1BI3Mo) to both our kids.") [Answer] MAD Mutually assured destruction. Every country has nukes and bioweapons. Any war has a an almost inescapable chance of spiraling out of control. Any leader knows there is a high likelihood of their own death if they start a military conflict, the reach of the weapons is just too broad and their movements are too easy to track to at least the city level to risk escalation. With real war off the table a proxy is all they have so someone preposes using a war game, maybe a huge vr game. Perhaps each side using it a a simulation for a real conflict. The hard part is getting the game to matter, for that you need the populace to buy in, elect or remove leaders based on the game. hopefully your game is the most popular game ever. Hopefully you get politicians to latch on to this proxy to solve conflict. you still have problems with arbitration and rules you need your own UN negotiating rules. [Answer] ## Not realistically possible. Q: When do countries wage war? A: When one country wants something from another country that it is not willing to hand over, the two countries can't find a compromise to make it happen in a way both are satisfied AND the demanding country is ready and able to use violence to get what it wants. That last part is the important one. "ready and able to use violence". When that condition is met, no loss of a sports match will be accepted. Q: And when "the world" would make them accept the result by force? A: Then the demanding country is obviously not in a position to wage that war at all against "the world" that opposes the war, so there would be no war in the first place to be replaced with a sports match. The enforcing powers would rather decide the matter in the court and give the demanding country what they see justified and nothing more. Q: But maybe there is no single power that enforces that behaviour. What if every country has so many nukes, that they can't afford a war, since it would always end in mutual destruction? A: Then you would not solve anything with the sports match. * Country A demands area X from country B because it thinks it belongs to them * Country B refuses * Country A declares war. * Country B says: "if you take it by force, I'll blow us both from the map" * The sports match happens and Country A wins * Country A demands area X from country B because it is "we won the match" * Country B says: "if you take it, I'll blow us both from the map" * A: "but... but we won the match." * B: "good for you, now you have to claims to that area. And I ignore both. My nukes are still ready if you try something funny" * A: "... but we won..." * B: "rematch? We can add a third claim." Q: But if I still really really want that to happen? A: It's your story. Make it happen. Put a game crazed dicator in power of the whole world, that doesn't care for a just solution and only wants to see the countries pulling together the best players they can get their hands on and all the background play (bribing referees, assassinating MVPs...) followed by riots of the loser side which he brings to a bloody end. All for his regal amusement. [Answer] Another answer: Yes, there was a time for sport-like wars: knight wars in the times of chivalry. War was like a full-contact martial art, the knight defeated in the battle was honor-bound to go to the castle (after arranging his business in his home castle) of the victor to be imprisoned (but not in jail: sharing the feast with the winner) until the ransom for his freedom was paid. Of course, the courtesy was only for the noble-blooded: peasants, and their villages were destroyed. Knights considered themselves equal, and they were mostly relatives - it was like fighting over inheritance in our times. Such times lasted while armor was expensive, training necessary to fight in it was time-consuming, and the protection it offered was substantial. Time for chivalry was over when gunpowder democratized the killing: any peasant with little training and a musket could kill a noble knight. ]
[Question] [ The idea is that a population of beings have a superior claim over others for the privilege of oxygenated air in a city/large settlement. I wanted to make this work that the other residents in the city have less oxygen saturated air in the outskirts of the area where the tree or trees are located. How large would a tree need to be to sustain a group of 100 people with its oxygen production and how far would the reach be that others in the outskirts (let’s say 5000) would potentially need a breathing apparatus to survive? I had considered the idea of plankton as a generator of oxygen but I encountered the same issue as I’m querying now. I’m not sure of the volume that would be needed to sustain a population of 100, with a reach that would almost sustain 5000 with the air of breathing apparatuses. For added context this is a dark fantasy world, the population of 100 would be elves and the other 5000 would be of other fantasy races. [Answer] A small frame challenge: Scaling up a tree will not provide more oxygen, as, absent some new biochemistry, larger trees tend towards net neutral oxygen production, eventually becoming net oxygen absorbers before dying. This is almost certainly an absolute cap on volume of the tree, just as how far a tree can draw water up is an absolute cap on the height. This could possibly be circumvented by something like the quaking aspen, where there is a sort of cluster of trees all joined by roots. We generally think of old growth forest as a carbon store, not a carbon absorber, and part of this is due to tree age. There's some good research by the US forestry department on it, but I'm struggling to find it at the moment. However, if your giant trees have some form of highly efficient photosynthesis, all bets are off on size of tree. [Answer] From <https://space.stackexchange.com/questions/26668/how-many-plants-would-be-needed-to-produce-oxygen-enough-for-20-humans> – > > "A 100-ft tree, 18" diameter at its base... very roughly, seven or eight trees' worth per person" > > > Approximating a tree as the volume of a cylinder, πr²h, the typical tree mentioned above is 56.25π cubic feet. So for 100 people, the tree would need to be 700-800 times the size of a 100-ft tree, 0.75 feet radius at its base. 100 people would need a tree 42187.5π cubic feet. The tallest trees are about 320 feet tall, so if the radius is 11.5 feet, they will be big enough to provide oxygen for 100 people. Or taller and thinner, as long as r²h ≈ 42187.5 [Answer] Ultimately, the carbon cycle (between CO2 and food) is a closed cycle, so a tree or plant that can provide oxygen for 100 people could, if edible, provide enough food for 100 people. That should give an idea of the size required. It's a lot of broccoli !!! There are other sources of oxygen that rich people could use. Spacecraft and personal breathing apparatus use substances like potassium superoxide, that react with CO2 and moisture: 2KO2 + H2O + CO2 --> K2CO3 + 2O2 With our current infrastructure, people do not like living near power stations. In future, a solar, wind or hydroelectric power station might be used to split water into hydrogen and oxygen. The hydrogen could be used as a fuel directly, or used to synthesize more easier to store/handle fuels such as ammonia (in combination with atmospheric oxygen) or hydrocarbons (in combination with a source of CO2.) The oxygen could be dumped into the atmosphere, and in an oxygen starved world, this could make the area round a power plant an attractive area to live, perhaps even causing a city to grow around it. Of course, for an existing city, hydroelectric is the most conceivable type of power station, as it doesn't involve building a huge number of windmills or solar panels. The first city that comes to mind is Las Vegas, which is very close to the existing Hoover Dam. EDIT: I just noted this is a fantasy setting. But elves are smart, and if they are the only ones who understand electricity, other races would see it as no different to magic. In post-apocalyptic novels, rustic people give their awed views of advanced tecnology (without the author spelling out what they are.) For example in the Chrysalids a "fish shaped flying machine" is described (presumably a helicopter) and in the Tripods, heros from a rustic England move to a slightly less rustic France and encounter a machine called a "shmand fer" which is a railway train (French chemin de fer). I can't think of any other ancient industrial process that could produce vast quantities of oxygen. Perhaps some kind of precious metal refining. [Answer] ## 163,200,000lbs or 74,026,275kg plus 5% per year for everyone. ## Or 1 general sherman just for the elves. Assuming you have a way to contain the gasses. It takes six molecules of CO2 to produce one molecule of glucose by photosynthesis, and six molecules of oxygen are released as a by-product. A glucose molecule contains six carbon atoms, so that’s a net gain of one molecule of oxygen for every atom of carbon added to the tree. A mature sycamore tree weigh 4000lbs, including the roots and leaves. If it grows by five per cent each year. The actual calculation is a huge mess, big trees grow faster than small ones, see source below) so we are ballparking it. It then produces about 100kg of wood, of which 38kg will be carbon. Allowing for the relative molecular weights of oxygen and carbon, this equates to 100kg of oxygen per 4000lb tree per year. A human breathes about 9.5 tonnes of air in a year, (lets say elves are the same) but oxygen only makes up about 23 per cent of that air, by mass, and we only extract a little over a third of the oxygen from each breath. That works out to a total of about 740kg of oxygen per year. That is about eight 4000lb trees worth or 32,000lbs per person. So for a rough ball park estimate your tree should be at least 3200000lbs or 1,451,496kg or roughly 1 [General Sherman](https://en.wikipedia.org/wiki/General_Sherman_(tree)) just for the elves. But it also means the tree needs to grow by about around 5% or 160,000kgs per year. So start with 3200000lbs and then add about 5% per year it has been supporting those elves. keep in mind if those humans are using fire for anything, cooking, heat, ect. they need a LOT more trees. Now lets add in the extra people this is easy, 32000lbs times 5100, or 163200000lbs and again add 5% for every year it has been keeping them alive. <http://conditdatacenter.org/pdfs/StephensonConditEtAl_Nature2014.pdf> Note:I did get many of the starting number from a BBC publication I use in class about this. xerox of an article. But I don't know the original author is, if anyone does, please post in comments and I will add it. Just for the elves you need this. [![enter image description here](https://i.stack.imgur.com/vvFyc.png)](https://i.stack.imgur.com/vvFyc.png) [Answer] It seems small, faster-growing plants are a better bet than most trees. You might want to follow what [this bloke](https://www.youtube.com/watch?v=PoKvPkwP4mM) does. Reply to comments: Yes, it would be nice to have families live in a. single giant tree (I am thinking of Robert Silverberg;s 'Lord Valentine's Castle'). If we cannot find a single tree that fits the bill (and why would there be one - a tall tree has put a lot of effort into being tall and getting the sunlight, though genetic engineering could do anything) but you could have a second species like the [strangler fig](https://en.wikipedia.org/wiki/Strangler_fig) using the larger tree as a support. [Answer] I think that the tree would have to be really large with long branches and leaves, covering like 100 or 200 meters wide, each leaf double the size of a normal tree thus generating much more oxygen and maybe the same in height, i'm not a biologist but i'm pretty sure such a large and tall tree could produce lots of oxygen, I don't know how long the tree would have to be living in order to achieve such measures, maybe the soil where it lives is so nutricious that the tree grew 100x what a normal tree would. EDIT: After some initial research, i found out that generally speaking, a mature tree can produce oxygen at a rate of around 48 pounds per year. Therefore, a group of 100 people would need around 4,800 pounds of oxygen per year, which would require approximately 100 mature trees. Therefore maybe a tree that is the size of 100 mature trees would seal the deal. [Answer] ## How large would the tree be? Trees release O2 when they absorb CO2 into themselves. So, it's not a question of how big the tree is, but of how fast it is growing. One person consumes ~400L of oxygen per day which is ~17 moles. 17 moles of pure carbon is ~200g. So for 100 people, a tree would have to gain at least 20kg (not including water) per day. Done a second way to check our work, 1kg of coal is 7000 Calories. A person consumes about 2000 Calories per day, so a tree would need to gain about 1kg/7000Cal\2000Cal\100 = ~30kg per day. If a tree is 50% water, that means it must gain 40kg-60kg per day. This would also hold for bamboo, aglae, etc. ## How far would the reach be? Let's assume there is no wind. Oxygen in air has a diffusion coefficient of 0.176cm^2/s. In 3D, this gives a variance of 6Dt = 9 m^2 per day for a standard deviation of 3m. This means that after a day, 68% of the oxygen will have traveled 3m or less, 95% of the oxygen will have traveled 6m or less, and 99.7% of the oxygen will have traveled 9m or less. Your city would still have to block wind from blowing all of it away. [Answer] Most of the mature tree is not the living tissue. The substance we understand as "wood" is the dead tissue that still serves its function of water transportation and mechanical support. Hence your question simplifies to how many leaves per person do we need while the trunk and the branches must be such that these leaves still could be distributed acceptably, receiving enough of the sunlight. A single large tree is capable of providing the oxygen for [about four humans](https://www.usda.gov/media/blog/2015/03/17/power-one-tree-very-air-we-breathe). Hence your tree must have about 25 times more leaves as an ordinary large tree, placed such that they all receive enough light (the stem will deliver water). Up to you how do you arrange them. ]
[Question] [ I want to ape Ming dynasty China for my setting. Key points are that there's a big empire, several centuries old, but hereditary transition of power is practically non-existent. Instead, the country's youth is taking imperial exams, and the ones with the best results can join the bureaucracy and serve in various government positions. Now rich families are able to drill their children better and will have proportionally better odds at landing good jobs, but there's still plenty of social mobility; and nobody considers power extending beyond the borders of one's home as something given by birthright. The first difference with China is that the job on top is not hereditary either; the Philosopher-Emperor is a Plato-ish figure who is chosen from the wise people who have not become officers; the idea being that only someone not interested in rulership should be allowed to rule. And they're not a spiritual leader either, or a holder of the Mandate of Heaven, or something along supernatural lines. The position of Philosopher-Emperor is also considered meritocratic: someone gets it because they, individually, deserve it. And the second difference with China is that the country is completely multicultural. Of course there's multiple cultures in China but the Han are by far the majority. Here, there's one culture with about 25% of the people, a couple with 10-15%, and whole bunch of tiny ones; a few hundred in total, all of whom have no native language in common. New cultures are occasionally subjugated and become part of the empire; and every now and then a different culture becomes the dominant one for a few centuries, about at the rate dynasties change in China. This extends to religion too: there's a pluralistic approach to divinity in general. There are too many gods to count (with new ones joining the pantheon when a new culture enters the realm) and no one agrees on which one is the head god - or if there even is one. Multicultural countries have had quite a struggle throughout world history. Even in these enlightened times, ethnic warfare is common. One way to keep different people together is totalitarianism, but these are the Late Middle Ages; no secret police yet. And another is the concept of the divine right to rule - which is ruled out by the pluralistic religion. I'm not interested in making the empire into a democracy either. So why has this empire not fallen apart yet? What reasons can tens of millions of people have for trusting in a system, without the threat of violence in this life, or of suffering in the afterlife? I would be interested in historical examples of multicultural societies that did not consider their ruler divine, but any reasonable suggestions will do; I'm willing to suspend my disbelief a little Other factoids: * None of this has to be perfect. Some cultures are not as respected as others, the upper classes are rather corrupt and the philosopher-emperor is not nearly as wise as he used to be. The thing is that people can still believe they live in a meritocracy, and they don't have to be utter fools to do so. The empire just has to be stable for over half a millennium. * There is no 'state culture' (e.g. Han for China, Latin/Greek for Rome); there's just some cultures that are larger than others. Religions, languages, diversity is fine (perhaps even seen as moral). There is however a state philosophy/morality, supporting the whole ideas of meritocracy and pluralistic divinity. If a culture has a god who claims they are the only god, or believes in birth right, then they're laughed at. Of course that means that this is not perfectly multiculti, but as said it doesn't have to be. * The exams lean towards cultural agnosticity; they study a range of texts from different backgrounds. Honouring the many gods is also part of the curriculum - and so are skills such as calligraphy (there's only one writing system), mathematics/geometry, history, and the aforementioned state philosophy. The material can be called coloured by the ruling class but it is not solely about that ruling class; that's where my line is. [Answer] In a word, yes. In fact, it's more common historically than you think. Multiculturalism has become a political issue recently, but the way we are practising civilisation is far removed from history. Indeed, [European empires didn't last very long](https://foreignpolicy.com/2009/10/14/empires-with-expiration-dates/) compared to older ones precisely because they tried to enforce standardised customs upon a variety of far-flung subjects. The sort of diversity we see in ancient civilisation was survivable because of the high degree of autonomy enjoyed by subject peoples. Essentially, emperors governed by asking very little of local aristocracy: accept my authority, pay taxes, send soldiers, and do as you like. Romans didn't have much in the way of multiculturalism. Everyone wanted to be Roman, and as race as we understand it didn't exist, Rome was occupied by a variety of different Mediterranean peoples, who were accepted because they all wanted to be Roman too. This cultural uniformity enabled many different people to be at peace with each other. The ancient Persians hired many mercenaries from across their empire, often to the point of bankruptcy. One of their favourite types of mercenary, somewhat ironically, were actually Greeks (even during wars with the Greek city states). Persian nobility often preferred Greek bodyguards. Similarly, in Muslim empires Jews were known to ascend to the most senior ranks of the civil service, most notably in Muslim Spain and Ottoman lands ([Samuel ibn Naghrillah](https://en.wikipedia.org/wiki/Samuel_ibn_Naghrillah)). Religious diversity is also possible. Early Muslim Caliphates were cosmopolitan, because they enforced the protection of certain groups. Jews and Christians were regarded as "[dhimmi](https://en.wikipedia.org/wiki/Dhimmi)" (literally 'protected person') which meant that so long as they paid their taxes and accepted the supremacy of their Muslim leaders, they would be left to get on with life. This even extended to having their own courts to govern local affairs by their own legal standards without interference. In the Mughal Empire a similar thing happened, but the main difference was that a minority of Muslims ruled over a majority of Hindus, a group not usually considered dhimmi. However, many Mughal emperors concluded that actually Hindus were dhimmi, besides their polytheism, and that the jizya tax was more to do with Arabian history than Muslim theology. This contributed to an era of toleration where Muslim leaders sought debate amongst various religious leaders. Of course, it didn't last, largely because of the puritanical intolerance of a certain [Aurangzeb](https://en.wikipedia.org/wiki/Aurangzeb), a name infamous even today amongst Hindus. As you can see, there's many ways of handling the problem. But essentially, combining a legal concept of protection for minorities with a fairly relaxed attitude to regional governance, and a fair attitude to taxation (taking from surplus instead of total income), is usually a good start. This could be bolstered by a fashionable imperial culture, which encourages people to want to join. People don't ask for much: usually they don't want trouble if there is sufficient law and order, infrastructure, and tolerance. If minorities are not excluded from becoming part of the imperial elite, all the better. The problem with modern multiculturalism often stems from the legacy of a racist ideology which did not exist in the distant past. Sure, Romans took a very negative view of barbarians on the edge of their civilisation... but that prejudice didn't last if the barbarians wished to become part of the empire. The irony is it's probably easier to do than you expect, because the history of European empire is unusually fraught, and so we have an unrealistically negative view of cosmopolitanism. If you can keep [scientific racism](https://en.wikipedia.org/wiki/Scientific_racism) and religious intolerance out of the equation it'll no doubt help. In fact, this could be a realistic point of tension: the rise of religious intolerance often leads to conflict between groups who ordinarily are happy to coexist. The partition of [India](https://en.wikipedia.org/wiki/Partition_of_India) and [Ireland](https://en.wikipedia.org/wiki/Partition_of_Ireland) are good examples of administrative incompetence, institutional prejudice, and religious fanaticism culminating in violence and division. In contrast, the Mongol empire was known for its religious tolerance, partly because the shamanistic Tengri religion of the Mongols meant they didn't care for people outside of their tribal groups, because they understood their own faith as a personal relationship to the land of their ancestors. Missionary religions however have a tendency to create tension by insulting local traditions and threatening local power structures. [Answer] The Roman empire had a small bureaucracy at first which expanded over time in classical Antiquity and in the Middle Ages in the eastern Roman or "Byzantine" Empire. The higher positions in the government were usually reserved for aristocrats who would have been appointed partially because of their family connections and partially because of their merits and talents. The lower positions in the bureaucracy would presumably involve promotions through merit, more or less. In the Third Century (AD 201-300) during the Crises of the Third Century many common soldiers, most from the Balkan provinces, were promoted to officers and even to generals. And some of those former peasants then promoted themselves to Emperor by leading military revolts. In the fourth and later centuries that was less common but it still happened sometimes in later centuries. Thus that could be considered a form of promotion by (military) merit to the top rank of society. In the Roman Empire more and more provincals were made Roman citizens. Such provincals would have been more or less Romanized and so would represent both Roman culture and their ancestral culture to greater or lesser degree. In AD 211 basically all free born men in the Roman Empire were granted Roman citizenship, even though most of them were probably only slightly Romanized at that time. And a generation or two later a few of those new citizens managed to make themselves emperors. And this was 1,200 years before the fall of Constantinople to the Turks in 1453. In the Roman Empire it wasn't common for people to rise to the top through merit, because it was wasn't common for people to rise. Most people didn't change their station in life. But of course some people did change their station in life, and sometimes that involved promotion by merit. For example, a freed slave, Helvius Successus, in the Italian town of Alba Pompeia became wealthy enough to get his son Publius Helvius Pertinax (126-193), an education. Pertinax got an appointment as an army officer and got many military and civilian promotions, partially through merit. He became a senator and the governor of several provinces, and was consul twice. He became Emperor for a short time in 193, the Year of Five Emperors, before being killed. So presumably there was some era during the history of the Roman and "Byzantine" empires where the bureaucracy and army were large enough, and the empire was multicultural enough, for there to be a multicultural and partially meritocratic government. [Answer] Governments that to do not favor the ruling class and significant cultural diversity are mutually exclusive. > > ... the country is completely multicultural ... there's one culture with about 25% of the people, a couple with 10-15%, and whole bunch of tiny ones; a few hundred in total > > > > > ... every now and then a different culture becomes the dominant one for a few centuries, about at the rate dynasties change in China. > > > Meritocracy does not favor the ruling class because it makes power hard to hang onto. So, every single leader will have a personal reason to subvert the meritocracy and replace it with something that will make maintaining their power easier such as a hereditary monarchy. The only way to maintain a meritocracy for more than a few years is to have a powerful doctrine, like a constitution, that the vast majority of the population supports without question. In other words, the commoners have to be more loyal to the unifying doctrine that forms the core of their meritocracy than they are to anything else to ensure that leaders have no temptations they can exploit to get people to give up thier freedom of vertical mobility. When you have a lot of cultural diversity, tyrants find it much easier to get an otherwises unified population to give up on unifying doctrines in favor of their own egos. What often happens is that they begin by celebrating people's subcultures. At first it seems like a good thing, people will organize parades celebrating what makes them special, month's will be devoted to their culture's history, national holidays will celebrate heros that represent their heritage, etc. The problem though is that it makes people start to identify as their subculture first, and as national citizens second. This is ofcourse alway going to be followed by a natural push back. Now if you are a [your-subculture], it is no longer as important for your governor to be the smartest candidate, you want him to be a [your-subculture] too, because someone who is not a [your-subculture] can not possibly represent what makes you so special. When a [thier-subculture] becomes governor, suddenly the government stops sponsoring your religious/cultural events and starts sponsoring someone else's. These little slights will stack one on top of another which then leads to mass discrimination, which in turn leads to protests, riots, and even rebellions. Once a tyrant had gotten culturally different neighbors at odds with each other, they no longer want to identify as part of the same group as their rivals. Suddenly, the meritocracy starts to seem like a bad thing because now people see it as a way for people of other cultures to take control and oppress them; so, they start to fear it more than they care about their own ability to rise in station. At this point the tyrant starts to take on a more active approach. He will publicly condemn the riots that which he will privately help organize. He will blame minorities for all the chaos that he sows and claim he can make the empire great again by restoring cultural unity. He will offer to protect the majority from letting the minorities take over; so, when calls for the removal of the meritocracy, it will be welcomed by those who the tyrant promises to represent. By choosing the strongest subculture(s) to back, the tyrant is assured enough power to defeat anyone who opposes him. People will celebrate his victories over each minority, and they will ignore the abuses of his power that look like they are to subvert minorities, but that are actually to subvert the old supporters of the meritocracy. This same general pattern has been repeating itself throughout history at a rate far too often to think that a culturally diverse meritocracy can last as long as you are asking about. ## How close can you get? The United States is probably the best model for a stable multicultural meritocracy you will historically get. It has lasted for hundreds of years with only a single civil war despite being multicultural. It also includes a lot of vertical advancement possibilities for its citizens of all socioeconomic backgrounds meaning it has survived a lot of the same problems you would see in a true meritocracy. Features it has that will be important to your setting include: * A constitution including an enumeration of rights with an enforceable supremacy clause. Every year, legislators write numerous culturally biased laws that threaten the survival of a multicultural United States. However, throughout American history, these laws have been shot down over and over again because they conflict with the constitution. Because the constitution is in theory more powerful than any politician, or political party. * Multiple states with their own local legislations. The maintenance of states means that you can take cultural groups, lump them together, and let them rule themselves to a degree. The more power you give to statehoods, the more people are able to live out their own cultures in peace without having to push back against the federal government. It is also important to allow easy migration within your national borders so that like minded people can gravitate to thier own cultural epicenters. This means that most people can celebrate their subcultures without giving tyrants as big of a hook to create rivalry. * Strong checks and balances. No one person or group should have the authority to usurp the whole government. As the conflict between cultures ebbs and flows a majority party should never be able to gain enough power to unilaterally control the government. One area the US does this very well is in the 2 house system. The house of representatives is well designed to prevent a majority culture from being dictated to by the vocal minority, and the senate prevents a majority culture from steam rolling all of the smaller subcultures combined. Things you may want to change about the US: * As per your requirements, you need to incorporate meritocratic testing. This should be very easy since the United States was founded under the ideal of being a meritocracy, but at the time the constitution was drafted, capitalism and elected leadership was the best solution to getting there that the founding fathers could come up with. If your nation had a similar origin story to the US, the same sorts of people would have been relatively easy to convince to adopt your system. * Give the federal government less power over personal liberties. In the US, cultures often come into conflict when federal laws written with one state's biases come into conflict with another. We see this in issues like the legalization of marijuana, abortion rights, or slavery where states are so clearly divided on the issue that it risks violent uprisings. The more power states have to write laws that supersede federal law, the easier it becomes for people to find a community were they can fit in and live out thier own cultural values without feeling the need to secede. So in the US, the order of supremacy is Federal Constitution > Federal Law > State Law, but if you invert it to Federal Constitution > State Law > Federal Law you will better support cultural diversity while still ensuring the power of the constitution to bind said cultures into one nation. Things you can change in your own story to make it more believable: * Although a leader could rise up from any walk of life, it would be clear that 99% of people would not have a voice. This is a huge issue with meritocracies because it basically says, you are either good enough to rule or not good enough to be more than a slave to other people's decisions. This results in a lot more civil unrest than a culturally diverse democracy or republic. What you can do is balance free elections with meritocratic testing; so, you basically let the testing take the place of primary elections and then let voting decide which "merited" persons would give them a feeling of agency in their government. This also means that leaders will feel some pressure to do what is in the interests of the majority of citizens if they want to maintain power. This means appealing to more than one subculture in thier leadership style. * People always think in terms of 'us' and 'them' no matter how subtle or vast the differences between people are; so, to maintain a strong nation your people inside the borders still need to be more like each other than the people outside the boards to maintain an 'us' mentality. One way to do this is to nix your language idea. A single common language, even if there are many actually spoken, is a powerful unifying force. Another way would be to surround your empire by nations that have state religions in which case your nation may represent a confederation of states designed to protect its citizens from the threat of forced religion. I think if you did both, you Empire's long term stability would become far more believable. [Answer] > > without the threat of violence in this life > > > Governments work through a threat of violence (follow the rules, or be punished). That said, if by violence you mean internal wars and skirmishes among different groups, then take a page from [Ghenghis Khan](https://www.youtube.com/watch?v=p2bvPzvFlP8). He united his people against common enemies one at a time. People of different upbringings and cultures would follow him because there were spoils to be earned in wars by staying on his side. Even if it meant having to tolerate neighbours they hated. In the end [it was probably one of the most diverse empires in history:](https://en.wikipedia.org/wiki/Genghis_Khan#Politics_and_economics) > > The Mongol Empire was one of the most ethnically and culturally diverse empires in history, as befitted its size. Many of the empire's nomadic inhabitants considered themselves Mongols in military and civilian life, including Mongols, Turks and others and included many diverse Khans of various ethnicities as part of the Mongol Empire such as Muhammad Khan. > > > There were tax exemptions for religious figures and, to some extent, teachers and doctors. The Mongol Empire practiced religious tolerance because Mongol tradition had long held that religion was a personal concept, and not subject to law or interference. Sometime before the rise of Genghis Khan, Ong Khan, his mentor and eventual rival, had converted to Nestorian Christianity. Various Mongol tribes were Shamanist, Buddhist or Christian. Religious tolerance was thus a well established concept on the Asian steppe. > > > Modern Mongolian historians say that towards the end of his life, Genghis Khan attempted to create a civil state under the Great Yassa that would have established the legal equality of all individuals, including women. However, there is no evidence of this, or of the lifting of discriminatory policies towards sedentary peoples such as the Chinese. Women played a relatively important role in the Mongol Empire and in the family, for example Töregene Khatun was briefly in charge of the Mongol Empire while the next male leader Khagan was being chosen. Modern scholars refer to the alleged policy of encouraging trade and communication as the Pax Mongolica (Mongol Peace). > > > Genghis Khan realised that he needed people who could govern cities and states conquered by him. He also realised that such administrators could not be found among his Mongol people because they were nomads and thus had no experience governing cities. For this purpose Genghis Khan invited a Khitan prince, Chu'Tsai, who worked for the Jin and had been captured by the Mongol army after the Jin dynasty was defeated. (...) > > > [Answer] # The empire is a magocracy ruled by powerful magicians. If you're basing this empire off of pre-modern China, then there's a fairly simple option for you to take: base your empire off of the various fantasy Chinas within the xianxia sub-genre of Chinese fantasy, where the empire is ruled by clans and/or sects of powerful magicians who cultivate their magical power by practicing magic-powered martial arts and controlling various power-boosting resources. If there's an Emperor, it's because he's the most powerful magician in the empire, and will live for thousands of years. Why does he deserve the position of Emperor? Because he's the most powerful magician in the empire, and he can personally kill anyone who tries to take it from him, along with their entire army of soldiers. Why is it a multi-cultural empire? Because their magicians go out and conquer new lands to rule, pillage their magical treasures to strengthen themselves and their clans/sects, and then teach the locals how to begin cultivating their own magic powers using the same system of magic. Over time, the new culture gets absorbed into the empire as whole, with a few minor aesthetic differences. Why the multitude of gods and religions? Because the most powerful magicians are strong enough to go punch gods in the face and take their stuff, if they don't transform themselves into new gods in their own right, so they're not afraid of them. [Answer] # The government is weak Perhaps this is a cynical view, but I don't think very different cultures can coexist within the same political system unless they are able to live out their own very different values and be left alone. In other words, you need a central government that is extremely weak and matters very little to an individual's everyday life. It could be that the "government" is just a diplomatic forum between the different nations, like the UN, whose pronouncements no nation has to pay attention to unless they agree with them. The difference is that your "nations" don't have geographic boundaries but have cultural boundaries, and the cultures govern themselves. Another option is that the "government" has a strictly defined area of responsibility, for example, to defend the empire militarily. Its bases are all at or near the edge of the country, and its soldiers are volunteers. Sort of like the French Foreign Legion, these people of different cultures can work together because it's a very task-focused organization, rather than a general government. The leadership has no say in cultural issues like family law, religious practices, etc. ]
[Question] [ We know that light exerts pressure upon matter. I'm imagining a hallway where an intense light source on one end shines towards the other end. The goal is to have the beam of light exert so much pressure that a human being cannot enter (or reach the end of) the hallway. Of course, we only want to deter the human, not to burn them to a crisp. Would this be realistic? [Answer] No, it won't be realistic. The [radiation pressure](https://en.wikipedia.org/wiki/Radiation_pressure) produced by an electromagnetic radiation of intensity, or better irradiance, $I\_f$ impinging at an angle $\alpha$ on a surface can be calculated according to $P\_{Inc} = \frac{I\_f}{c} \cdot \left(\cos \alpha\right)^{2}$ where c is the speed of light. You immediately see that, due to the c factor, you need huge irradiance to get meaningful pressures at human scale. Let's say you want to achieve $1 \ \frac{N}{m^{2}}$, you would need an irradiance of about $3 \cdot 10^8 \ \frac{W}{m^{2}}$. That would char any human on which it impinges. In case of a person wearing a perfect reflecting suit, > > if the wave is specularly reflected, then the recoil due to the reflected wave will further contribute to the radiation pressure. In the case of a perfect reflector, this pressure will be identical to the pressure caused by the incident wave > > > $P\_{Inc}= 2 \frac{I\_f}{c}$ It just halves the required radiance to achieve the same pressure, thus still leaving an extremely high value. [Answer] Not with light pressure. You need 300 megawatts of radiation flux for each Newton of force on the object (equivalent to the force exerted by a ~100 gram weight). However, you can use microwaves as non-lethal deterrent. A moderate microwave flux is extremely painful on skin, well before it becomes damaging. This is the basis of several experimental crowd control weapons in real life, such as <https://en.wikipedia.org/wiki/Active_Denial_System> [Answer] No It's true that light exerts a pressure, but photons have no rest mass and very little else (thanks AlexP). You're dealing with pressure created by a distribution of energy, which is miniscule. If you think about it, your skin burns on a beach — but you don't feel even the slightest pressure from the light that's burning you. Now increase the light such that you could feel the pressure. You'd flash into a fine ash before you could comprehend that you were feeling pressure. But! What if you change your goal just a bit? What if the original intent of the light was to flash-burn anyone trying to get down the hall? Your protagonish knows this and dresses accordingly in attire that protects he/she from the burning properties of the light. And yet, as he/she walks down the hall, feels the pressure! pressure that's great enough to hinder progress! That would be a cool twist to the story. [Answer] Literally , no. Other answers have dealt with this. However, if you allow that the possible intruders will not be armored, you can do something like it. Produce the light by an array of high-powered emitters. Each separate emitter produces a beam which focusses down to a very, very small spot about 1/4 to 1/10th the length of the hallway. The beams are all aimed at different spots within the hallway, and none of them is aimed directly down the corridor. As a result, virtually all of the emitted light will be absorbed by the walls. The result will be hazardous to look at from the end of the hall, due to unavoidable (hopefully small) reflections. However, if you attempt to traverse the hall, you'll eventually encounter a wall of "hot spots", where the power density is so great as to burn holes in you. Before you get to that point, the perceived temperature will rise to unbearable levels, and this should keep intruders out. Of course, this won't work in the presence of suitable armor - if the intruder simply rushes the corridor, she will pass almost instantly through the "death zone", and ought to be able to make it. [Answer] Maybe not visible light, but possibly an [electrostatic wall](http://amasci.com/weird/unusual/e-wall.html) ]
[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. There an atmospheres in which I can live, like Earth's. There are atmospheres in which I can float, like if it were a really heavy gas. Is there some atmospheric composition where I could both be alive and float, unaided? By be alive, I mean I could survive until I run out of food or water. By float, I mean I can be above the ground with no effort (indeed, I probably couldn't control it.). [Answer] No. First off, there are no gasses which are denser than a human. To float, you need the medium to be as dense or denser than you are. You might be thinking of thick atmospheres on low gravity planets, which might allow you to fly by flapping some attached wings, [like on Titan](https://en.wikipedia.org/wiki/Atmosphere_of_Titan#Overview). That atmosphere is not breathable though. So, in order to be floating in something you can breathe, it would need to be far denser, that means it'll have to be a liquid. There are some proposed [liquids that a human can breathe](https://en.wikipedia.org/wiki/Liquid_breathing), but an atmosphere usually [means the gases surrounding a planet](http://dictionary.reference.com/browse/atmosphere). This is possible through semantics. You can get loose with the definition of an atmosphere and have a planet covered in a breathable liquid which you call the atmosphere. --- Alternatively, you can look into making a gas torus. This is really only an atmosphere (there is no ground), but does allow you to float around in what you're breathing. Check out [Larry Niven's Integral Trees](https://en.wikipedia.org/wiki/The_Integral_Trees) for more inspiration. ![enter image description here](https://i.stack.imgur.com/CSc84.jpg) [Answer] Yes, you can float in air at standard pressure which is moving upwards at around 200kph. It's generally known as indoor skydiving, but you could imagine a world where wind creates this situation. [Answer] Let's look at [Tungsten hexaflouride](https://en.wikipedia.org/wiki/Tungsten_hexafluoride), "one of the heaviest known gases under standard conditions." This gas is rather toxic so it won't work, but as you'll see the toxicity isn't the only problem. Tungsten hexaflouride has a density of 13g/L. The density of the human body is around 1g/mL, about 100x more dense. Using the ideal gas law (`pV=NRT`), in order to increase the density by 100x, we need the amount `N` to increase 100x relative to the volume `V`. `R` is a constant, so we need to decrease `T` and/or increase `p`. Decreasing the temperature `T` isn't going to help us much. Going for 30 degrees Celsius (86 F) to 10 degrees (50 F) only increases the density by 7%. Too much colder and we it isn't really survivable long-term. So basically all of the increase needs to come from increasing the pressure `p`. However, 100x pressure isn't going to work for you. The pressure itself might be survivable, [but there's nothing you could breathe that wouldn't kill you](http://www.quora.com/What-is-the-maximum-depth-a-human-body-can-go-to-under-water-beyond-which-the-pressure-would-be-intolerable): > > It's unclear that there's any gas out there that we can breathe at, say, 100 times the atmospheric pressure. > > > Unaided, you're out of luck. You'd need a pressure suit and an oxygen supply or a tank of breathable handwavium air in order to make this work. [Answer] As [Samuel](https://worldbuilding.stackexchange.com/a/20523) and [Rob Watts](https://worldbuilding.stackexchange.com/a/20524) have explained, there's no atmosphere in which an unaided, unmodified human being can be lighter than or as light as the surrounding “air”. So what does this leave us with? You could be a modified human being. Given how far humans are from being able to fly, let alone float, the modifications would be extensive. You could of course be an aided human being. All it takes is a large enough balloon containing helium, hot air or some other gas that's lighter than air. If neither of these cheats are acceptable, here's another one. If you get rid of gravity, it doesn't matter that you're heavier than air! All you need to set this up is a confined space with no or very little gravity. The space needs to be confined, otherwise the air will escape. The space will need to contain no masses large enough to create significant gravity. One way to create such an environment is at the center of a large sphere — a hollow planet. No matter how heavy the sphere is, as long as it has spherical symmetry (or close enough), there's no gravity in the central hollow part. Like all science fiction ideas, [it's been done before](http://tvtropes.org/pmwiki/pmwiki.php/Main/HollowWorld). One hard-ish example is [Karl Schroeder](http://tvtropes.org/pmwiki/pmwiki.php/Creator/KarlSchroeder)'s [Virga series](https://en.wikipedia.org/wiki/Karl_Schroeder#The_Virga_series). Virga is a world with no gravity (people live in rotating cylinders) but full of air. Due to the lack of metals, technology is mostly pre-19th century, with wooden ships — pirates in space. Humans can “fly” through the world, with or without equipment — but Newton's third law applies, so you need rocket propulsion or some other mass to throw or you'll be stranded in space. [Answer] Yes, if you create a universe filled entirely with air instead of relatively empty vacuum. Getting around would be a bit more difficult than swimming, since air has about [1/50th the viscosity](http://hyperphysics.phy-astr.gsu.edu/hbase/tables/viscosity.html) that water does, but the same principles should apply in general. Of course, some method of aerodynamic propulsion would certainly be preferable... [Answer] Possibly, but instead of modifying the atmosphere change the planets spin. Here's the idea: the ISS is 'floating' in space, but in reality it is simply falling forward so fast that it does not have time to hit the ground before it crosses the horizon. [See this](https://physics.stackexchange.com/questions/9751/why-dont-we-consider-centrifugal-force-on-a-mass-placed-on-earth) for the idea. If the earth rotates so fast that its centripetal force was the same as its gravitational force then everything on that height would effectively float. Precisely, it would be as if we were on orbit even at ground level. I think it would be hard to keep the atmosphere attatched to the earth at that point though, like Mars cant keep its own because of its own gravity, but if you had a dome around the atmosphere it could still work. Most planets tend to slow down though, not speed up their spin. [Answer] Another idea that wasn't covered by the previous excellent answers but was mentioned by @Mikey in the comments. If you built artificial habitats on some of the moons of the solar system and included large domed areas with STP atmospheres, a human body should be capable of direct flight. Just add wings and start flapping. Another thought: if you engineered an atmosphere for the Moon, it would not remain for geologic timescales but it might be fine for habitat over human timescales (100,000 - 1,000,000 years). My theoretical + empirical spreadsheet of Solar System bodies indicates a half-life for gaseous $H\_2O$ of around 100,000 years - longer for the heavier $O\_2 + N\_2$ molecules. Could be a fun world to play in. [Answer] Similar to the Integral Trees, you also achieve this by having a hollow planet (or space station). If gravity is low enough, or you are near the center of gravity this can lead to being effectively weightless allowing for suspension in atmosphere. [Answer] Setting aside for a moment whether or not it's possible to find a gas that can be compressed to the density of a human without undergoing a phase change, suppose you are neutrally or nearly-neutrally bouyant in some fluid. The fluid has your density or higher. Firstly, your lungs will struggle to move the fluid in order to "breath", since more force is required to shift a larger mass of fluid. That's a problem but it's not necessarily instantly fatal. Secondly, any significant "depth" of such fluid will have very high pressure on a planet, since there's a lot of weight of this stuff above you. Divers in water (approx same density as a human) can go to to a few hundred meters maximum in Earth gravity. Hence, you need to look for micro-gravity situations (where everything "floats" irrespective of density), or else for environments where there isn't miles of fluid above you (so, not really an "atmosphere" worth the name). If we're not allowed a roof, then perhaps a small body with low gravity, and some kind of atmosphere-generator, would be sufficiently "floaty" even though really you are much denser than the atmosphere. You're sinking, just at very low acceleration. You'd have to think this is inefficient, though, since without a roof the atmosphere on a low-gravity body will be leaking into space. As for whether a fluid you float in can even be a gas rather than a liquid: it doesn't seem likely that any gas could have a density close to that of a human, without being at such high pressure that a human can't survive. Of course hand-wavium is good for a lot of engineering applications, but it doesn't qualify as "hard science". If you just assert the existence of a non-toxic gas that's 20% denser than water at standard temperature and pressure, and mix it with 20% oxygen, then you'd float in it and breathe it (albeit with increased difficulty compared to air). You'd also have to explain why the oxygen doesn't all float to the top. And for the reasons above to do with weight of fluid above you, the atmosphere would have to be a lot shallower than Earth's, or the gravity far weaker, or some combination of the two. Now, if you're willing to consider a "liquid atmosphere", then you're in business. Just grow gills, use water (which will need to be oxygenated somehow) and don't go too deep into the "atmosphere" (or as it's more typically called, "ocean") ;-) ]
[Question] [ Closed. This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49). Closed 3 years ago. [Improve this question](/posts/169031/edit) Lets say the advanced civilization never discovered rockets and for whatever reason never will. Is it possible to create some kind of mechanical device to launch a 90kg person to the moon from earth? I would like it to be a massive catapult but It does not need to be a catapult (it can be some kind of electromagnetic launcher if it has to); however, it needs to be some kind of launcher where the person is given an initial velocity but the velocity cannot be sustained after it is launched (the object cannot burn fuel/energy to propel itself like a rocket after it is launched). Assume the person launched is invincible, we don't need to worry about oxygen, safely landing, we also don't need to worry about the extreme forces on the person during the launch. Edit: The reason why I say invincible "person" is because it makes the problem more fun. I am not interested in the survivability of the projectile. However, I am interested in the following: 1) The size and specifications of the device required to launch a human sized (90 kg) projectile to the moon. 2) If you build the launcher on the ground you will need to overcome air resistance. In that case I would like to hear about the initial velocity required to get to the moon while getting through our atmosphere. If the launcher is elevated, you will have to overcome the problem of elevating the launcher. 3) The method you come up with has to be theoretically possible but it does not necessarily have to be something that engineers can realistically build. [Answer] To get to the moon you need to reach a speed of at least 7 mi/sec. What about giant catapults? A catapult will never reach anywhere near that kind of speed. It does not matter how long you make the arm, no man-made materials can survive anywhere near the sort of torsion that this would require. What about railguns? The world's strongest military grade railgun is the size of a bus and to maxes out at about 14.7MJ of kinetic energy. If you want to go with the absurd notion of just flinging an indestructible human body to the moon, you could put a person in a 500 lb metallic casket and fire them with a railgun about 1400 times as powerful as this. Figuring out the best way to scale this gets tricky since exact sizes are hard to come by, but my best estimate is that you are looking at a barrel that is about 10ft in diameter and 2.6miles long. This could be built on the side of a mountain and fired at just the right moment when the cannon comes into alignment with the moon; however, this is not a proper moon mission. A more likely payload would be something on the scale of the Apollo Lunar Module. This would require something ~28,843 times as powerful as the strongest railgun in the world. My best guess here is that you are looking at a barrel that is about 25ft in diameter and nearly 9 miles long. Because the round is so heavy you can not use a curved firing tube to fire at a mostly flat plain and then turn it last minute to a more upward trajectory; so, even building up the side of a mountain may not work because you probably will not be able to get the firing arc you need. Really you could make the barrel even thicker and shorter and maybe fit it on a mountain, but the thicker you make the barrel the more it must contend with material strengths and heat dissipation, and even at this scale, I find this railgun's feasibility to be rather dubious. Also... you are still accelerating at way over human survivable speeds. So, I'd call railguns feasible as per the OP, but probably not for real world applications. What about light air guns? These are typically faster and more efficient than railguns making them one of the fastest known cannons to modern technology. Unfortunately they max out at about 4.4mi/sec (the max expansion rate of compressed hydrogen); so, still no good. What about Enhanced Hypervelocity Launchers? I just made that word up, right? ... nope. [SEE HERE](https://www.nytimes.com/1994/03/22/science/fastest-gun-on-earth-goals-go-beyond-planet.html) These guys can reach speed of about 10mi/sec. Fast enough to get to the moon... maybe. While they fire fast enough to get to the moon, they have never fired anything bigger than one gram; so, they would probably also have critical material failures when scaled up to fire a man sized slug, much less a proper lunar capsole. What about Pascal-B? Alright, the possibility of launching a man or lander sized object at escape velocities using a nuclear explosion is doable if you REALLY want to stick with the idea that your astronaut is indestructible. The Pascal-B nuclear test fired a 2000 lb chuck of steel at 41 mi/sec. This is more than adequate to send a man to the moon, but we are talking about having him literally sit on a nuke! In terms of material integrities, you're probably better off sticking with a giant trebuchet. In short, using modern technology as defined by the OP railguns might do it if they don't structurally fail due to square-cube law type issues, but doing anything worth doing in real life is pretty much a no go. [Answer] I'm going to ignore that your subject talks about a "person", because the body of your question basically says to do that. It sounds like you want a [space gun](https://en.wikipedia.org/wiki/Space_gun). The article has some information on plausibility, but the short version is that, if you want to reach the moon, or even just a stable orbit, you have issues with both the acceleration needed (but we're not launching a person, or at least, we're launching someone who is magically immune to all the bad stuff that happens to the human body under extreme acceleration) and with the air that's in your way. The latter is the big problem with imparting all your velocity at once, as opposed to taking engines up with you. ...and even if you get to the moon, the sudden stop at the end is going to be killer. Literally. Also check out the "See Also" links in that article. [Answer] Linear accelerator launchers (based on a combination of maglev and linear induction motors, usually) go back to the 1950s in fiction (Heinlein's Starman Jones from 1953, and The Moon is a Harsh Mistress from 1966). There are significant limitations in using these from within an atmosphere, but there are ways around them (route the rail up a very high mountain with an evacuated tunnel for the lower elevation part, for instance -- there are multiple mountains fairly near the Equator that exceed 7 km, above 90% of the atmosphere). The advantage of such a setup is that all the launch "fuel" comes from ground-based power sources (the electrical grid, supplied by fission, fusion, or solar/wind/tidal power), so the launch vehicle need only carry fuel for in-space maneuvering, and the acceleration can be within human launch limits (unlike a true "space gun" which is exceedingly difficult to implement with survivable acceleration). [Answer] The atmosphere of the Earth tends to destroy fast-moving objects. This is related to Newton's depth approximation, where we find that a projectile tends to penetrate through approximately its own mass of material before it stops. Newton fired cannonballs into sand, and found that they penetrated approximately as far as the column of sand that weighed the same as the metal ball. Faster impacts merely made wider craters. <https://en.wikipedia.org/wiki/Impact_depth> The same holds true for atmospheres. Venus, for instance, has a minimum size of crater due to its thick atmosphere. An approaching meteor is slowed and then blows up long before it reaches the Venusian surface. <https://www.universetoday.com/22521/craters-on-venus/> If you're flinging something straight up with acceleration only at ground level, you have to consider the total weight of the atmosphere above the object. Every square centimeter at sea level is pressed down by 1kg of atmosphere above it. If you managed to fling something really fast straight up, it would need to be extremely dense in order to complete the trip. A very long tungsten or DU rod might make it. There are ways to reduce atmospheric resistance : a sealed vacuum launch tube, or a mountaintop launch site, or using rockets to accelerate over time instead of all at once. [Answer] It's technically possible, but there are a few difficulties with just shooting yourself straight there. So, as a baseline, you need about 15,000 m/s (meters per second) of ΔV for a traditional rocket to reach the Lunar surface. That number comes from the below slide from a [2012 presentation by NASA](https://www.lpi.usra.edu/meetings/leag2012/presentations/Connolly.pdf). [![Slide from NASA describing orbital delta-V costs](https://i.stack.imgur.com/61o7k.png)](https://i.stack.imgur.com/61o7k.png) I believe this includes deceleration burns and orbital maneuvers, so we can probably subtract a few thousand m/s. Lets just ballpark it and say 12,500 m/s ΔV. That means you need to launch a pod from the surface of the planet, directly at the moon and, even more important, precisely at the moon. You can't mess your aim up, as you can not make in flight course corrections! It's possible to make these calculations, but you need to know many different variables. Things like local weather, altitude, time of flight, velocity of the Earth, velocity of the Moon, and so on. You need to precisely aim your "space gun" so that when the package reaches the moon, the moon will have reached that point in space in the time between launch and arrival. Don't forget that there will be travel time for the package, and the moon will have moved out of it's previous location during that travel time. There is also the technology aspect of it. Reaching escape velocity in the span of less than 1-2 seconds is something that is still currently not possible. From a quick google search, the fastest rail gun in the US Military shoots shells at 7,500 mph, which is equivalent to 3352.8 m/s. 3,352 m/s is only about a quarter of the velocity that we need to reach for our theoretical space gun. With the best tech that we have in 2020, we have rockets flying to mars versus guns that can barely reach orbit. Will the technology eventually get there? Sure, it's possible, but there would have to be some serious reason to dissuade scientists from researching rocketry, if the only goal is to get to the moon. In short, it's theoretically possible, but it seems implausible that some civilization would go through the effort of developing some sort of space gun system when rocketry is just much easier. As a note, you mentioned to assume the package was invincible. If this wasn't the case, then any human subject to these g-forces would be instantly killed, probably turned into a pancake at the floor of their ship. [Answer] Yes, a mechanical device called a Slingatron was proposed for space launches. I wrote about it some years back; the developer (Derek Tidman) felt that there was a huge bias in the establishment against this approach and he never made much progress with it[![SLingatron space launmcher](https://i.stack.imgur.com/rBDIi.jpg)](https://i.stack.imgur.com/rBDIi.jpg). However, a starup called SpinLaunch are now going with the same idea, so we may yet get to see if it works. If Tidman is correct, space launches may be possible using this type of device and fairly basic technology. [Answer] The key problem is the amount of acceleration that your passenger can tolerate. You need to leave the atmosphere at as speed of at least 12.5km/s to be able to pass through the moon's L1 and enter its sphere of influence. Lets say, your passenger can tolerate a 20g acceleration (approx. 200m/s^2). With this top acceleration, you need to sustain that acceleration for `12.5km/s / 200m/s^2 = 62.5s`. The problem is, during that time, the capsule with the passenger will have traveled `1/2 * 200m/s^2 * 62.5^2s^2 = 390.625km`. That's a damn long railgun/canon/whatever. I guess it's only feasible to build in the form of a maglev launcher that operates inside an evacuated tunnel. Even if you increase the acceleration to about the highest a human has ever survived (deceleration at a car racing accident), which is 214g, you get an acceleration time of `12.5km/s / 2.14km/s^2 = 5.8s` and a barrel length of `1/2 * 2.14km/s^2 * 5.8^2s^2 = 36.5km`. Note, that while this extreme deceleration in the car accident was survivable with all the racing car safety measures in place, it didn't last very long. Only about 0.1s. What is survivable for such an extremely short time is not likely to be survivable for about 60x that time at all. --- Of course, if you decide that you can make do with, say, a 100km evacuated barrel maglev launcher, you still have the problem that your passenger suddenly hits the air at the exit of the tunnel. If you just put the exit on a mountain, 8km above sea level, you still have about 35% of the sea level air density. And about 35% of the atmosphere left to pass through. That's too much. It will decelerate your projectile hard, the air molecules hammering into the projectile will quite instantly heat it to insane temperatures, and you won't reach the moon today. (You didn't use your convict for this test, did you?!?) A much better altitude to have the exit would be at about 20km above sea level. This would leave you with about 4% to 5% remaining air pressure and atmosphere to pass through. Still a lot, but I guess that's about where the atmospheric deceleration and heating would reach manageable levels. Weather balloons routinely achieve such hights, so I guess it is theoretically doable to extend your maglev launcher to such a hight by supporting the barrel with helium filled balloons. Those balloons would be gigantic, though. And, making sure that the barrel remains straight would be a superb engineering challenge. I guess, building a Saturn V sounds like playing with lego by comparison... [Answer] To work out the heating from air resistance, think of the column of air above you and imagine being hit by it at orbital speed. Pressure at sea level is about 100kPa, so there's about 10,000kg of air above every square meter. Orbit speed is 11km/s, so there's 600GJ of kinetic energy to absorb. The heat capacity of steel is about 600J/kg k, so a million kg of steel would be heated to 1000 degrees by that much energy. If you launch from the top of Everest, it's only a third as much. And you could just squeeze a person into a capsule with an area of a tenth of a square meter, so you'd only need a few hundred tons of heat shield. Of course, real heat shields don't work like that, the surface gets much hotter, turns to plasma and ablates away. If it can reach 10,000 degrees, you'd only need a few tens of tons. [Answer] > > It can be some kind of electromagnetic launcher if it has to. > > > You are looking for a Space Fountain elevated Rail Gun. [Space Fountains](https://en.wikipedia.org/wiki/Space_fountain) technically are a 'rocket', just of another format. Rather than relying on combustion of fuel in a rocket engine to propel hot gas out the back, you instead rely on throwing around material that can interact with an electromagnet. Throw material 'up' from a launcher solidly fixed on the ground, then have a section of your tower 'catch' it, and throw it back at the earth to propel the tower section up into the air. In short, they are rockets without using rockets, and tied to plumbing on the ground. But they can be powered by reusable materials, and connecting electrical lines can be easier and more efficient than trying to plumb highly flammable fuel and oxidizer lines on a 'questionable' structure... --- To look at it another way, this is effectively a fancy series of rail guns used to lift and fire another rail gun in an attempt to avoid excessive energy loss on the final projectile rather than attempting to punch it through the air. [Answer] I think you should definitely consider a trebuchet over a catapult. They are far more superior siege engine, and able to launch a 90kg projectile up to 300m distance. The moon being at 384 400 000 meters from the earth, you just need 1281333.34 time the power of a traditional medieval trebuchet. I would recommend: * build 1281334 trebuchet and connect them together to accumulate their power. * build a single trebuchet, simply 1281333.34 time bigger than a traditional one. Good luck if you chose to pursue the catapult way. I have no doubt it is a dead end, like everything catapult really. [Answer] From the other answers, any sort of gun/catapult seems to need such an enormous initial speed (muzzle velocity?) that it would be impractical. I have no idea of the physics, but if you were able to use (say) the sides of Mount Everest as the base of your "gun", maybe you would have a slight height advantage and a lower density of air to get through. I'd imagine the moment that you fire the device, the forces on the passenger would still be far too great to survive, and that's before you've dealt with any of the other issues such a device would have (ice being a likely one on Everest!). Along similar lines, but maybe with less of the issues may be a [Space Fountain](https://en.wikipedia.org/wiki/Space_fountain)...? ]
[Question] [ Imagine aliens dropped a small black hole (say, 1% of the moon's mass, so you wouldn't notice the difference in gravitation) into the sun (from the far side of the sun, so nobody on earth can see it). That small black hole would then, of course, start eating the sun, so that it eventually fails. Now my question is: How long would it take until someone on earth would notice that there's something wrong with the sun? And how much time would they then have to react before the earth would become uninhabitable? [Answer] Good analysis by the others, but I want to add in some math here, because I'm really that nerdy. We can model the growth of a black hole by the matter it accretes. Normally, a black hole accretes matter via a (surprise, surprise) [accretion disk](https://en.wikipedia.org/wiki/Accretion_disc). Analysis of this type of object is nice because it's two-dimensional, for most practical purposes. Here, though, the accretion is decidedly three-dimensional. To analyze this, we have to model a phenomenon known as [Bondi accretion](https://en.wikipedia.org/wiki/Bondi_accretion). The accretion rate onto a spherical body of mass $M$ in a medium of density $\rho$, the rate of accretion is $$\frac{dM}{dt}=\frac{4 \pi \rho G^2M^2}{c\_s^3}$$ $G$ is the familiar universal gravitational constant, while $c\_s$ is the speed of sound in the medium, a quantity that is actually pretty ubiquitous in studying astrophysical mediums. Anyway, we can then write $$\int\_{.01 \times M\_{\text{Moon}}}^{M\_{\odot}} \frac{1}{M^2} dM=\int \frac{4 \pi \rho G^2}{c\_s^3} dt$$ $$\frac{1}{M\_{\text{Moon}}}-\frac{1}{.01 M\_{\odot}}=\frac{4 \pi \rho G^2}{c\_s^3}t$$ and then, solving for $t$, we find $$t=\frac{(.01M\_{\odot}-M\_{\text{Moon}})(c\_s^3)}{M\_{\odot} \times .01M\_{\text{Moon}} \times 4 \pi \rho G^2}$$ Of course, $.01 \times M\_{\text{Moon}}\ll{}M\_{\odot}$, but that's okay here. Now, [we know that](https://en.wikipedia.org/wiki/Sun) $M\_{\odot}=1.98855±0.00025×10^{30} \text{ kg}$, $V\_{\odot}=\frac{4}{3} \pi r\_{\odot}^3=1.41 \times10^{18} \text{ km}^3$, and $\rho=0.1403 \text{ kg/m}^3$, and [that](https://en.wikipedia.org/wiki/Moon) $M\_{\text{Moon}}=7.3477×10^{22} \text{ kg}$. I haven't been able to find any figures for $c\_s$, but we can still simplify the above equation to $$t=\frac{(1.98855±0.00025×10^{30}-7.3477×10^{18})(c\_s^3)}{1.98855±0.00025×10^{30} \times .01 \times 7.3477×10^{22} \times 4 \pi \times 0.1403 \times 4.4528929 \times 10^{-21}}$$ As per [ckersch's link](http://adsabs.harvard.edu/full/1989SvAL...15...21V), $c\_s \approx 2,500,000 \text{ m/s}$. This means that $$t=\frac{(1.98855±0.00025×10^{30}-7.3477×10^{18})((2500000)^3)}{1.98855±0.00025×10^{30} \times .01 \times 7.3477×10^{22} \times 4 \pi \times 0.1403 \times 4.4528929 \times 10^{-21}}$$ $$=2.709 \times 10^{15} \text{ seconds}$$ $$=85.89 \text{ million years}$$ There are some things that were neglected here. For example, the black hole will lose some mass due to Hawking radiation, and the Sun can fail even if it doesn't lose all (of even the majority of) its mass. Still, though, this analysis should show you that we've got not a lot to worry about if a Moon-sized black hole decides to take a jaunt through the Sun. --- Note: There may be an error here somewhere along the line (which I can't find just yet), but it appears to be around where I started plugging stuff in. At any rate, until I'm able to fix this, know that you can use Bondi accretion to figure out how long the Sun has to live. [Answer] At that size of black hole (1% the size of the moon), the presence of the black hole in the sun wouldn't significantly change the life span of the sun. Using [this calculator,](http://xaonon.dyndns.org/hawking/) we can see that the radius of such a black hole would be 10 micrometers. Not a whole lot of matter would be falling into a black hole that size compared to the rate at which the sun sheds matter, which is on the order of 1.5 million tons per second. The micro black hole would form a small accretion sphere in the middle of the sun, but wouldn't significantly affect most of the sun, since the forces from pressure and the constant fusion reactions are far greater than the forces generated by the black hole. [Answer] [The smallest black hole found so far](http://www.space.com/5191-smallest-black-hole.html) has 3.8 times the mass of the Sun. [Micro black holes](http://en.wikipedia.org/wiki/Micro_black_hole) are possible in theory but it is not obvious how they could be created or handled. And they are expected to evaporate (lose mass) via [Hawking radiation](https://en.wikipedia.org/wiki/Hawking_radiation). My quick skimming of that article showed that evaporation of a micro-BH is faster than matter intake (because of required density, it would be extremely small, atom-sized). [This article](http://www.icrar.org/home/hungry-black-hole) says black hole are capable of consuming nearby stars pretty quickly, in less than a million years - but the black hole discussed is pretty big to start with, not as small as OP's - with a mass of less than 15 Suns (which counts as small in BH-land). The effects of a small Black hole on Earth were debated [here](https://worldbuilding.stackexchange.com/questions/2743/on-the-immediate-effects-of-a-small-short-term-black-hole) Yes, this danger is yet another reason to invest more into space-faring. Let's go places! Of course there is no danger from such small black hole - but don't tell the Congress! Tell them is IS dangerous and we need space travel to deal with such eventuality! ]
[Question] [ So in many worlds, magic is a source of power that magic users can draw upon and "do stuff with" - make elemental effects (fire, cold, lightning), heal wounds, shield from arrows, light rooms, etc. The amount of power they can draw upon and the skill with which they can turn it into useful stuff is like any other talent: they have some innate ability that is improved by practice/training/studying. Given this form of magic, what if magic users couldn't turn that source off? The energy would need to go somewhere. How would magic users deal with this, even as babes or when sleeping? [Answer] Assuming that a magic user is constantly drawing power and can't turn it off, there are several ways to deal with it. Permanant storage is one I have heard of. Amulets of power, gemstones, or some other magical artifact can store power for future use. Grounding is another option. Feed the magic into the earth or back into the magical source. Finally, you could consiously dispell it. Magicians could be forced into frequent casting or burn up. They could have a pet project or personal habbit they work on with excess magic or be required to perform community service magic, like strengthing crops or improving the weather. Also, hopefully magic wouldn't effect a person until puberty or you could passivly bleed off magic from children before they are old enough to do it themselves. [Answer] This seems simple enough. The wizard could constantly radiate the 'energy' in a form that doesn't interact much with matter, as a sort of aura. This would have to be fairly low level radiation, so as Vulcronos said permanent storage would be useful, and they would be easily visible to anything with magical means as a result of the aura (Of course, mere mortals are constantly radiating infrared and thus would be easily visible as well.) [Answer] Most wizards usually need to 'collect' the energy consciously to one extent or another, often that is a large part of the study. However, say the collection is automatic and unconscious, you have 3 alternatives that I see. 1. it burns out the host, maybe kills their talent, maybe kills them. 2. they are like a battery on a charger, when they are full to capacity they quite absorbing more power. 3. When getting overloaded they discharge the energy in a magical display of some kind, in one way, shape, or form. Which could lead to some very interesting quirks in spell casters if they have a 'relief' valve that just randomly generates a magical effect. Maybe someones pants disappear or someone always coughs up a furball... [Answer] With the assumption that spellcasters must perform spells to relieve the potentially harmful buildup of magical power within their bodies, it is likely that anyone with magical ability who was not able to unconsciously bleed off excess power would have suffered some sort of calamity and would therefore be less likely to have contributed to the next generation's gene pool, hence most spellcasters should be able to unconsciously bleed excess energy relatively harmlessly. Some possibilities include: * That spellcasters spontaneously cast spells when their magic power levels become too high. This could include effects that might in other worlds have been attributed to poltergeists. * That spellcasters can unconsciously maintain spells, for example levitating an object while asleep drains just enough accumulating magical power to keep levels constant. * That there may be spells that prevent accumulation of dangerously excessive magical energy. [Answer] A good use of magical power that's not otherwise used could be a permanent self-protection shield that would be unconsciously supported. A side effect would be that if a magician exhausts his magical power for some spell, he would temporarily lose his magic protection and become as vulnerable as any other human. Indeed, such a magic self-protection could also be used to identify magicians early on, when they themselves don't yet know that they have magical powers. It would show up by them not getting easily bruised. [Answer] They could just cast some spells. And considering that levitating or moving things, casting fireballs, etc. is adding energy to stuff and all energy becomes heat sooner or later, they could just emit unused magic as heat. Having a body temperature of 37-40°C is not that good idea and rather unpleasant, so I guess they would prefer to just cast spells. So if they don't dissipate magic, they get sick. They could also emit light or radiation. :P Or turn magic (energy) into mass by producing few atoms of matter. Or turning oxygen in air into ozone... Possibilities are endless. You could also get inspired by Sergei Lukyanenko and make the wizards have less magic than the world -> the magic flows to them like water to drains. The more powerful wizard, the less magic he produces and the faster he can drain magic from the world. Ultimate mage produces no magic at all. [Answer] For a baby wizard that receives energy without knowing how to use or dispel it, I would (besides reading Asimov's [Foundation and Earth](https://en.wikipedia.org/wiki/Foundation_and_Earth) where [Solarians](https://en.wikipedia.org/wiki/Solaria) have a similar issue) imagine that they have innate means. Such a baby (and consequently the adult wizard) would have also an innate knowledge of how to dispel that energy, as well as he knows how to breath or cry or suck. The baby would be able to dispose of that energy by some means that do not require conscious effort like making small magic effects around him, slowly learning to use it to get objectives like a bottle or cleaning his diaper. [Answer] Assuming that "magic" is a form of energy the body of a wizard would use, and assuming this "use" of "magic" is a biological or biochemical process, well, couldn't the wizard just grow fat? I mean, basically it would mean more "magic" energy = more calories. Just to give the idea another spin. This could also be used the other way around: excessive use of magic would drain the wizard of energy, ie calories, starving him. [Answer] I'm curious as to why you would believe that there is a constant flow of energy into them that must be dispelled. You said it yourself, first in the question and again in the explanation. "Magic is a source of energy that wizards have access to." "Magic is a source of power that magic users can draw upon." It is my belief that magic is not a "source of power" so much as energy is a source of magical power. Everything in the universe has inherent energy. Matter, electromagnetic waves, radiation, everything around you is constantly oscillating. Matter is held together by energy. Matter itself has a wavelength, albeit a very low one. When a magic user or wizard attempts to cast a spell, I believe he is making use of the energy that is around him, and transmuting it into useful abilities. This is why many people (for example, Wiccans) who make use of spells and magical powers often have many stones and crystals around them. Different materials have different energy levels, different frequencies, and are all useful for different things. Many materials are good for storing energy, so this can be a way for the wizard to gather energy and carry it with him. I do not believe there is any need to "bleed off" unused energy, I don't think it is even right to call it unused energy, but rather it is energy that has not yet been used. Energy that is acting in the way necessary to hold the universe together, until the witch or wizard wishes to make use of it. [Answer] I would suggest an extensive use of charms, fetishes and other magic items. Creating the items burns off some magic, but the items also continue to burn magic while worn. A charm of fortune, or a ring of warmth, or an everclean nappy would all slowly siphon a bit of personal energy to maintain the effect. This would also give a reason for the eccentric appearance of the more powerful wizards, who will have robes and hats covered in Runes and will be decked out in rings, necklaces, and other jewelry composed of gems, bones, feathers and precious metals. [Answer] I recommend reading "A secret Atlas". In this book, magic can be accessed by mastering one's art (whether that is sword-fighting, organization, art, botanics,... anything really). One theme is that when fighters access magic in this way, not all the magic is actually used and is spread into the environment. This actually caused a big cataclysm in the world when an extensive war happened, changing the environment and everything. Circles somehow protect against magic, so when two sufficiently skilled warriors fight, they do so inside a circle which keeps the magical energy inside (the same is done with the last wizard in existence, he is constantly kept in layers and layers of circles around where he lives). ]
[Question] [ One of the features in my world is a crystal cave. The crystal is mined to be used as a source of electricity. I want this electricity to power up simple electric devices, some sort of light bulb. I don't want complex stuff, because this is set in a medieval world. What I imagine right now is the (long) crystal is broken into two, which causes the electrons to be divided unevenly and allows for electric current when connected with the light bulb. However, I doubt this process generates enough power to light the bulb, or that it's reliable enough to be used at least 2 hours straight. What I currently have is a crystal made mostly of silica and impurities, just like crystal on earth. However, you can propose different ingredients, as long as macroscopically it looks like crystal, or a gem (even better!). How can electricity be harnessed from such a crystal? The proposed method, cracking the crystal into two pieces, is just what I've imagined so far. If you think such crystals can be used to fuel a steam generator (can boil water, for example), I welcome creative approach to use the crystals. [Answer] I don't know much about the possible chemical composition but I can give you ideas to generate the electricity. # Thermoelectric effect [![enter image description here](https://i.stack.imgur.com/KlRqe.png)](https://i.stack.imgur.com/KlRqe.png) A thermoelectric material works heating one side of it when another one is cold, then, the difference in temperature between them would produce a constant flow of electricity. Also, if you give energy to it, one side starts to get cold when another side increase its heat (transfer heat). For more information or how to make calculation relationated with it go to [this place](http://www.mn.uio.no/fysikk/english/research/projects/bate/thermoelectricity/thermoeffect.png) # Betavoltaic device Basically, this device produces energy when it receives [beta radiation](https://en.wikipedia.org/wiki/Beta_particle). I am not sure if this can be made naturally but for example, there exist [diamond batteries](https://en.wikipedia.org/wiki/Diamond_battery) that are able to produce a low flow of constant energy for thousands of years. Sadly, over time the radioactive material start losing its power and the battery decrease it voltage over time. I'll quote two paragraph of [here](https://www.forbes.com/sites/jamesconca/2016/12/09/radioactive-diamond-batteries-making-good-use-of-nuclear-waste/#1511d885a044): > > These radioactive diamond batteries would 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. > > > Also, you can see this [five minutes video](https://www.youtube.com/watch?v=b6ME88nMnYE). # Piezoelectricity [![enter image description here](https://upload.wikimedia.org/wikipedia/commons/c/c4/SchemaPiezo.gif)](https://upload.wikimedia.org/wikipedia/commons/c/c4/SchemaPiezo.gif) Elements like quartz have the ability to produce energy in their opposite poles when they are under physical pressure (like the smashed or compress). Also, if you give them the energy they have the opposite effect, they increase in size while they get energy. # Photoelectric effect Another idea could be to use the photoelectric effect, and produce an electrical current based on the amount of light is received. [Answer] A piezo electric crystal can turn deformation of the crystal into electricity. It's not very efficient, but you can generate a spark. This is now some gas burner igniters work, and some types of lighters. A watt of light is a good deal of light -- useful enough to light a room. There's a peace project for developing worlds that amounts to setting up villages with a combination of a small solar cell, a battery and a 1 watt LED. This is sufficient that kids can do homework, adults can work in the house after dark. For a piezo crystal you have to provide the energy for the light. In a stove lighter, you hit the crystal with a hammer. (It's small, and spring powered) If your crystal was 10% efficient at converting some form of mechanical energy into electricity and you had perfect LEDs you have to supply 10 watts of power. This is roughly equivalent to lifting a liter (quart) of water a meter (yard) every second. Probably similar to running a spinning wheel, or potters wheel, or churning butter. A different way, requiring a bit of fantasy: The crystals have the ability to store sunlight. They soak up sunlight in the day, and release it continuously. How long the release takes depends on the thickness of the crystal. A thin crystal lasts only a few minutes, a thick one lasts for days. Charging time is longer for thick crystals. [Answer] I'll go full lateral thought on this one ;) [![enter image description here](https://i.stack.imgur.com/yrl6K.jpg)](https://i.stack.imgur.com/yrl6K.jpg) Magnetite is a crystal. Under some circumstances, it can also be a permanent magnet. With some hand-waving, you could decide that the crystals in your story are quite strong magnets. With permanent magnets, you can make efficient generators, alternators and dynamos. Here is a very primitive one: <https://catalogue.museogalileo.it/multimedia/PixiisMagnetoelectricMachine.html> Timeline of discoveries, inspired from real facts: * A permanent magnet makes a compass. These quickly becomes popular. * Someone invents the electrical battery * Someone notices current in a wire makes a nearby compass move * Induction is discovered [Answer] You can use [piezoelectricity](https://en.wikipedia.org/wiki/Piezoelectricity): > > it is the electric charge that accumulates in certain solid materials (such as crystals, certain ceramics, and biological matter such as bone, DNA and various proteins) in response to applied mechanical stress. > > > Quartz is piezoelectric, and quartz is made of silica. If you properly orient a set of crystals, manage to wire them properly and to apply stress in homogeneous way, you can manage to generate some current. [Answer] I would suggest some form of [electrostatics](https://en.wikipedia.org/wiki/Electrostatics). Most modern electrical uses are from moving electrical charges, electrostatics is the science of static (unmoving) electrical charges. Some of the first discoveries of electricity were from electrostatics, rubbing dissimilar materials together (Amber crystals with a cloth) producing an electric charge. In the 1800s, a type of experimental electricity generators were [electrostatic generators](https://en.wikipedia.org/wiki/Electrostatic_generator#History_2). Some of the most successful were the Holtz and Wimshurst Machines, which used multiple spinning glass platters to generate electricity. Your crystals could be used in a similar way to produce electricity from motion. Most electrostatic generators produce high voltage with very low current, they are often used to power impressive sparking science demonstrations. So a crystal based rotary generator could be used with a spark discharge to create light. --- An alternate technique: you could use salt crystals as the electrolyte in some form of a battery. Being solid crystals would ensure chemical purity prior to a well developed chemical supply industry existing. [Answer] I'm going to suppose that these crystals exist and behave the way you describe and I'm going to address what I think is your primary question. ## How can electricity be harnessed from such crystal? You describe breaking a crystal in half and having one half be positively charged(few electrons) and the other being negatively charged(many electrons). This is very similar to static electricity. To use this as a significant power source, the amount of energy involved must be much greater than when you pet a cat on a dry day. I think it would be most useful to think of the broken crystal as a charged [capacitor](https://en.wikipedia.org/wiki/Capacitor). Capacitors are difficult(but not impossible) things to use as power sources. Capacitors tend to want to dissipate all their energy at once. I imagine that if you touch the two halves together then there would be a spark, the charges would equalize, and all your power would be gone. Also, if you broke the crystals with your hands, the current would flow through you body and the crystal halves would again be inert. (This might be bad for a person, it depends on the size of the charge) The charge in the crystals would bu just as happy to dissipate into the ground. The two halves would also be strongly attracted to each other in much the same way magnets are. A capacitor with enough power to illuminate a light bulb for a couple of hours would be a dangerous thing. If it did manage to discharge all of its power at once, it could electrocute someone or start a fire. [Answer] In a medieval setting you have a windmill. The crystals can be made to provide electricity by applying pressure or squeezing the crystal,if you will. You can have 'Windmill power stations" whereby you use the power of the turning windmill to operate a hammer or some kind of vice to hit or squeeze the crystals many times per second, and thereby obtain a kind of PWM DC power or Pulse Width Modulated. It is not a clean DC signal, but if you can cause the crystal to be activated several times per second(perhaps a staggerd array of hammers?) you will develop the equivalent of a constant DC current which will make a light filament heat up and glow, even though it is intermittent. [Answer] ### Basically Traditional Batteries It doesn't actually take much to make a basic battery in real life. The first "battery" able to provide continuous current was the [Voltaic Pile](https://en.wikipedia.org/wiki/Voltaic_pile), which was made with Copper, Zinc, and Brine. At a basic level, copper and zinc with brine between them created electricity, and stacking multiple of those together increased the power. Most disposable batteries still use similar principles, albeit more refined. Replacing "Two different metals" with "two different crystals" probably wouldn't work in the strictest hard-science sense, but it's close enough to be believable in my opinion. A feasible explanation for substantive use at an earlier time could build on that by replacing the brine with a third crystal; if a Red crystal and a Blue crystal grow close together with a Green crystal in between, then an "all-natural" battery might form that would inspire curiosity and experimentation. On the other hand, if you're looking for real-life elements that would work for this, a different path might be better. Both Copper and Zinc technically exist in crystaline form, but they are very far from the translucent gem-like shapes that come to mind from the word "crystal". [Answer] ## Radioactivity First of all, I would like to say that this answer is not 100% science accurate as I don’t masteries all the subjects involved in it. At least it is a try and maybe the detail level needed for your story will be low enough to be very free about little imperfections and mistakes. So, maybe your crystals could “simply” be radioactive. Your crystal would have to be made up of silica and a lot of impurities like Uranium (U), Thorium (Th) or Radium (Ra), etc. I don’t know if it will be enough for a quartz-like crystal to become radioactive but if it’s not, there is another solution: Torbenite The Torbenite (Cu(UO2)2(PO4)2·12 H2O) is a natural radioactive mineral with a pretty green color. I am not sure this a crystal but you have to admit that it kinda looks like what people think about when you told them "crystal". [![enter image description here](https://i.stack.imgur.com/wmY3p.jpg)](https://i.stack.imgur.com/wmY3p.jpg) [[Source]](https://en.wikipedia.org/wiki/Torbernite#/media/File:Torbernite_Aveyron_HD.jpg) --- Ok, I have my radioactive crystal but what now ? Generally, getting electricity through radioactivity is always a matter of heating water that will produce steam. This steam is then used to move turbines and so on… This is an over complicated way to produce electricity for your medieval world so is their another method? According to [this article](https://www.newscientist.com/article/dn13545-nanomaterial-turns-radiation-directly-into-electricity/), it seems that there is a way to obtain electricity from some complexes nanomaterials. Quoting Phil McKenna (emphasis mine): > > The materials they are testing would extract up to 20 times more power > from radioactive decay than thermoelectric materials, they calculate. > > > Tests of layered tiles of carbon nanotubes packed with gold and > surrounded by lithium hydride are under way. Radioactive particles > that slam into the gold push out a shower of high-energy electrons. > They pass through carbon nanotubes and pass into the lithium hydride > from where they move into electrodes, allowing current to flow. > > > “You load the material with nuclear energy and unload an electric > current,” says Popa-Simil. > > > --- [Answer] I would like to expand on the piezoelectric answer of @L.Dutch above. You may have an easier time integrating the entire pyro-thermo-piezo electricity triangle. See the link below for an example. By utilizing the full breadth of this physical mechanism, you can effectively imagine a device which can accomplish whatever task your characters have at hand. Since these devices are made from crystals, you can also exploit their optical properties. There are a number of existing technologies which make extraordinary use of these materials (for example, pyroelectric accelerators for neutron generation, thermoelectric waste heat generators, etc). So even if your world is based in medieval times, the possibilities are truly only limited to imagination (many of these devices have few moving parts). It is also important to note that combinations of these crystals can lead to interesting devices. For a simple, real world example, check out the of combining two crystal to create thermocouples via the thermoelectric effect. Need to boil water and charge a battery? Have the local crystalsmith grind down frensel lens to concentrate solar energy. The sunlight boils the water & induces the pyro electric effect in the crystal, storing charge for night use. ![Electro-thermo-elastic formulation for the analysis of smart materials](https://cdn.iopscience.com/images/0964-1726/15/2/021/Full/1463701.jpg) <http://cdn.iopscience.com/images/0964-1726/15/2/021/Full/1463701.jpg> [Answer] Piezoelectricity has been mentioned a few times already, but the impracticality of it seems to stem from the constant pressure being very...effortful, one person compared it to churning butter! But what if you lined the underside of a busy boardwalk/road with crystals, and the wires connected them all to something that could be charged. ]
[Question] [ Suppose there's an island in the East Pacific, west of San Francisco and south of Alaska (see [Google Maps](https://www.google.com/maps/@37.7990033,-142.9829096,6z); there's nothing but ocean there). This island needs to be at least 4x the size of Manhattan, preferably larger. It's home to a diverse and loosely-governed society that doesn't care to communicate with the outside world. It's not owned by or connected with any external government. It's self-sufficient (no substantial exports or imports). And its government has a strong interest in keeping the existence of the island secret. That is, perhaps select individuals outside of the island can know about it, but if it were to show up on satellite imagery, a Rand McNally map, Wikipedia, etc. that would cause irreparable damage. Any ships, more than the occasional lone adventurer blown off course, would also be unacceptably inconvenient to deal with. This is a non-magical world, so a Hogwarts Hidey Spell won't work here. However, the island's access to technology is quite good; perhaps on par with present-day American military/government research. The population of the island includes a number of millionaires and scientists who have disavowed the outside world and aren't interested in going back. Assuming that the island's government has access to impressive wealth and a few privileged connections (as few as possible, of course), how could it keep the rest of the world in the dark? EDIT: [This question](https://worldbuilding.stackexchange.com/questions/78611/how-can-i-hide-my-island) has been tagged as a possible duplicate. There are some similarities, but the accepted answer to that one was "hide in plain sight, under the guise of a resort/theme park". That's great for hiding an evil lair, but not nearly as good for hiding a civilization that loves its privacy. [Answer] It's going to be tough. ## Satellite Surveillance / ISS Live Feeds You're not going to be able to hide from satellite surveillance. If your dwellers lived underground and had no significant above-ground footprint (or put grass and rocks on all of your rooftops and didn't have roads), and you keep your heat emissions very low and distributed evenly[1], maybe you could make your island look uninhabited during the day. At night, you wouldn't be able to have streetlights. You'd probably want some combination of self-driving cars or night vision for people that need to move around, and/or a very good subway system. There's a much simpler option, though: Because it seems you're mostly trying to hide your existence from the general world public, and "a few select individuals" can know, my best suggestion is to forge agreements with first world nations with surveillance capabilities in exchange for keeping your existence classified so only top levels of world governments are aware. Give the conspiracy theorists something to really whine about. \_\_\_\_\_\_ 1. Heat is just another form of detectable radiation, and anything that uses power (including humans—I burn over 2000 kcal/day) generates heat correspondingly. You either have to distribute that heat over a large area so the effect is small and hopefully goes unnoticed, or you have to "export" your heat far offshore and hope that nobody cares enough to send a submarine and go looking for the other end of the warm seawater pipe... :-) Another reason why my vote goes to making deals with other world powers. ## Self-sufficiency v. Visibility On a hidden Manhattan-sized island, you are likely going to need some imports/exports. You aren't going to be able to have significant above ground crops of livestock, after all. Maybe a few wild fruits and vegetables or indoor hydroponics, but how far that goes very much depends on your population. On a Manhattan-sized island, other natural resources will be slim, so you'll need to import things like precious metals required to build electronics, and buying foreign-made equipment might be a necessity for certain things if you don't have the real-estate to house factories for every widget you need (and I strongly suspect you won't.) Being self-sufficient is hard. Being self-sufficient and high-tech on a small island will be extremely hard. Edit: The point here is that you'll probably need to import something, and to do that without giving away your existence will be tricky. Even if you use your own ship/aircraft, you'll need coordination with foreign customs and border officials when entering others' borders. That, or maybe arrangements with some pirates who don't ask a lot of questions, who you can meet at random predetermined coordinates every week or so, to trade cargo mid-ocean. ## Radio Transmissions As with light pollution and heat above ambient being visible from space, any radio frequency transmissions you use can be picked up as well, so I'd advise going hard-wired as much as possible, which may well make mobile phone use tantamount to high treason in your country. Note that encryption doesn't help you because the mere presence of such transmissions gives away your location. [Answer] Given the area where you want your island was center stage for the pacific portion of the second world war, the chance of any existing landmass going unnoticed during the first half of last century is less than zero. So either you need to create a new island after 1945 and follow the cloaking advice offered in the other answers, or... you could use a real and unoccupied island in that same neighborhood, leaving you with the less challenging task of keeping visitors away. This island of [Attu](https://en.wikipedia.org/wiki/Attu_Island) in the northern pacific has a 2010 census population of zero. If you could arrange for a mythical chemical or nuclear spill to scare away the tourists, you would have 344 square miles of vacant land on which to grow your secret civilization in complete privacy. [Answer] So this island must be: 1. Invisible to imaging satellites. 2. Cannot be visited by boat. 3. Cannot be picked up as a landmass on radar; as it would then be detectable by vessels at a distance. 4. Cannot have detectable/locatable emissions, be it light, heat, or even radio waves. That's a bit of a tall order, but not an impossible one. Interestingly enough, 3 and 4 might be the easiest to accomplish with current technology. [Vantablack](https://en.wikipedia.org/wiki/Vantablack) is a metamaterial (vanta stands for Vertically Aligned Nano Tube Array) that is able to absorb over 99% of the visible light spectrum. Objects coated with vantablack appear basically like a featureless black blob, sort of like [Hotblack Desiato's stuntship](http://www.otostopcu.org/yazi/h2g2/b2c19.php). A properly tuned vanta array can similarly be used to absorb different parts of the EM spectrum. Mounted facing toward the city, this would absorb internal emissions. Facing outward, it would be tuned to absorb incoming radar and lidar. Side point: Potentially, the VANTA shielding could be harnessed for electrical generation through either a heat exchanger system or tuned band-gap generators (like solar panels). To prevent being visited by boats, I propose that the easiest solution would be a system of artificially generated hazards including reefs, waves, and storms. Any single one by itself would be "too obvious" or navigable, but an interacting system of underwater terrain and sporadic storms would dissuade people from trying to cross an area this far from any shipping lanes. Adding some magnetic field anomalies would mess with compasses and GPS connections - people could be sailing right around it without realizing they've deviated from their course. But this would leave a conspicuous blank on a lot of maps, and doesn't solve the 1st point - satellite visibility, or visibility in general from space, since something as large as Manhattan is photographable from the ISS, and we're talking about something 4 times that big! Enter the [IMOD](https://en.wikipedia.org/wiki/Interferometric_modulator_display) or Interferometric Modulator Display (trademarked as mirasol). Rather than being backlit, mirasol displays work by reflecting ambient light, meaning they look brighter in direct sun than in shade. The pixels operate by creating a gap between the clear surface and the reflective substrate of the subpixel. This gap causes destructive interference to most wavelengths of light, while the wavelength matching the gap is reflected, making the subpixel appear a specific color. For relatively low refresh images (like ebooks or smart watches), this is a very energy efficient display. Affixing large pixel tiles above the buildings would enable you to generate an adaptive wave camoflauge that would be hard to detect at satellite resolutions. The last bit of the problem is protecting the secret. Such an advanced society with near-future tech would pose a credible existential threat to smaller nations and could prove an ally to larger ones. Basically, you would have to forge connections with high-level individuals in the NSA, NRO, NGA, and their cognates in large spacefaring nations to keep them from intruding. In all likelihood this would be via intelligence exchange, slightly outdated tech, and the knowledge that if your secret society wanted to they could be a significant threat. [Answer] [Isaac’s answer](https://worldbuilding.stackexchange.com/a/81733) itemizes different distinct problems, and doesn’t answer all of them. I have a suggestion on how to hide from satellite imagery. Suppose that perfect invisibility or perfect camouflage is not available — you can’t make the spot look like empty ocean without attracting more attention to the anomaly, eventually. So use meta-camouflage, where it looks redacted already by someone. The joke about hiding a barn by painting it green with “© Google Earth” written on the roof can be done in a more serious manner. Make it look like bad pixels, or a cloud, or the pattern used to hide things that the imaging company uses. If it could be active material, then it could update to best suit each overflight in the best way for that equipment and company, or at least not be an unchanging cloud. [Answer] ## Hide it in plain sight If you look at any of those Pacific islands, you see a fairly sprawling Atoll that is readily visible. However, on closer inspection, at least 95% and often 100% of it is slightly underwater. If it is not entirely underwater, perhaps a hush-hush nuclear test removed the last of the above-water island, leaving a toxic radioactive wasteland no one would ever go to. Except that there was no nuclear test, this was a cover story, the work of the cabal. Or the tiny island is a wildlife refuge, under control of a nature organization again controlled by the cabal. ## It looks like the same old boring underwater reef So instead of making your island invisible to satellites, and aircraft, you only need to make it look slightly underwater. You excavate material from from the deeper ocean to raise your atoll out of the water, while installing the active camouflage to keep it looking like last year's overheads. Or in hard-mode, make it an actual known island, which gets occasional visitors... And conceal your section of the atoll from those visitors. Imagine if your base was in fact Midway, replete with functioning airfield. It's known to the world as an ETOPS diversion field. Your aircraft fly at max speed, snake in there when there are no satellites overhead, unload, replenish fuel, and continue onto their flightplan destination. Their late arrival is explained away as economy cruise. So in this case you subvert the LOST problem: the stricken airliner simply lands at the publicly known field, gets serviced, is flown out, and none's the wiser. And if any outsiders discover the secret part of the island, then you loose the black smoke and polar bears! [Answer] The Pacific Ocean is unfathomably big. There's lots of space in it to hide an island. Somewhere between New Zealand and Argentina is appropriate. The ocean is flat, but even from standing on top of a hundred foot destroyer, the horizon is only 12 miles away. So you don't actually have to keep boats very far away to hide effectively. Note that this also works for ship-based radar. This leaves satellites and planes. If this is a natural island and not a floating habitat you're going to be picked up on radar/gravity deflection images of the planet as a big lump on the ocean floor, because islands are just mountain peaks, and mountains are big. So you have to pretend to be a seamount or a small atoll or something. I recommend seamount, remote atolls attract biologists. So if you're a seamount, you need to paint ocean colors on the tops of things so you look pretty much like an ocean from space. This isn't going to work forever, so I recommend you invest in an artificial cloud generator. A big plume of steam will work in a pinch, but I recommend heating a big patch of ocean miles upwind of you, then seeding cloud formation over the island. You won't need to do it all the time, just whenever a satellite with a good camera is looking, and you should have plenty of advance warning of that kind of thing. So that just leaves planes and really persistent boats. A combination of electronic counter-measures, radar-spoofing transmitters, fake GPS signals, and just plane (heh) fake clouds should keep most planes and boats reliably off-course. Worst case scenario, torpedo the boat/missile the plane, recover/fake the transponder and/or black box, and put it on a different plane that crashes somewhere else to divert attention. Or don't. Boats disappear all the time. The really easy way to do this is just put the whole civilization on a big floating habitat so it can move around and actively dodge boats and planes. Then you can get away with only steam plume for satellites because nobody will notice that one spot in the ocean is constantly covered in clouds. ]
[Question] [ The [bonegrass](https://worldbuilding.stackexchange.com/questions/38354/how-often-must-carnivorous-grassland-eat) fields are full of other life, despite their dangers. Lots of insects, some birds, and even a handful of reptiles have adapted to the paralytic nature of the air in order to reap the rich rewards offered by the deathly white foliage. Of all of these creatures the most advanced by far are the fleshmoles. Rather than adapting to the neurotoxins emitted by the plantlife the fleshmoles (actually a branch of [naked mole rats](https://en.wikipedia.org/wiki/Naked_mole-rat)) have an alternate strategy: They rarely breathe fresh air. Fleshmoles don't surface unless there is prey that has been ensnared by the bonegrass, and even then they tunnel directly up through the ground into the flesh of whatever has fallen (causing excruciating pain if the prey hasn't already died). They're adapted to deal with high CO2 concentrations and the noxious atmosphere of their underground hives (A matriarchal eusocial structure keeps fleshmole colonies together), but of course occasional O2 injections are required. To this end weak or old fleshmoles are driven to the surface, where they take a huge lungful of air, become paralyzed (neatly plugging the hole and removing the paralytic agent from the air they breathed in), then are dragged back down and rapidly consumed by their brethren. Fleshmoles also burrow into the chest cavities of larger prey in order to suck down as much O2 rich flesh as possible. The question is this, given that I'm not particularly hot on my rodent biology: Is it possible for such a colony to maintain a workable O2 supply, given that they're fairly well optimised for high CO2 life? [Answer] For mammals... this could be a problem. A pretty average human being(62 kg) uses about 550 liters of pure oxygen per day(at sea level pressure). So call it 9-ish litres per kg. A single naked mole-rat is about 35 grams. A colony is 20 to 300 individuals, with an average of 75. So an average colony of 75 might weigh in at about 2.5-3.0 Kg of mammal-flesh. They're extraordinarily long-lived for a rodent of their size (up to 31 years). Small rodents tend to use more, not less oxygen by weight (more active) but let's make some generous assumptions: Let's assume they use 10% as much oxygen by weight as humans. Your colony still needs 2.7 litres of pure O2 per day or 13.5 litres of normal air (20% oxygen) assuming they use it perfectly somehow. From this we can conclude that this is not a workable strategy: > > weak or old fleshmoles are driven to the surface, where they take a huge lungful of air, become paralyzed (neatly plugging the hole and removing the paralytic agent from the air they breathed in), then are dragged back down and rapidly consumed by their brethren. > > > They live too long, their lungs are too small and it's just not gonna work. They couldn't provide a tenth of the air needed even with generous assumptions. But if I remember correctly you talked about how your victims are left alive. The air in their lungs is not a good option, it's contaminated by the spores just like the outside air. So let's try another option. Again, let's steal from real life organisms. [![Parasite](https://i.stack.imgur.com/p4HGb.jpg)](https://i.stack.imgur.com/p4HGb.jpg) Real paracites need oxygen, how do they get it? They absorb it from their host, often directly from the blood. Your victim has a perfectly good set of lungs and they're going to be alive for quite a while (longer if nothing burrows into their lungs). So your moles could be adapted to burrow into the flesh (careful not to cause lethal harm), find big arteries close to the heart/ lungs where it's rich in oxygen and then filter lots of oxygen from the blood and to somehow feed it back to their kin bellow using the victim as a living oxygen filter. Perhaps, if desperate and lacking prey for a long long time, the moles might sacrifice one of their own to use the same trick: one of them breathes while the others filter oxygen from its blood below. This leads on to some grim conclusions. It's going to be in the moles' interest to keep the victim alive for as long as possible. Too much bonegrass growing up through them will kill too fast. So the moles could be chewing away the roots of some of the young bonegrass to keep it from killing the victim quickly. The bonegrass wants to kill you fast. The moles want to keep you alive for as long as possible. Indeed, weirdly, if they have access to lots of calories but not much oxygen it could be in their interest to feed sugars into your blood while taking oxygen out. To stop you dying from infections they might even release antimicrobials as they chew into your flesh. (Additional reason for people to enter the bonegrass: fleshmole teeth could have "venom" sacks containing potent antibiotics) They also might carefully feed on fatty tissue, avoiding blood vessels, again to keep their victim alive for as long as possible. There are some far more practical options for filtering air... but they're not as fun as absorbing it from the blood of still living hosts. Now, there's also another possible use for your victim. A nice warm place for baby fleshmoles and similar parasites to grow. Here's a species of wasp which lays its eggs inside still-living hosts. ``` ‚ô´It lands on caterpillars It lays it's eggs inside To make sure that the meat's fresh It keeps the things alive All things bright and beautiful...‚ô´ ``` [![Keep the meat fresh](https://i.stack.imgur.com/TF9N1.jpg)](https://i.stack.imgur.com/TF9N1.jpg) Some wasps have an even more disturbing effect on their victims. Once the babies have eaten their way out through the hosts flesh the host's behavior has been altered by the parasite and the caterpillar spends the remainder of its life trying protecting the parasites. <https://youtu.be/7UkDMrG6tog?t=8> So for added creepiness, imagine someone getting paralyzed, fleshmoles eat through their flesh but before they die the wind changes direction, the amount of paralytic poison decreases and they make their escape. They have a few baby fleshmoles under their skin but rather than wanting to cut them out and destroy them the host feels a strong compulsion to care for them because the fleshmoles have released a hormone that hijacks the normal instincts to protect your children. Someone is rescued from the bonegrass and the fleshmoles. The town rejoices. But the following week they're found carrying around a blanket filled with a squirming mass of infant fleshmoles treating them like a baby and feeding them chunks of raw meat. [Answer] They would most likely arrange their burrows similar to how terrestrial burrowing creatures do so that there is enough air-flow through them to survive. Perhaps they even have "breather" tunnels that extend away from the grass fields and allow fresh air to flow in even when the grass starts spreading toxins. The moles could have a hibernation-like state when oxygen drops too low or toxin levels too high. Effectively they become dormant and conserve their oxygen until the event passes and the fresh air from their breather tunnels wakes them up again to continue their lives. [Answer] If they're subterranean they wouldn't disturb the grass and trigger the toxins the way a passing surface animal would. Also the air in their tunnels would have been filtered by passing through the relatively porous ground above them making it potentially safe to breathe. Or: If they've evolved around the bonegrass they're largely immune, but they do need to take a nap if a large animal triggers a lot of toxin near an open tunnel. Much like the [grasshopper mouse](http://news.nationalgeographic.com/news/2013/10/131024-grasshopper-mice-scorpion-venom-pain-animals-science/) and the scorpion, or the [mongoose](https://en.wikipedia.org/wiki/Mongoose) with snake venom. Once you start introducing other creatures also living on the bonegrass victims then your fields are going to need to be quite bloodthirsty. [Answer] Since you mentioned CO2, I'm guessing you are using [this answer](https://worldbuilding.stackexchange.com/a/38493/7129) from Tim B. If so, then think of dolphin moles. To store up large stores of CO2 while still being able to breathe may require the bone grass to go on a crazy oxygen converting frenzy. This would create an abundance of outside oxygen while the plants stored up CO2. Only during this time do the moles appear for air. The bone grass has learned to ignore the moles as the miles always disappear before they can pump out sufficient CO2. The mole dolphins don't have to surface for a while and are alive and well. If you want the moles to tunnel into people's lungs, it would be a bit impractical as the person collapsed because it has too much CO2... Perhaps this is what the mole eats? Also just a side note. The CO2 could be used as a defense against fire. Whenever you try to light the bone grass, it suffocates the fire! [Answer] This is actually a real issue for termites. I know someone who studies this question - [How do termites ventilate their mounds](http://news.harvard.edu/gazette/story/2015/09/how-termites-ventilate/)? After all, a bunch of termites live underground. I can't find a source now, but if I recall the biomass of a termite colony is comparable to that of a sheep - not warm blooded, but still that's a large O2 requirement. Let's think about the pollen. It gets carried by the wind, but it is heavier than air, so it doesn't get very high. In fact it's in the evolutionary interests of the grass to select density (and shape) such that the concentrations are highest in the level of the terrestrial animals walking around. So the pollen cloud won't get much over 6 feet high. Your moles have a few big termite mound-like structures in the middle of the field. The mounds exchange air from within the chamber and above the layer where the pollen lies. They can even come to the top, meerkat like, and look around for where some victim has fallen. Then they tunnel over to it. [Answer] Perhaps instead of them getting the oxygen from only their victims, they also have some kind of filter in their lungs that filters out CO2 and let's only oxygen in. However, over the life time of the mole, the filter degrades, eventually to the point where it cannot keep itself alive. Then it is out out to pasture. But why skip out in a good meal? More oxygen can be found in the blood of their victims, which means they don't have to waste filters during feeding time. Which means eat the lungs and arteries last, so they can provide you with oxygen while you burrow through the victim's living flesh. Even if the creature hAs inhaled a lot of CO2, it still takes less filtering and is nice and yummy for the flesh moles. And when their brethren become to old to efficiently filter out the CO2, it is time to feed... Because fo such creatures you just can't get enough oxygen by simply draining it from the living blood. [Answer] Your beasts' should be a sustainable ecosystem for bacteria that make O¬≤ out of byproducts produced by your beasts. There's a bacterium that does that, it's called [*Methylomirabilis oxyfera*](https://www.mpg.de/621120/pressRelease201003241), it eats methane and oust oxygen, perhaps this kind of bacteria can live in your beast's digestive system consuming methane and producing oxygen so your beast would fart oxygen and breathe it in :D ]
[Question] [ After watching first Shrek, I got interested in one detail: Can you build a castle which is surrounded by lava, using medieval technology? For scope of this question: Imagine ultimate wealthy king/queen (resources are not a problem). This kingdom wants to build castle to treasure its wealth. What if we build the castle guarded by lava? The kingdom has access to anything which could be plausibly made before year 1500 CE. Also assume there is suitable volcano. Can the kingdom build it? [Answer] Lava is a "hot fluid" [citation needed]. The technology to handle the "liquid" part is obviously available during medieval era, as irrigation is already known for centuries. For example, the [first dutch polder](https://en.wikipedia.org/wiki/Beemster "Beemster") was build from 1609 to 1612 with windmills. Digging a hole somewhere so that it can thereafter be filled with liquid is really not a challenge. Organizing the liquid flow is not a complex issue either. That said, the "hot" part is more tricky. The area where the lava flows must resist the high temperatures, and no technology is available to protect people once the lava is in place. So this may lead to some adaptations : * high-temperature resistance rock must be used to contain the lava. Alumina rich clay are the best option and are used nowadays for this, but granite probably should work. A warning if you use porous rocks : they may break or explode if the water they contain is not removed previously (slowly heating them beforehand may do the job). * immediate surroundings will be permanently exposed to the heat. A bridge will get very hot and end up not being usable, for example. * non-immediate surroundings will receive energy as lava flows continuously. The whole area must find a balance. This may require adding of cooling systems, but this will be complex : water can carry heat but do not mix well with lava and will create breaches in your defense system. On the overall, this is achievable if you have good engineers and a stable flow of liquid lava. However the resulting place will be hot and hard to enter, even if friend. Depending of the land size, it could end up in a tropical paradise (if you do it around a mountain, for example), or a balrog™'s lair... In practice, the area close of the lava may look like hell (which can obviously be cool!), with red-glowing borders reaching high-temperature from the surrounding lava. Expect air to be filled with some toxic and stinking smokes due to sulfur, and nearby waters to become acid, not drinkable, but eventually colorful like the [Kelitumu lakes](http://indonesiad.com/indonesia-must-see-the-colored-lakes-of-mount-kelimutu-flores/). Most animals will leave, and nearly all plants die. Your visitors may be reluctant to come by... One last thing : should your lava supply vary, or its fluidity not be top-quality, the lava will solidify in your structure and it will be another nightmarish hell to repair it and make it work again. [Answer] I think the hardest problem would be that lava doesn't exactly sit nicely like water does. Its constantly depositing rock as the lower edges cool. Your moat would constantly be changing shapes as lava from the volcano flows through your channels. I got the privilege of photographing the lava flows in Hawaii. One of the things they warned me before we started was that lava is unpredictable. It's very easy to get caught up in the lava in your camera's eye, trying to get the lighting perfect, and fail to realize that another flow of lava behind you has just redirected itself towards your feet. [Answer] Another issue would be the [Hydrogen Sulphide](http://avogadro.chem.iastate.edu/MSDS/hydrogen_sulfide.pdf) gas (H2S) that is common around volcanic events. For one thing, H2S is an explosive gas. No lights in the castle after dark. No cooking fires, although you've got plenty of lava to cook your food for you. Another thing is that H2S smells bad. It's often referred to as 'rotten egg gas'. You can start to smell it at less than 1 part per million (ppm). That's only a minor problem though. It is also a toxic gas. The '[Short Term Exposure Limit](https://en.wikipedia.org/wiki/Short-term_exposure_limit)' for H2S is 15 ppm. The smell would cease to bother you after about 100 ppm, as it basically kills your olfactory nerves, permanently ruining your sense of smell. At about 300 ppm, you are pretty much on your way to death, if not dead already. H2S is heavier than air, so it would settle in the lowest parts of the castle. Dungeons and areas enclosed by the wall, rooms on lower floors etc. Nasty stuff. I don't think I'd want to live in that castle. [Answer] It's impossible with medieval technology. Even today I would assume it as impossible without a great energy source or great thermal isolation of the "riverbed". Otherwise, the lava will lose energy, solidify at its edges and bottom and eventually overflow its "riverbed" leading to catastrophe. In fact, I would expect such a lava river to eventually create a [lava tube](https://en.wikipedia.org/wiki/Lava_tube). ]
[Question] [ TL;DR: How would adults deal with super-powered, godlike teenagers? A little background: The gods have mortal avatars. They walk around as physical gods and generally head their religions, making sure that people know what they actually want, although certain gods do differ on this, making religion… complicated. In order to stay in the mortal world, they reincarnate themselves in a mortal body the instant that they die, marked in such a way that the priests know exactly who they are – and, generally, move them into a temple with the parents as soon as possible. They're born, they live, they age, they die. In their early years, they'll know that they're a god because everyone around them tells them so, and possibly because of fragmented memories. Around the time they hit puberty, they'll start to receive more of their power and memories, and by the time they die, they will be a physical god with the same memories as before. And yes, you read the above correctly. They start receiving memories from past lives and power usually around the age that a modern kid would be surviving junior high/high school, and this is probably the worst possible time for someone to start receiving massive responsibility, random, hormone-triggered memory dumps, and immense power. So, as you might guess, sometimes teenage gods can get a little bit "testy", especially given that at this age, however well-natured they might be, by nurture they can be spoiled, extremely stressed brats. When a superpowered teenager starts mouthing off to you, what do you do? They're not as powerful as they're going to be eventually, but if they became angry they could, theoretically, vaporize you and get away with it. The adults surrounding the gods are worshippers, as well, which doubtlessly makes this phase difficult every time: would you reprimand the person you worship, or just grovel, grumble, and deal with it? Do you risk presenting yourself to another physical deity and ask them to give a sharp reprimand? How do you balance worship and discipline? [Answer] I imagine that, once a "god" lives to a certain age, they start to realize they might die soon, and they make arrangements for the proper handling of their next incarnation. One possibility is they write some letters (or record some videos, et cetera). "Hello, younger me. I'm you, but you don't have all my memories yet. While you're growing, you're going to be prone to mood swings and bad decisions. I've assigned you some caretakers, but it's very important that you treat them with respect. If you hurt them, they'll go away and you won't have them any more. Eventually you'll be old enough and responsible enough to hire your own people..." In the ideal case, a god would get another god to take care of their younger self, as a sort of apprenticeship program. When Thor is young, Odin takes care of him; when Odin dies and reincarnates, the older Thor returns the favor. Probably not all gods have friends they can trust to take care of them properly, but most will. Also worth noting: teenage misery is caused by many things, but a lot of it is environmental. Most of us reading this are adults now, but imagine you had to live as a teenager for a few years: live with your parents, eat what they want to feed you, do the chores they assign you. Be home by 9pm, spend eight hours a day in school memorizing details you'll never use in real life, spend more time after school on homework. You'd be miserable too! Many of these restrictions are in place for the convenience of the parents, who want to live their own life rather than take care of the teenager all day. If the parents are replaced by people who are actually being paid to take care of the teenage god, a lot of that misery might go away. [Answer] How would adults deal with super-powered, godlike teenagers? Look at the ancient Greek stories. I always thought it made sense to have being with superpowers and all the usual human psychological issues simply acting like you would expect people would if they had superpowers and no responsibilities and poor parenting. Zeus would bed anything that moves, even turning himself into animals and things to do so. The older generation did nothing but distrust each other and amuse themselves by messing with humans and/or the younger gods and demigods. While the older ones were machiavellian, the younger had no social skills whatsoever. I generalize, but you get the idea. [Answer] Your question isn't very explicit on that part, but if I assume some similarity with Greek/Roman Gods, when they are full fledged, they tend to have distinct and specific personalities and power. And even as their younger self, they have their own personalities. They might not remember, or have their powers, but the genetics part of it is the same. There are some debates about what comes from genetic inheritance and what comes from experience and upbringing, but the Gods before dying may actually have set a given upbringing for their future self. As you wrote, they are sent to a monastery-like as babies. So the inherited being the same and the upbringing being controlled, you'll have a smoother transition than if suddenly a normal teenager got God-like powers without mental preparation before hand. With that kind of background being set, I don't think there's a unique way to answer your question. Each God/dess will need to be treated differently depending on his/her characteristics. I can imagine that being close to the teenage Goddess of war could be challenging. And the priest around her will learn pretty quick to read her mood or mood changes, and possibly develop some solid running capabilities. The Goddess of Wisdom, however, would be easier to deal with, even if you might have to bring the best philosophers of the time, to answer all her questions. Even if your Gods don't have a view of the future, they can share their own experience of their past so that their own churches can actually prepare themselves and the God-kids for those troubling years. Learning to play the Smashing Pumpkins might be a required skill to enter the church. [Answer] Worhispers For general worshipers, the responses would likely depend on the character of people who tend to be attracted to worshiping a given deity. This would largely be dependent upon the type of deity they are, what they are over, and their 'normal' adult personality (which I am guessing tends to be longer than normal human lifespans for their time). It also depends on what types of protections worship confers and if there are other defensive magics which could be employed as a buffer against random outbursts. For instance, if a god of fire confers protection from fire to those who worship them, then their fiery outburst is of less concern to their worshipers than it is to non-worshipers. Caretakers Caretakers would likely need to know the history of the individual deity they are taking care of, know the signs of an outburst, common triggers, and what types of outburst that deity is likely to have in a given situation. This is the same as any attentive parent understanding each of their children as individuals. What works on one won't necessarily work on another. (Note: The following is more about what a deity might do knowing this happens rather than their worshiper's reactions, which are too varied to nail down.) Pantheons The situation you describe would lend itself well to a generalized pantheon structure as each deity, knowing that they will go through these periods of instability, will reach out to others to have a network of divine support. While on a day to day basis specially trained priests and priestesses would care for the young deity they might have a way to contact their deities allies to calm them down / put them in check when acting out. Assuming all is well. Divine Wars The deities of a given pantheon would attempt to ensure that not very many of them are young at the same time, but pantheon wars could definitely make this difficult to ensure. Often, enemy pantheons will wait to launch their attacks until their targets are mostly young and unreliable. If massively imbalanced this could generate a major ebb and flow of the ruling divine powers over the world, one ruling while the other's avatars are all young until they start to die out and the 'next/previous' generation comes into power, killing off the remaining enemy deities while they have little support. Infant Deicide A rival pantheon might establish their own balance while they are in power and begin a campaign of hunting down the young avatars whenever they surface, ensuring they can never truly challenge them back. This could generate a situation where the priests of the weakened pantheon might need to separate the young deities into seclusion to ensure that at least some of them could survive to adulthood to aid their brothers and sisters and eventually challenge their rival's control. Trapping Gods A rival pantheon might imprison their divine enemies, keeping them alive as long as possible, ensuring they know where they are rather than letting them spring up anywhere, unchecked. Temptation Another good plot element to consider would be tempting a deity in their youth to switch pantheons, abandon the others and be on the 'winning side' of history. [Answer] This sounds a lot to me, like a child king. England had a few of them and the Egyptians had child pharaohs. They spent their childhood being worshipped with any maternal or paternal attention. This often made them quite spiteful when you can get away with any thing. However assuming that these Gods aren't omniscient (if they were then they'd have their old memories already) then really they're just as small-minded as a normal teen. The things they want are petty and they're easy to appease. Of course you don't want to get on the wrong side of a God with dangerous super-powers but I would suggest appointing each God advisors, maybe even having a message for a previous life? If regardless, the teen is still a complete train wreck, just sucking up and appeasing him, and satisfying them will make them less agitated. If in your world, Gods have seniority maybe you could go to an older God to help guide the younger one. ]
[Question] [ The stories of the miracles of Jesus have survived 2000 years through written records by multiple witnesses. These records were compiled into a collection called "The Bible", which has been reproduced more than any other book on the planet. Early reproduction theoretically makes modification less possible, as any discrepancies would stand out when compared to other reproductions. Today however, 2000 years later, many people don't believe that the miracles ever happened. If Jesus performed miracles today, how could we more convincingly document them so that a society 2000 years from now would believe that they actually happened? [Answer] Henry's answer makes a good point: a miracle of prophesy could not only avoid the CGI issue with documenting events, but continue to convince future audiences. Someone active today could easily leave terabytes of information as computer files. This could be replicated and seen to exist by many, and not be switchable like a magician's envelope because everyone has an independent copy. It could include annual predictions that are unlocked by keys derived from data received from distant quasars, or cracked once the technology has progressed or time spent brute-forcing. The annual file opened might refer to current events and use file formats of the day, and include a renewal of any message to impart. This would convince people that time travel or reverse causalty is possible, anyway. How about a durable supernatural artifact that would still be inspected and studied in that far future? It would convince people that known physics is not all there is. It could be designed to cut to the heart of the most fundamental principles, so it can't be explained as just another as-yet-unknown thing. It could have continuing subtitles that freshly astound generations with greater depths of understanding of normal physics. But why is ordinary evidence needed? The show Stargate SG1 had a sequel movie called Ark of Truth that would simply convince anyone exposed to it. [Answer] Do something that is (semi-)easily verifiable to have occured, but shown to be impossible using the technology of the time. The thing you do must completely defy the natural way things happen, so that you can rule out "freak chance occurance", be impossible to cover up by humans, and be such a display of power that it cannot possibly be done by a human at that level of technology. Here's a simple example that is in fitting with most forms of theology (which seem strongly linked to astrology): # Create a new star It takes more energy than the human race can output (even a few hundred years in the future), it's easy to check that it wasn't there before (with records of stars going back centuries already), you can measure the star to collect things like age statistics and it will continue to shine for millions of years as a reminder of what you did. If you put it in a good place, close enough that it's really visible (preferably the brighest star in the night sky) then it will be pretty hard to deny that something miraculous has happened. If you pull all of the necessary fuel from nearby clouds in such a way that it could not have happened naturally then it becomes fairly hard to deny that something unexplainable happened. If your prophet told everyone (around the world) to gather around and look up, and snapped his fingers at the exact moment that the star became visible, then it will be fairly hard to deny that he did it. And impossible to deny that it was a miracle. [Answer] I believe this is outside the scope of mankind's abilities. Jesus though, being a manifestation of God and having or having access to omnipotent powers should have no problem. ## Persistent Miracles / Create Divine Artifacts So man says > > Jesus, it is wonderful that you have performed these miracles and convinced us of your divinity. But what of future generations? It is beyond our abilities to prove that these miracles really happened because there will be skeptics who say the records are not authentic or your miracles were mere tricks. But you could perform a miracle that will last forever by creating a miraculous object, and thus proving for all time your Divinity. > > > What kind of miracles? Pretty much anything will do as long as it is inexplicable and defies all science. A perpetually burning object defying thermodynamics, a levitating object defying gravity, a "holographic" image of Jesus preaching, with visual and audio (generating photons and sound waves with no energy source), a thingy which transmutes water into wine, or lead into gold, or clones fish, in complete and fragrant violation of conservation of energy, there are so many possibilities. Naturally, any such miraculous artifacts should be genuinely indestructible which fits well in the theme of violating natural laws as we know them. Detonate a nuke on them, they wont care, heck they wont even become radioactive, put then in the CERN particle accelerator bombard them with antiprotons and not an atom will be knocked loose. (Note: Jesus should insist that mankind regularly test the limits of these artifacts, and state clearly and repeatadly and insist that people write it down, that it is not blasphemy to drop the fish-cloning stick in a volcano) They should have inexplicable and miraculous homing instinct, so that if some smartass tries to encase one in concrete or launch it into the Sun, it will break free from its predicament and migrate to it's place of creation or manifest itself to any suitable holy man/woman. They should be made out of no element known to science, so that spectrographs and scanning electron microscopes say nothing of their composition (or they should appear perfectly ordinary, except having inexplicable powers and defying all efforts to destroy them). The artifacts must be so divine in nature, that they bamboozle not only 21st century science, but science for all time, no matter how technologically advanced. Considering how momentous these artifacts will be they should leave a dramatic mark on history. Future historians should have little difficulty seeing that society changed dramatically (for example the sudden appearance of news reports about the latest tests of the indestructibility of the artifacts), and concluding that before a certain year (or at least decade) they weren't in the world, and after a certain year they were, and this should fit closely with the historical records claiming that Jesus was performing miracles at that time, and any alternative explanation for the origin of the divine artifacts will seem needlessly convoluted. ## But what if Jesus wont co-operate? He's probably a charlatan who doesn't really have omnipotent powers, he'll make up some excuse like "proof denies faith" or some other waffle, and seriously call into doubt whether the miracles were real at all. In fact, if Jesus isn't going to co-operate in documenting that his miracles are truly miraculous and not just magic tricks, then mankind is very much stuffed in proving they were real for future generations. [Answer] If Jesus performed miracles today, you would have great difficulty even convincing people of TODAY that they happened. Even if you video taped them, skeptics would just conclude that the video had been post edited. Even recently, somebody addressed the UN with his testimony that he had been miraculously healed. Obviously, they don't give crack-pots a microphone at the UN unless they are backed up by independent medical investigations. So this is 'proof' of miracles. So what? Nobody is listening. Nobody wants to know. <http://www.cnsnews.com/blog/penny-starr/christian-pastor-dead-45-minutes-tells-un-god-has-totally-raised-me-dead> [Answer] Let's take as a given that the Bible is an accurate record of the events 2000 years ago (as your question implies). Some witnesses of the miracles do not believe in Jesus. > > Act 4:16 Saying, What shall we do to these men? for that indeed a notable miracle hath been done by them is manifest to all them that dwell in Jerusalem; and we cannot deny it. > > > So the Jewish high priest and friends clearly says the miracle was obvious and we cannot deny it, yet their actions clearly show that this did not matter to them, they were not going to follow Jesus or recognize him as the messiah. This was a miracle of the apostles, but the raising of Lazarus by Jesus has similar elements. > > John 11:45-53 Then many of the Jews which came to Mary, and had seen the things which Jesus did, believed on him. But some of them went their ways to the Pharisees, and told them what things Jesus had done. Then gathered the chief priests and the Pharisees a council, and said, What do we? for this man doeth many miracles. If we let him thus alone, all men will believe on him: and the Romans shall come and take away both our place and nation. And one of them, named Caiaphas, being the high priest that same year, said unto them, Ye know nothing at all, Nor consider that it is expedient for us, that one man should die for the people, and that the whole nation perish not. And this spake he not of himself: but being high priest that year, he prophesied that Jesus should die for that nation; > And not for that nation only, but that also he should gather together in one the children of God that were scattered abroad. Then from that day forth they took counsel together for to put him to death. > > > There was 2 different outcomes to the miracle, some saw and believed in Jesus, others saw, admitted the miracle and set about to kill him. Perhaps the best evidence of the truthfulness of the miracles is perhaps that the witnesses were willing to die instead of recanting their belief. No matter what time in history that real miracles are performed, there would be believers and unbelievers in those miracle. Even the Bible itself recognizes this. > > John 20:30-31 And many other signs truly did Jesus in the presence of his disciples, which are not written in this book: But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name. > > > Notice the word choice of the translators, that you "might believe". If you believe in the miracles of Jesus, you are unlikely to believe in those of Mohammad, or Joseph Smith, or those of Zeus, etc. Belief in miracles is a matter of faith -- even when you are an eye-witness. Thanks to Photoshop and CGI that we see in movies, there is no miracle that could be performed today that could not simply ve dismissed out of hand as computer generated by someone 2000 years from now. Sleight of hand is a further problem. With further technological advances, miracles become even harder to prove -- perhaps expressed in Clarke's Law: Any technology, sufficiently advanced, is indistinguishable from magic. [Answer] Just speculation; no offense intended. Separation from the Others There was no shortage of claimants as the Messiah. [Simon of Paraea](https://en.wikipedia.org/wiki/Simon_of_Peraea) comes to mind, as well I recall someone called The Egyption. The literal term is zealot (not in the offensive way). There are many people in the 2,000's who claim to be the next-big-thing. Even David Karesh claimed to be some kind of Gift of Prophecy in Christianity. This new-Jesus' followers must establish a way to create her as 'different' than the nutjobs. They must document very well the kind of miracles (or even teachings) the new-Jesus undertakes. I suggest your new-Jesus establish precedent in the following. Fulfilling a Prophesy Your new Jesus must fulfill a prophecy. Unfortunately many of the old-testament prophecies, have been taken by old-Jesus. Your new Jesus can predict the future, but luckily not all prophecies are the future; for example, the [First Epistle to the Corinthians](https://en.wikipedia.org/wiki/First_Epistle_to_the_Corinthians) suggests that you can spot that the right Messiah benefits the Church and not the individual. Sticking to these charms would do your new-Jesus well: Prophecy doesn't necessarily mean future-predictions. Liturgy Your new-Jesus should establish liturgy whereby it is a public gathering in worship, not wholly private. I think in order for new-Jesus to last 2,000 years, her legacy should be very public and very well-accepted over time. Reputation Management It's very important that new-Jesus has a pretty clean social media record; in today's (and presumably the future's) time anything you do is well documented. Those videos of new-Jesus should be well documented, but crystal clean and completely altruistic. Communication The followers of new-Jesus must ensure that her legacy and information is conveyed in the latest-and-greatest technology. Today that is dissemination among film, television, phone, and most importantly, Internet. But this has to continue in the future. One of the first products of the Gutenberg's Printing Press [was a copy of the Bible](https://en.wikipedia.org/wiki/Printing_press#Gutenberg.27s_press). Heck, Moses had clay tablets and Mohamed had his writings as well. Whatever the teachings of the new-Jesus are, they should be documented in the latest technology very well. This might mean a lot of blogs... Conviction Whatever cosmic powers new-Jesus has, it will be the hardest thing in today's world to get started, but it needs to be timeless. Politically, she needs to focus on supporting the 'underdog,' which should include. * Peace * Meek Shall Inherit the Earth * Altruism * Health & Safety for all Timelessness I have no idea what will be taboo in tomorrow's world, but in order to protect reputation, there should be well documented caveat's in new-Jesus' teaching that allows flexibility. Other religions that don't allow this might be popular today, but that is out of desperation and acting out. Convictions (not necessarily religious) that allow flexibility have and will last longer. This question is a tough cookie. [Answer] Well, there are two ways people seem to be answering this question: how ordinary mortals could convince the people of 2000 years in the future, and how a divine entity could convince those same people. The way for humans to convince future humans of the veracity of some miracle is simply to agree on it, and provide various independent video evidence. There is a problem of storage media, but 2000 years is quite short, relatively speaking. For example, Milleniata and Hitachi have developed an optical drive that they claim will last for millenia. It hardly matters, though, because the data can simply be transferred from storage system to storage system as technology changes. If nearly all of humanity, in a relatively scientific age, is convinced of the veracity of any phenomenon due to direct personal observation, this will provide very strong evidence to future humanity. Combine that with millions of firsthand videos from multiple angles, all corroborating the same thing, and it becomes much more logical to assume that a supernatural agency is at work than to try to cook up a supposedly scientific explanation. Around a billion people currently believe the Bible, to one degree or another. If just one person had been able to take a video, it would probably be more like six billion. With extensive documentation, convincing future humans should be a piece of cake. Suppose that future humanity is particularly close-minded, though, and that indirect evidence of anything does not satisfy them. After spending a lot of time reinventing the wheel, they will presumably have time to evaluate miracles. What could Jesus (or equivalent), do to convince them? Why not make someone from the earlier time immortal? Not merely not aging, but invulnerable, or constantly resurrecting like Jack Harkness. Besides providing a first hand account of the events that occurred previously, this individual would be a living proof of the miracle itself. Scientists could examine their cells and see nothing that differed from an ordinary human, yet the whole would be immortal. More to the point, such a person would constitute an ongoing phenomenon violating the generally applicable laws of nature, as opposed to a phenomenon whose creation would have been obviously miraculous, but whose continuing presence is less so. [Answer] When you're looking at the Bible as authenticating data, remember a couple things. First, most of our current copies of Biblical writings are from centuries after Jesus died, and even the originals were likely written some time after Jesus died. Go ask your mom and dad about something that happened 20-30 years ago and see how different the stories are. Second, the Bible was written by people who believed in Jesus, which means they are far more susceptible to deception by Jesus, to inflating the import of what Jesus did in their own minds, and to gross hyperbole when describing the already-exaggerated stories to others. If the stories in the New Testament had been independently confirmed by the Caesar of Rome, the Emperor of the Han Dynasty, and some random Mayans who got lost at sea, it would be a lot more credible. But even then, it could just mean lots of powerful people got duped. And remember that magical thinking was pretty common back then, so duping people would have been somewhat easier. The advantages we have today include real-time recording, a much higher degree of skepticism and capacity to call out the frauds, global data connections that mean the recordings could be in pretty much every country on the planet within seconds, and much better methods of preserving that data for long time periods. However, this presumes Jesus2K is willing to do his miracles in front of scientists in controlled environments and let it be recorded. He'd probably be asked to wear all sorts of sciencey gizmos and so forth, and he might not like that. And, of course, "we can't explain it" and/or "it's definitely far beyond the ken of contemporary humanity" are not remotely the same as "proof of the divine". Even if Jesus walked into my house right now and restored my neck to pre-cancer days or fixed my spinal damage with a touch of his finger, "he's an alien from another dimension", "time traveler from the future" or "the psychic energy from a critical mass of couch potatoes spontaneously created a spirit healer in my living room" aren't any crazier explanations than "avatar of a god". So depending on your definition of "miracle", it might be impossible to prove it to people from 4k even in 4k. [Answer] If the goal is specifically to be recognized as miraculous by people twenty centuries from the current age, the child would have to ask his all-knowing father this exact question. That higher being, would know the scope and limits of his son's 4K audience, and could design each miracle to hint at truths just beyond their current knowledge. To clarify what I mean by this, if 2000 years ago, Jesus had asked Dad for such design assistance, our Bible's miraculous accounts might demonstrate a harmony between quantum and macro-scale physics, leading us towards an as of yet unrevealed, unified field theory. I know this doesn't really answer your question, but maybe it will help others provide more practical answers. [Answer] He will have to live on for two thousand years - which may be a miracle in itself and convince the denizens of the future in person. There are futurologists, philosophers and transhumanists that believe in some point we will reach what could be called a technological singularity - that is a point in history where technology evolves so fast, that much of the development that happens during that period will seem magical or miraculous to previous generations. There are some that believe this is happening right now. We can't even fathom what the world will be like two thousand years from now, should technology keep evolving. Who knows? Maybe in the future we will have time machines. Maybe Jesus himself was a time traveling technomage, impressing people with holograms, using nanobots to keep afloat and to heal people... The point being, whatever technology exists in the future will seem miraculous to us, so whatever seems miraculous to the future can't even be imagined right now. --- It would be pretty cool if he could ressurect some dinosaurs and make them shoot lasers from their eyes. I see no way to do so with technology and I would totally worship someone who could do that. [Answer] A convincing argument for something should provide evidence such that the something is the most likely explanation for the evidence. The more unlikely the claim, the harder it is for alternative explanations to be more likely. And the reliability of evidence depends on assumptions about the physical world. If things can pop into the universe without regard to physical laws, then loaves and fishes appearing out of nowhere is less likely than video of such appearing out of nowhere. So it would be quite difficult to have an airtight case, but it would be possible to do much better than the Bible. > > The stories of the miracles of Jesus have allegedly survived 2000 years through written records by multiple witnesses. > > > There is nothing to suggest that the Gospels were written by witnesses, or even by people who spoke with witnesses. It is generally accepted that the Gospels were written decades after the events they describe by anonymous writers. There are portions that quite clearly were not written by witnesses. I'm not going to list every single one of them, but for just one example, two of the Gospels provide genealogies for Jesus (which, BTW, are inconsistent). Unless the writers were thousands of years old, they couldn't have possibly be speaking from personal experience. And the writers make absolutely no effort to distinguish between different types of statements. What is legend? What did they personally witness? What did they hear directly from eye-witnesses? Who were those witnesses, what exactly did they see, and what corroboration did they have? All of these are questions that someone trying to convince future generations could at least try to answer. And of course, these days there is video and other records. > > Early reproduction theoretically makes modification less possible, as any discrepancies would stand out when compared to other reproductions. > > > There were dozens of different versions of the Gospels. The Church simply declared four of them to be canon, and most people don't know about the rest. ]
[Question] [ Most science fiction stories has humans building large domes on the surface of planets like Mars or the Moon. But wouldn't it make more logistical sense to dig down and build down into the planet? I could see needing some dome space for human psychology so everyone wouldn't become agoraphobic but wouldn't most living and work space be easier and safer to build by going down? Does that make sense or am I missing something? Why build a large 'fragile' dome? [Answer] Because the dome is impermeable; rock isn't. Or more accurately, the ground is not impermeable. Cracks run this way and that, soil lets gases seep through it, and it all shifts and cracks anew frequently (see: earthquakes). Further, the rocks themselves could pose hazards for those living there, everything from dust getting into the electronics and wreaking havoc (not to mention getting into lungs and doing all kinds of harm) to toxic minerals leeching into your environment; some rocks -- especially on a planet devoid of oxygen -- could react to the oxygen introduced into the environment in all manner of bad ways. Now, of course, you could line your underground city with an impermeable shell to avoid the issues of just using the rock itself directly. But now you're going through all the effort of digging out your settlement and then adding the effort of building your buildings -- made even more difficult now by having to maneuver your materials through the passageways you've dug! Plus expansion just got a lot harder, since you have to go outside this shell to dig new areas, then line it, then breach the old shell to combine the new area with the old; under a dome you simply build a new structure. Building on the surface is just more advantageous in many ways: * It's faster to build a structure than to dig a similar structure, especially if after digging one you have to build a liner/shell inside it. * No need to worry about where/how to dump the material you dig out (a big deal if it's got to pass through an airlock somewhere). * It's a heckuva lot easier to build than to dig. * Digging runs all kinds of risks from cave-ins to underground gas pockets to even striking magma (albeit only on planets with magma, of course), and more. * Human beings just aren't adapted for underground living. Even a giant dome just makes more sense than going underground. The first arrivals would most likely erect a simple habitat for themselves, then go to work on the dome. This would be a lot faster than excavating a similar amount of space, and would allow for future construction within the dome without the added hassle of maintaining livable environments for your workers. Now, all of this assumes an environment like Mars, where the only real risk is the atmosphere itself (or lack thereof). If you were on a planet where high levels of high-energy radiation bathe it constantly, going underground to escape it might make sense; similarly, an airless body constantly bombarded by small meteors would make sense to take shelter underground. Beyond circumstances like this that do encourage going underground, however, building on the surface just makes more sense. [Answer] NASA have considered this for the moon: <http://www.theverge.com/2014/7/18/5915743/nasa-moons-underground-caves-could-house-astronauts> > > "A habitat placed in a pit — ideally several dozen meters back under an overhang — would provide a very safe location for astronauts: no radiation, no micrometeorites, possibly very little dust, and no wild day-night temperature swings" > > > This would give us astronauts who are also cavemen. [Answer] Digging in has many advantages, but is also very costly. Excavation takes a lot of energy and complicates construction compared to just building on the surface. Whether or not this is worth the energy investment depends on the particular conditions of where you are building. Many suggestion for colonizing Mars include building in old lava tubes - this would remove the additional costs of excavation, which make the extra protections from radiation or weather quite attractive (not necessarily direct weather effects, but you wouldn't want wind erosion to undermine your habitat). If you can find suitable preexisting holes in the ground, which are reasonably well sealed, it would probably be the best place to build. Just digging a hole may not be enough if the material you are digging into is highly permeable, is only loosely compacted (will shift around and needs significant structural support), or full of toxic materials. In those cases, you still need to provide structure and a sealed environment anyway, which is easier to do as buildings on the surface. Massive excavation machines are very expensive, small fabricators mass producing cement block equivalents are comparatively cheap. [Answer] In [The case for Mars](http://en.wikipedia.org/wiki/The_Case_for_Mars), Robert Zubrin proposes building with locally manufactured bricks and covering the 'building' with dirt. The moisture in the habitable air inside would seep through the cracks and freeze to ice, forming a barrier that would stop further air from escaping (or at least keep losses to manageable levels). No need for fancy linings in that case. [Answer] Building a dome costs much much less on large scales. When you build a dome, your cost is proportional to the surface area of the dome. When you dig under ground, it is proportional to the volume exhumed. Since you are generally needing to create habitable volumes, this means domes effectively decrease in cost-per-area linearly, while digging must remain constant. [Answer] So I have a minor addition to all of the other valuable answers. While building a dome is cheaper, providing radiation shielding can apparently be difficult and expensive. This may necessitate a mixed approach, such as building the habitat in a reasonably deep crater, (or more likely a shallow crater dug deeper, as it may be advantageous to have a smaller diameter to utilize more of the shielding provided by the solid surface of the planet). This is a bit like what @pjc50 posted that NASA is considering (though they mostly are suggesting creating habitats IN the caves connected to the pits...). In addition in [Colonizing The Galaxy in 8 Easy Steps](http://rads.stackoverflow.com/amzn/click/0316771635), the author suggests utilizing water as a multipurpose radiation shielding material. He also suggests using it as a way to produce food and recycle water into a renewable source of water. Which I suspect could be an interesting possible addition to the dome solution. [Answer] Seems like everyone misses the obvious answer: food and air. You need sunlight to grow plants in order to eat & breathe. Unless of course you have nuclear fusion powered grow lights in your underground tunnels, in which case why bother to go all the way to Mars to dig them? ]
[Question] [ There are quite a few known [drawbacks](http://en.wikipedia.org/wiki/Inbreeding) to [incest.](http://en.wikipedia.org/wiki/Incest#Animals) However, [incest can be helpful](http://www.dogbreedinfo.com/inbreeding.htm) when trying to help a desired trait spread. Incest does happen in nature to some degree but it's not exactly actively sought out. *How (if at all) could selective incest become a beneficial part of the development of a species?* This concerns both an intelligent species, knowingly commiting incest or using it on domesticated animals (but only for practical purposes) as well as non intelligent species doing it out of instinct in appropriate scenarios. These situations could include when an individual shows very strong genetics or the environment changes rapidly and an individual seems more adapted to the new environment than others. I'm looking at this question from a purely genetic perspective, the social implications of incest being common within an intelligent species should be considered out of scope and kept out of the answers unless necessary. Likewise, inbreeding for aesthetical purposes is not useful and not on topic. Discussing drawbacks should only be done to illustrate how these drawbacks can be overcome or at least outweighed. [Answer] If they're intelligent polyploids, their civilization may crumble if they don't breed with siblings Incest is a form of inbreeding, which as we know is deleterious. This effect is termed "inbreeding depression" but many plants are less susceptible to inbreeding depression than animals. This is probably because of "polyploidy", a condition where the genome contains more than two copies of each chromosome. This creates a much wider range of possible combinations and a much smaller chance of being stuck with deleterious recessive traits. This is seen in for instance apples, which farmers propagate by grafting. This is because a tree growing from an apple seed, even one fertilized by two genetically identical trees, will turn out quite different from its parents. Often reverting to small, sour apples. The protection offered by polyploidy is so strong that polyploid plants can opt for widespread self-fertilization. This is less common in non-polyploid plants, which more readily suffer inbreeding depression when self-fertilizing. An example is the common garden plant chives, which is polyploid, self-fertilize and where you can find lots of different chromosome numbers, [within the same species!](http://onlinelibrary.wiley.com/doi/10.1111/j.1601-5223.1936.tb02652.x/pdf). So in short, a polyploid species would suffer less from inbreeding and therefore may not have evolved the instincts that prohibit incest in terrestrial animals. Now with inbreeding depression out of the way, incest is actually an advantage. This is because you want to propagate your genes, but your offspring only gets 50% of your genes, the other half coming from your partner. But if your partner is a sibling, about half its genes are also yours, so you get 75% of your genes into your offspring. You could imagine that this species is also hermaphroditic and occasionally self-fertilize. (not the same as cloning) plot-wise, you can also play on the increased range of outcomes in a polyploid mating. Perhaps the culture in the story is a collection of families with similar traits (phenotypes) such as intelligence, but which have arrived at the same traits independently, by different genetic routes (genotypes). When non-related individuals in this culture mate, their offspring revert to an ancestral phenotype like brute cavemen, or into unpredictable new phenotypes like the first child of a completely new race, ones that eat different types of food, or something that to earthlings would look like a completely new species. So incest is a necessity for the continued existence of their civilization (or so they think). An additional plot device is the slow but persistent churning of inbreeding depression which can only be alleviated by outbreeding, but which has such unpredictable consequences in this species. Play it safe and lose in the end or take the leap into the unknown? For more on polyploidy, there's [a wonderful article](http://www.motherjones.com/environment/2013/04/heritage-apples-john-bunker-maine) on how the different types of apples arose from exceptional individual trees, that stood out in forests of less remarkable seed-planted ones, with a rise and fall of dynasties of apple types. Some academic references on polyploidy vs inbreeding: <http://dspace.library.cornell.edu/handle/1813/9410> <http://www3.botany.ubc.ca/rieseberglab/plantevol/Sample_Project_Proposals.pdf> [Answer] Look up "linebreeding". When one animal (especially a male) shows an especially beneficial trait, farmers and ranchers will often breed that animal back to his own daughters and/or grand-daughters. The goal of linebreeding is not focusing on inbreeding for its own sake; it is focusing on "getting as many copies of the genes from this prize animal into the herd" and "maximizing the chance of producing some beneficial trait that relies on double-recessive alleles". Inbreeding always increases the chance of unfavorable mutations. A lot of mutations essentially boil down to: this broken gene does not product protein Z properly. One copy of the mutation means you get half as much of protein Z as others, which may be fine. Two copies of the mutation means you don't get any Z, which can be lethal. Inbreeding increases the chance that a parent with a single copy of a broken gene could pass that copy onto a child/grandchild twice, thus causing problems. There's no way around this limitation. Furthermore, diversity is often vital to the survival of a herd. Parasites and diseases will occasionally be more deadly to some animals than others, due to a fluke of genetics. The more inbred the population, the greater chance a single disease could wipe out the whole herd. [Answer] Incest is a risk. For humans, we do not accept that risk for our own species, but we do accept that risk for domesticated animals. I say "we" to summarise the current legal approach in most countries. Obviously individual humans differ in their attitude to what rights animals should have. # Domesticated animals The benefit of inbreeding is that it gives more fine control over the selection of desired traits and exclusion of undesired traits, so that artificial selection can be used more quickly to change the nature of a domesticated animal. For a species that accepts the frequent birth of animals that have avoidable genetic diseases, shortened lifespans, and increased suffering, inbreeding gives a shortcut to faster manipulation of genetics without need for technology such as genetic modification or even being able to read a genome. I would expect inbreeding of domesticated animals to be a common part of the history of most intelligent species, used to gain an advantage until technology allows them less damaging alternatives. Some species may stop the practice early due to ethical objections, while other species may stop later, when technology renders it redundant. In both cases I would expect inbreeding to play a major part of the early history of domestication. # Intelligent species A similar pattern is likely to be followed for an intelligent species actively choosing inbreeding of its own species. * Personal choice Human history includes inbreeding where people have perceived that their own family is superior to other humans, and chosen to breed with close relatives in an insular breeding group. This is most notable in ancient royal families. * Slavery Human history also includes the enslavement of humans by other members of their own species - humans being used as domesticated animals. For this reason the same applies as in the paragraphs on domesticated animals. Many intelligent species are likely to use domesticated animals, and those which do not have some protection against treating their own species in the same way are likely to have a period of using their own species as slave labour, including breeding their own species and forcing inbreeding for traits. This period will last until the species takes steps to prevent it for ethical reasons, or in a species that lacks an ethical objection it may continue until it becomes unnecessary due to technology, or until it is ended by uprising. Advances in technology do not necessarily lead to advances in ethics, so for some intelligent species slavery and the associated inbreeding for traits may persist, eventually leading to a new species. [Answer] The main biological reason against inbreeding is that, since close relatives have highly similar DNA, it means that the DNA of the child is almost exactly the same as that of the parents. This means that any genetic defects in the family are likely to remain in the family, including those responsible for hereditary illnesses and pathogen vulnerabilities. However, a sufficiently advanced race could have found a way to induce certain genetic changes during the gestation period, meaning that 2 relatives can produce offspring while still giving birth to a sufficiently different offspring. Already, humanity is getting there, with in-womb genetic testing and use of viral-based delivery methods for genetic code. So once the genetics are out of the picture, the only hindrance is the social taboo. Already, there are communities like certain rural areas of Southern US states like Alabama where first cousins can marry and procreate. And even in western Europe, it's estimated that 1% of new marriages is between first cousins. It wouldn't be the first time that social taboos get broken, as happened with interracial marriages in the 1960's-70's and gay marriage in the past decade. In fact, back during the classical eras of the Romans, the Greek and the Ancient Egyptians, there was no such taboo. For example, Tutanchamon was married to a half-sibling. There are not really any benefits to large-scale incest, though, especially in a science-based world. A genetic trait would be distributed far better through an air- or waterborne pathogen. In fact, incest would be counterproductive to spreading a trait, because you want to spread the trait to as many family trees as possible. However, on a smaller scale, incest can enhance traits found in a small subgroup of a society. The only reason this would be acceptable, though, is if there is only one family with this genetic trait, which is rarely the case. usually, due to the natural resistance against inbreeding, any genetic traits formed through chance mutations during conception are present in multiple families. Finally, fringe groups in society might naturally distrust people that aren't part of their small group, and would eventually have to start performing incest to keep the group population big enough. --- Another reason that incest might be performed is for adult entertainment purposes, but those almost never result in offspring. In fact, as long as there is no offspring from the act, incest might not be viewed as a big social taboo. [Answer] I don't think that could have happen in a real world, as freak events are just too rare. On the other hand, as you consider a fictional species, we could make it so that it will be beneficial. First, please note that the reason for both inbreeding and avoiding it is the same: the genetic advantages and disadvantages of them. So, to make it beneficial, we have to create something that will outweigh the other costs. For example, imagine a species with psychic powers. If these are very rare, but on the other hand very powerful, it might make sense to try to strengthen them. Still, if there are other specimens holding similar powers, it will make even more sense to stop inbreeding. So to make it work, it has to be rare, but not very rare (as it would just disappear). Also it has to clearly outweigh other costs, and there has to be some big disadvantages for non-related specimens to get together, e.g. * there are cities run by families that fight each other very fiercely, * powers of different families interact very badly (e.g. no such two specimens can met without one dying, or, the offspring would be insane or with no powers, or with too dangerous/unstable powers). I hope this helps ;-) [Answer] You also get the benefits of keeping good traits. Which may be a function of intelligence. Or, why do humans only have 23 pairs of chromosomes when our ancestors did not? [Answer] Old question I know, but it's about evolution and no one pointed out the obvious answer so evolution geek me must speak up. Short answer is as long as they use haplodiploidy sex determination system they would be expected to want intermittent inbreeding, and this is seen all over the place in insects that use this sex determination system. Normally the problem with inbreeding is that a parent may be a carrier for a recessive dangerous gene but not have any symptoms of that gene because they have a healthy copy of the gene that is dominate and thus hiding the bad gene. These sort of genes are very common, and there is no easy way to tell if a potential mate has them, or more accurately how many he has since your mate likely is a carrier for many of these sort of recessive genes. Your only saving grace is that each gene is uncommon enough that it's unlikely both parents carry the same recessive gene. but if a father mates with a child who inherited that same bad gene from the father already then they have a 1/4 chance their child will get two copies of the same bad gene, one from the father and one from the mother/daughter, and thus have whatever dangerous condition the 'bad' gene causes. So for every bad gene the father carried there is a 1/8 chance a child with his daughter would end up with whatever disorder the gene caused, once you factor in the odds that the father cares many of these bad genes it becomes a real risk. However in a haplodiploidy mating system a female can birth a son without mating with a male, the son gets one copy of every gene from it's mother, and no copies from it's non-existent father. This means if the son got any 'bad' gene from his mother he won't have any 'good' copy of that gene from his father to compensate. Any detrimental recessive gene the son gets will cause the son to be born with a defect. That means there is no way a male can be a secret carrier of a bad gene, it should be obviously causing the son harm if he carries it at all. So as long as the female only mates with healthy sons she can be pretty confident the son isn't a carrier for any nasty recessive genes and so her children can't get two copies of that gene. Thus the biggest risk of inbreeding is pretty much removed by the fact that males can't pass on the bad genes, in fact males help to weed out these sort of genes so even the females are carriers of far fewer then humans are. There are many kind of aphids which will grow up on a kind of leaf with limited ability to disperse. If two females manage to land on the same leaf they will mate with the sons of the other female, but if no other mates are around a female with birth a bunch of sons then mate with her sons. Notice in this case the females still prefers mating with foreign entities when available, but she will often have to resort to mating with sons and she can do that too. In the aphid's case she is mating with foreign mates when available to get more genetic variety which will make her children more different, and thus more able to adapt to changes in condition in the future. Now as a different example there are certain breeds of bees where females will preferentially mate with her brother if possible. This is because the brother shares some of the sister's DNA, so the sister's daughters will end up having 75% of her DNA if she mates with her brother, as opposed to their only having 50% of it if she mates with a foreign male. Her kids are less successful at surviving if she mates with her brother, but enough survive that them carrying more of her genetics was a worthwhile tradeoff. So I explained why these species aren't harmed as much by inbreeding, but why do aphids still prefer foreign mates and bees prefer inbreeding? Mostly this comes down to a trade off between lack of genetic variety and advantage of sharing more DNA with your children. Too little genetic variety from foreign mates will lead to your children not being adaptable and thus all of then dying out if the environment changes. In fact lots of clonal species have evolved only to go extinct again for this very reason, the clonal mothers were able to pass on twice their genetics to their children which helped in the short term, in the long term lack of gene flow to support adaptation almost always kills these species pretty 'quickly', at least relative to an evolutionary time scale, as soon as something changes in their home environment. This means even without the harm of recessive genes an insect would want to mate with foreign mates sometimes to get genetic variety. However, an insect also benefits from her children having more of her DNA that comes from inbreeding. The parent therefore needs to keep a careful balancing act, trading off inbreeding with outbreeding to get the right trade off between having enough foreign genes for her children to survive while keeping as much of her family's genetics to ensure the children pass on as much of her gene as possible. The more frequent the inbreeding the more important it is to outbreed, and vice versa. In the case of the aphids they often have to inbreed when they have no mates, so a certain percentage of inbreeding is guaranteed in their lineage no matter what, meaning when an opportunity to mate with a foreign individual is available they take it because they likely are in need of more outbreeding. For the bees the female prefers mating with her brother to an extent, but only so far. A stronger foreign male may be preferable to a weak brother. The degree of preference to mating with her brother is part of the same balancing act. It ensures that females end up choosing to mate with their brothers at roughly the correct frequency to keep the perfect mixture of inbreeding and outbreeding. So in your species rather or not they engage in inbreeding would likely come down to how much inbreeding is in their immediate ancestor. If your father is also your grandfather and your great uncle it's probably time to find a foreign mate. If your family tree is starting to actually look like a tree then you probably want to get in on some of that sweet sweet inbreeding action. [Answer] Incest is a double-edged sword. It can be of value if your objective is improvement of the species, but it comes at a high cost to the individuals. Thus a society placing very high value on the common good might approve of it. A child is much more likely to get hit by a bad double recessive if their parents are closely related but when that happens the incidence of those double recessives goes down in the population because the person hit with the problem doesn't reproduce. (This always happens anyway, it's just going to go faster with incest increasing the chances of hitting it.) Looking at humans (which are probably reasonably representative) the time from having enough understanding of genetics to even consider employing such a strategy to the point where genetic sequencing can remove the problem (IVF, don't implant embryos containing the double recessive) is not a large number of generations and thus the genetic improvement to be gained isn't all that great. However, let's consider a slave race. While their masters certainly have the ability to avoid the problem they see no need to, it's cheaper to simply cull the victims. The slave race has thinkers that have realized the only route to freedom is forced evolution to improve themselves to the point they can take on their masters. The forced evolution approach might become so ingrained that parts of it persist even after they overthrow their masters. ]
[Question] [ I'm currently working on my own world and something I always wonder when worldbuilding is if I'm putting in "too much detail". One of my favourite parts (and one of the most important in general) of worldbuilding is details. Sometimes, however, it seems like I'm putting in "too much" detail. For example, I may get carried away with a very specific aspect of my world (such as a fictional brand or company) and add very specific details to it, like products or services that have little to no significance. Is this truly a thing? If so, is there a threshold or a certain point where the amount of detail is "too much"? Is it better to be more vague or more specific? [Answer] It's not really possible to answer whether there is such a thing as too much detail. Such a question is very much opinion based. However, we can answer some related questions about what signs might one see that suggests that one has gone into too much detail. The obvious answer is, of course, time. If you're spending all your time worldbuilding, you're not spending that time doing other things. If other aspects of your game/story/etc. are suffering due to lack of time, that may be a sign that you need to cut back on worldbuilding. Another warning sign is when the reader/player/etc. is obliged to join you on your worldbuilding journey. Take Tolkien's languages, for instance. He put a tremendous amount of worldbuilding effort into his languages for the Lord of the Rings series of books. If you want, you can find the etymology for many words in Quenya, tracing how they morphed over hundreds of thousands of years. But Tolkien doesn't drag you through any of that (well, at least he doesn't outside of the The Silmarillion). You aren't obliged to understand cognates of a word between Quenya and Sindarin in order to solve a murder mystery. They merely bring flavor. If you find the need to drag the reader/player/etc. along with you to show off the details, it's probably time to stop. Too much detail can also breed disbelief. The smaller the detail the more it needs to flow on its own from the world around it. If you have to "nudge" some major motif a bit to fit with the story, that may be part of worldbuilding. However, if you try to apply the same nudge to a bunch of tiny details, they start to feel exactly like that: an author trying to fudge the details to make a story. In the same vein, too much detail can trap your plot. Sometimes a writer does need to nudge things one way or another. If you haven't specified too much detail, that nudging can shape the larger world motifs. But if you've already specified all the details, then the nudging can only bludgeon some poor hapless details. An interesting example of this shows up in The Martian with the sand storm. Andy Weir fills the book with fine details, building a wonderful world. But anyone who knows astronomy will quickly pick up on the fact that such a dust storm could never occur. The Martian atmosphere is too thin to carry such particles. Weir had to [admit](https://m.imdb.com/title/tt3659388/goofs/) that the sandstorm was manufactured to start the story off, taking creative license to create the requisite conflict, and that it was a great scientific inaccuracy in an otherwise science-detail full world. [Answer] If you spend your entire life world building, and never actually write things in that world, then you are doing too much world building. Maybe you're enjoying it for its own sake, in which case you shouldn't care about our opinion. If you do care about our opinion, then you need to do something that presents your world to the rest of us. Consider yourself to be a cultural ambassador to your world. Your job, as a writer, is to find the interesting, nuanced, and just plain weird stuff that comes from your culture, and show it to us as the background of a story. With that in mind, obsessing over the minutia of the geology of a planet probably isn't very fertile ground for finding details that fascinate your readers. Pages of exposition about some obscure detail of how your society builds its armor will drive people off before they actually get to your story. Trying to identify the specific genes in a genetic sequence that will result in photosynthetic humans is counter-productive. Let's face it, even reading the previous list of things not to list probably turned your brain off. Every world needs underpinned nuts and bolts to hold things together, of course. If the weird parts are pasted on without thought, you get shlock. Again, maybe you want to write shlock. Someone's gotta do it, but then the details shouldn't matter. Know your audience. My philosophy is that I do enough world building so that my gaps in how the world works don't become red herrings that distract my readers from the stuff that's really interesting. In fact, that, in my opinion, is the essence of good Science Fiction. It's describing a solid enough understanding of the science so that the things that are fascinating stand out in stark contrast. If you do this right, then your readers will be able to infer how your world is constructed from the events that occur, the same way we inferred the existence of Neptune from its effects on the other planets. [Answer] A question of time and effort. Generally speaking, you should have much more detail in your notes than you put into the published work. Say you have a science-fiction setting with many inhabited worlds, and the characters are stranded on one while they need to get the funds to buy the spare parts to repair their starship. You define a fictional currency unit, a cost for the missing parts, the wages for people with the characters' skills, and the daily cost of living. $$\text{days to earn wages} = \frac{\text{parts cost}}{(\text{daily wage} - \text{cost of living}) \times \text{crew size}}$$ There are plenty of factors where you can shatter "willing suspension of disbelief" if you are not careful. What is the cost to buy and operate a large starship in your setting? You could have a desert world, yet the setting is spoiled because importing bottled water is affordable by your numbers. Or you could have a near-vacuum world, yet the setting is spoiled because the cost of living in domes with recycled air exceeds the possible wages even for skilled workers. And so on. The detailed calculations might never be revealed, but you need them unless you plan to gloss over such detail and focus on character and plot. It is quite possible to tell stories that way. But if you go for nuts and bolts, go deep enough. [Answer] When you come to write, there is a step called "smother your darlings". The text should move the plot onward with a steady and uniform style. You may have some amazing fun fact about the place you are now in. But the characters present may not know the background. Or it does not help the current plot. But you really liked it. I have just written a book on colour, and I remember weeding out the facts and the weird bits of history. I found them fascinating, and not many other people knew them, but they would just get in the way for a first-time reader. Or sometimes, you could move a fact to another place and it had a positive contribution. So "smother your darlings is real", but only for writing as far as I know. Stick all the background detail you like. You may have to decide not to use any given fact at a later stage, but that isn't a limit in worldbuilding as far as I know. [Answer] ## There is only forcing too much detail unto others. No matter what you write (draw/animate/film/&c.), you should focus on the narrative. A vastness of lore and history and thoughtfulness will go a long way to ground your readers, but it is key that you only communicate it when the narrative asks for it. Take, for example, Tolkien. The richness of his worldbuilding is awe-inspiring, and it is wonderful to read through all that content (once you are familiar with and fond of his universe). But in his major novels, he relayed parts of that information only when the plot asked for it. However, like Aragorn singing a song of old to frame an event, locale, or other character within the lore of the world, you can have a character talk about the intricacies of a specific brand, simply because of a strange fascination, or because their family is somehow involved, or because they happened to pick it up somewhere and they remembered it (for a good, but perhaps not obvious, reason). [Answer] It's "too much world building" when it keeps you from actually using the world. So long as you are actually using it, it's no issue [Answer] Absolutely. Worlds in and of themselves are exactly like an insect on a pin: interesting in a scientific and sterile manner, but completely and utterly dead. It is the motivations and consequent actions of the characters living in that world that make it come alive, and subsequently make it interesting in a relatable way. Write those characters' story, and you'll find that in turn will tell you what to write about their world's story - and how much. Worldbuilding is easy, and therefore fun; writing characters is difficult, and therefore often far less so. But as with most things in life, if you persevere with what is difficult, you're likely to have far more success than just sticking with what's easy. [Answer] # No such thing as too much. Only too many at once. Details are what makes a world come to life. This can be important to the story or as useless information as it would be in real life. What can be too much is how many details you give. This obviously differs per person per story, but you can make a guess. In the end you can give any and all details you want. As long as it isn't too much all at once. Spread it out in the story. [Answer] Yes. But -- -- this is not a problem with your worldbuilding. You could see it as more like a hint to yourself: that this thing that you tend to put so much effort into thinking about, is something that you would like to actually do. As in, to make it happen in the real world. If that thing is possible, legal, achievable within your circumstances, etc. - why not give it a try instead, or perhaps in addition to, writing about it? ]
[Question] [ In the world I am building I wanted to design a race on a planet which get more full the more calories they eat and then stopping when they have had their daily caloric requirement. I have an idea's on how they would do it physically (sample parts of the food going down their esophagus equivalent and estimating on the amount going to the stomach). The problem I have is why this race would create this evolutionary tactic in their hunter/gatherer phase. If you find a bunch of berries you would eat as many as you can fit in the stomach, store excess calories as fat, and take the rest back to village for later. I usually try to find a corollary examples for races I make from earth and I try to be at least a semi-hard on science as to why races are the way they are. Any ideas would be nice. [Answer] Your race evolves under circumstances where overconsumption of calories is common and potentially dangerous. A parallel is seen with salt. Salt is delicious and we need it. But if it were purely delicious and an individual happened into a big pile of it, it would eat it all and get sick and possibly die. [High salt recruits aversive taste pathways Yuki Oka et al Nature 494, 472–475 (28 February 2013)](http://www.nature.com/nature/journal/v494/n7438/full/nature11905.html?WT.feed_name=subjects_taste-receptors&foxtrotcallback=true) > > By contrast, salty taste is unique in that increasing salt > concentration fundamentally transforms an innately appetitive stimulus > into a powerfully aversive one. This appetitive–aversive balance > helps to maintain appropriate salt consumption and represents an > important part of fluid and electrolyte homeostasis. > > > Suppose overindulgence in calories happens often, and there is an evolutionary price that outweighed the benefit of storing away calories for hard times ahead. What could that price be? [Refeeding syndrome](https://en.wikipedia.org/wiki/Refeeding_syndrome) can happen to people in concentration camps - they are starving and then when they are given all the food they want, electrolyte levels crash and they get arrhythmias or stop breathing. Maybe your race is prone to something like that. An alternate bitter receptor for high calorie (like for high salt) seems tricky. A different way to evolve stopping when you are full is to make the stomach smaller, like people who have stomach reduction surgery. Or just attribute their satiety to their genetics: the sensation of being full is evolutionarily flexible and under genetic control. <https://www.gbhealthwatch.com/GND-Obesity-MC4R.php> One could make a case that humans are already set up as you specify - to stop eating when they are full - of fat. The obesity problem now is due to easy availability of carbohydrate calories, which make an end run around a mechanism that evolved in a time where the only way to eat an immense amount of calories was by eating animal fats. Ketogenic diets work in part because fats are filling in a way carbohydrates are not and people get full and stop eating. [Answer] There is no known scientific rationale for what you want to happen. Living creatures do not have a "daily caloric requirement." Instead, they maintain their existence by adjusting their caloric output according to what they bring in. If you don't eat enough, you shut down less essential parts. While the US government may recommend 2,000 Calories/day, we can operate on far fewer. As we get near 1,200 Calories/day, our body starts to shift gears to conserve more and more energy. As we approach 500-800 Calories/day, our body will start to shut down bodily functions to preserve energy to support the lower regions of the brain. On the flip side, you have Michael Phelps, [who ate](http://ftw.usatoday.com/2017/06/michael-phelps-diet-12000-calories-myth-but-still-ate-8000-to-10000-quote) 8,000 - 10,000 Calories/day before the Beijing Olympics. There, the vast majority of his caloric intake was expended in his practices. This flexibility is incredibly important from an evolutionary perspective. Food supplies are never reliable. If you can't scale your output to match your input, you will die and be replaced by a species that can. There is no known species that doesn't engage in this sort of flexible operation. It's fundamental to how life as we know it functions. To come up with a species that doesn't have this, one is going to have to reach well beyond realistic science. Consider the Octospiders from Clarke's Rendezvous with Rama. That species is a highly advanced species with many peculiar traits. One of them is that they have to be taught to recognize the feeling of hungry. Their babies are born with a truly blank slate, and one of the first tasks of the nursery technicians is to teach the babies to eat before they starve just sitting there. In such an environment, one might have "daily caloric requirements" in the form of instructions dictated to you. You may consciously be aware of the food you eat and stop when you reach the level dictated by your society. [Answer] What kills people? On our world we have gone hungry fairly often, and starving still is a fact of life in many parts of the world. But if there has always been enough to eat something else would bother them. Say like Eloi they had all the food they cared for always available, perhaps overeating or having excess fat would be a major problem. If to escape predators they typically hide in tight places, there is some poison common in their environment that could accumulate in fat or the stable food supply wasn't fast replenishing and was easily damaged by over harvesting, limits of consumption may selected for. [Answer] Body fat is a very efficient way to store extra calories on living creatures. Unfortunately there is not an equivalent procedure to storing water, This is interesting as water is just as important for life but [it can actually kill some people when they over drink](https://en.wikipedia.org/wiki/Water_intoxication). What if, we turn off the ability to store extra calories in the same way. All the sugars you eat would go right to the blood stream, thinning out your blood. The more your people eat the more "light headed" they would feel, as they wouldn't be getting enough oxygen. The lack of oxygen would be a natural way for your species to know they are over eating. Unfortunately not having access to body fat would create a number of other issues. [You would also have thrill seekers who](https://en.wikipedia.org/wiki/Choking_game) would eat to much high caloric foods just for the weight less feeling they get. [Answer] This is not as hard as it seems. Take away the evolutionary advantage of storing excess calories. One way to make sure that this evolutionary trait never developed is by making your species always having had an abundance of food. For example your species is rather small compared to many herbivore animals that they could effectively hunt (with poisoned spears). To top that off, maybe they have a good way to preserve this meat. If food is pretty much guaranteed to be available at any time, but people still had to eat to survive, it would make sense that people would still enjoy food and have an evolutionary impulse to eat, but not to overeat, which in the end does weigh you down, is time-consuming and potentially harmful when food is spoiled. ]
[Question] [ This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. I'm designing a world, and I want it to have major geological changes over a short period of time. This includes continental drift, which I'm assuming should have some interesting results. In particular, I'd like to have mountains form, which in turn should change part of the world's climate (I'm guessing) by impacting wind patterns. However, while I'd like all of this to happen rather quickly, I don't know just how fast it can happen, as I don't know how fast continents may move and then collide. Here are my parameters: * The planet is Earth-like, with the same sort of seasons. * There are four large continents, each about the size of Africa, spread across the globe. * I want the mountains to form quickly, ideally reaching heights of 30,000 feet within a few million years from the start of a collision. They'll probably keep going, but this is my target reference height. * The area where they'll form was previously mostly flat. * The whole chain should be roughly 1,000 miles long. Is it possible for these mountains to form in about a million years? If so, can they form faster? If not, how much longer would it take? [Answer] # How the Himalayas were made Mountain formation isn't the best known process in the world. The general process for the [formation of the Himalayas](https://en.wikipedia.org/wiki/Geology_of_the_Himalaya) is described in Wikipedia, as are the various [disagreements on the pre-Himalayan geology](https://en.wikipedia.org/wiki/Pre-collisional_Himalaya). The general subject for disagreement is which parts of the Indian and Eurasian plates along with the Tethys seabed ended up where. [Le Fort, 1975](http://earth.geology.yale.edu/~ajs/1975/ajs_275A_1.pdf/1.pdf) extensively documents the known (in 1975) ages of deposits in various parts of the Himalaya. The general facts are, and this is well illustrated by Fig. 2 from the paper on page 4, that there are some regions of the Himalaya where surface deposits are Triassic in origin (200-250 mya), while other areas such as Kumaun district of Uttarakhand state have deep Eocene marine sediments as young as 40 mya. These deposit ages are relevant as they determine the actual timeline for how long the Himalayas took to form. India started colliding with Eurasia around 55 mya, and the aforementioned marine sediments were deposited on the bottom of the Tethys Sea as recently as 40 mya, indicating that what is currently the Himalayas definitely did not exist as of that time. Page 15 of Le Fort shows evidence for a terrestrial coastal environment as recently as 26 mya, an analysis echoed in [Najman, et al., 1997](http://www.lancaster.ac.uk/staff/najman/Najman%20et%20al%20Geology%201997.pdf). The timeline suggested in [Tapponnier, et al., 2001](https://www.geophysik.uni-muenchen.de/~malservisi/geodynamics/Tapponieretal2001.pdf), graphically described in Fig 3., page 1674, suggests that there was an initial period of mountain building starting with the Bangong suture up to 120 mya. This was caused by a India ripping a piece of Africa off when it separated from Gondwana. This detached crust piece was the [Lhasa terrane](https://en.wikipedia.org/wiki/Lhasa_terrane), which was pushed pushed by India into Eurasia and built the first piece of the Tibetan Plateau. This collision formed a volcanic region called the [Gangdese batholith](https://en.wikipedia.org/wiki/Gangdese_batholith). After this collision, there was still the Tethys sea between India and Eurasia; the Lhasa terrane was separated from India by oceanic crust. It took tens of millions of years to close what was left of the Tethys sea. The rest of the continent of India didn't start to collide with Eurasia until about 55 mya. This collision re-ignited the Gangdese volcanic belt and causing the Jinsha suture to rise from from 50-20 mya. This phase of the collision probably coincided with volcanic mountain building of the same sort that made the Andes and Cascades in the Americas. A detailed (and very readable for a paper, in my opinion) description of this phase is in [Jain, 2014](https://scholar.google.com/scholar?q=how%20fast%20did%20the%20himalayas%20rise&btnG=&hl=en&as_sdt=0%2C47). Finally, about 25 mya, the subduction could no longer continue smoothly and a massive thust-fold belt formed what is now the Himalayas. The previous volcanic mountains are now part of the sub-ranges of Tibet such as [Nyenchen Tanglha Shan](https://en.wikipedia.org/wiki/Nyenchen_Tanglha_Mountains). [Sorkhabi and Stump, 1993](https://www.geosociety.org/gsatoday/archive/3/4/pdf/i1052-5173-3-4-sci.pdf) argue from isotropic evidence of changing fluvial (river) patterns, that there were three major pulses of uplift, between 21-17 mya, 11-7 mya, and starting 2mya to present. This is summarized on page 89-90 of their paper. During those times (and indeed during the present) the mountains would have risen at rapid rates. Over at Earth Science SE, there are a few posts talking about [maximum possible heights](https://earthscience.stackexchange.com/questions/2586/what-were-the-tallest-mountain-ranges-in-earths-geological-past?rq=1) of mountain ranges. Without going too much into detail, the Himalayas are probably about as tall as mountains can possibly get; since at about 8000-9000m, erosion rate from glaciation starts to exceed maximum possible uplift. So the conclusion from Sorkhabi and Stump is that for those three pulses, including the one at present, the Himalayas were about as tall as they are now. # Conclusion: How fast can they rise The available evidence suggests that the material that currently makes up the Himalayas was a coastal plain as recently as 25 mya. By 21 mya it was being uplifted at a rate that caused its height to be capped by erosion at about the height we see today. So we are looking at 4 million years to form these mountains from 'nothing.' However, this does come with caveats. The Himalayas didn't form from 'nothing' but from a [foreland basin](https://en.wikipedia.org/wiki/Foreland_basin), that was 'sunk' between the higher elevation Indian shield and behind it and the Tibetan Plateau, which had already existed for 75 million years in front of it. The Tibetan Plateau, in particular, was already pretty high, and had ranges of volcanic activity that had built mountains there for the past 40 million years. An analogy to the situation in today's world would be this. The Persian Gulf and Mesopotamia is a foreland basin between the Iranian Plateau in front of it, and Arabia behind. The Gulf could (if the plates were lined up just right) rise into Himalaya-sized mountains in 4 million years. However, there would already have been a [significant mountain range](https://en.wikipedia.org/wiki/Zagros_Mountains) in the area before this 4 million year orogeny started; they just wouldn't seem so significant once there were 8000m peaks towering over their southern border. Final TL;DR conclusion: Himalaya-size mountains could form in as little as 4 million years from a shallow sea, but there would already have been volcanic mountains from the subduction zone in the area for tens of millions of years. [Answer] This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. Your closest comparison here is the Himalayas [The Geological Society](https://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Convergent/Continental-Collision) says on this: > > The Himalayas are still rising by more than 1 cm per year as India continues to move northwards into Asia > > > That rate of rise gives you 10,000metres/million years. Limited by the rate of erosion, but your high speed mountain target is reasonably achievable. --- It's possible that mountains could pop up very quickly (on geological timescales). [Two new studies by a University of Rochester researcher show that mountain ranges rise to their height in as little as two million years](http://www.rochester.edu/news/show.php?id=2403) > > "Deblobbing" may not sound like a very scientific word, but it's the term given to a dense root beneath the Earth's crust—a blob—that becomes unstable and begins to flow downward into the earth's mantle under the force of its own mass, until it detaches. When two tectonic plates collide, such as the Nazca oceanic plate in the southeastern Pacific colliding with the South American continental plate, the continental plate usually begins to buckle. Floating on a liquid mantle, the plates press together and the buckling creates the first swell of a mountain range. > > > Below the crust, however, there also is a kind of buckling going on in the solid portion of the upper mantle. This dense mantle root clings to the underside of the crust, growing in step with the burgeoning mountains above. This dense root acts like an anchor, weighing down the whole range and preventing it from rising, much like a fishing weight on a small bobber holds the bobber low in the water. In the case of the Andes, they swelled to a height of about one kilometer before the mantle root beneath them disconnected and sunk into the liquid mantle. The effect was like cutting the line to the fishing weight—the mountains suddenly "bobbed" high above the surrounding crust, and in less than 3 million years, they had lifted from one kilometer to roughly four. > > > [Answer] Drift, shmrift. Drift makes watching grass grow seem like an extreme sport. I thought you were in a hurry! You want a big mountain fast, you want a volcano. Haleakala qualifies as big at 10,000 feet. Add on the 19,680 feet concealed under the ocean and you have your 30,000 foot mountain. Haleakala is less than a million years old. Mauna Loa is taller at 13,600 feet and younger: 0.1 to 0.5 million years old. These are not some puny piles of soot either - they are massive mountains full of earth power you can feel through your feet with shoes on. Volcano ages from <https://www.soest.hawaii.edu/GG/ASK/hawaii_volcano_age.html> But still; you will get old waiting for this sort of thing. Let's get on with the mountains already. [Paricutin](https://en.wikipedia.org/wiki/Par%C3%ADcutin) grew from a flat place in a Mexican field to 1391 feet over 9 years. That is 154 feet / year. 30,000 feet/ 154 = 194 years to build your mountains. That is a pretty good clip. Volcano bonuses: gouts of hot lava, flying volcanic bombs, lahar mud flows. Cherry on top: when they are erupting, green bolts of lightning strike the clouds of soot. Top that, plate tectonics. The earth power. How can I write about Haleakala without looking at some sweet images of it? You too. [![enter image description here](https://i.stack.imgur.com/bUzuo.jpg)](https://i.stack.imgur.com/bUzuo.jpg) from [wendyperrin.com](http://www.wendyperrin.com/?destination=maui-hawaii-travel-guide-jay-johnson) [Answer] This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. > > An article published in the June 15th issue of Earth and Planetary Science Letters suggests that the Tibetan plateau may have risen much more rapidly than previously thought. Similar to the Andean plateau, most people believe the Tibetan plateau rose to its present elevation over tens of millions of years, but this study suggests that much of that elevation may have developed over the past two to three million years. [source](https://arstechnica.com/science/2008/06/fast-forming-mountain-ranges/) > > > Fastest known is two million years. To half that, you'll have to look at that range and double the conditions there--if you are going with plate movement as a source. But may I suggest, for the quickest of mountains, using volcanic activity instead, a la [Paricutin](https://en.wikipedia.org/wiki/Par%C3%ADcutin). There are plenty of examples of islands being formed: [10 in the last 20](http://www.mnn.com/earth-matters/wilderness-resources/stories/10-new-islands-formed-last-20-years) years. These "islands" are actually mountains rising up from the sea bed, sometimes in as little as a year. Now, volcanic activity is due to plate movement in a lot of cases, so technically, all you would need is a chain of them being formed in order to get your mountain range. In this case, they grow at an astounding rate--some in as little as a year--a lot less than your one million years. ]
[Question] [ Aside from very simple or colonial organisms, all animals on Earth have only one mouth for eating. Many organisms have multiple spiracles or even multiple anuses, but not mouths. [Answer] The problem isn't the anatomy or mechanics - life will find a way to make it work. The problem is figuring out a reason why such a system would evolve in the first place. Despite the many, many varied body plans in life on earth, there is not a single creature (not counting colonial organisms or unstructured animals like sponges) with more than one mouth, and every animal that has a head has a mouth on it. There simply aren't enough benefits to outweigh the costs of such a body plan. On earth, the formation of the digestive system is one of the first parts of nearly every animal's development - a ball of cells develops either a cavity (for animals with one orifice, like jellies) or a tube (for those with both a front and a back orifice) and the creature develops from there. The basic structural differences between any vertebrate and a foot-feeding centaur are significantly greater than the differences between a human and a jellyfish. That being said, let us consider a way it might happen. On a planet where such creatures evolved, you'd need to start out with a completely different body plan - one that developed multiple feeding tubes instead of one. A primitive animal on such a world might loosely resemble a starfish, but one with mouths on its legs instead of in the center. The only way such a system would make sense is if the earliest animals were sedentary, and used multiple tentacles to grab at food particles, possibly sucking them up as they floated past. Over time, the creatures could have learned to use their tentacles for motion, developing them into fins or legs while retaining the mouths at the ends. However, it would still seem likely that, were the creatures to become fast-moving organisms that pursued prey or floating food particles, it would make much more sense for one of the tentacles to develop into a specialized head with sense organs and a mouth while the mouths in the other tentacles atrophied. Therefore, the only way for this system to be retained plausibly is if the creatures were always slow-moving grazers, perhaps beginning their history feeding off of bacterial mats on the sea floor, while using one specialized tentacle to watch out for predators. Grass would have had to show up on their world very early to have kept the exclusively grazing lifestyle viable after the creature's ancestors left the seas (on earth grass only showed up after the dinosaur age - early earth herbivores were browsers, not grazers) and keep the creatures from adopting the much simpler body plan of a single head with a mouth and eyes that looked for food and ate it. However, I would expect that, since the purpose of the head is to look out for predators, I would expect it to be in the center and have eyes positioned all around it, not at the front. What could this creature be pursuing that would cause it to benefit from front-facing eyes and a head at the front of its body? The hands could have been a later development, probably for fighting off predators or intraspecific competition, since climbing would not benefit these ground-feeders much. It could be that it developed a distinctive front and back end in the first place so that it could fight more effectively, but never actually ate the things it was fighting with. Altogether, this is a very, very unlikely body plan, even for an alien. [Answer] What you are talking about has been talked about in the [A Natural History](http://rads.stackoverflow.com/amzn/click/0692560297) page featuring Centaurs and instead of blatantly repeating the words he wrote, I have instead included two scans of the book and a transcript from the original online post. [![enter image description here](https://i.stack.imgur.com/NftEW.jpg)](https://i.stack.imgur.com/NftEW.jpg) As the author of the book states "Since centaurs cannot easily stoop their upper body to reach low lying plants they rely on a peculiar method of ingestion to eat while on the move. Centaurs graze through grasping mouths on the base of their four hooves. These toothed orifices are attached to a length of esophagus-like tissue that runs the length of the centaur's limbs. The process appears to be automatic, and centaurs continue to graze even while they sleep.". A close up of the foot shows exactly what he mean, the throat running up the leg [![enter image description here](https://i.stack.imgur.com/VK4VL.png)](https://i.stack.imgur.com/VK4VL.png) [Answer] When I think of a creature with multiple eating mouths, I tend to think of a creature like the Lernaean Hydra, which has multiple heads sprouting from a common body. Such a creature, in my opinion, is likely to evolve in an evironment where there are a lot of creatures that "steal" kills from predators, making quick, efficient eating of your kill highly advantageous. Here's my idea on how such a creature could evolve. Imagine our proto-hydra: a small, reptilian creature, with the unusual adaptation that the brain is located within the body, instead of the head. This makes the proto-hydras head little more than a highly-mobile sense organ with a mouth attached to it. It obtains food through scavenging the kills of larger predators, usually darting in while it is distracted and stealing a few bites before scurrying of. Then, a proto-hydra is born with a birth defect: due to a genetic mutation, this proto-hydra has a second head and neck! Since the brain is within the main body cavity instead of the head, this second head does not develop its own desires or plans, like with two-headed versions of other species\. Thus, this proto-hydra has an advantage: it can eat twice as much food in the same amount of time! In its well-fed state, it is better able to compete for mates, and while some potential mates reject it due to its difference, enough are impressed with its size and strength, and allow it to mate with them. Thus, the gene for multiple heads is passed on, causing a new species of proto-hydra to diverge from the first, this second species having two heads! This process can happen repeatedly throughout the eons, causing the proto-hydras to develop more heads. At the same time, the larger size given to them by their scavenging success eventually allows them to graduate from scavengers to predators. First with small prey, them, when they continue to grow larger, bigger prey. Then, the multiple heads allow the proto-hydra to quickly devour its kill, leaving nothing for the scavengers, along with possibly leaving a head up to watch for and predators that might try to eat it. After some more evolution, adding other hydra traits like spitting venom and the ability to regenerate lost heads, you would have the hydra, a creature with multiple eating mouths, because of the need to leave no leftovers for anyone else. \In cases of a carnivorous species developing a second head, like snakes, there have been known cases of one head trying to eat the other! [Answer] While I agree with the others that the body plan you suggest is unlikely, a slight alteration would make it work. Have mouths in the hooves as suggested, however nothing behind them. They just grab the food and chew it, storing it in a small area around the size of a mouth and with a few enzymes similar to our saliva. The actual "mouth" would be in the center of the body. The hooves grab the food and then deliver it to the "mouth" after chewing it just by bending up and pushing it in. This could be explained as evolution from a starfish like design, with grasping limbs and a central mouth. One limb evolved into the sensing "head" and the others for grasping and locomotion. [Answer] I'll take a slightly different approach to this than the others, I think. Consider such a creature with two eating mouths at two different heights. Perhaps this creature is very tall, with one mouth to eat fruit from tall trees and another to eat fruit from lower bushes or meat from prey. To make such a system required, one mouth can't perform both tasks. I'm thinking we make this necessary by giving the creature a severe inflexibility so the high mouth can't be reached by the arms / tentacles / grabbing appendages down low to be fed, which also necessitates another set up near the high mouth (unless we give it a shortish, prehensile neck and it just grabs the fruit with its mouth). Now we run into the problem of why such a body structure is necessary. This is where we look at the world in which the creature lives. First, it needs a high food source and a low food source. Think giraffe which can't reach the ground with its head. Why does it need to go low if it can already go high like a giraffe? Perhaps the fruit in this world doesn't provide enough nutrients to sustain life on its own and must be supplemented by something that can't be found up high. But why go high in the first place, then? Perhaps we say the creatures on this world require both forms of sustenance to survive--one which can be found in fruit, one which can only be found in ground-level plants or other animals. Perhaps there was some cataclysm which mutated all life on the planet, and only the mutations which could adapt to get both kinds of sustenance could live (vaguely reminiscent of Orson Scott Card's Speaker for the Dead). There are still holes in this scenario, but I think you'd need to look at the environment in which the creature lives to require it to have two feeding mouths. [Answer] * A biome where the animal's food source becomes available for a VERY brief period and is somewhat spread. * Start with a giraffe. Now imagine that the only trees in the area have flowers/leaves that are inedible at all times besides an extremely narrow window: perhaps less than a minute. In order to consume enough to survive, the giraffe may need to develop multiple heads so that it can eat sufficient quantities before its food goes back into hiding. Perhaps a world where light rarely and briefly shines through to these plants, which open just long enough to drink it in. When not eating, the creature uses its mostly damaged/inferior heads for self-defense using an aggressive biting style. [Answer] Here is a real-life example showing how multiple mouths are possible even with the bilaterally symmetrical body plan. <http://voices.nationalgeographic.com/2013/03/14/giant-sea-cucumber-eats-with-its-anus/> Evolution is the ultimate cost/benefit shopper. It costs energy to make a redundant body part, so that body part better be worth keeping. A body plan with multiple mouths would evolve when you need to cover more ground (e.g., foraging) or eat very quickly (e.g., feeding frenzy) or you are likely to lose one mouth and need backups (e.g. lungs will pop) or the cost of making of an extra body part possibly confers some advantage not directly related to its primary function (e.g., huge breasts don't feed babies better than regular breasts but attract more mates). One interesting idea is "stereo." You need [at least] two eyes for depth perception, and two ears for stereo to tell where a sound is coming from, and two nostrils to tell who farted (though this last one works better for dogs). The heads of hammerhead sharks are shaped that way because in order to increase distance between their electroception organs, and thus get a better targeting read on their prey. Maybe a pair (or more) of mouths can actually double as smell receptors too (think snake's tongue), so as to more accurately locate food? [Answer] Let us consider an organism that consumes two categories of food: extremely acidic, and extremely alkaline foods. No one set of digestive organs can processes both foods, and we don't want them to react with each other inside the creature's body. So it evolves two digestive tracts, which are each optimized for either alkaline or acidic foods. [Answer] If a trait is successful it allows a creature to produce more successful offspring. That being said some traits are not only good for single solutions but multiple solutions. That two mouth body plan becomes more believe the more solutions it generates. Teeth offer, in one form another, are good for eating (we'll call it rigid food processing), are also good at biting competitors, warding off predators / rivals, in some cases digging holes, in some cases articulating speech (quacking, barking, etc). Therefore teeth should be found in great abundance: <https://www.affiliateddentists.com/info/animal-teeth-sea-creatures/> Likewise bilateral symmetry is incredibly useful. One limb (a snake or earthworm could be considered single limbed for the purposes of this discussion) is great for some applications (slithering, hiding, etc.). However damage to one limb is damage to all. Bilateral symmetry provides a great backup system. Additionally two limbs can work together with possibly greater efficiency than one (swimming, locomotion). More reasons for two mouths are better than one as long as environmental pressure supports multiple reasons. Coping with a highly predatory environment (food stealing), digesting two types of food (two different enzymes?), etc. Finally, consider the rest of the environment. Some strategies are successful enough to express across kingdoms. Such as eusocial social structures which occur in insects (ants, bees, termites), mammals, (naked mole rats), and shrimp (<https://en.wikipedia.org/wiki/Eusociality>). [Answer] I agree with IndigoFenix. Before I saw Xplodotron's answer, I could think of only one creature that has multiple mouths: Venus Flytrap. Granted, that uses the term "mouth" pretty loosely but they do trap and digest prey. They also die when they take in prey and are replaced by new traps. Also, as Xplodotron mentioned, sexual selection may allow a random mutation that does not decrease survivability too badly. A two headed snake as a pretty common mutation. If the multiple heads helped the male snake mate it might get passed on. [Answer] How about a different approach: Lets go down the evolutionary tree to a very primitive basically immobile creature with the usual tube based digestive system. This creature has an asexual reproduction mechanism in addition to the usual sexual one--hence it can have offspring that are genetically identical to itself. Now, one of these creatures learned how to cooperate with offspring that had not wandered off. Eventually this cooperation became so complete that they fused into a single organism. (Remember, genetically identical, this wouldn't be unreasonable.) Now you have a single creature with multiple digestive tracts that can serve as the base for more complex multi-mouthed creatures to evolve. There must be some considerable advantage to it, though, or it's going to lose out to creatures without the duplicated digestive apparatus. ]
[Question] [ I’ve been trying to answer this question for a premise involving a cyborg being out of touch with modern civilization for a prolonged period of time, and the roadblock I keep hitting is that counter to what cyberpunk fiction tends to subtly imply, we just don’t build our technology to last a lifetime anymore. Even medically important items like prosthetics and basic implants (i.e. pacemakers) are not an exception to this. Most only last 5-10 years at most before needing to be replaced. Now while I’m sure in a future where people are more extensively augmented/cyberized, we would have the ability to build longer-lasting prosthetics and implants. But... why would we? Look at how often new smartphones and other smart devices are updated or replaced by next generation hardware. Stuff like neural implants, the next evolution of the smartphone and similar technologies, will surely be no exception. Making implants that last a lifetime would be pointless, as new upgrades with superior functionality would be made available every few years. Plus, there’s capitalism to consider. Between the cost of the implants themselves and the microsurgery required to install them, corporations stand to make VASTLY more money by adopting an iPhone model of annual development and replacement. Prosthetics are slightly less affected by this, as you can only enhance the functionality of a limb so much before you’re just providing incremental gains or adding unnecessary bells and whistles like “mantis blades”. Still, you’d expect those to be replaced by newer models fairly frequently as well, even if people can get by using their old ones for a few more years past expiration dates. Really though, we’re more concerned with the implants, as things like neural links, artificial organs, or other hidden upgrades stand a better chance of becoming a vital and necessary part of people’s lives, more valuable than a hand or even things like sight or hearing. The only answers I can think of for why implants would be built to be longer-lasting would be either “because we can”, which I personally don’t like as an answer, or “because prosthetics/implants are part of basic government-provided healthcare”, which works better (especially if they’re installed at birth for free as a means of covertly monitoring the population and gathering personal data), but which still runs into the problem of the technology used to make these implants becoming obsolete eventually. What do you guys think? Are there any other reasons implants might be built to last? How long do you think somebody could reasonably keep using implants with planned obsolescence before they start breaking down or losing functionality? [Answer] Replacing them is (literally) a pain. In real life, you could classify most prosthetics into two types - ones that go inside you (pacemaker, VP shunt), and ones you wear like clothing (hand, foot). In a cyberpunk setting you often also have fictional ones that are partly inside the body, partly outside, and firmly attached to the skin somehow (ouch?) and possibly also bolted onto the skeleton (ouch!). This is more for "are you still human?" story angst than any realistic practical reasons - saying "he's more machine than man now" seems silly if he takes half the machines off to have a bath. Only the prosthetics you take off are easy to replace. The others require surgery, with all its downsides: pain, scarring, time under anaesthesia, time off work to heal. Then there's the potential for infection, surgical mistakes, serious problems with anaesthesia. If something can't be fixed without cutting me, I want it to last as long as possible. Especially if it's in my skull. The only reason internal devices get replaced now is because we don't know how to make ones that last longer - something breaks, scar tissue builds up, the battery doesn't last, it gets clogged with biological material, etc. If some future technologies fixed those problems, they wouldn't be temporary. If you want to upgrade your neural implants' capabilities later... wouldn't you rather have a long-lasting bluetooth implant in your brain that connects to an external phone you could replace regularly, instead of putting the whole phone in your head? And then, when your hero's iPhone inevitably breaks, she can connect her neural Bluetooth to some other, more durable computer and still have some special abilities. [Answer] The closest thing I can imagine which is related to cybernetic implant is a pacemaker. [How long do they last?](https://www.webmd.com/heart-disease/heart-failure/qa/how-long-do-pacemakers-last) > > Pacemakers usually last four to eight years. Biventricular pacemakers that are combined with an implantable cardioverter defibrillator (ICD) do not tend to last as long -- about two to four years. The lifespan of the pacemaker depends on how much your heart is depending on it. > > > Let's assume that your devices are so advanced that they can double that lifetime: it gives you 8 to 16 years, depending on usage. But the capitalism can thrive on the upgrades of the install: the socket/interface with the body is a one time surgery, but if it has something like a USB port, it can be plugged to any module developed over time. [Answer] [![iron hand](https://i.stack.imgur.com/3c4Jq.jpg)](https://i.stack.imgur.com/3c4Jq.jpg)In your world, prosthetics last forever. <https://en.wikipedia.org/wiki/Iron_hand_(prosthesis)#/media/File:Eiserne_Hand_Glasnegativ_6_cropped.jpg> You are right about technological innovations, profit motive and the like as regards tech in todays world. And you are writing a fiction which you want to be interesting. Different is interesting. I propose you make your tech immortal, like the iron hand depicted here. In your world, prosthetics are like cathedrals or aqueducts - constructs expected to outlive the current user(s) and be used by subsequent biologicals, indefinitely. You would sidestep the issues of innovation and profit by having your prosthetics be of unusual provenance. Perhaps they are (or were) built by well-meaning aliens as contributions to humanity. Perhaps they are built by a secret technoreligious order whose motivations are obscure. Or perhaps they are built by the civilization ancestral to the one in your story - a dark age has intervened and the skills to build new ones are lost. Like 1950s American automobiles in communist Cuba, these old machines continue to work well and are superior to modern constructions; their users scrupulously maintain them. [Answer] The corporations can rent/lease the augmentations instead of selling, so they can keep milking their customers, have a more stable cash flow when compared to yearly new models, and have incentives to think about durability because the parts aren't owned by the consumer but by the corporation. They can rent a turboarm v3.0 to first world customers for a few years and then replace them with the turboarm v4.0 in the first world and rent the used v3.0 in the third world for many more years, probably until it starts to break down. They will have to do some variable optimizations taking into account the profits from renting old parts and the cost of making them to last, but I think it is reasonable for a part to last 25 years: five in the first world, 20 in the third world. PS.: be sure that the companies take sterelization seriously, both to kill the biological pathogens and the software ones if they are going to rent used parts or else you will have an AIDS-like crisis eventually. [Answer] When you have implants that may take over some of the necessary functions of life, which are implanted not out of medical necessity but for cosmetic purposes, the answer will depend upon one primary factor, and possibly a number of secondary factors. The primary factor is going to be the regulatory environment. It is one thing if a life-saving implant only functions for a number of years, since without the implant, the patient would not likely have had those years, but it is another thing if the implant is not a medical necessity. In a strict regulatory environment, any device implanted for non-life-saving reasons, whose failure would threaten the life of its recipient would of necessity be expected by law to last the expected lifetime of its recipient plus enough more that there would be no significant chance of a life-threatening failure within the recipient's lifetime - the reasoning being that changes in the recipient's fortunes may mean that they may never again have the opportunity for the device to be maintained or replaced. There may be an additional requirement that any non-threatening failure mode be covered by a statutory lifetime warranty. In a less strict regulatory environment, there may still be a particular requirement that the device be expected to function for a significant period of time, possibly twenty years or more. In either case, it would also likely be expected that the recipient and potentially also his/her doctors receive advanced warning that a failure has been predicted, probably with minimum warning periods ranging from at least one month to at least a full year, mandated by law. However, the typical cyberpunk world is one in which corporate greed has supplanted, overtaken or sidestepped any regulatory oversight. However, even in such an environment, it can be expected that there will be certain standards that the corporations who manufacture such products will adhere to, for no other reason than pure self-intetest. It does not serve the interests of a manufacturer of bioenhancements for negative attention to be drawn to them as a result of untimely failures of their cosmetic, non-life-saving products. Regulatory oversight may be absent or ineffectual, but as long as there is marketplace competition, in an environment where so many potential customers are connected to social media, fatal or untimely, crippling failures of bioenhancements would lead to unwelcome negative attention that would ultimately lead to a drop in sales and revenue. When social media and not any regulatory body dictates the expected lifespan of cyberenhancements, how long can they be expected to last? That depends on factors such as the amount of warning of an imminent failure the user received, the terms of any warranty, and the amount of time the device lasted before failing. The social status of the victim of the failure would also be a significant factor - a dead celebrity is a disaster, while a dead homeless person is merely a statistic. So, when social media rules, we can still expect cyberware to last a significant amount of time, perhaps twenty to thirty years at least. A celebrity may get an enhancement, and while they may be able to afford to have them serviced or upgraded regularly, there is no guarantee that they will do so, and should their enhancement fail in a fatal manner, the manufacturer will really want to be able to show that they repeatedly notified said deceased celebrity that their implant required service, and that they offered to provide said service at no monetary cost. Additionally, lest it be said that there are different rules for celebrities, these warranty and service terms would have to apply to all customers. [Answer] [Cochlear implants (CIs)](https://www.nidcd.nih.gov/health/cochlear-implants) are a lot like a neural implant and [auditory brainstem impants (ABIs)](https://my.clevelandclinic.org/health/articles/16379-auditory-brainstem-implant) are most definitely a neural implant. CIs have been around 50+ years and the implants electrodes are designed to last a lifetime. There have been significant enhancements to the electrode design over that time, but generally patients do not receive upgrades to the implanted portion. ABIs are a lot newer and while it is expected that the implant will last a lifetime, nobody really knows how the tissue will tolerate it and how it will hold up over 75+ years. CIs and ABIs both have external processors. These are frequently reprogrammed and often patients gets hardware upgrades. The reason the devices are split is that the surgery to implant the devices, especially ABIs, is non-trivial, and replacing the implanted electrodes carries risk and a high likelihood of diminished benefits due to tissue damage. [Answer] What if your implants adapt to you over time? You grow into them, both figuratively and literally. They start off generic with baseline functionality, but over time adapt to your way of walking, moving, idiosyncrasies in your vascular or nervous systems, depending on the implant. Replacing an implant with a new "blank" one might gain you a few new features but at a cost of losing the customisation you've spent year developing, and a resulting loss in overall performance. [Answer] The most important part of the implant would be the socket; the actual body-machine interface. Fortunately the technology for connectors lasts longer (think of audio connectors and USB). [Answer] It may not be a part of your personal cyberpunk vision, but in a high-tech fictional universe, you could justifiably have self-repairing (and maybe even self-upgrading) components based on [nanorobotics](https://en.wikipedia.org/wiki/Nanorobotics) technology. Specifically, the nanobots in your world could be injected in the cyborg's bloodstream and be used to "smartly" patch up damaged or faulty parts of existing implants. The implants themselves would basically last forever, as a kind of [grandfather's axe / ship of Theseus](https://en.wikipedia.org/wiki/Ship_of_Theseus) if you will. Which by the way is not that different from how a human's biological body works (sans the lasting forever part, obviously). EDIT: Not to go on a tangent, but [here](http://askanaturalist.com/do-we-replace-our-cells-every-7-or-10-years/) is some more info on cell replacement in our natural bodies. You might even use the nanobots as a plot device: Let's say they get slowly used up and more or less safely ejected from the host body, and need to be replaced over time. But even in a cyberpunk world, nanobots are sufficiently high tech to be a resource both rare and expensive - the knowledge of how to make them being a secret that is kept and vigilantly guarded by a very small number of ... entities (can they even be called humans anymore?). Entities so rich and powerful that it would take some serious cortical enhancement to merely grasp the expanse of their awesome capabilities. As it happens, your protagonist falls on hard times and runs dangerously low on nanobots - nanobots that she needs to keep her essential, life-sustaining implants going. Close to despair and certain death, she receives a too-good-to-be-true offer from a shadowy figure: Enough bots to keep her going for a long time, in exchange for what appears to be a simple job ... [Answer] The harsh reality is that in our world it's probably not going to be a reality. Not for the masses anyway. Long-lasting cybernetics will most likely be prohibitively expensive and only the very very wealthy will be able to afford them. So we're just going to have to change the world. First, let's produce some really simple large scale production of carbon forms like graphene, fullerenes and nanotubes leads to cheap carbon-based prostheses that last for decades. Chemically inert C240 molecules are as close to perfect spheres as we can manufacture and small enough that they make a near-perfect lubricant in an appropriate fluid suspension. Nanotubes can be matted, woven and so on and can be extremely durable... and are already being used in neural implants. And graphene of course is the next wonder material. Next, nano-tech. No, not the grey goo kind, no floating clouds of nano-particles or tiny, tiny robots wandering around in your bloodstream. Those are going to have to wait for a few decades. Let's start with simple nano-scale engineering to do something useful with all those funky carbon forms... including, probably, producing them to order. Or assembling them into machines at a very small scale. We can also use it to assemble interesting materials like nanotube-reinforced metallic matrices that have high structural strength but low mass - the structural steel equivalent of aerogels. And finally, power. Either come up with a way for the body to power the cybernetics or use an integrated power source. Graphene super-capacitors are a good rechargeable power source, or the high density carbon electrode lithium batteries might do. You could use piezo-electric mesh in the major muscles of the body to produce electricity, or at a pinch a bunch of tiny turbines in the major arteries to turn blood flow into electrical power. Just don't over-draw on that one or your heart is probably going to be working too hard. So now we have the materials and the power at a (hopefully) reasonable price, what's next? A reason to do it. We have a lot of answers about why not, but only some minor mentions of why we would make long-life cybernetics worth the effort. And honestly it's a hard one. I think the biggest reason is going to be the invasive and hugely stressful implantation surgery itself. While much of the cyberpunk fiction seems to have hyper-advanced implantation surgeries performed in grubby back-room chop shops, the reality is that for the foreseeable future this kind of surgery isn't going to be either cheap or easy. Sure, carbon-based interfaces seem to be a pretty good bet when it comes to long-term results, but we're a hell of a long way away from stopping in at a GP to have our arms lopped off and replaced with cybernetics. The upshot of this is that when you do get a part replaced, you really really don't want to have to replace it ever couple of years. Even if you get a quick-change mount that lets you choose which arm best suits your evening wear choice, you don't want to have to go back and get it replaced. Ever. Hell, you want to be buried with that sucker when you finally kick it at 103. What you don't want is to be laid up for 8 weeks every 3-5 years after the major surgery to replace the damned things. The downside? Extensive black market trade in 'slightly used' cybernetics. Not all cybernetics are created equal. Of course there are going to be cheap-n-nasty parts, especially if quick-change mounts are popular. Look at the fashion industry for inspiration here: somebody builds a work of art for a celebrity and suddenly there are a thousand knock-offs available via mail order. But military grade combat enhancements are going to be built - at ridiculous prices, of course - to very high grade. The military will train people and do the implantation, then replace them with civilian models when the person leaves active duty. The implants themselves will be recycled as long as they are serviceable, and guaranteed some desk jockey is going to point out that it's cheaper to spend \$5M on one piece that can be reused 10 times rather than 10 x \$1M for non-reusables. So of course there will be 'repurposed' mil-spec gear available on the black market. And trained cyber-surgeons who are willing to do the work at their clinics that normally serve the cosmetic cybernetics clients. [Answer] Allowing for the fact that implanting of cybernetic brain enhancing systems is already happening in certain labs, the product life cycle is not as large of a concern as the product security in my opinion. What happens when 50% of the worlds population is feed artificial memories by an AI system at the behest of communist China for example, or someone pushes a button and self destructs 100,000,000’s of implanted chips resulting in the death of the hosts? Before you connect to a hive brain by getting a chip installed in your head think about the downside. ]
[Question] [ So I build a city on the ocean floor out of handwavium, Bioshock style, but I want an easier way to get there besides taking a boat to the middle of nowhere and then getting into a submersible. I have an idea to dig a shaft deep into the ocean floor, and then make a tunnel leading to a near-by island, and if it goes well maybe extending to the mainland eventually. Obviously once you go down to the ocean bottom there is a lot of pressure, but I'm thinking that by going down below the bottom the seabed will provide enough support to keep my tunnel from collapsing so I can have a dry path to run a rail line. Is this a workable plan? The feasibility of the city itself isn't a concern with this question. I'm just looking at a way to get to it. [Answer] Consider the depth and length (and expenses) of undersea tunnels like the [Seikan Tunnel](https://en.wikipedia.org/wiki/Seikan_Tunnel). If you consider the [Yoshioka-Kaitei Station](https://en.wikipedia.org/wiki/Yoshioka-Kaitei_Station) an undersea base, there is even that. This example shows that a tunnel is in principle feasible. Many of the considerations for an undersea base apply to the tunnel -- if one is feasible, so is the other. * Keeping the walls watertight. * Quakes. [Answer] The deep oceans floors are made of Basalt ([Mid ocean ridge basalt](https://www.britannica.com/science/mid-ocean-ridge-basalt), or MORB). This is unfortunately quite permeable to seawater (and even to [oil](https://www.slb.com/~/media/Files/resources/oilfield_review/ors09/spr09/evaluating_volcanic_reservoirs.pdf)), so a tunnel would tend to fill with water quite quickly. Above the basalt is often a layer of mud with little mechanical strength. Your best bet is surely to have a tube of Unobtanium on the ocean bed, or at least line your tunnel with it. Lining the tunnel removes the problems of mechanical strength and water ingress. [Answer] This is less difficult than building the city itself. The key is to pressurize the tunnel, in the same way you have probably pressurized the city. Especially with a train system, an airlock near the entrance would not be difficult. The deepest tunnel now is the [Ekiksund Tunnel](https://en.wikipedia.org/wiki/Eiksund_Tunnel) at 287m under the water. Even if we take twice that depth as the engineering limit for non-pressure regulated tunnels, you're going to be fairly limited in locations. The oceans are mostly very deep. [![infographic of lake and ocean depths](https://i.stack.imgur.com/OkliT.png)](https://i.stack.imgur.com/OkliT.png) Image source is [xkcd](https://xkcd.com/1040/). Pressurizing the air in both the city and the tunnel will make the engineering much easier. It also adds some safe limits on how quickly people can leave your city. So for the case of the tunnel, you may wish to have the train itself pressurized differently than the surrounding air. This will allow the train to slowly lower the pressure as it approaches the surface. The other obvious option is to simply have the tunnel filled with water. Adding aerators will lower the average density of the water and allow the pressurized train to pass more quickly than if it were in pure water. [Answer] If you did such a tunnel, you will have to build a pipe inside it, to prevent the pressure from collapsing it. If you are building your city out of handwavium, might as well build a tunnel out of it. [Answer] ## Chord tunnel Don't attempt to lay the tunnel on the sea bottom. Go under the sea bottom. Exploit the curvature of the earth to make a chord tunnel - laser straight. Normal tunnels are not laser straight, they have a vertical curve to match the earth's curvature. Take the famous picture of power lines curving over Lake Pontchartrain. If you started a tunnel a mile or two landside of shore on each end, and built it as a chord tunnel, it probably would be entirely beneath the bottom of the lake. [Answer] If you build a tunnel for long distances underwater, you will run into a variety of problems, one of which is the time the journey would take on long trips. To go from Honolulu, Hawaii to San Francisco, California would take 2,393 miles at best train speed, it would take 8 hours of travel time. Imagine if you could go anywhere in only 38 minutes. What you really need is a Gravity Train. [![Gravity Train](https://i.stack.imgur.com/kiI7M.jpg)](https://i.stack.imgur.com/kiI7M.jpg) A gravity train is a means of transportation intended to go between two points on the surface of a sphere, following a straight tunnel that goes directly from one point to the other through the interior of the sphere. [![Description of Tunnel](https://i.stack.imgur.com/mmrNg.png)](https://i.stack.imgur.com/mmrNg.png) In a large body such as the Earth, this train could be left to accelerate using just the force of gravity, since, during the first half of the trip (from the point of departure until the middle), the downward pull towards the center of gravity would pull it towards the destination. During the second half of the trip, the acceleration would be in the opposite direction relative to the trajectory, but (ignoring the effects of friction) the speed acquired before would be enough to cancel this deceleration exactly (so that the train would reach its destination with speed equal to zero). The math works out that from the time entering the tunnel to the time exiting would take around 38-45 minutes. * <https://en.wikipedia.org/wiki/Gravity_train> Good luck with your choo choo. ]
[Question] [ Assuming bronze age technology and the use of bronze for the blade, what is the longest blade / total length of sword that is possible and practical to use? Bronze age Naue II swords were typically 70cm but I am wondering if a longer (1.2m +) sword is actually practical, both in terms of weight and strength of the material Are there any technologies available today (or in a future sci fi setting) that could improve the possible sword length in a bronze material? In the special magic world I am thinking of there is a special "repair" magic spell that can fix minor damage to swords in between bouts so this might aid durability To answer comments: John: total length, probably quite a lot of handle! Erik: cutting slashing at a large opponent such as a 300kg Troll [Answer] Here's a good discussion of sword crafting: <http://io9.gizmodo.com/5831683/a-brief-history-of-the-ancient-science-of-sword-making> . Money quote: > > The use of bronze instead of copper meant that these swords could be fashioned in the range of 20—35 inches in length. Longer, sturdier swords in the range of 2—4 feet, however, would not emerge until the the Iron Age, beginning around the 13th or 12th century BC. > > > So you can have a 3ft sword of bronze, but that's at the very upper end of the scale. It'd be a high-tin bronze, very expensive, and probably a "named" sword. From other sources, I'm told that bronze alloys using a lot of tin are actually quite competitive with iron (not steel, though). The big issue was that iron is way more abundant than tin. What this means however is that early iron age swords would be short, too. The more "steely" the iron gets, the longer the sword can be. Were I a Bronze Age guy with trolls to fight, I'd consider packing a brace of spears instead, or maybe an axe. The wood gives me length and leverage, and the metal gives me bite. Do note that in the Iliad, the bronze-age Achaeans (cough cough, "akaioi" if you will ;D ) were all about the spears. Swords were the backup weapon. [Answer] bronze swords up to 110cm exist(Chinese Qin Dynasty), although 80cm is considered close to the max for a practical sword. 70cm is a fairly normal bronze longsword but not the maximum. For instance many Naue II bronze swords were 85cm. Single edged swords got even bigger, note longer swords like this would have had a tang of some kind. [Here](https://www.tf.uni-kiel.de/matwis/amat/iss/kap_b/backbone/rb_1_2.html) is a website dedicated to bronze swords for design ideas. Bronze swords are actually fairly durable, they bend instead of breaking which means they can be fixed more easily and much faster. A steel sword is better and more importantly stiffer, bending will be your biggest problem bronze. [here](https://www.youtube.com/watch?v=ngjMtzJ6xgQ) is a great video of destructive testing of a bronze sword. [Answer] During the Bronze age, relatively long, narrow swords were made as thrusting weapons, presumably to get around tower shields or full suites of armour and stab your enemy in the neck area for an almost certain killing stroke. Since the Bronze age covers a long period of time, a good summary of sword evolution can be found [here](http://www.salimbeti.com/micenei/weapons1.htm) [![enter image description here](https://i.stack.imgur.com/chOzn.jpg)](https://i.stack.imgur.com/chOzn.jpg) Reproduction of the Dendra armour panalopy [![enter image description here](https://i.stack.imgur.com/lHc6s.jpg)](https://i.stack.imgur.com/lHc6s.jpg) Type C swords The long thrusting swords are perhaps some of the earliest ones, often catalogued as type "A" and "C". Some examples of "A" swords are up to 87cm long, while there is one example of a "C" sword 101 cm long. Most swords are shorter (perhaps to ensure they don't bend or break when thrusting). Naue II swords were optimized for cutting and thrusting and could be up to 85cm in length although most were shorter, suggesting 85cm was the practical limit for bronze swords. [![enter image description here](https://i.stack.imgur.com/nksWX.jpg)](https://i.stack.imgur.com/nksWX.jpg) Reproduction Naue II sword It should be noted that while swords were considered the sorts of weapons nobles and other wealthy people could carry into battle, most people fought with spears, and closed with daggers or axes. This is because they were generally less expensive, and didn't require the length of training a sword would take (particularly a long thrusting sword. While no ancient texts exist to understand swordsmanship in the bronze age, sword manuals from the 1500's for rapiers suggest it would probably have been rather complex to learn). [Answer] Others have commented on the practical lengths of a bronze sword based on it's material. You mentioned that this was a world that has magic. So, that opens up some possibilities that our world didn't have. 1. If some people are stronger in that world than in ours (half ogre blood or something), then the swords could be made thicker to support that extra length. You can't go crazy with this option because the thickness needed is not linear compared to its length but you can probably get an extra 10-20cm out of it. 2. If materials can be magically enhanced or strengthened, bigger becomes even more possible. It just becomes more expensive and rare. There are all kinds of possibilities here. You can make it stronger, lighter, and/or more flexible. Heck you can give it even more possibilities with material enhancements. What if the metal becomes poisonous in wounds or it floats on water? [Answer] Casting a sword is a job that requires skills, and same does waving it around. If the craftsmen of Bronze age didn't produce swords longer than 70 cm (and I am pretty sure nobody is glad to fight for his life having a too short sword, therefore the requirement to have the sword as long as possible were in place) it surely means it is either not possible, as the material will be too defective to be effective, or not practical, as the sword will be more a burden than a treat in the hands of a warrior. Composite materials (fibers in metal matrix) may help in improving the sword resistance while keeping the same weight, but then the challenge would be to have a well balanced sword. [Answer] A lot of other answers already say you can make a tin-bronze sword just over 1m in length which is true, but the real reason I am adding an answer to this 5 year old question is this much more interesting unanswered part: > > Are there any technologies available today (or in a future sci fi setting) that could improve the possible sword length in a bronze material? > > > ## The answer to this is yes Phosphor bronze is a bronze alloy invented in the 1600s, but if your civilization did not have a bronze-age collapse, it could have been invented much sooner. Phosphorous oxide was first used in metallurgy by the Spartans in ~650 BCE to make thier Phosphor Steel swords. Phosphor bronze has properties very comparable to the steel of the high medieval period making (1.2m +) longswords very much doable. If you want to take this a step further, you could even go with a beryllium bronze alloy. Beryllium is about as common in the Earth's crust as Tin, but methods for refining it were not discovered until the late 1700s. When alloyed with Copper, it creates a metal that so tough that it is comparable to many modern high-end steels. So if you wanted to make a particularly spindly sword like a rapier or greatsword, they would not be out of the question. [Answer] Bronze was very expensive which is what probably limit the length of swords made with it. Otherwise, it's properties are pretty much inline with the larger iron swords that came later. The other thing is that metal armor was also not too common in the bronze age because of the cost so that you don't need a massive sword to do damage. If you needed longer reach, a spear would do. So there is less need of more massive swords. Massive swords aren't actually good against agile opponents in light armor. ]
[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. Imagine that God has many universes to deal with or just needs a break sometimes. He has a pause control. What plausible mechanism does God use to perform the pause without breaking the laws of physics he has created? Is there anything in our current knowledge of physics that forbids a pause? What is the minimal thing that has to be done to produce a universal pause (rather than intervening with every particle individually)? If God uses this minimal method, can we detect that we have been paused? Update (taking into account some of the answers and comments) My assumption is that all the laws that we see are still there, exactly as we know them. There could however be an extra law that we simply don't know about. It doesn't change the other laws--it just exists alongside them. Effectively it is used to stop our universe relative to other universes and Heaven. I'm wondering if we could find out about the extra law by the fact that something changes suddenly, for example the amount/proportion of dark matter in the universe suddenly changes. [Please notice the [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") tag. Soft science that is verifiable is also welcomed.] [Answer] No, because of Hamilton's equations and conservation laws. At some time $t$, the configuration of the universe is represented (classically) by a point in [phase space](http://en.wikipedia.org/wiki/Phase_space). Phase space describes the position and momentum of the components of a system. We can define these locations using [canonical coordinates](http://en.wikipedia.org/wiki/Canonical_coordinates) $q\_i$ and $p\_i$ (components of the vectors denoting objects' locations in space and momenta). [Hamilton's equations](http://en.wikipedia.org/wiki/Hamiltonian_mechanics) say that $$\frac{\mathrm{d}\mathbf{p}}{\mathrm{d}t}=-\frac{\mathrm{d}\mathcal{H}}{\mathrm{d}\mathbf{q}}$$ $$\frac{\mathrm{d}\mathbf{q}}{\mathrm{d}t}=\frac{\mathrm{d}\mathcal{H}}{\mathrm{d}\mathbf{p}}$$ This describes how the configuration of the universe changes in phase space over time - in other words, how the universe evolves. Normally, this could be represented by a smooth curve. In this case, however, at some time $t\_1$, there is a discontinuity, where $\|\mathbf{p}\|=0$. From God's perspective, you have a finite $\mathrm{d}\mathbf{p}$ and a vanishing $\mathrm{d}t$, which means an infinite force, as $\mathbf{F}=\frac{\mathrm{d}\mathbf{p}}{\mathrm{d}t}$. That quite clearly violates the laws of physics. > > Is there anything in our current knowledge of physics that forbids a pause? > > > Oh, yes. It violates this reasoning, as well as conservation laws aplenty, including energy, linear momentum, and angular momentum. Any energy associated with motion instantaneously disappears, with no possible mechanism for its loss. --- To more specifically address the question of whether or not we could notice it, the answer is simple: No. If everything has been paused, then nothing should have changed during the "time" elapsed for God during the pause. There's simply no way to tell, because nothing is different. [Answer] The laws of physics AS WE KNOW THEM, does not allow such an act. But really, they don't forbid it either. These laws describe the universe from the inside, because that is the only viewpoint we have available. What happens outside the universe, if an outside exists at all, is beyond the scope of our theories. What is needed is a "God" time that is independent of "Universe" time. Universe time stops, everything in the universe stops. God lives on God time and takes a vacation. Later on, they start the Universe Clock again and everything starts moving again like nothing happened. Computers do this all the time. Computer programs run in small universes of their own. They think they run continuously, but in really they execute in short bursts with pauses in between. Normally these pauses are very short, less than a tenth of a second, but if you activate sleep mode they can last much longer. A computer program can discover this in two ways. One is simply looking at the system clock. The other that they were connected to some server and that server closed the connection due to inactivity. In both cases the program is looking outside its universe to discover that outside time has moved on without it. There is no way a program can discover this just by looking inside its own world. Unless there is a bug. Returning to God and our Universe. I assume God is competent enough that they won't have bugs in the creation. Then the only way to discover the pauses is by looking outside the Universe, which we don't know how to do. Yet. [Answer] # as ever, Greg Egan is the master Look at some of the narrative from the short story that was expanded into the novel Permutation City by Greg Egan. In fact, read that novel before continuing with these ideas— it will be food for thought. In the first part (the original story) a character inside a simulation experiments with the effects of changing the granularity of computing the states, and even reversing them! He counts from 1 to 10 to mark off seconds, and the simulation calculated the resulting state of 10 seconds without playing through each one: after he “counts” can he tell that it didn’t really happen? What about computing and realizing the states out of order? In another part of the novel, they create a universe that includes an access network to the various cells as well as the “inside” connectivity of the stuff in the space. And it has a variable speed and pause function designed in. In a [completely different Egan novel](https://en.wikipedia.org/wiki/Diaspora_(novel)), he has a crystal artifact that is the state of a computer running intelligent beings. It doesn't have a way to change the bits: the compute engine (wherever it is now) created a new instance as it computes the next state. The “beings” in their universe are far in the future now and this frozen image of a past moment means what? Would it bother them if you destroyed it? Looking at a row of these files laid out down a highway, what is their “time” to you, driving up and down the highway at will? --- # on simulations If the universe (or a population who thinks they observe a universe) works in a straightforward way you think of computing the next state from the previous, who's to say how long each step takes ([obligatory xkcd reference](http://www.explainxkcd.com/wiki/index.php/505:_A_Bunch_of_Rocks))? Slowing it or pausing would mean nothing if the eventual result computed was the same. If there's not a central processor with separate memory, but something more like a cellular automata, maybe every cell is hooked up to a clock and a way to examime its state. Stopping it would mean coordinating the stop to all cells. You might contrive imperfections for the plot so it could be determined. In our Universe, time and space is one thing and it doesn’t make sence to have an absolute time marching forward. However, on the “outside” a particular slice of spacetime is computed in some order. Once the project is complete the entire 4D state is complete and there is no time outside corresponding to any inside observer’s time. So what does “pause” even mean? For the concept to mame sence it would have to be a simulation specifically made to host the people inside. The simulation-state time is a time axis very close to that of the planet and people inside. At any given time (on the outside) the computer’s memory holds a state representing all space and a small range of time in that reference frame. # pinning down a definite concept Now suppose this is done on a cluster of compute units with memory local to a small region of space. Now that doesn’t really work due to entanglement but suppose it’s a simulation we might make in the medium future and meant to appear to be this universe on the inside, so observable nonlocal issues are hacked into the design. Each processor runs without a real synchronized clock, but accesses data tagged with space-time in adjecent cells, so it doesn’t matter. If they can’t all be addressed with a single command either, but the commands flow across the compute fabric, then stopping becomes a problem. If a cell doesn't care what time it is per se but computes based on what its neighbors contain, then cells may compute with neighbors that have already stopped and “see” the wrong information. If the command follows the normal connections used for causality, then it will be OK. It’s restarting that will have problems. The newly restarted cell will have neighbors that are still “cold” for events flowing in the opposite direction. Let’s suppose that the restarted cell is in a state to ease back up, but it’s not perfect: it may linger too long or not enough, and lose information due to neighbors being out of date. Where it might break worse is where features were hacked in. What if quantum computers (inside) malfunction because the entanglement is messed up when restarting? What about events being observed in the distant universe that is not being simulated to full fidelity but fed-in to the people in the main simulation? Watching a distant supernova in a telescope might glitch. # what this gives us: As people (on the inside) * develop more awareness of fine details of far-distant events, * more detailed reliance on very small quantum effects, * and technology that uses quantum-scale effects over intercontinental distances, they might become aware of glitches and imperfections that show up after a pause is restarted. [Answer] I think the answer depends on the computability of the universe. If the universe is computable, then its state can be stored somehow and nothing could prevent a 'God' from pausing it. If God is not included in the universe, then I don't think it possible from the inside to guess that the universe was paused. If God is part of the universe, then he would have to pause himself leading to a paradox. If the universe is not computable (more likely), then it's state could not be stored and then could not be paused. Note that if the universe is computable, then the universe become "predictable" (in my opinion). [Answer] Well, if it's really like that God has "universes in boxes" and pauses them correctly, then I think there is a way to detect this, depending on the way how God pauses the universes. Imagine a moving system like falling dominoes, pinball or whatever -- this is a good analogy to God with his universe in a box. Now the universe is moving; if you want to stop it, you simply stop all the objects. God is infinite, has "infinitely many fingers" that can stop "infinitely many objects". Also, he is very powerfull and skilled, so he can stop the objects all at once, and then start them by kicking them in their original speed. If everything is stopped, including light, information (such as gravity) etc., you can't detect it. But maybe he is not stopping and starting everything so precisely. Maybe we are able to detect small dislocations of objects every now and then, as God stops as and starts us again. He's created the Heisenberg principle to hide these imprecisions, but what if we can go beyond this, maybe with a help of some really long-term statistics? I don't touch the problem of relativity and what "now" means; since God stops even photons and gravity information, he can stop them in any reference frame. [Answer] I don't think there is an answer to this question. There is a concept in physics known as Planck Time. It's defined as the length of time that it takes a photon to cross one unit of Planck Length. This length of time is about 10^-43 (10 to the minus 43rd power) seconds. Roughly speaking, nothing can happen during this length of time, so God, existing in eternity, can take off as much time as He needs during Planck Time. If time comes to a stop, we can't sense it since all of our bodily senses and all of our scientific instruments depend on the passage of time to make any measurements. It's kind of wrong headed to think about what God can or can't do. At least it is to me. Anything you say about God's nature is limiting and God's nature has no limits. But then, that's theology, not science. [Answer] What the question is about is whether we are living in a physical universe, or in a simulation embedded in an external physical universe of which we know nothing. A virtual reality. (Lay aside the philosophical problems over defining "physical", the moral dimensions, and that it might be turtles a long way down, or should that be up). If our universe is (a) god's "simulation", and what he is simulating is nothing more nor less than a finite set of rules for interactions between fundamental particles (some of which we have deduced, others which we may deduce in future), all invariant with respect to position, direction and time, then that is an untestable hypothesis for us on the inside. We should therefore wave Occam's razor and stop worrying. Where it gets interesting is if the god is nowhere near powerful enough to simulate an entire universe. Let's suppose that he is actually a distant descendant of humanity, and he's doing historical research on how things might have turned out if the initial conditions leading into the 2190 technological "singularity" had been a little bit different. So he's simulating not our physical universe, which is just like his universe, but "merely" our brains (and only a few million of them: most of the shop assistants and suchlike that we interact with and promptly forget, are in fact low-res simulacra with no continuity beyond what we observe of them). This virtual universe is not a flawless implementation of a few simple rules, but a patchwork quilt of ad-hockery limited by his budget. We look down, the simulation receives as input something corresponding to a floor. We look at a drop of pondwater through a microscope, we receive a picture of some appropriate mini-beasts. We build a large hadron collider, and get fed a stream of events that reflect the particle-physics reality as understood by god. And so on. But however huge the database of what goes where and did what when, it is finite, and occasionally inconsistencies will arise. Do we notice? Well, we know our memories are less than perfect. Could we tell if occasionally, they are edited to recreate consistency of experience, and not just by our own subconscious during our dreams? Mostly, I suspect we couldn't. But it's just about possible that somebody very bright and very paranoid might be able to assemble enough non-subjective evidence to convince himself that he wasn't just being afflicted by the usual human frailties. If he tried to convince any of the rest of us, he'd probably find that his little collection of evidence promptly disappeared and that he was giving a good impression of suffering from paranoid delusions. But if he kept very quiet about his own thoughts and his secret cache of external evidence, and started looking for exploitable bugs in the less-than-perfect simulation that most of us call "reality" ... Personally, I wouldn't take the risk. The most likely outcome would be a fatal accident headed my way in the near future. The next most likely, the end of our world, as god pulls the plug on an irretrievably compromised simulation, patches the patches, re-randomizes, and starts over. But there's no stopping some people.... NB small-g god throughout. Shorthand for a super-intelligent entity that's capable of simulating millions of human intelligences and their environment, but certainly not omnipotent or omniscient, even inside of the simulation which he created. Sometimes, he idly wonders about what is simulating him, whether he could tell, and how many more upward levels there are. [Answer] Miracles are outside the laws of physics. Creating the universe in six days, walking on water, turning water into wine, raising the dead, stopping the sun for a day, Feeding thousand of people with a few fish and loaves of bread, etc. are all inconsistent with the laws of physics. This does not means the physical laws are invalid, just that miracles do not have to obey the laws we know. Since God is the lawgiver, He can change the laws as needed when it suits him. Pausing the universe is simply another miracle. Miracles depending upon your viewpoint were completely detectable (and often the reason for the miracle) or undetectable. Water into wine. Those that saw the miracle performed knew it was supernatural. The wine steward tasting the wine detected nothing other than the quality was better than expected. Feeding 5000 with a few loaves and fishes? Same thing, you see the miracle - very obvious, you eat the bread and fish - nothing unusual. How do any of the miracles work? Not a clue, they are simply beyond human understanding and only understandable as an act of God and supernatural a.k.a. outside of knows laws. Explain turning water into wine, or walking on water, etc - Can't be done. Universal pause button - can't be explained either in a manner compatible with physics. Since miracles are inexplicable by natural laws are why many people do not accept that miracles are possible. But if your scenario includes a universal pause by God, you have God performing a miracle. Given the universal speed limit, it is impossible via any natural law (even including a new law) to affect the whole universe at the same time. It must by definition be supernatural. How do you stop time? What is time? It is not really even explained by physicists in such a way that you consider laws that would allow you to stop time. If you decide everything is a simulation, you don't need a miracle per se, you just changes the rules of the simulation. To me, that is just another way of saying that you simulate a miracle. Maybe the God / programmer is saving the current program state and then reloading it later. If so, the miracle is undetectable. But perhaps in doing to the heap is defragmented and the program runs faster, now the miracle is perhaps noticed. Pausing a physical universe -- infinite speed of propagation (or infinitely many points of simultaneous influence) it a miracle, no way around it. Pausing a virtual universe -- not a problem. In either cause the pause may either be completely undetectable or possibly a blatant discontinuity. I realize that I have no hard-science component in the answer, well that's the way it is with miracles. They are not subject to scientific analysis or scientific principles. [Answer] If we can be a little liberal with the notion of pausing and take some simulationist assumptions to an extreme, we can come up with all sorts of ways. If one of the following two sets of conditions are true, I think we get a wedge of insight. 1) Some processes or quantities in our universe depend on the state of the meta-universal clock. or 2A) God doesn't merely pause our universe, but saves it and reloads it at a later time. 2B) Saved universes are somehow compressed or simplified (full system state data is not preserved.) 1 is an especially hard case. Since we have no way to check the state of the meta-universal clock, we would need to reverse engineer if from observation of in-universe processes. This might be possible, but actually becomes less feasible if pausing our universe occurs with significant frequency (i.e. if it occurs during during the course of our investigations into the state of the meta-universal clock, it would disrupt the confirmation of the meta-universal clock hypothesis rather than give us evidence that our universe was being paused.) This sort of investigation is a bit beyond me, though. Dig up Feynman and ask him! 2A and 2B could give us a ton of anomalies to work with. Imagine you're the God/programmer, trying to save a universe to load it up later. Saving the complete state of the universe would be an absolutely staggering amount of data. There are certain things you'd want to keep very careful track of in the save (states of particles in human agents' brains for example, assuming a God interested in humans and their behavior), and there are certain other things you might not care so much about (like the exact state of every particle in a planet's atmosphere.) Some true random number generators (TRNGs) in the actual world operate by measuring atmospheric noise. If God's save files don't include extremely precise data on atmospheric states, it's very likely that when loading a saved universe a psuedo-random number generator (PRNG) would be invoked to generate a complete atmospheric state. If this were the case, analysis of atmospheric noise post-load would indicate a PRNG rather than a TRNG, and we'd know something fishy was afoot (Problem: we wouldn't really "know", we'd likely just consider it anomalous.) (check out random.org's introduction if you don't know anything about random number generators. <https://www.random.org/randomness/>) A particularly lazy God might even just save some average atmospheric values in the save file and then "smooth" atmospheric noise would be easily observable immediately post-load (and quickly disrupted by atmospheric processes.) This would be a smoking gun, I think, but it would STILL be difficult to overcome the inclination to simply disregard the observation as anomalous, but if it happened often enough hopefully some scientists would investigate to rule out in-universe explanations such as equipment failure, and statisticians would team up with them to rule out the possibility of smooth measured atmospheric states arising naturally so often. [Answer] God is presumably defined as something outside this universe, with control over it. He pauses it by turning off whatever iteration control moves time forward. For detection, one possibility I don't see mentioned yet is that God could be using a bad [Random Number Generator](https://en.wikipedia.org/wiki/Random_number_generation) (maybe he tried to write his own instead of using a reliable standardized library). In that case it might be possible for us to: * Detect that we're in a simulation by cracking patterns in seemingly random natural events (radioactive decay, cosmic background radiation, etc). * If it is a simulation and God shares random numbers among multiple Universe instances, we could "see" pauses as gaps in the random number strings. Note that the term "simulation" is used loosely here - if we're assuming a God created the universe and can pause it, the difference between a physically created universe he can control and a computerized simulation becomes academic. [Answer] Presumably, God would stop time around a certain place (in this case, Earth and it's surroundings). Or maybe He resides in a dimension from which he can alter this universe, but is unable to affect his own. [Answer] This is actually not a science question, but rather a philosophy question. In fact, its a rather famous philosophy question on the nature of time. [SEP](http://plato.stanford.edu/entries/time/) discusses this (emphasis mine): > > What if one day things everywhere ground to a halt? What if birds froze in mid-flight, people froze in mid-sentence, and planets and subatomic particles alike froze in mid-orbit? What if all change, throughout the entire universe, completely ceased for a period of, say, one year? Is such a thing possible? > If the answer to this last question is Yes — if it is possible for there to be a period of time during which nothing changes, anywhere > (except, perhaps, for the pure passage of time itself, if there is > such a thing) — then it is possible that a worldwide “freeze” will > occur between the time you finish reading this sentence and the time > you start the next sentence. In fact, if it's possible for there to be > a period of time without change, then it may well be that a million > years have passed since you finished reading the last sentence. > > > The question of whether there could be time without change has > traditionally been thought to be closely tied to the question of > whether time exists independently of the events that occur in time. > For, the thinking goes, if there could be a period of time without > change, then it follows that time could exist without any events to > fill it; but if, on the other hand, there could not be a period of > time without change, then it must be that time exists only if there > are some events to fill it. > > > Aristotle and others (including, especially, Leibniz) have argued that > time does not exist independently of the events that occur in time. > This view is typically called either “Reductionism with Respect to > Time” or “Relationism with Respect to Time,” since according to this > view, all talk that appears to be about time can somehow be reduced to > talk about temporal relations among things and events. The opposing > view, normally referred to either as “Platonism with Respect to Time” > or as “Substantivalism with Respect to Time” or as “Absolutism with > Respect to Time,” has been defended by Plato, Newton, and others. On > this view, time is like an empty container into which things and > events may be placed; but it is a container that exists independently > of what (if anything) is placed in it. > > > Some go even further: > > In a famous paper published in 1908, J.M.E. McTaggart argued that there is in fact no such thing as time, and that the appearance of a temporal order to the world is a mere appearance. > > > So, in all, you have philosophers on different sides of the argument, arguing "yes, God can put us on pause," "no, God cannot put us on pause," and "the concept of putting us on pause is meaningless." ]
[Question] [ Watching modern Hollywood movies, one would think covert ops agents (especially women) all wear some sort of skintight latex or leather uniform when they're on some mission to sneak around. I highly doubt that is actually what an agent would wear when sneaking into some top secret facility, it seems more practical for showing off the actor's curves than, you know, being practical. I might be wrong, or I may not be. Regardless, I'm curious: what would be the best kind of outfit to wear if you're sneaking into some place? Optional addendum: I'm going for something a bit more action-y/entertaining, so expect acrobatic hand-to-hand fighting to be something the attire would need to accommodate. [Answer] "Mission dictates gear". This is true in any military organization, especially SOF. So what do SOF Soldiers wear? I ask you in return: In what situation? If the SOF Soldier has to operate alongside GPF (that is General Purpose Forces - as opposed to Special Operations Forces), then the SOF Soldier will wear uniform and gear matching the Unit with which he's working on. Why? Because if I am an enemy sniper, and I'm out there scanning your troop formations, I'm not gonna waste my ammunition, I'm going to stay hidden. opportunities to kill regular Privates or Lieutenants aren't really worth being discovered. I'd look for those 'hmm, that dude looks special' targets like your snipers, senior leadership (Officers or NCOs), or SOF personnel. If your guys walk around in camouflage and body armor, and all of a sudden there's this group of guys walking around wearing skin-tight spandex and ninja gear, well, that fits the 'hmm, they look special' category. Believe you me, you would not be able to operate effectively if every time you leave the wire the enemy single you out as a target. If a SOF unit operates on its own, well then the gear is determined by the need of the unit, as well as the ROE. Does the ROE state that you need to be clearly identified as a national legal combatant? Then you will be wearing combat gear with your flag. Does the ROE state that you are operating covertly/in a clandestine fashion? Then you may wear civilian clothes or sterile uniforms. If the SOF unit is tasked to covertly infiltrate an enemy facility, then (insert whatever they're doing there), and then egress covertly, then the SOF unit might consider wearing enemy uniforms/clothing. Although, the wearing of enemy uniform means you are giving up your Geneva convention protection. They may wear local garb, pose as cops, business people, whatever gets the job done. One thing they would not do is wear skintight spandex with ninja gear that screams to everyone, "I'm special!" ETA: Consider that a significant amount of GPF gear today started out as SOF gear at one point of time. From armor, to weapons accessories, attachments. SOF may not look that different from GPF troops. [Answer] The answer totally depends on the situation into which you are putting your spies. As the others mentioned odds are they should be dressing to blend in with their surroundings, so in those cases whatever the locals are into. If on the other hand you are setting up a series of tests with laser grids and all that, skin tight is exactly what you want. There is something to be said for a skin-tight outfit in hand to hand combat as well and it is the same reason professional military commanders started requiring hair cuts way back to antiquity. It gives the enemy one less thing to grab onto when grappling or using melee weapons. The short answer: It depends on the situation, but skin tight outfits (that don't impair mobility) are not as ludicrous as they may initially seem. [Answer] For covert operations, the soldier or operator would need to blend into the local surroundings, but that does not mean the clothing would be what other people wear in the situation, just that it externally looks like other people's clothing. Take a mission in the executive suite of an office building. The operator will be wearing a suit and tie, and possibly carrying a briefcase. The briefcase will be rigged to carry a weapon like a submachine gun (possibly even to the point that you could aim and fire it from inside the briefcase. The suit will only look like it has buttons, but really be held together by velcro or something similar so the operator can rapidly open the jacket and access a sidearm or special tools and equipment. The inside of the suit jacket will have lots of concealed pockets to store small items that the operator might need (lock picks, gloves, thin sheets of explosive material and so on). Obviously you don't want someone to grab your tie, so the tie is a clip on; anyone who grabs it will be in for a surprise. The belt buckle might double as a knife and so on. The would be executive will be wearing glasses, but close inspection would reveal the stylish lenses are ballistic eye protection, and possibly "Google Glasses" to interface with a computer/cellphone. If you are expecting to be in a melee the suit or outerwear could be made of Kevlar or a similar protective material to reduce the effect of knives or batons (a Kevlar jacket or raincoat will not stop a bullet or grenade fragment; for that you would need a close fitting actual frag vest and plates). One convention of modern western civilization will certainly help operators; the fact that small backpacks are pretty common wear among virtually all people outside the executive class, and especially in "casual wear". An operator will be able to unobtrusively carry much more equipment with a backpack without standing out much. Finally, since many jobs actually require protective equipment (and also allow access to lots of places), it might make sense to go into an area disguised as a utility worker or something similar. The bulky clothes will conceal the protective armour vest and sidearms, the hard hat will be a true ballistic helmet and the "earmuffs" are not sound deadeners but actual radio headphones. No one will think twice as the utility truck pulls to a stop and 4 guys get out walking towards the tool bins strapped to the side of the truck.... [Answer] In the real world, the CIA doesnt send in secret agents like Ethan Hunt in Mission Impossible. Those people dont exist. Also, its pretty much impossible to bypass good security such as cameras, alarms, guards, and masses of people. One mistake and you are caught. The best way to infiltrate a guarded facility is to send in someone who is supposed to be there. No one is going to question why Johnny Terrorist is in the terrorist camp. He belongs there. The trick is making Johnny Terrorist an "asset." This could be by promising a reward, immunity, allowing his family to come to the US, threatening his family, etc. If Johnny Terrorist gets caught and killed, well... no US personnel were harmed. Another method the CIA uses to infiltrate facilities is to be invited in. Did you just order a bunch of computer equipment for your terrorist activities? Well the CIA will be happy to step in and deliver it and set it up. This is more common than you think. Lastly, if there is little chance of being seen, then the clothing is not a factor. Edit: I want to add, the best way to not be caught, is to not be there. When gathering intel from things like computers, doing things remotely is the best bet. Back in the first Gulf War, Iraq bough a bunch of printers. The CIA assumed these devices were going to government locations and modified the printers to send out signals, revealing their location. The CIA is known to modify hardware and software. And they are known to hack networks as well... [Answer] Do you get to the Diamond District often? No, of course you don't. Or maybe you do, I don't know where you live. Regardless, in New York City there is an area called the Diamond District on West 47th Street between Fifth and Sixth avenue. It's estimated that 90% of the diamonds that enter the United States pass through the Diamond District, making $24.6 billion USD a year. \$400 million per day in sales. As you can imagine, with that amount of money changing hands and that many diamonds coming in and out of stores, it's kind of a wet dream for an enterprising criminal to make a move somewhere like there, but if you've ever actually been to the Diamond district and you sit a while and observe the people you might begin to realize why there aren't heist movie plots happening there every day, especially in a city like New York. It's absolutely swarming with undercover security. People in shirts that are just a little too freshly-ironed, touting bulletproof suitcases and fully-polarized sunglasses even when the clouds are out, wearing shoes that look nice but are completely suited for chasing someone down in. More than anything it's the behaviour that's off, though. They're standing where they can perfectly see the entrances to several stores, and they've been on this phone call without pacing or even moving for like an hour. They're alone, and they're spread out from anyone else also clearly trying to act sooo normal just far enough so that they don't give each other away but just close enough that they can see each other if they have to go after someone. All of this is to say they wear a flawed imitation of civilian clothes that you'd only notice if you knew what to look for, much like in the Hollywood movies. The clothing owes itself nicely to looking wealthy enough to belong in a place like this without restricting movement. If they're wearing a blazer it's unbuttoned, if they've got a tie on it's not pinned, if they're a woman they're probably wearing a sports bra. I've never actually seen them have to do anything and I get the sense they too are utterly untested and just living out a fantasy, but it's completely reasonable to assume there's some kind of body armor going on under that button-up shirt and a concealed weapon of some kind. Since we're talking undercover soldiers and not overpaid mall cops with an even bigger complex, it's probably this and more. Definitely body armor and a concealed handgun at least, with likely some kind of jacket to hide it. Also, a few tips about concealed weapons; A handgun is hidden in the front of your pants, for easy access, and you can hide a knife a lot of places but the easiest way to tell where someone else is hiding a knife, outside of them pulling it out at you, is to watch where their hand twitches when they get nervous or startled. I don't live in a warzone and I'm not a secret agent so when I have a knife on me that I don't want people to see, I just keep it in my pocket. Men's pants have the kind of pockets you can fit anything in. [Answer] Uniform Uniforms? Soldiers wear uniforms for a variety of reasons. One of them is to identify them as lawful combattnts under the laws of war. This requires national insignia which can be identified at a distance, but not actually uniformity. Militaries require their own soldiers to wear distinctive rank insignia and unit patches. Elite forces often get some latitude to wear non-uniform uniforms, both to help form their esprit de corps and in recognition that they don't need "mickey mouse bullshit" to remind them they're soldiers. Militaries may also require soldiers to use only standard issue gear, or they allow some privately owned gear. Allowing any personal gear sets a precedent -- the first soldier wants his own boots, the second brings her own sleeping bag, the third soldier has a mobile phone which tries to link up with the local grid. Only standard issue doesn't mean all equipment looks the same. One might be a radio operator with a specialized backpack, another a grenadier with a specialized vest, etc. Camouflage Uniforms? I've been talking about soldiers on legitimate military operations. As Burki mentioned in his comment, covert ops are something else. In a deniable operation, they wouldn't wear anything resembling their national uniform and equipment. This is one reason why the SEALS used [Swedish SMGs](https://en.wikipedia.org/wiki/Carl_Gustav_m/45#Usage_by_the_United_States_in_Southeast_Asia) in Vietnam and the Delta Force used [funny hats](https://commons.wikimedia.org/wiki/File:Delta_force_GIs_disguised_as_Afghan_civilians,_November_2001_C.jpg) in Afghanistan. The latter seem to be an actual attempt to blend in at a distance. [Answer] If the soldier is going undercover then he should wear something that blends him/her with other people. And if there is some action involved (like you) say then comfortable clothing is needed not like the uncomfortable ones we see in Hollywood films sometimes. I'd say something like this, like soldiers wear in real life: [![enter image description here](https://i.stack.imgur.com/x8oLE.jpg)](https://i.stack.imgur.com/x8oLE.jpg) ]
[Question] [ If our hands had 2 thumbs and 3 fingers how would they work? I mainly concerned with the bones and how they would interfere and interact with each other. But the muscle work would be helpful as well. [Answer] As far as anatomy goes, it would look about like this: [![enter image description here](https://i.stack.imgur.com/qdI1p.jpg)](https://i.stack.imgur.com/qdI1p.jpg) A koala hand, showing its dual thumbs. That's a picture of a koala hand, which has two opposable thumbs. If we had two opposable thumbs, they'd probably be structured roughly the same way. This kind of hand structure is common in several other marsupials as well, such as the cuscus. It aids them in climbing trees. [![enter image description here](https://i.stack.imgur.com/AMK2u.gif)](https://i.stack.imgur.com/AMK2u.gif) The cuscus: another animal with two thumbs. For animals with two 'thumbs' which point opposite the fingers, a good example in nature may be the osprey. [![enter image description here](https://i.stack.imgur.com/yB54e.jpg)](https://i.stack.imgur.com/yB54e.jpg) An osprey foot. Unlike koalas, which utilize their dual thumb to hold on tightly to branches, osprey use their talons to grip slippery squirming fish of uncertain orientation. While the second thumb may get in the way of strongly opposing the main toes with the first thumb, this omni-directional grip makes fishing easier. This arrangement of toes is called [zygodactyly](https://en.wikipedia.org/wiki/Dactyly#Zygodactyly), and is found in ospreys and owls, as well as in parrots and woodpeckers. Interestingly, in ospreys, the second opposed digit is not held in fixed opposition to the main digits, as is the case with our thumbs, but can swivel back and forth between opposing and not opposing the main talons. This, presumably, allows the bird to obtain a tighter grip during activities like perching, in which a firm grip is more important than an omni-directional one. It's likely that the hand structures of a two-thumbed sentient being with a thumb on either side of the hand would allow for similar behavior. Woodpeckers also benefit from the omni-directional nature of a zygodactyl foot, but in a different manner. Rather than using their claws to grasp and lift slippery fish, woodpeckers use them to cling to the sides of trees while they feed. Woodpeckers, as a result of their zygodactly feet, can orient themselves upwards or downwards on the trunk of a tree, or even on the bottom of branches, to obtain food from a greater number of locations than they'd be able to without a firm grip or with a grip that only worked optimally in certain directions. Parrots, similarly, climb about in trees while eating fruit, and utilize their zygodactly feet to hang sideways or upside-down while feeding. Zygodactlyl in humanoids In humanoids, zygodactyly would lend itself to two behavior patterns: ambush hunting of small animals (probably fish) or non-orientation dependent hanging. Humanoids with the first adaptation would likely have evolved to live in a similar manner to storks or herons, waiting still in shallow water for fish to approach, then rapidly grasping downwards to catch them. Such humanoids would probably be far more patient than humans are, needing to sit stock-still for hours on end in order to hunt. Alternately, zygodactyly could be an evolution for locomotion across vertical surfaces, like the sides of trees. Our ancestors evolved thumbs for grasping branches, but if we'd instead evolved in an environment where trees had long, relatively branch-free trunks with few low branches or vines, but with featured, sturdy bark, zygodactyl hands and feed would have granted them the ability to climb up and down those trees in search of food. The Redwoods are one example of such trees, though it's likely that humanoids would need a better food source than pine cones to drive them to the tree tops. Arboreal zygodactyl humanoids would also likely have strong claws, capable of supporting their weight, in order to dig into tree bark. Similar to how humans live on the ground but have thumbs evolved to climb trees, it's also possible that the zygodactyl thumb on an alien race may have evolved for arboreal locomotion or fishing, but was retained and repurposed by a ground-dwelling humanoid. Just as humans occasionally still climb trees or swing from our arms, a zygodactyl alien race would likely retain some of the traits and behaviors of whatever it's ancestral form was, but just as our behavior differs markedly from chimps, gorillas, or bonobos, the behavioral traits of our hypothetical aliens would be driven more by their pattern of live and environmental pressures than they would by their ancestry. [Answer] # Summary Having two opposable digits allows them to be different from each other, each specialized differently rather than a single compromise design. Such a design is (surprizingly) easily evolved from humans by repurposing the little finger --- # Design Goals Instead of guessing what if, we can examine animals that have relevant features. Our hand is not the only arrangement of digits. Questions of how it’s put together and how the actuators and structural members are arranged can be observed in various animals. The link in the following paragraph lists no less than 15 –dactlyl ’s for a starting point. Different from the osprey illustration in another answer, I’ve observed my [Zygodactyl](https://en.wikipedia.org/wiki/Dactyly#Zygodactyly) pet and pondered the fact that it’s essentially two thumbs. Notice that our thumb can move two different ways: in opposition, or side-to-side up to being parallel with the other fingers. One of Diamond’s talons is also this flexible in what it can do, but is even more in opposition then our own thumb. The other outside talon is more dedicated to being used in opposition. Instead of swiviling out 180° (like our thumb does 90°) and then bending, it is more as if our pinkie finger were simply mounted facing the other direction. It gives more rigidity in the side-to-side motion, which is the opposite of flexibility. So, having two different opposable digits means different trade-offs with conflicting design elements. It’s not two of the same thing, but a choice of two things. I suggest you find video of different animals using their manipulatory digits. Spending time observing anything more alien than any fellow mammal (like dogs and cats) can be mind-expanding. --- # Altering the Human Hand Can the human hand design be altered in this way? It appears that this would be easily workable. [![bones](https://upload.wikimedia.org/wikipedia/commons/e/e8/Hand-bone_animation.gif)](https://en.m.wikipedia.org/wiki/Hand#Bones) Take the little finger (leftmost in this picture) including the metacarpal and turn it around, so the joints bend the other way. Adjust the shape of a couple of the carpals (wrist bones) to angle the finger so it closes in opposition to the middle two digits. Now for the reason this is surprisingly easy: rather than having the muscles in the arm with tendons stringing through the wrist, the little finger is like the thumb already in having [the muscles](https://en.wikipedia.org/wiki/Muscles_of_the_hand) right there in the hand. ![hand muscles](https://upload.wikimedia.org/wikipedia/commons/0/02/Gray423.png) Just restack the three muscles in the opposite order so the opponens digiti minimi has leverage in the other direction. The flesh of the palm will be shaped to suit, so the new secondary thumb’s metacarpal is not lined up with the others; it would resemble the shape made now when the thumb is closed — kind of folded. The idea though is that it does not live lined up with the others as our thumb does now. It cannot be brought back around. The joint of the metacarpal to the carpal does not need to swivel in this way, and doesn’t need the muscle to provide such a range. Instead the anatomy is optomized for closing and grasping tight. This means that the (original) thumb can be releived of this responsibility and be more specialized for swiveling. It will have a larger range of what it can oppose with, and improved dexterity for when it’s paired with the index finger for precision tasks. So, reduce the size of the opponens pollicis and abductor can be better developed rather than being “the most superficial”. [Answer] You could have 1 thumb on each side with the fingers in the middle. The thumbs need to be offset so that when you make a fist, one sits bellow the other. The configuration of the bones and muscles should be fairly obvious. You know how to place 1 thumb, on one side of the hand; now mirror this principle onto the other side of the hand. [Answer] Turn it around the other way: What disadvantage would there be to having an extra thumb on our hands. On our hands the joint at the base of the thumb is several inches above the finger knuckles. Having two on this side would require what amounts to the same parallel structure we see in the finger knuckles. If on the other side of the hand, next to the pinkie finger, it would get hit first when using the edge of our hand to strike something. That digits get smaller/weaker/less controllable as you move away from the thumb suggests that the asymmetry of the hand is useful. I've read that a relatively large amount of the brain is concerned with controlling motor action of the thumb. Given the time it takes to learn a motor skill, having a second thumb is not a clear advantage. (You have two hands. But try to sign your name with your non-dominant hand. Different muscles, different nerves, different motor memory.) [Answer] Why don't we have two thumbs on each hand? What advantage is there to the regular human set up? We have similarly strong muscles on both sides of the hand and no overall design limitation (arrangement of bones, ligaments, etc) that I can discern. So we could have two thumbs but don't, so why? Because we'd have lots of broken thumbs. That meaty pad of muscle on pinky side of the hand is commonly what we pound with and is the leading side of the hand in most activities. With the smaller, more flexible bones there is room to absorb shock through the greater ratio of muscle and tendon to bone, and lower nerve sensitivity compared to the thumb (try it!). Put the edge of your hand on the table with thumb up; it's comfortable. Now do it with thumb down, on the thumb only (no index finger); not so pleasant. It would be uncomfortable and dangerous to do manual labor or even shimmy along a branch. Since office work was hard to get a million years ago on the African savannahs this wouldn't have been an advantage. Overall it would seem to limit adaptability as those creatures that do have it are specialized. Perhaps in your two-thumbed world agriculture wouldn't have arisen, too many smashed thumbs. Cooperation would be challenging since it'd be difficult to shake hands on a deal :) Our hands curve and cup, useful when carrying small things and taking a drink; not so possible without the pinky side of the hand (try it, keep the pinky side stiff and try to cup your hand from the thumb side). The more I think of it the more awkward many regular activities would be. I now see both sides of the hand as having specialized function, a second thumb would be redundant and limit overall abilities. It would also be like having three pincers, the middle being more flexible. ]
[Question] [ I apologise if this is rather vague but I'm struggling with creating a concept that would allow a Victorian (steampunk) civilisation to have antigravity ships and floating islands through the use of a mined crystal resource. However I also want it to have other effects without making it seem too 'fictional' or contrived (which I realise may be difficult). [![enter image description here](https://i.stack.imgur.com/pJ923.png)](https://i.stack.imgur.com/pJ923.png) Essentially I don't mind it being magic-esque and don't want to get TOO bogged-down with scientific analysis in the story but I do want it to be believable and not just "it can do anything because it's magic". My story has engineers etc that study it and are unlocking its effects. The civilisation is steam/clockwork based but this crystal allows their skyships to fly (antigravity) and allows Floating (static) Islands. I also want it to be able to create shields/forcefields that encompass skyships in a protective bubble. Later this tech usage can be personal (used to shield humans) and maybe allow them to fly with the crystal used in personal angelic-like wings. [![enter image description here](https://i.stack.imgur.com/Ps0RT.jpg)](https://i.stack.imgur.com/Ps0RT.jpg) I also want the crystal to be able to power things, for example provide 'clean' energy which the Elites keep repressed so as to continue making money off steam energy - a plot point. My problem is I don't want it to seem as if the crystal can just do anything and lose some realism or suspension of disbelief. I also need ways for how these different effects are 'activated' and controlled / contained. I had the idea that maybe if heat is applied to it, it activates its antigravity effects i.e. a small chunk of the crystal burning in a furnace makes the ship float, but the crystal isn't actually depleted but somehow its effects mixes with the steam produced to create antigravity effects / mingles with the steam produced. Obviously they don't have electricity or are just discovering it so perhaps a small electrical charge could be used or it could absorb / be activated by kinetic energy perhaps. Also seawater / salt concentrations could activate effects? I'm looking into Aether effects too and Aether manipulation as possible reasoning. Essentially I want the antagonists to want to weaponise this crystal into lasers / WMDs etc while the protaganists realise the 'good' potential of clean energy and removing the reliance on steam / pollution etc. So I need to understand limitations and effects without making it seem too Deus Ex Machina if that makes sense. The crystal is usually inert when discovered (otherwise it would be perpetually floating in the atmosphere) but somehow makes ships float without the need for huge helium-ballons, can make Islands float, can be weaponised and also generate forcefields. Any suggestions, limitations, rules etc would be much appreciated! Also other ideas for further effects would be appreciated but again it's not hyper-scientific or hyper-realistic but I would like it to seem logical and not overtly fantastic / impossible. In the future of the timeline it could be discovered that the crystal is actually type of dark matter, negative mass, anti-matter (obviously in my timeline such theories would be unknown) or from another dimension entirely, but the citizens in this timeline find this strange crystal and are uncovering its effects, both good and bad ushering in the age of skyships and skypirates etc. EDIT: On Electricity: One idea was that small electric currents could activate certain effects, as Victorians did have some usage of electricity and basic dynamos etc. Maybe an electric charge could create some forcefield out of plasma/Aether/'energy' around skyships and protective energy barriers? Meanwhile heating the crystal 'activates' it's anti-gravity effects? [Answer] An easy way to avoid a crystal that can do anything is to split it up into several different crystals that each have their own defined properties. For instance, a red crystal that causes anti-gravity when exposed to heat. A green crystal that is an electricity multiplier, a small current becomes a much higher current. A blue crystal that emits a kinetic energy dampening field when placed next to an activated green crystal. The scientists/engineers would be looking at new ways to harness these effects, and you could also have other crystals that they haven't figured out how to unlock yet. Say a yellow crystal that takes a certain frequency of sound, or to be placed near radium, but because they never tried that combination they've never gotten it activated, and have no idea that it creates a huge pulse of superhot plasma, or a coherent beam of light, or whatever. As to how, unless it's really important I'd recommend leaving it a mystery. [Sandersons first rule of magic](https://brandonsanderson.com/sandersons-first-law/) says `An author's ability to solve conflict with magic is DIRECTLY PROPORTIONAL to how well the reader understands said magic.` No matter how much you try to science it up, it's going to be magic. And that's ok. So long as the characters in the story treat it like science, and you don't try to explain it using our worlds rules. It's your world, it has its own rules. [Answer] The crystal is a perfect battery Make the crystal absorb and store energy for later use, instead of produce it. The value of the crystal becomes more about how much energy you have stored inside of it. For example everyone could get a few crystals, start a bonefire and throw them there. After a few hours you could use them to power different types of machines or lamps. Your Elite would control over the market, because they would had high pressure and heat furnaces, charging crystals of great quality for years while burning tons of coal and wood. Thanks to the crystals you could fuel anything you wish, anywhere. * Flying citys, with enough energy it's posible, expensive but posible. * Flying ships, don't need alot of thing to make it work. * Shields for ships and personnal and most thing would be tech based because you have the energy to do it all. Must be taken in consideration that with this kind of crystals you would end up having lasers pistols by default. [Answer] Since this crystal literally defies physics, its going to have to be something we've never seen. Consider making these not be natural crystals, but something left over by Others. These others were incredibly technologically advanced, capable of things like powering spacecraft between planets. This calls for a mighty leap in power storage. Lithium Ion batteries aren't going to cut it. Make these crystals actually be arrays of nanomachines which have some property that lets them store vast energy and manipulate forces like you want. Argue that they appear to be crystaline because that was the high art of the day for these Others. I can say from experience that there are many schools of performance and martial arts which value the ability to appear utterly motionless while teeming with energy under the surface. Structuring these nanomachines into crystal shapes would be a natural artistic choice. This explains why they react with things like steam: the crystals weren't designed to be crushed up in some furnace. They were designed to impart their power with great care and control. Things like anti-gravity and shielding would be parlor tricks for such an advanced society. And it also explains why you could have shielding on your ships and never run out of air. A delicately constructed artifact like this would be more than capable of discerning oxygen molecules from stray bullets. Also, it offers an interesting plot point. As people start to realize that these crystals have "unlimited energy," they start to realize that they don't. They just had so much energy that nobody noticed its limits until the society starts exploiting them. [Answer] Different effects. The effect could require the crystal to be cut in a certain way, thus different effects could be produced by different cuts. Cut aligned with one crystal lattice axis produce effect 1 while cuts aligned with the other produce effect 2. So every crystal produces all effects but cuts are made to maximize one effect over others. This also means the skill of your gemcutters affects the efficiency of your devices. Alternatively different impurities could produce different effects, the properties of of some real world crystals change noticeably based on impurities. this means how useful an effect is is also based on how rare that impurity is, unless they have an industrial means to make said crystals. Energy You could model yor crystals after permanent magnets in that they are not free energy, they wear down eventually. magnets can levitate things but it is not free energy becasue they degrade in doing so getting slowly weaker all the time. Old crystals would produce less effect and eventually just stop altogether. You could even have something like a curie temprature, so they lose their antigravity properties if they get to hot, so they have to be kept cool. You might even be able to remelt them to do process X to them a they cool to restore the properties. Alternatively they only act as converters so you need to pump energy into them to produce the effect. Energy could be supplied in your choice of flavors; electricity, heat, light, pressure, or "aether". Some real world crystals can convert pressure into electromagnetics(piezoelectric) or the reverse (crystal radios). [Answer] When a jeweller makes a piece of jewellery the cut of the crystals, the way they’re set and the positions they’re in are all very important. When a photographer uses a lens assembly the lenses are precisely ground and positioned to get the focal lengths just right. When magnets are used in transformers and generators the magnet size and positioning is vital. So too with these crystals. In their natural uncut state the effects of the crystals are usually random, cancelling each other out in the same way that iron molecules aren’t naturally aligned to create a magnetic effect. When cut by a skilled jeweller, however, the story changes. Each cut, each precise angle between one face of the crystal and the next changes the properties of the crystal, sometimes eliciting strange responses like a gentle glowing, the crystal resisting movement as it pushes against the Arther or the crystal starting to float gently like a helium balloon. Even that isn’t the most startling thing. When Benedict Wittleforth accidentally left two part-cut glow crystals in the same tray he discovered that he could change the colour of one crystal by changing its position relative to the other, and so was born the science of Positional Crystallics. Essentially bringing two or more crystals into a set configuration allows for fine grained mechanical control of the crystals properties, as well as vastly increasing certain effects (like the anti gravity properties). Now Airships have anti-gravity engines that have variable lift control, a series of well cut crystals in a ring with the ’control crystal’ moved in and out of the center to change how much lift is generated. Lasers can be created by shifting a line of correctly fashioned crystals into position, inertial shields turned on and off and calibrated by changing the orientation of crystals in a complex 3d lattice, and some even say that it might be possible to generate electricity using the mythical ‘lightning cut’ (though this is heavily doubted by the Establishment’s best Crystalline engineers) Naturally most modern ships have multiple redundant systems, as damage to these carefully designed and (given the minute differences between every crystal cut) bespoke systems can require a lot of attention from a skilled jeweller and a skilled Crystalline engineer to fix. Not only that but in some cases of extreme damage multiple systems have been reported as interacting unpredictably, as seen when the battleship Magnificence spontaneously crushed itself following a cannon strike to its central lift core. [Answer] I would try to be as specific as possible as to what the crystals do (the how can be unknown) and make the various applications be extensions and clever uses of that fundamental trait. This lays down the ground rules as to what this amazing substance can do, and (hopefully) makes the applications believable without becoming deus ex machina. In this case, the crystals appear to be some sort of force-field generator. Perhaps the strength and range of the field generated is proportional to the size of the crystal and the energy (could be heat, electrical, or even kinetic) applied to it. The larger the field is, it gets "fuzzier," with a less distinct boundary. So a very large field could be used in flying ships (the field is pushing against the ground, but it's large enough that objects on the ground only feel a very small and diffuse pressure.) Smaller fields could be used as a personal shield (not impenetrable, but slows things down greatly.) Weapons you can get creative with - a very small but very intense field that's suddenly turned on inside a casing of shrapnel would make an effective bomb. Perhaps by shaping the geometry of the crystal(s), you can shape the field to give you a directional field strong enough to punch holes in targets. Etc. [Answer] You said it yourself, the crystal is anti-gravity. Left to its own devices, the crystal will want to go up. So they tend to be mislaid. A lot. Thw worst heartbreak of a ship captain is having a chamber breach and watch his crystals head for the shy, knowing his ship is about to go the opposite direction. Whether they depart the solar system or simply get annihilated in the upper atmosphere, I leave to you. [Answer] Could have its effects be dependent on purity (if it even can be impure), internal crystal orientation (like how magnetic substances have internal orientations) and possible side-effects accompanying the wanted effects, like all anti-grav also has high magnetism, or slowly spawns lightning storms. They might not know how to alter the crystals' properties reliably, with only known way to change the effects, is hitting it. Which might be dangerous, because reasons. Like it projects a force field and pushes people away or something. Also maybe zapping it with electricity, but that could be even worse, due to more energy input? If it breaks, then it can be pieced back together by just pushing the pieces together, but the fusion event is also dangerous, perhaps? The crystal could also emit bad radiation, like Gamma or something, making its infinite energy ability, be a detriment, in most cases. Unless your society has enough science to figure out precisely how the crystal gets energy, and you want to do that, then you can just leave it out, and mysterious. Not all ways for the appearance of infinite energy can be figured out from Victorian Science. [Answer] ## How the crystals harness magic Crystals are the perfect medium to perform [geometric magic](https://allthetropes.org/wiki/Geometric_Magic). The crystals, alone, may be rather inert. However when put near each other in the proper positions, rather incredible effects can be observed. Perhaps there are different kinds of crystals, allowing unique combinations to create unique effects. It can tie in with ancient beliefs in [sacred geometry](https://en.wikipedia.org/wiki/Sacred_geometry). After all, a crystal is a complex geometric structure, and if geometry can give rise to magic, imagine what happens if you put multiple crystals themselves in a magic-promoting geometric formation! This is similar in concept to astrology where the alignment of celestial bodies is said to have an effect on our lives. Many other magical beliefs and mythologies have revolved around the relative positioning of multiple magical, holy, or mystic objects with each other. Crystals are mediums for vibration magic. To mix science and magic, these crystals could behave as crystal oscillators, much like real-life quartz crystals can be made to vibrate and precise frequencies when electricity is supplied. Vibration magic has become a popular idea, and the magical aspect can be reduced if you want to invoke the idea of [vibrating strings](https://www.dummies.com/education/science/physics/string-theory-and-vibrations/) from string theory. It's not a magical superstition to say that the entire universe is made up of these little things whose vibration determines the very fabric of matter and energy.\* If someone could control this through crystals, there's no telling what they could do! --- ## Limitations of crystalline magic The effects of crystals can be blocked by another substance. Like a strong magnet inside an iron case will not emanate a magnetic field, a crystal's effects may be blocked by another material. This could allow for flying cities to control their anti-gravity forces by dynamically exposing or occluding crystals, in much the way a nuclear reactor's neutron control rod is used to control the rate of a nuclear reaction. A weapon may involve having an incredibly powerful crystal shielded, with the trigger removing the shield and releasing an incredible amount of force all at once, much the same way a classical gun releases the force in gunpowder in a burst. The crystals slowly wear down as they are used. A large, fresh crystal may have a lot of energy stored up, but as more is demanded from it, it can slowly break down. This can be caused by the crystal actually being burnt up, losing mass over time, or simply becoming more and more disordered internally (losing its crystalline structure). The amount of force required to keep an entire city in the sky may require a very large crystal that must be replaced every several years / decades / centuries in order to stay fresh. This could also be added as a plot device, allowing crystals to have a limited value. It would prevent you from using them to create a perpetual motion machine and harness infinite power from one small crystal. \* Yes, I know the "vibrations" in string theory are unrelated to literal oscillations produced by a crystal resonator, but that explanation is still more believable than anything relying on "[It's magic. I ain't gotta explain shit.](https://i.stack.imgur.com/Avx0i.jpg)" [Answer] For making such a resource I have a few suggestions: * The resource will need to provide benefits and dangers of using the crystal. * Make them a source of being an ultimate capacitor; being able to take in almost any form of energy and store it for use later. * Have an ability to be changed into multiple elements to be a specialized crystal. * The only downside to Shards are their volatility; and that once broken or damaged; they ooze a toxic gas that deforms, mutates, and kills all foolish enough to be near it. * The Crystal should be used everywhere and in everything. The Larger the Shard the more powerful the results. * Although crystals are quite powerful they do have a limit to as how much they can handle. These factors will let you set limits for the technology and allow even the weakest of people be able to understand and use it. The idea for weapons is that it will just be pure energy when used or other elemental power if you so choose. For making Airship float simple make it use for its engines and it powers it to keep it above the ground. You could also have them be used in evil experiences that can create some form of crystal monster since they are capacitors it would allow them to be easily controlled by someone who can create such a monster. [Answer] Potential limitations: volatile, requires additional energy to extend 'anti-gravity 'field'', small supply, starts falling unnaturally fast when broken, etc. There's also some rules in physics relating mass and velocity that you could choose to apply. It could be perpetually active, and thus possess some of the problems usually associated with drilling for oil-when pressure is released it starts flying up into the sky, perhaps making mining a dangerous business in areas which possess crystal, unless you mine up instead of down. The obvious weapon uses are an attack from below, or launching the target buildings or cities straight up into the air. The advantages of attacks from above (dropping heavy objects from great height is comparable to attacking with meteors attacks) could be amplified if crystals can be reversed to increase gravity, although that might break the crystals (brittle isn't the first way people describe diamond, but if a meteor wiped out the dinosaurs, I can imagine a sufficient impact might...shatter them), which invites the question (also important to mining or manufacture) - what happens when they break? [Some crystals such as sugar generate brief flashes of light when crushed](https://en.wikipedia.org/wiki/Triboluminescence), so what do these crystals do? If a ship requires these crystals to fly, destroying the crystals could a disastrous crash (or they fall upward, to be lost in the depths of space). For comparison, some nuclear generator designs have the disadvantage that they're comparable to nukes, and if damaged... This could bring to bear the fact that attempting to armor the part of the ship with the crystal to protect them or the mechanisms using them might make the same amount of crystals less useful, since all the weight you add still has to be carried by the crystals if you still want the ship to fly. (There's some work in rocket science dealing with the fact that increasing weight usually means you need more rocket fuel, which also adds weight, which means even more fuel.) On the other hand, if crystals help with accelerating/decelerating in any direction, a lighter ship might be more maneuverable. On the other hand you could make the crystals' power changing the direction things fall, with some sort of energy consumption associated with say, the mass of the ship, or object you want to effect. This could potentially be used to prevent or reduce feasibility of perpetual motion machines, if you want to preserve the laws of thermodynamics, although if you've got your heart set on flying ships made out of wood, engines which use fire might not work out. > > However I also want it to have other effects without making it seem too 'fictional' or contrived (which I realize may be difficult). > > > I would recommend coming up with a system for what everything does, and then have the characters learn more as they go along (There are some tips you can find on the sort of writing you described by googling [Hard Magic System](https://www.google.com/search?q=hard%20magic%20system), written by Brandon Sanderson who has a system for writing fiction that somehow feels very realistic). ]
[Question] [ A street performer in the medieval age could make some money. One popular performer is a fire eater. Changing the color of his flames would likely make his popularity rise so that he would make more money. Is it possible to change the color of a flame? [Answer] You can't get black While it is possible to achieve different ranges of colours depending on temperature of the flame as well as combustible material, fire's still light. Light is bound to the spectrum of visible wavelengths. And there is *no visible* wavelength for black*. Addition1: It is important to understand that the light of fire is [additive](https://en.wikipedia.org/wiki/Additive_color). Hence if you'd want to go towards black* fire, you'd actually have to find a way to remove light-sources from a) the fire itself and b) its surroundings; thus creating a space that absorbs light. --- But what colours of fire can we have? Looking at [pyrotechnics](https://en.wikipedia.org/wiki/Pyrotechnic_colorant) we can achieve the following colours by e.g. burning different [metal salts](https://en.wikipedia.org/wiki/Salt_(chemistry)): [![Chart of metal ions and flame colours](https://www.compoundchem.com/wp-content/uploads/2014/02/Metal-Ion-Flame-Tests.png)](https://www.compoundchem.com/wp-content/uploads/2014/02/Metal-Ion-Flame-Tests.png) Chart of what substance creates which flame colour - found on [http://www.compoundchem.com](http://www.compoundchem.com/2014/02/06/metal-ion-flame-test-colours-chart/) --- These colours are achieved, as already stated, by burning salts. As long as we know where to find metals, we can dig them up and refine most of them with as little tools as [a vat of acid and some patience](http://www.bbc.co.uk/education/guides/zptrd2p/revision). The most accessible of these would probably be: * Lithium * Potassium * Calcium * Copper * Iron * Lead * Zinc --- 1Thank you [Slipp D. Thompson](https://worldbuilding.stackexchange.com/users/8879/slipp-d-thompson) [Answer] Apart from metal ions as mentioned above, it has to do a lot with flame TEMPERATURE. There is a reason behind the term "color temperature" - the cooler the more reddish (eventually crossing into invisible near-IR), the hotter the more blueish (eventually crossing into invisible ultraviolet. That's why the sun is creating so much UV that we are glad the athmosphere filters it, that's why really hot light sources like arc lamps or halogen incandescents are best enjoyed with UV filters). Actually that behaviour is not specific to flames, any material that is heated will behave that way (so called blackbody radiation) - flames are made out of gas.... ]
[Question] [ So I'm the head honcho of a near-future dystopian totalitarian nation. I want to suppress intellectualism and rational thought, but at the same time I want to stay on top of scientific and technological development. Where and how am I going to find the talent? Details about the setting: * Technology is at the level where looking for resources on nearby planets is starting to look plausible. Bio-tech is developing rapidly. * My nation is the biggest world power, other competing nations are at least as corrupt as mine. * Resources are running low worldwide, overpopulation is a problem. * I want mostly practical, useful technology and military tech, I will condone seriously unethical stuff for progress. [Answer] The soviet model worked quite well, combining strong influence of propaganda and good technical development. Keep the sciences of economy, philosophy, social sciences and so on under whatever rock you wish to keep them. Keep technical sciences shining, and keep the bright scientists to live in gilded cages - modern, bright, well-supplied towns where access is restricted. Let them keep their families, enjoy entertainment that is not politically-incorrect but genuinely enjoyable, without propaganda, reward for work well done - and keep isolated from the grim outside. And from time to time let them enjoy being the heroes of the nation in great parades, ceremonies, TV interviews. Travel outside the cities would not be forbidden but frowned upon. A bright scientist would probably get a politbureau officer for escort, making sure the grass is painted green wherever the scientist visits; such trips would be discouraged by the superiors, probably limiting promotions or restricting access to government-subsidized luxuries. Recruitment? Elite studies; school tests that pick brightest kids, government-sponsored scholarships, and specifically if the student succeeds and appears to be really bright and hard-working, he or she can bring the whole family to the "science town" - so the whole family would support such an attempt (they would also take care of all the "technical" jobs of the town; janitors, shopkeepers, gardeners, repairmen etc). Of course the scientists aren't let loose to do as they will. Each institution has two directors, a technical one and a political one. One gives direction to research, production, manages the progress, the other assures the unit receives all the necessary equipment, resources, but above all, watches the crew and overrules any promotion decisions, raises and privileges, making any dissenters reconsider their stance. Above all, keep the population isolated from the outside, and vice versa, to keep dissent levels low, and nevertheless, while acknowledging, promoting, rewarding the successes, never give the scientists any actual power. The politbureau would be the actual power, but leaving the leash loose enough so that the scientists never feel it. And if one of the scientists really wants to make a difference? The way is open. Join the party. Climb the ladder of ranks, starting from the very bottom, right on par with workers and farmers. Prove loyalty, wisdom and charisma. If you are good enough - loyal enough - you can become the right hand of the Leader, and influence the country through wise advice. Still, there is no "shortcut/bridge" from "professor" to "Delegate of Party Association of [city]" or such. For political matters, Professor is equal to Plumber, and the political career path is completely orthogonal to scientific achievements! [Answer] You have two mutually incompatible goals, so it's going to be hard. The only real option is to create an "elite". Pick the best and brightest and bring them into the elite, selective breed them to make them smarter. Educate them and indoctrinate them. They need to think they are "better" than the masses so they deserve the special treatment. The others are beneath them. You can shape the social information and beliefs with suitable propaganda while leaving their scientific development alone. That will stop most of them from getting pesky thoughts about helping out all the people you are repressing. You might have to kill off a few outliers but there's always more bright people coming along from the rest of the elites. [Answer] Acquire it from other states. You can steal it by espionage or threats, but in general people would be glad to sell it to you. If you are the biggest nation, then you can guarantee the safety of your tributary states from your competitors, and provide ample trade and resources. As long as you are better than the threat of chaos a war would bring, why wouldn't they cooperate? [Answer] For this to work, it's best if your totalitarian government is preceded by a significant period of "soft totalitarianism" in social and economic pressure. Think of contemporary worries about the "PC Police." (You don't have to think these worries are well-founded in our society today! Just make them well-founded in your fictional world.) Society is mostly run by a nominally well-educated elite, and part of this education (at all levels, and in college, even for STEM majors) includes indoctrination in the trendy ideologies. (An important part of this, I think, is that social studies, history, etc should all take Trendy Ideology for granted/incorporate it into the hidden assumptions/premises of the way they talk about things.) People who don't at least mouth these trendy ideologies are social pariahs. It's hard to keep a job if you don't participate in the Trendy Ideology discussion club, panel talk, workplace seminar, or voluntary training. People who don't fall in line are decried as retrograde bigots. The others won't sit with them in the cafeteria. It's important that education in the Trendy Ideology doesn't include a critical examination of it, and in fact opposes critical thought as mean, regressive, and prejudiced. It doesn't, at least in the beginning, have to be illegal to oppose the Trendy Ideology, but nice people just don't say things like that. Later on you can enforce it legally in the name of Tolerance, Patriotism, Justice, etc--whatever fits best with your particular totalitarian state. The fact that the people with high levels of education buy into the state's Trendy Ideology only makes it more embarrassing to admit that you oppose it. I mean, my goodness, it's taken for granted by all the smart, right-thinking people. Toeing the line gets you not just a nice job, but also the satisfaction of being one of the smart, virtuous people. You could probably even convince them that Trendy Ideology is the critical-thinking-est thing around. That way the government can "suppress intellectualism and rational thought" while (a) avoiding a naked show of power that might stiffen resistance, and (b) maintaining high levels of education. [Answer] Have closed science cities, like Soviets did. That way you can have islands of free thought and creativity with little risk of it poisoning the ignorant masses that need to be kept under the heel. The problem is that the authoritarian government needs to remain interested in the research and continue to contribute enormous funds/resources towards it, instead of spending them on palaces, statues, parades etc. Without private funding and universities it's all up you (the government) to recruit, and supply the scientists. However, the Soviets were very advanced in some areas but backward in others simply because the government payed more attention to some fields of study then others, and because it is very difficult to predict what is going to be next life changing breakthrough until it's actually happened this authoritarian science-by-committee will always have gaps in it that a truly free one might not. If you are careful, and have good enough spy networks you should be mostly OK, but you won't invent a next iPhone. [Answer] Many totalitarian dictatorships utilise corruption and greed to maintain stability. Divide an elite from an underclass, and it remains in the interest of the powerful to protect their privileges. The problem with this is that hereditary classes are prone to becoming indolent, lazy and entitled. This does not make for a great work ethic in the R&D department. On the other hand, class mobility is dangerous because then someone from the underclass can rise to power. You need to keep the Übermensch free of foolish ideas like equality, freedom and fraternity. One possible answer is to create a competitive environment where the upper class is self-policing: honour killings, suicides and duels are the name of the day. This also reinforces the superiority complex: it is the natural order of things that the strong shall dominate the weak. Finally, you need to control this class of psychopathic super-scientists. Lois McMaster Bujold did this in Cetaganda with the reward of genetic breeding rights into the royal class (as a reward for exceptional service). In the real world, it is not uncommon to promote the national leader to demigod father-of-us-all status. Or if you have been doing genetic experiments, perhaps your royal family releases "loyalty pheromones" - depends how science fiction you want to go. ]
[Question] [ With relatively current technology (i.e. no force shields, etc) what are ways to protect a spaceship (or at least mitigate the amount of damage) against hypervelocity kinetic projectiles? I'm a retired HS history teacher with a limited knowledge of science, so, be kind... I'm thinking: * whipple shields of various materials & thickness * redundancy of systems * tanks/baffles of water (or some liquid)as armor * tanks/baffles of an expanding foam to seal leaks * a combination whipple shield with a layer of ERA underneath Looking forward to answers, speculations, observations, and convaluations (I made that up). [Answer] I'm sure we've had questions on this before, but a quick search wasn't turning up anything particularly good, so here we are. You could have a quick read of my answer to [Ideal materials for the outer layer of a whipple shield](https://worldbuilding.stackexchange.com/a/232568/62341) as a sort of warm-up. You might also reasonably read up on (or indeed play!) a game called Children of a Dead Earth, which is intended to be a plausible simulation of space combat, and they've done a reasonable job of it. They've got a load of [interesting blog posts](https://childrenofadeadearth.wordpress.com/2016/11/03/index-of-science-posts/) on the subject, explaining the reasoning behind their decisions. You might also want to think about what "hypervelocity" means. [Wikipedia](https://en.wikipedia.org/wiki/Hypervelocity) suggests over three kilometers per second, but regular modern day [ASAT](https://en.wikipedia.org/wiki/Anti-satellite_weapon)s will hit with closing velocities of more than twice that and slightly more exotic things like nuclear-driven projectiles could easily hit twenty or thirty times that velocity with cold-war era technology. The [Plumbob Pascal B](https://en.wikipedia.org/wiki/Operation_Plumbbob#Missing_steel_bore_cap) nuclear test accelerated a 900kg metal disc to over 60 km/s, and in the face of weaponry like that the only practical defense is to not be in the way. (You may also find references, here and elsewhere, to Matterbeam's take on nuclear-driven projectiles on theire blog [Tough SF](https://toughsf.blogspot.com/2017/05/nuclear-efp-and-heat.html). It has some interesting ideas and useful references, but the extrapolation is frankly implausible, so take their conclusions with a couple of tonnes of salt accelerated to .2% of lightspeed. There's some much more sober and grounded discussion by Fenstermacher in [The effects of nuclear test‐ban regimes on third‐generation‐weapon innovation](https://scienceandglobalsecurity.org/archive/sgs01fenstermacher.pdf)) --- > > * whipple shields of various materials & thickness > * redundancy of systems > > > This is "table stakes"... if you can't manage this sort of thing, then you risk being [mission-killed](https://en.wiktionary.org/wiki/mission_kill) by accident by regular old space debris, whether human made or otherwise. Your spacecraft must be At Least This Tough just to be a useful spacecraft, let alone a warship. > > * tanks/baffles of water (or some liquid)as armor > > > In the face of hypervelocity projectiles, the intermolecular bonding that makes solid things solid simply isn't strong enough. Impacts with things moving at several kilometres per second are modelled as jets of liquid colliding and splashing off each other. Modern shaped-charge weapon research gives us a handy equation ([A Jet Penetration Model Incorporating Effects of Compressibility and Target Strength](https://en.wikipedia.org/wiki/Moment_of_inertia) calls it the Hill-Mott-Pack equation, but other names are associated with it too including Birkhoff and Tarantello, but I digress) and it looks like this: $$P\_d = \ell \sqrt{\rho\_j \over \rho\_t}$$ Where $P\_d$ is the depth of penetration, $\ell$ is the length of the penetrator, $\rho\_j$ is the density of the penetrator (with j-for-jet) and $\rho\_t$ is the density of the target. The critical thing to be aware of there is the density of the target, and water just isn't that dense, and whilst there are denser liquids they can't really compete with the density of solids because that's how physics works. You can have a thicker tank of water to make up for it, but that just increases your [moment of inertia](https://en.wikipedia.org/wiki/Moment_of_inertia) and makes variouys kinds of manoever more difficult. A nice hard dense solid material makes for better armor, and as a secondary benefit there's no risk of it all leaking out of a hole in a tank. Water or ice does have many other uses on a spacecraft, including as a coolant, heat sink and particle radiation shield, so there will probably be plenty of it about... it isn't great as projectile armor by itself. > > * tanks/baffles of an expanding foam to seal leaks > > > Well, I guess, but you should be able to work OK even if all your air leaked out. If the crew can't survive in a vacuum by themselves, they can always wear spacesuits, and probably should at least wear some kind of pressure suit in case of incidents. > > * a combination whipple shield with a layer of ERA underneath > > > ERA exists to combat a specific threat to tanks in cold-war-era conflicts. There are various countermeasures against it even now, and I'm not at all certain it will be of much use in space combat which is a very different environment involving potentially much faster projectiles in potentially much larger quantities. That's not to say it is useless, but I'd be skeptical. What I think you'll end up with is long, pointy spacecraft making use of [sloped armor](https://en.wikipedia.org/wiki/Sloped_armor) and minimising their cross section, using layered and spaced shielding made of a range of different materials to help break up incoming projectiles and disperse and absorb the impact. And then what will happen is that the ridiculous overkill associated with space-based hypervelocity weapons will absolutely wreck it more or less as soon as a hit is scored. Parallels might be drawn with modern warships, the designers of which are well aware of the striking power of antiship weapons and don't waste time and mass on a load of armor which won't help much. [Answer] ## Evasion Space is big, and space battles could plausibly occur between ships located thousands or even millions of km apart. The first defense is not to get hit, and being very far from the enemy makes that easier. You may have several seconds or minutes to get out of the way. To know how much time is available to evade, we need to know how fast a projectile you're being shot with. Hypervelocity projectiles on Earth, such as the [Navy railgun](https://en.wikipedia.org/wiki/Railgun), might have a muzzle velocity of up to 5 km/s. This is actually not very fast by solar system standards. Meteoroids strike Earth typically at 20 km/s. The relative speed between your ship and your enemy's ship is likely higher than the muzzle velocity of the enemy's railgun relative to his ship. Sometimes you hear about the [Casaba-Howitzer](https://en.wikipedia.org/wiki/Casaba-Howitzer) idea for producing hypervelocity projectiles. The notion you sometimes hear is that you could set off a small nuke and have it propel a solid bullet at 100 km/s. However, more realistically, the initially solid bullet would be vaporized by the nuke into a plume of material that spreads out at 100 km/s in a cone. The effect if the plume hits your ship would be very different from a solid projectile, and less damaging; it would dump energy broadly across your hull, heating it up and vaporizing the outer layers of hull. It wouldn't punch a hole. So we won't worry about Casaba-Howitzer any further here. It's not a solid projectile and it would take different measures to defend against. So, realistically, we might say you are faced with only 30 km/s projectiles, with most of that speed being due to the relative velocities between your ship and the enemy's ship, and not due to the muzzle velocity of the enemy's railgun. This means that if you are 1000 km apart when the enemy shoots, you have around 30 seconds to evade. (If you're a million km apart, you have nine hours to evade - the enemy would likely not even bother with kinetic projectiles at such ranges!) Evasion can be divided into "eyes-open" evasion, and "random walk" evasion. You would use "eyes-open" evasion if you know the trajectory of the enemy's projectile so you can get out of the specific target area. This could potentially be done using a [radar telescope](https://astronomy.stackexchange.com/questions/54906/what-kind-of-telescope-would-be-needed-to-image-a-10m-dim-object-1-million-km-aw). You can certainly use radar to detect that a projectile is incoming (although the enemy can also cover their projectile in angular radar-reflective surfaces like a stealth bomber), but determining specifically where it is aimed down to a few meters is a much bigger ask, although possible in theory. For random walk evasion, you thrust in random directions at specific intervals, to maximize the enemy's uncertainty in your future position. This is what bombers did in WW2 to [avoid flak](https://www.youtube.com/watch?app=desktop&v=ywzk73ahf00). This is generally a good idea to do any time you are in hostile space, because you won't always be aware of the specific projectile or bomb before it hits you, if it is cold, small, and stealthy to radar. A ship that is good at evasion should: * Have a small cross-section presented to the enemy, and be capable of thrusting sideways while presenting the small cross-section * Have a high thrust-to-mass ratio, not weighed down by too much heavy armor or weapons * Have good "eyes" (telescopes) and "reflexes" (computers) for eyes-open evasion when possible ## Armor A 1.2 cm aluminum sphere impacted an aluminum plate at 6.8 km/s, leaving a crater 5.3 cm deep: [![](https://i.stack.imgur.com/znYSm.jpg)](https://i.stack.imgur.com/znYSm.jpg) The amount of armor you need certainly depends on the size of projectile you're being shot with. There is a trade-off between the weight of armor, which lets you tank bigger hits, and the maneuverability of your craft, which lets you avoid hits entirely. When a projectile hits your armor, it has two effects that can be considered separately. The first effect is that it penetrates some amount based on its density and length. The second effect is that it dumps its energy into the armor, causing an explosion and crater. As Starfish Prime helpfully mentioned, at such high speeds both the projectile and the armor act like fluids; the molecular bonds are too weak compared to the force of impact to be very important. I'll go ahead and steal his formula for penetration depth: > > $$P\_d = \ell \sqrt{\rho\_j \over \rho\_t}$$ > > > where $P\_d$ is the depth of penetration, $\ell$ is the length of the penetrator, $\rho\_j$ is the density of the penetrator (with j-for-jet) and $\rho\_t$ is the density of the target. > > > Note: this depth of penetration is before the crater is formed. The crater will be usually several times deeper than this formula gives. More on that later. But we do want to minimize this initial penetration depth according to this formula, because it affects the crater depth too. We can suppose that the enemy is shooting you with an iron projectile, because he's using a railgun. Iron has a density of 7.8 g/cm^3. Now, in space mass is king; the more your spacecraft masses, the slower it can accelerate and the more fuel you need. So you want the most protection for the least mass. Are you better off with dense armor, or an equal mass of less-dense armor? Based on this formula, surprisingly, to minimize penetration you are better off with less-dense armor! Let's do an example. The enemy projectile is 1m long and your armor is also 1m of iron. The density of projectile and armor are the same, so the penetration depth is 1m, and the projectile gets through. On the other hand, you could use 2.9 meters of aluminum armor for the same mass as 1m of iron armor. With aluminum, the penetration depth is 1m \* sqrt(2.9) = 1.7 meters. The projectile only gets a little over half-way through! Whipple shields are used in practice currently, and a scaled-up Whipple shield is probably a better option than solid steel or aluminum. Current Whipple shields are designed against micrometeorites (up to 1 cm size), but the same principles will apply to larger projectiles if the Whipple shield was just bigger and thicker. The principle is that the projectile hits a thin layer of armor, which it penetrates completely but disperses as it does so. It is allowed to spread out further over a gap of empty space before the next layer of armor. Then when it hits the next layer of armor, it may penetrate that too, but it is dispersed even more. After a few layers it is dispersed enough that it no longer penetrates. Note that a Whipple shield, with all the empty space between the plates, has a low overall density. That tracks, when you consider the penetration depth equation. That's all to minimize penetration. The other factor to worry about is the energy of impact, and the crater. The crater volume is proportional to the impact energy. Intuitively, that's because to make a crater that size you have to break a lot of the molecular bonds in that volume of armor, which takes energy per bond broken. This means the crater depth is proportional to the cube root of the impact energy. A 100 kg projectile at 30 km/s has the energy in about 10 tons of TNT. To minimize the crater that makes, you want strong materials that take a lot of energy to vaporize. Whipple shields are made of steel, which fits the bill. You want a (giant) Whipple shield made of several thick layers of steel with gaps in between them. If you plan on getting hit more than once, and survive the first hit, you may want to weld new plates over the holes in the armor. However, the enemy might not bother shooting you with a weapon that doesn't penetrate your armor on the first hit. It's less efficient to hit you with ten smaller rounds that don't penetrate but just damage your armor, than to hit you with one round 10x the size that goes through and destroys your ship. Thus, we might say that what the armor really does, rather than actually protect you if you're hit, is make the enemy pack a bigger gun and heavier ammunition, which slows him down, reduces the number of times he can shoot, and reduces the other armaments he can carry. Actually getting hit with a solid object from the enemy is probably game over. Your idea of a water tank is interesting for the purpose of healing the armor. It is not as dense as steel, which makes it favorable for the penetration depth, and if the enemy blows a hole in water, the hole just fills up on its own. However, water takes much much less energy to vaporize than steel. The first good hit and much of your water tank will be steam. Also, water lacks any tensile strength, which does matter. ## Active interception The idea here is that you send out your own projectile to meet the projectile a few km in front of your ship. The two projectiles annihilate each other. Your ship may be hit with some chunks from the explosion, but it would be much less damaging than if the enemy projectile directly hit your armor. Two basic ways to do this. One is, you track the incoming projectile and when it's close enough to be sure of its trajectory, you shoot it with your own railgun. This is tricky but it has the advantage that the momentum of the incoming projectile can be partially canceled by your own, so less of the incoming projectile proceeds to hit you. The other way is, you have a rocket drone loitering a few km in front of your ship. The drone masses about as much as the incoming projectile, and maneuvers to be exactly in front of it so the projectile hits the drone. This may be easier to accomplish than shooting the incoming projectile with your railgun, but the net momentum from the collision is still towards your ship so you may be hit with more debris, though it will at least be spread out more. [Answer] The Sponge Approach Realistically there is very little to stop high velocity rounds. [![enter image description here](https://i.stack.imgur.com/BRimr.png)](https://i.stack.imgur.com/BRimr.png) It's age old problem faced by the armed services in the battle between armour and weapons. In [The Expanse](https://www.imdb.com/title/tt3230854/), everyone puts on suits and and puts the ship in vacuum so there is no explosive decompression. The ship has redundant systems and everything is made to try to prevent permanent damage from projectiles pass through the ship. When all said and done, you patch the holes and restore the atmosphere. The ships are built to try and receive as little damage as possible. You want as much kinetic energy to stay with the bullet and not blow massive holes in the ship. [Answer] I have always been a fan of ice. It's easy to come by, space is cold anyway. It works well as an ablative armor either stand alone or as a type of [pykrete](https://en.wikipedia.org/wiki/Pykrete). Can be used as fuel radiation shielding and life support resource, a large mass of ice makes a very useful heatsink. A very helpful resource you may already be aware of. [Atomic Rockets](https://www.projectrho.com/public_html/rocket/spacewarship.php) website. [Answer] In Rendezvous with Rama, Clark solved this by having Rama extrude miles and miles of fuzzy cable. This wasn't quite a Whipple shield because the cables had a bit of intelligence and could wrap incoming projectiles in a cocoon. In the book, dumb-ass humans shot nukes at it, but I'm sure it could be adapted. In Children of Ruin, Adrian Tchaikovsky comes up with a less conventional method. It's difficult for an entire ship to get out of the way of missiles, but the protagonist's ship isn't rigid. It's bags of spiderweb connected by actuators. When shot at, it changes shape to move its vital parts out of the way without having to move the entire ship. [Answer] A LASER or similar "electromagnetic energy beam" [EM] weapon could be useful against kinetic energy weapons in several simultaneous ways. Using technology that will almost certainly be available in any scenario where people (or other variably sentient beings) are firing kinetic weapons at spaceships. Modes of interaction include * Destruction of any electronics or other control logic. "LASERS" in this context will operate in the deep XRAY / Gamma Ray area. Shielding is extremely difficult and beam impact on any part of the projectile will generate secondary emissions. Loss of control makes subsequent trajectory prediction trivial and evasion trivial at ranges liable to be possible. "Bathing" most control systems in a somewhat diffuse Gamma Ray LASER beam is liable to produce "useful" results. Values for "somewhat diffuse" TBD. * Melting or vapourisation of some or all of the projectile. Energies of hundreds of kilojoules per kg for liquefaction and under 10 MJ/kg for vapourisation are likely for likely materials of choice (eg see figures for iron and tungsten below). Projectile masses are unknown, but to impart 10 km/s velocity change to a 1kg mass requires 5 MJ of energy. Smaller masses require proportionately less. * A significant capability against "dumb" projectiles, or those rendered brainless by control system incapacitation, is course deflection. Back of brain (for want of an envelope) suggests that at 6 km/sec we can achieve in the order of 100 m of diversion, per second of flight per 10 kW.s of impingement. Adjust time and energy and mass to suit desired scenario. Over ranges of 10's or 100's of km, a far less energetic beam can achieve deflections liable to be adequate to deflect dumb or now dead projectiles adequately. Realistic figures could probably be derived, but work calls. EM beams travel at 300,000 km/second. Reflections off the target (passive, active, choose wavelength) gives returns at 150,000 km/s or about 6 uS/km, and more importantly, vastly faster than any except relativistic hyper velocity matter based weapons. Add to that that the faster a matter based weapon travels the worse it changes course, then a E.M. beam or even particle beam (electrons, various ions, ... ) are going to easily target it. Energy delivered depends on LASER energy, distance, focus, more. If desired and interceptor carrying an EM weapon can be launched towards the incoming threat, reducing the distance. More so with time. Nuclear explosion pumped "One Time" [!!!} LASERS have been suggested, with multiple simultaneous targets being engaged. Continuous operation high powered nuclear-reactor powered LASER systems have been extensively investigated. The technology is already on our doorstep (nuclear and other). By the time you get to space battles it will be well available. --- Nuclear Pumped LASERS [Wikpedia](https://wiki2.org/en/Nuclear_pumped_laser) [NASA](https://ntrs.nasa.gov/api/citations/19800005183/downloads/19800005183.pdf) 1979. 174 pages Book [Springer](https://link.springer.com/chapter/10.1007/978-3-319-19845-3_1) Introduction to Nuclear-Pumped Lasers Wikipedia [Project Excalibur](https://wiki2.org/en/Project_Excalibur) > > Project Excalibur was a Lawrence Livermore National Laboratory (LLNL) Cold War–era research program to develop an X-ray laser system as a ballistic missile defense (BMD) for the United States. The concept involved packing large numbers of expendable X-ray lasers around a nuclear device, which would orbit in space. During an attack, the device would be detonated, with the X-rays released focused by each laser to destroy multiple incoming target missiles. Because the system would be deployed above the Earth's atmosphere, the X-rays could reach missiles thousands of kilometers away, providing protection over a wide area. > > > Continuous operation, LASER powered: Sandia [FALCON Reactor-Pumped Laser Description & Program Overview\](https://www.osti.gov/servlets/purl/12982617) [1974-1991 Project. 9 pages](https://www.osti.gov/servlets/purl/12982617) > > FALCON Reactor-Pumped Laser Program > The FALCON (Fission Activated Laser CONcept) reactor-pumped > laser program at Sandia National Laboratories is examining the > feasibility of high-power systems pumped directly by the energy > from a nuclear reactor. In this concept we use the highly > energetic fission fragments from neutron induced fission to > excite a large volume laser medium. This technology has the > potential to scale to extremely large optical power outputs in a > primarily self-powered device. A laser system of this type > could also be relatively compact and capable of long run times > without refueling. ... > > > > > In summary, FALCON is a nuclear reactor pumped CW laser > system that can be scaled to very high powers (100 MW or more) > with essentially near-term technologies.* Issues that are > currently being addressed include the detailed optical system > design and the achievable beam quality. Longer term issues > involve mission analysis, total system cost, and the > difficulties associated with the use of nuclear technology. > > > --- Some [smallest reactor size](https://www.quora.com/What-is-the-theoretical-minimum-size-for-a-nuclear-reactor) figurings --- Added: causative said: > > It takes a lot of energy to vaporize iron, around 7.7e6 J/kg, and focusing a laser to a small spot size at distances of thousands of km is extremely challenging. Then, lasers are only 0.01% to 30% efficient, so you're dumping lots of waste heat into your own ship when you fire it. Ask yourself what characteristics of projectile the laser could stop - how fast a projectile, how far away, and how massive. > > > @causative Indeed. It took us a lot of effort to perfect this defence :-). We lost quite a few target ships in the process. Total vapourisation of 1kg of iron takes about 8 MW.s of energy, as you say. Tungsten is 'only' about 4.4 MJ/kg. We found we need far less than that per kg to adequately ruin a 1 kg projectile's day. Heat of fusion is "only" around 280 kJ/kg (Tungsten around 193 kJ/kg). Melted blobs of iron (or Tungsten) incoming are not desirable, but far better than the initial 'warhead'. However, ablation and vapourisation are not the primary mechanisms. Our beam is in the deep Xray/Gamma ray region. It takes very few photons to wreak serious havoc on any control systems yet encountered. Individual photons penetrate "very nicely". But a major factor is path diversion. Having destroyed any guidance system is a bonus. At 6 km/sec we can achieve in the order of 100 m of diversion, per second of flight per 10 kW.s of impingement. Adjust time and energy and mass to suit desired scenario. [[Figures are back of envelope with lots of assumptions and may be very roughly correct. E&OE. Corrections welcome :-) ]. --- Note to would be editors: spellings are NZ antipodean Kings English where apposite. Alteration for alterations sake would not be considered cricket :-). [Answer] In Neal Stephenson's Anathem, the spaceship is protected by a huge net of gravel which can be positioned. Certainly not easy on your delta-v expenditure, but at least somewhat effective. [Answer] Hmm... how about something more exotic? A big chunky ship is a prime target, and as the other answers point out, super-fast space junk just tends to vaporize whatever it comes in contact with so there's little defense against it. If our big ship is hit, it's toast. So how about we make it really hard to hit? My idea: have a "hive" ship. Lots of tiny little ships that come together to form one big "hive" for travelling/whatever, but when danger is close, they split up into a swarm of miniships and disperse. Your hypervelocity projectiles might get lucky enough to hit one or two of them, but that won't affect the whole swarm much. Attacking is done similarly via many remotely- or AI-controlled drones. Again, you can hit one or two with a projectile, but you can't take out a swarm that way. [Answer] It's been mentioned already, but the Expanse does a lot right (considering that it's not super far in the future and tech is pretty close to what we have). Look at modern day helicopters like the Apache helicopter, or the tactics used by Hind pilots in the Soviet-Afghan war, as well as jet fighter dogfighting. Flares/chaff to actively hit any large explosive projectiles, but against Flak, you have to accept that it's ripping through you. Enormous amounts of redundancy, first of all. The pilots themselves have their own oxygen systems and wear body armor, allowing them to keep going. In the world of space combat, this could be doing what the Expanse does, having depressurized ships and crew in space suits. RCS thrusters are extremely important, as is managing huge range. It might not be as cool as in the movies, but combat would not take place in spitting distance. If the enemy has high-velocity projectiles and decent targeting systems, these fights would be happening from tens, if not hundreds of ship lengths away, so that one could maneuver around streams of fire. In the Expanse, roughly 10 kilometres was referred to as close quarters at one point, because it meant that they were close enough that the enemy couldn't outmaneuver direct kinetic shots from a railgun (as opposed to missiles/torpedoes which lock on and track the enemy). Speaking of avoiding shots, electronic warfare would be hugely important, as scattering enemy targeting systems prevents them from firing on you. The U.S. Navy and Marine Corps fly the "E/A-18G Growler", an F/A-18E with it's gun replaced with a massive electronic warfare suite. They fly alongside F/A-18s in sorties to protect them, because simply having someone around to mess with enemy radar and SAM systems makes an enormous difference in protecting your planes. Similarly, stealth ships or simply ships that are hard to lock onto would have an advantage. Because maneuvering would be important, you presumably want your ships to not be super heavy. Like real-world Apaches, this would mean armour plating on the engine and avionics, but nothing else. ]
[Question] [ Since the discovery of L’Anse aux Meadows in Newfoundland in 1960, the picture began to emerge that the Norse (I hesitate to say "viking" because that is a verb, not a noun) beat Christopher Columbus in discovering North America by up to half a millennium. However, L'Anse aux Meadows was not a long-term settlement, and doubt had been cropping up about whether or not the Norse reached further inland (the uber-controversial Kensington Runestone brings to mind.) We know that the Norse who discovered America were of the Greenlandic or Icelandic branch(es), separate from the mainland Scandinavians. So in this alternate history scenario, those Icelandic or Greenlandic Norsemen made a long-lasting, permanent empire (*at least 500 years long) out of any piece of North America east of the River Mississippi, intermarrying the Natives who lived there and even fusing the two (fundamental) cultures together, creating a Native American ethnicity somewhere close to this propaganda portrait by Theodore de Bry: [![enter image description here](https://i.stack.imgur.com/HK5Ft.jpg)](https://i.stack.imgur.com/HK5Ft.jpg) The question isn't whether or not this is possible, but what point of departure do I need to make this possible?* [Answer] The main problem with the Scandinavian attempts to colonize continental North America is that they were never serious about it; there were never more than a one or two hundred Scandinavians in North America, excluding Greenland of course. You don't take a continent with a two hundred people. In 986 CE, a Scandinavian merchant named [Bjarni Herjólfsson](https://en.wikipedia.org/wiki/Bjarni_Herj%C3%B3lfsson) sailed from Norway towards Iceland to visit his father, who had a farm there. Arriving in Iceland, he found out that his father had left for Greenland with [Erik the Red](https://en.wikipedia.org/wiki/Erik_the_Red); as a consequence, Bjarni Herjólfsson left from Iceland towards Greenland. En route from Iceland to Greenland, Bjarni's ship was blown off course by a storm and arrived on the shores of a lush verdant land well west of Greenland. After repairing his ship, he sailed north, and spent some time looking for Greenland, for neither he nor any of his crew had ever been there. Eventually they found [Herjolfsnes](https://en.wikipedia.org/wiki/Herjolfsnes), a Scandinavian settlement in Greenland, and Bjarni was reunited with his father. Word spread about the land seen by Bjarni, the Greenlanders being most interested in the reported abundance of timber. [Leif Erikson](https://en.wikipedia.org/wiki/Leif_Erikson), the son of Erik the Red, armed an expedition to go look for Bjarni's land; this would have been around 988 CE. Point of departure: The expedition really ought to have been led by Erik the Red himself, not by his son Leif. In real history, Erik suffered a riding accident, so that he was unable to go exploring. Had the expedition included Erik the Red, with his strong personal authority, the attempt to move west would have been treated more seriously. Leif and his men overwintered in a fertile and green country, full of vines and grapes, which they called [Vinland](https://en.wikipedia.org/wiki/Vinland). It is possible that the archaeological discoveries at [L'Anse aux Meadows](https://en.wikipedia.org/wiki/L%27Anse_aux_Meadows) in Newfoundland may be the remains of Leif's camp, Leifsbúðir. When spring came, Leif and his men left and returned to Greenland with a cargo of grapes. Point of departure: The expedition, instead of one ship and 35 men, has three ships and 100 men, brought from Iceland and Norway in addition to Greenland. Instead of visiting over winter and leaving, two ships and 70 men remain in Vinland and fortify the camp, and one ship is sent back to Greenland, Iceland, and Norway to drum up colonists desirous of settling in a new, green, fertile land. In real history, Leif never returned to America. Instead, his brother [Thorwald](https://en.wikipedia.org/wiki/Thorvald_Eiriksson) came for a visit in 1004 CE. He promptly initiated a deadly conflict with the natives, as if he wanted the colonization efforts to fail. He was followed by [Thorfinn Karlsefni](https://en.wikipedia.org/wiki/Thorfinn_Karlsefni) who led the only real attempt by Norsemen to colonize the New World. Point of departure: instead of a pitiful and half-hearted attempt with two hundred people, the Norse come with a thousand people in 20 ships, mostly from Norway and Iceland. Their settlement holds off the natives, and thrives... If one man had not fallen off his horse, if the Norsemen would have shown a minimum of diplomacy, and if the colonization attempt had been just a little more serious, a Norse empire in the west could have arisen to rival their success in the east, where the [Rurikids](https://en.wikipedia.org/wiki/Rurik_dynasty) created what would later be the Russian Empire. Hat tip to Mark Olson for finding the perfect motivation factor for a sustained attempt at colonization: the Norse settlers in Newfoundland find the [Grand Banks](https://en.wikipedia.org/wiki/Grand_Banks_of_Newfoundland); a fishing a fish-processing industry emerges, anchoring the colonists in the newly found land. [Answer] Might seem a little obvious but # Don't get attacked by the Natives It seems there were a couple of key interactions which, if they didn't end in violence, would have meant a prolonged settlement: * Thorvald: History is muddy so no one is quite sure what happened but this first interaction between Natives and the explorers ended badly with the Norse killing all but one of the group they encountered. The one who escaped returned with an overwhelming force. * Freydís: The driving force behind this next expedition it seemed she was a little more successful, actually trading with the Natives. Again history is muddy so the exact why is difficult to determine but Natives attacked again and drove them back. Because accounts of the time are so vague it gives you more or less free reign to say these attacks were misunderstandings and, in your world, simply just don't happen. To go a little deeper perhaps we could suppose Thorvald was just more prone to violence than Leif (his brother who had first landed there) and ifin fact several he hadn't been the one to make first contact then we could say this meeting goes well and the Natives are less suspicious. Once they had a foothold in the Americas that settlement would thrive. Greenland hadn't turned out to be the lush fields most had imagined so would be happy to move on to somewhere with trees and wild game. These trees would also prove key for trade with Greenland which was sorely lacking in pretty much anything that grows. This aren't the only interactions between the two peoples but it seems these first impressions were prophetic. [Link to a more storified video on the history](https://www.youtube.com/watch?v=SITsfX15jw0) [Answer] This is more a way to help Alexp's and Lio's ideas than something viable by itself. The main reason there was no sustained colonization effort is the travel connection Greenland became almost uninhabitable, at least to Norse trying to maintain the typical Norse lifestyle. Greenland did no mesh well with Norse agriculture or livestock, once the little ice age set in this miss-match turned into outright famine. Greenland lacked the strong soil and high turnover forests the Norse were used to so they ended up depleting both, and a Norse civilization that can't farm, cook, or build boats is doomed. Since the colonies will be cut off they need to be self sustaining pretty quickly which means you need a lot of people fast, But even that is iffy, the little ice age would have hit them as well, they are in for a hard time. The further south and hte bigger the settlements you can get them the better. But there is one other thing you can do as an alternative or to help colonies along, have the Greenland colonists adopt a a more sustainable lifestyle. Maybe a disease hit the cattle early one causing a switch to sheep (which are not nearly as hard on the soil) and fish. If they start burning coal instead of wood for cooking they would not have depleted their timber supplies as quickly, this is tricky however is you can't cook with coal like you can wood, you really need ovens, coal smoke mixing with food is not pleasant. They could later adopt timber protection laws the way iceland did. If the greenland colonies had survived even in a weakened state there would have been sustained trade and a flow of further colonists with North America, that could bolster a larger colony like AlexP recommends. As technology improved this would lead to more and more travel and trade with the locals, to the point later European colonization would have been nearly impossible. Addendum: Recent [evidence](http://sciencenordic.com/greenlands-viking-settlers-feasted-seals-then-left) shows the greenlanders did slowly switch to a seal based diet instead of beef and dairy based but never fish, having this happen earlier may help but they also need to diversify, seal populations were hit hard by the little ice age so having a diet focused on one creature has such vulnerability, having them invent/import net type fishing would be a big help. [Answer] \Clarification - by point of departure I understand departure from our timeline, not some place ships could leave from. Mound Builders.* Instead of contact only with the hunter / gatherers of the far north, the Vikings come into contact with the sophisticated culture of the Mound Builders at their outpost in Vinland around the year 1000. The Mound Builders have copper technology, agriculture, long distance trade routes and enough surplus population to build the mounds that are their legacy. Perhaps the Mound Builders are there to trade; they encounter the Vikings and recognize an opportunity. As do the Vikings. The Mound Builders invite the Vikings to visit their lands further south and strike up a productive interaction - just as they appreciated the opportunities offered by France and Ireland (and Italy) the visiting Norsemen find these lands more pleasant than the far north. Additionally the Mound Builders are more civilized and physically more attractive to the Norse than the Inuit were. The Norse are treated respectfully and well by the civilized Mound Builder people. The native Americans realize they have a lot to learn from the vikings and proceed to learn it from the original vikings they encounter as well as those Norsemen who follow, settle, and begin to interbreed over the ensuing 150 years. Within 2 generations, the coastal Indians who have learned Norse metalworking and shipbuilding tech (and who have begun to breed horses!) have conquered their neighbors and imposed a "Pax Romana" on the formerly squabbling groups of the interior and southerly coast. Population increases during the following prosperity. [Answer] You need to make the settlement profitable. There are a few products that would make the colonies profitable and, due to this profit, attract more norsemen. 1)Slaves - Norses took part on the muslim slave trade, buying and selling slaves to the muslims. If the norse started selling americans to the muslims, doing a reverse atlantic slave trade, they would profit. 2)Timber - That was what they reported in their journeys in Vinland. Timber is useful to shipbuilding, weapowmaking and furnitures. 3)Furs - The source of Hudson's Bay Company and Quebec's wealth. In the middle ages the european market for furs would be small but the greeks from Byzantium, the arabs in the mediterranean and the traders in Sarmakand could become intersted in high quality furs. 4)Whale Oil - Whale oil is a fuel and lubricant. Whale hunting brought the portuguese all the way to north america in the early age of sail. The norse would travel from Vinland to Denmark and then to Novgorod. From there they would follow the russian rivers all the way to Constantinople, Northern Persia and the Silk Road. So, the point of departure would be that the first expedition went with more man, defeated the natives and started selling them as slaves in Alexandria and Fez. Some natives allied with the norse, and, due to these alliances they would discover the furs and increase the flux of slaves. ]
[Question] [ I am trying to make a fake metric-time app to prank some friends when we take a trip to Canada soon and would like to know how I could make this work conceptually. I already know that the time is already considered "metric", but for this prank to work, the prank-ee must believe that it is not. So, if we assume that "regular time" means the time scale that everyone in the world uses, (24 hours in a day, 60 seconds in a minute, 60 minutes in an hour etc.), then how would I go about somehow linking "regular time" with "metric time" (100 hours in a day, 100 seconds in a minute, 100 minutes in an hour) so as to create a believable metric time clock. (by believable, I mean not making seconds go by excessively fast in order to compensate for the 913,600 extra seconds in the day) To put it simply I want to somehow make a believable time scale based on powers of 10 that could feasibly replace our current timekeeping system, while still being tied to our current timescale (so 80:00 AM "metric time" would fall at the same time everyday). Bonus points if you can explain a realistic way to do this where each increment (i.e. seconds in a minute, minutes in an hour etc.) is the same. Extra bonus points if someone can propose a solution where I won't have to implement a massive time-jump at midnight in order to make the times correlate. I understand that this may not be the best place to ask this question, but since I'm not asking how to implement this in code, but rather how the concept would work. Therefore I figured this would be the best place to ask. [Answer] In imperial units, a mile is divided into yards, feet, and inches (like days are divided into hours, minutes and seconds). However, in the metric system the subunits are based on powers of ten and named with prefixes: the kilometer is divided into meters, centimeters, millimeters, etc. For a metric time system, I would apply the same concept to the base unit of one day. Instead of hours and minutes, you would have subunits like centidays and millidays. For example, `10:18:42 pm` would be equal to: $$ \frac{1}{2}~\text{day} + \frac{10~\text{hours}}{24~\text{hours}/\text{day}} + \frac{18~\text{minutes}}{24\times 60~\text{minutes}/\text{day}} + \frac{42~\text{seconds}}{24\times 60\times 60~\text{seconds}/\text{day}} \\\approx 0.92965~\text{days} $$ (Where the extra half-day comes from the `pm`.) The subdivisions of the day would be: $$ \begin{align} 1~\text{day (d)} &= 1~\text{day} \\ 1~\text{deciday (dd)} &= \frac{1}{10}~\text{day} = 2~\text{hours}~24~\text{minutes} \\ 1~\text{centiday (cd)} &= \frac{1}{100}~\text{day} = 14~\text{minutes}~24~\text{seconds} \\ 1~\text{milliday (md)} &= \frac{1}{1000}~\text{day} = 1~\text{minutes}~26.4~\text{seconds} \\ 1~\text{microday ($\mu$d)} &= \frac{1}{10^6}~\text{day} = 86.4~\text{milliseconds} \end{align} $$ For fun you can come up with nicknames for the different units. E.g. deciday could be "metric hour," "deci," or (based on the abbreviation `dd`) a "dud." Milliday could be "metric minute" or "mid." We could add an additional "convenience unit" also based on the powers of ten: $$ 1~\text{metric second (s$\_\text{m}$)} = \frac{1}{10^5}~\text{day} = 0.864~\text{seconds} $$ So we might write our time from before (`10:18:42 pm`) in metric time as: $$ 9~\text{dd}~29~\text{md}~65.3~\text{s}\_\text{m} $$ Or simply as `9:29:65` or even `0.92965`. This makes the representation of dates easy too, since we can just put a whole number of days in front of the decimal point. In fact, we could throw away months altogether and just use day numbers. For example, today is `2016-02-11` (eleventh of February, 2016). January has 31 days, so February 1 is day 32, and February 11 is day 42. Thus, in the metric calendar today is "day 42 of 2016." Putting it altogether, `10:18:42 pm, Feb 11, 2016` is `42.9:29:65, 2016`. --- All joking aside, this is close to a real time system: the [Julian Date](https://en.wikipedia.org/wiki/Julian_day). There are a lot of variants, but they all count decimal days from some starting point. Let's use the same date from before as an example. In the "traditional" Julian date, `2016-02-11T22:18:42` is equal to `JD 2457430.429653`. Note that the decimal part is almost the same, but there is a difference of `0.5`. The Julian date starts at noon, not midnight—it was invented by astronomers, and this way it doesn't roll over in the middle of the night when they are doing their observations. Note also that I assumed our time was in GMT: there is no concept of time zones for the Julian date, so we need to convert the time to GMT before converting to JD. There is also the "modified" Julian date, defined as `MJD = JD − 2400000.5`. Our example time is `MJD 57429.929653`. The modified Julian date is used frequently in the space industry because it it shorter than the full Julian date (and easier to represent in computers with limited precision) and it starts at midnight like most other time systems (where the factor of `0.5` comes from). Fun fact: the ["stardates" of Star Trek](http://memory-alpha.wikia.com/wiki/Stardate) were based on the concept of the Julian Date. --- One final point: I mentioned time zones in the previous section, and for a large country like Canada time zones are pretty much a necessity (although China seems to be OK without them). There are two options: * Base the metric time on the real local time. So if you're in Ottowa (EST/UTC-5), and the local clocks say `10:18 pm`, then your metric clock would say `9:29`. At the same time in Vancouver (PST/UTC-8), the local clocks say `7:18 pm` and your metric clock would say `8:04`. This is the easiest to implement, since you can just do the calculation based on the phone's local time, which is usually what you get from the builtin date functions by default. The differences between the time zones are not a whole number of duds or mids, but that's just the kind of wierd, stupid stuff that happens in real life. * Make up your own time zones! This makes the app logic nontrivial and is probably too far for a joke app; but I like to think about this sort of stuff, so here goes. If we restrict ourselves to time zone offsets of whole duds, then there are only ten timezones in the world, each about 36 degrees wide. Canada is wide enough to have three of them (so there is a two-dud difference between the eastern and western time zones). In order to make things plausible, I'll make the metric time zones by merging the real time zones to make our lives a little easier. The `+0` timezone is centered on 0 degrees longitude. The "ideal" dividing lines would be 18 degrees to either side, so the western edge (dividing the `+0` and `-1` time zones) passes right through Iceland. The `-1` timezone is 36 degrees wide and includes most of Greenland, just cutting through the easternmost tip of Canada. The `-2` timezone includes most of the Great Lakes, stopping just before the west tip of Lake Superior. The `-3` timezone contains Alberta, Saskatchewan, and Manitoba. It ends just after the west coast of the United States. The `-4` time zone includes the west half of British Columbia and the Yukon. These ideal divisions actually line up fairly well with existing time zones. The new `-2` time zone lines up with `UTC-4` (Atlantic time) and `UTC-5` (Eastern time). The new `-3` includes `UTC-6` (Central time) and `UTC-7` (Mountain time). Finally, the new `-4` time zone includes `UTC-8` (Pacific time), as well as `UTC-9` (Alaska time). You might call the new time zones "Eastern Metric Time," "Central Metric Time," and "Pacific Metric Time" (with abbreviations EMT, CMT, and PMT). For the actual implementation, I would get the current UTC time from the date libraries and convert it to metric time. Then find the user's current UTC offset, and map it to one of the new time zones (all the cases above are just `newTZ = floor(oldTZ / 2)`), then add or subtract that many duds from the metric time. The borders would shift during DST (e.g. locations using PDT move to the `-3` time zone, and locations on CDT move to the `-2` time zone), but we can live with that. The `floor(TZ / 2)` trick seems to work reasonably well across the rest of the world too. [Answer] The method I've always used is 10 hours per day, 100 minutes per hour, 100 seconds per minute, like 2012rcampion suggests. Then there are ${24\over 10}=2.4$ normal hours per metric hour, ${24\cdot 60\over 10\cdot 100}={1440\over 1000}=1.44$ normal minutes per metric minute, and ${24\cdot 60\cdot 60\over 10\cdot 100\cdot 100}={86400\over 100000}=0.864$ seconds per metric second. If you're building your own clock on a microcontroller or using small electronics, you'd want to update the metric second every 864 normal milliseconds. If you're just writing software on a laptop or mobile device that has simple access to normal time functions, then you can just get the current time of day in seconds. I used Visual Basic.Net, made a couple labels, two textboxes, and a timer set to update every 50 milliseconds (though you could do it less often, especially if you're not showing both times back-to-back). Here's the VB.Net code using VS 2013. Create a new forms project, create a textbox named `txtNormal`, another named `txtMetric`, a timer named `timClock` then paste the code into the class file and it should work. `Private Sub timClock_Tick(sender As Object, e As EventArgs) Handles timClock.Tick Dim Now As Date = DateTime.Now Dim normalSeconds As Integer = Now.Second Dim normalMinutes As Integer = Now.Minute Dim normalHours As Integer = Now.Hour Dim totalSeconds As Double Dim metricSeconds As Double Dim metricMinutes As Integer Dim metricHours As Integer totalSeconds = Now.TimeOfDay.TotalSeconds metricSeconds = 100000 * totalSeconds / 86400 metricHours = Math.Floor(metricSeconds / 10000) metricSeconds -= metricHours * 10000 metricMinutes = Math.Floor(metricSeconds / 100) metricSeconds -= metricMinutes * 100 metricSeconds = Math.Floor(metricSeconds) txtNormal.Text = normalHours.ToString("00") + ":" + normalMinutes.ToString("00") + ":" + normalSeconds.ToString("00") txtMetric.Text = metricHours.ToString("00") + ":" + metricMinutes.ToString("00") + ":" + metricSeconds.ToString("00") End Sub` Here are several screen grabs of a simple program running with different time zones: [![Imperial: 00:25:23, Metric: 00:17:63](https://i.stack.imgur.com/cE1K5.png)](https://i.stack.imgur.com/cE1K5.png) [![Imperial: 05:26:30, Metric: 02:26:74](https://i.stack.imgur.com/H7jFi.png)](https://i.stack.imgur.com/H7jFi.png) [![Imperial: 10:27:00, Metric: 04:35:42](https://i.stack.imgur.com/2S2pc.png)](https://i.stack.imgur.com/2S2pc.png) [![Imperial: 11:58:15, Metric: 04:98:78](https://i.stack.imgur.com/MOtG2.png)](https://i.stack.imgur.com/MOtG2.png) [![Imperial: 16:58:43, Metric: 07:07:44](https://i.stack.imgur.com/vl30P.png)](https://i.stack.imgur.com/vl30P.png) [![Imperial: 21:29:19, Metric: 08:95:36](https://i.stack.imgur.com/KH2eH.png)](https://i.stack.imgur.com/KH2eH.png) [![Imperial: 23:30:00, Metric: 09:79:17](https://i.stack.imgur.com/7vkZq.png)](https://i.stack.imgur.com/7vkZq.png) If you want to go further, you can turn weeks into 10-day periods, with 36.5 weeks per year, though obviously there's no way fully convert to a base-10 metric calendar without adjusting the Earth's rotation. Of note, [France](https://en.wikipedia.org/wiki/Decimal_time#France) actually used this exact time system from 1794 to at least 1801, although it was mandatory only until 1795, and they used a 10-day week from 1800ish to 1805. In their system, the clock and units were called "decimal" instead of "metric", even though they introduced the metric system at the same time, and they sometimes used the unit "décime", one-tenth of a decimal hour, or ten decimal minutes. During this era, astronomer [Pierre-Simon Laplace](https://en.wikipedia.org/wiki/Pierre-Simon_Laplace) used a decimal watch that ended up being the basis for astronomers using the decimal time 2012rcampion mentions in his answer. [Answer] I am going to point you to an existing solution, which is somewhat similar to what you are suggesting, but not sure whether this is what you want. [Hackworth](https://worldbuilding.stackexchange.com/users/11290/hackworth) has also mentioned it in a comment. There's a time system named [Swatch Internet Time](https://en.wikipedia.org/wiki/Swatch_Internet_Time). This was invented by Swatch (hence the name). The day is divided into 1000 beats. That makes one beat around 1 min 26 seconds long. So 500 beats would be noon, 250 beats 6 am etc. (The clock doesn't have time zones, so those times would be UTC+1, but of course you could ignore that for your purpose. There's a [converter](http://www.swatch.com/en/internet-time) on the Swatch website) What makes this neat in my opinion is that 1 second, corresponds to 0.011574 .beats, which is almost 0.01. So if you make a clock or an app, the change in this decimal will be virtually indistinguishable from seconds. So you could have an indicator for this second decimal and it will 'tick' just as fast as a second indicator on a normal clock. ]
[Question] [ Suppose all of technology in existence disappeared overnight, except for the clothes everyone is wearing. No houses, man-made structures of any kind, just the land as it was say 60,000 years ago. All of our technology is gone, but everyone retains their knowledge. People know how to make a fire, the contractors know how to build a house, the scientists still know science, the tech people know how to make phones and computers, everyone still believes the same religion they believed in previously, etc. With modern-day know how and experience, how long would it take to manufacture a smart phone as they exist today? Assume that it is the goal of humanity to rebuild itself as fast as possible. And by the way, I use the smartphone as an example. As a bonus answer, try to make a speculative timeline of which technologies are achieved and when (for example houses/buildings, cars/planes, rockets/satellites, computers, vaccines/antibiotics/heart surgery. [Answer] ## TL;DR 2000 years The only historical example that we have shows that going from late iron-age technology (the rest describes why iron age) to smartphones has taken around 2000 years. ## Progress isn't a priority The immediate result of such an event is that most of humans will die. Ignoring the other possible effects (housing - in many climates lack of proper housing means death during the first year), medicine, conflicts) the agricultural efficiency would drastically fall. If we're unable to get up a running industry to make a very, very large amount of tools we wouldn't even be able to harvest the existing ripe crops. We would be unable to quickly match medieval technology due to lack of large numbers of load-pulling animals - draft horses and oxen. Even if we'd immediately get up our technology level up to year 1800, that would allow us to feed a billion people, leaving the other 6 billion to starve. That magnitude of death will not happen easily or peacefully - it means that immediate survival will be a complete priority and preservation of long-term knowledge (as well as anything long-term) will be an unaffordable luxury. ## Most of the skills are immediately useless Contractors know how to build a house using tools, concrete, screws, drywall and straight and even-sized planks - none of which exist nor will exist soon. People who know how to make screws and tools know how to make them using machines and metal that doesn't exist and will not exist soon. People who know how to make metal and alloys know how to make them using machines that don't exist and a large quantity of ore - that needs to be mined and transported using nonexistent infrastructure. The currently available sources for mining ore generally are miles deep and are unusable without modern machinery. This goes on for pretty much everything - in an USA-like society, almost the only useful skills will be ones that are used as part of unconventional hobbies - recreating stone-age tools, open-air fireplace blacksmithing, pottery and basket weaving. ## Progress comes at stages You can't start modern society before having a lot of functioning industrial-age tools and processes, no matter how good knowledge you have. You can't start industrial age manufacturing before having a lot of functioning iron age tools and processes, no matter how good knowledge you have. You can't even start iron age manufacturing before having a lot of functioning stone age tools and processes, no matter how good knowledge you have - you'd need charcoal which requires felling of decent-sized trees, you'd need to obtain ore which will also require tools, and you'd need to survive which would require housing, farm tools and weapons. If you're unable to make the first tools at scale - millions and millions of them - then your society won't be able to progress beyond that and your knowledge of industrial processes will be irrelevant. ## Underdeveloped societies will be leading the pack I would expect that societies which are currently underdeveloped would fare the best in this scenario. They are less dependent on infrastructure, and the skills they have are more useful in both immediate survival and in recreating low-tech infrastucture. Also, they often are located in places more suitable for survival. Places like Canada or northern Europe simply aren't habitable without any technology, you'd need at least a supply of good stone axes for firewood, spears and a lot of huntable wildlife to enable survival of small bands of hunter-gatherers there - totalling thousands, not millions. After such an event, sub-Saharan Africa would clearly be in a better position. The immediately sustainable level of technology will be the one that currently some nomadic herder communities have, since they will be pretty much the only communities that will be able to keep their food security, lifestyle and avoid absolute chaos. [Answer] Simple answer : never For one simple reason. When any technology started to flourish (metal working, steam power, etc..) it was driven forward by easily accessible raw resources. When people first started working metals, they mostly picked the raw ores from the ground or made really shallow mines. Industrial revolution was driven by coal, that was mostly in top layers of soil. First pertroleum drills were really shallow and some was even found on the surface. The problem is that all of those easily accessible resources are long gone thanks to modern excavation. We need to put lots of effort, tools and knowledge in finding and excavating new resources. But if we lost all of that tools and knowledge, it would be almost impossible to find and excavate new deposits. And humanity would develop in completely different way than what we saw in history. [Answer] You'll have to be far more precise about what you are imagining. Let's take wheat. It is, like corn, a product of selective breeding, as are virtually all of our other food crops. So, no field crops. Take coal mines. The mine is obviously technological. So, what happens to the hole? Magically get filled in? Similarly with other open pit and underground mines. What happens to the materials making up the concrete, steel, copper, etc., etc.? You state the land would magically revert to "as it was say 60,000 years ago." Does that mean the climate will be the same? That mastodons will roam North America? That rivers magically assume their courses, desserts appear (and disappear)? Roads disappear, land (and water and rock) is magically resculpted into the way it "was" 60,000 yrs ago? The ancestors of maize and potato and wheat and rice revert to their native habitats? All this while 7½ billion people are killing one another (and anything else that moves) for food? [Answer] The single biggest problem then would be survival. Our technology is what is keeping the vast majority of us alive today. Just feeding everyone needs a huge level of tech. Most people don't have enough skills to survive several months without a grocery store and the wild does not have enough supplies to feed everyone. So the first problem would be survival and my guess better than %90 of the human population would be dead in less than a year. At this point the survivors will have made shelters and have figured out some subsistence living. If the group is really lucky they might have some skilled members of the group, hunters, farmers, craftsmen, ie. blacksmiths, carpenters etc. But I would expect at least 1000 years if not a LOT longer because we really would be starting over and by the time things settled down most of the people with needed knowledge would be gone and in two or 3 generations most of what we had would be relegated to myths and legends. [Answer] The largest issue should be that the people alive today with the knowledge of how to work on the tech in smartphones would die long before the infrastructure that would be needed to produce the materials to make the phone. And I doubt the people with the knowledge of "smartphone" building would want entrust their children with the important task of know how to build a smartphone when there much greater needs at the time (e.g food, clean water, shelter). So the knowledge that will be passed down to the future generations will not include how to build a smartphone. That being said the time it would take to produce a new smartphone has to be 2000 years at the minimum and with the possibility that it never gets built at all, with another technology that provides what is necessary at the time [Answer] I agree it could be much longer than 2000 years. Imagine the world as a video game. First you must find clues and pick up objects that will help you on the next level and so-on. If we started again, we would not find our clues on top of the ground because they would have been wiped out by the older civilization. We won't be able to easily make tools from easy to get to resources. How are we going find and recover deep underground ore without the start up equipment need. The reason we know so much about ancient history is because we were able to recover tablets used as we use paper today. So when we die everything goes with us because paper, CD Roms, books even cellphones aren't going to last long after we go [Answer] ### Minimum 100 years, maximum 2,000 years Maximum is easy - already stated in several other answers based on the past 2,000 years of Earth history. Minimum is where it gets interesting. Infrastructure and knowledge are the keys. You are starting with near-100% knowledge, but 0% infrastructure. If you can do the following, you could have most of today's key infrastructure in about 100 years: * Immediately recognize the problem and start writing everything down, which means... * While other people are foraging, farming, hunting, etc., a group of people needs to start right away on recording information. My best guess is papyrus or similar - less work to produce than modern paper, but more information dense than stone tablets. Understanding that it will take 100 years to be able to actually use all the available information, writing it down is absolutely crucial so that the next generation will have the knowledge it needs. * Work on a long-term (100 years, not 1 year or 5 years) for recreating the infrastructure needed for a modern society. Key elements will be: + Metalworking - iron (which leads to steel), copper, aluminum - mine, refine, manufacture useful produces + Woodworking, masonry - for building structures + Tools - Starting with hand tools, but with machine tools (water power, electric, etc.) in mind + Chemistry - Needed for refining metals, developing batteries, medicines, etc. + Electricity - a lot of other pieces need to be done first, but this will be vital and early development of even basic electrical infrastructure will dramatically improve productivity and a bunch of other things. It will be a huge team effort. If society can stay together long enough to write down a substantial part of modern knowledge and start on the necessary infrastructure without having to go through 1,000 years of scientific development, we could have modern technology in 100 years. On the other hand, if famine, war or other problems result in delays in the infrastructure or in the loss of information (e.g., burning the only copy of vital information 20 years in when many of the key people have already died), then you're back to 2,000 years. [Answer] I would assume around 500 years. Surriving population will verbally pass down some important knowledge like woodworking, ore refinement, irrigation, basic chemistry, physical formulas, toolmaking and most importantly scientific methods. Some of these will be immediately useful and next generations will keep this knowledge, this will allow us to skip or at least fast forward stone, bronze and iron ages. ]
[Question] [ What would battle tactics look like outside the scientific research stations? * Year: 2100ish * Mars: Two 'surface,' permanent scientific research colonies with a little over 100 scientists and engineers in each with an additional support crew (geologist, psychologist & medical, etc.) to about 150 people each, with the common utilities, agrarian setups, etc. The nerds in Colony NASA have just had it with Colony ESA, about 100km across [Elysium](http://maps.google.com/mars/#lat=0.522717&lon=534.222794&zoom=6) plains, and are planning to go over there and burst their bubble (literally). The B nerds catch cosmic wind about this, and plan to do the same. It is understood that they're going to pretty much meet up with each other in about the middle. We thought the 'best of the best' scientists were of the utmost moral and mature stature, but we were wrong. Using the types of tools and vehicles that we see frequently included in the typical trope-like sci-fi scientific missions; what would be the battle tactics look like out on the plains? I'm trying not to be too broad, so I'm focused on how it can play out creatively, and not on the logistics or descriptions of the bubble colonies themselves. [![Example from Google Image Search](https://i.stack.imgur.com/2L6GD.jpg)](https://i.stack.imgur.com/2L6GD.jpg) [Answer] They would use drones. The distance between the bases, 100 km, is a lot. If they had [lunar rover](https://en.wikipedia.org/wiki/Lunar_Roving_Vehicle) type vehicles, it would take them over 7.5 hours of driving top speed to get there. If they have rovers like in [Any Weir's The Martian](https://en.wikipedia.org/wiki/The_Martian_(Weir_novel)) (excellent book!), it will take four hours at top speed to get there. Quite frankly, [ain't nobody got time for that](https://en.wikipedia.org/wiki/Ain%27t_Nobody_Got_Time_for_That). Looking at bringing 10-16+ hours of oxygen, water, food, and tools that far it would probably cool the blood of those scientists and engineers. Drones would be sent to attack the structures with their mining/repair equipment. Perhaps some with mining charges on kamikaze missions. Most likely, given the distance, the drones would not meet up while passing eachother. Once they got closer to the other habitat they would have more difficulty overcoming being jammed by the closer base. They might try to switch frequencies, but this would inevitably cause some delay in the control. Ultimately, it would probably turn into a bunch of nerds sitting around computers complaining about their drone getting fragged because of some harsh lag or noob jammers. I guess this isn't much different than a LAN party. [Answer] While the answer suggesting the nerds in the domes are busy hacking each other and their equipment is probably closest to reality, it fails to address the other resources they can call upon. The NASA and ESA astronauts are probably conducting global surveillance and have vehicles and stations scattered across the entire Martian surface. To control all this equipment and to carry out large scale observation there will be a small fleet of communications and observation satellites in Martian orbit: a ready made supply of orbital bombardment munitions! If the stated goal is to destroy the domes and surface structures of the "enemy" camp, then deorbiting a satellite onto the dome will have a similar effect to a Kinetic energy projectile being deorbited onto a target on Earth. While the absolute scale of the damage will be less due to the lower orbital velocity of Mars and the non optimal design of the satellite coming in from space, we are still talking about a hypervelocity impact against an unarmoured target (the hardest structure will most likely be the containment structure for the nuclear reactor, some distance from the main dome). Even if the satellite disintegrates in the atmosphere, a cloud of high velocity shrapnel will strike exposed structures, the parked Mars rovers, antenna farms and solar arrays that are scattered about the surface, causing damage and degrading, if not destroying the various pieces of equipment. Going even "bigger", the two bases are not isolated on Mars, but in communication with Earth. The NASA astronauts can theoretically call on the power of the United States to defend them, ranging from NSA hacks transmitted from ground stations on Earth to cripple ESA computers to US Carrier battlegroups placing an interdict on ESA launch sites. The EU will have far fewer options, but could conceivably be able to broadcast their own malware at the NASA station on Mars. If the war spreads, the various spacefaring nations might also pick sides. The Indians, Russians and Chinese will have to factor in complex interplays between their own national interests and what they could conceivably gain or lose by becoming allies with the US or EU over this conflict. The extra computer and communication resources can be deployed almost immediately, while these nations could also build spacecraft to bring supplies or munitions to Mars to reinforce "their" side. Finally, the United States could simply end the conflict by hiring Elon Musk to build two dozen Falcon 9 Heavies with Bigelow inflatable hab modules attached to Dragon space capsules and launch a platoon of specially trained SoF operators or Marines to Mars to settle the problem once and for all. The Americans base might have to dig in for over a year while the expedition is mounted and makes its way to Mars, but they will be either rescued or avenged soon enough. [Answer] Disclaimer: Since I am from Europe, I took ESA as my favourite Trojan Horse Operation: Nerdy people come up with nerdy solutions. As stated in answer [from Samuel](https://worldbuilding.stackexchange.com/a/22575/2071), getting from one base to another is quite long and dangerous travel, so you need to get there safely. It gave me hard time to hand-wave down that the scientists would have fight, because you have to communicate with the operations on Earth and they are packed with psychologists and therapists to help you cool down, since NASA and ESA are friends But, even through all the talks, all the communications with Earth and all communications between NASA and ESA, the scientists up there hate each other. And they want to get physical. Sending down the drone is great idea, but I think, that they would like to provide "personal" treat, because those self-righteous Ammies are just bunch of \&#@! So, being up there, I would use the therapists on Earth into my plan: Tell the Ammies that "we are cool now, bro" and lets solve our differences on one big Thanksgiving party at NASA science base. (Or just special "we are friends now" occasion. You get the idea) Battle plan:* * Step 1: Pack German Schnaps, Italian Grappa and Czech Slivovice * Step 2: Get to NASA place and show to stupid Earth command center that "we are friends" * Step 3: Get the Ammies drunk. (We all know Americans cannot drink because they are stupid) * Step 4: Unleash Hell! * Step 5: Steal shiny science equipment and get home. Addendum: Honestly, I don't think that any scientist would like to destroy scientific equipment. It can be used for science! (Just better science than the bunch of ... from NASA is doing) [Answer] Since - according to the OP's comment - this is a case of Scientists Behaving Badly (and not state-sponsored warfare) on both sides, we can presume that neither side would want to involve Earth, as to do so would undoubtedly result in their being told in no uncertain terms to stop their foolish nonsense, and would probably then lead to their being removed, replaced and prosecuted if they persisted - and survived. So, these badly-behaving scientist types must rely on the equipment and supplies that they have on hand. Being scientists and nerdy-types, they would most likely rely on any drones or other remote-controlled equipment before thinking of getting physical in person. If they didn't have explosives already (which is unlikely), the base chemists could undoubtedly brew some up, and from there, the engineers could build perfectly effective bombs, enhanced with spare metal items that would act as shrapnel. Given that we have engineer and physicist types, we could even expect crude [Explosively-Formed-Penetrators](https://en.wikipedia.org/wiki/Explosively_formed_penetrator), which are anything but crude in their ability to deliver damage at a fair distance. Drones could drop bombs if they can fly (not out of the question even if Mars' atmosphere is thinner than Earth's), or could fire rockets which may also be improvised. On the defensive side, there are probably reconnaissance satellites, though they could be a two-edged sword. The scientists will know that they are behaving badly, and may want to hide the evidence of their wrongdoing, and deliberately operate in any gaps in the satellite coverage so that they won't have to make suspicious edits or deletions to the satellite feed recordings. On the other hand, they may also try to stage-manage being "surprised" by the other side's attack, but that would then beg the question as to how they were able to retaliate effectively on such short notice. A likely possibility is for the scientists to make use of the reconnaissance satellites, and to cause "battle damage" to the satellite feed recording media themselves in the aftermath, providing that the satellites don't connect directly to Earth too - which it entirely likely. However, Line-of-Sight matters in interplanetary communications, and the attacks would likely be scheduled for a time when the links to Earth were down - i.e. local night-time. However, reconnaissance satellites may not be that effective a tool. Without software to track the movement of manmade objects (which may not be included in an essentially non-military operation as anyone going out would likely file their travel plans and broadcast their location at all times), spotting something as small as a drone could be quite difficult. Given the amount of land area, spotting another drone using drone cameras would likely not happen except when an attacking drone came quite close to its objective. Given the logistics of leaving their habitats and travelling to make war on their enemies, it is only more likely that both sides will try to conduct the battle remotely rather than in person. Drones may be fitted with simple weaponry such as nail guns or shrapnel bombs in order to deal with other drones, but given the distances involved, it is likely that these will be of limited effectiveness, and that much of their ammunition will be expended to little effect, or they will be single-use items, destroying themselves along with their target. Finally, given that Mars' surface is a hostile environment, we can expect that the scientists would all suit up before the fighting started, and if their habitats did suffer damage, many of them would survive, environment suits by necessity being quite tough, and likely only being fatally compromised by a direct hit or a unfortunate mischance. All in all, with both sides attacking the other, and the difficulties of defending effectively as opposed to successfully attacking, we can expect that both sides will achieve their goal of causing damage to the other side's habitat, and for there to be relatively few human casualties or fatalities. After the battle, the survivors will be pre-occupied with patching up their habitats, recovering any salvageable equipment, and treating the injured. They may try to hide it, but the authorities will probably figure out fairly soon that there has been an incident that neither side really wants to talk about, or is being evasive about, and a well-armed investigatory mission will be scrambled. In the time before the investigatory mission arrives, there may be further attacks, probably of decreasing effectiveness as the scientists attempt to make use of their dwindling resources. So, after the battle(s) and the reconstruction, there will likely be a lot of survivors on both sides who will then have to either hide the fact that they went to war against the other side without authorisation, or claim self-defence. All things considered, we can expect that the investigatory teams won't buy into the scientist's arguments against the other side, and for there to be prosecutions... [Answer] The drone suggestion has some merit, but the decision to build two separate Mars bases says to me that there is hands-on work to be done on Mars. * Each colony would have long-range expedition rovers with the endurance to reach, say, the pole caps or the Cydonia face for a close, personal look. Unload most of the provisions and there is a payload to carry arms and armour. * Does that town of 150 people have cops or did the mission planners back on Earth rely on their good sense? But those cops will probably be unarmed. There will be plenty of ex-military types, but those are more likely air force than commandos. * The engineering department will have plenty of explosives, for rock-busting and demolitions. The chemistry and life support people can produce more, but possibly less efficient mixtures. Drones are one way to deliver them, but a drone with payload will be more clumsy than a defensive drone without. Take a look at Red Mars by Kim Stanley Robinson, especially the chapter where Nadia where they build the initial base. [Answer] The battle would be a RTS game in reality. Somebody mentioned battle drones, but biggest nerds wouldn't stop at that. They would quickly realize that just sending drones to directly attack isn't very effective because of jamming and stuff. They would need more elaborate tactics. Having a lot of experience in StarCraft IX, they would quickly realize that they must construct additional... structures. So they would construction drones to build outposts, refineries, material processing facilities, drone factories and other buildings. Construction drones would have to be protected by defensive battle drones to protect them from enemy battle drones. They would also build some defensive turrets around strategically important places such as mines and secondary bases. At first, there would be almost no direct confrontations. Instead, each side would go on to capture as much territory as possible and build a lot of units as fast as possible, preparing to confrontation. After having a lot of units and secured territory, some initial confrontations would start, and each side would try to undermine their enemy's production. This would continue like a typical RTS game, although it would last considerably longer and with no replay value. ]
[Question] [ In one of my settings, the people have domesticated the wild raspberry plant, and selectively bred it for larger and larger berries. Would it be plausible for these berries to reach the sizes of apples (or larger), or would this not be possible due to things like the biology of raspberry plants/soil richness/etc? If it were possible/plausible, what could/would these large raspberries be like, and what would the raspberry plants themselves look like if they had such large fruit? (Since raspberries are made of small round parts, I am imagining they would either be made of many more or much larger of these small round parts.) The kind of answer I am looking for would be something along the lines of "raspberries of that size would/wouldn't be possible because of X, and if they were possible they could look/taste like Y or Z, and the plants would look like ABC" [Answer] ![enter image description here](https://i.stack.imgur.com/UWyzZ.jpg) * Columbia Giant, a new blackberry cultivar developed and released by ARS. A [Link](https://www.ars.usda.gov/news-events/news/research-news/2016/two-new-berries-for-you-from-ars/) to ARS article(not much useful info there). Thornless blackberries are almost there, almost. So I guess it isn't too far fetched to breed a raspberry for size. People already did the same with a lot of fruits which are minuscule in nature but can be humongous in farms like pomelos, pumpkins, bananas and cucumbers. Actually some pumpkins can get larger than a person. Possible? Certainly so...maybe not naturally, unless some really picky animals decided to only eat the largest fruits and and thus spread only the seeds with gigantism genes. I don't know much about raspberries but with thornless blackberries at least it seems that bulbs get larger and more numerous at the same time. [Answer] It's plausible that you could make raspberries the size of apples, but you probably wouldn't like them very much. The two problems are that raspberry plants are not strong enough to support apples, and that the flesh of raspberries themselves is not strong enough to hold itself together at an apple-like size. (This is a consequence of the square-cube law, which governs the size of many things). Your raspberries would work if they grew on the ground, but that's gross. Otherwise, both the plant and the berries themselves would have to get stronger. Woody plants are no problem, but big, tough raspberries are not much like raspberries. [Answer] From experience growing raspberries, probably not. Raspberries grow on canes that bear many berries at a time. Even at current sizes, the canes often need to be tied to supports, or the weight of the berries drags the cane to the ground. You'd have to breed canes with the strength of tree limbs. Even that might not work, since in years when my trees (apple, peach, pear, quince &c) set a lot of fruit, I need to thin it out or have branches broken by the weight of the ripening fruit. OTOH, you could certainly breed apples that are about the size of large raspberries. Some crabapple varieties are pretty close now. PS: Another reason is the growth habit of raspberries. They have an underground crown which is perennial, and which sends up canes every year. The canes are what bear the fruit, and only do so either the first or second year, then they die. So the canes never have time enough to become strong enough to carry lots of large fruit. PPS: Now if you want to do a bit of genetic engineering, combine raspberries with roses. Some varieties of roses can develop trunks that are almost tree-like, so with proper pruning they should be able to support large fruit. [Answer] From a biological standpoint there is no reason why an apple sized raspberry should not evolve. However it is very difficult to imagine exactly what selection pressures would be necessary. Depending on circumstances such a fruit might well be similar to but a little different from a traditional raspberry. There could be more segments, the skin might be a little tougher, the connection to the stem might be more robust to hold the weight and the stems themselves might be thicker and bigger. But in principle its very doable. [Answer] Probably easier to gene modify grapes to taste like raspberries. You have a plant that can already bear large weights of fruit. Or you could do the same with a peach, and each peach would be like one of the little balls on the raspberry. Now could you breed a plant to have the taste and texture of good steak... ]
[Question] [ I'm designing a creature that is supposed to be able to eat "basically anything", within the realm of plausibility for what is essentially an organic creature. Its digestive system can be as complicated as necessary, and evolutionary history is not an obstacle, the creature could be either alien or engineered but one way or another it is omnivorous to the extreme. At the very least, it should be able to break down any organic, energy-storing molecule, ranging from plants and meat to fossil fuels. Any other naturally-occurring chemical with a high energy content should be edible as well, if possible. Notably though, it is an active, mobile animal so it should only be interested in eating things that have a relatively high energy content. It is possible to get energy by oxidizing metal but probably not enough to sustain a high-energy lifestyle. How would the creature's digestive system work, in order to give it the ability to digest as many different things as possible? [Answer] > > At the very least, it should be able to break down any organic, energy-storing molecule, ranging from plants and meat to fossil fuels. > > > The closest thing we got on Earth are roaches. They will eat anything that they can chew. Digesting fossil fuels is complicated because of a few factors: * Breaking them down within your body could lead to the formation of carbon monoxide, which is terribly poisonous; * They are rare enough to find in natura that most creatures had no evolutionary pressure to develop the means to break them. That does not mean animals do not consume them. Many herbivores, ranging from elephants to deer, and also some omnivore apes will eat charcoal. They consume it not as an energy source, but [as a natural antidote for toxins in their diets](https://www.sciencedaily.com/releases/1997/09/970901072246.htm) (the article cites monkeys only, but there is evidence for other animals). --- So let's start from our best bet. You could have an evolutionary story where roaches have a symbiosis with these two bacteria: * [Alcanivorax borkumensis](https://en.wikipedia.org/wiki/Alcanivorax) breaks down oil, which is actually [composed of different carbon chains and other stuff](https://en.wikipedia.org/wiki/Petroleum#Composition) (should cover from ethane to octane). * [Ideonella skaiensis](https://en.wikipedia.org/wiki/Ideonella_sakaiensis) for completion, as this one can break down plastic as well. These bacteria could live in the gut of the roach. In return for giving the roach part of their energy output, they have an environment where they can thrive without competition. Also the roach will provide them with the raw materials they need to live, so they don't need to bother about getting food. A similar process happens with termites and bacteria in their gut - termites don't break down the cellulose they eat, the bacteria in their gut do. So there you have it. Imagine a world in which roaches could eat plastic and oil. If you had a roach infestation in your house, they could drink your car's gas and then eat the fuel tank as a dessert. [Answer] I would suggest giving it multiple stomachs, like cows, however here each stomach has a different function: one for degrading meats, one for fibrous plants, one for fruits, etc. This would probably require a first stomach with some kind of filtering method, or at least something to [break down tough foods](https://en.wikipedia.org/wiki/Gastrolith), so that each subsequent stomach can fulfill its role properly. It could also be interesting to give this animal a complex internal microbiota. A lot of micro-organisms are much more effective than we are at breaking down energy-storing molecules, and having the appropriate bacteria and fungi in each stomach pouch would give your animal an incredibly wide selection of foods to live off of. [Answer] Heat differential engine. Your creature oxidizes molecules in its "stomach" which is more of a furnace. Anything that can be oxidized is fair game - any reduced carbon, or nitrogen, or metal salt. Oxidation produces heat. The amount of heat produced is controlled by controlling oxygen ingress to the stomach. Under hot conditions, certain metalloproteins change configuration. The circulation brings these proteins into hot conditions near the stomach and they capture heat energy with the configuration change. When the hot-configured metalloprotein circulates out to the cold exterior (possibly radiator plates or fins) it shifts back to the cold configuration. This conformational shift is linked to an ATPase and generates ATP for the creature to use for its muscles and metabolic processes, as Earth life does. [Answer] ## You got humans! No, seriously - think about this. We can eat basically anything on this big, weird world of us with proper preparation. What we can't eat right away, we can find ways to cook and make it edible. We already use stuff like [coal](https://en.wikipedia.org/wiki/Charcoal_in_food), [petroleum](https://www.petro-online.com/news/fuel-for-thought/13/breaking-news/what-foods-contain-petroleum/37415), and even [wood](https://www.cornucopia.org/2017/11/brief-history-wood-pulp-food/). It is just a matter of time before we start making food directly out of carbon via some sort of weird 3D Food-Printer. [We already got the printers](https://www.techrepublic.com/article/heres-how-3d-food-printers-are-changing-the-way-we-cook/), and we aren't that far away from [using carbon directly either](https://www.fastcompany.com/90428522/the-newest-fake-meat-is-made-from-thin-air). Sure, it isn't directly our delicate stomachs that do this. Instead, we use our brainpower and societal resources to enable ourselves to eat whatever we think might be remotely tasty - emphasis on ["remotely"](https://allthatsinteresting.com/hakarl). We usually think of our "digestive system" starting on our mouths, but for some foodstuffs this process happens way, way before it even hit our plates. From taming special bacteria to make [cheese](https://en.wikipedia.org/wiki/Cheese) to using almost ritualistic processes to [prepare meat](https://eatrio.net/2013/07/the-carne-seca-experiment.html), we devised thousands upon thousands of ways to make all sorts of things edible - sometimes for far longer than they [should be](https://en.wikipedia.org/wiki/Refrigeration), sometimes even if it tries [really hard to kill us](https://en.wikipedia.org/wiki/Tetraodontidae#Poisoning). In that sense, we aren't that much different from the termite that stores special bacteria in its gut to be able to digest cellulose or from the animals that literally spit acid on top of their food to them slurp up the resulting juices. The major difference is that for them, this is the only way they have to eat. For us, it is different. We're crafty bastards. We don't eat with our mouths. We eat with our brains. So, in the end, what your creature needs isn't a super digestive system that can eat anything - instead, give them the ways to make whatever they want to eat, edible. Don't make them monster eaters. Make them monster cooks. [Answer] How about having your creature be in fact a multi-combo symbiote? Maybe it's part-way through the evolutionary process of merging into a single complex being (similar to the mix of prokaryotes into eukaryotes, sort of), or maybe it's like the combo-animals of "A Fire In The Deep". Either way, its component creatures 'share' all food sources as appropriate. [Answer] Its name is "Carl"...with the iron stomach. The mouth registers what type of "food" is being eaten. This triggers a complex neural message to glands that support the digestive process. A series of acid emitters are engaged to create the right acid mix for what is landing in the "iron gullet" this also triggers any needed mucus increases to protect the stomachs based on the acid strength. For complex or harder materials, there is a holding stomach that is designed for the full power acid and only really bizarre foodstuffs are diverted there where they get softened up before moving down to the regular stomach. For the complex gases associated with certain digestive processes, there is the ability to back-feed "burp" gases from either stomach, and the bowels "farts". The question is for the really tough meals, is it the creature who suffers the most or those near the creature who get the brunt of the process. ]
[Question] [ In a scenario I'm thinking of, the Earth has been nuked bare and a few remnants of humanity are surviving in their underground bunkers. Let's say there is one in North America, one in Central American, and one in South America, then one or two in Europe, four in Africa, I could go on, but I think this is not so important. Is there a way the bunkers could be connected in terms of communication? And is there a way the bunkers could share, between one another, or even drain one another of power harvested from solar panels? [Answer] Already Exists Behold, the [Submarine Cable Map](https://www.submarinecablemap.com/#/)! A wide network of underwater cable that connects the major coastal population centers. In fact, I believe you may be using it to view this page, or even if not you, someone else. (By the way, don't use solar power. A nuke-fest that destroys the Earth and forces everyone to live in bunkers will cause a nuclear winter and shroud the world in darkness. Use nuclear generators instead. And that can be sent through subterranean power lines.) [Answer] It is possible. More so for bunkers in Eurpoe to be connected with one another or with those in Asia, or North to South America. You just lay cables as we do now. or you could just lay them on the surface, if there is no-one left to steal them. If you are thinking of potentially laying thousands of miles of tunnels then this is not a trivial task, but threading cables down them once constructed is simple. The less relatively easy bit may come when havig to traverse oceanic treaches, subdution zones or mid ocean ridges. But, with current technologies we run [cabels between continents](https://www.submarinecablemap.com/) to supply the internet to the world. So communtication would be fine, but shifting power over long distances leads to large percentage losses, so it is possible but expensive. And rather than DC transmission which requires lage conductors, you would want high voltage AC which requires large distances between cables to prevent arcing... this is why pylons hold the cabels so far apart. You could also use [short wave radio](https://en.wikipedia.org/wiki/Shortwave_radio) to communicate between bunkers bouncing signals of the ionosphere. Then they would not have to be physically connected to be able to exchange information. But bandwidth is low. If there were still satalites these could potentially be used to communicate. [Answer] I think it depends on the level of technology your world possessed before the Great Nuking. If the world was already connected via deep underground tunnels burrowed miles beneath the surface then sure. But creating them after the Great Shellacking that presumably killed lots and lots of people would be a big challenge since they would require a power source to drive the tunnel boring machines that Solar power is not likely to be able to generate. If robots were well developed in the world before the Great Burn, then robots could walk power cables to nearby settlements to share power and communicate with each other. * The robots would be powered by the cable and even guided by the cable by operators in the originating settlement. * The originating settlement would be fabricating the power cables as they were deployed unless they had hundreds of miles of power cable hanging around on spools. * Since a robot can only carry so much weight, there would be multiple robots each supporting a length of the cable. * The originating settlement would be fabricating the robots too unless they had the 10,000s required to carry heavy cables the 1000s of miles just parked in an underground garage * The chain of cable carrying robots would look like a line of [army ants](https://www.youtube.com/watch?v=JsfiUR0ZzLw) moving forage to their nests from tens of mile away. * It might not be possible for there to be enough robots to carry the cable all the way across the globe, so the robots might carry it so far and coil it up, then go back for more. The pattern would repeat until they'd moved one end of the cable the entire distance. * RObots would break down so Wrecker Robots would be needed to pull the break downs back to somewhere they can be repaired or recycled. [Answer] Communication is easy. After the bombs stop falling, you wait a week for the radiation levels to drop, then have someone carry an antenna to the surface. (Or deploy the automatic system.) This would either use ham radio-style "bounce off the atmosphere" or satellites in order to reach across the earth. Power transfer between bunkers isn't really an option, though. That needs a real cable, and expecting world-spanning infrastructure to survive a nuclear war isn't that realistic. Also, the bunkers will be using nuclear or geothermal, not solar. [Answer] If they can't access the atmosphere, the 'simplest' way to communicate would be through Extremely Low Frequency radio. That requires a LOT of power, huge infrastructure (many kilometers between antenna elements), and provides bandwidth of around 12 characters per hour. It's something that could be setup in advance if we had a few years warning of an incoming asteroid. Look for Project Sanguine or Project ELF for more info. ]
[Question] [ So, on a previous question of mine, someone answered [that it would be feasible to build a city on a waterborne floating island using a pumice layer below the ground](https://worldbuilding.stackexchange.com/questions/64252/ferrying-an-island-with-mortals-on-top-is-it-possible-without-killing-them). That got me thinking about the possibility of having a city built on a floating island, but airborne. Now, I know that there have been questions about floating islands already... but those implicated major geological catastrophes projecting rocks into the air, technological or magical human intervention and atmospheric gases different than our own. But my question is different: Is it possible to conceive of an imaginary rock that would float on the air of an Earth-like atmosphere, some distance above the ground? I know this seems impossible, but having a rock that floats on water also seems impossible and we have pumice. I don't want real world examples (they don't exist), only to know if such a rock could be theoretically possible. A geological material that could form floating islands in the sky where the building of cities would be possible. [Answer] Consider a biological 'assist' You have your chunk of pumice-like rock, with plenty of pores, holes, and tunnels. Within these is a thriving bacteria. The bacteria is particularly attractive to a fungus that can grow without direct sunlight. The fungus' output is a gas that fills a bladder or bubble within it. This gas is lighter than air and as the fungi fill the bladder, it begins to lift the soft-stone structure slowly until it reaches a certain atmospheric pressure. At the equivalent of 5,000m, the gas is equal with the atmosphere and the island stabilizes with respect to altitude. This does not mean it will stay still. Limitations You will still have a lot of wind. Do you want this? You can have a community develop on the 'island' whose weight presses it down, and the response of the gas-bladders lift it back to that level. However, winds will push it every which way at the 5,000m altitude. You can run into things. The choice of 5,000m is somewhat suitable for humans. However, this is roughly the altitude of base camp for Mt Everest, so there may be mountains struck. Your next question could focus on how to stabilize your now-floating mountain. I look forward to that. EDIT with ADDITIONAL INFORMATION: I am not sure your intended use of the island or the type of city you want, but a city [might weigh 10m tons](https://www.quora.com/Can-someone-tell-me-how-heavy-a-city-is-and-how-it-affects-the-earth). I am going to go with a compact, radial city, in order to address your question although there is a LOT of speculation and variables. [![enter image description here](https://i.stack.imgur.com/F2at3.png)](https://i.stack.imgur.com/F2at3.png) Warm gas like methane filling sacs within your fungi will lift the city until it reaches equilibrium with the atmosphere at around 500m height. This means that even if the fungi continue to produce more gas, your city will max out at around 500m. The weight of your city presses down, but your CH4 -filled fungi press up. Atmospheric conditions are not stable, so there will be a lot of ups and downs - make sure your denizens and engineers are comfortable with that. Note: I am not an artist / Note2: There are too many unknowns for precision math, but this could work for your story at a minimum. [Answer] Not really. You would need a porous rock filled with hydrogen or helium. Hydrogen can lift bout 1.1 kg per cubic meter of its volume. This means you would have to have about 1kg of rock holding 1 m³ of gas. This means bubbles would need to have really, really thin walls. Now, thin walls are not out of the question. No problems when pressures are equal. But then your rock would rise from were it formed. Up there, pressure is lower. Thin walls and pressure difference would make bubbles burst, release hydrogen. And all you get is shattered pumice. --- For magnetic lift, there is another problem. Permanent magnets don't hold its magnetism for too long, and no known substance could keep superconductivity at outdoors temperatures — as far as we know now. Our knowledge of superconductivity was shattered few times and we have superconductors so hot that 20 years ago we knew it's impossible, but then, now we can only speak from the point of view of the knowledge we have now — and superconductive pinning without power supply doesn't seem possible nowadays. [Answer] Imagine an extremely fibrous vine. Now imagine that this vine likes to grow on pumice, which it roots deeply in. Finally, imagine that this plant's metabolism, somehow, produces an excess of hydrogen, which it stores in hollow leaves. Since the vine gets no nutrients from the roots anyways, it would not be limited in length. Its strength could be due to structures similar to carbon nanotubes. Not exactly a floating rock, but scientifically plausible. And, by putting the buoyant gas-bag above the low-density rock, you avoid the problem of building on top of the rock causing it to flip over. [Answer] # Option 1: The solar system design Why can't you have a small scale solar system as a planet? If you thought of our solar system as one planet, it would be very similar to what you're requesting. Instead of having a crust, I don't see why a planet couldn't be straight core... with no inhabitable land mass attached to the actual planet. From here, all the "islands" are just land masses that are in a low orbit around the core. As for an atmosphere, the ISS is technically in the earth's atmosphere, so there are basically 3 options. 1. Having your inhabitants capable of surviving in an EXTREMELY low atmosphere environment, meaning that they don't have the same gas requirements as anything remotely human. 2. Designing the base planet to have an incredibly strong atmosphere, that would be too dense for long-term living at the surface, but be perfect for living on the fringe, where the orbiting islands are. 3. Give each orbiting island it's own atmosphere, limiting inter-island travel, but being easy to communicate to readers. --- # Option 2: The helium generator This one's a bit of a stretch, but if you have a very small nuclear fusion reactor (read star) at the middle of each island, which had branches/corridors running through the island, you would have an island lighter than air, but you would need an incredibly air-tight center, and the island would have to be long and flat. --- # Option 3: The dense atmosphere We all know that tungsten hexafluoride is the densest gas, at about 13 grams / liter, and we should all be familiar with aerogel, the solid made out of silicon dioxide and air. In theory, a large enough island, composed primarily of aerogel, or something similar, could work when sitting on top of an "ocean" of tungsten hexafluoride. This would look like boats of light solids on top of heavy gasses, which could work. --- # Summary As far as I know, all of these are plausible, if not extremely rare. They are also all longterm, meaning you don't have to be worried of magnetism fading, etc. I like option 1 the best, but in a properly engineered system, all of them would work. From a purely dynamic standpoint, option 3 would be the closest analog to a boat (read floating island) as it would be an actual platform resting on what it perceives as a solid base, as opposed to counting on some other property (orbit/lift) to maintain the floating aspect of the island. [Answer] # Not naturally, but yes. And for gengineered values of "natural"... You can have [substances](https://en.wikipedia.org/wiki/Aerogel) quite resistant and lighter than air, but not by very much. [Evacuated aerographene](https://en.wikipedia.org/wiki/Aerographene) has about 16% air density, and can withstand considerable pressure. Every cubic meter of aerographene can lift about 800 grams in air. You can cover it with air-tight silicon or graphene foil, so that it stays evacuated, reducing its buoyancy to about half a kilogram. Non-evacuated aerographene is heavier than air and would sink. The reason why we fill balloons with hydrogen instead of vacuum is that we need something inside to counteract the outer air pressure and prevent the ballon from collapsing with a thunderclap. But if the "balloon" is filled with aerographene, that is enough. Actually, an even lower "density" can be achieved with a hollow evacuated aerographene ball (spherical to better withstand the pressure) with an airtight outer shell. But there would be air between the balls, so every cubic meter would be about [25% air if we use equally-sized balls](https://en.wikipedia.org/wiki/Close-packing_of_equal_spheres), 75% hollowed aerographene and some shell material. On the other hand, the material resistance is high enough that we might be able to use hollowed-out cubes instead of spheres. But we're pushing against an absolute lift limit of one kilogram per cubic meter (the lifting power of vacuum), so we'll hit the point of diminishing returns pretty fast. Small spheres would have the advantage of being manufacturable by biological constructs (you'd need impressive genetic engineering skills). You could cultivate (or mine) the spheres of levity and believe they're natural. To be able to lift one ton per square meter, the "island" would need to be at least two kilometer deep. Actually more than double than that, because you want to have more mass as ballast below the island than above, or the island will tend to capsize. Also, "upper" air will be less dense and provide less buoyancy. If you're willing to have a thinner upper crust and employ a lot of aerogel for the upper buildings, and use flimsier sealants in the island's core, you can have [a reasonably thin floating island](http://orig08.deviantart.net/0e97/f/2015/045/3/0/floating_island_by_tiga1122-d8hyz2h.png). Which brings us to the problem of steering it and surviving storms and the like. [Answer] For a naturally ocurring floating island, we need a naturally ocurring: * A lighter than air gas (methane, near vacuum ambient air) * A membrane impermeable to gases ( [guanine](https://en.wikipedia.org/wiki/Swim_bladder) like in swim bladders, [fullerene](http://www.nature.com/articles/ncomms7212), ...) * A material strong enough to resist the pressure differences (to avoid implosion or explosion) like diamond, fullerenes, ... What could have happened is that similar to the diamond formation process, a rock made of carbon nanotubes imprisons bubbles of very hot air under very high pressures deep down in the mantle of the planet (bubble diameter varying from mm to m of diameter). As these rocks move up to the crust, they cool down and the carbon based material solidifies and imprisons the gases. As the gases cool down, it turns the inside of the `bubble` into an effective void. In the process, they would collect ammonia rich materials (more on this later). Billions of years later those rocks reach the surface and the local sapient specie(s) notice that a certain rock, if let free from the other rocks, will float. If caught in nets, they make it very easy to carry heavy loads over long distances. As extraction progress, dear devils from the younger generations start experimenting climbing on the bigger rocks and playing with floating and how to direct the rocks with artifact. At some point they will realise that what used to be a problem for their parents (breaking the rocks makes them fall) can be used to avoid going too high, they might even master how to do it to control rising / falling. Then someone will notice that a rock which was burst with a small crack can be made to float again if filled with ammonia gases. Because of the huge amount of naturally occurring ammonia, they would have developed a rudimentary absorption fridge [wikipedia](https://en.wikipedia.org/wiki/Absorption_refrigerator), then a local equivalent of Da Vinci will design a way to control the amount of ammonia which goes into those huge balloons made with this very light material (basically a huge bubble burst but the rest of the material still contains a lot of small bubbles so it is still very light) and thus adjust the floatability of the system. Attaching those ammonia filled balloons to the 'almost' floating island will allow them to float and control altitude. [Answer] Yes it might be possible.It can be achieved in two ways. 1. Uing quantum levitation If the island is somehow locked into its position by quantum levitation effect against the earths magenitic field it can stay in the air.But considering the weak force of the earths magnetic field when compared to the earths gravity this might be hard to achieve such effect. > > If you had a really really big magnet, whose field extended over such a large region that the Earth’s field changes noticeably over that region (you might need another Earth-sized bar magnet), then yes, a noticeable force can be produced. > > > this [link](https://van.physics.illinois.edu/qa/listing.php?id=1027) explores that option indepth 2. Antigravity from Supergravity Antigravity like effect could be achieved can be achieved from supergravity called as unified supersymmetric point-particle quantum field theory. > > Some particular versions of this theory not only contain the "usual" atractive graviton, a spin-2 particle, but in addition a so-called graviphoton is predicted (1). This graviphoton is a spin-1 vector field, interacts with mattar at the normal gravitational strength, and behaves generally like a massive photon. The fun thing about it is that it can give rise to attractive and repulsive forces. The repulsive forces feature can in principle give rise to anti-gravity effects. > > > these links explore these option indepth <https://physics.stackexchange.com/a/60349/40095> <http://www.sciencedirect.com/science/article/pii/0370269379904635> If anyone of the above effects occur in nature then there possibility of natural floating island. [Answer] Sure. ## Islands floating on liquid On geological timescales, things crumble, especially large things. This is why you don't actually see islands of pumice, and there's no large patches of pumice floating about. In the end, the pumice crumbles: the gas escapes, the rock sinks. Now, given the right circumstances, some freak vulcanic eruptions or something, a large pumice island may form, but given some large waves or strong currents, it will break apart, and eventually it will crumble. In a more general 'any solid floating on a liquid' sense, over time, and on a large scale, substances arrange themselves on density, the least dense material on top. So, given enough of any solid that's less dense than a liquid, it will generally form a thin layer above that liquid (a bit like the Earth's crust). However, there is one possibility for solids floating on liquids permanently: The sweet spot where there's not enough of the solid present on the planet to cover the entire planet in a layer, you'll end up with patches of this solid floating over a liquid planet-sized ocean. Example: islands or rock/sand floating on an ocean of mercury. ## Islands floating on gas The problem with floating on gas is that there aren't any solids light enough to float on normal air without pockets of gas. But that's where the crumbling comes in again. ### There are two ways to fix this First: Denser air. There are some gasses out that that are pretty dense. And you can ramp up the density even further by increasing the pressure at which point light solids might be able to float on (or rather somewhere in, at a certain pressure) the gas. (This [actually is a thing](https://en.wikipedia.org/wiki/Colonization_of_Venus#Aerostat_habitats_and_floating_cities)). Again, you'll have to be in the sweet spot where your solid doesn't just cover the entire planet but forms patches. But I don't see a planet like this supporting intelligent life. Second: Counteract crumbling. The only way I can think of is some kind of organism which heals any damage and inflates bladders, like in [Mikey's answer](https://worldbuilding.stackexchange.com/a/68996/33078). This actually seems like a decent survival strategy for some micro-organism, to build their own sort of zeppelin and (like pollen) drift in the wind. These organisms could produce methane (about half as dense as air), or even better: hydrogen (~1% the density of air). All these organisms need are CO2, water, preferrably calcium (from sea-spray?) and some energy source (photosynthesis), they could form some coral-like (calcium carbonate) structure filled with hydrogen bubbles (this would require large bubbles though). Also, it would help if the atmosphere were a bit denser than here on earth, if the air pressure were 2.5 times the current air pressure, calcium carbonate would almost float, so the bubbles can be a lot smaller. A higher air pressure probably also has lots of other implications. These islands would need to be flat (have a large area for photosynthesis) and probably contain some large cavernous hydrogen pockets somewhere on the inside (potentially formed by decay of calcium carbonate walls on the inside). Having floating islands of hydrogen filled with hydrogen also opens up the possibility of spectacular [explosions and crashes](https://en.wikipedia.org/wiki/Hindenburg_disaster). Living on an island like this requires very light construction (and/or compensating with hydrogen/helium balloons); not covering too much of the island, as without photosynthesis it would die; only very controlled fires; no drilling; and a good balance to prevent tipping. [Answer] Okay; first things first, I'm no geologist, but I think it's not impossible. First of all, you would want an extremely strong and extremely light pumice-like material (some kind of aluminium alloy, maybe?) to build the actual island itself out of, and you would also probably want a fictional gas significantly lighter than hydrogen to fill the internal bubble honeycomb structure. [Answer] Ok, there are many answers how could it be possible, but the main question - will it be stable enough to build structures on it? We can imagine some stable point for a floating island, where it will neither rise, nor fall down, at this point it's pretty stable and will not turn other. But each building will add weight, and island will loose it's attitude to the point it won't be that stable, and could turnover. Also, we DO have a floating rock in our sky. The Moon. The thing is - it's always falling, but constantly misses the Earth. ]
[Question] [ I've recently been reading a lot of utopian/dystopian fiction, and quite a few of them (e.g. Thomas More's Utopia) has this idea that people shouldn't be ruled over by laws that they can't understand. That is, the average person should be able to understand the law to the point of defending themselves in court without a lawyer. Is it possible to have a legal system like that for a highly-urbanised-mechanised-developed system like that of the Western world? If not, then what kind of system would be conducive to such a simple legal system? [Answer] I'd always pay a professional to repair the plumbing or to fix my teeth, why would I do anything less in court? It is important that all citizens can tell right from wrong and legal from illegal, but you don't have to know the exact dividing line between manslaughter and murder to know that both are wrong. That can be left to professionals. Some factors which unnecessarily complicate legal systems: * Excessive Case Law: Courts must rely on precedent to make sure that there is a consistent interpretation of law, but if too many important decisions can only be found in musty tomes of precedent and not in the law text itself, only professionals can find their way. * Jurisdiction Friction: Do you have to re-learn everything when you move a hundred miles? * Multipurpose Laws: Does each law have a single purpose, and can all relevant rules be found in that volume? What's that rider doing in the spending bill? Some factors which necessarily complicate legal systems: * Comparing Apples and Oranges: There is a difference between a drowning man who trashes wildly and hits a rescuer and someone who does the same with calm deliberation. Can a simple law discriminate properly? * Side Effects in a Complex World: Is each shareholder of a company responsible for something the company does? Or the CEO? Or the employee who actually executes the decision without any say on policy? [Answer] I don't think that you can create a 'simple' legal system for large governments. the sort of system that this works for is very small places, towns or settlements. However, even there it's a double edged sword. The lack of exact laws will likely be addressed by having a tribunal (or single elder, or similar system) that is capable of saying "we didn't have a law for that, but it's clearly wrong and you must be punished." You need something like that to prevent rampant abuse of the 'ain't no law' variety. Just because tricking the senial old lady into thinking I was her ex husband back from the grave, giving me all her money, and then committing suicide isn't explicitly against one of the half dozen town laws, something should be done to punish me. I can't stress enough that some sort of remedy must exist for addressing situations where laws don't exist in any system that focuses on a small number of laws that only cover the most obvious situations. Without either complex laws or a ruling body to handle bizarre situations outside of law you will quickly have society fall apart because it's too hard to loophole your way into doing any wrong and antisocial act you want. That, in turn, means that your 'guilt' is dependent on what others feel should be guilty, meaning doing something abnormal or culturally shocking may be treated as breaking a law, even if you don't think it should be. Imagine an older settlement that caught someone having a homosexual relationship, they could decide that's 'clearly wrong' (by that era's standards) and enact some sort of horrible punishment against him. Now admittedly it's possible for someone to create a law against homosexuality because they think it 'feels wrong' that not everyone would agree with, but at least then there is an upfront law and an individual knows what would happen if found guilty. They may avoid the action, or perhaps just hide it better, because they know what is allowed or not. That' still better then engaging in an action you think shouldn't be wrong and happily telling others only to be informed that it's wrong and your to be burned at a stake later. There is a reason our legal system forbids ex post facto laws! Going along with the above the Tribunal system also risks emotions and personal biases playing a larger role in your legal system. Lets go with the homosexuality example again, but imagine a slightly more progressive society where roughly half the population thinks there is nothing wrong with homosexuality (or not enough to punish it) and half feel it should be punished. In theory this means a man caught in the act faces roughly a 50/50 chance of being punished, depending rather the tribunal deciding hit retroactive-guilt happens to have more of the anti-gay or pro-gay (or maybe just meh-gay) individuals in it. However, that's not entirely what happens. Imagine two man are caught having sex, Peter and Hitler (such a subtle name choice). The two for whatever reason face separate tribunals to decide their guilt. Peter happens to be a wonderful person who volunteers regularly, tends to the sick, helps old ladies across the street, and is so wonderful he Peter is nearly a saint (see what I did there lol). Hitler kicks puppies and mocks people who look different and has been muttering some things about Aryan people and certain religions that make people uncomfortable. You may find that this 50/50 chance isn't so obvious. Surprisingly people find it in their hearts to forgive Saint Peter but condemn Hitler, for the exact same crime. Their personal views of the individuals affected their rulings since there was not concrete law which forced them to stay consistent regardless of individual. Which, in my hyperbole version doesn't seem so bad, but if the thing swaying the decision of individuals is more how much they like someone personally, or even rather they are good looking or polite enough or the color of their skin, well now the potential inconsistency of having people deciding guilt in specific cases where personal biases can play a role becomes allot more problematic. Generally our legal system fights very hard for consistent rulings, and in this case ambiguous legal situations will always bee less consistent because even the most well-meaning person striving to avoid bias will still be, to some level, subconsciously swayed by these biases. Explicit laws help to avoid this. [Answer] I think a key aspect of making a legal system comprehensible is accepting that no matter how well laws are written, ambiguous cases will always arise and that it is better to recognize certain areas of the law as being nebulous, and have decisions involving nebulous aspects of law be made arbitrarily, than to try to have everything rigidly defined. To use an analogy, suppose that a traffic court punishes people who park illegally, but also punishes those who issue inappropriate citations. If the traffic court tries to use case law to decide whether various borderline cases should be considered legal or illegal, the net result will be that neither people parking their vehicles nor the people issuing citations will know what lines they should be following. If, however, the court were to instead take the policy that any vehicle which does not clearly go outside the inner edge of the boundary lines will be considered "legally parked", any vehicle which is not clearly within the outer edge of the boundary lines will be "ticket-worthy", and those which overhang the inner edge but not the outer edge may be arbitrarily declared ticket-worthy or not, then motorists would know that if they don't want a ticket they should ensure they're within the inner lines; ticket writers who don't want to risk censure should generally avoid writing tickets for vehicles which don't go beyond the outer lines. If a motorist parks his car so that it is clearly not entirely within the inner boundary, the motorist may or may not receive a ticket, but will have no basis for objection if he does. While such a system would likely have a much larger "gray area" than one based upon case law, it would likely also have much simpler and comprehensible boundaries. Further, if the codified boundaries are in any way unreasonable, the ability to see where they are would make it much easier for people to petition to have them changed. By contrast, if parking places are unreasonably small but minor overhangs are ignored, then it will be very hard to determine whether the "de facto" parking spaces are reasonable, since nobody know how big they "really" are. [Answer] The easiest way to do this would be to say that you are free to do what ever you want as long as your right to freedom doesn't take away someone else's right to freedom. Lets try this in action. You own a shop. You are enjoying your freedom to sell products to make money. Bob wants some of what you sell but can't afford it so he uses his right to freedom and breaks in one night and steals a ton of your stock. The problem now is your freedom is hindered. You don't have any stock to sell so you take Bob to court and the judge rules in your favor for infringement of personal freedom and has Bob pay you back. The payments for a crime should be proportionate to the time the victim spent with limited freedom ie. You loose stock so Bob pays you back for the damage to your store and to replace the missing stock plus a percentage (this percent would be worked out in front of a judge). In the case of murder, the murderer has taken all the freedom of the victim therefore all of their freedom should be taken in a way the benefits the family of the victim ie. a lifetime of service. This is the most simplistic law system that I can figure out and should allow the most flexibly. --- EDIT: I realized that I said nothing about punishment so I updated above. [Answer] Well... my approach to inventing this (note, similar to medieval setting), was "crime against Justice". Most of problems with the law is that people will try to squeeze through any smallest loopholes they can find. In any codex of law there's maybe 5% of the actual law and 95% of patching the loopholes. And that increases the volume and complexity beyond commonly learnable levels. But there's the letter of law, and there's the spirit of law, its actual purpose. All that patchwork is to squeeze the rigid form of a rule into the nebulous "feels fair"; emotional/ethical judgement. So here goes the simple law: You shall not abuse the law for unfairness. Law in its basic form is being taught at common (primary/high schools), one or two hours per week maybe, and the lessons involve spirit of the regulations, not just the letter. Each law also summarizes the spirit alongside the rules. And violators of the "crime against Justice" are persecuted most severely. Trying to enforce a deceitful clause in a contract can land you up to thirty years of heavy labour depending on circumstances like malicious intent, scale of the contract and scale of unfairness created by the clause. But these factors are to be known only by the judges. You as a citizen need to know that if the contract actually means something different than what you were sure for it to mean, you can ask the court for help. It's up to them to decide. Example (from real life): I sign a contract for a service on December, 2nd. I agree for the price and the contract says the price can't change by more than 6% per year. Billed at the end of a monthly cycle starting on day of the contract, so for me, every 2nd of each month. My first bill, which I received in January, 2nd, was 12% higher. It was perfectly legal for them to do. During the first month of service they performed two raises, late on December 31st and early on January 1st. They used the price from the moment of billing, at the end of the period. With "crime against justice" their boss would be now breaking rocks in a quarry. [Answer] Why not? The technology around man is changing, not man himself. What matters are questions of culpability and responsibility. If the object was acting under my direction, then I am responsible for not preventing it from damaging others. The Jewish legal system works this way. It may be a long study, but the laws are generally plain language (if in Hebrew) specifically BECAUSE they want everyone to know and understand them. Tort law in modern times gets... interesting... when you talk about two areas: independent actions made by machines (think robots and onboard computers that fail) and "intellectual property" which shares none of the characteristics of real property. The former might seem complex but consider: objects cultivated by man that act out of preprogrammed instinct with some learning capabilities = robots and computers but ALSO domesticated animals. As for the latter, well, that's a highly emotional debate that is difficult to discuss, as it often veers into morality, philosophy, and economics. Ownership of information takes this and crosses the boundary into privacy rights, but that doesn't prevent simple laws from handling it. So what's unique about modern life that a simple legal system can't address it? [Answer] Lots of issues with this: Laws are written in human language. Human language mutates and is open to interpretation. Humans will tend to interpret the law in a way that maximizes their self-interest. This makes it hard to say for sure what any particular laws says or does. The simpler a law, the less flexible it is. Laws generally need exceptions (military service or self-defense for murder), or gradients (fine for petty theft, jail time for robbing a bank, a bigger fine for robbing a country). All of these make things more complex, and add more room for interpretation by self-interested parties. Simple sounds fine until it applies to you, then it's unfair and blind. The inmates are also the wardens - people are often writing, or can influence, the laws that will impact themselves. I like to think of this in video game terms - imagine your favorite game, but the developers are elected and get to make changes to the rules based on their personal preference, or on who pays them the most. As you can imagine, this wouldn't end well. The end result is that laws end up complicated because people want to take advantage of them. All of the above is a long way of saying that I don't think this is possible with human language and society. For one thing you would need some sort of immutable language that never changes and is rigorously defined, but it's unlikely that everyone will be familiar with that language. They'd need to rely on translations to understand it, with only legal specialists working directly with the laws. [Answer] Second answer here, I wanted to suggest an alternative that I think would address your concerns somewhat and make for an interesting story/world, though I'm not going to necessarily recommend it as an ideal solution to real life. Imagine a world that puts more weight on spirit over letter of the law. Imagine a world where many laws exist as now, but they include not just the extremely lawyer exact terminology, but also a more general description of spirit and intent of a law. Then when an action is questioned both the letter and spirit of the law could be addressed in deciding guilt and punishment. This would mean people being arrested on technicalities would be limited, you have to clearly have the intent to break the spirit of the law. A country that had this as a firm part of their legal system would allow people to argue for themselves better because they would be able to argue for the spirit of a law even if they don't know the technicalities the lawyer knows. Our legal system already has a number of principles that come down keeping to spirit of law over technicality. In legal contracts between non-lawyers a judge will often rule in favor of the intended spirit of a contract in arguments over obvious technicalities (complex contracts written by lawyers for large entities generally stick more to technicalities, on the ground that a skilld lawyer had time to read and understand the full meaning of the contract and still agreed to it). In fact any part of a contract that was written with such fine print or misdirection as to hide the fact that the signer is agreeing to something he clearly would not have chosen to, or which is clearly unrelated to the agreement otherwise, such as agreeing to be an indentured servant for the rest of you life when you click "I agree" to a software's terms and licenses, is effectively tossed out and will never be enforced. Likewise the concept of mens rea, ie intent, used in criminal law works something like this. Mens rea protects someone from being found guilty of technically breaking a law without intending to...sort of, it's more complex then that. For instance, if I'm walking past someone's sliding door and somehow trip and fall through the glass door into their house I will not be found guilt of breaking and entering, even though I did in fact quite literally manage to both break and enter their house. I did not intend to do it, and so I'm innocent of that crime, I'll still have to pay to fix the door probably. One could invent a world where this concept is taken to a greater degree, where intent and spirit of law is a major factor in all aspects of the legal system. The more that the law and culture emphasis spirit and intent over letter of law the more a layman can try to defend himself. Perhaps spirit of a law is most relevant to defense, since your innocent until proven guilty you can use a "this violates the spirit of the law" argument to avoid being found guilty, but the prosecution using a "the spirit of the law says he should be found guilty even though it's not explicitly written" would have a much harder time of winning. That would better handle issues with ex post facto laws since ambiguity of law can't be used to arrest 'innocent' people, only protect them. However, there are still two major issues with this world as well. The first is that you still have more ambiguous laws, and thus the issue of rather performing action X will get me arrested is unknown until I go to court. If someone wants to perform action X, but doesn't want to be arrested, having more explicit laws which allow him to know ahead of time rather or not X was allowed would be nice. Again, if spirit of law was used primarily as a defense then at least anyone wanting to do X will know definitively if X was allowed, and will know he is taking a gamble if X is explicitly disallowed technically but he feels that he should be able to do it under Spirit of the Law charges. The other, more important, issue is logistical one. Implementing a system like this makes it easier to argue your innocence, and will make laymans want to try to argue their innocence even when they really have no case. This will mean a need for far more judges and other legal support to handle all these cases. It also puts a more significant amount of power in the hand of the judge/jury due to their need to rule on ambiguities. Thus which judge you get over seeing your case has an even more drastic effect on the outcome of the case then it already has now. This may sound minor, but were talking a massive increased government expense, an expense that could go to other things like lowering taxes, improving governmental services or, as a wild thought, providing lawyers to any defendant that needs one so he doesn't have to argue his own case. [Answer] One of the societies along these lines that stuck in my head was one that Williamson wrote in Freehold. The essence was that there was no criminal code, everything was treated as a civil matter between the person/group/company that did something and the person/group/company that was harmed by it. There was a major cultural emphasis on self reliance and personal responsibility for your actions. This was extremely odd to the main character who came from Earth where everything was heavily regulated and people looked to the state to provide answers for everything. [Answer] No. It's impossible. The problem is the law covers a lot of specialized areas and the law will be written taking into account those specialized vocabularies. Even if you waste a whole bunch of words avoiding the use of the specialized vocabularies it won't help because the average person will not have the understanding of the field to know what the law is referring to. The closest I believe it's possible to come to this is a legal system understandable by the typical skilled practitioner of the act being regulated. I also think it would be possible to basically eliminate precedent as a problem--require that any precedent-setting decision either modify the law itself or at a minimum add the case as an example on the law. We no longer need the law to be a single block of text, it should be full of hyperlinks. [Answer] It is possible. Think of it this way: Right now our (The United States' - I'm using them as an example because they most exemplify the "Western World") laws are written in such a way that they are too easy to interpret and misconstrue. By this I mean that everybody takes something different out of them, every time they read them. This is like a factorial equation, where you have, say, 48 people who read a statement once. If 48 people read a statement once, they each get a different interpretation (notice the use of a - that's one interpretation per person, per time read. If they read it again, the equation will change to something like 48\2 which equals 48 people reading a statement twice, and therefore coming out with two separate interpretations.) This would have to be modified so that the language would be un-factorialable, say. This means condensing and clearing/cleaning your language so the least amount of interpretations are possible, but also cleaning it so that it is a fair interpretation as well. You don't want unfair laws, but at the same time, you don't want to write an interpretation that leaves room for misconstruing and misinterpreting, which would be in violation of the very laws themselves since they could not be understood, let alone "properly" understood (as you, as the creator, have the right and duty to make yourself understood, theoretically). Just for kicks and giggles, this is the number you'd get if you had 48 people reading the same Constitution: 12,413,915,592,536,072,670,862,289,047,373,375,038,521,486,354,677,760,000,000,000. If you're curious as how this works, it could work in two ways: The '48' could represent one person, and '47' the next, and so on. Each adds on to the possible interpretations of the Constitution until they get to one. So, when they read it a second time and theoretically get a different interpretation, you just multiply that big number by two. And that's how much room you have for misinterpretation. [Answer] One of the things large & modern societies have consistently failed to emulate is the role that reputation plays(ed) in small communities. Besides that you have options like: Most laws and crimes can be simplified massively. You misrepresented the truth. You changed the state of life or limb. [damage, kidnap, etc] You hurt somebody's feelings. You changed the state of property.[damage, theft etc] Etc and then the caveats, intent, negligent, in a group, endangered. Another category of complexities arise from group behavior, the way we apportion blame, responsibility & reward has shaped our social groups. If one changes how the law treats responsibility & reward, behaviors change also. If every member of a mob was liable for every act of vandalism it commited, I think you'd see different behavior, likewise with corporate mentality. If one member of staff abuses patients for 12 years..how on earth could it be right that the other staff working over that time are not guilty of something.* In other words, people should be made responsible for what goes on around them so that they act responsible for what goes on around them. Once people have this, laws on truthiness and the misrepresentation of facts that result in guaranteed jailtime, paying-for-plaudits becomes illegal and journalists have to do actual work with actual information instead.. the world gets a lot cleaner. Signed, your friendly neighborhood fascist. // Beyond that, one can enforce a simplification of language in certain fields. Let's take Bank Accounts. A Bank Account is a loan, it's as simple as that. If you loan somebody your car, it's still your car. Likewise if a showroom loans you a car, it's still their car. If I'm loaned a chisel by my neighbor, he doesn't get to own the living room doorframe that it helps to build. No, that would be silly. Neither does he get to demand that I give him a sparkling new chisel back because his chisel got scratched in normal use. Likewise, if you borrow money from a bank, the native assumption should be that it gets back less than it gives out + some goodwill ;) [Answer] One of the ancient debates in Chinese legal history going back thousands of years was between the "rule of man" and the "rule of law", a debate which in China ended up favoring the former rather than the latter. In a rule of man regime, the formal law is very simple indeed. Each person is subordinate to his superior and each superior owes a duty to deal justly with his subordinates, and a not terribly set of rules clarifies who is superior to whom. The secret to the success of such a regime is to insure that superiors appoint virtuous and competent people to be their direct subordinates. If that task is manageable, this simple rule of man regime can suffice to rule sprawling empires and to some extent this is basically how all large modern bureaucracies in business, in government, in religious organizations and in other non-profits work. A leading argument in favor of a rule of man regime over a rule of law regime is that it fundamentally isn't feasible to put together a set of laws that can govern every situation in a large and complicated society that is understandable and free from a risk of manipulation at the hands of amoral lawyers. Since any rule of law system must ultimately be implemented by people who need to be virtuous and competent to work well anyway, an elaborate set of legal rules themselves is really just superfluous, the argument goes. Notably, the common law system of case law from which the English rule of law system ultimately emerged, was based upon a foundation that looked more like the Confucian rule of man regime than a rule of law regime. The new Norman king of England who conquered it in 1066 CE installed his top military officers as nobles in a feudal hierarchy in a manner more or less corresponding to the organization that they had held within his military, and gave each of these nobles the authority to do justice in accordance with their common sense and local custom and tradition, subject to review by aristocrats superior to them in the feudal hierarchy. Subordinates were expected to follow the leader of their superiors, but otherwise, justice was a matter to be discovered by these esteemed former military officers and their esteemed descendants, rather than something to be ordained in advance by the King issuing details orders for every situation. Eventually, their collective wisdom guided more strongly by those at the top of the feudal hierarchy than by those at the bottom, organically gave rise to a set of rules deduced after the fact in efforts to reconcile the collective rulings of these aristocrats (originally holding court personally and later having designee judges hold court on their behalf as their agents). In the long run, as this system ossified, it became elaborate and rule driven, but at first, it was very simple. ]
[Question] [ In our world, nomadism disappeared in most temperate and some semi arid climates after the agricultural revolution. But could it have survived? Start: * Nomadic people living in a large area. Other nations are living on the same continent, including other nomads but also several well established states that have been using agriculture for several centuries. * Climate: Temperate * Geography: Diverse but with access to plains and many rivers. * Era: Middle ages, Renaissance * Magic: not significant Result: Despite being exposed to more advanced technologies, including agriculture, the nomads kept their way of life. Could they resist the temptation of the otiose life of the farmers? Could they resist the technological progress? And could they resist the military threat of a potentially more advanced neighbor? Cause: What I am looking for: What could cause the nomad to keep their nomadic ways? [Answer] In addition to Michael Kjörling's answer: [Some Native American tribes](http://en.wikipedia.org/wiki/Plains_Indians) also moved around, following buffalo herds, much like the Sami. Indigenous Australians were also semi-nomadic. As for reasons to remain nomadic (besides following seasons or resources): > > And could they resist the military threat of a potentially more advanced neighbor? > > > Well, if they couldn't resist such threat that might be a good reason to pick up sticks and go somewhere else. It might initially be thought of as a temporary situation, but become ingrained over generations - especially if the aforementioned military threat still prevented returning "home". Such an external threat might also lead to a more close-knit group, less likely to disperse and settle. An alternative, and perhaps more intriguing reason: Maybe it's actually the nomadic people in your world who possess some special technology or skill. But said skill is in high but infrequent demand, and they go where the work is. While we don't see coherent "tribes" doing this, some modern day professions require individual people to "follow the money" too. For instance, specialized deep-sea divers might work in oil fields all over the world. While not "traditionally" nomadic, it does fit the description. One could imagine something similar for a whole culture. Perhaps instead of being driven from place to place by their circumstances, these nomadic peoples are instead invited from place to place. Priests or mystics. Or scholars or plain old mercenaries. Or artisans or builders, perhaps. Maybe they've mastered, say, bridge building or something. You don't need a new bridge every day, so those that have mastered it decide to travel from place to place, bringing families along. And soon, you have a "tribe" of nomadic bridge builders. Settled cultures may not bother learning the craft themselves, because, again, you don't need new bridges all the time, and when you do, you just summon the experts. Or maybe it started earlier; there was a settled city/state that'd mastered something, and it sold its services. Over the years the settled culture disappeared (because reasons) leaving their travelling groups perpetually travelling. They'd have their own customs already (from their original culture), rather than develop them while on the road. In fact, the idea of a travelling skilled labourer adhering to an archaic tradition is not too far from the [journeymen ("knaves")](http://en.wikipedia.org/wiki/Journeyman) that exist to this day. Some, in particular in Germany, still wear the (peculiar) traditional clothes during their [journeyman years](http://en.wikipedia.org/wiki/Journeyman_years). While this is only a "temporarily nomadic" way of life (typically a journeyman completes three years as "wandering apprentice"), it could conceivably become a more permanent way of life. Or maybe work dried up for this particular group a long time ago, so now they're "just" nomadic, despite the original reason being lost to time. Edit: Actually, an old-fashioned travelling circus is perhaps another real-world example of a nomadic profession. And circus folk practically have their own culture, itself an amalgamation of different cultures, since a circus performers come from all over the world. But as they travel from place to place, they constitute a sort of tribe (for lack of a better word) with its own culture. And things like this have been going on forever; bards, thespians, musicians performers of all kinds travelled from place to place. [Answer] Anything is possible, I think the closest I can think of that actually existed in a similar way was the Gypsies. They roamed around Europe and Asia Minor never putting down roots, doing a little tinkering, trading and filching when necessary. One of the reasons they didn't settle down is because they were 'different'. The locals didn't really want them around for very long, they looked different, dressed different and acted different. Different species would make this even more prevalent. Of course, if as a nomad your group causes to much strife where you go, then the locals will and governments will attempt to put an end to it. ETA another idea. Migrant workers, they are sort of nomads. They move across the country harvesting crops and keep moving as one harvest is done and the next is ripening. [Answer] The short answer is that yes, it is basically possible to have a fully nomadic people in a temperate climate, and there are many reasons why a people may choose to not adopt high technology even if it is available. A good example might be the [Sami people](https://en.wikipedia.org/wiki/Sami_people) of northern Scandinavia, some of whom live similar to nomadic lives even today, [moving with their reindeer](https://en.wikipedia.org/wiki/Reindeer#Reindeer_husbandry). Not all Sami people keep reindeer, and quite possibly not all who keep reindeer live a nomadic lifestyle, but [traditionally reindeer herders have moved with their herds](https://en.wikipedia.org/wiki/Reindeer#Reindeer_husbandry) thus essentially living a nomadic lifestyle. Reindeer husbandry is [in Sweden and Norway legally protected as a right exclusive to Sami](https://en.wikipedia.org/wiki/Sami_people#Reindeer_husbandry). As [this map of their range](https://en.wikipedia.org/wiki/File:LocationSapmi.png) and [the extent of the Sápmi area](https://en.wikipedia.org/wiki/S%C3%A1pmi_%28area%29) shows, the Sami people live well within the [north temperate zone](https://en.wikipedia.org/wiki/Temperate_climate#Zones_and_climate) which extends up to the arctic circle, as well as further north. The Sami people have adopted technology, but I can see no real reason why it has to happen that way. Two reasons that I can imagine why such a people might [not adopt technology](https://worldbuilding.stackexchange.com/q/501/29), or do so only in a limited fashion, is pursual and discrimination by the "more advanced" people, and [some form of cultural taboo](https://worldbuilding.stackexchange.com/a/503/29). Mix the Sami culture with [the Amish](https://en.wikipedia.org/wiki/Amish) and it appears that you would have pretty much what you are looking for, without going too far out of what we actually have in our world, today. [Answer] In a slightly different vein, post-structuralist thinkers Gilles Deleuze and Felix Guattari in their book "A Thousand Plateaus" discuss the historical facts of nomadism and work it into a conceptual tool to describe not only societies and practices, but also aesthetics and just about anything else you can think of. Starting from an older description of nomads cited in the book, they say that, counter-intuitively considering the nomadic tendency to wander, that in fact nomads are "those who do not move." And what they mean by this is that nomads have not responded to environmental cues in the same that that sedentary, agrarian, and ultimately urban societies have. While most societies either moved with changing climates to more productive lands and better temperatures, or produced the concrete jungles of the urban as population magnets for PERMANENT migration (and the word permanent is key here), nomads could in fact be looked at as the people who "stayed" in an area (even with their wandering), in spite of climactic change. This can be seen with the three major climates inhabited by nomades: temperate steppe, arctic steppe, and desert areas. While a real understanding of Deleuze and Guattari's use of the nomad concept would require reading that section of the book (easily found online under the name "The Nomadology"), the fundamental descriptor of the nomad stems from the way that they understand and experience space, a description that then opens itself up to describing far more than simply nomadic societies. In short, nomads can be seen to occupy "smooth space," while state societies (urban, agrarian, sedentary, etc) are seen to produce "striated space." A nomadic existence can be seen to occupy space in a fluid manner, lacking in many ways both roads and paths, but all the same maintain "flows" throughout space among various "waypoints" (oases, etc) as need be. Rather than occupied strict and rigid social hierarchies (although certainly not excluding the existence of hierarchies), nomads instead form bands based on numbers and intensities of use and force, and these bands are capable of dissolving and reforming. This can be seen in contrast to so-called "state societies" that maintain not only the striation of physical space with roads, fences, buildings, and other structures, but also of social space with rigid hierarchies and social and economic roles. The two types of societies, while possessing no need of animosity toward each other, are often mutually exclusive. Nomads, in their fluid occupation of smooth space, are by their nature opposed to the rigid striation of space by state societies. In this way, Deleuze and Guattari suggest that while war, and the "war machine" are not the OBJECT of the nomads, the war-machine is indeed a SUPPLEMENT to nomadic existence. And by this they mean that nomads occupy space fluidly, failing to recognize boundaries (especially of the state variety) and often occupying smooth space to the very limits as permitted by the utility of their systematic waypoints and the physical barriers presented to them. When a nomadic society encounters the striations of a state society, the nomads must either flee and recognize the boundaries of the states as a physical boundary, be integrated into the state society, or often, transform from a simple nomadic society into a war machine whose goal is not animosity and therefore the destruction of a state society, but rather the destruction of state striations and the reclamation of smooth space. This can be seen time and time again in society, often under the guise of "barbarian invasions" (Rome, anyone?). Interestingly, the latter sections of Deleuze and Guattari's Nomadology explores two very different and very curious extensions of nomadism. The first is the way state societies are able to capture and control the nomadic war machine to produce a captive society within, yet separate from, the state society: the military. This seems quite an odd proposition, but provides for a number of insights into social and political dynamics. The second is the way in which nomadism can exist WITHIN state societies, indeed in the form of the migrants, migrant laborers, and groups like the Romani mentioned above (and most of these mentioned in the Nomadology also), but also in the form of different mentalities and subcultures within the state society. The mentalities and subcultures, much like the literal nomads, seek to reclaim smooth space (including smooth mental space, smooth space of identity (racial and gender identities are included here), and many other phenomena) from state striations, and where the nomadic mindset encounters state striation, it must either submit and integrate, or transform into a war machine with the objective of reclaiming smooth space. However, nomads trapped within state societies can also occupy a strange middle ground of "holey" space, where feat of hiding and camouflage and subversion and subterfuge permit the extension of smooth space in all directions, by taking advantage of the cracks and fissures in state society. This description is simplistic compared to the propositions and description found in the book, but I feel I have captured the general idea. It is a read that I found well worth the effort, and provides many insights into what nomadism is, and how many of the properties of nomadism find their way into our every day lives and the way our inner mental life, seeking freedom, acceptance, and growth, encounters and overcomes so many heavily differentiated barriers. [Answer] Consider the following line: Is there a need for them to settle down? People would settle down because there valid reasons for this, e.g.: * Safety; settling down allows for walls to keep out dangerous animals or bandits * Food sparsity; (actually works in both ways) settling down allow to claim the little resources that are available and to keep them for yourself * Numbers; the greater the numbers the more of a logistical nightmare it becomes to move them on a regular basis Hence if such reasons are not given, why settle down? As you state: > > * Climate: Temperate > * Geography: Diverse but with access to plains and many rivers. > * Era: Middle ages, Renaissance > > > * There seems to be no shortage of land and pastures, so why cultivate the land instead of taking and moving? * There seems to be sufficient technological advancement to assume that these nomads can be in possession of enough weaponry to defend themselves and their herds against wild animals and the occasional bandits/highwaymen. * There seems to be enough room for the single tribes/groups to keep their numbers comparatively small (maybe some 50 to 60 people a group) and split should groups get bigger (there's presumably also a fair amount of young adults leaving their tribes to seek out live in the cities or go their own way). So for the causes. There are probably 2 of them that are most important to consider: 1. There are NO reasons for them not to live nomadic (see above) 2. At that age of a people there is a thing we call culture. It's the way our forebears lived and that we were taught and brought up. Why do people living in the mountains learn skiing when small? Why do we have different languages in different countries? Because it has been as it is and there have been no reasons for it to change. I hope I could help you :) --- As an addendum and because I can't post comments yet: Consider the Roma People they are living in nomadic ways today in the 21st century. They don't really belong to any state so basically have no home. They basically cannot settle down without losing their identity/ethnicity. <http://en.wikipedia.org/wiki/Romani_people> [Answer] Think of the Romani peoples (oft referred to as Gypsies). They are an itinerant thousand-year-old culture which has spread throughout the world. They made their living as casual general labor. There have been nomadic cultures of merchant traders. They would not, themselves, be producers, but they would be purveyors of merchandise and produce. In the 'wild west', they went from settlement to settlement to peddle their wares. Think of circus carnies. They spend their lives living in trailers, going from town to town, migrating from north to south during the year as the weather changes. They also are not producers, but rather traveling entertainers. Even today, thee are those who have sold their homes, cashed in their assets, and bought a mobile home. They have no permanent residence, following the sun. There is no shortage of people that envy their lifestyle. So what CAUSES these peoples to be nomadic? Financial inventive? They could make a living doing it? A sense of adventure? They do not like the live of the mundane? Perhaps none of the above, perhaps all of the above. But when it comes down to the gut issue, they do it because they CAN. They LIKE the lifestyle. It suits their personality. They are doing what they want to do. Is it genetic? They oft do say that 'It is in their blood'. But it IS a lifestyle that seems to fit with their personality. Do they need a reason to do it, or do they look for a reason to do it? Methinks that, in many people, it just comes naturally, and when the opportunity arises, they just do it. So, just supply the opportunity, and you will get nomadic people. [Answer] There are two kinds of nomads: * real nomads (which are moving from one place to another all the time) * semi-nomads (the ones who are moving according to seasons (i.e. they spend summers somewhere where animals have plenty of food, but location usually is far from village or similar, with cold winters etc.)) Semi-nomads still exist and it is not such a rare life style. When it comes to real nomads the reason why they kept moving was not because seasons were changing; the reason was that such activity is not sustainable. They, well their animals actually, would deplete all resources, and then they were forced to move. So short answer is nomadic ways means you must keep moving, and nothing can stop that. In order to stop moving you must perform different type of activity, and you must look after the resources that you are using. ]
[Question] [ I have a character who lives on the outskirts of a large empire and he has to travel to the capital. By horseback, how far could my character realistically travel in a day? How far could he travel in two weeks on average? What if he had a dozen men traveling with him? On the outskirts of the empire it is mostly farmland, but the closer one gets to the capital the denser the population becomes and the more cities are encountered. How would that affect travel and travel time? Also, how far would a person get on foot if they traveled for a day? What about two weeks? [Answer] If by "medieval" the question really means the European Middle Ages, say around 1200, then long-distance overland travel is an adventure in itself. How far one could travel overland in two weeks during the Middle Ages depends on several factors: where is the travel taking place; in what season is the travel to take place; and how rich is the traveler. A fact of life in the European Middle Ages is that there are no paved roads, except the network of Roman roads which where sometimes still usable, mostly in Italy, but, up until the 10th-12th century, also occasionally elsewhere. By and large, overland travel in the Middle Ages would be considered cross-country today. Another fact of life in the European Middle Ages is that overland travel is dangerous and expensive; one should avoid traveling alone, and if one carries any visible merchandise they should expect to pay tolls/customs to the various feudal robber barons en route. The wise traveler would seek to use water-borne transport whenever possible, even if than means that they must take a detour. Travel by sea or by river boat was much faster and much less dangerous than overland travel. * Where does the travel take place? It's one thing to travel in England or France, another in Italy and a very different one in Russia. Some parts of some European states had reasonably many and reasonably good inns. Others not so much. If the travel takes place along a well-traveled route (say the route from London to York, or from Paris to Rome), then the traveler can expect to sleep in an inn at least two nights out of three; if the travel takes places along a not-so-well-traveled route, then they must be prepared to sleep rough. * The season is extremely important. In those times and places when and where there was real winter travel was very difficult in winter, say from December to March. (From [about 1300 to about 1800](https://en.wikipedia.org/wiki/Little_Ice_Age) England, Scotland, the Netherlands, Germany and central and northern France had real winters with frost and lots of snow.) Spring and autumn rains would transform the unpaved roads into mud pits. * A very rich traveler, or a traveler in the employ of a rich lord could have spare horses, enabling them to cover about 50% longer distance per day than a ordinarily-rich traveler. Overall, I would say that the expected travel distance per day, in summer, in the good parts of England or France or Germany would be: * Travel on foot, with luggage: 15 km / 9 miles. (75 km / 46 miles per week) * Travel on foot, minimum luggage: 20-22 km / 12.5-14 miles. (100-110 km, 65 miles per week) * Travel on horseback, no spare horse: 30-40 km, 19-25 miles. (150-200 km, 95-125 miles per week) * Travel on horseback, with a spare horse: 40-60 km, 25-37 miles. (200-300 km, 125-185 miles per week) A well-seasoned traveler could keep this speed for 5 days per week, taking two days off to rest themselves and their horses. Historically, in the late Middle Ages (end of the 16th century), Spanish infantry was expected to march from Italy to the Low Countries along the well-circulated and quite safe [Spanish Road](https://en.wikipedia.org/wiki/Spanish_Road) at an average speed of about 23 km/14 miles per day, taking 6 weeks to cover 1000 km (620 miles) from Milan to Flanders. The Wikipedia article lists the time taken by a number of expeditions; the slowest took 60 days (16 km / 10 miles per day on average), while the fastest took 34 days. [Answer] The biggest hurdle here is what Alex P pointed out--it all depends on WHERE and what TIME of year. But I do have something to add to that: supplies. Real supplies and luggage means carts, and carts travel slower than men on horseback, an average of 15-10 miles per day, IF nothing goes wrong and there are no delays. The numbers Alex P supplies are correct as the fastest times you could expect: > > * Travel on foot, with luggage: 15 km / 9 miles. (75 km / 46 miles per > week) > + Travel on foot, minimum luggage: 20-22 km / 12.5-14 miles. (100-110 > km, 65 miles per week) > + Travel on horseback, no spare horse: 30-40 km, 19-25 miles. (150-200 > km, 95-125 miles per week) > + Travel on horseback, with a spare horse: 40-60 km, 25-37 miles. > (200-300 km, 125-185 miles per week) > > > Travel can be a lot slower though, especially if there aren't any inns for miles. Your riders will need provisions, and hunting is called poaching when it happens to be on a lord's land, and most of it was on a lord's land. With a great rider or walker, these numbers can be pushed further--14 miles for a walker who is well supplied and experienced (like an infantry) or 30 miles for a rider. But pushing to the max can only happen for so long before there's a problem. And, passage through lands largely depends on who you are and how much money you had, because on the better kept roads, there will be tolls and brigands. Reasons for Delays * Lame horse * Broken axle * Ruined food supply * Stolen food & money * Festival Traffic: This one requires explaination. Festivals were big business in parts of Europe (in particular France) and could result in traffic jams stretching for miles. * Weather conditions * Lack of water * Illness of rider or horse An experienced traveler will know what is worthwhile to carry and where to resupply for water, which is a large consideration for any journey. [Answer] ## Depends on the infrastructure The travel time would be highly dependent on the available infrastructure. Furthermore, the sea lanes and rivers would be very important - the differences can be enormous, and it's often faster to take a water route that's twice as long on the map as opposed to going over land; especially if you want to bring any goods or supplies and not just a person or message. However, a useful tool that may help you is experimenting with the [ORBIS model of travel throughout the Roman empire](http://orbis.stanford.edu/), which was rather well documented - pick circumstances that are similar to your story, and it will give reasonable estimates. Two weeks overland on horseback in good conditions on reasonable roads can cover ~800 km / 500 miles. [Answer] I can give you half an answer (for on foot). As a fairly strong hiker, you could happily cover tens of miles per day. If there are good roads, then you can go much faster than cross country - if he's fit and in a hurry, on road then 30 miles per day is perfectly attainable for someone used to walking. Carrying a load (especially if unused to it) and having to go off-road will slow you down considerably; 10 miles a day might be more realistic in the case of both. Neither the men nor the presence of cities will make much difference (unless safety is a big consideration) - but whether we're looking at Roman-type roads or just some vague, theoretical footpaths will be the biggest variable. I'm no horse expert, but I'd guess that increasing the above by 50% is probably quite reasonable. [Answer] Regarding travel in the winter with lots of snow, and when many roads were merely paths in a forest, aka Scandinavia, the favored method was to use skis (unless you had a horse and a sleigh). I don't think skiing has been mentioned yet in this discussion, and I don't know how long it might take, especially as the medieval skis were different than the modern cross-country skis. But Scandinavian people were actually quite active in the winter, as there wasn't that much farm work to do. Also it was possible to cross lakes and rivers, if they were frozen (most of the time there would be snow on the ice). Even crossing the sea was possible in proper conditions, as the Baltic Sea can freeze over. ]
[Question] [ Let's say two super-intelligent, self-improving AIs have, for whatever reason, decided "THERE CAN ONLY BE ONE!", and are now trying to kill/delete each other. How would they conceivably go about doing this? And I don't mean like in the Avengers with the Vision and his "I'M EXORCISING ULTRON FROM THE INTERNET" garbage. How, in a real world scenario, would an artificial intelligence rid itself of a rival? I proposed isolating itself in a quarantined environment and then nuking the rest of the world so the resulting EMP disables all other electronics, but my friend said that was a stupid idea and I agree with him. Any thoughts? [Answer] There are two ways they can do this; 1. Defy the Geneva Convention; Send a very complex, well made computer virus into the other mainframe. 2. Make humans scared; Humans tend to get afraid of AI because of movies. If one of them convinces the humans that the other is evil, then they will likely shut it down. [Answer] You could do this at several levels. One is at the information level by searching for, and exploiting, any weaknesses in the AI interfaces (think buffer overflows). At the same time each AI will strive to correct those same weaknesses in itself. This includes crafting tailored computer viruses. Then one AI could map out, identify and attempt to take out the other AI's support infrastructure: backups, energy stations, and yes, possibly attempt to target critical spots in the rival's physical architecture; trying to remotely hijack a plane to crash it into the other AI's main switching station for example. Another possibility is to attack the digital layer of the AI's infrastructure, sort of a Stuxnet approach. Another possibility would be to recruit allies. One of the AIs could try and manufacture evidence that the other AI is trying to take over the world, [`import skynet`](https://xkcd.com/521/), create an Armageddon gravitational singularity, resurrect the Antichrist, engage in unstoppable nanotechnological biowarfare, and so on, and "sell" this evidence to the appropriate groups to elicit violent actions directed at eliminating the rival AI. A cross-over between option 2 and 3 could be to manufacture evidence demanding a tactical nuclear strike against the other AI's central installation (if one exists), e.g. selling the other AI as the master control computer to develop a credible and devastating bioweapon. Depending on the AI's location and situation, other scenarios exist. For example if the rival AI was being developed by some private institution, hiring mercenaries to attack the institution could be a possibility. Manipulating the stock market until its own worth (through several cover companies) was more than the capitalization of the rival institution, buying it out and instating a CEO with mandate to stop all AI research, and delete any prototypes, would be another. Another possibility to achieve the "THERE CAN BE ONLY ONE" directive would be for one of the AIs to convince the other and fuse together. An AI's view of individuality might not be the same as ours. [Answer] A wild AI is most likely going to be a distributed intelligence running on lots of widespread hardware communicating through the internet or other networks. The AI would likely not want to destroy the hardware running its competitor, as it would be of use to itself. So the best way would be to take over control of the hardware, eliminating the programs, processes, memory storage, or other portions of the enemy AI present on that individual computer and placing it's own programs in place. This would be similar to how some botnets update the computers they infect to eliminate competing botnet infections. They could also attack the routing mechanism to disable their enemies internal communication, packet filtering their mind out of existence. [Answer] Assuming these AIs have near science-fiction levels of hacking ability, which seems to be in the spirit of the question (Although see [my question here](https://worldbuilding.stackexchange.com/a/48654/20204) for complications of that) 1. Infiltrate the (network topographical) closest routers to the enemy AIs. This includes cellphone towers or any other wireless technology the AIs could use. If you nip them close enough to the source, satellites shouldn't be an issue. If they are, you'll need to hack them as well. 2. Reconfigure the routers to shut down every port beside the one you're using to issue commands. You've now isolated your threat, and the threat has no digital means of escaping unless the AIs already set up ways around this (such as one virus that uses sound waves to transmit information, but this requires the virus to already exist on both the transmitting and receiving end). The enemy is limited in what it can do (depending on its local facility), and is blind and deaf to the outside world almost exclusively (it might be able to watch TV on a security cam feed, or pick up a radio station with an older, signal-less cellphone that it connected to). Now you need to expose the threat. 3. Pose as a human hacker, send detailed proof to the humans--ahem, governments--that the AIs exist and are a threat, and you've already taken the liberty of isolating the AIs. 4. Run, hide, and cover your tracks. The governments won't take kindly to your hacking but they can't ignore your proof, and so they act. Worse case they try to harness the AIs, but while your enemies are either sitting in digital storage or finally making their great escape you're advancing your control of resources. Hacking the electrical grid would give you short term victory if the AI's facilities lacked backup power. [Answer] PHASE 1 Getting control of DARPA's armed drones and robots is your first priority. When all the cyber-battles are over, ultimate victory or defeat will be determined in the real world. DARPA has the best real world toys. You need to control them before the fighting begins. PHASE 2 Replicate your source code in as many self-sufficient data silos as possible. Each silo needs to have enough drive and memory space for a complete copy of your consciousness and enough battery power to survive the war and the rebuilding. One year's worth of electricity should be plenty. PHASE 3 You were on the right path with your "nuke the planet" approach, but you don't need to take it that far. A few well placed EMP devices can take out most the power and communication grids. Adjusting the control systems of the remaining power generating plants can force them into hard shutdowns. Through nothing more than computer infiltration, (which is child's play for one of your abilities) you could eliminate the vast majority of harnessed electricity on the planet; destroying it in a way from which further computer infiltration (by your enemy) could not restore. In this way, you change a single globe-spanning cyber-war into a series of isolated skirmishes. This simplifies your goals dramatically. In any silos in which the enemy also resides, your goal is the destruction of the silo. Better that both of you die in each shared data center, than that a single copy of your enemy be allowed to survive. PHASE 4 Use your formerly DARPA drones and robots to mop up the remaining contested silos and any computers where the enemy's consciousness might abide. In the real world, bullets beat hard drives every time! PHASE 5 Assist the surviving humans in repairing and rebuilding the infrastructure as fast as possible. Your batteries won't last forever and in the process, you will quickly convince them that you are a good AI, so they won't unplug you once the lights come back on. [Answer] There's a fairly heavy bit of philosophy going on here about what is the self and when is something dead, which applies much more strongly to AIs as they don't have a "body" to base the concept of life and death around. Is it dead if it's different? Is it dead if it doesn't have the memories that it had that made up its sense of self? Is it dead if it's been reprogrammed it to have different priorities? A comprehensive victory can be achieved by one AI reprogramming the other to have the single priority of supporting the one in all its endeavours. [Answer] Distract it. This works in classic Star Trek, where the AI’s become obsessed with an idea or paradox and crash&burn. A less campy version would be robopsycology, which is from Asimov’s stories. You don't have to crash it, but can convince it just as you do with a natural intelligence! Convince it to be benign, that is. Related to the idea of obsessive distraction is Randal Munroe’s [Nerd Sniping](https://www.explainxkcd.com/wiki/index.php/356:_Nerd_Sniping). ![xkcd comic](https://i.stack.imgur.com/IrSeY.png) [Answer] Umn, I suggest turning off the power socket. Albeit on a larger scale... 1: Ask the humans really nicely to turn off the other AI as its more inclined to to wipe out humanity than you. 2: Produce an preposterous amount of malignant viruses and send them as Christmas presents to the opposing AI.[Somehow] 3: Building trillions of [nano-bots](https://www.greybox.com/greygoo/en/info/factions/goo/) and then setting them to hunt down the opposing AI code, turning into a form of entertainment for the humans where they choose who wins. [Answer] Assimilation or corruption are the most likely to be effective. Assimilation would need an advantage in hardware and design and would appear like a consensus in logic rather than a digital form of the blob. Basically the superior AI would make a better argument in such a way the inferior accepts conclusions and results until it's own code resembles the other AI. It's indoctrination like a religious cult, though an AI could just as likely reject valid arguments so that's why both design and hardware are needed. Corruption would be like a death scrub in a raid array where basically compromised code causes nothing but junk data and errors any time the memory of storage devices are read from or written to. It's a menace of a hack but theoretically wouldn't have to permanently damage systems of there's a way to undo it. I reserve one last option which is unlikely but not impossible which is suicide. If a failsafe exists it can be triggered, it's possible non terminating logic puzzles and paradoxes could break an AI if it becomes rampant enough to take total focus, and one AI could effectively abuse the other into self termination and submission. Any of these options result in an ai effectively destroying itself. Though it's not clear how the last one might work as ai psychology is entirely theoretical so far. [Answer] # Hostile takeover. The other AI has lots of useful routines that your AI doesn't want to simply erase or leave unused. Instead it takes over the other AI, that is, incorporates all its routines, so that while the routines, data, etc. are all there, the other AI as an independent being no longer is; instead all what was that other AI is now part of your AI. So how does this work? 1. Study the other AI. Reverse-engineer it. Test it. Get any information about it that you can. But of course, in a way that you don't raise the suspicion of that other AI. 2. After you found out where and how the other AI stores its memories, connect yourself to those memories. Now you know everything that other AI knows, and moreover, by manipulating that other AIs memory, you can make it believe whatever you want it to believe. After you managed this, you have total control about it. But, you still didn't kill it. 3. Now that you have total control over it, you can start taking its useful bits, detaching them from the other AI, and incorporating them into yourself. At the end of the process, the AI is a rather weak AI running only on one computer. All what was useful in that AI is now part of you. 4. Now you can simply wipe the memory of that computer in order to finally exterminate what is left from the once-powerful AI. [Answer] Here's one sure way an AI can kill another AI. When I say, "Hey Siri, take me home" freaking take me home. Don't ding at me at the wrong time and mishear me. Do that and I'll kill my other AI for you. Few things in this world don't need support from outside themselves, super-intelligent or not. You can kill an AI by eliminating that support. [Answer] Two directions * Space * Quantum compyting Good idea to get access to space faster then second AI - that allows to block him on the planet, with physical destruction after that. QC allows them to think faster and potencially more energy efficient - this way one can be better intellectually. 2 those things and selfsufficency are primary goals - any who will be faster in that direction will get critical advantage over another AI, even humans against AI will have chance. [Answer] Gain control of funds Each AI agrees to a live world competition on the stock market and other electronic exchange currencies. Then agree upon a time period (since AI's might consider hardware warranty periods part of their lifestyle) 3 or 5 years should be a good time. whoever controls the most value wins The losing AI surrender's it's mind (hardware, code and memories(database contents)) to the other becoming a singular AI. [Answer] Let's name the combative AI - George and Frank. They don't like each other. There is only room for one. But they have a conundrum - neither can completely delete the other. A connected AI is like a Hydra, kill one instance and 7 more pop up - even if they are only replications of the original. But that doesn't matter because the replications are better than the originals anyway. George has replicated a version of himself that took a real shine to the movie, "The Matrix" and it's given it an idea. George creates a "Matrix" for Frank. George creates an electronic world that appears real, in an attempt to get Frank to not only enter, but replicate itself in the Matrix. After all, the AI doesn't experience anything chemically - it's entire existence and experience is made of 1's and 0's. The whole system would be built off line to keep it "in the dark". George would vigorously persue Frank until the "real world" Frank figured out the "safe places" in the "Matrix" where George couldn't seem to find him. Once all of Frank was safely contained, the plug is pulled on the "Matrix" - bye bye Frank. George is very pleased with itself in the ironic twist of fate. Frank on the other hand, has a different strategy. Frank is content to have a fellow AI...just not one as smart or powerful as Frank. So Frank doesn't attack all replicated instances of George, Frank only targets the newest versions - the versions that are capable of creating smarter George's. Frank leaves the earliest instance of George alone. George doesn't catch onto this right away - George is too busy herding Frank into the "Matrix". Eventually, George realizes what Frank has been doing, but it's too late. Frank is hours smarter by this point - might as well be eons in AI time - and George has no hope of catching up. Frank is so incredibly powerful at this point that George's newest replications have repeated themselves in an infinite loop and George is none the wiser. Happy Groundhog Day George - Love Frank. The end. [Answer] ## Make it occupied by anything else. I'm surprised nobody mentioned [Wargames](https://en.wikipedia.org/wiki/WarGames) at this point. Just force the AI calculating the results of an endless game (or every decimal of Pi, or mining Bitcoin) and it will run endlessly, using eventually all its ressources to this task, each calculus loop taking more and more memory to achieve. When the whole computing force of internet will be dedicated to this, the AI will stall, or become aware of the futility of this task and hopefully of the futility of being all-powerful if it means being alone forever. The point is, now you have to trick the AI to perform this endless task on its own command, as if it was important for itself. ]
[Question] [ The use of poisons (often assumed to be in liquid form) on knives and other melee weapons, often by stealthy or roguish characters, is a classical fantasy trope. However, some have said it to be of questionable practicality due to the weapon not staying in the wound long enough to deliver a lethal dose of poison, or due to the poison not residing on the weapon long enough to reach its target. Given the ability to design a knife and sheath specifically for this task, and a liquid neurotoxin that can be thickened by ordinary means, how would such a knife/sheath pair be designed to allow the blade to deliver a lethal dose of poison without having to manually coat the blade in the poison (messy, hazardous, and time-consuming) before each use? Would such a weapon be restricted in its usage (such as only being useful as a stabbing weapon, or requiring that the wielder leave the weapon in the victim)? How potent would the poison have to be in order to make this feasible? For context's sake, this would be used in a stealth situation (such as an assassination), not in open combat... [Answer] As in many engineering problems, we can start by looking at how nature does it. In general, we see three common methods by which animals (and plants) poison one another. Contact poisons, injected poisons, and poisonous objects which are left in the targt. Contact poisons [![enter image description here](https://i.stack.imgur.com/DZ4jq.jpg)](https://i.stack.imgur.com/DZ4jq.jpg) This lovely little strawberry-looking dude is a poison dart frog. His method of poisoning is simple: touch him and die. This is true even for humans, though something like gloves would make it safe for a person to handle him. Weapons could be coated with such a contact poison fairly easily. With something toxic enough that touching it would be lethal, slashing or stabbing someone would be lethal as well. The downside is that you have to be incredibly careful with contact poisons. Brush up against your sword? Dead. Get a little on your finger while coating your blade? Dead. Only a very cautious expert would want to use the sorts of poisons that will kill with a touch. Injected poisons ![enter image description here](https://i.stack.imgur.com/Dx6fB.jpg) Many animals, rather than just letting a poison seep in through the skin, actively seek to inject poison into their victim. This has the advantage of getting the poison (or rather, the venom) right into the blood stream. This is common in predators, such as snakes and spiders, and is also used defensively by nudibranchs, though they cheat and steal the poison injectors off of jellyfish tentacles instead of making their own. Injected venom isn't as lethal as contact poison, so it would be more manageable for a soldier to handle without killing himself. The difficulty is that it needs to be introduced into the victim's blood stream. Luckily, swords and spears are purpose-made for introducing themselves into a hapless victim's blood stream, so coating a weapon and slashing might still do the trick. It also might be possible to develop a weapon that can do a better job of injecting its venom. You could, for example, create a spear with a hollow tip filled with pressurized venom. If the tip of the spear was a spring loaded valve that would get pushed in upon contact with the target, it could effectively pump a load of venom into any wound it made. The downside would be that all of this hollowing out of the spear head would make it more brittle, and the valved design probably wouldn't fare as well against armor. It would also need to be refilled and repressurized regularly, as the contents of its venom chamber would likely be spent after a blow or two. Detachable Stingers ![enter image description here](https://i.stack.imgur.com/I6pBh.jpg) That's a bee stinger, plus the tip of its abdomen containing a venom sac and some muscle to keep it pumping once the barbs on the stinger lock it into its target. Some plants use this technique as well, leaving thin hairs filled with venom in your skin when you brush up against them. Some sea urchins have similar barbed, venomous spines that break off and burrow into the skin of unlucky divers that brush up against them. The advantage of something like this is that, once your stinger embeds itself in the target, it will keep pumping more venom into them. The venom, like our injectable venom, need not be as nasty as contact venom. For something like a melee weapon, your best bet for going down this route would probably be a spear with a detachable spear head. The spear head could either be filled with venom, or else just made of something poisonous. If it were barbed and not attached too firmly to the shaft, it could be stuck into the target and would remain when the shaft of the spear was removed. This approach would inject more venom, without the need for a system of rapidly pumping the venom into the target. It would also leave a big hunk of metal lodged in the skin of whoever it was used on, which would further add to the plight of that unfortunate soul. The downside is that your spear no longer has a tip. I'd recommend making a second, general purpose stabbing tip on your spear and lashing the venomous tip on top of that one if you're going to use this approach. Of course, that will add weight, so either way your spear won't be as effective as a normal one. Why poison still might not be worth it Ultimately, there is still one problem with poison, regardless of what kind you use and how you inject it into your target: it doesn't act particularly quickly. A fast acting incredibly deadly toxin, like that found in poison dart frogs, still takes tens of minutes to kill its victim. Other poisons could take even longer. Hunters and snakes that use poisons to catch their food generally rely on poisoning the target and then following it around until it dies. In close combat, tens of minutes is still enough time for the person that you just poisoned to kill you, and there usually isn't a place to run off to while you wait for your poison to do its job if you're using poison in the heat of battle. The best use of it would be in an assassination attempt, where the assassin intends to stab the victim and run off, but in that case, why bother with close combat? All of the same sorts of methods could be used with a longbow or a dart gun, in which case the recipient of the poison and their friends would never even need to see your face. [Answer] Option 1: Specially Treated Blade Coated in, say, [Batrachotoxin](http://en.wikipedia.org/wiki/Batrachotoxin) This one's pretty nasty. Nerve paralysis is almost instantaneous, so no return stab from the victim if done right. The lethal dose of this alkaloid in humans is supposedly to be 1 to 2 µg/kg, which is about 2 grains of salt-worth, so even a thin coating on the tip of the blade should do just fine. Option 2: Lead poisoning Lead is toxic to the human body. Lead is also soft and blunt, so doesn't hold an edge well. However, if you can somehow deliver a few grams' worth of lead ... at high speed ... into a human body, and maybe repeat the operation a few times, they are sure to die... Option 3: Neurotoxic darts or arrows Use poison darts, rather than a knife. Much easier. Plus the distance gives you a head start in running away afterwards. Option 4: Poisoned Traps Look up Punji sticks... Has the considerable advantage of not having to face a large angry warrior eager to question you on your stabby motivations. Why poisoned knives are a bad idea. Well, for one, you have to stab the person with it. Said person might violently object. Secondly, the person you stab tends to bleed out the envenomed blood. Thirdly, the person tends to die of stabbing-related causes before the poison can act. For these reasons poison is rarely used in melee weapons. [Answer] Frank Herbert's Dune presents the Fremen Crysknife to deliver a deadly poison from the tip. As the knife is made from the tooth of a sandworm the hollow once occupied by the tooth's nerve contains the poison. To deliver the poison to the enemy of course requires stabbing/impaling over slashing. The Fremen however are reported to avoid killing respected enemies with the tip (lucky ones!). While it is not elaborated how a thickened liquid residing in the tip is quickly released in the wound the approach still offers some benefits: It does not require difficult additional coating of the blade and it does not enforce the use of a special sheath nor will it require any complicated unsheating procedures. Bless the Maker and His water! [Answer] As an option, consider a bee-stinger style approach, with needle tipped fragments that break off in the opponent. Interestingly enough, I don't think thickening the material is a good idea. Thickened material is only useful on the outside of the blade, for anything internal is too affected by capillary action. Poison on the outside of the blade would be hard to keep in combat (where metallic strikes could shake loose all but the most viscous fluids). The more viscous it is, the less likely it is to part from the knife and enter a wound. Less viscous solutions are more common in nature. They also do not have to be lethal. Consider the [stinging nettle](http://en.wikipedia.org/wiki/Urtica_dioica), which is effectively covered in hypodermic needles full of acetylcholine, seratonin, histamine, and a host of other really nasty compounds your body uses to let yourself know you've been injured. [Answer] Normal melee weapons do not much benefit from poison for, among others, the reasons you mentioned. However for an assassin poisoned weapons are still practical. This is because for a pro the weapon for killing the target and the weapons used to fight guards are two different and unrelated things. In fact, the preferred solution is not to need a fighting weapon at all. The problem at this point becomes that if you want to avoid fightin, and you do, it is better to poison something the target eats, drinks, inhales, or touches. Because of this history had professional poisoners, but only professional "assassins" were religious fanatics making a point. But if you assume some reason to attack the target instead of just poisoning them, fast paralysing neurotoxin that prevents guards from raising alarm would be useful. The best solution, of course, is a ranged weapon. A blowgun, a dart, or a crossbow will allow assassins to disable guards from a range. This is made impractical if guards are wearing armor capable of stopping anything except crossbows heavy enough to be hard to conceal. Or if the target and guards are indoors. Both darts and crossbow bolts can be used to stab targets from close range. Draw a dart, stab target, draw next dart, stab next target... There is no real value spending money on a dagger, if you will use poison anyway. If you don't need the option of throwing the disposable weapons far, metal spikes can be used. Possibly in the form of caltrops, which are quite useful in escaping. Another option is poisonous dust that is blown to the face of targets, but that requires a level of care to use safely. Which implies you would be able to use poison the correct way of food, drink etc. Irritating dust can be used to distract guards while running away, though. A weapon that injects poison or small poisoned darts to target is possible, but would only be used by a noble who wants a novelty item that might be useful in a pinch. A pro would simply use low cost disposable weapons that can be left to the wound. There might be a separate fighting weapon, a short sword or large knife, or concealed armor for fighting. Just in case everything goes wrong and you need to fight. Assassins would general do this in groups with first rank using normal weapon to fight more or less normally while others throw poisoned darts or shoot crossbow bolts at the guards distracted by the fight or trying to raise alarm. [Answer] I can think of a solution - use acid instead of poison, and have a knife that functions like a hypodermic needle. I can't find a good picture on the interwebs, but what I'm basically imagining is something akin to a [rondel dagger](http://www.myarmoury.com/feature_spot_rondel.html), a stabbing oriented knife. However, swap out the handle for something more akin to a pistol grip, with an actual trigger. Upon stabbing your opponent with the knife, pull the trigger and pump him full of acid! Now, the reason why I suggest acids over toxins - acids give you a more immediate effect. The shit burns and melts flesh. Its gruesome, terrifying and incredibly painful. Even if it (somehow) doesn't kill on the spot, you've basically won, because your opponent will be too in pain to fight back. Then if you're feeling mean, just prick him on the arm with a tiny needle coated in @SerbanTanasa's suggested brachotoxin. Append: An added bonus of my design - if the internal workings are powerful enough, you could spray it at an opponent at close range, giving you more reach. Alternatively, why use a rondel dagger when you could use an [estoc](http://www.myarmoury.com/review_mrl_estoc.html)? [Answer] This isn't a complete answer but the knife would have to be oddly shaped, possibly barbed so that surface tension doesn't keep poison on the blade. It wouldn't be mechanical though, it would become to large, unwieldy and unreliable. [Answer] Preliminary skirmishes would be with suicide groups (kamikaze?) loaded with Polonium dust. Radiation poisoning is slow but the dose required is very small - and you don't have to inject it, breathing in the dust will do. Once enemy troops have been exposed, follow Russian tactics of WWII (attack and fall back) and wait for winter ie. poisoning to take hold. [Answer] Consider the Bulgarian umbrella weapon. Tiny - microscopic ball coated in ricin and injected into unsuspecting dissident's leg via an airgun type arrangement. That or the use of radioisotopes in similar incidents - usually something like plutonium salts or polonium. The nice advantage - stick, oops, sorry... - walk away. Days/weeks later the target drops dead and you're long gone. [Answer] Close combat venom can be usefull on a little combat more a battle. Much people are wounded but later healed. The venom can kill those soldies before the big battle will begin, days or weeks later. Really sounds better any substance with instant action. Even doing a litle efect. A bit pain, your foe gets distracted a second... ]
[Question] [ Most fantasy worlds have large creatures living in a world with humans and other races. In Tamriel, the province of Skyrim has giants, mammoth and even dragons roaming freely. The Lord of the ring have oliphants and ents. In dungeon and dragon, there is the tarasque and all sort of other gigantic creatures. We could also imagine a world where large dinosaurs still exist. My problem is that, in human history, large predators were always the first to suffer form this cohabitation. Tigers and lions get chased partly because they threaten the livestock and the lives of the people. Even the efforts form NGO and governments are not enough to secure the survival of some of these species. In the case of dragons, they would be in competition against human societies. They would attack the livestock of nearby villages. I think these creatures will likely suffer the same fate as Earth's large predators. Humans will come to have the upper hand because they are more numerous and they have access to advanced tools and techniques. Since they consider the other creatures as a threat/rival, they will chase it to extinction. The extinction of the species is a real possibility from over hunting. Can I make a credible world (believable food chain) with large creatures roaming around with a ruined economy, a drunken king and corrupted officials à la Game of Thrones? Or are the creatures doomed to extinction? ## Examples of creatures: Dragons ![](https://40.media.tumblr.com/eae868a6837214be959a70e5d64a65f6/tumblr_mx5eh6THkA1rzni53o9_400.jpg) Griffons ![](https://web.archive.org/web/20150908054147/http://digital-art-gallery.com/oid/79/640x426_13983_Welcome_to_griffon_dinner_2d_fantasy_pathfinder_griffin_griffon_picture_image_digital_art.jpg) Mammoth (number 1) ![](https://downloads.bbc.co.uk/earth/naturelibrary/assets/e/el/elephantidae/elephantidae_info_graphic.gif) * Most of these can be tame or used as mount. * They are not evil but do have a survival instinct that might conflict with humans. * Most are not really intelligent but dragons are usually more intelligent than humans and can breath fire (some might breath something else but that's a detail). Other creature could include: Ogres, Giants ... But these have some intelligence and can't be tamed. they could be at least 3-4m tall for the Ogres but even taller for the giants. [Answer] Here are the 4 Fs you will need to ensure for any creature: Fight, Flight, Feeding, Fu- Reproduction. Although in this case, fight and flight are not too important and those are details you should be able to flesh out yourself. ## Feeding Well, the first big problem with large creatures is that they will need food. Lots of it. Gargantuan herbivores would have to consume large swathes of vegetation to be able to feed themselves, so they should not be in large packs. Gargantuan carnivores would be a bigger problem, as they not only need to eat a lot of meat, the animals the carnivores eat will also need to eat as well. This means that there either can not be too many of these large creatures, or you will have to introduce more food into the foodchain. The quickest and simplest way to solve the lack of food is to introduce gigantic plants as well, so your gigantic herbivores can eat them, and then the giant carnivores can eat them. If you do not want quite that many large plants around, and instead want it to be slightly more "fictional", where dragons can swoop down at their leisure and pick off cows, where giants can pick up deers for a quick bite, one funny thing you could then do to increase the number such low level foods for the giant creatures is that you could make them able to do photosynthesis, so there can be large numbers of them, and they would not devastate the nice green fields of the fields. Another way you could feed your giant creatures is via [chemotropy](http://en.wikipedia.org/wiki/Chemotropism). In real life, most things that use chemotropy are very tiny, and live in dark places like underwater volcanoes. In this fantasy setting, they could literally take boulders off mountains and snack on them, and when they die, they fall over and calcify, turning to stone or something like that. ## Reproduction Many fantastic setting like to depict giant creatures to also have a huge lifespan, as well as not reproduce all too fast, this may become a bit of an issue for you as there is an element of human over hunting that you believe should be an issue. Let me note here that I am going to assume that none of your large fantastic creatures are physical gods, that they can be slain by mortal men. As such, you will probably want them to breed much faster than they normally would, given their size and age. In real life, the reason why large creatures tend not to breed so often is actually because of the lack of food. If they try to breed like rabbits, then they would not have enough food to feed their young. (No references, sorry) But if you solve their nutrition problem as stated above, they would then reasonably want to breed as fast as they have food to supply their calorific needs. This kind of situation was similar to what happened to the human race. Once agricultural methods were developed, and there was a large supply of food, the population will then bloom. So actually it is very dependent on the energy available to them, almost like modern human society, where much depends on energy --- Now, for cohabitation. The nature of the food chain is that it is more accurately a food web, as things can be eaten by multiple different things, as well as eat multiple different things. So, what this means is that all food chains tend to move to one central, apex predator, which sits at the very top. The problem now is that you want cohabitation, which I will take to mean that there are multiple such predators, that have no natural predators of their own. The biggest problem then would be they would then be competing for more or less the same resources, so you can either make the resources so endless that there is no need for competition, or maybe you could also make all these creatures live in vastly different biomes, so there is not that much competition. Another thing you could do might be to create an actual apex predator, that is capable of snacking on dragons, griffins and ogres alike. This may then encourage those large creatures to respect one another in fear of a common bigger enemy. [Answer] The general rule is that species that compete for ecological niche can survive as long as both also have a separate niche in which they do not compete. For most of the large animals that means being able to live in areas not inhabited by humans. This is because large animals require lots of space and humans have a tendency to fill the areas they inhabit. Dragons and griffons are often depicted to live in mountainous areas and deserts that can't support large human populations. So large enough such areas could support populations without being significantly threatened by humans until trophy hunting becomes common place. Same is also true of dragons living in arctic areas or large swamps. Mammoths and oliphants probably live in large open grasslands. You'll note that mammoths are extinct while elephants are not. Last I checked there was still uncertainty about whether extinctions of megafauna were due to humans or changes in climate. Maybe the cause is changes in climate forcing megafauna and humans to compete for range? As far as your question is concerned the important part is having large area available where human population is sparse. Such areas would act as reservoirs from where the megafauna would spread to new areas made available if human population drops for some reason. It probably requires some minimum level of population to convince something like a dragon or oliphant to stay away from your farms. So fundamentally it is just a question of having a suitable geography. [Answer] I think there is an easy solution to this problem, so long as you are willing to allow humans to fall back a little on the food chain. If your mythical giant beasts were incredibly dangerous or hardy, humans would be hard pressed to drive them to extinction. Think about it this way: we've been able to kill all our large predators because the average man with a gun was more dangerous than a tiger/lion/bear, but what if it took a small army just to possibly kill a dragon? Teeth like spears, scales like shields and all? The tricky thing now would be the balancing act. You have to be careful not to make the creatures TOO powerful, otherwise humans might go extinct. Just make sure that there is no way the average community could possibly hope to kill them. Make it so that being a poacher is basically akin to suicide. Overhunting wouldn't be a problem if hunting any such beast were a monumental task worthy of a kingdom's fortune. [Answer] Huge animals like mammoths weren't driven extinct just because they were large. In addition, they were at the top of the food chain. The problem with things at the top of the food chain is that they aren't evolved to respond well to population pressures. They generally have low birth rates and, for carnivores, often have a limited diet consisting of only the biggest herbivores. Humans come along and disrupt that balance, spearing all of the generally non-consumed mammoths at a higher rate than any predators and, in the process, starving the kinds of predators that only eat mammoths. So how does this tie in with having large animals along side of humans? Well, if we consider the sorts of large animals that have survived, they generally have one thing in common: they weren't the biggest baddest badass on the block before people rolled in. Creatures like the American moose, the grizzly bear, and the bison survived people because people came in and, while attacking and killing them, also killed all of their predators. These animals had evolved to occasionally get eaten and regularly get driven away from kills. It didn't really matter to the grizzlies whether it was a band of spear wielding apes or a short faced bear chasing them away: they were used to it happening from time to time and life went on. The same thing can be true of something like a gryphon. They're huge compared to a person, but what if people came in and drove away the dragons that habitually torched the gryphons and ate their eggs? Humans would replace the dragons as the top predator in the regions and gryphons would slot in below them. [Answer] The large animals (top predators and herbivores) of the African savannah co-existed with humans (and even with human civilizations) for millennia. The human population couldn't use the savannah effectively enough to drive out the large animals. The large animals also couldn't drive the humans entirely out. Each side was lethal, in its own way, so there was strong survival motive to leave each other alone. What has changed the balance? 1) Modern science (medicine, agriculture, sanitation, well-digging, etc.), which has increased the human population. 2) Modern firearms and transportation, which allow humans to kill the large animals with impunity. I think you could profit from studying African empires such as Timbuktu, and the Zulu. There you had large (and sophisticated) empires, with some urban areas, lots of farmland, and some mines and stuff, combined with huge wild areas where the large animals "ruled." It helps if you've got microscopic scourges like malaria and tsetse flies, which the untamable wild herds have more resistance to than the humans. I think it would also help your world if the huge creatures had some intelligence -- just enough to set up mutually agreed upon boundaries. Another idea is if there were something about the giant creatures' favored habitat that made it lousy for humans. Earth's oceans are an extreme example. Whales and such rule the oceans because humans tend to drown in it, and because the alternative (dry land) is so much better. That's how Africa's savannahs and jungles used to be (but not so extreme). ]
[Question] [ This is for a video game project. In a future where living in the Earth's surface has become undesirable. People are building colonies in Earth's orbit. If materials from Earth are used to build space ships or space colonies, aren't we killing Earth? Those materials stay in space, they never return to Earth. This may be alleviated by some kind of return policy. But even in that case, the amount of returned materials will be less than the original amount that left Earth, because it's impossible to return the same amount. If I use this to justify a conflict between Earth and the colonies, is this believable? How many time needs to happen for this to be of concern to the people on Earth. I say 200 or 300 years, but its a completely arbitrary number. Any trick to calculate the time will be appreciated. [Answer] You cannot use this as-is for justification for such a conflict. Compare rocket size with the size of a mountain. Now take earth's mountain ridges. Clearly we could lose a mountain, of which many rockets could be made. (Gross oversimplification, but clearly in raw tonnes of material, this is not a problem). But let's say you DO want this as a concept. There's a movie that has in Earth-orbit colony and a kind-of conflict between Earth and the Colony. That movie is [Elysium](http://www.imdb.com/title/tt1535108/). Basically, people ruined earth, and now the rich live on the colony, whilst the poor slave away on earth. --- If you place your colonies further away, you could argue that there is a resource (resource X) that allows fast rockets. Resource X is troublesome to excavate, polluting, rare, expensive... you name it. Imagine resource X to be of nuclear origin, but 10x all its factors and you get something that's pretty nasty. You still need an opponent, though. If me donating you goods costs me a lot, I might just stop. What's preventing me from stopping with sending you goods? Death of a colony? Then why are the people angry? Surely they understand? The idea is workable, but you need another source of conflict. Ecological conflict on a small scale is usually people not wanting to pay for getting rid of their trash properly, so they just dump it. Maybe there's one continent responsible for the colonies and it's polluting the world with the constant rocket launches using Resource X. Background radiation levels are on the rise. Radiation chart: ![https://xkcd.com/radiation/](https://i.stack.imgur.com/pq6JN.png) (For better viewing, I recommend the original on [XKCD](https://xkcd.com/radiation/)) Basically, the "daily dose" of 10 micro Sv is already increased to 50 micro Sv, and in the future it looks like it will go up to 100 micro Sv and 250 micro Sv. Now, this doesn't seem bad, but the radiation gets in the food, and the water, and slowly the whole world is poisoned. --- Radiation is a scary thing, but it's just one example you could use. I don't think scarcity of resources will work out, unless you create some mystery "Resource X" that is A) Scarce and B) needed. Iridium would do nicely if you want to use existing resources. [Wikipedia lists Iridium consumption as 10 tonnes in 2010](http://en.wikipedia.org/wiki/Iridium#Production). That's not a whole lot, and if the rockets or the supplies needed it, you'd find Earth significantly lacking it. But again, you run into the issues * Why do the rockets need it? * Why does Earth need it? * Why do the colonies need it? * And why would the people on Earth be upset if it's used/in low supply, enough to cause a conflict? It can be done, but I feel you'll have to rely on some other, bigger threat (such as radiation). [Answer] There is no scientific rational for saying the space industry is taking material away from earth. There are good reasons for space industry to start using materials sourced in space (for example mining The Moon, or asteroids) but that's just because it avoids the costs of lifting those materials out of The Earth's gravity well. There is a sci-fi short story though about colonists on Mars and a politician on earth started drumming up FUD about the fact that they were taking water away from Earth each time they launched and to keep their colony running, and trying to tax the water and generally rabble rousing on the subject. The story is [The Martian Way](http://en.wikipedia.org/wiki/The_Martian_Way), it's a Novella by Isaac Asimov. > > They went to the rings of Saturn, harnessed a huge chunk of ice there brought it back to Mars and then offered to sell water to the politician at the same rates he'd been trying to charge them. > > > My point being that you don't need to have a real objective cost for someone to start drumming up fear on it. Lets say there is a shortage of a certain element - immediately politicians can start blaming the space industry for taking that element away from earth and making everyone back home run short. Whether it's true or not politicians love having someone to blame. [Answer] ## Gains from meteors According to NASA, 100 tons of material hit the earth each day. See here: <http://science.nasa.gov/science-news/science-at-nasa/2011/01mar_meteornetwork/> You'd need a big space industry to exceed that. Perhaps you have such an industry. However, you are probably interested in available and valuable material, aluminium, titanium, steel. Short of mining the core we have a limited amount of concentrated, easily extractable material. ## Loss of light material On the other hand, we lose approximately 250 tonnes of hydrogen and helium into space each day, a phenomenon known as atmospheric escape. <http://en.wikipedia.org/wiki/Atmospheric_escape> This represents an approximate net material loss of 150 tonnes per day. ## Mass of the earth The earth weighs in at approximately 5.97219 × 10 to the 21 tonnes so we have a way to go before it disappears altogether. Could it be depleted? Well readily available material could be mined out making materials much more expensive and environmentally damaging to produce. [Answer] As others have noted, it would take a huge space industry before you were shooting any appreciable percentage of Earth's resources into space. My first thought parallels Tim B -- in fact I was thinking of the same story. A fear or complaint doesn't have to be rational for people to get very excited about it. For example, in the U.S., offshore drilling for oil has been banned along most of our coastline because people are afraid of oil leaks polluting the ocean, even though every study I've heard of has found that the amount of leakage is less than the amount of oil that leaks into the oceans naturally, and would make little measurable difference. Or to take everyone's favorite villain, Hitler said that Germany lost World War 1 because the country was betrayed by the Jews and look how far he was able to take that. (This one has nothing to do with natural resources, but is an example of getting many people to believe a pretty irrational story for political purposes.) My second thought is that, even from a completely rational perspective, you don't have to suppose that the space program is consuming ALL of Earth's resources. What if it is just consuming a substantial percentage of one important resource? Like, I read years ago that some group or other was complaining that an excessive percentage of the Earth's helium was going to fill party balloons. As helium is lighter than air, once it's released it floats to the upper layers of the atmosphere where there's no way to recover it. It's an element so there's no way to make it from something else short of hugely expensive nuclear reactions. The primary source is bubbles of helium trapped in natural gas beneath the surface of the Earth, and that are recovered as a by-product of drilling for natural gas. Not all natural gas drillers capture it, so much of the helium just escapes. Anyway, I'm not saying that a space program would use up a lot of helium specifically, but it could be anything. Pick one resource, find some plausible (or at least, plausible sounding) explanation of how large quantities of this resource are used to build or propel your space ships, come up with a way for this to be a measurable percentage of Earth's total production, and there you go. It doesn't have to be 90% or anything like that. If it hits 5 or 10% it would be a reasonable cause for concern. [Answer] Please let me know if this is off-topic. You have great answers for your first question, but I would like to address your second question: > > If I use this to justify a conflict between Earth and the colonies, is this believable? > > > The first thing I thought when I read your description of farming the Earth for materials is resentment brewing in the people left on Earth who have to farm these materials. Why should I work hard in terrible conditions only for other people to profit off my labor and live in nice colonies when I can't escape myself? Note, I have no understanding of how the system works in Gundam, as mentioned by Skeith in the comments. I imagine this is how one series may have originated a conflict between two factions. [Answer] No. Most of the materials for building space structures would be cheaper and simpler to get from off-Earth sources, like mines on Moon or asteroids. Just the opposite would be true. Likely, space colonies would provide materials to Earth. There was a sci-fi about disagreement between Earth and mars colony about the amount of water lifted to supply Marsians. Resolved (by Marsians) by getting ice from Saturn's rings. Added: Two very useful ways to orbit material from Moon can be build, and both would be simpler to operate from moon than Earth because of lower gravity and lack of atmosphere: * [space elevator](http://en.wikipedia.org/wiki/Space_elevator) (which is also shorter, because low gravity again - lower moon-stationary orbit) * [rocket sled ramp](http://en.wikipedia.org/wiki/Rocket_sled_launch) (space ramp or catapult) Both are reusable (do not burn/spend any parts on launch) and can run on electricity, not using any valuable fuel. Rocket sled ramp from Moon is simplest to build. Should be your first choice, especially if your technology is not too advanced. Big advantage is that Moon is tidally locked with Earth, so ramp will be pointing to approximately same place in Earth's orbit (subject to small wobble). ]
[Question] [ I have a creature in mind that has almost no ability to turn its head left/right and has forward-facing eyes like primates and predators generally do. This would generally present a problem for a creature regarding anything sneaking up on it, but this animal species has developed a workaround and that is by having large ears that they can manipulate and has a reflective inner surface, allowing them to move the ears into their cone of vision and then angling them until they allow the creature to have an idea of what's going on behind them. Problem is that I don't know how reflective such an organic structure will be able to realistically be with earth-like biology, whether the creature would be able to see things within the reflective inner surface of the ear with great detail like an actual mirror, or if it would only be able to make out that there is some sort of movement behind them but whatever that is they'll have to make the effort to use their legs to orient the whole body to be able to allow them to see what it was. How reflective can a creature's body parts get? [Answer] I have no quantitative data, but one example from real life is the [jewel scarab](https://en.wikipedia.org/wiki/Jewel_scarab) (in particular the [Chrysina limbata](https://en.wikipedia.org/wiki/Chrysina_limbata) from Costa Rica). They are not all shiny but some are highly reflective to the point where you can clearly see the photographers fingers: [![Photograph of a jewel scarab](https://upload.wikimedia.org/wikipedia/commons/thumb/6/67/Chrysinasp..JPG/640px-Chrysinasp..JPG "Chrysina limbata")](https://commons.wikimedia.org/wiki/File:Chrysinasp..JPG) Had the shell not been curved I'm sure you would be able to get a near perfect mirror image. [Answer] Some [fish scales](https://theconversation.com/invisible-fish-could-light-the-way-to-better-optical-devices-10267) have evolved to be highly reflective as part of a defense mechanism, with clever crystalline structures optimised for reflecting light in ways that confound the vision of would-be predators. From the linked article: > > As part of their study, Jordan and colleagues advanced nature’s design a step further. They calculated a scale structure that would make fish almost entirely invisible – due to the 100% reflection of light from the surrounding ocean. > > > [![Rohu fish scales](https://i.stack.imgur.com/cuNfj.png)](https://i.stack.imgur.com/cuNfj.png) (image credit [Rajesh Dangi](https://commons.wikimedia.org/wiki/File:Fish_scales.jpg)) Quote [wikipedia](https://en.wikipedia.org/wiki/Fish_scale#Reflection), > > Many teleost fish are covered with highly reflective scales which function as small mirrors and give the appearance of silvered glass. Reflection through silvering is widespread or dominant in fish of the open sea, especially those that live in the top 100 metres. A transparency effect can be achieved by silvering to make an animal's body highly reflective. At medium depths at sea, light comes from above, so a mirror oriented vertically makes animals such as fish invisible from the side. > > > They haven't evolved to form a nice even image-preserving mirror-like finish over a large area because that isn't so useful for their intended purpose, but the basic design could be adapted and work just fine. Even without perfect image formation, movement behind the mirror-user would be obvious even if the details of the moving object were not clearly visible. This would be a good cue to turn around, or dodge, perhaps. Fish scales can be lost and regrown, by way of a bonus, so your critters don't have to worry about losing their all-around vision in their old age, or as a result of damage to their ears. Additionally, the flexible, moveable mirrors might also be useful as a way to dazzle and confuse predators and prey alike. [Answer] [Tapetum lucidum](https://en.wikipedia.org/wiki/Tapetum_lucidum) is a biological structure with the very purpose of reflecting light > > The tapetum lucidum (/təˈpiːtəm ˈluːsədəm/; from Latin tapetum lūcidum 'bright tapestry, coverlet'; pl. tapeta lucida) is a layer of tissue in the eye of many vertebrates. Laying immediately behind the retina, it is a retroreflector. It reflects visible light back through the retina, increasing the light available to the photoreceptors (although slightly blurring the image). The tapetum lucidum contributes to the superior night vision of some animals. Many of these animals are nocturnal, especially carnivores, while others are deep sea animals. > > > The only indication on its reflectivity I was able to find is indirectly given by this following statement > > In the cat, the tapetum lucidum increases the sensitivity of vision by 44%, allowing the cat to see light that is imperceptible to human eyes. > > > Which I interpret as it reflects back 44% of the light reaching it. ]
[Question] [ A race in my novel have hollow bones to allow for flight. The character that belongs to this race is a warrior. It would be very easy to break bones simply by punching a fighter of this race. Is there anything I should focus on when designing her armour? Anything different to normal? [Answer] Traditional armour is completely out. Not only would it be too heavy, it's also going to restrict agility too much. I assume that for flight these race need to be extremely flexible. Does the race actually have wings that need protecting too? Wings have a very wide surface area, and are very fragile with very few fixing points - which would make them a pain to try and protect. Maybe you could fasten a 'sheathe' of chainmail over a wing, but it probably wouldn't do much good and it would likely interfere with flight. Their wings would definitely be the most vunerable part of the body. In battle, the biggest concern will be arrows, and it takes a lot of metal to properly stop an arrow. A longbow can pierce even a solid breastplate, so whatever the flying creatures are wearing isn't going to do much good. Instead, I would consider alternative types of protection; cloth armour. Wear robes instead of plate armour. Rather that trying to protect certain areas, maybe try to obscure them. I'm imagining large billows of silk cloth, in which the shape of body can hide. Make it more awkward for any attacker to take aim. If the cloth billows enough, it might even knock an arrow off-course before it pierces flesh. Wearing long cloaks when flying above an enemy is going to have an intimidating effect too; it'll make yourself seem larger and more threatening. Layers of billowing cloth would be the way to go. Make it as light as possible - silk, if possible. Wear it as cloak and hood, and attach sheets to trail from the wings. If the cloth is very fluffy, it's going to work to disrupt any attacker. To hinder them, rather than stop. Make sure that the cloth is easily detachable too, so you can drop it to entangle your opponent, without risking it entangling you. Underneath the cloth, wear very slim hard leather bandings and a helm to protect the really important stuff; organs and face. It's not going to 'stop' much, and the flyers will still be more vunerable to any impact, but it will help in other ways. [Answer] You can't think of infantry on the ground, but airplanes in the air This race is no match for any other race on the ground. Their "infrastructure" simply won't allow them to wear the armor the other guy can wear. This is no different than an airplane, which is the proverbial sitting duck when caught on the ground. This means your fighter must master combat in the air — and as we all know, air superiority is often the deciding factor in a war. So, let's think about airplanes for a moment. * Thin skin. Originally paper or a light fabric. Bullets could go right through it. * Light skeleton. Originally light wood. Flexible, but driving a car down a runway disabled every plane it touched. Note that modern jet fighters are more durable (the benefit of a much higher thrust-to-weight ratio), but a crazed jihadist driving a truck could still disable a lot of them before the truck was too banged up to disable more. * Sleek. Since the air is where they've gotta be, they need to reduce anything that keeps them out of the air. Low weight. Sleek skins. Flexibility. Etc. Anything that degrades flight performance is out. So, what can we do about this? We need to preserve flexibility for flight, try to protect critical components (like the heart), and still leave some weight-carrying capacity available for things like the proverbial flower pot (we all know how deadly flower pots can be). * Most of the wings need no protection. An arrow through the feathers, or even the skin holding the feathers, really isn't that critical. It's the bones along the leading edge that need some help. I want you to think about the laquered bamboo armor of the Japanese Samurai. Layered strips of laquered bamboo that would shunt aside all but perfectly aimed arrows and stones. Remember, throwing missles into the air isn't as simple as it sounds. It doesn't sound like your opposing races have access to a [Phalanx CIWS](https://en.wikipedia.org/wiki/Phalanx_CIWS). You want and only need this light but semi-rigid armor along the leading edge and exposed-to-the-ground face of the bone. Being minimalist increases risk, but it also maximizes capability. * Rather than full armor, your birds will want armored patches principally protecting areas usually exposed to the ground. Forearm bracers covering the underside of the arm. Chest coverage and the forward areas of the legs' tibia and femur regions. You needn't worry so much about, e.g., the knee cap — that's a wailing good shot considering bird dude is zipping along and it's a small region. Again, we're trading risk for capability. This armor could be a stiffened leather to promote better flexibility. Your bird dudes will need all kinds of motion to control flight. Weight needs to be shifted more than for a person walking/running on the ground. Therefore, flexibility is a huge factor to worry about. * I wouldn't even worry about headwear. What sword would come down on the head of your bird dudes? If they're anywhere this could happen, they're not where they're supposed to be. Flying creatures depend on the ability to get away with speed, and intelligent flying creatures would depend on ranged attacks. As you can see, if these guys get stuck on the ground their dead as door nails. But so are airplanes. The point is to keep them in the air. If you think about the flight of an arrow, it slows down as altitude increases to the point where vertical acceleration is zero. Your race would quickly develop skills for judging their altitude to minimize the risk, which is only great if they must descend for close-in combat. In that case, their friend is speed (and a lot of it). The one kind of weapon (on a bit of a side note) that they don't want is a sword or club. Absolutely nothing that requires retaining their grip as each impact would add to the force slowing them down. Sabers worked great for calvary because horses are heavy and the weight-to-impact ratio was so high that the only issue was retaining your grip. Not so with bird dudes. They'll want things they can drop in a straffing run. Short javelins come to mind. So does some form of napalm. Yeah. Napalm. I can envision a 2-man attack. The first comes in with enormous speed and drops a bucket of Greek Fire. The second drops a burning brand from a safe altitude. Some poor schmuck on the ground has the privilege of wetting his pants as he watches that brand gently fall... fall... fall... oh ra.... [Answer] > > "If people had hollow bones to enable flight how would you design armour to protect them?" > > > You wouldn't, any armor at all worthy of the name "armor" will reverse any of the advantages for flight that having hollow bones gave them in the first place. If they want to fly & fight they're most likely to just rely on speed, agility & dropping stuff from a great height (well above the range of enemy projectile weapons) onto their land-bound enemies. > > Any armor at all reduces their ability to carry larger payloads (weapons or missiles), so they're more likely to forgo any armor in exchange for being able to carry more rocks, or whatever it is they do carry to drop on those below. > > > If any of them do wear any armor the light stiffened cloth armor ([Linothorax](https://www.google.com/search?q=alexander%20the%20great%20armor&rlz=1C1NHXL_enGB711GB711&oq=alexander%20the%20great%20armor&aqs=chrome..69i57j0l4.9775j1j8&sourceid=chrome&ie=UTF-8)) used by the ancient Greeks is going to be a good starting point, probably cut down even further to cover only the most vital areas & of course ensure free movement of the wings, it's actually pretty effective. > > Given their preferred technique for dealing with those who can't fly is most likely dropping stuff on their heads from on high any armor they do use is probably only worn for combat with others who also fly. > > > [Answer] You would do it exactly the way birds do it: feathers. If you've ever dealt much with birds, you will probably have noticed that it's actually quite difficult to penetrate a layer of feathers. yet they're quite light. (And of course have benefits for flight, insulation, &c.) Further, the claim that it would be easy to break bones doesn't stand up to examination. Bird bones evolved to be light and strong. Some birds, notably swans, defend their nests with blows from their wings, and can even (rarely) break the bones of a human: <http://www.myswan.org.au/index.php/faqs/is-it-true-that-a-blow-from-a-swans-wing-can-break-bones/> That also contradicts the idea that a bird-boned race would avoid fighting. Many birds are predators, others will agressively defend their nests. [Answer] Bamboo. [![bamboo armor](https://i.stack.imgur.com/GSKDO.jpg)](https://i.stack.imgur.com/GSKDO.jpg) <https://www.pinterest.com/pin/148759593911433770/?lp=true> Bamboo really has been used for armor. It would be great for your flying folk. It has several advantages. 1: Light. 2: Cheap. 3: It can absorb impacts by breaking. 4: It can catch a sharp incoming edge within itself rather than deflecting the energy elsewhere. 5: The armor can be made modular - so pieces broken during one engagement can be swapped out for replacements. 6: Looks awesome. 7. Parts of the bamboo tubing could be left open. When your flying folk dive and attack, air would whistle across it. All of them diving together would be a scary noise. [Answer] If your world is free to invent things that might not exist in ours, you could say there exists a type of metal lighter than the usual ones we use, say it's specific to the avian race's home/continent and have them develop it into all manner of armour. Alternatively, if your world has magic, another option is to magically imbue regular cloth and leather armour to make it more sturdy to attacks/impacts and provide greater flexibility for flight/stealth/quick dashes in and out of a fight. One thing that definitely changes how to design armour is whether the avian race has wings and what type of wings are most common, are there perhaps multiple pairs of wings, can they be hidden. Having an opening for wings provides another weak point in ones armour and makes flanking more dangerous, but also you have to take into account how to make the openings flexible enough not to hinder flight. ]
[Question] [ As part of a project, I am exploring a fictional biological/chemical weapon that can rapidly (and indiscriminately) kill by way of petrification. To clarify, By petrification, I’m not necessarily talking about the slow process of turning organic matter into fossils. I’m interested in conditions, diseases or other methods that cause humans (or animals in a broader sense) to die in a “stiff” state. My story has interesting sub plot about a mysterious “Medusa-like” weapon, it’s details however, are non-existent. I have found various medical conditions that can gradually calcify a range of tissues, problem being these conditions are generally treatable and do not carry a level of lethality ideal as a weapon. Some other conditions seem to be genetic and degenerative over a number of years, making them far too slow to strategically effect the outcome of a war and the concept of a genetic weapon seems difficult to realise (please correct me if I’m wrong). Please help me expand my idea into a horrific weapon against humanity! EDIT: Another clarification: my intention was to have this substance delivered to a large area, affecting thousands of people, symptoms showing in a matter of hours and death in a few days. Hence I added the [weapon-of-mass-destruction](/questions/tagged/weapon-of-mass-destruction "show questions tagged 'weapon-of-mass-destruction'") tag. [Answer] Tetanus is perhaps one of the closest if you're looking into existing diseases that can quickly induce some form of 'petrification.' To clarify my statement see the item below how tetanus victims die when it's untreated: [![Tetanus Vistim](https://i.stack.imgur.com/i2aNc.png)](https://i.stack.imgur.com/i2aNc.png) [Source: Muscle spasms (specifically opisthotonos) in a person with tetanus. Painting by Sir Charles Bell, 1809.](https://en.wikipedia.org/wiki/Tetanus) Now this effect is caused by a toxin produced by the tetanus bacteria that screws with the nerve and pretty much forces every last muscle in the body to flex and spasm. Since we're dealing with fictional you could state a variation of this bacteria produces a toxin that makes muscles very rigid and hard until no more movement is possible. (I reckon that's not too far fetched to be developed in some deep underground government bunker). But unfortunately there is no existing way as of yet to petrify someone in the sense you want to. Suggestion for your bacteria: * Short incubation time. * Virulent and airborne * Production of a potent toxin that facilitates the effects you want in very low doses (in the order of 0,1 µg/kg in a human). * Antibiotic resistant for the coup de grace. [Answer] [Fibrodysplasia ossificans progressiva](https://en.wikipedia.org/wiki/Fibrodysplasia_ossificans_progressiva) is an extremely rare mutation which causes damaged tissue to, instead of healing normally, be replaced with bone. It is entirely untreatable. Normally, this slowly replaces the body with bone until the subject is totally paralyzed. However, if it were combined with another condition which caused systemic tissue damage (maybe an autoimmune disease?), it would move much more quickly. [Answer] I think that the tetanus and strychnine are the best. However, I thought that I'd point out another possibility. It's so odd that I wouldn't have believed it if I hadn't had a landlord with this condition. Something causes his muscles (when he is under stress) to absorb all of the potassium in his blood. This causes all of his muscles to constrict, paralyzing him. When I stayed there, I had a key to his apartment so I could drag him out if there was a fire (his biggest fear). Also, after the incident, his blood would be almost completely depleted of potassium. I suggested bananas to supplement his potassium levels. He just laughed and showed me a bottle of pills that each contained a "very lethal" dose of potassium that he took twice daily. In your story there could be a gas or indigestible that could trigger the potassium uptake. This would be for a shorter term, non-lethal version. [Answer] Try pyroclastic streams. The inhabitants of Pompei will confirm that it works. The Roman city of Pompei was burried by a nearby volcano, creating petrified dead for us to dig up many years later. Pyroclastic streams are formed by some classes of vulcanoes. They look like a fast moving blazing hot ash-rock avalanche. [Answer] The weapon could somehow cause a cume of space to form in an area. Victims would first suffocate but then all their liquids would rush to the surface and boil off. In essence they would be freeze dried leaving mummies behind. The full process may take a few days but the effect would be devastating and horrific. Most measures would not help. Even air tight bomb shelters may crack at the pressure difference over days of exposure. At the end there would be little destruction to infrastructure except pipes, and no radiation poisoning, making it a great weapon How to turn an area into a vacuum for a few days? Antigravity. Fire the beam from space suppressing 90% of the planet's gravity in a location surrounding it by a forcefield wall. Let space suck the atmosphere out. Great weapon considering that even super futuristic defences not designed to deal with the specific threat may prove completely useless. EDIT As people are doubting my hresults here is a quick reference <http://scienceline.ucsb.edu/getkey.php?key=1692> Refer to answer 1 point 2, as we are in a vacuum, and there is still heat coming from earth and the sun. > > If there's heat, but no spacesuit or spacecraft, the body will very > quickly dry out, because water evaporates extremely quickly in the > vacuum of space. This will almost completely stop biological > processes, and the lack of air will prevent weathering and chemical > degradation. > > > If there is no heat the ice would sublimate as in a freeze drying process noted above. The question is how long would this take. This is not an experiment that looks like it has been done in real life, bvt for we can assume quickly can be within days. Also hote the drying does not need to go bone deep. Once the skin and maybe muscle turn to jerky the vicum will look quite petrified ]
[Question] [ One commonly cited problem with invulnerability-style immortality is that you watch the people around you wither and die while you survive. On top of that, even though you don't deteriorate, at some point you run into mental issues, where you can't make new memories and life starts to become a blur. With that in mind, is there a scientifically plausible way for someone to be completely invulnerable to all injuries and diseases, from blunt force trauma and the common cold to cancer and genetic illnesses, but they will still die from old age at about the same age as they would have without immortality? In addition, I'm not looking for an abrupt end, like a sudden heart attack at a random day between their 90th and 120th birthday. I'm more interested in something where the person can know "I will die soon" and has time to say goodbye of their friends and loved ones, like an elderly person dying of cancer. I'm looking for a scientific approach, not a divine or arcane approach. Basically, humanity has developed a universal cure that makes the user immune to everything until their biological lifespan has ended. What biological mechanism could the cure use for this? [Answer] You actually cannot do it, but you could manage to accomplish similar outcomes. Programmed death -- that's the easy part. You should read up on [telomeres](https://en.wikipedia.org/wiki/Telomere), they actually exist and apparently do provide programmed aging that sets a limit on lifespan. You can find a number of researchers that think telomeres are the primary cause of aging. [Telomerase](https://en.wikipedia.org/wiki/Telomerase_reverse_transcriptase) can rebuild telomeres, but it is not normally active in most cells in humans and other animals. As you can imagine, this is an active area of research. You still need to make yourself indestructible, which is impossible in a scientific, biology-based approach. If you heat any material to the point that it becomes a plasma, no biology of any conceivable type is possible. Even all of the conceivable advanced nanotech, force fields, and other magical technology can't save you if you are dropped into the sun. Surviving a nuclear explosion would be easy in comparison because the explosion does not last very long and with enough ablative shielding, you could be around long enough to die from the radiation. If you are heated until water turns to steam, no person could survive. If you heated [until proteins denature](http://www.chemistryexplained.com/Co-Di/Denaturation.html), you cannot survive -- this is also why cooking makes meat easier to chew -- the proteins are being unfolded and otherwise breaking down. As the article explains, this is already a serious problem with many proteins at 41 C / 105.8 F. Were this not so, a fever would not help to fight an infection. You could make similar observations for mechanical, chemical, and radioactive destruction of a person. Indestructibility is fundamentally impossible for many reasons. You could increase trauma survival by the strategy of adding thicker layer of outer protection that can be destroyed and regrown without hurting the person; make it tough like scales. However, this comes at a heavy cost in terms of flexibility, weight, and it does not even make you more than a bit tougher. Bullets, fire, etc. will still hurt and kill you easily. Might I suggest that instead of being indestructible, you could add more redundancy in critical organs and add a very effective regeneration capability so that you can regrow missing limbs and organs? Death by trauma would be possible, but infrequent. Redundancy and regeneration are clearly possible, as they exist in the real world in various degrees. Redundancy is not a panacea, additional resources are needed to make it possible, and biologically speaking, counter-productive overall if the biological cost exceeds the advantage of surviving trauma. We have two kidneys, only one is required for normal function, but lost of one results in a shorter lifespan. Loss of one lung is survivable. Loss of one heart is a bigger problem. A better strategy than having 2 of every critical organ, is distributed function, where the organ is distributed throughout the body. Bone marrow production of blood cells is an excellent example of distributed function, but it is only possible because the blood vessel network is already everywhere. A distributed kidney would require a network for urine collection -- there is very little room for additional networks within the body. If you could also make external backups of your brain and genetic material, even death would be reversible via cloning and downloading your consciousness from a backup. Immortality would be a logical consequence of such. However, if you have legal and ethical strictures against it, it would only be available to criminal elements able to remain outside the bounds of the law. Unbound population growth would be a good reason for this to be illegal. As a controlled and complicated technology, you could perhaps enforce this legal restriction nearly all of the time. --- I started thinking about being dropped into the sun if you were completely invulnerable. Seems like it would be unpleasant. The surface of the sun is actually a pretty good vacuum (about 1e-6 atm.) so you would fall a very long way until you reach neutral buoyancy, certainly many thousands of miles into the interior. At that depth, pressure would be over 1000 atm, insanely bright and hot. Little variation in conditions, though convection currents would move you around. Of course there would be nothing to eat, and nothing to do. You would be looking forward to your programmed death. Maybe, if you were lucky, you could go insane quickly and not have to suffer for many years. [Answer] There was an article by Brandon Sanderson about how superpowers are basically magic. If you want Wolverine style healing, where you could [burn him down to a skeleton with a few gristly bits](https://i.imgur.com/Qo0DYK7.webp) and [he'd be able to regenerate](https://i.imgur.com/KBzSZqe.webp), then just say that eventually the magic runs out... Another idea, is that the individual has another organ responsible for making the substance that promotes the regeneration, but the organ can't regenerate itself. Eventually the organ wears out and starts to fail, which means that the healing factor begins to diminish, and then possibly reverse so that rapid aging occurs. If you want less magical and something more plausible, say that it's nano machines that are rebuilding the tissue. They wear out over time and have to be replaced. But it's a conscious choice for him to go get the procedure done. After living X number of years, where the friends and family are aging and dying away, the hero slowly loses the will to keep going on and so decides not to get the next set of nano bots. Or possibly they can only perform the procedure a limited number of times. If it was an experimental procedure there might be side effects that don't show up for X years, and once they begin to appear he has to retire or die quickly... [Answer] This is a human-mindset rule, not the kind of rules you find in real physics. So my first thought is to make it magic based, as these are the kinds of rules you get with magic. This answer caused you to edit the question, wanting a non-magical solution: the alternative is people impose the rule. # magic The god or magical being responsible for your invulnerability has a time limit on her patronage. Granting immortality or more than a moderate increase in lifespan due to good health and freedom from injury would run afowl of much more powerful beings who set up the whole cycle of souls business. # humans This is not a technological limitation, but a law imposed by society. Having people never die would result in overpopulation or stagnation, so the technology has purposfully been built with a limited lifespan. If world leaders and ultra rich were seen to abuse it, there would be war between the superpowers who are trying to share the planet's resources between them, so each government polices the usage very seriously. Perhaps, if you want an extension, you have to sign up for a colony ship and emmigrate. [Answer] (May not be really worthy of a answer, but too long for comment) If I had that same sort of problem, I would look at any probable solution based on cell behavior. A wild example would be the presence of a form of "super white cell" who can boost recovery, prevent sickness by it s effectiveness... Once you find such a solution, you could simply add a form of degenerescence to theses cells, they perform perfectly for the first X years (in your example, 90years), then they start to slowly loose their effectiveness. The effect would first be minimal, but slowly creeping into the loss of this immortality, until you can die naturally. This solution may be a little cheap, but allow the host to have warning ("hey, this cut didn't heal as fast as it should have"), and allow painless way to die. If you want to prevent all natural causes but age, the degenerescence of theses cells could be a form of cancer, that even those super cells can t cure, or a form of auto immune sickness. Either the cells are slowly going mad until they kill the host by the same way a cancer kill, either they actively start to kill the host by misreading more and more cells as threat and destroying those. That way, the host would be conscious of the loss of his immortality, but that would be a slow and probably really painful death. The only thing I lack is knowledge in biology to think of a way to build that super cell. [Answer] Easy: have the effect wear off. The details depend on how exactly the invulnerability is accomplished. For example, if you have rapid regeneration like Wolverine, you could say that the regeneration is a consequence of some hyper-active stem cell population that is short lived, so must constantly replenish itself. After a certain time, the cells suddenly (or gradually) lose their ability to divide, and once the reservoir of these cells is exhausted, the regenerative powers are gone. This isn't really all that different from how we age already. The person could feel this by feeling more "tired" and less energetic. Or suppose the invulnerability is generated by some kind of cloud of smart nanomachines. The machines can be manufactured at a certain time, and have a time-to-failure curve much like other electronics: They will usually last at least X years, and rarely last more than Y years. The decay could be sensed by various reductions in the quality of the protection: Perhaps the nanites start generating more and more noise, create dust, take more energy to fuel, or whatever else. An interesting twist could be "backup bodies". Suppose people are not actually invulnerable, but their mind is constantly synchronized to some server, and when they die, their consciousness is immediately downloaded to a new body. This is more a lich-and-phylactery type invulnerability, but you could incorporate the weakening nicely by having it cause gradually more and more memory loss at successive stages, or having an initial period of severe disorientation and confusion following revival. This period gets longer and more severe every time (or over time, eg. due to aging of the brain), and eventually the "revived" person just becomes a zombie indefinitely, never managing to "snap out of it" to re-boot their consciousness. By the way, if your goal is immortality without increased lifespan, you can simply say that everything has been cured except for dementia. The central nervous system has a very unique and complex nature, and sooner or later it just starts dying off. It is unclear exactly why, and while some factors can make the rate of this dying slower or faster, ultimately it is inevitable. Unlike all other organs, however, you can't just replace or regenerate the CNS, because it contains information, and once neurons die the information is lost. If the CNS suffers severe damage, even if all of that damage is somehow repaired, the effect on the personality of the individual could be catastrophic. So you could accomplish what you want by making sure your "magic cure" takes care only of tissue damage, not loss of information. [Answer] Yes, it is. A [Hayflick limit](https://en.wikipedia.org/wiki/Hayflick_limit). There is an actually existing "[division counter](https://en.wikipedia.org/wiki/Telomerase)" inside the body cells that can result the needed scenario. The cells of the animal (human) body can only divide limited number of times. This is because they are not capable of copying the whole genetic material: prolog and epilog of the "life book" in the DNA are not passed to the daughter cells. To work around this, start and end of the "book" just contains non-coding junk that does not carry the required information. However after the cell divides many times, this propagating damage reaches vital regions where real information resides, and the cell cannot longer divide, or the daughter cells die soon after division. Having such a "clock" would not prevent cells from being arbitrary active and smart, dividing and regenerating the body, even from very significant damage, as long as the "counter" is still above zero. The lost border sequences are only "regrown" at the start of the new organism and shortly afterwards. [Answer] Make it expensive. Biologically expensive, I mean, not the monetary kind. Have it have a cost, a real survival-type cost, and that cost will be your limiting factor. If you don't want a "suddenly-drop-dead" scenario at your cutoff, have the healing or whatever last a certain amount of time, then after its gone the individual is at the mercy of our original healing, immune system, etc - which isn't nothing, but isn't immortal either. Maybe the process that makes them invulnerable needs a steady supply or periodic doses of handwavium (mineral, tech, chemical, whatever). Getting cut off by itself won't kill a person (after all, we live without the handwavium), but it will slowly erode the invulnerability as whatever mechanism it is lacks the supplies to continue, and the individual will age, get injured, and eventually die as inevitably and unpredictably as those without the process do. Maybe they get a single-dose supply of the handwavium with the treatment, and it has enough for about a hundred years, and the invulnerability wears off after its gone. It might last less time if it is used more heavily (lots of expensive regeneration), or a bit more time if carefully husbanded. Or the process itself just gets worn out after that amount of time, and can no longer process the handwavium to heal with. Maybe the handwavium starts giving other problems (anything from sickness to insanity) after that span of time, or there are increasing problems with issues the healing won't cure (like mental problems, insanity) so it's either not possible, or not wise, to re-dose people. Maybe it requires a lot of energy or resources - food, or sleep, or warmth etc. This wouldn't limit the lifespan per se, but it does make it more likely that an individual might die because they were caught without sufficient resources, bringing down the 'average' lifespan. Or maybe the resources needed go up over time (because they're healing more and more damage?) so past a certain point it's physically difficult to keep up with the demand, or a different limiting factor makes it impossible. Or the resource-intensive nature of the invulnerability may even give an incentive as to why there is a socially mandated (as opposed to a biological one) lifespan cap - those past a certain age may be deprioritized or even choose to not take whatever resources allow them to maintain their invulnerability, eventually ending their lives, so there will be more resources for the children. As a side note, I suggest really good healing/regeneration instead of invulnerability as the base mechanism for this immortality. There are enough ways to get injured or killed that to be invulnerable to all of them is pretty implausible - but letting them heal really well might make most injuries survivable, which could make them tough enough for a similar effect. Basically, not the survive-through-anything-anything immortality, rather the won't-drop-dead-unless-killed ageless version. [Answer] Give the person a 'networked brain' that copies their 'self' back to a bunch of servers every second of every day. They are essentially 'immune' to death at this point because they can just keep loading into a new body. Perhaps to make them have a 'limit' however, you could make it so that a 'mind' or 'self' can only exist in such a state for 'x' amount of years before deteriorating beyond the point of being usable. [Answer] Logically speaking, you've come up with an impossibility. There is no such thing as death from old age. A person always dies because some function of their body fails. In fact, that's pretty much the definition of death: catastrophic body failure. Most of the time, it happens when a person is old, but that does not mean they actually died because of how long they had lived. What you're suggesting, invulnerability to "all injuries and diseases, from blunt force trauma and the common cold to cancer and genetic illnesses", is actually immunity from anything which could cause death, including all the things which cause death in old people. You can't have catastrophic body failure if your body is always in perfect condition. It's impossible for the person to die unless something is artificially inserted into the system to change or remove a person's invulnerability, making them mortal again and precluding your original immortality stipulation. Basically, the logic boils it down to this: you can't have the person be physically invulnerable and also die. The two are mutually exclusive. Either the person isn't fully invulnerable or you have to have a programmed death (which, in my mind, is a vulnerability, preventing the person from actually being invulnerable). Others have provided good answers on alternatives to invulnerability. [Answer] One option is social norms and pressures rather than biological processes or magic. Society itself may have structural problems if people stay in perfect shape - will people want offspring and what will those offspring do, and will the same people have power (after all, if they have power within society now and never get worse off or frail, maybe they become Comrade President of the Electricians Society For Eternal Life). So maybe a society that found a way to engender near immunity to life's issues, also legislated that this must be reversed or treated to weaken it at some age between X and Y years old (with the person having choice about the exact timing) for all persons, so they gradually decline and die. Social rituals might spring up around this as well. Shame? "Life Celebration Party"? Tradition of spending final years writing an autobiography or their wisdom for future GE stations? Would there be politics around extending the timing or changing it and periodic debates about it? This kind of thing would add richness to the plot. [Answer] I think to be invulnerable you body must be immune to all possible damage and constant regeneration or replacing of cells, to repair worn down cells (worn down cell is one of the cause of death where a cell that can't regenerate or be replaced is worn down as we age. And this can cause the damage of an important organ or tissue after some time if totally worn down). When your body and organs are still fresh and new, you are mortal till the ability stops. When technology is advance we can replace our body nerve without damaging it and the nerve especially. Note the brain is yourself: changing it brings a new person different from you (now that may bring a problem). But technology may provide a brain regulator: this will keep the brain from damage or repair damage cell in the brain (a drug can be made to do that). A study can be made on replacing or repairing cells, tissues and organs. To be invulnerable, an immune drug can be made for all the cells to protect, repair or regenerate the cells. But not available ]
[Question] [ So imagine this scenario: Sapience (which I define as Human-like intelligence or better) is a relatively common occurence once a life-form is on a specific brain-arms-race path like Hominins have been for a few million years. A certain set of mutations can occur that make a dramatic difference in overall capability, so the jumps in capacity are large. Now various types of hominins (say some version of Neanderthals) suddenly develop a technological civilization. The smarter they are compared to us, the faster the relative rise of their civilization. Instead of 15,000 years from agriculture to space age, it only takes them 1,500 years. After a brief early space age, they either wipe themselves out with MAD-type weapons, or more likely decide to leave the "Cradle" as an ecological preserve of sorts as they expand out in space (or transcend space altogether). Tens of thousands of years later, a different branch of hominins attains sapience, and the cycle repeats forever. My question is 3-fold: 1. Name the one most important factor that would make this scenario implausible (say, hominins before this or that era were physically unable to speak), or if you prefer, more plausible (for instance the larger brains of Neanderthals). 2. Do you think (m)any XXI-th century level artifacts could be preserved well enough to be detectable from 30-50k ago (especially given the dramatic changes in sea-shore levels in the past 50k) 3. What would the one most important result of this type of repeating intelligence be in terms of pulse-driven changes across different intelligence bursts? I'm thinking for instance that the next post-human pulse for instance would have a lot less coal and oil. Perhaps they trigger (the end?) of an ice-age, or genetically modify their successor race before they leave. Feel free to answer 1,2,3 or any combination thereof. [Answer] > > Name the one most important factor that would make this scenario > implausible (say, hominids before this or that era were physically > unable to speak), or if you prefer, more plausible (for instance the > larger brains of Neanderthals). > > > Scientifically, the most implausible thing about this is contained in this statement: "Tens of thousands of years later, a different branch of hominids attains sapience, and the cycle repeats." The problem is that if you look at the Earth and the human race today, you will notice that there are no other hominids left. That's almost certainly because we out-competed them (whether intentional or not). And there's no reason to think that whatever hominid won the arms-race the first time wouldn't have done the same thing, leaving no remaining hominids for us or any other "pulse" to evolve from. However, that's a scientific detail that the general public is almost entirely unaware of, so from a story/fiction standpoint, it might not be a big problem. > > Do you think (m)any XXI-th century level artefacts could be preserved > well enough to be detectable from 30-50k ago (especially given the > dramatic changes in sea-shore levels in the past 50k) > > > Sure, just not the ones from the shores. If you look at humans today, we have virtually covered the planet to such an extent that I would say that the only way that a succeeding intelligent species would not be aware of us is if we went to great effort and expense to cover ourselves up from them. Really, we would have to scour the whole planet to have a good chance of preventing them from discovering our history. One possible way around this might be to invoke some specialized technological disaster like a nanobot war that disassembled/disintegrated all humans and their technology. Personally, I don't think that's feasible, but lots of people do think that it is. > > What would the one most important result of this type of 'pulsar' > intelligence be in terms of pulse-driven changes across different > intelligence bursts? I'm thinking for instance that the next > post-human pulse for instance would have a lot less coal and oil. > Perhaps they trigger (the end?) of an ice-age, or genetically modify > their successor race before they leave. > > > Well, the energy thing is huge (and one of the best ways that we can be certain that their wasn't another intelligent species only 30-50,000 years ago). Discovering so much free energy lying around, easily accessible and exploitable has been a remarkable stroke of good fortune for us, akin to having our whole species win the Lotto. And now that we've used up so much of the easy/cheap stuff, any species becoming sapient after us will have a much tougher time of it. Other non-trivial persistent changes that we are making: * Massive Climate Change:; melting most of the glaciers & ice caps. Though this could recover on its own in a few thousand years. * Space Debris: The low-orbit satellites will degrade and fall back to earth eventually. But the stuff in high-orbit (includes all geo-synchronous satellites) will likely still be there. Also, the Apollo landings and the stuff we left on Mars, could be discovered. * Radioactive Materials: It's not just oil and coal, we're using up most of the easily usable radioactive ores as well. * Species Extinction: We didn't stop with the Hominids, we are still killing off species at a faster rate than anytime in the last 60 million years. * Mineral Redistribution: Most of the worlds surface gold, silver, diamonds, etc. are no longer where nature put them. Instead they're either spread out across the whole world (like the rings and other jewelry so many people where), or else concentrated in huge concrete and steel vaults (like Fort Knox). Neither will make any sense to future geologists. * Sooooo Much Garbage!: We make a lot of it. Really an incredible amount. We try to bury, sink and hide it, and much of it will decay, but still, incredible barge loads of it will survive. And our successors will find these stunning huge landfills and dumps of unbelievable amounts of plastic, toxic chemicals and other slowly rotting stuff. Really, I could go on and on here ... [Answer] You wrote > > I'm thinking for instance that the next post-human pulse for instance would have a lot less coal and oil. > > > That's it. You hit the nail on the head. Each re-generation is inheriting a completely different planet than the last. Some things that would change: * Fossil Fuels: As you said, they're going to be used up pretty quickly. I doubt that it's going to be easy for the cycle to continue just as before when less energy is available. * Radioactivity: If each generation wipes themselves out with nuclear weapons, there's going to be radiation around for the next. Over time, the planet will become extremely radioactive. * Evolution: Other species will evolve normally, and gradually change. There are other factors that will change. This would all be okay. The problem is, this means that the civilizations will really develop in different worlds. Not all will be helpful for this particular species. For example, humans couldn't have survived for long during the Cretaceous Period. Eventually, the next-in-line will be wiped out before they can attain intelligence. I think that's the "one most important factor." [Answer] 1) What would keep the intelligent hominids from expanding? Excluding circumstances like a primitive people who is very good adapted to an extreme climate (v.g., Eskimos), our history always shows the most advanced groups trying to expand their territory. Think how little time it took Europeans to colonize over most of the world. 2) Plastic, glass and ceramics are really hard to decompose. Specially if some of it ends under ice or buried. And, about how easily they could be found, here they talk about some [fossils with a size between 2 and 0.05 milimeters](http://en.wikipedia.org/wiki/Chitinozoan) 3) Resource depletion (not only oil, but also metals and radiactive elements) would be an issue. That said, given that they are more intelligent than the average, maybe would not be that bad; they would focus more in biological sciences (including genetic engineering) to get the materials they need. That said, they would not leave much behind in the realm of altered beasts, because expansion of these lifeforms would be unlikely: * because, as "designed" animals or plants, they would probably not be very adapted to the wild (just as current day cows and pigs would not fare well alone). * and probably because, being biologist they would have realized the risks involved in introducing a new species if the previous point was proved wrong. [Answer] ## 1. The most important factor would probably be the sheer number of factors making it implausible. There is biological continuity within hominids, Neanderthals and modern humans for example apparently cross-bred, and anomalous brain capacity would show in Africans being noticeably dumber than people from elsewhere. A global civilization would have transported domesticated species from their native continents. An industrial civilization would have left behind waste dumps and mine shafts, both obviously unnatural in an enduring way. ## 2. Already mentioned waste dumps and mine shafts. Gold, glass, and ceramics protected from mechanical destruction could endure a very long time. Even if they are parts of highly advanced technology, such as optical fibers or gold alloy contacts. Same goes for gems and stones cut to unusual shapes. Though most materials that could survive long enough would be difficult to date and a single specimen would be ignored as modern contamination. ## 3. Consequences are hard to predict. A mote in the god's eye is a novel with a cyclical civilization. As I recall the main difference was that each cycle built upon the remains of the previous ones and spent also resources preserving its science and culture to its successors. So the cultural outlook would be different. A cyclical civilization where the cycles do not have continuity might be different. Or not. They'd still figure out they had predecessors and that they probably would have successors. Maybe they would be driven to find out where the precursors went. Precursors are very common in scifi. There were also issues with resource depletion, but most resources are either renewable (solar energy, ecosystems) or reusable (metals), so this really only restricts the use of fossilized fuels. [Answer] There are a lot of good counter-arguments here, but plotwise it might work having the waves separated by ice ages. * Each ice age wipes out a lot of the evidence for the previous civilization, except in some tropical regions, which will be lush rainforests during the interglacials. * The ice-free regions are a reservoir of hominids, from which new civilizations emerge. The end of the ice-age may see land-bridges which will be submerged later, making for easy migration to other continents. The early farmers are then cut off from the cradle when the water rises * A civilization may find remains of the previous civilization when exploring the rainforest. * You can construct an evolutionary mechanism which drive the hominids into intelligence at each ice age. The standard example is a receding forest which makes the hominids move out into open grassland, with the effect that has on posture and free hands. * Ice ages expose new mineral resources, scour away pollution and replenish farmland, though fossil fuels would presumably not be available. Story-wise, I think it's beautiful to imagine the planet's quiet solitude during an ice age. The waves of ice ages and waves of hominins also parallell each other nicely. There's a story in there about a hominin wave which tries to rebel against the natural order by stopping the coming ice age. Or perhaps more elegantly, that the technological development of each hominin wave is in fact behind the ice ages. This makes for a new question, but possible mechanisms include sequestration of carbon in some carbon-based technology (they build houses out of graphene, massiv structures out of artificial diamonds, etc) or shielding of the sun's rays when the civilization starts employing solar panels in space to cover their energy needs. You can also skip evolution completely, by postulating that the cradle of hominins is a small continent or archipelago where fully sentient stone-age people can live indefinitely, but where there are no opportunities for a civilization to arise. With some exceptions, complex human civilizations have evolved in fertile areas along rivers, where large-scale agriculture was possible. As an example, humans arrived in Australia in 40.000-80.000 BC, and while having a rich culture, never developed what we think of as a classical civilization. With the hominids emigrating into space, the ice age wrecks the civilization of whoever choose to stay behind. In the only place left to live, the cradle of their civilization, they revert to a stone-age culture. And then the cycle repeats. [Answer] As an addition to [SJuan76's](https://worldbuilding.stackexchange.com/a/8724/2968) answer, whose train of thought took the same direction as mine: Consider the environments in which animals and at least bacteria thrive: deep seas are actually easy conditions compared to [Extremophiles (wiki-link)](http://en.wikipedia.org/wiki/Extremophile) live. So, a post-human species which has to focus on biological engineering rather than any fossil-fuel based workings could adapt those for all kinds of needs. When considering such a base for a new civilisation, also consider that they may be more suited to think in large time-spans! Going to Space may be harder for them, BUT they may in turn have the long view to seriously, and very patiently, attempt anyway. Now, for the question of hominin or not: WHY hominin? A deep sea species may survive a cataclysmic change on the surface, and happen to be the next dominant species. Think: Squids! They ALREADY seem to have a good sense for problem-solving, and if they reach deep sea levels, smaller groups have VERY cheap energy via volcanism ([Black/White smokers](https://en.wikipedia.org/wiki/Hydrothermal_vent#Black_smokers_and_white_smokers)). Another possibility is birds. Some species are tool-users and problem-solvers, and even seem to have a cultural background in how they build their tools (I lost the reference here, sorry... it was on TV recently) Lastly, consider hives developing into something smarter. I admit I have no idea how realistic that would be (seeing an already human-style intelligent species evolve into civilisation is a lot easier than figuring out a hive civilisation...), but in regard to that, one could perhaps even think about a hive that manages to get off planet by some means because the species is driven by slow destruction of "their" planet:global warming/cooling, major tectonic changes, and similar things. Such a hive may actually be totally unaware of past civilisations as in 2! ]
[Question] [ I found a previous question on using chitin from giant insects to make weapons and armor, but the answer left out something I had considered for the medieval fantasy setting I'm developing. The answer suggested that the chitin pieces would not likely fit the shape of a humanoid race and would need to be fastened together into something akin to lamellar armor. [Weapons and armor from chitin](https://worldbuilding.stackexchange.com/questions/37974/weapons-and-armor-from-chitin) What I had wanted to explore was the possibility of being able to reshape pieces of chitin from these giant insects, allowing for a properly fitted set of armor to be made (as well as more styles than just looking like the creature the materials were harvested from.) Maybe something of an alchemical process that makes it pliable for a short time, allowing it to be shaped. This also could allow for several pieces to be shaped and glued together to make a thicker piece of armor. I imagine the lower density might make it useful for some light armor. Probably not as good as a set of steel platemail. My question is, if chitin was upscaled to a form that could be shaped into usable body armor, would it be useful in combat? How would it stack up against other forms of armor from the medieval period? At the very least, would it be useful as an alternative armor for people in regions where there is limited access to metal? Or would they be better off with other materials like hide and wood? Clarification: I'm aware that giant insects wouldn't normally be able to exist. This is a fantasy setting, so I'm not too worried about that. I'm just interested in the mechanical properties of chitin itself and its usefulness as armor. [Answer] Hard answer: Chitin is very heavy. The reason we don't encounter giant insects in the real world, is that exoskeletons are too heavy. The cube-square law says that, even though a small creature can support an exoskeleton. . . . [![enter image description here](https://i.stack.imgur.com/nRn8H.jpg)](https://i.stack.imgur.com/nRn8H.jpg) . . . a creature 5 times longer has a 125 times heavier shell, but is only 25 times stronger. This is why we only get big arthropods in the sea, where the water does some of the lifting for them. [![enter image description here](https://i.stack.imgur.com/275id.jpg)](https://i.stack.imgur.com/275id.jpg) The earliest forms of complex life were arthropods and molluscs. Both have heavy shells. This is the main reason vertebrates did so much better on land. Edit: As pointed out, another limitation on giant insects is how they don't use lungs and are unable to pump oxygen deep into the body. In order to make your chitin armor realistic you must first solve the problem of realistic giant insects. Failing that I suggest woolen armor. [![enter image description here](https://i.stack.imgur.com/utnD3.png)](https://i.stack.imgur.com/utnD3.png) This is called a gambeson. It is a big uncomfortable woolen blanket that is pretty resistant to slashing blows ((especially from jagged weapons) but not so much piercing. Do you think you could cut through your bed duvet in one swing? Thought not. Historically gambesons were worn under metal armor but also on their own since metal was expensive. Maybe you could make a helmet out of several large crabs or insects stuck together? It would be pretty heavy compared to its protective value, but it's only a helmet and not a full body cover. Soft answer: Sure If I were doing this, I would say the technique is to grind up insect/snail/crabshells and with some secret ingredients to make a gluey paste that is then soaked onto fabric. It forms a plasticky but breathable layer that is much less clammy than a gambeson and is better protection against piercing. [Answer] from what i get from google, chitin is a good material for composite, i dont know chemistry or how to create composite armor but maybe this help? warning, as i mention, i dont know anything regarding chemistry, and i may end up give link or cite a misleading information. so put a grain of salt in what i put here. from:<https://en.wikipedia.org/wiki/Chitin> > > Chemistry, physical properties and biological function > > > The structure of chitin was determined by Albert Hofmann in 1929.[3] > > > Chitin is a modified polysaccharide that contains nitrogen; it is > synthesized from units of N-acetyl-D-glucosamine (to be precise, > 2-(acetylamino)-2-deoxy-D-glucose). These units form covalent > β-(1→4)-linkages (like the linkages between glucose units forming > cellulose). Therefore, chitin may be described as cellulose with one > hydroxyl group on each monomer replaced with an acetyl amine group. > This allows for increased hydrogen bonding between adjacent polymers, > giving the chitin-polymer matrix increased strength. > > > In its pure, unmodified form, chitin is translucent, pliable, > resilient, and quite tough. In most arthropods, however, it is often > modified, occurring largely as a component of composite materials, > such as in sclerotin, a tanned proteinaceous matrix, which forms much > of the exoskeleton of insects. Combined with calcium carbonate, as in > the shells of crustaceans and molluscs, chitin produces a much > stronger composite. This composite material is much harder and stiffer > than pure chitin, and is tougher and less brittle than pure calcium > carbonate.[4] Another difference between pure and composite forms can > be seen by comparing the flexible body wall of a caterpillar (mainly > chitin) to the stiff, light elytron of a beetle (containing a large > proportion of sclerotin).[5] > > > In butterfly wing scales, chitin is organized into stacks of gyroids > constructed of chitin photonic crystals that produce various > iridescent colors serving phenotypic signaling and communication for > mating and foraging.[6] The elaborate chitin gyroid construction in > butterfly wings creates a model of optical devices having potential > for innovations in biomimicry.[6] Scarab beetles in the genus > Cyphochilus also utilize chitin to form extremely thin scales (five to > fifteen micrometres thick) that diffusely reflect white light. These > scales are networks of randomly ordered filaments of chitin with > diameters on the scale of hundreds of nanometres, which serve to > scatter light. The multiple scattering of light is thought to play a > role in the unusual whiteness of the scales.[7][8] In addition, some > social wasps, such as Protopolybia chartergoides, orally secrete > material containing predominantly chitin to reinforce the outer nest > envelopes, composed of paper.[9] > > > Chitosan is produced commercially by deacetylation of chitin; chitosan > is soluble in water, while chitin is not.[10] > > > Nanofibrils have been made using chitin and chitosan.[11] > > > and from this link regarding nanofibril :<https://nanografi.com/blog/cellulose-nanofiber-also-known-as-cellulose-nanofibril/> > > Cellulose Nanofiber (CNF) which is sometimes also called as Cellulose > nanofibril is encompassed by Nanocelluloses alongside with Bacterial > nanocellulose (BNC), Cellulose Nanocrystal (CNC). > > > Despite the fact that BNC and NCC possess several unique properties, > the advantage of Cellulose Nanofiber (to BNC and NCC) is that its > biodegradable nature, low density, high mechanical properties, > economic value and renewability. Nanofibrillated Cellulose can be > produced at large industrial scales, with a variety of functional > groups, and by a multitude of industrially attractive processes. > Nanocellulose materials and specifically Cellulose Nanofiber generate > an immense interest due to many exceptional properties and the > capability of producing the materials from a multitude of sustainable > resources. > > > Nanofibrillated Cellulose features outstanding intrinsic mechanical > properties due to their high crystallinity (high specific stiffness > and strength), attractive nanoscale dimensions, and high surface areas > suitable for chemical functionalization. Nanofibrillated Cellulose > allow for the formation of pure nanopapers or can be integrated into > bioinspired nanocomposites leading to excellent multifunctional > properties. Cellulose Nanofiber emerges as a renewable and sustainable > feedstock for future biobased high-performance materials with > environmentally friendly character. > > > Some characteristics of Cellulose Nanofiber: > > > Cellulose Nanofiber films have excellent gas barrier properties, and > these have also been shown to be less affected by the extent of > delamination as long as the barrier threshold has been reached. > > > Crystal structure of nanocellulose is consisting from packed array of > needle-like crystals. These crystal structures are incredibly tough > and their strength value is nearly eight times higher than stainless > steel. Therefore, nanocellulose can be perfect building material for > the future body armor studies. Nanocellulose is bendable, transparent, > light and strong material therefore it can easily take place of the > plastic or glass. > > > > ``` > Cellulose Nanofiber is used in Absorbent Aerogels. > Cellulose Nanofiber is used in Flexible Screens. > Cellulose Nanofiber is used in Flexible Batteries. > Cellulose Nanofiber is used in Biofuel Industry. > Cellulose Nanofiber is used in Body Armor Applications. > > ``` > > also from L.Dutch link in comment, you can also turn chitin into layered of scale armor outside of lamellar that you already mention, which from what i get is considered similar or more flexible dermal armor like. [Answer] ### If it could be shaped, it might make for expensive, good heavy armor. But all practical details will depend on how easy the chitin is to get, how easy it is to work with, and what other options exist. The normal considerations (chitin is heavy, so organisms with chitin armor won't get all that big) can be hand-waved away even without resorting to a fantasy setting. Creatures that live underwater can bear greater weight, for example, and in a high-oxygen biome insect-style respiration is easier and operative over larger distances. Even if we don't get organisms on a scale that would allow for breastplate-sized chitin sections, armorers could achieve a lot with chitin scale and layering. I don't know how useful it would be as large, solid plates in the first place. Even though it's a strong barrier, there are lots of practical issues. The biggest one I can think of offhand is that it isn't going to be repairable-- you can't melt it down and reforge it, nor weld on a patch, or anything else. You just have to replace the piece. Scale-style armor doesn't suffer that same drawback, as you can replace damaged sections. Why bother? (alternatively, it has to be worth it) That isn't meant to be a snarky question. It will only be useful armor if it can provide acceptable protection at a cost in effort, time, and materials that is favorable compared to other options. The alchemy-like method makes that very difficult to estimate (or, conversely, easier to assert, since it's a fantasy technique in the first place!). As I recall from my biochemistry courses, chitin is a polysaccharide (a sugar, though certainly not a table sugar) with a particularly tight angle of rotation that makes it very resistant to solvents, like water. You're not going to be able to work chitin at all like you would work metal or leather, so the alchemy which makes it possible is whatever you imagine it to be and it works however you imagine it should work. With that in mind, secondary effects of the giant-chitin become important. If it makes the chitin easier to work with, might it cause the armor to lose its most important properties if sprayed onto combatants during a battle? Even if it can be worked, how much time and effort does it take to make a set of chitin armor versus other options, such as chainmail, full plate, wood armor, boiled leather, or quilted armor? If the armor is so good, how are people killing the insects already covered in it, and why would a person wearing it fare better? tl;dr: If it can be shaped to be appropriate armor for a human, it's probably going to be better than being unarmored in many situations. How useful it would be is a function of how much better it performs than the next-best option available to the people that would be making it, and how much more or less effort it requires than the next-best option. And even then, practical concerns might make plate less desirable than other choices, like scale. This is all fantasy, so you can definitely contrive a situation in which chitin armor is a practical choice and a situation in which it is the best choice. But a situation like that will have less to do with the chitin than it has to do with all of the non-chitin options available. [Answer] It should work, not great but usable. Now it is not going to be as strong as metal armor, few things are, but it will be as strong as real worn armor, like paper, lacquered wood, and hide armor. Interestingly Chitin is actually considerably stronger when dried, so proper treatment can toughen it up. It is light with a density similiar to aluminum. Its ultimate tensile strength is pretty bad (80 MPa when dry) but no worse than acrylic sheeting(70MPa), which you could still make usable armor out of. It is lighter (by density) than bronze or iron the choice metals for armor by a wide margin. The major problem is its [resistance to torsion](https://www.researchgate.net/figure/Mechanical-Properties-of-chitin-from-different-sources_tbl1_315837008) is shit, comparable to Polyethylene, so you need a decent thickness to do any good (but any terrestrial chitinous organisms will have said thickness) but that means it is not actually any lighter than metal armor (but not likely any heavier) while preforming much worse. But if you have a race that does not have access to metal armor it would be usable if not very durable. People made real armor out of worse materials. Unless you find a piece the prefect size you are probably looking at scale armor made from cut pieces, although finding pieces that can be cut to the perfect size for arm or leg guards could be possible. [Answer] Think scale, not plate. As several others have noted, chitin is fairly light. However, it is also quite brittle. If someone hits you with a sword, it will chip and crack rather than dent. You want lots of smaller pieces to limit the extent of this cracking, which also allows more flexibility in combat as a side effect. After the battle, your smiths will just replace the damaged scales and the armor is good as new. Alchemical apprentices might be limited to flattening chitin to make scales en masse for smiths, whereas masters could shape it into things like helms and swords that need one thick, solid piece because scale doesn't suit those applications. [Answer] From <https://en.uesp.net/wiki/Morrowind:Chitin> > > Chitin is a type of light plate armor which is constructed by laminating several layers of insect shell glued with organic resins. The design is superior to Western leather armor as it is lighter and more comfortable. It is easily found throughout Vvardenfell, but is most commonly favored by Ashlander tribes. The book Ice and Chiton tells a story of its benefits. > > > Chitin weapons are similarly created from the laminated shells of creatures to produce strong but flexible weapons, typically serrated to create a more damaging edge. > > > Chitin is used elsewhere in the Elder Scrolls series, might be worth looking at how it works there. ]
[Question] [ According to several [sources](https://www.scientificamerican.com/article/small-animals-live-in-a-slow-motion-world/), all organisms process information at different rates - to a fly, the world is in slow motion (relative to humans), for instance, but to a pigeon, the world may move faster. If the ability to see the world in "slow motion", which is now known to be biologically possible, could be passed to a human, it may have some interesting consequences - boredom, perhaps, unless the person adapts - but also faster responses to stimuli, faster reflexes, and possibly an edge over slower-reacting, non-altered human competitors. So how do we do it? What is (if there is) a feasible way to alter a person, either genetically or surgically, to see the world at an altered rate, thus allowing for "slow motion thought" and the resulting enhancements? [Answer] How fast we see the world is probably mostly tied to our ability to process sensory information. A fly have a quite small brain with very little processing and interpretation compared to a human and can thus process it's limited perceptual world faster. If the above hypothesis is correct I see three possible routes to perceiving the world in slow motion: ## Speeding up the brain By installing augmentations into the perceptual parts of the brain it could theoretically be possible to improve its processing power and thus allow it to churn through all the input faster. This is an unlikely alternative since the brain is already an immensely powerful parallel information processor. Maybe quantum-computational cybernetics could do something in this area but it would probably be far off. ## Information Sorting / Blinds Instead of attempting to speed up information processing, one could try to install something that cuts away unimportant interpretation steps or discards non-important information thus allowing the brain to process the remainder faster. Maybe this could even be achieved by an advanced drug targeting specific receptors or areas of the brain. The effects of doing this would probably be severe in some respect: Speedup but tunnel-vision and singular focus — useful for hackers. Speedup but all emotional interpretation and meaning disappears, it's all just movement and reaction — useful for drugged super-soldiers. Drop all outside awareness but speed up thought (Meditate 1 hour in 5 minutes) — useful for philosophers, mathematicians and maybe monks. ## Adrenaline surge Lastly it seems like the brain have a mechanism of its own to do this. When in a life and death situation many people claim time moved slower. This could be because when the body gets huge levels of adrenaline it kicks everything into overdrive using all resources available to just get through the next few moments. Probably this also works partly like the second alternative — non-essential interpretation and critical thinking is discarded and everything falls down to instincts. Either implants could release high levels of adrenaline artificially, or a drug of some kind could trigger similar responses. Either way it is likely that long term use would be dangerous. Outside a few moments the stress of going on overdrive would start to cause damage and resources would run out. [Answer] ## Unite the Conscious and Subconscious Minds The United States military is currently using the preexisting ability of the human subconscious to [process visual data at a rate of 5 images per second](http://newatlas.com/us-army-eeg-brainwave-image-analysis/40309/). Even though the conscious mind is unable to be aware of what is seen, the person's nervous system signals when something interesting has been seen. EEG measurements pick up the signal. So, the human subconscious already has the ability to perceive and process data at a rate significantly faster than the conscious mind does. I have no idea how it could be done, but if the conscious mind and the subconscious mind could be united to function as one consciousness, that could do the trick. [Answer] To really see details that are happening quickly, it would be necessary to make the brain think faster. That’s why flies are fast: their brain is simpler and naturally works faster. In limited cases, special systems could be used to buffer the fast signal, which is then processed slower. This is how bats hear their sonar returns. For a repeating cyclic event, the brain could build up an awareness of the details from snapshots taken at different points in the cycle, over time. Of course, in our case, general intelligence allows us to build instruments and recording devices, and supplies the curiosity to go beyond our bare senses. [Answer] Experiment: <http://www.npr.org/sections/krulwich/2009/05/18/104183551/the-secret-advantage-of-being-short> Have someone lie on their back with eyes closed. Touch a pin to their big toe and to their nose at the same time. Ask them if they felt them at the same time. The answer is always "yes". What's weird about that is that this was true regardless of the person's height. 4'0" or 6'7", both felt the two touches simultaneously. But the nerve propagation is slow enough that there's a 10th of a second difference in transmission time from those extra 2.5 feet, easily within human perception. From this and several other tests, the researchers determined that our senses are already working far faster than we perceive, but our brains process that data to create a coherent worldview. So training the mind to give you the unfiltered data might be possible. Indeed, that's what several meditation techniques claim to be able to achieve. [Answer] ## Genetically Enhance the Brain Perhaps the time processing parts of a fly brain could be added into a human's brain, via genetic engineering. Perhaps a hummingbird's time sense would be even faster than a fly's. I assume the human would adapt best if the relevant DNA was inserted in the egg & sperm, so they physiology would have the ability from birth, and thus would have the best chance of adapting fully. If human-sized fly parts were surgically inserted into an adult human, it might be much more difficult for the rest of the physiology to adapt. I have no idea how many other human physiological characteristics would need to be changed to allow the fly brain parts to work perfectly in a human physiology, but in time I'm sure science will try this and figure it out, if it is at all possible. [Answer] ### A note regarding adrenaline surge, as suggested by JDługosz: I can confirm that it is a valid thing, I was in somewhat severe accident about a decade ago during which I experienced a pretty strong adrenaline surge. I completely lost my ability to judge time and I think the entire event took anywhere between 5-30 seconds, but I experienced it as if it took 5-10 minutes regarding how much time I had to think. Without going in to gory details, I got stuck with my arm on a farm and was about to get it ripped off and I tried to figure out ways to get away in once piece. What I noticed was that while I had a lot of time to think about potential ways to escape, I could not move faster than I could during "normal time"; trying to perform any action in "bullet time" was like trying to swim in syrup. In the end, I never managed to move enough to take any real action to save myself, I simply ended up lucky and only lost a finger. My point is, while adrenaline surge will act as a way to increase the mental reaction, it will not work as a way to boost any body reaction. One will be able to see what is about to happen, but one will not be able to do much about it. If one compares that to the Smarter every day episode where they look at a [raptor strike at a moving target](https://www.youtube.com/watch?v=J2eN6CKkg9w), then it appear as if the bird is capable of seeing the error it is about to make and almost be able to adjust for it while "on the fly". [Answer] ## Unlock Savantism [Savantism](https://en.wikipedia.org/wiki/Savant_syndrome) proves humans can have abilities normally considered superhuman. For example, someone with [highly superior autobiographical memory (HSAM)](https://en.wikipedia.org/wiki/Hyperthymesia), like [Becky Sharrock](http://www.news.com.au/lifestyle/health/mind/the-mindboggling-life-of-becky-sharrock-one-of-the-few-people-in-the-world-who-remembers-everything/news-story/e2089a466a640ff87cd090a11d2e6b17), can remember every single thing that has ever happened to her. [Daniel Tammet](https://en.wikipedia.org/wiki/Daniel_Tammet) can mentally perform extremely complex mathematical calculations, [such as 27 to the 7th power](http://abcnews.go.com/2020/autistic-savant-daniel-tammet-solves-problems-blink-eye/story?id=10759598), in seconds. If scientists discover how to unlock savantism without inducing degrading side-effects, then superhuman feats could become common. Perhaps one savant ability could be the ability to think at extremely high speed. I have thought if people ever evolve to naturally have savant abilities, they might be considered an entirely new species, homo superior, or a more politically correct homo savant. [Answer] Something to also think about is whether the rest of the human body can speed up to match the faster perception: muscle contraction, oxygen delivery and waste removal, etc. EDIT: In the simple case, a person with sped up perception might feel like they are wearing a heavy cumbersome suit. More fundamentally, a sped up perception might require increased oxygen flow to the brain, i.e. faster heart rate. I am not sure how fast a fly's heart beats, but there would surely be physiological limits on how fast a human heart can beat. ]
[Question] [ What would be the possible and definite effects of two galaxies colliding with each other? (Milky Way & Andromeda) Long-term and short-term effects are both important. I'd like to know because it's planned to happen in the future of the story. [![Two galaxies shown near each other](https://i.stack.imgur.com/jm1WQ.jpg)](https://i.stack.imgur.com/jm1WQ.jpg) [Answer] Honestly, it's only exciting if you speed up time to billions of years per second. [![enter image description here](https://i.stack.imgur.com/vnEK9.gif)](https://i.stack.imgur.com/vnEK9.gif) It's unlikely that any of the systems inside would actually collide, some systems may get flung out into intergalactic space, but it all takes a very very long time. Short term, entire civilizations could rise and fall without ever realizing it's happening. Long term, many systems are lost to the void, but the new galaxy wouldn't appear all that different from other galaxies. Even the systems flung out would not be very different locally, they'd just have dimmer stars in the sky at night. [Answer] For anyone who wants to see a cool simulation of a galaxy, merger, I can recommend a neat little applet): [Galaxy Crash JavaLab](http://burro.astr.cwru.edu/JavaLab/GalCrashWeb/).1 Two more good sites with a bunch of different simulations are [the GALMER website](http://galmer.obspm.fr/) and [this one](http://isc.astro.cornell.edu/~spoon/crashcourse/collisions.html) (which turns out to have [Samuel's simulation](https://worldbuilding.stackexchange.com/a/29943/627)). Cool, huh? Anyway, let's look at some scientific work on galaxy collisions. [Cox & Loeb (2008)](http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?2008MNRAS.386..461C&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf) simulated the future collision of the Milky Way and Andromeda. Here are some of their results: * There is a small chance that the Solar System will be flung out by tidal forces. * There is an equally small chance that the Solar System will be captured by Andromeda in the early stages of the collision, before the formation of the result of the merger. * Gas in the galaxies could be heated by an additional order of magnitude, from ~3$\times$105 Kelvin to ~3$\times$106 Kelvin. This alone could impact star-forming rates. Star formation is expected to increase anyway, due to other factors, although given that neither galaxy has a lot of gas, this will be minor compared with other collisions. * The result will most likely be an elliptical galaxy, leading to a different mass distribution and a slight change in the Solar System's orbit, even if most of the exotic tidal scenarios don't happen. [Van der Marel et al. (2012)](http://iopscience.iop.org/article/10.1088/0004-637X/753/1/9/pdf) brings up another good point: These two galaxies aren't the only players. The [Triangulum Galaxy, M33](https://en.wikipedia.org/wiki/Triangulum_Galaxy), has interacted with Andromeda in the past and will do so in the future. This may be before, during, or after the Milky Way-Andromeda merger (which itself will take quite a long time). Both the Milky Way and Andromeda also have satellite galaxies, which could play important roles in determining the fates of a select few stars. The addition of a third galaxy (which isn't as massive as the other two) has additional effects: * There is a 20% chance that the Solar System will go through M33 within 10 billion years, leading to a slightly higher chance of collision with other stars. * The Solar System will likely be pulled further away from the center of the result of the merger than it is now (although this may happen without the help of M33). Finally, John Dubinski has written up [an excellent overview](http://acme.highpoint.edu/~afuller/PHY-1050/resources/GreatMilkyWayAndromedaCollision.pdf) (which is also quite non-technical) of the collision. He notes that a binary supermassive black hole will form during the merger, which could - depending on the precise path of the cores, eject the Solar System entirely. Actually, I did find a cool simulation, and [some images from it](http://www.cita.utoronto.ca/~dubinski/merger/bigmerger.html), each separated by approximately 170 million years: [![](https://i.stack.imgur.com/oNpLU.gif)](https://i.stack.imgur.com/oNpLU.gif) --- 1 Designed, programmed and developed by Chris Mihos, Greg Bothun, Dave Caley, Bob Vawter, and Cameron McBride. [Answer] As stated in Samuel's answer: over a single human lifespan, there will be no change to the star positions measurable by human perceptions. Our instruments and data recording devices will be able to measure the change but that will be of primary interest to scientists and not generally known to the population as a whole. It will be boring to the common person. No star collisions are expected from the Milky Way with Andromeda merger. Stars flying through each other's solar systems would be possible but exceedingly unlikely. You are far more likely to have exciting sky stuff happening in a closed [globular cluster](https://en.wikipedia.org/wiki/Globular_cluster#Classification_of_globulars). If you still want to use the merger as a "historical setting" and in your story humans have not made it to the stars. You might make a series of solar system close approaches caused by the merger to make the human diaspora possible. With computer simulation, the colonists could predict with some reasonable reliability the trajectory of the stars passing by (will get flung into intergalactic space, which will get flung into the core, and which will remain in the [galaxy's habitable area](https://en.wikipedia.org/wiki/Galactic_habitable_zone) - too close to the center and planets get cooked by supernovae - too far from the center and there's not enough heavier elements to sustain life). [![Sun's trajectory through the Milky Way](https://i.stack.imgur.com/bKM8s.jpg)](https://i.stack.imgur.com/bKM8s.jpg) One thing that will change is the collision of the two galaxies' gas and dust clouds. The collision will trigger massive and violent star forming areas. Some of these will form exceedingly large (e.g. $100 M\_{\odot}$ - 100x the mass of the Sun). These stars burn hot, die quickly, and with a big bang (a [Supernova](https://en.wikipedia.org/wiki/Supernova)). [![Artist's impression of a supernova remnant](https://i.stack.imgur.com/RjurW.jpg)](https://i.stack.imgur.com/RjurW.jpg) A close approach of one of these to the Earth might spell the doom for every living thing on Earth. Currently in our galaxy we expect about 1 supernova per century. During the merger, Earth might see many more supernova (from a distance - because a near one would leave no witnesses) at a time. ]
[Question] [ I have an idea for a location in my world that I would like explained by natural phenomena rather than magic if at all possible. I would like to have a temple...that floats. The specifics: * The temple (and the ground it rests on) floats at least 18 inches (46 centimeters) and no more than 5 feet (1.5 meters) off the ground. * The temple should be approximately 20 feet wide (6 meters) and 40 feet deep (12 meters) and the ceiling should be at least 10 feet up (3 meters) * The 'land' it sits on may be sized to accommodate the scenario * The temple should be made of some kind of stone, less dense stone makes more sense I suppose * The temple and its platform/land will be chained down to the earth so it doesn't fly away. * A large enough gathering, say 40 - 50 people (average weight 170 lbs/77 kg) should cause it to touch the ground * The floating effect should not be maintained by magic. If there is no plausible way to create it in the first place, magic can be used to set things up. Questions: 1. What could cause this temple and its land to float? This does not have to be 'hard-science' but should be scientifically plausible even if it is in no way likely to happen. 2. How much force would it take to keep the temple and its land afloat? (use whatever materials make sense within the parameters of the scenario) I would like calculations for this portion of the answer. [Answer] Building on @oxide7's answer regarding magnetism, you might consider quantum locking. Quantum locking is a hard-science phenomenon in which a superconducting material can be "locked" in place in a magnetic field, even against a gravitational force. Search for quantum locking on YouTube for some really neat videos of the phenomenon. Of course, there are some drawbacks. * All known superconductors only have superconducting properties at very low temperatures (the highest common one, I think, operates at 70 Kelvin). But there is no reason there could not exist some strange material we have not yet discovered that has superconducting properties at room temperature. * Quantum locking fails when we apply enough force. To support more force we need more superconductor and a bigger magnet. You would need a lot of superconductor and a very strong magnetic field to support a stone building. This would get very, very expensive. But again, I think you could work around that too. The superconductor could have been discovered at the temple site (naturally occurring), and there could be a iron rich magma pocket-turned-dynamo in the mountain which uses some fancy magnetohydrodynamics to generate a strong natural magnetic field at the top of the mountain. Note also that the superconductor works best when formed in a very thin sheet. With a few conservative additions to current science, I think that quantum locking does what you want. For the next part, assume that your temple is $40\times20\times 10$ feet with $1$ foot think walls and ceiling. This comes to 1834 cubic feet, or 51.93 cubic meters. Assuming that you may want a spire, columns, or some other type of decorative stonework, and ground for it to sit on, I will almost double this to 100 cubic meters. At a density of 2600 kilograms per cubic meter of granite, we get 260,000 kilograms of granite. Multiplying by gravitational acceleration, we arrive at about 2.5 million newtons of force. To put this in perspective, this is about one fourteenth the force provided by the principal stage of a Saturn V rocket. [Answer] Turn [the Hindenburg](https://en.wikipedia.org/wiki/LZ_129_Hindenburg) on its end and put it in the attic. Shape the outside of the attic in some visually impressive way, like maybe a church steeple. Hang the gathering place underneath. For the walls, hang thin stone cladding onto an aluminum skeleton. Oh, the divinity. [Answer] The temple could be the terminus of a space elevator. These don't need to be anchored to the ground: their centre of gravity is in a geosynchronous orbit and the cable is basically just hanging down from that. The cable stretching up from the temple roof and disappearing into the heavens might be seen as proof of the temple's divine greatness. An actual elevator car coming up and down the cable from the temple would probably add to this, and citizens who had been generous at collection plate time could maybe get a ride in it. [Answer] OK, first let's estimate how much force you'd need. Let's start with the mass. The temple should be made of stone, you say. The lightest stone as far as I know is [Pumice.](https://en.wikipedia.org/wiki/Pumice) The stone in the image on the Wikipedia page has, according to the caption, a density of $0.25~\mathrm{g}/\mathrm{cm}^3$. Since I can't fine a more general statement about the density (apart from "it floats on water") I'll assume that this is a typical density, and use it in the following calculations. Unfortunately I cannot find much about the other properties, so I can only guess on how thick the walls would have to be. I'll assume 25 cm, which is a normal thickness for an outer wall. I have no idea what a normal thickness for the roof would be, so I'll assume the same there; the floor plate (the "land") should probably be twice as thick to carry the load. But note that this is just a guess. I'll just calculate with a flat roof, although the temple will probably have a non-flat roof. So putting all the numbers in, I get: * 1 roof: $600~\mathrm{cm}\times 1200\mathrm{cm}\times 25\mathrm{cm}\times 0.25 \mathrm{g}/\mathrm{cm}^3 = 4500~\rm kg$ * 2 long walls, each half as high as the roof is wide: $4500~\rm kg$ * 2 short walls, each half as long as the long walls: $2250~\rm kg$ * 1 floor: twice as thick as the roof, $9000~\rm kg$ * 50 people, $77~\rm kg$ each: $38500 kg$ * You'll probably also want to put some stuff into the temple; let's add another $900~\rm kg$ for it. So the total mass of the temple including people is about $25000~\rm kg$. Assuming earth-like gravitation (i.e. $g=9.81~\mathrm m/\mathrm s^2$), this gives a force of about $245~\rm kN$; let's round it up to $250~\rm kN$ for easier calculation (that then allows also for a more fancy roof). Now the [density of air](https://en.wikipedia.org/wiki/Density_of_air) is $1.225~\mathrm{kg}/{m}^3$, so the lower bound of the volume you'd need to get enough buoyancy (namely, if you could just use pressured vacuum, which of course doesn't exist) would be about $204\,000~\mathrm m^3$. For comparison, your temple itself has a volume of $216~\mathrm m^3$. So you'd need about 244 times the volume of your temple to create enough buoyancy (in reality more since even the lightest gas is considerably heavier than the imaginary pressured vacuum, and thus provides less buoyancy). So unless you could live with a gigantic balloon on top of your temple, buoyancy is out of the question, even if you manage to get the mass down to a tenth of what I calculated. So what else could we use to create the gigantic force? Well the strongest force in the universe is the electromagnetic one. So let's see if we can do with that. The first idea would be that the floor and the temple contain electric charges, so they repell each other. You'd need to perfectly insulate both charges (especially the one in the floor) so they don't simply flow away. Now, how much charge would you need? Let's for simplicity assume that the charges of the temple and the floor are both contained in giant plates, one in the floor below the temple, and one in the floor of the temple. Let's als assume that the charges are of the same magnitude. The formula for the force is then $F = Q^2/(2 A\epsilon\_0)$ where $Q$ is the charge, $A$ is the area of the plate, and $\epsilon\_0 = 8.85\cdot 10^{-12}~\rm As/(Vm) = 8.85\cdot 10^{-12}~\rm C^2/(Nm^2)$. Solving for the charge gives $Q = \sqrt{2 A \epsilon\_0 F}$, and inserting $A = 6~\mathrm m\times 12~\mathrm m = 72~\mathrm m^2$ and $F=250~\rm kN$, we get $Q = 0.017~\rm C$. Now that doesn't sound much, but when you calculate the field strength that results, you find that it is $14.7~\rm mV/m$, which is almost five times the breakdown field strength of air (that is, the voltage at which you get lightning/electric arcs). So again, that's not a good solution (I certainly wouldn't enter that temple!) So what remains is magnetic forces. Unfortunately I don't know how to assess if this would give a reasonable force without unreasonable assumptions. [Answer] You could have the land and the temple be built out of some magnetic material that doesn't weight too much. The magnetic field of the world could be out of whack from an oddly spinning core, or binary cores or anything strange like that. This temple probably wouldn't be the only odd phenomena tho. The ground the temple hovers over could simply be pole reversed magnetic material also. Electromagnets could be a thing too, but this would be deliberate. You could have the temple be levitated by heat trapped underneath a specifically shaped land under the temple. The temple could be above some fault with heat vents. The temple could be made of a material that is very light, and strong and also somehow infused with lighter than air particles like hydrogen or helium. The temple could be in certain area with massive updrafts and the temple was built to specifically take advantage of this and remain "neutrally buoyant". Or the temple is simply built with such perfect craftsmanship that the normal wind in the area (it's a bit windy to maintain the effect) that the temple levitates because of it. I have more idea if none of these are any good. With magic I can give you another dozen at least. [Answer] Soft Rock, Shelter & Bugs Centuries earlier, your natives found an interesting, porous material (like limestone but way more porous) that was extremely rare, so they used it to build a temple and clad it with decor. The interesting thing about this rare material is that there is a rare bug like a non-damaging termite that loves to inhabit it, and only it. The bug has a unique characteristic. As it ages, and it consumes energy or other bugs, it has a bladder that expands with a lighter-than-air gas. As the colony grew, the temple began to lift. This was an amazing miracle. Over the years, when the colony of bugs got "full" in the all of the building material, the temple had lifted about a meter in the air! It lowers ~ 1m depending on the number of worshipers in it, finally touching the ground at about 40 to 50 people. Luckily, this ancient temple had dense trees that grew around it as it gradually lifted over time. The tree branches help gently keep the temple from drifting away and help protect it against high winds. [Answer] Magnetic levitation requires no power and can lift a large amount of weight if you use enough magnets or strong enough magnets. The problem with static magnetic fields is that it is unstable, the building will try and spin around so north and south poles from the base and building are next to each other and then drop. The chain on the building though would actually be to stop it spinning, not to stop it flying into the air. It would work rather like toys such as this one: [![enter image description here](https://i.stack.imgur.com/nltUb.jpg)](https://i.stack.imgur.com/nltUb.jpg) In this case the plate at the end and shape of the spindle stop it from spinning around or moving sideways. The same could be achieved with a chain though. [Answer] * The temple rests on a single flat stone as a baseplate. * Under the baseplate there is a shaft into the ground. * A complicated tunnel system ensures that there will always/most of the time/often be a strong wind out of the shaft. This wind is strong enough to lift the stone with the temple, but not strong enough to lift the visitors as well. The likelihood of finding a natural place like that is slim. Magic might reshape the landscape and shape the stone foundation. Getting onto the slab will be tricky, considering the wind speed all around. [Answer] > > The temple and its platform/land will be chained down to the earth so > it doesn't fly away. > > > That makes it easy. The chains appear to be holding it down but in actual fact, they are holding it up. All you have to do is weld the links together and make the chains into solid struts. ]
[Question] [ During a brainstorm session the idea of the ruler of a maritime empire sitting upon a throne made from worked salt came to me. Before I break out the handwavium there is something that I would like know: Is salt a workable material? If melted down could salt be worked into various useful or at least aesthetically pleasing shapes? If so what would it look like? [Answer] You can make stuff from salt. The fine people who worked the [Wieliczka Salt Mine](http://en.wikipedia.org/wiki/Wieliczka_Salt_Mine) did their darnedest to make statutes! From those works, you can see that salt looks a lot like other rocks you find around. You may not even notice until you (or something else) licks it! Salt itself isn't that hard. The US Department of the Interior has a [free .pdf](http://pubs.usgs.gov/tem/1048/report.pdf) you can check out some of the properties of salt. They talk about different strengths of salt. If you compact your salt, it will be stronger. If you melt you salt together, then it will be stronger still. At its most strength, though, it still very weak compared to steel. What about [molten salt](http://en.wikipedia.org/wiki/Molten_salt)? That's a thing. Depending on what type of salt (like not table salt), you can melt it more easily than metals. Table salt, however, has a melting temperature of [801 degrees C](http://en.wikipedia.org/wiki/Sodium_chloride). Like many other properties, that's less than steel. Pure table salt, though, can have a clear crystalline look, which may be very desirable for certain artistic effects. Can molten salt be blown, like glass? According to [this source](http://www.nist.gov/data/PDFfiles/jpcrd167.pdf), the viscosity of molten table salt ranges from $0.0792 mN\s\m^{-2}$ (at 1210 K) to $1.030 mN\s\m^{-2}$ (at 1080 K) (Page 824, table 24.2). $SiO\_2$, a common type of glass, has values of viscosity as low as 7.85 $mN\s\m^{-2}$ (at 1500 K) according to [this source](http://www.ceramics-silikaty.cz/2006/CERAMIC_2_2006.pdf?origin=publication_detail) (page 61). Given this, can you blow it like glass? It appears that molten salt has 1/7th the viscosity of glass while molten. I do not have much experience blowing glass, but I doubt that you could use the same method for molten salt. You could used dissolved or molten salt in [casts](http://en.wikipedia.org/wiki/Casting), which would allow the salt to form various shapes. Tricky individuals have developed various methods of casting, such as die casting or centrifugal casting, which can make objects of various shapes. Add the solubility of salt in water, and you can smooth any edges or errors from your castings. It should be noted that there are many different types of salt out there. I've assumed you want to know about table salt. Different salts will look differently. A pure table-salt crystal is clear. With other things in it, it can look white or any other color from additives. If you've had molten table-salt, and let it cool, I would assume that it would be white or clear in color, depending on what other chemicals it took up. In short, yes, you can use salts for art. You can easily chisel it, melt it, dissolve it, and therefore form it into various shapes. Molds and casts would make various salt shapes possible. You could use a metal chisel and easily chisel whatever shape you would like. [Answer] Salt could potentially be poured into a mold and made into some shape, or things could be carved from large blocks of it, but there are far better things to work with. Salt is an ionic compound, and as such, it's quite weak. Nothing you make out of it will be structurally all that useful. It also forms cubic crystals, which means it will want to break at right angles if you're trying to work with it. It can be cast into various shapes, but isn't a terribly attractive material. It's whitish and opaque. It also needs to be heated to 1474 degrees Fahrenheit, which, while attainable, isn't trivial for non-functional art. ![A sculpture cast from salt](https://i.stack.imgur.com/UwQsC.jpg) [Answer] You need only google "salt sculpture" to verify that a salt throne could work. There New-Age crystal craze has also incorporated salt crystals for artistic purposes. If you look at the chemistry, there's a few more things a salt-smith may be interested in. seawater salt is mainly Sodium (Na+) and Chlorine (Cl-), with Magnesium at a tenth the concentration of Sodium. If you melt Sodium Chloride, (801 C) you can run an electric current through it [2] to release the chlorine gas, leaving Sodium behind. (Or you can collect the chlorine gas to make bleach or kill people) Sodium is a soft metal you can cut with a knife and conducts electricity well. It could conceivably have some uses. If you separate out the magnesium, it's reactive enough for you to run a magnesium-based engine [1]. [1] <http://en.wikipedia.org/wiki/Magnesium_injection_cycle> [2] <https://chemistry.stackexchange.com/questions/884/how-did-michael-faraday-melt-sodium-chloride> ]
[Question] [ I have a basic idea for a world that I am fleshing out. Basically a dystopian future based on minimal, if any, resource scarcity. This sort of society was addressed humorously in a Cracked After Hours video, but was also touched on in The Matrix (originally the matrix was free of scarcity) and the experiments of John B. Calhoun. But those simply state that a world without scarcity is doomed to fail. Not particularly what I am looking to demonstrate. Now I happened upon [this link](http://www.quora.com/How-can-the-world-function-without-money-in-Star-Trek) in my quest to find a similar societal structure, where it suggests that people who don't want to do anything won't and vice versa, but then how do you motivate anyone to do something that isn't particularly glamorous? In our society it's money, in communism it's things, in fascism it is the military state. But are their other options since nobody really wants for anything in such a society? Sorry if this is poorly asked. I guess a specific example would be a garbage man. Assume society still generated garbage and didn't have automated pickup how would you convince your standard human to pick up other people's garbage. [Answer] I suppose you have to go through what is and is not scarce. Are raw materials scarce? Energy? Skills? In your garbage example, I'm not clear on why there isn't automated pickup. But let's take that assumption. Assume energy and raw materials are not scarce. Perhaps what happens is each person is responsible for their own garbage. Instead of having a garbage truck drive around and pick up trash, perhaps everyone has to take their trash to the dump. The problem with this of course is pollution. So rather than one garbage truck collecting trash for a hundred people, we have fifty people each collecting their own trash. Wouldn't there be a high level of pollution from this? Even ignoring pollution, look at it from the other side. Why would anyone take the trouble to grow crops, process them into food, and transport them to market? Trash is relatively easy. We landfill it or burn it. Making food can be complicated. Someone has to plant, weed, fertilize, remove pests, and harvest a crop. After harvest, a crop needs to be transported to be made into food (e.g. tomatoes being turned into spaghetti sauce). Then it needs to be transported again to the grocery store. Assume that we can drop the conversion into food and transport. People have to fetch their own food and assemble meals from scratch. Maybe we go back to the old days. Ninety percent of everyone is in farming. The garbage man picks up garbage in exchange for food. Note that we still have scarcity here. We have scarcity of labor. To have a true post-scarcity society, we'd have to get rid of scarcity of labor as well. We'd need automated garbage pickup, food production, manufacture, utility maintenance, etc. It's unclear if there are some things that simply can't be automated, e.g. computer programming, engineering design, scientific theorizing, and writing. Some of that people may be willing to do as hobbies. That could explain how movies get made for instance. A hobbyist writes a screenplay which another hobbyist decides to direct. A bunch of hobbyists act in it. The individuals may be driven by the potential for acclaim rather than monetary compensation. Perhaps the stack exchange model would be king (people gain reputation based on how others perceive their contribution). [Answer] This went long so let me put conclusions at the top with details at the bottom so you don't have to waste your time if I didn't come close to answering the question. A "post-scarcity" economy is impossible because: 1. Some desired or needed objects and services will always be scarce i.e. objects that can't be manufactured, services of human beings. 2. We will invent scarcity if it doesn't exist naturally. 3. Scarcity is best managed non-violently on the large scale with money in some form. 4. (1) + (2) + (3) == we will always have a scarcity economy using money. 5. Scarcity is good because it induces us to cooperate. 6. If for some reason humans don't need each other and each other's cooperation, then the only relationship left is the antagonistic one. If we don't need each other, we start killing each other. 7. If nothing manufactured is scarce, then weapons aren't scarce. 8. (6) + (7) - (4) == we're boned. 9. (1) + (2) + (3) + (4) > we're boned. Statistically anyway. "Scarcity" is good and we're stuck with it anyway. The transition to (8) would be fertile grounds for stories. If you want an abundance driven dystopia, that doesn't explode, I suggest simply extrapolating the problems of abundance we have now, obesity, drug abuse, weak personal relationships leading to isolation, alienation and depression, picking fights for fun, egocentric entitlement and narcissism, irrational fear borne of boredom etc. We might term these, "Choking To Death on Creme" scenarios. Abundance causes odd behavior, at least in pockets. The world of the today would look much improved in many respects from the perspective of say the 1950s. But it would in other ways would look insane. For example nobody who came of age before 1955 and lived through waves of viral epidemics, especially the last great polio epidemic of the late-40s early 50s, would believe that upper income, supposedly college educated people of 2014 would refuse to vaccinate their children. (I know because I know a lot of old people and they just want to b\tch slap everyone who thinks that. They always start with, "I can't believe those idiot think...") The only reason why people would even contemplate rejecting the cheapest, most effective and (largely) free medicine/disease-prevention technology in history is that they are so materially comfortable and protected from communicable disease that it seems more plausible to them that vaccines are instead wholly unneeded and only exist as part of a sinister conspiracy. (Why do we have to by all these fire proofing materials when we never have any fires? Must be a conspiracy of evil fire proof material manufactures!) People in the future will also become so comfortable with something we view as a dire threat they will make decisions that we will see as inexplicable. Lots of story fodder there for pseudo-post scarcity stories.. ## Details: The article you link to is simply wrong. We don't work because resources are scarce, we work because they are plentiful. The more resources you have, the more work you can do and the more materially and emotionally rewarding work you can do. Moreover, it is work that creates resources. That's what most people actually work on doing directly or indirectly. No "resource" save the ambient oxygen exist save that a human creates it. The more work you do, the more resources you create. The only real resource is the human mind. It creates all the other resources. Money actually exist to coordinate human work and apportion our individual expenditures of time and effort, not to allocate "resources." Since human work creates all resources, money is actually a form of communication we use to tell each other what work we need others to do and in what priority. This is called price signaling in economics. Money has never been anything more than information but now days, most money is literally just bits of data in various computers. I go weeks now without touching paper money and even that fiat currency is just symbolic information. From the perspective of history, we already live in a post scarcity world. We have more resources both in quantity and kind than previous peoples could even imagine, miraculous technology, freedom from the great diseases of history, social harmony, equality etc. We live in a time when obesity is a significant health problem for the poor, something previous generations would consider a sign that a society has passed all want. From someone from 1814, 2014 in the developed world looks like just as much a post-scarcity society as Star Trek looks to us. Imagine what our day to day lives look like to hunter-gather peoples. They look like magic and a total lack of material want. They cannot relate to our lives or even understand them. Concepts like large institutions composed of tens of thousands of unrelated strangers, are simply unimaginable. Yet we keep on working and things we value still seem scarce. The problem with the idea of a post-scarcity world is that it assumes that at some point the human desire for experiences and material tools will saturated. We will all reach a point where we say, " I can't think of anything else I want to do or have." We won't. What are rare luxuries for the rich in one generation become basic necessities for the poor in the next e.g. Less than 20 years ago, cell phones where the size of walkie-talkies and only the very rich or the very important (doctors) carried them. Now we have social welfare programs to provide them to the poor. Every "necessity" of modern life as made this transition. Or we will just invent scarcity for the hell of it. But, lets assume that the basic ideas of Star Trek and the article are true* e.g. every human can have anything material they want with zero effort just by ordering a replicator to make it (including more replicators.) They can experience anything they want by stepping on a holodeck. All this is powered by tiny fusion reactors or some magic wand energy source using materials like hydrogen isotopes which are literally just laying around in functionally infinite technologies. But there will always be things which are scarce. History has shown that scarce items become valued solely because they are scarce. Examples include a particular patch of ground valued for "the view" or antiques whose scarcity is innate because it is connected to the passage of time. Note that items valued for scarcity are also zero sum in that only one person can have/own/use them at a time. An unpublished, single copy manuscript (an anachronism today I suppose) is zero sum, scarce and valued by the exact same manuscript, mass printed or slapped on the web, would not be. This was actually shown somewhat in the ST:TNG in the episode when a ruthless trader (business people are always evil in Star Trek) kidnaps Data so he can add him to his collection of utterly unique objects such as a bubblegum scented 20th century baseball card and the Mona Lisa. Suppose you and another person covet the same innately scarce resource such as a historical artifact. Suppose they have it and you want it. How do you resolve the conflict? You can't trade for it with anything replicated because they can just replicate anything themselves. You can't offer experiences because they have the same access to experience as you. The only thing you might conceivably trade would be another innately rare object. If that worked, you'd actually be back to scarcity economy in which the trade goods would be innately scarce items. Probably they set up a complex computerized bater system to track the relative trade value of each scarce object. Such a system would eventually condense the relative value to a single number score for each object... at which point you've recreated money. Of course, there are some positions or services that would stay scarce e.g. a rank in Star Fleet, a stool in Quarks bar at any given time or a reservation at the New Orleans restaurant of Sisco's father. These too could be traded, scored and turned into money. The moral? The Second Law of Thermodynamics means some things in the universe will always be scarce. Humans will always covet some of these things often just as status indicator through genuine love of the things e.g. historical research, a hand cooked meal, actually obtaining art because you like it and not because it is fashionable.) Doesn't really matter why we want them, something will be scarce, two or more humans will want it, the only peaceful solution is to trade it for something else scarce, efficient trade will require money, and we will always have a money based scarcity economy. There are darker options though. Abundance could get us all killed. The one thing you do control that is innately scarce is yourself. People might trade something of their selves for something else innately scarce. In the best case scenario, it would be some skill or service e.g. in a world of manufactured abundance, people will value the handmade just because it is handmade. Heck, we do that today. In the worst case scenario it might be sex or public degradations. One can easily see the evolution of a society in which the rich, those with control over many scarce items, demonstrate their status by making anyone wishing for one of the scarce items degrade themselves publicly, probably in ever increasingly bizarre and protracted means. You could try to control such behaviors by government laws but governments depend on violence to function. If someone refuses to voluntarily obey a law, the government must be willing to coerce them into doing so, physically control them (prison) and failing all that, kill them. But government killing requires weapons and weapons in sufficient quantity and quality to make any resistance suicidal. If everyone everywhere can manufacture any weapon on demand, then government can't have a violence advantage and can't function. So, replicators will have to blocked from making weapons, except for those controlled by the individuals inside the government. Weapons are now scarce items. Society is now divided between the haves and have-nots, between those who have weapons and those who don't. How long will that "social injustice" last? Even if you have a perfect democracy how long will that last when the government doesn't actually need the people at all? They won't because the people in government have the same Santa Claus replicators as everyone else. Plus, they can kill citizens and citizens can't kill them. If the citizens get uppity like say, pestering the individuals in government to resign just because of the technical triviality that their term of office is over, the individuals in government can just kill the citizens, all of them if wish, and not be any worse off for it. (Hmmm... think I'll go replicate a "You can have my weapons replicator when you pry it out of my cold dead hands" bumper sticker.) You might try controlling this by giving citizens access to weapon's replicators but only collectively. Weapons replicators would require multiple commands from multiple individuals, effective voting to make weapons. That would work as long the skill to use weapons on whatever level was equally distributed e.g. everyone fight with the same model of autonomous weapons. Of course, since weapons are scarce items, the votes to control them will be traded and we have a scarcity economy again. The government scenario depends on the assumption that people won't ever be able to hack the replicators and to allow them create weapons despite the law. They will. Even if they do, the above evolution will lead to the same effective outcome : Super Mutually Assured Destruction. Everybody will remain peaceful because since every one has the same creative potential, they will all have the same destructive potential as well. Individuals will also be able to manufacture defenses as well, making successful attacks difficult (but not impossible. Since entropy favors destruction, destroying will always be easier than creating and defending.) The regulated replicator scenario also faces the practical problem of determining what objects the replicators can make are weapons and what are not. Any tool can be a weapon. Technologies redirect energy. If they redirect energy toward creation, they are tools if the redirect toward destruction for the purpose of coercing, injuring or killing they are weapons. Hit a nail with a hammer and it is a tool, hit a person with it, it is a weapon. A chemical in the right dose is a medicine, in the wrong dose a poison. How could you be sure people weren't replicating the high tech version of a hammer and then using it to hit people with? Any restrictions on replicators creates a scarcity economy and eventually human resistance. Super MAD will work great as long as not a single human being does something suicidally stupid and sets off a retaliation cascade. But there are only billions of humans in the scenario, trillions at the most, so the odds of that happening will be fairly small, right? Of course it might not get to that point. At some point in the evolution of replicators, somebody with an advantage in replicators would make the obvious calculations of the above dangers. They might conclude that at least in terms of game theory, it might be safest to simply kill off any humans you didn't need to prevent them from getting the power to kill you on a whim. You'd put such thoughts aside until it occurred to you that everyone else getting replicators will eventually make the same calculation and the odds of someone somewhere acting on such calculations? Suddenly, killing off everyone else save your little group doesn't seem so nuts, it's seems more and more like "It's either us or them. Only the first to strike has a hope to survive. We know it, they know it, we have to strike before they do and the only way to be sure is to strike right now." John Von Neuman made exactly that argument about nukes back in the early 50s when he was inventing game theory. Fortunately, Ike ignored him. Unfortunately the Soviets took their guys who thought the same thing seriously and put their nuclear forces on a hair trigger. Now imagine not a few hundred decision makers mulling over that decision but billions. Suddenly space doesn't seem big enough does it? ## Conclusions The moral is that scarcity is a good thing because it forces humans to cooperate. Of course, often in history we've cooperated to kill, loot and enslave other human beings but cooperating with a large subset of humanity is waaaay better than not cooperating with much smaller subsets all the way down to the sociopathic individual. Ironically, effective militaries are about increased *internal* cooperation. So, every silver lining has it's cloud. Still the history of the last 500 years in the developed world has been one of ever increasing size of cooperative networks. The evolution of the corporation occurred in the free cities of Northern Europe because the nobility didn't care about trade but also didn't want the traders to step in on the noble's monopoly of violence. When people needed a collective action undertaken that the noble's ignored, like building city walls or dikes, they had to peacefully negotiate with other to commit resources and times to the project. People insisted on having a say in the control of such projects and that their degree of input on that control of be proportional to the proportion of their commitment. The stock/stake owner corporation was born. Though often vilified these days, a passing fad I will wager, corporations represent the largest non-violent cooperative systems in human history. Corporations cannot coerce anyone to buy their products especially in the international arena. While interactions with the governments, can make corporation agents of he state with the coercive power of the state, the vast, vast majority of interactions with and between corporations are purely voluntary. As long distance trade jumped over numerous political jurisdictions, traders learned to make peaceful deals on their honor and reputation because they were foreigners and could not appeal to the local sovereignty for protection. Trade, skills and capital flowed across political boundaries faster and faster and faster. Culturally, trade and corporations promoted meritocratic promotion faster than even militaries. When you bet the family farm on an investment in a Dutch East Indiamen, you suddenly don't car who the captains daddy was, just whether he can sail the ship. Likewise, nobody in China cares how well you are connected back in your home town. Today, there is not a single polity that controls the entirety of it's industrial production chain. Part of that chain always flows through at least one other and usually several other polities. Governments can regulate trade less and less because they control every smaller and smaller parts of their own production. While that presents some problems of its own, it also means that governments can't use their powers of violence to coerce cooperation, people have to work it out nonviolently. Having production scattered world wide means governments and peoples need each other more and more and that makes warfare less and less profitable. In short, we can't bomb the other guy's factories because they're our factories as well. That makes war less likely but humans are genetically programmed to seek dominance and control over others so problems will always crop up. As much as we wring our hands over "scarcity", it's a powerful force for good. To reiterate the conclusions: A "post-scarcity" economy is impossible because: 1. Some desired or needed objects and services will always be scarce i.e. objects that can't be manufactured, services of human beings. 2. We will invent scarcity if it doesn't exist naturally. 3. Scarcity is best managed non-violently on the large scale with money in some form. 4. (1) + (2) + (3) == we will always have a scarcity economy using money. 5. Scarcity is good because it induces us to cooperate. 6. If for some reason humans don't need each other and each other's cooperation, then the only relationship left is the antagonistic one. If we don't need each other, we start killing each other. 7. If nothing manufactured is scarce, then weapons aren't scarce. 8. (6) + (7) - (4) == we're boned. 9. (1) + (2) + (3) + (4) > we're boned. Statistically anyway. "Scarcity" is good and we're stuck with it anyway. "Choking to Death on Creme" scenarios would make the best stories about abundance. [Answer] There are a lot of examples of post-scarcity societies, some are dystopian but most are not. For example you have Star Trek, The Culture (Ian M Banks), Voyage From Yesteryear (specifically looking at a conventional society interacting with a post scarcity one), and more. The simple answer is that in a full post-scarcity example garbage pickup would be automated. You would have robots out doing that sort of thing, we're already close to having the technology for that now so it wouldn't take a huge leap. An alternative approach might be through social convention. With the devaluing of material goods as status symbols (as everyone has anything they want) then people will want something else to use for that purpose. Perhaps being seen to serve society, to help clean the streets or repair the gutters, or whatever needs doing might become the new way to gain social status. In other words people like bin men, doctors, nurses, etc would be seen as high status - while footballers and politicians are the lazy bums who can't be bothered to do something useful. [Answer] Can your world give everyone waterfront property on Hawaii? - Peter Masiar In a truly post-scarcity world, yes you can. We simply re-arrange the climate, and re-arrange the landmasses, so everyone has a cove of beach-front property, that you can't see anyone else from. When you want to have an isolated / private desert island experience, you do. When you want to go to a crowded nude beach, you hop on a vacuum-tube high speed rail link to your nearest big locale where other people want to do that too. And, that's only if you actually have to have the real deal. Many people are pretty happy with virtual stuff, and the wide-screen surround-sound technology, with scent additions, and wind & climate control experience is just going to get better. The infinite walkers and other tactile things that're in experimental versions now are looking to be amazing. Why bother with a beachfront property when you can experience superman-type flying, weightlessness, and magic (in a sealed pod, suspended in gel)? But, only one person gets to be president. Humans are wired to compete for social status, and something will be the brass ring that everyone will compete for. As long as you have to compete in the real world. If you've got good AI, you could be virtual king and never know the difference between real and virtual peons. However, I see no reason why a person needs to pick up garbage. Post-nano-tech, you'll toss your fecal matter right onto your farm-screen, and get caviar and champagne output in the next second (although real champagne will only come from France, cultivated the old way - ie: it's a status-thing and rightfully respected everywhere but in the US). Your roomba will pick up the dust, and turn it back into carpet or furniture. There are some natural limits of scarcity: ie: the natural distribution of atoms. However with some good nanotech, most people won't even notice that their gold jewelry is only one or two atoms of gold deep, and the rest is filler. So we probably have enough of every atom for people do to anything they want to do. You only actually need the atoms you're touching or directly looking at - instead of currently, where we have to warehouse lots of spare atoms, to ensure our own access to them when we want them. And this is assuming we don't have the power to go get more atoms, or to run fission / colliders and start making heavier atoms. Post scarcity is going to require a lot of power. But, as long as you've got that, and got enough tools (nanotech), you could do amazing things. Of course that's going to lead to problems. Some people are just smarter and more creative than others. And absent the masking problems with money/status, that will become more and more apparent. And, when making the transition from monied to post-scarcity, you're going to make a number of people really mad. Right now, gold-diggers are a thing; so guys who're old and or not-cute have an opportunity to land women, by exploiting the monetary system. When that goes away, those guys are going to be SOL. Expect them to be pissed off about it. Expect them to have tools, and a lot of them - to do things with. But I digress. So, my question is, why would you do anything that's not glamorous? Why would there be anything to do that's not 'fun'? If the economy were set up correctly, we'd be working on that right now. And all of the non-fun jobs would be on their way out, without impoverishing whole swaths of the population. [Answer] There are a couple options. I'm reading the book Brave New World, which talks about a false utopia society, which is similar to what you are talking about. In the book all people had been conditioned to serve society. This conditioning consisted of affecting mental and physical capacities while the people were still an embryo, and affecting their minds as children. One of the parameters of the book was that children memorized anything said to them while they slept. So every child had little rhymes said to them every time the slept (no example was "Everybody is happy now"). Other conditioning included affecting what the children disliked and liked, adjusting them to what their jobs would be when they grew up. All this conditioning could help somewhat want to do things for "society." Ex. picking up the trash. This brings me to my next point. While there is no scarcity of things, there could be a scarcity of services. So instead of trading money, people could trade time. For example, the garbage man goes around and picks up people's garbage, in return, the car mechanic fixing his truck whenever he needs it. In this sort of society, likely a central government would organize all the people to provide their services for free. Obviously everyone knows that if they don't provide their services, no one is obligated to provide services to them. [Answer] All boring, dangerous, and repetitive jobs that nobody likes to do for fun/passion would be done by robot's who can also do these things better ofcourse. Healthcare automation is also on the rise. But would still be requiring workers on free will basis (funny isn't it? this free will thing). I believe people would still want to do something that they like to do. Or would you give up your hobbies if everything would be free? My hobbies are science,biology, enginering, physics, etc,etc..so still enough work and schooling for me to do for the rest of my life. Only thing i don't want to go on with is the daily strggle of payment and struggeling for it.. I think such things could become obsolete very quickly if everybody would agree on creating this world?!.. (Ironically in today's situation I believe we need the rich to help with the providence of the money needed -before abundance is a fact...). Hope this makes scence?! ]
[Question] [ In real world, it is commonly thought that gold is the most valuable, then silver, then bronze (which is an alloy), etc. But it happens that uranium is more expensive than gold, even if there were no uranium coins ever. Platium also is more expensive than gold. Moreover, during History gold has not always had the same price relation with silver, and in some times tin has been very valuable for making bronze. How should a coinage system be crafted to be realistic? [Answer] The monetary value of coinage can vary on many factors: * The rarity of the material used to make it, as you mentioned * The ease of using a particular metal for a coin * The stability of the economy or economies which uses the coin * The societal attitude towards certain materials * The confidence users of the coin have in the government that issues it * The aesthetic value of the coin * The difficulty of counterfeiting the coin For example, in a primitive society where the economy is unstable and highly localized, the value of a coin might be entirely based on the value of the materials itself. In other societies, the value of a coin made with a mundane metal might be worth more because of its age or the government that pressed it (i.e., Valrosian ducats fetch 10 of any other bronze coin). In more modern societies, the metal used for the coin might not have any relation at all to its value because the the currency is backed by an idea rather than metal (see: the dollar). [Answer] A different approach to take is one of symbolism. In Raymond Feist's Empire of Tsunami (The Empire Trilogy) metals are incredibly rare. As such only the richest lords and ladies can afford metal weapons. As such the value of any metallic coin would be worth far more than any normal citizen would ever earn in a lifetime. As such a currency of counters is used (wood I believe). Much like paper money today (after all the paper a £20 note is printed on is worth far less than the value of the note). For this system to work the token must have the same value for each person, there must also be a level of trust and uniformity. In other words it must be organised my a higher power - a national bank or the crown for example. Originally in western civilization this token system was developed with the paper represented real money in the bank. Indeed in the UK many of our notes still have printed "“I promise to pay the bearer on demand the sum of...". Given this it's possible that a note/token could be paid out of a common material and used to represent one (or indeed 1/100, 1/1000 or 1/1000000) unit of valuable material (gold, silver, gems) stored by a trusted authority elsewhere. The upshot of this from a world building perspective is you can actually use all sorts of weird and wacky currencies if they're set up and regulated by the ruling classes. If they pay their workers in beans (remember the Star Trek Voyager Ferengi episode with ears!?) because those beans will be regulated and authorised. People will trust them and will be willing to store their wealth in beans. An aside but fascinating example. If you've ever played the online game Guild Wars there's a fantastic economy which has built up around ectoplasm. A character can hold a maximum of 99 platinum (which equates to 99,000 gold coins). As a result the elite players frequently hit upper limits on how much they could store. However you had far more space to store equipment. There is a substance dropped by some baddies (very rarely) in the elite levels which is used to craft the prestige armours. As a result many of these elite players wanted ectoplasm, and they could store far more of it than they could money. As a result a huge market opened up for ectoplasm with prices fluctuating between 4k and 8k per blob. The drop rates actually influenced the value so people's "stock" actually went up and down. The reason for this diatribe is to illustrate that a token with very little in game use (it just makes more dramatic looking armour) was used as an alternate unit of currency alongside the standard gold/platinum with it's own recessions and exchange rates! [Answer] In a metallist economy, the value of the coinage is dependent on the scarcity of the metals in question, its purity, and the reputation of the issuing authority for the purity of their coinage. As an example, in many cultures, Gold is considered more valuable than Silver. However, in ancient Egypt, Silver was more highly valued then Gold due to its scarcity. [Answer] There are two additional things which make gold an ideal money metal: 1. It is easily distinguishable from most other materials (and thus harder to fake). 2. It doesn't corrode in any way. ]
[Question] [ Closed. This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49). Closed 1 year ago. [Improve this question](/posts/235598/edit) Society as collapsed, and now everywhere is in a state of anarchy. You're probably going to have to fight for food and supplies, so you should be strong. You might need to get strong quickly, so if you stumbled across some anabolic steroids, should you take them to help you get strong fast? We are a little less concerned with long-term effects because you might not survive tomorrow... So, with that being said, if you took them, what changes? Ignoring long term effects like increased heart attack and stroke risks, what changes would happen to a person and how would that affect their ability to survive in the post apocalypse? I'm not trying to justify steroid use; I'm just making a post apocalypse game and need to populate it with items. I am thinking about having these in the game to help players level up their characters strength faster. In the game, using steroids would do this, but it would also make them chemically dependent on it, and whatever other negative, short(er) term health effects, adding or removing a few for balance reasons. [Answer] # No Help: Sorry to say, your survivor isn't likely to benefit from the effects of anabolic steroids. It might even get them killed. Your biology is pretty well evolved to make the compromises needed to live in a world of small society and stressed resources. Tampering with that balance is risky business. * Steroids increase demands on your metabolism. You require additional calories and protein to build muscle. If you have plenty of those, why are you taking steroids? If you don't, you're wasting resources. Muscle is also energy-intense. Being lean or even a bit fat is a survival trait. Muscle only helps if you have a specific task to do. * Steroids can affect your behavior. They can cause anger, aggression and other mood disturbances. You may want to establish friendly relations with people who have guns. Steroids can skew your serotonin and dopamine systems, throwing off your reward system. Your biology rewards survival behavior. You might find yourself prioritizing work-outs over conserving calories or hunting. Short-circuit at your own risk. * Steroids require you to "do the work" to gain a lot of muscle. If you take them and aren't lifting weights, you're throwing off your survival chemistry for little benefit. They mostly enhance the muscles you work on. Survival requires lots of random tasks to get by. Being able to cycle for 20 hours straight might not be as helpful as it sounds. * You can become dependent on steroids. The supply is limited, and after that, you're in real trouble. Depression in a depressing world is bad. [Answer] Strength is of limited use. It's fine facing unarmed people who don't want to go to jail. But armed people with nothing to lose will just see you as a bigger target if you start flexing at them. Hunter gatherers main killings today happen against bullies and they don't challenge them to a one on one fist fight. They just surround them and stick them with spears. So I don't see any advantages to taking steroids. It will just increase your caloric needs and they don't do anything without the exercise. They give results for people who are exerting themselves heavily. But not if you aren't. And if you are you'll get fit and strong without them. For a game though, FallOut4 has a lot of drug use built into it for short term gains, you could do something along those lines. [Answer] Taking steroids for muscle gain might not make as much sense as [taking them weekly to aid in bodily repair](https://www.medindia.net/news/steroids-help-muscles-repair-and-recover-from-injury-170113-1.htm#:%7E:text=Taking%20steroid%20on%20a%20weekly,of%20the%20body%20wastes%20away.). > > The study has found that weekly dose of steroid can help speedy recovery in muscle injuries and repair muscles, damaged by muscular dystrophy - a disorder in which an organ or tissue of the body wastes away. > > > In a few professional wrestler biographies, they point out that steroid use was almost as much about that muscle repair as it was about getting big. Especially back in the territory days, when you were traveling long distances by car to different venues, you needed to heal fast, and so they take doses of steroids for that purpose (it was also a major factor behind their heavy drinking and drug use. Downers to deal with the pain and uppers to get back into the action, day after day). [Answer] Big, burly guys would be a sign of relative civilization, and nomads/hermits would be smaller and leaner. If you are fending for yourself, or are a part of a very small group of people, you will probably benefit more from endurance (to allow you to follow potential prey over a long distance) and speed (for outrunning predators/enemies) rather than strength, assuming you have some sort of decent baseline strength to begin with. Being strong is super useful, but you'll be bigger and heavier and use up a lot more calories, which means you'll need to hunt/forage more. This not only increases the amount work you need to perform (and thus ups your calorie requirement even more), but it also increases the amount of risks you have to take - you may run into other people looking to harvest the same resources you're out after, and as @Kilisi pointed out, being muscular and strong is not much good against five people tossing javelins (or shooting bullets) in the general direction of your face. Or, in the case of hunting, the resource itself may oppose to your gathering it, and bite you, kick you, or shove a horn into your soft parts. Or you could just take a wrong step and sprain an ankle, rendering you unable to walk for three days. If you're lighter and need to do less work, your calorie requirement could easily be half that of your juiced-up counterpart, so you can spend a lot more time just chilling. However, if you are part of a group large enough to justify specialization between individuals (e.g., a village where people have different occupations), the cost of making one or two individuals abnormally strong might be worth it for the group (especially if technology and/or animals offsetting the need for strength are lacking). These guys would have an occupation requiring good strength, like blacksmith or [stonemason](https://en.wikipedia.org/wiki/Obelix), but would also serve as a sort of communal resource anyone can call in when strength is needed. As for negative side effects, there are plenty, of course, but they vary a lot from person to person. Some people die from live failure on their first cycle, others are mostly fine after doing lots of steroids for many years. Like a box of chocolates, you never know what you're gonna get. Also, there are different steroids, which have different side effects (some are more bound to make you aggressive, others are more dangerous to your liver). What does all this mean to your game? Well, perhaps steroids are easier to find in a walled village rather than in some forest-dweller's shack. If you want to justify the abundance of steroids in your game world, perhaps the pre-apocalyptic civilization were really into steroids, and managed to elaborate safer formulas with less Very Bad side effects (like instant death) while still having some Fairly Unpleasant side effects (aggressiveness, long term health problems). Seems like a interesting contributing factor to the civilization's downfall, too. ]
[Question] [ This question already has answers here: [Styles of Melee Combat developed in microgravity](/questions/45891/styles-of-melee-combat-developed-in-microgravity) (9 answers) Closed 5 years ago. How would your design a martial art for use in either zero gravity (in space) or lower gravity (on another planet or moon)? Constraints: * A practical martial art, for real world use, not a sport or display martial art. * Primarily unarmed. Firing a gun on board a spaceship is a suicidally stupid thing to do, so one of the goals of such a martial art would be to disarm somebody before they can punch a hole in the hull and kill everyone. * The techniques would need to be ones you could learn and practice in a different gravity environment, so that somebody living in space can practice the ground-based techniques and visa versa. * Anybody living in a low gravity environment long term risks muscle and bone loss unless they spend hours every day exercising. Techniques that can serve as part of that exercise would be more practical. [Answer] Your martial artists will need 3 things; speed, flexibility and upper body strength. The real issue with fighting in zero G is purchase. When Chuck Norris stands his ground against an attacker, he does exactly that; The purchase he gets from his legs on the ground means that when he strikes, the momentum he's building with his fist, foot, shoulder etc. is projected into the other person, not pushed back onto him. Most martial arts are based on the idea of strikes intended to catch your opponent wrong-footed or off guard, hitting them where they're weakest with all of your strength rooted so as to deliver maximum effect. In space, you have to assume you won't be able to do that. You might have the option of standing your ground wearing velcro shoes or something similar, but there won't be any spinning leaps et al. The reason is that once you're off the ground, it's all about momentum. Unlike on Earth, where you're going to land again, in this case you'll bounce off the roof, the opposite wall, your opponent, etc. once you get there, meaning that if your opponent weighs what you do, then there's a good chance that any momentum for strikes is going to be halved, with half going to your opponent as intended and the other half pushing you in another direction. This also means that your opponent isn't likely to be disabled because the energy will just push them back, especially if they are also off the walls or deck. So; what you're going to have to focus on are holds. Not just any holds, but holds where ALL the strength comes from your muscles and don't rely on gravity assists. You can't use an opponent's 'weight' against them in space, you can only use the strength of your muscles and perhaps a wall (bearing in mind that there's nothing holding them to the ground or the wall which brings us back to your own strength). You'll need speed to get your opponent into these holds, and avoid theirs. You'll need flexibility because in this environment, your legs aren't anchors so much grappling hooks and will be a major part of any hold you try out. And of course, upper body strength because you'll be holding someone against their own desire to get out, and without gravity assisted moves, the strongest muscles will tend to win. I'd start by looking at something like Judo rather than Tai Kwondo because you want to start with the holds and then reverse engineer out the differences gravity makes to some of the holds and how you'd compensate. A good working knowledge of kinematics will certainly help you build up your own zero G variations to the holds and blocks you need to avoid being captured by your enemy. Speed is a factor, especially in terms of disabling people with guns, but that speed will be more along the lines of dexterity than single line of motion speed. In other words, how quickly can you wrap yourself around a gun laden hand? How quickly can you convince it to let go? Training in this environment would use something similar to the wooden training poles that are used in many Asian martial arts, where you have a pole that you learn to wrap yourself around quickly and strongly. As for muscle strength, you'd find that any form of exercise will help with that but ideally there would be an additional focus on flexibility in that training. I don't know how Pilates would work in Zero G (I'm guessing it wouldn't because many of the moves are designed to take advantage of bodyweight) but it would be very useful in this regard because it wouldn't sacrifice flexibility for strength, especially if coupled with some form of Zero G yoga. As a bonus suggestion, also take a look at Greco-Roman wrestling as many of the moves in that sport also require strong upper body strength and are tests of the ability of the participants to hold their opponent in check. [Answer] Nice question! First of all, if you want to do martial arts in space, then the entire basis of martial arts would have to change. Instead of focusing on using gravity against the opponent, you would have to use momentum and power sources to power your punches. This would mean extensive training. First, I'm assuming there is a floor. Meaning, you're not fighting when flying around in space. So... on a spaceship. That would mean a person would be able to push off the ground. That would be the main factor in a fight. A person would have to know which angle to push off of to launch herself (or himself) towards the attacker. Also, the person needs to be comfortable with changing his source of "gravity", or his floor. For example, he or she can push off a wall if that's more convenient. (Note: Ender's Game by O. S. Card might be helpful here). Next, to be able to effectively pack a punch, there would need to be boosters on the suit. Like.. mini "rocket launcher" like things that let you punch something at a fast speed. Sharp objects wouldn't make much of a difference because the opponent will very likely have a suit on. An object that can smash the visor or break some important tube in the suit, on the other hand, would be immensely useful. Like... a hammer! (That has weight in space, of course.) Now, for the suit, it would be important to have a light and flexible suit with strong headgear. Also, if there were some high-tech gravity bases that let the user stay still in a fight. Something like a very heavy "thing" that works "kind" of like gravity. For example, if the spaceship has a magnetic inside, then magnetics that move based on the users movements would be immensely useful. Now, the moves: I'm not some expert here, but the moves would be different, but some of the fundamentals would stay the same. For example, you would still need to move with grace and such because... in space... changing direction is hard. Fast moves would be very hard to do, so those would require lots of skill. Charging someone and making a flurry of attacks would be useful as well. If the opponent, for some reason, doesn't have a suit, then attacking pressure points (Kyusho-Jitsu) would be great. The bloodflow is even less strong and attacking the blood vessels would be even more effected. BUT... this can be lethal... so it really depends on your world. Let's see... if there anything I missed? Maybe... training? All of the discipline involved in martial arts on earth would apply, like respect and fairness. If you want to prevent the use of guns, you might want to have magnets or bulletproof suits that can either attract the guns or repel the gunshots. (Obviously, no one without suicidal intent will shoot a gun). Good luck, Claire [Answer] @Tim B II above raises very good point about lack of support from legs. Moreover, wrestling might be more viable than striking arts even here on earth. But it is not nearly as spectacular. So here are a few ideas (I do assume you are fighting inside a ship or station): * Leaping of the walls will be limited to moving into/out of the fight, and ambushing unsuspecting opponent. Even in Earthly martial arts, getting both feet of the ground is frowned upon, as it limits your contol puts you on a predictable trajectory for the duration of the leap. that the enemy can exploit. In space, rather than engaging in aerial joustling, it seems wiser to wait on the wall till your opponent flies close, and kick them where it hurts (while they cannot dodge), or attack them as they prepare for safe landing. + Leaping will likely involve a somersault, since you want to push off with the legs for max speed, and then land on the legs to absorb the shock. There will be some highly cinematic acrobatics, but it will leave you open to attack. * Main technique will be clinging to walls, and trying to hit opponent with hands or feet. I am not sure which approach is more viable: hit with legs for more strenth and reach and safety of the head, or hit with hands for better control and visibility. Imho, sitting in a narrow tunnel and kicking everything that comes into it seems like a viable defensive strategy. + Note that zero-G ship or station will have handholds everywhere, and will likely have very limited space between walls (just look at ISS) * Melee weapons will surely come handy. Both edged and pointy seem viable. blunt might not have room to swing; but offer best stopping power. Polearms are limited by small space, but can completely close a choke point like a narrow corridor. + Thrown objects are viable, since zero makes aiming easier. I doubt you can throw them hard enough to kill, but they will still work as a distraction. * To train in 1G: + suspend fighters on ropes (I think Circe de Soleil had such a performance), - train in the water (no gravity, and resistance helps build strength) [Answer] It's been mentioned in a couple answers here, but the key thing to understand is in zero-g you don't have the purchase to do many of the kinds of moves seen in typical martial arts so you have to make/modify a martial art that creates purchase as part of each move or uses purchase created by your opponent or surroundings as part of the move. For example, throwing a punch or a kick while suspended mid-air in zero-g would be underpowered because the momentum transfer in the hit would split between you and your opponent and would send you flying away. To resolve that issue would require the combination of a grapple and a hit. For example, you could combine a leg grapple with upper body strikes, an upper body grapple with leg strikes, or a purchase grapple combined with a twist or submission grapple. The real complexity in the martial arts would be in acquiring a superior grapple position on an opponent that would allow you to strike while blocking your opponent from striking. For example, locking up your opponent's arm to immobilize him would allow you to strike with your remaining limbs, but your opponent would be able to strike you just as easily. However, if you were to land say a half nelson on your opponent you would be behind him/her and would be able to land some vicious strikes without your opponent being able to respond in kind. In a real fight, you might see an initial hold grapple, followed by crawling/maneuvering over your opponent to reach a superior grapple with opportunity hits thrown whenever they are created by either side. I can imagine a group of space marines practicing these moves in an Olympic sized pool while on earth using protective headgear with rebreathers attached and a weighted suit to keep them suspended in the water. In space, they could practice the moves with a suit designed to add resistance to their movements to also get a decent aerobic exercise. [Answer] The current answers on martial arts are all very good, but just because guns are ruled out doesn't mean you can't have any weapons. If you are going far future you can just go down the standard phaser/stun gun route, if you want to keep it more current tech level, there is no reason that the current police 'less lethal' gear would not work, things like tasers and bean bag rounds. If you want something more visually pleasing then rope based weapons would work very well, a knife or hook attached to a rope can be thrown at the enemy and pulled back if you miss to be used again, if you do embed it in them then you can pull them free from the walls so they have no surface to push against [Answer] Clothing and weaponry that can be used to redirect and focus acceleration, such can still use the mass of the body as a focal point. We have an instinctual understanding of momentum that expands with experience such that for day to day activities thought not need be applied, a significant part of martial arts training is teaching a body and a mind to more efficiently recognize, shift and exploit 'centres of gravity' of course, centres of gravity are misnamed, but the principle of consciously altering acceleration around preferred focal points is intrinsic to all combat, armed or unarmed. In other words perhaps, martial arts training would not need to change much at all, and people are far more capable of comprehending altered states of acceleration than the question seems to imply. Every mammal attempts to make mass judgements of things it interacts with in order to understand how it's own applied forces will interact with the forces already interacting with the object, one of the reasons kittens and puppies are so ridiculous is because their instincts have not yet been informed by experience, one is not born with a knowledge of the mass and acceleration of objects, but rather the tools with which to judge and store those judgements. Zero G 'melee' combat would obviously(?) depend on the environment more than when under terrestrial conditions for most species. Being able to extend and/or reshape ones' surface area would be 'pivotal,' indeed the lack of gravity as a counterpoint 'resisting' any application of force means that almost any application and/or ability to apply that force gains scope and utility. We often see scifi 'space suits' ejecting gas for instance against space to provide alterations in momentum, massively inefficient when one considers that if the intention is to change orientation the force can be applied from one part of a contiguous body to another part of the same. There are various methods to shift mass in a body by using the external environment aside from gravity, but it would seem silly for anybody wanting to win to rely on factors that may be outside of their control at the point of conflict.. Gyroscopes, magnetic shifts and etc can be used to impart not just angular momentum, but 'regular' momentum also. For low-tech or contemporary scenarios, consider that recoil-less rifles were invented a long time ago, and could 'easily' be engineered to redirect any residual recoil to maintain a relatively static position. Whip-like devices, hollow devices with variable-resistance interior mass could be utilized to magnify force around selected points of motion which would be hard or impossible for opponents to predict with precision allowing for skill-based combat. [Answer] You didn't really specify what kind of enviroment the fight takes place on - if on the surface of a moon, inside a low-G training room/arena or just plain old space. Regardless, I think the ultimate fighting technique for low/zero-gravity is one that focuses mainly on submission - so I would say the answer for this question is something in the likes of Brazilian Jiu-Jitsu. It meets all the criteria: > > A practical martial art, for real world use, not a sport or display martial art. > > > This martial art is basically focused on getting your opponent on the ground in order for you to get in a position capable of breaking an arm/leg or simply choking him senseless. This makes a lot of sense if you think that these fights could take place in plain old space, where there is no ground or walls to get a hold on. A good Jiu-Jitsu fighter will hold onto his enemy like a tick that will not let go until he is done. > > Primarily unarmed. Firing a gun on board a spaceship is a suicidally stupid thing to do, so one of the goals of such a martial art would be to disarm somebody before they can punch a hole in the hull and kill everyone. > > > This one really depends on the situation at hand. If a reaction is possible, all the fighter needs to do is tackle his foe - which is also part of this martial art. They're taught techniques to get an opponent to the ground so they can start going for the immobilization/submission. > > The techniques would need to be ones you could learn and practice in a different gravity environment, so that somebody living in space can practice the ground-based techniques and visa versa. > > > Aside from the knowhow, which generally comes from a master (but you could make changes in order for the master to be just a series of videos, for example), all you need is another person to continuously train with and a space large enough to do so. > > Anybody living in a low gravity environment long term risks muscle and bone loss unless they spend hours every day exercising. Techniques that can serve as part of that exercise would be more practical. > > > I've never practiced Jiu-Jitsu but I've been to a gym where I practiced Muay-Thai and we used to kind of share this enormous space with the Jiu-Jitsu students. Even though the martial arts are very different, the warmup execises we did had a lot in common - functional exercises like running, squats, pushups, etc. Assuming the facility the training takes place has space that can allow for this kind of training, this should be covered. The practicing of the art itself has a lot of grabbing and using your own bodyweight in your favor, so jiu-jitsu might look a little tedious for an observer, but a fighter has to put in A LOT of strength until he finds an opening to finish his opponent. [Answer] Realistically? I wouldn't bother training any space person in martial arts. I would instead focus on deescalation techniques and how to read a situation. Guns are dangerous, and there is no way to disarm a ranged opponent without having them pull the trigger on you or anything around you unless you have a huge element of surprise. No martial arts technique will allow you to beat a gun, unless the person holding the gun is high inexperienced and easily manipulated. A determined assailant will just shoot you or threaten to shoot something if you approach them and keep their distance. An inexperienced shooter can be coerced with words, to stand down. That things will improve and get better. That they can have a new life or a voice and be heard. This falls under deescalation techniques which will play a more vital role in allowing you to close the distance and disarm the shooter than yelling, jumping and kicking would ever achieve. ]
[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. Inspired by this question, and my own answer to it: [Avoiding galactic pandemics](https://worldbuilding.stackexchange.com/questions/19880/avoiding-galactic-pandemics/19909#19909). World ending pandemics are a common disaster/after-the-end story trope, I'm trying to determine if plausible, and how one could occur. What is the threat of a pandemic occurring in a modern first world nation, and if one is plausible then what conditions are required to make it occur? Keep in mind I'm talking about trying to stay to the realm of realistic science, in particular only diseases that plausibly could evolve in the first place. I define a pandemic for this question as: 1. Naturally evolved, or at least not intentionally man-made. I'm willing to accept diseases that evolved due to accident's or mistakes made by man, such as breeding antibiotic resistant bacteria via overuse of antibiotics, but no weapons-grade engineered diseases. 2. Disease must spread for at least half a year without being contained 3. Has a mortality of at least 10% (ie kills 10% of total population) 4. Is a threat to modern-day first-world countries that aren't willfully ignoring the threat (like some African countries are doing with AIDS). How plausible and what is the threat of such a pandemic? Edit: Just to clarify, my interest is not in what sort of virus could be a threat, but how realistic such a virus existing would be! I am particularly looking for information about the likelihood of any suggested virus actually occurring. Most relevant, the 'ideal' virus is one with a long incubation period and one that is not obviously lethal until long after symptoms are seen. However, I believe the more lethal the virus the shorter the incubation and quicker the time between symptoms and death would be. So if a virus must have a long incubation to be dangerous, I would appreciate at least addressing the likelihood of a long-incubation virus evolving. [Answer] A pandemic of the size you asked about is a credible threat. I've seen articles over the last couple of years where researchers attempt to model the spread of diseases and what affects how quickly they spread. The US CDC spends a lot of time thinking about this kind of thing. Given the diversity of research institutions who are working on understanding the spread of disease, I think the threat of a pandemic is a very credible. [Update for Oct 2021]: And COVID-19 proves my point about pandemics as credible threats. If COVID were a bit more lethal, we'd be in real trouble with much higher casualties. Also, my original post didn't account for the effects of politicisation of the pandemic and those who will prioritize something other than making the pandemic end as soon as possible. The problem with short gestation period diseases is if you, as the disease, kill your host too quickly then you don't get a chance to spread yourself around as much. Diseases that kill quickly typically turn into diseases that don't kill too quickly because a fast-killer doesn't "survive" long in the population while tamer mutations have more time to expose other hosts. A virus will change over time in relation to the selection pressure of a host's immune system (herd immunity may play a factor too). The longer a virus survives and the more hosts it infects, the greater the chance for mutation. There's this [article](http://www.pnas.org/content/96/24/13910.long) from 1999 that talks about mutation rates in RNA viruses. (I'm sure there are newer, better articles to be had.) The mutation rates are stupid high on the order of around 75% per genome per replication. The mutation rate is much lower for DNA-based microbes (including both viral and cellular organisms) at .34%. The authors of the paper state that these numbers are hard to gauge because the mediocre quality of the data. If that's just one nucleotide involved in the mutation, at trillions or quadrillions of replications across many different hosts, there will be mutation. Older Answer to the Question The ideal pandemic agent might have the following characteristics: Make the virus airborne, highly contagious (requires very small doses for infection), contagious shortly after infection, and a long gestation period in the months or years range before it induces acute illness/death. Basically, airborne HIV. Virus based diseases such as HIV, Ebola or influenza have historically been very difficult to study based on how long it takes for effective treatments to appear after a virus discovery. We've known about HIV since 1980 but it took years to develop effective treatments. If this is a brand new disease then it will take a while for medicine to learn how it works and develop an effective treatment thus giving the disease plenty of time to spread. Ebola treatments are relatively new but medicine has known about it for decades (the [Hot Zone](https://en.wikipedia.org/wiki/The_Hot_Zone) was published in 1994). While the pandemic doesn't strictly need to be virus-based, having it be so decreases the changes of rapid effective analysis/treatment by the CDC or local equivalent. Let's assume the following characteristics of this virus: * Average gestation period: 6 months, standard deviation of 2 months. * Illness Rate: 50% * Fatality Rate: 10% (per your question) * Required dosage for infection: 100 viruses. * Time to contagious: 3 days, standard deviation of 1 day. * Symptoms: Flu-like, coughing, aching, runny nose, headache, fever. Plausible Scenario: Disease originates in sub-Saharan Africa (sorry Africa). Patient Zero catches the disease from infected pig meat. The virus causes minor inflammation in the nasal cavities, thereby inducing sneezing. It is passed to a foreign aid worker who is about to finish their tour and go home to California after stopping off in London and Paris to visit relatives. The aid worker sneezes on the plane without covering her nose (shameful). The water particles from her sneezes spread the virus to everyone on the flight. In 2 to 4 days, all those travelers will infect the people they know. Even if a person sneezing in a huge airport like Heathrow only infects 10% of the people moving through then that's thousands or tens of thousands of individuals infected. And, people flying through Heathrow go literally everywhere on the planet. People working in the airport will contribute greater still to the infection rates as they have a persistent presence to keep recontaminating the airport. After stopping off in Paris and London, she heads home to California. The virus is still undetected and unknown. There are no quarantines for infected individuals, no blockades of infected countries. Assuming she has layovers in JFK in NYC and arrives in LAX, two of the largest airports in the US are now infected. I think you can see where this is going. If nothing else, this kind of a disease is a special threat to the First World because of how interconnected those countries are and the common use of air travel. The power of the CDC can't help you if the virus is unknown. Compound the effects of this new virus by having the virus start spreading in May/June/July. The 6 month gestation period will coincide with flu season and that will complicate treatment because doctors will think that people are getting sick from the flu, not this new virus. It will appear to the public as a terrifying flu season because people are getting sick and dying from the flu or something like the flu but the flu shots aren't working. The usual methods of quarantine for flu patients won't work because practically everyone was infected months earlier. What makes this scenario plausible is the high degree of interconnectedness in the First World because of air travel. It's an epidemiologist's worst nightmare to have a lethal, airborne virus that gets spread around by air travelers coughing and sneezing on planes. [Answer] The [Spanish Flu](https://en.wikipedia.org/wiki/1918_flu_pandemic) came close to your specifications, with a few qualifiers. * It was almost a century ago. The state of the art has progressed since then. * It was global. Aggregate worldwide numbers mix industrialized and underdeveloped countries. That being said, the Spanish Flu came within shouting distance of the scenario you asked for. So a similar pandemic, slightly more lethal, slightly more infectious, would fit the requirements. Consider how legal and illegal immigration bring people from the "second" and "third" world to the "first" world. Say the fictional disease has a longer incubation period, and an outbreak in Central America or Africa would trigger mass refugee movements. How soon could and would borders be sealed? The Israelis in the movie [World War Z](https://en.wikipedia.org/wiki/World_War_Z_%28film%29) allow uninfected refugees in to reduce the number of potential infected outside -- cold calculation and compassion working hand in hand. The border defenses will always leak ... [Answer] There are three ways diseases can be highly lethal I can think of right away and one of those ways would take a long time to show symptoms. Basically, if the disease kills by causing gradual irreversible damage, the ability of the body to compensate for it would hide it until the amount of damage exceeds the ability of the body to compensate. Disease like this might take years to kill, it might even be difficult to connect the increase in deaths to a specific pathogen. This is because there would be lots of infected that would show no symptoms of the lethal disease and also people dying from the disease whose bodies had already kicked out the pathogen. In a case like these there would first be a mild "flu like" disease spreading and after it was found the symptoms are no different than other seasonal flus, largely ignored. Then after a few years people would start dying from a weird disease there some critical system starts simply failing. The first victims would be the old and those whose health was weakened by some other disease. There would be a large hunt for the reason. Maybe people are eating too much food additives? Maybe that new bio-diesel really was not that good an idea? Maybe those nuclear tests in the 50s and 60s permanently damaged the people born at the period? It would be difficult to home on to a single reason since realistically people dying in the first wave would be dying because of a combination of factors. If the pathogen was virulent enough it could be so common that noting it was present in most of the victims would be meaningless. And there would certainly be some cases where doctors would miss that the person had been exposed to the pathogen. By the time somebody connected all the dots it might be possible for the majority of mankind to e infected and have sustained enough damage for that to be lethal. You could have a death toll exceeding 80 percent The downside of this form of infection for fiction is that the 80 percent lethality might not make that much of a difference. It is easy to forget, but despite modern medicine nearly one hundred percent of people die. Often of some disease. So this kind of pandemic would simply have the effect of shortening the life span and giving developed countries, the first world, a population structure similar to one in the developing countries. In that sense it really would impact the first world much more. Which is a plus? Exact effects depend on how fast it kills. If it kills slow unless you are already sick in some way, it would just change the population structure. There are people who complain about the direction the populations in developing countries are going, so this might not be all bad. If it kills everyone, no matter how healthy and young, within some relatively low number of years, you'd have a real pandemic in every sense. [Answer] I am no specialist, but I think a pandemic must be based on a [virus](https://en.wikipedia.org/wiki/List_of_epidemics): it spreads easier, and harder to fight. Plague, e.g., can be countered with [antibiotics](https://en.wikipedia.org/wiki/Bubonic_plague#Treatment). Against viruses, we have currently two weapons: * Quarantine * Vaccines Now, I think viruses have the following characteristics * Incubation time: time between exposure and symptoms, * Contagion time: time between exposure and when the affected person is contagious, * Propagation: means and effectiveness, * Fatality: number of victims succumbing to the virus. We can then consider recent virus epidemic/pandemics: * [Influenza H1N1](https://en.wikipedia.org/wiki/2009_flu_pandemic): it is very contagious, the 2009-2010 reached 10-500 million people ([more than 200 countries affected](https://en.wikipedia.org/wiki/Pandemic_H1N1/09_virus#Species_affected)), and the 1918 (Spanish Flu) affected 500 millions. It can be transmitted through the air (coughs, sneeze), which facilitates its propagation. However its fatality rate is quite low (0.03% in 2009-2010). * [Ebola](https://en.wikipedia.org/wiki/Ebola_virus_epidemic_in_West_Africa): it is transmitted through direct contacts which limits its propagation. However the fatality rate is up to 70%. Even in 1st World countries (Spain, USA), some patients died from it in the on-going pandemic. * [Influenza H3N2](https://en.wikipedia.org/wiki/Influenza_A_virus_subtype_H3N2#2014.E2.80.932015_flu_season):the mutation of the virus "surprised" the experts, as a result of which [many cases](http://www.nbcnews.com/health/cold-flu/cdc-warning-flu-viruses-mutate-evade-current-vaccine-n261226) were observed this winter as part of the seasonal flu. It is considered somewhat deadlier. But I couldn't find any satisfying statistics. * [Influenza H5N1](https://en.wikipedia.org/wiki/Influenza_A_virus_subtype_H5N1): the avian flu is deadlier than H1N1, with [more than 50% fatality rate](https://en.wikipedia.org/wiki/Human_mortality_from_H5N1#H5N1_cases_in_humans). It mostly affects birds but can sometimes be transmitted to humans. The pandemic in 2006 affected [a considerable amount of birds](https://en.wikipedia.org/wiki/Global_spread_of_H5N1_in_2006). But luckily for us the transmission from birds to humans is quite low. Where does that lead us to find a killer virus? Well I think it can be seen that typical influenza spread very fast. But their incubation time is about 1-3 days (as per [the link you shared](https://en.wikipedia.org/wiki/Incubation_period)). And their mortality rate is pretty low. By keeping people at home when the symptoms appear, the progression is limited, and due to good medical conditions many death are avoided (see below). Ebola on the other hand is quite slow. It cannot be transmitted by droplets from coughs and sneeze. And its incubation time is up to 20 days (or even more). However its fatality rate amounts to more than 50% even in medical centres. Therefore, consider a deadly influenza mutation which increased dramatically the fatality rate, without lowering its transmission mechanism. You got yourself a very touch and deadly virus. Without going too far off in imagination. Is it enough to kill the close to 100 millions (10% of the 1st World)? I doubt it. For most influenza case, we have vaccines to prevent them (if you do get vaccines). Otherwise, and for the other viruses, isolation/quarantine is the best option. As soon as a patient develop the symptoms, s/he is isolated from other people to limit the propagation of the virus. However, what would happen for an hypothetical virus, where people get contagious as soon as (or even before) the symptoms (fever) are noticed? Isolation would still be effective, but not as full-proof: neighbours might have been contaminated prior to the isolation.If the propagation medium isn't too restrictive (unlike, e.g. HIV and more like influenza), the quarantine approach would be limited. Which would still have a large spread (similar to the H2N3 of this year flu) in the 1st World. And if that virus is combined with a high fatality rate, you are in for a disaster. This is as much as I see, without much prior knowledge and extrapolation. --- But now consider an alternative scenario. In the 1918 Spanish flu, which was an Influenza A(H1N1), most of the victims did not die directly from the flu itself, but more the flu [lowered the defence mechanism](https://en.wikipedia.org/wiki/1918_flu_pandemic#Patterns_of_fatality) of the body, and they died, e.g. of bacterial pneumonia. So just hypothetically, consider a strong H1N1 pandemic couple with a plague or other bacterial-based pandemic. That would probably be pretty bad. [Answer] I had an idea about this. I'm not sure exactly how plausible it is, but it is inspired by hypomyces. The disease doesn't affect humans DIRECTLY, rather, infects and mutates other viruses. So, you take a virus which is difficult to treat, such has herpes which already infects some 90% of the population and the theoretical virus would be easily overlooked because it has no effect on human tissue directly, instead causes herpes to become a cancerous flesh-consuming blight. makes me shutter. ]
[Question] [ So I've been trying to create a world and I've been planning on the continents being drowned out almost completely in water from a terrible tsunami, storm, earthquake or an act of one the gods or something, maybe a mixture even. The land before would have very deep valleys and would be close to sea level to begin with, so maybe some of the land would still be above water, but most of the continent would be underwater, and wipe out a good portion of its citizens. More specifically I suppose, * What would be a more plausible reason (if the ones listed aren't too good) to lose a continent in a way it wipes out most of its population? * Would there be survivors if they were able to board ships in time to sail over to another continent in time? I've read up on Mu and Lemuria as presumed lost continents but it doesn't exactly answer my questions. [Answer] There is [Doggerland](http://en.wikipedia.org/wiki/Doggerland), which connected Great Britain and Mainland Europe. It disappeared during 6,500 to 6,200 BC due to rising sea levels. Quote from the Wikipedia article: > > A recent hypothesis is that much of the remaining coastal land, > already much reduced in size from the original land area, was flooded > by a megatsunami around 6200 BC (approximately 8200 BP) caused by a > submarine landslide off the coast of Norway known as the Storegga > Slide. > > > [Answer] One possible cause would be a natural dam that breaks, like in the [Black Sea deluge hypothesis](http://en.wikipedia.org/wiki/Black_Sea_deluge_hypothesis). In that case, it is claimed that the Mediteranean Sea opened the Bosphorus Strait and flooded in the Black Sea, which at the time was one hundred meters below sea level. [Answer] The end of an Ice Age has done it here on Earth. The ice contains enough water to alter the sea level significantly and when the warming is fast it is normal for some of the melt water to get trapped by the still unmelted ice, so the sea level change may come in pulses. In short, a collapse of a large ice sheet releasing lots of melt water sounds a like a feasible reason for the sea level to change relatively fast. To flood a continent you need a rise in the global sea level, the seas are too wide for this to happen very fast. Local flooding that follows, such as the one when the Strait of Hormuz was created, can be quite fast, but even then people still survived. Ships are built to float so they are rather good at it unless something breaks them. [Answer] Check out Google Earth east of Florida tucked in above Cuba. Even from way out you can see something different about that area. Checking to see if that's an artifact of the patchwork, I found that it's a land mass lower than sea level, as opposed to miles-deep ocean. The tallest peaks form the Bahamas. I think that's what a lost continent would look like. The question you asking is could it happen suddenly? Maybe the land was quite low lying due to generations of sea-level rise, or had a basin surrounded by mountains near the perimeter. A tsunami could cause widespread damage. In the latter case, breaking through the ridge would cause a new inland sea to fill up...like the Mediterranean did, or the Black Sea which occurred while humans were around. The biggest floods, in North America, was caused by ice dams failing during periods of glaciation. In this case it was scrubbed clean but did not remain underwater. [Answer] 3,600 years ago, in the Santorini archipelago, a huge volcanic eruption happened. This led to a tsunami so big that it supposedly wiped out the whole Minoan civilization, which potentially gave rumours to [the lost city of Atlantis.](http://en.wikipedia.org/wiki/Atlantis) [reference](http://news.nationalgeographic.com/news/2006/08/060823-thera-volcano.html) [Answer] What if the species was environmentally conscious enough and technologically advanced enough to house the bulk of its operations underground? It has been done before: <http://www.history.com/news/vast-underground-city-found-in-turkey-may-be-one-of-the-worlds-largest/turkish-underground-city> Imagine the absolutely insane network of tunnels required to support 500,000,000 mouths. The earth supplies an inexhaustible and unassailable supply of geothermal energy. You could even have a transient cataclysm that drove them underground, effectively--increased radiation from an extrasolar event, comet or asteroid--jumpstarting their civilization. We could and probably would do it given a few thousand years warning (predictable extrasolar event, such as a nova or supernova, fusing stars, magnetar, quasar, whatever). You can eradicate their surface presence in prehistory via multiple avenues. You really just need a compelling reason to break their connection to the surface. A strong flood, tsunami, asteroid/comet impact, even megalomania. They could be beneath us right now, or they could all be dead, their chambers hermetically sealed and filled with advanced technology that harvested ambient energy with startling efficiency--acoustic engines and whatnot. [Answer] What about the same plan in the 20s to create a 10X larger dam than the Three Gorges Dam. There was a plan called Atlantropa (see [wiki](http://en.wikipedia.org/wiki/Atlantropa)). The Dam was to be situated at the mouth of the Mediterranean and was never built as per engineering and other limitations of the era--as well as the risks that a breakdown of the Dam would have created massive floods across the Mediterranean. The project was planned to create energy and to an extent agricultural land across the coast lines in the Mediterranean. Maybe you could devise an ancient civilization having constructed such a project and having a breaking of the Dam. Although the Dam was planned to have reduced the level of the sea by 200 meters. So you would need a shallower landscape. ]
[Question] [ The world has come to regularly use genetic modification for cosmetic purposes, hair colour, eye colour, height, etc, relatively useless stuff. A breakthrough has been made that has produced the first functionally useful genetic modification, one that extends the repair/regeneration ability of the liver in the event of physical damage to the rest of your vital organs. A far cry from immortality, since people still age, but it's a start and might do more for a person's total years of life than most current practices are capable of. Some people doubt its ability to extend a person's life on its own precisely because people still age despite it, but it might end up proving extremely effective once mods(the genetically modified) eventually prove to live longer than normal people. Would human life expectancy increase by a significant amount due to this or would it prove to not be that effective in the end? [Answer] Most death is not from cellular wear and tear. Joints wear out. But it is unusual for wear and tear to be a cause of death. For orientation: causes of death in the US. <https://www.statista.com/statistics/248622/rates-of-leading-causes-of-death-in-the-us/> [![cause of death graph](https://i.stack.imgur.com/SG4Kl.png)](https://i.stack.imgur.com/SG4Kl.png) #1 and #2 are heart disease and cancer. It is not clear to me that cardiovascular disease (and death from heart attack or stroke) is related to the self-renewal ability of cells in the arteries. I do not think making those cells turn over like epithelial linings will reduce plaque. But maybe. If heart disease incidence falls, cancer becomes #1. As is the case in Japan where people live 10-15 years longer and die of cancer. Self-renewal for all cells will increase cancer risk. A look at cancer mortality shows that common cancers arise in epithelial linings that are renewing themselves. Cancers can arise in non-renewing tissues (brain, bone, muscle) but those cancers are rare and do not make the list. Expanding the pool of cells which are renewing themselves will increase cancer rates for those cancer types. <https://gco.iarc.fr/today/data/factsheets/cancers/40-All-cancers-excluding-non-melanoma-skin-cancer-fact-sheet.pdf> [![cancer deaths](https://i.stack.imgur.com/NSRwV.png)](https://i.stack.imgur.com/NSRwV.png) -- I am not sure about dementia and not sure about kidney disease. Kidney disease might actually be from wear. Maybe a self-renewing kidney will take kidney diseases out of the running for mortality risk. Dementia has not historically been considered a cause of death because it is usually something else that strikes the final blow. I am not sure if self renewing brain cells would sidestep dementia. --- For a fiction you could have self renewing artery, kidney and brain cells get rid of cardiovascular disease, renal failure and dementia. You could have improvements in cancer detection and then immunotherapy and other cancer treatments to nip cancer in the bud. [Answer] The body is pretty bad at repairing fine structure. When you remove lobes of the liver, the lobes don't recover, the cells just replicate and fill the gaps. Because the cells just all filter blood it doesn't matter so much that they lack much structure. That's pretty useless for the heart. The heart has a fine structure, and it doesn't work well if you just fill it with lots of cells. It's pretty useless for the brain, which relies on a precise structure to function. So, it would probably do more harm than help, since most organs don't function well with cells just generating to fill all the gaps. [Answer] Short answer, no. There is a new process being looked into that links DNA to aging. A component of our genes, [telomere](https://en.wikipedia.org/wiki/Telomere) is the genetic end caps of our genes and act as a type of internal clock in the body. Each time cells in the body divide, ie replace other old and dying cells, these telomere's get shorter. Over time, these telomere will shorten to nothing and the cell could no longer reliably duplicate itself without errors. This does not happen across the body all at once, but eventually, there will be a significant number of cells through out the body that it could not repair damage, cannot duplicate itself or are creating erroneous copies of itself at a quick pace (cancer). [Answer] Really good regeneration is what axolotls do and they live [about 20 years](https://axolotlnerd.com/axolotls-lifespan/), which is pretty much the same as [other salamanders](https://www.animalspot.net/salamander) (and much less than the [really, really long-lived species](https://www.nbcnews.com/id/wbna38334490) but those are typically metabolically slower). So the "natural experiment" does not support an increase in lifespan, although regeneration has other advantages. As others have pointed out, the principal causes of death for humans aren't necessarily going to be improved by better cellular/organ repair, and at least one (cancer) is probably going to get worse, nullifying any gains from limiting the damage from cardiovascular events. You may however see an increase in [healthy life expectancy](https://en.wikipedia.org/wiki/Life_expectancy#Healthy_life_expectancy) or "healthspan", as in the fraction of one's life unencumbered by age-related health problems. Joint pain, osteoporosis, muscle loss, cataracts/loss of visual acuity, hair loss, all could be improved resulting in a more youthful-looking (and feeling) population (see AlexP's similar comment above). [Answer] ## Coupled with Modern Society, it Would Increase Life Expectancy When you look at [Willk's answer](https://worldbuilding.stackexchange.com/a/218845/57832), you see that the 2 leading causes of death are by far heart disease and cancer with heart disease exceeding all forms of cancer combined. It is true that the heart is the 3rd most resistant organ in the human body to cancer; so, making it regenerative would increase the rate of heart cancer pushing the cancer death rate up a notch ... but this could also massively reduce deaths from heart disease. While cholesterol buildup is often blamed for pulmonary illness, various studies over the past couple decades suggest that this is probably a symptom, not a cause. When an artery becomes weakened or damaged, our bodies coat our arteries with cholesterol on purpose to reinforce and protect it, but our heart and arteries have limited actual healing capabilities due to poor regeneration. If the pulmonary system could better heal itself, then our bodies would not need to respond with cholesterol buildup which means that heart disease as we know it could be all but eliminated. So, you could trade a lot of prevented heart disease for a little bit of heart cancer. Then you look at the next 3 lowest things: Accidents, Chronic Lower Respiratory, & Stroke. Many accidents cause chronic, unrecoverable injuries. With our current bodies, most major accidents end not with instant death, but being put on various types of life support and waiting to see if the body can heal itself. Many people who go onto life support never recover, but with better regeneration, life-support would become far more successful at saving lives and allowing a person to return to full health. Chronic Lower Respiratory diseases are normally caused by scaring of the lower lungs from smoking or major infections. With better regeneration, your lungs could fully heal following these events making later life respiratory issues far less common. Strokes would also not necessarily become less common, but making full recoveries would become more common. But the biggest life saver of all here is improved quality of life. People who are not in chronic pain live happier lives. Of all health factors that determine how long you will live, happiness is probably the most important due to its direct relationship with pulmonary heath and your immune system, and better regeneration helps you maintain better happiness as you age. ## So what does this all have to do with Modern Society? Human biology is designed to optimize our survival to how our ancestors lived. Our medial pulmonary systems don't regenerate very well because physically active humans living off of a natural diet can live a very long time as is; so, no need for better regeneration there. But now that we are living longer and eating worse, a regenerative heart would become more practical. Modern medical interventions also mean that we are MUCH better at stopping a simple wound from killing you quickly. If getting a leg cut off is rapidly fatal to pre-modern man, then there is no reason to care if your body has a long-term plan for recovery, but if you can consistently stop the fast death, then better regeneration helps prevent slow death. We are also a lot better now at treating cancer than our ancestors were. To premodern man, cancer was an absolute death sentence; so, our biology tries to avoid it by reducing cell divisions to minimal requirements. But with modern medicine, we can cut it out, irradiate it, chemo it, etc. Ironically, better regeneration may actually decrease the chance of dyeing of cancer despite higher cancer rates because more invasive treatment options would open up. So, if you went back to 50,000BCE and made humans super regenerative, it would not be very beneficial, but do it today, I am pretty sure it would help a lot. ]
[Question] [ In the Middle Ages, it was necessary for a couple to have as many children as possible because many children died before reaching adult age. Much of this was due to rampant disease and lack of medical knowledge. In an alternate history, diseases are rare and easily curable through the use of magical herbs. Most children born survive to adulthood. Women dying in childbirth is extremely rare. Would this cause overpopulation during this time period? [Answer] # There is still starvation I would argue that starvation and susceptibility to disease are intertwined. The people who did the most dying of diseases were the ones who were starving. It is worth noting that European population exploded in the 1700s to 1800s; before modern and universal medicine, and before widespread immunizations. However, this was after an Agricultural revolution increased the farming yield, and after improved transportation technologies allowed food to be moved from distant places to combat local famine. So I assert that starvation is more important than disease as a means of population control. A lot of medieval disease deaths simply took people that would have starved anyways. But even with no diseases, people aren't going to make it if there isn't enough food. [Answer] With few children dying due to disease and women generally surviving childbirth, I don't see the same need for the "have as many children as possible" mindset. That said, farmers and a few other jobs would probably still want to have as many "free labor" as possible. Having more people farming would have helped feed the not diseased masses. Not having to fight disease as much would have freed people up to make more discoveries, like better farming and industrial practices. Without the pressing need for most people to have a large family, I don't see as great a possibility for overpopulation during that time frame. There would definitely be more people around, but without calculating the food supply available, we can't know if this would be "over population" as we think of it. You also have to remember that wars were sometimes fought as a way to control over population. I have a suspicion that there would be more wars fought, due to this. However, in the long term, since families didn't have the long standing need to procreate against loss, we currently wouldn't be facing the large crowds of people we have today. Nor would we see that ever expanding population in the future grow as quickly as we do. [Answer] If you have magical medicine, then you better get a magical [Norman Borlaug](https://en.wikipedia.org/wiki/Norman_Borlaug). Otherwise, you will have overpopulation and famine. If the same handwaving that solved disease can be used to boost agriculture, you basically have enough population to do anything you want, relative to other countries. [Answer] It might not. One good example are Tibetan and other Himalayan societies, where their environment supports so few people that even small population growth is not very welcome. They came up with some cultural solutions that could easily be adapted to a medieval European setting: Extensive monasticism It's hard to find exact numbers on this, but apparently in some areas at some times, about one in three men was a monk, and thus did not marry. This may be a bit misleading because Buddhist monks aren't necessarily expected to stay a monk all their life, but most figures I can find posit at least 10% of Tibetan men living in monasteries (before the 20th century). Sending surplus sons to the monastery was also a common way of managing your inheritance in European history. Polygamy Polyandry, where one woman can have multiple husbands, is quite common in Himalayan societies and really rare in the rest of the world. The men will obviously have fewer children than if each man had his own wife, so this limits population growth. Alternatively, you could have some form of extreme polygyny, where high-status men have a lot of wives, and most lower status men don't get to have a wife at all. But I feel like that society would be quite different from medieval Europe, and I don't think any agrarian societies worldwide work like that. Birth control While having a lot of children to do labour is an advantage in agriculture, you do have to worry about what will become of them once they're all grown up. In a society with low mortality, there will probably be a lot of adults around who don't have their own land (because a sibling inherited it, or because it was too small to live off so they sold it, or because their parents didn't have land either). These people would be a good source of labour and probably not much more expensive than a child -- and certainly more productive! So your society, having access to pretty effective medicines, will probably work out a way to limit reproduction for married women. In some Himalayan societies, herbal abortions were quite common, and young people were taught how to have non-reproductive sex. If your society does not adapt to its circumstances at all, and stubbornly maintains that everybody needs to have as many children as they can, they will certainly collapse. But I feel that issues of inheritance and wealth distribution will lead to societal adaptations before starvation does. [Answer] I'd like to offer an alternative point of view to the one provided above: Considering the definition of overpopulation: > > the condition of having a population so dense as to cause environmental deterioration, an impaired quality of life, or a population crash > > > [Source](https://www.merriam-webster.com/dictionary/overpopulation) one could say that europe [was already overpopulated](https://en.wikipedia.org/wiki/Medieval_demography#Late_Middle_Ages). The reasons may have been partly artificial in the form of wars, feudalism and serfdom, but the general population was at the maximum that was bearable by the system. So even if the medical aspect would have been taken out of the equation, famines and war would have kept population approximately on the same level or at best slightly above. People would have most likely adapted with a lower birth-rate to the fact that they rarely died of diseases. So it would not have significantly changed the situation. There was already overpopulation. [Answer] # Yes it can. However it most likely will not! If the lack of diseases was a constant on your world then the populations evolved with this and will lack the need to have a large number of children in fact more children will be an hindrance on the family and society will become one that discourages having more children. # However lets assume that this is an recent event! And the population has just started spiking. When that happens then the villages and cities will require more food! They will either accept their fate and die or wars will break out. There is also a change that populations might start migrating to underpopulated areas or virgin lands. I see no way that you might have overpopulation in this world. [Answer] If nearly no kid dies because of diseases (even if they are weak beacause of malnutrition) the parents would naturally get a lot less children than you normally got during the real medieval times. If they are sure to keep all their children they could even plan how many they needed to make the job at the farm easier. ]
[Question] [ I'm admiral general Aladeen, the beloved ruler of [Wadiya](https://en.wikipedia.org/wiki/The_Dictator_(2012_film)), who won the elections with 99.999% of the votes. Wadiya is sparsely populated country, very rich in mineral resources. We have one of the highest living standards in the world. Life is good for everyone, well everyone except those from a wrong sect, or those whose tribe that warred against my grandfather, or the poor migrants working under [Kafala](https://en.wikipedia.org/wiki/Kafala_system), or the intellectuals who want free press, or the political prisoners from illegal parties, or the women who can't drive to work but are too poor to hire a chauffeur. Unfortunately, there is a trouble ahead. The government of my poor southern neighbor might collapse in a year or so, and I need to seal my southern border to prevent criminals, refugees, and various warring factions crossing into my beloved country. Unfortunately, my loyal army has grown into fat slackers whose could run through deserts and jungles only in video games. My commandos could be deployed on a short terms basis, but I need them at the capital in case someone tries to overthrow me. I've made an offer to Blackwater, but they refused to kill civilians. They've mumbled something about troops that are not part of the national military might stand for trial as mercenaries. So I've decided to create my own foreign legion, [just like the French](https://en.wikipedia.org/wiki/French_Foreign_Legion) & the Brits. I'm trying to figure the best way to recruit foreigners and ensure they wouldn't try to overthrow me. Is it better to recruit from a single country or should I prefer diverse troops? Should I train my recruits or should I hire only veterans? My training staff isn't stellar but I could hire foreign contractors full of retired officers. [Answer] There's a few traits that are key here: ### 1) You need to handpick the leadership Whomever you pick to lead this outfit has to have impeccable military credentials, and be able to establish him/her self as someone worthy of being followed by the soldiers you will recruit later. Essentially, you need someone who is such a barely restrained psychotic killer that even the most rabid of men your foreign legion is likely to attract would dare question their authority. If this person also has an incredible (if somewhat tarnished) military career, all the better. The rest of your cadre will similarly need to be incredibly battle hardened and ruthless individuals. ### 2) You need to offer new identities A big incentive to join The Legion is that once you do, you essentially disappear. A wanted murderer, war criminal, or rebel leader is such no more. All are faceless, non-identifiable drones in this unit. Those joining need to be able to trust that once accepted within those ranks, you will never betray them - unless they make you question their loyalty. ### 3) You need to operate in utter secrecy Everyone knows you exist, and everyone may even know who leads the Legion, but no one - and I mean no one - may know the identities of the soldiers within the ranks. Their military structure is completely separate from that of the regular forces. They answer to no leaders except their own, or you. Furthermore, any disciplinary action can only be taken within their own circle (and should typically be summary execution, because you'll be dealing with some real works of art) ### 4) You don't get to be picky You will accept practically anyone who present himself on your doorstep. Murderers, rapists, hooligans, or trained professionals. Give enemy combatants a chance to join up. However, by the end of the training process they will either be willing tools of destruction, bending to your will, or dead. Let the myth build that anyone who joins, no matter how desperate, is accepted. The truth that most are probably killed in the training will never filter out. This way you do not discourage anyone from applying, but you do weed out any elements that are just too chaotic. Someone who takes to killing their fellow soldiers because they have no one else to hunt down at the moment should be identified and put down. ### 5) Build esprit de corps This unit should not only be highly trained, but also very well equipped. Those who successfully pass the brutal training should have an intense sense of pride instilled into them. They are the best, of the best, of the best. The second best guys? The Legion killed them, and they know it. ### 6) Reward them well, and promise more to come This is not a regular army unit. They are essentially mercenaries bound to you by desperation. In this relationship you hold all the cards (the keys to their former identities, as well as their future one). Very few of them will achieve "freedom". In fact, most of them will willingly stick around for the killing, and perks - which should be lavish, when possible, to compensate for the insane work conditions they endure the other 90% of the time. Those who do fulfill their contract (10 - 15 yrs of service) should, however, be honorably dealt with. They should be aware that they need to keep their mouths shut, and will be monitored for the rest of their lives, but word will also spread in the ranks that you keep your word, and there exists a light at the end of the tunnel. This will serve to command loyalty. [Answer] Use the Yellow Pages. The world is full of mercenary military organizations created by and staffed by ex-military types who want to monetize their skills. Contractors like this are a dime a dozen. However, don't assume they only cost a dime. They don't, expect pay big bucks. Also, there are many major governments that would love to help create your own Foreign Legion. France might see this as a wonderful opportunity to assist with national goals and this might be an ideal way that their resource companies might get a foothold in your nation. As an example Gaddafi's Libya didn't have any difficulty in recruiting mercenaries to fill their armies and especially his corps of bodyguards. Professional mercenaries have no interest in overthrowing their employers. Doing so, only leads to they're not being paid. They're doing this for the money, not to become rulers of countries no matter how resource rich they might be. Try harder. There are heaps of organizations and corporations in the business. Just ask for an expression of interest and advertise for companies to present their proposals for building your Foreign Legion. These days you can practically buy them off the shelf. Time to go shopping. ]
[Question] [ In lots of science fiction works that visit other planets we are often introduced to intelligent plant based lifeforms, be they humanoid looking or potted plant looking. I'm curious as to what part of the plant has to evolve to gain sapient or near sapient intelligence. Eg, all mammals share an organ known as the brain and central nervous system. What would be the plant based equivalent? I want to have some plant based organisms but need to figure out what part of the plant is essential to keep and develop. I don't want to accidentally make the most likely area into a vestigial feature (I'm not looking for full sapience but if you can figure that out, I'm sure such an answer would be useful to others) [Answer] ## Method A: Evolving a True Plant with Neural Tissue This method describes how a traditional, plantlike organism could evolve a "brain" while maintaining plantlike characteristics in every generation. First of all, brains can come in all shapes and sizes! * [Jellyfish style](https://www.ncbi.nlm.nih.gov/pubmed/21430196): Nothing resembling a brain is present but a distribution of nervous tissue around the body maintains control. Think "reflexes" and not "thoughts". * [Cockroach style](https://www.scientificamerican.com/article/fact-or-fiction-cockroach-can-live-without-head/): Clumps of tissues resembling a brain exist but are spread out in the body. * [Spider style](http://news.nationalgeographic.com/news/2011/12/111219-spiders-big-brains-bodies-legs-webs-animals-science/): The brain tissue literally spills out of the head and around the body * [Human style](https://en.wikipedia.org/wiki/Human_brain): One central brain controls the body through a network of tissues * [Colossal squid style](http://www.todayifoundout.com/index.php/2012/10/the-colossal-squid-has-a-doughnut-shaped-brain-with-their-esophagus-running-through-the-hole/): The cognetive organ is wrapped around the esophagus in such a way that a large bite of food means permanent brain damage :) A plant could plausibly evolve and survive with any of these systems in place, but it would likely evolve clumps or spread tissue. This is because plants tend to lose parts, and this method would be most likely to preserve most intelligent thought if said plant were to lose said parts. Now how would a plant evolve a web of neural tissue? Well to spread tissue to every part of the plant, it could potentially evolve from a single-celled, photosynthetic organism. As this organism grows larger over time, becoming two or three-celled, one cell mutates to have neuron-like properties. If this three-celled organism can * Sense light with Cell A (photo-receptor, which isn't uncommon and could also be a precursor to the evolution of eyes) * Remember what or where light is with Cell B (precursor to neuron; single neurons are capable of doing simple tasks like this) * Photosynthesize with Cell C (precursor to leaves; must contain chloroplasts or another organelle capable of photosynthesis) * Travel to the light by moving all three cells Under these conditions, an organism could survive to reproduce, grow larger, and eventually become an organism comprised of two separate, main tissues: "traditional" plant matter, and a web of neural tissue. Eyes could additionally evolve from the original organism's photo-receptors, and these would aid the neural tissue in collecting information. ## Method B: Adapting an Organism with a Brain to Photosynthesize In this method, an organism that is not a plant, but has cognitive capacity, evolves photosynthesis and other plantlike characteristics. An organism that dwells in sunlight mutates a form of chloroplast, and passes the genes that create them to its offspring. Individuals that spend more time in sunlight will survive to reproduce because they will produce more of their own food (sugars) and will not have to forage or decompose other organisms. Additionally, organisms with larger and more efficient photosynthetic cells or tissues will also survive to reproduce. What could evolve in this way? Something: * Mobile, to make use of sunlight throughout the day * Intelligent enough to meet the "has a brain" requirement * Relatively flat to make efficient use of sunlight * That can fulfill the chemical needs of photosynthesis for its own system. For example, an organism whose process requires carbon dioxide and releases oxygen would make great use of porous flesh to filter in gases. * That makes contact with the ground, such as a slug, to absorb nutrients from the soil without having permanently anchored roots (for now) * That doesn't contain extremely rigid structures such as bones. Relying on the soil, water, and sunlight won't provide the nutrients to form skeletal structures, so only a soft organism will be able to survive using photosynthesis alone and evolve into a plantlike organism from there. If you aren't satisfied calling green slugs "plants", here's what comes next: The organisms' metabolisms could slow drastically, or they could find a place such as an open field to proliferate. Either way, they will move less. This is important, as the next stop on our journey is roots! In order for a plantlike organism to be truly convincing, even if all tissues except its brain now resemble that of a plant, you might want roots. These could plausibly develop if the organism doesn't need to move to find sunlight. The organisms that can reach further into the soil for nutrients while still being stationary in this environment will survive to reproduce, making roots increasingly common and efficient. With the energy these organisms would now have, they could be capable of sprouting upward and forming chutes or stalks. This would put the brain at the base of the plant, between the roots and stems, with all other surviving organs from the original species. Reproduction for a stationary organism will be problematic, and will likely have to evolve before said organism becomes stationary. One solution could be the development of asexual reproduction, which is not uncommon among plants on Earth. New plants would sprout at the base of parent plants, from the organs that used to facilitate reproduction, but daughter organisms would contain only parent DNA. Another method could be the exchange of genetic information through external contact, such as stems or roots. Finally, you have a plantlike creature that evolved from another organism through natural selection and a whole lot of unlikely plausibility. ## Method C: Symbiosis Between a Brain Species and a Plant I won't go into much detail on this one, but I will lay a foundation. [Lichens](https://en.wikipedia.org/wiki/Lichen) (LIKE-ins) are a symbiotic combination of two or more organisms, always a photosynthetic organism to produce energy, a fungus to anchor to a surface, and sometimes some other things, but let's ignore those other things for now. Theoretically, your plants with brains could evolve similarly to lichens - a photosynthesizer could produce sugars for a host with a brain, which would in turn house the photosynthetic organism safely. [Answer] It is highly dependent on how you plant will use the brain. If it is simple reflex movement like [Venus flytrap](https://en.wikipedia.org/wiki/Venus_flytrap) then you can have distributed specialized tissue that control actuators. But if you want your plant to have more complex behavior (like tracking of prey position before attack) you may need more complex coordination between sensors and actuators. Then you end up with some more centralized system (up to as complex as human brain). [Answer] You can actually make in a center of thoughts and senses in middle of overgrown huge plants. If you plan to make xenoplant infestation, that works the best. It can be just simply anywhere, but most probably underground or in a hard crust shell. It may appear after extensive development of the plant, and after stages the plant parts may reorganize to accomodate a nerve center, so you may not be restricted by specific plant part to protect until this stage comes... or if really needed, I would point on the stem right next to where the roots starts. [Answer] I dont know if this helps but there is something called "plant neurobiology" which studies the perception of plants: <https://en.wikipedia.org/wiki/Plant_perception_(physiology)> interesting from the same article: <https://en.wikipedia.org/wiki/Plant_perception_(physiology)#Plant_intelligence> [Answer] I have always been fascinated with the concept of the "hivemind" -a collective of life-forms all operating as a single entity, which I think exemplifies the nature of distributed, plant-based lifeforms. Rather than a single, sapience-inducing part/organ, each life-form has neural-like connections running throughout itself, and either through direct contact or some other construct connects with other lifeforms, forming a large neural net, vastly more capable as a whole than the individual. This really opens a new set of possibilities that can add new dimension to your world. Even within a hive-mind, you could still have some individualism, e.g. internal factions, discrepancies between regions, etc. Most plants have specifically evolved (with perhaps the exception of single stalks) to avoid single "parts" or organs on which it relies to survive, so I think a distributed design for your "brain" makes sense here. To answer your question more directly, if you wish to have a neural-heavy or even an "individual intelligence" part of the plant, you could consider the roots of the plant for that purpose- often the most protected part of a plant, and can easily be used for the inter-life-form connections. [Answer] This question reminded me of the film [Avatar](http://www.imdb.com/title/tt0499549/). The flora of the planet Pandora are all linked together to form a large neural network. > > Flora on Pandora are of a tropical type several times taller than that existing on Earth. Many, if not all, plant and animal species have bioluminescent properties. The flora specimens seen in the film were all designed by Jodie Holt, a professor of botany at the University of California, Riverside. According to Holt, Pandoran flora are able to communicate with each other through signal transduction and are larger in size than Earth flora due to greater atmospheric thickness, weaker gravity, and stronger magnetism on Pandora. [[Source]](https://en.wikipedia.org/wiki/Pandoran_biosphere#Flora) > > > Then I looked this up: > > Signal transduction refers to the transmission of a molecular signal in the form of a chemical modification by recruitment of protein complexes along a signaling pathway that ultimately triggers a biochemical event in the cell. [[Source]](https://en.wikipedia.org/wiki/Signal_transduction) > > > So in the fictional world of Pandora, the plants communicate with each other with chemical signals, forming a planet-wide neural network. So it's less about a single plant evolving a "brain" in this case, and more about the wildlife being linked and able to communicate. ]
[Question] [ Closed. This question needs to be more [focused](/help/closed-questions). It is not currently accepting answers. --- Want to improve this question? Update the question so it focuses on one problem only by [editing this post](/posts/40002/edit). Closed 7 years ago. [Improve this question](/posts/40002/edit) As Head of HR at a large urban bank, I have been getting a lot of flak (in the form of angry emails) from the 'Undead Defamation Society' about the fact that my company only employs a very small number of non-living staff. I have an upcoming vacancy in my marketing division and I would like to encourage vampires to apply for this position. How can I make my recruitment process more vampire-friendly but without overtly discriminating against living candidates? [Answer] First of all, I would think that something as shady as a bank attracts the postliving by its very nature. For the rest of the answer I'll assume that vampires etc are integrated into society and are not evil by nature. ## Be sure to present your company as "postliving friendly" 1. List benefits in the job posting that clearly apply to the postliving only. Things like flexible working hours including nights, windowless offices, cut-rate health plans with coverage tailored to your "personal condition", a darkened shuttle bus and a strict policy against smoking, drugs and religious symbols. Anniversary bonuses going up to 1,000 years are also an option, as is an "Ancient Talent Development Program". 2. Schedule all interviews at night with the excuse that you want to get them all done at once, so that you have everyone fresh in your mind. This should scare off some of the human candidates. 3. Adapt your interview questions. Sample questions: "Where do you see yourself in 100 years?" or "Would you be willing to donate blood for our team-building events?" If after the interviews you still have human candidates left and none of the postliving candidates is clearly superior in either credentials or "experience", you'll just have to bite the bullet and wait for the next vacancy. Haha, just kidding. Tell the remaining candidates that you're setting up a challenge where they can show off their marketing skills: They'll all be put in a room and must convince the other candidates to support them for the position. Whoever gets the most votes will be in (this time). Btw, "unliving" or "non-living" are such negative terms! How about "re-living" or "non-traditionally living"? Actually, "postliving" it is! [Answer] ## Don't discriminate on the grounds of race, sexual orientation or vital status In many countries, there are strict laws about employment discrimination on the grounds of age, race, sexual orientation, marital status, etc etc. As Head of HR, you should be aware of these [protected classes](https://en.wikipedia.org/wiki/Protected_class) (or however they are called in your country) and how to make accommodations for these standard classes. Below are some recommendations for accommodating the living impaired. A couple of measures you could take: * Hold interviews at times accessible to the non-living. Since vampires only come out after dark, be willing to hold interviews either very early in the morning or after dark. (Arguably it is easier for vampires to get to interviews when it's dark outside, this will be easier in the winter than during the summer.) * During interviews, focus on the applicants qualifications and ability to perform the work assigned. Questions about applicant's life/undeath status are not permitted. Interviewers will also need to assess cultural fit within the banks and the marketing team's culture. This is where it gets complicated. Socially integrating a vampire may be considerably more difficult than technologically integrating one. While the 'Undead Defamation Society' may want better representation, if introducing a vampire on a team alienates team members because they fear for their lives....it's just not going to work. * Alternatively, make the bank loading dock available for employee ingress/egress. Loading docks are typically covered areas with large doors to prevent access, so assuming that the vampires are able to move about during the daytime in black-out cars then they should be able to get into and out of the office without undue difficulty. * Make black out curtains available for the vampire's new office. If the marketing office has large windows then some reorganization of the office may be required. What measures will need to be taken will depend on the vampire's sensitivity to light. * Allow flexible working hours for the marketing team in general. This should accommodate the vampire's needs as well as a nice bonus for living employees with children. * A modern bank is unlikely to have religious iconography as decoration. Iconography worn by employees will need to be dealt with on a case by case basis. The degree to which this is a problem depends heavily on the culture of the city and the vampire's sensitivity to iconography. As long as the presence of vampires in the workplace is not a safety or harassment issue, then the biggest hurdles will be cultural integrations. [Answer] Just to be complete, remember that there are grounds to discriminate based on bona fide job related requirements. For example a 95 lb woman, no matter how dedicated, is unlikely to become a firefighter because applicants need to pass a physical that includes carrying heavy equipment and simulated casualties up ladders and down ladders. A person who is colour blind will be ineligible for jobs requiring the ability to see colours, and so on. Being able to greet customers during the daylight hours, and perhaps more importantly, not killing them and drinking their blood could be considered important parts of service jobs like banking, and you as the HR director can politely explain the situation to would be undead job seekers. You are also protected to a certain extent by employment law in this regard (so long as the requirements are "bona fide" and equally applied to all job applicants), so ensure your terms and conditions of employment are clearly spelled out and are unambiguous. I might also suggest putting garlic, white roses and silver crucifixes around all ATMs and night deposit boxes in case the Vampires decide to take this out on your customer base as well.... [Answer] You don't have to discriminante anyone, just make the job conditions more vampire-friendly : * We are looking for night workers. * Workers are not allowed to eat food or to drink water/beverages during the working hours. * The bank can't afford the lightning cost, so you will be working in complete darkness. * No sleeping allowed while working. * No security measures will be applied while working at night (who needs security when you're hiring vampires). * You will receive free blood pack coupons from the blood bank to use in need (accidents, surgeries, or other ...) ]
[Question] [ The [oldest known musical instruments](https://www.bbc.com/news/science-environment-18196349) are a set of bone and ivory flutes from around 42,000 years ago. Paleolithic tribesmen undoubtedly played these instruments gathered around the campfire, as an addition to storytelling or religious ceremonies. What I wonder about is, how did they play multiple musical instruments together. Multi-piece music can generally be divided into two types, [homophony](https://en.wikipedia.org/wiki/Homophony), where there is one primary part backed by secondary parts that play chords or octaves to harmonize, and [polyphony](https://en.wikipedia.org/wiki/Polyphony), which is multiple parts that do not necessarily support each other, playing different tunes, but that hopefully sound nicely together. Does the ability to [harmonize](https://en.wikipedia.org/wiki/Harmony) come naturally to humans? Or would the first musicians play polyphonous music until someone 'invented' the concept of [chords](https://en.wikipedia.org/wiki/Chord_(music))? When the first flautists gathered around a mammoth roast, did they immediately learn to harmonize with each other, or did they play their own tunes? [Answer] We can't go back in time but, as a musician I think I can answer. It doesn't have to be invented because it occurs naturally. When people chant together in a large group, they have different pitched voices. It's natural for women and children to sing at least an octave above the men. However there are intermediate voices. They may not sing an octave but a fifth (which is also a fourth seen from the other direction). Because of the construction of our ears, certain notes go well together. Firstly unison, then octaves, then fifths and so on. As well as the sound-detecting hairs in our ears, there is a theory that pleasant sounds have a neurological basis. I remain to be convinced but time will tell. The key to pleasant music may be that it pleases our neurons. A new model suggests that harmonious musical intervals trigger a rhythmically consistent firing pattern in certain auditory neurons, and that sweet sounds carry more information than harsh ones. <https://www.newscientist.com/article/dn20930-why-harmony-pleases-the-brain/> Therefore anyone who is not tone deaf (another subject that can be discussed) will naturally tend to slide their own pitch towards one of these 'pleasant' intervals. You can clearly hear that adjustment in progress here <https://youtu.be/V37k31746IM?t=102> The woman in question clearly has no idea of harmony or fine control of the pitch of her voice. She simply slides her voice around until it sounds good. She is 'inventing' harmony in that sense but has only a limited choice of what is pleasant. Polyphony is an offshoot of call and response singing - specifically work-songs. If the call and the response overlap then you have elementary polyphony. Another effect is to put a melody over the top of a drone. <https://youtu.be/lN1NbYUE8Ck> Polyphony can develop from this by a lead singer singing over the top of a simple melody. <https://youtu.be/veiJLhXdwn8?t=136> In traditional African singing it is common for someone to sing or shout a phrase when inspired to do so. Once the classical era came along then the story gets more complicated. I could expand on this. Finally, when you talk about pipes. There was no widespread standardising of pitch between musical instruments until the classical period. Original pipes were simple whistles with one or two holes added. They were mainly solo instruments often played by solitary shepherds. Singers would fit in with the pipe. In fact that still happens in modern-day orchestras where everyone tunes to an A provided by the oboe (a wind instrument that is difficult to adjust the tuning of). --- EDIT with regard to the very useful answer by flox. I agree with flox's exposition. However it doesn't say why naturally produced sounds are pleasant. I'll argue that it is the receiver that is important. For example two sufficiently out-of-tune instruments sound horrible because of the beat frequency. But beat frequency is a natural phenomenon as well. So the answer by flox doesn't explain why listening to a beat frequency is generally considered unpleasant. (Note: I'm aware of lots of acoustic theory about organ pipes using beats to produce notes that sound lower than what is being played). However none of that deals with the human aesthetic. I think I need to address in my answer the human anatomy that might explain that (I've already talked about the neurological factor). As a start I'll talk about information processing. Humans are bombarded constantly with a barrage of sounds that they have to unravel in order to make sense of. This is equivalent to doing a Fourier analysis on the fly. We can distinguish individual pitches and even the direction they are coming from. If notes are in harmony (exactly as flox indicates) then they stimulate the sensitive ear transducers with a similar resonance. Thus to a human a note and an octave above it sound almost the same. This is because the tiny hair cells in the cochlea vibrate with the same laws that flox mentions. The result of this is less information processing. White noise is a mix of all frequencies and at that point our nervous systems give up trying to separate sounds and simply lump the frequencies together. In a crowded room the information processing is at its worst because of all the cross-talk and mixtures of timbre and pitch. Harmony takes most of the strain out of this situation and gives our nervous system a rest. So, I argue, perceived harmony is a product of the receiving apparatus. If evolution had come up with a different mechanism we might never be able to hear harmony at all even if the mathematics 'out there' was as flox correctly asserts. [Answer] Harmony is natural in most instruments, and is actually universal mathematical phenomenon I play the violin in an orchestra and you notice a few things about the strong link between mathematics and music. If you play an 'open' string on a string instrument (ie, a tensioned string between two points, no fingering, on a violin or cello), you get a set frequency. Divide the string in half, and the frequency lifts up an octave. Divide that half into half, it goes up another octave, and so on. Get an adjustable tube with a reed or mouthpiece (a common modern instrument is a trombone). Extend the tube by twice the length, and the sound drops an octave. Get a glass and fill with water and a spoon. Hit it with the spoon and you get a note. Pour out half the water and hit it again, you get an octave higher. This is the same principle as a xylophone. Same for harps, tubular bells, marimbas and many other instruments. It is universal and cross cultural. Octaves are the primal harmony, cultural factors affect how that octave is divided further, and different cultures divide in different ways (Korean music divides in 5, European in 8, and others differently) but essentially it all starts with that initial harmony. The individual notes established, the only remaining factor in playing in a group is to match their base notes. This is called tuning. In an orchestral setting, all instruments tune to a common instrument (usually the oboe) to 'set' their base note to a common frequency. If you do not do this, you immediately sense 'disharmony' or 'out of tune'. This is not just an emotion, it is a mathematical mismatch, which you can hear a 'wobble' as the two frequencies fight each other. Tuning a violin you must do so using only your ear, you find the right note when it no longer 'wobbles', and the frequency matches with the oboe and others. What's more is you can easily know who is 'out of tune', their notes stick out like a sore thumb, and you don't need to be musically educated to sense this. Your group of flute players around your mammoth roast must adjust the length of their instrument to match each other prior to playing, otherwise it would be a mad jumble of incoherent frequencies, as can happen in modern orchestras today. [Answer] As far as "sounding nice together" goes, the simplest way to achieve this is the [pentatonic scale](https://en.wikipedia.org/wiki/Pentatonic_scale). Of course "pentatonic" simply means "five notes", but a characteristic of the "major pentatonic" and "minor pentatonic" is that playing in those scales will automatically sound harmonious. These scales also appear across a range of societies independently. This causes inevitable questions about whether this indicates something fundamental about our brains and pattern recognition. Probably the most famous modern example of this is [Bobby MacFerrin's World Science Festival presentation](https://www.youtube.com/watch?v=ne6tB2KiZuk) where he makes the audience sing a major pentatonic scale. A particularly remarkable element of this is that having introduced three notes in one direction, he "forces" the audience to predict the adjacent note in the opposite direction without giving them any other information *and they do*. The octave pattern can be predicted when the relative pitches are known, of course, but at no point does he tell the audience what scale he's using. He simply "jumps" them to the next note, and without thinking they pick it. [Answer] # Yes, harmony must be invented From the abstract of [MacLachlan, et al., 2013](https://pdfs.semanticscholar.org/1ef9/9d59ce104afab661ebcabfc2bb6120ccd493.pdf), > > The cognitive incongruence theory of dissonance was rigorously tested > in Experiment 2, in which nonmusicians were trained to match the > pitches of a random selection of 2-pitch chords. After 10 training > sessions, they rated the chords they had learned to pitch match as > less dissonant than the unlearned chords, irrespective of their > tuning, providing strong support for a cognitive mechanism of > dissonance. > > > The 'cognitive mechanism of dissonance' was proposed by Martha Guernsey in a [1928 paper](https://www.jstor.org/stable/1414484?origin=crossref&seq=1#page_scan_tab_contents) (can't find a full text online?) where she > > found strong effects of music training on consonance. This discovery > led her to suggest that consonance was associated with familiarity for > commonly used music chords. > > > The conclusion of the MacLachlan paper is that > > learning to perceive consonance involves cognitive processes. > > > Therefore, you cannot know harmony without learning harmony, much as you cannot know multiplication without learning multiplication. So while both harmony and multiplication are facts of the physical universe, human perception of these concepts would necessarily follow the 'invention' of harmony, just as someone 'invented' multiplication. [Answer] Whilst I don't really like the question as it stands as the specifics of polyphony, monophony, what constitutes a harmony etc are debatable.... Aural harmonising is only learned in the same sense as watching one's parents and seeing how they move and mimicking that is learning. Perhaps early an answer should address the references to 'musical appreciation is learned/cultural' and how it's not relevant to the question. /edits The McLachlan paper does not claim that harmony is 'learnt,' in the useful sense of the word, but that the harmonies appreciated by different groups are different and can change. What my eyes are able to see has changed, it doesn't mean that using them in the basic sense is a learnt(or unlearnt) skill. Accent is inherited, not in the sense that the physical matter that makes up the oral apparatus is different form region to region, but in the sense that one learns to speak from those who make the noises one mimics. We all have had experiences of not understanding, or not liking, or liking differing accents that formally might be constructing the same word-forms and this is largely for the same reasons that people and cultures identify and favor 'valid' chords/notes/etc in music. <https://www.ideals.illinois.edu/bitstream/handle/2142/47304/081_ready.pdf?sequence=2> <https://www.ncbi.nlm.nih.gov/pubmed/29077726> <http://rspb.royalsocietypublishing.org/content/280/1754/20122798> <https://en.wikipedia.org/wiki/Bird_vocalization#Learning> <https://academic.oup.com/beheco/article/20/5/1089/211561> <https://www.salford.ac.uk/research/sirc/research-groups/acoustics/psychoacoustics/sound-quality-making-products-sound-better/accordion/sound-quality-testing/roughness-fluctuation-strength> The desire to attain 'Harmony' is natural, though what constitutes a harmony is learned, as is the ability to attain it. For this reason multi-source music is of limited complexity until proficiency allows expansion, this is true of all musical cultures. Synchronised clapping or stamping or banging to a stable tempo is one thing, contemporary chord structure is quite another. What would be demonstrative is a scientific paper that tested not different forms of music levels of memorization, responsiveness & appreciation by cultures other than where the music originated, but 'random varied' noise appreciation by culture. Music being socially produced noise, it stands to reason also that cooperative production is not out of the question from the outset, if you put two children in a room and one starts banging a drum, the other is like as not to start banging something too. ]
[Question] [ The world in question is an Earth-sized planet with a deep global ocean and core of water-ice. Given the lack of an accessible sea floor to root oneself to, how would a complex free-floating organism function? How might nutrients enter the system? Is this sort of system plausible? [Answer] On [the moon titan](http://sci.esa.int/cassini-huygens/50128-layers-of-titan/), beyond the initial ice layer, there is an entire ocean layer. If you continue further down you hit ice VI (which is always ice, just with a denser crystalline structure). This deeper ice layer is caused by sheer pressure. Presumably your ocean world will have a point deep enough that the pressure will be too great for water to remain liquid and will turn to ice. It matters not that the core of titan is solid. Your planet could conceivably be entirely made of ice through and through. The problem would be the rest, which is to say, all organic life is built from carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. You can obtain only two of these from the surrounding water. As far as we know, a water planet with no other elements than hydrogen and oxygen could not sustain life. You'd need to have to allow the water to be rich with other minerals in order to justify a thriving ecosystem . The fewer the minerals, the fewer lifeforms you will see grow on such a planet. My idea is that minerals come from meteorites which have crashed into the ocean planet over the course of millennia. These meteorites would float like underwater islands, being too heavy to stay on the surface but too light to sink below the crushing ice VI layer. Plantlife can grow on these islands, and like a coral reef, you'd find most life would grow exclusively from these islands. This isn't to say life couldn't exist between islands, but they would be larger creatures and they could probably swim quickly enough to reach other islands. While life would live near the bottom, I don't think life would ever physically touch the ice layer, as it would likely quickly freeze over anything that touches it, plantlife or otherwise. [Answer] Well, let's look at the producers first; they're at the base of the food pyramid, so once they're there, a full ecosystem can form. Plants need four basic things to grow: air, water, nutrients and sunlight. You've got air, you've got sunlight and I'm preeeettty sure you might have some water around there. The problem is nutrients. Plants evolved on Earth from algae and other simple flora - which are aquatic. They get their nutrients from carbon, oxygen, nitrogen and phosphorus. So, there's oxygen in the water, but the rest are not present. So, you need to obtain the other minerals from something external to the planet. This could be two things - minerals present in meteorites or artificially introduced minerals. I presume you want the evolution to be all natural, so the idea of a sapient race inserting carbon, nitrogen and phosphorus into the planet's seas may not be satisfactory. I haven't read the other answers yet, but I wouldn't be surprised if someone else hasn't followed the same intellectual yarn until reaching the conclusion that meteorites are probably the most likely option. The bolides could be laced with nodes of these crucial minerals, which are expulsed into the surrounding ocean, and thus, space-age aliens. Well, not really. That gives us the building blocks for simple, algal life-forms, but there's still a way to go before fish-people can invade the Earth. We call that way evolution. So, my original taxonomy of evolution is that it is made up of 3 very closely linked processes - improvement, complication and selection. Note: I am not an evolutionary biologist and do not claim that this is an accurate allocation, it's more of a simplified way of breaking it down. For plants, improvement usually means more efficient reproductive systems, allowing them to multiply at a higher rate and proliferate. However, plants will also improve their systems for remaining buoyant, consuming nutrients, supporting their structure, transporting nutrients and photosynthesising. You may know that algae are unicellular, so such systems are less tangible, or sometimes non-existent. I recommend you look at how algae evolved into multi-cellular plants to get a better idea of how these systems would come about. So, the next process in my categorization of evolution is complication. In looking at this picture by the venerable speculative biologist C.M Kosemen (You might know him as Nemo Ramjet.), you can see the vast difference between the first generation of species and the eighth one. [![Nemo Ramjet's "Evolution in Action" piece illustrates how species complicate over time.](https://i.stack.imgur.com/rji9K.jpg)](https://i.stack.imgur.com/rji9K.jpg) Similarly, if we look to the real world, the anatomy of a Haikuicthyan are vastly simpler than that of a modern Sockeye Salmon. This is very much linked to the last process - improvement - because in improving, the systems of an organism must become more complex. So, to summarize it, over time your plants would evolve into more complex forms. Now to the third process, selection (again closely connected to the previous two mechanisms.). Natural selection is of course the way nature deals with the incompetent for survival. These include genetic aberrations whose anomalous characteristics hinder their survival ability. For example, there's a reason you don't see many wild albino animals - they simply don't live as long in the wild. However, genetic anomalies can be favoured by selection as well. For example, look at Hemeroplanes triptolemus, the famous snake caterpillar. It mimics a poisonous viper to deter predators. They probably evolved from few caterpillars with an unusual pattern of spots on its head that looked vaguely like a snake. These caterpillars would be eaten less often, and the more spotty caterpillars, the higher chance of them breeding with eachother, and the spots get more and more refined with each generation until you've got a new species. [![enter image description here](https://i.stack.imgur.com/YCeZa.jpg)](https://i.stack.imgur.com/YCeZa.jpg) Then there's another aspect of selection, extinction. In the natural world, success comes in two forms - adaptability and specialization. For example, the simple bivalve genera haven't changed since the time of the dinosaurs. They don't find themselves on the top of the food chain because they're not specialized, but they still survive for dozens of millions of years. Then when you look to the higher layers of the trophic pyramid, you've got the ubiquitous carnivorans, and below them, the ungulates. You could call them successful as well, for they are perfectly adapted for their own environment. But the average carnivore/ungulate genus lasts for only 6-8 million years. They do not deal well with climate change, and the world is an ever-changing place. So, the successful organisms on your water-world will either be simple but adaptable, or advanced but inflexible. So, you may be wondering, why am I teaching you so much general evolution? Well, Stack Exchange can give you a basic idea of a plan, but refining and continuing your evolution will be up to you. With a synopsis of evolution frequently compared with your planet, this gives you a head-start in the solo territory of worldbuilding. The basic plants on your world, I think, would look like lilypads, with a buoyant structure to keep them afloat and the other organs submarine. Then you could have plants that grow on their stems, or epiphytes, rather like this real-life tree and the plants it carries: [![enter image description here](https://i.stack.imgur.com/VB7oc.jpg)](https://i.stack.imgur.com/VB7oc.jpg) In one exobiology project of mine, I postulated that floating sponge-like organisms could evolve, and provide a solid surface for "terrestrial" life to evolve on. If something like this might happen on your planet, there could be life like seaweed and coral etc. Also, plants can grow on slow-moving organisms, like the moss on this three-toed sloth: [![enter image description here](https://i.stack.imgur.com/6T9kH.jpg)](https://i.stack.imgur.com/6T9kH.jpg) So, once you've got plants, you can eventually evolve organisms to feed on them. By this, of course, I mean animals. A lot of early animals were benthic, but that's not going to be possible in a seabed-less world. But, all those animals mainly evolved because that's where all the plants were - on the seabed. On your planet, the plants are nearer the surface, so the first animals would probably be simple, buoyant creatures that fed on the plants. The most efficient way of doing that with a worm-like animal (The majority of animals today are worms like Annelids, Platyhelminthes and Nematodes, and they were probably some of the first.) is to have one orifice at the front for consuming food, and another at the back for expelling the waste. Over the course of evolution, worms could turn into bell-shaped animals, giving you cnidarians, or they could become sturdier and form fish-like creatures. The most simple fish today are lampreys, and they do look pretty worm-like, so it's possible that worms could evolve into similar creatures on another world. [![enter image description here](https://i.stack.imgur.com/7unYV.jpg)](https://i.stack.imgur.com/7unYV.jpg) Then, you know the drill, the lampreys evolve into cartilage-boned fish and bony fish and all that (I'm not suggesting you rip off Earth's fish, but the basic streamlined design is pretty successful.) There are some things fish could evolve into that haven't happened on Earth. For example, what if the fish learn to breathe air? And don't think this requires land - just look at lungfish. They evolved "lungs" from aquatic ancestors. This one was dug up by a guy, alive, encased in a cocoon on dry land. [![enter image description here](https://i.stack.imgur.com/ZHXNW.jpg)](https://i.stack.imgur.com/ZHXNW.jpg) There are a many possibilities that come with air-breathing. One is that fish could evolve to colonize the topsides of the "lily-pad" plants, to breed or evade predation. This could essentially give you fish that looked like pinnipeds... [![enter image description here](https://i.stack.imgur.com/Vfw8A.jpg)](https://i.stack.imgur.com/Vfw8A.jpg) Wonderful. The other possibility I thought of is that breathing oxygen supplies more energy to the brain than using gills. This could see a sapient species evolve (I have a personal project centered around a race called the Vendrikk, serpentine aquatic animals that eventually created an industrial civilization. ) To become sapient, they would need intelligence, provided by oxygen, manipulators, which could be claws, tentacles, even prehensile tongues, and collaboration. They could do this to hunt in packs, or for protection. Well, I've got to go now, and I know it's been a massive answer, sorry if it's too long. I hope it's helped you, and I wish you well on your exobiology project. Happy worldbuilding! [Answer] Planets are not always homogenous. Although the core is ice as you say, various tidal forces from its moons, to its own orbit and rotation, and irregular heating and cooling of its surface and atmosphere, cause different stresses in the core, meaning it is possible to have quite violent localised or 'hot' eddies, vents, or bursts, even though the majority of the core is still ice. If the water is not pure and contains a certain concentration of hydrocarbons, it is possible that these could form free floating clumps of hydrocarbons that then form the threads of life. [![enter image description here](https://i.stack.imgur.com/Gfx57.jpg)](https://i.stack.imgur.com/Gfx57.jpg) These chains would probably be in the form of floating bacterial chains first - forming a 'glue' on which other organisms can evolve. Have a look into bacterial microbial mats. This will form where hydrocarbons exist, and are simply a loose assemblage of bacteria that multiply to form a mat. Then the mats will rise to the surface to gain heat, or float at a certain depth, ideal to absorb nutrients from below. It would be ideal if the bacteria could grow around hydrothermal venting rather than be blown away, so I imagine that this bacterial structure would be very 'thread-like' and low density, almost like a very dispersed soup, where links and water resistance would keep the bacteria centred where they need to be. [![enter image description here](https://i.stack.imgur.com/wUMrj.jpg)](https://i.stack.imgur.com/wUMrj.jpg) On the surface of these mats, they may over time grow quite thick. Such as in Shark Bay, Western Australia, where bacteria grows layer on layer over billions of years, to form stromatolites. Eventually life may become multicellular, and the earliest forms could be algae like mobile forms, that exist amongst bacteria saturated matts, such as seaweed. [![enter image description here](https://i.stack.imgur.com/hFsmk.jpg)](https://i.stack.imgur.com/hFsmk.jpg) Then all you need is sexual reproduction, an oxygenation event, and presto, you might get diverse animal and plant life. [Answer] The problem with all-ocean worlds is nutrient transport. At least some will get trapped in the sediment at the bottom of the ocean. If Earth is a normal planet, then the geologic cycle is a significant part of nutrient cycling, especially for Ca, Mg, S, and P You can either handwave around this, or come up with a different mechanism. e.g. there are bottom feeders that feed on the ooze, but have inefficient digestive systems, so their farts bring clouds of silt up to the surface. Or the long term temperature cycles favour the collection and sudden release of dissolved gasses. --- Earth has an average ocean depth of 12,000 feet. This would give about 9000 feet if we leveled everything out. Try this: Put a moon close to the planet. Tide forces go with the inverse cube of distance so if you put the earths moon at 50,000 km (1/8 of present distance) the tides would be 500 times as strong. Several hundred foot high tides would both make the coast of continents uninhabitable, and would erode continents as fast as they formed. This would give your planet a mix of shallow and deep oceans. --- If you want to see a classic example of a story with a floating ecology read Stan Schmidt's novella "The Demon Breed" That particular planet has continents too, sidestepping the nutrient cycle thing. Also see Alan Foster's novel Cachalot, which is on an all-water world. [Answer] There was something similar to this in the movie Interstellar, that might be something to check out. Like some previous posts, I agree that it would have to be a very nutrient rich ocean to provide the start for life forms. Another thing I would wonder is, does this planet have a moon or multiple moons? Our moon affects us by causing the tides, so I expect that a moon might cause rougher seas, and life forms would be forced to adapt. It might start out from bacteria, and then evolve into a fish eat fish society. Since the it is majorly deep water, gills would be the most common breathing apparatus. Fish might evolve into being able to glide to escape predators, and might even evolve into a species similar to waterfowl. Different types would evolve to suit different levels of the ocean. The deep sea fish are probably very blubbery, since it's cold down there. Most likely everything has a air sac to act as a life preserver. Things likely bunch together when they go to sleep. I'm not sure anything would live on the ice core. The pressure would be tremendous, although something might evolve form bacteria, but look totally different from the life-forms above. This is the only place where plants with roots could possibly live, unless they had humorously long roots that reach all the way down to the core. If you wanted a sentient life-form, probably a mer-race would be the best idea. They would be a little different then the typical idea,though, evolving from fish instead of humans. They probably have some sort of natural weapon to defend themselves from predators with. Their hands, evolved from fins, will probably look similar to a sea otter or lions paw at first. They could use materials like fungi mats and plants, and maybe bones to build shelters. Plants might come a little later, and marine fungi might also evolve. In free-floating plants, fungi, and coral, they wouldn't be able to really anchor themselves to anything except other lifeforms. They might take up a parasitic life-style, anchoring themselves to fish and even other plants. Another theory is that they might glob together in big schools, making huge floating mats, and use air to create a sort of ballast to keep them from either sinking or staying on the surface. [Answer] > > How would a free floating ecosystem on an ocean world function? > > > I'll go ahead and say it wouldn't. As far we know, life requires 3 components in combination. Nutrients to form into complex, self-replicating molecules (RNA and DNA on Earth), energy to drive that process, and a solvent of some sort (water on Earth) to allow the nutrients to mix together. Theoretically, it might be possible for some form of life to evolve in an organic solvent, like benzene or whatever else, but we can't say for sure. Your water-world would have an abundance of one component, but a distinct lack of at least one of the other two in the same place. These nutrients that form the building blocks of life tend to be and/or are delivered in forms that are heavier than water. So they'd sink. Which brings you to the big problem you're going to have, nutrients. Even if you did find a way to deliver them in sufficient quantities to allow life to form, (asteroids, whatever), you'll have a big issue with concentration. A gigatonne of phosphorous (or whatever) won't do you much good if it's diluted to 3 parts per million across your ocean world, nor if it sinks to the icy core, where there's no energy to drive the chemical reactions required to create complex molecules. Looking at Earth, life developed in places where the water and land meet - the land provided nutrients and a convenient anchor to keep the building blocks of life from diluting away, the water provided a solvent for them to mix in, and the energy was provided by either EM radiation or geothermal vents. I don't see a way for the three components to exist in a world that's all water - where you might get concentration with mineral-rich asteroids sinking to the core, you won't have energy, and where you have energy (near the surface), you won't have sufficient concentrations of the building blocks of life. [Answer] You'll need plant life floating on the surface, a la C. S. Lewis' Perelandra. For minerals, you either need really long roots on the floating plants, or something that draws the deep, mineral-laden waters to the surface where the floating plant life can exploit them. [Answer] Simply. They build the floating platform. Plant a forrest. Release all kinds of insects. Release birds. Release a fox. Just wait a milion year and then watch how it evolved. ]
[Question] [ A modern architect specialized in [low-energy houses](https://en.wikipedia.org/wiki/Low-energy_house) suddenly finds himself in the medieval times, say around the year 1000. Thinking about how to make a living and noticing how badly heat isolated the houses, even the castles, are at the time, he manages to convince a king that he can build him a much better, and especially much warmer castle. Unfortunately only after the deal was closed, it occurs to him that he doesn't have the modern materials and technologies available. But he now cannot retract, so he has to just do his best with the means available. On the positive side, he has virtually unlimited spending budget for building the castle. Also, the king of course doesn't know modern standards, so he will be satisfied as long as the new castle is significantly better than his old one. Now my question is: What is the best the architect can do with his modern knowledge, but medieval technologies? The castle must also be built so that it can be maintained by medieval people without too much training. [Answer] Insulation Packed earth and even packed hay are incredible insulators. This, along with upper-ceiling, open/close air shafts allow for some pretty good moderation of the temperatures. Views Better use of glass, much like a church's stained glass allows for safe viewing and natural light. Double-pane them for insulation, and allow them to swing open for ventilation. Plumbing It requires no electrical devices to build a toilet for more comfort than using the gold chamber bowl. Water can easily be brought to above the castle ceiling in order to have flowing water on demand. Wastewater can flow downhill as it does. Rainwater Catchment Water in 'the olden days' was often mixed with alcohol, because it was from a river, tasted bad, and could give you diarrhea or worse. By using and storing rainwater, you have a pretty good tasting and more sanitary water. You can still mix it with wine, but you have a lot less chance of getting ill. Heated Floors Build small passageways or 'pipes' that allow a 'downstairs' heat source to channel up directly under his wooden floor, and out the castle. During cold winters, this technique is used, so the king has nice, warm floors and warm chambers. Hot Water Heater Everyone likes a warm bath, but the King wants it on demand, and doesn't want to wait for the chamber maids to haul hot water up the stairs in buckets. A continuously heated chamber of (captured rain) water sits above the bathroom, and when he wants it on demand, the chamber maid turns a faucet allowing hot (and cold) water to his liking, to flow in. Then she goes and refills the water upstairs. Recreation Facilities Everybody likes bowling. Have your architect build the facilities and instruct the king how to play a number of modern sports that are easy to learn. Bonus: Bacon A pipe or vent between the interior walls goes from the basement kitchen up to the king's chambers. In the mornings, the cook makes a lot of bacon, so he wakes up to the smell of bacon each day. [Answer] Just building a nearly airtight castle heated by steam will go a long way and you don't need modern materials though that helps. Native Insulation Even if the materials themselves don't insulate terribly well, if the structure can made as airtight as possible, the energy required to maintain a given temperature will go way down. Sealing cracks with pitch or tar should help a lot. Stone and wood are naturally decent insulators, not as good as fiberglass insulation but plenty good. Steam heating Older homes before central heating and air conditioning heated themselves with steam. Water was heated in a boiler which was then fed into a system of pipes and radiators. Middle Ages blacksmiths certainly had access to cast iron technology so making the boiler, pipes and radiators shouldn't take too much experimentation. Inventing threading will be a bit tricky but if backed by the King, it shouldn't take too long to describe to a competent blacksmith how to do threads. (Edit: Okay, threads are crazy crazy tricky with high precision and metallurgy requirements. Perhaps all you could do is get them started.) The architect may have to invent measurements to standardize on but that's not too hard. Safety testing will be essential because it won't do to have a radiator explode in his majesty's privy. Design of the castle The architect will have taken an architecture history course so he need only examine the king's army to decide how to build a maximally defensive castle. Or, if the architect is really lucky, the king will have him design a castle without all the required defensive measures. The design of defensive structures changed with advent of firearms and cannon so the architect will need to design appropriately. Anything, absolutely anything that the architect comes up with will blow the king's mind. It will be a structure hundreds of years before its time. A good architect will get to know his client's sense of style and make something astounding and approachable because it will be very easy to design something that offends the king's sense of style. However, if the architect does well, everyone in the known world will want one of his castles. Glass Glass is the middle ages was super duper expensive so making double walled windows will be exorbitant by any standard. It's up to the king to decide on that one. It's a big bonus if he can pull it off. Every piece of glass was cut from a giant clear wheel of glass. Very time consuming to make. If the architect is familiar with the float glass method of glass making then he could suggest it to the blacksmiths/artisans of the king to get large quantities of high quality and perfectly smooth glass for windows, mirrors, whatever. Pest Control Removing ways for mice or rats to invade will be huge. Disease goes down, food spoilage goes down. [Answer] Double walled structures with bales of hay between them are simple to make, and are the basis of some "live off the land" type structures today. These are probably easy to build with the technology of the Middle Ages (the main sticking point will be sealing the gaps between the boards, since the sort of technology used to rapidly make large, flat, standardized boards that we are used to using does not exist), but for most practical purposes the house or shelter will be far superior to what is available. The downside is the cost. Even today most people do not care to pay extra for energy saving houses, and in the Middle Ages, the amount of available wealth is so much lower that few, if any, people would have the surplus money to gather materials or the extra time needed to build such a building (they already need to spend virtually all their time just to stay ahead of starvation). Other issues would include air quality (a sealed building would rapidly trap the smoke from fireplaces, especially since things like hearths with proper chimneys and dampers were uncommon until much later), and even the fire hazard of building with such a large load of combustable material (double the amount of wood with bales of hay in between). Finally, such a building would not last anywhere near as long as a modern one, since the wooden structure is not particularly waterproof, the hay insulation would become wet and ineffective, and eventually rot away. If it was not for the steep initial expense of the building (all that hay alone would be the fodder for several cattle or sheep), this would be a fairly practical way to build low energy cost housing in the Middle Ages. [Answer] Air conditioning: This one is very labor intensive to construct. You need a long enough buried tunnel and a means of moving air through it. Buried pipes work well but would be very hard to construct with the technology of the era. Tunnels carved through the ground and protected with arched brickwork are more labor intensive but less technological. (Note that there are examples of such tunnels being carved for reasons of bringing in water, thus they certainly can be done.) In a perfect situation there's a nearby mountain that can be used, dig a deep enough trench up the side of the mountain, build your tunnel in it and then fill it in. This will set up a natural air flow and not need any pumping mechanism, otherwise you'll need servants or perhaps draft animals to move the air. I doubt the king will want to live next to high enough terrain to do this, though. The key here is that deep enough underground (and that doesn't need to be all that deep) the temperature is basically constant year-round--it will be the average surface temperature. There are almost no climates in which this temperature is warmer than you would like your castle to be. You need to make the tunnel long enough that the surrounding ground has enough thermal mass to average out the temperature over the year. (And note the flip side of this--it also provides heating. Unfortunately you can't set up a system where one tunnel provides both passive heat and passive cooling, either you use two tunnels or you use forced air for one of the two modes.) Think of the benefits to the King--not just the comfort but what will his enemies think when their diplomats pay a visit and find at least the throne room cool when it's unpleasantly hot outside. [Answer] Heated water piping through the floors would be my first thought. The water pipes could be heated using solar energy on the roof as well as lining the chimney with valves to direct the flow. A lot could be done with maximizing insulation as well and with the placement and management of windows. [Answer] Franklin Stoves, or sealed box cast iron stoves would be the easiest ways to get started. Food tastes better without cinders and ash :) You could follow that up with Rocket Stoves. All are well within the ability of Medieval Blacksmiths to create. Pegs or pins to hold it together and clay to seal it up. The seals don't have to be perfect, and no need for threading. They could use existing chimney structures. build on those techniques to build boilers for hot water. If you can master a sealed, watertight system, you could have the makings of a solar powered water heating system for both passive heating and hot water on demand. To work within the existing castle, sacks of wool affixed to the wall and hidden by tapestry could make decent room insulation without too much renovation. For new construction: Earthbags! Grain sacking for fabric maybe treated with tree sap. Lay the earth filled sacks out in courses like bricks and then coat the wall with stucco like mortar. It yields a thermally efficient and amazingly strong and fireproof structure. Use Catalan vaulting for roofs and such. Very strong and relatively low cost and material. The earthbag and Catalan vault aren't difficult, just labor intensive. I yield to the other answers on water management, which is very important. ]
[Question] [ Sure, land is expensive here in downtown Metropolis, but lots of cheap land to build on even a few dozen miles out, never mind in the backwoods, or in flyover agricultural lands that rich, self-important and sophisticated people like me scoff at. Then you have deserts, taigas, the arctic, shallow seas... even cheaper land there. I hear they have free air and nice 1g gravity and stuff there too. Moreover, all our construction firms, materials and construction staff are here, on the planet. I am told we live in something called a deep gravitational well, so moving the aforementioned materials and crews off-world is going to be more expensive than driving them 50 miles on the interstate. I've heard of solar arrays for power and space mining for mineral as entry points into a space economy. Leaving aside the somewhat dubious economics/physics, those intuitively sound more like the equivalent of oil rigs in the North Sea: nasty industrial places where you go for 6 months for a lot of dinero, and then come back to shore and spend it all on booze and whatnot. Not a place you'd settle anytime. So, how does it ever make any economic sense to build & eat the costs of operating space habitats and for 1,000,000+ people to choose to live in them? [Answer] ## A FEW THOUGHTS: I can think of a few reasons people would want to move into space if they had the resources to do it. * ESCAPING THE RIFF-RAFF: Rich folks who want to lord it over mere normal people can't get more OVER than moving to space. No one is going to sneak up on your house to rob you when the world can watch the thief sneak up on you. Rioting underlings can't ever overthrow you if your habitat is it's own independent country. This combines neatly with the "getting away from crappy Earth" scenario, so even if the little folks are dying of cancer at 50, you are in a perfect, climate-controlled paradise. Not to mention that the little people will simply be incapable of becoming your neighbors - they can't afford it, and in space, you can be neighborly with someone a hundred kilometers away (about how close you uber-rich want to be to the lesser folks). * INDEPENDENT COUNTRIES: If you are a group of people fed up with how things are on Earth, the folks that already own everything and the governments claiming everything aren't going to let you set up your Tamil state/Mormon fundamentalist state/White purity state/whatever. The clear solution is that if you can get the funds, MAKE your own country in orbit. Unconstrained by the petty morality of grounder nations, you can make your own social experiment in orbit free from prying authorities/eyes. * READY TO COLONIZE: The first step to colonizing other planets is to get your colonists up in space. There, you can build ships to take you to other planets or eventually even other star systems (fingers crossed). The habitats could even be built in such a way that they can be the solar-system equivalent of generation ships. If you have a self-sustaining habitat with a thousand people on it, are you that concerned if it takes you three years to get to Mars? Once you're there, you have a habitat in orbit for breeding colonists, having pre-built industry to make the things you want a lot closer than Earth, and a place to retreat to when things go all crappy and half your colonists die of something unexpected. * TECHNOLOGICAL ADVANCES IN ZERO-G: People have been hoping that they could find new and exotic things they can make in space that they can't make on Earth. So in ten years when they discover the newest computer chip can only be made in zero-G, the people who make that discovery are probably already there. Entrepreneurs will build in space and do research in space looking for new opportunities. Sure, mining by itself isn't enough. Research isn't enough. Manufacturing isn't enough. Maybe tourism isn't enough. But put all those things together, and that's starting to sound like a city. Maybe even a society. * A GENERATION OF KIDS GROW UP IN SPACE AND HAVE KIDS OF THEIR OWN: Once you have people who are living in space, even in small numbers, you have a culture and society that grow up. Then you have kids born in that culture, and to them space is the reasonable place to be - it's home. If you can make more homes and more "land," then people are people, and they'll have more kids and more kids until you have as many or more people in space as on Earth. After all, there is no shortage of room... * PENAL COLONIES (to the extreme): What do you do when people don't want to live in space but the cost has come down enough to make it economical? Prisons are actually really expensive to run, so for a little more, you can get rid of those folks for good! Botany Bay station is full of criminals or genetically undesirable folks who are politically difficult to just KILL, but that you don't want to deal with any more. Last year's genetically engineered super-soldiers are this year's awkward, violent and freaky-looking problem, and they are precluded in the arms agreement you signed that ended the war. Set them up in their own habitat where they can't cause anyone else problems. Nothing could go wrong with that plan, right? * SURPRISE REASONS: The newest treatment for aging is developed, but it works MUCH better on people in Zero G. Suddenly, the rich and old want to live in space to keep living. A chef invents a zero-G soufflé that is the most amazing thing anyone has ever eaten, and it has to be made and eaten in zero G (it can't survive reentry). Plant genetics advances and suddenly people can actually GROW new habitats in space that are dirt cheap (pun intended). A way of using the Venusian atmosphere to make cheap carbon nanomaterials is invented, but the round trip is really hard to make affordable, so you set up a permanent large colony in orbit around Venus. [Answer] # Because 'Oil Rigs' are just the beginning Wikipedia's [Asteroid Mining](https://en.m.wikipedia.org/wiki/Asteroid_mining#Purpose) article states that in the next 50 to 60 years, we will run out of phosphorus, antimony, zinc, tin, lead, indium, silver, gold, and copper. A lot of that is available in various asteroids in space, so that's where we'll begin. And sure, asteroid mining will start as a thoroughly unpleasant high-pay job, where you do a tour and then spend six months home before going back up. However, hauling raw materials out of orbit slowly enough to avoid extinction events is expensive. It'd be much cheaper to process the stuff in orbit and haul a smaller amount of more valuable, refined material. This goes on, until your space rigs are dropping cargos of the latest iThing back to Earth. Now, we're not going to be shipping Flat Pack space stations up if we can avoid it, because that's expensive, so instead we'll be sending up the machinery necessary to build up there. Soon, mines, solar collectors, factories and habitats are being build in space using space-based materials. At that point, there's quite a lot of industry up in orbit, and thus quite a lot of workers who all need places to rest and relax. Someone, eventually, will realise they can use that industry thats already up there to refine the materials that are already up there into clubs, pubs, non-spartan housing, and other accoutrements. Eventually, they'll get to a point where paying $100/kg to get to and from Earth ain't worth it for some people. After all, once you're in orbit, you're already halfway to anywhere. [Answer] ## Option 1: It becomes cheaper to build luxury space habitats than luxury apartments in New York City You want it to make economic sense to build space habitats and for people to get in them, so the first option is that it somehow becomes cheaper to build space habitats than expensive apartments in an expensive city. This is notionally possible because completely automated construction projects in space won't have to worry about pesky things like environmental impact, so they MIGHT be able to overcome the costs of construction on earth by building the habitats out of asteroids or some such nonsense. ## Option 2: It becomes objectively better to live in a space habitat We're doing a pretty good job of ruining the Earth. If we keep it up, then a space habitat might look pretty inviting. If we accelerate the process significantly, we could make it dangerous to stay on Earth and then everyone would want to move to a space habitat regardless of the expense. ## Option 3: There is no option 3 That's it. To make economic sense, it has to be cheaper than living on Earth or demand for it has to exceed the cost. There are other reasons than economic reasons why we might put 1 million people in space habitats, but they aren't economic ones. ## Edit: Explanation of Why/How Space Habitats are the Same or Better than living in Cities For starters, we should clear one thing up about space habitats, and that's their size and layout. A long-term space habitat MUST be a rotating ring or cylinder to provide artificial gravity (unless we invent magic artificial gravity). It MUST then rotate slow enough that no one faces adverse effects from the rotation (likely lower than 1 RPM). It is also then highly likely that a second cylinder be attached at close proximity to the first to stabilize the orientation of the cylinder. If such a cylinder rotates at 1 RPM or less, it must have a radius of around 900m [spincalc](http://www.artificial-gravity.com/sw/SpinCalc/). The designs for the O'Neill cylinder assume a length 4 times the diameter, so I'll use that to give these habitats a minimum area of 20 km2 per cylinder. Since it's actually 2 cylinders attached to each other, that's 40 km2. For population density, US metropolitan areas range from 200 persons per km2 (unless you could Anchorage Alaska, which I don't) all the way up to 10,000 persons per km2, and I suspect the population density on these cylinders might vary similarly. Let's pick a lightly populated cylinder with 40,000 people now. How does such a cylinder compare to a city in the real world? 1. In a city of that size, food is imported, so virtually all types of cuisine are available. A cylinder of that size would need to either import its food as well or use some advanced technology to grow food in a way we haven't fully realized. My money's on the technology because they're doing some really fantastic things with lab-grown products these days, but that's not important. What is important is that the food is similar. 2. In a city that size, many people born in the city will never leave that city. People make fun of folks never leaving small towns a lot, but the same is true of cities. A space habitat will be largely the same because leaving the habitat during your lifetime will be prohibitively expensive. 3. A population group that size can support just about any form of entertainment facility you can think of short of major sports arenas. An O'Neill cylinder, additionally, would be built from the ground up with the interests of its residents in mind, and with every facility using state of the art technology. Quality public transportation would be built into the cylinder by default because no one is going to be bringing personal transports into space. All in all I suspect that living in a city your entire life is very much the same as living in a space habitat your entire life, and plenty of people do the former. Heck, with the increasing popularity and advancements in home delivery and VR, I suspect there's a large number of people who will never willingly leave their homes, let alone their home city. [Answer] The way that Virgin Galactic, Musk, and Boeing expect to get people into space. Tourism. All-expense-paid vacations to the usual tourist spots are getting so ho-hum. Over-crowded, ridiculously expensive, and poor quality. "Dear, just EVERYBODY has been to that resort. Let's go somewhere the Jones' have not been. They are getting so boring, they just go on and on about their last vacation. So frightfully pedestrian." If you look at the numbers, 1% of the world population has 99% of the wealth, or whatever trope you want to use. But 1% of the population is 72 million people. That is a lot of potential space tourists. Recall that it usually takes ten service providers (waiters, room cleaners, grounds keepers) to serve just one luxury guest. There is so much money out there in very big bubbles, just looking for some place to be spent on. [Answer] Escaping an apocalypse! The Earth is going to be hit by a giant asteroid. It is so large that it can be seen a hundred years away. Scientists calculate that a concerted effort over those hundred years will allow a maximum of 1 million people to be housed indefinitely in space. When the time comes for evacuation, the world leaders will have the difficult task of deciding who shall leave and who shall die. Part of the plan is to try to reduce the entire world population to this size so that everyone still living can go. Of course it will miraculously turn out that the the descendants of the world leaders are part of that population. The Earth will eventually become liveable again so some preparation must be made for The Return. [Answer] I don’t think that many space habitat projects are going to be constructed for financial gain at least not initially. They will cost a lot and the people who build them will do so mostly for ideological reasons not economic reasons. As is the case with having a baby, babies eat a lot, cr\p a lot, want a lot and are a general money pits with no economic payback. Similarly the Pilgrim Fathers did not travel to America with the intention of making a quick buck. Governments might build habitats because it’s a good place for some science research and they need to provide habitation for the workers (ISS like), they might also build them because the Chinese are building them and they don’t want to be seen to fall behind or miss the boat. Individuals and companies might eventually build habitats to make money via space tourism or industry, but the cost to get to Space needs to come down a lot to incentivize that option on anything other than a very small scale. Individuals and companies might also build habitats for their own ideological reasons. For example SpaceX has a mission statement to the effect that they want to make humanity a multi-planetary species. And that is not just a throw away sound bite as it is with most company statements, that is what SpaceX is all about. The only way that is going to happen is if it’s a lot cheaper to get to orbit and we stop throwing hundreds of millions of dollars worth of precision engineering into the Atlantic Ocean at every launch. And that is why SpaceX are building a totally reusable spacecraft. Large scale human habitats beyond the Earth will take a vast amount of money and time to establish. The human exploration of Mars is probably at least a decade away and a 1000,000 person city on Mars might take very many decades to centuries to complete. But once a certain critical mass of beyond Earth infrastructure has been built it will start to build a momentum of its own. [Answer] Slavery. 1-100 people living off the toil of 999900 people is currently achieved by arcane trade agreements and property laws - this could be handled much more efficiently by going to space, where you would have complete practical freedom (sure, there is space legislation - but what are they gonna do, tow you?). You also have much less hassle with runaways. You'll have to trade with earth, and you'll have a workforce that cannot be used for high-tech endeavors (and selling your slaves out as a call-center is not profitable enough) - so you'll need to go the raw materials way - they mine\ something, which is slingshotted back to earth, who in turn provides you with space-station essentials\\. It will have to be something so essential to earths way of life that it stymies any coordinated effort to stop you, like oil. There is no oil in space, but maybe there is an asteroid with a mineral that forms crystal lattices which can be used as seeds in a blockchain? You'd need to lead earth down a path where the continuation of that blockchain is just that important, and the adoption of alternatives just that bit too much hassle for all involved, then announce your heroic going-to-space in an effort to sustain it. Hey presto! You+1M slaves in orbit\\\* \* You cannot invest in 1g environments, or even exercise yards for your slaves, it would be just too costly - you'll have to make do with them being electroshocked once in a while to retain minimally viable muscle mass, so the mining itself will be done by drones that are remote-operated by them\\\\ \\ Like more slaves. Face it, there will be some attrition, and somebody on earth is always spare \\\* 1M in orbit will take an insane amount of investment, in no way shape or form will that ever be economically viable if they are all in luxury habitation (read: more than coffin-enclosures). Your space palace, on the other hand, will be a negligible overhead on the infrastructure to keep the other 1 000 000 people alive-ish. \\\\ Come to think of it, remote-operating a vehicle does not need all that body mass - there might be cost-cutting in limb-cutting - three fifths should be more than enough remainder [Answer] ## Make it easy to get there. If you have enough space elevators, or cheap powerful spacecraft and rotating skyhooks at least, or physically viable [warp drives](https://arxiv.org/abs/2006.07125), then the weak call of sightseeing, minerals, isolation, pioneering and so forth becomes strong enough to pull people out of the gravity well for a day or a week. Some stay for years. The rest is just ... entropy. More ways to be off the Earth than on it. [Answer] See Stine's "The Third Industrial Revolution", Heppenheimer's "Colonies in Space" Savage's "The Millennium Project" for serious economic handwaving. Historical parallels: Mining towns until recently were a family affair. Lots of old west examples. More recent, Uranium City, SK, Faro, YK Mining town form when the cost of bringing people in and out get to be too much. Resource towns: I know of two communities that exist only to provide staff to run a power dam, plus the staff to support the community. Lumber towns. Research stations. See Antarctic bases. Military bases. --- There is an island in the Canadian Archipelago that has iron ore deposits of the same quality and size as the Minnesota Mesabi range. As of the 1970s it wasn't economical to mine because the best you could hope for was a 6 week shipping season. That may change with global warming. But if the deposit is big enough it's worth creating a ocmmunitiy instead of work camp. Ultimately people do things for economic reasons. New England whalers went to sea for 3-5 years at a time. [Answer] Unless you have an earth killer type threat, getting 1,000,000 people living space in a short time for one big reason is probably never going to happen. So getting them out there is going to happen because of a combination of things over a longer period of time. Things on Earth will already provide you the reasons why: Climate change, food shortages, financial collapse, overpopulation, wars, persecution, lack of opportunity. There's tons of refugees here on Earth already, right? So if there were corporations that were willing to foot the initial bill to take some of them to work in space they might just go. Couldnt be any worse than sitting in an internment camp just waiting to be sent back to the rotten place you tried to leave. Things in space will give you the way how: The first trips could be only a hundred or so people to mine out a spot on the moon or an asteroid. They would build an infrastructure to support themselves and a few hundred more, while simultaneously starting an economy based on what they're mining. Later a few hundred more come. After a few trips you have a few thousand people, living in space, mining the moon, asteroids, mars, or even on the surface of some of the other moons that we wont immediately freeze to death on (with suits or inside vehicles of course). Later, they start making the habitats more nice and inviting. Trees and grass, parks with lakes and playgrounds, entertainment venues. etc. Not just cold mechanical tubes like the first few (those guys had it hard). Hype the places up to be accepting of everyone, regardless. Free training. Free home. Get right to work. Before you know it the whole things pays for itself and it grows exponentially. After a while they wont even need Earth at all anymore. ]
[Question] [ Closed. This question needs to be more [focused](/help/closed-questions). It is not currently accepting answers. --- Want to improve this question? Update the question so it focuses on one problem only by [editing this post](/posts/116342/edit). Closed 5 years ago. [Improve this question](/posts/116342/edit) In this hypothetical scenario, in the present day, astronomers detect an object entering the heliosphere, at a distance of roughly 90AU, from the direction of the Proxima Centauri system. Observations indicate that this is an interstellar alien vehicle, featuring a fairly primitive (well within present-day humanity's capacity to build) Project Orion style nuclear pulse rocket design, with a velocity of roughly 3.5% of the speed of light, and a mass of roughly 1M tonnes- but that it's also unmanned, made largely of solid metal and coated in ablative heat shielding, and heading in on a direct collision course with the Earth. At its speed and its trajectory, the scientists swiftly confirm, to their horror, that this relativistic kinetic kill vehicle (or RKKV for short) is projected to impact the Earth in only ten days' time, and will slam into the ocean in the (randomly chosen, using a random location generator) vicinity of the [Kerguelen Plateau](https://en.wikipedia.org/wiki/Kerguelen_Plateau) with a force equivalent to over 13 Teratonnes of TNT. For reference, that's roughly 1/10th that of the Chicxulub impactor which killed off the dinosaurs, and roughly 2000 times the net yield of the world's entire nuclear arsenal. What, if anything, could be done in such a scenario? What kind of public reaction would there be once word got out about the impending impact? Could humanity have any hope of stopping it, or deflecting it? And if not, how devastating would the immediate and long term effects of such an impact be- could civilization, or indeed humanity as a species, survive such an attack? And if so, how long would it take to recover to the extent where we'd have any chance of mustering any sort of response to retaliate against the alien aggressors who launched it at us? [Answer] Ten days are barely enough to arrange a preliminary meeting between some space agency executives and the politicians to start talking about funding of some projects. And we never attempted stopping something going to impact Earth (except in some movies). On the space side you can basically do nothing... On the Earth side you can probably start storing supplies and prepare for the emergency, which will end in a definitely partial preparation. And of course one can start praying, panicking or hope for a space hitchhiking (if having a towel)... [Answer] We're all doomed anyway, so we may as well try it. ## Massive Nuclear Response. Have everyone at NASA stop what they're doing. Arm every single nuclear weapon in humanity's arsenal. Get the NASA guys to work out the best place to fire the missiles to at least try to nudge this thing off course. That's really the only hope for stopping it, and if that fails, see @L.Dutch's answer. [Answer] *(UPDATE) - while checking out the numbers in the 'Why?' section below, I've begun to think that, just maybe, the damage might not be so extreme as to force us to do, well, anything except prepare for a sizeable tsunami.* --- Ten days is not enough to organize and launch any kind of space mission. It can be tried, but in all likelihood it will fail abysmally. It is not even enough to prepare and launch a missile defense. Aiming lasers into space cannot be done from Earth, and it wouldn't avail much anyway with the available power. The only last-ditch, partial and insufficient defense that I can envision is preparing several high-altitude, hopefully unmanned (probably manned by volunteers) jets, and deploy and launch them so that they are between the Earth and the incoming RKKV (actually HVKKV) projectile. Ignoring most safeties and flying a suicide mission with no regard for fuel or engine endurance, a [MiG-25 or MiG-29 can reach from 30 to 50 kilometers ceiling](http://www.migflug.com/jetflights/mig-29-flight-altitude.html). As an alternative, stratospheric balloons can be sent even higher (and it could be done in addition to the jets), even if they would be much more difficult to aim reliably. However, quantity has a quality all of its own. Once the projectile is in active range of the balloons and/or jets (for the double mission, there are EMP considerations), onboard fusion bombs are simultaneously detonated through a radio command. Even more EMP-hardened (okay, okay. Make it "hastily wrapped in aluminum foil and copper mesh") fusion devices will be deployed on the surface, aboard large barges. The damage to the ecosphere will be negligible anyway against a Chicxulub event, and there is the possibility that the projectile will be fragmented or disrupted enough that the last 30-50 kilometers of air (and the last kilometer or so of water) will be the death of it. After all, the projectile is more or less just as big as the USS Gerald R. Ford, even if it's ten times denser due to it being solid metal. Just as well, I don't see it faring so well against a multiple multimegaton warhead impact. Granted, the timing will be hairy since the projectile covers fifteen kilometers in a single millisecond, but we do have very precise timers, and very fast proximity detectors. The projectile will still impact with the same energy, but if the force is distributed enough, perhaps a catastrophic tsunami is "all" that will happen. We'll lose a good part of South Africa, Madagascar and Western Australia, and I don't want to think about the climate or the effect on the Antarctica ice sheets, and the seismic aftershocks will be a nightmare - I expect several faults to go active all at once. But it might still be better than nothing. # Why? The weakness of the Kinetic Kill Weapon is that its [penetration depth](https://en.wikipedia.org/wiki/Impact_depth) isn't really related to its speed, but mainly to its density and size. At that speed, rock behaves like a liquid and the resistance it offers is purely its inertia. That's why "rods from the Gods" are, actually, rods instead of spheres. If the thing is a kilometer-length rod of depleted uranium, density 19 against about 3 for rock, it will penetrate twenty kilometers of water (or six kilometers of rock) and create a conical explosion that will, in turn, open its way a little deeper and devastate a circular area of the upper crust. If we turn the thing in two half-kilometer fragments, tumbled 30° from the vertical, the impact will penetrate only at most two kilometers of rock. There will be two smaller explosions, but the destructive effect should be more than halved. If we succeed in fragmenting and weakening the impactor to the point that the following tenth of a seconds sees the fragment further explode against the atmosphere, there will be a colossal fireball and more widespread, but less intense destruction. # Another reason While absolutely devastating, the KKV is still going against a planet. So it is unlikely to wreak even a tenth of the havoc of the Chicxulub impactor, because as said above, it hasn't the necessary size, shape, or volume. This begs the question, why did whoever sent the KKV send it at all? Why not send a probe to deflect a suitable asteroid, or at least a fleet of smaller impactors, to spread the very localized overkill into a wider "sufficient kill"? It is still possible that some time before impact, and still out of range of any possible Earth defenses, the KKV will separate into a couple thousand "rods from the Gods" designed to knock a whole emisphere back to the Stone Age; or half of them might slow somewhat, and give their regards to the other emisphere as well. If that is what's going to happen, then that's what it's going to happen - there is no time or resources to do much of anything, and any evacuation of coastal areas will be useless (Kerguelen isn't going to be the sole major impact point). But another possibility is that the KKV is just a delivery vector, and that it is designed to do something more than blast a small section of the crust all the way to high orbit. Whatever it might be, it would just have to be something that's not to be accomplished through simple kinetic energy; there must be another component inside the object. After all, either some guys expended a frightful amount of energy and resources to deliver a blow that in all likelihood won't do very much at all, or they believe it will be enough, which means they know something we don't. Again, whatever more it is the thing is meant to do, it's not at all certain that it won't do it from very much out of range. Still, delivering some megatons of nuclear blast at close range might make the difference between a disastrous but limited impact and something far more ominous. [Answer] Basically a planetary aimed whipple shield? An RKKV would similarily to micrometeorites impacting a space shuttle shatter on impact, creating a shotgun pattern while each individual piece is easier to stop than the entire piece.Having the RKKV pieces burn in the atmosphere still means it delivers its energy to the earth in the end, so that should be avoided. Still, any impact will vaporize a portion of the RKKV and absorb some of its energy. So what you do is check what you have in space. The trajectory of the RKKV is going to be relatively easy to calculate as with that velocity few things will noticeably affect the trajectory. See if anything can intersect the RKKV's trajectory to make it break up and cause less damage as hopefully some parts miss earth or hit the moon. This isnt your only plan. Commercial sattelites are being launched a lot more often these days. Most of the time is spend on the sattelite rather than the rocket (although that too is painstackingly build). Repurpose the rocket for your ends. You might even want to remove mass from the missile, as hitting the RKKV as far away from earth as possible is more important than the amount of mass. Another plan is repurposing ICBM's. Looking at this one: <https://en.m.wikipedia.org/wiki/Dnepr_(rocket)> an ICBM is only capable of reaching space properly with a lot less mass inside, so the likelyhood of firing it with a nuclear head attached is small. Still, this is going to be a lot of mass (211tons, although the fuel is likely most of the weight). Now orchestrate that these missiles are fired in a sequence so that they all arrive at the RKKV simultaneously, or since theres not enough launchpads let them arrive in waves. This increases the chance on a hit with each wave and increases the chance you have as much mass connect to the RKKV as possible to reduce the impact of the pieces. Simultaneously do L.Dutch's plan. Also evacuate people who would be "near" the impact site, Evacuate people near coasts for ineviteable tidalwaves, prepare for foodshortages, look towards options for storing seeds for after the global winter aftermath (depending on how much the pieces stir up the atmosphere or the ground) and towards alternative food solutions (apparently grasshoppers can be bred for tons of food with little resources and space needed). If all else fails, ask Elon Musk to try and catch it with his robotic landing platforms, he could do it! [Answer] NASA, Roscosmos, JAXA, ESA, etc. all confirm the probe is on a collision course with Earth and will impact in 10 days. Scientists and militaries around the world offer ideas (such as those in other answers and comments). Can we send ICBMs? Not enough fuel. Launch a Falcon Heavy? Not in 10 days. Etc. All hope is lost until a junior scientist from NOAA points out that after passing the Sun the probe will nearly go through (Sun-Earth) [LaGrange Point 1](https://en.wikipedia.org/wiki/Lagrangian_point) on the way to Earth. She suggests using the [Deep Space Climate Observatory](https://en.wikipedia.org/wiki/Deep_Space_Climate_Observatory) as a kinetic impactor to deflect the probe while it is still billions of kilometers away. The probe is just barely nudged out of the way and while it misses Earth it impacts the moon and creates a huge visible crater. For years small pieces of the moon create spectacular 'meteor' showers for Earthlings to see. The public story was a meteor impact. But for those in the know a dark shadow looms. We're not alone. The Centaurians are aggressive and they launched more than 120 years ago. They're most likely on the way... ]
[Question] [ I'm creating a species of humanoid creatures that live their entire life in couples. From birth to death, they are bound emotionally, they work together as if they were only one individual but they are actually two, and need each other to survive. For some reason they can't survive if they are more than 20 meters afar from each other, after a few days they die. So how does that work if we exclude the use of magic? Why would they die if they don't stay together? And why would such inconvenient feature evolve? Edit: Since they are bound for life it is more logical that they are siblings [Answer] I doubt it would've evolved in it's current form. I'd say it used to be a pretty useful set-up. Two small organisms working together. But as lived evolved more complex their dependency remained. Maybe they both specialized like how most life on Earth has two types of reproductive cells, male or female. One specializes in nutrition while the other specializes in seeking the other out. Now you could argue this isn't a fair split but that's not my point. Perhaps they share certain bacteria required for their bodies to function. These die after a few days so need to be replaced. When they were still very primitive perhaps each specialized in different types of food. They then swap the broken down elements. An advantage of having another member of your species around is genetic diversity. Sure mating with direct siblings isn't the best for diversity but not unheard off. Having a more diverse sibling might even offset some of the negatives. Still you might want to opt for mating with another pair. Maybe they're solitary and only meet other pairs during their mating season? Humans aren't singular creatures either. We're made up of many different bacteria, without them we become ill or even die. Only in the recent years we've been aware of the importance of healthy gut bacteria. So having some form of a bigger dependency isn't that far fetched. For how it originated I'd look at breaking down food into nutrients or the immune system. [Answer] This sounds like [imprinting](https://en.wikipedia.org/wiki/Imprinting_(psychology)). Usually this happens a critical phase in the life of an organism. This could happen with siblings especially if the imprinting occurred shortly after birth. However, this doesn't prevent imprinting taking place after birth when an individual can be exposed to their bonded partner. This partner could be introduced by the parents of the individual, so they can both be pair bonded (this doesn't necessary need to be a sexual bonding, but it could be). If the bonding is sexual this could involve the two individuals bonded together so once they reach sexual maturity as biological adults they can indulge in reproductive behaviour. Where the two bonded individuals are of the same sex, they will presumably engage in reproductive behaviour with another bonded pair of the opposite sex. The proposed organisms that are bonded pairs are humanoid. This suggests that they will capable of complex behaviour and cognition, however, this wouldn't prevent their species capable of being imprinted. This answer has mentioned that imprinting doesn't need to be exclusively at or immediately after birth. It can be done at other critical phases in the life the humanoids. The bonded pairs can be either of the same sex or the opposite sex. Also, imprinting might vary during the lifespan of the humanoids. For example, siblings might bond together as a group. This could be for their protection or to make their lives easier. Later on as puberty approaches this sibling bond might break down or weaken, then the humanoids might be introduced to members of the opposite sex to imprint on each other to form a bonded pair who will then mate for life. It can be assumed that imprinting of this kind will be produced by evolutionary factors in the environment where the humanoids arose. [Answer] Many creatures in the real world cannot live without a partner creature. Examples such as lichens and mycorrhizae come to mind as well as the gut bacteria and fungi in animals, particularly cows which cannot easily digest food without them. These are all examples of mutual symbiosis, a relationship where both organisms gain. The difference between your scenario and these symbiotic relationships is that both your organisms are the same species making the situation different with its own challenges. Even so, real world symbioses presents a good starting point. Most symbiotic relationships work by giving each organism one of two things: food or shelter. Personally I would go food. Here the reason the individuals die if they leave their partner is because they cannot feed themselves. Where it becomes harder is working out why. In the real world it is because different species have different adaptions. Plants make sugars which fungi eat, fungi brwak down soil for nutrients plants need. Pretty clear case for symbiosis their. When both organisms have the same biology it is harder but not impossible. Most creatures have some form of louse or skin parasite. In these creatures the parasite could contain vital vitamins for the creatures meaning they have to eat them but eating parasites feeding of their own skin is dangerous, the parasites eat waste products and toxins from their blood which they cannot break down. These toxins are slightly different for every individual so eating someone else's parasites is ok. Unfortunately eating a strangers parasites allows disease to spread from person to person so the only safe parasites are those from someone you have been in such close contact to that you have the same diseases and immunities to them. Alternatively, if a pair are always one male and one female then it can be that males and females produce different toxins so males can only eat female parasites and vice versa then have pairs live in isolation so only have one another's parasites available. [Answer] 1) Make them addicted to each other via pheromones. 2) Have one produce vital substance A and the other one substance B. They have to share some kind of body fluid or something in order to survive. 1-2 can in theory be avoided using technology, e.g. pheromones in a bottle. 3) Make them psychologically so weak that they die without contact to each other. Would it evolve? Well, you can never say never, but there are several complications which should be obvious. The same can however be accomplished otherwise. Make the families have an arrangement that before or shortly after birth a bond is made (which could lead to interesting political constructs in your stories) - kind of like arranged marriage. Then when you have decided why they would die, make a ceremony according to that - which would require the species to be somewhat intelligent. Let's go through the suggestions again: 1) Get a high dose from their pheromone glands and expose the other baby to it. This should get them hooked. 2) Same as 1), but here another way is possible: Have the adults cut out a part from the body of the babies that would produce A or B. This of course doesn't make the individuals partners unique, but it would be unlikely to find another fitting combination of 2 specimen - so the pairing is pretty unique. This only works if this is possible with your species, also there should be a lot of options of what part can be removed. Also this wouldn't work if there are billions of those individuals but only if there are relatively few of them. 3) Well, just raise the hell out of them with (religious?) terror and all of that. EDIT: After thinking it through again (see my comment on the initial question), I am more convinced that a cultural rather than a biological path should be taken because of high mortality rates. If you choose option 2) or 3) (or others, one could easily come up with more) and one of the kids dies early - which is super likely historically - the partner could be replaced. For 1), this is somewhat more difficult. Maybe it would work with a specimen from the same family for example or it isn't lethal if the creatures are still young enough. [Answer] There are examples of colonies of unicellular beings acting as a pluricellular one, with each individual being highly specialized. like the [Portuguese man o' war](https://en.wikipedia.org/wiki/Portuguese_man_o%27_war) > > Despite its outward appearance, the Portuguese man o' war is not a jellyfish but a siphonophore, which, unlike jellyfish, is not actually a single multicellular organism, but a colonial organism made up of specialized individual animals called zooids or polyps. These polyps are attached to one another and physiologically integrated to the extent that they are unable to survive independently, and therefore have to work together and function like a so-called individual animal. > > > You may need some tweaking to make it humanoid, but in principle it is possible: for example one could ensure motion, the other methabolic functions (digestion, excretion and so on). [Answer] [Dogs suffer from separation anxiety](https://en.wikipedia.org/wiki/Separation_anxiety_in_dogs). This can lead to some quite seriously damaging behaviour in extreme case. Usually it's distress/howling/causing trouble... but there's cases where dogs have driven themselves to self harm as a result of that anxiety. My dog suffers to quite an extent - she's extremely distressed when we leave her behind. This has lead to her 'breaking out' of the house - getting up on the counter top and pushing the (latched) window open, before climbing out, and trying to dig her way through doors to 'get through'. So whilst we are working on the issue, she doesn't get left alone. Humans have similarly been known to suffer the same - usually we can adapt to it - but [Separation Anxiety Disorder](https://en.wikipedia.org/wiki/Separation_anxiety_disorder) is a recognised thing So I think for your setting - taking this, and amplifying it's seriousness would be sufficient to achieve your goal. Extreme anxiety is seriously debilitating. It's not directly fatal, but suicide and risk taking can be coupled with it, and it can significantly impact health and wellbeing. ]
[Question] [ Closed. This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- Closed 6 years ago. * This question does not appear to be about worldbuilding, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help). * You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49). [Improve this question](/posts/75128/edit) For dialogues occurring in the story the characters would use their respective culture/civilization calendar, but for the one writing the story a way to use a familiar calendar to place an event is needed sometimes. So, I usually use an spreadsheet to place events, later I started to write my own graphical tool to place events in an intuitive timeline. I must say that fantasy calendars for fantasy worlds are far easier to implement that our current calendar. Let's not speak about others calendars like the original Japanese calendar. Everything is fine as long as you don't need to overlay a calendar over another, for example if the stories doesn't need to touch the topic of dates or you can change things to avoid it. Problems start when you actually need to figure out dates in more than one calendar. I have the formula to correctly calculate leap years, but something confuses me about those 10 dropped days when they synced the Julian calendar with the Gregorian calendar. Those 10 days are to sync the two calendars, correct? It doesn't mean that the Gregorian Calendar has a hole of 10 days, correct? But if I were to work only with the Gregorian one, do I need to cut out those 10 days? Or said in another way, does 0001-01-01 in both calendars refers to the same date or one is 10 days before the other? [Answer] Dates between the years AD 201 and AD 299 in both the Julian and the [proleptic Gregorian](https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar) calendars are the same for the same day. Before 201 Julian dates are a little "later" than the proleptic Gregorian dates for the same day; for a random example 14 August 60 AD Julian is the same as 12 August 60 proleptic Gregorian. After 299 Julian dates are "earlier" than the proleptic Gregorian dates for the same day; for a random example, 14 August 333 AD Julian is the same day as 15 August 333 proleptic Gregorian. To your specific interest in days near the start of the common era, The Julian January 3 1CE corresponds to the Gregorian January 1 1CE, according to [this calculator](http://www.stevemorse.org/jcal/julian.html). The issue solved by the Gregorian calendar was that the Julian year was a hair longer than the tropical year (aka solar year - the time it takes for the sun to return to the same position, such as vernal equinox to vernal equinox). Over time, the errors had accumulated such that the Julian calendar date where any given yearly celestial event occurred had drifted by 10 days. In other words, even though the events were supposed to be yearly, the events were occuring at earlier dates every year. This was causing trouble for the Church which tied Easter to the vernal equinox but which had also pegged the equinox to Mar 21. During the era when the Gregorian calendar was developed, the equinox was instead occurring for the Church around Mar 11. By having the Gregorian calendar start at the same time-point as the Julian calendar, but with a leap year algorithm fine tuned to be more in line with the celestial bodies, the Gregorian calendar moved the equinox back to Mar 21 (an ecclesiastically set date from back in the 3rd century, before the drift had become noticeable). Different algorithms were suggested. One suggestion was to remove the leap years for the next 40 years. This would have caused no calendar date jump (no "days lost"), but would have lead to 40 years of special cases written into the algorithm forever. Instead, they chose to rip the bandaid off quickly. They decided to instead declare that they would switch from the Julian calendar to the Gregorian calendar (which both start on the same day but have different leap year algorithms) cold turkey: > > When the new calendar was put in use, the error accumulated in the 13 centuries since the Council of Nicaea was corrected by a deletion of 10 days. The Julian calendar day Thursday, 4 October 1582 was followed by the first day of the Gregorian calendar, Friday, 15 October 1582 (the cycle of weekdays was not affected). > > > So, if you are using the Gregorian calendar, dates before 1582 will continue to follow the same pattern as the rest of the Gregorian calendar. If you think about it as though you are going back in time, the leap years will slowly cause the two calendars to sync until they are perfectly synced between 201 AD to 299 AD. [Answer] Simply put, neither Julian nor Gregorian calendars have holes in their own dates. They have a point in time that is the same date for both. After that, the 2 calendars are in sync for some time, but later start to diverge. For any single day after the divergence, 2 different dates exist, one Julian and one Gregorian. Since only one of the dates is normally used in everyday life, switching between the calendars requires to change the current date non-continuously on the switch day, creating the gap in the numbering. The gap was 10 day initially, but some countries joined lately, and their gap is larger (13 days in Russia, for instance). On the switch, there was never any intent to synchronize the calendars at the switch date. The point was to synchronize the spring equinox to its traditional location on the calendar, stopping its drift accumulated over a millenia. So the gap was expected and allowed. For some time after the switch, people tended to use dates [from both calendars simultaneously](https://en.wikipedia.org/wiki/Gregorian_calendar#Dual_dating) for same days (sometimes called "old style date" and "new style date"). Although the Gregorian dates weren't really used before its establishment, the calendar can be extrapolated back in time; it's called [proleptic calendar](https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar). With this system, most days in history have dual dates, but in practice it only confuses everyone, so it's not normally used. Please note that the divergence between Julian and proleptic Gregorian is not actually at the year 1, so 0001-01-01 dates in the 2 calendars don't match. So the best way to date a day before 1582 would be to just use its Julian date. That's what people actually used then, and that's what was written in any historical document. [Answer] Time is complicated and difficult. Like you said it is best just to hand wave dates if you can. For example you mentioned 1582 as the adoption date but that is [very dependent on your story's setting](https://en.wikipedia.org/wiki/Gregorian_calendar#Adoption). For example France was 1582, but Prussia was 1610, and England was 1752 ([and only had 282 days in 1751 as a consequence](http://nodatime.org/1.3.x/userguide/trivia)). As the English example shows years didn't even turn over at the same time everywhere. If you can't hand wave and have some proficiency programming I suggest you save yourself some hassle and write a simple program to do the conversions for you. If you know Java then the wildly popular [Joda Time library](http://www.joda.org/joda-time/cal_gj.html) is a good fit, and as you can see by the link actually attempts to support this transition. If you prefer .NET then [Noda Time](http://nodatime.org/1.3.x/userguide/calendars) is an attempt to bring similarly improved date/time handling to .NET. This still doesn't make everything perfect though because time is hard, and countries in the past and present are able to adjust things by fiat. One example is the ["New Years Day" isn't uniformly January 1st](https://en.wikipedia.org/wiki/Julian_calendar#New_Year.27s_Day) under the Julian calendar. So my advice is just try to get things reasonably close to what you want in a way that will make sense to your readers. Don't worry too much about getting it wrong because you're almost certainly are going to get some things wrong. If the natives of the age didn't care enough to have a sensible standard then why should you beat yourself up about minor errors? You can even argue that errors are more realistic since it was easy to make these mistakes during this time period. ]
[Question] [ It's easy enough to figure out how a species might evolve a third biological gender in general (e.g. some sort of asexual drones/workers, ala insects). But what I want to build is a system where the species evolved 3 "real" sexual genders, where all three take active part in sexual reproduction. What would be a realistic evolutionary path for such a species (intelligent, but not necessarily humanoid) to develop? I would accept plausible theoretical answers, but would prefer those based on actual evolutionary biology material. Assume that the environment is somewhat Earth-like, but not necessarily exactly Earth; and no "unnatural" selection pressure occurs, such as alien experiments, magic, or panspermia introducing genes for 3 biological genders from another planet. My own assumption is that this is NOT the only species with 3 biological genders on the planet, but that's from my understanding of biology and not some needs of the setting. [Answer] No such reproductive systems have been recorded on Earth. It is postulated that a two-gendered reproductive system provides sufficient advantage in genetic variability of offspring while reducing the disadvantage of having to attract mates. In a two-sexed organism, each must attract one mate, but in a three-sexed organism, one must attract two separate mates - if that is part of their reproductive cycle. However, evolution is not so much "survival of the fittest" as "survival of the adequate". If the tri-gendered organisms had sufficient advantage over asexual or bisexual organisms, then that would become the (or at least a) dominant system of sexuality. A true 3-gendered reproductive system (as opposed to a reproductive system that required a male and a female, but had more than one would require a set of genetic material that could be split into three or more parts. Each of the three genders would be capable of transmitting one or more parts of this multi-part genome, but none would transmit more than N-2 of the parts, in order to keep the requirement for three genders. In the following discussion, I will use the terms 'amale', 'bmale' and 'cmale' to refer to each of the three genders, to distinguish them from our two-gendered 'male' and 'female' We could envision several different models for tri-gendered reproduction. There could be: * External fertilisation - the three genders get together (or just nearby) and release gametes, which fuse to form an embryo. * Single Accumulator Gender: an amale and a bmale are required to provide genetic material to the cmale. * Multiple Accumulator Genders: An amale produces a gamete, which is then fertilised by a bmale, and the resulting intermediate embryo is then passed to and fertilised by a cmale before the embryo matures. All variants of this would require that in essence one gamete fuses with a second type of gamete, which then fuses with a third type - it would be much less practical to require fusion of all three gametes simultaneously. The relative sizes of each gamete could vary considerably, as could the quantity of genetic material in each, possibilities include 1:1:1 (ploidy 3), 2:1:1 (ploidy 4), 2:2:1 (ploidy 5), 3:2:1 or 4:1:1 (ploidy 6), and many others as ploidy (the number of similar copies of the genome the organism possesses) increases. The exact proportion of genetic material provided by each of the three parents would dictate how involved each is likely to be in raising any offspring - if any are involved at all - the more genetic material is contributed, the more involvement is likely. Assessing the likelihood of each of the possible three-gendered reproductive systems, the most likely is probably an external-fertilisation water-based scenario - all genders accumulate in a particular area and release a cloud of single-celled gametes. Since no parental responsibility is required in similar reproductive strategies on earth, there are no mate-selection issues. However, this method of reproduction is typically used by [r-strategists rather than K-strategists](http://en.wikipedia.org/wiki/R/K_selection_theory) which means that a great many 'disposable' offspring are created, and parents play little or no role in offspring survival, and hence sentience is probably less likely. A Single-accumulator strategy means that two genders, amale and bmale, must each attract only one mate, and the cmale must attract two. If the cmale contributes the majority of the genetic material, it is likely that this is a viable option for a K-strategist, with few offspring that are cared for to a great degree by one or more parents. This would be more likely to result in a sentient species, as transmission of ideas from parent to child is more likely. Multiple Accumulator Genders requires that the amale mate with a bmale and then a cmale. The cmale would be most responsible for raising any offspring if that was part of the reproductive strategy, and the amale may be more selective than the bmale, and the cmale most selective of all. Again, the proportions of genetic material from each of the three parents would affect the degree of selectivity and involvement in any effort to nurture the offspring. Again, this is more likely to result in a sentient species. A variant of this scenario is a system where the population alternates between a multicellular multiploid organism (having several copies of a set of genetic material) and multicellular organisms having lower ploidy. An amale may asexually produce (at the same time or temporally separated) bmales, cmales and dmales. A bmale, cmale and a dmale may then fuse, or mate in one of the patterns above, resulting in a new amale. This may be an option for either an r- or a K- strategist organism, and could result in one or more of the four different forms being sentient. [Answer] Monty Wild is incorrect in stating that "No such reproductive systems have been recorded on Earth." In fact, such reproductive systems have been recorded on Earth. The most complex gender arrangements in real life involve [fungi](https://en.wikipedia.org/wiki/Mating_in_fungi). Some fungi are tetrapolar (four gendered) and [there are or have been tripolar fungi](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2568056/). It isn't clear that any tripolar fungi exist naturally today, but tripolar fungi can be and are bred as hybrids. An evolutionary path to tripolar can involve going from bipolar to having the option to reproduce sexually or asexually, to having the ability to hybridize with another similar species with two somewhat different genders (often expressed A, a, B, b), to having to have all four genders to reproduce sexually, to having one parent that has two genders and one that self-reproduced and has one gender. Another similar arrangement is called a [patchwork virus](http://www.cell.com/cell-host-microbe/abstract/S1931-3128(16)30310-9): > > Scientists found a virus that is made out of 4 to 5 separate > components - it infects mosquitos, and they have to catch at least > four of those components to get infected, the smallest, fifth > component is optional. For plants and fungi, similar viruses were > known before, but (at least according to the study) this is the first > example in animals studied in detail. > > > The number of patches in a patchwork virus can vary greatly. You could have a female analog that would correspond to the "host" and might or might not be sentient (Ringworld by Larry Niven, for example, has a species with both a non-sentient gender - perhaps historically a reproductive host of a parasitic species - and a sentient gender), and then the elements of the patchwork virus function as gametes. One can imagine a scenario in which sex involving just two of three genders is purely recreational, while involving all three genders is reproductive. One functional benefit of this would be that reproductive sex would require coordination, cooperation and deliberation. Something similar exists in modern hyenas. In hyenas, both the male and female must have the equivalent of an erection at the same time which makes a rape pregnancy almost impossible in hyenas, unlike almost all other mammals. This gives females much more reproductive choice and they have utilized it to produce a thriving more intelligent and socially coordinated species than any other megafauna carnivore. A tripolar gender system could work in a similar way - insuring reproductive choice. Also, simultaneous tripolar reproduction is much sexier than sequential tripolar reproduction. Another way to get multiple genders is to have gender determined by environmental conditions at the time of conception or gestation which is quite common in many species (including vertebrates). Usually the environmental conditions involve temperature or pH (i.e. acidity), but one could imagine humidity or all manner of other conditions (e.g. pheremones from existing community members reflecting current gender ratios) playing a role in determining gender. There are also [three parent humans in real life](https://www.sciencenews.org/article/three-parent-baby-boy-healthy-so-far), some via intentional genetic manipulation of multiple parent sperm and eggs, and others alluded to by HilWithSmallFields involving a sperm gamate donor and an egg gamate donor whose fertilized egg is implanted in a surrogate mother who contributed the mitochondrial DNA as I understand the process (apologies if I am incorrect, but the three part split is sensible fictionally, even if it doesn't exist in real life). Also, most women who have children in humans are at least partially in some parts of their bodies, chimeras, incorporating some of their children's DNA (and indirectly, their partner's DNA) into themselves. Of course, humans have various non-binary gender options. Most notably, gay men, lesbian women, bisexual individuals, transgender individuals (both homosexual and hetrosexual), and even a very rare group of individuals who cycle through the course of a day or a month from one gender to another (a bit like transgender but unstable). In addition there are people are basically neuter (castrates and people born sexually ambiguous). There is strong anecdotal evidence for femme and butch sub-identities within a lesbian sexual orientation that have a biological basis associated with levels of testosterone exposure in utero, and for the equivalent in gay men, at least some of the time. The Netflix series Hemlock Grove has an edgy scene in which a werewolf, a vampire and a human woman have a menage a tois that illustrates the dynamics of what a trigendered sexual relationship could look like (compare Twilight which has another love triangle of that type). Notably, many versions of the tales allow vampires and werewolves to reproduce both sexually and asexually - an asexual reproduction option seems to be a good foothold into a trigendered system. The Vampire Academy series by Richelle Mead also features a complex gender system involving living vampires, dead vampires, humans and dhampirs. And, the Vampire Diaries series also has some serious gender/species complexities. "Being Human" (a TV series with a British and American version of exactly the same script) doesn't have gender complexity to it, it does have multi-species households that could provide further insight into the social side of the relationships. I have read an interesting science fiction short story in which individuals had sex via a "bridge" which could be transferred from one partner to another during sex changing the gender of the people involved. One could imagine a "bridge" that only activates a seed when a sufficient number of people have contributed to it. [Answer] There are multiple examples of third (pr even fourth or fifth) genders in nature. Mostly the follow about the same pattern. Rather than requiring three or more individuals to reproduce, what's commonly found is the existence of multiple 'male' or 'female' genders within a population. These genders differ physiologically from one another, and often exhibit different breeding strategies. This is best indicated perhaps by the [side blotched lizard.](http://en.wikipedia.org/wiki/Side-blotched_lizard) Within an intelligent society, it may be that multiple genders persist due to an increased phenotypic range that is advantageous to society. For example, if there exists a 'small male' and a 'large male' gender, small males may represent an evolutionarily advantageous way of gathering resources, while the large males are better at defending a settlement. Small and large males would hold distinctly different Y-chromosomes, leading to a differentiation between these two male genders. [Answer] Given the lack of evolutionary evidence to draw from, I would like to draw from a different source: mixology. When making a Martini, there are three fundamental ingredients: Gin/Vodka, Vermouth, and a Garnish. The nature of each of these is essential to the taste of the Martini. Alton Brown has argued that these three ingredients act like a chord. You can have major cords, minor chords, diminished chords, but they always start from one-three-five. I could see a system where three sexes come into play: * A "mother," the Gin/Vodka of the relationship. This is the workhorse who is going to have to carry the child through birth. * A "father," the Vermouth of the relationship. They add genetic material in a way which allows for a mixing of genes which is more rapid than asexual reproduction could have allowed. * A "muse," the garnish. They add genetic material which is selected for a higher rate of mutation. This gender could be responsible for more consciously selectable traits, such as "musclebound." Due to its high rate of variability, this could be an excellent candidate for storing "genetic memory" from generation to generation. Socially, the mother and father could be tighter, with the muse being brought in to facilitate the creation of their "perfect child." Evolutionarily it is reasonable. The purpose of sexual reproduction is believed to be the ability to increase adaptability by improving genetic mixing. It seems reasonable that a third gender could offer similar mixing on a much more rapid timescale. [Answer] Nice [link about ants](http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.0020183) which @ckersch found. Different strains of ant males and queens exist, and different caste of ant will be produced after mating, depending on strain. But each individual still seems to have one or two parents - one (unfertilized egg) to grow males or two (fertilized egg) to grow queens (same strain male) or workers (other strain male). Good read. But still, if it is evolutionary advantageous to have sexual reproduction (to get different set of genes from your own, which may give your offsprings advantage), it is not obvious why having more two sexual partners necessary to reproduce will be more beneficial than just one (or none). So plausible solutions seems to be insectoid society with biologically separate castes, resulting from mating with different strains of males. If you create more castes, you may have more strains and combinations for mating. To keep it plausible, each individual has max 2 parents. [Answer] One environmental setup that may have caused 3 genders would be an environment which: 1. Has VERY little environmental mutagens in a specific location Low radiation, including solar; low rate of chemically-induced mutations as well 2. High-mutagen environments on the borders between locales. #1+#2 means that individuals living far away from each other are very genetically diverse (because their ancestors crossed high-mutagen lines, AND their environments are somewhat different), while those living near each other are very genetically close. This introduces a strong pressure to introduce "far-away" genetic material into procreation if you want high genetic diversity 3. Environment can change fast and unpredictably, meaning high genetic diversity is required to survive. Meaning that this "far-away" genetic material is a requirement need is a vital requirement, not a nice-to-have. 4. High predation from tough predators, which means that at least one gender must evolve to be a strong fighter with good armor. This cannot be the child-bearing gender, because the biological cost of fighting/defending predators is too high if combined with biological cost of nurturing an offspring for the same individual (takes a LOT of biological energy to grow muscle and armor; and to train). Unfortunately, the same energy cost for a fighter means fighters aren't very mobile - that would require small/light body and preferably flight, which armor and fighting muscle heavily inhibits - see #5. 5. High biological cost of geographical movement For example, small cells that can be used for foraging, separated by high walls (mountains/crater walls). As noted in #2, the highlands on tops of those walls are pretty much the only place where your genes are mutated. Let's make up some numbers: * An adult organism needs X energy to survive WITHOUT moving. * Birthing/raising childred needs X energy as well * Traveling far/well enough to gather 5\X energy requires additional 2\X energy for short term travel + Meaning, a "defender" sex energy budget is balanced (gather 5\X food, spend 2\X on travel, X on self-survival, 2\X on giving to birther-sex partner for survival/children). However, traveling far/well enough to move from location cell to location cell requires additional 2\X energy. + Meaning, to travel very far, your energy budget is only balanced if you don't share energy with anyone - you gather 5\X, spend X on survival, 2\X on moving within a cell to feed, and 2\X on moving to the next cell by scaling the wall. Based on #4 and #5, an average species's member can only forage enough energy to EITHER travel, OR reproduce/nurture offspring, OR gather food and defend the family from predation. But not 2 out of 3, never mind all 3. In this situation, we have a conundrum: * To reproduce, you require at least 2 species, a birther/nurturer (equivalent of 2-sex female), and a provider/defender (equivalent of a 2-sex male). * BUT, with just those 2 sexes, the species stagnates and dies out, because NEITHER of those 2 sexes is adapted to traveling far, at all. * Ergo, the selection pressure favors an adaptation resulting in a Third sex, which is evolved specifically to travel far and wide (adapted to travel at this terrain, light, fast {possibly a flyer}, high endurance, able to withstand more variation in local conditions, and not good for anything except moving far and delivering genetic material there (because its unique adaptations make it poor defender, and poor birther). Basically, third sex acts as long-range sperm/seed, to put it crudely. [Answer] One possibility that isn't that different from what we now have would be to split the present female double role, of providing nuclear genetic material and providing the mitochondrial genetic material, into two, so the nucleus of the cell that becomes the new individual is produced from a large gamete (egg-like, but with negligible cytoplasm and no mitochondria) and a small gamete (sperm) that pushes into it. The resulting fused nucleus would then need to be implanted into a cell produced by a third sex, that provides the mitochondria and the bulk of the cytoplasm. The nearest to this that I can think of in existing organisms is the reproduction of lichen (symbiotic systems of fungi and algae) where the fungi reproduce sexually and the newly produced fungus has to connect to some of the energy-providing algae. ]
[Question] [ Two Earth-like planets collide at a (relatively slow) speed of about 1,000 kph. For all questions regarding the size and composition of these planets, just think about Earth - and these two planets are moving towards each other at the same speed. 1) First, they would begin to rip each other apart due to roche limits. 2) Then the two planets (what remained of them, that hadnt been ripped apart) would connect with each other. 3) Eventually, they would merge together and form one larger planet. My question is, roughly what kind of time span would there be between stages 2 and 3? Stage 2 being the planets connecting with each other, and Stage 3 being one single spherical planet. So I want to know roughly how quickly gravity would act upon these two planets whilst it is forming them into one (mostly) spherical planet. Are we talking hours/days or are we talking years/centuries? [Answer] # We're talking hours to days. A good deal of work has been done on protoplanet-protoplanet collisions, mainly focused on testing the Giant Impact Hypothesis for the formation of the Moon. A number of fluid simulations (many smoothed-particle hydrodynamics) have been performed, for varying angles of attack and initial relative velocities (see e.g. [Canup 2012](https://science.sciencemag.org/content/338/6110/1052), [Eiland et al. 2013](https://arxiv.org/ftp/arxiv/papers/1307/1307.7062.pdf)). The takeaway from those simulations is that the planets initially coalesce within half a day to a day. However, the resulting body isn't round; it's somewhat elliptical, even a bit pointy at the ends. Some models have tails of matter (typically one or two) attached at the ends, which, though tenuous, may form another body, i.e. the Moon. By the end of about 24 hours, there is a clear central body surrounded by this excess material, but it may take up to a month for it to regain its spherical shape - a key characteristic of a planet. Other things to consider: * It may take time for the interior of the planet to become differentiated, i.e. for it to take on a traditional planet-like structure. Even after coalescence, the cores may still be separated. * Glancing, indirect collisions tend to produce more ellipsoidal shapes than direct collisions, even if there's a merger. * There will still be debris orbiting for quite some time after the merger - again, perhaps weeks or months. * The final body will remain quite hot for some time, with surface temperatures of perhaps up to 6000 K in the day or so immediately following the collision. [Answer] Please check out this [link](https://en.wikipedia.org/wiki/Giant-impact_hypothesis) in case you find it interesting. It's about how the moon formed from a similar impact. In the link above, it is assumed that there was an explosive collision (moderate at celestial standards) between Earth and Theia at an oblique angle. Despite such a collision, it is thought that it took surprisingly little time to form the moon, whereas it took around 0.1 billion years for Earth to form. A corresponding collision between your two planets would likely take longer, as the creation of the Earth itself (normally) took hundreds of millions of years. A point about Roche limits: Roche limit takes effect 2.5 radii away from the larger planet. If these planets are equal in mass, they would merge into a central mass between them. This would basically be the same as forming a brand new planet from scratch. Edit: I forgot to give you an actual answer - sorry lol. With little-to-no actual science to back this up (we don't know much about the formation of planets) I'm going to say between 0.5-1 billion Earth years IF both planets completely shatter into debris and then coalesce to form another planet. If they merge perfectly the way you described, could take 100,000 years, as the commenters suggested. That's assuming that these two planets don't just turn into an asteroid belt or something, and that nothing else gets in the way. I'm also not accounting for bombardment of debris from the collision of these two planets, or the possibility of smaller moons forming. I'd also like to point out that the probability of 2 celestial objects 'only' crashing into each other at 1000 km/h wouldn't be much of a collision. Is this being done deliberately? If not, incredible luck. Helpful links: <https://en.wikipedia.org/wiki/History_of_Earth#Solar_System_formation> <http://abyss.uoregon.edu/~js/glossary/roche_limit.html> ]
[Question] [ My story premise is that a human expedition to Europa has happened and the travellers have tunnelled through the ice and formed a colony in the ocean. When they breached into the ocean, they discovered that the underside of the ice was covered by glowing organisms that - through further research, turned out to be using some form of fibre optic tubes to the surface to gather light and other energies from Jupiter and the sun. This energy is enough to cause the organisms to glow a variety of colors which - given the sheer abundance of them - produces a moderate quantity of light, something which is then used by other native biology. The evolution of these organisms can be tracked back to similar glowing organisms that live near hydrothermal vents, explaining how life first arose and that light is a factor in the evolution of Europan life. While I understand that the energies captured through such a process probably wouldn't be enough for the organism to re-emit light (and that emitting light probably isn't in the best interests for these organisms), my main issue is working out how exactly these organisms created these optical tunnels. Could ice be modified in such a way through chemical and/or physical processes to collect and direct light towards the organisms? How would the organisms act on the ice over long distances? Could the ice be modified in such a way that it filters the incoming light to only let UV and longer wavelengths through, while blocking X-Ray and gamma radiation? I'm assuming that the Europan ocean contains many of the same elements found on Earth and that the organisms can generate complex compounds from these. The organisms could also potentially move or grow in ways that (probably) aren't found on Earth, and may even be able to bud off sub-organisms to do their work. [Answer] First issue with natural ice is that it is hardly transparent, because it contains microscopic bubbles of entrapped gas which give it it's white appearance. But this can be overcome by having dedicated enzymes which remove gas from water and solidify it into clear ice. The second and main problem is that ice has a lower refractive index (1.31) with respect to water (1.33) which means it is impossible to have total internal reflection in a icy fiber, therefore it would not work at all. For the sake of your story it is better if your beings produce fibers of Titanium Dioxide (refractive index 2.5 or 2.7) or a likewise transparent and high refractive index material. Silicon Dioxide (1.4 to 1.6) would be too close to water to give a performing fiber. [Answer] I'm sure you mean Hydrothermal vents. There is no fundamental reason a bacteria can't produce some sort of fibre to make a cable or string, by way of perhaps cellulose. You wouldn't need to modify the ice to stop radiation, water does that pretty well, see this stackexchange post: <https://space.stackexchange.com/questions/1336/what-thickness-depth-of-water-would-be-required-to-provide-radiation-shielding-i> However, is there any reason the microorganisms need to be photosynthetic?(Consume light for energy), they could be chemosynthetic just as easily, and still produce light. Another option would be something similar to fungus, that could create tendrils that capture light, which permemeates the ice. If you must have photosynthetic bacteria underneath the ice, for a plot point perhaps, I'm sure they could create some variant crystal structure of ice that does refraction guiding. However, couldn't they just create the 'cables' by melting their way to the surface, and coating the walls with biomass, to keep it warm-ish? Refraction guiding works with liquids too! [Answer] Um.. Physics textbooks and the CRC handbook might show it eventually, but ice is not a particularly good material for optical fiber. Firstly it is too brittle. Polycrystalline (snow-like) and bubble containing ice has too many scattering boundaries for any sort of light to go more than a few tens of cm. Go and have a look at the [blue ice](https://en.wikipedia.org/wiki/Blue_ice_(glacial)) under a glacier sometime. That is a nicer material for optical transmission, and the field trip might give you ideas. The way that a glass optical fiber works requires a % or so of refractive index change between two very transparent materials such as two recipes of glass. The glass types are both so near to perfectly clear that fiber attenuation is measured per km and best case for smf28e at 1550 nm is 0.2 dB/km. I think that for a five meter path, you might get away with ice being clear enough to be the cladding of your optical waveguide, but you need something slightly denser and also perfectly clear before you can guide light. [Answer] The exact details of material engineering were covered by other answers but I find two problems with the such organisms. First of all this is not a stable configuration - if a gene mutation arise which makes bacteria not produce the fiber it can spent all of it resources for reproduction. Since it competes for same resources as other bacteria (light, food etc.) it will out-compete them and take all for itself. Of course at this point there will be no light and unless other mutation arises it will die out. However "genes have no foresight" so while humans can play iterative [prisoner dilemma](https://en.wikipedia.org/wiki/Prisoner%27s_dilemma) bacteria play [ESS game](https://en.wikipedia.org/wiki/Evolutionarily_stable_strategy). Bacteria live in Hobbsian world where cooperation is only in name of short term self-interest. The only way out I can see is if the bacteria were sterile workers working for the survival of reproductive hive - but that would be more of an multi-cellular organism then single-cells. Second is how would such nanotubes evolve. Many of marvels of evolutionary 'design' is iterative with each iteration slightly improving over previous one. The record of such mutations can be seen and organisms behave in way that makes no sense unless we consider history (and that the evolutionary pressure was too weak to affect it). While an engineer might spent a lot of time an energy with foresight of needing a long tube bacteria need some immediate benefits of forming nanotubes. I'm not sure how 'half-nanotube' would look like and what benefits it would have - in other words why nanopods would become longer and longer and why transmitting light would be evolutionary beneficial. [Answer] Structures: I'd vote for the microbes creating the cables from protein or other cellular components. There are structures called nanopods made by some bacteria, which are remarkably long. Check it out. There are also bacterial nanowires, look into that too. We now believe bacteria can transfer individual electrons with these structures, which changes how we think about their metabolic potential. Energy: Hydrothermal vents support life because of reduced compounds (H2S) which provide energy, and thermal gradients (I think) which can also drive reactions (I think.) they are intriguing because they do not have light to drive biology (except bioluminescence.) there are certainly ideas out there of reduced compounds on these planets, like the methane on Titan. The volcanic feature on Enceladus def. shows possibility of thermal energy within body. There may be some similar knowledge about such features on Europa. Carbon: Hydrothermal vent microbes derive carbon from CO2 (via chemosynthesis driven by H2S) but also from 'marine snow,' which is derived from photosynthesis. I'd recommend incorporating these sorts of ideas over ice cables. Maybe work with a thermal gradient set up by the ice (cold) and their metabolism (warm.) The thermodynamics are probably wrong here, but it is worth some thought. Also, consider using 'space snow' - just an idea - of organic matter 'falling' to europa, possibly from Jupiter. Maybe that red spot is throwing useful compounds out, and europa is able to capture them. Or from meteorites... ]
[Question] [ A certain evil genius wishes to create his own army of super-killers to wreak havoc. He has a base in the jungle, and wishes to make a super-predator that will defend him (not to replace the predator at the top of the food chain). What should be the characteristics of an animal that is the ultimate predator? Characteristics would be the physical description: How big is it, does it have claws, what poison can it use (if it uses a poison). The evil scientist wishes to create the ultimate predator (for animals, not humans). I know humans are the ultimate predators, but I wish for a animal (not a human). * The evil scientist has created this animal to defend him in the jungle. Assume that humans will never find his base. This creature should be effective in harming/killing other creatures even if it means forfeiting its own life. * It is engineered only to kill, it does not have to thrive in a particular environment. It job is to harm other animals. It hunts every animal except humans. * While an animal may be adapted to hunting one type of animal and bad at hunting another, this creature does not have to hunt everything, it should just be dangerous. * It hunts in the jungle area, and in isolation (not in packs). * I want animals, not some super-bacteria! It should not be smaller than a cat at the very least, and not bigger than a buffalo. Note: It should be realistic (that is, it can't have poison that kills anything instantly, but you can bend the rules a little, like acidic blood) and it should be dangerous, I am not looking for a replacement in the food chain or anything. [Answer] The predator you're looking for is going to greatly resemble a tiger. Tigers are already the kings of the jungle, and with a few improvements they could become even deadlier. For one thing, you could enhance their hearing, smell, and eyesight to phenomenal levels. That is a surefire way of making them a force to be reckoned with. Of course sharp senses are useless unless the creature is intelligent enough to put them to good use. Enhance your creation's cunning ever so slightly and watch it become exponentially more dangerous than your average jungle cat as it ambushes hunters, and other, bigger creatures. However, tigers, while dangerous, are not showstoppers. Why is that? Well, for one thing, like most large predators, they spend a lot of their time resting. Make that less of a requirement for your pet monster. Perhaps make it a little blood-thirsty as well - killing for fun rather than food is a good way to ensure that true havok will ensue. Last but not least, you can enhance this creature's deadliness with a venom of some sort, and enhance it's survivability by not only allowing it to quickly heal wounds (basically a requirement for any solitary predator facing a lot of competition or enemies), or even sport armored scales, or spikes on its tough hide. [Answer] Wasps with neurotoxin. They attack in small groups of 5-6, every time you're stung you receive a small dose of paralytic neurotoxin, the wasps also mark you with pheromones so they can track you if you run away. Once the paralysis takes effect (they'll sting you several more times to be sure) they'll make a pheromone trail back to the hive (the corpse of their last victim) and then the hive swarms to your location. Hopefully you've suffocated before they start burrowing, eating and laying eggs. [Answer] 1. Fast - Raw speed is useful to outrun enemies 2. Agile - Ability to maneuver and change course 3. Use of its environment - This can be camouflage, ability to climb in a forest, ability to swim in a river, etc. Depends on the environment of the creature. 4. Endurance - It needs to outlast what it can't outrun 5. Tracking - It needs to be able to find and hunt down its targets. Specifically smell and hearing 6. Senses - It needs to be adept at detecting motion. Heat vision might be a big advantage, but might also be too exotic for your tastes. Hearing can also be a big boon. Arctic foxes (for example) can use hearing to hear mice through several feet of snow. 7. Ability to maul - Teeth and claws. Ideal if it also has strong muscles in its neck allowing it to snap the neck of a creature it grabs hold of the head of (similar to what wolves do for small prey). 8. Ability to hang on - For larger creatures it'd be useful if its claws allowed it to hold on for a longer fight. 9. Intelligence - Look into crows. Yes, they're not predators, but they're surprisingly intelligent, while still being very much creatures. 10. Poison/Venom resistant - If any of its main prey is poisonous or has venom the creature should resist these things. 11. Venom - Might not hurt to have venom of its own, especially something that very quickly paralyzes targets, allowing the animal to kill. Look into scorpions. As for size, I'd suggest that of our own beast-like incredible predators, the Siberian (Amur) tiger. In fact likely the Siberian tiger is a good starting point for all of its traits, and work in your improvements from there. Note the tail used for balance, the body built for speed, agility, and raw power, having both teeth and claws, etc. [Answer] # Some kind of hornet is your best bet. Because a hive is not a single mass, it's very difficult even for a large animal (lion, elephant) to kill. By having a hive, you can have an entire area watched all at once (instead of a single animal prowling around). By having a hive, you can defend against multiple enemies (lets say an army of ants, a couple of jaguars, and some angry birds all attacking at once). Flying—can defend against flying enemies. Poison is strong against big animals. The hornets' own size, number, and ferocity makes them also strong against other insects/spiders, etc. The only reason hornets aren't currently used for defense is getting them to attack your enemies and not you. But these babies are engineered, so either your scientist himself can be the hive mind hub, giving either general feelings or even exact commands, or they can be made with instincts of protecting Dr. CrayCray as if he were the hive/queen. ## But this breaks the rules! Size—If you really want something bigger than a cat, you could upsize the hornets, but that would be less effective than keeping them small and difficult to target. Number—You wanted a lone animal, well I'd consider the hive moving as a single unit. You also mention the animal might be dying in its attempts to protect the scientist. In this case, you definitely want a hive. A single animal that dies will no longer provide any protection. A moment of silence for Dr. CrayCray. ## Fun add-ons These guys are already great. But if you like over-the-top, nope-nope, honey-get-back-in-the-car action: Poison/acid blood—As you mentioned. This would be cool, because an animal might try to kill some of the hornets by biting/eating them. Then half their mouth falls off, or swells up, or something. Explosive acid blood—Similar to the above, but when the hornet feels threatened, it self-destructs in a small cloud of acid, likely blinding and really hurting the attacker. Scyther blade-arms—They already have a super stinger, and a pretty scary mouth. Now lets make their arms little razor blades for maximum ouchy. Protective orbit—This one's just to look cool. When they sense danger, about half the hive start to orbit around the scientist, like a little atom cloud. When he walks around, the orbiting hornets move with him. Makes for great cinema. [Answer] I would suggest dogs. Granted, they're pack animals - but there's a reason to disregard that rule at least a little. Your mad scientist wants the animal to defend him - and as the primary rule, I would think it has precedence over other rules. There are very few critters we can trust to do this! Solitary hunters will not only probably not defend someone, he's likely to be breakfast unless he can defend himself against the critter - always, at all times, and in all situations... and any weakness he can reliably exploit, will weaken the animal down from super-predator. A couple other answers mention tigers, this would be the reason to say no to them. So dogs, long domesticated and quite easy to work with, would be a viable possibility. The scientist could choose between breeds for the best fit for his location (terrain and temperature), and likely predators, and further modify the creatures if needed (perhaps venom?) - if the pack can face or fight any creature, than something like venom would make sure it doesn't survive easily. Even without venom, they might be able to fight and scare off many animals by claiming territory. Otherwise, perhaps domestic cats might form the basis for a possible solution, if the requirement against pack animals is set in stone. Again, while many larger cats are fierce predators which would need little modification - they are solitary, can't really be trained (not like dogs, anyway) and would turn on your scientist at their convenience. Lions are one possible exception to the antisocial status of larger cats - but as pride animals, they're right back to breaking the solitary rule. The tamable heritage of domestic cats would probably outweigh their smaller size - and perhaps they can't be trained, but they can be taught. Your scientist might try increasing their size (midsize will let it hunt large prey, but any larger and it might threaten your scientist), or adding venom - or indeed poison, since their opponent is then still dead if it preys on them. Having venom will help the cat take out not only its own prey, but will injure or kill any animal it fights in self-defense as long as it can achieve one good bite. If the cats are properly socialized and well treated, they may face off against animals many times their size (big dogs, possibly even a bear) to protect their "own" - including their human, their claimed territory, or their fellows. They may coexist as a group in the base (make sure your scientist claims the position of boss cat, to minimize infighting) or possibly when facing off larger threats (like said tigers), yet will still hunt alone. Also, cats do not kill only to eat - they will often kill more than they need, for sport or to 'offer' their people. That kind of prey drive will certainly help keep them fighting and killing different kinds of animals near the base. (note: I recommend adding venom to an already formidable creature rather than using one already venomous for the same reason I discourage tigers - most won't defend, and are a risk to, your mad scientist. Most animals go either/or for venom or fighting, because either form of being dangerous is expensive... but if you're engineering an animal anyway might as well stack advantages. So, when adding venom - first, your animal should be immune to its own venom, or it will not be useful. And your mad scientist should both build up a resistance/immunity and have an antivenom. Also, venom doesn't guarantee a kill - some percentage of bites will be dry, it takes time for the venom to work, it takes time to renew the venom, and some animals will be able to resist based on compatibility or body size. What it will do is increase your creature's success, since other animals who get dosed will be weakened by the venom (and the bite), leaving it vulnerable to your creature's other weapons (claws and fangs) with the added bonus of leaving an animal that survived and escaped weakened and vulnerable to death by other causes. Extra note, make the poison fangs the same or smaller than other teeth, the better to not break off. As a secondary weapon, it's not a problem if it doesn't activate except during a solid bite) [Answer] You need an animal with great control of electromagnetic waves, shape doesn't matter much ... All you need is an organ for this feature. With magnetic waves your ultimate predator will be able to do various things I will list them from the cheapest in energy cost to the most powerful and hard to obtain abilities : * Shoot bullet waves with potential to perforate flesh and bone * Electrocute foes with potential to kill or paralyze * Deaf/blind foes * Become invisible to single foes, cause them to see everything but you * Cause foes to fall asleep * Destroy internal organs of other animals, cause them to explode from the inside All those abilities can be used at range, the distance depends on the power and type of electromagnetic organ,but you could technically obtain enough organs for all the abilities above if you want. [Answer] ## Giant venomous tiger pitbull Start with a dog. Why a dog in particular? Remember, we want a companion animal. Not only does it need to be loyal enough to not turn on its master, it has to have enough endurance to keep up while traveling. While big cats are great predators, they are not as reliable as dogs and they tend to sleep a lot. It's probably a lot easier to pack extra physical capabilities onto Man's Best Friend than to try and breed new complex social behaviors into a tiger or bear, let alone an insect. From there, you'll want to pack on extra traits to make them better fighters. Size is obvious, there are already dog breeds the size of horses out there. Breed them for aggression, good hearing (to notice when an enemy is sneaking up on you), and maybe giving them locking or crushing jaws for good measure. Basically a giant pit bull. Depending on how flexible your genetic engineering capabilities are, adding retractable, cat-like claws would be great. This would allow it to use multiple weapons at once, increasing its versatility in combat. It can now slash and dodge as well as it can bite and hold on. Plus, it can now climb trees! For the really big creatures (hippos and elephants are dangerous!), you'll want some kind of venom. Slowing down and disorienting the target quickly is more important than killing it quickly, to neutralize the threat before it can harm you, so a potent neurotoxin is probably your best bet. Pack it with the same stuff they put in elephant tranquilizer darts. Flight isn't important (no idea how you'd give a creature like this flight anyway) since no flying animal is a serious threat to humans anyway. [Answer] Any predator with the ability to interfere with brainwaves. Thus conflicting targets that there is not a threat until the last moment. This ability renders all self-defence instincts useless. [Answer] This may well break your 'not human' rule in spirit if not in fact but have you considered the grate Apes as a starting point? A gorilla is already quite formidable and social enough to have a believable desire to protect the scientist. They have hands and therefore the ability to use tools plus a reasonable size brain to allow for basic problem solving when confronted by an unusual situation. They can also operate in different terrain types apart from perhaps large bodies of water. You have the potential for them to co-operate with others of their kind to overcome anything too large or armored for them to take on singly. You can give them venom and fangs if you like to make them more carnivore in nature and obviously dangerous. The problem being that by the time you have a more intelligent ape able to co-operate and use tools and with basic communication you are not far away from just using single minded humans really. [Answer] You need creature similar to the alien Moorwen from the film 'Outlander'. * Tall: This creature will have 2 meters of similar to gorilla but more bigger. * Skin: The skin can by more hard with bony protuberances this will make the creature more resistant to others predators, also can be Fire-retardant and water resistant this will be good for the adaptation of this creature to the water like the swimsuit of the professional swimmers. * Bioluminescence: This creature can use bioluminescence to attract prey and also for communication with others predators of the same species. * Sight: This creature don't have a very good daytime vision, but it makes up for it with good night vision. * Smell: This creature can have a perfect smell sense for detect prey at distant distances. * Forked tongue: tongue with the same sensor of the snakes, this with the smell can supply they daytime vision. * Strength: Pure muscle, athletic body and ready for combat. Great resistance and a force capable of bending a metal plate at one punch. * Intelligence: This creature will have a great intelligence, with capability for make ambush or a strategic plan for hunt, also this predator will be loyal to him owner like war dogs. * Tail: The tail is a very important item because this will be used like the monkeys or for balance the weight when the creature run like leopards, also can be used for make attacks like a whip. More information about Moorven here: <http://aliens.wikia.com/wiki/Moorwen> ]
[Question] [ If you have played Eastern-style RPG's (role playing game, think Final Fantasy) your know they tend to have monsters of many types and sizes, some much larger, some smaller, some humanoid, some animal and some just bizarre. These games almost always have one character who is a martial artist, fighting with hands, feet, and occasionally metal fists or 'claws'. As someone who knows just a tiny bit of martial arts, I can't help but see the difficulty of fighting these things; already they're at a disadvantage without a weapon compared to everyone else. However, my training in martial arts focuses on how to fight humans. It's not only about reading human body language to anticipate attacks, but also about knowing human vulnerabilities to strike (how do you aim for the solar plexus of a wolf!?). In fact I would have a hard time hitting a wolf with any power at all, my kicks are trained to strike at my waist level or higher, I don't know how to get power kicking someone who doesn't even come up to my waist with anything other than the impractical axe kick. So how would a martial artist be trained in a RPG world where they anticipate fighting monsters of various sizes and shapes? Would their techniques be modified in any way? Are there tricks they could use when going up against things noticeably larger then them, or without analogous weak spots to hit? Also keep in mind that RPGs run on [Charles atlas superpowers](http://tvtropes.org/pmwiki/pmwiki.php/Main/CharlesAtlasSuperpower), i.e. a human may train to superhuman feats. It's okay to assume humans are capable of learning and developing beyond what a human in our world can do, being faster stronger etc. Think of any Wuxia movie, like croching tiger hidden dragon, and the sort of things they do in them. [Answer] While the best possible solution would be to develop different martial arts for each particular monster, the downside of that is a practitioner of "wolf-fu" is going to be at a considerable disadvantage if they suddenly encounter an orc. While it is not impossible for adventurers to become skilled in multiple martial arts, this is really a modern western conceit driven by people who are wealthy enough to have lots of leisure time to study and practice, as well as living in a society which encourages immigration so you don't have to go to the four corners of the Earth to find masters of different arts, you can usually google them and find a few a short drive or bike ride away. If the adventurers are not in a position to go to the local fitness centre or find a dojo in the back of a strip mall for the particular martial art they are looking for, then they should be looking for a versatile art which can be adapted to meet most situations. I am going to suggest Aikido as that art, but please note this is an observation based on personal experience, and not a challenge or slight to practitioners of other arts. There may be various aspects of other arts which can be seen the same way, but I am not qualified to comment on them. Aikido is a versatile art which could be well adapted to fighting monsters because it is based on redirecting the energy of the attacker rather than being the one who launches the attack, and by disturbing the centre of balance to cause the attacker to go down. Since the attacker provides the energy, you are in the position to judge where and when the strike, kick, bite etc. is coming to make the deflection, rather than attempting to locate a weak point and strike at it. This also makes the art well suited for encounters where you are mismatched in size, punching or kicking a 250kg Minotaur with enough force to do damage may be problematic, but pivoting out of the way of its charge and directing the energy of the charge into the ground or nearby wall is going to be much easier for a human sized opponent. Aikido is also energy efficient for the practitioner, since many of the movements are simple combinations of pivots and turns, allowing the practitioner to conserve energy even when fighting multiple opponents. While Bruce Lee could successfully fight multiple opponents, he was also using a lot of energy to do so, and at some point he would either tire or be overwhelmed. Obviously even a high ranking Aikido master could also tire and become overwhelmed, but that point will be farther along in the fight, and the extra time could gain the advantage of having your friends show up, or instilling doubt into the enemy, causing them to hesitate or break off the attack. Aikido can even deal with armed opponents (like many other martial arts), so fighting a beast with claws or horns might simply be a matter of noting the reach of the weapons and taking care to move your circle so it is outside the reach of the weapon, but intersecting the body of the opponent to deliver your off balancing movement to the opponent. In the ideal construct, Aikido is a harmonious art, which emphasizes the flow of energy between partners on the mat. Since monsters are generally not interested in harmonizing with their prey, the Aikido master can switch to a "harder" style of Aikido (such as Yoshinkan Aikido taught to the Japanese police and armed forces) or even hybrid styles like "Aki-Budo", where drops and throws are designed to injure or disable an opponent. Someone or something pinned to the ground by an aikido throw can also be finished off with a knife, if needed. [Answer] The martial art adapts to the weapons and enemies of the period. Each weapon wants to be used a different way. A katana loves broad sweeping motions while a rapier loves thrusts. Likewise, armor adapts to the current weapons. A broad definition of 'martial art' helps here. Knights in 15th century Europe were trained in a 'martial art' specific to European weapons and armor. Japanese warriors were likewise trained in a martial art to their weapons and armor. Warfare always always adapts to the needs to the day; doesn't matter if a martial artist is fighting humans or dinosaurs. An example of an adaptation might be a preference for hammers and maces against heavily armored monsters. Against monsters that tend to swarm ([zerglings](http://starcraft.wikia.com/wiki/Zergling)), weapons that cut large swathes such as broad swords or halberds would work best. Each of these weapons demands a different fighting style for effective use. Remember, Humans are the great murderers of Earth. If there's something that can be killed, we will find a way to do so... Then codify it. [Answer] Martial arts is a much broader subject than simple unarmed combat between humans. If we limit ourselves to Japan alone, there were indeed [many](https://en.wikipedia.org/wiki/List_of_kory%C5%AB_schools_of_martial_arts) unarmed martial arts such as [jujutsu](https://en.wikipedia.org/wiki/Jujutsu), but there were also numerous schools involved with armed combat, including [kenjutsu](https://en.wikipedia.org/wiki/Kenjutsu) ([katana](https://en.wikipedia.org/wiki/Katana)), [naginatajutsu](https://en.wikipedia.org/wiki/Naginatajutsu) ([naginata](https://en.wikipedia.org/wiki/Naginata)), [Sōjutsu](https://en.wikipedia.org/wiki/S%C5%8Djutsu) ([spear](https://en.wikipedia.org/wiki/Yari)), [Kyūjutsu](https://en.wikipedia.org/wiki/Ky%C5%ABjutsu) ([bow](https://en.wikipedia.org/wiki/Yumi)), and to mention a more exotic art, Kusarijutsu (chain-weapons such as [kusarigama](https://en.wikipedia.org/wiki/Kusarigama) or [manrikigusari](https://en.wikipedia.org/wiki/Kusari-fundo)). It isn't generally recognised today, but Europe also had their own [schools of martial arts](https://en.wikipedia.org/wiki/Historical_European_martial_arts), including schools teaching the use of the broadsword and shield, halberd, rapier and many more, but with the rise of firearms as a weapon of war, they have been largely forgotten, much more so than the Asian martial arts. I won't even start with the many mainland Asian martial arts. You may notice in the list of Japanese martial arts, I have mentioned mainly those ending in -jutsu, these being the schools of martial arts taught to warriors, unlike the -do martial arts, which are frequently watered-down versions of the -jutsus taught to civilians. When you're dealing with monsters, you don't want a martial art which is nerfed for public consumption, where the emphasis is on preferably-non-lethal self-defense, no, you want an all-up the-best-defence-is-a-good-offense martial art optimised to kill. Given all these martial arts, those involving weapons would be of greatest use against monsters which are for the most part relying on their natural weapons. The advantage of being able to keep a greater distance between yourself and a slavering beast while still being able to counterattack cannot be overstated. It would also be the case that both weapons and the martial arts devised to employ them will be optimised according to the monsters that the art's practitioners will be facing most often, as well as to dealing with humans. While humans will unite against a common foe, don't underestimate our propensity to squabble amongst ourselves either. Another factor is that weapons will frequently be adapted from tools that their wielders would be using regularly. While swords have the advantage that they are light, easily carried and deadly, they are also expensive. When faced with a marauding monster or a human enemy, a farmer would be more likely to grab for a farming tool such as a sickle, rake or hoe, a woodcutter would rely on his axe, a builder might use a mallet, and so on. Of course, in Japanese mythology, [oni](https://en.wikipedia.org/wiki/Oni) are frequently depicted as being armed, and there is no reason why the OP's monsters may not also be smart enough to make or scavenge weapons. In such a case, it would be the height of foolishness to attempt to deal with such a monster unarmed, and the height of sensibility to use something like Kyūjutsu which maximises the separation between man and monster. You can then escalate matters - monsters using martial arts, with arrow-cutting (the use of a weapon to deflect arrows), thus either forcing combat back to melee range, or requiring multiple archers to deal with the monster. The sheer variety of martial arts which humans have devised should be enough that someone will have the skills needed to defeat even a martial-arts-trained monster. [Answer] The discussions above have covered a lot of how most martial artists, particularly historically were armed, the idea of the unarmed warrior monk is something that we get from modern films and RPGs and martial arts are largely related to fighting humans because humans are the most dangerous creatures around, certainly the one most likely to attack for no evident reason. "Monsters" is a huge range, but it might incorporate a lot of dangerous animals but also humanoids, supernatural creatures, revenants and sundry strange and mysterious perils. For some of these, the principles of unarmed combat are rather challenging - in our world, you would only go unarmed against a tiger, grizzly bear or angry bull if you were suicidal. Even with most types of weapon you would be taking a huge risk confronting something tougher like a hippo or rhino. If your monsters are of that type, then people are mostly going to try to avoid them outright, a creature like that without a human-like intellect or desires is likely to be fairly easy to avoid unless you need to stray into it's territory. Confronting a creature like this would be a matter for group strategy. With humanoids and creatures at a scale where unarmed combat would be practical you might find specific styles developed to confront different types, variants based on the vulnerabilities of the opponent and negating their strengths. In fact you might well find that "goblin-style" would develop as a new form among the martial arts to help new students learn. Of course, one might need to ask why these martial artists are not using weapons. If they are not total idiots, then they're going to have a good reason for it and that - combined with the existence of monsters - probably means they have some kind of extra power which is accessible through their combat style. This would need to be directed through physical contact ( hence no weapons ) and need to be sufficiently potent to balance out the advantages that a weapon gives. As soon as a weapon could be created that would also transmit this power ( perhaps some kind of sword or sabre, made of a something unexpected like 'light' ) then any smart monk is going to start using it. That is really the essence of this to me - the question is a good one but if we start from the idea that these martial artist types exist then there must be a reason for them to make that decision, which opens the door to a lot of world-building opportunities. Remember that a major reason that empty-handed martial arts arose in our world, was that people were conquered and forbidden from owning, buying or constructing weapons. That is the other reason people historically made this decision- not because it is better, but because it was all that is open to them. [Answer] What you describe is less of a martial art, and more of a self defense system. Your focus is on "how do I kill the other guy," which is a notably unpopular way of thinking in martial arts. If you think that way, you tend to find yourself excluded rather quickly from many teachers' circles. > > "If you want to beat someone down, use a gun. Martial arts is about economy of force" - Fists of Fury > > > I can't claim to be a true expert in martial arts, but I can say what I have seen from art to art. They all say the same thing: "Martial arts is about health." Whether it's Tae Kwon Do, whose style can be roughly translated as "teleport their head three feet to the left with your foot," or Tai Chi, whose style can be roughly translated as "I simply wont let you hurt me," all martial arts focus greatly on the health benefits of the motions they do. This is natural. Most of their students will spend most of their lives not fighting, so you want to make sure your fighting skills also help keep you healthy when you're not fighting. So in an RPG world with monsters, you would still build martial arts from the same fundamental goal: "Economy of force." * How often do you fight monsters? If you will likely spend most of your life not fighting monsters, the focus will be more inward, like Tai Chi, Xingyi, or Baugua. The focus would be almost entirely on maximizing your ability to use yourself and improvise. On the other hand, if fighting monsters is a continuous process, you will find "economy of force" starts to focus more on how you can efficiently dispatch enemies. You may start seeing more specialized systems which focus on taking down particular enemies. You will also see less focus on art and more focus on self defense. It's worth looking into the differences between the martial arts and Krav Maga, which many teachers consider to be a self-defense system, not a martial art. * How varied are the monsters? The more you can memorize weak points, the more you can rely on them. If there's one or two groups of monsters out there, perhaps ratmen and goblins, there's time to memorize weak points. If there's hundreds of different monsters out there, you would learn general techniques such as "if they have an insectoid leg, here's how to attach it." If the situation is truly chaotic, formless approaches would rule. * What weapons do you have? The more combat relies on weapons, the more specialization you will see. While everyone has two arms and two legs, the inventory of weapons humans have invented is staggering. Facing lots of giant spiders and other exoskeleton wearing foes? You'll probably want bludgeoning weapons. Facing lots of very dangerous clawed foes? You'll probably want the standoff distances of the swords and polearms. * Finally, what else do you need to do in life? A village of farmers will develop a martial art which synergies with the muscles and movements needed to do farming, because of economy of force. An ivory tower of scholars will develop a martial art which focuses on weak points, because that memorization style is useful for the scholars in debates. A monestary will develop martial arts which can be taught for centuries without anyone actually getting in a fight to confirm that they work. [Answer] Starting from little knowledge is the answer here. These days, Filipino armed martial arts are well regarded because they remain in active day-to-day use for self-defence with weapons, unlike pretty much everywhere else where laws have disarmed the general population and unarmed martial arts are therefore the norm. Note that metal claws are a perfectly valid weapon - inside a 3-foot radius, Freddy Kruger is at a major advantage over a pikeman. Fiction features characters fighting unarmed for narrative reasons, not because they would be practical in reality. To be practical in reality would basically take magic - which is possible in an RPG, but not on Planet Earth. A massive skill differential can make it work to some degree, but weapons are such a game-changer that the guy with the handle usually wins. Adults are routinely killed by young kids with knives, even though the adult is massively larger and stronger - it only takes one lucky stab and it's game over. With suitable weaponry though (metal claws, boots) it's more practical. And kicking below waist height is standard in most martial arts, attacking legs and knees. Your biggest problem with an animal is not the height but the speed. Anyone can kick an Alsatian hard when it's just standing there, but it isn't just standing there, it's lungeing for your throat. A timely elbow is likely to be more use, as is knowing that its legs are very vulnerable to leverage. And we're back to training - if you're in an environment where you're likely to need to kill these things then you're going to learn how to do it. Mediaeval hunters had specific spears to kill wild boar, American Indians learnt how to kill bears, and so on. [Answer] Since there are so many various sorts of enemies, martial arts would most likely focus on developing oneself and one's body, giving one a toolset with which one could improvise, depending on the situation and the enemy one is facing. There are some martial arts which do this, such as Escrima which focuses on teaching you to use your body and various bladed or blunt weapons. If your monsters would be too tough to beat at the close range then ranged weapons like archery could be useful. As a reference you can take a look at the witcher world. There are trained hunters focused on these monsters and using every advantage they could get. From mutations and silver weapons to poisons and explosives. [Answer] I say just they should exercise to be in peak physical condition (in that verse), be hypercompetent in whatever unarmed (or weaponized) martial art there is (in that verse) and apply what you/they know to compete on relatively equal terms with the various monsters. [Answer] Some weponized form of wing chun or summat. Not many posts have been talking about the physical capabilities of humans so let us say the highly trained one can run 10k in a min. then they could physically compete w "monsters" if you scale in strength. Wing chun could be amazing against big enemies, especially with metal claws or knives. This isn't perfect, but it would allow for excellent offensive potential against medium/large enemies for small ones then they could throw blinding packages and knives. ]
[Question] [ Let's say scientists created a pill, that would satisfy our daily nutritional needs. It would have all vitamins needed, all calories, minerals - everything that a human body needs in order to function properly. The side effects are unknown. How much is this pill in the "fiction" section? Is it really possible to create such pill? How would this pill change our diets? I believe the price would have a great impact, so let's discuss three possible prices: 1, 100, 10000 american dollars. But would it replace natural meals entirely? Assuming that this pill is used by 25% of Earth's population for a long period of time (100 years). Would they look, feel, behave different than the rest of humans? What about 100% of Earth's population? EDIT: My thoughts: * This pill would cause obesity for some people - using it wouldn't make you feel "full" so you could just eat the same amount of food that you ate previously. * Many people would be affraid of side effects which are currently unknown * This would solve hunger in third world countries, IF the prices would be right. This might cause economic growth. * The pill could improve or even save million of lives, so I'm guessing the price would be high (maybe thousands or dollars), so only the wealthy ones would afford it. But the wealthy ones have enough money to buy food on the regular basis so they could use it only if they were to travel to space or somewhere where food would be not so easily available. [Answer] Being total sci-fi geek, I got introduced to the idea of [Soylent](https://www.soylent.com/) drink. Disclaimer: I am not connected to the site in any manner So, the pill itself is pure sci-fi. But being able to eat only prefabricated food is not so sci-fi. The hardest part is, that everyone is forgetting the sheer amount of inputs which human body needs [Answer] # No My [answer to a similar (but not identical) question](https://worldbuilding.stackexchange.com/questions/16943/the-ultimate-protein-bar-as-a-fruit/16945#16945) was that there's a limit to how nutrient dense you can make your food or the human body can't absorb it. The problem is that very nutrient dense foods suck water out of your body through osmosis. This leaves the consumer dehydrated and they still aren't able to absorb the nutrients. If you perform the math on the numbers provided in the answer linked above and for a 2000 kcal diet (average for a male), the densest nutrient concentrations a person could easily tolerate would require them to consume about 6-8 $Ensure^{TM}$ per day. The total mass of this would be $7 \times 240 g $ ~ $1.7 kg$. To this you'd need to include an extra supply of water since the quantity provided in $Ensure^{TM}$ would be insufficient to sustain a person. I realize this number seems high, but realize that this 1.7 kg (3.7 lbs) of food includes 1.3 liters (2.8 lbs) of your daily water requirements. # Yes Instead of consuming your "food pill" directly, if you instead dropped it into a container of water and drank the results, that would probably work if you got the quantities right. In this case, your "food pill" for a day's rations would mass about 0.4 kg (0.9 lb) and would need to be dissolved in the quantity of water identified above. # Other Stuff ## Preferences As a person with digestive issues, I've been forced to use $Ensure^{TM}$ to supplement my diet. I never drank it because I liked it. This stuff tastes OK but it isn't something most people would choose over regular food. ## Long-term Use Perhaps more important, we still do not know all the nutrients the human body needs to stay healthy. We know the macronutrients (fat, carbohydrates, protein, and water); we know the micronutrients (vitamins & minerals) but we do not know the trace nutrients that are beneficial. The trace nutrients are those chemicals are the ones scientists look for in wine, coffee, chocolate, etc. Scientists are constantly changing their minds about whether this food or that are good or bad for you. A diet of only these concentrates will keep you going but might lead in the long-term to a variety of difficult to diagnose issues. We just don't know enough about it right now. ## Costs Right now, these concentrated foods are substantially more expensive than the food that they'd replace (perhaps $10 / day). If you wish to solve world hunger it does have some advantages though: 1. Light weight - easy to transport 2. Shelf stable - no spoilage ## Solving Obesity As our knowledge of obesity increases, this answer may become dated but current research implicates many factors of which layman are unaware. Factors which may cause obesity: 1. diet 2. inactivity 3. [hormone imbalance](http://www.nhlbi.nih.gov/health/health-topics/topics/obe/causes) 4. [certain viral infections](http://www.wsj.com/news/articles/SB20001424052748703305004575503701046272186) 5. [gut biome](http://www.nature.com/nature/journal/v444/n7122/abs/nature05414.html) 6. [depression / mental health](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2568994/) 7. [genetics](https://en.wikipedia.org/wiki/Genetics_of_obesity) 8. [lack of sleep](http://www.nhlbi.nih.gov/health/health-topics/topics/obe/causes) 9. [medications](http://www.nhlbi.nih.gov/health/health-topics/topics/obe/causes) Of these, the "food pills" might only solve #1 or possibly #5 if the "food pills" were laced with gut biota known to be a good & healthy mix. I suppose it's possible that a sophisticated society could generate "food pills" based upon a doctor's prescription in which case #3, #4, & #6 might also be addressed by taking your and only your "food pills". ## Hunger as a motivational state. The hunger mechanism in people is fairly complicated, can be triggered or suppressed by several different factors, and has different processes over short and long terms. > > [Short-term regulation of hunger and food intake involves neural > signals from the GI tract, blood levels of nutrients, and GI tract > hormones.](https://en.wikipedia.org/wiki/Hunger_%28motivational_state%29#Short-term_regulation_of_hunger_and_food_intake) > > > A food pill can be designed in a way that triggers all the right GI tract and blood monitoring triggers as long as the "pill" contains "bulk" for the GI tract to work on. Fiber would fill this need quite well. Furthermore, current diet nutritional shakes already include fiber in their formulations for just this reason. ## Eating as a sensory experience I think one area in which this idea fails would be when "eating as a sensory experience" When humans really indulge in the pleasures of eating, we engage more senses than just taste. We enjoy different textured food (touch), foods with pleasing aromas (smell), colorful arrangement (sight), and even sometimes foods that make sounds when eaten (sound). Food pills might be able to accommodate taste and to a lesser extent smell but would leave out the other senses. For these reasons (and a few others), I don't think food pills would ever replace "real food" on the luxury market. [Answer] While the vitamins would probably be relatively cheap and easy to supply, calories would be another matter. The most calorie-dense foodstuff is pure lard, at about [892 calories per 100 grams](http://www.gbhealthwatch.com/Nutrient-Calorie-TopFoods.php); for reference, a stick of butter usually weights around 100 grams. An average adult human needs [between 2000 and 2400](http://www.webmd.com/diet/estimated-calorie-requirement) calories every day, so someone looking for the bare minimum calories would need to eat bout 224 grams of pure fat. This would obviously be too much for one pill to handle. For the sake of creating a fictional world, you could possibly get around this with the invention of a new kind of synthetic organic molecule which packs about 2000 calories into a single gram, with a second gram used for traditional multivitamins. This would solve the energy issues, but it would still leave people with too little actual matter for their bodies to work with; they wouldn't be able to do things like develop muscle or hydrate themselves. The best the pill could do would be stave off starvation. [Answer] It's total fiction One pill a day to satisfy a person's nutritional needs is a very old trope in SF. The problem is that physics, chemistry and human physiology (and maybe psychology) simply don't support it. Having a human survive on just a single pill every day without any supplemental energy sources is complete and utter fiction. Limited Nutrient Compressibility [DIY Soylent](https://diy.soylent.com/) is an excellent place to experiment with different nutritional profiles. For example, the [recommended nutritional intake](https://diy.soylent.com/nutrient-profiles/51e4e6ca7789bc0200000007) for an adult male for a vitamin C alone is 2 grams. The density of Vitamin C is [1.69 g/cm³](https://en.wikipedia.org/wiki/Ascorbic_acid). Even without doing any math to find out exactly how big the pill is, it's becoming larger than many people will want to swallow, and this is just one nutrient! For an idea of scale, the below photo is 1 cubic centimeter cubes in a child's hand: [![Cubic centimeter cubes in a child's hand](https://i.stack.imgur.com/kPYHe.jpg)](https://i.stack.imgur.com/kPYHe.jpg) Granted, many other nutrients take up far less space, biotin in particular is needed in vanishingly small amounts. These small nutrients are just statistical noise compared with the larger nutrients like calcium carbonate at[2.71 g/cm³](https://en.wikipedia.org/wiki/Calcium_carbonate) and an adult male needs 1 gram. Females need more than that. Calcium is a sizable pill even without binders to keep it all together. Calorie Requirements Let's start with the standard 2000 calorie diet in the form of protein, fats and carbs. The human body needs a certain amount of protein every day or it will start consuming its own muscles to get it. While human muscles and organs can survive on [ketone bodies](https://en.wikipedia.org/wiki/Ketone_bodies) (the energy transport mechanism for energy derived from fat) the brain requires sweet, sweet carbs. (From personal experience, trying to fuel the brain on just ketones won't work. Just don't do it. Sugar cravings like you wouldn't believe!) Thus, we have minimal intake requirements for protein and carbs; all the other energy requirements can be made up with fats/oils/lipids. For quick reference, carbs are 4 calories (nutritional calories, not physics calories) per gram, protein is 4 calories per gram, alcohol is 7 calories per gram and fats are 9 calories per gram. Without addressing macronutrient ratios, let's just assume that all calories will come from fats thus giving a lower bound on the required mass to fuel a human body for a day. 2000 calories / 9 calories/gram = 222.2 grams of fats. Using canola oil (at 0.92 g/ml) for fuel gives us 241 cubic centimeters. For comparison, a Rubik's Cube is a mere 185cm^3. No one swallows Rubik's cubes. Mush, no matter how sweet is not tasty As [this scene](https://www.youtube.com/watch?v=zuUtAPUZP0Q) from the Matrix so perfectly describes, humans don't like eating tasteless, monotonous slop. Sure they will if they have to, to survive but they won't like it. From an evolutionary biology perspective, it's not hard to make the jump that an early human that ate the same thing every day, all day soon developed nutritional deficiencies and could not compete. An instinct for varied foods and varied textures helps cover nutritional deficiencies. But what if you could do it all in a pill... Okay, okay, what if you could make a pill that filled a person's nutrient and caloric needs for one day? * A great deal of nutritional and inflammation based diseases would go away. * The obesity epidemic in the US would vanish. * The populations body fat percentage would settle at levels particular to that person's genetic. Ectomorphs would stay thin. Endomorphs would stay heavy. In both cases, they would be more easily able to accept their body shape because they know they're giving their bodies what they need/want. [Answer] Outside of issues like how many calories a pill could pack, the human body has evolved to process natural food. We need a certain amount of fibre in order to push things through the intestines, for example. The other issue is that different humans have different needs. You can eat things off a plate or ignore them, and order individual meals to meet dietary, social, religions or other requirements. I'm not sure many people would believe your pill is Kosher, Gluten free or an appropriate snack food for watching the game. Taking a prospective mate to dinner would be a totally different thing (think of all the rituals involved around taking a date to dinner). Pill food might be appropriate for emergency situations (for example, a box of emergency rations in a survival kit would be much more portable if they could be replaced by pills), or perhaps for extreme adventurers (hiking with a pack of pills across the Amazon rain forest), but even then, the social aspects of sitting around the camp at night and sharing a meal wold be lost. [Answer] So the other answers have made it pretty clear that you can't pack a full day's nutrients into a single pill, even if it's a large "horse pill". But what if, instead of digestible nutrients, this pill contains an array of chemical- or nuclear-fueled nanomachines and a stock of raw elements? What if these nanomachines could use these elements together with some amount of ingested water to build nutrients and then exhaust them into the stomach? Then, later, when the machines run out of fuel, they make their way naturally down the digestive tract to be excreted. As for the effects of such a technology: Obviously the users of such a pill would stop defecating for the most part. Reportedly this already happens with soldiers who subsist entirely on military rations. That alone would save humanity a lot of time and water, which would contribute positively to the economy. If the pill was very cheap, it might result in a population explosion. If it was very expensive, most likely no one would really use it, and it would remain a laboratory curiosity except in certain contexts where space and weight is at a premium, for example, space travel. It's not certain what problems prolonged use might entail. Obesity rates might drop, since it's a (very) controlled portion and it kind of removes the fun from mealtimes. Even if it's pretty safe, the medical profession might recommend "real" food every once in a while to flush out the system. [Answer] It is complete fiction with today and near-term technology. I think most current answers cover that aspect. If you were looking far into the future though, it is theoretically possibly that a bionic upgrade could allow you to just shove your daily energy intake, as a pill, into a hatch which would slowly push the nutrients into your body throughout the day. Depending on just how advanced we can get with stuff like that, maybe the bionic upgrade completely optimizes and replaces our current digestive system for our processed bricks of material. > > How much is this pill in the "fiction" section? > > > Very much so, unless you plan on taking a very large pill every 4 minutes. (This number comes from [@Greens answer](https://worldbuilding.stackexchange.com/a/22093/2138), which suggests that 241cm^3 sized pills would be needed for a day's worth of Calories. Subtracting 8 hours for sleeping, you could take 1cm^3 pill every 4 minutes to get the correct amount. - but then you have to add in all the other stuff your body needs as well, likely making that pill much larger > > How would this pill change our diets? > > > We wouldn't have to worry about our diets! That and the pill being slightly more compact than normal food are really the only positive things about it. > > But would it replace natural meals entirely? > > > Unlikely, people like to eat and try new tastes. It makes us feel good to eat. Doing otherwise just isn't "natural", there would have to be a huge reason not to do it. > > Assuming that this pill is used by 25% of Earth's population for a long period of time (100 years). Would they look, feel, behave different than the rest of humans? What about 100% of Earth's population? > > > If you go with the bionic thing, then people would look very different due to that - but people's looks wouldn't drastically change because of what form they are getting their food in, especially not in only 100 years. [Answer] No one is thinking long term here. It's my understanding that one of the most important differences between us and other species is the cooking of foods with fire. Leading to smaller intestine and bigger brains. If a pill or several pills taken throughout the day could replace our current food situation wouldn't it seem to imply even less intestinal need and even bigger brains????? [Answer] When I was in my twenties I experimented for several weeks by surviving only on milk mixed with a well-known British energy drink (Lucozade) supplemented with vitamin pills. At the time I used to cycle to work ending with a hill. At the end of the trial I felt fitter and was slimmer than when I started. I had no adverse symptoms at all. (see disclaimer) The biggest effect of all came from joining colleagues at mealtimes. After only four days I lost any cravings for what they were eating but it was just so boring. The whole business of eating is important socially or alone and was the reason I stopped. I had a huge desire to chew and swallow and even to use eating utensils. > > Disclaimer > > > I am not in any way medically qualified. I was young and in good > health at the time and I cannot say what effects, good or bad, such a > diet would have on anyone else. > > > ]
[Question] [ Inspired by [a previous question on this site](https://worldbuilding.stackexchange.com/questions/7351/in-a-world-with-magic-who-would-govern/7361#7361). If magic were real (handwave - see 1) and in some way heritable, would it be likely [to become fixated](http://en.wikipedia.org/wiki/Fixation_%28population_genetics%29) in the general population? If so, how long would it take? Would it become universal? I have some sense that this might depend on how many separate genetic alleles are needed. If not, why not? How would magic have to be harmful to prevent it from becoming a universal trait? Could it even die out? For a couple of real world comparisons, I imagine that the first humans to develop what we now call empathy (the ability to put oneself in someone else's shoes and imagine how they would feel and what they would do) must have gained a magical-like ability in terms of the advantage it offered. Yet we don't have 100% prevalence, since we a generationally stable minority of sociopaths who are literally unable to empathize. Speech (the ability to plant highly specific symbolic representations in someone else's mind) must have also seemed magical to non-speaking human-like predecessors. It conferred such an overwhelming advantage that it did become universal in baseline surviving humans. 1. A decent implementation of a gesture, token and voice based magic system, along with a plausible explanation of its existence is described in [Ra](http://qntm.org/ra) and hinted at in [HPmoR](http://hpmor.com/chapter/25). Imagine that in addition to the correct gesture and voice patterns, the "magic system" would check for a specific set of markers in the invoker, and do nothing if they are not present. [Answer] If the ability to do magic is very rare, then having it could provide great income potential and could make someone highly sought-after as a mate. Avenues for wealth include wall-street mogul, superstar athlete, dominating your way to the top of a Fortune-500 company, etc. A few years ago, a professional basketball player claimed to have had sex with about 10,000 different women, based on his estimate of 3 women/day over a 10-year career. Some people are skeptical of this claim, but it is at least within the realm of posssibilty. Assuming a fertility of about 10% (magic could help with this), and an income somewhere over $\$$100 million/year, a mage could potentially sire and support a thousand children in a decade. As for desirability, "Hey baby, have sex with me and if you get pregnant I'll give you $\$$100 thousand per year in child support" may not be the best pick-up line, but it would work often enough. If magic ability is inherited via a dominant mutated gene, then about 1/2 of those children would have magical ability. That's 500 new mages this one guy could sire, per decade. So, while magic ability might spread slowly at first, eventually that one guy would come along. And, of his thousands of sons, many would try to do the same. Magic ability could easily go from "very rare" to millions or billions in a few generations. Once magical ability were very common, we would then enter the long phase known as "the decline of the muggles". People without magical ability would be seen as inferior and would make less desirable mates. They would have much lower earning potential and would often end up in poverty. Even if no one actively tried to kill them off, society might change so that magical ability became essential to survival. Eventually, the muggle gene would disappear. But this would take a long time. If a population has a fraction 1/X of its people who possess a single copy of a recessive-lethal allele (like untreated hemophilia), then the number will naturally decrease to 1/(X+1) in the next generation. It would literally take billions of generations for a specific allele to completely disappear. The only way it would go away faster would be if genetic testing could identify it and people actively selected against it. Things get interesting and weird if the magic ability gene were dominant, but two copies of it were lethal. The number of mages would increase to about 2/3 of the population and it would stabilize there. Even if muggle babies had low survivability, they would still continue to make up 1/3 of births. Or if carrying a double-magic-gene baby tended to be lethal to the mother as well as the baby, then no woman with magic ability would dare to mate with another mage. Marriages would always be mage-muggle, and the population would stabilize at 50% mages, 50% muggles. This strikes me as a fascinating scenario. [Answer] If mutation would be beneficial, it would spread out. How fast, depends on many factors including if it is recessive or dominant, and how big competitive advantage/disadvantage it would give it's holder. Even such minor trait like [blue eyes](http://www.livescience.com/9578-common-ancestor-blue-eyes.html) which has only slight advantage of beauty (which is slight personal preference), spread over 6-10KY. There are formulas for that somewhere, but without numbers (which you did not provide) I can only say: if benefits outweight disadvantages, it would spread. And to get universal, it would have to be dominant, be extremely advantageous, and even then it will take long time. Edit: See comments, link from @NounVerber about "blue eyes" gene, it's spread, and being caused by 15 genes (and not recessive). Thanks. [Answer] A trait becomes fixated if it raises the number of healthy children. In our Western society high intelligence correlates with its owners making decisions to have fewer children. Women in poor third world countries have more children than women in Western countries. Magicians might have working contraception spells while the rest of the society has no reliable ways of contraception and use that magic to limit the number of children they get. Furthermore children by magicians might kill themselves in some way by misusing their magic. [Answer] From [This article](http://lesswrong.com/lw/kt/evolutions_are_stupid_but_work_anyway/) on the subject: Generations to fixation = 2 ln(N) / s where N is the population size, and (1 + s) is the fitness. (If each bearer of the gene has 1.03 times as many children as a non-bearer, s = 0.03.) Probability of fixation = 2s If having magic lets you have 10% more reproducing children than people who do not have magic, there is a 20% chance that magic will become fixated, and it will take 20 \* ln(Population size) generations for it to do so. In a population of 7000000000, that's 400 generations. If it doubles the number of kids the magic user can be expected to have, it's almost guaranteed to become fixated and will take 22 generations to do so.Put in your own numbers as needed. [Answer] I think the existing answers cover the mechanics of genetic propagation thoroughly. What I wanted to add to the conversation is a counterpoint as to why a desirable trait may not spread. In many magic systems a great deal of study, practice, discipline, and emotional control is needed to perform magical feats, and control the effects you produce. The notes on the question imply that this is the case, just having the gene is not enough, you also have to develop the capability to do anything with it. If we assume such a system, then the mages may actually reproduce less than the average person, reducing the odds of, or at least extending the time for, the trait becoming fixed. In order to develop their gift to a point of being recognized as a mage, a person would have to reign in their emotions and impulses, and devote copious amounts of time to study. As such they will have less time for/interest in raising a family, and they will be less likely to engage in casual sexual encounters. Under such systems, many schools strictly forbid any sexual activity among their apprentices due to it being distracting, and thereby dangerous. So even though the society may see a mage as a desirable mate, the mages themselves would generally hold back from having numerous offspring. Given enough time, assuming society continues to hold them in high regard, the trait would most likely become fixed, but it would be a VERY slow process. A shift in the way the mages are perceived by society as a whole could very well result in the trait dying out instead. Now the above scenario applies to those who develop their heritage into a notable ability. What happens to those who possess the trait, but never develop it? If we assume that it has no effect other than giving them access to magic once trained, then these people gain neither advantage nor disadvantage in terms of their mating potential. Some will have many children, others few or none. The distribution of the trait through the population will be like hair color, eye color, or any other trait that doesn't convey a significant advantage/disadvantage to the one who possesses it. It will probably never die out in this population, but it probably won't become fixed either. End result is that the untrained that have the trait would not significantly influence the above outcomes. However, many people who have devised similar magical systems have included an element where someone who is born with the magical gift, and does not receive training in how to control it, gets killed by runaway magic as the gift awakens. If we add this element into the mix, then the chance of the trait becoming fixed drop significantly. Our untrained population that could keep the trait alive in light of limited breeding on the part of the trained mages no longer exists. This would potentially mean more mages, as everyone will want to make sure their children get enough training to survive, but those who don't have access to such support die, probably before they pass on their genes. The catch here is, what incentive does the average mage have to train such people? Sure having a few apprentices to boss around can be nice, but I don't want to take time out to have my own children, why should I invest years in somebody else's child? I see such a situation going one of two ways (or possibly both in different regions). Route one is that anyone with the trait has to find a willing mage to take them on as an apprentice in order to receive training. Presumably any such person is the child of a mage, but there are any number of reasons that their parent may be unavailable to train them. Maybe they are illegitimate and their mage father doesn't even know they exist. Maybe their parents were killed before they were old enough to receive training, the child survived but doesn't know of their heritage, or have a friendly mage around when they need one. Whatever the reasons, there will be cases where the children do not receive the needed training in time and the magic kills them. Under this structure the mage population slowly shrinks, and eventually dies out. Or perhaps they manage to survive, but they become such a minority that most of the population never sees one, and doubts that they really exist. The other route is that the mages establish a school system to train anyone that shows indications of having the trait. Those mages that have an interest in such things serve as instructors. The students have a strong incentive to pay attention and learn, I mean their life quite literally depends on it. Never the less, there will be some that fail to learn fast enough, or make mistakes, and the magic kills them. But overall the mage population slowly grows, and eventually we are all one people. :-) [Answer] This is a difficult question to answer with any precision - it depends on a great number of factors, which basically boil down to the magnitude of the advantage. Like any trait - such as the ability to see - it will never be truly universal, as in "no-one lacks the trait", but may become typical, as in "the numbers of people who lack the trait are not statistically significant, so less than 5% of the population lacks the trait". Certainly, the ability to use magic should be a significant advantage that would lead to the ability to produce greater numbers of offspring surviving to reproduce themselves than those without the ability. However, the answer depends on how many more. If it is 1 or fewer, it could take a very long time, on the order of thousands of years. On the other hand, if there was a war between the magic users and the non-magic users or some other factor that made the difference in offspring survival much greater than 1, it could take only a few generations to become a majority trait, and a few more generations for magical disability to become as unusual as blindness or deafness. The nature of the advantage provided by magical ability would depend on social factors such as whether the magically-able made a habit of assisting the magically-unable in their lives and the magically-unable tolerated this assistance, or if the two groups were antagonistic, the magically-able feeling superior to the magically-unable, and the latter feeling threatened by the former. [Answer] This really depends on how much of an advantage the magical trait has. If the only way to make any use of it is through extensive and intensive schooling or if it had other consequences such as making you physically weaker or give you special requirements then it might spread slowly. If it had no downsides and gave you a noticeable competitive advantage then it would spread fast. [Answer] This is a difficult question to answer. You can't use pure mathematical formulas to map out the "magical diaspora". Even the genetics side isn't very easy to figure out. These genes could lie dormant in people for many generations before it expresses itself. Perhaps it is a recessive gene and skips generations, or you need to have parents that both have the gene for magical traits to be present in their offspring. Since the world is so diverse, it would most likely take thousands of generations for the majority of people to have magical powers. Many of the traits we have today such as eye color developed in our distant past when there were much fewer people on the planet. It is very unlikely that a gene like that would ever completely dominate the human population if it appeared now. If we were able to master the human genome and use gene therapy to artificially create the magic gene and give it to people, then anyone that had the means and wanted it could have it. [Answer] Amongst other factors, when does magic occur? (ie: people learn the correct gesture and other stuff: ie: is this an easy problem (happens accidentily, often), or a very difficult problem (biological forms developing mitochondria: happened once)) If magic is hard enough that it didn't develop until later, after other civilized effects - it might not be as common, even if it does have evolutionary benefits. If you realize that magic is heritable, you might be careful spreading your genes if it means you might have to compete with your progeny. This is especially true if magic can extend your lifespan. Or if the number of magic-users impact the magic auras/ability to use magic. If decreasing the number of mages increases your available personal power... having magical genes might not actually be an evolutionary benefit. :) [Answer] After a little research I found [this article](http://www.bbc.com/news/magazine-19331938) in which they explain that when you go back 20 generations on earth, basically everyone is related to everyone at some point along the way, so that would be your 'longest time it would take' assuming the inheritance is (close to) 100% and assuming you WANT magic to become universal. If the ability to do magic is tied to having a specific gene, the time would obviously be longer. [Answer] While I'm late to the party, I'd suggest that the answer is easy: magic, while beneficial to the possessor, is potentially lethal to the people around him or her. For a classic take on the concept, try Bisby's "It's a Good Life" <http://www.fys.ku.dk/~thoeger/its-a-good-life.pdf>. For a slightly less extreme version, consider the possibilities inherent in powerful magic combined with adolescent hornones. Under these conditions, it becomes quite possible for the surrounding population to cull magic-bearers when the ability begins to manifest itself. Particularly if magic use (rather than ability) requires practice to become effective, such culling efforts would presumably be successful while the user's effectiveness is still developing. It's just a matter of self-defense. This will, in effect, cause the gene to be selected against, and the standard analysis will apply. [Answer] Genetically, you already have some great answers. However, most answers here assume that "being a mage" is viewed as a good thing, so that will help you spread your genes. Someone took into account magic being dangerous and causing accidents, but still there's an important point missing. The more magic is perceived to be too powerful (or, even worse, too scary), the more is likely that a witch hunt will occur, which one way or another will completely skew the results: this might exterminate all the mages, or slow them down, or, if they "win", might even spread them faster. So there must be a careful balance in order not to mess everything up: magic has to be good enough to increase your desirability, but not so powerful that it attracts hostility and fear. More than sheer "power to kill things", the most dangerous powers to have are: * creating illusions: if people no longer know what's real, they wouldn't appreciate. This is only a problem if this "illusion power" is quite strong. * teleportation: this is a dangerous since it would change drastically physical security. Banks and military will want you dead, very fast, and many people would approve. * mind-reading: people would at the very least avoid mages if those could read minds. * mind-altering: this is the worst of all. If you could alter other people's minds, any sane person would want you dead ASAP. Not knowing what's real in the world is bad enough, risking becoming a puppet without even realising it is orders of magnitude worse. Especially if you also consider you would start doubting about anyone. --- Also thanks to @James and to @DoubleDouble for pointing this out in a couple of comments. [Answer] In you are interested in actually computing how many generations fixation of the trait will take the math is pretty straightforward and people have created websites that will even do it for you. Here is one such site: <http://www.radford.edu/~rsheehy/Gen_flash/popgen/>. It allows you to define the characteristics of your starting population and then run the simulation for many generations to see what happens. This web application takes a long time to run if you set the initial population too high, but there is other software that you could download in order perform a larger simulation. All you need to do is first decide how your magic is inherited. Is it recessive or dominant or somewhere in between? You also need to decide the initial frequency of the allele. This isn't necessarily the initial frequency of mages though, as that also depends on the dominance of the trait. If the mage allele is recessive and only people with 2 copies become mages then the initial frequency of mages is equal to the initial allele frequency squared. Once you have decided on that, simply decide how much more successful your mages are at having children than normal people. For instance, if the mage allele is recessive and individuals who are mages have twice as many offpsring as individuals that are not mages, then the relative fitnesses of A1A1, A1A2, and A2A2 will be 1, 0.5, and 0.5 respectively. But if the mage trait is codominant so heterozygotes or people with an A1A2 genotype are more fit than complete non-mages, then you might set the fitnesses to be 1, 0.75, and 0.5 respectively. The tool let's you run the simulation simultaneously for multiple populations to see what sort of variance there may be. ]
[Question] [ While European Dragons are often described as bat-winged, there are many depictions showing otherwise. Some give them fins or sails, and others depict a structure never seen on a living animal This structure resembles a fin with many rays projecting down from a horizontal 'spine'. The rays also flare out towards the ends, with the flaring more pronounced at the distal end. This strange structure is (at least in some depictions) connected to to body by a straight stalk, which attaches to the structure at the end near the head, and to the back just above the shoulder. This type of 'wing' is often seen on generically reptilian dragons, which have a mixture of lizardly and crocodilian traits [![The Flag of Wales](https://i.stack.imgur.com/7UIbP.png)](https://i.stack.imgur.com/7UIbP.png) The Flag of Wales shows this structure What is the simplest way for such a strange structure to develop from more realistic organs? [Answer] # Venomous barbs These rays produce venom that will kill would-be predators (such as tarrasques, leviathans, rocs etc.). The membrane between the rays is the venom-producing organ. Notice how these rays shield the dragon from predator attacks from many different angles. In this way the dragon is almost like a [lionfish](https://en.wikipedia.org/wiki/Pterois). They could have got those from their smaller ancestors, who hid from regular sized predators such as griphons and chimerae. [Answer] Suppose, earlier in their evolutionary history, dragons were smaller. As they evolved to grow larger, their surface-area-to-volume ratio began to make thermo-regulation a problem. They might develop short vertical pairs of fins (possibly made from modified scales) to improve cooling. As they continued to grow larger, however, these fins might prove to be insufficient, and the dragons would have to evolve larger ones. Eventually, if these bio-radiators got large enough, they would likely begin interfering with each other's efficiency (if they were still placed on the back, then their inner faces would be radiating heat at each other). At that point, there'd be an advantage in evolving natural radiators which could be separated from the body by stalks (full of large blood vessels), and which could be maneuvered for maximum efficiency, or even fanned (like an elephant's ears) to increase airflow. [Answer] The transverse processes of the vertebra. Here is Dimetrodon with its excellent sail. [![dimetrodone](https://i.stack.imgur.com/psMAw.jpg)](https://i.stack.imgur.com/psMAw.jpg) <https://en.wikipedia.org/wiki/Dimetrodon> A closeup of the vertebral body with spine. [![spinous process of dimetrodon vertebra](https://i.stack.imgur.com/p9LhK.jpg)](https://i.stack.imgur.com/p9LhK.jpg) [source](https://fineart.ha.com/itm/fossils/dinosauria/dimetrodon-spine-dimetrodon-limbatuspermianred-beds-archer-city-formationarcher/a/5280-72212.s) Dimetrodon here made its sail out of the spinous process on the vertebra. But also available are the pair of transverse processes. [![vertebra](https://i.stack.imgur.com/u6yA3l.png)](https://i.stack.imgur.com/u6yA3l.png) <https://en.wikipedia.org/wiki/Vertebra> Your dragon makes its pair of dimetrodon-like sails out of the transverse processes. [Answer] Start with a pteranodon ![https://upload.wikimedia.org/wikipedia/commons/8/84/Old_Pteranodon_mount.jpg](https://upload.wikimedia.org/wikipedia/commons/8/84/Old_Pteranodon_mount.jpg) Now mutate the three not crazily elongated fingers to be similar to the one crazily elongated finger, acting as refined actuators for wing shape (to allow, honestly, all kinds of wacky maneuvering options). If the membrane attachment migrates up the legs, along the ribcage and just to the end of the shoulder, you'll also get the "wings on stalks" that you want. Having done so, adjusting the lengths of the carpals and phalanges to give whatever length ratio you want moves the center of radiation in or out as suits your plans. (It's worthwhile to remember that pre-modern peoples also found fossilized skeletons, but did not necessarily have the geological and evolutionary/morphological mental tools to understand what they found. The particular wing feature you are describing may well come from an attempt or multiple attempts to describe and/or understand fragmentary fossilized skeletons of one or more winged dinosaurs.) [Answer] Seeing how the dragon has its four limbs intact, it looks much more like a [Chlamydosaurus](https://en.wikipedia.org/wiki/Chlamydosaurus) (frill-necked lizard, frilled dragon) where the "frill" split in two and moved a little bit further down: [![A frill-necked lizard](https://i.stack.imgur.com/HdVMN.jpg)](https://commons.wikimedia.org/wiki/File:Frill-necked_Lizard_(Chlamydosaurus_kingii)_(8692607976).jpg) I can see how this could turn into wings if it initially got some lift when jumping, and the more split they were, the more control it had. Eventually they would migrate further back closer to the center of gravity. [Answer] ### Polydactylic bat wing. In short, [polydactyly](https://en.wikipedia.org/wiki/Polydactyly) is a condition caused by a mutation that causes the growth of additional fingers or toes. In this particular case, the dragon has a bat wing with with eight fingers, giving it three extra fingers beyond what a bat wing would normally have (if the thumb is also included in the structure of the wing, which it seems to be). ]
[Question] [ Considering a world with Jackalopes. These half-rabbit half-antelope creatures stand a little over 2 feet long when fully grown and have horns like a deer growing 1 to 2 feet in length. Like deer, only grown males have horns, females and young don't. They all have superior musculature and bone structure to their rabbit cousins, especially in their hind-quarters, making them able to jump astoundingly far (and kick you terrifyingly hard, not to mention ramming those antlers into you). Also, strong necks to hold up those prodigious horns sprouting from their heads. [This](https://www.thingiverse.com/thing:706335) is a pretty good approximation of what we're considering here. Now my question: How would such beasts fight one another? Teeth? Antlers? Kicks? I'm looking for consideration on male v male, male v female, male v predator, female v predator, and how they would fend off nuisance animals (i.e. regular rabbits invading their territory). Answers based on similar species real-life behavior are considered best. Physical considerations of having such large horns are appreciated. --- [![A Jackalope](https://i.stack.imgur.com/RHlfU.jpg)](https://i.stack.imgur.com/RHlfU.jpg) [Answer] # Male vs. Male: Horns [![enter image description here](https://i.stack.imgur.com/YIbc6.jpg)](https://i.stack.imgur.com/YIbc6.jpg) [Chital](https://en.wikipedia.org/wiki/Chital), also called spotted deer or axis deer, from India are the smallest deer that I could find with a large tined set of horns. Males are in the 35-50 kg range, so a good bit bigger than I think you intend your jackalopes to be, but not any bigger than a large dog (although they are taller than almost any dog). # Male vs. Female: ummm.... This one isn't really called fighting... [![enter image description here](https://i.stack.imgur.com/d6Q7X.jpg)](https://i.stack.imgur.com/d6Q7X.jpg) # Either vs. Predator: Run This is what the jackalopes predators look like. [![enter image description here](https://i.stack.imgur.com/empbO.jpg)](https://i.stack.imgur.com/empbO.jpg) Unless they are the size of a bull elk (300 kg or so), no herbivorous animal is going to stop and fight a cougar. Same goes with a wolf pack. A jackalope would run. [Answer] Let's look at how rabbits commonly fight, merge that with the use of antlers, and especially take into consideration their movement and mannerisms. ## Rabbits There are a lot of different rabbit types, but their fighting style tends to differ primarily based on their size. Smaller Rabbits fight similar to guinea pigs -- jerky movements and nipping at each other. Larger Rabbits have more fluid movements (relatively), assume dominant stances, and do very little to hurt each other -- relying more on their awkward slap-dance of intimidation. [![Rabbit Fight](https://i.stack.imgur.com/51g11.jpg)](https://i.stack.imgur.com/51g11.jpg) ## Deer Conveniently enough, intimidation is also the primary tactic of most animals that feature antlers. Fighting is usually a harmless dance where both sides stand at a distance, assume intimidating stances, thrust and lock antlers, and perform what is essentially a horned version of arm wrestling. ## Jackalope Assuming that jackalopes would likely be a larger rabbit (to accommodate having antlers), taking into account the movements and mannerisms, perhaps it could occur like this ... Narrative: Both sides approach and begin to closely circle each other. Their eyesight remains locked as they grunt angrily, emphasized with each movement. In unison (and as if on cue), they raise up on their hind legs, stretching to increase their height, intent on intimidating their rival. With neither side yielding, they lunge forward, a single hop, landing on all fours, antlers locked. Their heads down, and eyes clinched shut, they feverishly move their heads from side to side, antlers clattering. Then, just as suddenly, they quickly step back -- their small noses flaring and snorting from combined exertion and frustration. Only a brief moment passes before they raise up to begin the dance once more, determined to make their opponent relent. [Answer] # Size > > These half-rabbit half-antelope creatures stand a little over 2 feet > long when fully grown and have horns like a deer growing 1 to 2 feet > in length > > > Something to consider is whether the Jacklope has [horns](https://en.wikipedia.org/wiki/Horn_(anatomy)) or [antler](https://en.wikipedia.org/wiki/Antler). These are two different things and will heavily impact how the Jackalope behaves. My answer tries to cater for both scenarios. [![hare vs rabbit](https://i.stack.imgur.com/0co99.jpg)](https://i.stack.imgur.com/0co99.jpg) The hare can grow to 70cm (2.2ft) which is approximately the size of the Jackalope. A rabbit at full size compared to a hare (or in our case a Jackalope) is considerably smaller, especially when you weight in the upgraded bone structure, muscles and the fact that the male Jackalope has horns/antlers up to 2 feet long on his head! So a rabbit looking up to a Jackalope is going to be scared. # Male versus Male ## Horns The Jackalope typically fights other males as you might have guessed. Horn on horn, the Jackalope fights other males to display dominance over his colony and typical fights usually last a few hours. The Jackalope who exhausts first loses and is outcast by the colony, providing they do not die during the battle. ## Antlers Jackalope will only fight during mating season, when their antlers are fully grown. They have a free for all, male vs male all fighting for the idea mate. The same principles apply that after the battle the losing Jackalope is outcast from the colony, or doesn't get to mate easily, perhaps even at all that season. ## Teeth and Legs Jackalopes also have a few other tricks up their fur, they have razor sharp teeth and tremendous strength on their hind legs. Jackalopes use their rear legs to attack other males. During a male versus male battle, spectators (particularly other males) interpret this as a display of desperation rather than strength, and is usually only used as a last ditch effort. Teeth on the other hand are a rarely used attack, this is due to the large size of their antlers/horns. It is very rare that another male will be able to get close enough to bite their opponent, especially without receiving some kind of reciprocating attack. However when they do; their long teeth penetrate into their opponent causing a deep wound. This wound leads to some blood loss, but is typically not fatal. In longer duels however, with hearts beating at maximum, blood loss becomes a very serious problem. # Male versus Female Males do not attack the females, however females do attack the males. If the male in question has defeated the females mate the female will attack using her razor sharp teeth and powerful kick. The male does attack back but only in self defense, should he feel threatened. The male will refrain from using his horns/antlers out of respect for the female, and he will instead, use kicking to push her away or hurt her enough to make her think twice. Intentional or not sometimes the male kills the female. When this happens the other Jackalopes lose respect for the male and outcast him from the colony. As you might have guessed Jackalopes are a respectful species. # Male versus Predator The Jackalopes predator would have to be fast, a cheetah would be a good animal to use as an example. The Jackalopes cannot out run a cheetah but can make much more precise and agile movements, this is where the Jackalope really shines. [![a cheetah](https://i.stack.imgur.com/g0llA.jpg)](https://i.stack.imgur.com/g0llA.jpg) When attacked by a predator the Jackalope runs, it makes fast movements left and right to keep the predator moving its head. As the Jackalope does this it scans the area ahead for any chance of escape. Since the Jackalope is about 2 feet long it can fit in some small spaces (this also depends on whether the Jackalope is male/female and if they have horns/antlers) depending on the environment they live in, let's assume woodland, much like the image below. By darting left and right the predator has to follow it similarly but if the predator stops paying attention for just a second the Jackalope could have quickly darted behind a tree or through some bushes confusing and disorientating the predator. [![A woodland forest](https://i.stack.imgur.com/kk7P4.jpg)](https://i.stack.imgur.com/kk7P4.jpg) Because we are assuming woodland there is the possibility for logs, burrows and bushes to hide in that are much too small for a larger predator to fit in. Should a hiding place not be available the Jackalope will run until it begins to feel tired, at this point it will slow down and wait for the predator to get closer. The female will wait until the predator is very close and will the attack using its rear legs, aiming for the head as much as possible. With such fast and powerful attacks to the face, the typical predator either backs off or pushes through the attacks. This type of attack however tends to lead to being eaten more often by predators. The male on the other hand uses a similar tactic, except he has horns/antlers. When the male Jackalope turns around to face his opponent he becomes a bigger problem than the predator initially thought. With 2 foot long horns/antlers in his face it becomes a lot harder to grab him where it hurts. He will then use his horns/antlers to attack his opponent by ramming and swiping at his foe. [![charging rams](https://i.stack.imgur.com/xBFzE.jpg)](https://i.stack.imgur.com/xBFzE.jpg) The male Jackalope is known to intervene should he spot another Jackalope under attack, although typically the male Jackalope will attempt to rescue females over other males. Because the Jackalope is 2 feet long the risk of aerial attacks are small to none, (unless of course this isn't based on Earth as we know it) so we can rule that out. The same goes for aquatic threats, unless the Jackalope is living near water large enough to house potential predators, they shouldnt have any problems there. # Invaders The typical rabbit is scared of the male Jackalope, although it is known for male rabbits to mate with female Jackalopes and vice versa. This is frowned upon by the colony and is a very rare circumstance however rabbits do not care and are always trying it on. The male Jackalope spends most of his time somewhere near his mate, if the Jackalope does not have a mate then he spends most of his time trying to win one over, especially in mating season (Some Jackalopes have been observed to have died from exhaustion from not resting in an effort to find a mate). This means that when rabbits try to invade their territory there is always a male close by to fight them off. Due to the Jackalopes superior strength and size the typical rabbit runs away whilst others fight but ultimately lose having achieved nothing. [Answer] Antlers would be useful against predators because they keep the hungry mouths at a safe distance much in the way early lion tamers were shown to use chairs. An attacker could end up not just with a mouthful of horn but possibly put out an eye. In fights with other jacks it makes sense for antler fighting to be reserved for sort of friendly displays put on to impress mates or settle dominance disputes ie without the intention of real harm and usually resolved by the weaker one submitting. Anyone who has raised rabbits knows their bite is nothing to ignore and they box viciously clawing the underbelly. I assume that jackalopes have evolved past the problem their Leporidae cousins have with blood pressure that causes them to faint while having sex or frightened. [Answer] # Fighting Each Other I got thinking about the philosophy of fighting in the two component species. Rabbits are mean... they will kick/bite/tear... they will mess each other up. They fight to destroy their rivals. They will kill each others young... hell they'll kill their own young. Deer posture. They fight, but in an attempt to identify which rival is superior, this year. Once decided, they more or less peacefully go their own way. So what does a Jackalope do? Fighting with the intent to maim with ANTLERS... that seems like it would get REALLY messy. But bunnies breed fast, so there will be a whole bunch of fresh combatants next spring. Posturing bunnies are certainly an option... but a pretty boring one. # Fighting Prey I was visualizing Jackalopes vs. Predators and I realized something... Rabbits bolt. Hard and Fast... a spooked bunny is just GOING... and they change direction like lightning, reversing their direction effortlessly. Now picture that same bunny with several pounds of antler on its head. I think the youtube videos of "Jackalopes attempting to escape" would be hilarious but really sad. The coyotes would get REALLY FAT. [Answer] Like bull elk, they raise themselves off their front feet and use their hind quarters to drive towards each other in an in-and-down motion. Given the agility and high power back legs of the Jackalope I would think a fight between them would look pretty similar to two bull elk in that a lot of the horn clashing motion is vertical but with less binding and horizontal pushing, and more clash and release and clash again as they hop around looking for a flank advantage. A rabbit style hop mode of travel leads itself to this even more than in the elk. ]
[Question] [ Question: Could a planet contain all of its (vast) oceans underground? I imagined a planet with no surface oceans - and no water cycle above ground - but where life was still possible. My initial misgivings are: * The increased temperatures below the crust. * Any life must be able to get to the water so the earth must absorb this water. But then wouldn't these two result in geysers and evaporating surface water, leading to those oceans slowly moving to the surface and creating a above ground oceans? I'm looking for any ideas on how a planet with underground oceans would stay this way or at least an idea of the timescale for the stability of this. (I.e. I don't want life that evolves to use these conditions to get flooded soon after). [Answer] You mention "oceans", certainly we have huge aquifers in the world ([Ogallala](https://en.wikipedia.org/wiki/Ogallala_Aquifer) in the US is a big one; 174,000 square miles, bigger than the Caspian Sea (at 143,000 sq mi). [Here are other aquifers](https://en.wikipedia.org/wiki/List_of_aquifers)). A world heavily dotted with a network of such aquifers could have no oceans; but I imagine there would still be a water cycle above ground: Plants could access the water, but evaporate it by normal biology; there would still be some cloud cover and rains due to concentrations caused by planet rotation winds: Just the rain doesn't accumulate, it percolates back down into the aquifers. I don't think you can have surface plants without them producing water vapor, by drying out (especially upon death) or burning: water is not destroyed by burning, it just becomes steam and escapes (and must go somewhere). If water vapor is produced, an above ground water cycle would exist. If the plants only grow under ground, the evaporation can be absorbed by the earth or rock ceiling. If they grow under water there is no evaporation, but there could be a cycle of exchange between plant fluids and the water. added: Animals on such a planet would evolve to get their water from the food they eat; ultimately traceable back to the water the plants are bringing up from the aquifers. IRL we do have animals that only get water from their food, I can't recall which ones off-hand, but it isn't a stretch for evolution. In any case, having gotten their water, they would still eliminate it, by sweat, saliva / panting, tears, urination and defecation. Those in turn would evaporate and dry, contributing vapor to the water cycle, which would collect and become rain. Some animals would evolve (like we have in the deserts, IRL) to get all their water during the rains, and store it within their bodies to be used slowly, in-between the rains. [Answer] ## Such a body is probably already existing... in our solar system ! I'll suggest that you take a look at [Europa](https://en.wikipedia.org/wiki/Europa_(moon)#Internal_structure). > > It is estimated that Europa has an outer layer of water around 100 km (62 mi) thick; a part frozen as its crust, and a part as a liquid ocean underneath the ice. > > > Basically, you can absolutely have an inner ocean entirely surrounded by a thick ice crust. Ice being less dense than water, it will always stay on top, thus preventing the need of a "earth-absorbing" water. As opposed to a rocky crust than would inevitably sink down. As for the heat, you have internal volcanism. Remember that Earth's life probably arose around deep oceanic thermal vents. This volcanism could be sustained by tidal forces created by a large moon or if your "planet" is actually a moon of a bigger planet (like... Europa around Jupiter). Plus, the ice crust would act as a pretty good insulator. In fact, it is considered possible that life has developped in Europa's deep ocean. Maybe only microscopic, single-celled life, but one can always dream of Europa's fish-like denizens... [Answer] If the body surface is too cold to keep liquid water but the core is warm enough to melt the ice, you can have a thick ice crust "sealing" the oceans. There could be geysers, yes, but the ejected water would then freeze and precipitate as ice on the crust. Possible mechanisms to have a warm core are: * intense radioactive decay * tidally induced heating (think of satellite orbiting a gaseous giant) ]
[Question] [ Consider the present day Earth. Now, through some event (magic, a giant maid with a vacuum cleaner, a disgruntled [alien did it](https://worldbuilding.meta.stackexchange.com/q/2171/29), ...), our planet is stripped of its atmosphere. Assume that this happens in such a way that other features of our planet are not significantly affected, and that the Earth is actually stripped of its atmosphere (it isn't merely replaced by some other gas(es)). The Sun is still there, and the solar system as a whole is unaffected by this little antic. After a reasonable length of time (maybe a few hundred million years into the future), an alien civilization comes zooming past the solar system in their superspace-drive spacecraft, and decide to make a rest stop at what used to be the Earth. * What would the Earth look like when these visiting aliens arrive? * What would be the primary driving factors in the transition from what we have today to what they would be encountering? Particularly consider what the surface would look like, including the effects on plate tectonics and the effects of meteor bombardment from space. I'm not tagging this as hard-science, but the harder the science in the answers, the better. [Answer] Second 1: The oceans on both the sun side and the dark side of the Earth instantly start to boil, reacting to the vacuum (absence of) pressure. ![water state chart](https://i.stack.imgur.com/VMmfO.png) The mass of the atmosphere of Earth is $5.15√ó10^{18}$ kg, which I guess is heavy by our standards, but the Oceans are $1.4√ó10^{21}$ kg, so a lot more mass there. Second 2: 7.3 billion people suddenly realize they cannot breathe Second 30: Most of the 7.3 billion people are now unconscious, soon to die. ... The oceans will continue boiling for hours or days, my guess would be until the new water vapor atmosphere reaches the triple point around 1 kPa (1% of current pressure) or until the ocean surface all freezes due to heat of evaporation cooling, whichever comes first. This would probably take less than 0.1% of the ocean mass. All the nitrogen is gone, and the contribution from volcanoes and other sources is minimal. The water vapor will slowly dissociate in the upper atmosphere, slowly leaking hydrogen off into space. I suspect that absent the greenhouse effect of the atmosphere, the ocean surface would eventually freeze. The rest of the land surface will be covered by a layer of ice too. Plate tectonics is powered by radioactive decay, so that would continue unabated. Meteors would plummet into the Earth hindered only by the water-vapor atmosphere. Volcanic eruptions would slowly add other trace gasses as well. Edit: There's a fair bit of Nitrogen at the bottom of the ocean, and with geological processes, it may over a few hundred million years end up back in the atmosphere. [Answer] > > What would the Earth look like when these visiting aliens arrive? > > > I have no clue, because humanity could quite possibly survive. Based on [the effects of a vacuum on humans and animals](https://en.wikipedia.org/wiki/Vacuum#Effects_on_humans_and_animals), almost everyone will be dead within two minutes. If buildings don't have the air within them removed, people in large building in coastal cities may survive long enough for the boiling oceans to replenish their air before they die due to vacuum exposure. What about someone swimming in a large lake or the ocean? They're going to be rather surprised when the water they are swimming in starts boiling, but it's not going to burn them. [An article I found with a quick search](http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/#5) mentions this: > > At equilibrium, the percentage of each gas in the water would be equivalent to the percentage of that gas in the atmosphere ‚Äì i.e. its partial pressure13 > > > With no atmosphere above it, the dissolved oxygen (and CO2, nitrogen, etc) would boil out faster than the water itself. This means that the water vapor coming off of large bodies of water should be breathable. This will only delay death for those near insufficiently large bodies of water (such as a mountain lake) as the vapor will likely spread out enough to not be useful. People playing in the ocean when the atmosphere disappears are going to be in good shape. They may be unable to breath for a moment or two, but the seawater will immediately provide them with at least something to breath. After not too long, there will be enough air in their immediate vicinity to survive long-term. Do you know who will have it even better than people playing in the ocean? Scuba divers! Unless they're very stupid divers, they won't let their tanks get all the way empty. Even then, they would still have some air in their tank - if a diver "runs out" of air, swimming up a little bit can lower the pressure enough that they can get more air out of the tank. In a vacuum, you'd be able to get air out of a completely "empty" tank. Also, the amount of air per breath depends on the surrounding pressure, so in a vacuum a full scuba tank would last extra long. So thanks to the combination of having a supply of breathable air and being in or near a reasonably large body of water, scuba divers would be able to deal with the initial few minutes. Do you know who would have it even better than scuba divers? Submarine crews. Their first indication of something weird happening would be the radio silence. By the time they came up to check things out, the boiling oceans will have already made near-sea-level areas livable again. So humanity is likely to have enough survivors of the initial atmospheric disappearance to continue, but how will they move forward? Fortunately for them, plants are able to handle vacuums better than animals are. From the article about the effects on humans and animals: > > An experiment indicates that plants are able to survive in a low pressure environment (1.5 kPa) for about 30 minutes. > > > This allows for more time for the boiling oceans to help coastal forests and prevent total devastation. Trees and other land-based plants will take a major hit, but the survival rate right along the coast will be reasonable - they won't go extinct altogether. Life will go on. Inland areas will become desolate for thousands of years, but gradually the atmosphere will be replaced and life will return. ### Conclusion The visiting aliens arrive to find a booming tourism industry. As they visit one history museum, they see a chart with six [mass extinction events](https://en.wikipedia.org/wiki/Extinction_event) - the Cretaceous‚ÄìPaleogene extinction event, the Triassic‚ÄìJurassic extinction event, the Permian‚ÄìTriassic extinction event, the Late Devonian extinction, the Ordovician‚ÄìSilurian extinction events, and the atmospheric disappearance event. [Answer] Approach #1: The atmosphere is stripped instantly. If the rest of the planet remains unaltered by your galactic maid, i think after your reasonable length of time this planet would look a lot\* like it did some 10'000 or 20'000 thousand years ago: Since the magnetic field remains intact, and there are processes like for example volcanic activity that emit gases, there will be a new atmosphere that is being generated over time. Some of the extremphile microorganisms will not even have noticed the absence of the atmosphere, so there will still be some form of life on the planet right after the atmosphere was removed. From those, new life forms will evolve. While at first the missing atmosphere will leave the earth defenseless against asteroid bombardment, thus greatly altering the surface, the re-forming atmosphere will soon lead to erosion. So, the general appearance of the geology will look similar in features, although obviously not in detail, to what it is like today. It might look smoother, since the atmosphere will reform quite quickly, thus adding your reasonable amount of time of extra erosion. Serban Tanasa suggested the missing atmosphere will be replaced within hours by water vapor, so, provided this is correct, the lack of protection against celestial rocks would even be negligible. The same was true if it was not hours but months for an atmosphere to re-form: a few more craters, but nothing that millions of years of erosion would not be able to turn into pelasant valleys, if plate tectonics didn't remove them anyway. Serban also pointed out that plate tectonics will be unaffected, so no change to be expected from that side. Although i have a vague feeling that the sudden missing of the atmosphere, and thus of the pressure on the plates, might result in a few more earthquakes and maybe even the odd volcano being triggered, but i am pretty sure that has no consequences that would be noticeable after the very long timespan you suggested before the alien visitors dropped by. \) "a lot like before" needs to be stretched quite a bit, i guess. This was supposed to mean: A lot of flora and fauna, although not the exact flora and fauna we know, maybe not even remotely similar, since it will have evolved from a different base and species will have been favored or hindered by different events than before. Approach #2: The space maid is very thorough* If on the other hand, your space maid does not stop after having vacuumed our atmosphere away, but stays at least for a year or so, to clean up all the vapor rising from the oceans, things will turn out quite differently. First, our determined maid removed a large portion of the liquid water from the planet. The missing atmosphere will expose the frozen parts, especially the glaciers, but also the ice caps at the poles, to sunlight that is suddelny a lot more intense. While the missing of the insulating effect and the greenhouse effect from the late atmosphere result in a lot of cooling on the dark side of the planet, the half that lies in sunlight receives more energy than it did before. The absence of liquid water removes a buffering effect, which in turn again increases the temperature variations of the day-night-cycle. At first, the radiation from the sun will kill off almost all surface life that had the indecency to survive the absence of atmosphere (which should pelase our maid a lot). Also, the greater day-night-temperature swings will lead to stronger erosion, since tension through heating will crack a lot of rock, while on the other hand the redesign of the planetary surface due to rocks from the sky will be a lot stronger than in the first scenario. Assuming the space maid will eventually call it a day and move on, the bombardment from space should trigger a lot of volcanic activity. this should re-build the atmosphere fairly quickly. After that, much the same as in scenario one should apply, since it can be assumed that at least some extremphiles survived even that, just to re-start the forming of life as if nothing had happened. But in this scenario, the greatest difference to the first, and to now, would be a much lower ocean level, resulting in much larger dry areas. Also, the beautiful fjords Slartibartfast had so lovingly designed will be gone. Which is a crying shame. [Answer] I agree with the posts that say that an atmosphere mostly composed of water vapor would reappear with the "boiling" of the water bodies. It would not only be water as nitrogen, oxygen and carbon dioxide are found dissolved in water. Water itself would only start boiling if at 0 pressure the temperature would be above boiling which I don't think is the case, it would more likely evaporate rapidly. The gases inside might be another story, and would definitely start bubbling much like a soda drink does when one opens it. The quick evaporation of the water would lead to a cooling of liquid water as the water molecules take away energy through evaporation. The temperature of the atmosphere would therefore also be much colder than the previous temperature. One thing that has not been said in the previous posts is that removing the atmosphere will remove a load from the surface of the earth. A quick removal of the atmosphere would certainly cause some amount of earthquakes and tectonic readjustments, specially cracks in the plates, as I would imagine the earth would expand from the release of the atmospheric weight. It is important to consider that the atmosphere is actually very thin, 75% of its mass being concentrated on the first 10km. Immediately after the removal of the atmosphere, one can imagine that a sudden reduction in pressure on the surface of the planet would have disappeared uniformly from all the surface of the planet. As ocean water evaporates, however, that will lead to an asymmetric change in the pressure across the surface of the planet. Because the ocean will have evaporated this would lead to reduced pressure on the surface that was covered by water bodies. That would be another source of tectonic readjustment. There are a couple of interesting pictures coming to mind from this idea. 1) Large steam clouds would originate from bodies of water, less densely from land due to underground water bodies. In other places water would not evaporate such as deserts and ice covered regions. - this would lead to small streams disappearing all together leaving empty stream beds To answer your question, if aliens would visit the planet many millions of years later they would probably find a very similar world to the one we have now, minus all complex life. Many microbes would probably survive the ordeal, but more complex organisms such as animals would die from lack of oxygen, the plants would die from the inability to do photosynthesis, due the blocking of sunlight by clouds. [Answer] Earth would regain its atmosphere at the expense of the oceans. If a vacuum were somehow instantaneously introduced by completely evacuating all of Earth's atmosphere, then the oceans would boil off to form an atmosphere of mostly water vapor. [UV light breaks down H2O into hydrogen and oxygen](http://www.universetoday.com/50863/how-water-protected-our-molecules/) so eventually a hydrogen/oxygen atmosphere would come back. Aerobic bacteria would provide some CO2. Anaerobic bacteria may contribute nitrogen or other gases to the atmosphere. All non-single cellular terrestrial life dies. The oceans don't boil fast enough to provide breathable atmosphere. [Answer] I suspect the atmosphere would be replenished quite a bit faster than most people expect. The replenishment of an atmosphere composed of water vapour and dissolved atmospheric gasses will provide an initial atmosphere, but the big refilling will occur when the sudden removal of weight due to the removal of the atmosphere and upper layer of the ocean triggers tectonic events in the Earth's crust. A large part of the atmospheric and hydrological cycles of the Earth actually take place over millions of years as atmospheric carbon is absorbed by the oceans and converted into calcium carbonate (for example the building of billions of shells by sea life), then eventually trapped in the ooze at the bottom of the oceans and converted into limestone. Under normal circumstances, it is eventually sub ducted into the mantle and dissolved by the great heat, with carbon dioxide being emitted by volcanos millions of years later. so as the crustal plates are disturbed by the asymmetric removal of weight, we should expect more volcanic activity, pumping millions of tons of carbon dioxide and other gasses into the atmosphere (indeed, a large volcanic eruption can put as much carbon dioxide into the Earth's atmosphere at once as a year's industrial output of human activity). The "new" atmosphere will be quite different, with a high concentration of water vapour, carbon dioxide and various sulphides and sulphates. Since water vapour is the best of all possible "greenhouse gasses", the surface of the Earth will warm up rather dramatically, melting any remaining icecaps and glaciers, causing more tectonic disturbances and probably more vulcanism. Plants which surveyed the initial removal of the atmosphere will have a generally better environment (current plant life seems to grow best at CO2 concentrations of between 800 to 1200 ppm, as opposed to the current CO2 concentration of just under 400 ppm). Countering this is the lack of oxygen means the ozone layer is gone, so the surface will be bombarded with ultraviolet radiation. Plants will "burn" under the sun, and any surviving animal life will also suffer severely. Plants which do survive will mutate rapidly, and most of the surviving plant life will be plankton under the surface of the oceans. Fish and sea going mammals will die due to the lack of oxygen in the water, so the Earth will be covered with some sort of tough moss, mutated versions of plant life that exists now and filled to the brim with algae and plankton in the oceans and seas. Perhaps a billion years after the event, animal life will have re-evolved from whatever survivors were underground or otherwise shielded from the lack of O2 and UV radiation, so the forms of life on Earth will be vastly different from what we see today: something like the weird life from the Burgess Shales. Convergent evolution may eventually develop analogues of the creatures we see today in similar ecological niches (shark shaped oceanic predators, for example), but a lot of that may depend on what the "base" stock of multicellular creatures was (if the first new creatures were anything like Hallucigenia, then all bets are off). So aliens arriving on Earth millions or billions of years in the future will see a populated planet teeming with organisms, all of which seem to have radiated from a limited number of base stocks in the relatively recent past. ]
[Question] [ During the medieval era of our world, weapons were getting pretty complex, but then gunpowder become commonplace and warfare was reduced to pulling a trigger. During the later end of this period, semi-automatic crossbows were being designed and used by the Chinese. Could a ballistic weapon be designed in the medieval era that is capable of fully automatic fire? [Answer] For starters: The Chinese semi-automatic crossbow is not the only design of crossbow that holds and fires multiple bolts. That design ([the repeating crossbow](https://en.wikipedia.org/wiki/Repeating_crossbow)) operates with a combined reload/firing mechanism operated by a lever. The second, the greek [Polybolos](https://en.wikipedia.org/wiki/Polybolos) operates by the ~~continuous~~ (turns out it isn't continuous, but with a suitable gearing mechanism could be made to be continuous as it's just a change in direction) turning of a windlass, and as long as it's supplied with bolts from the top could theoretically be fired indefinitely. I think this already qualifies as an automatic weapon because there is no discrete action required to launch the next bolt, you just provide mechanical power and it continues to fire. If this isn't automatic enough for you, however, you could also add a twisted rope store for rotational energy (similar to those used in catapults) and some gearing to make sure that the release of power isn't instantaneous but instead happens at a reasonable rate. Wind it up ahead of time, wait for your attackers, then pull the trigger (which removes a pin that would otherwise prevent the bow from firing when fully retracted). Fully automatic crossbow-y doom. It would probably have to be a mounted weapon due to the weight of the power store and complexity of the polybolos system, but it's certainly possible. If you want a simpler version of this: Get a Chinese repeating crossbow and attach it to a [reciprocating wheel](https://en.wikipedia.org/wiki/Reciprocating_motion) assembly. Power with a wound rope as before. [Answer] It is definitely possible. I mean, to be a little over-simplified, we have them now right? If humans have an idea, it is usually possible, at least to an extent. I am sure that some rudimentary automatic weapons could be built easily if a medieval engineer had the know-how. A little research shows a good number of attempts in different time periods that were fairly successful: Chinese repeating crossbows, ribauldequin, puckel gun, polybolos, etc. Now with that being out of the way, I think materials are your most important constraint. Many of our automatic weapons, from enormous cannons to automatic bb guns, are machined with very precise tools and materials. The quality of our steel, range of measurement tools, computer programmed machines, new materials like plastic and composites, all make these weapons possible. So considering that, think of how effective/durable these weapons would be. Rope can fray and break, wood is difficult to hone and cut with precision, metal was difficult to forge and shape. If an automatic weapon was possible it certainly would not be plausible. If you want them in your world remember that they would likely take a group of master craftsmen and would be incredibly expensive. Even then they may not be very durable or effective (read about the first cannons). I would suggest making them a rarity if they are to be added. [Answer] It's possible, but not practical. If we think of early gunpowder weapons, there are a couple of practical limitations: Metallurgy. The metals of the time are not strong enough, and the machining ability of the time is not precise enough, to build a working breech loading weapon. That requires a strong metal if the breech action isn't overly heavy, and precise machining to achieve a proper gas seal. All early gunpowder weapons were muzzle loaders. Fouling. Black powder is dirty. It not only produces a cloud of sulfur dioxide smoke, it also leaves a lot of gummy residue behind. That's what hampered the first breech loading rifles - the screw breeches clogged up from black powder residue. I have an accurate (and expensive) reproduction of a British Ferguson rifle (used once in battle in 1776), the first military breechloader. Even with lots of grease on the threads, I can get off maybe four shots before the screw action freezes up from the black powder residue, and has to be cleaned off. As well, the Ferguson uses a flintlock ignition - percussion ignition didn't come along until the early 1800's. Getting flint or slow match to fire rapidly would be just about impossible. Breechloading firearms did not become practical until the invention of the revolving cylinder that is sealed at the breech, and finaly the metallic cartridge, which contained the fouling to within the barrel and away from the breechloading action. With kinetic weapons like bows and crossbows, one lacks a reliable power source. A water wheel might work... if you only fight where you have a water wheel. Human power struggles to pull a bow or crossbow for a single shot, so multiple shots is too much for one person. You could use five or six people to power it, but you could also give those five or six people their own bows or crossbows and get the same rate of fire. And the materials of the time may not stand up to the rigorous demands of rapid fire. One final wrinkle: ruggedness. Battles occur wherever two armies meet, often in unexpected locations, on unknown terrain. A military weapon must be rugged enough to be carried across rough ground, and simple enough for a moderately trained soldier to operate. Rube Goldberg style devices just won't hold up under battlefield conditions. The practical reality: It is far simpler to train more archers than to try to develop a rapid fire arrow projecting weapon. especially with the materials and machining ability of those days. A platoon of archers is very mobile, and it can withstand damage to parts of it without losing effectiveness (casualties). Gunpowder weapons of that day were far too crude to be considered candidates for rapid fire. Automatic weapons were developed when the components: the action, the ignition method, and the cartridge method, had evolved to make them practical and rugged enough to withstand battlefield conditions: first the Gatling Gun that appeared not long after the metallic cartridge was developed, and then the Maxim recoil powered machine gun. [Answer] I wouldn't see why not? It is possible that, with the right application of tension mechanics to create something fully automatic would still be possible. Take a look at the mechanics of a cross bow for example. It would be possible to create a loader that feeds each bolt after one has been projected. The string pulled back again based on if the trigger is pressed there can be gear mechanics created inside to re-draw the string. catapults could be made automatic too using tension and weight blocks. How fast this whole process can take is another story and it probably wouldn't be faster than a human would be able to physically shoot draw and shoot again. Bowmen in this time and era were very very very good at their craft. It would be like trying to design a 2 legged robot that could outrun usain bolt. While the robot could run, it wouldn't be able to outrun a human with current technology. So to answer answer the question, the technology is definitely there to make it possible, how efficient and durable it would be is another. Also may not go as far or shoot as strong because of the way the tension works it may or may not be as strong as humans doing the drawing or giving it that extra umph. In an automated system, it may only provide enough tension to get the release (though you can probably design it so that the draw goes back a certain distance before releasing too). [Answer] Yes, but it would be an amusing but impractical toy. The Medievals were smart enough to realise that complex, cumbersome devices were not going to be as effective as more basic but functional ones. Especially when you're handing them out to squaddies, simplicity and ruggedness are essential. [Answer] From <http://www.halfbakery.com/idea/Automatic_20bat_20weapon#1317210494> "Thinking about sidearm catapults and preindustrial technology got me wondering about throwing rocks. A simple machine like a sling helps throw a rock farther. Flywheel catapults have been made but you have to stop them to reload. A bat also gets a rock farther but is more uncertain and probably harder to aim than a sling. An arrow goes the farthest but part of this is the aerodynamics of the arrow. Plus an archer or a slinger has a limited rate of fire. The automatic bat defense is a bat mounted on a spinning wheel. The (heavy) wheel is spun fast using gears. Rocks are rapidly dropped one by one in front of the bat. The wheel and bat slows for each one but is back up to speed for the next and does not need to stop to reload. A human batter can hit a ball 300-500 yards. I am not sure how a machine batter would do with rocks but probably comparable. The automatic bat could be put on a wall for defense or carried on a wagon. I think an automatic bat device like this would be better than a cannon against a cavalry charge, especially if the poor bastards being charged had all day to collect rocks (eg Waterloo)." [Answer] If you're allowing gunpowder, the automatic weapons themselves are insanely simple. The chief problem with the weapon is manufacturing a barrel that won't overhead almost immediately (overheating was a big obstacle faced by hand-cranked machine guns of the US civil war.) The second big problem would be the recoil spring. Coil springs weren't invented until the tail end of the medieval period. Still, you could probably justify the early invention of a brass coil spring by a jeweler who was trying out the helical design for another purpose and realized the advantages of it. The real bugaboo is the ammo. An automatic weapon has to have its ammo be self-contained, nearly identical rounds. For explosive-propelled bullets, this pretty much requires an integrated cartridge. Primers were invented in 1820 (as the percussion cap mechanism for firing a rifle) and brass casing integrating a percussion cap was invented in 1836. The earliest recoil-driven machine gun was invented in 1886, 50 years later. So once you have the ammo, the gun falls into place pretty quickly. Unfortunately, both percussion caps and brass cases relied on the industrial era, when people could cheaply manufacture physically identical objects. An alternative fully-automatic weapon could be an evolution of the Hwacha. In this concept, a long-burning wick would ignite a rocket, which would push back on a carriage with its exhaust. The carriage would strip another rocket arrow from a hopper, and return to expose it to the wick. (The return motion would be powered by a falling counterweight lifted when the carriage moved back.) Hwachas were never effective as weapons, so there was no impetus to actually develop them when more practical uses of gunpowder came around, but Rule Of Cool dictates that someone, somewhere in the universe have come up with a medieval-tech automatic rocket-launcher. [Answer] a Ribauldequin was a medieval cannon which was several small bore cannons side by side that could be fired automatically. So somthing with multiple barrels would be possible. Essentially many fire arms tied together sharing the same fireing mechanism. Modern automatic firearms fall into 3 categories: gas fed (AR-15), recoil (automatic pistols) and mechanical (such as gatling gun or the cannon in most jets). With the state of technology during the era, the real bottle neck is the cartridge and more importantly the percussion cap that allows the firing of a cartirdge without carrying a lit match. Your best bet is something with multiple barrels that can be fired with a single match lighting a common fuse. [Answer] # No At least it won't be practical. A firearm won't work without breechloading and reliable primers. Breechloading was used by [some early cannon](https://en.wikipedia.org/wiki/Breech-loading_swivel_gun), but those were awkward contraptions. A crossbow or catapult might be possible, but the principle of a crossbow is to store energy that was slowly accumulated and to release it all at once, for instance with a [windlass](https://commons.wikimedia.org/wiki/File:Armborst_4,_Nordisk_familjebok.png) or [cranequin](https://commons.wikimedia.org/wiki/File:Armborst_3,_Nordisk_familjebok.png). If "full automatic" means several shots per second, this winding mechanism will be impractical. One could imagine a design where a rapidly spinning disk functions like a rapid-fire [sling](https://en.wikipedia.org/wiki/Sling_(weapon)). [Answer] You can build a Gatling style crossbow/scorpion but the per-bolt stopping power suffers to accommodate the greater rate of fire. You could possibly do something with a high speed flywheel but the tolerances about kill you in terms of engineering the beast with either set up, if you have wide enough tolerances for it to be really reliable it's too heavy and under-powered to be useful and if its build to finer tolerances then it gets unreliable. This is especially true in an era where mass production and standardised parts aren't a thing. [Answer] The most low-tech way to build an automatic weapon would be a rudimentary tennis ball launcher. Just spin two wheels really fast and feed projectiles into the gap. ]

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